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  Subjects -> CHEMISTRY (Total: 894 journals)
    - ANALYTICAL CHEMISTRY (55 journals)
    - CHEMISTRY (628 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (28 journals)
    - INORGANIC CHEMISTRY (43 journals)
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    - PHYSICAL CHEMISTRY (71 journals)

CHEMISTRY (628 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 14)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 28)
ACS Catalysis     Hybrid Journal   (Followers: 44)
ACS Chemical Neuroscience     Hybrid Journal   (Followers: 22)
ACS Combinatorial Science     Hybrid Journal   (Followers: 23)
ACS Macro Letters     Hybrid Journal   (Followers: 26)
ACS Medicinal Chemistry Letters     Hybrid Journal   (Followers: 42)
ACS Nano     Hybrid Journal   (Followers: 303)
ACS Photonics     Hybrid Journal   (Followers: 14)
ACS Symposium Series     Full-text available via subscription  
ACS Synthetic Biology     Hybrid Journal   (Followers: 24)
Acta Chemica Iasi     Open Access   (Followers: 5)
Acta Chimica Slovaca     Open Access   (Followers: 2)
Acta Chimica Slovenica     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 8)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 7)
Acta Scientifica Naturalis     Open Access   (Followers: 3)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 8)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 9)
Adsorption Science & Technology     Open Access   (Followers: 6)
Advanced Functional Materials     Hybrid Journal   (Followers: 60)
Advanced Science Focus     Free   (Followers: 5)
Advances in Chemical Engineering and Science     Open Access   (Followers: 73)
Advances in Chemical Science     Open Access   (Followers: 18)
Advances in Chemistry     Open Access   (Followers: 23)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 19)
Advances in Drug Research     Full-text available via subscription   (Followers: 25)
Advances in Environmental Chemistry     Open Access   (Followers: 7)
Advances in Enzyme Research     Open Access   (Followers: 10)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 9)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 12)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 26)
Advances in Nanoparticles     Open Access   (Followers: 15)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 17)
Advances in Polymer Science     Hybrid Journal   (Followers: 45)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 3)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 8)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Al-Kimia : Jurnal Penelitian Sains Kimia     Open Access  
Alchemy : Journal of Chemistry     Open Access   (Followers: 3)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 69)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 22)
American Journal of Chemistry     Open Access   (Followers: 32)
American Journal of Plant Physiology     Open Access   (Followers: 11)
American Mineralogist     Hybrid Journal   (Followers: 16)
Anadolu University Journal of Science and Technology A : Applied Sciences and Engineering     Open Access  
Analyst     Full-text available via subscription   (Followers: 38)
Angewandte Chemie     Hybrid Journal   (Followers: 179)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 256)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 5)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 13)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Open Access   (Followers: 2)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 9)
Applied Spectroscopy     Full-text available via subscription   (Followers: 24)
Applied Surface Science     Hybrid Journal   (Followers: 32)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 3)
Asian Journal of Chemistry and Pharmaceutical Sciences     Open Access  
Atomization and Sprays     Full-text available via subscription   (Followers: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 3)
Avances en Quimica     Open Access  
Biochemical Pharmacology     Hybrid Journal   (Followers: 11)
Biochemistry     Hybrid Journal   (Followers: 376)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 11)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 2)
Biomacromolecules     Hybrid Journal   (Followers: 22)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 5)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 138)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 87)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 1)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 11)
Canadian Mineralogist     Full-text available via subscription   (Followers: 6)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 70)
Catalysis for Sustainable Energy     Open Access   (Followers: 8)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 7)
Catalysis Science and Technology     Free   (Followers: 8)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 11)
Cellulose     Hybrid Journal   (Followers: 9)
Cereal Chemistry     Full-text available via subscription   (Followers: 5)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 22)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 75)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 27)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Hybrid Journal   (Followers: 22)
Chemical Reviews     Hybrid Journal   (Followers: 204)
Chemical Science     Open Access   (Followers: 27)
Chemical Technology     Open Access   (Followers: 32)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 57)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 24)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 7)
Chemistry & Biology     Full-text available via subscription   (Followers: 33)
Chemistry & Industry     Hybrid Journal   (Followers: 8)
Chemistry - A European Journal     Hybrid Journal   (Followers: 166)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 16)
Chemistry and Materials Research     Open Access   (Followers: 21)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Open Access   (Followers: 3)
Chemistry Letters     Full-text available via subscription   (Followers: 45)
Chemistry of Materials     Hybrid Journal   (Followers: 266)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 20)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 1)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 12)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 11)
Chromatographia     Hybrid Journal   (Followers: 23)
Chromatography     Open Access   (Followers: 2)
Chromatography Research International     Open Access   (Followers: 6)
Cogent Chemistry     Open Access   (Followers: 2)
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 11)
Colloids and Interfaces     Open Access  
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 6)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 22)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Communications Chemistry     Open Access  
Composite Interfaces     Hybrid Journal   (Followers: 7)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 1)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 10)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 4)
Copernican Letters     Open Access   (Followers: 1)
Corrosion Series     Full-text available via subscription   (Followers: 7)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 8)
Croatica Chemica Acta     Open Access  
Crystal Structure Theory and Applications     Open Access   (Followers: 4)
CrystEngComm     Full-text available via subscription   (Followers: 13)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Chromatography     Hybrid Journal  
Current Green Chemistry     Hybrid Journal   (Followers: 1)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Microwave Chemistry     Hybrid Journal  
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 14)
Current Research in Chemistry     Open Access   (Followers: 9)
Current Science     Open Access   (Followers: 73)
Current Trends in Biotechnology and Chemical Research     Open Access   (Followers: 3)
Dalton Transactions     Full-text available via subscription   (Followers: 23)
Detection     Open Access   (Followers: 4)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)

        1 2 3 4 | Last

Journal Cover
Catalysts
Number of Followers: 11  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2073-4344
Published by MDPI Homepage  [205 journals]
  • Catalysts, Vol. 8, Pages 569: Switchable Stimuli-Responsive Heterogeneous
           Catalysis

    • Authors: Irene Vassalini, Ivano Alessandri
      First page: 569
      Abstract: Heterogeneous catalytic systems based on the use of stimuli-responsive materials can be switched from an “on” active state to an “off” inactive state, which contributes to endowing the catalysts with unique functional properties, such as adaptability, recyclability and precise spatial and temporal control on different types of chemical reactions. All these properties constitute a step toward the development of nature-inspired catalytic systems. Even if this is a niche area in the field of catalysis, it is possible to find in literature intriguing examples of dynamic catalysts, whose systematic analysis and review are still lacking. The aim of this work is to examine the recent developments of stimuli-responsive heterogeneous catalytic systems from the viewpoint of different approaches that have been proposed to obtain a dynamic control of catalytic efficiency. Because of the variety of reactions and conditions, it is difficult to make a quantitative comparison between the efficiencies of the considered systems, but the analysis of the different strategies can inspire the preparation of new smart catalytic systems.
      Citation: Catalysts
      PubDate: 2018-11-22
      DOI: 10.3390/catal8120569
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 570: Synthesis of Small-Sized SAPO-34 Crystals
           with Varying Template Combinations for the Conversion of Methanol to
           Olefins

    • Authors: Yanjun Zhang, Zhibo Ren, Yinuo Wang, Yinjie Deng, Jianwei Li
      First page: 570
      Abstract: SAPO-34 molecular sieves were synthesized under hydrothermal conditions using different combinations of tetraethyl ammonium hydroxide (TEAOH)/morpholine (Mor)/triethylamine (TEA) as templates, with different silicon:aluminum ratios. The physicochemical properties of the synthesized SAPO-34 were characterized using XRD, SEM, N2 adsorption–desorption, XRF, TG, NH3-TPD, FT-IR, and 29Si MAS NMR analyses. According to the SEM and the N2 adsorption–desorption of the catalysts produced by the ternary template exhibited a larger surface area and a smaller crystal size than those produced by the single or binary templates. The FT-IR analysis indicated the increased acidity of the catalyst prepared by the ternary template. A high activity and selectivity to olefins (C2= + C3=) and an optimal silicon to aluminum ratio of 0.4 were obtained from the catalyst synthesized with the ternary template. At the reaction temperature of 450 °C, the methanol conversion approached 100% and the ethylene–propylene selectivity and the lifetime of the catalyst reached maximums of 89.15% and 690 min, respectively.
      Citation: Catalysts
      PubDate: 2018-11-22
      DOI: 10.3390/catal8120570
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 571: Structural and Electrical Characterization
           of Sputter-Deposited Gd0.1Ce0.9O2−δ Thin Buffer Layers at the
           Y-Stabilized Zirconia Electrolyte Interface for IT-Solid Oxide Cells

    • Authors: Nunzia Coppola, Pierpaolo Polverino, Giovanni Carapella, Chiara Sacco, Alice Galdi, Alberto Ubaldini, Vincenzo Vaiano, Dario Montinaro, Luigi Maritato, Cesare Pianese
      First page: 571
      Abstract: The use of a doped Ceria buffer layer and Physical Vapour Deposition (PVD) techniques for Solid Oxide Fuel Cells (SOFC) fabrication can limit the former, the formation of electrical insulating lanthanum, and strontium zirconates at the cathode/electrolyte interface, whereas the latter allows a better control of the materials interfaces. These effects allow for operation at intermediate temperature ranges. In this work, we study the structural and electrical properties of Gadolinium Doped Ceria (GDC) barrier layer deposited via the room temperature RF Sputtering technique on anode supported electrolytes and then annealed at high temperature. The crystal structure and the surface morphology of the GDC barrier layers have been analyzed and optimized varying the temperature ramp of the post-growth annealing procedure. The electrical behavior of the obtained samples has been investigated by Electrochemical Impedance Spectroscopy and compared to that of standard SOFC with screen-printed GDC barrier layers, the former showing a maximum high frequency and low frequency resistances reduction of about 50% and 46%, respectively, with respect to the latter at an operating temperature of 650 °C. The results clearly show an important improvement of SOFC performances when using sputter deposited GDC layers, linking the electrical properties to the structural and stoichiometric ones.
      Citation: Catalysts
      PubDate: 2018-11-22
      DOI: 10.3390/catal8120571
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 572: Carbon-Black-Supported Ru Catalysts for the
           Valorization of Cellulose through Hydrolytic Hydrogenation

    • Authors: Maria Dolores Adsuar-García, Jhony Xavier Flores-Lasluisa, Fatima Zahra Azar, M. Carmen Román-Martínez
      First page: 572
      Abstract: The one-pot hydrolytic hydrogenation of cellulose (HHC) with heterogeneous catalysts is an interesting method for the synthesis of fuels and chemicals from a renewable resource like lignocellulosic biomass. Supported metal catalysts are interesting for this application because they can contain the required active sites for the two catalytic steps of the HHC reaction (hydrolysis and hydrogenation). In this work, Ru catalysts have been prepared using a commercial carbon black that has been modified by sulfonation and oxidation treatments with H2SO4 and (NH4)S2O8, respectively, in order to create acidic surface sites. The correlation between the catalysts’ properties and catalytic activity has been addressed after detailed catalyst characterization. The prepared catalysts are active for cellulose conversion, being that prepared with the carbon black treated with sulfuric acid the most selective to sorbitol (above 40%). This good behavior can be mainly explained by the suitable porous structure and surface chemistry of the carbon support together with the low content of residual chlorine.
      Citation: Catalysts
      PubDate: 2018-11-22
      DOI: 10.3390/catal8120572
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 573: Prominent Conductor Mechanism-Induced
           Electron Transfer of Biochar Produced by Pyrolysis of Nickel-Enriched
           Biomass

    • Authors: Wenbing Tan, Renfei Li, Hanxia Yu, Xinyu Zhao, Qiuling Dang, Jie Jiang, Lei Wang, Beidou Xi
      First page: 573
      Abstract: Biochar is redox-active and can function as a sustainable electron shuttle in catalyzing relevant redox reactions. It plays a crucial role in environmental remediation. In this work, we used different-nickel (Ni)-level biochars produced by the pyrolysis of plant biomass with correspondingly different Ni levels as extracellular electron shuttles for microbial reduction of ferrihydrite by Shewanella oneidensis MR-1. A high Ni level of the precursor considerably enhanced the conductor mechanism of the produced biochar and thus enabled the biochar to catalyze increased microbial reductions of the Fe(III) mineral, but it did not promote the charging and discharging capacities of the produced biochar. This study can aid in the search for natural biomass with high Ni content to establish low-cost biochars with wide-ranging applications in catalyzing the redox-mediated reactions of pollutants.
      Citation: Catalysts
      PubDate: 2018-11-22
      DOI: 10.3390/catal8120573
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 574: Oscillatory Behavior of Pd-Au Catalysts in
           Toluene Total Oxidation

    • Authors: Tarek Barakat, Joanna C. Rooke, Dayan Chlala, Renaud Cousin, Jean-François Lamonier, Jean-Marc Giraudon, Sandra Casale, Pascale Massiani, Bao-Lian Su, Stéphane Siffert
      First page: 574
      Abstract: In this work, the activity of bimetallic Pd-Au doped hierarchically structured titania catalysts has been investigated in the total oxidation of toluene. In earlier works, doping titania with group Vb metal oxides ensured an increased catalytic performance in the elimination of VOC molecules. A synergy between gold and palladium loaded at the surface of titania supports provided better performances in VOC oxidation reactions. Therefore, the main focus in this work was to investigate the durability of the prepared catalysts under long time-on-stream periods. Vanadium-doped catalysts showed a stable activity throughout the whole 110 h test, whereas, surprisingly, niobium-doped catalysts presented a cycle-like activity while nevertheless maintaining a high performance in toluene elimination. Operando Diffuse Reflectance Infrared Fourrier Transform spectroscopy (DRIFT) experiments revealed that variations in the presence of OH radicals and the presence of carbonaceous compounds adsorbed at the surface of spent catalysts varies with the occurrence of oscillations. X-ray Photoelectron Spectroscopy (XPS) results show that interactions between the material and the active phase provided extra amounts of mobile oxygen species and participated in easing the reduction of palladium. An enhanced redox reaction scheme is thus obtained and allows the occurrence of the cyclic-like performance of the catalyst.
      Citation: Catalysts
      PubDate: 2018-11-22
      DOI: 10.3390/catal8120574
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 575: Photocatalytic Degradation of Methylene Blue
           over TiO2 Pretreated with Varying Concentrations of NaOH

    • Authors: Chentao Hou, Bo Hu, Jiaming Zhu
      First page: 575
      Abstract: In this paper, different NaOH concentrations (2, 5, 10, and 15 M) were used to treat {001}TiO2. The effect of NaOH on the crystal structure, morphology, optical properties, light raw electronic-hole recombination, and degradation performance of {001}TiO2 on methylene blue were studied. The results demonstrate that rutile TiO2 appeared when the NaOH concentration was as high as 10 M, showing much better photolytic performance than others. As the concentration of sodium hydroxide increases, the morphology changes accordingly. The specific surface area increases and the optical electronic-hole recombination rate decreases. Radical scavenging tests showed that hydroxyl radical and hole are very important in photocatalysis.
      Citation: Catalysts
      PubDate: 2018-11-22
      DOI: 10.3390/catal8120575
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 576: Toward an Accurate Spectrophotometric
           Evaluation of the Efficiencies of Photocatalysts in Processes Involving
           Their Separation Using Nylon Membranes

    • Authors: Halema Al-Kandari, Peter Kasak, Ahmed M. Mohamed, Shekhah Al-Kandari, Dusan Chorvat Jr., Aboubakr M. Abdullah
      First page: 576
      Abstract: Many works include the use of nylon membranes to separate the solid particles of photocatalysts from the photocatalytic reactors, before using spectrophotometers to evaluate the catalysts’ performance in the photocatalytic degradation of many pollutants. This might lead to significant errors due to the adsorption of some pollutants within the structure of the membranes during the filtration process used to separate the solid particles of the photocatalysts to get a clear filtrate. This, consequently, leads to incorrect calculations, which in turn are translated into false high photocatalytic efficiencies of the used catalysts. In this work, the authors study the interaction between nylon membrane filters and five different model compounds—phenol red, methylene blue, rhodamine B, rhodamine 6G, and phenol. The study reveals a significant interaction between the nylon membranes and both rhodamine B and phenol red.
      Citation: Catalysts
      PubDate: 2018-11-22
      DOI: 10.3390/catal8120576
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 577: Identification of Key Amino Acid Residues
           Determining Product Specificity of 2,3-Oxidosqualene Cyclase in Siraitia
           grosvenorii

    • Authors: Jing Qiao, Jiushi Liu, Jingjing Liao, Zuliang Luo, Xiaojun Ma, Guoxu Ma
      First page: 577
      Abstract: Sterols and triterpenes are structurally diverse bioactive molecules generated through cyclization of linear 2,3-oxidosqualene. Based on carbocationic intermediates generated during the initial substrate preorganization step, oxidosqualene cyclases (OSCs) are roughly segregated into a dammarenyl cation group that predominantly catalyzes triterpenoid precursor products and a protosteryl cation group which mostly generates sterol precursor products. The mechanism of conversion between two scaffolds is not well understood. Previously, we have characterized a promiscuous OSC from Siraitia grosvenorii (SgCS) that synthesizes a novel cucurbitane-type triterpene cucurbitadienol as its main product. By integration of homology modeling, molecular docking and site-directed mutagenesis, we discover that five key amino acid residues (Asp486, Cys487, Cys565, Tyr535, and His260) may be responsible for interconversions between chair–boat–chair and chair–chair–chair conformations. The discovery of euphol, dihydrolanosterol, dihydroxyeuphol and tirucallenol unlocks a new path to triterpene diversity in nature. Our findings also reveal mechanistic insights into the cyclization of oxidosqualene into cucurbitane-type and lanostane-type skeletons, and provide a new strategy to identify key residues determining OSC specificity.
      Citation: Catalysts
      PubDate: 2018-11-22
      DOI: 10.3390/catal8120577
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 578: Policies and Motivations for the CO2
           Valorization through the Sabatier Reaction Using Structured Catalysts. A
           Review of the Most Recent Advances

    • Authors: Juan C. Navarro, Miguel A. Centeno, Oscar H. Laguna, José A. Odriozola
      First page: 578
      Abstract: The current scenario where the effects of global warming are more and more evident, has motivated different initiatives for facing this, such as the creation of global policies with a clear environmental guideline. Within these policies, the control of Greenhouse Gase (GHG) emissions has been defined as mandatory, but for carrying out this, a smart strategy is proposed. This is the application of a circular economy model, which seeks to minimize the generation of waste and maximize the efficient use of resources. From this point of view, CO2 recycling is an alternative to reduce emissions to the atmosphere, and we need to look for new business models which valorization this compound which now must be considered as a renewable carbon source. This has renewed the interest in known processes for the chemical transformation of CO2 but that have not been applied at industrial level because they do not offer evident profitability. For example, the methane produced in the Sabatier reaction has a great potential for application, but this depends on the existence of a sustainable supply of hydrogen and a greater efficiency during the process that allows maximizing energy efficiency and thermal control to maximize the methane yield. Regarding energy efficiency and thermal control of the process, the use of structured reactors is an appropriate strategy. The evolution of new technologies, such as 3D printing, and the consolidation of knowledge in the structing of catalysts has enabled the use of these reactors to develop a wide range of possibilities in the field. In this sense, the present review presents a brief description of the main policies that have motivated the transition to a circular economy model and within this, to CO2 recycling. This allows understanding, why efforts are being focused on the development of different reactions for CO2 valorization. Special attention to the case of the Sabatier reaction and in the application of structured reactors for such process is paid.
      Citation: Catalysts
      PubDate: 2018-11-22
      DOI: 10.3390/catal8120578
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 579: Environmental-Friendly Synthesis of Alkyl
           Carbamates from Urea and Alcohols with Silica Gel Supported Catalysts

    • Authors: Yubo Ma, Lei Wang, Xiaodong Yang, Ronghui Zhang
      First page: 579
      Abstract: TiO2/SiO2, Cr2O3-NiO/SiO2, and TiO2-Cr2O3/SiO2 were prepared by the impregnation method for alkyl carbamate synthesis using urea as the carbonyl source. Up to 97.5% methyl carbamate yield, 97% ethyl carbamate yield, and 96% butyl carbamate yield could be achieved, respectively. The catalysts were characterized by ICP-AES, BET, XRD, XPS, NH3-TPD, and EPMA. Catalytic activity investigation revealed that TiO2/SiO2, Cr2O3-NiO/SiO2, and TiO2-Cr2O3/SiO2 were effective catalysts for methyl carbamate (MC), ethyl carbamate (EC), and butyl carbamate (BC), respectively. The recycling tests suggested that these silica gel supported catalyst system is active, stable, and reusable. A total of 96–97% alkyl carbamate (methyl, ethyl, and butyl) could be obtained in a 2 L autoclave, and these data suggested that our catalyst system is relatively easy to scale up.
      Citation: Catalysts
      PubDate: 2018-11-23
      DOI: 10.3390/catal8120579
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 580: Mixed-Phase (2H and 1T) MoS2 Catalyst for a
           Highly Efficient and Stable Si Photocathode

    • Authors: Jemee Joe, Changdeuck Bae, Eunsoo Kim, Thi Anh Ho, Heejun Yang, Jong Hyeok Park, Hyunjung Shin
      First page: 580
      Abstract: We describe the direct formation of mixed-phase (1T and 2H) MoS2 layers on Si as a photocathode via atomic layer deposition (ALD) for application in the photoelectrochemical (PEC) reduction of water to hydrogen. Without typical series-metal interfaces between Si and MoS2, our p-Si/SiOx/MoS2 photocathode showed efficient and stable operation in hydrogen evolution reactions (HERs). The resulting performance could be explained by spatially genuine device architectures in three dimensions (i.e., laterally homo and vertically heterojunction structures). The ALD-grown MoS2 overlayer with the mixed-phase 1T and 2H homojunction passivates light absorber and surface states and functions as a monolithic structure for effective charge transport within MoS2. It is also beneficial in the operation of p-i-n heterojunctions with inhomogeneous barrier heights due to the presence of mixed-phase cocatalysts. The effective barrier heights reached up to 0.8 eV with optimized MoS2 thicknesses, leading to a 670 mV photovoltage enhancement without employing buried Si p-n junctions. The fast-transient behaviors via light illumination show that the mixed-phase layered chalcogenides can serve as efficient cocatalysts by depinning the Fermi levels at the interfaces. A long-term operation of ~70 h was also demonstrated in a 0.5 M H2SO4 solution.
      Citation: Catalysts
      PubDate: 2018-11-23
      DOI: 10.3390/catal8120580
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 581: Photoreduction of Carbon Dioxide to Methanol
           over Copper Based Zeolitic Imidazolate Framework-8: A New Generation
           Photocatalyst

    • Authors: Sonam Goyal, Maizatul Shima Shaharun, Chong Fai Kait, Bawadi Abdullah, Mariam Ameen
      First page: 581
      Abstract: The efficient reduction of CO2 into valuable products such as methanol, over metal-organic frameworks (MOFs) based catalyst, has received much attention. The photocatalytic reduction is considered the most economical method due to the utilization of solar energy. In this study, Copper (II)/Zeolitic Imidazolate Framework-8 (Cu/ZIF-8) catalysts were synthesized via a hydrothermal method for photocatalytic reduction of CO2 to methanol. The synthesized catalysts were characterized by X-ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM) coupled with Energy Dispersive X-ray (EDX), Ultraviolet-visible (UV-vis) spectroscopy, and X-Ray Diffraction (XRD). The host ZIF-8, treated with 2 mmol copper prepared in 2M ammonium hydroxide solution showed the highest photocatalytic activity. The crystal structures of ZIF-8 and 2Cu/ZIF-8N2 catalysts were observed as cubic and orthorhombic, respectively and the XPS analysis confirmed the deposition of Cu (II) ions over ZIF-8 surface among all the prepared catalysts. The orthorhombic structure, nano-sized crystals, morphology and Cu loading of the 2Cu/ZIF-8N2 catalyst were the core factors to influence the photocatalytic activity. The yield of Methanol was found to be 35.82 µmol/L·g after 6 h of irradiations on 2Cu/ZIF-8N2 catalyst in the wavelength range between 530–580 nm. The copper-based ZIF-8 catalyst has proven as an alternative approach for the economical photocatalytic reduction of CO2 to CH3OH.
      Citation: Catalysts
      PubDate: 2018-11-25
      DOI: 10.3390/catal8120581
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 582: Biocatalytic Oxidations of Substrates
           through Soluble Methane Monooxygenase from Methylosinus sporium 5

    • Authors: Yeo Reum Park, Hee Seon Yoo, Min Young Song, Dong-Heon Lee, Seung Jae Lee
      First page: 582
      Abstract: Methane, an important greenhouse gas, has a 20-fold higher heat capacity than carbon dioxide. Earlier, through advanced spectroscopy and structural studies, the mechanisms underlying the extremely stable C–H activation of soluble methane monooxygenase (sMMO) have been elucidated in Methylosinus trichosporium OB3b and Methylococcus capsulatus Bath. Here, sMMO components—including hydroxylase (MMOH), regulatory (MMOB), and reductase (MMOR)—were expressed and purified from a type II methanotroph, Methylosinus sporium strain 5 (M. sporium 5), to characterize its hydroxylation mechanism. Two molar equivalents of MMOB are necessary to achieve catalytic activities and oxidized a broad range of substrates including alkanes, alkenes, halogens, and aromatics. Optimal activities were observed at pH 7.5 for most substrates possibly because of the electron transfer environment in MMOR. Substitution of MMOB or MMOR from another type II methanotroph, Methylocystis species M, retained specific enzyme activities, demonstrating the successful cross-reactivity of M. sporium 5. These results will provide fundamental information for further enzymatic studies to elucidate sMMO mechanisms.
      Citation: Catalysts
      PubDate: 2018-11-26
      DOI: 10.3390/catal8120582
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 583: Coordinated “Naked” Pnicogenes
           and Catalysis

    • Authors: Anna Vízi-Orosz, Gergely Berzeviczy, Gyula Pályi
      First page: 583
      Abstract: Diphosphorous (P2) side-on coordinated to a dicobalt (Co–Co) moiety was described 45 years ago. This discovery had several links to actual problems of homogeneous molecular catalysis. The new type of organometallic complexes induced several ingenious new ramifications in main-group/transition metal cluster chemistry in the last decades. The present review traces the main lines of these research results and their contacts to actual problems of industrial catalysis.
      Citation: Catalysts
      PubDate: 2018-11-26
      DOI: 10.3390/catal8120583
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 584: Effect of Nickel Oxide Doping to
           Ceria-Supported Gold Catalyst for CO Oxidation and Water-Gas Shift
           Reactions

    • Authors: Miao Shu, Shuai Wei, Chun-Jiang Jia, Dao-Lei Wang, Rui Si
      First page: 584
      Abstract: Ceria-supported gold catalyst has drew much research interest owing to its high reactivity on CO oxidation and water-gas shift (WGS) reactions. However, till now, there were relatively limited studies on the effect of secondary metal/metal oxide component into gold-ceria system to enhance its catalytic performance. In this work, we synthetized the ceria supported gold-nickel samples via a deposition-precipitation method with the base of NaHCO3 to adjust final pH value of 8~9. We found that the addition of nickel oxide drove off the gold species from the stock solution during synthesis, and thus resulted in a dramatical decrease on doped Au concentration. No crystallized phases of gold and nickel were observed on the surface of ceria nanorods in both X-ray diffraction (XRD) and transmission electron microscopy (TEM). The valence of nickel was maintained as Ni2+ for all the measured samples by X-ray photoelectron spectroscopy (XPS), while gold was oxidized with the increased nickel amount after analysis of X-ray absorption near edge spectroscopy (XANES). The corresponding catalytic tests showed that with the introduction of nickel oxide, the activity of gold-ceria catalyst was promoted for the WGS reaction, but inhibited for the CO oxidation reaction.
      Citation: Catalysts
      PubDate: 2018-11-26
      DOI: 10.3390/catal8120584
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 585: Transformation of 2-Butene into Propene on
           WO3/MCM-48: Metathesis and Isomerization of n-Butene

    • Authors: Derun Hua, Zheng Zhou, Qianqian Hua, Jian Li, Xinning Lu, Yongrong Xie, Hong Xiao, Mei Li, Jin Yang
      First page: 585
      Abstract: The metathesis of 2-butene (Trans and Cis) to propene was investigated over W-based catalysts. Thermodynamic calculations for metathesis and isomerization were carried out at various temperatures to test the reactions. The results showed that the WO3/MCM-48 catalyst had good catalytic activity. The metathesis activity depended on the acidity of the catalyst and the dispersity of the WO3 on the supports. High temperatures promoted the isomerization of 2-butene to 1-butene. According to thermodynamic analysis, however, this is adverse to the metathesis reaction, making it important to determine an appropriate reaction temperature.
      Citation: Catalysts
      PubDate: 2018-11-26
      DOI: 10.3390/catal8120585
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 586: Palladium Nanoparticles Supported on
           Triphenylphosphine-Functionalized Porous Polymer as an Active and
           Recyclable Catalyst for the Carbonylation of Chloroacetates

    • Authors: Yali Wan, Zaifei Chen, Dingfu Liu, Yizhu Lei
      First page: 586
      Abstract: Dialkyl malonates are important organic intermediates that are widely used as building blocks in organic synthesis. Herein, palladium nanoparticles supported on a triphenylphosphine-functionalized porous polymer were successfully developed as an efficient and recyclable catalyst for the synthesis of dialkyl malonates via the catalytic carbonylation of chloroacetates. The influence of reaction parameters such as solvent, base, and promoter on activity was carefully investigated. With a 1 mol% of palladium usage, excellent yields of dialkyl malonates were obtained. Importantly, the catalyst can be easily separated and reused at least four times, without a significant loss in reactivity. Furthermore, the developed catalyst was also highly active for the alkoxycarbonylation of α-chloro ketones.
      Citation: Catalysts
      PubDate: 2018-11-26
      DOI: 10.3390/catal8120586
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 587: Biocatalytic Pickering Emulsions Stabilized
           by Lipase-Immobilized Carbon Nanotubes for Biodiesel Production

    • Authors: Lihui Wang, Xinlong Liu, Yanjun Jiang, Liya Zhou, Li Ma, Ying He, Jing Gao
      First page: 587
      Abstract: Biodiesel is a promising renewable energy source that can replace fossil fuel, but its production is limited by a lack of high-efficiency catalysts for mass production and popularization. In this study, we developed a biocatalytic Pickering emulsion using multiwall carbon nanotube-immobilized Candida antarctica lipase B (CALB@PE) to produce biodiesel, with J. curcas L. seed oil and methanol as substrates. The morphology of CALB@PE was characterized in detail. A central composite design of the response surface methodology (CCD-RSM) was used to study the effects of the parameters on biodiesel yield, namely the amount of J. curcas L. seed oil (1.5 g), molar ratio of methanol to oil (1:1–7:1), CALB@PE dosage (20–140 mg), temperature (30–50 °C), and reaction time (0–24 h). The experimental responses were fitted with a quadratic polynomial equation, and the optimum reaction conditions were the methanol/oil molar ratio of 4.64:1, CALB@PE dosage of 106.87 mg, and temperature of 34.9 °C, with a reaction time of 11.06 h. A yield of 95.2%, which was basically consistent with the predicted value of 95.53%, was obtained. CALB@PE could be reused up to 10 times without a substantial loss of activity. CALB@PE exhibited better reusability than that of Novozym 435 in the process of biodiesel production.
      Citation: Catalysts
      PubDate: 2018-11-27
      DOI: 10.3390/catal8120587
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 588: Asymmetric and Selective Biocatalysis

    • Authors: Cesar Mateo, Jose M. Palomo
      First page: 588
      Abstract: The synthesis of compounds or chiral building-blocks with the desired configuration is one of the greatest challenges of chemistry and is of great interest in different fields such as analytical chemistry and especially in fine and pharmaceutical chemistry. [...]
      Citation: Catalysts
      PubDate: 2018-11-28
      DOI: 10.3390/catal8120588
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 589: Screening of a Novel Glycoside Hydrolase
           Family 51 α-L-Arabinofuranosidase from Paenibacillus polymyxa KF-1:
           Cloning, Expression, and Characterization

    • Authors: Yanbo Hu, Yan Zhao, Shuang Tian, Guocai Zhang, Yumei Li, Qiang Li, Juan Gao
      First page: 589
      Abstract: Paenibacillus polymyxa exhibits remarkable hemicellulolytic activity. In the present study, 13 hemicellulose-degrading enzymes were identified from the secreted proteome of P. polymyxa KF-1 by liquid chromatography-tandem mass spectrometry analysis. α-L-arabinofuranosidase is an important member of hemicellulose-degrading enzymes. A novel α-L-arabinofuranosidase (PpAbf51b), belonging to glycoside hydrolase family 51, was identified from P. polymyxa. Recombinant PpAbf51b was produced in Escherichia coli BL21 (DE3) and was found to be a tetramer using gel filtration chromatography. PpAbf51b hydrolyzed neutral arabinose-containing polysaccharides, including sugar beet arabinan, linear-1,5-α-L-arabinan, and wheat arabinoxylan, with L-arabinose as the main product. The products from hydrolysis indicate that PpAbf51b functions as an exo-α-L-arabinofuranosidase. Combining PpAbf51b and Trichoderma longibrachiatum endo-1,4-xylanase produced significant synergistic effects for the degradation of wheat arabinoxylan. The α-L-arabinofuranosidase identified from the secretome of P. polymyxa KF-1 is potentially suitable for application in biotechnological industries.
      Citation: Catalysts
      PubDate: 2018-11-28
      DOI: 10.3390/catal8120589
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 590: Compositing Two-Dimensional Materials with
           TiO2 for Photocatalysis

    • Authors: Yu Ren, Yuze Dong, Yaqing Feng, Jialiang Xu
      First page: 590
      Abstract: Energy shortage and environmental pollution problems boost in recent years. Photocatalytic technology is one of the most effective ways to produce clean energy—hydrogen and degrade pollutants under moderate conditions and thus attracts considerable attentions. TiO2 is considered one of the best photocatalysts because of its well-behaved photo-corrosion resistance and catalytic activity. However, the traditional TiO2 photocatalyst suffers from limitations of ineffective use of sunlight and rapid carrier recombination rate, which severely suppress its applications in photocatalysis. Surface modification and hybridization of TiO2 has been developed as an effective method to improve its photocatalysis activity. Due to superior physical and chemical properties such as high surface area, suitable bandgap, structural stability and high charge mobility, two-dimensional (2D) material is an ideal modifier composited with TiO2 to achieve enhanced photocatalysis process. In this review, we summarized the preparation methods of 2D material/TiO2 hybrid and drilled down into the role of 2D materials in photocatalysis activities.
      Citation: Catalysts
      PubDate: 2018-11-28
      DOI: 10.3390/catal8120590
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 591: Titanium Dioxide Photocatalysis

    • Authors: Vladimiro Dal Santo, Alberto Naldoni
      First page: 591
      Abstract: Dating from the seminal work of Fujishima et al. [...]
      Citation: Catalysts
      PubDate: 2018-11-29
      DOI: 10.3390/catal8120591
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 592: A CeO2/ZrO2-TiO2 Catalyst for the Selective
           Catalytic Reduction of NOx with NH3

    • Authors: Wenpo Shan, Yang Geng, Yan Zhang, Zhihua Lian, Hong He
      First page: 592
      Abstract: In this study, CeZr0.5TiaOx (with a = 0, 1, 2, 5, 10) catalysts were prepared by a stepwise precipitation approach for the selective catalytic reduction of NOx with NH3. When Ti was added, all of the Ce-Zr-Ti oxide catalysts showed much better catalytic performances than the CeZr0.5Ox. Particularly, the CeZr0.5Ti2Ox catalyst showed excellent activity for broad temperature range under high space velocity condition. Through the control of pH value and precipitation time during preparation, the function of the CeZr0.5Ti2Ox catalyst could be controlled and the structure with highly dispersed CeO2 (with redox functions) on the surface of ZrO2-TiO2 (with acidic functions) could be obtained. Characterizations revealed that the superior catalytic performance of the catalyst is associated with its outstanding redox properties and adsorption/activation functions for the reactants.
      Citation: Catalysts
      PubDate: 2018-11-30
      DOI: 10.3390/catal8120592
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 593: The Role of Impregnated Sodium Ions in
           Cu/SSZ-13 NH3-SCR Catalysts

    • Authors: Chen Wang, Jun Wang, Jianqiang Wang, Zhixin Wang, Zexiang Chen, Xiaolan Li, Meiqing Shen, Wenjun Yan, Xue Kang
      First page: 593
      Abstract: To reveal the role of impregnated sodium (Na) ions in Cu/SSZ-13 catalysts, Cu/SSZ-13 catalysts with four Na-loading contents were prepared using an incipient wetness impregnation method and hydrothermally treated at 600 °C for 16 h. The physicochemical property and selective catalytic reduction (SCR) activity of these catalysts were studied to probe the deactivation mechanism. The impregnated Na exists as Na+ on catalysts and results in the loss of both Brönsted acid sites and Cu2+ ions. Moreover, the high loading of Na ions destroy the framework structure of Cu/SSZ-13 and forms new phases (SiO2/NaSiO3 and amorphous species) when Na loading was higher than 1.0 mmol/g. The decreased Cu2+ ions finally transformed into CuxO, CuO, and CuAlOx species. The inferior SCR activity of Na impregnated catalysts was mainly due to the reduced contents of Cu2+ ions at kinetic temperature region. The reduction in the amount of acid sites and Cu2+ ions, as well as copper oxide species (CuxO and CuO) formation, led to low SCR performance at high temperature. Our study also revealed that the existing problem of the Na ions’ effect should be well-considered, especially at high hydrothermal aging when diesel particulate filter (DPF) is applied in upstream of the SCR applications.
      Citation: Catalysts
      PubDate: 2018-11-30
      DOI: 10.3390/catal8120593
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 594: Metal Micro-Monoliths for the Kinetic Study
           and the Intensification of the Water Gas Shift Reaction

    • Authors: Nuria García-Moncada, Gianpiero Groppi, Alessandra Beretta, Francisca Romero-Sarria, José Antonio Odriozola
      First page: 594
      Abstract: A kinetic study of the water gas shift (WGS) reaction has been carried out on a Pt-based catalyst promoted by a Zr-based proton conductor. The investigation was first performed on powders with diluted feed mixtures and then extended to more severe and representative conditions by using a catalyst coated metallic micromonolith. Temperature measurements reveal that isothermal conditions were obtained along the micromonolith during the tested conditions. In addition, the very thin catalytic layer allows for the discarding of intraporous resistances, providing excellent conditions to analyse the kinetics of the WGS reaction under the integral regime. The proposed rate expression accounts for independence on CO concentration, an inhibiting effect of H2 and a promoting effect of H2O; kinetic orders on CO and H2 are in line with those reported in the literature for the Pt-based catalyst. Instead, the obtained reaction order of water (0.36) is significantly lower than that reported for unpromoted catalysts (typically 0.77–1.10) in good agreement with the proposed water-enhancer effect of the proton conductor on the rate-limiting step. Metallic micromonoliths turn out to be a powerful tool for the kinetic investigation, due to the absence of mass and heat transport limitations and represent a strategy for the intensification of the WGS unit for future applications of fuel processors in small mobile devices.
      Citation: Catalysts
      PubDate: 2018-11-30
      DOI: 10.3390/catal8120594
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 595: Acetalization Catalysts for Synthesis of
           Valuable Oxygenated Fuel Additives from Glycerol

    • Authors: Andrey A. Smirnov, Svetlana A. Selishcheva, Vadim A. Yakovlev
      First page: 595
      Abstract: Biodiesel is one of the most attractive sources of clean energy. It is produced by the transformation of vegetable oils with up to 10% formation of glycerol as a by-product. Therefore, development of new approaches for processing bio-glycerol into such value-added chemical compounds as solketals is necessary. Thus, various six- and five-membered cyclic compounds can be prepared by acetalization of glycerol with aldehyde or ketone. The resulting glycerol oxygenates are excellent fuel additives that increase viscosity, octane or cetane number, and stability to oxidation. In addition, these products significantly reduce carbon monoxide emissions from standard diesel fuel. In this review, we highlight recent advances in the glycerol valorization for the sustainable production of bio-additives. The review includes a discussion of the innovative and potential catalysts to produce solketals.
      Citation: Catalysts
      PubDate: 2018-12-01
      DOI: 10.3390/catal8120595
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 596: Photocatalytic Oxidation of Toluene on
           Fluorine Doped TiO2/SiO2 Catalyst Under Simulant Sunlight in a Flat
           Reactor

    • Authors: Lu Qiu, Yanan Wang, Hanlinag Li, Gang Cao, Feng Ouyang, Rongshu Zhu
      First page: 596
      Abstract: Improving the capacity of TiO2 semiconductors for visible light response is a key problem for utilization of solar energy in photo-catalytic degradation of organic pollutants. Both catalyst character and reactor conditions are important for the reaction efficiency. The fluorine ion doped TiO2/SiO2 catalyst was prepared by sol-gel method using HF solution as fluorine source. The activity test and UV–vis results indicated that this catalyst was superior to TiO2 P25 in photocatalytic oxidation of gaseous toluene under simulant sunlight irradiation due to the enhancement of visible and ultraviolet light absorbance. GC-MS results indicated that the main intermediates accumulated on active sites included benzoic acid, benzaldehyde, and phenol. A flat interlaid reactor was designed for continuous treatment of the stream with F-TiO2/SiO2 film. The results showed that coating the catalyst on the surface of both top and bottom glass substrates, through the knife coating method with an optimal reactor height, attained the highest efficiency. In addition, the presence of water and oxygen enhanced the oxidation of toluene due to the generation of hydroxyl radicals and peroxy radicals, respectively. The toluene oxidation rate increased with the increase in water vapor concentration in the range of 0~60 vol.%.
      Citation: Catalysts
      PubDate: 2018-12-01
      DOI: 10.3390/catal8120596
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 597: Metal Nanotube/Nanowire-Based Unsupported
           Network Electrocatalysts

    • Authors: Muench
      First page: 597
      Abstract: Combining 1D metal nanotubes and nanowires into cross-linked 2D and 3D architectures represents an attractive design strategy for creating tailored unsupported catalysts. Such materials complement the functionality and high surface area of the nanoscale building blocks with the stability, continuous conduction pathways, efficient mass transfer, and convenient handling of a free-standing, interconnected, open-porous superstructure. This review summarizes synthetic approaches toward metal nano-networks of varying dimensionality, including the assembly of colloidal 1D nanostructures, the buildup of nanofibrous networks by electrospinning, and direct, template-assisted deposition methods. It is outlined how the nanostructure, porosity, network architecture, and composition of such materials can be tuned by the fabrication conditions and additional processing steps. Finally, it is shown how these synthetic tools can be employed for designing and optimizing self-supported metal nano-networks for application in electrocatalysis and related fields.
      Citation: Catalysts
      PubDate: 2018-12-01
      DOI: 10.3390/catal8120597
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 598: Reduced Graphene Oxide/TiO2 Nanocomposite:
           From Synthesis to Characterization for Efficient Visible Light
           Photocatalytic Applications

    • Authors: Elena Rommozzi, Marco Zannotti, Rita Giovannetti, Chiara Anna D’Amato, Stefano Ferraro, Marco Minicucci, Roberto Gunnella, Andrea Di Cicco
      First page: 598
      Abstract: In this study, a green and facile thermal reduction of graphene oxide using an eco-friendly system of d-(+)-glucose and NH4OH for the preparation of reduced graphene oxide was described. The obtained reduced graphene oxide dispersion was characterized by SEM, Dynamic Light Scattering, Raman and X-Ray Photoelectron Spectroscopy. TiO2 nanoparticles and reduced graphene oxide nanocomposites were successively prepared and used in the preparation of heterogeneous photocatalysts that were characterized by Atomic Force Microscopy and Photoluminescence Spectroscopy and subsequently tested as visible light photocatalysts for the photodegradation of Alizarin Red S in water as target pollutant. Obtained results of photocatalytic tests regarding the visible light photocatalytic degradation of Alizarin Red S demonstrated that the use of reduced graphene oxide in combination with TiO2 led to a significant improvement for both adsorption of Alizarin Red S on the catalyst surface and photodegradation efficiencies when compared to those obtained with not doped TiO2.
      Citation: Catalysts
      PubDate: 2018-12-01
      DOI: 10.3390/catal8120598
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 599: Steam vs. Dry Reformer: Experimental Study
           on a Solid Oxide Fuel Cell Short Stack

    • Authors: Linda Barelli, Gianni Bidini, Giovanni Cinti
      First page: 599
      Abstract: Solid Oxide Fuel Cell (SOFC) systems operating with methane usually are equipped with an external reformer to produce syngas. The conventional applied technology is steam methane reforming. Recent studies, instead, are presenting dry reforming as potential alternative. Advantages come from the substitution of steam with CO2 to be handled in the system, representing a potential strategy of CO2 reuse. This study compares, the performance of a SOFC short stack operating with dry reforming and with steam reforming mixtures respectively. Results show that higher performances can be obtained under same operating conditions, due to the high concentration of syngas (that has low content of inert species) produced via dry reforming. The analysis of different dry reforming concentrations shows that the amount of methane seems to be more relevant, in terms of voltage performances, than high hydrogen concentration. Among tested dry reforming compositions, the most performing exhibits an improvement of at least 5% in produced voltage in the range 150–375 mA cm−2 with respect to mixture produced by steam reforming (S/C ratio of 2.5). It was also proved that this performance enhancement does not imply greater thermal stresses, since stack temperature slightly reduces and lower temperature variations arise at anode and cathode when operating current varies.
      Citation: Catalysts
      PubDate: 2018-12-02
      DOI: 10.3390/catal8120599
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 600: BF3·Et2O-Promoted Decomposition of Cyclic
           α-Diazo-β-Hydroxy Ketones: Novel Insights into Mechanistic Aspects

    • Authors: Francesco Venturoni, Bruno Cerra, Maura Marinozzi, Emidio Camaioni, Antimo Gioiello, Roberto Pellicciari
      First page: 600
      Abstract: We report novel insights into the cascade rearrangement of destabilized vinyl cations deriving from the BF3·Et2O-induced decomposition of cyclic α-diazo-β-hydroxy ketones in turn prepared by aldol-type condensation of cycloalkanones with diazoacetone. Complexation of the hydroxy group of the α-diazo-β-hydroxy compound with the Lewis acid is the first event, followed by the generation of the cycloalkanylidenediazonium salt that, after nitrogen loss, produces the highly reactive vinyl cation. The subsequent ring expansion results in the formation of a cycloalkenyl vinyl cation that affords the allylic cation by 1,2-methylene shift and ring contraction. The cation can then trap the solvent, the fluoride or the hydroxide released from the [BF3OH]− to afford different reaction products. The effect of both solvent and substrate ring size on products types and ratios were analyzed and discussed from a mechanistic point of view.
      Citation: Catalysts
      PubDate: 2018-12-02
      DOI: 10.3390/catal8120600
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 601: Switchable Intrinsic Defect Chemistry of
           Titania for Catalytic Applications

    • Authors: Jayashree, Ashokkumar
      First page: 601
      Abstract: The energy crisis is one of the most serious issue that we confront today. Among different strategies to gain access to reliable fuel, the production of hydrogen fuel through the water-splitting reaction has emerged as the most viable alternative. Specifically, the studies on defect-rich TiO2 materials have been proved that it can perform as an efficient catalyst for electrocatalytic and photocatalytic water-splitting reactions. In this invited review, we have included a general and critical discussion on the background of titanium sub-oxides structure, defect chemistries and the consequent disorder arising in defect-rich Titania and their applications towards water-splitting reactions. We have particularly emphasized the origin of the catalytic activity in Titania-based material and its effects on the structural, optical and electronic behavior. This review article also summarizes studies on challenging issues on defect-rich Titania and new possible directions for the development of an efficient catalyst with improved catalytic performance.
      Citation: Catalysts
      PubDate: 2018-12-02
      DOI: 10.3390/catal8120601
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 602: Polynuclear Cobalt Complexes as Catalysts
           for Light-Driven Water Oxidation: A Review of Recent Advances

    • Authors: Dmytro S. Nesterov, Oksana V. Nesterova
      First page: 602
      Abstract: Photochemical water oxidation, as a half-reaction of water splitting, represents a great challenge towards the construction of artificial photosynthetic systems. Complexes of first-row transition metals have attracted great attention in the last decade due to their pronounced catalytic efficiency in water oxidation, comparable to that exhibited by classical platinum-group metal complexes. Cobalt, being an abundant and relatively cheap metal, has rich coordination chemistry allowing construction of a wide range of polynuclear architectures for the catalytic purposes. This review covers recent advances in application of cobalt complexes as (pre)catalysts for water oxidation in the model catalytic system comprising [Ru(bpy)3]2+ as a photosensitizer and S2O82− as a sacrificial electron acceptor. The catalytic parameters are summarized and discussed in view of the structures of the catalysts. Special attention is paid to the degradation of molecular catalysts under catalytic conditions and the experimental methods and techniques used to control their degradation as well as the leaching of cobalt ions.
      Citation: Catalysts
      PubDate: 2018-12-02
      DOI: 10.3390/catal8120602
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 603: Immobilization of Arylmalonate Decarboxylase

    • Authors: Kristína Markošová, Jana Husarčíková, Monika Halásová, Robert Kourist, Michal Rosenberg, Radek Stloukal, Ludmila Zajoncová, Martin Rebroš
      First page: 603
      Abstract: Arylmalonate decarboxylase (AMD) is a monomeric enzyme of only 26 kDa. A recombinant AMDase from Bordetella bronchiseptica was expressed in Escherichia coli and the enzyme was immobilized using different techniques: entrapment in polyvinyl alcohol (PVA) gel (LentiKats®), covalent binding onto magnetic microparticles (MMP, PERLOZA s.r.o., Lovosice, Czech Republic) and double-immobilization (MMP-LentiKats®) using the previous two methods. The double-immobilized AMDase was stable in 8 repeated biocatalytic reactions. This combined immobilization technique has the potential to be applied to different small proteins.
      Citation: Catalysts
      PubDate: 2018-12-02
      DOI: 10.3390/catal8120603
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 604: Application of BiOX Photocatalysts in
           Remediation of Persistent Organic Pollutants

    • Authors: Robert B. Arthur, John C. Ahern, Howard H. Patterson
      First page: 604
      Abstract: Bismuth oxyhalides have recently gained attention for their promise as photocatalysts. Due to their layered structure, these materials present fascinating and highly desirable physicochemical properties including visible light photocatalytic capability and improved charge separation. While bismuth oxyhalides have been rigorously evaluated for the photocatalytic degradation of dyes and many synthesis strategies have been employed to enhance this property, relatively little work has been done to test them against pharmaceuticals and pesticides. These persistent organic pollutants are identified as emerging concerns by the EPA and effective strategies must be developed to combat them. Here, we review recent work directed at characterizing the nature of the interactions between bismuth oxyhalides and persistent organic pollutants using techniques including LC-MS/MS for the determination of photocatalytic degradation intermediates and radical scavenging to determine active species during photocatalytic degradation. The reported investigations indicate that the high activity of bismuth oxyhalides for the breakdown of persistent organic pollutants from water can be largely attributed to the strong oxidizing power of electron holes in the valence band. Unlike conventional catalysts like TiO2, these catalysts can also function in ambient solar conditions. This suggests a much wider potential use for these materials as green catalysts for industrial photocatalytic transformation, particularly in flow chemistry applications.
      Citation: Catalysts
      PubDate: 2018-12-02
      DOI: 10.3390/catal8120604
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 605: Organocatalysis: A Brief Overview on Its
           Evolution and Applications

    • Authors: Vanessa da Gama Oliveira, Mariana Filomena do Carmo Cardoso, Luana da Silva Magalhães Forezi
      First page: 605
      Abstract: The use of small organic molecules as catalysts has gained increasing importance recently. These substances, the so-called organocatalysts, present a lot of advantages, like being less toxic, less polluting, and more economically viable than the organometallic catalysts that dominate asymmetric synthesis. This work intends to briefly show some classic works and recent publications, explaining the advantages of organocatalysis and the different types of compounds used in this field, as well as their course of action.
      Citation: Catalysts
      PubDate: 2018-12-03
      DOI: 10.3390/catal8120605
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 606: Criticial Assessment of the Photocatalytic
           Reduction of Cr(VI) over Au/TiO2

    • Authors: Anh Binh Ngo, Hong Lien Nguyen, Dirk Hollmann
      First page: 606
      Abstract: The purification of drinking water is one of the most urgent challenges in developing countries, for which the efficient removal of traces of heavy metals, e.g., Cr(IV), represents a key technology. This can be achieved via photocatalysis. In this study, we compare the performance of Au/TiO2 to bare TiO2 P25 catalysts. Furthermore, the influence of the sacrificial reagent citric acid under UV-Vis and Vis excitation was investigated and a detailed investigation of the catalysts before and after reaction was performed. During the photocatalytic reduction of Cr(IV) under acidic conditions, both leaching of Au, as well as absorption of Cr, occur, resulting in new catalyst systems obtained in situ.
      Citation: Catalysts
      PubDate: 2018-12-03
      DOI: 10.3390/catal8120606
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 607: Thermal Stability and Potential Cycling
           Durability of Nitrogen-Doped Graphene Modified by Metal-Organic Framework
           for Oxygen Reduction Reactions

    • Authors: Harsimranjit Singh, Shiqiang Zhuang, Bharath Babu Nunna, Eon Soo Lee
      First page: 607
      Abstract: Here we report a nitrogen-doped graphene modified metal-organic framework (N-G/MOF) catalyst, a promising metal-free electrocatalyst exhibiting the potential to replace the noble metal catalyst from the electrochemical systems; such as fuel cells and metal-air batteries. The catalyst was synthesized with a planetary ball milling method, in which the precursors nitrogen-functionalized graphene (N-G) and ZIF-8 are ground at an optimized grinding speed and time. The N-G/MOF catalyst not only inherited large surface area from the ZIF-8 structure, but also had chemical interactions, resulting in an improved Oxygen Reduction Reaction (ORR) electrocatalyst. Thermogravimetric Analysis (TGA) curves revealed that the N-G/MOF catalyst still had some unreacted ZIF-8 particles, and the high catalytic activity of N-G particles decreased the decomposition temperature of ZIF-8 in the N-G/MOF catalyst. Also, we present the durability study of the N-G/MOF catalyst under a saturated nitrogen and oxygen environment in alkaline medium. Remarkably, the catalyst showed no change in the performance after 2000 cycles in the N2 environment, exhibiting strong resistance to the corrosion. In the O2 saturated electrolyte, the performance loss at lower overpotentials was as low compared to higher overpotentials. It is expected that the catalyst degradation mechanism during the potential cycling is due to the oxidative attack of the ORR intermediates.
      Citation: Catalysts
      PubDate: 2018-12-03
      DOI: 10.3390/catal8120607
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 608: Improving Fe/Al2O3 Catalysts for the Reverse
           Water-Gas Shift Reaction: On the Effect of Cs as Activity/Selectivity
           Promoter

    • Authors: Laura Pastor-Pérez, Mihir Shah, Estelle le Saché, Tomas Ramirez Reina
      First page: 608
      Abstract: The conversion of CO2 into CO via the Reverse Water–Gas Shift (RWGS) reaction is a suitable route for CO2 valorisation. Fe-based catalysts are highly active for this reaction, but their activity and selectivity can be substantially boosted by adding Cs as a promoter. In this work we demonstrate that Cs modifies the redox behaviour and the surface chemistry of the iron-based materials. The metallic dispersion and the amount of metallic Fe centres available for the reaction depends on Cs loading. 5 wt. % of Cs is an optimum amount of dopant to achieve a fair activity/selective balance. Nevertheless, depending on the RWGS reactor operational temperature, lower concentrations of Cs also lead to acceptable catalytic performance. Along with the excellent activity of the prepared materials this work showcases their robustness for long-term runs and the strong impact of H2/CO ratio in the overall catalytic performance.
      Citation: Catalysts
      PubDate: 2018-12-03
      DOI: 10.3390/catal8120608
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 609: Maximizing Anhydrosugar Production from Fast
           Pyrolysis of Eucalyptus Using Sulfuric Acid as an Ash Catalyst Inhibitor

    • Authors: Dongyan Zhang, Yuyang Fan, Anqing Zheng, Zengli Zhao, Fengyun Wang, Haibin Li
      First page: 609
      Abstract: Anhydrosugars, such as levoglucosan (LG), are high value-added chemicals which are mainly derived from fast pyrolysis of pure cellulose. However, fast pyrolysis of raw lignocellulosic biomass usually produces a very low amount of levoglucosan, since alkali and alkaline earth metals (AAEM) present in the ash can serve as the catalysts to inhibit the formation of levoglucosan through accelerating the pyranose ring-opening reactions. In this study, eucalyptus was impregnated with H2SO4 solutions with varying concentrations (0.25–1.25%). The characteristics of ash derived from raw and H2SO4-impregnated eucalyptus were characterized by X-ray fluorescence spectroscopy (XRF) and X-ray diffraction (XRD). The pyrolysis behaviors of raw and H2SO4-impregnated eucalyptus were performed on the thermogravimetric analysis (TGA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). TG analysis demonstrated that the H2SO4-impregnated eucalyptus produced less char than raw eucalyptus. Py-GC/MS analysis showed that even small amounts of H2SO4 can obviously improve the production of anhydrosugars and phenols and suppressed the formation of carboxylic acids, aldehydes, and ketones from fast pyrolysis of eucalyptus. The rank order of levoglucosan yield from raw and impregnated eucalyptus was raw < 1.25% H2SO4 < 1% H2SO4 < 0.75% H2SO4 < 0.25% H2SO4 < 0.5% H2SO4. The maximum yield of levoglucosan (21.3%) was obtained by fast pyrolysis of eucalyptus impregnated with 0.5% H2SO4, which was close to its theoretical yield based on the cellulose content. The results could be ascribed to that H2SO4 can react with AAEM (e.g., Na, K, Ca, and Mg) and lignin to form lignosulfonate, thus acting as an inhibitor to suppress the catalytic effects of AAEM during fast pyrolysis of eucalyptus.
      Citation: Catalysts
      PubDate: 2018-12-03
      DOI: 10.3390/catal8120609
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 610: Acetylene Abatement Over Micro/Mesoporous
           Active Carbon-Supported Low-Mercury Catalysts

    • Authors: Luo Jiang, Ning Liu, Chengna Dai, Ruinian Xu, Biaohua Chen, Jirui Zhang
      First page: 610
      Abstract: A series of low HgCl2-supported catalysts (K-TX-O, K-WG-O, K-S20-O, K-S40-O, K-Fe0.8-O, K-Fe0.8-M, D-Fe0.8-M) was prepared and investigated for C2H2 catalytic abatement during highly purified HCl (HP-HCl) production process. The samples of D-Fe0.8-M, K-Fe0.8-M, and K-Fe0.8-O were found to exhibit much higher activities and better thermal stabilities than those of other samples. The characterization results of XRD, N2 adsorption/desorption, SEM, back scattered electron (BSE) and thermogravimetry (TG) revealed that: (i) the larger mesoporous volumes constituted one of the key factors leading to superior catalytic performances of D-Fe0.8-M, K-Fe0.8-M, and K-Fe0.8-O, which greatly facilitated better dispersions of the loaded HgCl2 species in comparison to other samples; (ii) the KCl additive could further improve the dispersions and thermal stabilities of the loaded the HgCl2 species due to the strong interactions between KCl and HgCl2 species, resulting in relatively higher catalytic behaviors of D-Fe0.8-M and K-Fe0.8-M than that of K-Fe0.8-O; (iii) the KCl/HgCl2 step-by-step loading strategy, wherein the KCl was initially loaded on the Fe0.8-AC substrate thereafter followed by HgCl2 loading, could further improve the catalytic behavior for D-Fe0.8-M due to additional improvements of HgCl2 dispersions. The deactivation and reactivation of D-Fe0.8-M during HP-HCl were also investigated, which suggested that partial deactivated D-Fe0.8-M by C2H3Cl accumulation could be efficiently reactivated by HCl treatment at T = 220 °C.
      Citation: Catalysts
      PubDate: 2018-12-03
      DOI: 10.3390/catal8120610
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 611: Non-Stoichiometric Redox Active Perovskite
           Materials for Solar Thermochemical Fuel Production: A Review

    • Authors: Anita Haeussler, Stéphane Abanades, Julien Jouannaux, Anne Julbe
      First page: 611
      Abstract: Due to the requirement to develop carbon-free energy, solar energy conversion into chemical energy carriers is a promising solution. Thermochemical fuel production cycles are particularly interesting because they can convert carbon dioxide or water into CO or H2 with concentrated solar energy as a high-temperature process heat source. This process further valorizes and upgrades carbon dioxide into valuable and storable fuels. Development of redox active catalysts is the key challenge for the success of thermochemical cycles for solar-driven H2O and CO2 splitting. Ultimately, the achievement of economically viable solar fuel production relies on increasing the attainable solar-to-fuel energy conversion efficiency. This necessitates the discovery of novel redox-active and thermally-stable materials able to split H2O and CO2 with both high-fuel productivities and chemical conversion rates. Perovskites have recently emerged as promising reactive materials for this application as they feature high non-stoichiometric oxygen exchange capacities and diffusion rates while maintaining their crystallographic structure during cycling over a wide range of operating conditions and reduction extents. This paper provides an overview of the best performing perovskite formulations considered in recent studies, with special focus on their non-stoichiometry extent, their ability to produce solar fuel with high yield and performance stability, and the different methods developed to study the reaction kinetics.
      Citation: Catalysts
      PubDate: 2018-12-03
      DOI: 10.3390/catal8120611
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 612: A Middle-Aged Enzyme Still in Its Prime:
           Recent Advances in the Field of Cutinases

    • Authors: Efstratios Nikolaivits, Maria Kanelli, Maria Dimarogona, Evangelos Topakas
      First page: 612
      Abstract: Cutinases are α/β hydrolases, and their role in nature is the degradation of cutin. Such enzymes are usually produced by phytopathogenic microorganisms in order to penetrate their hosts. The first focused studies on cutinases started around 50 years ago. Since then, numerous cutinases have been isolated and characterized, aiming at the elucidation of their structure–function relations. Our deeper understanding of cutinases determines the applications by which they could be utilized; from food processing and detergents, to ester synthesis and polymerizations. However, cutinases are mainly efficient in the degradation of polyesters, a natural function. Therefore, these enzymes have been successfully applied for the biodegradation of plastics, as well as for the delicate superficial hydrolysis of polymeric materials prior to their functionalization. Even though research on this family of enzymes essentially began five decades ago, they are still involved in many reports; novel enzymes are being discovered, and new fields of applications arise, leading to numerous related publications per year. Perhaps the future of cutinases lies in their evolved descendants, such as polyesterases, and particularly PETases. The present article reviews the biochemical and structural characteristics of cutinases and cutinase-like hydrolases, and their applications in the field of bioremediation and biocatalysis.
      Citation: Catalysts
      PubDate: 2018-12-03
      DOI: 10.3390/catal8120612
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 613: Ir-Based Bimetallic Catalysts for Hydrogen
           Production through Glycerol Aqueous-Phase Reforming

    • Authors: Francisco Espinosa-Moreno, Putrakumar Balla, Wenjie Shen, Juan C. Chavarria-Hernandez, Miguel Ruiz-Gómez, Saúl Tlecuitl-Beristain
      First page: 613
      Abstract: Iridium, Iridium-Nickel and Iridium-Copper catalysts were prepared by incipient wetness impregnation and evaluated in the aqueous-phase reforming of glycerol using La2O3 or CeO2 as supports. The catalysts were characterized by N2 physisorption, XRD, H2-TPR, XPS, and EDS. The reactions were carried out in a fixed bed reactor feeding a solution of glycerol (10 wt %) in water, at 270 °C and 58 bar. All IrNi catalysts showed higher activity than Ir and IrCu, and in general, La2O3 catalysts showed a better performance when compared to CeO2 catalysts. The highest hydrogen production yield was reached by bimetallic IrNi catalysts with over 250 µmol min−1 gcat−1 for La2O3 and 150 µmol min−1 gcat−1 for CeO2.
      Citation: Catalysts
      PubDate: 2018-12-03
      DOI: 10.3390/catal8120613
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 614: Highly Active Nickel-Based Catalyst for
           Hydrogen Evolution in Anion Exchange Membrane Electrolysis

    • Authors: Alaa Y. Faid, Alejandro Oyarce Barnett, Frode Seland, Svein Sunde
      First page: 614
      Abstract: Anion exchange membrane (AEM) electrolysis is hampered by two main issues: stability and performance. Focusing on the latter, this work demonstrates a highly active NiMo cathode for hydrogen evolution in AEM electrolysis. We demonstrate an electrolyzer performance of 1 A cm−2 at 1.9 V (total cell voltage) with a NiMo loading of 5 mg cm−2 and an iridium black anode in 1 M KOH at 50 °C, that may be compared to 1.8 V for a similar cell with Pt at the cathode. The catalysts developed here will be significant in supporting the pursuit of cheap and environmentally friendly hydrogen fuel.
      Citation: Catalysts
      PubDate: 2018-12-03
      DOI: 10.3390/catal8120614
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 615: Enzymatic Synthesis of Novel Glycyrrhizic
           Acid Glucosides Using a Promiscuous Bacillus Glycosyltransferase

    • Authors: Longhai Dai, Jiao Li, Jiangang Yang, Yan Men, Yan Zeng, Yi Cai, Yuanxia Sun
      First page: 615
      Abstract: Glycyrrhetinic acid (GA) and glycyrrhizin (GA-3-O-[β-d-glucuronopyranosyl-(1→2)-β-d-glucuronopyranoside], GL) are the major bioactive components of Glycyrrhiza uralensis and possess multifarious notable biological activities. UDP-glycosyltransferase (UGT)–catalyzed glycosylation remarkably extends the structural and functional diversification of GA-glycoside derivatives. In this study, six glucosides (1–6) of GA and GL were synthesized using a Bacillus subtilis 168–originated flexible UDP-glycosyltransferase Bs-YjiC. Bs-YjiC could transfer a glucosyl moiety from UDP-glucose to the free C3 hydroxyl and/or C30 carboxyl groups of GA and GL and further elongate the C30 glucosyl chain via a β-1-2-glycosidic bond. Glycosylation significantly increased the water solubility of these novel glucosides by 4–90 folds. In vitro assays showed that GA monoglucosides (1 and 2) showed stronger antiproliferative activity against human liver cancer cells HepG2 and breast cancer cells MCF-7 than that of GL and GL glucosides. These findings provide significant insights into the important role of promiscuous UGTs for the enzymatic synthesis of novel bioactive GA derivatives.
      Citation: Catalysts
      PubDate: 2018-12-04
      DOI: 10.3390/catal8120615
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 616: The Mechanism of Adsorption, Diffusion, and
           Photocatalytic Reaction of Organic Molecules on TiO2 Revealed by Means of
           On-Site Scanning Tunneling Microscopy Observations

    • Authors: Peipei Huo, Parveen Kumar, Bo Liu
      First page: 616
      Abstract: The interaction of organic molecules and titanium dioxide (TiO2) plays a crucial role in many industry-oriented applications and an understanding of its mechanism can be helpful for the improvement of catalytic efficiency of TiO2. Scanning tunneling microscopy (STM) has been proved to be a powerful tool in characterizing reaction pathways due to its ability in providing on-site images during the catalytic process. Over the past two decades, many research interests have been focused on the elementary reaction steps, such as adsorption, diffusion, and photocatalytic reaction, occurring between organic molecules and model TiO2 surfaces. This review collects the recent studies where STM was utilized to study the interaction of TiO2 with three classes of representative organic molecules, i.e., alcohols, carboxylic acids, and aromatic compounds. STM can provide direct evidence for the adsorption configuration, diffusion route, and photocatalytic pathway. In addition, the combination of STM with other techniques, including photoemission spectroscopy (PES), temperature programmed desorption (TPD), and density functional theory (DFT), have been discussed for more insights related to organic molecules-TiO2 interaction.
      Citation: Catalysts
      PubDate: 2018-12-04
      DOI: 10.3390/catal8120616
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 617: Functionalized Ordered Mesoporous Silicas
           (MCM-41): Synthesis and Applications in Catalysis

    • Authors: Gabriel Martínez-Edo, Alba Balmori, Iris Pontón, Andrea Martí del Rio, David Sánchez-García
      First page: 617
      Abstract: Mesoporous silica sieves are among the most studied nano-objects due to their stable pore structure and easy preparation. In particular, MCM-41 have attracted increasing research attention due to their chemical versatility. This review focuses on the synthesis and regioselective functionalization of MCM-41 to prepare catalytic systems. The topics covered are: mono and di-functionalized MCM-41 as basic and acid catalysts, catalysts based on metallic complexes and heteropolyacids supported onto MCM-41, metallic nanoparticles embed onto functionalized MCM-41 and magnetic MCM-41 for catalytic purposes.
      Citation: Catalysts
      PubDate: 2018-12-04
      DOI: 10.3390/catal8120617
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 618: Direct Dehydrogenative Coupling of Alcohols
           with Hydrosilanes Promoted by Sodium tri(sec-butyl)borohydride

    • Authors: Maciej Skrodzki, Maciej Zaranek, Samanta Witomska, Piotr Pawluc
      First page: 618
      Abstract: Alkoxysilanes find application in many areas of chemistry ranging from research-scale organic synthesis to multi-ton production of materials. Classically, they are obtained in stoichiometric reaction of alcoholysis of chlorosilanes, however, recent years brought development in the field of direct dehydrogenative coupling of hydrosilanes with alcohols, which is a more atom-economic and benign alternative to the former process. In this paper, we report the use of sodium tri(sec-butyl)borohydride as a convenient promoter of this reaction. Exemplary syntheses carried out under mild conditions and without additional solvents, followed by very easy work-up procedure, show excellent potential for application of so devised catalytic system.
      Citation: Catalysts
      PubDate: 2018-12-04
      DOI: 10.3390/catal8120618
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 619: Advancement of Metabolic Engineering
           Assisted by Synthetic Biology

    • Authors: Hyang-Mi Lee, Phuong N. L. Vo, Dokyun Na
      First page: 619
      Abstract: Synthetic biology has undergone dramatic advancements for over a decade, during which it has expanded our understanding on the systems of life and opened new avenues for microbial engineering. Many biotechnological and computational methods have been developed for the construction of synthetic systems. Achievements in synthetic biology have been widely adopted in metabolic engineering, a field aimed at engineering micro-organisms to produce substances of interest. However, the engineering of metabolic systems requires dynamic redistribution of cellular resources, the creation of novel metabolic pathways, and optimal regulation of the pathways to achieve higher production titers. Thus, the design principles and tools developed in synthetic biology have been employed to create novel and flexible metabolic pathways and to optimize metabolic fluxes to increase the cells’ capability to act as production factories. In this review, we introduce synthetic biology tools and their applications to microbial cell factory constructions.
      Citation: Catalysts
      PubDate: 2018-12-04
      DOI: 10.3390/catal8120619
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 620: Non-Classical Anionic Naked N-Heterocyclic
           Carbenes: Fundamental Properties and Emerging Applications in Synthesis
           and Catalysis

    • Authors: Mei Yi Leow, Curtis C. Ho, Michael G. Gardiner, Alex C. Bissember
      First page: 620
      Abstract: Ongoing research exploring the chemistry of N-heterocyclic carbenes (NHCs) has led to the development and discovery of new NHC subclasses that deviate beyond Arduengo’s prototypical N,N′-disubstituted imidazol-2-ylidene-based structures. These systems continue to enable and extend the fundamental role of NHC ligands in synthesis and catalysis. In this regard, the advent of protic NHCs has garnered particular interest. This derives in part from their applications to the selective preparation of unique molecular scaffolds and their unprecedented bifunctional reactivity, which can be exploited in transition metal-catalyzed processes. In comparison, the synthetic applications of closely related anionic naked NHCs remain rather underexplored. With this in mind, this review highlights the interesting fundamental properties of non-classical anionic naked NHCs, and focuses on their emerging applications in synthesis and catalysis.
      Citation: Catalysts
      PubDate: 2018-12-04
      DOI: 10.3390/catal8120620
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 621: Insights into the Recent Progress and
           Advanced Materials for Photocatalytic Nitrogen Fixation for Ammonia (NH3)
           Production

    • Authors: Manh-Hiep Vu, M. Sakar, Trong-On Do
      First page: 621
      Abstract: Ammonia (NH3) is one of the key agricultural fertilizers and to date, industries are using the conventional Haber-Bosh process for the synthesis of NH3 which requires high temperature and energy. To overcome such challenges and to find a sustainable alternative process, researchers are focusing on the photocatalytic nitrogen fixation process. Recently, the effective utilization of sunlight has been proposed via photocatalytic water splitting for producing green energy resource, hydrogen. Inspired by this phenomenon, the production of ammonia via nitrogen, water and sunlight has been attracted many efforts. Photocatalytic N2 fixation presents a green and sustainable ammonia synthesis pathway. Currently, the strategies for development of efficient photocatalyst for nitrogen fixation is primarily concentrated on creating active sites or loading transition metal to facilitate the charge separation and weaken the N–N triple bond. In this investigation, we review the literature knowledge about the photocatalysis phenomena and the most recent developments on the semiconductor nanocomposites for nitrogen fixation, following by a detailed discussion of each type of mechanism.
      Citation: Catalysts
      PubDate: 2018-12-04
      DOI: 10.3390/catal8120621
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 622: Metals on ZrO2: Catalysts for the Aldol
           Condensation of Methyl Ethyl Ketone (MEK) to C8 Ketones

    • Authors: Zahraa Al-Auda, Hayder Al-Atabi, Keith L. Hohn
      First page: 622
      Abstract: Methyl ethyl ketone (MEK) was converted to heavier ketones in one step, using a multi-functional catalyst having both aldol condensation (aldolization and dehydration) and hydrogenation properties. 15% Cu supported zirconia (ZrO2) was investigated in the catalytic gas phase reaction of MEK in a fixed bed reactor. The results showed that the main product was 5-methyl-3-heptanone (C8 ketone), with side products including 5-methyl-3-heptanol, 2-butanol, and other heavy products (C12 and up). The effects of various reaction parameters, like temperature and molar ratio of reactants (H2/MEK), on the overall product selectivity were studied. It was found that with increasing the temperature of the reaction, the selectivity to the C8 ketone increased, while selectivity to the 2-butanol decreased. Also, hydrogen pressure played a significant role in the selectivity of the products. It was observed that with increasing the H2/MEK molar ratio, the 2-butanol selectivity increased because of the hydrogenation reaction, while decreasing this ratio led to increasing the aldol condensation products. In addition, it was noted that both the conversion and selectivity to the main product increased using a low loading percentage of copper, 1% Cu–ZrO2. The highest selectivity of 5-methyl-3-heptanone reached ~64%, and was obtained at a temperature of around 180 °C and a molar ratio of H2/MEK equal to 2. Other metals (Ni, Pd, and Pt) that were supported on ZrO2 also produced 5-methyl-3-heptanone as the main product, with slight differences in selectivity, suggesting that a hydrogenation catalyst is important for producing the C8 ketone, but that the exact identity of the metal is less important.
      Citation: Catalysts
      PubDate: 2018-12-05
      DOI: 10.3390/catal8120622
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 623: Surface Probing by Spectroscopy on
           Titania-Supported Gold Nanoparticles for a Photoreductive Application

    • Authors: Matteo Compagnoni, Alberto Villa, Elnaz Bahdori, David J. Morgan, Laura Prati, Nikolaos Dimitratos, Ilenia Rossetti, Gianguido Ramis
      First page: 623
      Abstract: The continuous increase in scientific reports concerning photocatalysis and in particular CO2 photoreduction in recent years reveals the high degree of interest around the topic. However, the adsorption and activation mechanisms of CO2 on TiO2, the most used photocatalyst, are poorly understood and investigated. Gold nanoparticles were prepared by a modified deposition-precipitation method using urea and a chemical reductant. Bare P25 was used as reference. Combined spectroscopic investigations of fresh and spent samples with photoactivity studies reported in this article provide new insights to the role of CO2 adsorption and carbonate formation on Au/TiO2 during CO2 photocatalytic reduction. The key intermediates’ and products’ adsorption (CO, methanol, ethanol) was studied, coupled with X-ray photoelectron microscopy (XPS) and UV-Visible spectroscopy. The adsorption of CO2 on fresh and spent catalysts changes radically considering the carbonate formation and the gold surface presence. Methanol and ethanol revealed new adsorbed species on Au with respect to bare titania. The characterisation of the spent catalysts revealed the good stability of these samples.
      Citation: Catalysts
      PubDate: 2018-12-05
      DOI: 10.3390/catal8120623
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 624: Biotechnological Methods of Sulfoxidation:
           Yesterday, Today, Tomorrow

    • Authors: Wanda Mączka, Katarzyna Wińska, Małgorzata Grabarczyk
      First page: 624
      Abstract: The production of chiral sulphoxides is an important part of the chemical industry since they have been used not only as pharmaceuticals and pesticides, but also as catalysts or functional materials. The main purpose of this review is to present biotechnological methods for the oxidation of sulfides. The work consists of two parts. In the first part, examples of biosyntransformation of prochiral sulfides using whole cells of bacteria and fungi are discussed. They have more historical significance due to the low predictability of positive results in relation to the workload. In the second part, the main enzymes responsible for sulfoxidation have been characterized such as chloroperoxidase, dioxygenases, cytochrome flavin-dependent monooxygenases, and P450 monooxygenases. Particular emphasis has been placed on the huge variety of cytochrome P450 monooxygenases, and flavin-dependent monooxygenases, which allows for pure sulfoxides enantiomers effectively to be obtained. In the summary, further directions of research on the optimization of enzymatic sulfoxidation are indicated.
      Citation: Catalysts
      PubDate: 2018-12-05
      DOI: 10.3390/catal8120624
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 625: Photocatalytic Degradation of Estriol Using
           Iron-Doped TiO2 under High and Low UV Irradiation

    • Authors: Irwing M. Ramírez-Sánchez, Erick R. Bandala
      First page: 625
      Abstract: Iron-doped TiO2 nanoparticles (Fe-TiO2) were synthesized and photocatalitically investigated under high and low fluence values of UV radiation. The Fe-TiO2 physical characterization was performed using X-ray Powder Diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Diffuse Reflectance Spectroscopy (DRS), and X-ray Photoelectron Spectroscopy (XPS). The XPS evidenced that the ferric ion (Fe3+) was in the TiO2 lattice and unintentionally added co-dopants were also present because of the precursors of the synthetic method. The Fe3+ concentration played a key role in the photocatalytic generation of hydroxyl radicals (•OH) and estriol (E3) degradation. Fe-TiO2 accomplished E3 degradation, and it was found that the catalyst with 0.3 at.% content of Fe (0.3 Fe-TiO2) enhanced the photocatalytic activity under low UV irradiation compared with TiO2 without intentionally added Fe (zero-iron TiO2) and Aeroxide® TiO2 P25. Furthermore, the enhanced photocatalytic activity of 0.3 Fe-TiO2 under low UV irradiation may have applications when radiation intensity must be controlled, as in medical applications, or when strong UV absorbing species are present in water.
      Citation: Catalysts
      PubDate: 2018-12-05
      DOI: 10.3390/catal8120625
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 626: Kinetic Modeling of Catalytic Olefin
           Cracking and Methanol-to-Olefins (MTO) over Zeolites: A Review

    • Authors: Sebastian Standl, Olaf Hinrichsen
      First page: 626
      Abstract: The increasing demand for lower olefins requires new production routes besides steam cracking and fluid catalytic cracking (FCC). Furthermore, less energy consumption, more flexibility in feed and a higher influence on the product distribution are necessary. In this context, catalytic olefin cracking and methanol-to-olefins (MTO) gain in importance. Here, the undesired higher olefins can be catalytically converted and, for methanol, the possibility of a green synthesis route exists. Kinetic modeling of these processes is a helpful tool in understanding the reactivity and finding optimum operating points; however, it is also challenging because reaction networks for hydrocarbon interconversion are rather complex. This review analyzes different deterministic kinetic models published in the literature since 2000. After a presentation of the underlying chemistry and thermodynamics, the models are compared in terms of catalysts, reaction setups and operating conditions. Furthermore, the modeling methodology is shown; both lumped and microkinetic approaches can be found. Despite ZSM-5 being the most widely used catalyst for these processes, other catalysts such as SAPO-34, SAPO-18 and ZSM-23 are also discussed here. Finally, some general as well as reaction-specific recommendations for future work on modeling of complex reaction networks are given.
      Citation: Catalysts
      PubDate: 2018-12-05
      DOI: 10.3390/catal8120626
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 627: Recent Advances in the Gold-Catalysed
           Low-Temperature Water–Gas Shift Reaction

    • Authors: James H. Carter, Graham J. Hutchings
      First page: 627
      Abstract: The low-temperature water–gas shift reaction (LTS: CO + H2O ⇌ CO2 + H2) is a key step in the purification of H2 reformate streams that feed H2 fuel cells. Supported gold catalysts were originally identified as being active for this reaction twenty years ago, and since then, considerable advances have been made in the synthesis and characterisation of these catalysts. In this review, we identify and evaluate the progress towards solving the most important challenge in this research area: the development of robust, highly active catalysts that do not deactivate on-stream under realistic reaction conditions.
      Citation: Catalysts
      PubDate: 2018-12-05
      DOI: 10.3390/catal8120627
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 628: Microcystis aeruginosa Synergistically
           Facilitate the Photocatalytic Degradation of Tetracycline Hydrochloride
           and Cr(VI) on PAN/TiO2/Ag Nanofiber Mats

    • Authors: Lei Wang, Changbo Zhang, Rong Cheng, Jafar Ali, Zhenbo Wang, Gilles Mailhot, Gang Pan
      First page: 628
      Abstract: Cyanobacterial blooms can cause serious damage to aquatic ecosystems. However, we have demonstrated that typical algae-blooming species Microcystis aeruginosa (M. aeruginosa) combined with photocatalysts could synergistically facilitate the photodecontamination of tetracycline hydrochloride (TC) and Cr(VI). In this study, for the first time, harmful algae were successfully converted into photoreactive bionano hybrid materials by immobilizing M. aeruginosa cells onto polyacrylonitrile (PAN)-TiO2/Ag hybrid nanofibers, and their photocatalytic activity was evaluated. The addition of M. aeruginosa significantly improved the photodecontamination, and the reaction rate constant (k) values of TC and Cr(VI) degradation by M. aeruginosa-PAN/TiO2/Ag nanofiber mats were 2.4 and 1.5-fold higher than that of bare PAN/TiO2/Ag nanofiber. Photoreaction caused damage to algae cells, but no microcystin was found that had been photodegraded simultaneously. The effects of various active species were also investigated, and the photodegradation mechanism was proposed. Recycling tests revealed that this flexible M. aeruginosa-PAN/TiO2/Ag hybrid mat had potential application in the removal of mixed organic and inorganic pollutants with high efficiency and without secondary pollutants. Thus, harmful algae blooms could serve as an efficient materials to remove toxic pollutants in a sustainable way under visible light irradiation.
      Citation: Catalysts
      PubDate: 2018-12-05
      DOI: 10.3390/catal8120628
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 629: Electro-Reduction of Molecular Oxygen
           Mediated by a Cobalt(II)octaethylporphyrin System onto Oxidized Glassy
           Carbon/Oxidized Graphene Substrate

    • Authors: Camila Canales, Leyla Gidi, Roxana Arce, Francisco Armijo, María J. Aguirre, Galo Ramírez
      First page: 629
      Abstract: The oxygen reduction reaction (ORR) is the most important reaction in life processes and in energy transformation. The following work presents the design of a new electrode which is composed by deposited cobalt octaethylporphyrin onto glassy carbon and graphene, where both carbonaceous materials have been electrochemically oxidized prior to the porphyrin deposition. The novel generated system is stable and has an electrocatalytic effect towards the oxygen reduction reaction, as a result of the significant overpotential shift in comparison to the unmodified electrode and to the electrodes used as target. Kinetic studies corroborate that the system is capable of reducing molecular oxygen via four electrons, with a Tafel slope value of 60 mV per decade. The systems were morphologically characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) Electrochemical impedance spectroscopy studies showed that the electrode previously oxidized and modified with cobalt porphyrin is the system that possesses lower resistance to charge transfer and higher capacitance.
      Citation: Catalysts
      PubDate: 2018-12-06
      DOI: 10.3390/catal8120629
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 630: Photocatalytic Degradation of Humic Acids
           Using LaFeO3

    • Authors: Nazli Turkten, Isabella Natali Sora, Ayse Tomruk, Miray Bekbolet
      First page: 630
      Abstract: TiO2 photocatalytic degradation of dissolved organic matter (DOM), namely humic substances composed of humic (HA) and fulvic acids, has been investigated for decades. However, the application of non-TiO2 photocatalysis for this purpose has only received recent attention. Aiming to fill this gap, this study was performed to elucidate the photocatalytic degradation of HAs using the novel photocatalyst LaFeO3 (LF) under simulated solar light irradiation. HA was selectively fractionated by ultrafiltration to two different molecular size fractions representing high molecular fraction as 100 kDa and lower molecular size fraction comprised of humic components expressing size fractions smaller than 30 kDa. Photocatalyst LF was prepared by the citrate auto-combustion method and characterized by using various techniques and Brunauer–Emmett–Teller (BET) surface area. Ultraviolet (UV)-vis and excitation-emission matrix (EEM) fluorescence spectroscopic features were used to characterize the treated HA and photocatalytic mineralization extend was followed by dissolved organic carbon (DOC) contents. Photocatalytic performance of LF was compared to the metal modified version as Cu-doped LF. Highest mineralization was achieved upon the use of a photocatalyst dose of 0.25 mg/mL of LaFe0.90Cu0.10O3−δ (Cu-LF) for 30 kDaHA, whereas lowest mineralization was attained for 100 kDaHA upon the use of LF. Photocatalytic degradation kinetics indicated the possible use of LF and Cu-LF for the degradation of HA.
      Citation: Catalysts
      PubDate: 2018-12-06
      DOI: 10.3390/catal8120630
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 631: Enhanced Photocatalytic Activity of Titania
           by Co-Doping with Mo and W

    • Authors: Osmín Avilés-García, Jaime Espino-Valencia, Rubí Romero-Romero, José Luis Rico-Cerda, Manuel Arroyo-Albiter, Dora Alicia Solís-Casados, Reyna Natividad-Rangel
      First page: 631
      Abstract: Various W and Mo co-doped titanium dioxide (TiO2) materials were obtained through the EISA (Evaporation-Induced Self-Assembly) method and then tested as photocatalysts in the degradation of 4-chlorophenol. The synthesized materials were characterized by thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy (RS), N2 physisorption, UV-vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The results showed that the W-Mo-TiO2 catalysts have a high surface area of about 191 m2/g, and the presence of an anatase crystalline phase. The co-doped materials exhibited smaller crystallite sizes than those with one dopant, since the crystallinity is inhibited by the presence of both species. In addition, tungsten and molybdenum dopants are distributed and are incorporated into the anatase structure of TiO2, due to changes in red parameters and lattice expansion. Under our experimental conditions, the co-doped TiO2 catalyst presented 46% more 4-chlorophenol degradation than Degussa P25. The incorporation of two dopant cations in titania improved its photocatalytic performance, which was attributed to a cooperative effect by decreasing the recombination of photogenerated charges, high radiation absorption capacity, high surface areas, and low crystallinity. When TiO2 is co-doped with the same amount of both cations (1 wt.%), the highest degradation and mineralization (97% and 74%, respectively) is achieved. Quinones were the main intermediates in the 4-chlorophenol oxidation by W-Mo-TiO2 and 1,2,4-benzenetriol was incompletely degraded.
      Citation: Catalysts
      PubDate: 2018-12-06
      DOI: 10.3390/catal8120631
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 632: Nucleophilic Dearomatization of Activated
           Pyridines

    • Authors: Giulio Bertuzzi, Luca Bernardi, Mariafrancesca Fochi
      First page: 632
      Abstract: Amongst nitrogen heterocycles of different ring sizes and oxidation statuses, dihydropyridines (DHP) occupy a prominent role due to their synthetic versatility and occurrence in medicinally relevant compounds. One of the most straightforward synthetic approaches to polysubstituted DHP derivatives is provided by nucleophilic dearomatization of readily assembled pyridines. In this article, we collect and summarize nucleophilic dearomatization reactions of - pyridines reported in the literature between 2010 and mid-2018, complementing and updating previous reviews published in the early 2010s dedicated to various aspects of pyridine chemistry. Since functionalization of the pyridine nitrogen, rendering a (transient) pyridinium ion, is usually required to render the pyridine nucleus sufficiently electrophilic to suffer the attack of a nucleophile, the material is organized according to the type of N-functionalization. A variety of nucleophilic species (organometallic reagents, enolates, heteroaromatics, umpoled aldehydes) can be productively engaged in pyridine dearomatization reactions, including catalytic asymmetric implementations, providing useful and efficient synthetic platforms to (enantioenriched) DHPs. Conversely, pyridine nitrogen functionalization can also lead to pyridinium ylides. These dipolar species can undergo a variety of dipolar cycloaddition reactions with electron-poor dipolarophiles, affording polycyclic frameworks and embedding a DHP moiety in their structures.
      Citation: Catalysts
      PubDate: 2018-12-06
      DOI: 10.3390/catal8120632
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 633: Carbonate-Catalyzed Room-Temperature
           Selective Reduction of Biomass-Derived 5-Hydroxymethylfurfural into
           2,5-Bis(hydroxymethyl)furan

    • Authors: Jingxuan Long, Wenfeng Zhao, Yufei Xu, Hu Li, Song Yang
      First page: 633
      Abstract: Catalytic reduction of 5-hydroxymethylfurfural (HMF), deemed as one of the key bio-based platform compounds, is a very promising pathway for the upgrading of biomass to biofuels and value-added chemicals. Conventional hydrogenation of HMF is mainly conducted over precious metal catalysts with high-pressure hydrogen. Here, a highly active, sustainable, and facile catalytic system composed of K2CO3, Ph2SiH2, and bio-based solvent 2-methyltetrahydrofuran (MTHF) was developed to be efficient for the reduction of HMF. At a low temperature of 25 °C, HMF could be completely converted to 2,5-bis(hydroxymethyl)furan (BHMF) in a good yield of 94% after 2 h. Moreover, a plausible reaction mechanism was speculated, where siloxane in situ formed via hydrosilylation was found to be the key species responsible for the high reactivity.
      Citation: Catalysts
      PubDate: 2018-12-07
      DOI: 10.3390/catal8120633
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 634: Recent Progress in Constructing Plasmonic
           Metal/Semiconductor Hetero-Nanostructures for Improved Photocatalysis

    • Authors: Liang Ma, Shuang Chen, Yun Shao, You-Long Chen, Mo-Xi Liu, Hai-Xia Li, Yi-Ling Mao, Si-Jing Ding
      First page: 634
      Abstract: Hetero-nanomaterials constructed by plasmonic metals and functional semiconductors show enormous potential in photocatalytic applications, such as in hydrogen production, CO2 reduction, and treatment of pollutants. Their photocatalytic performances can be better regulated through adjusting structure, composition, and components’ arrangement. Therefore, the reasonable design and synthesis of metal/semiconductor hetero-nanostructures is of vital significance. In this mini-review, we laconically summarize the recent progress in efficiently establishing metal/semiconductor nanomaterials for improved photocatalysis. The defined photocatalysts mainly include traditional binary hybrids, ternary multi-metals/semiconductor, and metal/multi-semiconductors heterojunctions. The underlying physical mechanism for the enhanced photocatalysis of the established photocatalysts is highlighted. In the end, a brief summary and possible future perspectives for further development in this field are demonstrated.
      Citation: Catalysts
      PubDate: 2018-12-07
      DOI: 10.3390/catal8120634
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 635: Characterization of Highly Dispersed Rod-
           and Particle-Shaped CuFe19Ox Catalysts and Their Shape Effects on WGS

    • Authors: Lingjuan Ma, Dawei Han, Hongbin Ma, Longgang Liu, Huichao Guo
      First page: 635
      Abstract: Highly dispersed CuFe19Ox catalysts with different shapes were prepared and further characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR), and in-situ XRD. XRD and TEM results showed that the synthesized CuFe19Ox nanoparticles consisted of CuO and Fe2O3, while CuFe19Ox nanorods consisted of CuFe2O4 and Fe2O3. The reduction properties of CuFe19Ox samples were finely studied by H2-TPR, and the phase composition was identified by in-situ XPS, HR-TEM, and surface TPR (s-TPR). In-situ X-ray photoelectroscopy (XPS) indicated that the metallic Cu and Fe3O4 were the main species after reduction. Moreover, s-TPR studies showed that the reduction performance of copper was significantly affected by the shapes of the Fe3O4 supports. Low-temperature water gas shift (LT-WGS) was chosen to characterize the Cu species on the surface. It was found that reduced CuFe19Ox nanorods had no activity. On the contrary, reduced CuFe19Ox particles showed higher initial WGS activity, where the active Cu0 should originate from the reduction of Cu2O at lower temperatures, as confirmed by the s-TPR profiles.
      Citation: Catalysts
      PubDate: 2018-12-07
      DOI: 10.3390/catal8120635
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 636: Copper(II) Complexes of Arylhydrazone of
           1H-Indene-1,3(2H)-dione as Catalysts for the Oxidation of Cyclohexane in
           Ionic Liquids

    • Authors: Gonçalo A. O. Tiago, Ana P. C. Ribeiro, M. Fátima C. Guedes da Silva, Kamran T. Mahmudov, Luís C. Branco, Armando J. L. Pombeiro
      First page: 636
      Abstract: The copper(II) complexes [CuL(H2O)2]∙H2O (1) and [CuL(dea)] (2) [L = 2-(2-(1,3-dioxo-1H-inden-2(3H)-ylidene)hydrazinyl)benzenesulfonate, dea = diethanolamine] were applied as catalysts in the peroxidative (with tert-butyl-hydroperoxide or hydrogen peroxide) conversion of cyclohexane to cyclohexanol and cyclohexanone, either in acetonitrile or in any of the ionic liquids [bmim][NTf2] and [hmim][NTf2] [bmim = 1-butyl-3-methylimidazolium, hmim = 1-hexyl-3-methylimidazolium, NTf2 = bis(trifluoromethanesulfonyl) imide]. Tert-butyl-hydroperoxide led to better product yields, as compared to H2O2, with a selectivity directed towards cyclohexanone. The ILs showed a better performance than the conventional solvent for the copper complex 1. No catalytic activity was observed for 2 in the presence of an IL.
      Citation: Catalysts
      PubDate: 2018-12-07
      DOI: 10.3390/catal8120636
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 637: Catalytic Processes from Biomass-Derived
           Hexoses and Pentoses: A Recent Literature Overview

    • Authors: Jesús Esteban, Pedro Yustos, Miguel Ladero
      First page: 637
      Abstract: Biomass is a plentiful renewable source of energy, food, feed and chemicals. It fixes about 1–2% of the solar energy received by the Earth through photosynthesis in both terrestrial and aquatic plants like macro- and microalgae. As fossil resources deplete, biomass appears a good complement and eventually a good substitute feedstock, but still needs the development of relatively new catalytic processes. For this purpose, catalytic transformations, whether alone or combined with thermal ones and separation operations, have been under study in recent years. Catalytic biorefineries are based on dehydration-hydrations, hydrogenations, oxidations, epimerizations, isomerizations, aldol condensations and other reactions to obtain a plethora of chemicals, including alcohols, ketones, furans and acids, as well as materials such as polycarbonates. Nevertheless, there is still a need for higher selectivity, stability, and regenerability of catalysts and of process intensification by a wise combination of operations, either in-series or combined (one-pot), to reach economic feasibility. Here we present a literature survey of the latest developments for obtaining value-added products using hexoses and pentoses derived from lignocellulosic material, as well as algae as a source of carbohydrates for subsequent transformations.
      Citation: Catalysts
      PubDate: 2018-12-07
      DOI: 10.3390/catal8120637
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 638: Palladium Supported on Carbon Nanotubes as a
           High-Performance Catalyst for the Dehydrogenation of
           Dodecahydro-N-ethylcarbazole

    • Authors: Mengyan Zhu, Lixin Xu, Lin Du, Yue An, Chao Wan
      First page: 638
      Abstract: Hydrogen storage in the form of liquid organic hydrides, especially N-ethylcarbazole, has been regarded as a promising technology for substituting traditional fossil fuels owing to its unique merits such as high volumetric, gravimetric hydrogen capacity and safe transportation. However, unsatisfactory dehydrogenation has impeded the widespread application of N-ethylcarbazole as ideal hydrogen storage materials in hydrogen energy. Therefore, designing catalysts with outstanding performance is of importance to address this problem. In the present work, for the first time, we have synthesized Pd nanoparticles immobilized on carbon nanotubes (Pd/CNTs) with different palladium loading through an alcohol reduction technique. A series of characterization technologies, such as X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectrometer (ICP-AES), X-ray photoelectron spectroscopy (XPS) and transmission electron spectroscopy (TEM) were adopted to systematically explore the structure, composition, surface properties and morphology of the catalysts. The results reveal that the Pd NPs with a mean diameter of 2.6 ± 0.6 nm could be dispersed uniformly on the surface of CNTs. Furthermore, Pd/CNTs with different Pd contents were applied in the hydrogen release of dodecahydro-N-ethylcarbazole. Among all of the catalysts tested, 3.0 wt% Pd/CNTs exhibited excellent catalytic performance with the conversion of 99.6% producing 5.8 wt% hydrogen at 533 K, low activation energy of 43.8 ± 0.2 kJ/mol and a high recycling stability (>96.4% conversion at 5th reuse).
      Citation: Catalysts
      PubDate: 2018-12-08
      DOI: 10.3390/catal8120638
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 639: Catalytic Oxidative/Extractive
           Desulfurization of Model Oil using Transition Metal Substituted
           Phosphomolybdates-Based Ionic Liquids

    • Authors: Yunlei Li, Yanjie Zhang, Panfeng Wu, Caiting Feng, Ganglin Xue
      First page: 639
      Abstract: Polyoxometalates based ionic liquids (POM-ILs) exhibit a high catalytic activity in oxidative desulfurization. In this paper, four new POM-IL hybrids based on transition metal mono-substituted Keggin-type phosphomolybdates, [Bmim]5[PMo11M(H2O)O39] (Bmim = 1-butyl 3-methyl imidazolium; M = Co2+, Ni2+, Zn2+, and Mn2+), have been synthesized and used as catalysts for the oxidation/extractive desulfurization of model oil, in which ILs are used as the extraction solvent and H2O2 as an oxidant under very mild conditions. The factors that affected the desulfurization efficiency were studied and the optimal reaction conditions were obtained. The results showed that the [Bmim]5[PMo11Co(H2O)O39] catalyst demonstrated the best catalytic activity, with sulfur-removal of 99.8%, 85%, and 63% for dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), and benzothiophene (BT), respectively, in the case of extraction combining with a oxidative desulfurization system under optimal reaction conditions (5 mL model oil (S content 500 ppm), n(catalyst) = 4 μmol, n(H2O2)/n(Substrate) = 5, T = 50 °C for 60 min with [Omim]BF4 (1 mL) as the extractant). The catalyst can be recycled at least 8 times, and still has stability and high catalytic activity for consecutive desulfurization. Probable reaction mechanisms have been proposed for catalytic oxidative/extractive desulfurization.
      Citation: Catalysts
      PubDate: 2018-12-08
      DOI: 10.3390/catal8120639
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 640: Recent Advances in Homogeneous
           Metal-Catalyzed Aerobic C–H Oxidation of Benzylic Compounds

    • Authors: Garazi Urgoitia, Raul SanMartin, María Teresa Herrero, Esther Domínguez
      First page: 640
      Abstract: Csp3–H oxidation of benzylic methylene compounds is an established strategy for the synthesis of aromatic ketones, esters, and amides. The need for more sustainable oxidizers has encouraged researchers to explore the use of molecular oxygen. In particular, homogeneous metal-catalyzed aerobic oxidation of benzylic methylenes has attracted much attention. This account summarizes the development of this oxidative strategy in the last two decades, examining key factors such as reaction yields, substrate:catalyst ratio, substrate scope, selectivity over other oxidation byproducts, and reaction conditions including solvents and temperature. Finally, several mechanistic proposals to explain the observed results will be discussed.
      Citation: Catalysts
      PubDate: 2018-12-08
      DOI: 10.3390/catal8120640
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 641: Highly Selective Photocatalytic Reduction of
           o-Dinitrobenzene to o-Phenylenediamine over Non-Metal-Doped TiO2 under
           Simulated Solar Light Irradiation

    • Authors: Hamza M. El-Hosainy, Said M. El-Sheikh, Adel A. Ismail, Amer Hakki, Ralf Dillert, Hamada M. Killa, Ibrahim A. Ibrahim, Detelf W. Bahnemann
      First page: 641
      Abstract: Photocatalytic reduction and hydrogenation reaction of o-dinitrobenzene in the presence of oxalic acid over anatase-brookite biphasic TiO2 and non-metal-doped anatase-brookite biphasic TiO2 photocatalysts under solar simulated light was investigated. Compared with commercial P25 TiO2, the prepared un-doped and doped anatase-brookite biphasic TiO2 exhibited a high selectivity towards the formation of o-nitroaniline (85.5%) and o-phenylenediamine ~97%, respectively. The doped anatase-brookite biphasic TiO2 has promoted photocatalytic reduction of the two-nitro groups of o-dinitrobenzene to the corresponding o-phenylenediamine with very high yield ~97%. Electron paramagnetic resonance analysis, Transient Absorption Spectroscopy (TAS) and Photoluminescence analysis (PL) were performed to determine the distribution of defects and the fluorescence lifetime of the charge carriers for un-doped and doped photocatalysts. The superiority of the doped TiO2 photocatalysts is accredited to the creation of new dopants (C, N, and S) as hole traps, the formation of long-lived Ti3+ defects which leads to an increase in the fluorescence lifetime of the formed charge carriers. The schematic diagram of the photocatalytic reduction of o-dinitrobenzene using the doped TiO2 under solar light was also illustrated in detail.
      Citation: Catalysts
      PubDate: 2018-12-09
      DOI: 10.3390/catal8120641
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 642: Structure–Activity Relationship Study of
           Mn/Fe Ratio Effects on Mn−Fe−Ce−Ox/γ-Al2O3 Nanocatalyst for NO
           Oxidation and Fast SCR Reaction

    • Authors: Yan Gao, Tao Luan, Mingyang Zhang, Wenke Zhang, Wenchen Feng
      First page: 642
      Abstract: A series of Mn−Fe−Ce−Ox/γ-Al2O3 nanocatalysts were synthesized with different Mn/Fe ratios for the catalytic oxidation of NO into NO2 and the catalytic elimination of NOx via fast selective catalytic reduction (SCR) reaction. The effects of Mn/Fe ratio on the physicochemical properties of the samples were analyzed by means of various techniques including N2 adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H2-temperature-programmed reduction (TPR), NH3-temperature-programmed desorption (TPD) and NO-TPD, meanwhile, their catalytic performance was also evaluated and compared. Multiple characterizations revealed that the catalytic performance was highly dependent on the phase composition. The Mn15Fe15−Ce/Al sample with the Mn/Fe molar ratio of 1.0 presented the optimal structure characteristic among all tested samples, with the largest surface area, increased active components distributions, the reduced crystallinity and diminished particle sizes. In the meantime, the ratios of Mn4+/Mnn+, Fe2+/Fen+ and Ce3+/Cen+ in Mn15Fe15−Ce/Al samples were improved, which could enhance the redox capacity and increase the quantity of chemisorbed oxygen and oxygen vacancy, thus facilitating NO oxidation into NO2 and eventually promoting the fast SCR reaction. In accord with the structure results, the Mn15Fe15−Ce/Al sample exhibited the highest NO oxidation rate of 64.2% at 350 °C and the broadest temperature window of 75–350 °C with the NOx conversion >90%. Based on the structure–activity relationship discussion, the catalytic mechanism over the Mn−Fe−Ce ternary components supported by γ-Al2O3 were proposed. Overall, it was believed that the optimization of Mn/Fe ratio in Mn−Fe−Ce/Al nanocatalyst was an extremely effective method to improve the structure–activity relationships for NO pre-oxidation and the fast SCR reaction.
      Citation: Catalysts
      PubDate: 2018-12-09
      DOI: 10.3390/catal8120642
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 643: Acetic Acid/Propionic Acid Conversion on
           Metal Doped Molybdenum Carbide Catalyst Beads for Catalytic Hot Gas
           Filtration

    • Authors: Mi Lu, Andrew W. Lepore, Jae-Soon Choi, Zhenglong Li, Zili Wu, Felipe Polo-Garzon, Michael Z. Hu
      First page: 643
      Abstract: Catalytic hot gas filtration (CHGF) is used to precondition biomass derived fast pyrolysis (FP) vapors by physically removing reactive char and alkali particulates and chemically converting reactive oxygenates to species that are more easily upgraded during subsequent catalytic fast pyrolysis (CFP). Carboxylic acids, such as acetic acid and propionic acid, form during biomass fast pyrolysis and are recalcitrant to downstream catalytic vapor upgrading. This work developed and evaluated catalysts that can convert these acids to more upgradeable ketones at the laboratory scale. Selective catalytic conversion of these reactive oxygenates to more easily upgraded compounds can enhance bio-refinery processing economics through catalyst preservation by reduced coking from acid cracking, by preserving carbon efficiency, and through process intensification by coupling particulate removal with partial upgrading. Two metal-doped molybdenum carbide (Mo2C) supported catalyst beads were synthesized and evaluated and their performance compared with an undoped Mo2C control catalyst beads. For laboratory scale acetic acid conversion, calcium doped Mo2C supported catalyst beads produced the highest yield of acetone at ~96% at 450 °C among undoped and Ca or Ni doped catalysts.
      Citation: Catalysts
      PubDate: 2018-12-09
      DOI: 10.3390/catal8120643
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 644: Effect of Additives on the Activity of
           Nickel–Tungsten Sulfide Hydroconversion Catalysts Prepared In Situ from
           Oil-Soluble Precursors

    • Authors: Mariia Kniazeva, Anton Maximov
      First page: 644
      Abstract: The nickel–tungsten sulfide catalysts for the hydroconversion of hydrocarbons were prepared from oil-soluble nickel and tungsten precursor compounds in situ with the use of silica, alumina, titania, zeolite Y, and amorphous aluminosilicate as additives in a vacuum gas oil medium. It was found that the catalytic activity in hydrocracking depends on the concentration of acid sites in the resulting catalyst. With the use of oxide additives, the dispersion and the promoter ratio of the in situ formed sulfide particles increased in the order SiO2–Al2O3–TiO2. It was noted that the promoter ratio of sulfide particles obtained with the use of aluminosilicate additives depended on their porous structure peculiarities. The use of titanium dioxide as a catalytic system component made it possible to reach high activity in hydrocracking, hydrodearomatization, and hydrodesulfurization, which was comparable to that of a system based on zeolite Y, a highly acidic component.
      Citation: Catalysts
      PubDate: 2018-12-10
      DOI: 10.3390/catal8120644
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 645: Hydrotreatment Followed by Oxidative
           Desulfurization and Denitrogenation to Attain Low Sulphur and Nitrogen
           Bitumen Derived Gas Oils

    • Authors: Sandeep Badoga, Prachee Misra, Girish Kamath, Ying Zheng, Ajay K. Dalai
      First page: 645
      Abstract: To lower the sulphur content below 500 ppm and to increase the quality of bitumen derived heavy oil, a combination of hydrotreating followed by oxidative desulfurization (ODS) and oxidative denitrogenation (ODN) is proposed in this work. NiMo/γ-Al2O3 catalyst was synthesized and used to hydrotreat heavy gas oil (HGO) and light gas oil (LGO) at typical operating conditions of 370–390 °C, 9 MPa, 1–1.5 h−1 space velocity and 600:1 H2 to oil ratio. γ-Alumina and alumina-titania supported Mo, P, Mn and W catalysts were synthesized and characterized using X-ray diffractions, N2 adsorption-desorption using Brunauer–Emmett–Teller (BET) method, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). All catalysts were tested for the oxidation of sulphur and nitrogen aromatic compounds present in LGO and HGO using tert-butyl hydroperoxide (TBHP) as oxidant. The oxidized sulphur and nitrogen compounds were extracted using adsorption on activated carbon and liquid-liquid extraction using methanol. The determination of oxidation states of each metal using XPS confirmed the structure of metal oxides in the catalyst. Thus, the catalytic activity determined in terms of sulphur and nitrogen removal is related to their physico-chemical properties. In agreement with literature, a simplistic mechanism for the oxidative desulfurization is also presented. Mo was found to be more active in comparison to W. Presence of Ti in the support has shown 8–12% increase in ODS and ODN. The MnPMo/γ-Al2O3-TiO2 catalyst showed the best activity for sulphur and nitrogen removal. The role of Mn and P as promoters to molybdenum was also discussed. Further three-stage ODS and ODN was performed to achieve less than 500 ppm in HGO and LGO. The combination of hydrotreatment, ODS and ODN has resulted in removal of 98.8 wt.% sulphur and 94.7 wt.% nitrogen from HGO and removal of 98.5 wt.% sulphur and 97.8 wt.% nitrogen from LGO.
      Citation: Catalysts
      PubDate: 2018-12-10
      DOI: 10.3390/catal8120645
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 646: Mn Modified Ni/Bentonite for CO2 Methanation

    • Authors: Yuexiu Jiang, Tongxia Huang, Lihui Dong, Tongming Su, Bin Li, Xuan Luo, Xinling Xie, Zuzeng Qin, Cuixia Xu, Hongbing Ji
      First page: 646
      Abstract: To enhance the low-temperature catalytic activity and stability of Ni/bentonite catalyst, Ni-Mn/bentonite catalyst was prepared by introducing Mn into Ni/bentonite catalyst and was used for CO2 methanation. The results indicated that the addition of Mn enhanced the interaction between the NiO and the bentonite carrier, increased the dispersion of the active component Ni and decreased the grain size of the active component Ni, increased the specific surface area and pore volume of the Ni/bentonite catalyst, and decreased the average pore size, which suppressed the aggregation of Ni particles grown during the CO2 methanation process. At the same time, the Mn addition increased the amount of oxygen vacancies on the Ni/bentonite catalyst surface, which promoted the activation of CO2 in the methanation reaction, increasing the low-temperature activity and stability of the Ni/bentonite catalyst. Under the reaction condition of atmospheric pressure, 270 °C, V(H2):V(CO2) = 4, and feed gas space velocity of 3600 mL·gcat−1·h−1, the CO2 conversion on the Ni-Mn/bentonite catalyst with 2wt% Mn was 85.2%, and the selectivity of CH4 was 99.8%. On the other hand, when Mn was not added, the CO2 conversion reached 84.7% and the reaction temperature only raised to 300 °C. During a 150-h stability test, the CO2 conversion of Ni-2wt%Mn/bentonite catalyst decreased by 2.2%, while the CO2 conversion of the Ni/bentonite catalyst decreased by 6.4%.
      Citation: Catalysts
      PubDate: 2018-12-10
      DOI: 10.3390/catal8120646
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 647: Ag/Ag2O as a Co-Catalyst in TiO2
           Photocatalysis: Effect of the Co-Catalyst/Photocatalyst Mass Ratio

    • Authors: Soukaina Akel, Ralf Dillert, Narmina O. Balayeva, Redouan Boughaled, Julian Koch, Mohammed El Azzouzi, Detlef W. Bahnemann
      First page: 647
      Abstract: Mixtures and composites of Ag/Ag2O and TiO2 (P25) with varying mass ratios of Ag/Ag2O were prepared, employing two methods. Mechanical mixtures (TM) were obtained by the sonication of a suspension containing TiO2 and Ag/Ag2O. Composites (TC) were prepared by a precipitation method employing TiO2 and AgNO3. Powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirmed the presence of Ag(0) and Ag2O. The activity of the materials was determined employing methylene blue (MB) as the probe compound. Bleaching of MB was observed in the presence of all materials. The bleaching rate was found to increase with increasing amounts of TiO2 under UV/vis light. In contrast, the MB bleaching rate decreased with increasing TiO2 content upon visible light illumination. XRD and XPS data indicate that Ag2O acts as an electron acceptor in the light-induced reaction of MB and is transformed by reduction of Ag+, yielding Ag(0). As a second light-induced reaction, the evolution of molecular hydrogen from aqueous methanol was investigated. Significant H2 evolution rates were only determined in the presence of materials containing more than 50 mass% of TiO2. The experimental results suggest that Ag/Ag2O is not stable under the experimental conditions. Therefore, to address Ag/Ag2O as a (photo)catalytically active material does not seem appropriate.
      Citation: Catalysts
      PubDate: 2018-12-10
      DOI: 10.3390/catal8120647
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 648: Theoretical Study on the Mechanism of
           Hydrogen Donation and Transfer for Hydrogen-Donor Solvents during Direct
           Coal Liquefaction

    • Authors: Haigang Hao, Tong Chang, Linxia Cui, Ruiqing Sun, Rui Gao
      First page: 648
      Abstract: As a country that is poor in petroleum yet rich in coal, it is significant for China to develop direct coal liquefaction (DCL) technology to relieve the pressure from petroleum shortages to guarantee national energy security. To improve the efficiency of the direct coal liquefaction process, scientists and researchers have made great contributions to studying and developing highly efficient hydrogen donor (H-donor) solvents. Nevertheless, the details of hydrogen donation and the transfer pathways of H-donor solvents are still unclear. The present work examined hydrogen donation and transfer pathways using a model H-donor solvent, tetralin, by density functional theory (DFT) calculation. The reaction condition and state of the solvent (gas or liquid) were considered, and the specific elementary reaction routes for hydrogen donation and transfer were calculated. In the DCL process, the dominant hydrogen donation mechanism was the concerted mechanism. The sequence of tetralin donating hydrogen atoms was α-H (C1–H) > δ-H (C4–H) > β-H (C2–H) > γ-H (C3–H). Compared to methyl, it was relatively hard for benzyl to obtain the first hydrogen atom from tetralin, while it was relatively easy to obtain the second and third hydrogen atoms from tetralin. Comparatively, it was easier for coal radicals to capture hydrogen atoms from the H-donor solvent than to obtain hydrogen atoms from hydrogen gas.
      Citation: Catalysts
      PubDate: 2018-12-10
      DOI: 10.3390/catal8120648
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 649: Electrochemical Oxidation of Amines Using a
           Nitroxyl Radical Catalyst and the Electroanalysis of Lidocaine

    • Authors: Katsuhiko Sato, Tetsuya Ono, Yusuke Sasano, Fumiya Sato, Masayuki Kumano, Kentaro Yoshida, Takenori Dairaku, Yoshiharu Iwabuchi, Yoshitomo Kashiwagi
      First page: 649
      Abstract: The nitroxyl radical of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) can electro-oxidize not only alcohols but also amines. However, TEMPO has low activity in a neutral aqueous solution due to the large steric hindrance around the nitroxyl radical, which is the active site. Therefore, nortropine N-oxyl (NNO) was synthesized to improve the catalytic ability of TEMPO and to investigate the electrolytic oxidation effect on amines from anodic current changes. Ethylamine, diethylamine, triethylamine, tetraethylamine, isopropylamine, and tert-butylamine were investigated. The results indicated that TEMPO produced no response current for any of the amines under physiological conditions; however, NNO did function as an electrolytic oxidation catalyst for diethylamine, triethylamine, and isopropylamine. The anodic current depended on amine concentration, which suggests that NNO can be used as an electrochemical sensor for amine compounds. In addition, electrochemical detection of lidocaine, a local anesthetic containing a tertiary amine structure, was demonstrated using NNO with a calibration curve of 0.1–10 mM.
      Citation: Catalysts
      PubDate: 2018-12-10
      DOI: 10.3390/catal8120649
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 650: Methanol-Tolerant M–N–C Catalysts for
           Oxygen Reduction Reactions in Acidic Media and Their Application in Direct
           Methanol Fuel Cells

    • Authors: Carmelo Lo Vecchio, David Sebastián, María Jesús Lázaro, Antonino Salvatore Aricò, Vincenzo Baglio
      First page: 650
      Abstract: Direct methanol fuel cells (DMFCs) are emerging technologies for the electrochemical conversion of the chemical energy of a fuel (methanol) directly into electrical energy, with a low environmental impact and high efficiency. Yet, before this technology can reach a large-scale diffusion, specific issues must be solved, in particular, the high cost of the cell components. In a direct methanol fuel cell system, high capital costs are mainly derived from the use of noble metal catalysts; therefore, the development of low-cost electro-catalysts, satisfying the target requirements of high performance and durability, represents an important challenge. The research is currently addressed to the development of metal–nitrogen–carbon (M–N–C) materials as cheap and sustainable catalysts for the oxygen reduction reaction (ORR) in an acid environment, for application in polymer electrolyte fuel cells fueled by hydrogen or alcohol. In particular, this mini-review summarizes the recent advancements achieved in DMFCs using M–N–C catalysts. The presented analysis is restricted to M–N–C catalysts mounted at the cathode of a DMFC or investigated in rotating disk electrode (RDE) configuration for the ORR in the presence of methanol in order to study alcohol tolerance. The main synthetic routes and characteristics of the catalysts are also presented.
      Citation: Catalysts
      PubDate: 2018-12-11
      DOI: 10.3390/catal8120650
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 651: Catalytic Tuning of Sorption Kinetics of
           Lightweight Hydrides: A Review of the Materials and Mechanism

    • Authors: Ankur Jain, Shivani Agarwal, Takayuki Ichikawa
      First page: 651
      Abstract: Hydrogen storage materials have been a subject of intensive research during the last 4 decades. Several developments have been achieved in regard of finding suitable materials as per the US-DOE targets. While the lightweight metal hydrides and complex hydrides meet the targeted hydrogen capacity, these possess difficulties of hard thermodynamics and sluggish kinetics of hydrogen sorption. A number of methods have been explored to tune the thermodynamic and kinetic properties of these materials. The thermodynamic constraints could be resolved using an intermediate step of alloying or by making reactive composites with other hydrogen storage materials, whereas the sluggish kinetics could be improved using several approaches such as downsizing and the use of catalysts. The catalyst addition reduces the activation barrier and enhances the sorption rate of hydrogen absorption/desorption. In this review, the catalytic modifications of lightweight hydrogen storage materials are reported and the mechanism towards the improvement is discussed.
      Citation: Catalysts
      PubDate: 2018-12-11
      DOI: 10.3390/catal8120651
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 652: Efficient Reduction of Bromate by
           Iodide-Assisted UV/Sulfite Process

    • Authors: Tuqiao Zhang, Jiajie Wang, Dingyun Yan, Lili Wang, Xiaowei Liu
      First page: 652
      Abstract: Bromate ( BrO 3 − ) residue in drinking water poses a great health risk. Ultra-fast reduction of BrO 3 − , under aerobic conditions, was realized using an ultraviolet (UV)/sulfite process in the presence of iodide (UV/sulfite/iodide). The UV/sulfite/iodide process produced BrO 3 − removal efficiency of 100% at about 5 min with complete conversion to bromide, while UV/sulfite induced 13.1% BrO 3 − reduction under the same conditions. Hydrated electrons, generated from the photolysis of sulfite and iodide, was confirmed as the main contributor to BrO 3 − degradation (77.4% of the total contribution). As the concentration of iodide was kept constant, its presence remarkably enhancing the generation of hydrated electrons led to its consideration as a homogeneous catalyst in the UV/sulfite/iodide system. Sulfite played a role not only as a hydrated electron precursor, but also as a reactive iodine species shielding agent and a regenerant of iodide. Results surrounding the effects on common water quality parameters (pH, bicarbonate, nitrate, natural organic matter, and solution temperature) indicated that preferred degradation of BrO 3 − occurred in an environment of alkaline pH, low-content natural organic matter/bicarbonate/nitrate, and high natural temperature.
      Citation: Catalysts
      PubDate: 2018-12-11
      DOI: 10.3390/catal8120652
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 653: 9,10-Phenanthrenedione as Visible-Light
           Photoredox Catalyst: A Green Methodology for the Functionalization of
           3,4-Dihydro-1,4-Benzoxazin-2-Ones through a Friedel-Crafts Reaction

    • Authors: Jaume Rostoll-Berenguer, Gonzalo Blay, José R. Pedro, Carlos Vila
      First page: 653
      Abstract: A visible-light photoredox functionalization of 3,4-dihydro-1,4-benzoxazin-2-ones through a Friedel-Crafts reaction with indoles using an inexpensive organophotoredox catalyst is described. The reaction uses a dual catalytic system that is formed by a photocatalyst simple and cheap, 9,10-phenanthrenedione, and a Lewis acid, Zn(OTf)2. 5W white LEDs are used as visible-light source and oxygen from air as a terminal oxidant, obtaining the corresponding products with good yields. The reaction can be extended to other electron-rich arenes. Our methodology represents one of the most valuable and sustainable approach for the functionalization of 3,4-dihydro-1,4-benzoxazin-2-ones, as compared to the reported procedures. Furthermore, several transformations were carried out, such as the synthesis of the natural product cephalandole A and a tryptophol derivative.
      Citation: Catalysts
      PubDate: 2018-12-12
      DOI: 10.3390/catal8120653
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 654: Application of Uniform Design Method in the
           Optimization of Hydrothermal Synthesis for Nano MoS2 Catalyst with High
           HDS Activity

    • Authors: Haiping Zhang, Hongfei Lin, Ying Zheng
      First page: 654
      Abstract: The optimization of catalyst synthesis conditions using traditional single factor method involves extensive experimental time and costs. To overcome the drawbacks, a uniform design method was applied in the hydrothermal synthesis of nano MoS2 catalyst. An optimal synthesis condition is reached with only a few trials. Catalyst synthesis temperature is reduced to 200 °C. The catalyst synthesized at the screened condition shows high hydrotreating activities. The results conclude that the catalyst has thread-like slabs with a lattice structure that is less mature than fully developed MoS2. The characterization results indicate that the appearance of such structure may be due to the weak links of successive MoS2 nuclei. The high catalytic activity is a result of the layered structure and a significantly large number of defects on the slabs.
      Citation: Catalysts
      PubDate: 2018-12-12
      DOI: 10.3390/catal8120654
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 655: Photocatalytic Hydrogen Evolution via Water
           Splitting: A Short Review

    • Authors: Yifan Zhang, Young-Jung Heo, Ji-Won Lee, Jong-Hoon Lee, Johny Bajgai, Kyu-Jae Lee, Soo-Jin Park
      First page: 655
      Abstract: Photocatalytic H2 generation via water splitting is increasingly gaining attention as a viable alternative for improving the performance of H2 production for solar energy conversion. Many methods were developed to enhance photocatalyst efficiency, primarily by modifying its morphology, crystallization, and electrical properties. Here, we summarize recent achievements in the synthesis and application of various photocatalysts. The rational design of novel photocatalysts was achieved using various strategies, and the applications of novel materials for H2 production are displayed herein. Meanwhile, the challenges and prospects for the future development of H2-producing photocatalysts are also summarized.
      Citation: Catalysts
      PubDate: 2018-12-12
      DOI: 10.3390/catal8120655
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 656: Increased Aromatics Formation by the Use of
           High-Density Polyethylene on the Catalytic Pyrolysis of Mandarin Peel over
           HY and HZSM-5

    • Authors: Young-Kwon Park, Muhammad Zain Siddiqui, Yejin Kang, Atsushi Watanabe, Hyung Won Lee, Sang Jae Jeong, Seungdo Kim, Young-Min Kim
      First page: 656
      Abstract: High-density polyethylene (HDPE) was co-fed into the catalytic pyrolysis (CP) of mandarin peel (MP) over different microporous catalysts, HY and HZSM-5, with different pore and acid properties. Although the non-catalytic decomposition temperature of MP was not changed during catalytic thermogravimetric analysis over both catalysts, that of HDPE was reduced from 465 °C to 379 °C over HY and to 393 °C over HZSM-5 because of their catalytic effects. When HDPE was co-pyrolyzed with MP over the catalysts, the catalytic decomposition temperatures of HDPE were increased to 402 °C over HY and 408 °C over HZSM-5. The pyrolyzer-gas chromatography/mass spectrometry results showed that the main pyrolyzates of MP and HDPE, which comprised a large amount of oxygenates and aliphatic hydrocarbons with a wide carbon range, were converted efficiently to aromatics using HY and HZSM-5. Although HY can provide easier diffusion of the reactants to the catalyst pore and a larger amount of acid sites than HZSM-5, the CP of MP, HDPE, and their mixture over HZSM-5 revealed higher efficiency on aromatics formation than those over HY due to the strong acidity and more appropriate shape selectivity of HZSM-5. The production of aromatics from the catalytic co-pyrolysis of MP and HDPE was larger than the theoretical amounts, suggesting the synergistic effect of HDPE co-feeding for the increased formation of aromatics during the CP of MP.
      Citation: Catalysts
      PubDate: 2018-12-12
      DOI: 10.3390/catal8120656
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 657: Earth-Abundant Electrocatalysts in Proton
           Exchange Membrane Electrolyzers

    • Authors: Xinwei Sun, Kaiqi Xu, Christian Fleischer, Xin Liu, Mathieu Grandcolas, Ragnar Strandbakke, Tor S. Bjørheim, Truls Norby, Athanasios Chatzitakis
      First page: 657
      Abstract: In order to adopt water electrolyzers as a main hydrogen production system, it is critical to develop inexpensive and earth-abundant catalysts. Currently, both half-reactions in water splitting depend heavily on noble metal catalysts. This review discusses the proton exchange membrane (PEM) water electrolysis (WE) and the progress in replacing the noble-metal catalysts with earth-abundant ones. The efforts within this field for the discovery of efficient and stable earth-abundant catalysts (EACs) have increased exponentially the last few years. The development of EACs for the oxygen evolution reaction (OER) in acidic media is particularly important, as the only stable and efficient catalysts until now are noble-metal oxides, such as IrOx and RuOx. On the hydrogen evolution reaction (HER) side, there is significant progress on EACs under acidic conditions, but there are very few reports of these EACs employed in full PEM WE cells. These two main issues are reviewed, and we conclude with prospects for innovation in EACs for the OER in acidic environments, as well as with a critical assessment of the few full PEM WE cells assembled with EACs.
      Citation: Catalysts
      PubDate: 2018-12-13
      DOI: 10.3390/catal8120657
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 658: Combining Carbon Fibers with Ni/γ–Al2O3
           Used for Syngas Production: Part A: Preparation and Evaluation of Complex
           Carrier Catalysts

    • Authors: Lei Yu, Min Song, Yuexing Wei, Jun Xiao
      First page: 658
      Abstract: To promote the adsorption and activation of carbon dioxide in the dry reforming of methane (DRM), Ni and Al2O3 were coprecipitated on activated carbon fibers (ACF). Various characterization methods were adopted in order to investigate the surface characteristics of different catalysts. Chemisorption characterization results, such as H2-temperature programmed reduction (H2-TPR), H2-temperature programmed desorption (H2-TPD), and CO2-temperature programmed desorption (CO2-TPD) illustrated that ACF in a nickel-based catalyst could enhance the basic sites and improve the metal dispersion on a catalyst surface, which is beneficial for the adsorption and activation of feed gas. The coprecipitated coating on ACF proved by scanning electron microscope (SEM) can prevent the carbon of ACF from participating in the reaction, while retain good surface properties of carbon fibers. X-ray diffraction (XRD) patterns illustrated that the ACF in a nickel-based catalyst could decrease the crystallite size of the spinel NiAl2O4, which is beneficial for methane reforming. In addition, the Fourier transform infrared spectroscopy (FTIR) of different catalysts revealed that the added ACF could provide abundant functional groups on the surface, which could be the intermediate product of DRM, and effectively promote the reaction. Different to the catalyst supported on single alumina, the performance evaluation and stability test proved that the catalyst added with ACF exhibited a better catalytic performance especially for CO2 conversion. Moreover, based on the characterization results as well as some related literature, the dry reforming mechanism over optimum catalyst was derived.
      Citation: Catalysts
      PubDate: 2018-12-13
      DOI: 10.3390/catal8120658
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 659: Catalytic Pyrolysis of Biomass and Polymer
           Wastes

    • Authors: Laibao Zhang, Zhenghong Bao, Shunxiang Xia, Qiang Lu, Keisha B. Walters
      First page: 659
      Abstract: Oil produced by the pyrolysis of biomass and co-pyrolysis of biomass with waste synthetic polymers has significant potential as a substitute for fossil fuels. However, the relatively poor properties found in pyrolysis oil—such as high oxygen content, low caloric value, and physicochemical instability—hampers its practical utilization as a commercial petroleum fuel replacement or additive. This review focuses on pyrolysis catalyst design, impact of using real waste feedstocks, catalyst deactivation and regeneration, and optimization of product distributions to support the production of high value-added products. Co-pyrolysis of two or more feedstock materials is shown to increase oil yield, caloric value, and aromatic hydrocarbon content. In addition, the co-pyrolysis of biomass and polymer waste can contribute to a reduction in production costs, expand waste disposal options, and reduce environmental impacts. Several promising options for catalytic pyrolysis to become industrially viable are also discussed.
      Citation: Catalysts
      PubDate: 2018-12-13
      DOI: 10.3390/catal8120659
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 660: Critical Review of Low-Temperature CO
           Oxidation and Hysteresis Phenomenon on Heterogeneous Catalysts

    • Authors: Rola Mohammad Al Soubaihi, Khaled Mohammad Saoud, Joydeep Dutta
      First page: 660
      Abstract: There is a growing demand for new heterogeneous catalysts for cost-effective catalysis. Currently, the hysteresis phenomenon during low-temperature CO oxidation is an important topic in heterogeneous catalysis. Hysteresis provides important information about fluctuating reaction conditions that affect the regeneration of active sites and indicate the restoration of catalyst activity. Understanding its dynamic behavior, such as hysteresis and self-sustained kinetic oscillations, during CO oxidation, is crucial for the development of cost-effective, stable and long-lasting catalysts. Hysteresis during CO oxidation has a direct influence on many industrial processes and its understanding can be beneficial to a broad range of applications, including long-life CO2 lasers, gas masks, catalytic converters, sensors, indoor air quality, etc. This review considers the most recent reported advancements in the field of hysteresis behavior during CO oxidation which shed light on the origin of this phenomenon and the parameters that influence the type, shape, and width of the conversion of the hysteresis curves.
      Citation: Catalysts
      PubDate: 2018-12-14
      DOI: 10.3390/catal8120660
      Issue No: Vol. 8, No. 12 (2018)
       
  • Catalysts, Vol. 8, Pages 561: Construction of a Vitreoscilla Hemoglobin
           Promoter-Based Tunable Expression System for Corynebacterium glutamicum

    • Authors: Kei-Anne Baritugo, Hee Taek Kim, Mi Na Rhie, Seo Young Jo, Tae Uk Khang, Kyoung Hee Kang, Bong Keun Song, Binna Lee, Jae Jun Song, Jong Hyun Choi, Dae-Hee Lee, Jeong Chan Joo, Si Jae Park
      First page: 561
      Abstract: Corynebacterium glutamicum is an industrial strain used for the production of valuable chemicals such as L-lysine and L-glutamate. Although C. glutamicum has various industrial applications, a limited number of tunable systems are available to engineer it for efficient production of platform chemicals. Therefore, in this study, we developed a novel tunable promoter system based on repeats of the Vitreoscilla hemoglobin promoter (Pvgb). Tunable expression of green fluorescent protein (GFP) was investigated under one, four, and eight repeats of Pvgb (Pvgb, Pvgb4, and Pvgb8). The intensity of fluorescence in recombinant C. glutamicum strains increased as the number of Pvgb increased from single to eight (Pvgb8) repeats. Furthermore, we demonstrated the application of the new Pvgb promoter-based vector system as a platform for metabolic engineering of C. glutamicum by investigating 5-aminovaleric acid (5-AVA) and gamma-aminobutyric acid (GABA) production in several C. glutamicum strains. The profile of 5-AVA and GABA production by the recombinant strains were evaluated to investigate the tunable expression of key enzymes such as DavBA and GadBmut. We observed that 5-AVA and GABA production by the recombinant strains increased as the number of Pvgb used for the expression of key proteins increased. The recombinant C. glutamicum strain expressing DavBA could produce higher amounts of 5-AVA under the control of Pvgb8 (3.69 ± 0.07 g/L) than the one under the control of Pvgb (3.43 ± 0.10 g/L). The average gamma-aminobutyric acid production also increased in all the tested strains as the number of Pvgb used for GadBmut expression increased from single (4.81–5.31 g/L) to eight repeats (4.94–5.58 g/L).
      Citation: Catalysts
      PubDate: 2018-11-19
      DOI: 10.3390/catal8110561
      Issue No: Vol. 8, No. 11 (2018)
       
  • Catalysts, Vol. 8, Pages 562: Biochars and Their Use as
           Transesterification Catalysts for Biodiesel Production: A Short Review

    • Authors: John Vakros
      First page: 562
      Abstract: Biodiesel can be a significant alternative for diesel. Usually, it is produced through transesterification with a base catalyst. Using heterogeneous catalysts for transesterification, the process can be more efficient. Among the possible catalysts that can be used, biochars combine high performance for transesterification and valorization of waste biomass. Biochars are cheap materials, and are easy to activate through chemical treatment with acid or base solutions. In this short review, the application of biochar as solid heterogeneous catalysts for transesterification of lipids to produce biodiesel is discussed.
      Citation: Catalysts
      PubDate: 2018-11-20
      DOI: 10.3390/catal8110562
      Issue No: Vol. 8, No. 11 (2018)
       
  • Catalysts, Vol. 8, Pages 563: Promotional Effect of Gold on the WGS
           Activity of Alumina-Supported Copper-Manganese Mixed Oxides

    • Authors: Tatyana Tabakova, Ivan Ivanov, Yordanka Karakirova, Daniela Karashanova, Anna Maria Venezia, Petya Petrova, Georgi Avdeev, Elitsa Kolentsova, Krasimir Ivanov
      First page: 563
      Abstract: The water-gas shift (WGS) reaction is a well-known industrial process used for the production of hydrogen. During the last few decades, it has attracted renewed attention due to the need for high-purity hydrogen for fuel-cell processing systems. The aim of the present study was to develop a cost-effective and catalytically efficient formulation that combined the advantageous properties of transition metal oxides and gold nanoparticles. Alumina-supported copper- manganese mixed oxides were prepared by wet impregnation. The deposition-precipitation method was used for the synthesis of gold catalysts. The effect of the Cu:Mn molar ratio and the role of Au addition on the WGS reaction’s performance was evaluated. Considerable emphasis was put on the characterization of the as-prepared and WGS-tested samples by means of a number of physicochemical methods (X-ray powder diffraction, high-resolution transmission electron microscopy, electron paramagnetic resonance, X-ray photoelectron spectroscopy, and temperature-programmed reduction) in order to explain the relationship between the structure and the reductive and WGS behavior. Catalytic tests revealed the promotional effect of gold addition. The best performance of the gold-promoted sample with a higher Cu content, i.e., a Cu:Mn molar ratio of 2:1 might be related to the beneficial role of Au on the spinel decomposition and the highly dispersed copper particle formation during the reaction, thus, ensuring the presence of two highly dispersed active metallic phases. High-surface-area alumina that was modified with a surface fraction of Cu–Mn mixed oxides favored the stabilization of finely dispersed gold particles. These new catalytic systems are very promising for practical applications due to their economic viability because the composition mainly includes alumina (80%).
      Citation: Catalysts
      PubDate: 2018-11-20
      DOI: 10.3390/catal8110563
      Issue No: Vol. 8, No. 11 (2018)
       
  • Catalysts, Vol. 8, Pages 564: V-Containing Mixed Oxide Catalysts for
           Reduction–Oxidation-Based Reactions with Environmental Applications: A
           Short Review

    • Authors: M. Olga Guerrero-Pérez
      First page: 564
      Abstract: V-containing mixed oxide catalytic materials are well known as active for partial oxidation reactions. Oxidation reactions are used in industrial chemistry and for the abatement of pollutants. An analysis of the literature in this field during the past few years shows a clear increase in the use of vanadium-based materials as catalysts for environmental applications. The present contribution makes a brief revision of the main applications of vanadium containing mixed oxides in environmental catalysis, analyzing the properties that present the catalysts with a better behavior that, in most cases, is related with the stabilization of reduced vanadium species (as V4+/V3+) during reaction.
      Citation: Catalysts
      PubDate: 2018-11-20
      DOI: 10.3390/catal8110564
      Issue No: Vol. 8, No. 11 (2018)
       
  • Catalysts, Vol. 8, Pages 565: Three Component Controls in Pillared
           Metal-Organic Frameworks for Catalytic Carbon Dioxide Fixation

    • Authors: Jinmi Noh, Dasom Kim, Jihyun Lee, Minyoung Yoon, Myung Hwan Park, Kang Mun Lee, Youngjo Kim, Min Kim
      First page: 565
      Abstract: Three components of pillared metal-organic frameworks (MOFs, three components = metal ion, carboxylic acid ligand, and N-chelating ligand) were controlled for CO2 cycloaddition catalysts to synthesize organic cyclic carbonates. Among the divalent metals, Zn2+ showed the best catalytic activity, and in DABCO (1,4-diazabicyclo[2.2.2]octane)-based MOFs, hydroxy-functionalized DMOF-OH was the most efficient MOF for CO2 cycloaddition. For the BPY (4,4’-bipyridyl)-type MOFs, all five prepared BMOFs (BPY MOFs) showed similar and good conversions for CO2 cycloaddition. Finally, this pillared MOF could be recycled up to three times without activity and crystallinity loss.
      Citation: Catalysts
      PubDate: 2018-11-20
      DOI: 10.3390/catal8110565
      Issue No: Vol. 8, No. 11 (2018)
       
  • Catalysts, Vol. 8, Pages 566: Nickel Nanowires: Synthesis,
           Characterization and Application as Effective Catalysts for the Reduction
           of Nitroarenes

    • Authors: Tomasz Wasiak, Lukasz Przypis, Krzysztof Z. Walczak, Dawid Janas
      First page: 566
      Abstract: We have demonstrated a convenient method of synthesizing nickel nanowires (NiNWs), which could be easily tuned to produce materials with a carefully defined nanostructure. By varying the concentration of the Ni precursor, pH of the medium or reaction temperature, we directly affected the diameter of the formed product as well as the yield of the process. The obtained material consisted of straight bundles of NiNWs, which revealed powerful catalytic action for the reduction of nitroarenes to appropriate amine derivatives. A selection of substrates were employed and all of them were successfully converted into the corresponding aromatic amine despite the presence of different substituents on the aromatic ring with high yields, even in large scale reactions. The results showed that NiNW-based catalysts could constitute efficient catalytic systems for the synthesis of aryl amines at industrial levels.
      Citation: Catalysts
      PubDate: 2018-11-20
      DOI: 10.3390/catal8110566
      Issue No: Vol. 8, No. 11 (2018)
       
  • Catalysts, Vol. 8, Pages 567: In Situ Regeneration of Alumina-Supported
           Cobalt–Iron Catalysts for Hydrogen Production by Catalytic Methane
           Decomposition

    • Authors: Anis H. Fakeeha, Siham Barama, Ahmed A. Ibrahim, Raja-Lafi Al-Otaibi, Akila Barama, Ahmed E. Abasaeed, Ahmed S. Al-Fatesh
      First page: 567
      Abstract: A novel approach to the in situ regeneration of a spent alumina-supported cobalt–iron catalyst for catalytic methane decomposition is reported in this work. The spent catalyst was obtained after testing fresh catalyst in catalytic methane decomposition reaction during 90 min. The regeneration evaluated the effect of forced periodic cycling; the cycles of regeneration were performed in situ at 700 °C under diluted O2 gasifying agent (10% O2/N2), followed by inert treatment under N2. The obtained regenerated catalysts at different cycles were tested again in catalytic methane decomposition reaction. Fresh, spent, and spent/regenerated materials were characterized using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), laser Raman spectroscopy (LRS), N2-physisorption, H2-temperature programmed reduction (H2-TPR), thermogravimetric analysis (TGA), and atomic absorption spectroscopy (AAS). The comparison of transmission electron microscope and X-ray powder diffraction characterizations of spent and spent/regenerated catalysts showed the formation of a significant amount of carbon on the surface with a densification of catalyst particles after each catalytic methane decomposition reaction preceded by regeneration. The activity results confirm that the methane decomposition after regeneration cycles leads to a permanent deactivation of catalysts certainly provoked by the coke deposition. Indeed, it is likely that some active iron sites cannot be regenerated totally despite the forced periodic cycling.
      Citation: Catalysts
      PubDate: 2018-11-21
      DOI: 10.3390/catal8110567
      Issue No: Vol. 8, No. 11 (2018)
       
  • Catalysts, Vol. 8, Pages 568: TiO2-SiO2-PMMA Terpolymer Floating Device
           for the Photocatalytic Remediation of Water and Gas Phase Pollutants

    • Authors: Valentina Sabatini, Luca Rimoldi, Laura Tripaldi, Daniela Meroni, Hermes Farina, Marco Aldo Ortenzi, Silvia Ardizzone
      First page: 568
      Abstract: Floating photocatalytic devices are highly sought-after as they represent good candidates for practical application in pollutant remediation of large water basins. Here, we present a multilayer floating device for the photocatalytic remediation of contaminants present in water as well as of volatile species close to the water surface. The device was prepared on a novel tailored ter-polymer substrate based on methylmethacrylate, α-methylstyrene and perfluoroctyl methacrylate. The ad hoc synthesized support presents optimal characteristics in terms of buoyancy, transparency, gas permeability, mechanical, UV and thermal stability. The adhesion of the TiO2 top layer was favoured by the adopted casting procedure, followed by a corona pre-treatment and by the deposition of an intermediate SiO2 layer, the latter aimed also at protecting the polymer support from photocatalytic oxidation. The device was characterized by contact angle measurement, UV-vis transmittance and scanning electron microscopy. The final device was tested for the photocatalytic degradation of an emerging water pollutant as well as of vapors of a model volatile organic compound. Relevant activity was observed also under simulated solar irradiation and the device showed good stability and recyclability, prospecting its use for the photocatalytic degradation of pollutants in large water basins.
      Citation: Catalysts
      PubDate: 2018-11-21
      DOI: 10.3390/catal8110568
      Issue No: Vol. 8, No. 11 (2018)
       
 
 
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