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ChemCatChem
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Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1867-3880 - ISSN (Online) 1867-3899
Published by John Wiley and Sons

[1577 journals]

In Situ Formation of Metal Carbide Catalysts
- Authors: Megan M Moyer; Canan Karakaya, Robert J. Kee, Brian Trewyn
  Abstract: Metal carbide catalysts are essential to many widely used chemical processes. Fischer-Tropsch synthesis, methane dehydroaromatization, and biomass conversion catalysts are typically prepared in situ from a metal oxide precursor with a carbon-containing gas. The reduction process of the metal oxide affects the final catalyst, as does the carburization gas mixture, and metal promoters. By looking at materials that are carburized in situ, new insights can be gained about catalyst activation, fuel processing, and deactivation stages. The main focuses of this review are iron carbide, molybdenum carbide, and nickel carbide; analyzing catalyst synthesis methods, reduction steps, in situ carburization, and improvements to the native processes. By combining years of research on these catalysts, trends and similarities are observed that can be used to improve current catalytic studies.
  PubDate: 2017-04-25T12:20:32.248212-05:
  DOI: 10.1002/cctc.201700304
Boron Nitride-supported Sub-nanometer Pd6 Clusters for Formic Acid
Decomposition: A DFT Study
- Authors: Roberto Schimmenti; Remedios Cortese, Dario Duca, Manos Mavrikakis
  Abstract: A periodic, self-consistent planewave DFT study was carried out to explore the potential use of Pd6 clusters supported on a boron nitride sheet as a catalyst for the selective decomposition of formic acid (HCOOH) to CO2 and H2. The competition between formate (HCOO) and carboxyl (COOH) paths on catalytic sites, with different proximities to the support, was studied. Based on energetics alone, the reaction may mainly follow the HCOO route. Slightly lower activation energies were found at the lateral sites of the cluster as compared to top face sites. This is particularly true for the bidentate to monodentate HCOO conversion. Through comparison of results with similar studies on HCOOH decomposition on extended Pd surfaces, it was demonstrated that the existence of undercoordinated sites in the sub-nanometer cluster could play a key role in preferentially stabilizing HCOO over COOH, which is a common CO precursor in this reaction. A hydrogen spillover mechanism was also investigated; migration toward the boron nitride support is not favorable, at least in the early stages of the reaction. However, hydrogen diffusion on the cluster has low barriers compared to those involved in formic acid decomposition.Sub-nano key: Density functional theory calculations offer atomistic insights into the catalytic activity of a Pd6 sub-nanometer cluster, supported on a boron nitride sheet, for formic acid decomposition. Undercoordination of the cluster sites may be a key factor for avoiding CO production and poisoning.
  PubDate: 2017-04-25T07:31:29.176994-05:
  DOI: 10.1002/cctc.201700248
Analysis of the Magnetic Entropy in Oxygen Reduction Reactions Catalysed
by Manganite Perovskites
- Authors: Jose Gracia; Julen Munarriz, Victor Polo, Ryan Sharpe, Yunzhe Jiao, J.W. Niemantsverdriet, Tingbin Lim
  Abstract: Manganese oxides with a half-metallic ground state are particularly active for oxygen reduction reactions (ORR). La0.67Sr0.33MnO3 (LSMO) perovskite is the archetypal example for compositions with a Curie temperature (TC) above room temperature, and with a high intrinsic activity for the partial reduction of triplet state O2. The ferromagnetic (FM) character of the superexchange interactions in LSMO facilitates both the charge and spin transport below 370 K. Other than the enhanced electronic conductivity, the reduced spin entropy seems to be of relevance in oxygen catalysis, as the magnetic ordering extends to the surface. The sign of the exchange interactions determines the adsorption of the triplet oxygen molecule with its spin antiparallel to the FM catalysts. On the basis of transition state theory, we report that on LSMO the hindrance due to the magnetic entropy for the initial reduction of O2 by two antiparallel electrons to diamagnetic intermediates (like H2O2) is minimum. On the other hand, the additional reduction of H2O2 to H2O, diamagnetic steps, prefers paramagnetic catalysts, with higher magnetic entropy like La0.4Sr0.6MnO3, to avoid spin accumulation.
  PubDate: 2017-04-25T04:34:37.834396-05:
  DOI: 10.1002/cctc.201700302
Effect of F-modification over Phillips Cr/SiO2 catalyst for ethylene
polymerization
- Authors: QiaoQiao Sun; Ruihua Cheng, zhen liu, Xuelian He, Ning Zhao, Boping Liu
  Abstract: In this work, the fluoride modified Phillips catalyst was investigated using combined experimental and computational methods. The addition of fluoride to the Phillips Cr/SiO2 catalyst can increase the activity of the catalyst calcined at low temperature, as well as the molecular weight of the polyethylene product. Density functional theory (DFT) calculations show that the difference of Gibbs free energy barriers between the chain transfer and the chain propagation increase after the introduction of the fluoride onto the silica surface, which is in accordance with the increased molecular weight of the polyethylene produced by the fluoride modified Phillips Cr/F-SiO2 catalyst. The computational results also support that the activity of the ethylene/1-hexene copolymerization increases after the introduction of the fluoride, although the modification has little effect on the regioselectivity of the produced ethylene/1-hexene copolymer. Moreover, the copolymers produced by the fluoride modified Phillips catalyst with more short chain branches (SCBs) in the high molecular weight fraction and significant enhancement of the environmental stress crack resistance (ESCR) can also be explained on the basis of the DFT calculations.
  PubDate: 2017-04-25T03:21:38.166564-05:
  DOI: 10.1002/cctc.201700375
Preyssler heteropolyacids in the self-etherification of
5-hydroxymethylfurfural to 5,5'(oxy-bis (methylene))bis-2-furfural (OBMF)
under mild reaction conditions
- Authors: Alexander Paez; Hugo A. Rojas, Omar Portilla, Gabriel Sathicq, Carlos A M Afonso, Gustavo P Romanelli, José J. Martínez
  Abstract: The synthesis of 5,5'(oxy-bis(methylene))bis-2-furfural (OBMF) from 5-hydroxymethylfurfural (5-HMF) was studied using bulk and alumina-supported Preyssler heteropolyacids. The formation of OBMF was related to the amount of Brönsted acid sites, the lowest yield to OBMF being obtained with supported heteropolyacids. However, the Lewis acidity of HPA supported on Al2O3 favored the formation of 2,5-dimethylfurane. The effects of solvent, catalyst loading, temperature and reaction time on the selectivity to OBMF from 5-HMF were studied in order to optimize OMBF production using bulk Preyssler heteropolyacids; a yield of 84 % to OBMF was obtained at 5 h and 343 K. These results demonstrate that bulk Preyssler heteropolyacid is a good candidate for OBMF synthesis under mild reaction conditions.
  PubDate: 2017-04-24T22:20:34.882832-05:
  DOI: 10.1002/cctc.201700457
Au(I) complex-titania hybrid photocatalyst for hydrogen production
- Authors: Elisabet Aguiló; Lluís Soler, Albert Casanovas, Artur J Moro, Joao Carlos Lima, Laura Rodríguez, Jordi Llorca
  Abstract: Integration of TiO2 and an Au(I) complex containing a thio-coumarin moiety results in a very efficient photocatalyst for the generation of H2. The molecular structure of the complex is preserved under photoreaction due to the strong Au(I)-S bond. The Au(I) complex plays a determinant role in the photogeneration of H2 by accepting the photoinduced electrons originated in TiO2 upon light exposure. This is the first example of an Au(I) complex-semiconductor hybrid photocatalyst. The rate of H2 generation under dynamic conditions from water-ethanol is about one order of magnitude superior on a metal basis to that obtained over conventional TiO2 decorated with Au metal nanoparticles.
  PubDate: 2017-04-24T14:20:28.332249-05:
  DOI: 10.1002/cctc.201700518
Semi-rational engineering accelerates the laboratory evolution of
nitrilase catalytic efficiency for nicotinic acid biosynthesis
- Authors: Jin-Song Gong; Ting-Ting Dong, Bing-Chen Gu, Heng Li, Wen-Fang Dou, Zhen-Ming Lu, Zhe-Min Zhou, Jin-Song Shi, Zheng-Hong Xu
  Abstract: The nitrilase-mediated green synthesis of nicotinic acid, an important reaction in synthetic organic chemistry, has attracted considerable attention in recent years. However, the application potential of nitrilase is hindered by several limitations, such as low catalytic efficiency and byproduct formation. In this study, the site saturation mutagenesis of asparagine 40, phenylalanine 50, and glutamine 207 in recombinant nitrilase from Pseudomonas putida CGMCC3830 was conducted to improve the specificity of nitrilase for nicotinic acid. The resulting mutants, which contain the mutations N40G (asparagine glycine), F50W (phenylalanine tryptophan), and Q207E (glutamine glutamic acid) produced higher nicotinic acid yields than the wild type. Furthermore, double and triple mutations were introduced, and four mutants containing N40G/F50W, N40G/Q207E, F50W/Q207E, and N40G/F50W/Q207E were obtained and evaluated for their capacity to produce nicotinic acid. The double mutant F50W/Q207E and triple mutant N40G/F50W/Q207E displayed the highest activity, which was nearly two-fold higher than that of the wild type. The kinetics analysis of nicotinic acid synthesis with the mutant nitrilase revealed the higher catalytic capability of all the mutants compared with the wild type. These results provide new insights into the catalytic performance of P. putida nitrilase toward 3-cyanopyridine to promote nicotinic acid production.
  PubDate: 2017-04-24T08:22:11.121456-05:
  DOI: 10.1002/cctc.201700665
Hydrodeoxygenation of Fatty Acids, Triglycerides, and Ketones to Liquid
Alkanes by a Pt–MoOx/TiO2 Catalyst
- Authors: Kenichi Kon; Takashi Toyao, Wataru Onodera, S. M. A. H. Siddiki, Ken-ichi Shimizu
  Abstract: Various supported metal catalysts are screened for hydrogenation of lauric acid and 2-octanone as model reactions for the transformation of biomass-derived oxygenates to liquid alkanes (biofuels) in a batch reactor under solvent-free conditions. Among the catalysts tested, Pt and MoOx co-loaded on TiO2 (Pt–MoOx/TiO2) shows the highest yields of n-alkanes for both of the reactions. Pt–MoOx/TiO2 selectively catalyzes the hydrodeoxygenation of various fatty acids and triglycerides to n-alkanes without C−C bond cleavage under 50 bar H2 and shows higher turnover numbers than the catalysts in the literature. Pt–MoOx/TiO2 is effective also for the hydrodeoxygenation of various ketones to the corresponding alkanes. In situ IR study of the reaction of adsorbed acetone under H2 suggests that the high activity of Pt–MoOx/TiO2 is attributed to the cooperation between Pt and Lewis acid sites of the MoOx/TiO2 support.Hydrodeoxygenation without cleavage: Pt–MoOx/TiO2 shows high activity for the selective hydrodeoxygenation of fatty acids, triglycerides, and ketones under solvent-free conditions to give n-alkanes without C−C bond cleavage. H2 is dissociated by Pt sites and the C=O group coordinated to the Mon+ site undergoes Lewis acid activation.
  PubDate: 2017-04-24T07:55:29.280934-05:
  DOI: 10.1002/cctc.201700219
Iron and cobalt corroles in solution and on carbon nanotubes as molecular
photocatalysts for hydrogen production by water reduction
- Authors: Miguel A. Morales Vásquez; Mariana Hamer, Nicolas I. Neuman, Alvaro Y. Tesio, Andrés Hunt, Horacio Bogo, Ernesto J. Calvo, Fabio Doctorovich
  Abstract: Here we report the use of cobalt and iron corrole complexes as catalysts of H2O reduction to generate H2. Electro and photocatalysis has been used in the case of dissolved corroles for water reduction with inspiring results. Carbon nanotubes doped with corroles were used as photo-electrochemical catalysts allowing getting very low overpotential values and increased hydrogen production, achieving incredibly high turnover numbers and turnover frequencies of ca. 107 and 105, respectively. Through this last process we were able to obtain 1mmol of H2 by using minuscule amounts of catalyst, in the order of pictograms. The reactions can be carried out in water, without the need of organic solvents. Remarkably, the photoelectrochemical catalytic efficiency was increased by five orders of magnitude when adsorbing the molecular catalysts onto carbon nanotubes.
  PubDate: 2017-04-24T03:21:57.921591-05:
  DOI: 10.1002/cctc.201700349
Construction of Hierarchical Copper-Based Metal–Organic Framework
Nanoarrays as Functional Structured Catalysts
- Authors: Tianyu Zhang; Wenxian Liu, Ge Meng, Qiu Yang, Xiaoming Sun, Junfeng Liu
  Abstract: The immobilization of metal–organic framework (MOF) materials in a three-dimensional (3 D) and oriented arrangement is critical for their application in heterogeneous catalysis. In this work, a coordination replication strategy was developed to construct Cu-based MOFs into 3 D hierarchical nanoarray architectures by using Cu(OH)2 nanorod arrays as a sacrificial template. The Cu(OH)2 nanorod arrays served as the Cu source and coordinated with an organic ligand to form MOF crystals, and they also served as the 3 D substrate to support the growth of the Cu-based MOFs. This strategy could also be applied to synthesize various hierarchical Cu-based MOF arrays, which demonstrated the general efficacy of the method. Owing to their unique structural advantages (hierarchical porosity, large surface area, and intimate contact with the 3 D substrate), these MOF nanoarrays exhibit excellent catalytic activity and cycling stability in heterogeneous catalysis as structured catalysts. This strategy opens up new possibilities for the construction of immobilized MOF-based 3 D nanoarrays for multipurpose applications.A little bit of structure: A general coordination replication strategy is developed to fabricate hierarchical copper-based metal–organic framework (MOF) arrays by using Cu(OH)2 nanorod arrays as a template and metal source. Owing to their unique structural advantages, the as-prepared hierarchical MOF-2 nanoarrays exhibit excellent catalytic activity and cycling stability in heterogeneous catalysis as a structured catalyst.
  PubDate: 2017-04-24T02:40:40.681618-05:
  DOI: 10.1002/cctc.201700060
Metal–Organic Framework Mediated Cobalt/Nitrogen-Doped Carbon Hybrids as
Efficient and Chemoselective Catalysts for the Hydrogenation of
Nitroarenes
- Authors: Xiaohui Sun; Alma I. Olivos-Suarez, Lide Oar-Arteta, Elena Rozhko, Dmitrii Osadchii, Anastasiya Bavykina, Freek Kapteijn, Jorge Gascon
  Abstract: A Co@N-doped carbon (Co@NC) hybrid was synthesized by thermal decomposition of the metal–organic framework (MOF) ZIF-67 under N2 atmosphere. These hybrid materials exhibit outstanding catalytic activity and chemoselectivity for the conversion of a wide range of substituted nitroarenes to their corresponding anilines under relatively mild reaction conditions. The high catalytic performance is attributed to the formation of cobalt nanoparticles and to the presence of atomically dispersed Co species in close interaction with nitrogen-doped graphene. Both active species are formed in situ during the pyrolytic transformation of ZIF-67. The catalysts could be reused in consecutive runs, exhibiting a slightly lower activity ascribed to blockage of the active sites by strongly adsorbed reaction species. These results open up a pathway for the design of noble-metal-free solid catalysts for industrial applications.A hybrid for hydrogenation: The one-step thermal decomposition of the metal–organic framework ZIF-67 under a N2 atmosphere is a straightforward approach to synthesize a scalable, recyclable, and active heterogeneous catalyst for the hydrogenation of nitroarenes. The resulting cobalt-containing carbon composites exhibit an excellent catalytic performance in the hydrogenation of a wide range of nitroarenes to their substituted anilines under relatively mild conditions.
  PubDate: 2017-04-24T02:40:38.182195-05:
  DOI: 10.1002/cctc.201700095
Proton-Reduction Reaction Catalyzed by Homoleptic
Nickel–bis-1,2-dithiolate Complexes: Experimental and Theoretical
Mechanistic Investigations
- Authors: Athanasios Zarkadoulas; Martin J. Field, Vincent Artero, Christiana A. Mitsopoulou
  Abstract: A series of homoleptic monoanionic nickel dithiolene complexes [Ni(bdt)2](NBu4), [Ni(tdt)2](NBu4), and [Ni(mnt)2](NBu4) containing the ligands benzene-1,2-dithiolate (bdt2−), toluene-3,4-dithiolate (tdt2−), and maleonitriledithiolate (mnt2−), respectively, were employed as electrocatalysts in the hydrogen-evolution reaction with trifluoroacetic acid as the proton source in acetonitrile. All complexes are active catalysts with TONs reaching 113, 158, and 6 for [Ni(bdt)2](NBu4), [Ni(tdt)2](NBu4), and [Ni(mnt)2](NBu4), respectively. The Faradaic yield for the hydrogen evolution reaction reaches 88 % for 2−, which also displays the minimal overpotential requirement value (467 mV) within the series. Two pathways for H2 evolution can be hypothesized that differ in the sequence of protonation and reduction steps. DFT calculations are in agreement with experimental data and indicate that protonation at sulfur follows the reduction to the dianion. Hydrogen evolves from the direduced–diprotonated form via a highly distorted nickel hydride intermediate. The effects of acid strength and concentration in the hydrogen-evolving mechanism are also discussed.Reduction first: A series of homoleptic monoanionic nickel dithiolene complexes are employed as electrocatalysts in the hydrogen-evolution reaction in acetonitrile with trifluoroacetic acid as the proton source. DFT calculations indicate that, for the two proposed pathways, protonation at sulfur follows the reduction to the dianion, in agreement with experimental data.
  PubDate: 2017-04-21T03:21:32.778639-05:
  DOI: 10.1002/cctc.201601399
The Influence of Alcohols in Driving the Morphology of Magnesium Chloride
Nanocrystals
- Authors: K. S. Thushara; Maddalena D'Amore, Alessandro Piovano, Silvia Bordiga, Elena Groppo
  Abstract: MgCl2 nanocrystals prepared in the presence of methanol and ethanol were characterized by complementing surface-science tools with a systematic quantum-mechanical investigation of the stability order (in terms of Gibbs free energy) of different MgCl2 surfaces in the presence of the two alcohols. Both alcohols drastically change the overall stability and the stability order of the exposed surfaces, mainly as a consequence of the entropic contribution to the Gibbs free energy, hence inhibiting or promoting crystal growth in certain directions. The environment-dependent occurrence of the MgCl2 surfaces may influence the structure and properties of the supported TixCl4−x sites in the MgCl2/TiCl4 precatalyst, which has important implications in the design of morphologically controlled Ziegler–Natta catalysts.The effects of alcohol: Calculations at the DFT-D level coupled with FTIR spectroscopy of CO adsorbed at 100 K allows the morphology of disordered MgCl2 nanocrystals formed in the presence of different alcohols as Lewis bases to be predicted and validated.
  PubDate: 2017-04-21T03:21:27.255233-05:
  DOI: 10.1002/cctc.201700101
A Multifunctional Zirconium-Based Metal–Organic Framework for the
One-Pot Tandem Photooxidative Passerini Three-Component Reaction of
Alcohols
- Authors: Davood Azarifar; Ramin Ghorbani-Vaghei, Saba Daliran, Ali Reza Oveisi
  Abstract: A porous multifunctional zirconium-based metal–organic framework (MOF) was achieved by combined covalent and dative post synthetic modification (PSM) of the UiO-66-NH2, and characterized by a variety of techniques, including FTIR spectroscopy, powder XRD, N2 temperature-programmed adsorption/desorption, scanning electron microscopy, thermal gravimetric analysis, inductively coupled plasma atomic emission spectroscopy, and UV/Vis diffuse reflectance spectroscopy. The MOF (Zr–MOF–FePC, PC=2-pyridinecarboxaldehyde) is an active, efficient, and reusable catalyst for the one-pot tandem photooxidative Passerini three-component reaction of alcohols. This is a new type of tandem photocatalyst and cooperative catalyst and was obtained in the course of developing MOFs as versatile heterogeneous catalysts for diverse tandem oxidative multicomponent reactions. This work illustrates the potential of MOFs as multifunctional heterogeneous catalysts for sustainable chemistry.Three in one-pot: A novel porous zirconium-based metal–organic framework (MOF) is synthesized and explored in the one-pot tandem photo-oxidative Passerini three-component reaction of alcohols to afford α-acyloxy amides at room temperature without using any additive. Multiple functionalities into the MOF enrich its application in the photocatalysis and catalysis.
  PubDate: 2017-04-21T02:02:32.932792-05:
  DOI: 10.1002/cctc.201700169
Role of water on the activity of magnesium silicate for
transesterification reaction
- Authors: Longfei Lin; Damien Cornu, Maya Mounir Daou, Cyril Domingos, Virginie Herledan, Jean-Marc Krafft, Guillaume Laugel, Yannick Millot, Helene Lauron-Pernot
  Abstract: This study aims to reveal how water adsorbed on a solid influences its catalytic properties for transesterification reaction in liquid phase. The reactivity of a commercial magnesium silicate was studied after various thermal pretreatments for the reaction of transesterification of ethyl acetate with methanol. It was observed that the conversion decreases with the increase of the pretreatment temperature, therefore with the release of the water content of the magnesium silicate. Thermogravimetric analysis, DRIFT and 1H NMR spectroscopies show that physically adsorbed water has little influence on the reactivity, while water incorporated within the catalysts thus desorbing at higher temperatures plays a key role on the conversion. Calorimetry, in situ DRIFT spectroscopy and 1H NMR indicate that two kinds of active sites exist, that are created from the water coordinated to magnesium located on the edge of the clay-like particles or in the defects present in the silicate layer, respectively. Their role could be to stabilise methanol deprotonated by basic Mg-OH groups, activate ester or help the departure of the alkoxyl moiety .
  PubDate: 2017-04-20T11:46:25.683762-05:
  DOI: 10.1002/cctc.201700139
Selective Oxidation of Methanol to Dimethoxymethane at Low Temperatures
through Size-controlled VTiOx Nanoparticles
- Authors: Rui Sima; Guojuan Liu, Qiyan Wang, Ping Wu, Tingting Qin, Gaofeng Zeng, Xinqing Chen, Ziyu Liu, Yuhan Sun
  Abstract: A vanadium/titanium mixed-oxide catalyst with a narrow particle-size distribution, large BET surface area, high dispersion of vanadium, and enhanced acidity and redox capabilities was prepared by a cetyltrimethylammonium bromide (CTAB) surfactant-associated vanadium oxide and titanium oxide co-precipitation route. The impact of the CTAB content on the catalyst properties, including structure, chemical states, and acidity and redox activities, was investigated by X-ray diffraction, BET surface area, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, H2 temperature-programmed reduction, and temperature-programmed desorption of ammonia. Relative to the catalyst prepared without CTAB, the resultant catalyst exhibited significantly improved low-temperature activity for the oxidation of methanol to dimethoxymethane (DMM). A maximum methanol conversion of 53 % with 93 % selectivity to DMM were achieved over the VTiS–CTAB catalyst at 120 °C, and this optimized reaction temperature is 25 °C lower than that needed for the reference catalysts and the yield of DMM is comparable.V for victory! The VTiS mixed-oxide catalyst with a narrow particle-size distribution, large surface area, high V dispersion, and enhanced acidity and redox capabilities is prepared by surfactant-associated co-precipitation; this catalyst exhibits excellent performance in the oxidation of methanol to dimethoxymethane at low temperatures.
  PubDate: 2017-04-20T06:10:43.120232-05:
  DOI: 10.1002/cctc.201700074
Preparation of a Nanobiocatalyst by Efficiently Immobilizing Aspergillus
niger Lipase onto Magnetic Metal–Biomolecule Frameworks (BioMOF)
- Authors: Gao-Hui Xia; Shi-Lin Cao, Pei Xu, Xue-Hui Li, Jian Zhou, Min-Hua Zong, Wen-Yong Lou
  Abstract: A biocompatible support made of ZnGlu-coated magnetic iron oxide nanoparticles (ZnGlu–MNPs) was prepared by a simple electrostatic self-assembly technique and structurally characterized. Aspergillus niger lipase (ANL) was immobilized onto the ZnGlu–MNPs with high protein loading (118.0 mg g−1) and high enzyme-activity recovery (more than 82.0 %). The as-prepared immobilized ANL exhibits high catalytic performance and a wide pH and temperature adaptability. Moreover, the stabilities and the solvent tolerance of ANL@ZnGlu-MNPs were clearly superior to those of the free counterpart. The novel ANL@ZnGlu-MNPs was easily recycled from the reaction medium by magnetic forces. Therefore, the as-prepared ZnGlu-MNPs is a promising novel carrier for immobilized enzymes.Go Fish! Aspergillus niger lipase immobilized onto magnetic iron oxide nanoparticles exhibits high catalytic performance, a wide pH and temperature adaptability, and superior stabilities and solvent tolerance to those of the free counterpart. It can be easily recovered simply by using a magnet.
  PubDate: 2017-04-20T06:10:40.859254-05:
  DOI: 10.1002/cctc.201700070
Heterogeneous Ketone Hydrodeoxygenation for the Production of Fuels and
Feedstocks from Biomass
- Authors: Rhodri W. Jenkins; Cameron M. Moore, Troy A. Semelsberger, Andrew D. Sutton
  Abstract: In this work, we describe a simple, heterogeneous catalytic system for the hydrodeoxygenation (HDO) of 5-nonanone and 2,5-hexanedione, which we use as model compounds for more complex biomass-derived molecules. We present the stepwise reduction of ketones by using supported metal and solid acid catalysts to identify the intermediates en route to hydrocarbons. Although monoketone HDO can be achieved rapidly using moderate conditions (Ni/SiO2.Al2O3, HZSM-5, 200 °C, 1.38 MPa H2, 1 h), quantitative γ-polyketone HDO requires higher pressures and longer reaction times (Pd/Al2O3, HZSM-5, 2.76 MPa H2, 5 h), although these are more facile conditions than have been reported previously for γ-polyketone HDO. Stepwise HDO of the γ-polyketone shows the reaction pathway occurs through ring-closure to a saturated tetrahydrofuran species intermediate, which requires increased H2 pressure to ring-open and subsequently to fully HDO. This work allows for further understanding of bio-derived molecule defunctionalization mechanisms, and ultimately aids in the promotion of biomass as a feedstock for fuels and chemicals.Towards biomass feedstocks: A simple, heterogeneous catalytic system is used for the hydrodeoxygenation (HDO) of 5-nonanone and 2,5-hexanedione, as model compounds for more complex biomass-derived molecules. Although monoketone HDO can be achieved rapidly by using moderate conditions, quantitative γ-polyketone HDO requires higher pressures and longer reaction times, but these conditions are still more facile than those reported previously.
  PubDate: 2017-04-20T05:01:56.096269-05:
  DOI: 10.1002/cctc.201601678
Effect of the Structure and Mesoporosity in Ni/Zeolite Catalysts for
n-Hexadecane Hydroisomerisation and Hydrocracking
- Authors: P. Lanzafame; S. Perathoner, G. Centi, E. Heracleous, E. F. Iliopoulou, K. S. Triantafyllidis, A. A. Lappas
  Abstract: The hydroisomerisation/hydrocracking properties of Ni-zeolite catalysts (H-MFI and H-Beta) are studied using n-hexadecane as model compound and compared with those of Ni/ASA (amorphous silica-alumina) as reference catalyst. In the case of H-Beta, the effect of the introduction of mesoporosity by controlled desilication is also investigated. The results indicate that Ni on desilicated H-Beta catalysts shows very interesting characteristics for the potential use in the production of biofuel from vegetable/algal oil, or the upgrading of biomass-derived Fischer–Tropsch waxes. Ni/H-Beta shows lower activity with respect to Ni/H-MFI, but significantly lower formation of gases and much better hydroisomerisation activity. The introduction of mesoporosity by desilication enhances the activity, while still maintaining an acceptable gas formation and good hydroisomerisation properties. Furthermore, the desilication treatment improves the stability with respect to carbon formation.Upgrading oil: Nickel on desilicated H-Beta zeolite catalysts shows interesting characteristics that would be applicable for use in the production of biofuel from vegetable/algal oil, or the upgrading biomass-derived of Fischer–Tropsch waxes.
  PubDate: 2017-04-20T01:36:18.850713-05:
  DOI: 10.1002/cctc.201601670
Highly Dispersed Nickel Particles Encapsulated in Multi-hollow
Silicalite-1 Single Crystal Nanoboxes: Effects of Siliceous Deposits and
Phosphorous Species on the Catalytic Performances
- Authors: David Laprune; Alain Tuel, David Farrusseng, Frédéric C. Meunier
  Abstract: Multi-hollow silicalite-1 single crystals (MH) were prepared for the first time by an original synthesis pathway by using tetrabutylphosphonium hydroxide (TBPOH) as a mild desilicating agent. This new generation of hierarchical zeolite allowed the encapsulation of nanoparticles (NPs) featuring an enhanced confinement of the metallic guest and a thin wall thickness. The MH catalyst exhibited a better stability for methane steam reforming at 700 °C than a single-hollow counterpart (SH). Ni average particle size could be kept lower than 4 nm after 20 h on stream for the MH sample. However, a detailed analysis of kinetic data of the structure-insensitive CO methanation used as a model reaction revealed that the sample activity was adversely affected by two main factors deriving from the preparation steps. First, a siliceous over-layer derived from the decomposition of intermediate Ni phyllosilicates, which partly covered the resulting Ni nanoparticles. Second, phosphorus from the templates remained in the samples, probably forming a Ni–P compound upon reduction. The overall catalytic activities observed here were therefore a complex interplay of improved dispersion and poisonous effects.Encapsulation of Ni nanoparticles in multi-hollow silicalite-1 single crystals provides greatly different properties compared with single-hollow zeolite crystals, including better dispersion, but also some surface poisoning towing to synthesis steps through siliceous and P compounds.
  PubDate: 2017-04-19T07:27:29.814449-05:
  DOI: 10.1002/cctc.201700233
Unconventional Pd@sulfonated silica monoliths catalysts for selective
partial hydrogenation reactions under continuous flow
- Authors: Francesca Liguori; Pierluigi Barbaro, Bilel Said, Anne Galarneau, Vladimiro Dal Santo, Elisa Passaglia, Alessandro Feis
  Abstract: Doubly functionalized, hierarchical porosity silica monoliths were synthesized by post-grafting of sulfonic groups and in-situ growth of Pd nanoparticles in the order. PdNP of 3.1 nm size located in the mesopores of the material showed to be evenly distributed within 4.6% wt Pd monoliths. The system was explored in the continuous flow, catalytic partial hydrogenation reaction of 3-halogeno-nitrobenzenes and 3-hexyn-1-ol in the liquid phase, showing remarkable conversion, selectivity and resistance under very mild conditions.
  PubDate: 2017-04-18T07:20:40.860682-05:
  DOI: 10.1002/cctc.201700381
Dual Gold(I)-Catalyzed Cyclisation of Dialkynyl Pyridinium Salts
- Authors: Svetlana Tšupova; Alban Cadu, Fabian Stuck, Frank Rominger, Matthias Rudolph, Joseph S. M. Samec, A. Stephen K. Hashmi
  Abstract: Novel dialkynyl pyridines were synthesised and protected as alkyl salts for dual gold(I)-catalysed cycloisomerisation. Different alkyl groups and counter ions were screened for the salts, with benzyl and PF6- providing the best results. The cyclisation led to NMR yields of >95% being obtained for a number of substrates. Step-wise hydrogenation of products could be carried out in one-pot by Pd/C, with selective reduction of the double bonds, followed by deprotection of the Bn group.
  PubDate: 2017-04-18T06:20:56.953545-05:
  DOI: 10.1002/cctc.201700018
Chromium Catalyzed Highly Selective Oligomerization of Ethene to 1-Hexene
with N,N-bis{chloro(aryl)-phosphino}-amine Ligands
- Authors: Uwe Rosenthal; Martha Höhne, Normen Peulecke, Katharina Konieczny, Bernd Harald Müller
  Abstract: Different N,N-bis{chloro(aryl)-phosphino}-amines were synthesized and characterized. All synthesized compounds were tested as ligands in the chromium catalyzed oligomerization of ethene. The dependence of successively increasing the steric bulk either at one of the phosphorus´ substituents or at the nitrogen center on the product distribution of the oligomerization reaction was examined. We found a highly active and selective trimerization system with purities of the hexene fraction up to 99.9 % of 1-hexene. Furthermore we suppose an in situ methylation of the chlorinated ligands into the corresponding N,N-bis{methyl(aryl)-phosphino}-amines.
  PubDate: 2017-04-18T05:20:49.370606-05:
  DOI: 10.1002/cctc.201700448
Effects of Linking the Cyclopentadienyl and Ketimide Ligands in Titanium
Half-sandwich Olefin Polymerization Catalysts
- Authors: Vojtech Varga; Miloš Večeřa, Robert Gyepes, Jiří Pinkas, Michal Horáček, Jan Merna, Martin Lamac
  Abstract: The role of ketimide ligand geometry in titanium half-sandwich complexes and the consequential effects in olefin polymerization catalysis (ethylene, styrene, 1-hexene polymerization, and ethylene/1-hexene copolymerization) were investigated under various conditions. The known complex [CpTiCl2(N=Ct-Bu2)] (1) was used as a reference compound for comparison with the recently described [{h5-C5H4CMe2CMe2C(t-Bu)=N-κN}TiCl2] (2a) and the newly prepared derivative with a longer linker between Cp and the ketimide [{h5-C5H4CH2CH2CMe2C(t-Bu)=N-κN}TiCl2] (9). It was found that the presence of distorted intramolecularly tethered ketimide moiety reduces the polymerization activity significantly in systems containing aluminum-based cocatalysts (MAO, triisobutylaluminum). On the other hand, in aluminum-free systems both types of compounds provided active polymerization catalysts. Notably, the recently reported activation system Et3SiH/B(C6F5)3 was for the first time demonstrated to activate titanium complexes for ethylene and 1-hexene (co)polymerization catalysis by hydride transfer.
  PubDate: 2017-04-18T04:20:39.937256-05:
  DOI: 10.1002/cctc.201700498
An Importance of Ligand Effects Breaking the Scaling Relation for
Core-Shell Oxygen Reduction Catalysts
- Authors: Seoin Back; Yousung Jung
  Abstract: Tremendous recent efforts have been made toward developing highly active oxygen reduction reaction (ORR) catalysts with a minimized usage of noble metal Pt via using Pt-alloys and core-Pt shell structures. A main computational framework for such a goal has been the search for a new material with the *OH binding slightly weaker than Pt based on the conventional volcano relation of ORR activity vs. *OH binding energy. In this work, using carbides and nitrides as a core material, we demonstrate that a conventional scaling relation between *OH and *O can be completely broken due to a significant ligand-Pt orbital interactions in a core-Pt shell structure, and in such cases, the usual catalyst design strategy of tuning the *OH binding energy of Pt to a weaker leg of the volcano can mislead the prediction. In these cases, one needs to consider all reaction intermediates to appropriately predict the activity of ORR catalysts. We additionally show that, while the transition metal nitrides and carbides studied here as core materials all induce an undesired tensile strain to the Pt overlayers with a stronger *OH binding, a proper tuning of the ligand (core) effects in the Pt1 and Pt2 overlayers core-shell configurations can lead to an activity comparable to or slightly better than Pt.
  PubDate: 2017-04-18T03:20:45.171697-05:
  DOI: 10.1002/cctc.201700497
Polymer encapsulated Cobalt based catalysts (Co EnCatTM) for selective
continuous hydrogenation of 1-iodo-4-nitrobenzene
- Authors: Hannes Alex; Patrick Loos, Todor Baramov, John Barry, Tanmay Godiawala, Jorma Hassfeld, Norbert Steinfeldt
  Abstract: New Cobalt catalysts confined in an EnCat™ polyurea matrix by micro-encapsulation of Al5Co2 or Al5Co2/Al3Ni2 phase-containing alloys are disclosed for the reductive hydrogenation of 1-iodo-4-nitrobenzene 1. The product 4-iodo-aniline 2 readily undergoes hydro-desiodination and was used to demonstrate the extraordinary selectivity. Co EnCatTM significantly suppressed this follow-up reaction under both, batch and flow modes. Correlation between performance, elemental composition, and alloy content is presented for these novel catalysts. Among them, hybrid micro-encapsulated Co-Ni catalyst showed higher activity than its Ni free analogue. In a flow process, this catalyst gave high yield of 2 and very low level of 3. Hence, these novel Co EnCat™ catalysts hold promise with respect to the continuous flow hydrogenation of challenging halogenated nitroaromatic compounds.
  PubDate: 2017-04-13T11:28:13.390989-05:
  DOI: 10.1002/cctc.201700391
Palladium on polydopamine: its true potential in catalytic transfer
hydrogenations and Heck coupling reactions
- Authors: Attila Kunfi; Vivien Szabó, Ágnes Mastalir, Imre Bucsi, Miklós Mohai, Péter Németh, Imre Bertóti, Gabor London
  Abstract: The application of Pd-polydopamine and magnetic Fe3O4@Pd-polydopamine catalysts in catalytic transfer hydrogenation reactions and Heck-arylation is reported. The reduction of a wide range of aromatic nitro-compounds bearing both electron donating and withdrawing substituents to the corresponding anilines could be efficiently performed, while the reduction of carbonyl compounds found to be less general. In the latter case, only aromatic ketones could be reduced to the corresponding alcohols, while aldehyde substrates were unaffected, which may be due to their reaction with the catalyst support leading to catalyst deactivation. Using magnetic Fe3O4@Pd-polydopamine system, facilitated catalyst recovery and reuse for five consecutive cycles without considerable loss of activity in nitro-group reduction. The efficiency of the catalyst in Heck reactions was comparable to that in transfer hydrogenation, however, no catalytic activity was observed upon reuse in this case, likely due to metal leaching. We also explored tandem Heck reaction/catalytic transfer hydrogenation sequences, however, the two reactions showed limited compatibility under the applied conditions.
  PubDate: 2017-04-13T11:27:26.586352-05:
  DOI: 10.1002/cctc.201700609
Separating Thermodynamics from Kinetics—A New Understanding of the
Transketolase Reaction
- Authors: Stefan R. Marsden; Lorina Gjonaj, Stephen J. Eustace, Ulf Hanefeld
  Abstract: Transketolase catalyzes asymmetric C−C bond formation of two highly polar compounds. Over the last 30 years, the reaction has unanimously been described in literature as irreversible because of the concomitant release of CO2 if using lithium hydroxypyruvate (LiHPA) as a substrate. Following the reaction over a longer period of time however, we have now found it to be initially kinetically controlled. Contrary to previous suggestions, for the non-natural conversion of synthetically more interesting apolar substrates, the complete change of active-site polarity is therefore not necessary. From docking studies it was revealed that water and hydrogen-bond networks are essential for substrate binding, thus allowing aliphatic aldehydes to be converted in the charged active site of transketolase.Textbook catalysis revised: The initially kinetically controlled transketolase-catalyzed lithium hydroxypyruvate reaction has been so far mistakenly described as thermodynamic controlled. A new understanding of this effect and of the reasons why hydrophobic substrates are converted by an enzyme that naturally has a high affinity to hydrophilic substrates sheds new light on textbook biocatalysis.
  PubDate: 2017-04-13T09:59:59.968806-05:
  DOI: 10.1002/cctc.201601649
Insight on CuO-SnO2 Catalysts for Catalytic Oxidation of CO:
Identification of Active Copper Species and Reaction Mechanism
- Authors: Xueqin Bai; shujing Chai, Cheng Liu, Kui Ma, Qingpeng Cheng, Ye Tian, Tong Ding, Zheng Jiang, Jing Zhang, Lirong Zheng, Xingang Li
  Abstract: Herein, we report the high activity of the CuO-SnO2 catalysts for catalytic oxidation of CO. Especially, the SnCu30 catalyst shows the highest activity, as well as the high water resistance. Comparing with the XRD, XAFS and H2-TPR results of the SnCu30 catalyst before and after the nitric acid treatment, we found the existence of three kinds of copper species in the catalysts, i.e., highly dispersed CuO, bulk CuO and incorporated copper in SnO2 lattice. The highly dispersed CuO and the surface lattice oxygen species are the active sites for catalytic oxidation of CO. The XPS and in-situ DRIFTS results confirm the existence of Cu+ species on the surface of the CuO-SnO2 catalysts, which can provide the adsorption sites for CO. Our results show that the reaction pathways upon catalytic oxidation of CO over the CuO-SnO2 catalysts follow the Mars-van Krevelen model.
  PubDate: 2017-04-12T12:51:21.83323-05:0
  DOI: 10.1002/cctc.201700460
The Birth of Nickel Phosphide Catalysts: Monitoring Phosphorus Insertion
into Nickel
- Authors: Sophie Carenco; Zhi Liu, Miquel Salmeron
  Abstract: Tri-n-octylphosphine (TOP) is used widely as a phosphorating agent to yield metal phosphide nanocatalysts, which are receiving intense attention because of their high performance in both electrochemical and hydrotreatment catalytic processes, such as the hydrogen evolution reaction and the hydrodesulfurization reaction. We used in situ ambient-pressure X-ray photoelectron spectroscopy to investigate the formation of nickel phosphide on the surface of a nickel foil at temperatures close to those employed to form nickel phosphide nanoparticles in the colloidal route. We showed that the onset of phosphorus insertion into nickel occurs at as low as 150 °C, which is much lower than that reported previously (>210 °C). Moreover, the formation of sp2 carbon was observed on the surface as the consequence of TOP alkyl chain decomposition. These findings provide new insights into the surface chemistry of metal phosphide nanoparticles, which are increasingly employed in several fields of catalysis. Our results demonstrate that even below 150 °C, significant phosphorus and carbon incorporation can occur during metal nanoparticle syntheses if TOP is employed as the stabilizing agent.TOP class: A mechanistic study of tri-n-octylphosphine decomposition at a nickel surface shows phosphide formation at temperatures as low as 150 °C accompanied by sp2 carbon deposition. These two results are confirmed on nickel nanoparticles.
  PubDate: 2017-04-12T08:11:37.858454-05:
  DOI: 10.1002/cctc.201601526
Production of High Quality Syncrude from Lignocellulosic Biomass
- Authors: Yannick Mathieu; Laurent Sauvanaud, Len Humphreys, William Rowlands, Thomas Maschmeyer, Avelino Corma
  Abstract: Wood chips were hydrothermally treated in near critical point water in the presence of a catalyst to yield a raw biocrude, containing a wide range of organic components. This product was subsequently distilled to remove its heaviest fraction, which tends to yield chary products if heated above 350 °C. The biocrude obtained has an oxygen content of 12 wt % and was subsequently hydrotreated to obtain a hydrocarbon stream. Varying the hydrotreatment operating conditions and catalyst yielded a deoxygenated syncrude which quality improved with operation severity. The hydroprocessed stream produced under very mild conditions can be further upgraded in conventional refinery operations while the stream produced after more severe hydrotreatment can be mixed with conventional diesel. This proof of concept was demonstrated with commercial hydrotreating catalysts, operating between 350 and 380 °C, 40 to 120 bar pressure and 0.5 to 1 h−1 contact time.No O in fuel: Raw biocrude was obtained from wood chips that were hydrothermally treated in near critical point water in the presence of a catalyst. The product is a high quality hydrocarbon stream with very low oxygen content, suitable for further upgrading in refinery or direct blending with diesel.
  PubDate: 2017-04-12T07:36:18.324688-05:
  DOI: 10.1002/cctc.201601677
In vivo synthesis of polyhydroxylated compounds from a 'hidden reservoir'
of toxic aldehyde species
- Authors: Thomas Bayer; Sofia Milker, Thomas Wiesinger, Margit Winkler, Marko D Mihovilovic, Florian Rudroff
  Abstract: Synthetic enzyme cascades in living cells often lack efficiency due to formation of by-products by endogenous enzymes, or toxicity of cascade intermediates. Highly reactive aldehyde species can trigger a metabolic stress response, leading to undesired side reactions and decrease yields. Due to the metabolic background of Escherichia coli (E. coli), aldehydes may be irreversibly oxidized to carboxylic acids or reduced to the corresponding alcohols. Herein, we applied an approach to equilibrate the aldehyde concentration in vivo. We oxidized primary alcohols to the corresponding aldehydes by AlkJ, an alcohol dehydrogenase (ADH) from Pseudomonas putida (P. putida). Introduction of a carboxylic acid reductase from Norcadia iowensis (CARNi), allowed retrieving the target compound from the carboxylate sink. Further reduction of aldehydes to the alcohols by endogenous E. coli enzymes completes the equilibration between alcohols, aldehydes, and carboxylic acids.Thus, aldehyde concentrations remained below non-viable concentrations. We demonstrated the concept on several primary alcohols, which reached the redox equilibrium within 6h and persisted up to 24 h. Subsequent combination with a dihydroxyacetone (DHA) dependent aldolase (Fsa1-A129S, E coli) demonstrated, that the reactive aldehyde species are freely available and resulted in the formation of aldol product (3S,4R)-1,3,4-trihydroxy-5-phenylpentan-2-one in 70% isolated yield within short reaction times.
  PubDate: 2017-04-11T10:30:29.147939-05:
  DOI: 10.1002/cctc.201700469
Catalytic Au "nano wool balls"
- Authors: Xiuxiu yin; Nagappa Teradal, ahiud morag, Raz Jelinek
  Abstract: New gold nanoparticles mimicking "wool-balls" were synthesized through simple, spontaneous crystallization / reduction of gold thiocyanate [Au(SCN)4-] in water, without co-addition of neither nucleating seeds, templating compounds, nor reducing agents. The Au nano wool-balls were highly uniform in size and displayed remarkable nanoribbon surface morphology. Size- and structural-modulation of the particles were accomplished through both tuning the concentration of the gold complex, as well as upon adding small quantities of organic solvents. The unique corrugated morphology and high surface area of the Au nano wool-balls enabled their use as effective catalytic substrates for methanol oxidation and nitrophenol reduction.
  PubDate: 2017-04-11T07:20:25.809489-05:
  DOI: 10.1002/cctc.201700459
Recyclable Acid-Base Bifunctional Core-Shell-Shell Nanosphere Catalyzed
Synthesis of 5-Aryl-NH-1,2,3-triazoles via "One-Pot" Cyclization of
Aldehyde, Nitromethane and NaN3
- Authors: Lei Liu; Yongjian Ai, Dong Li, Li Qi, Junjie Zhou, Zhike Tang, Zixing Shao, Qionglin Liang, Hong-bin Sun
  Abstract: A magnetically separable core-shell-shell nanosphere Fe3O4@nSiO2-SO3H@MS-NHCOCH3 has been fabricated as an acid-base collaborative catalyst for the three-component cyclization of aromatic aldehyde, nitroalkane, and sodium azide to afford NH-1,2,3-triazoles. The bifunctional heterogeneous catalyst takes advantages of high activity, good chemoselectivity and no toxic HN3 releasing. A variety of aldehydes have been transformed to corresponding 5-aryl-NH-1,2,3-triazoles with up to 98% yield. Furthermore, the catalyst could be recycled by an external magnetic field and reused for many times without any activity lossing. Contrastly, a homogeneous catalyst system ammonium acetate/acetic acid also works to the three-component cyclization to afford NH-1,2,3-triazoles
  PubDate: 2017-04-11T05:20:38.312134-05:
  DOI: 10.1002/cctc.201700401
Diastereoselective Radical-Type Cyclopropanation of Electron-Deficient
Alkenes Mediated by the Highly Active Cobalt(II)
Tetramethyltetraaza[14]annulene Catalyst
- Authors: Andrei Chirila; Braja Gopal Das, Nanda D. Paul, Bas de Bruin
  Abstract: The front cover artwork for Issue 8/2017 is provided by the homogeneous catalysis group in Amsterdam. The image shows [Co(MeTAA)], a fast cyclopropanation catalyst, rapidly approaching Earth's atmosphere like a comet. See the Full Paper itself at https://doi.org/10.1002/cctc.201601568.“[Co(MeTAA)] is a cheap and easy to prepare metalloradical cyclopropanation catalyst that is active enough to mediate carbene transfer from tosyl hydrazones even at room temperature.” This and more about the story behind the research featured on the front cover can be found in this issue's Cover Profile. Read the full text of the corresponding research at https://doi.org/10.1002/cctc.201601568.
  PubDate: 2017-04-10T07:26:10.76479-05:0
  DOI: 10.1002/cctc.201700556
Rhodium(III) Catalyzed Solvent-Free Tandem Isomerization–Hydrosilylation
From Internal Alkenes to Linear Silanes
- Authors: Susan Azpeitia; María A. Garralda, Miguel A. Huertos
  Abstract: The selective synthesis of linear silanes from internal alkenes or alkene mixtures is reported. Unsaturated 16 electrons hydrido–silyl–RhIII complexes are efficient catalysts for a tandem catalytic alkene isomerization–hydrosilylation reaction at room temperature under solvent-free conditions. Such a process would be of value to the chemical industry, as mixtures of internal aliphatic olefins are substantially cheaper and more readily available than the pure terminal isomers.Silane -ing Away: Unsaturated 16 electrons hydrido–silyl–RhIII complexes are efficient catalysts for a tandem catalytic alkene isomerization–hydrosilylation reaction at room temperature under solvent-free conditions.
  PubDate: 2017-04-10T06:41:21.574678-05:
  DOI: 10.1002/cctc.201700222
Influence of the Ligand of Palladium(0) Complexes on the Rate of the
Oxidative Addition of Aryl and Activated Alkyl Bromides: Csp2−Br versus
Csp3−Br Reactivity and Selectivity
- Authors: Bárbara Noverges Pedro; Mercedes Medio-Simón, Anny Jutand
  Abstract: Kinetic data obtained by means of electrochemical techniques are used to characterize the reactivity of aryl bromides and activated alkyl bromides in the oxidative addition to palladium(0) complexes generated from three precursors: Pd0(PPh3)4, {Pd0(dba)2+2 PPh3} (dba=dibenzylideneacetone) and {Pd0(dba)2+2 P(o-Tol)3} in dimethylformamide (DMF) at 25 °C. It is established that, for the investigated substrates 1–6 and 7–11, the oxidative addition at the Csp3−Br bond is much faster than that at the Csp2−Br bond if the palladium(0) is ligated by two PPh3. This explains why the regioselectivity in Suzuki–Miyaura reactions performed from substrates bearing both Csp2−Br and Csp3−Br groups is in favor of the substitution at the Csp3−Br bond. This is in agreement with DFT calculations, which propose a SN2-type mechanism from the bis-ligated Pd0(PPh3)2. The oxidative addition at the Csp2−Br bond is much faster if the palladium(0) is ligated by P(o-Tol)3 than by PPh3, in agreement with the DFT calculations, which support a concerted mechanism involving the mono-ligated Pd0[P(o-Tol)3] as the reactive species. This explains why the regioselectivity in Suzuki–Miyaura reactions performed from substrates bearing both Csp2−Br and Csp3−Br groups might be in favor of the substitution at the Csp2−Br bond if the ligand is P(o-Tol)3.The ligand does the job! The kinetics of oxidative additions of aryl and activated alkyl bromides is affected by the ligand of Pd0 complexes. If ligated by PPh3, the Csp3−Br bond activation is faster than the Csp2−Br bond activation, inducing regioselectivity at the Csp3−Br. If Pd0 is ligated by P(o-Tol)3, the Csp2−Br activation is faster than for PPh3. Regioselectivity at Csp2−Br is thus feasible.
  PubDate: 2017-04-10T06:36:06.442948-05:
  DOI: 10.1002/cctc.201700041
Highly Selective Continuous Gas-Phase Methoxycarbonylation of Ethylene
with Supported Ionic Liquid Phase (SILP) Catalysts
- Authors: Santosh G. Khokarale; Eduardo J. García-Suárez, Rasmus Fehrmann, Anders Riisager
  Abstract: Supported ionic liquid phase (SILP) technology was applied for the first time to the Pd-catalyzed continuous, gas-phase methoxycarbonylation of ethylene to selectively produce methyl propanoate (MP) in high yields. The influence of catalyst and reaction parameters such as, for example, ionic liquid loading, metal concentration, and ligand loadings was studied, and in particular the SILP catalyst activity and stability was found to be strongly dependent on the ligand to metal ratio.It′s all in the ratio: Supported ionic liquid phase (SILP) technology was applied to the Pd-catalyzed continuous, gas-phase methoxycarbonylation of ethylene to selectively produce methyl propanoate in high yields. Studying the influence of catalyst and reaction parameters showed that the SILP catalyst activity and stability was strongly dependent on the ligand to metal ratio.
  PubDate: 2017-04-10T06:35:57.813135-05:
  DOI: 10.1002/cctc.201601428
Multi-Step Organic Transformations over
- Authors: Guohua Liu; Han Liao, Yajie Chou, Yu Wang, Han Zhang, Tanyu Cheng
  Abstract: Assembly of multiple catalytically functionalities within a single mesoporous silica as a catalyst for multi-step enantioselective organic transformation in an environmentally friendly medium is a significant challenge in heterogeneous asymmetric catalysis. Herein, taking advantage of BF4− anion hydrogen bonding strategy, we anchor conviently a chiral cationic rhodium/diamine complex within base-functionalized mesostructured silica nanoparticles, constructing a bifunctional heterogeneous catalyst. Solid-state carbon spectrum discloses its well-defined chiral rhodium/diamine active species, and its X-ray diffraction, nitrogen adsorption-desorption measurement and electron microscopy reveal its ordered mesostructure. As presented in this study, the combination of bifunctionality in silica nanoparticles enables two kinds of efficiently enantioselective organinc transformations with high yields and enantioselectivities, where asymmetric transfer hydrogenation of α-haloketones followed by an epoxidation process provides various chiral aryloxirane while the amination of α-haloketones with anilines followed by asymmetric transfer hydrogenation produces various β-amino alcohols. Furthermore, catalyst can be recovered and recycled for seven times without loss of its catalytic activity, showing an attracting feature for multi-step organic transformations in a sustainable benign process.
  PubDate: 2017-04-07T04:23:25.661902-05:
  DOI: 10.1002/cctc.201700436
Carbon Dioxide Oversolubility in Nanoconfined Liquids for the Synthesis of
Cyclic Carbonates
- Authors: Maria V. Zakharova; Freddy Kleitz, Frédéric-Georges Fontaine
  Abstract: The physical phenomenon of gas oversolubility in nanoconfined liquids was successfully applied for the catalytic cycloaddition of carbon dioxide to epoxides to generate organic cyclic carbonates. Hybrid adsorbents based on MCM-41 and SBA-15 mesoporous silica materials were synthesized, and efficient nucleophile deposition on the surface of the support was achieved through a grafting procedure, which allowed for an effective and durable metal-free catalytic system. Room-temperature transformation of styrene and hexene oxides to the corresponding organic carbonates at atmospheric pressure of carbon dioxide was explored.Solving the problem: The physical phenomenon of gas oversolubility in nanoconfined liquids is applied for the catalytic cycloaddition of carbon dioxide to epoxides to generate cyclic carbonates at room temperature under atmospheric pressure. A hybrid adsorbent based on the MCM-41 silica material exhibits enhanced catalytic properties and multicycle stability, providing an effective and sustainable catalytic system.
  PubDate: 2017-04-07T03:21:06.169578-05:
  DOI: 10.1002/cctc.201700247
Supercritical Antisolvent Precipitation of Amorphous Copper–Zinc
Georgeite and Acetate Precursors for the Preparation of Ambient-Pressure
Water-Gas-Shift Copper/Zinc Oxide Catalysts
- Authors: Paul J. Smith; Simon A. Kondrat, James H. Carter, Philip A. Chater, Jonathan K. Bartley, Stuart H. Taylor, Michael S. Spencer, Graham J. Hutchings
  Abstract: A series of copper–zinc acetate and zincian georgeite precursors have been produced by supercritical CO2 antisolvent (SAS) precipitation as precursors to Cu/ZnO catalysts for the water gas shift (WGS) reaction. The amorphous materials were prepared by varying the water/ethanol volumetric ratio in the initial metal acetate solutions. Water addition promoted georgeite formation at the expense of mixed metal acetates, which are formed in the absence of the water co-solvent. Optimum SAS precipitation occurs without water to give high surface areas, whereas high water content gives inferior surface areas and copper–zinc segregation. Calcination of the acetates is exothermic, producing a mixture of metal oxides with high crystallinity. However, thermal decomposition of zincian georgeite resulted in highly dispersed CuO and ZnO crystallites with poor structural order. The georgeite-derived catalysts give superior WGS performance to the acetate-derived catalysts, which is attributed to enhanced copper–zinc interactions that originate from the precursor.Water gives performance: Cu/ZnO catalyst precursors are prepared by supercritical CO2 antisolvent precipitation with water addition effecting the meso- and nanostructure of the resulting material. Optimum catalysts are derived from zincian georgeite, which thermally decompose mildly to give highly dispersed metal-oxide crystallites inside a carbonate matrix.
  PubDate: 2017-04-07T03:21:04.600531-05:
  DOI: 10.1002/cctc.201601603
Disassembling Metal Nanocrystallites into Sub-nanometric Clusters and
Low-faceted Nanoparticles for Multisite Catalytic Reactions
- Authors: Judit Oliver-Meseguer; Irene Dominguez, Rafael Gavara, Antonio Leyva-Pérez, Avelino Corma
  Abstract: Metal nanocrystallites present saturated atoms, in planes, and unsaturated metal atoms, in corners and vertices, for catalytic applications. However, both sites are spatially complementary and simultaneously excluding for a given particle, thus their number cannot be independently maximized for a catalytic process. Here, it is shown that the independent dosage of Au clusters and metallic Au nanoparticles dramatically improves the catalytic activity of Au for the Sonogashira reaction, enabling the coupling of a wide range of iodo-, bromo-, and activated chloro-derivatives with aromatic and aliphatic alkynes, and outperforming ligand-free Pd and Cu catalysts. Mechanistic studies reveal that the unsaturated atoms of the cluster activate the alkyne and that the saturated atoms of the metallic nanoparticle preferentially activate the halide, to finally perform the coupling. Thus, a precise combination of sub-nanometric metal clusters and metal nanoparticles, together, constitute a new catalytic strategy to substitute metal nanocrystallites in reactions in which both unsaturated and saturated atoms play a key role.Disassembled, but working together: Metal nanocrystallites have saturated atoms, in planes, and unsaturated metal atoms, in corners and vertices, which perform different roles in catalysis: both sites are spatially complementary so their number cannot be independently maximized for a catalytic process. However, by independently adding sub-nanometric Au clusters and metallic Au nanoparticles, not only iodo- and bromobenzenes, but also chlorobenzenes can react with a wide variety of alkynes in the Sonogashira reaction, outperforming any previous Au catalyst and ligand-free Pd and Cu catalysts.
  PubDate: 2017-04-07T03:21:01.091772-05:
  DOI: 10.1002/cctc.201700037
Self-assembly- and Preshaping-assisted Synthesis of Molybdenum Carbide
Supported on Ultrathin Nitrogen-doped Graphitic Carbon Lamellas for the
Hydrogen Evolution Reaction
- Authors: Lishan Peng; Yao Nie, Ling Zhang, Rui Xiang, Jun Wang, Hongmei Chen, Ke Chen, Zidong Wei
  Abstract: Herein, we report a self-assembly and preshaping strategy for the controllable synthesis of highly dispersed Mo2C nanoparticles supported on porous graphitic carbon lamellas. This simple but effective method prevents the serious overlapping of carbon and excessive growth of Mo2C and endows Mo2C/C with a 2 D lamellar structure even after high-temperature carburization. The constructed Mo2C/C-lamellas exhibits higher activity in the hydrogen evolution reaction than traditional bulk Mo2C/C and shows long-term stability. This self-assembly and preshaping assisted carburization method represents a rational strategy for the preparation of robust carbon composite materials with hierarchically ordered structures, especially high melting points, and a high tendency to undergo aggregation.In control: The controllable synthesis of highly dispersed Mo2C nanoparticles supported on porous graphitic carbon lamellas is reported. Serious overlapping of carbon and excessive growth of Mo2C are prevented, and Mo2C/C has a 2 D lamellar structure even after high-temperature carburization. The constructed Mo2C/C-lamellas exhibits higher activity in the hydrogen evolution reaction than traditional bulk Mo2C/C and shows long-term stability.
  PubDate: 2017-04-07T03:16:20.42215-05:0
  DOI: 10.1002/cctc.201700239
Aerobic Oxidation of Alkynes to 1,2-Diketones by Organic Photoredox
Catalysis
- Authors: Hai-Tao Qin; Xiao Xu, Feng Liu
  Abstract: A method for the synthesis of 1,2-diketones through the mild and metal-free catalytic photooxygenation of alkynes is described. This reaction, using 9,10-dicyanoanthracene as a catalytic sensitizer with/without biphenyl as a co-sensitizer, readily furnished a variety of desired products upon visible-light irradiation. Mechanistic studies indicated that a radical cation process might have been involved. This report provides the first examples of the transformation of alkynes via acetenyl radical cation intermediates, which have thus far not been explored in organic synthesis.Photo op: A method for the synthesis of 1,2-diketones through the 9,10-dicyanoanthracene (DCA)-sensitized photooxygenation of alkynes upon visible-light irradiation is reported. Mechanistic studies indicate that a radical-cation intermediate might be involved. The first examples of the transformation of alkynes via acetenyl radical cation intermediates are provided.
  PubDate: 2017-04-07T03:16:17.359548-05:
  DOI: 10.1002/cctc.201700061
Oxygen Vacancies in reduced Rh- and Pt-ceria for Highly Selective and
Reactive Reduction of NO into N2 in excess of O2
- Authors: Michiel Makkee; Yixiao Wang, Ramon Oord, Daniel van der Berg, Bert Weckhuysen
  Abstract: The issue of current commercial DeNOx abatement systems for lean-burn engine are that the NOx emissions on the road exceed its regulation limit. Commercial DeNOx catalysts exhibit poor performance in the selective conversion NO into N2, especially at high temperature and high gas hourly space velocities. In this study, oxygen vacancies of reduced ceria and Pt/ or Rh/ceria are found to be the efficient and selective catalytic sites for NO reduction into N2. Even at low concentration of NO can compete with excess O2 at high temperature of 600°C and high GHSV of 170.000 L/L/h, where SCR and NSR DeNOx system are not working properly. N2O is not detected over the whole range of conditions, while NO2 is only formed when the catalyst is oxidised, where both NO and O2 start to breakthrough. For consideration of the fuel economy, the working temperature should be between 250 and 600°C. Above 600oC, most of the injected fuel was used for combustion with O2. Below 250oC, ceria support will not be reduced by fuel and the oxidation rate of the deposited carbon via oxygen from ceria lattice will be too low.
  PubDate: 2017-04-06T09:20:51.700419-05:
  DOI: 10.1002/cctc.201700578
Poly(ethyleneimine)-tethered Ir Complex Catalyst Immobilized in Titanate
Nanotubes for Hydrogenation of CO₂ to Formic Acid
- Authors: Yasutaka Kuwahara; Yuki Fujie, Hiromi Yamashita
  Abstract: Production of formic acid (FA) by hydrogenation of CO₂ using a ternary hybrid catalyst, poly(ethyleneimine)-tethered Ir-iminophosphine complex (Ir-PN-PEI) immobilized in titanate nanotubes (TNTs), is reported herein. On the basis of comprehensive structural analyses, we show that Ir-PN-PEI is tightly immobilized within the cavity space of TNT without affecting the electronic/coordination states of Ir atoms. Liquid-phase CO₂ hydrogenation under pressurized CO₂ and H₂ demonstrates that the Ir-PN-PEI catalyst immobilized in Na+-type TNT exhibits the highest FA yields (TON > 1000 for 20 h under mild reaction conditions (2.0 MPa, 140 °C)) and improved reusability, which far outperform those of unimmobilized prototype Ir-PN-PEI. The improved catalytic performances are attributed to the ability of TNT to efficiently capture CO₂ and to stabilize PEI, where Na+-type TNT with higher basic property provides more productive effect. The catalyst is reusable over multiple cycles with activity comparable to those of heterogeneous catalysts ever reported, rendering this material suitable for efficient transformation of CO₂ into FA.
  PubDate: 2017-04-06T08:20:42.537663-05:
  DOI: 10.1002/cctc.201700508
The Effects of Secondary Oxides on Copper-Based Catalysts for Green
Methanol Synthesis
- Authors: James S. Hayward; Paul J. Smith, Simon A. Kondrat, Michael Bowker, Graham J. Hutchings
  Abstract: Catalysts for methanol synthesis from CO2 and H2 have been produced by two main methods: co-precipitation and supercritical anti-solvent (SAS) precipitation. These two methods are compared, along with the behaviour of copper supported on Zn, Mg, Mn, and Ce oxides. Although the SAS method produces initially active material with high Cu specific surface area, they appear to be unstable during reaction losing significant amounts of surface area and hence activity. The CuZn catalysts prepared by co-precipitation, however, showed much greater thermal and reactive stability than the other materials. There appeared to be the usual near-linear dependence of activity upon Cu specific area, though the initial performance relationship was different from that post-reaction, after some loss of surface area. The formation of the malachite precursor, as reported before, is important for good activity and stability, whereas if copper oxides are formed during the synthesis and ageing process, then a detrimental effect on these properties is seen.Supercritical anti-solvent (SAS) precipitation and co-precipitation methods were used to make catalysts for methanol synthesis from CO2 and H2, utilising Cu supported on Zn, Mg, Mn, and Ce oxides. The SAS method produces initially active materials with high Cu specific surface area, but they are unstable. Co-precipitation led to much greater stability materials. There was a near-linear dependence of activity upon Cu specific area (see picture), but the initial performance was different from that post-reaction, after loss of surface area.
  PubDate: 2017-04-06T04:01:07.474827-05:
  DOI: 10.1002/cctc.201601692
Lithium-Catalyzed anti-Markovnikov Intermolecular Hydroamination Reactions
of Vinylarenes and Simple Secondary Amines
- Authors: Stéphane Germain; Meije Lecoq, Emmanuelle Schulz, Jérôme Hannedouche
  Abstract: Various β-arylethylamine derivatives were straightforwardly obtained by the lithium-catalyzed anti-Markovnikov selective intermolecular hydroamination reaction of secondary aliphatic amines with vinylarenes. The use of only 1.5 mol % LiCH2TMS as a solid base in THF proved to be efficient to deliver the target products at room temperature with up to complete conversions. Both reaction partners were, moreover, used in equivalent amounts; thus, this protocol best respects the concepts of sustainable chemistry for the easy preparation of lead structures for pharmaceutically active compounds.Amines to an end: Various β-arylethylamine derivatives are straightforwardly obtained by the lithium-catalyzed anti-Markovnikov selective intermolecular hydroamination reaction of vinylarenes with secondary aliphatic amines. The use of as little as 1.5 mol % LiCH2TMS as a solid base in THF proves to be efficient to deliver the target products at room temperature with full conversions and stoichiometric amounts of the partners.
  PubDate: 2017-04-06T04:00:56.95443-05:0
  DOI: 10.1002/cctc.201700043
Asymmetric Reduction of Substituted 2-Tetralones by Thermoanaerobacter
pseudoethanolicus Secondary Alcohol Dehydrogenase
- Authors: Odey Bsharat; Musa M. Musa, Claire Vieille, Sulayman A. Oladepo, Masateru Takahashi, Samir M. Hamdan
  Abstract: Ketones bearing two bulky substituents, named bulky–bulky ketones, were successfully reduced to their corresponding optically enriched alcohols by using various mutants of Thermoanaerobacter pseudoethanolicus secondary alcohol dehydrogenase (TeSADH). Substituted 2-tetralones, in particular, were reduced to 2-tetralols with high conversion and high enantioselectivity. The pharmacological importance of substituted 2-tetralols as key drug-building blocks makes our biocatalytic reduction method a highly essential tool. We showed that changing the position of the substituent on the aromatic ring of 2-tetralones impacts their binding affinity and the reaction maximum catalytic rate. Docking studies with several TeSADH mutants explain how the position of the substituent on the tetralone influences the binding orientation of substituted 2-tetralones and their reaction stereoselectivity.Perfect fit: Substituted 2-tetralones are reduced to optically enriched 2-tetralols by using mutants of Thermoanaerobacter pseudoethanolicus secondary alcohol dehydrogenase. Docking studies explain how the substituent's position on the 2-tetralone influences the binding orientation of the substrates and their reaction stereoselectivity.
  PubDate: 2017-04-06T02:15:44.040144-05:
  DOI: 10.1002/cctc.201601618
Edge-hydroxylated Boron Nitride for Oxidative Dehydrogenation of Propane
to Propylene
- Authors: Lei Shi; Dongqi Wang, Wei Song, Dan Shao, Wei-Ping Zhang, An-Hui Lu
  Abstract: Oxidative dehydrogenation of propane to olefins is a promising alternative route to industrialized direct dehydrogenation, but encounters the difficulty in selectivity control for olefins because of the overoxidation reactions that produce a substantial amount of undesired CO2. Here we report edge-hydroxylated boron nitride, a metal-free catalyst, that efficiently catalyzed dehydrogenation of propane to propylene with superior selectivity (80.2 %) but with only negligible CO2 formation (0.5 %) at a given propane conversion of 20.6 %. Remarkable stability was evidenced by the operation of a 300 h test with steady conversion and product selectivity. The active BNO. site, generated dynamically through hydrogen abstraction of B−OH groups by molecular oxygen, triggered propane dehydrogenation by selectively breaking the C−H bond but simultaneously shut off the pathway of propylene overoxidation towards CO2.Olefin generation without a metal: Edge-hydroxylated boron nitride shows superior selectivity for the oxidative dehydrogenation of propane to propylene with only negligible CO2 formation. The dynamically generated active BNO. site triggers propane dehydrogenation by selectively breaking the C−H bond by concomitantly avoiding propylene oxidation to CO2.
  PubDate: 2017-04-06T02:15:39.170068-05:
  DOI: 10.1002/cctc.201700004
Bi2WO6 Nanosheets Decorated with Au Nanorods for Enhanced Near-Infrared
Photocatalytic Properties Based on Surface Plasmon Resonance Effects and
Wide-Range Near-Infrared Light Harvesting
- Authors: Xiaolin Hu; Jian Tian, Yanjun Xue, Yujie Li, Hongzhi Cui
  Abstract: Recently, near-infrared light (NIR) photocatalysts, such as up-converting materials, Bi2WO6, Cu2(OH)PO4, and carbon quantum dots, have been found and are attracting attention for environmental cleaning and energy conversion, because NIR light constitutes nearly half of the energy output. However, the photocatalytic efficiency is low for these new types of NIR photocatalysts, which has limited their widespread application owing to their insufficient NIR-light absorption. In this work, we use gold (Au) nanorods to enhance the NIR-light absorption of Bi2WO6, a typical visible and novel NIR-light photocatalyst, thus the enhancement of its NIR-light photocatalytic and photoelectrochemical properties are achieved. This can be attributed to the surface plasmon resonance (SPR) effects and wide-range NIR light harvesting of the Au nanorods. The present work provides key guidelines for the improvement of NIR-light photocatalysts and could also help design and prepare novel photocatalysts.Rods of gold: Au nanorods are used to enhance the NIR-light absorption of Bi2WO6, a typical visible-light and novel NIR-light photocatalyst. The enhancement of the composite's NIR-light photocatalytic and photoelectrochemical properties can be attributed to the surface plasmon resonance (SPR) effects and wide-range NIR light harvesting of the Au nanorods.
  PubDate: 2017-04-06T02:15:34.442722-05:
  DOI: 10.1002/cctc.201601719
Terminal-Alkyne-Induced Decomposition of a Phosphine-Free Ruthenium
Alkylidene Catalyst
- Authors: Maciej Gierada; Izabela Czeluśniak, Jarosław Handzlik
  Abstract: The transformations of the third-generation Grubbs catalyst [RuCl2(=CHPh)(3-Br-py)2(H2IMes)] (py=pyridine, H2IMes=1,3-bis(2,4,6-trimethylphenyl)imidazolidin-2-ylidene) in the presence of a terminal alkyne (phenylacetylene) were studied theoretically. The ruthenium η3-vinylcarbene complex is the most probable product of the reaction between the 14-electron ruthenium alkylidene species and phenylacetylene. Its subsequent transformation into the ruthenium vinylidene complex and stilbene, both being experimentally observed earlier, is possible. The former is believed to be the active species catalyzing the dimerization of terminal alkynes. The calculated pathway also predicts the formation of [RuCl2(H2IMes)] species, which might initiate the cyclotrimerization of terminal alkynes or transform into the experimentally detected [RuCl2(3-Br-py)3(H2IMes)] complex. An alternative mechanism of the Grubbs catalyst decomposition through an intermediate Ru species having alkylidene and vinylidene ligands in the coordination sphere of ruthenium is also proposed.Mechanisms for the Grubbs catalyst: The third-generation Grubbs catalyst most likely transforms to ruthenium η3-vinylcarbene complex in the presence of phenylacetylene. Further reactions can lead to stilbene and ruthenium vinylidene species. The formation of spectator ruthenium tris(3-bromopyridine) complex is also predicted.
  PubDate: 2017-04-06T02:15:28.9248-05:00
  DOI: 10.1002/cctc.201601647
Intermetallic Compounds as Potential Alternatives to Noble Metals in
Heterogeneous Catalysis: The Partial Hydrogenation of Butadiene on
γ-Al4Cu9(1 1 0)
- Authors: Laurent Piccolo; Lidiya Kibis, Marie-Cécile De Weerd, Emilie Gaudry, Julian Ledieu, Vincent Fournée
  Abstract: Recently, non-noble intermetallic compounds have shown promising catalytic performances in the partial hydrogenation of alkynes and alkenes. In this work, the properties of γ-Al4Cu9(1 1 0) toward the gas-phase hydrogenation of butadiene were investigated at total pressures of 2–20 mbar and temperatures of 110–180 °C. The model catalyst is active and 100 % selective to butenes. Moreover, although less active than Al13Fe4(0 1 0), which was evaluated previously for the same reaction, it is more selective and more stable. The combination of catalytic tests with pre- and postreaction Auger electron spectroscopy measurements and comparative tests with Cu(1 1 0) shows that Cu governs the reaction on γ-Al4Cu9(1 1 0). However, the lower activity of the (more Cu-rich) sputtered Al4Cu9 surface with respect to the annealed one and the differences between Al4Cu9 and Cu surfaces in terms of butene isomer distribution, butene conversion kinetics, and sensitivity to poisons, demonstrate the unique character of the intermetallic compound.Interesting intermetallics: Intermetallic compounds are potential catalyst alternatives to noble metals. Using surface-science methods, the catalytic properties of the γ-Al4Cu9 phase have been investigated for the first time. This material is highly selective for the partial hydrogenation of butadiene to butenes, that is, no butane is produced. Although the active sites are likely composed of Cu atoms (blue), neighboring Al atoms (grey) may strengthen the hydrocarbon–surface bond.
  PubDate: 2017-04-06T02:15:26.736851-05:
  DOI: 10.1002/cctc.201601587
Synthesis of Sebacic Acid Using a De Novo Designed Retro-Aldolase as
a Key Catalyst
- Authors: Konrad B. Otte; Elena Maurer, Marko Kirtz, Daniela Grabs, Eric Althoff, Sebastian Bartsch, Andreas Vogel, Bettina M. Nestl, Bernhard Hauer
  Abstract: The production of new organic compounds from natural feedstocks drives the construction of new biosynthetic cascades. To develop and generate valuable complex chemicals, it is necessary to go beyond natural enzymes towards de novo designed and engineered variants for both natural and non-natural compounds. Herein, we exploit the applicability of a de novo retro-aldolase for the synthesis of sebacic acid, a valuable precursor for bio-based polymers. From ricinoleic acid, a route composed of four individual enzyme-catalyzed steps was developed. As a result of the narrow substrate scope of natural aldolases, this enzymatic route could only be realized by the design and engineering of a de novo retro-aldolase. We further highlight the outstanding potential of this technology for the realization of non-natural reactions and pathways.Going retro: We apply the principles of “biocatalytic retrosynthesis” to the synthesis of the medium-chain α,ω-dicarboxylic acid sebacic acid using a de novo designed and engineered retro-aldolase for a key biocatalytic step.
  PubDate: 2017-04-06T02:15:22.222912-05:
  DOI: 10.1002/cctc.201601551
Graphene and Their Hybrid Electrocatalysts for Water Splitting
- Authors: Jiayuan Li; Zeqiong Zhao, Yuanyuan Ma, Yongquan Qu
  Abstract: Water electrolysis is considered a potentially practical technology for massive production of hydrogen with very high purity. Electrocatalytic water splitting achieved by graphene hybrids has been the subject of extensive investigations, in which graphene plays multiple roles as electroactive component and/or functionalized support. In this Minireview, we summarize the recent significant advances in graphene hybrid electrocatalyst development for water-splitting, especially highlighting the design strategies of graphene hybrids and the roles of graphene as electrocatalyst and/or support. Finally, the remaining challenges and future perspectives on graphene hybrid electrocatalyst design for water-splitting are also discussed.Catalyst or support: Graphene hybrids have been considered as very promising electrocatalysts for water electrolysis. This Minireview summarizes the recent advances of graphene hybrid electrocatalysts for overall water-splitting, especially highlighting the detailed roles of graphene as catalysts and/or supports in electrochemical water-splitting.
  PubDate: 2017-04-06T01:55:55.231862-05:
  DOI: 10.1002/cctc.201700175
DFT Study of Nickel-Catalyzed Low-Temperature Methanol Synthesis
- Authors: David S. McGuinness; Jim Patel, Mohamad Hassan Amin, Suresh K. Bhargava
  Abstract: Low-temperature methanol synthesis (CO+2 H2CH3OH) catalyzed by a homogeneous nickel/alkali metal alkoxide system has been studied theoretically. Two broad mechanistic possibilities, the direct hydrogenation of CO by nickel formyl species and indirect hydrogenation via methyl formate formation, have been examined. The most favorable mechanism involves the methanolysis of CO to methyl formate catalyzed by an ether complex of sodium methoxide followed by the stepwise hydrogenation of methyl formate to formaldehyde and then to a nickel methoxide, in which both steps are mediated by a nickel hydride. In the final step the nickel methoxide is hydrogenated to release methanol. The conversion of methyl formate to the nickel methoxide is predicted to be rate limiting, and the nickel hydride is the most likely catalyst resting state. The theoretical results are discussed in the context of existing experimental observations, and a good agreement with past studies was obtained.Direct or Indirect? The mechanism of CO hydrogenation to methanol catalyzed by the Ni/alkali alkoxide system is studied by DFT. Direct hydrogenation of CO by nickel formyl species and indirect hydrogenation via methyl formate formation, have been examined. The theoretical results are discussed in the context of existing experimental observations, and a good agreement with past studies was obtained.
  PubDate: 2017-04-06T01:50:15.824081-05:
  DOI: 10.1002/cctc.201700213
Bifunctional Catalysts Based on Tungsten Hydrides Supported on Silicated
Alumina for the Direct Production of 2,3-Dimethylbutenes and Neohexene
from Isobutene
- Authors: Cherif Larabi; Anthony Garron, Pascal Rouge, Kai C. Szeto, Sébastien Norsic, Aimery De Mallmann, Nicolas Merle, Mostafa Taoufik
  Abstract: Well-defined bifunctional supported catalysts that comprise tungsten hydride moieties and Brønsted acid sites were prepared successfully. The catalysts showed outstanding activities and selectivities toward the formation of high-value-added products, 2,3-dimethylbutenes and 3,3-dimethylbutene, through a combination of the metathesis and dimerization of isobutene. The relationship between the physicochemical properties of the catalysts and their activities and selectivities indicated that isobutene conversion increased from 4 to 95 % as a function of the silica content of the silicated alumina (obtained from Sasol). Nevertheless, the selectivity toward branched hexenes showed a volcano-shaped curve that presented a maximum for the catalyst with 5 wt % silica. Therefore, the control of the support acidity by the silica loading on alumina resulted in an increase of the selectivity toward neohexene.Cat got your tungsten? We study the influence of the acidic properties of silicated alumina on the catalytic performances of supported tungsten hydride catalysts for isobutene conversion. The positive effect of moderate doping on the catalytic productivity is evidenced. Indeed, the sample with 5 wt % of SiO2 allows us to obtain high selectivities to 2,3-dimethylbutenes and neohexene.
  PubDate: 2017-04-06T01:50:04.071768-05:
  DOI: 10.1002/cctc.201700106
Less Frustration, More Activity - Interesting Theoretical Insights into
Frustrated Lewis Pairs for Hydrogenation Catalysis
- Authors: Kumar Vanka; Manoj Mane
  Abstract: The field of frustrated Lewis pair (FLP) chemistry has seen rapid development in only a few years time. FLPs have performed most spectacularly in the area of hydrogenation catalysis: a wide variety of FLP based systems can catalyse the hydrogenation of a range of different substrates, including imines, enamines, ketones, alkynes and alkenes. However, FLP based hydrogenation catalysts are yet to match the efficiency of their transition metal counterparts. The current investigation addresses this issue, and reveals an important aspect of FLPs that can be exploited to improve their efficiency. What is shown is that the more sterically hindered the FLP catalyst, the lower is its turnover frequency (TOF). Full quantum chemical calculations with density functional theory (DFT) for a family of different, experimentally known hydrogenation FLP catalysts shows that in every case, superior FLP catalysts can be designed by reducing the frustration (by reducing the steric demand and acid/base strength) in the FLP. However, since lowering the sterics without reduction in the frustration can result in unwanted side reactions (also taken into account in this work) what becomes clear is that the design of the most efficient FLP catalysts depends on tuning the system so that both the sterics and the frustration are reduced appropriately.
  PubDate: 2017-04-05T11:21:15.347641-05:
  DOI: 10.1002/cctc.201700289
Copper-Porphyrin-MOFs as oxidative heterogeneous catalysts
- Authors: Kelly Castro; Flavio Figueira, Ricardo Mendes, Jose Cavaleiro, Maria Neves, Mario Simoes, Filipe Almeida Paz, Shirley Nakagaki, Joao P. C. Tome
  Abstract: The synthesis and structural characterization of novel MOF-type materials obtained from the reaction of 5,10,15,20-tetrakis[2,3,5,6-tetrafluoro-4-(4-pyridylsulfanyl)phenyl]porphyrin (H2P1) and 5,10,15,20-tetrakis(4-pyridyl)porphyrin (H2P2) with copper(II) acetate is reported. The new material CuP1S shows high heterogeneous catalytic activity in the oxidation of catechol into ortho-benzoquinone in the presence of air (O2) or H2O2 (30%), when compared to the homogeneous porphyrin copper(II) complex CuP1.
  PubDate: 2017-04-05T10:23:05.454378-05:
  DOI: 10.1002/cctc.201700484
Mechanistic insights into the catalytic hydrolysis of ammonia borane with
proton-responsive iridium complexes: an experimental and theoretical study
- Authors: Wan-Hui Wang; Hui-Peng Tang, Wen-Duo Lu, YANG LI, Ming Bao, Yuichiro Himeda
  Abstract: For homogeneous catalytic hydrolysis of ammonia borane (AB), a series of water-soluble proton-responsive iridium complexes bearing hydroxyl groups were utilized. Among the examined catalysts, [Cp*Ir(6,6′-(OH)2-bpy)(OH2)]SO4 exhibited the best catalytic performance in AB aqueous solution. Results obtained from experimental and theoretical studies revealed that hydrolysis of AB is assisted by synergistic effects between pendent hydroxyl group and metal center.
  PubDate: 2017-04-05T04:21:34.035573-05:
  DOI: 10.1002/cctc.201700325
Structural Changes of Binary/Ternary Spinel Oxides During Ethanol
Anaerobic Decomposition
- Authors: Olena Vozniuk; Cristian Bazzo, Stefania Albonetti, Nathalie Tanchoux, Françoise Bosselet, Jean-Marc M. Millet, Francesco Di Renzo, Fabrizio Cavani
  Abstract: Several M-modified iron oxides of the spinel family have proven to be effective electron and O2− vectors for the production of hydrogen in the chemical-loop reforming of bio-alcohols. The present work is specifically focused on investigation of ethanol anaerobic decomposition over spinel oxides, which results in significant structural changes of the oxygen carrier material itself and corresponds to a first step of the chemical-loop reforming process. In particular, a series of binary/ternary M-modified ferrospinels were prepared by a co-precipitation method and tested in terms of both redox properties and intrinsic catalytic activity in addition to a complex ex situ study that encompasses the solid-state chemistry investigations of the fresh and reduced oxygen carrier materials. It was found that Co/Cu incorporation facilitates total/partial oxidation of ethanol, giving rise to high yields of H2, COx, and H2O; whereas Mn incorporation predominantly favored dehydrogenation and condensation reactions, leading to the formation of acetaldehyde and acetone. In addition, the incorporation of Mn contributed to significantly reduce the amount of coke formed; however, it caused a lower intrinsic reducibility, which was explained by the formation of a thermodynamically stable and hardly reducible layer of MnxFeyO solid solution.Reducing it down: The reduction profile of spinel-type mixed ferrites is investigated in the presence of ethanol as the reactant/reducing agent. The model developed for spinel reduction accounts for the reactivity behavior shown under anaerobic conditions, which is greatly affected by ferrite composition.
  PubDate: 2017-04-05T03:36:16.08263-05:0
  DOI: 10.1002/cctc.201601605
Selective Oxidation of Activated Alcohols by Supported Gold Nanoparticles
under an Atmospheric Pressure of O2: Batch and Continuous-Flow Studies
- Authors: Pascal D. Giorgi; Nelli Elizarov, Sylvain Antoniotti
  Abstract: In the hunt for a simple, mild, and scalable protocol for gold nanoparticle-catalyzed oxidation of benzylic and allylic alcohols under O2, we have used commercially available gold nanoparticles supported on alumina to selectively oxidize a large range of activated alcohols to the corresponding carbonyl compounds in good yields (68–99 %) and with excellent selectivity (ca. 100 %). The true heterogeneous nature of the catalysis by gold was demonstrated, allowing us to further adapt this protocol to continuous-flow reactors by using the tube-in-tube technology, in which higher yields were obtained thanks to an improved oxygenation of the reaction medium.Continuously higher yields: Commercially available Au nanoparticles (NPs) supported on alumina were used to selectively oxidize a large range of activated alcohols to the corresponding carbonyl compounds in good yields (43–99 %). The true heterogeneous nature of the catalysis by gold was demonstrated, and the protocol adapted to continuous-flow reactors, in which higher yields were obtained (84–99 %).
  PubDate: 2017-04-05T03:36:08.28474-05:0
  DOI: 10.1002/cctc.201700179
Highly Efficient Atom-Economic Synthesis of Chiral Bis(indolyl)methanes
Bearing Quaternary Stereogenic Carbon Centers
- Authors: Yan Zhang; Si-Xiang Zhang, Li-Na Fu, Qi-Xiang Guo
  Abstract: A highly efficient atom-economic method for the preparation of chiral 3,3'-bis(indolyl)methanes (BIMs) is described. In the promotion of 1 mol % chiral phosphoric acid 3m, structurally divers BIMs with quaternary stereogenic carbon centers are produced in excellent yields and enantioselectivities. Control experiments indicate that the formations of two hydrogen bonds simultaneous between catalyst and substrates are the key factors to obtain good stereoselective outcomes.
  PubDate: 2017-04-05T03:20:30.764762-05:
  DOI: 10.1002/cctc.201700368
Synthesis and Catalysis of Redox-active Bis(imino)acenaphthene (BIAN) Iron
Complexes
- Authors: Axel Jacobi von Wangelin; Dieter Schaarschmidt, Matteo Villa, Dominique Miesel, Alexander Hildebrandt, Fabio Ragaini
  Abstract: Reactions of various substituted bis(imino)acenaphthenes (R-BIAN) with FeCl2(thf)1.5 afforded the tetrahedral complexes (R BIAN)FeCl2 (2) from bulky α-diimines and the octahedral complexes [Fe(R-BIAN)3][FeCl4]2 (3) from less bulky ligands. The driving force of the formation of complexes 3 is the high ligand-field stabilization of the low-spin Fe(II). The two sets of complexes exhibit distinct CT band intensities and redox activities. (R BIAN)FeCl2 complexes showed reversible ligand-centered reductions at -0.9 V (vs. FcH/FcH+); further reduction led to decomposition. Irreversible oxidations were observed at 0.2 and 0.4 V associated with a reduction at -0.4 V as well as a ligand-centered redox event at 1.0 V. First applications of the Fe(BIAN) complexes to hydrogenations of alkenes documented good catalytic activity under mild conditions.
  PubDate: 2017-04-04T08:20:28.960189-05:
  DOI: 10.1002/cctc.201700144
One-Pot Synthesis of Polyhydroquinoline Derivatives through
Organic-Solid-Acid-Catalyzed Hantzsch Condensation Reaction
- Authors: Sujan Mondal; Bidhan Chandra Patra, Asim Bhaumik
  Abstract: We report the synthesis of a new porous polymeric network (PPN) using triphenylamine and α,α-dibromo-p-xylene by a Friedel–Crafts alkylation promoted by anhydrous FeCl3 as an oxidizing agent. Sulfonation of PPN led to a sulfonated porous polymeric network (SPPN) having high surface acidity and high BET surface area. We characterized the PPN and SPPN materials thoroughly by using powder XRD, FTIR spectroscopy, 13C solid-state magic-angle spinning NMR, field-emission SEM, high-resolution TEM, and N2 sorption techniques. The sulfonated material SPPN was then employed as a heterogeneous, reusable, and environmentally benign organic solid-acid catalyst for the one-pot synthesis of biologically important polyhydroquinoline derivatives under microwave irradiation.One pot, four components, and a sulfonated catalyst: A new and efficient sulfonic-acid-functionalized organic solid-acid catalyst SPPN with a large surface area shows excellent catalytic activity in the one-pot synthesis of biologically important polyhydroquinoline derivatives.
  PubDate: 2017-04-04T07:55:59.80887-05:0
  DOI: 10.1002/cctc.201601409
Cyclopentanone as an Alternative Linking Reactant for Heterogeneously
Catalyzed Furfural Aldol Condensation
- Authors: Jennifer Cueto; Laura Faba, Eva Díaz, Salvador Ordóñez
  Abstract: The use of cyclopentanone, instead of acetone, in the synthesis of diesel precursors by furfural aldol condensation is proposed. This reaction is catalyzed by a magnesium–zirconium mixed oxide. To optimize the C15 selectivity, different temperatures (293, 303, 313, and 323 K) and initial furfural/cyclopentanone ratios (1:1, 3:1, 5:1, and 10:1) were tested. Under the optimum conditions, yields for the desired C15 adduct are higher than 60 % in less than 4 h under mild conditions (303 K).The strongest link: The use of cyclopentanone in the synthesis of diesel precursors by furfural aldol condensation is proposed. This reaction is catalyzed by a magnesium–zirconium mixed oxide. To optimize the C15 selectivity, different temperatures and initial furfural/cyclopentanone ratios are tested. Under the optimum conditions, yields for the desired C15 adduct are higher than 60 % in less than 4 h.
  PubDate: 2017-04-04T07:55:54.093849-05:
  DOI: 10.1002/cctc.201601655
Single-Pot Conversion of Tetrahydrofurfuryl Alcohol into Tetrahydropyran
over a Ni/HZSM-5 Catalyst under Aqueous-Phase Conditions
- Authors: Elmira Soghrati; Catherine Choong, Chee Kok Poh, Sibudjing Kawi, Armando Borgna
  Abstract: Ni-based catalysts were examined in the hydrogenolysis of tetrahydrofurfuryl alcohol, resulting in the selective C−O bond cleavage to produce 1,5-pentanediol, along with 1,2,5-pentanetriol, which was detected for the first time under aqueous-phase conditions. 70 % yield to tetrahydropyran was achieved using one-pot conversion over bifunctional Ni/HZSM-5 catalysts.A concerted action: A highly efficient earth-abundant and low-cost Ni/HZSM-5 catalyst for upgrading biomass-derived THFA into valuable chemicals was developed. THFA participates in a parallel hydrolysis/hydrogenolysis pathway over Ni/HZSM-5 to produce pentane polyols under aqueous-phase conditions, followed by acid-catalyzed dehydration pathways to form tetrahydropyran.
  PubDate: 2017-04-04T07:55:45.848347-05:
  DOI: 10.1002/cctc.201601708
The Synergistic Effect to Promote the Direct Conversion of Bioethanol into
Isobutene over Ternary Multifunctional CrxZnyZrzOn Catalysts
- Authors: Feng Liu; Yong Men, Jinguo Wang, Xiaoxiong Huang, Yuanqiang Wang, Wei An
  Abstract: A significant beneficial effect of introducing chromium over mesoporous Cr1Zn1Zr8On oxide composite catalysts was observed in the upgrading and direct conversion of bioethanol into isobutene (ETIB), and a 38 % enhancement in the selectivity (yield) to isobutene was observed relative to that observed with its binary Zn1Zr8On counterpart. Two critical factors were related to the surface properties of this catalyst: a proper surface acid/base balance and favorable redox properties dictated the selectivity to isobutene. Through combined experimental and theoretical efforts, synergistic effects of redox-active Crδ+ in promoting the dehydrogenation of ethanol were elucidated and therefore the production of isobutene. This work provides a guide for the rational design of efficient catalysts for a highly active and selective cascade ETIB reaction, for which the relative strengths of the redox/acid and base/acid sites of the catalyst serve as catalytic descriptors.A select few: The introduction of chromium into the mesoporous Zn1Zr8On catalyst to give the Cr1Zn1Zr8On composite results in a 38 % increase in the selectivity to isobutene in the direct conversion of bioethanol. Two critical factors affect the surface properties of this catalyst and thus the selectivity to isobutene, that is, a balance of acid/base sites and favorable redox properties.
  PubDate: 2017-04-04T07:51:33.706451-05:
  DOI: 10.1002/cctc.201700154
Silver-Promoted Dehydroaromatization of Ethylene over ZSM-5 Catalysts
- Authors: Ming-Feng Hsieh; Yunwen Zhou, Hari Thirumalai, Lars C. Grabow, Jeffrey D. Rimer
  Abstract: The shape selectivity of ZSM-5 (MFI type) catalysts is ideal for the production of C6–C8 aromatics. Developing high-performance zeolite catalysts with improved selectivity to aromatics, particularly from diversified (non-petroleum) feedstocks, has broad commercial appeal. Non-oxidative coupling (NOC) of ethylene was examined over Ag-ZSM-5 catalysts at 400 °C and shows that Ag+ sites promote dehydroaromatization with enhanced selectivity to toluene and xylenes. Metal exchange of H-ZSM-5 results in Ag zoning wherein Ag+ site density is higher on the exterior of ZSM-5 particles. Catalyst performance was characterized with varying Ag loading as well as the use of methane co-feed. Aromatic selectivity is about 60 % on Ag-ZSM-5 compared to 20 % on H-ZSM-5, which is qualitatively consistent with density functional theory (DFT) showing that ethylene forms strong complexes with Ag+ (Lewis acid) sites. DFT calculations also reveal that ethylene activation on H+ (Brønsted acid) sites is more energetically favorable, and likely constitutes the first mechanistic step in ethylene-to-liquids (ETL) reactions. Ag-ZSM-5 is thus identified as an effective catalyst for low-temperature ETL reactions that has the potential to outperform conventional metal-exchanged zeolites.A silver lining: Comparison of Ag- and H-ZSM-5 catalysts in ethylene to liquids (ETL) reactions reveals that Ag+ (Lewis acid) sites promote ethylene dehydroaromatization with higher xylene selectivity than has been reported for other metal-exchanged zeolites, whereas H+ (Brønsted acid) sites are responsible for ethylene activation.
  PubDate: 2017-04-04T07:51:28.622592-05:
  DOI: 10.1002/cctc.201700192
Renewable Surfactants through the Hydroaminomethylation of Terpenes
- Authors: Thiemo A. Faßbach; Tom Gaide, Michael Terhorst, Arno Behr, Andreas J. Vorholt
  Abstract: A catalytic system was developed to enable the use of industrially available terpenes (e.g., β-myrcene, β-farnesene) in hydroaminomethylation to obtain renewable building blocks for surfactants in two steps. This homogeneously catalyzed tandem reaction includes both hydroformylation and enamine condensation steps, followed by hydrogenation. Under the optimized conditions, the Rh/1,2-bis(diphenylphosphino)ethane catalytic system delivers products in high yields (70 %) after short reaction times (3 h) with unprecedentedly high turnover frequency (TOF) values for the hydroformylation of 1,3-dienes of over 739 mol mol−1 h−1. This is the highest TOF reported to date for the hydroformylation of a 1,3-diene. Furthermore, regioselectivities of 97 % and above were observed in the hydroformylation step, which is extraordinarily high for the conversion of 1,3-dienes. The terpene-derived amines obtained were further functionalized to quaternary ammonium compounds that were found to show surface activity quite similar to that of industrially available quaternary ammonium compounds. The hydroaminomethylation of terpenes achieves higher step efficiency than industrial means and makes use of an alternative, renewable feedstock to synthesize more environmentally friendly surfactants.Soap opera: Renewable building blocks for surfactants are obtained by the hydroaminomethylation of terpenes with conjugated 1,3-diene functionalities. With the Rh/1,2-bis(diphenylphosphino)ethane catalytic system, extraordinarily high turnover frequencies (up to 739 mol mol−1 h−1) and regioselectivities (S=97 %) are achieved. The synthesized cationic surfactants show surface activity similar to that of industrially established ones.
  PubDate: 2017-04-04T07:51:25.644172-05:
  DOI: 10.1002/cctc.201700097
Iron-Containing SSZ-39 (AEI) Zeolite: An Active and Stable
High-Temperature NH3-SCR Catalyst
- Authors: Nuria Martín; Peter N. R. Vennestrøm, Joakim R. Thøgersen, Manuel Moliner, Avelino Corma
  Abstract: The preparation of the iron-containing SSZ-39 zeolite is described for the first time through two different synthesis methods: post-synthetic cation exchange and one-pot synthesis. The nature and stability of the iron species within the different Fe-SSZ-39 materials have been studied through different characterization techniques, and their catalytic activity has been evaluated for the selective catalytic reduction (SCR) of NOx with ammonia. The directly synthetized Fe-SSZ-39 performs better for the SCR of NOx with ammonia than other related Fe-zeolites, particularly at elevated reaction temperatures (above 450 °C), and presents improved hydrothermal stability when aged under severe conditions.Irons in the fire: Iron-containing SSZ-39 zeolite performs as a very active and hydrothermally stable catalyst for the selective catalytic reduction (SCR) of NOx with ammonia, particularly at elevated reaction temperatures (above 450 °C).
  PubDate: 2017-04-04T03:10:44.688289-05:
  DOI: 10.1002/cctc.201601627
Dynamics of Bulk Oxygen in the Selective Oxidation of Acrolein
- Authors: Maurice Heid; Stefan F. Knoche, Niklas S. A. Gora, Dominik Ohlig, Alfons Drochner, Bastian J. M. Etzold, Herbert G. Vogel
  Abstract: Gas phase oxidation of acrolein to acrylic acid on a hydrothermal prepared mixed oxide catalyst was investigated by steady state isotopic transient kinetic analysis (SSIKTA) as well as different types of concentration programmed techniques (CPR-Pulse, CPO) under in situ or process relevant conditions. Balancing the amounts of active oxygen gives an overview of the quantities of participating bulk oxygen species. The dynamics of bulk oxygen leads to re-oxidation processes on the catalyst surface and thus influences the selectivity pattern of the network of acrolein oxidation. Furthermore, the bulk-dynamics is activated by temperature.
  PubDate: 2017-04-03T14:22:51.348774-05:
  DOI: 10.1002/cctc.201700124
Alcohol Dehydrogenases Catalyze the Reduction of Thioesters
- Authors: Sabry H. H. Younes; Yan Ni, Sandy Schmidt, Wolfgang Kroutil, Frank Hollmann
  Abstract: Alcohol dehydrogenases are well-established catalysts for various reduction reactions. However, the reduction of carboxylic acid derivatives has not yet been reported with these enzymes. In this contribution, we demonstrated that carboxylic acid thioesters could be readily reduced by a range of alcohol dehydrogenases, albeit at significantly reduced rates relative to those observed for corresponding ketones. A molecular explanation, especially for the lower turnover rates for thioesters relative to those obtained for ketones, is presented, as is a preliminary substrate scope.It's the going rate: Carboxylic acid thioesters are readily reduced by a range of alcohol dehydrogenases (ADHs), albeit at rates that are significantly reduced relative to those obtained for ketones. A molecular explanation for this rate difference is presented, as is a preliminary substrate scope.
  PubDate: 2017-04-03T09:30:25.380693-05:
  DOI: 10.1002/cctc.201700165
Baeyer-Villiger oxidation of cyclic ketones using tin-silica pillared
catalysts
- Authors: Jan Prech; Marta Arroyo Carretero, Jiří Čejka
  Abstract: Baeyer-Villiger oxidation is an important transformation of ketones into esters and particularly cyclic ketones to lactones. We report here preparation and catalytic activity of layered Sn-silicate catalysts and mesoporous ordered silica catalysts in this reaction. Sn was introduced using so-called tin-silica pillaring or impregnation using a mixture of tetraethyl orthosilicate and tin (IV) alkoxide. The prepared catalysts were characterized using XRD, N2 physisorption, SEM, UV/Vis, and ICP-OES and studied in Baeyer-Villiger oxidation of cyclopentanone, norcamphor, and 2-adamantanone with aqueous hydrogen peroxide. Norcamphor and 2-adamantanone were oxidized easily with selectivity up to 99%. Sn-MS and IPC-1-SnPI materials exhibited the highest conversions (e.g. norcamphor: Sn-MS 37%, IPC-1-SnPI 36% after 8 h vs. Sn-MCM-41 22%). On the other hand, oxidation of cyclopentanone suffered from product hydrolysis to corresponding 4-hydroxybutanoic acid.
  PubDate: 2017-04-03T07:25:44.24702-05:0
  DOI: 10.1002/cctc.201700162
Formation of cyclic carbonates from CO2 and epoxides catalysed by a cobalt
coordinated conjugated microporous polymer
- Authors: Jian Xiong; Ruixia Yang, Yong Xie, Nianyu Huang, Kun Zou, Weiqiao Deng
  Abstract: A cheap and effective cobalt coordinated conjugated microporous polymer (Co-CMP-2) was synthesized by the ethanediamine-based salen ligand cross-linked with 1, 3, 5-triethynylbenzene. Co-CMP-2 exhibited extremely high catalytic efficiency in product of cyclic carbonates from CO2 and epoxides, which is superior to previous Co-CMP. The TOF of Co-CMP-2 could reach 23300 h-1 for ethylene carbonate. Moreover, it can be reused more than 10 times without significant loss in its catalytic activity.
  PubDate: 2017-03-31T23:25:44.911842-05:
  DOI: 10.1002/cctc.201700386
A chlorine-tolerant ruthenium catalyst derived from unique anion-exchange
properties of 12CaO·7Al₂O₃ for ammonia synthesis
- Authors: Jiang Li; Masaaki Kitano, Tian-Nan Ye, Masato Sasase, Toshiharu Yokoyama, Hideo Hosono
  Abstract: Poisoning is defined as deactivation by strong adsorption of, usually, impurities on active sites, which is a serious problem in many important catalytic processes. For example, the activity of ruthenium (Ru) catalyst is significantly degraded by chlorine in ammonia synthesis due to its electron-withdrawing property. Here we demonstrate that 12CaO·7Al₂O₃ with subnanometer-sized cages prevents the poisoning of Ru catalyst by chlorine ions in ammonia synthesis. Conventional supported Ru catalysts exhibit negligibly small activity when a tiny amount of chlorine ions remain on the catalyst surface. In contrast, the catalytic activity of Ru/C12A7 is not influenced by chlorine ions even though the amount of chlorine in Ru/C12A7 is one order of magnitude higher than that of the conventional Ru catalysts. The chlorine resistance of Ru/C12A7 is attributed to the unique anion-exchange properties of C12A7; i.e., the chlorine ions are preferentially trapped in the positively charged sub-nanometer-sized cages of C12A7 instead of OH¯ ions under ammonia synthesis conditions.
  PubDate: 2017-03-31T12:25:23.505259-05:
  DOI: 10.1002/cctc.201700353
Use of the Trost Ligand in Ruthenium-Catalyzed Asymmetric Hydrogenation of
Ketones
- Authors: Johannes Gerardus de Vries; Mattia Cettolin, Pim Puylaert, Luca Pignataro, Sandra Hinze, Cesare Gennari
  Abstract: The Trost ligand (1S,2S)-1,2-diaminocyclohexane-N,N'-bis(2'-diphenylphosphinobenzoyl) L is reported for the first time as ligand in the asymmetric hydrogenation (AH) of ketones. Ligand (S,S)-L was screened in the presence of several metal salts and found to form active catalysts when combined with ruthenium sources in the presence of hydrogen and a base. Reaction optimization was carried out by screening different Ru sources, solvents and bases. Under the optimized conditions, the complex formed by combination of (S,S)-L with RuCl3(H2O)x in the presence of Na2CO3, is able to promote the AH of several ketones at r.t. with good yields and up to 96% ee. The reaction kinetics measured under the optimized conditions revealed the presence of a long induction period, during which the initially formed Ru species is transformed into the catalytically active complex by reaction with hydrogen. Remarkably, ketone S8, precursor of the antiemetic drug Aprepitant, was hydrogenated with excellent yield and good ee.
  PubDate: 2017-03-31T10:20:25.683616-05:
  DOI: 10.1002/cctc.201700545
Palladium-Catalyzed Ligand-Controlled Selective Synthesis of Aldehydes and
Acids from Aryl Halides and Formic Acid
- Authors: Xiao-Feng Wu; jin-bao peng, Fu-Peng wu, Ling-Shen Meng, Xinxin qi
  Abstract: Selective synthesis is in the core of modern organic chemistry. In this communication, a novel ligand-dependent palladium-catalyzed carbonylation procedure for the divergent synthesis of aldehydes and carboxylic acids from easily available aryl halides has been established. Under the same reaction conditions, the reaction pathways can be controlled by the ligands applied to give formylated and carboxylated products selectively. Sterically hindered monodentate ligand facilitates the reductive carbonylation and provides aldehydes, while bidentate ligand prefers carboxylation reaction and produce carboxylic acids. A wide range of functional groups were tolerated with moderate to excellent yields in general.
  PubDate: 2017-03-31T07:20:32.62673-05:0
  DOI: 10.1002/cctc.201700517
Nitrogen-doped Carbon Nanofibers for the Oxygen Reduction Reaction:
Importance of the Iron Growth Catalyst Phase
- Authors: Marthe E. M. Buan; Navaneethan Muthuswamy, John C. Walmsley, De Chen, Magnus Rønning
  Abstract: A systematic evaluation of the oxygen reduction reaction (ORR) on nitrogen-doped carbon nanofibers (N-CNFs) has been performed by tuning the properties of the N-CNFs by using chemical vapor deposition. Analysis of the as-synthesized N-CNFs shows that the iron used as the growth catalyst consists of iron carbides, including Fe7C3, χ-Fe5C2, and θ-Fe3C, depending on the carbon activity of the synthesis feed. Furthermore, a relationship between the growth catalyst phase, the N-CNF properties, and the electrocatalytic activity for the oxygen reduction in acidic electrolyte is revealed. The best catalytic activity and selectivity was achieved if the N-CNFs were grown from Hägg carbide, χ-Fe5C2, suggesting that this carbide phase favors the incorporation of active sites into the N-CNFs. Controlling the phase of the iron particles used as growth catalysts is therefore essential for obtaining N-CNFs with a high active site density for the oxygen reduction reaction.Importance of the growth catalyst phase: The oxygen reduction activity of nitrogen-doped carbon nanofibers (N-CNFs) is improved by using a growth catalyst rich in χ-Fe5C2. The iron carbide phase composition can be manipulated by tuning the synthesis conditions to incorporate a high density of oxygen reduction reaction (ORR) active sites.
  PubDate: 2017-03-31T06:25:36.299616-05:
  DOI: 10.1002/cctc.201601585
Enantioselective Transfer Hydrogenation of Ketones Catalyzed by a
Manganese Complex Containing an Unsymmetrical Chiral PNP′ Tridentate
Ligand
- Authors: Afrooz Zirakzadeh; Sara R. M. M. de Aguiar, Berthold Stöger, Michael Widhalm, Karl Kirchner
  Abstract: Manganese complexes of the types [Mn(PNP′)(Br)(CO)2] and [Mn(PNP′)(H)(CO)2] containing a tridentate ligand with a planar chiral ferrocene and a centro chiral aliphatic unit were synthesized, characterized, and tested in the enantioselective transfer hydrogenations of 13 ketones. The catalytic reactions proceeded with conversions up to 96 % and ee values up to 86 %. The absolute configuration of all products was determined to be (S). Notably, the presence of dihydrogen (up to 20 bar) did not affect the reduction. On the basis of DFT calculations, preliminary mechanistic details including the origin of the (S) selectivity are presented. The molecular structure of [Mn(PNP′)(Br)(CO)2] was studied by X-ray diffraction.Going into hyd-ing: The first enantioselective transfer hydrogenation of ketones catalyzed by a well-defined Mn-based complex containing a chiral PNP′ pincer ligand with a planar chiral ferrocene and a centro chiral aliphatic unit is reported. The asymmetric transfer hydrogenation reactions procced under mild conditions with conversions up to 96 % and ee values up to 86 %.
  PubDate: 2017-03-31T06:25:28.140194-05:
  DOI: 10.1002/cctc.201700042
Renewable Aromatics from Kraft Lignin with Molybdenum-Based Catalysts
- Authors: Lisa Cattelan; Alexander Kah Liem Yuen, Matthew Lui, Anthony Frederick Masters, Maurizio Selva, Alvise Perosa, Thomas Maschmeyer
  Abstract: The catalytic depolymerization of Kraft lignin in supercritical ethanol was explored in the presence of Mo2C- and MoS2-based catalysts. At 280 °C, Mo2C and Mo2C/Al2O3 afforded aromatic yields of 425 and 419 mg/g lignin, respectively: amongst the highest yields reported to date. Ionic-liquid-assisted delamination of MoS2 resulted in highly active catalysts, capable of quantitative conversion of lignin at the expense of aromatic yield (ca 186 mg/g lignin). Across all the catalysts studied, between 0.04 wt% and 0.38 wt% of molybdenum leached into solution under supercritical conditions, according to ICP analyses (corresponding to 27-570 µg of molybdenum in the reaction supernatant). A small contribution to the molybdenum in solution comes from the reactor itself (Hastelloy C contains 16 wt% Mo). Analysis of a depolymerization performed with fresh Kraft lignin and the soluble portion of the reaction mixture from a previous reactor run indicated that the leached species were neither active enough to afford the high conversions observed, nor selective enough to give high yields of aromatic products. In conjunction with the ICP data and differential chemoselectivities of the Mo2C- and MoS2-based catalysts, these results suggest that the bulk of the catalysis is heterogeneous.
  PubDate: 2017-03-30T21:26:28.974107-05:
  DOI: 10.1002/cctc.201700374
Nickel phosphide/silica catalysts for the gas-phase hydrogenation of
furfural to high value-added chemicals
- Authors: Carmen Pilar Jiménez-Gómez; Juan A. Cecilia, Ramón Moreno-Tost, Pedro Maireles-Torres
  Abstract: A series of nickel phosphide-based catalysts, supported on a commercial silica, with a metallic Ni loading between 5-20 wt.% and initial P/Ni molar ratio 0-3, has been prepared by incipient wetness impregnation. Catalyst precursors were reduced and characterized by X-ray diffraction, CO chemisorption, NH3-TPD, N2 adsorption-desorption at -196 ºC and X-ray photoelectron spectroscopy, among other techniques and then tested in the furfural hydrogenation in gas-phase. Almost full furfural conversion and a 2-methylfuran yield of 73% can be achieved with the Ni2P based catalysts with nickel content of 15 wt.%, at 190 ºC after 5 h of TOS. The high selectivity towards 2-methylfuran is attributed to both the high hydrogenating capacity of metallic sites leading to furfuryl alcohol and the presence of reduced phosphorus species that favor the hydrogenolysis process. However, catalysts undergo deactivation along the catalytic test, due to formation of carbonaceous deposits in the form of coke and reactants and/or products.
  PubDate: 2017-03-30T21:26:18.263005-05:
  DOI: 10.1002/cctc.201700312
Selective Reduction of Nitroarenes with Silanes Catalysed by Nickel
N-Heterocyclic Complexes
- Authors: Beatriz Royo; Rita Lopes, Mariette M Pereira
  Abstract: An efficient catalytic system for the reduction of nitroarenes to amines was developed using a well-defined nickel-NHC complex as catalyst and phenylsilane as reducing agent. The excellent activity of the catalyst provides access to anilines containing a wide array of reactive functionalities at 20 °C, and without using any base or additive. Notably, the catalytic system allows the reduction of 5,10,15,20-tetra-(nitrophenyl)porphyrin (TNPP) and Cu(II) β-nitroporphyrin to the corresponding aminoporphyrins
  PubDate: 2017-03-30T13:25:24.090391-05:
  DOI: 10.1002/cctc.201700218
Synthesis of 2,3-Disubstituted Indoles from α-Diketones and N-Substituted
Anilines: One-Pot Pd-Catalyzed Reductive Amination
- Authors: G. Eliad Benitez-Medina; Manuel Amézquita-Valencia, Armando Cabrera, Pankaj Sharma
  Abstract: Herein, we report a new straightforward catalytic synthesis of 2,3-disubstituted indoles from α-diketones 1 and N-substituted anilines 2 by employing a palladium(II) trifluoroacetate/1,1′-bis(diphenylphosphino)ferrocene ([Pd(tfa)2]/dppf; 1:1.5) under reductive conditions and without an external oxidant. The tandem reaction involves ketoenamine and ketoamine as intermediates and a final dehydration–annulation reaction to obtain the 2,3-disubstituted indole. New palladium hydride species, which catalyze the reaction, could not be isolated but Pd–H species were observed by NMR and IR spectroscopy and mass spectrometry (FAB+) studies. This work presents a new regioselective route with a plausible mechanism to synthesize 2,3-disubstituted indoles under reductive conditions.2,3-Disubstituted indoles synthesis: A palladium(II) trifluoroacetate/1,1′-bis(diphenylphosphino)ferrocene ([Pd(tfa)2]/dppf) catalytic system is used in the tandem synthesis of 2,3-disubstituted indoles from α-diketones and N-substituted anilines under reductive conditions and without an external oxidant.
  PubDate: 2017-03-30T08:01:17.789977-05:
  DOI: 10.1002/cctc.201601557
Samarium-Catalyzed Diastereoselective Double Addition of Phenylphosphine
to Imines and Mechanistic Studies by DFT Calculations
- Authors: Jianfeng Li; Carlos Alvarez Lamsfus, Changhong Song, Jinxi Liu, Guilan Fan, Laurent Maron, Chunming Cui
  Abstract: The catalytic hydrophosphination of imines represents the most straightforward and atom-economical strategy for the preparation of α-aminophosphines, which are useful as biologically active molecules and ligands for catalysis. The first catalytic protocol for the rapid and high-yielding hydrophosphination of common imines enabled by an ene–diamido samarium methoxide catalyst was developed. The reaction allowed the efficient and diastereoselective synthesis of various bis(α-amino)phosphines through the double addition of PhPH2 to common imines. The catalytic reaction has a relatively wide substrate scope and offers high diastereoselectivities (up to 99:1 dr for meso products) and high yields (up to 97 %). DFT calculations disclosed an inner-sphere mechanism involving unprecedented activation of a Sm−O bond by a phosphine and stabilization of the addition intermediates by the metal center.In rare form: A protocol for the rapid and high-yielding hydrophosphination of aromatic imines without using specific substrates is developed by using a well-defined rare-earth alkoxy complex catalyst. DFT calculations disclose an unprecedented activation mode involving Sm−O bond cleavage. The double hydrophosphination protocol allows the diastereoselective formation of bis(α-amino)phosphines. DME=1,2-dimethoxyethane.
  PubDate: 2017-03-30T08:00:45.20153-05:0
  DOI: 10.1002/cctc.201700003
On the Reactivity of Dihydro-p-coumaryl Alcohol towards Reductive
Processes Catalyzed by Raney Nickel
- Authors: Gaetano Calvaruso; Jorge Augusto Burak, Matthew T. Clough, Marco Kennema, Fabian Meemken, Roberto Rinaldi
  Abstract: There are several established approaches for the reductive fractionation of lignocellulose (e.g., “catalytic upstream biorefining” and “lignin-first” approaches) that lead to a lignin oil product that is composed primarily of dihydro-p-monolignols [e.g., 4-(3-hydroxypropyl)-2-methoxyphenol and 4-(3-hydroxypropyl)-2,6-dimethoxyphenol]. Although effective catalytic methods have been developed to perform reductive or deoxygenative processes on the lignin oil, the influence of the 3-hydroxypropyl substituent on catalyst activity has previously been overlooked. Herein, to better understand the reactivity of the depolymerized lignin oil obtained from catalytic upstream biorefining processes, dihydro-p-coumaryl alcohol was selected as a model compound. Hydrogenation of this species in the presence of Raney Ni with molecular hydrogen led to ring saturation (100 % selectivity) in the absence of hydrodeoxygenation, whereas under hydrogen-transfer conditions with 2-propanol, hydrogenation occurred (≈55 % selectivity) simultaneously with hydrodeoxygenation (≈40 % selectivity). In a broader context, this study sheds light not only on the reactivity of dihydro-p-monolignols but also on the intricacies of the catalytic upstream biorefining reaction network in which these species are revealed to be key intermediates in the formation of less-functionalized p-alkylphenols.Fifty shades of green: The advent of catalytic upstream biorefining has made available new platform chemicals from lignin. In this Communication, the reactivity of dihydro-p-coumaryl alcohol is explored in reductive processes catalyzed by Raney Ni under H2 pressure as well as under H-transfer conditions. Under H2 pressure, Raney Ni is a selective hydrogenation catalyst. However, under H-transfer conditions, the catalyst also produces 4-alkylphenols.
  PubDate: 2017-03-30T04:05:32.865213-05:
  DOI: 10.1002/cctc.201601590
“Side-Product Catalysis”: Substrate Autoxidation as an Overlooked Side
Reaction Generating a Co-Catalyst for Enhancing Asymmetric Aldol Reactions
- Authors: Marcel Heidlindemann; Albrecht Berkessel, Harald Gröger
  Abstract: An acid formed autoxidatively from an aldehyde substrate as a side product was found to alter the reaction kinetics and selectivity significantly in the direct asymmetric aldol reaction between an aldehyde and acetone, both in aqueous media and cyclohexane. Furthermore, this side-product catalysis (“impurity catalysis”) was also observed upon using commercial samples of aldehydes without purification prior to their use (owing to the presence of the acid formed therein during storage), which thus underlines the impact of substrate purity on the reaction course of the catalytic process.Helpful side-products: An acid formed autoxidatively from an aldehyde substrate significantly alters the reaction kinetics and selectivity in the direct asymmetric aldol reaction between an aldehyde and acetone, both in aqueous media and cyclohexane. This “side-product catalysis” is also observed upon using commercial aldehyde samples without purification prior to their use, which thus underlines the impact of substrate purity.
  PubDate: 2017-03-30T04:03:45.469681-05:
  DOI: 10.1002/cctc.201601530
Thermally Converted CoO Nanoparticles Embedded into N-Doped Carbon Layers
as Highly Efficient Bifunctional Electrocatalysts for Oxygen Reduction and
Oxygen Evolution Reactions
- Authors: Hyeonghun Kim; Youngmin Kim, Yuseong Noh, Seonhwa Lee, Jaekyung Sung, Won Bae Kim
  Abstract: Hybrid materials that consist of transition-metal oxides and heteroatom-doped carbon materials have been researched recently as promising bifunctional electrocatalysts for both oxygen-reduction reaction (ORR) and oxygen-evolution reaction (OER) in alkaline media. Herein, CoO nanoparticles embedded into N-doped carbon layers were synthesized by a thermal conversion process of polypyrrole-coated Co3O4 nanoparticles supported on a carbon layer in Ar atmosphere at 900 °C. During the process, the initial Co3O4 phase was transformed to the CoO phase along with the thermal carbonization of the polypyrrole layer to the N-doped carbon layer. Owing to the oxidative combustion induced by the O species released from the Co3O4 nanoparticles, the N-doped carbon layer could contain pores around the CoO nanoparticles. Alkaline electrolytes could penetrate the N-doped carbon layer toward the CoO nanoparticles through the pores. The nanocomposites with the well-assembled CoO nanoparticles and porous N-doped carbon layer could exhibit superior catalytic activity for ORR and OER. In addition, the N-doped carbon layers effectively prevent the degradation of the catalyst by protecting the CoO nanoparticles from aggregation during the electrocatalytic processes. The hybrid material of CoO and N-doped carbon showing highly active and durable catalytic characteristics for ORR and OER is a promising electrocatalyst in fuel cells, metal–air batteries, and water-splitting systems and could be used instead of precious metals such as Pt, Ru, and Ir.Different phases: CoO nanoparticles embedded into N-doped carbon layers are synthesized by phase transformation of cobalt oxides and polypyrrole carbonization. The excellent performance of the catalyst in the oxygen-reduction and oxygen-evolution reaction is facilitated by pores in the N-doped carbon layer around the CoO nanoparticles.
  PubDate: 2017-03-30T03:59:53.390492-05:
  DOI: 10.1002/cctc.201601705
Bi-functional Squaramides as Organocatalysts for lactide polymerization:
Catalytic Performance and Comparison with Mono-functional Analogues
- Authors: Samuel Dagorne
  Abstract: A series of variously substituted squaramides (1-5) were prepared for use as organocatalysts in lactide ring-opening polymerization (ROP). Amino-functionalized squaramides 1 and 2 were prepared and shown to be suitable polymerization organocatalysts for the controlled ROP of L-lactide (L-LA) in the presence of an alcohol source such as BnOH (acting as initiator) to afford chain-length-controlled and narrowly disperse poly(L-lactide) (PLLA) under mild reaction conditions. All ROP experimental and polymer analysis data are consistent with 1 and 2 acting as bifunctional H-bonding catalysts able to activate both the lactide monomer and initiator BnOH thanks to their dual HB acceptor and donor properties. As a comparison, amino-squaramide 3, a direct analogue of 1 but less HB donor due to the absence of electron-withdrawing NH-substituents, displays little lactide ROP activity, highlighting the key role of monomer activation through HB in the present systems. Unlike amino-squaramides 1 and 2, related mono-functional squaramides 4 and 5 are inactive in lactide ROP in the presence of BnOH, but the addition of NEt3, as an external HB acceptor, allows the ROP to proceed with the production of well-defined PLLA. A cooperative dual activation with an activated-monomer/activated chain-end mechanism is most likely operative in the lactide ROP mediated by catalysts 1 and 2 in the presence of BnOH.
  PubDate: 2017-03-29T21:20:28.727674-05:
  DOI: 10.1002/cctc.201700272
Copper-Decorated Microsized Nanoporous TiO2 Photocatalysts for CO2
Reduction by H2O
- Authors: Tewodros (Teddy) Asefa; Tao Zhang, Jingxiang Low, Xiaoxi Huang, Jafar F. Al-Sharab, Jiaguo Yu
  Abstract: A series of metallic copper (Cu)-decorated microsized, nanoporous titanium dioxide (TiO2) materials with different loadings of Cu were synthesized by in situ hydrolysis of Sn2+-grafted titanium glycolate microspheres in the presence of Cu2+ ions. The resulting materials showed good photocatalytic activity for CO2 reduction with water. In particular, the material prepared with an optimal loading of Cu (~0.4 wt.%) exhibited the highest photocatalytic activity for reduction of CO2 to hydrocarbon fuel (CH4), with a 21-fold higher efficiency than the most commonly studied and utilized commercial TiO2 (Degussa P25) photocatalyst for the same reaction under similar reaction conditions.
  PubDate: 2017-03-29T13:20:32.293462-05:
  DOI: 10.1002/cctc.201700512
Highly Efficient and Selective Catalytic Synthesis of Quinolines Involving
Transition-Metal-Doped Carbon Aerogels
- Authors: M. Godino-Ojer; A. J. López-Peinado, F. J. Maldonado-Hódar, E. Pérez-Mayoral
  Abstract: Carbon aerogels doped with transition metals are found to be efficient and reusable catalysts involved in the selective synthesis of quinolines. Interestingly, we report herein the first aldol-based reactions, particularly the Friedländer reaction, catalyzed by zero-valent metal nanoparticles, the activity of which is mainly related with the nature of the metal. Co0- and Cu0-doped aerogels resulted in the most active catalysts. Resorcinol–formaldehyde Cu-doped and steam-activated (RFCuS) aerogel represents an alternative nanocatalyst to the metal–organic framework CuBTC showing similar reactivity but superior thermal and chemical stability. The unusual reactivity observed could be explained by the in situ generation of the Co0–CoII catalytic system formed in the activation of ethyl acetoacetate.Alternative: aerogels! Transition-metal-doped carbon aerogels can efficiently catalyze the Friedländer reaction to produce quinolines. Although the carbon matrix contributes to a certain extent to the catalytic performance, the predominant active catalytic species are the zero-valent transition-metal nanoparticles.
  PubDate: 2017-03-29T09:40:36.020699-05:
  DOI: 10.1002/cctc.201601657
Aluminum Location and Acid Strength in an Aluminum-Rich Beta Zeolite
Catalyst: A Combined Density Functional Theory and Solid-State NMR Study
- Authors: Shikun Li; Zhenchao Zhao, Rongrong Zhao, Danhong Zhou, Weiping Zhang
  Abstract: Density functional theory was performed to investigate the specific Al distribution and the origination of Brönsted acid strength in the Al-rich Beta zeolite catalyst. The most preferable sites for Al atoms of Al-rich and Si-rich Beta zeolites represented by 1Al and 2Al atoms are compared by electrostatic potential analysis and substitution energies. IT1 and T9 sites are the most favorable locations for 1Al distribution, while 5MR1-T92, 5MR2-T15 and 6MR1-T66 sites are inclined to be occupied by Al atoms for 2Al distribution. Al atoms in 5MR1-T17 sites would be dealuminated more easily to become the extra-framework Al species when Al-rich Na-Beta is ion-exchanged to H-Beta. As for NNNN sequences in Al-rich Beta, 6MR1-T66 sites are the most easily substituted by Al atoms, facing different channels and showing the properties of isolated Al site. Proton affinities, NH3 adsorption energies and 1H chemical shifts of [D5]pyridine adsorbed in Beta zeolites were used to analyze the Brönsted acidity. Si-rich Beta has stronger Brönsted acid strength than the Al-rich counterpart. This agrees with the experimental results from 1H MAS NMR with [D5]pyridine as probe molecule. The Brönsted acid strength of Al-rich and Si-rich H-Beta zeolites was correlated to the Al location at the specific T-site on the zeolitic framework.Seating preferences: The preferable Al locations at specific T-sites in the framework of Al-rich Beta catalyst were investigated. Their relationship to the corresponding Brönsted acid strength was demonstrated by the characterization of DFT computations and solid-state 1H MAS NMR spectroscopy with adsorption of [D5]pyridine.
  PubDate: 2017-03-29T09:40:33.976859-05:
  DOI: 10.1002/cctc.201601623
First-Principles investigation of the relevant surfaces exposed by
polycrystalline LaFeO3
- Authors: Dimitri Blanck; Elise Christine Berrier, Jean-François Paul
  Abstract: A systematic comparison of surface energy values computed over a series of possible surfaces and terminations exposed by lanthanum orthoferrite (LaFeO3) was performed for elucidating the nature of the exposed surfaces of LaFeO3-based three way catalysts. Surface reconstruction of polar surfaces was attempted, which did change the ranking of the most stable surfaces. Indeed, the non-polar (121) and (100) surfaces were found to remain the most stable ones in vacuum. The relative stability of surfaces was also questioned when a partial pressure of water was applied, as is expected under the operating conditions of three-way catalysis. Our results show that the predominance of (121) and (100) surfaces is even strengthened upon water exposure.
  PubDate: 2017-03-29T09:25:44.953444-05:
  DOI: 10.1002/cctc.201700110
Enzyme-promoted Asymmetric Tandem Passerni Reaction
- Authors: Ryszard Ostaszewski; Anna Zadlo, Dominik Koszelewski, Daniel Paprocki, Arleta Madej, Monika Wilka
  Abstract: A versatile and highly efficient three-step, one-pot, enzyme-promoted Passerini tandem reaction has been developed. Chemoenzymatic sequence involved simultaneous enzyme catalyzed hydrolysis, subsequent Passerini reaction and enzymatic kinetic resolution of the Passerini product was evaluated. This methodology combining the diversity served by multicomponent reactions with the selectivity of biocatalysts resulted in efficient synthesis of target compounds with excellent enantiomeric excesses up to 99%. With a small set of substrates, large library of complex molecules was obtained within a short time using developed procedure.
  PubDate: 2017-03-29T06:50:24.663179-05:
  DOI: 10.1002/cctc.201700427
The role of various chlorides on xylose conversion to furfural:
experiments and kinetic modeling
- Authors: Olga Ershova; Kaarlo Nieminen, Herbert Sixta
  Abstract: In this paper, the catalytic activity of thirteen different metal chlorides in aqueous solution for the conversion of xylose into furfural was studied in comparison with both the auto- and HCl catalyzed reactions. A maximum furfural yield of 60.3 mol% was reached with the addition of FeCl3 to the aqueous xylose solution. However, the catalytic efficiency of FeCl3 decreased when birch hydrolysate was used as a raw material resulting in 43.5 mol% furfural yield. The obtained experimental results were incorporated in a kinetic modelling study. The assessed reaction rates for xylose dehydration to furfural and xylose decomposition to by-products, in the presence of AlCl3 and CrCl3 are significantly higher than during acid-catalyzed conversion. The logarithms of the reaction rates show a linear correlation with the ionization energy as well as with the acidity of the metal ions.
  PubDate: 2017-03-29T06:20:52.463668-05:
  DOI: 10.1002/cctc.201700269
Palladium-Catalyzed Isomerization/(Cyclo)carbonylation of Pentenamides: a
Mechanistic Study of the Chemo- and Regioselectivity
- Authors: Bart Limburg; Yann Gloaguen, Hans M. de Bruijn, Eite Drent, Elisabeth Bouwman
  Abstract: A new isomerizing ring-closing amidocarbonylation reaction is reported using Pd-catalysis with bulky diphosphane ligands. From terminal as well as internal pentenamide isomers (PAs), cyclic imides were obtained in good yield (92%) with cationic Pd catalysts supported by bis-PCg ligands (PCg = 6-phospha-2,4,8 trioxa-1,3,5,7-tetramethyladamant-6-yl). An excess of strong acid is required to obtain high selectivity for imide products. From a low-temperature NMR study it was deduced that N-coordination of the amide moiety is responsible for a high selectivity to cyclic imide products. In weakly acidic conditions O-coordination of the amide functionality leads to the formation of cyanoacids (i.e., 5-cyanovaleric acid, 2-methyl-4-cyanobutyric acid and 2-ethyl-3-cyanopropionic acid). It is proposed that the formation of these cyanoacids occurs through a novel intramolecular tandem de-hydrating hydroxycarbonylation reaction of PA's. This reaction also occurs in intermolecular versions of amidocarbonylation with mixtures of alkene and amide substrates. Experiments with N-alkylated amides have been instrumental in developing mechanistic models. The strong acid co-catalyst ensures double-bond isomerization to occur faster than product formation, resulting in the same product mixture, irrespective of the use of terminal or internal pentenamides. The remaining challenge is to arrive at the desired adipimide by overcoming the undesirable regioselectivity caused by chelation of the amide.
  PubDate: 2017-03-28T09:20:30.15267-05:0
  DOI: 10.1002/cctc.201700345
Synthesis of [Bis(hexamethylene)cyclopentadienone]iron Tricarbonyl and its
Application to the Catalytic Reduction of C=O Bonds
- Authors: Sofia Vailati Facchini; Jörg-Martin Neudörfl, Luca Pignataro, Mattia Cettolin, Cesare Gennari, Albrecht Berkessel, Umberto Piarulli
  Abstract: Herein, we report the synthesis of [bis(hexamethylene)cyclopentadienone]iron tricarbonyl (1 b) by the reaction of cyclooctyne with Fe(CO)5 and the investigation of its catalytic properties in C=O bond reduction. As a result of the peculiar reactivity of cyclooctyne, 1 b was formed in good yield (56 %) by intermolecular cyclative carbonylation/complexation with Fe(CO)5. Compound 1 b was characterized fully and its crystal structure was determined by using XRD. Catalytic tests revealed that, upon in situ activation with Me3NO, 1 b promotes the hydrogenation of ketones, aldehydes, and activated esters as well as the transfer hydrogenation of ketones and shows a higher activity than the classical “Knölker complex” (1 a). Studies on the hydrogenation kinetics in the presence of 1 a and 1 b (respectively) suggest that this difference in activity is probably caused by the better stability of the 1 b-derived complex than that of the in situ generated Knölker–Casey catalyst.The family grows: The first efficient synthesis of [bis(hexamethylene)cyclopentadienone]iron tricarbonyl under mild conditions is reported. This new member of the (cyclopentadienone)iron complex family shows an improved catalytic activity compared to the classical “Knölker complex” in the reduction of C=O bonds.
  PubDate: 2017-03-28T04:21:19.975626-05:
  DOI: 10.1002/cctc.201601591
In Situ XRD Study on Promotional Effect of Potassium on Carburization of
Spray-dried Precipitated Fe2O3 Catalysts
- Authors: Liwei Niu; Xingwu Liu, Xi Liu, Zhengang Lv, Chenghua Zhang, Xiaodong Wen, Yong Yang, Yongwang Li, Jian Xu
  Abstract: A study of the promotional effect of potassium on the carburization behavior of a series of spray-dried precipitated Fe2O3 catalysts (100 Fe, 100 Fe/0.52 K, 100 Fe/1.54 K, and 100 Fe/2.4 K) has been performed by using in situ XRD. The average crystallite size evolution for species such as α-Fe2O3, Fe3O4, χ-Fe5C2, and θ-Fe3C were followed. The potassium promoter clearly inhibits the reduction of α-Fe2O3 to Fe3O4, where the decreasing binding energy in the Fe 2p3/2, O 1s and K 2p3/2 spectra from X-ray photoelectron spectroscopy (XPS) suggests an electron density increase in Fe and O upon potassium promotion, leading to the enhanced covalency in the Fe−O bond. In terms of crystallite size during carburization, an optimum potassium loading exists in catalyst 100 Fe/0.52 K, which shows the fastest reduction to Fe3O4 with minimum crystallite sizes of around 7 to 15 nm. Potassium has no clear effect in determining the final crystallite size of χ-Fe5C2. An arch-shaped curve in the evolution of crystallite size of the Fe3O4 intermediate was observed, which can be explained by the activation energy difference between the bidirectional steps of the outward oxygen diffusion and the inward carbon diffusion.Promoting Potassium: The promotional effect of potassium on the carburization behavior of a series of spray-dried precipitated Fe2O3 catalysts is studied by using in situ XRD. The potassium promoter inhibits the reduction of α-Fe2O3 to Fe3O4, in which X-ray photoelectron spectra suggest an electron density increase in Fe and O upon potassium promotion, leading to enhanced covalency in the Fe−O bond. An optimum potassium loading exists in catalyst 100 Fe/0.52 K, which shows the fastest reduction to Fe3O4 with minimum crystallite sizes of around 7 to 15 nm.
  PubDate: 2017-03-28T03:25:55.216914-05:
  DOI: 10.1002/cctc.201601665
Iron nanoparticles embedded in graphitic carbon matrix as heterogeneous
catalysts for the oxidative C-N coupling of aromatic N H compounds and
amides
- Authors: Jinbao He; Amarajothi Dhakshinamoorthy, Ana Primo, Hermenegildo García
  Abstract: Fe or Co nanoparticles (NPs) and two nanoparticulate Fe-Co alloys having different Fe/Co atomic ratio with average particle size ranging from 10.9 to 26.5 nm embedded in turbostratic graphitic carbon matrix have been prepared by pyrolysis at 900 oC under inert atmosphere of chitosan powders containing Fe2+ and Co2+ ions in various proportions. The resulting Fe/Co NP@C samples have been evaluated as heterogeneous catalysts for the oxidative C-N coupling of amides and aromatic N-H compounds. It was observed that sequential addition of two aliquots of tert-butyl hydroperoxide (TBHP) in an excess of N,N-dimethylacetamide (DMA) as solvent affords the corresponding coupling product in high yields, the most efficient catalyst being Fe NP@C. Fe NP@C is reusable and exhibits a wide scope. The catalytic activity of Fe is supported by the use of highly pure Fe salt and by the observation that purposely addition of Cu2+ impurities even plays a detrimental effect on the catalytic activity. Mechanistic studies quenching with TEMPO have shown that the amide radical is the key reaction intermediate and the role of Fe NP@C is to generate the first radicals by TBHP decomposition.
  PubDate: 2017-03-27T10:30:28.137355-05:
  DOI: 10.1002/cctc.201700429
First Neutral and Cationic Tungsten Imido Alkylidene N Heterocyclic
Carbene Complexes
- Authors: Dominik Imbrich; Iris Elser, Wolfgang Frey, Michael Rudolf Buchmeiser
  Abstract: The synthesis of W(NAr')(NHC)(=CHR)(2,5-Me2pyr)2 (1, Ar' = 2,6-iPr2C6H3, NHC = 1,3-diisopropylimidazol-2-ylidene, 2,5-Me2Pyr = 2,5-dimethylpyrrolide, R = CMe2Ph), W(NAr')(NHC)(=CHR)(2,5-Me2pyr)(OC6F5) (2), W(NAr')(NHC)(=CHR)(OSiPh3)2 (3), [W(NAr')(NHC)(=CHR)(OSiPh3))(MeCN)+][B(ArF)4-] (4, B(ArF)4- = B(3,5-(CF3)2-C6H3)4-), [W(NAr')(NHC)(=CHR)(2,5-Me2pyr))+][B(ArF)4-] (5), [W(NAr')(NHC)(=CHR)(OC6F5))(tBuCN)+][B(ArF)4-] (6), W(NAr')(NHC)(=CHR)(OtBu)2 (7), [W(NAr')(NHC)(=CHR)(OtBu)+][B(ArF)4-] (8), W(NAr')(NHC)(=CHR)(OCMe(CF3)2)2 (9), and their reactivity in olefin metathesis and cyclopolymerization is reported. The cationic complexes 4, 5 and 6 showed high productivity and activity in olefin metathesis reactions with turnover numbers up to 40,000 and turnover frequencies (TOF5min) up to 31 s 1 and also substantial functional group tolerance versus esters, nitriles, alcohols and sulfides particularly in the cyclopolymerization of α,ω-diynes.
  PubDate: 2017-03-27T05:15:47.511753-05:
  DOI: 10.1002/cctc.201700189
Highly Active Noble-Metal-Free Copper Hydroxyapatite Catalysts for the
Total Oxidation of Toluene
- Authors: Dayan Chlala; Jean-Marc Giraudon, Nicolas Nuns, Madona Labaki, Jean-François Lamonier
  Abstract: Hydroxyapatite (Hap) supported Cu materials prepared by the wet impregnation method were designed as noble-metal-free catalysts for the total oxidation of toluene. Cu/Hap materials with different Cu loadings (2.5–20 wt %) calcined at 400 °C were characterized by using inductively coupled plasma optical emission spectroscopy, N2 physisorption, XRD, Raman spectroscopy, IR spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion MS. The tenorite CuO phase was detected in all materials, and the libethenite Cu2(PO4)OH phase was observed for the sample with 20 wt % Cu. The presence of libethenite was accompanied by the formation of Ca2CO3H+ ions at the Hap surface. Residual NO3− species that interact with Cu and Ca were also found, and their amount increased with the increase of the Cu content in the sample. Interestingly, the specific activity in the total oxidation of toluene increased with the decrease of the Cu content in the catalyst. The rate per mole of Cu was increased by 10 times if the Cu content was decreased by four times. This noticeable result could be related to the presence of acid sites with a moderate strength as well as finely dispersed CuO species on the Hap, which allow the activation of toluene molecules and their oxidation through a redox mechanism. Moreover, Cu2.5 wt %/Hap showed a remarkably stable catalytic performance for 45 h time-on-stream, which evidences that this material has a high potential for applications in the removal of volatile organic compounds.Hap Hap Hooray! Hydroxyapatite-supported copper oxides are efficient noble-metal-free catalysts for toluene oxidation. High activity, CO2 selectivity, and stability are achieved over materials with a low copper content. Copper in association with hydroxyapatite can be considered as a realistic material to replace noble-metal-based solids in catalytic formulations for the oxidation of volatile organic compounds.
  PubDate: 2017-03-27T04:01:51.279772-05:
  DOI: 10.1002/cctc.201601714
Water-Gas-Shift over Metal-Free Nanocrystalline Ceria: An Experimental and
Theoretical Study
- Authors: Curtis J. Guild; Dimitriy Vovchok, David A. Kriz, Albert Bruix, Bjørk Hammer, Jordi Llorca, Wenqian Xu, Abdelhamid El-Sawy, Sourav Biswas, Jose A. Rodriguez, Sanjaya D. Senanayake, Steven L. Suib
  Abstract: A tandem experimental and theoretical investigation of a mesoporous ceria catalyst reveals the properties of the metal oxide are conducive for activity typically ascribed to metals, suggesting reduced Ce3+ and oxygen vacancies are responsible for the inherent bi-functionality of CO oxidation and dissociation of water required for facilitating the production of H2. The degree of reduction of the ceria, specifically the (1 0 0) face, is found to significantly influence the binding of reagents, suggesting reduced surfaces harbor the necessary reactive sites. The metal-free catalysis of the reaction is significant for catalyst design considerations, and the suite of in situ analyses provides a comprehensive study of the dynamic nature of the high surface area catalyst system. This study postulates feasible improvements in catalytic activity may redirect the purpose of the water-gas shift reaction from CO purification to primary hydrogen production.Are you cerias? Combining experimental and theoretical investigations reavealed a mechanistic view of the water-gas shift reaction over nanocrystalline ceria. The degree of reduction of the ceria, specifically the (1 0 0) face, is found to significantly influence the binding of reagents, suggesting reduced surfaces harbor the necessary reactive sites.
  PubDate: 2017-03-27T03:35:48.815367-05:
  DOI: 10.1002/cctc.201700081
Tertiary Amines as Ligands in a Four-Step Tandem Reaction of
Hydroformylation and Hydrogenation: An Alternative Route to Industrial
Diol Monomers
- Authors: Sarah Fuchs; Dominik Lichte, Morten Dittmar, Gregor Meier, Heinz Strutz, Arno Behr, Andreas J. Vorholt
  Abstract: A highly selective synthesis of diols is presented by simple auto-tandem catalysis to connect hydroformylation and hydrogenation reactions by a rhodium-catalyst with tertiary amines as ligands. This system allows the hydroformylation/hydrogenation of non-conjugated cyclic olefins to selectively provide diols under mild reaction conditions. As a model substrate, the industrially relevant dicyclopentadiene (dcpd) was chosen. With the reaction system [Rh(octanoate)2]2 and triethylamine, diols are produced in a high yields of up to 79 % with full conversion of intermediate aldehyde and no evidence of olefin hydrogenation. The scope of the reaction was evaluated and the optimised reaction conditions were successfully scaled up to a 2 L reactor. Finally, the Rh/amine catalyst complex was recycled by a simple water extraction of the diol-product.Hopscotch: how far can you jump directly? Rh complexes with tertiary amine ligands allow for a one-pot synthesis of diols through a tandem reaction of hydroformylation and hydrogenation. Reaction conditions were optimised and successfully scaled up.
  PubDate: 2017-03-27T03:31:40.853405-05:
  DOI: 10.1002/cctc.201601518
A Triflamide-Tethered N-Heterocyclic Carbene–Rhodium(I) Catalyst for
Hydroalkoxylation Reactions: Ligand-Promoted Nucleophilic Activation of
Alcohols
- Authors: Abir Sarbajna; Pragati Pandey, S. M. Wahidur Rahaman, Kuldeep Singh, Akshi Tyagi, Pierre H. Dixneuf, Jitendra. K. Bera
  Abstract: A triflamide-tethered N-heterocyclic carbene (NHC)-bound RhI dicarbonyl catalyst was highly effective for both intermolecular hydroalkoxylation and intramolecular heteroannulation reactions. The involvement of both the amido nitrogen and triflato oxygen atoms of the triflamide functionality for alcohol activation and 1,2-hydrogen shift, respectively, was proposed.Alcohol activation: A triflamide-tethered N-heterocyclic carbene (NHC)-bound RhI(CO)2 catalyst is highly effective for both intermolecular hydroalkoxylation and intramolecular heteroannulation reactions. The involvement of both the amido nitrogen atom and the triflato oxygen atom of the triflamide functionality for alcohol activation and 1,2-hydrogen shift, respectively, is proposed. DMAc=N,N-dimethylacetamide.
  PubDate: 2017-03-27T03:26:22.872345-05:
  DOI: 10.1002/cctc.201601667
Photocatalytic Hydrogen Production: A Rift into the Future Energy Supply
- Authors: Konstantinos C. Christoforidis; Paolo Fornasiero
  Abstract: Photocatalytic hydrogen (H2) production is a process that converts solar energy into chemical energy by means of a suitable photocatalyst. After the huge amount of systems that have been tested in the last forty years, the advent of nanotechnology and a careful design at molecular level, allow to obtain attractive activity, even using pure visible light. At the same time we are approaching reasonable photocatalyst stability in laboratory test, and the attention is paid to identify cost-effective photocatalysts that might find real applications. This Review provides a broad overview of the elementary steps of the heterogeneous photocatalytic H2 production, including an outline of the physico-chemical reactions occurring on semiconductors and cocatalysts. The use of different renewable oxygenates as sustainable sacrificial agent for the H2 production is outlined, in view of a transition from fossil fuels to pure water splitting. Finally, the recent advances in the development of photocatalyst are discussed focusing on the current progress in organic and hybrid organic/inorganic photocatalysts.A sacrifice to the Sun god: Photocatalytic hydrogen production from water and renewable feedstocks is gaining tremendous attention as a potential standalone process for efficient energy production. In this Review, the crucial effect of the cocatalyst and the sacrificial agent are critically discussed and the recent progress on the development of novel photocatalysts is presented with particular attention to organic and hybrid organic/ inorganic materials.
  PubDate: 2017-03-27T03:21:11.356195-05:
  DOI: 10.1002/cctc.201601659
A facile one-step synthesis of Fe-doped g-C3N4 nanosheets and their
improved visible light photocatalytic performances
- Authors: Jingtian Gao; Yun Wang, Shijian Zhou, Wei Lin, Yan Kong
  Abstract: Compared with routine method (liquid exfoliation and impregnation), a simple one-step pyrolysis process was designed to synthesize Fe-doped graphite carbon nitride (g-C3N4) nanosheets with NH4Cl as "dynamic gas template" and FeCl3 as Fe source, respectively.The samples were well characterized by various analytical techniques. Results of XPS and DRS indicated that the Fe species might exist at the state of Fe3+ and form Fe-N bonds with N atoms, thereby expanding visible light absorption regions and reducing the band gap of g-C3N4 nanosheets. Besides, doping certain amounts of Fe could promote the exfoliation and further Increase the specific surface area, while excessive Fe might break the sheeting structure. The specific surface area of the optimized Fe-doped g-C3N4 nanosheets reached 236.52 m2 g-1, which was 2.5 times higher than that of g-C3N4 nanosheets. Among various photocatalysts prepared, the sample (0.5 wt% FeCl3) exhibited maximum photocatalytic performance in degradation of MB and water splitting under visible light irradiation. The degradation rate of MB was about 1.4 and 1.7 times higher than that of pure g-C3N4 nanosheets and bulk g-C3N4, respectively. The H2 production rate was 536 μmolh-1g-1, which was 1.8 and 6 times higher than that of pure g-C3N4 nanosheets and bulk g-C3N4, separately.
  PubDate: 2017-03-25T12:00:27.985332-05:
  DOI: 10.1002/cctc.201700492
Ring-Opening Co-polymerization of Epoxides with Cyclic Anhydrides promoted
by Bimetallic and Monometallic Phenoxy-Imine Aluminum complexes.
- Authors: Mina Mazzeo; Florence Isnard, Claudio Pellecchia, Marina Lamberti
  Abstract: Abstract: Two dinuclear aluminum alkyl complexes bearing salen ligand with alkyl backbone of different length between the nitrogen atoms (1,3-propylene (1) and 1,5-pentylene (2)) and the related hemi-salen aluminum complex (3) were tested as catalysts in the ring-opening copolymerization of cyclohexene oxide (CHO) and limonene oxide (LO) with succinic anhydride (SA) and phthalic anhydride (PA). The eﬀects of diﬀerent reaction conditions (cocatalyst and reaction solvent) on the productivity and selectivity of the reactions were evaluated. The comparison of the catalytic behavior of the dinuclear complexes bearing the aluminum reactive centers at different distances as well as of their mononuclear counterpart suggested that the copolymerization follows a monometallic pathway differently from what observed in the homopolymerization of CHO.
  PubDate: 2017-03-25T01:05:32.162374-05:
  DOI: 10.1002/cctc.201700234
Graphene Quantum Dot Modified Fe3O4 Nanoparticles Stabilize PdCu
- Authors: Mohammad Gholinejad; Jahantab Ahmadi, Carmen Nájera, Mohammad Seyedhamzeh, Fatemeh Zareh, Mohsen Kompany-Zareh
  Abstract: In this report, Fe3O4 nanoparticles are modified for the first time with graphene quantum dots (GQD) and used for the stabilization of PdCu bimetallic nanoparticles. The new magnetic compound, PdCu@GQD@Fe3O4, is characterized by different methods such as SEM, high-resolution (HR)-TEM, energy-dispersive X-ray spectroscopy (EDS) mapping, XRD, and X-ray photoelectron spectroscopy (XPS). This material is applied as an efficient catalyst for the Sonogashira reaction of aryl iodides, bromides, and chlorides in toluene or N,N-dimethylacetamide at 60–110 °C in very high yields with 0.3 mol % of Pd loading. According to different tests, such as polyvinylpyridine poisoning, hot filtration, and kinetic studies, this catalyst works under heterogeneous conditions. By magnetic separation of the catalyst, it can be recycled for six consecutive runs with only a small decrease in activity without appreciable structural modification of the reused catalyst, which is characterized by TEM and XPS.Going dotty: Fe3O4 nanoparticles modified with graphene quantum dots (GQD) are used for the stabilization of PdCu bimetallic nanoparticles. This material is applied as an efficient catalyst for the Sonogashira reaction of aryl iodides, bromides, and chlorides in toluene or N,N-dimethylacetamide at 60–110 °C in very high yields with 0.3 mol % of Pd loading.
  PubDate: 2017-03-24T07:40:52.601311-05:
  DOI: 10.1002/cctc.201601519
High-Yield Synthesis of Ethyl Lactate with Mesoporous Tin Silicate
Catalysts Prepared by an Aerosol-Assisted Sol–Gel Process
- Authors: Nicolas Godard; Alvise Vivian, Luca Fusaro, Lorenzo Cannavicci, Carmela Aprile, Damien P. Debecker
  Abstract: An aerosol-assisted sol–gel method is used to prepare mesoporous tin silicate catalysts that exhibit a record activity in the synthesis of ethyl lactate from dihydroxyacetone and ethanol. The method is based on the formation of an aerosol from a solution of precursors and surfactant. During the fast drying of the droplets, the surfactant self-assembles and the Sn-silica matrix is formed by polycondensation reactions. After calcination, the resulting material is composed of a true tin-silicon mixed oxide in the form of spherical microparticles with calibrated mesopores of 5–6 nm. Sn species are incorporated in the silica network, mainly in the form of single sites. This makes these catalysts highly active for the targeted reaction, as shown by record turnover numbers. The catalyst is recyclable and truly heterogeneous as it can be reused for several cycles and it does not leach.Get the most from mixed oxides: An aerosol-assisted sol–gel method is used to prepare mesoporous tin silicate catalysts that exhibit a record activity in the synthesis of ethyl lactate from dihydroxyacetone and ethanol.
  PubDate: 2017-03-24T03:32:35.636061-05:
  DOI: 10.1002/cctc.201601637
A Sol–Gel Ruthenium–Niobium–Silicon Mixed-Oxide Bifunctional
Catalyst for the Hydrogenation of Levulinic Acid in the Aqueous Phase
- Authors: Luciana Minieri; Serena Esposito, Vincenzo Russo, Barbara Bonelli, Martino Di Serio, Brigida Silvestri, Alessandro Vergara, Antonio Aronne
  Abstract: A mixed-oxide nanomaterial with composition (RuO2)0.038(Nb2O5)0.024(SiO2)0.938 was prepared by a one-pot sol–gel route. The synthesis was entirely performed at room temperature, by using easy-to-handle precursors and avoiding the employment of any toxic and/or polluting reactant. One of the samples was synthesised in the presence of a non-ionic surfactant acting as both pore directing agent and metal complexing agent, obtaining a high-specific-surface-area material characterized by a very good dispersion of the metallic species. In both cases, nanomaterials characterized by a complete reducibility of Ru species were obtained. The reduced nanomaterials acted as effective bifunctional catalysts in the hydrogenation of levulinic acid (LA) to γ-valerolactone, performed under mild conditions in the aqueous phase. The catalyst prepared without surfactant showed good stability and no activity loss during all the performed cycles. By contrast, some deactivation phenomena took place with the surfactant-templated catalyst. These phenomena were ascribed to both the partial surface oxidation and the surface adsorption of LA molecules giving deactivation during the second run.Cooperation is better: A (RuO2)0.038(Nb2O5)0.024(SiO2)0.938 bifunctional catalyst was prepared by a one-pot sol–gel route. The presence of both acid and hydrogenation functionalities leads to an active, selective and stable catalyst for the conversion of levulic acid into γ-valerolactone.
  PubDate: 2017-03-24T03:23:31.848869-05:
  DOI: 10.1002/cctc.201601547
Selective Oxidation of n-Butane and Isobutane Catalyzed by Boron Nitride
- Authors: Juan M. Venegas; Joseph T. Grant, William P. McDermott, Samuel P. Burt, Jack Micka, Carlos A. Carrero, Ive Hermans
  Abstract: Hexagonal boron nitride (hBN) is presented as an outstanding catalyst for the selective production of C4 olefins by the oxidative dehydrogenation of n-butane and isobutane. Unlike catalysts reported previously, hBN limits the amount of undesired COx and instead forms C2 and C3 olefins as the main side products. Kinetic experiments suggest a mechanism in which the rates of n-butane and isobutane consumption are dependent on O2 adsorption. Kinetic and spectroscopic insights are used to formulate mechanistic hypotheses for the formation mechanisms of C2–C4 olefins.Catalysis by boron nitride: The oxidative dehydrogenation of n-butane and isobutane is catalyzed by hexagonal boron nitride. This material shows a remarkable selectivity towards C4 olefins with only a minimal production of CO and CO2. C−C bond cleavage reactions to form ethene and propene become particularly significant under oxygen-lean conditions.
  PubDate: 2017-03-24T03:15:38.910356-05:
  DOI: 10.1002/cctc.201601686
Selectively Converting Biomass to Jet Fuel in Large-scale Apparatus
- Authors: Jie Li; Jian Sun, Ronggang Fan, Yoshiharu Yoneyama, Guohui Yang, Noritatsu Tsubaki
  Abstract: Jet fuel is not easy to synthesize by the biomass-to-liquid (BTL) process owing to the limitation of the Anderson–Schulz–Flory (ASF) hydrocarbon distribution law in Fischer–Tropsch synthesis (FTS) with biomass-derived syngas (CO+H2). Here, we realized an anti-ASF distribution to selectively produce jet fuel from biomass on a large scale by addition of small amounts of 1-olefin, a FTS product, into syngas, enhancing jet fuel selectivity in hydrocarbons up to 64 % and that in oil product to as high as 91 %. The Co/SiO2 catalyst (300 g) was loaded into a flow-type three-phase reactor and 120 h continuous operation was conducted by using the real-time on-line biomass-derived syngas from an entrained bed gasifier of biomass (240 kg day−1) of Mitsubishi Heavy Industries, Ltd. The production rate of liquid oil reached 720 g kgcat−1 h−1. The structure of the fresh and used catalyst was characterized in detail, accompanied with lab-scale data on reaction performance and catalyst properties. The stable technology process from biomass gasification to FTS, stable catalyst structure, and novel design of 1-olefin addition are the key to success in selectively converting biomass to jet fuel on a large scale.Leaving on a jet plane: Jet fuel is not easy to synthesize by biomass–to–liquid processes owing to the limitation of the Anderson–Schulz–Flory (ASF) hydrocarbon distribution law in Fischer–Tropsch synthesis (FTS). Thus, anti-ASF distribution is realized to selectively produce jet fuel from biomass on a large scale by addition of small amounts of 1-olefin, a FTS product, into syngas derived from woods, enhancing jet fuel selectivity in hydrocarbons up to 64 % and that in oil product to as high as 91 %.
  PubDate: 2017-03-24T03:15:32.729711-05:
  DOI: 10.1002/cctc.201700059
Three-dimensional probing of catalyst ageing on different length scales: A
case study of changes in microstructure and activity for CO oxidation of a
Pt-Pd/Al2O3 catalyst
- Authors: Torben Nilsson Pingel; Sheedeh Fouladvand, Marc Heggen, Rafal E. Dunin-Borkowski, Wolfgang Jäger, Peter Westenberger, Daniel Phifer, Jace McNeil, Magnus Skoglundh, Henrik Grönbeck, Eva Olsson
  Abstract: In the present study the effects of thermal treatment on the microstructure of a Pt-Pd/Al2O3 oxidation catalyst and its activity for CO oxidation have been studied. The microstructural analysis was performed using several high-resolution electron microscopy techniques like STEM, FIB/SEM slice & view, SEM and EDX. A combination of these analysis techniques and advanced TEM specimen preparation allowed for three-dimensional probing at different length scales avoiding the random character of conventionally crushed powder specimens due to site specificity. A core-shell distribution of Pt-Pd nanoparticles within the alumina support particles, with enlarged nanoparticles (≈ 1.5 to 40 nm) being present in the shell and small nanoparticles (< 1.5 nm) in the core, was revealed in the untreated catalyst. A more uniform spatial distribution developed during thermal treatment at 700 °C or higher with larger nanoparticles forming in the core. Accompanying measurements of the catalytic activity for CO oxidation showed the detrimental effect of sintering of the small nanoparticles on the reaction rate and apparent activation energy of the reaction.
  PubDate: 2017-03-23T22:05:42.298022-05:
  DOI: 10.1002/cctc.201700479
Peptide FlgA3 Based AuPd Bimetallic Nanoparticles toward Oxygen Reduction
Reaction in Alkaline Solution
- Authors: Dongliang Li; Zhenghua Tang, Shaowei Chen, Yong Tian, Xiufang Wang
  Abstract: Given the synergetic properties from different metal species, bimetallic nanoparticles are of immerse scientific interests and technological importance in catalytic field. Peptide based method represents a new avenue to fabricate bimetallic nanocatalysts with controllable size, shape, composition and subtle surface microstructure. However, the electrocatalytic capability of these peptide based bimetallic nanoparticles remained largely unexplored. Herein, by employing peptide sequence FlgA3, a series of AuPd alloys were fabricated and subjected as catalysts toward oxygen reduction reaction (ORR). Among a series of samples tested, the Au33Pd67 sample exhibited the best activity, evidenced by the most positive onset potential and largest diffusion-limited current. Notably, the ORR activity of the Au33Pd67 sample was comparable with that of commercial Pt/C, while the long-term durability was significantly superior than Pt/C. The study suggests that peptide enabled approach might pave a pathway for fabricating bimetallic nanomaterials with enhanced electrocatalytic properties under mild conditions.
  PubDate: 2017-03-23T22:05:39.104111-05:
  DOI: 10.1002/cctc.201700299
Core/Shell Structured NiS2@Ni-Bi Nanoarray for Efficient Water Oxidation
at Near-Neutral pH
- Authors: Xuping Sun
  Abstract: The development of high-performance and cost-effective water oxidation catalysts operating under mild conditions is attractive for the conversion of electricity into chemical fuels. In this communication, we report the in situ electrochemical development of Ni-Bi layer (5-8 nm in thickness) on NiS2 nanoarray supported on carbon cloth (NiS2@Ni-Bi/CC) for efficient water oxidation in 0.1 M potassium borate electrolyte at pH 9.2. As a durable 3D catalyst electrode, such core/shell structured NiS2@Ni-Bi/CC shows excellent catalytic activity for water oxidation approaching a geometrical catalytic current density of 20 mA cm-2 at an overpotential of 486 mV, with long-term electrochemical stability for at least 24 h with a high turnover frequency of 0.28 mol O2 s-1 at the overpotential of 500 mV and nearly 100% Faradic efficiency for oxygen evolution.
  PubDate: 2017-03-23T22:05:28.80999-05:0
  DOI: 10.1002/cctc.201700350
Nitrogen-Doped Carbon Encapsulated Nickel/Cobalt Nanoparticle Catalysts
for Olefin Migration of Allylarenes
- Authors: Søren Kramer; Jerrik Mielby, Kasper Buss, Takeshi Kasama, Soeren Kegnaes
  Abstract: Olefin migration of allylarenes is typically performed with precious metal-based homogeneous catalysts. In contrast, very limited progress has been made using cheap, earth-abundant base metals as heterogeneous catalysts for these transformations - in spite of the obvious economic and environmental advantages. Herein, we report on the use of an easily prepared heterogeneous catalyst material for the migration of olefins, in particular allylarenes. The catalyst material consists of nickel/cobalt alloy nanoparticles encapsulated in nitrogen-doped carbon shells. The encapsulated nanoparticles are stable in air and easily collected by centrifugation, filtration, or magnetic separation. Furthermore, we demonstrate that the catalysts can be reused several times providing continuously high yields of the olefin migration product.
  PubDate: 2017-03-23T10:05:40.007916-05:
  DOI: 10.1002/cctc.201700316
Role of Composition and Size of Cobalt Ferrite Nanocrystals in the Oxygen
Evolution Reaction
- Authors: Kalapu Chakrapani; Georg Bendt, Hamidreza Hajiyani, Ingo Schwarzrock, Thomas Lunkenbein, Soma Salamon, Joachim Landers, Heiko Wende, Robert Schlögl, Rossitza Pentcheva, Malte Behrens, Stephan Schulz
  Abstract: Sub-10 nm CoFe2O4 nanoparticles with different sizes and various compositions obtained by (partial) substitution of Co with Ni cations have been synthesized using a one-pot method from organic solutions by decomposition of metal acetylacetonates in the presence of oleyl amine. The electro catalytic activity of CoFe2O4 towards the oxygen evolution reactions (OER) is clearly enhanced with smaller size (3.1 nm) of the CoFe2O4 nanoparticles (as compared to 4.5 and 5.9 nm). In addition, the catalytic activity is improved by partial substitution of Co with Ni, which also leads to a higher degree of inversion of the spinel structure. Theoretical calculations explain the positive catalytic effect of Ni by lower binding energy differences between adsorbed O and OH as compared to pure cobalt or nickel ferrites, resulting in higher OER activity. Co0.5Ni0.5Fe2O4 exhibited a low overpotential of ~340 mV at 10 mA cm 2, a smaller Tafel slope of 51 mV dec-1 and stability over 30h. The unique tunability of these CoFe2O4 nanocrystals provide great potential for their application as an efficient and competitive anode material in the field of electrochemical water splitting as well as for systematic fundamental studies aiming at understanding the correlation of composition and structure with performance in electrocatalysis.
  PubDate: 2017-03-23T09:05:37.642776-05:
  DOI: 10.1002/cctc.201700376
Spherical Boron Nitride Supported Gold–Copper Catalysts for the
Low-Temperature Selective Oxidation of Ethanol
- Authors: Yang Wang; Lei Shi, Wenduo Lu, Qiang Sun, Zifeng Wang, Chunyi Zhi, An-Hui Lu
  Abstract: The oxidation of ethanol to acetaldehyde in the fine-chemical industry is a burgeoning process that requires leading-edge technology. A major challenge is to find a catalyst with high ethanol conversion and high acetaldehyde selectivity at a high gas hourly space velocity (GHSV) and a low operation temperature. Boron nitride nanosphere supported Au–Cu nanoparticles offer much opportunity for low-temperature ethanol oxidation. A catalytic ethanol conversion of 77 % and a selectivity of 94 % towards acetaldehyde were achieved at a temperature of 180 °C and a high GHSV of 100 000 mL gcat−1 h−1, values that far exceed those obtained with Au–Cu/SiO2. The immobilized Au–Cu nanoparticles have an average size of approximately 3 nm, and the majority of Au species are assigned Auδ−. The weak interaction of acetaldehyde with both Au–Cu active phases and the boron nitride support facilitates the adsorption–desorption behavior of acetaldehyde. As a result, the progression of secondary reactions is slowed and the degree of coverage of the active sites is minimized.Avoiding the heat: A boron nitride nanosphere-supported gold–copper catalyst is synthesized for the selective oxidation of ethanol to acetaldehyde. This catalyst exhibits excellent activity and selectivity at a high gas hourly space velocity and a low operation temperature owing to its unique geometric and electronic structures.
  PubDate: 2017-03-23T09:00:24.282229-05:
  DOI: 10.1002/cctc.201700002
Spatial Distribution of the Vanadium Atomic Species in MoVTeO and MoVTeNbO
Oxide Catalysts as Revealed by High-Angle Annular Dark-Field Scanning
Transmission Electron Microscopy
- Authors: Thierry Epicier; Mimoun Aouine, Thi Thao Nguyen, Jean-Marc M. Millet
  Abstract: High-angle annular dark-field scanning transmission electron microscopy (STEM–HAADF) was used to characterize a light-alkane mild-oxidation catalyst corresponding to two different MoVTe(Nb)O M1 phases. For that purpose a semiautomatic integration routine was developed, which allows the analysis of several hundred atomic columns with a normalization procedure to quantitatively determine the vanadium content of mixed (V, Mo) crystallographic sites with a low statistical variability. The obtained results were compared with data previously obtained on other M1 phases with different compositions. The comparison showed that the V distribution over the sites was not strongly influenced by the presence or absence of niobium, the method of synthesis used, and the nature of the Te or Sb cations in the hexagonal channels, but depended mainly on the total V content of the phases. Extrapolation to low V content enabled a discussion on the possible location of the vanadium active sites.Probing the vanadium content: A light-alkane mild-oxidation catalyst corresponding to two different MoVTe(Nb)O M1 phases was characterized by high-angle annular dark-field scanning transmission electron microscopy (STEM–HAADF). Comparison with previous data reveals that the vanadium distribution depends mainly on the total V content of the phases.
  PubDate: 2017-03-23T08:55:24.790931-05:
  DOI: 10.1002/cctc.201601542
Ring-Opening Reaction of Furfural and Tetrahydrofurfuryl Alcohol on
Hydrogen-Predosed Iridium(1 1 1) and Cobalt/Iridium(1 1 1)
Surfaces
- Authors: Weiming Wan; Glen R. Jenness, Ke Xiong, Dionisios G. Vlachos, Jingguang G. Chen
  Abstract: The ring-opening of furfural is crucial for its conversion into value-added chemicals such as 1,5-pentanediol (1,5-PeD), an important polymer precursor. Ir-based catalysts have shown activity in ring-opening reactions, and the use of an oxophilic metal additive is reported to be beneficial. To better understand the effect of an oxophilic metal on Ir for the opening of the furan ring, a combination of DFT calculations and experimental surface science studies were performed to investigate the ring-opening of furfural and tetrahydrofurfuryl alcohol. The experimental results suggest that Co/Ir(1 1 1) has a higher ring-opening activity for an unsaturated furan ring, however, the difference in activities between Ir and Co/Ir(1 1 1) is insignificant for a saturated furan ring. The DFT results reveal that Co/Ir(1 1 1) has a stronger interaction with an unsaturated furan ring than Ir(1 1 1); both surfaces show a weaker interaction with the saturated furan ring, which causes the lower ring-opening activity than that of furfural.Selective surfaces: A study of the mechanism of the ring-opening reaction on Ir(1 1 1) and Co/Ir(1 1 1) surfaces is presented. Ir(1 1 1) has ring-opening activity for both furfural and tetrahydrofurfuryl alcohol, and Co/Ir(1 1 1) enhances the ring-opening of furfural. The interaction between the furan ring and the metal surface determines the activity of the ring-opening reaction.
  PubDate: 2017-03-23T08:40:35.075463-05:
  DOI: 10.1002/cctc.201601646
Water as Cosolvent: Nonviscous Deep Eutectic Solvents for Efficient
Lipase-Catalyzed Esterifications
- Authors: Nadia Guajardo; Habil Pablo Domínguez de María, Katherine Ahumada, Rodrigo A. Schrebler, Rodrigo Ramírez-Tagle, Fernando Crespo, Carlos Carlesi
  Abstract: The use of deep eutectic solvent (DES)/water mixtures were explored for the selective enzymatic synthesis of α-monobenzoate glycerol (α-MBG) from glycerol and benzoic acid as substrates. Experiments were performed with four DES, three of them containing choline chloride (ChCl), combined with urea (URA), glycerol (GLY), and ethylene glycol (ETA) (in all cases ChCl/HBD 1:2 mol ratio), and another one formed with methylammonium chloride and glycerol (MA/GLY 1:3 mol ratio). The best conversions (99 %) were achieved with immobilized lipase B from Candida antarctica (CAL-B) when ChCl/GLY was used as the solvent and the substrate at the same time. The use of water as a cosolvent (8 % v/v) led to a significant decrease in the viscosity of the DES, and full conversions were then reached. Reusability studies of the biocatalyst revealed a 37 % decrease in activity after the first batch, but the activity remained mostly constant for the rest of the cycles.Skills acquisition by solvents: Blends of deep eutectic solvents and water lead to less viscous media that enable lipase-catalyzed synthetic reactions and that dissolve substrates with different polarities. These blends show enzyme compatibility, retain their nonconventional nature, are nonviscous, and are excellent solubilizers for challenging substrates.
  PubDate: 2017-03-23T08:40:25.490124-05:
  DOI: 10.1002/cctc.201601575
Highly Active Gold and Gold-Palladium Catalysts Prepared by Colloidal
Methods in the Absence of Polymer Stabilizers
- Authors: Laura Abis; Simon Freakley, Georgios Dodekatos, David Morgan, Meenakshisundaram Sankar, Nikolaos Dimitratos, Qian He, Christopher Kiely, Graham John Hutchings
  Abstract: Catalytic properties and stability of Au nanoparticles are sensitive to factors such as the dimensions, shape and composition of the metal nanoparticles. Although colloidal methods provide an easy and quick way to synthesize supported metal catalysts, they typically involve using polymers such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) as steric stabilizers, which can sometimes be detrimental in subsequent catalytic reactions. Here we report the synthesis of supported gold and gold-palladium nanoparticles without the addition of stabilizing polymers. The catalysts prepared with and without the addition of polymers performed very similarly in the selective oxidation of glycerol and benzyl alcohol suggesting that polymers are not essential to make active catalysts for these reactions. Thus, this new stabilizer free method provides a facile and highly effective way of circumventing the inherent problems of polymer stabilizers when preparing gold and gold palladium catalysts.
  PubDate: 2017-03-23T07:50:02.666874-05:
  DOI: 10.1002/cctc.201700483
Concerted Catalysis in Tight Spaces: Palladium-Catalyzed Allylation
Reactions Accelerated by Accumulated Active Sites in Mesoporous Silica
- Authors: Ken Motokura; Marika Ikeda, Masayuki Nambo, Wang-Jae Chun, Kiyotaka Nakajima, Shinji Tanaka
  Abstract: The mesoporous silica surface was modified with a Pd-bisphosphine complex and/or a tertiary amine group for concerted acceleration of allylation reactions. Mesoporous silica-supported catalysts with 1.6 nm pore diameter showed a higher performance than nonporous or larger mesoporous silica-supported catalysts due to the accumulation of active sites into a confined space. In case of the reaction using allylic alcohol, the presence of the silanol group on the surface was quite effective: the turnover number (TON) of Pd was nine times more than that of the homogeneous Pd complex.
  PubDate: 2017-03-22T09:22:25.411423-05:
  DOI: 10.1002/cctc.201700439
Asymmetric Autoamplification in the Oxidative Kinetic Resolution of
Secondary Benzylic Alcohols Catalyzed by Manganese Complexes
- Authors: Evgenii Talsi; Denis Samsonenko, Konstantin Petrovich Bryliakov
  Abstract: Herewith, chiral Mn-aminopyridine complexes have been shown to catalyze the oxidation of alkylarenes to enantiomerically enriched 1-arylalkanols with hydrogen peroxide. The observed enantiomeric excess values result from the direct enantioselective benzylic C-H hydroxylation, accompanied by stereoconvergent oxidative kinetic resolution of the resulting alcohol. Testing several (S,S)-bipyrrolidine derived Mn complexes has revealed a novel catalyst (6) exhibiting the best kinetic resolution in the series (krel up to 8.8), along with sufficient reactivity and efficiency (> 1000 TN). The mechanistic study of the Mn mediated alcohol oxidation witnesses electrophilic active species ( = -1.2), with rate-limiting H abstraction (kH/kD = 2.2), followed by oxygen-rebound and dehydration of the resulting gem-diol to form the ketone. Intriguingly, while for the resolution of the relatively bulky 1,2-diphenylethanol, krel is virtually constant throughout the reaction, for less bulky alcohols, the krel increases with increasing conversion, in line with the rising optical purity of the 1-arylalkanol. The latter participates in the oxidation as an auxiliary ligand, assisting the chiral recognition. This effect is related to the previously described asymmetric autocatalysis and asymmetric autoinduction, but is not identical with either of those, which different is discussed. To unambiguously identify this effect, the term asymmetric autoamplification (chiral autoamplification) is proposed.
  PubDate: 2017-03-21T23:27:06.853337-05:
  DOI: 10.1002/cctc.201700438
Platinum-Catalyzed Multicomponent Alcoholysis/Hydrosilylation and
Bis-hydrosilylation of Alkynes with Dihydrosilanes
- Authors: Li-Wen Xu
  Abstract: A new type of hydrosilylation of alkynes controlled by platinum catalyst with a monophosphine ligand (called as TBSO-MOP) was presented in this work. The platinum-catalyzed multicomponent and sequential silylation of alkynes and alcohols with dihydrosilane, resulted in high stereoselective as well as high-yield construction of functional (E)-vinylsilyl ethers. Moreover, the one-pot bis-hydrosilylation of terminal alkynes with dihydrosilane was also achieved with the same platinum catalyst system in this work.
  PubDate: 2017-03-21T22:20:46.266151-05:
  DOI: 10.1002/cctc.201700390
Relationship between acid-base properties and the activity of ZrO2
catalysts for the Cannizzaro reaction of pyruvaldehyde to lactic acid
- Authors: Elise M. Albuquerque; Luiz E.P. Borges, Marco A. Fraga, Carsten Sievers
  Abstract: The Cannizzaro reaction of pyruvaldehyde to lactic acid is investigated in a flow reactor using ZrO2 catalysts with different structures and acid-base properties. The results show that the difference in crystalline structures of two ZrO2 polymorphs strongly affects the conversion of pyruvaldehyde. The monoclinic phase of zirconia is the most active for this reaction. A good correlation is observed between the reaction rate and the concentration of Lewis acid sites of sufficient strength, showing that these sites play a major role in the reaction. A reaction mechanism is proposed involving coordinatively unsaturated Zr4+ cations as sites for activating pyruvaldehyde molecules, while Zr4+-O2- pairs generate terminal OH groups through water dissociation.
  PubDate: 2017-03-21T16:21:47.019443-05:
  DOI: 10.1002/cctc.201700305
Vapor Phase Hydrogenolysis of Furanics Utilizing Reduced Cobalt Mixed
Metal Oxide Catalysts
- Authors: Taylor P Sulmonetti; Bo Hu, Zachary P Ifkovits, Sungsik Lee, Pradeep K. Agrawal, Christopher W Jones
  Abstract: Vapor phase hydrogenolysis of both furfuryl alcohol and furfural are investigated over reduced Co based mixed metal oxides derived from the calcination of layered double hydroxide precursors. Although a reduced cobalt aluminate sample displays promising selectivity towards 2-methylfuran (2-MF) production, the addition of an Fe dopant into the oxide matrix significantly enhances the activity and selectivity per gram of catalyst. Approximately 82% 2-MF yield is achieved at high conversion when furfuryl alcohol is fed into the reactor at 180 °C over the reduced 3Co-0.25Fe-0.75Al catalyst. Based on structural characterization studies including TPR, XPS, and in-situ XAS, it is suggested that Fe facilitates the reduction of Co, allowing for formation of more metallic species. Overall, this work demonstrates that non-precious metal catalysts offer promise for the selective conversion of a key biomass oxygenate to a proposed fuel additive.
  PubDate: 2017-03-21T07:21:14.544945-05:
  DOI: 10.1002/cctc.201700228
Efficient synthesis of furfuryl alcohol and 2-methylfuran from furfural
over mineral derived Cu/ZnO catalysts
- Authors: Xiaohai Yang; Xiaomin Xiang, Hongmei Chen, Hongyan Zheng, Yong-Wang Li, Yulei Zhu
  Abstract: Two kinds of typical mineral derived Cu/ZnO catalysts consisted of aurichalcite and zincian malachite were introduced for furfural hydrogenation to furfuryl alcohol and 2-methylfuran via a fixed-bed reactor. Under the proper reaction conditions, high yields of furfuryl alcohol (above 99%) and 2-methylfuran (94.5%) could be obtained over the aurichalcite Cu/ZnO catalyst (AC-CZ), while the best yield of 2-methylfuran was only 76.9% (0.5h-1) over the zincian malachite Cu/ZnO catalyst (ZM-CZ). The normalized productivity of 2-MF was 43.5mol*kgCu-1h-1 and 17.4mol*kgCu-1h-1 for AC-CZ and ZM-CZ respectively (LHSV=1.5h-1). Catalysts were characterized via XRD, Raman spectra, CO-IR, H2-TPR, N2O- titration, NH3-TPD and XPS. The much more excellent performance for furfural hydrogenation of AC-CZ was due to its higher dispersion of copper species, superior copper surface area, better surface acidity distribution and stronger Cu0-ZnO synergy. In addition, surface acidity of the catalysts seemed to contribute more obviously to 2-MF production than Cu surface area, but the optimized balance of them needed to be investigated systematically.
  PubDate: 2017-03-21T04:21:24.545041-05:
  DOI: 10.1002/cctc.201700279
Metal-Carbon Covalent Bonds Stabilized Palladium Nanoparticles as
Expeditious Heterogeneous Catalyst for Oxidative Dehydrogenation of
N-Heterocycles
- Authors: Xiao-Tao Sun; Jie Zhu, Yun-Tao Xia, Lei Wu
  Abstract: We reveal here the first dehydrogenation of nitrogen heterocycles catalyzed by a palladium nanocatalyst. The carbon-metal covalent bonds-stabilized nanoparticles were proved to be efficient for the dehydrogenation process in the existence of TBHP. A variety of N-heterocycles were transformed into functionalized quinolines with medium to excellent yields in water solvent under mild conditions with simple operation.
  PubDate: 2017-03-20T22:20:38.509549-05:
  DOI: 10.1002/cctc.201700370
Oleylamine stabilized copper(0) nanoparticles: Efficient and low cost
catalyst for the dehydrogenation of dimethylamine borane
- Authors: Saim Ozkar; Sibel Duman
  Abstract: Copper(0) nanoparticles, in situ generated from the reduction of copper(II) 2-ethylhexanoate during the dehydrogenation of dimethylamine borane (DMAB) at 50.0 ± 0.1 °C in toluene solution, are active catalyst in hydrogen generation from DMAB, but not very stable against agglomeration. Addition of 5.0 equivalent oleylamine (OAm) was found to stabilize copper(0) nanoparticles noticeably, while possessing high catalytic activity. Oleylamine stabilized copper(0) nanoparticles could be isolated from the solution and characterized by XRD, TEM, UV-vis, ATR-FTIR and 11B NMR spectroscopies. Our report also includes (i) comparative catalytic activities of copper(0) nanoparticles in the absence and presence of OAm depending on the initial [OAm]/[Cu] ratio, catalyst concentration, substrate concentration, and temperature, (ii) the catalytic lifetime of copper(0) nanoparticles in the absence and presence of OAm in the dehydrogenation of DMAB at 50.0 ± 0.1 °C, (iii) testing the isolability and reusability of copper(0) nanoparticles in the absence and presence of OAm in the dehydrogenation of DMAB, (iv) the results of quantitative kinetic poisoning experiments using 1,10-phenanthroline showing that copper(0) nanoparticles are kinetically competent catalyst in the dehydrogenation of DMAB.
  PubDate: 2017-03-20T02:06:12.836494-05:
  DOI: 10.1002/cctc.201700367
Access to (hetero)arylated selenophenes via palladium-catalysed Stille,
Negishi or Suzuki couplings or C-H bond functionalization reaction
- Authors: Aymen Skhiri; Ridha Ben Salem, Jean-Francois Soulé, Henri Doucet
  Abstract: (Hetero)aryl-substituted selenophenes exhibit important physical properties especially for optoelectronics. Palladium-catalysed coupling reactions currently represent the most efficient methods to prepare such (hetero)arylated selenophene derivatives. Initially, Stille coupling was the most efficient reaction for the synthesis of these compounds; however, over the last decade, Suzuki coupling is the most commonly employed coupling reaction. Recently, Pd-catalysed arylation via the C-H bond activation of selenophenes has proved to be a very convenient alternative method for the preparation of several arylated selenophenes as there is no need to prepare organometallic derivatives. In this review, the progress and substrate scope in the synthesis of both C2- and C3-arylated selenophenes via Pd-catalysis are summarized.
  PubDate: 2017-03-20T02:06:09.277504-05:
  DOI: 10.1002/cctc.201700256
Bifunctional Hierarchical Zeolite-Supported Silver Catalysts for the
Conversion of Glycerol to Allyl Alcohol
- Authors: Giacomo M. Lari; Zupeng Chen, Cecilia Mondelli, Javier Pérez-Ramírez
  Abstract: The establishment of suitable processes for the conversion of glycerol into allyl alcohol is hindered by the fast deactivation of solid acids in the dehydration of the substrate to acrolein and by the requirement of hydrogen donors to enhance the selectivity of the subsequent reduction step. In this work, silver nanoparticles deposited onto a hierarchical ZSM-5 zeolite are proved to be an effective bifunctional catalyst to conduct the two reactions in the gas phase and in the presence of hydrogen by using a continuous fixed-bed reactor. The acidic function was accomplished by using a ZSM-5 zeolite modified by facile alkaline and acid treatments, which decreased the amount of Lewis acid centers while preserving the amount of Brønsted acid centers, and introduced an auxiliary network of intracrystalline mesopores, thus boosting the selectivity to acrolein (62 %) and the resistance to coking. Upon screening of various metals supported on the aluminosilicate, silver was identified as a superior hydrogenation catalyst, enabling a relatively high activity with>50 % allyl alcohol selectivity. Tuning of the metal loading, temperature, pressure, and contact time led to 15 % yield of allyl alcohol, thus approaching the state-of-the-art transfer hydrogenation systems, and stable behavior for 100 h on stream. Our results highlight the advantage of conducting the two transformations over a bifunctional material rather than over two separate single-function solids.Coupling of Components: The conversion of glycerol into allyl alcohol is efficiently catalyzed by a bifunctional catalyst comprising silver nanoparticles supported on a hierarchical ZSM-5 zeolite. This material combines the high stability of the zeolite and the remarkable selectivity of the metal for the dehydration and hydrogenation steps, respectively.
  PubDate: 2017-03-15T09:15:39.089826-05:
  DOI: 10.1002/cctc.201601635
Understanding the Role of Gallium as a Promoter of Magnesium Silicate
Catalysts for the Conversion of Ethanol into Butadiene
- Authors: Juliana Velasquez Ochoa; Andrea Malmusi, Carlo Recchi, Fabrizio Cavani
  Abstract: In this study we explore the use of Ga as a new component in MgO-SiO2 catalysts for the Lebedev reaction (the one-pot conversion of ethanol to butadiene). Several characterisation techniques (XRD, temperature-programmed desorption of NH3, BET measurements, IR spectroscopy) and in situ spectroscopic studies (DRIFTS-MS) were performed with the aim to correlate the properties of the modified materials with the catalytic results. We concluded that the wet impregnation of Ga3+ on the MgO-SiO2 catalyst creates new Ga−O(H)−Si sites. These sites interact strongly with alcohol and not only facilitate its dehydrogenation to acetaldehyde and its transformation into the intermediate crotyl alcohol but also enhance the dehydration of the latter because of an improved acidity. However, an appropriate amount of gallium oxide is needed to avoid excessive acidity, which is conducive to an increased selectivity to ethylene.Feel the Lebedev: Gallium oxide is an activity and selectivity promoter for MgO-SiO2 catalysts for the direct transformation of ethanol into butadiene (Lebedev process).
  PubDate: 2017-03-15T09:15:36.718352-05:
  DOI: 10.1002/cctc.201601630
Production of Glucosamine from Chitin by Co-solvent Promoted Hydrolysis
and Deacetylation
- Authors: Jiaguang Zhang; Ning Yan
  Abstract: Production of renewable chemicals with established market and high value is highly desirable in biomass utilization. Herein, glucosamine, an amino sugar with various applications, was generated in a single step by the acid-catalyzed transformation of chitin. Aprotic polar solvents were mixed with water to promote the hydrolysis as well as the deacetylation reactions, significantly enhancing product yield and/or reducing the concentration and amount of acid catalyst required. By employing the optimized co-solvent system, glucosamine was achieved with 80 % yield at 175 °C in 1 h from ball-milled chitin, in sharp contrast with the pure water system with the same acid concentration in which less than 1 % glucosamine was obtained. Correlations between the promotional effect and various solvent property parameters were discussed and proposed, providing guidance on the choice of solvent for further optimization of the co-solvent system for similar applications.Food additives from chitin: Glucosamine, an amino sugar with various applications in medicine, nutritional supplements, food and beverages, was generated in high yield by co-solvent promoted, acid-catalyzed transformation of chitin in a one-step procedure. The optimized gave glucosamine in 80 % yield at 175 °C in 1 h from ball-milled chitin, in sharp contrast with the pure water system with the same acid concentration in which less than 1 % glucosamine was obtained.
  PubDate: 2017-03-15T03:00:45.891187-05:
  DOI: 10.1002/cctc.201601715
Substituent Effects in Molecular Ruthenium Water Oxidation Catalysts Based
on Amide Ligands
- Authors: Ahmed F. Abdel-Magied; Wael A. A. Arafa, Tanja M. Laine, Andrey Shatskiy, Markus D. Kärkäs, Björn Åkermark, Eric V. Johnston
  Abstract: The production of clean and sustainable energy is considered as one of the most urgent issues for our society. Mastering the oxidation of water to dioxygen is essential for the production of solar fuels. A study of the influence of the substituents on the catalytic activity of a series of mononuclear Ru complexes (2 a–e) based on a tetradentate ligand framework is presented. At neutral pH, using [Ru(bpy)3](PF6)3 (bpy=2,2’-bipyridine) as the terminal oxidant, a good correlation between the turnover frequency (TOF) and the Hammett σmeta parameters was obtained. Additionally, a general pathway for the deactivation of Ru-based catalysts 2 a–e during the catalytic oxidation of water through poisoning by carbon monoxide was demonstrated. These results highlight the importance of ligand design for fine-tuning the catalytic activity of water oxidation catalysts.R⋅⋅⋅u single? Single-site Ru complexes are synthesized and evaluated as water oxidation catalysts. The catalytic activity is enhanced by the presence of electron-donating groups, and a linear relationship between the Hammett parameters of the substituents and the turnover frequencies is established. A general pathway for deactivation of these Ru catalysts during water oxidation through poisoning by CO is also established.
  PubDate: 2017-02-24T05:10:25.306506-05:
  DOI: 10.1002/cctc.201601382
Coke-Tolerant Gadolinium-Promoted HZSM-5 Catalyst for Methanol Conversion
into Hydrocarbons
- Authors: Sungtak Kim; Yong Tae Kim, Ahron Hwang, Ki-Won Jun, Geunjae Kwak
  Abstract: The role of Gd as a coke inhibitor was studied for the methanol-to-hydrocarbons reaction. It was revealed that thin films of gadolinium oxide covered the ZSM-5 crystals and that the Gd atoms that were uniformly dispersed on the surface enhanced the basicity of the parent ZSM-5. These synergetic effects improved the durability of the acidic function and diminished the growth of coke precursors, which resulted in an increased lifetime of the catalyst.Release your inhibitions: The role of Gd as a coke inhibitor is studied for the methanol-to-hydrocarbons reaction. Thin films of gadolinium oxide cover the ZSM-5 crystals and decrease the rate of formation of coke species, and uniformly distributed Gd atoms in the pores of ZSM-5 help to modify the surface acid–base properties. These synergetic effects help to improve the lifetime of the H-ZSM-5catalyst.
  PubDate: 2017-02-24T05:05:34.320203-05:
  DOI: 10.1002/cctc.201601559
The Role of Ruthenium on Carbon-Supported PtRu Catalysts for
Electrocatalytic Glycerol Oxidation under Acidic Conditions
- Authors: Youngmin Kim; Hyun Woo Kim, Seonhwa Lee, Jisu Han, Daewon Lee, Jeong-Rang Kim, Tae-Wan Kim, Chul-Ung Kim, Soon-Yong Jeong, Ho-Jeong Chae, Beom-Sik Kim, Hyunju Chang, Won Bae Kim, Sung Mook Choi, Hyung Ju Kim
  Abstract: A series of binary PtRu catalysts with different Pt/Ru atomic ratios (from 7:3 to 3:7) were synthesized on a carbon support using the colloidal method; they were then used for electrooxidation of glycerol in acid media. X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy analyses were used to investigate particle size, size distribution, and structural and electronic properties of the prepared catalysts. Ru added to the Pt-based catalysts caused structural and electronic modifications over the PtRu alloy catalyst formation. The electrocatalytic activities of PtRu/C series catalysts were investigated using cyclic voltammetry. The Pt5Ru5/C catalyst shows enhanced catalytic activity at least 40 % higher than that of the Pt/C catalyst, with improved stability for glycerol electrooxidation; these improvements are attributed to structural and electronic modifications of the Pt catalysts. Using an electrocatalytic batch reactor, product analysis after the oxidation reaction was performed by high-performance liquid chromatography to determine and compare the reaction pathways on the Pt/C and PtRu/C catalysts. To understand different catalytic activities of glycerol oxidation on the PtRu alloy surfaces, density functional calculations were performed.Atomic ratio inspected: Reaction product analysis and density functional calculations unveil the promotional effects of ruthenium addition to Pt/C catalysts for glycerol electrooxidation in acid media. The role of structurally and electronically modified PtRu surfaces in glycerol binding and bond breaking is evidenced.
  PubDate: 2017-02-23T04:35:43.646855-05:
  DOI: 10.1002/cctc.201601325
Octyl Co-grafted PrSO3H/SBA-15: Tunable Hydrophobic Solid Acid Catalysts
for Acetic Acid Esterification
- Authors: Jinesh C. Manayil; Vannia C. dos Santos, Friederike C. Jentoft, Marta Granollers Mesa, Adam F. Lee, Karen Wilson
  Abstract: Propylsulfonic acid (PrSO3H) derivatised solid acid catalysts have been prepared by post-modification of mesoporous SBA-15 silica with mercaptopropyltrimethoxysilane (MPTMS), and the impact of co-derivatisation with octyltrimethoxysilane (OTMS) groups to impart hydrophobicity to the catalyst was investigated. Turnover frequencies (TOFs) for acetic acid esterification with methanol increase with PrSO3H surface coverage across both families, suggesting a cooperative effect between adjacent acid sites at high acid site densities. Esterification activity is further promoted upon co-functionalisation with hydrophobic octyl chains, with inverse gas chromatography (IGC) measurements indicating that the increased activity correlates with decreased surface polarity or increased hydrophobicity.Propylsulfonic acid (PrSO3H) derivatized solid acid catalysts were prepared by post-modification of mesoporous SBA-15 silica with mercaptopropyltrimethoxysilane (MPTMS) and octyltrimethoxysilane (OTMS). Turnover frequencies (TOFs) for acetic acid esterification with methanol increase with PrSO3H surface coverage. Inverse gas chromatography measurements show that increased activity correlates with decreased surface polarity or increased hydrophobicity.
  PubDate: 2017-02-15T15:20:46.601393-05:
  DOI: 10.1002/cctc.201601370
Role of Water in Catalyzing Proton Transfer in Glucose Dehydration to
5-Hydroxymethylfurfural
- Authors: Feng Zhou; Xiang Sun, Di Wu, Yugen Zhang, Haibin Su
  Abstract: 5-Hydroxymethylfurfural (HMF) is one of the most important and versatile biomass-derived platform chemicals for the synthesis of a wide range of industrial chemicals, including biofuels. HMF can be obtained by dehydration of glucose with acid catalysts. The conversion proceeds through two steps, that is, glucose–fructose isomerization and dehydration of fructose to HMF. During the first step, water plays an important role as a proton shuttle to promote the reaction and reduce the energy barriers, which results in the acceleration of the reaction. Besides, water can also block the side reaction. The role of water joining and catalyzing the reaction is further proved by experimental findings, that is, by using DMSO/D2O as solvent deuterium was found at C1 of HMF from NMR analysis.Water shuttle for proton transfer: Water plays a substantial role, functioning as a proton shuttle to promote the conversion of glucose–fructose isomerization and reduce the energies of the transition states, which results in the acceleration in the reaction.
  PubDate: 2017-02-15T15:20:32.319434-05:
  DOI: 10.1002/cctc.201601522
From Active-Site Models to Real Catalysts: Importance of the Material Gap
in the Design of Pd Catalysts for Methane Oxidation
- Authors: Hieu A. Doan; Munish K. Sharma, William S. Epling, Lars C. Grabow
  Abstract: Rapid computational screening to aid novel catalyst design has evolved into an important and ubiquitous tool in modern heterogeneous catalysis. A possible shortcoming of this approach, however, is the material gap, that is, simplified computational models used for catalyst screening do not always capture the complexity of real catalytic systems. Here we investigate the importance of the material gap for complete methane oxidation over supported Pd/γ-Al2O3 catalysts using a combination of DFT simulations and temperature-programmed oxidation experiments. The Pd/γ-Al2O3 active site was approximated by four models of increasing complexity, namely Pd(1 0 0), Pd(2 1 1), PdO(1 0 1), and Pd10/γ-Al2O3(1 1 0), and each was also modified with metal promoters to discover reactivity trends. Although the unpromoted Pd model surfaces exhibit different methane activation activities, our DFT results indicate that an experimentally verified performance trend can be predicted for their promoted counterparts irrespective of the active-site representation. We attribute the robustness of the trend predictions in this particular system to localized changes in the electron density during methane activation. Overall, our work supports the commonly practiced active-site model simplifications during computational catalyst screening and provides fundamental insight into the qualitative agreement between theory and experiment for methane oxidation over promoted Pd catalysts.Model and experiment shake hands: Consistent trends are found for methane activation over a series of modified Pd/γ-Al2O3 catalyst computational models, which are in agreement with experimental activity measurements. This supports the common practice of using simplified catalyst representations for computational catalyst screening.
  PubDate: 2017-02-14T06:05:32.527941-05:
  DOI: 10.1002/cctc.201601333
Guerbet Reaction over Strontium-Substituted Hydroxyapatite Catalysts
Prepared at Various (Ca+Sr)/P Ratios
- Authors: Lishil Silvester; Jean-François Lamonier, Carole Lamonier, Mickaël Capron, Rose-Noëlle Vannier, Anne-Sophie Mamede, Franck Dumeignil
  Abstract: The Guerbet reaction of ethanol to heavier products was performed over a series of extensively characterized Sr-substituted hydroxyapatites (HAPs) with different (Ca+Sr)/P ratios, and thus different structural, textural, and acid–base properties. The acid–base properties were correlated with the reactivity of the solids and an optimal ratio between the amount of acid and basic sites was determined (ca. 4), whereas the ethanol conversion was mainly depending on the specific surface area of the solids. The stoichiometric 100 mol % Sr-substituted sample (SrAp-100) was especially efficient in higher alcohols production, which can be illustrated by a total alcohol selectivity (76.4 %) higher than that of all the other solids at a 13 % ethanol isoconversion.One base, four acid sites: In the Guerbet reaction of ethanol to higher alcohols performed over a series of Sr-substituted hydroxyapatites, an optimal ratio of approximately four between the amount of acid and basic sites is determined.
  PubDate: 2017-02-14T02:55:32.962912-05:
  DOI: 10.1002/cctc.201601480
Direct C3-Arylation of 2 H-Indazole Derivatives with Aryl Bromides by
using Low Loading of a Phosphine-free Palladium Catalyst
- Authors: Fatma Belkessam; Mohand Aidene, Jean-François Soulé, Henri Doucet
  Abstract: The palladium-catalyzed direct arylation of 2 H-indazoles with aryl bromides for the preparation of 3-aryl-2 H-indazoles was found to proceed in high yields when using only 0.5–0.1 mol % Pd(OAc)2 catalyst and KOAc as inexpensive base. A wide variety of electron-deficient and electron-rich aryl bromides and also heteroaryl bromides has been successfully employed. Both electron-withdrawing and electron-donating substituents on the 2 H-indazoles are also tolerated. Moreover, the reaction can be performed in the “green” solvent cyclopentyl methyl ether.Direct indazole arylation: The palladium-catalyzed direct arylation of 2 H-indazoles with both electron-deficient and electron-rich aryl bromides for the preparation of 3-aryl-2 H-indazoles was found to proceed in high yields when using only 0.5–0.1 mol % of phosphine-free Pd(OAc)2 catalyst and KOAc as inexpensive base.
  PubDate: 2017-02-09T07:25:53.819047-05:
  DOI: 10.1002/cctc.201601420
Low-Temperature Preparation of a Mesoporous Silica Superbase by Employing
the Multifunctionality of a La2O3 Interlayer
- Authors: Ning Liu; Zhimin Wu, Meng Li, Shanshan Li, Zhantao Luo, Yongfei Li, Langsheng Pan, Yuejin Liu
  Abstract: A simple and effective approach for the preparation of the solid superbasic La2O3–SBA-15-supported KF (KF/La2O3–SBA-15) was developed by a low-temperature strategy. The KF/La2O3–SBA-15 with ordered mesostructure and a high base strength (H−=27.0) was realized at 350 °C in still air, which breaks the traditional method of thermally induced decomposition of basic metal nitrate derived species KNO3 under higher temperatures (>600 °C). The resultant mesoporous basic materials were adopted for the production of 1-methoxy-2-propanol from propylene oxide and methanol. It showed excellent catalytic performance exhibiting 93 % conversion of propylene oxide and 93 % selectivity to 1-methoxy-2-propanol. This performance is better than that over the catalysts without mesoporous silica despite having a higher KF content.Resisting the structural collapse: Mesostructured superbasic sites were generated by employing the formation of La2O3–SBA-15-supported KF through thermal treatment at a low activation temperature of 350 °C under air atmosphere.
  PubDate: 2017-02-08T09:00:46.512479-05:
  DOI: 10.1002/cctc.201601246
MFI Acid Catalysts with Different Crystal Sizes and Porosity for the
Conversion of Furanic Compounds in Alcohol Media
- Authors: Margarida M. Antunes; Sérgio Lima, Auguste Fernandes, Ana L. Magalhães, Patrícia Neves, Carlos M. Silva, Maria F. Ribeiro, David Chadwick, Klaus Hellgardt, Martyn Pillinger, Anabela A. Valente
  Abstract: Solid acid catalysts possessing MFI topology and different crystal sizes and porosities were explored for the conversion of carbohydrate-biomass-derived α-angelica lactone and 5-(hydroxymethyl)furfural, in 1-butanol at T=120–170 °C, to give levulinate esters and furanic ethers. Micro/mesoporous microcrystalline catalysts were prepared by post-synthesis base/acid treatments of ZSM-5 zeolite; the influence of the desilication (base) conditions on the material properties was investigated. A nanocrystalline ZSM-5 sample was synthesised by using hydrothermal, dynamic conditions and used as a reference material. A comparison of the catalytic performances of materials featuring different morphological, textural, and acid properties highlights a complex interplay between the acid and textural properties. The best-performing catalyst (MZS0.6) was obtained by post-synthesis-treatment; fairly good catalytic stability was confirmed by catalyst recycling, contact tests, and characterisation of the spent catalyst. MZS0.6 was compared with the macrorecticular ion-exchange resin Amberlyst-15, chosen as a benchmark solid acid catalyst, in the two reaction systems.Material changes: Zeolite ZSM-5 can be modified to improve the potential as a heterogeneous catalyst for the conversion of biomass-derived compounds. Solid acid catalysts possessing MFI topology and different crystal sizes and porosities were explored for the conversion of α-angelica lactone (AnL) and 5-(hydroxymethyl)furfural (HMF), in 1-butanol at T=120–170 °C, to give levulinate esters (LE) and furanic ethers.
  PubDate: 2017-02-06T04:41:02.804024-05:
  DOI: 10.1002/cctc.201601236
Cover Picture: Diastereoselective Radical-Type Cyclopropanation of
Electron-Deficient Alkenes Mediated by the Highly Active Cobalt(II)
Tetramethyltetraaza[14]annulene Catalyst (ChemCatChem 8/2017)
- Authors: Andrei Chirila; Braja Gopal Das, Nanda D. Paul, Bas de Bruin
  Pages: 1356 - 1356
  Abstract: The Front Cover shows [Co(MeTAA)], a fast metalloradical catalyst, rapidly approaching Earth's atmosphere like a comet. [Co(MeTAA)] means “comet” in Romanian (“Cometa”). Since Romania is the home country of the first author of this paper, and since [Co(MeTAA)] is faster than most other cobalt catalysts for olefin cyclopropanation reactions, a comet is the appropriate way to highlight this catalyst.In their Full Paper, A. Chirila, B. Gopal Das et al. describe the activity of [Co(MeTAA)], a cheap and easy to prepare metalloradical catalyst, in olefin cyclopropanation reactions using both diazo compounds and tosyl hydrazones as carbene precursors. Interestingly, the [Co(MeTAA)] catalyst is active enough to mediate carbene transfer from tosyl hydrazones even at room temperature. This intriguing fact triggers new investigations, and holds the promise to develop a series of new metalloradical ring-closing reactions. More information can be found in the Full Paper by A. Chirila, B. Gopal Das et al. on page 1413 in Issue 8, 2017 (
  DOI : 10.1002/cctc.201601568).
  PubDate: 2017-04-24T03:03:35.486307-05:
Inside Cover: Renewable Surfactants through the Hydroaminomethylation of
Terpenes (ChemCatChem 8/2017)
- Authors: Thiemo A. Faßbach; Tom Gaide, Michael Terhorst, Arno Behr, Andreas J. Vorholt
  Pages: 1357 - 1357
  Abstract: The Cover shows a cationic surfactant dispenser, on which the structures of the species involved in its catalytic synthetic route were scribbled.In their Communication, T. A. Faßbach et al. demonstrate that Rh/1,2-bis(diphenylphosphino)ethane can achieve extraordinarily high turnover frequencies (up to 739 mol mol−1 h−1) and regioselectivities (S=97 %) as catalytic system in the hydroaminomethylation of terpenes with conjugated 1,3-diene functionalities for the synthesis of renewable building blocks for surfactants. More information can be found in the Communication by T. A. Faßbach et al. on page 1359 in Issue 8, 2017 (
  DOI : 10.1002/cctc.201700097).
  PubDate: 2017-04-24T03:03:34.519391-05:
Diastereoselective Radical-Type Cyclopropanation of Electron-Deficient
Alkenes Mediated by the Highly Active Cobalt(II)
Tetramethyltetraaza[14]annulene Catalyst
- Authors: Andrei Chirila; Braja Gopal Das, Nanda D. Paul, Bas de Bruin
  Pages: 1413 - 1421
  Abstract: A new protocol for the catalytic synthesis of cyclopropanes using electron-deficient alkenes is presented, which is catalysed by a series of affordable, easy to synthesise and highly active substituted cobalt(II) tetraaza[14]annulenes. These catalysts are compatible with the use of sodium tosylhydrazone salts as precursors to diazo compounds in one-pot catalytic transformations to afford the desired cyclopropanes in almost quantitative yields. The reaction takes advantage of the metalloradical character of the Co complexes to activate the diazo compounds. The reaction is practical and fast, and proceeds from readily available starting materials. It does not require the slow addition of diazo reagents or tosylhydrazone salts or heating and tolerates many solvents, which include protic ones such as MeOH. The CoII complexes derived from the tetramethyltetraaza[14]annulene ligand are easier to prepare than cobalt(II) porphyrins and present a similar catalytic carbene radical reactivity but are more active. The reaction proceeds at 20 °C in a matter of minutes and even at −78 °C in a few hours. The catalytic system is robust and can operate with either the alkene or the diazo reagent as the limiting reagent, which inhibits the dimerisation of diazo compounds totally. The protocol has been applied to synthesise a variety of substituted cyclopropanes. High yields and selectivities were achieved for various substrates with an intrinsic preference for trans cyclopropanes.Cobalt on call: We present a new protocol for the synthesis of cyclopropanes using electron-deficient alkenes catalyzed by a series of affordable, easy to synthesize, and highly active substituted cobalt(II) tetraazaannulenes.
  PubDate: 2017-04-24T03:03:36.367466-05:
  DOI: 10.1002/cctc.201601568
Back Cover: Highly Efficient and Selective Catalytic Synthesis of
Quinolines Involving Transition-Metal-Doped Carbon Aerogels (ChemCatChem
8/2017)
- Authors: M. Godino-Ojer; A. J. López-Peinado, F. J. Maldonado-Hódar, E. Pérez-Mayoral
  Pages: 1517 - 1517
  Abstract: The Cover shows a Co0-doped carbon aerogel that can efficiently catalyze the Friedländer reaction to produce quinolines.In their Full Paper, M. Godino-Ojer et al. demonstrate that although the carbon matrix contributes to a certain extent to the catalytic performance, the predominant active catalytic species are the zero-valent transition-metal nanoparticles. More information can be found in the Full Paper by M. Godino-Ojer et al. on page 1422 in Issue 8, 2017 (
  DOI : 10.1002/cctc.201601657).
  PubDate: 2017-04-24T03:03:39.577611-05: