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  Subjects -> CHEMISTRY (Total: 902 journals)
    - ANALYTICAL CHEMISTRY (55 journals)
    - CHEMISTRY (636 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (28 journals)
    - INORGANIC CHEMISTRY (43 journals)
    - ORGANIC CHEMISTRY (48 journals)
    - PHYSICAL CHEMISTRY (71 journals)

CHEMISTRY (636 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: 29)
ACS Catalysis     Hybrid Journal   (Followers: 49)
ACS Chemical Neuroscience     Hybrid Journal   (Followers: 23)
ACS Combinatorial Science     Hybrid Journal   (Followers: 23)
ACS Macro Letters     Hybrid Journal   (Followers: 27)
ACS Medicinal Chemistry Letters     Hybrid Journal   (Followers: 42)
ACS Nano     Hybrid Journal   (Followers: 321)
ACS Photonics     Hybrid Journal   (Followers: 14)
ACS Symposium Series     Full-text available via subscription  
ACS Synthetic Biology     Hybrid Journal   (Followers: 25)
Acta Chemica Iasi     Open Access   (Followers: 6)
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: 7)
Advanced Functional Materials     Hybrid Journal   (Followers: 62)
Advanced Science Focus     Free   (Followers: 5)
Advances in Chemical Engineering and Science     Open Access   (Followers: 77)
Advances in Chemical Science     Open Access   (Followers: 20)
Advances in Chemistry     Open Access   (Followers: 25)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 20)
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: 17)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 12)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 27)
Advances in Nanoparticles     Open Access   (Followers: 17)
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: 19)
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: 4)
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: 68)
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: 13)
American Mineralogist     Hybrid Journal   (Followers: 15)
Anadolu University Journal of Science and Technology A : Applied Sciences and Engineering     Open Access  
Analyst     Full-text available via subscription   (Followers: 37)
Angewandte Chemie     Hybrid Journal   (Followers: 185)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 268)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 4)
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: 14)
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: 26)
Applied Surface Science     Hybrid Journal   (Followers: 34)
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: 378)
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: 24)
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: 92)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 19)
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: 25)
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: 25)
Carbon     Hybrid Journal   (Followers: 70)
Catalysis for Sustainable Energy     Open Access   (Followers: 8)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 9)
Catalysis Science and Technology     Hybrid Journal   (Followers: 9)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 13)
Cellulose     Hybrid Journal   (Followers: 11)
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: 216)
Chemical Science     Open Access   (Followers: 28)
Chemical Technology     Open Access   (Followers: 35)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 58)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 22)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry     Open Access  
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: 176)
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: 46)
Chemistry of Materials     Hybrid Journal   (Followers: 281)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 10)
Chemistry World     Full-text available via subscription   (Followers: 21)
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: 22)
Chromatography     Open Access   (Followers: 3)
Chromatography Research International     Open Access   (Followers: 5)
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: 7)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 23)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Communications Chemistry     Open Access   (Followers: 1)
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: 13)
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: 74)
Current Trends in Biotechnology and Chemical Research     Open Access   (Followers: 2)
Dalton Transactions     Full-text available via subscription   (Followers: 26)
Detection     Open Access   (Followers: 4)

        1 2 3 4 | Last

Journal Cover
Catalysts
Number of Followers: 13  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2073-4344
Published by MDPI Homepage  [216 journals]
  • Catalysts, Vol. 9, Pages 207: Synthetic Biomimetic Coenzymes and Alcohol
           Dehydrogenases for Asymmetric Catalysis

    • Authors: Laia Josa-Culleré, Antti S. K. Lahdenperä, Aubert Ribaucourt, Georg T. Höfler, Serena Gargiulo, Yuan-Yang Liu, Jian-He Xu, Jennifer Cassidy, Francesca Paradisi, Diederik J. Opperman, Frank Hollmann, Caroline E. Paul
      First page: 207
      Abstract: Redox reactions catalyzed by highly selective nicotinamide-dependent oxidoreductases are rising to prominence in industry. The cost of nicotinamide adenine dinucleotide coenzymes has led to the use of well-established elaborate regeneration systems and more recently alternative synthetic biomimetic cofactors. These biomimetics are highly attractive to use with ketoreductases for asymmetric catalysis. In this work, we show that the commonly studied cofactor analogue 1-benzyl-1,4-dihydronicotinamide (BNAH) can be used with alcohol dehydrogenases (ADHs) under certain conditions. First, we carried out the rhodium-catalyzed recycling of BNAH with horse liver ADH (HLADH), observing enantioenriched product only with unpurified enzyme. Then, a series of cell-free extracts and purified ketoreductases were screened with BNAH. The use of unpurified enzyme led to product formation, whereas upon dialysis or further purification no product was observed. Several other biomimetics were screened with various ADHs and showed no or very low activity, but also no inhibition. BNAH as a hydride source was shown to directly reduce nicotinamide adenine dinucleotide (NAD) to NADH. A formate dehydrogenase could also mediate the reduction of NAD from BNAH. BNAH was established to show no or very low activity with ADHs and could be used as a hydride donor to recycle NADH.
      Citation: Catalysts
      PubDate: 2019-02-26
      DOI: 10.3390/catal9030207
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 208: Bioprocess Intensification Using Flow
           Reactors: Stereoselective Oxidation of Achiral 1,3-diols with Immobilized
           Acetobacter Aceti

    • Authors: Valerio De Vitis, Federica Dall’Oglio, Francesca Tentori, Martina Letizia Contente, Diego Romano, Elisabetta Brenna, Lucia Tamborini, Francesco Molinari
      First page: 208
      Abstract: Enantiomerically enriched 2-hydroxymethylalkanoic acids were prepared by oxidative desymmetrisation of achiral 1,3-diols using immobilized cells of Acetobacter aceti in water at 28 °C. The biotransformations were first performed in batch mode with cells immobilized in dry alginate, furnishing the desired products with high molar conversion and reaction times ranging from 2 to 6 h. The biocatalytic process was intensified using a multiphasic flow reactor, where a segmented gas–liquid flow regime was applied for achieving an efficient O2-liquid transfer; the continuous flow systems allowed for high yields and high biocatalyst productivity.
      Citation: Catalysts
      PubDate: 2019-02-26
      DOI: 10.3390/catal9030208
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 209: Heterometallic CoIIIZnII Schiff Base
           Catalyst for Mild Hydroxylation of C(sp3)–H Bonds of Unactivated
           Alkanes: Evidence for Dual Mechanism Controlled by the Promoter

    • Authors: Oksana V. Nesterova, Katerina V. Kasyanova, Elena A. Buvaylo, Olga Yu. Vassilyeva, Brian W. Skelton, Dmytro S. Nesterov, Armando J.L. Pombeiro
      First page: 209
      Abstract: The novel Schiff base complex [CoIIIZnIIL3Cl2]·CH3OH (1) was synthesized by interaction of zinc powder, cobalt(II) chloride and methanol solution of the pre-formed HL in air (HL is the product of condensation of o-vanillin and methylamine) and characterized by IR, UV-Vis and NMR spectroscopy, ESI-MS and single crystal X-ray diffraction analysis. In the heterometallic core of 1 the two metal centers are bridged by deprotonated phenoxy groups of the L− ligands with the cobalt-zinc separation of 3.123 Å. Catalytic investigations demonstrated a pronounced activity of 1 towards mild alkane oxidation with m-chloroperbenzoic acid (m-CPBA) as an oxidant and cis-1,2-dimethylcyclohexane (cis-1,2-DMCH) as the model substrate. The influence of the nature of different promoting agents of various acidities (from HOTf to pyridine) on the catalytic process was studied in detail and a pronounced activity of 1 in the presence of nitric acid promoter was found, also showing a high retention of stereoconfiguration of the substrate (>99% for cis-1,2-DMCH). The best achieved yield of tertiary cis-alcohol based on the oxidant was 61%, with a turnover number (TON) of 198 for nitric acid as promoter. The 18O-incorporations into the alcohols when the reactions were performed under 18O2 atmosphere using acetic and nitric acid promoters, suggest that the cis-1,2-DMCH hydroxylation proceeds by two distinct pathways, a non-stereoselective and a stereoselective one (with and without involvement of a long-lived free carbon radical, respectively). The former dominates in the case of acetic acid promoter and the latter is realized in the case of HNO3 promoter.
      Citation: Catalysts
      PubDate: 2019-02-26
      DOI: 10.3390/catal9030209
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 210: Developing Nickel–Zirconia Co-Precipitated
           Catalysts for Production of Green Diesel

    • Authors: Georgios Zafeiropoulos, Nikolaos Nikolopoulos, Eleana Kordouli, Labrini Sygellou, Kyriakos Bourikas, Christos Kordulis, Alexis Lycourghiotis
      First page: 210
      Abstract: The transformation of sunflower oil (SO) and waste cooking oil (WCO) into green diesel over co-precipitated nickel–zirconia catalysts was studied. Two series of catalysts were prepared. The first series included catalysts with various Ni loadings prepared using zirconium oxy-chloride, whereas the second series included catalysts with 60–80 wt % Ni loading prepared using zirconium oxy-nitrate as zirconium source. The catalysts were characterized and evaluated in the transformation of SO into green diesel. The best catalysts were also evaluated for green diesel production using waste cooking oil. The catalysts performance for green diesel production is mainly governed by the Ni surface exposed, their acidity, and the reducibility of the ZrO2. These characteristics depend on the preparation method and the Zr salt used. The presence of chlorine in the catalysts drawn from the zirconium oxy-chloride results to catalysts with relatively low Ni surface, high acidity and hardly reduced ZrO2 phase. These characteristics lead to relatively low activity for green diesel production, whereas they favor high yields of wax esters. Ni-ZrO2 catalysts with Ni loading in the range 60–80 wt %, prepared by urea hydrothermal co-precipitation method using zirconium oxy-nitrate as ZrO2 precursor salt exhibited higher Ni surface, moderate acidity, and higher reducibility of ZrO2 phase. The latter catalysts were proved to be very promising for green diesel production.
      Citation: Catalysts
      PubDate: 2019-02-26
      DOI: 10.3390/catal9030210
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 211: Preparation of Amylose-Carboxymethyl
           Cellulose Conjugated Supramolecular Networks by Phosphorylase-Catalyzed
           Enzymatic Polymerization

    • Authors: Jun-ichi Kadokawa, Takuya Shoji, Kazuya Yamamoto
      First page: 211
      Abstract: Enzymatic polymerization has been noted as a powerful method to precisely synthesize polymers with complicated structures, such as polysaccharides, which are not commonly prepared by conventional polymerization. Phosphorylase is one of the enzymes which have been used to practically synthesize well-defined polysaccharides. The phosphorylase-catalyzed enzymatic polymerization is conducted using α-d-glucose 1-phosphate as a monomer, and maltooligosaccharide as a primer, respectively, to obtain amylose. Amylose is known to form supramolecules owing to its helical conformation, that is, inclusion complex and double helix, in which the formation is depended on whether a guest molecule is present or not. In this paper, we would like to report the preparation of amylose-carboxymethyl cellulose (CMC) conjugated supramolecular networks, by the phosphorylase-catalyzed enzymatic polymerization, using maltoheptaose primer-grafted CMC. When the enzymatic polymerization was carried out using the graft copolymer, either in the presence or in the absence of a guest polymer poly (ε-caprolactone) (PCL), the enzymatically elongated amylose chains from the primers on the CMC main-chain formed double helixes or inclusion complexes, depending on the amounts of PCL, which acted as cross-linking points for the construction of network structures. Accordingly, the reaction mixtures totally turned into hydrogels, regardless of the structures of supramolecular cross-linking points.
      Citation: Catalysts
      PubDate: 2019-02-26
      DOI: 10.3390/catal9030211
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 212: Selective Conversion of Phenol in a
           Subcritical Water Medium Using γ-Al2O3 Supported Ni–Co Bimetallic
           Catalyst

    • Authors: Yuzhen Shi, Shanshuai Chen, Liang He, Ping Ning, Qingqing Guan
      First page: 212
      Abstract: The selective conversion of phenolic materials is a well-adopted solution to upgrade lignin-based bioresources into high-value bio-oil in biomass refinery industries. This study focused on four main aspects: characterization, selection of catalysts, reaction dynamics behaviors, and mathematical modelling. A model lignin, that is, phenol, was selectively transformed into cyclohexanol by using the prepared Ni–xCo/γ-Al2O3 catalysts in a subcritical water medium. The hydrogenation results showed that when using 15 wt% of Ni–3Co/γ-Al2O3 particles, both total mole yield and selectivity of cyclohexanol could reach approximately 80%, which further indicated that the particles are suitable for catalytic hydrogenation of phenol in subcritical water. Moreover, a reaction kinetics model was developed by chemical reaction kinetics and least squares regression analysis, the robustness and predictability of which were also verified.
      Citation: Catalysts
      PubDate: 2019-02-26
      DOI: 10.3390/catal9030212
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 213: Recent Developments in the Suzuki–Miyaura
           Reaction Using Nitroarenes as Electrophilic Coupling Reagents

    • Authors: Lou Rocard, Piétrick Hudhomme
      First page: 213
      Abstract: Palladium-catalyzed cross-coupling reactions are nowadays essential in organic synthesis for the construction of C–C, C–N, C–O, and other C-heteroatom bonds. The 2010 Nobel Prize in Chemistry to Richard F. Heck, Ei-ichi Negishi, and Akira Suzuki was awarded for the discovery of these reactions. These great advances for organic chemists stimulated intense research efforts worldwide dedicated to studying these reactions. Among them, the Suzuki–Miyaura coupling (SMC) reaction, which usually involves an organoboron reagent and an organic halide or triflate in the presence of a base and a palladium catalyst, has become, in the last few decades, one of the most popular tools for the creation of C–C bonds. In this review, we present recent progress concerning the SMC reaction with the original use of nitroarenes as electrophilic coupling partners reacting with the organoboron reagent.
      Citation: Catalysts
      PubDate: 2019-02-26
      DOI: 10.3390/catal9030213
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 214: Bio-based Catalysts from Biomass Issued
           after Decontamination of Effluents Rich in Copper—An Innovative Approach
           towards Greener Copper-based Catalysis

    • Authors: Tomasz K. Olszewski, Pauline Adler, Claude Grison
      First page: 214
      Abstract: The abundance of Cu-contaminated effluents and the serious risk of contamination of the aquatic systems combine to provide strong motivating factors to tackle this environmental problem. The treatment of polluted effluents by rhizofiltration and biosorption is an interesting ecological alternative. Taking advantage of the remarkable ability of the selected plants to bioconcentrate copper into roots, these methods have been exploited for the decontamination of copper-rich effluents. Herein, we present an overview on the utility of the resulted copper-rich biomass for the preparation of novel bio-sourced copper-based catalysts for copper-mediated reactions: from the bioaccumulation of copper in plant, to the preparation and full analysis of the new Eco-Cu catalysts, and their application in selected key reactions. The hydrolysis of a thiophosphate, an Ullmann-type coupling leading to N- and O-arylated compounds, and a CuAAC “click” reaction, all performed under green and environmentally friendly conditions, will be described.
      Citation: Catalysts
      PubDate: 2019-02-26
      DOI: 10.3390/catal9030214
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 215: Preparation and Characterization of
           Rh/MgSNTs Catalyst for Hydroformylation of Vinyl Acetate: The Rh0 was
           Obtained by Calcination

    • Authors: Su, Chen, Liu, Chuai, Liu, Zhu, Zhang, Huang
      First page: 215
      Abstract: A simple and practical Rh-catalyzed hydroformylation of vinyl acetate has been synthesized via impregnation-calcination method using silicate nanotubes (MgSNTs) as the supporter. The Rh0 (zero valent state of rhodium) was obtained by calcination. The influence of calcination temperature on catalytic performance of the catalysts was investigated in detail. The catalysts were characterized in detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS), atomic emission spectrometer (ICP), and Brunauer–Emmett–Teller (BET) surface-area analyzers. The Rh/MgSNTs(a2) catalyst shows excellent catalytic activity, selectivity and superior cyclicity. The catalyst could be easily recovered by phase separation and was used up to four times.
      Citation: Catalysts
      PubDate: 2019-02-26
      DOI: 10.3390/catal9030215
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 216: Hydrocracking of Athabasca Vacuum Residue
           Using Ni-Mo-Supported Drill Cuttings

    • Authors: Thomas Kaminski, Qiang Sheng, Maen M. Husein
      First page: 216
      Abstract: Ni-Mo supported drill cuttings were used to catalyze the hydrocracking (HDC) of Athabasca vacuum residue (AVR) in an autoclave. Drill cuttings are a common waste product that are, depending on their origin, plentiful in acidic sites. The catalyst was prepared using the wet impregnation method. HDC was carried out at both low and high H2 pressure at 400 °C. Control thermal cracking (TC) and HDC runs with and without raw drill cuttings were performed to better examine the role of the supported drill cuttings catalyst. The quality in terms of viscosity and °API gravity, and the yield of various fractions making up the product oil were used to gauge the performance of the catalyst. Similar temperature and energy profiles between TC and HDC suggested strong overlap between the two different reactions, despite H2 presence. Nevertheless, supported drill cuttings runs at high H2 pressures promoted H2 consumption to a strong extent. Consequently, the liquid yield was the highest (~75 wt.%) and the coke yield was negligible. High temperature simulated distillation results revealed a residue conversion of ~55% for both low and high pressure HDC catalytic runs. The product oil quality with respect to viscosity and °API gravity was also found to be comparable between the low and high pressure HDC catalytic runs. Accordingly, no trade-off between liquid yield and quality was incurred at high H2 pressure. Effectively the supported drill cuttings drastically reduced coke formation, while maximizing the yield of the desired liquid product.
      Citation: Catalysts
      PubDate: 2019-02-26
      DOI: 10.3390/catal9030216
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 217: New Oxidovanadium(IV) Complexes with
           2,2′-bipyridine and 1,10-phenathroline Ligands: Synthesis, Structure and
           High Catalytic Activity in Oxidations of Alkanes and Alcohols with
           Peroxides

    • Authors: Iakov S. Fomenko, Artem L. Gushchin, Pavel A. Abramov, Maksim N. Sokolov, Lidia S. Shul'pina, Nikolay S. Ikonnikov, Maxim L. Kuznetsov, Armando J. L. Pombeiro, Yuriy N. Kozlov, Georgiy B. Shul’pin
      First page: 217
      Abstract: Reactions of [VCl3(thf)3] or VBr3 with 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen) in a 1:1 molar ratio in air under solventothermal conditions has afforded polymeric oxidovanadium(IV) four complexes 1–4 of a general formula [VO(L)X2]n (L = bpy, phen and X = Cl, Br). Monomeric complex [VO(DMF)(phen)Br2] (4a) has been obtained by the treatment of compound 4 with DMF. The complexes were characterized by IR spectroscopy and elemental analysis. The crystal structures of 3 and 4a were determined by an X-ray diffraction (XRD) analysis. The {VOBr2(bpy)} fragments in 3 form infinite chains due to the V = O…V interactions. The vanadium atom has a distorted octahedral coordination environment. Complexes 1–4 have been tested as catalysts in the homogeneous oxidation of alkanes (to produce corresponding alkyl hydroperoxides which can be easily reduced to alcohols by PPh3) and alcohols (to corresponding ketones) with H2O2 or tert-butyl hydroperoxide in MeCN. Compound 1 exhibited the highest activity. The mechanism of alkane oxidation was established using experimental selectivity and kinetic data and theoretical DFT calculations. The mechanism is of the Fenton type involving the generation of HO• radicals.
      Citation: Catalysts
      PubDate: 2019-02-26
      DOI: 10.3390/catal9030217
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 218: K-Modulated Co Nanoparticles Trapped in
           La-Ga-O as Superior Catalysts for Higher Alcohols Synthesis from Syngas

    • Authors: Shaoxia Guo, Guilong Liu, Tong Han, Ziyang Zhang, Yuan Liu
      First page: 218
      Abstract: Owing to the outstanding catalytic performance for higher alcohol synthesis, Ga-Co catalysts have attracted much attention. In view of their unsatisfactory stability and alcohol selectivity, herein, K-modulated Co nanoparticles trapped in La-Ga-O catalysts were prepared by the reduction of La1−xKxCo0.65Ga0.35O3 perovskite precursor. Benefiting from the atomic dispersion of all the elements in the precursor, during the reduction of La1−xKxCo0.65Ga0.35O3, Co nanoparticles could be confined into the K-modified La-Ga-O composite oxides, and the confinement of La-Ga-O could improve the anti-sintering performance of Co nanoparticles. In addition, the addition of K modulated parts of La-Ga-O into La2O3, which ameliorated the anti-carbon deposition performance. Finally, the addition of K increased the dispersion of cobalt and provided more electron donors to metallic Co, resulting in a high activity and superior selectivity to higher alcohols. Benefiting from the above characteristics, the catalyst possesses excellent activity, good selectivity, and superior stability.
      Citation: Catalysts
      PubDate: 2019-02-27
      DOI: 10.3390/catal9030218
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 219: Effect of Preparation Method of Co-Ce
           Catalysts on CH4 Combustion

    • Authors: Sofia Darda, Eleni Pachatouridou, Angelos Lappas, Eleni Iliopoulou
      First page: 219
      Abstract: Transition metal oxides have recently attracted considerable attention as candidate catalysts for the complete oxidation of methane, the main component of the natural gas, used in various industrial processes or as a fuel in turbines and vehicles. A series of novel Co-Ce mixed oxide catalysts were synthesized as an effort to enhance synergistic effects that could improve their redox behavior, oxygen storage ability and, thus, their activity in methane oxidation. The effect of synthesis method (hydrothermal or precipitation) and Co loading (0, 2, 5, and 15 wt.%) on the catalytic efficiency and stability of the derived materials was investigated. Use of hydrothermal synthesis results in the most efficient Co/CeO2 catalysts, a fact related with their improved physicochemical properties, as compared with the materials prepared via precipitation. In particular, a CeO2 support of smaller crystallite size and larger surface area seems to enhance the reducibility of the Co3O4/CeO2 materials, as evidenced by the blue shift of the corresponding reduction peaks (H2-TPR, H2-Temperature Programmed Reduction). The limited methane oxidation activity over pure CeO2 samples is significantly enhanced by Co incorporation and further improved by higher Co loadings. The optimum performance was observed over a 15 wt% Co/CeO2 catalyst, which also presented sufficient tolerance to water presence.
      Citation: Catalysts
      PubDate: 2019-02-27
      DOI: 10.3390/catal9030219
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 220: Applicability of V2O5-WO3/TiO2 Catalysts for
           the SCR Denitrification of Alumina Calcining Flue Gas

    • Authors: Ruliang Ning, Li Chen, Erwei Li, Xiaolong Liu, Tingyu Zhu
      First page: 220
      Abstract: V2O5-WO3/TiO2 catalysts with different V2O5 and WO3 loadings were prepared by the impregnation method. H2O and SO2 resistance of the catalysts under high H2O concentration (30 vol.%) was studied. Influence of various basic metal oxides, such as Al2O3, CaO, Na2O, and K2O on the catalytic performance was studied and compared. It is revealed that the inhibitory effect is in the sequence of K > Na > Ca > Al, which is consistent with their alkalinity. X-ray diffraction (XRD), N2 physisorption (BET), temperature-programmed desorption of NH3 (NH3-TPD), H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were carried out, and the results were well-correlated with the catalytic studies.
      Citation: Catalysts
      PubDate: 2019-02-28
      DOI: 10.3390/catal9030220
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 221: Industrial Application of
           2-Oxoglutarate-Dependent Oxygenases

    • Authors: Christin Peters, Rebecca M. Buller
      First page: 221
      Abstract: C–H functionalization is a chemically challenging but highly desirable transformation. 2-oxoglutarate-dependent oxygenases (2OGXs) are remarkably versatile biocatalysts for the activation of C–H bonds. In nature, they have been shown to accept both small and large molecules carrying out a plethora of reactions, including hydroxylations, demethylations, ring formations, rearrangements, desaturations, and halogenations, making them promising candidates for industrial manufacture. In this review, we describe the current status of 2OGX use in biocatalytic applications concentrating on 2OGX-catalyzed oxyfunctionalization of amino acids and synthesis of antibiotics. Looking forward, continued bioinformatic sourcing will help identify additional, practical useful members of this intriguing enzyme family, while enzyme engineering will pave the way to enhance 2OGX reactivity for non-native substrates.
      Citation: Catalysts
      PubDate: 2019-02-28
      DOI: 10.3390/catal9030221
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 222: Immobilised Cerium-Doped Zinc Oxide as a
           Photocatalyst for the Degradation of Antibiotics and the Inactivation of
           Antibiotic-Resistant Bacteria

    • Authors: Ian Zammit, Vincenzo Vaiano, Ana R. Ribeiro, Adrián M. T. Silva, Célia M. Manaia, Luigi Rizzo
      First page: 222
      Abstract: The threat of antibiotic resistance to the wellbeing of societies is well established. Urban wastewater treatment plants (UWTPs) are recognised sources for antibiotic resistance dissemination in the environment. Herein a novel cerium-doped zinc oxide (Ce-ZnO) photocatalyst is compared to ZnO and the benchmark TiO2-P25 in the immobilised form on a metallic support, to evaluate a photocatalytic process as a possible tertiary treatment in UWTPs. The catalysts were compared for the removal of two antibiotics, trimethoprim (TMP) and sulfamethoxazole (SMX), and for the inactivation of Escherichia coli (E. coli) strain DH5-Alpha in isotonic sodium chloride solution and of autochthonous bacteria in real secondary wastewater. In real wastewater, E. coli and other coliforms were monitored, as well as the respective fractions resistant to ofloxacin and azithromycin. In parallel, Pseudomonas aeruginosa and the respective sub-population resistant to ofloxacin or ciprofloxacin were also monitored. Photocatalysis with both ZnO and Ce-ZnO was faster than using TiO2-P25 at degrading the antibiotics, with Ce-ZnO the fastest against SMX but slower than undoped ZnO in the removal of TMP. Ce-ZnO catalyst reuse in the immobilised form produced somewhat slower kinetics maintained >50% of the initial activity, even after five cycles of use. Approximately 3 log10 inactivation of E. coli in isotonic sodium chloride water was recorded with reproducible results. In the removal of autochthonous bacteria in real wastewater, Ce-ZnO performed better (more than 2 log values higher) than TiO2-P25. In all cases, E. coli and other coliforms, including their resistant subpopulations, were inactivated at a higher rate than P. aeruginosa. With short reaction times no evidence for enrichment of resistance was observed, yet with extended reaction times low levels of bacterial loads were not further inactivated. Overall, Ce-ZnO is an easy and cheap photocatalyst to produce and immobilise and the one that showed higher activity than the industry standard TiO2-P25 against the tested antibiotics and bacteria, including antibiotic-resistant bacteria.
      Citation: Catalysts
      PubDate: 2019-03-01
      DOI: 10.3390/catal9030222
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 223: Cross-Linking with Polyethylenimine Confers
           Better Functional Characteristics to an Immobilized β-glucosidase from
           Exiguobacterium antarcticum B7

    • Authors: Ricardo Rodrigues de Melo, Robson Carlos Alnoch, Amanda Silva de Sousa, Hélia Harumi Sato, Roberto Ruller, Cesar Mateo
      First page: 223
      Abstract: β-glucosidases are ubiquitous, well-characterized and biologically important enzymes with considerable uses in industrial sectors. Here, a tetrameric β-glucosidase from Exiguobacterium antarcticum B7 (EaBglA) was immobilized on different activated agarose supports followed by post-immobilization with poly-functional macromolecules. The best result was obtained by the immobilization of EaBglA on metal glutaraldehyde-activated agarose support following cross-linking with polyethylenimine. Interestingly, the immobilized EaBglA was 46-fold more stable than its free form and showed optimum pH in the acidic region, with high catalytic activity in the pH range from 3 to 9, while the free EaBglA showed catalytic activity in a narrow pH range (>80% at pH 6.0–8.0) and optimum pH at 7.0. EaBglA had the optimum temperature changed from 30 °C to 50 °C with the immobilization step. The immobilized EaBglA showed an expressive adaptation to pH and it was tolerant to ethanol and glucose, indicating suitable properties involving the saccharification process. Even after 9 cycles of reuse, the immobilized β-glucosidase retained about 100% of its initial activity, demonstrating great operational stability. Hence, the current study describes an efficient strategy to increase the functional characteristics of a tetrameric β-glucosidase for future use in the bioethanol production.
      Citation: Catalysts
      PubDate: 2019-03-01
      DOI: 10.3390/catal9030223
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 224: Towards Higher Rate Electrochemical CO2
           Conversion: From Liquid-Phase to Gas-Phase Systems

    • Authors: Jun Tae Song, Hakhyeon Song, Beomil Kim, Jihun Oh
      First page: 224
      Abstract: Electrochemical CO2 conversion offers a promising route for value-added products such as formate, carbon monoxide, and hydrocarbons. As a result of the highly required overpotential for CO2 reduction, researchers have extensively studied the development of catalyst materials in a typical H-type cell, utilizing a dissolved CO2 reactant in the liquid phase. However, the low CO2 solubility in an aqueous solution has critically limited productivity, thereby hindering its practical application. In efforts to realize commercially available CO2 conversion, gas-phase reactor systems have recently attracted considerable attention. Although the achieved performance to date reflects a high feasibility, further development is still required in order for a well-established technology. Accordingly, this review aims to promote the further study of gas-phase systems for CO2 reduction, by generally examining some previous approaches from liquid-phase to gas-phase systems. Finally, we outline major challenges, with significant lessons for practical CO2 conversion systems.
      Citation: Catalysts
      PubDate: 2019-03-01
      DOI: 10.3390/catal9030224
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 225: An Innovative Biocatalyst for Continuous 2G
           Ethanol Production from Xylo-Oligomers by Saccharomyces cerevisiae through
           Simultaneous Hydrolysis, Isomerization, and Fermentation (SHIF)

    • Authors: Thais S. Milessi-Esteves, Felipe A.S. Corradini, Willian Kopp, Teresa C. Zangirolami, Paulo W. Tardioli, Roberto C. Giordano, Raquel L.C. Giordano
      First page: 225
      Abstract: Many approaches have been considered aimed at ethanol production from the hemicellulosic fraction of biomass. However, the industrial implementation of this process has been hindered by some bottlenecks, one of the most important being the ease of contamination of the bioreactor by bacteria that metabolize xylose. This work focuses on overcoming this problem through the fermentation of xylulose (the xylose isomer) by native Saccharomyces cerevisiae using xylo-oligomers as substrate. A new concept of biocatalyst is proposed, containing xylanases and xylose isomerase (XI) covalently immobilized on chitosan, and co-encapsulated with industrial baker’s yeast in Ca-alginate gel spherical particles. Xylo-oligomers are hydrolyzed, xylose is isomerized, and finally xylulose is fermented to ethanol, all taking place simultaneously, in a process called simultaneous hydrolysis, isomerization, and fermentation (SHIF). Among several tested xylanases, Multifect CX XL A03139 was selected to compose the biocatalyst bead. Influences of pH, Ca2+, and Mg2+ concentrations on the isomerization step were assessed. Experiments of SHIF using birchwood xylan resulted in an ethanol yield of 0.39 g/g, (76% of the theoretical), selectivity of 3.12 gethanol/gxylitol, and ethanol productivity of 0.26 g/L/h.
      Citation: Catalysts
      PubDate: 2019-03-01
      DOI: 10.3390/catal9030225
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 226: The Effect of Citric Acid Concentration on
           the Properties of LaMnO3 as a Catalyst for Hydrocarbon Oxidation

    • Authors: Sihaib, Puleo, Pantaleo, La Parola, Valverde, Gil, Liotta, Giroir-Fendler
      First page: 226
      Abstract: LaMnO3 (LM) catalysts with a molar ratio of citric acid (CA) to metal (La3+ + Mn2+) nitrates ranging from 0.5 to 2 (LM0.5 to LM2) were synthesized by the citrate sol–gel method with the aim of studying the effect of the citric acid ratio on the physicochemical properties and the catalytic performance in hydrocarbon oxidation. Structural and morphological properties of these catalysts were characterized by X-ray diffraction (XRD) and specific surface area (N2 adsorption) measurements, while the chemical composition was determined by inductively coupled plasma atomic emission spectroscopy (ICP-OES). In the selected samples, additional characterizations were carried out by thermogravimetric and differential thermal analysis (TGA/DTA), Fourier Transform Infrared Spectroscopy (FT-IR), temperature-programmed reduction by hydrogen (H2-TPR), and X-ray photoelectron spectroscopy (XPS). The results showed that the amount of citric acid used significantly influenced the TGA/DTA profile of gels along with the physicochemical properties of the catalysts. The XRD patterns are consistent with the perovskite formation as the main phase. The segregation of a small amount of Mn3O4, detected for molar ratios ranging between 0.5 and 1.5, suggested the formation of a slightly nonstoichiometric LaMn1−xO3 phase with a relatively high content of Mn4+. The catalytic performance was evaluated in the total oxidation of two selected hydrocarbons, toluene and propene, which represent typical volatile organic compounds (VOCs). Typically, three consecutive catalytic cycles were performed in order to reach steady-state performance in toluene and propene oxidation. Moreover, the stability of the catalysts under reaction conditions was investigated through 24-h experiments at 17% of toluene conversion. The catalysts LM1.2, LM1.3, and LM1.5 showed the best catalytic performance in both hydrocarbon oxidations, well comparing with the Pd/Al2O3 used as a reference.
      Citation: Catalysts
      PubDate: 2019-03-01
      DOI: 10.3390/catal9030226
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 227: CaRMeN: An Improved Computer-Aided Method
           for Developing Catalytic Reaction Mechanisms

    • Authors: Hendrik Gossler, Lubow Maier, Sofia Angeli, Steffen Tischer, Olaf Deutschmann
      First page: 227
      Abstract: The software tool CaRMeN (Catalytic Reaction Mechanism Network) was exemplarily used to analyze several surface reaction mechanisms for the combustion of H2, CO, and CH4 over Rh. This tool provides a way to archive and combine experimental and modeling information as well as computer simulations from a wide variety of sources. The tool facilitates rapid analysis of experiments, chemical models, and computer codes for reactor simulations, helping to support the development of chemical kinetic models and the analysis of experimental data. In a comparative study, experimental data from different reactor configurations (channel, annular, and stagnation flow reactors) were modeled and numerically simulated using four different catalytic reaction mechanisms from the literature. It is shown that the software greatly enhanced productivity.
      Citation: Catalysts
      PubDate: 2019-03-01
      DOI: 10.3390/catal9030227
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 228: Synthesis of Mono- and Dithiols of
           Tetraethylene Glycol and Poly(ethylene glycol)s via Enzyme Catalysis

    • Authors: Prajakatta Mulay, Gayatri Shrikhande, Judit E. Puskas
      First page: 228
      Abstract: This paper investigates the transesterification of methyl 3-mercaptopropionate (MP-SH) with tetraethylene glycol (TEG) and poly(ethylene glycol)s (PEG)s catalyzed by Candida antarctica Lipase B (CALB) without the use of solvent (in bulk). The progress of the reactions was monitored by 1H-NMR spectroscopy. We found that the reactions proceeded in a step-wise manner, first producing monothiols. TEG-monothiol was obtained in 15 min, while conversion to dithiol took 8 h. Monothiols from PEGs with Mn = 1000 and 2050 g/mol were obtained in 8 and 16 h, respectively. MALDI-ToF mass spectrometry verified the absence of dithiols. The synthesis of dithiols required additional fresh CALB and MP-SH. The structure of the products was confirmed by 1H-NMR and 13C-NMR spectroscopy. Enzyme catalysis was found to be a powerful tool to effectively synthesize thiol-functionalized TEGs and PEGs.
      Citation: Catalysts
      PubDate: 2019-03-02
      DOI: 10.3390/catal9030228
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 229: A Comprehensive Review on Catalytic
           Oxidative Desulfurization of Liquid Fuel Oil

    • Authors: Muhammad Nobi Hossain, Hoon Chae Park, Hang Seok Choi
      First page: 229
      Abstract: The production of green fuel oil is of the utmost importance for maintaining a healthy life and environment in the current world. Effective and complete removal of sulfur refractory compounds (such as 4,6-dimethyldibenzothiophene and other alkyl-substituted thiophene derivatives) from fuel oil is essential to meet the new requirements of sulfur standards. Several techniques have been proposed for desulfurization of fuel oil, such as hydrodesulfurization (HDS), selective adsorption, extractive distillation, biodesulfurization, and oxidative desulfurization (ODS). The removal of sulfur by the HDS process requires higher investment costs, high reaction temperature (up to 400 °C), and high pressure (up to 100 atm) reactors. On the other hand, studies have shown that the ODS process is remarkably successful in the removal of sulfur under mild reaction conditions. This review article presents a comparative analysis of various existing catalytic oxidation techniques: acetic acid/formic acid catalytic oxidation, heteropolyacid (HPA) catalytic oxidation, ionic liquid catalytic oxidation, molecular sieve catalytic oxidation, polyoxometalates catalytic oxidation, titanium catalytic oxidation, and ultrasound-assisted oxidation systems, as well as discusses research gaps, and proposes important recommendations for future challenges.
      Citation: Catalysts
      PubDate: 2019-03-02
      DOI: 10.3390/catal9030229
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 230: Perovskites as Catalysts in Advanced
           Oxidation Processes for Wastewater Treatment

    • Authors: María Luisa Rojas-Cervantes, Eva Castillejos
      First page: 230
      Abstract: Advanced oxidation processes (AOPs), based on the formation of highly reactive radicals are able to degrade many organic contaminants present in effluent water. In the heterogeneous AOPS the presence of a solid which acts as catalyst in combination with other systems (O3, H2O2, light) is required. Among the different materials that can catalyse these processes, perovskites are found to be very promising, because they are highly stable and exhibit a high mobility of network oxygen with the possibility of forming vacancies and to stabilize unusual oxidation states of metals. In this review, we show the fundaments of different kinds of AOPs and the application of perovskite type oxides in them, classified attending to the oxidant used, ozone, H2O2 or peroxymonosulfate, alone or in combination with other systems. The photocatalytic oxidation, consisting in the activation of the perovskite by irradiation with ultraviolet or visible light is also revised.
      Citation: Catalysts
      PubDate: 2019-03-02
      DOI: 10.3390/catal9030230
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 231: Mechanism Analysis and Kinetic Modelling of
           Cu NPs Catalysed Glycerol Conversion into Lactic Acid

    • Authors: Sergey A. Zavrazhnov, Anton L. Esipovich, Sergey Yu. Zlobin, Artem S. Belousov, Andrey V. Vorotyntsev
      First page: 231
      Abstract: Mechanism analysis and kinetic modeling of glycerol conversion into lactic acid in the alkaline media with and without heterogeneous catalyst Cu NPs are reported. The reaction pathways were determined in agreement with the experimental results and comprise several types of reactions, namely dehydrogenation, hydrogenolysis, dehydration and C–C cleavage. Experimental concentration-time profiles were obtained in a slurry batch reactor at different glycerol, NaOH and Cu NPs concentrations in a temperature range of 483–518 K. Power law, Langmuir–Hinshelwood (LH) and Eley–Rideal (ER) models were chosen to fit the experimental data. The proposed reaction pathways and obtained kinetic model adequately describe the experimental data. The reaction over Cu NPs catalyst in the presence of NaOH proceeds with a significantly lower activation barrier (Ea = 81.4 kJ∙mol−1) compared with the only homogeneous catalytic conversion (Ea = 104.0 kJ∙mol−1). The activation energy for glycerol hydrogenolysis into 1,2-propanediol on the catalyst surface without adding hydrogen is estimated of 102.0 kJ∙mol−1. The model parameters obtained in this study would be used to scale an industrial unit in a reactor modeling.
      Citation: Catalysts
      PubDate: 2019-03-02
      DOI: 10.3390/catal9030231
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 232: Overcoming Water Insolubility in Flow:
           Enantioselective Hydrolysis of Naproxen Ester

    • Authors: David Roura Padrosa, Valerio De Vitis, Martina Letizia Contente, Francesco Molinari, Francesca Paradisi
      First page: 232
      Abstract: Hydrolytic enantioselective cleavage of different racemic non-steroidal anti-inflammatory drugs (NSAIDs) ester derivatives has been studied. An engineered esterase form Bacillus subtilis (BS2m) significantly outperformed homologous enzymes from Halomonas elongata (HeE) and Bacillus coagulants (BCE) in the enantioselective hydrolysis of naproxen esters. Structural analysis of the three active sites highlighted key differences which explained the substrate preference. Immobilization of a chimeric BS2m-T4 lysozyme fusion (BS2mT4L1) was improved by resin screening achieving twice the recovered activity (22.1 ± 5 U/g) with respect to what had been previously reported, and was utilized in a packed bed reactor. Continuous hydrolysis of α-methyl benzene acetic acid butyl ester as a model substrate was easily achieved, albeit at low concentration (1 mM). However, the high degree of insolubility of the naproxen butyl ester resulted in a slurry which could not be efficiently bioconverted, despite the addition of co-solvents and lower substrate concentration (1 mM). Addition of Triton® X-100 to the substrate mix yielded 24% molar conversion and 80% e.e. at a 5 mM scale with 5 min residence time and sufficient retention of catalytic efficiency after 6 h of use.
      Citation: Catalysts
      PubDate: 2019-03-03
      DOI: 10.3390/catal9030232
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 233: Ceria Nanoparticles’ Morphological Effects
           on the N2O Decomposition Performance of Co3O4/CeO2 Mixed Oxides

    • Authors: Maria Lykaki, Eleni Papista, Nikolaos Kaklidis, Sόnia A. C. Carabineiro, Michalis Konsolakis
      First page: 233
      Abstract: Ceria-based oxides have been widely explored recently in the direct decomposition of N2O (deN2O) due to their unique redox/surface properties and lower cost as compared to noble metal-based catalysts. Cobalt oxide dispersed on ceria is among the most active mixed oxides with its efficiency strongly affected by counterpart features, such as particle size and morphology. In this work, the morphological effect of ceria nanostructures (nanorods (ΝR), nanocubes (NC), nanopolyhedra (NP)) on the solid-state properties and the deN2O performance of the Co3O4/CeO2 binary system is investigated. Several characterization methods involving N2 adsorption at −196 °C, X-ray diffraction (XRD), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (ΤΕΜ) were carried out to disclose structure–property relationships. The results revealed the importance of support morphology on the physicochemical properties and the N2O conversion performance of bare ceria samples, following the order nanorods (NR) > nanopolyhedra (NP) > nanocubes (NC). More importantly, Co3O4 impregnation to different carriers towards the formation of Co3O4/CeO2 mixed oxides greatly enhanced the deN2O performance as compared to bare ceria samples, without, however, affecting the conversion sequence, implying the pivotal role of ceria support. The Co3O4/CeO2 sample with the rod-like morphology exhibited the best deN2O performance (100% N2O conversion at 500 °C) due to its abundance in Co2+ active sites and Ce3+ species in conjunction to its improved reducibility, oxygen kinetics and surface area.
      Citation: Catalysts
      PubDate: 2019-03-03
      DOI: 10.3390/catal9030233
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 234: Characterisation of the First Archaeal
           Mannonate Dehydratase from Thermoplasma acidophilum and Its Potential Role
           in the Catabolism of D-Mannose

    • Authors: Dominik Kopp, Robert Willows, Anwar Sunna
      First page: 234
      Abstract: Mannonate dehydratases catalyse the dehydration reaction from mannonate to 2-keto-3-deoxygluconate as part of the hexuronic acid metabolism in bacteria. Bacterial mannonate dehydratases present in this gene cluster usually belong to the xylose isomerase-like superfamily, which have been the focus of structural, biochemical and physiological studies. Mannonate dehydratases from archaea have not been studied in detail. Here, we identified and characterised the first archaeal mannonate dehydratase (TaManD) from the thermoacidophilic archaeon Thermoplasma acidophilum. The recombinant TaManD enzyme was optimally active at 65 °C and showed high specificity towards D-mannonate and its lactone, D-mannono-1,4-lactone. The gene encoding for TaManD is located adjacent to a previously studied mannose-specific aldohexose dehydrogenase (AldT) in the genome of T. acidophilum. Using nuclear magnetic resonance (NMR) spectroscopy, we showed that the mannose-specific AldT produces the substrates for TaManD, demonstrating the possibility for an oxidative metabolism of mannose in T. acidophilum. Among previously studied mannonate dehydratases, TaManD showed closest homology to enzymes belonging to the xylose isomerase-like superfamily. Genetic analysis revealed that closely related mannonate dehydratases among archaea are not located in a hexuronate gene cluster like in bacteria, but next to putative aldohexose dehydrogenases, implying a different physiological role of mannonate dehydratases in those archaeal species.
      Citation: Catalysts
      PubDate: 2019-03-03
      DOI: 10.3390/catal9030234
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 235: Dye-sensitized Photocatalyst of Sepiolite
           for Organic Dye Degradation

    • Authors: Chitiphon Chuaicham, Radheshyam Pawar, Keiko Sasaki
      First page: 235
      Abstract: The photocatalytic activity of sepiolite was examined for degradation of several dye compounds under visible light irradiation. Higher adsorption capacities and greater photocatalytic performance of cationic dyes (rhodamine B and methylene blue) were observed on sepiolite, in comparison with anionic dyes (orange II and trypan blue). Superiority in the photocatalytic activity of cationic dyes is attributed to the strong electrostatic attraction and photosensitization properties of cationic dye molecules. Sepiolite has degraded 45.3% rhodamine B within 120 min, which is the greatest photocatalytic degradation efficiency when compared with other dyes. Subsequently, the reusability of spent sepiolite after adsorption of rhodamine B was evaluated by the degradation of trypan blue under the visible light irradiation. The photocatalytic degradation performance of trypan blue by spent sepiolite after adsorption of rhodamine B increased about twice as much as with pristine sepiolite, indicating that the dye-sensitized photocatalytic process could enhance the photocatalytic degradation ability of sepiolite. Through radical scavenger tests, it was found that a superoxide radical is mainly responsible for rhodamine B degradation. The possible mechanism of rhodamine B degradation under visible light irradiation was proposed. The sepiolite could be a potential catalyst for the degradation of organic pollutants in wastewater under solar light.
      Citation: Catalysts
      PubDate: 2019-03-04
      DOI: 10.3390/catal9030235
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 236: Advanced Rhodococcus Biocatalysts for
           Environmental Biotechnologies

    • Authors: Anastasiia Krivoruchko, Maria Kuyukina, Irena Ivshina
      First page: 236
      Abstract: The review is devoted to biocatalysts based on actinobacteria of the genus Rhodococcus, which are promising for environmental biotechnologies. In the review, biotechnological advantages of Rhodococcus bacteria are evaluated, approaches used to develop robust and efficient biocatalysts are discussed, and their relevant applications are given. We focus on Rhodococcus cell immobilization in detail (methods of immobilization, criteria for strains and carriers, and optimization of process parameters) as the most efficient approach for stabilizing biocatalysts. It is shown that advanced Rhodococcus biocatalysts with improved working characteristics, enhanced stress tolerance, high catalytic activities, human and environment friendly, and commercially viable are developed, which are suitable for wastewater treatment, bioremediation, and biofuel production.
      Citation: Catalysts
      PubDate: 2019-03-04
      DOI: 10.3390/catal9030236
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 237: Alkaline Modification of a
           Metal–Enzyme–Surfactant Nanocomposite to Enhance the Production of
           L-α-glycerylphosphorylcholine

    • Authors: Hui Li, Xun Cao, Yuanyuan Lu, Yan Ni, Xin Wang, Qiuhao Lu, Ganlu Li, Kequan Chen, Pingkai Ouyang, Weimin Tan
      First page: 237
      Abstract: Microenvironment modification within nanoconfinement can maximize the catalytic activity of enzymes. Phospholipase A1 (PLA1) has been used as the biocatalyst to produce high value L-α-glycerylphosphorylcholine (L-α-GPC) through hydrolysis of phosphatidylcholine (PC). We successfully developed a simple co-precipitation method to encapsulate PLA1 in a metal–surfactant nanocomposite (MSNC), then modified it using alkalescent 2-Methylimidazole (2-Melm) to promote catalytic efficiency in biphasic systems. The generated 2-Melm@PLA1/MSNC showed higher catalytic activity than PLA1/MSNC and free PLA1. Scanning electron microscopy and transmission electron microscopy showed a typical spherical structure of 2-Melm@PLA1/MSNC at about 50 nm, which was smaller than that of 2-Melm@MSNC. Energy disperse spectroscopy, N2 adsorption isotherms, Fourier transform infrared spectrum, and high-resolution X-ray photoelectron spectroscopy proved that 2-Melm successfully modified PLA1/MSNC. The generated 2-Melm@PLA1/MSNC showed a high catalytic rate per unit enzyme mass of 1.58 μmol mg-1 min-1 for the formation of L-α-GPC. The 2-Melm@PLA1/MSNC also showed high thermal stability, pH stability, and reusability in a water–hexane biphasic system. The integration of alkaline and amphiphilic properties of a nanocomposite encapsulating PLA1 resulted in highly efficient sequenced reactions of acyl migration and enzymatic hydrolysis at the interface of a biphasic system, which cannot be achieved by free enzyme.
      Citation: Catalysts
      PubDate: 2019-03-04
      DOI: 10.3390/catal9030237
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 238: Metathesis of Functionalized Alkane:
           Understanding the Unsolved Story

    • Authors: Tretiakov, Lebedev, Samantaray, Saidi, Rueping, Basset
      First page: 238
      Abstract: For the first time, we developed a method which enables a functionalized alkane to be metathesized to its lower and higher homologues. For this metathesis reaction, we used [(≡Si-O-)W(CH3)5] as a catalyst precursor and 9-hexyl-9H-carbazole as a reactant.
      Citation: Catalysts
      PubDate: 2019-03-04
      DOI: 10.3390/catal9030238
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 239: Overview of Photocatalytic Membrane Reactors
           in Organic Synthesis, Energy Storage and Environmental Applications

    • Authors: Molinari, Lavorato, Argurio, Szymański, Darowna, Mozia
      First page: 239
      Abstract: This paper presents an overview of recent reports on photocatalytic membrane reactors (PMRs) in organic synthesis as well as water and wastewater treatment. A brief introduction to slurry PMRs and the systems equipped with photocatalytic membranes (PMs) is given. The methods of PM production are also presented. Moreover, the process parameters affecting the performance of PMRs are characterized. The applications of PMRs in organic synthesis are discussed, including photocatalytic conversion of CO2, synthesis of KA oil by photocatalytic oxidation, conversion of acetophenone to phenylethanol, synthesis of vanillin and phenol, as well as hydrogen production. Furthermore, the configurations and applications of PMRs for removal of organic contaminants from model solutions, natural water and municipal or industrial wastewater are described. It was concluded that PMRs represent a promising green technology; however, before the application in industry, additional studies are still required. These should be aimed at improvement of process efficiency, mainly by development and application of visible light active photocatalysts and novel membranes resistant to the harsh conditions prevailing in these systems.
      Citation: Catalysts
      PubDate: 2019-03-04
      DOI: 10.3390/catal9030239
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 240: Ball Milling-Assisted Synthesis of
           Ultrasmall Ruthenium Phosphide for Efficient Hydrogen Evolution Reaction

    • Authors: Xiaofei Liu, Yanglong Guo, Wangcheng Zhan, Tian (Leo) Jin
      First page: 240
      Abstract: The development of scalable hydrogen production technology to produce hydrogen economically and in an environmentally friendly way is particularly important. The hydrogen evolution reaction (HER) is a clean, renewable, and potentially cost-effective pathway to produce hydrogen, but it requires the use of a favorable electrocatalyst which can generate hydrogen with minimal overpotential for practical applications. Up to now, ruthenium phosphide Ru2P has been considered as a high-performance electrocatalyst for the HER. However, a tedious post-treatment method as well as large consumption of solvents in conventional solution-based synthesis still limits the scalable production of Ru2P electrocatalysts in practical applications. In this study, we report a facile and cost-effective strategy to controllably synthesize uniform ultrasmall Ru2P nanoparticles embedded in carbon for highly efficient HER. The key to our success lies in the use of a solid-state ball milling-assisted technique, which overcomes the drawbacks of the complicated post-treatment procedure and large solvent consumption compared with solution-based synthesis. The obtained electrocatalyst exhibits excellent Pt-like HER performance with a small overpotential of 36 mV at current density of 10 mA cm−2 in 1 M KOH, providing new opportunities for the fabrication of highly efficient HER electrocatalysts in real-world applications.
      Citation: Catalysts
      PubDate: 2019-03-05
      DOI: 10.3390/catal9030240
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 241: Application of Heterogeneous Catalytic
           Ozonation for Refractory Organics in Wastewater

    • Authors: Wang, Zhang, Wang, Xiong, Tian, Sun, Yu
      First page: 241
      Abstract: Catalytic ozonation is believed to belong to advanced oxidation processes (AOPs). Over the past decades, heterogeneous catalytic ozonation has received remarkable attention as an effective process for the degradation of refractory organics in wastewater, which can overcome some disadvantages of ozonation alone. Metal oxides, metals, and metal oxides supported on oxides, minerals modified with metals, and carbon materials are widely used as catalysts in heterogeneous catalytic ozonation processes due to their excellent catalytic ability. An understanding of the application can provide theoretical support for selecting suitable catalysts aimed at different kinds of wastewater to obtain higher pollutant removal efficiency. Therefore, the main objective of this review article is to provide a summary of the accomplishments concerning catalytic ozonation to point to the major directions for choosing the catalysts in catalytic ozonation in the future.
      Citation: Catalysts
      PubDate: 2019-03-05
      DOI: 10.3390/catal9030241
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 242: Change of the Product Specificity of a
           Cyclodextrin Glucanotransferase by Semi-Rational Mutagenesis to Synthesize
           Large-Ring Cyclodextrins

    • Authors: Christian Sonnendecker, Wolfgang Zimmermann
      First page: 242
      Abstract: Cyclodextrin glucanotransferases (CGTases) convert starch to cyclodextrins (CD) of various sizes. To engineer a CGTase for the synthesis of large-ring CD composed of 9 to 12 glucose units, a loop structure of the protein involved in substrate binding was targeted for semi-rational mutagenesis. Based on multiple protein alignments and protein structure information, a mutagenic megaprimer was designed to encode a partial randomization of eight amino acid residues within the loop region. The library obtained encoding amino acid sequences occurring in wild type CGTases in combination with a screening procedure yielded sequences displaying a changed CD product specificity. As a result, variants of the CGTase from the alkaliphilic Bacillus sp. G825-6 synthesizing mainly CD9 to CD12 could be obtained. When the mutagenesis experiment was performed with the CGTase G825-6 variant Y183R, the same loop alterations that increased the total CD synthesis activity resulted in lower activities of the variant enzymes created. In the presence of the amino acid residue R183, the synthesis of CD8 was suppressed and larger CD were obtained as the main products. The alterations not only affected the product specificity, but also influenced the thermal stability of some of the CGTase variants indicating the importance of the loop structure for the stability of the CGTase.
      Citation: Catalysts
      PubDate: 2019-03-06
      DOI: 10.3390/catal9030242
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 243: Photoelectrocatalytic H2 and H2O2 Production
           Using Visible-Light-Absorbing Photoanodes

    • Authors: Ioannis Papagiannis, Elias Doukas, Alexandros Kalarakis, George Avgouropoulos, Panagiotis Lianos
      First page: 243
      Abstract: Hydrogen and hydrogen peroxide have been photoelectrocatalytically produced by electrocatalytic reduction using simple carbon electrodes made by depositing a mesoporous carbon film on carbon cloth. Visible-light-absorbing photoanodes have been constructed by depositing mesoporous CdS/TiO2 or WO3 films on transparent fluorine-doped tin oxide (FTO) electrodes. Both produced substantial photocurrents of up to 50 mA in the case of CdS/TiO2 and 25 mA in the case of WO3 photoanodes, and resulting in the production of substantial quantities of H2 gas or aqueous H2O2. Maximum hydrogen production rate was 7.8 µmol/min, and maximum hydrogen peroxide production rate was equivalent, i.e., 7.5 µmol/min. The same reactor was employed for the production of both solar fuels, with the difference being that hydrogen was produced under anaerobic and hydrogen peroxide under aerated conditions. The present data promote the photoelectrochemical production of solar fuels by using simple inexpensive materials for the synthesis of catalysts and the construction of electrodes.
      Citation: Catalysts
      PubDate: 2019-03-06
      DOI: 10.3390/catal9030243
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 244: Chiral Phase-Transfer Catalysts with
           Hydrogen Bond: A Powerful Tool in the Asymmetric Synthesis

    • Authors: Hongyu Wang
      First page: 244
      Abstract: Asymmetric phase-transfer catalysis has been widely applied into organic synthesis for efficiently creating chiral functional molecules. In the past decades, chiral phase-transfer catalysts with proton donating groups are emerging as an extremely significant strategy in the design of novel catalysts, and a large number of enantioselective reactions have been developed. In particular, the proton donating groups including phenol, amide, and (thio)-urea exhibited unique properties for cooperating with the phase-transfer catalysts, and great advances on this field have been made in the past few years. This review summarizes the seminal works on the design, synthesis, and applications of chiral phase-transfer catalysts with strong hydrogen bonding interactions.
      Citation: Catalysts
      PubDate: 2019-03-07
      DOI: 10.3390/catal9030244
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 245: Effect of Dilute Acid and Alkali
           Pretreatments on the Catalytic Performance of Bamboo-Derived Carbonaceous
           Magnetic Solid Acid

    • Authors: Yikui Zhu, Jiawei Huang, Shaolong Sun, Aimin Wu, Huiling Li
      First page: 245
      Abstract: Lignocellulose is a widely used renewable energy source on the Earth that is rich in carbon skeletons. The catalytic hydrolysis of lignocellulose over magnetic solid acid is an efficient pathway for the conversion of biomass into fuels and chemicals. In this study, a bamboo-derived carbonaceous magnetic solid acid catalyst was synthesized by FeCl3 impregnation, followed by carbonization and –SO3H group functionalization. The prepared catalyst was further subjected as the solid acid catalyst for the catalytic conversion of corncob polysaccharides into reducing sugars. The results showed that the as-prepared magnetic solid acid contained –SO3H, –COOH, and polycyclic aromatic, and presented good catalytic performance for the hydrolysis of corncob in the aqueous phase. The concentration of H+ was in the range of 0.6487 to 2.3204 mmol/g. Dilute acid and alkali pretreatments of raw material can greatly improve the catalytic activity of bamboo-derived carbonaceous magnetic solid acid. Using the catalyst prepared by 0.25% H2SO4-pretreated bamboo, 6417.5 mg/L of reducing sugars corresponding to 37.17% carbohydrates conversion could be obtained under the reaction conditions of 120 °C for 30 min.
      Citation: Catalysts
      PubDate: 2019-03-07
      DOI: 10.3390/catal9030245
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 246: The Use of Power Ultrasound for the
           Production of PEMFC and PEMWE Catalysts and Low-Pt Loading and
           High-Performing Electrodes

    • Authors: Bruno G. Pollet
      First page: 246
      Abstract: This short review paper highlights some of the research works undertaken over the years by Pollet’s research groups in Birmingham, Cape Town, and Trondheim, in the use of power ultrasound for the fabrication of low temperature fuel cell and electrolyzer catalysts and electrodes. Since the publication of ‘The use of ultrasound for the fabrication of fuel cell materials’ in 2010, there has been an upsurge of international interest in the use of power ultrasound, sonochemistry, and sonoelectrochemistry for the production of low temperature fuel cell and electrolyzer materials. This is because power ultrasound offers many advantages over traditional synthetic methods. The attraction of power ultrasound is the ability to create localized transient high temperatures and pressures, as a result of cavitation, in solutions at room temperature.
      Citation: Catalysts
      PubDate: 2019-03-07
      DOI: 10.3390/catal9030246
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 247: Investigation of Various Pd Species in
           Pd/BEA for Cold Start Application

    • Authors: Beibei Zhang, Meiqing Shen, Jianqiang Wang, Jiaming Wang, Jun Wang
      First page: 247
      Abstract: A series of Pd/BEA catalysts with various Pd loadings were synthesized. Two active Pd2+ species, Z−-Pd2+-Z− and Z−-Pd(OH)+, on exchanged sites of zeolites, were identified by in situ FTIR using CO and NH3 respectively. Higher NOx storage capacity of Z−-Pd2+-Z− was demonstrated compared with that of Z−-Pd(OH)+, which was caused by the different resistance to H2O. Besides, lower Pd loading led to a sharp decline of Z−-Pd(OH)+, which was attributed to the ‘exchange preference’ for Z−-Pd2+-Z− in BEA. Based on this research, the atom utilization of Pd can be improved by decreasing Pd loading.
      Citation: Catalysts
      PubDate: 2019-03-07
      DOI: 10.3390/catal9030247
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 248: Zeolites as Acid/Basic Solid Catalysts:
           Recent Synthetic Developments

    • Authors: Valentina Verdoliva, Michele Saviano, Stefania De Luca
      First page: 248
      Abstract: The zeolites are porous solid structures characterized by a particular framework of aluminosilicates, in which the incorporation of the Al+3 ions generates an excess of negative charge compensated by cations (usually alkali or alkali earth) or protons. In the latter case, they are employed as catalysts for a wide variety of reactions, such as dehydration, skeletal isomerization and cracking, while the catalytic activity of basic zeolites has not found, up to now, any industrial or whatever relevant application in chemical processes. In the present review, we firstly intend to give an overview of the fundamental chemical composition, as well as the structural features of the zeolite framework. The purpose of this paper is to analyze their key properties as acid, both Lewis and Brønsted, and basic solid support. Their application as catalysts is discussed by reviewing the already published works in that field, and a final remark of their still unexplored potential as green, mild, and selective catalyst is also reported.
      Citation: Catalysts
      PubDate: 2019-03-08
      DOI: 10.3390/catal9030248
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 249: Optimization of Ammonia Oxidation Using
           Response Surface Methodology

    • Authors: Marek Inger, Agnieszka Dobrzyńska-Inger, Jakub Rajewski, Marcin Wilk
      First page: 249
      Abstract: In this paper, the design of experiments and response surface methodology were proposed to study ammonia oxidation process. The following independent variables were selected: the reactor’s load, the temperature of reaction and the number of catalytic gauzes, whereas ammonia oxidation efficiency and N2O concentration in nitrous gases were assumed as dependent variables (response). Based on the achieved results, statistically significant mathematical models were developed which describe the effect of independent variables on the analysed responses. In case of ammonia oxidation efficiency, its achieved value depends on the reactor’s load and the number of catalytic gauzes, whereas the temperature in the studied range (870–910 °C) has no effect on this dependent variable. The concentration of nitrous oxide in nitrous gases depends on all three parameters. The developed models were used for the multi-criteria optimization with the application of desirability function. Sets of parameters were achieved for which optimization assumptions were met: maximization of ammonia oxidation efficiency and minimization of the N2O amount being formed in the reaction.
      Citation: Catalysts
      PubDate: 2019-03-09
      DOI: 10.3390/catal9030249
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 250: The Synthesis of Mannose-6-Phosphate Using
           Polyphosphate-Dependent Mannose Kinase

    • Authors: Zhu, Gao, Chen, Tan, Cao, Liu
      First page: 250
      Abstract: Mannose-6-phosphate (M6P) is involved in many metabolic pathways in life, and it has important applications in the treatment of diseases. This study explored a cost-effective enzyme catalytic synthesis method of M6P, using polyphosphate-dependent mannose kinase from Arthrobacter species. This synthesis uses polyphosphate to replace expensive ATP, and it is greener and safer than chemical synthesis. This study investigated the effects of key factors such as metal ions, temperature, and substrate addition on this enzymatic reaction, and improved the conversion efficiency. We moreover take advantage of the response surface method to explore the best catalytic conditions synthetically. The conversion was 99.17% successful under the optimal reaction conditions. After a series of optimizations, we carried out a 200 mL scale-up experiment, which proved that the method has good prospects for industrial applications.
      Citation: Catalysts
      PubDate: 2019-03-09
      DOI: 10.3390/catal9030250
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 251: Looking for the “Dream Catalyst” for
           Hydrogen Peroxide Production from Hydrogen and Oxygen

    • Authors: Federica Menegazzo, Michela Signoretto, Elena Ghedini, Giorgio Strukul
      First page: 251
      Abstract: The reaction between hydrogen and oxygen is in principle the simplest method to form hydrogen peroxide, but it is still a “dream process”, thus needing a “dream catalyst”. The aim of this review is to analyze critically the different heterogeneous catalysts used for the direct synthesis of H2O2 trying to determine the features that the ideal or “dream catalyst” should possess. This analysis will refer specifically to the following points: (i) the choice of the metal; (ii) the metal promoters used to improve the activity and/or the selectivity; (iii) the role of different supports and their acidic properties; (iv) the addition of halide promoters to inhibit undesired side reactions; (v) the addition of other promoters; (vi) the effects of particle morphology; and (vii) the effects of different synthetic methods on catalyst morphology and performance.
      Citation: Catalysts
      PubDate: 2019-03-11
      DOI: 10.3390/catal9030251
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 252: An Enzyme Cascade Synthesis of Vanillin

    • Authors: Tobias Klaus, Alexander Seifert, Tim Häbe, Bettina M. Nestl, Bernhard Hauer
      First page: 252
      Abstract: A novel approach for the synthesis of vanillin employing a three-step two-enzymatic cascade sequence is reported. Cytochrome P450 monooxygenases are known to catalyse the selective hydroxylation of aromatic compounds, which is one of the most challenging chemical reactions. A set of rationally designed variants of CYP102A1 (P450 BM3) from Bacillus megaterium at the amino acid positions 47, 51, 87, 328 and 437 was screened for conversion of the substrate 3-methylanisole to vanillyl alcohol via the intermediate product 4-methylguaiacol. Furthermore, a vanillyl alcohol oxidase (VAO) variant (F454Y) was selected as an alternative enzyme for the transformation of one of the intermediate compounds via vanillyl alcohol to vanillin. As a proof of concept, the bi-enzymatic three-step cascade conversion of 3-methylanisole to vanillin was successfully evaluated both in vitro and in vivo.
      Citation: Catalysts
      PubDate: 2019-03-12
      DOI: 10.3390/catal9030252
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 253: A Multiscale Approach to the Numerical
           Simulation of the Solid Oxide Fuel Cell

    • Authors: Marcin Mozdzierz, Katarzyna Berent, Shinji Kimijima, Janusz S. Szmyd, Grzegorz Brus
      First page: 253
      Abstract: The models of solid oxide fuel cells (SOFCs), which are available in the open literature, may be categorized into two non-overlapping groups: microscale or macroscale. Recent progress in computational power makes it possible to formulate a model which combines both approaches, the so-called multiscale model. The novelty of this modeling approach lies in the combination of the microscale description of the transport phenomena and electrochemical reactions’ with the computational fluid dynamics model of the heat and mass transfer in an SOFC. In this work, the mathematical model of a solid oxide fuel cell which takes into account the averaged microstructure parameters of electrodes is developed and tested. To gain experimental data, which are used to confirm the proposed model, the electrochemical tests and the direct observation of the microstructure with the use of the focused ion beam combined with the scanning electron microscope technique (FIB-SEM) were conducted. The numerical results are compared with the experimental data from the short stack examination and a fair agreement is found, which shows that the proposed model can predict the cell behavior accurately. The mechanism of the power generation inside the SOFC is discussed and it is found that the current is produced primarily near the electrolyte–electrode interface. Simulations with an artificially changed microstructure does not lead to the correct prediction of the cell characteristics, which indicates that the microstructure is a crucial factor in the solid oxide fuel cell modeling.
      Citation: Catalysts
      PubDate: 2019-03-12
      DOI: 10.3390/catal9030253
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 254: Ruthenium Supported on Ionically
           Cross-linked Chitosan-Carrageenan Hybrid MnFe2O4 Catalysts for
           4-Nitrophenol Reduction

    • Authors: Liew, Lee, Yarmo, Loh, Peixoto, Freire, Yusop
      First page: 254
      Abstract: Herein, we report a facile procedure to synthesize the hybrid magnetic catalyst (Ru@CS-CR@Mn) using ruthenium (Ru) supported on ionically cross-linked chitosan-carrageenan (CS-CR) and manganese ferrite (MnFe2O4) nanoparticles with excellent catalytic activity. The ionic gelation of CS-CR is acting as a protecting layer to promote the encapsulation of MnFe2O4 and Ru nanoparticles by electrostatic interactions. The presence of an active metal and a CS-CR layer on the as-prepared Ru@CS-CR@Mn catalyst was well determined by a series of physicochemical analyses. Subsequently, the catalytic performances of the Ru@CS-CR@Mn catalysts were further examined in the 4-nitrophenol (4-NP) reduction reaction in the presence of sodium borohydride (reducing agent) at ambient temperature. The Ru@CS-CR@Mn catalyst performed excellent catalytic activity in the 4-NP reduction, with a turnover frequency (TOF) values of 925 h−1 and rate constant (k) of 0.078 s−1. It is worth to mentioning that the Ru@CS-CR@Mn catalyst can be recycled and reused up to at least ten consecutive cycles in the 4-NP reduction with consistency in catalytic performance. The Ru@CS-CR@Mn catalyst is particularly attractive as a catalyst due to its superior catalytic activity and superparamagnetic properties for easy separation. We foresee this catalyst having high potential to be extended in a wide range of chemistry applications.
      Citation: Catalysts
      PubDate: 2019-03-12
      DOI: 10.3390/catal9030254
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 255: Approximating Catalyst Effectiveness Factors
           with Reaction Rate Profiles

    • Authors: Ville Alopaeus
      First page: 255
      Abstract: A novel approximate solution for catalyst effectiveness factors is presented. It is based on carefully selected approximate reaction rate profiles, instead of typical assumption of composition profiles inside the catalyst. This formulation allows analytical solution of the approximate model, leading to a very simple iterative solution for effectiveness factor for general nonlinear reaction stoichiometry and arbitrary catalyst particle shape. The same model can be used with all practical Thiele modulus values, including multicomponent systems with inert compounds. Furthermore, the correct formulation of the underlying physical model equation is discussed. It is shown that an incorrect but often-used model formulation where convective mass transfer has been neglected may lead to much higher errors than the present approximation. Even with a correctly formulated physical model, rigorous discretization of the catalyst particle volume may have unexpectedly high numerical errors, even exceeding those with the present approximate solution. The proposed approximate solution was tested with a number of examples. The first was an equimolar reaction with first order kinetics, for which analytical solutions are available for the standard catalyst particle geometries (slab, long cylinder, and sphere). Then, the method was tested with a second order reaction in three cases: (1) with one pure reactant, (2) with inert present, and (3) with two reactants and non-stoichiometric surface concentrations. Finally, the method was tested with an industrially relevant catalytic toluene hydrogenation including Maxwell-Stefan formulation for the diffusion fluxes. In all the tested systems, the results were practically identical when compared to the analytical solutions or rigorous finite volume solution of the same problem.
      Citation: Catalysts
      PubDate: 2019-03-13
      DOI: 10.3390/catal9030255
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 256: Catalytic Behaviour of Flame-Made CuO-CeO2
           Nanocatalysts in Efficient CO Oxidation

    • Authors: Zhao, Li, Wu, Yue, Li, Zha, Deng, Chen
      First page: 256
      Abstract: CuO-CeO2 nanocatalysts with varying CuO contents (1, 5, 9, 14 and 17 wt %) were prepared by one-step flame spray pyrolysis (FSP) and applied to CO oxidation. The influences of CuO content on the as-prepared catalysts were systematically characterized by X-ray diffraction (XRD), N2 adsorption-desorption at −196 °C, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and hydrogen-temperature programmed reduction (H2-TPR). A superior CO oxidation activity was observed for the 14 wt % CuO-CeO2 catalyst, with 90% CO conversion at 98 °C at space velocity (60,000 mL × g−1 × h−1), which was attributed to abundant surface defects (lattice distortion, Ce3+, and oxygen vacancies) and high reducibility supported by strong synergistic interaction. In addition, the catalyst also displayed excellent stability and resistance to water vapor. Significantly, in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) showed that in the CO catalytic oxidation process, the strong synergistic interaction led readily to dehydroxylation and CO adsorption on Cu+ at low temperature. Furthermore, in the feed of water vapor, although there was an adverse effect on the access of CO adsorption, there was also a positive effect on the formation of fewer carbon intermediates. All these results showed the potential of highly active and water vapor-resistive CuO-CeO2 catalysts prepared by FSP.
      Citation: Catalysts
      PubDate: 2019-03-13
      DOI: 10.3390/catal9030256
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 257: Direct Synthesis of Ti-Containing CFI-Type
           Extra-Large-Pore Zeolites in the Presence of Fluorides

    • Authors: Yichen Wang, Hongjuan Wang, Yuanchao Shao, Tianduo Li, Takashi Tatsumi, Jin-Gui Wang
      First page: 257
      Abstract: Ti-containing zeolites showed extremely high activity and selectivity in numerous friendly environmental oxidation reactions with hydrogen peroxide as a green oxidant. It will be in high demand to synthesize Ti-containing crystalline extra-large-pore zeolites due to the severe restrictions of medium-pore and/or large-pore zeolites for bulky reactant oxidations. However, the direct synthesis of extra-large-pore Ti-zeolites was still challengeable. Here, we firstly report a strategy to directly synthesize high-performance Ti-containing CFI-type extra-large-pore (Ti-CFI) zeolites assisted with fluorides. The well-crystallized Ti-CFI zeolites with framework titanium species could be synthesized in the hydrofluoric acid system with seed or in the ammonium fluoride system without seed, which showed higher catalytic activity for cyclohexene oxidation than that synthesized from the traditional LiOH system.
      Citation: Catalysts
      PubDate: 2019-03-14
      DOI: 10.3390/catal9030257
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 258: Heterogeneous Fenton-Like Degradation of
           p-Nitrophenol over Tailored Carbon-Based Materials

    • Authors: O. S. G. P. Soares, Carmen S. D. Rodrigues, Luis M. Madeira, M. F. R. Pereira
      First page: 258
      Abstract: Activated carbon (AC), carbon xerogel (XG), and carbon nanotubes (CNT), with and without N-functionalities, were prepared. Catalysts were obtained after impregnation of these materials with 2 wt.% of iron. The materials were characterized in terms of N2 adsorption at −196 °C, elemental analysis (EA), and the pH at the point of zero charge (pHPZC). The p-nitrophenol (PNP) degradation and mineralization (assessed in terms of total organic carbon–TOC–removal) were evaluated during adsorption, catalytic wet peroxidation (CWPO), and Fenton process. The textural and chemical properties of the carbon-based materials play an important role in such processes, as it was found that the support with the highest surface area -AC- presents the best performance in adsorption, whereas the materials with the highest mesopore surface area -XG or Fe/XG- lead to best removals by oxidation processes (for XG it was achieved 39.7 and 35.0% and for Fe/XG 45.4 and 41.7% for PNP and TOC, respectively). The presence of N-functionalities increases such removals. The materials were reused in consecutive cycles: the carbon-based materials were deactivated by hydrogen peroxide, while the catalysts showed high stability and no Fe leaching. For the support with superior performances -XG-, the effect of nitrogen content was also evaluated. The removals increase with the increase of the nitrogen content, the maximum removals (81% and 65% for PNP and TOC, respectively) being reached when iron supported on a carbon xerogel doped with melamine was used as catalyst.
      Citation: Catalysts
      PubDate: 2019-03-14
      DOI: 10.3390/catal9030258
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 259: Fischer–Tropsch: Product Selectivity–The
           Fingerprint of Synthetic Fuels

    • Authors: Wilson D. Shafer, Muthu Kumaran Gnanamani, Uschi M. Graham, Jia Yang, Cornelius M. Masuku, Gary Jacobs, Burtron H. Davis
      First page: 259
      Abstract: The bulk of the products that were synthesized from Fischer–Tropsch synthesis (FTS) is a wide range (C1–C70+) of hydrocarbons, primarily straight-chained paraffins. Additional hydrocarbon products, which can also be a majority, are linear olefins, specifically: 1-olefin, trans-2-olefin, and cis-2-olefin. Minor hydrocarbon products can include isomerized hydrocarbons, predominantly methyl-branched paraffin, cyclic hydrocarbons mainly derived from high-temperature FTS and internal olefins. Combined, these products provide 80–95% of the total products (excluding CO2) generated from syngas. A vast number of different oxygenated species, such as aldehydes, ketones, acids, and alcohols, are also embedded in this product range. These materials can be used to probe the FTS mechanism or to produce alternative chemicals. The purpose of this article is to compare the product selectivity over several FTS catalysts. Discussions center on typical product selectivity of commonly used catalysts, as well as some uncommon formulations that display selectivity anomalies. Reaction tests were conducted while using an isothermal continuously stirred tank reactor. Carbon mole percentages of CO that are converted to specific materials for Co, Fe, and Ru catalysts vary, but they depend on support type (especially with cobalt and ruthenium) and promoters (especially with iron). All three active metals produced linear alcohols as the major oxygenated product. In addition, only iron produced significant selectivities to acids, aldehydes, and ketones. Iron catalysts consistently produced the most isomerized products of the catalysts that were tested. Not only does product selectivity provide a fingerprint of the catalyst formulation, but it also points to a viable proposed mechanistic route.
      Citation: Catalysts
      PubDate: 2019-03-14
      DOI: 10.3390/catal9030259
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 260: Biocatalyzed Synthesis of Statins: A
           Sustainable Strategy for the Preparation of Valuable Drugs

    • Authors: Pilar Hoyos, Vittorio Pace, Andrés R. Alcántara
      First page: 260
      Abstract: Statins, inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, are the largest selling class of drugs prescribed for the pharmacological treatment of hypercholesterolemia and dyslipidaemia. Statins also possess other therapeutic effects, called pleiotropic, because the blockade of the conversion of HMG-CoA to (R)-mevalonate produces a concomitant inhibition of the biosynthesis of numerous isoprenoid metabolites (e.g., geranylgeranyl pyrophosphate (GGPP) or farnesyl pyrophosphate (FPP)). Thus, the prenylation of several cell signalling proteins (small GTPase family members: Ras, Rac, and Rho) is hampered, so that these molecular switches, controlling multiple pathways and cell functions (maintenance of cell shape, motility, factor secretion, differentiation, and proliferation) are regulated, leading to beneficial effects in cardiovascular health, regulation of the immune system, anti-inflammatory and immunosuppressive properties, prevention and treatment of sepsis, treatment of autoimmune diseases, osteoporosis, kidney and neurological disorders, or even in cancer therapy. Thus, there is a growing interest in developing more sustainable protocols for preparation of statins, and the introduction of biocatalyzed steps into the synthetic pathways is highly advantageous—synthetic routes are conducted under mild reaction conditions, at ambient temperature, and can use water as a reaction medium in many cases. Furthermore, their high selectivity avoids the need for functional group activation and protection/deprotection steps usually required in traditional organic synthesis. Therefore, biocatalysis provides shorter processes, produces less waste, and reduces manufacturing costs and environmental impact. In this review, we will comment on the pleiotropic effects of statins and will illustrate some biotransformations nowadays implemented for statin synthesis.
      Citation: Catalysts
      PubDate: 2019-03-14
      DOI: 10.3390/catal9030260
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 261: CLEAs, Combi-CLEAs and ‘Smart’ Magnetic
           CLEAs: Biocatalysis in a Bio-Based Economy

    • Authors: Roger A. Sheldon
      First page: 261
      Abstract: Biocatalysis has emerged in the last decade as a pre-eminent technology for enabling the envisaged transition to a more sustainable bio-based economy. For industrial viability it is essential that enzymes can be readily recovered and recycled by immobilization as solid, recyclable catalysts. One method to achieve this is via carrier-free immobilization as cross-linked enzyme aggregates (CLEAs). This methodology proved to be very effective with a broad selection of enzymes, in particular carbohydrate-converting enzymes. Methods for optimizing CLEA preparations by, for example, adding proteic feeders to promote cross-linking, and strategies for making the pores accessible for macromolecular substrates are critically reviewed and compared. Co-immobilization of two or more enzymes in combi-CLEAs enables the cost-effective use of multiple enzymes in biocatalytic cascade processes and the use of “smart” magnetic CLEAs to separate the immobilized enzyme from other solids has raised the CLEA technology to a new level of industrial and environmental relevance. Magnetic-CLEAs of polysaccharide-converting enzymes, for example, are eminently suitable for use in the conversion of first and second generation biomass.
      Citation: Catalysts
      PubDate: 2019-03-14
      DOI: 10.3390/catal9030261
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 262: Reactor Selection for Effective Continuous
           Biocatalytic Production of Pharmaceuticals

    • Authors: Lindeque, Woodley
      First page: 262
      Abstract: Enzyme catalyzed reactions are rapidly becoming an invaluable tool for the synthesis of many active pharmaceutical ingredients. These reactions are commonly performed in batch, but continuous biocatalysis is gaining interest in industry because it would allow seamless integration of chemical and enzymatic reaction steps. However, because this is an emerging field, little attention has been paid towards the suitability of different reactor types for continuous biocatalytic reactions. Two types of continuous flow reactor are possible: continuous stirred tank and continuous plug-flow. These reactor types differ in a number of ways, but in this contribution, we focus on residence time distribution and how enzyme kinetics are affected by the unique mass balance of each reactor. For the first time, we present a tool to facilitate reactor selection for continuous biocatalytic production of pharmaceuticals. From this analysis, it was found that plug-flow reactors should generally be the system of choice. However, there are particular cases where they may need to be coupled with a continuous stirred tank reactor or replaced entirely by a series of continuous stirred tank reactors, which can approximate plug-flow behavior. This systematic approach should accelerate the implementation of biocatalysis for continuous pharmaceutical production.
      Citation: Catalysts
      PubDate: 2019-03-14
      DOI: 10.3390/catal9030262
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 263: Fe-Doping in Double Perovskite
           PrBaCo2(1-x)Fe2xO6-δ: Insights into Structural and Electronic Effects to
           Enhance Oxygen Evolution Catalyst Stability

    • Authors: Bae-Jung Kim, Emiliana Fabbri, Ivano E. Castelli, Mario Borlaf, Thomas Graule, Maarten Nachtegaal, Thomas J. Schmidt
      First page: 263
      Abstract: Perovskite oxides have been gaining attention for its capability to be designed as an ideal electrocatalyst for oxygen evolution reaction (OER). Among promising candidates, the layered double perovskite—PrBaCo2O6-δ (PBC)—has been identified as the most active perovskite electrocatalyst for OER in alkaline media. For a single transition metal oxide catalyst, the addition of Fe enhances its electrocatalytic performance towards OER. To understand the role of Fe, herein, Fe is incorporated in PBC in different ratios, which yielded PrBaCo2(1-x)Fe2xCo6-δ (x = 0, 0.2 and 0.5). Fe-doped PBCF’s demonstrate enhanced OER activities and stabilities. Operando X-ray absorption spectroscopy (XAS) revealed that Co is more stable in a lower oxidation state upon Fe incorporation by establishing charge stability. Hence, the degradation of Co is inhibited such that the perovskite structure is prolonged under the OER conditions, which allows it to serve as a platform for the oxy(hydroxide) layer formation. Overall, our findings underline synergetic effects of incorporating Fe into Co-based layered double perovskite in achieving a higher activity and stability during oxygen evolution reaction.
      Citation: Catalysts
      PubDate: 2019-03-14
      DOI: 10.3390/catal9030263
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 264: High-Performing PGM-Free AEMFC Cathodes from
           Carbon-Supported Cobalt Ferrite Nanoparticles

    • Authors: Xiong Peng, Varchaswal Kashyap, Benjamin Ng, Sreekumar Kurungot, Lianqin Wang, John R. Varcoe, William E. Mustain
      First page: 264
      Abstract: Efficient and durable non-precious metal electrocatalysts for the oxygen reduction reaction (ORR) are highly desirable for several electrochemical devices, including anion exchange membrane fuel cells (AEMFCs). Here, cobalt ferrite (CF) nanoparticles supported on Vulcan XC-72 carbon (CF-VC) were created through a facile, scalable solvothermal method. The nano-sized CF particles were spherical with a narrow particle size distribution. The CF-VC catalyst showed good ORR activity, possessing a half-wave potential of 0.71 V. Although the intrinsic activity of the CF-VC catalyst was not as high as some other platinum group metal (PGM)-free catalysts in the literature, where this catalyst really shined was in operating AEMFCs. When used as the cathode in a single cell 5 cm−2 AEMFC, the CF-VC containing electrode was able to achieve a peak power density of 1350 mW cm−2 (iR-corrected: 1660 mW cm−2) and a mass transport limited current density of more than 4 A cm−2 operating on H2/O2. Operating on H2/Air (CO2-free), the same cathode was able to achieve a peak power density of 670 mW cm−2 (iR-corrected: 730 mW cm−2) and a mass transport limited current density of more than 2 A cm−2. These peak power and achievable current densities are among the highest reported values in the literature to date.
      Citation: Catalysts
      PubDate: 2019-03-15
      DOI: 10.3390/catal9030264
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 265: Byproduct Analysis of SO2 Poisoning on
           NH3-SCR over MnFe/TiO2 Catalysts at Medium to Low Temperatures

    • Authors: Tsungyu Lee, Hsunling Bai
      First page: 265
      Abstract: The byproducts of ammonia-selective catalytic reduction (NH3-SCR) process over MnFe/TiO2 catalysts under the conditions of both with and without SO2 poisoning were analyzed. In addition to the NH3-SCR reaction, the NH3 oxidation and the NO oxidation reactions were also evaluated at temperatures of 100–300 °C to clarify the reactions occurred during the SCR process. The results indicated that major byproducts for the NH3 oxidation and NO oxidation tests were N2O and NO2, respectively, and their concentrations increased as the reaction temperature increased. For the NH3-SCR test without the presence of SO2, it revealed that N2O was majorly from the NH3-SCR reaction instead of from NH3 oxidation reaction. The byproducts of N2O and NO2 for the NH3-SCR reaction also increased after increasing the reaction temperature, which caused the decreasing of N2-selectivity and NO consumption. For the NH3-SCR test with SO2 at 150 °C, there were two decay stages during SO2 poisoning. The first decay was due to a certain amount of NH3 preferably reacted with SO2 instead of with NO or O2. Then the catalysts were accumulated with metal sulfates and ammonium salts, which caused the second decay of NO conversion. The effluent N2O increased as poisoning time increased, which was majorly from oxidation of unreacted NH3. On the other hand, for the NH3-SCR test with SO2 at 300 °C, the NO conversion was not decreased after increasing the poisoning time, but the N2O byproduct concentration was high. However, the SO2 led to the formation of metal sulfates, which might inhibit NO oxidation reactions and cause the concentration of N2O gradually decreased as well as the N2-selectivity increased.
      Citation: Catalysts
      PubDate: 2019-03-15
      DOI: 10.3390/catal9030265
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 266: Atomic Layer Deposition for Preparation of
           Highly Efficient Catalysts for Dry Reforming of Methane

    • Authors: Soong Yeon Kim, Byeong Jun Cha, Shahid Saqlain, Hyun Ook Seo, Young Dok Kim
      First page: 266
      Abstract: In this article, the structural and chemical properties of heterogeneous catalysts prepared by atomic layer deposition (ALD) are discussed. Oxide shells can be deposited on metal particles, forming shell/core type catalysts, while metal nanoparticles are incorporated into the deep inner parts of mesoporous supporting materials using ALD. Both structures were used as catalysts for the dry reforming of methane (DRM) reaction, which converts CO2 and CH4 into CO and H2. These ALD-prepared catalysts are not only highly initially active for the DRM reaction but are also stable for long-term operation. The origins of the high catalytic activity and stability of the ALD-prepared catalysts are thoroughly discussed.
      Citation: Catalysts
      PubDate: 2019-03-15
      DOI: 10.3390/catal9030266
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 267: Heterostructure Cu2O/(001)TiO2 Effected on
           Photocatalytic Degradation of Ammonia of Livestock Houses

    • Authors: Pu, Wang, Zhu, Li, Long, Jian, Zeng
      First page: 267
      Abstract: In this paper, a heterogeneous composite catalyst Cu2O/(001)TiO2 was prepared by the impregnation-reduction method. The crystal form, highly active facet content, morphology, optical properties, and the photogenerated electron-hole recombination rate of the as-prepared catalysts were investigated. The performance of Cu2O/(001)TiO2 was appraised by photocatalytic degradation of ammonia under sunlight and was compared with lone P25, Cu2O, and (001)TiO2 at the same reaction conditions. The results showed that 80% of the ammonia concentration (120 ± 3 ppm) was removed by Cu2O/(001)TiO2, which was a higher degradation rate than that of pure P25 (12%), Cu2O (12%), and (001)TiO2 (15%) during 120 min of reaction time. The reason may be due to the compound’s (Cu2O/(001)TiO2) highly active (001) facets content that increased by 8.2% and the band gap width decreasing by 1.02 eV. It was also found that the air flow impacts the photocatalytic degradation of ammonia. Therefore, learning how to maintain the degradation effect of Cu2O/(001)TiO2 with ammonia will be important in future practical applications.
      Citation: Catalysts
      PubDate: 2019-03-15
      DOI: 10.3390/catal9030267
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 268: Hydrogenation of Bio-Oil Model Compounds
           over Raney-Ni at Ambient Pressure

    • Authors: Shumeiko, Schlackl, Kubička
      First page: 268
      Abstract: Lignocellulosic biofuels are the most promising sustainable fuels that can be added to the crude oil pool to refill the dwindling fossil resources. In this work, we tested a Raney-Ni catalyst for the hydrogenation of four bio-oil model compounds and their binary mixtures to assess their reactivity under mild conditions suitable for bio-oil stabilization preceding green diesel production from lignocellulosic biomass. The hydrogenation experiments were performed at ambient hydrogen pressure at temperatures in the range 30–70 °C. Raney-Ni was found to hydrogenate all investigated model compounds efficiently; both carbonyl groups and double bonds were saturated. In addition, it was also active in the demethoxylation of guaiacol. When studying the binary mixtures, furfuryl alcohol was found to significantly inhibit the hydrogenation of the other model compounds (guaiacol and methyl isobutyl ketone) due to their very strong adsorption.
      Citation: Catalysts
      PubDate: 2019-03-15
      DOI: 10.3390/catal9030268
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 269: Fabrication and Electrochemical Performance
           of Zn-Doped La0.2Sr0.25Ca0.45TiO3 Infiltrated with Nickel-CGO, Iron, and
           Cobalt as an Alternative Anode Material for Solid Oxide Fuel Cells

    • Authors: Nazan Muzaffar, Nasima Arshad, Daniel Bøgh Drasbæk, Bhaskar Reddy Sudireddy, Peter Holtappels
      First page: 269
      Abstract: In solid oxide fuel cells, doped strontium titinates have been widely studied as anode materials due to their high n-type conductivity. They are used as current conducting backbones as an alternative to nickel-cermets, which suffer degradation due to coking, sulphur poisoning, and low tolerance to redox cycling. In this work, anode backbone materials were synthesized from La0.2Sr0.25Ca0.45TiO3−δ (LSCTA-), modified with 5 wt.% Zn, and infiltrated with nickel (Ni)/ceria gadolinium-doped cerium oxide (CGO), Fe, and Co. The electrodes were further studied for their electrochemical performance using electrochemical impedance spectroscopy (EIS) at open circuit voltage (OCV) in different hydrogen to steam ratios and at various operating temperatures (850–650 °C). Infiltration of electrocatalysts significantly reduced the polarization resistance and among the studied infiltrates, at all operating temperatures, Ni-CGO showed excellent electrode performance. The polarization resistances in 3% and 50% H2O/H2 atmosphere were found to be 0.072 and 0.025 Ω cm2, respectively, at 850 °C, and 0.091 and 0.076 Ω cm2, respectively, at 750 °C, with Ni-CGO. These values are approximately three orders of magnitude smaller than the polarization resistance (25 Ω cm2) of back bone material measured at 750 °C.
      Citation: Catalysts
      PubDate: 2019-03-16
      DOI: 10.3390/catal9030269
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 270: Effect of Mg/Al2O3 and Calcination
           Temperature on the Catalytic Decomposition of HFC-134a

    • Authors: Caroline Mercy Andrew Swamidoss, Mahshab Sheraz, Ali Anus, Sangjae Jeong, Young-Kwon Park, Young-Min Kim, Seungdo Kim
      First page: 270
      Abstract: This paper evaluated the effect of calcination temperature and the use of Mg/Al2O3 on the decomposition of HFC-134a. Two commercialized catalysts, Al2O3 and Mg/Al2O3, were calcined at two different temperatures (500 and 650 °C) and their physicochemical characteristics were examined by X-ray diffraction, Brunauer–Emmett–Teller analysis, and the temperature-programed desorption of ammonia and carbon dioxide analysis. The results show that, in comparison to Al2O3, 5% Mg/Al2O3 exhibited a larger Brunauer–Emmett–Teller surface area and higher acidity. The relative amount of strong acid sites of the catalysts decreased with increasing calcination temperature. Although a more than 90% decomposition rate of HFC-134a was achieved over all catalysts during the sequential decomposition test of HFC-134a using a vertical plug flow reactor connected directly to a gas chromatography/mass spectrometry system, the lifetime of the catalyst differed according to the catalyst type. Compared to Al2O3, Mg/Al2O3 revealed a longer lifetime and less coke formation due to the increased Brunauer–Emmett–Teller surface area and weak Lewis acid sites and basic sites arising from Mg impregnation. Higher temperature calcination extended the catalyst lifetime with the formation of less coke due to the smaller number of strong acid sites, which can lead to severe coke formation. A valuable by-product, trifluoroethylene, was formed as a result of the decomposition. Based on the experimental results, a reaction is proposed which reasonably explains the decomposition reaction.
      Citation: Catalysts
      PubDate: 2019-03-16
      DOI: 10.3390/catal9030270
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 271: Pt/C and Pt/SnOx/C Catalysts for Ethanol
           Electrooxidation: Rotating Disk Electrode Study

    • Authors: Artem S. Pushkarev, Irina V. Pushkareva, Natalia A. Ivanova, Stephanus P. du Preez, Dmitri Bessarabov, Ratibor G. Chumakov, Vladimir G. Stankevich, Vladimir N. Fateev, Anatoly A. Evdokimov, Sergey A. Grigoriev
      First page: 271
      Abstract: Pt/C and Pt/SnOx/C catalysts were synthesized using the polyol method. Their structure, morphology and chemical composition were studied using a scanning electron microscope equipped with an energy dispersive X-ray spectrometer, transition electron microscope and X-ray photoelectron spectroscope. Electrochemical measurements were based on the results of rotating disk electrode (RDE) experiments applied to ethanol electrooxidation. The quick evaluation of catalyst activity, electrochemical behavior, and an average number of transferred electrons were made using the RDE technique. The usage of SnOx (through the carbon support modification) in a binary system together with Pt causes a significant increase of the catalyst activity in ethanol oxidation reaction and the utilization of ethanol.
      Citation: Catalysts
      PubDate: 2019-03-16
      DOI: 10.3390/catal9030271
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 272: Microwave-Assisted Homogeneous Acid
           Catalysis and Chemoenzymatic Synthesis of Dialkyl Succinate in a Flow
           Reactor

    • Authors: Laura Daviot, Thomas Len, Carol Sze Ki Lin, Christophe Len
      First page: 272
      Abstract: Two new continuous flow systems for the production of dialkyl succinates were developed via the esterification of succinic acid, and via the trans-esterification of dimethyl succinate. The first microwave-assisted continuous esterification of succinic acid with H2SO4 as a chemical homogeneous catalyst was successfully achieved via a single pass (ca 320 s) at 65–115 °C using a MiniFlow 200ss Sairem Technology. The first continuous trans-esterification of dimethyl succinate with lipase Cal B as an enzymatic catalyst was developed using a Syrris Asia Technology, with an optimal reaction condition of 14 min at 40 °C. Dialkyl succinates were produced with the two technologies, but higher productivity was observed for the microwave-assisted continuous esterification using chemical catalysts. The continuous flow trans-esterification demonstrated a number of advantages, but it resulted in lower yield of the target esters.
      Citation: Catalysts
      PubDate: 2019-03-16
      DOI: 10.3390/catal9030272
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 273: Efficient Dye-Sensitized Solar Cells
           Composed of Nanostructural ZnO Doped with Ti

    • Authors: Mati Ur Rahman, Mingdeng Wei, Fengyan Xie, Matiullah Khan
      First page: 273
      Abstract: Photoanode materials with optimized particle sizes, excellent surface area and dye loading capability are preferred in good-performance dye sensitized solar cells. Herein, we report on an efficient dye-sensitized mesoporous photoanode of Ti doped zinc oxide (Ti-ZnO) through a facile hydrothermal method. The crystallinity, morphology, surface area, optical and electrochemical properties of the Ti-ZnO were investigated using X-ray photoelectron spectroscopy, transmission electron microscopy and X-ray diffraction. It was observed that Ti-ZnO nanoparticles with a high surface area of 131.85 m2 g−1 and a controlled band gap, exhibited considerably increased light harvesting efficiency, dye loading capability, and achieved comparable solar cell performance at a typical nanocrystalline ZnO photoanode.
      Citation: Catalysts
      PubDate: 2019-03-17
      DOI: 10.3390/catal9030273
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 274: Advances in the Green Synthesis of
           Microporous and Hierarchical Zeolites: A Short Review

    • Authors: Tao Pan, Zhijie Wu, Alex C. K. Yip
      First page: 274
      Abstract: Hierarchical zeolites have been extensively studied due to their enhancement of intra-crystalline diffusion, which leads to the improved catalytic activity and resistance to coking-deactivation. Traditional synthesis strategies of hierarchical zeolites via post-treatment or directing synthesis with the aid of mesoporous template are often characterized by high energy consumption and substantial use of expensive and environmentally unfriendly organic templates. In the recent decade, new green synthesis protocols have been developed for the effective synthesis of conventional and hierarchical zeolites. In this review, the latest advancements on the green synthesis of hierarchical zeolites are summarized and discussed in detail.
      Citation: Catalysts
      PubDate: 2019-03-17
      DOI: 10.3390/catal9030274
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 275: Hydrogenation of Carbon Dioxide to
           Value-Added Chemicals by Heterogeneous Catalysis and Plasma Catalysis

    • Authors: Miao Liu, Yanhui Yi, Li Wang, Hongchen Guo, Annemie Bogaerts
      First page: 275
      Abstract: Due to the increasing emission of carbon dioxide (CO2), greenhouse effects are becoming more and more severe, causing global climate change. The conversion and utilization of CO2 is one of the possible solutions to reduce CO2 concentrations. This can be accomplished, among other methods, by direct hydrogenation of CO2, producing value-added products. In this review, the progress of mainly the last five years in direct hydrogenation of CO2 to value-added chemicals (e.g., CO, CH4, CH3OH, DME, olefins, and higher hydrocarbons) by heterogeneous catalysis and plasma catalysis is summarized, and research priorities for CO2 hydrogenation are proposed.
      Citation: Catalysts
      PubDate: 2019-03-18
      DOI: 10.3390/catal9030275
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 276: Photocatalytic Hydrogen Production: Role of
           Sacrificial Reagents on the Activity of Oxide, Carbon, and Sulfide
           Catalysts

    • Authors: Vignesh Kumaravel, Muhammad Danyal Imam, Ahmed Badreldin, Rama Krishna Chava, Jeong Yeon Do, Misook Kang, Ahmed Abdel-Wahab
      First page: 276
      Abstract: Photocatalytic water splitting is a sustainable technology for the production of clean fuel in terms of hydrogen (H2). In the present study, hydrogen (H2) production efficiency of three promising photocatalysts (titania (TiO2-P25), graphitic carbon nitride (g-C3N4), and cadmium sulfide (CdS)) was evaluated in detail using various sacrificial agents. The effect of most commonly used sacrificial agents in the recent years, such as methanol, ethanol, isopropanol, ethylene glycol, glycerol, lactic acid, glucose, sodium sulfide, sodium sulfite, sodium sulfide/sodium sulfite mixture, and triethanolamine, were evaluated on TiO2-P25, g-C3N4, and CdS. H2 production experiments were carried out under simulated solar light irradiation in an immersion type photo-reactor. All the experiments were performed without any noble metal co-catalyst. Moreover, photolysis experiments were executed to study the H2 generation in the absence of a catalyst. The results were discussed specifically in terms of chemical reactions, pH of the reaction medium, hydroxyl groups, alpha hydrogen, and carbon chain length of sacrificial agents. The results revealed that glucose and glycerol are the most suitable sacrificial agents for an oxide photocatalyst. Triethanolamine is the ideal sacrificial agent for carbon and sulfide photocatalyst. A remarkable amount of H2 was produced from the photolysis of sodium sulfide and sodium sulfide/sodium sulfite mixture without any photocatalyst. The findings of this study would be highly beneficial for the selection of sacrificial agents for a particular photocatalyst.
      Citation: Catalysts
      PubDate: 2019-03-18
      DOI: 10.3390/catal9030276
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 277: Catalysts of PtSn/C Modified with Ru and Ta
           for Electrooxidation of Ethanol

    • Authors: Queiroz, Ribeiro
      First page: 277
      Abstract: PtSn/C-type catalysts modified with Ta and Ru were prepared by the thermal decomposition of polymeric precursors with the following nominal compositions: Pt70Sn10Ta20/C, Pt70Sn10Ta15Ru5/C, Pt70Sn10Ta10Ru10/C and Pt70Sn10Ta5Ru15/C. The physicochemical characterization was performed by X-ray diffraction (XRD) and energy dispersive X-ray (EDX). The electrochemical characterization was performed using cyclic voltammetry, chronoamperometry and fuel cell testing. PtSnTaRu/C catalysts were characterized in the absence and presence of ethanol in an acidic medium (H2SO4 0.5 mol L−1). All the catalysts showed activity for the oxidation of ethanol. The results indicated that the addition of Ta increased the stability and performance of the catalysts, as the Pt70Sn10Ta20/C catalyst had the maximum power density of 27.3 mW cm−2 in an acidic medium. The results showed that the PtSn/C-type catalysts modified with Ta and Ru showed good performance against alcohol oxidation, representingan alternative to the use of direct ethanol fuel cells.
      Citation: Catalysts
      PubDate: 2019-03-18
      DOI: 10.3390/catal9030277
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 278: Cu(II)-Catalyzed Oxidative
           Trifluoromethylation of Indoles with KF as the Base

    • Authors: Xiaolin Shi, Xiaowei Li, Lina Ma, Dayong Shi
      First page: 278
      Abstract: This paper offers an efficient copper-catalyzed oxidative trifluoromethylation of indoles with low-cost CF3SO2Na via C–H activation. Notably, the use of a base is crucial for the trifluoromethylation of indoles. This reaction proceeds efficiently in good to excellent yields and is tolerance of a broad range of functional groups. Furthermore, melatonin, a medicine for sleep disorders, is converted to its 2-CF3 analogue in 68% yield. Studies of possible reaction pathways suggest that this reaction proceeds through a radical process.
      Citation: Catalysts
      PubDate: 2019-03-19
      DOI: 10.3390/catal9030278
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 279: Photocatalytic Activity of Nanostructured
           Titania Films Obtained by Electrochemical, Chemical, and Thermal Oxidation
           of Ti6Al4V Alloy—Comparative Analysis

    • Authors: Aleksandra Radtke
      First page: 279
      Abstract: Three different Ti6Al4V surface oxidation methods have been applied to obtain three types of titania materials of different nanoarchitecture. Electrochemical oxidation of titanium alloy allowed for obtaining titania nanotubes (TNT), chemical oxidation led to obtain titania nanofibers (TNF), and thermal oxidation gave titania nanowires (TNW). My earlier investigations of these nanomaterials were focused mainly on the estimation of their bioactivity and potential application in modern implantology. In this article, the comparative analysis of the photocatalytic activity of produced systems, as well as the impact of their structure and morphology on this activity, are discussed. The activity of studied nanomaterials was estimated basis of UV-induced degradation of methylene blue and also acetone, and it was determined quantitatively according to the Langmuir–Hinshelwood reaction mechanism. The obtained results were compared to the activity of Pilkington Glass ActivTM (reference sample). Among analyzed systems, titania nanofibers obtained at 140 and 120 °C, possessing anatase and anatase/amorphous structure, as well as titania nanowires obtained at 475 and 500 °C, possessing anatase and anatase/rutile structure, were better photocatalyst than the reference sample. Completely amorphous titania nanotubes, turned out to be an interesting alternative for photocatalytic materials in the form of thin films, however, their photocatalytic activity is lower than for Pilkington Glass ActivTM.
      Citation: Catalysts
      PubDate: 2019-03-19
      DOI: 10.3390/catal9030279
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 280: Preparation and Catalytic Performance of
           Expanded Graphite for Oxidation of Organic Pollutant

    • Authors: Ruijia Lan, Wenbin Su, Jitai Li
      First page: 280
      Abstract: A classic carbon material—expanded graphite (EG), was prepared and proposed for a new application as catalysts for activating peroxydisulfate (PDS). EG samples prepared at different expansion temperatures were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and other methods. It was observed that there existed a remarkable synergistic effect in the EG/PDS combined system to degrade Acid Red 97 (AR97). Unlike other carbon material catalysts, sp2 carbon structure may be the main active site in the catalytic reaction. The EG sample treated at 600 °C demonstrated the best catalytic activity for the activation of PDS. Degradation efficiency of AR97 increased with raising PDS dosage and EG loadings. The pH of aqueous solution played an important role in degradation and adsorption, and near-neutrality was the optimal pH in this research. It was assumed that the radical pathway played a dominant role in AR97 degradation and that oxidation of AR97 occurred in the pores and interface layer on the external surface of EG by SO4·− and ·OH, generated on or near the surface of EG. The radical oxidation mechanism was further confirmed by electron paramagnetic resonance spectroscopy. The EG sample could be regenerated by annealing, and the catalytic ability was almost fully recovered.
      Citation: Catalysts
      PubDate: 2019-03-19
      DOI: 10.3390/catal9030280
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 281: Review on the Macro-Transport Processes
           Theory for Irregular Pores able to Perform Catalytic Reactions

    • Authors: Iván Santamaría-Holek, Saúl I. Hernández, Consuelo García-Alcántara, Aldo Ledesma-Durán
      First page: 281
      Abstract: We review and generalize a recent theoretical framework that provides a sound physicochemical basis to describe how volume and surface diffusion are affected by adsorption and desorption processes, as well as by catalytic conversion within the space defined by the irregular geometry of the pores in a material. The theory is based on two single-dimensional mass conservation equations for irregular domains deduced for the volumetric (bulk) and surface mass concentrations. It offers a powerful tool for analyzing and modeling mass transport across porous media like zeolites or artificially build materials, since it establishes how the microscopic quantities that refer to the internal details of the geometry, the flow and the interactions within the irregular pore can be translated into macroscopic variables that are currently measured in experiments. The use of the theory in mass uptake experiments is explained in terms of breakthrough curves and effective mass diffusion coefficients which are explicitly related to the internal geometry of the pores.
      Citation: Catalysts
      PubDate: 2019-03-19
      DOI: 10.3390/catal9030281
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 282: Highly Dispersed Ni Nanocatalysts Derived
           from NiMnAl-Hydrotalcites as High-Performing Catalyst for Low-Temperature
           Syngas Methanation

    • Authors: Bin Lu, Jiahao Zhuang, Jinping Du, Fangna Gu, Guangwen Xu, Ziyi Zhong, Qing Liu, Fabing Su
      First page: 282
      Abstract: Increasing the low-temperature performance of nickel-based catalysts in syngas methanation is critical but very challenging, because at low temperatures there is high concentration of CO on the catalyst surface, causing formation of nickel carbonyl with metallic Ni and further catalyst deactivation. Herein, we have prepared highly dispersed Ni nanocatalysts by in situ reduction of NiMnAl-layered double hydroxides (NiMnAl-LDHs) and applied them to syngas methanation. The synthesized Ni nanocatalysts maintained the nanosheet structure of the LDHs, in which Ni particles were decorated with MnOy species and embedded in the AlOx nanosheets. It was observed that the Ni nanocatalysts exhibited markedly better low-temperature performance than commercial catalysts in the syngas methanation. At 250 °C, 3.0 MPa and a high weight hourly space velocity (WHSV) of 30,000 mL·g−1·h−1, both the CO conversion and the CH4 selectivity reached 100% over the former, while those over the commercial catalyst were only 14% and 76%, respectively. Furthermore, this NiMnAl catalyst exhibited strong anti-carbon and anti-sintering properties at high temperatures. The enhanced low-temperature performance and high-temperature stability originated from the promotion effect of MnOy and the embedding effect of AlOx in the catalyst.
      Citation: Catalysts
      PubDate: 2019-03-19
      DOI: 10.3390/catal9030282
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 283: Transient Operation: A Catalytic
           Chemoselective Hydrogenation of 2-Methyl-3-Butyn-2-ol via a Cooperative Pd
           and Radiofrequency Heating Directed Kinetic Resolution

    • Authors: Duaa Raja, Jabbar Gardy, Ali Hassanpour, Chun-Yu Ho, Javier Fernandez Garcia
      First page: 283
      Abstract: The effect of periodic temperature oscillations has been studied for the hydrogenation of 2-methyl-3-butyn-2-ol over a Pd-based catalyst in a micro-trickle bed reactor. This hydrogenation was investigated using a radiofrequency heated reactor under transient conditions using temperature cycling. The dynamic operation using this configuration was found to increase both conversion and selectivity towards 2-methyl-3-buten-2-ol compared to the steady-state operation with an improvement of up to 24% for the selectivity being observed. The developments made here also result in a lower activation energy in comparison to previous data, providing a starting point for radiofrequency heating to enhance reaction rate through the exploitation of thermal cycling at production scale.
      Citation: Catalysts
      PubDate: 2019-03-20
      DOI: 10.3390/catal9030283
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 284: Cyanosilylation of Aldehydes Catalyzed by
           Ag(I)- and Cu(II)-Arylhydrazone Coordination Polymers in Conventional and
           in Ionic Liquid Media

    • Authors: Gonçalo A. O. Tiago, Kamran T. Mahmudov, M. Fátima C. Guedes da Silva, Ana P. C. Ribeiro, Luís C. Branco, Fedor I. Zubkov, Armando J. L. Pombeiro
      First page: 284
      Abstract: The novel Ag(I) and Cu(II) coordination polymers [Ag(μ3-1κO;2:3κO′;4κN-HL)]n∙n/2H2O (1) and [Cu(en)2(μ-1κO;2κN-L)]n∙nH2O (2) [HL− = 2-(2-(1-cyano-2-oxopropylidene)hydrazinyl)benzene sulfonate] were synthesized and characterized by IR and ESI-MS spectroscopies, elemental and single crystal X-ray diffraction analyses. Compounds 1 and 2 as well as the already known complex salt [Cu(H2O)2(en)2](HL)2 (3) have been tested as homogenous catalysts for the cyanosilylation reaction of different aldehydes with trimethylsilyl cyanide, to provide cyanohydrin trimethylsilyl ethers. Coordination polymer 2 was found to be the most efficient one, with yields ranging from 76 to 88% in methanol, which increases up to 99% by addition of the ionic liquid [DHTMG][L-Lactate].
      Citation: Catalysts
      PubDate: 2019-03-20
      DOI: 10.3390/catal9030284
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 285: Photocatalytic Hydrogen Evolution Using
           Bi-Metallic (Ni/Pt) Na2Ti3O7 Whiskers: Effect of the Deposition Order

    • Authors: Garay-Rodríguez, Murcia-López, Andreu, Moctezuma, Torres-Martínez, Morante
      First page: 285
      Abstract: Photocatalytic hydrogen production through ethanol photo-reforming using Na2Ti3O7 whiskers increases if the sodium titanate is decorated with well-known metallic catalysts such as Ni and Pt. Whereas wet impregnation with nickel gives only a slight increase in the activity, photo-deposition of Pt increased the H2 production by more than one order of magnitude. Through the combination of both co-catalysts (Ni and Pt) a superior performance in terms of H2 production is further observed. However, hydrogen yield is largely enhanced (almost three-fold), up to 778 μmol·g−1·h−1, if the Pt is photo-deposited on the surface of the catalyst before wet impregnation with Ni species (NTO/Pt/Ni) compared to H2 yield (283 μmol·g−1·h−1) achieved with the catalyst prepared in the reverse order (NTO/Ni/Pt). Structural, morphological, optical, and chemical characterization was carried out in order to correlate physicochemical properties with their photocatalytic activity. The X-ray photoelectron spectroscopy (XPS) results show a higher concentration of Pt2+ species if this metallic layer is under the nickel oxide layer. Moreover, X-ray diffraction patterns (XRD) show that Na2Ti3O7 surface is modified for both metal decoration processes.
      Citation: Catalysts
      PubDate: 2019-03-20
      DOI: 10.3390/catal9030285
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 286: Aqueous Dehydration, Hydrogenation and
           Hydrodeoxygenation Reactions of Bio-Based Mucic Acid over Ni, NiMo, Pt,
           Rh, and Ru on Neutral or Acidic Catalyst Supports

    • Authors: Hočevar, Grilc, Likozar
      First page: 286
      Abstract: Hydrotreatment of mucic acid (also known as galactaric acid, an glucaric acid enantiomer), one of the most promising bio-based platform chemicals, was systematically investigated in aqueous media over alumina, silica, or carbon-supported transition (nickel and nickel-molybdenum) or noble (platinum, ruthenium and rhodium) metals. Mucic acid was only converted into mucic-1,4-lactone under non-catalytic reaction conditions in N2 atmosphere, while the 5 MPa gaseous H2 addition triggers hydrogenation in the bulk phase, resulting in formation of galacturonic and galactonic acid. However, dehydroxylation, hydrogenation, decarbonylation, decarboxylation, and cyclization occurred during catalytic hydrotreatment, forming various partially and completely deoxygenated products with a chain length of 3–6 C atoms. Characterization results of tested catalysts were correlated with their activity and selectivity. Insufficient pore diameter of microporous supports completely hindered the mass transfer of reactants to the active sites, resulting in negligible conversion of mucic acid. A comprehensive reaction pathway network was proposed and several industrially interesting compounds were formed, including levulinic acid, furoic acid, and adipic acid. However, selectivity towards adipic acid, a bio-based nylon 6,6 precursor, was low (up to 5 mol%) in aqueous media and elevated temperatures.
      Citation: Catalysts
      PubDate: 2019-03-20
      DOI: 10.3390/catal9030286
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 287: Optimization Parameters, Kinetics and
           Mechanism of Naproxen Removal by Catalytic Wet Peroxide Oxidation with a
           Hybrid Iron-Based Magnetic Catalyst

    • Authors: Huaccallo-Aguilar, Álvarez-Torrellas, Larriba, Águeda, Delgado, Ovejero, García
      First page: 287
      Abstract: This work presents a study of the assessment of the operating parameters of the catalytic wet peroxide oxidation (CWPO) of naproxen (NAP) using magnetite/multi-walled carbon nanotubes (Fe3O4/MWCNTs) as a catalyst. The effect of pH, temperature, and H2O2 dosage on CWPO process was evaluated by using the response surface model (RSM), allowing us to obtain an optimum NAP removal of 82% at the following operating conditions: pH = 5, T = 70 °C, [H2O2]0 = 1.5 mM, and [NAP]0 = 10.0 mg/L. Therefore, NAP degradation kinetics were revealed to follow a pseudo-second-order kinetic model, and an activation energy value of 4.75 kJ/mol was determined. Adsorption and using only H2O2 experiments, both considered as blank tests, showed no significant removal of the pollutant. Moreover, Fe3O4/MWCNTs material exhibited good recyclability along three consecutive cycles, finding an average NAP removal percentage close to 80% in each cycle of 3 h reaction time. In addition, the scavenging tests confirmed that the degradation of NAP was mainly governed by •OH radicals attack. Two reaction sequences were proposed for the degradation mechanism according to the detected byproducts. Finally, the versatility of the catalyst was evidenced in the treatment of different environmentally relevant aqueous matrices (wastewater treatment plant effluent (WWTP), surface water (SW), and a hospital wastewater (HW)) spiked with NAP, obtaining total organic carbon (TOC) removal efficiencies after 8 h in the following order: NAP-SW > NAP-HW > NAP-WWTP.
      Citation: Catalysts
      PubDate: 2019-03-20
      DOI: 10.3390/catal9030287
      Issue No: Vol. 9, No. 3 (2019)
       
  • Catalysts, Vol. 9, Pages 188: Combined Magnesia, Ceria and Nickel catalyst
           

    • Authors: Ahmed Sadeq Al-Fatesh, Samsudeen Olajide Kasim, Ahmed Aidid Ibrahim, Anis Hamza Fakeeha, Ahmed Elhag Abasaeed, Rasheed Alrasheed, Rawan Ashamari, Abdulaziz Bagabas
      First page: 188
      Abstract: This study investigated dry reforming of methane (DRM) over combined catalysts supported on γ-Al2O3 support doped with 3.0 wt. % TiO2. Physicochemical properties of all catalysts were determined by inductively coupled plasma/mass spectrometry (ICP-MS), nitrogen physisorption, X-ray diffraction, temperature programmed reduction/oxidation/desorption/pulse hydrogen chemisorption, thermogravimetric analysis, and scanning electron microscopy. Addition of CeO2 and MgO to Ni strengthened the interaction between the Ni and the support. The catalytic activity results indicate that the addition of CeO2 and MgO to Ni did not reduce carbon deposition, but improved the activity of the catalysts. Temperature programmed oxidation (TPO) revealed the formation of carbon that is mainly amorphous and small amount of graphite. The highest CH4 and CO2 conversion was found for the catalyst composed of 5.0 wt. % NiO-10.0 wt. % CeO2/3.0 wt. %TiO2-γ-Al2O3 (Ti-CAT-II), resulting in H2/CO mole ratio close to unity. The optimum reaction conditions in terms of reactant conversion and H2/CO mole ratio were achieved by varying space velocity and CO2/CH4 mole ratio.
      Citation: Catalysts
      PubDate: 2019-02-18
      DOI: 10.3390/catal9020188
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 189: Synergistic Effect of Photocatalytic
           Degradation of Hexabromocyclododecane in Water by UV/TiO2/persulfate

    • Authors: Qiang Li, Lifang Wang, Xuhui Fang, Li Zhang, Jingjiu Li, Hongyong Xie
      First page: 189
      Abstract: In this work, the elimination of hexabromocyclododecane (HBCD) is explored by using photodegradation of the UV/TiO2 system, the UV/potassium persulfate (KPS) system, and the homo/heterogeneous UV/TiO2/KPS system. The experimental results show that the dosages of TiO2 and potassium persulfate have optimum values to increase the degradation degree. HBCD can be almost completely degraded and 74.3% of the total bromine content is achieved in the UV/TiO2/KPS homo/heterogeneous photocatalysis, much more than in the UV/persulfate system and the UV/TiO2 system. Roles of radicals SO4•− and OH• in the photocatalysis systems are discussed based on experimental measurements. The high yield of the concentration of bromide ions and decreased pH value indicates that synergistic effects exist in the UV/TiO2/KPS homo/heterogeneous photocatalysis, which can mineralize HBCD into inorganic small molecules like carboxylic acids, CO2 and H2O, thus much less intermediates are formed. The possible pathways of degradation of HBCD in the UV/TiO2/KPS system were also analyzed by GC/MS. This work will have practical application potential in the fields of pollution control and environmental management.
      Citation: Catalysts
      PubDate: 2019-02-18
      DOI: 10.3390/catal9020189
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 190: Application of Cell-Free Protein Synthesis
           for Faster Biocatalyst Development

    • Authors: Jascha Rolf, Katrin Rosenthal, Stephan Lütz
      First page: 190
      Abstract: Cell-free protein synthesis (CFPS) has become an established tool for rapid protein synthesis in order to accelerate the discovery of new enzymes and the development of proteins with improved characteristics. Over the past years, progress in CFPS system preparation has been made towards simplification, and many applications have been developed with regard to tailor-made solutions for specific purposes. In this review, various preparation methods of CFPS systems are compared and the significance of individual supplements is assessed. The recent applications of CFPS are summarized and the potential for biocatalyst development discussed. One of the central features is the high-throughput synthesis of protein variants, which enables sophisticated approaches for rapid prototyping of enzymes. These applications demonstrate the contribution of CFPS to enhance enzyme functionalities and the complementation to in vivo protein synthesis. However, there are different issues to be addressed, such as the low predictability of CFPS performance and transferability to in vivo protein synthesis. Nevertheless, the usage of CFPS for high-throughput enzyme screening has been proven to be an efficient method to discover novel biocatalysts and improved enzyme variants.
      Citation: Catalysts
      PubDate: 2019-02-19
      DOI: 10.3390/catal9020190
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 191: Titanium Dioxide: From Engineering to
           Applications

    • Authors: Xiaolan Kang, Sihang Liu, Zideng Dai, Yunping He, Xuezhi Song, Zhenquan Tan
      First page: 191
      Abstract: Titanium dioxide (TiO2) nanomaterials have garnered extensive scientific interest since 1972 and have been widely used in many areas, such as sustainable energy generation and the removal of environmental pollutants. Although TiO2 possesses the desired performance in utilizing ultraviolet light, its overall solar activity is still very limited because of a wide bandgap (3.0–3.2 eV) that cannot make use of visible light or light of longer wavelength. This phenomenon is a deficiency for TiO2 with respect to its potential application in visible light photocatalysis and photoelectrochemical devices, as well as photovoltaics and sensors. The high overpotential, sluggish migration, and rapid recombination of photogenerated electron/hole pairs are crucial factors that restrict further application of TiO2. Recently, a broad range of research efforts has been devoted to enhancing the optical and electrical properties of TiO2, resulting in improved photocatalytic activity. This review mainly outlines state-of-the-art modification strategies in optimizing the photocatalytic performance of TiO2, including the introduction of intrinsic defects and foreign species into the TiO2 lattice, morphology and crystal facet control, and the development of unique mesocrystal structures. The band structures, electronic properties, and chemical features of the modified TiO2 nanomaterials are clarified in detail along with details regarding their photocatalytic performance and various applications.
      Citation: Catalysts
      PubDate: 2019-02-19
      DOI: 10.3390/catal9020191
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 192: NHC-Catalyzed Organocatalytic Asymmetric
           Approach to 2,2-Disubstituted Benzofuran-3(2H)-ones Containing Fully
           Substituted Quaternary Stereogenic Center

    • Authors: Zbigniew Rafiński
      First page: 192
      Abstract: A highly efficient and enantioselective approach to the synthesis of functionalized benzofuran-3(2H)-ones is presented. It proceeds via an intramolecular Stetter reaction using β,β-disubstituted Michael acceptors in the construction of five-membered rings with fully-substituted quaternary stereogenic centers and is promoted by terpene-derived triazolium salts. As a result, a series of chiral 2,2-disubstituted benzofuran-3(2H)-one derivatives with linear, branched, and cyclic aliphatic substitutions on the quaternary stereogenic center were obtained in high yields and with excellent enantioselectivities of up to 99% ee.
      Citation: Catalysts
      PubDate: 2019-02-20
      DOI: 10.3390/catal9020192
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 193: Photocatalytic Reversible Reactions Driven
           by Localized Surface Plasmon Resonance

    • Authors: Zheng Gong, Jialong Ji, Jingang Wang
      First page: 193
      Abstract: In this study, we review photocatalytic reversible surface catalytic reactions driven by localized surface plasmon resonance. Firstly, we briefly introduce the synthesis of 4,4′-dimercaptoazobenzene (DMAB) from 4-nitrobenzenethiol (4NBT) using surface-enhanced Raman scattering (SERS) technology. Furthermore, we study the photosynthetic and degradation processes of 4NBT to DMAB reduction, as well as factors associated with them, such as laser wavelength, reaction time, substrate, and pH. Last but not least, we reveal the competitive relationship between photosynthetic and degradation pathways for this reduction reaction by SERS technology on the substrate of Au film over a nanosphere.
      Citation: Catalysts
      PubDate: 2019-02-20
      DOI: 10.3390/catal9020193
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 194: Alkali and Alkaline Earth Cation-Decorated
           TiO2 Nanotube-Supported Rh Catalysts for Vinyl Acetate Hydroformylation

    • Authors: Hongyuan Chuai, Penghe Su, Hongchi Liu, Baolin Zhu, Shoumin Zhang, Weiping Huang
      First page: 194
      Abstract: Alkali and alkaline earth cation-decorated TiO2 nanotube (TNT)-supported rhodium catalysts were synthesized and characterized by inductively-coupled plasma optical emission spectrometer, surface characterization analyzer, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transforming infrared spectrum, respectively. Their catalytic performances were evaluated by the hydroformylation of vinyl acetate. Results showed that both the conversion rate of vinyl acetate and selectivity for aldehyde were improved after Rh/TNTs were modified by alkali or alkali-earth cations. Such improved selectivity for aldehyde might be attributed to the presence of alkali or alkaline earth cations which enhanced CO adsorption, while the high conversion rate of vinyl acetate was likely due to the proper interaction of Lewis acid–base between cations modified TNTs and vinyl acetate.
      Citation: Catalysts
      PubDate: 2019-02-20
      DOI: 10.3390/catal9020194
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 195: Aerobic Epoxidation of Low-Molecular-Weight
           and Polymeric Olefins by a Supramolecular Manganese Porphyrin Catalyst

    • Authors: Ivan Bernar, Floris P.J.T. Rutjes, Johannes A.A.W. Elemans, Roeland J.M. Nolte
      First page: 195
      Abstract: We report on the highly efficient epoxidation of low-molecular-weight and polymeric olefins catalyzed by a supramolecular manganese porphyrin complex using molecular oxygen as an oxidant and an aldehyde as a co-reductant. At ambient temperature and under optimized reaction conditions, the catalyst showed high activity and stereoselectivity. The efficiency of the supramolecular manganese porphyrin was higher than that of a reference porphyrin catalyst, possibly because it was more stable under the applied reaction conditions. Mechanistic studies suggest that a manganese oxo porphyrin complex may be an intermediate in the epoxidation reaction.
      Citation: Catalysts
      PubDate: 2019-02-21
      DOI: 10.3390/catal9020195
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 196: Editorial Catalysts: Special Issue on Plasma
           Catalysis

    • Authors: Annemie Bogaerts
      First page: 196
      Abstract: Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO2 conversion into value-added chemicals and fuels, N2 fixation for the synthesis of NH3 or NOx, and CH4 conversion into higher hydrocarbons or oxygenates [...]
      Citation: Catalysts
      PubDate: 2019-02-21
      DOI: 10.3390/catal9020196
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 197: Theoretical Study on Influence of Cobalt
           Oxides Valence State Change for C6H5COOH Pyrolysis

    • Authors: Si-Mei Fu, Yue Zhao, Jiang-Tao Liu, Wen-Sheng Liang, Gang-Sen Li, Wei Huang, Zhi-Jun Zuo
      First page: 197
      Abstract: Benzoic acid (C6H5COOH) is selected as coal-based model compound with Co compounds (Co3O4, CoO and Co) as the catalysts, and the influence of the valence state change of the catalyst for pyrolysis process is investigated using density functional theory (DFT). DFT results shows that the highest energy barrier of C6H5COOH pyrolysis is in the following order: Ea(CoO) <Ea(Co3O4) <Ea(no catalyst) <Ea(Co). In general, Co3O4 catalyst accelerates C6H5COOH pyrolysis. Then, the catalytic activity further increases when Co3O4 is reduced to CoO. Finally, Co shows no activity for C6H5COOH pyrolysis due to the reduction of CoO to metallic Co.
      Citation: Catalysts
      PubDate: 2019-02-21
      DOI: 10.3390/catal9020197
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 198: First-Principles Study of Optoelectronic
           Properties of the Noble Metal (Ag and Pd) Doped BiOX (X = F, Cl, Br, and
           I) Photocatalytic System

    • Authors: Shixiong Zhou, Tingting Shi, Zhihong Chen, Dmitri S. Kilin, Lingling Shui, Mingliang Jin, Zichuan Yi, Mingzhe Yuan, Nan Li, Xiaobao Yang, Qingguo Meng, Xin Wang, Guofu Zhou
      First page: 198
      Abstract: To explore the photocatalytic performances and optoelectronic properties of pure and doped bismuth oxyhalides D-doped BiOX (D = Ag, Pd; X = F, Cl, Br, I) compounds, their atomic properties, electronic structures, and optical properties were systematically investigated using first-principles calculations. In previous experiments, the BiOX (X = Cl, Br) based system has been observed with enhanced visible light photocatalytic activity driven by the Ag dopant. Our calculations also show that the potential photocatalytic performance of Ag-doped BiOCl or BiOBr systems is enhanced greatly under visible light, compared with other Pd-doped BiOX (X = Cl, Br) compounds. Furthermore, it is intriguing to find that the Pd-doped BiOF compound has strong absorption over the infrared and visible light spectrum, which may offer an effective strategy for a promising full spectrum catalyst. Indicated by various Mulliken charge distributions and different impurity states in the gap when Ag or Pd was doped in the BiOX compounds, we notice that all D-doped BiOXs exhibit a p-type semiconductor, and all impurity levels originated from the D-4d state. The charge transfer, optoelectronic properties, and absorption coefficients for photocatalytic activities among D-doped BiOX photocatalysts caused by the electronegativity difference of halide elements and metal atoms will finally affect the photocatalytic activity of doped BiOX systems. Therefore, it is significant to understand the inside physical mechanism of the enhanced Ag/Pd-doped BiOX photocatalysts through density functional theory.
      Citation: Catalysts
      PubDate: 2019-02-21
      DOI: 10.3390/catal9020198
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 199: The Support Effects on the Direct Conversion
           of Syngas to Higher Alcohol Synthesis over Copper-Based Catalysts

    • Authors: Xiaoli Li, Junfeng Zhang, Min Zhang, Wei Zhang, Meng Zhang, Hongjuan Xie, Yingquan Wu, Yisheng Tan
      First page: 199
      Abstract: The types of supports employed profoundly influence the physicochemical properties and performances of as-prepared catalysts in almost all catalytic systems. Herein, Cu catalysts, with different supports (SiO2, Al2O3), were prepared by a facile impregnation method and used for the direct synthesis of higher alcohols from CO hydrogenation. The prepared catalysts were characterized using multiple techniques, such as X-ray diffraction (XRD), N2 sorption, H2-temperature-programmed reduction (H2-TPR), temperature-programmed desorption of ammonia (NH3-TPD), X-ray photoelectron spectroscopy (XPS) and in situ Fourier-transform infrared spectroscopy (FTIR), etc. Compared to the Cu/Al2O3 catalyst, the Cu/SiO2 catalyst easily promoted the formation of a higher amount of C1 oxygenate species on the surface, which is closely related to the formation of higher alcohols. Simultaneously, the Cu/Al2O3 and Cu/SiO2 catalysts showed obvious differences in the CO conversion, alcohol distribution, and CO2 selectivity, which were probably originated from differences in the structural and physicochemical properties, such as the types of copper species, the reduction behaviors, acidity, and electronic properties. Besides, it was also found that the gap in performances in two kinds of catalysts with the different supports could be narrowed by the addition of potassium because of its neutralization to surface acidy of Al2O3 and the creation of new basic sites, as well as the alteration of electronic properties.
      Citation: Catalysts
      PubDate: 2019-02-21
      DOI: 10.3390/catal9020199
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 200: Effect of Pt Promotion on the Ni-Catalyzed
           Deoxygenation of Tristearin to Fuel-Like Hydrocarbons

    • Authors: Ryan Loe, Kelsey Huff, Morgan Walli, Tonya Morgan, Dali Qian, Robert Pace, Yang Song, Mark Isaacs, Eduardo Santillan-Jimenez, Mark Crocker
      First page: 200
      Abstract: Pt represents an effective promoter of supported Ni catalysts in the transformation of tristearin to green diesel via decarbonylation/decarboxylation (deCOx), conversion increasing from 2% over 20% Ni/Al2O3 to 100% over 20% Ni-0.5% Pt/Al2O3 at 260 °C. Catalyst characterization reveals that the superior activity of Ni-Pt relative to Ni-only catalysts is not a result of Ni particle size effects or surface area differences, but rather stems from several other phenomena, including the improved reducibility of NiO when Pt is present. Indeed, the addition of a small amount of Pt to the supported Ni catalyst dramatically increases the amount of reduced surface metal sites, which are believed to be the active sites for deCOx reactions. Further, Pt addition curbs the adsorption of CO on the catalyst surface, which decreases catalyst poisoning by any CO evolved via decarbonylation, making additional active sites available for deoxygenation reactions and/or preventing catalyst coking. Specifically, Pt addition weakens the Ni-CO bond, lowering the binding strength of CO on surface Ni sites. Finally, analysis of the spent catalysts recovered from deCOx experiments confirms that the beneficial effect of Pt on catalyst performance can be partially explained by decreased coking and fouling.
      Citation: Catalysts
      PubDate: 2019-02-22
      DOI: 10.3390/catal9020200
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 201: Titanium-Dioxide-Based
           Visible-Light-Sensitive Photocatalysis: Mechanistic Insight and
           Applications

    • Authors: Shinya Higashimoto
      First page: 201
      Abstract: Titanium dioxide (TiO2) is one of the most practical and prevalent photo-functional materials. Many researchers have endeavored to design several types of visible-light-responsive photocatalysts. In particular, TiO2-based photocatalysts operating under visible light should be urgently designed and developed, in order to take advantage of the unlimited solar light available. Herein, we review recent advances of TiO2-based visible-light-sensitive photocatalysts, classified by the origins of charge separation photo-induced in (1) bulk impurity (N-doping), (2) hetero-junction of metal (Au NPs), and (3) interfacial surface complexes (ISC) and their related photocatalysts. These photocatalysts have demonstrated useful applications, such as photocatalytic mineralization of toxic agents in the polluted atmosphere and water, photocatalytic organic synthesis, and artificial photosynthesis. We wish to provide comprehension and enlightenment of modification strategies and mechanistic insight, and to inspire future work.
      Citation: Catalysts
      PubDate: 2019-02-22
      DOI: 10.3390/catal9020201
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 202: Hierarchical ZSM-5 Zeolite with Enhanced
           Catalytic Activity for Alkylation of Phenol with Tert-Butanol

    • Authors: Ling Xu, Fan Wang, Zhiqiang Feng, Zongrui Liu, Jingqi Guan
      First page: 202
      Abstract: Using polyethylene glycol as a mesoporous soft template, a series of hierarchically porous ZSM-5 zeolites were prepared. X-ray diffraction, infrared spectroscopy, N2 adsorption–desorption, and transmission electron microscopy results demonstrated that the resultant materials contained a micro–mesoporous structure. Since the existence of mesoporous structure favors the diffusion of large molecular reactants and products, the phenol conversion and selectivity to 2,4-Di-TBP on the hierarchical ZSM-5 zeolite can be improved for the alkylation of phenol with tert-butanol.
      Citation: Catalysts
      PubDate: 2019-02-23
      DOI: 10.3390/catal9020202
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 203: Aldol Condensation of Furfural with Acetone
           Over Mg/Al Mixed Oxides. Influence of Water and Synthesis Method

    • Authors: Almudena Parejas, Daniel Cosano, Jesús Hidalgo-Carrillo, José Rafael Ruiz, Alberto Marinas, César Jiménez-Sanchidrián, Francisco J. Urbano
      First page: 203
      Abstract: Aldol condensation of furfural and acetone (an important initial step to obtain diesel from biomass) was studied over MgAl mixed oxides. The influence of the utilization of microwaves and/or a surfactant (Pluronic 123) during the synthesis as well as the use of water (either pre-hydrating the solids before catalytic studies or in water/toluene mixtures as the reaction medium) is discussed. The combined use of Pluronic 123 and microwaves led to solids with bigger pore sizes, exhibiting lower basicity and higher acidity than the conventional synthetic method, thus resulting in an increase in the yield of the desired product of condensation, comprising two molecules of furfural and one of acetone (F2Ac). As for the influence of water, re-hydration of the mixed oxides was detrimental to activity, probably as a result of the partial blocking (solvation) of active sites. On the contrary, the increase in water percentage in the reaction medium resulted in higher conversions, though selectivity to F2Ac decreased. The weakening of the C=O bond of furfural in the presence of water as well as the higher solubility of the first condensation product (FAc) in toluene, as compared to water, could account for that. A 44.5% yield of F2Ac (66% conversion) after 16 h was obtained with the most active solid, which maintained the activity for three consecutive reactions.
      Citation: Catalysts
      PubDate: 2019-02-23
      DOI: 10.3390/catal9020203
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 204: Radiative and Non-Radiative Recombination
           Pathways in Mixed-Phase TiO2 Nanotubes for PEC Water-Splitting

    • Authors: Rambabu Yalavarthi, Alberto Naldoni, Štěpán Kment, Luca Mascaretti, Hana Kmentová, Ondřej Tomanec, Patrik Schmuki, Radek Zbořil
      First page: 204
      Abstract: Anatase and rutile mixed-phase TiO2 with an ideal ratio has been proven to significantly enhance photoelectrochemical (PEC) activity in water-splitting applications due to suppressing the electron–hole recombination. However, the mechanism of this improvement has not been satisfactory described yet. The PEC water oxidation (oxygen evolution) at the interface of TiO2 photoanode and electrolyte solution is determined by the fraction of the photogenerated holes that reach the solution and it is defined as the hole transfer efficiency. The surface and bulk recombination processes in semiconductor photoanodes majorly influence the hole transfer efficiency. In this work, we study the hole transfer process involved in mixed-phase TiO2 nanotube arrays/solution junction using intensity-modulated photocurrent and photovoltage spectroscopy (IMPS and IMVS); then, we correlate the obtained hole transfer rate constants to (photo)electrochemical impedance spectroscopy (PEIS) measurements. The results suggest that the enhanced performance of the TiO2 mixed-phase is due to the improved hole transfer rate across the TiO2/liquid interface as well as to the decrease in the surface trap recombination of the holes.
      Citation: Catalysts
      PubDate: 2019-02-23
      DOI: 10.3390/catal9020204
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 205: Selective Catalytic Reduction of Nitric
           Oxide with Propylene over Fe/Beta Catalysts Under Lean-Burn Conditions

    • Authors: Hao Zhou, Mengyao Ge, Huishuang Zhao, Shiguo Wu, Mengyu Li, Yaxin Su
      First page: 205
      Abstract: Fe/Beta catalysts were used for the selective catalytic reduction of nitric oxide with propylene (C3H6-SCR) under lean-burn conditions, which were prepared by liquid ion-exchange (LIE), solid-state ion-exchange (SIE), and incipient wet-impregnation (IWI) methods. The iron species on Fe/Beta were characterized and identified by a combination of several characterization techniques. The results showed preparation methods had a significant influence on the composition and distribution of iron species, LIE method inclined to produce more isolated Fe3+ ions at ion-exchanged sites than IWI and SIE method. C3H6-SCR activity tests demonstrated Fe/Beta(LIE) possessed remarkable catalytic activity and N2 selectivity at temperature 300–450 °C. Kinetic studies of C3H6-SCR reaction suggested that isolated Fe3+ species were more active for NO reduction, whereas Fe2O3 nanoparticles enhanced the hydrocarbon combustion in excess of oxygen. According to the results of in situ DRIFTS, more isolated Fe3+ sites on Fe/Beta(LIE) would promote the formation of the key intermediates, i.e., NO2 adspecies and formate species, then led to the superior C3H6-SCR activity. The slight decrease of SCR activity after hydrothermal aging of Fe/Beta(LIE) catalyst might be due to the migration of isolated Fe3+ ions into oligomeric clusters and/or Fe2O3 nanoparticles.
      Citation: Catalysts
      PubDate: 2019-02-23
      DOI: 10.3390/catal9020205
      Issue No: Vol. 9, No. 2 (2019)
       
  • Catalysts, Vol. 9, Pages 206: Isolation of a Bacillus Aryabhattai Strain
           for the Resolution of (R, S)-Ethyl Indoline-2-Carboxylate to Produce
           (S)-Indoline-2-Carboxylic Acid

    • Authors: Yinjun Zhang, Jialin Chen, Changsheng Chen, Shijin Wu
      First page: 206
      Abstract: The strain screened from sludge can selectively hydrolyze (S)-ethyl indoline-2-carboxylate to produce (S)-indoline-2-carboxylic acid. It was identified as the Bacillus aryabhattai strain based on its morphology, metabolism, and 16S rDNA sequence analysis. Glucose and yeast powder were used as the best carbon and nitrogen sources to cultured cells with an initial pH of seven. Subsequently, we optimized the key parameters for selective hydrolysis. Finally, when the substrate concentration had reached 3%, with a 35 °C water bath, a pH of seven, and a speed of 600 rpm, the e.e.p value attained 96% with a 33% yield. Thus, we had developed a new method for producing (S)-indoline-2-carboxylic acid that used whole microbial cells as the biocatalyst.
      Citation: Catalysts
      PubDate: 2019-02-25
      DOI: 10.3390/catal9020206
      Issue No: Vol. 9, No. 2 (2019)
       
 
 
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