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  Subjects -> CHEMISTRY (Total: 841 journals)
    - ANALYTICAL CHEMISTRY (50 journals)
    - CHEMISTRY (593 journals)
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CHEMISTRY (593 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 8)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 34)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 18)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 23)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 233)
ACS Photonics     Full-text available via subscription   (Followers: 11)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 21)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription   (Followers: 1)
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 50)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 55)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 14)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 9)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 15)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 19)
Advances in Nanoparticles     Open Access   (Followers: 15)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
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: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
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: 14)
American Journal of Chemistry     Open Access   (Followers: 26)
American Journal of Plant Physiology     Open Access   (Followers: 14)
American Mineralogist     Hybrid Journal   (Followers: 14)
Analyst     Full-text available via subscription   (Followers: 40)
Angewandte Chemie     Hybrid Journal   (Followers: 222)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 213)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 3)
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: 8)
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: 15)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 28)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 295)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
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: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
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: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 121)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 98)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 66)
Catalysis for Sustainable Energy     Open Access   (Followers: 7)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 8)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 13)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 70)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 19)
Chemical Reviews     Full-text available via subscription   (Followers: 176)
Chemical Science     Open Access   (Followers: 22)
Chemical Technology     Open Access   (Followers: 16)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemical Week     Full-text available via subscription   (Followers: 8)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 57)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 26)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 142)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 18)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 44)
Chemistry of Materials     Full-text available via subscription   (Followers: 258)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 2)
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: 9)
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: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
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: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 2)
Copernican Letters     Open Access   (Followers: 1)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 3)
CrystEngComm     Full-text available via subscription   (Followers: 12)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 58)
Dalton Transactions     Full-text available via subscription   (Followers: 22)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 12)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 4)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 4)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EJNMMI Radiopharmacy and Chemistry     Open Access  
Elements     Full-text available via subscription   (Followers: 2)
Environmental Chemistry     Hybrid Journal   (Followers: 8)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)
Environmental Science : Nano     Partially Free   (Followers: 1)
Environmental Toxicology & Chemistry     Hybrid Journal   (Followers: 17)

        1 2 3 | Last

Journal Cover Catalysts
  [SJR: 1.123]   [H-I: 14]   [8 followers]  Follow
    
  This is an Open Access Journal Open Access journal
   ISSN (Online) 2073-4344
   Published by MDPI Homepage  [156 journals]
  • Catalysts, Vol. 7, Pages 244: DBD Plasma Assisted CO2 Decomposition:
           Influence of Diluent Gases

    • Authors: Debjyoti Ray, Rajdeep Saha, Subrahmanyam Ch.
      First page: 244
      Abstract: Carbon dioxide (CO2) partial reduction to carbon monoxide (CO) and oxygen has been conducted in a dielectric barrier discharge reactor (DBD) operating a packed bed configuration and the results are compared with that of no packing condition. The effect of diluent gas is studied to understand the influence on dielectric strength of the plasma gas on CO2 splitting, with the objective of obtaining the best CO selectivity and high energy efficiency. Typical results indicated that among N2, He and Ar gases, Ar showed the best decomposition efficiency. Glass beads packing has a strong influence on the performance, probably due to the enhanced field strength due to dielectric nature of the packed material. In a similar manner, Ar mole ratio in the gas mixture also played a significant role, where the maximum CO2 conversion of 19.5% was obtained with packed DBD at CO2:Ar ratio 1:2. The best CO yield (16.8%) was also obtained under the same conditions. The highest energy efficiency was found to be 0.945 mmol/kJ. The activated species formed inside the CO2 plasma were identified by optical emission spectroscopy.
      Citation: Catalysts
      PubDate: 2017-08-23
      DOI: 10.3390/catal7090244
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 245: Conversion of Carbohydrates into Platform
           Chemicals Catalyzed by Alkaline Ionic Liquids

    • Authors: Xiaojia Du, Jie Zhang, Yuehai Wang, Yongshui Qu
      First page: 245
      Abstract: A series of alkaline ionic liquids (ILs) including 1-butyl-3-methylimidazolium benzoate ([BMIM]PHCOO), 1-butyl-3-methylimidazolium carbonate ([BMIM]2CO3), 1-butyl-3-methylimidazolium acetate ([BMIM]OAc), 1-butyl-3-methylimidazolium hydroxide ([BMIM]OH), ethanolamine tetrafluoroborate ([MEA]BF4), and 1,1,3,3-tetramethylguanidine (TMG)-based ILs, etc., were synthesized and utilized as catalysts for the conversion of carbohydrates into 5-HMF. 1,1,3,3-tetramethylguanidine tetrafluoroborate ([TMG]BF4) was confirmed to exhibit excellent catalytic activity, and was much cheaper than other ILs such as 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) for use as a solvent in the conversion of C6 carbohydrates into 5-HMF. The 5-HMF yields from fructose, glucose, cellobiose, and microcrystalline cellulose (MCC) were 74.19%, 27.33%, 20.20%, and 17.73%, respectively. In addition, the possible pathway of carbohydrates (MCC, cellobiose, glucose, etc.) conversion into 5-HMF with [TMG]BF4 as a catalyst was speculated, and the conversion of glucose into 5-HMF was determined to likely be the committed step in the transformation of MCC catalyzed by [TMG]BF4.
      Citation: Catalysts
      PubDate: 2017-08-23
      DOI: 10.3390/catal7090245
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 246: Ethanol Oxidation Reaction on Tandem
           Pt/Rh/SnOx Catalyst

    • Authors: Phuong Mai, Akinori Haze, Masanobu Chiku, Eiji Higuchi, Hiroshi Inoue
      First page: 246
      Abstract: To elucidate the atomic arrangement of a Pt-Rh-Sn ternary catalyst with a high catalytic activity for ethanol oxidation reaction (EOR) and high CO2 selectivity, we prepared a tandem Pt/Rh/SnOx, in which a Rh adlayer was deposited on a Pt substrate (Rh coverage: 0.28), followed by depositing several layers of SnOx only on the Rh surface (Sn coverage: 0.07). For reference, Sn was randomly deposited on the Rh-modified Pt (Pt/Rh) electrode whose Rh and Sn coverages were 0.22 and 0.36 (random Pt/Rh/SnOx). X-ray photoelectron spectroscopy demonstrated that Pt and Rh were metallic, and Sn was largely oxidized. Both Pt/Rh/SnOx electrodes were less positive in onset potential of EOR current density and higher in EOR current density than Pt and Rh/Pt electrodes. In situ infrared reflection-absorption spectroscopy demonstrated that the tandem Pt/Rh/SnOx electrode did not produce acetic acid, but produced CO2 in contrast to the random Pt/Rh/SnOx, suggesting that a tandem arrangement of Pt, Rh and SnOx, in which the Pt and SnOx sites were separated by the Rh sites, was effective for selective CO2 production. In the electrostatic electrolysis at 0.5 V vs. RHE, the tandem Pt/Rh/SnOx electrode exhibited higher EOR current density than the Pt and Pt/Rh electrodes after 1.5 h.
      Citation: Catalysts
      PubDate: 2017-08-24
      DOI: 10.3390/catal7090246
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 247: Fabrication of Crumpled Ball-Like Nickel
           Doped Palladium-Iron Oxide Hybrid Nanoparticles with Controlled Morphology
           as Effective Catalyst for Suzuki–Miyaura Coupling Reaction

    • Authors: Seongwan Jang, Taewoo Kim, Kang Park
      First page: 247
      Abstract: We report a facile synthetic strategy for nickel-doped palladium-iron oxide hybrid nanoparticles with controllable morphology. In this synthetic method, the morphology of the nanoparticles was regulated by the amount of triphenylphosphine used. When 1 mmol of triphenylphosphine was used as a capping agent, the main morphology of the nanoparticles was crumpled balls composed of nanosheets with an average particle size of 215 nm. The nanoparticles showed higher catalytic activity in the Suzuki–Miyaura coupling reaction than did other nanoparticles at equal amounts of Pd. This strategy allowed the reduction of the Pd loading in hybrid nanoparticles while still providing the performance level required for the reaction.
      Citation: Catalysts
      PubDate: 2017-08-24
      DOI: 10.3390/catal7090247
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 248: A Zero-Power, Low-Cost Ultraviolet-C
           Colorimetric Sensor Using a Gallium Oxide and Reduced Graphene Oxide
           Hybrid via Photoelectrochemical Reactions

    • Authors: Seungdu Kim, Kook Han, In Lee, Yeojoon Yoon, Won Park, Suck Hong, Woo Yang, Wan Hwang
      First page: 248
      Abstract: A zero-power, low-cost ultraviolet (UV)-C colorimetric sensor is demonstrated using a gallium oxide and reduced graphene oxide (rGO) hybrid via photoelectrochemical reactions. A wide bandgap semiconductor (WBS) such as gallium oxide with an energy bandgap of 4.9 eV generates electron-hole pairs (EHPs) when exposed under a mercury lamp emitting 254 nm. While the conventional UVC sensors employing WBS convert the generated EHPs into an electrical signal via a solid-state junction device (SSD), our newly proposed UVC sensory system works by converting EHPs into an electrochemical reaction. The electrochemical reaction causes the degradation of a cationic thiazine redox dye, methylene blue (MB) and thereby spontaneously changes its color. As more rGO was hybridized with the gallium oxide, MB degradation was effectively expedited. Thus, the level of MB degradation under UVC can be evaluated as a UVC indicator. Unlike conventional SSD-based UVC sensors, our responsive colorimetric sensor can be applied where needed inexpensively and zero power.
      Citation: Catalysts
      PubDate: 2017-08-24
      DOI: 10.3390/catal7090248
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 249: Cross-Aldol Condensation of Acetone and
           n-Butanol into Aliphatic Ketones over Supported Cu Catalysts on
           Ceria-Zirconia

    • Authors: Minseok Kim, Jongha Park, Hari Prasad Reddy Kannapu, Young-Woong Suh
      First page: 249
      Abstract: A long-chain hydrocarbon biofuel of jet fuel range can be produced via aldol condensation of fermented products such as acetone and alcohols over the catalysts containing both metallic sites for the dehydrogenation of alcohols and basic sites for the condensation reaction. However, an efficient catalyst system has not been studied widely yet the route is promising for biofuel production. In this work, Cu catalysts supported on ceria-zirconia (Cu/xCeZr) were prepared using coprecipitated CexZr1-xO2 supports with different Ce/Zr ratios for the cross-aldol condensation of acetone and n-butanol into mono- and di-alkylated aliphatic ketones, 2-heptanone and 6-undecanone. The acetone conversion and 6-undecanone selectivity increased with specific Cu surface area due to formation of the dehydrogenation product butyraldehyde at a higher concentration. The total yield of cross-aldol condensation products was strongly dependent on a combination of Cu sites and basic sites. This was confirmed by the results in the reaction between acetone and butyraldehyde over supported Cu catalysts that additionally examined the adsorbed acyl species on Cu surface taking part in the aldol condensation reaction. The best catalytic performance was achieved with Cu/0.8CeZr showing the largest Cu surface and the highest base site density among Cu/xCeZr catalysts. While the activity of Cu/0.8CeZ was comparable to or a little higher than that of Cu/MgO, the former catalyst was more stable than the latter suffering from the transformation of MgO to Mg(OH)2 by the reaction. Consequently, it is suggested that Cu supported on ceria-zirconia of ceria rich contains such a dual function that it can efficiently catalyze the cross-aldol condensation of acetone and n-butanol.
      Citation: Catalysts
      PubDate: 2017-08-24
      DOI: 10.3390/catal7090249
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 250: Exploiting the Versatility of Aminated
           Supports Activated with Glutaraldehyde to Immobilize β-galactosidase from
           Aspergillus oryzae

    • Authors: Hadjer Zaak, Sara Peirce, Tiago de Albuquerque, Mohamed Sassi, Roberto Fernandez-Lafuente
      First page: 250
      Abstract: The enzyme β-galactosidase from Aspergillus oryzae has been immobilized in aminated (MANAE)-agarose beads via glutaraldehyde chemistry using different strategies. The immobilization on MANAE-supports was first assayed at different pH values (this gave different stabilities to the immobilized enzymes) and further modified with glutaraldehyde. Dramatic drops in activity were found, even using 0.1% (v/v) glutaraldehyde. The use of a support with lower activation permitted to get a final activity of 30%, but stability was almost identical to that of the just adsorbed enzyme. Next, the immobilization on pre-activated glutaraldehyde beads was assayed at pH 5, 7 and 9. At pH 7, full, rapid immobilization and a high expressed enzyme activity were accomplished. At pH 9, some decrease in enzyme activity was observed. Direct covalent immobilization of the enzyme was very slow; even reducing the volume of enzyme/support ratio, the yield was not complete after 24 h. The stability of the biocatalyst using pre-activated supports was about 4–6 folds more stable than that of the enzyme immobilized via ion exchange at pH 5, with small differences among them. Thus, the immobilization of the enzyme at pH 7 at low ionic strength on pre-activated glutaraldehyde supports seems to be the most adequate in terms of activity, stability and immobilization rate.
      Citation: Catalysts
      PubDate: 2017-08-25
      DOI: 10.3390/catal7090250
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 251: The Kinetic Resolution of Racemic Amines
           Using a Whole-Cell Biocatalyst Co-Expressing Amine Dehydrogenase and NADH
           Oxidase

    • Authors: Hyunwoo Jeon, Sanghan Yoon, Md Ahsan, Sihyong Sung, Geon-Hee Kim, Uthayasuriya Sundaramoorthy, Seung-Keun Rhee, Hyungdon Yun
      First page: 251
      Abstract: Amine dehydrogenase (AmDH) possesses tremendous potential for the synthesis of chiral amines because AmDH catalyzes the asymmetric reductive amination of ketone with high enatioselectivity. Although a reductive application of AmDH is favored in practice, the oxidative route is interesting as well for the preparation of chiral amines. Here, the kinetic resolution of racemic amines using AmDH was first extensively studied, and the AmDH reaction was combined with an NADH oxidase (Nox) to regenerate NAD+ and to drive the reaction forward. When the kinetic resolution was carried out with 10 mM rac-2-aminoheptane and 5 mM rac-α-methylbenzylamine (α-MBA) using purified enzymes, the enantiomeric excess (ee) values were less than 26% due to the product inhibition of AmDH by ketone and the inhibition of Nox by the substrate amine. The use of a whole-cell biocatalyst co-expressing AmDH and Nox apparently reduces the substrate and product inhibition, and/or it increases the stability of the enzymes. Fifty millimoles (50 mM) rac-2-aminoheptane and 20 mM rac-α-MBA were successfully resolved into the (S)-form with >99% ee using whole cells. The present study demonstrates the potential of a whole-cell biocatalyst co-expressing AmDH and Nox for the kinetic resolution of racemic amines.
      Citation: Catalysts
      PubDate: 2017-08-25
      DOI: 10.3390/catal7090251
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 252: SnSx (x = 1, 2) Nanocrystals as Effective
           Catalysts for Photoelectrochemical Water Splitting

    • Authors: Po-Chia Huang, Yu-Min Shen, Sanjaya Brahma, Muhammad Omar Shaikh, Jow-Lay Huang, Sheng-Chang Wang
      First page: 252
      Abstract: Two-dimensional SnSx (x = 1, 2) nanocrystals are attractive catalysts for photoelectrochemical water splitting as their components are earth abundant and environmentally friendly. We have fabricated SnS thin-film photoelectrodes by spin coating mixed-phase SnS nanocrystals synthesized via a hot-injection technique on glass/Cr/Au substrates. The obtained SnS thin films can be transformed into SnS2 by introducing structural phase changes via a facile low-vacuum annealing protocol in the presence of sulfur. This sulfurization process enables the insertion of sulfur atoms between layers of SnS and results in the generation of shallow donors that alter the mechanism for water splitting. The SnS2 thin films are used as stable photocatalysts to drive the oxygen evolution reaction, and the light-current density of 0.195 mA/cm2 at 0.8 V vs. Ag/AgCl can be achieved due to the high carrier density, lower charge transfer resistance, and a suitable reaction band position. Based on a combination of UV-Vis spectroscopy (ultraviolet and visible spectroscopy), cyclic voltammetry and Mott–Schottky analysis, the band positions and band gaps of SnS and SnS2 relative to the electrolyte are determined and a detailed mechanism for water splitting is presented. Our results demonstrate the potential of layered tin sulfide compounds as promising photocatalysts for efficient and large-scale water splitting.
      Citation: Catalysts
      PubDate: 2017-08-25
      DOI: 10.3390/catal7090252
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 253: Nano-Array Integrated Structured Catalysts:
           A New Paradigm upon Conventional Wash-Coated Monolithic Catalysts'

    • Authors: Junfei Weng, Xingxu Lu, Pu-Xian Gao
      First page: 253
      Abstract: The monolithic catalyst, namely the structured catalyst, is one of the important categories of catalysts used in various fields, especially in catalytic exhaust after-treatment. Despite its successful application in conventional wash-coated catalysts in both mobile and stationary catalytic converters, washcoat-based technologies are facing multi-fold challenges, including: (1) high Pt-group metals (PGM) material loading being required, driving the market prices; (2) less-than ideal distribution of washcoats in typically square-shaped channels associated with pressure drop sacrifice; and (3) far from clear correlations between macroscopic washcoat structures and their catalytic performance. To tackle these challenges, the well-defined nanostructure array (nano-array)-integrated structured catalysts which we invented and developed recently have been proven to be a promising class of cost-effective and efficient devices that may complement or substitute wash-coated catalysts. This new type of structured catalysts is composed of honeycomb-structured monoliths, whose channel surfaces are grown in situ with a nano-array forest made of traditional binary transition metal oxide support such as Al2O3, CeO2, Co3O4, MnO2, TiO2, and ZnO, or newer support materials including perovskite-type ABO3 structures, for example LaMnO3, LaCoO3, LaNiO, and LaFeO3. The integration strategy parts from the traditional washcoat technique. Instead, an in situ nanomaterial assembly method is utilized, such as a hydro (solva-) thermal synthesis approach, in order to create sound structure robustness, and increase ease and complex-shaped substrate adaptability. Specifically, the critical fabrication procedures for nano-array structured catalysts include deposition of seeding layer, in situ growth of nano-array, and loading of catalytic materials. The generic methodology utilization in both the magnetic stirring batch process and continuous flow reactor synthesis offers the nano-array catalysts with great potential to be scaled up readily and cost-effectively. The tunability of the structure and catalytic performance could be achieved through morphology and geometry adjustment and guest atoms and defect manipulation, as well as composite nano-array catalyst manufacture. Excellent stabilities under various conditions were also present compared to conventional wash-coated catalysts.
      Citation: Catalysts
      PubDate: 2017-08-28
      DOI: 10.3390/catal7090253
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 254: Nature and Location of Carbonaceous Species
           in a Composite HZSM-5 Zeolite Catalyst during the Conversion of Dimethyl
           Ether into Light Olefins

    • Authors: María Ibáñez, Paula Pérez-Uriarte, Miguel Sánchez-Contador, Tomás Cordero-Lanzac, Andrés Aguayo, Javier Bilbao, Pedro Castaño
      First page: 254
      Abstract: The deactivation of a composite catalyst based on HZSM-5 zeolite (agglomerated in a matrix using boehmite as a binder) has been studied during the transformation of dimethyl ether into light olefins. The location of the trapped/retained species (on the zeolite or on the matrix) has been analyzed by comparing the properties of the fresh and deactivated catalyst after runs at different temperatures, while the nature of those species has been studied using different spectroscopic and thermogravimetric techniques. The reaction occurs on the strongest acid sites of the zeolite micropores through olefins and alkyl-benzenes as intermediates. These species also condensate into bulkier structures (polyaromatics named as coke), particularly at higher temperatures and within the meso- and macropores of the matrix. The critical roles of the matrix and water in the reaction medium have been proved: both attenuating the effect of coke deposition.
      Citation: Catalysts
      PubDate: 2017-08-30
      DOI: 10.3390/catal7090254
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 255: Continuous-Flow Monolithic Silica
           Microreactors with Arenesulphonic Acid Groups: Structure–Catalytic
           Activity Relationships

    • Authors: Agnieszka Ciemięga, Katarzyna Maresz, Janusz Malinowski, Julita Mrowiec-Białoń
      First page: 255
      Abstract: The performance of monolithic silica microreactors activated with sulphonic acid groups and a packed bed reactor with Amberlyst 15 resin were compared in the esterification of acetic acid with n-butanol. The monolithic microreactors were made of single silica rods with complex pore architecture, differing in the size of mesopores, and in particular, flow-through macropores which significantly affected the flow characteristic of the continuous system. The highest ester productivity of 105.2 mol·molH+−1·h−1 was achieved in microreactor M1 with the largest porosity, characterized by a total pore volume of 4 cm3·g−1, mesopores with 20 nm diameter, and large flow-through macropores 30–50 μm in size. The strong impact of the permeability of the monoliths on a reaction kinetics was shown.
      Citation: Catalysts
      PubDate: 2017-08-30
      DOI: 10.3390/catal7090255
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 256: Controllable and Large-Scale Synthesis of
           Carbon Nanostructures: A Review on Bamboo-Like Nanotubes

    • Authors: Zirui Jia, Kaichang Kou, Ming Qin, Hongjing Wu, Fabrizio Puleo, Leonarda Liotta
      First page: 256
      Abstract: Bamboo-like carbon nanotubes are members of the carbon nanotubes (CNTs) family, whose structure is made up of separated hollow compartments and bamboo knots. Due to the peculiar structure of the CNTs species, the growth mechanism and related features have been widely investigated. Bamboo-like carbon nanotubes are widely applied in several fields, such as sensors, adsorbents, catalysts, and lithium-ion battery electrodes materials. Different methods have been applied for the synthesis of carbon nanotubes, among them, catalytic chemical vapor deposition has been singled out as the most used procedure due to low cost with a high quality product. The present review is devoted to increasing the literature dealing with the design, synthesis, and characterization of bamboo-like carbon nanotubes grown over different catalysts. Results on the methane dry reforming reaction, hydrocarbon thermal decomposition, special chemical vapor deposition as well as other methods applied to the preparation of bamboo-like carbon nanotubes are discussed. The differences in the carbon deposits between the dry reforming reaction and other reaction methods are compared and possible formation mechanisms of bamboo-like carbon nanotubes are discussed.
      Citation: Catalysts
      PubDate: 2017-08-30
      DOI: 10.3390/catal7090256
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 257: Characterization of a Novel Nicotine
           Hydroxylase from Pseudomonas sp. ZZ-5 That Catalyzes the Conversion of
           6-Hydroxy-3-Succinoylpyridine into 2,5-Dihydroxypyridine

    • Authors: Tao Wei, Jie Zang, Yadong Zheng, Hongzhi Tang, Sheng Huang, Duobin Mao
      First page: 257
      Abstract: A novel nicotine hydroxylase was isolated from Pseudomonas sp. ZZ-5 (HSPHZZ). The sequence encoding the enzyme was 1206 nucleotides long, and encoded a protein of 401 amino acids. Recombinant HSPHZZ was functionally overexpressed in Escherichia coli BL21-Codon Plus (DE3)-RIL cells and purified to homogeneity after Ni-NTA affinity chromatography. Liquid chromatography-mass spectrometry (LC-MS) analyses indicated that the enzyme could efficiently catalyze the conversion of 6-hydroxy-3-succinoylpyridine (HSP) into 2,5-dihydroxypyridine (2,5-DHP) and succinic acid in the presence of nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD). The kinetic constants (Km, kcat, and kcat/Km) of HSPHZZ toward HSP were 0.18 mM, 2.1 s−1, and 11.7 s−1 mM−1, respectively. The optimum temperature, pH, and optimum concentrations of substrate and enzyme for 2,5-DHP production were 30 °C, 8.5, 1.0 mM, and 1.0 μM, respectively. Under optimum conditions, 85.3 mg/L 2,5-DHP was produced in 40 min with a conversion of 74.9%. These results demonstrated that HSPHZZ could be used for the enzymatic production of 2,5-DHP in biotechnology applications.
      Citation: Catalysts
      PubDate: 2017-08-31
      DOI: 10.3390/catal7090257
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 258: Experimental Research of an Active Solution
           for Modeling In Situ Activating Selective Catalytic Reduction Catalyst

    • Authors: Tuo Ye, Donglin Chen, Yanshan Yin, Jing Liu, Xi Zeng
      First page: 258
      Abstract: The effect of active solutions suitable for the in situ activation of selective catalytic reduction (SCR) catalysts was experimentally investigated using a designed in situ activation modeling device. To gain further insight, scanning electron microscopy (SEM), specific surface area analysis (BET), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS) analyses were used to investigate the effects of different reaction conditions on the characteristics of the deactivated catalysts. The activation effect of loading V2O5, WO3 and MoO3 on the surface of the deactivated catalysts was analyzed and the correlation to the denitrification activity was determined. The results demonstrate that the prepared activating solution of 1 wt % vanadium (V), 9 wt % tungsten (W), and 6 wt % molybdenum (Mo) has a beneficial effect on the deactivation of the catalyst. The activated catalyst resulted in a higher NO removal rate when compared to the deactivated catalyst. Furthermore, the NO removal rate of the activated catalyst reached a maximum of 32%. The activity of the SCR catalyst is closely linked to the concentration of the active ingredients. When added in optimum amounts, the active ingredients helped to restore the catalytic activity. In particular, the addition of active ingredients, the availability of labile surface oxygen, and the presence of small pores improved the denitrification efficiency. Based on these results, active solutions can effectively solve the problem of denitrification catalyst deactivation. These findings are a reference for the in-situ activation of the selective catalytic reduction of nitrogen oxides (SCR-DeNOx) catalyst.
      Citation: Catalysts
      PubDate: 2017-08-31
      DOI: 10.3390/catal7090258
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 259: The Role of Non-Framework Lewis Acidic Al
           Species of Alkali-Treated HZSM-5 in Methanol Aromatization

    • Authors: Po-Chen Lai, Chi-Ying Hsieh, Chao-Huang Chen, Yu-Chuan Lin
      First page: 259
      Abstract: Mesoporous HZSM-5 prepared by alkaline treatment (also termed desilication) has drawn significant attention due to its potential in large-scale production and in versatile applications, such as separation and catalysis. Alkali-treated HZSM-5 contains considerable amounts of non-framework (amorphous) Lewis acidic Al species on the external surface, and is deemed to be essential in affecting its catalytic performances. This study intends to clarify the catalytic nature of amorphous Al species of alkali-treated HZSM-5 in methanol aromatization. Physicochemical characterizations, including N2 adsorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), magic-angle-spinning nuclear magnetic resonance (MAS NMR), inductively coupled plasma (ICP) analysis, NH3 temperature-programmed desorption (TPD), and methanol-TPD, were performed. The outcomes showed that non-framework Al promotes the hydride transfer in mesoporous HZSM-5, thereby facilitating the aromatization reaction. Among aromatic products, durene can be promoted by non-framework Al through methylation/transalkylation of other aromatics, particularly xylenes, instead of being promoted by reduced space confinement in mesoporous HZSM-5.
      Citation: Catalysts
      PubDate: 2017-09-01
      DOI: 10.3390/catal7090259
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 260: Polyoxometalate (POM)-Layered Double
           Hydroxides (LDH) Composite Materials: Design and Catalytic Applications

    • Authors: Tengfei Li, Haralampos Miras, Yu-Fei Song
      First page: 260
      Abstract: Layered double hydroxides (LDHs) are an important large class of two-dimensional (2D) anionic lamellar materials that possess flexible modular structure, facile exchangeability of inter-lamellar guest anions and uniform distribution of metal cations in the layer. Owing to the modular accessible gallery and unique inter-lamellar chemical environment, polyoxometalates (POMs) intercalated with LDHs has shown a vast array of physical properties with applications in environment, energy, catalysis, etc. Here we describe how polyoxometalate clusters can be used as building components for the construction of systems with important catalytic properties. This review article mainly focuses on the discussion of new synthetic approaches developed recently that allow the incorporation of the element of design in the construction of a fundamentally new class of materials with pre-defined functionalities in catalytic applications. Introducing the element of design and taking control over the finally observed functionality we demonstrate the unique opportunity for engineering materials with modular properties for specific catalytic applications.
      Citation: Catalysts
      PubDate: 2017-09-01
      DOI: 10.3390/catal7090260
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 261: The Beneficial Sinergy of MW Irradiation and
           Ionic Liquids in Catalysis of Organic Reactions

    • Authors: Barbara Floris, Federica Sabuzi, Pierluca Galloni, Valeria Conte
      First page: 261
      Abstract: The quest for sustainable processes is becoming more and more important, with catalysis playing a major role in improving atom economy and reducing waste. Organic syntheses with less need of protecting/de-protecting steps are highly desirable. The combination of microwave irradiation, as energy source, with ionic liquids, as both solvents and catalysts, offered interesting solutions in recent years. The literature data of the last 15 years concerning selected reactions are presented, highlighting the importance of microwave (MW) technology coupled with ionic liquids.
      Citation: Catalysts
      PubDate: 2017-09-01
      DOI: 10.3390/catal7090261
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 262: Expanding the Scope of Cu(I) Catalyzed
           “Click Chemistry” with Abnormal NHCs: Three-Fold Click to
           Tris-Triazoles

    • Authors: Nga Kim T. Ho, Sven O. Reichmann, Dennis Rottschäfer, Regine Herbst-Irmer, Rajendra S. Ghadwal
      First page: 262
      Abstract: Cationic copper(I) complexes [Cu(aIPrPh)(IPr)]I (3) and [Cu(aIPrPh)2]I (4) featuring an abnormal N-heterocyclic carbene (aNHC) (aIPrPh = 1,3-bis(2,6-diisopropylphenyl)-2-phenyl- imidazol-4-ylidene) and/or an NHC (IPr = 1,3-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene) ligand(s) are reported. Treatment of Cu(aIPrPh)I (2) with IPr affords complex 3. Reaction of (IPrPh)I (1) (IPrPh = 1,3-bis(2,6-diisopropylphenyl)-2-phenyl-imidazolium) with CuI in the presence of K{N(SiMe3)2} leads to the formation of 4. Complexes 3 and 4 represent rare examples of mixed aNHC-NHC and bis-aNHC metal complexes, respectively. They are characterized by elemental analysis, NMR spectroscopic, and mass spectrometric studies. The solid-state molecular structures of 3 and 4 have been determined by single crystal X-ray diffraction analyses. The catalytic activity of 2, 3, and 4 has been investigated in the [3+2] cycloaddition of alkynes and organic azides, affording triazole derivatives in an almost quantitative yield. Notably, complexes 2, 3, and 4 are excellent catalysts for the three-fold cycloaddition of a tris-azide with various alkynes. This catalytic protocol offers a high yield access to tris-triazoles in a shorter reaction time and considerably reduces the experimental work-up compared to the classical synthetic method.
      Citation: Catalysts
      PubDate: 2017-09-01
      DOI: 10.3390/catal7090262
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 263: Regioselective Synthesis of Lactulose Esters
           by Candida antarctica and Thermomyces lanuginosus Lipases

    • Authors: Luis Chávez-Flores, Hiram Beltran, Daniel Arrieta-Baez, Dolores Reyes-Duarte
      First page: 263
      Abstract: The interest in sugar esters as emulsifiers has been increasing in recent years because they have tunable surfactant properties that depend on the chain length of the fatty acid and the type of the sugar, covering a wide range of hydrophilic-lipophilic balance (HLB). In this work, ten biocatalysts were used for the transesterification reaction screening of lactulose, a prebiotic sugar, with vinyl laurate. The reactions were followed by thin layer chromatography (TLC) analysis, identifying two major monoesters mixtures defined as monoester fraction 1 and monoester fraction 2. Candida antarctica lipase B (Novozym 435) produces “monoester fraction 1”, while Thermomyces lanuginosus lipase (Lipozyme® TL IM) and Mucor miehei lipase (Lipozyme®) seem to produce the same “monoester fraction 2”. These three enzymes were selected as model biocatalysts for a kinetic study, and monoester fractions 1 and 2 from Novozym 435 and Lipozyme® TL IM, respectively, were used for product characterization. Monoester fraction 1 contained 86.9% of the major monoester in position 1-O-, and monoester fraction 2 contained 91.4% of 6′-O-. Although these lipases acylated three positions of lactulose, they mainly synthesize a monoester presenting regioselectivity. These results contribute to the study of the chemical structure diversity of biosurfactants to enhance their applications in foods, pharmaceutical products, and cosmetics.
      Citation: Catalysts
      PubDate: 2017-09-03
      DOI: 10.3390/catal7090263
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 264: Mechanistic Insight into the 2° Alcohol
           Oxidation Mediated by an Efficient CuI/L-Proline-TEMPO Catalyst—A
           Density Functional Theory Study

    • Authors: Siyu Li, Lin Cheng, Qi Wu, Qiancheng Zhang, Jucai Yang, Juming Liu
      First page: 264
      Abstract: Density functional theory (DFT) calculations have been performed to investigate the 2° alcohol oxidation to acetophenone catalyzed by the CuI/L-Proline-2,2,6,6- tetramethylpiperidinyloxy (TEMPO) catalyst system. Seven possible pathways (paths A→F) are presented. Our calculations show that two pathways (path A and path B) are the potential mechanisms. Furthermore, by comparing with experimental observation, it is found that path A—in which substrate alcohol provides the proton to −OtBu to produce HOtBu followed by the oxidation of substrate directly to product acetophenone by O2—is favored in the absence of TEMPO. Correspondingly, path B is likely to be favored when TEMPO is involved. In path B, the O–O bond cleavage of CuI–OOH to CuII–OH species occurs, followed by acetophenone formation assisted by ligand (L)2ˉ. It is also found that the cooperation of ligand (L)2ˉ and TEMPO plays an important role in assisting the formation of the product acetophenone in path B.
      Citation: Catalysts
      PubDate: 2017-09-05
      DOI: 10.3390/catal7090264
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 265: Hydrodeoxygenation of Lignin-Derived
           Phenols: From Fundamental Studies towards Industrial Applications

    • Authors: Päivi Mäki-Arvela, Dmitry Murzin
      First page: 265
      Abstract: Hydrodeoxygenation (HDO) of bio-oils, lignin and their model compounds is summarized in this review. The main emphasis is put on elucidating the reaction network, catalyst stability and time-on-stream behavior, in order to better understand the prerequisite for industrial utilization of biomass in HDO to produce fuels and chemicals. The results have shown that more oxygenated feedstock, selection of temperature and pressure as well as presence of certain catalyst poisons or co-feed have a prominent role in the HDO of real biomass. Theoretical considerations, such as density function theory (DFT) calculations, were also considered, giving scientific background for the further development of HDO of real biomass.
      Citation: Catalysts
      PubDate: 2017-09-07
      DOI: 10.3390/catal7090265
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 266: Flower-Like Au–CuO/Bi2WO6 Microsphere
           Catalysts: Synthesis, Characterization, and Their Catalytic Performances
           for CO Oxidation

    • Authors: Lili Wang, Baolin Zhu, Shoumin Zhang, Weiping Huang
      First page: 266
      Abstract: The flower-like Bi2WO6 microsphere was synthesized through a simple hydrothermal route, and three catalysts, Au/Bi2WO6, CuO/Bi2WO6, and Au–CuO/Bi2WO6, were prepared by a deposition–precipitation method. The morphology and structure of the catalysts were characterized by X-ray powder diffraction, surface area analyzer, inductively coupled plasma optical emission spectrometer, scanning electron microscope, transmission electron microscopy, UV/Vis spectrometer, as well as X-ray photoelectron spectroscopy. Their catalytic performances in catalytic CO oxidation were evaluated. For Au/Bi2WO6 and CuO/Bi2WO6, Au and CuO nanoparticles highly dispersed on Bi2WO6 are 3 and 10 nm, respectively, in average size. For Au–CuO/Bi2WO6, a part of the Au nanoparticles (Au NPs) strongly adheres to the CuO, due to the strong interaction between Au NPs and CuO, which has a positive effect on catalytic activity of Au–CuO/Bi2WO6. Au–CuO/Bi2WO6 can convert CO into CO2 completely at 40 °C, as the contents of Au and Cu are 0.438 wt % and 4.85 wt %, respectively.
      Citation: Catalysts
      PubDate: 2017-09-11
      DOI: 10.3390/catal7090266
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 267: Heck Reaction—State of the Art

    • Authors: Sangeeta Jagtap
      First page: 267
      Abstract: The Heck reaction is one of the most studied coupling reactions and is recognized with the Nobel Prize in Chemistry. Thousands of articles, hundreds of reviews and a number of books have been published on this topic. All reviews are written exhaustively describing the various aspects of Heck reaction and refer to the work done hitherto. Looking at the quantum of the monographs published, and the reviews based on them, we found a necessity to summarize all reviews on Heck reaction about catalysts, ligands, suggested mechanisms, conditions, methodologies and the compounds formed via Heck reaction in one review and generate a resource of information. One can find almost all the catalysts used so far for Heck reaction in this review.
      Citation: Catalysts
      PubDate: 2017-09-11
      DOI: 10.3390/catal7090267
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 268: Pulse Microcalorimetry Study of Methane Dry
           Reforming Reaction on Ni/Ceria-Zirconia Catalyst

    • Authors: Mikhail Simonov, Vladimir Rogov, Marina Smirnova, Vladislav Sadykov
      First page: 268
      Abstract: For Ni/CeZrO catalyst prepared in supercritical isopropanol main features of methane dry reforming reaction mechanism were studied by the pulse microcalorimetric technique. The reaction scheme is described by a step-wise redox mechanism with independent stages of CH4 transformation on Ni/support interface producing syngas with participation of support oxygen bridging species (the rate-limiting stage) and fast reoxidation of support sites by CO2 yielding CO regenerating reactive oxygen species.
      Citation: Catalysts
      PubDate: 2017-09-12
      DOI: 10.3390/catal7090268
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 269: Selective Acetylation of Small Biomolecules
           and Their Derivatives Catalyzed by Er(OTf)3

    • Authors: Monica Nardi, Maria Luisa Di Gioia, Paola Costanzo, Antonio De Nino, Loredana Maiuolo, Manuela Oliverio, Fabrizio Olivito, Antonio Procopio
      First page: 269
      Abstract: It is of great significance to develop sustainable processes of catalytic reaction. We report a selective procedure for the synthesis of acetylated bioactive compounds in water. The use of 1-acetylimidazole combined with Er(OTf)3 as a Lewis acid catalyst gives high regioselectivity and good yields for the acetylation of primary hydroxyl groups, as well as amino groups. The protection is achieved in short reaction times under microwave irradiation, and is successful even in the case of base-sensitive substrates.
      Citation: Catalysts
      PubDate: 2017-09-12
      DOI: 10.3390/catal7090269
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 270: Promotion of Ca-Co Bifunctional
           Catalyst/Sorbent with Yttrium for Hydrogen Production in Modified Chemical
           Looping Steam Methane Reforming Process

    • Authors: Samira Akbari-Emadabadi, Mohammad Rahimpour, Ali Hafizi, Peyman Keshavarz
      First page: 270
      Abstract: In this study, the application of a calcium-based bifunctional catalyst/sorbent is investigated in modified chemical looping steam methane reforming (CLSMR) process for in situ CO2 sorption and H2 production. The yttrium promoted Ca-Co samples were synthesized and applied as bifunctional catalysts/sorbent. The influence of reduction temperature (500–750 °C), Ca/Co and Ca/Y ratios (1.5–∞ and 3–18, respectively) and catalyst life time are determined in CLSMR process. The physicochemical transformation of fresh, used and regenerated samples after 16 redox cycles are determined using X-ray powder diffraction (XRD), N2 adsorption–desorption, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM) techniques. The effect of yttrium promoter on the structure of catalyst and regeneration step on the reversibility of bifunctional catalyst/sorbent was two important factors. The characterization results revealed that the presence of yttrium in the structure of Ca-9Co sample could improve the morphology and textural properties of catalyst/sorbents. The suitable reversibility of bifunctional catalyst/sorbents during the repeated cycles is confirmed by characterization of calcined samples. The Ca-9Co-4.5Y as optimal catalyst illustrated superior performance and stability. It showed about 95.8% methane conversion and 82.9% hydrogen yield at 700 °C and stable activity during 16 redox cycles.
      Citation: Catalysts
      PubDate: 2017-09-13
      DOI: 10.3390/catal7090270
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 271: Catalytic Characteristics of New
           Antibacterials Based on Hexahistidine-Containing Organophosphorus
           Hydrolase

    • Authors: Olga Maslova, Aysel Aslanli, Nikolay Stepanov, Ilya Lyagin, Elena Efremenko
      First page: 271
      Abstract: Catalytic characteristics of hexahistidine-containing organophosphorus hydrolase (His6-OPH) and its enzyme-polyelectrolyte complexes with poly-l-glutamic acid or poly-l-aspartic acid (His6-OPH/PLD50), hydrolyzing organophosphorous compounds, and N-acyl homoserine lactones were studied in the presence of various antibiotics (ampicillin, gentamicin, kanamycin, and rifampicin). The antibiotics at concentrations below 1 g·L−1 had a negligible inhibiting effect on the His6-OPH activity. Mixed inhibition of His6-OPH was established for higher antibiotic concentrations, and rifampicin was the most potent inhibitor. Stabilization of the His6-OPH activity was observed in the presence of antibiotics at a concentration of 0.2 g·L−1 during exposure at 25–41 °C. Molecular docking of antibiotics to the surface of His6-OPH dimer revealed the antibiotics binding both to the area near active centers of the enzyme subunits and to the region of contact between subunits of the dimer. Such interactions between antibiotics and His6-OPH were verified with Fourier-transform infrared (FTIR) spectroscopy. Considering all the results of the study, the combination of His6-OPH/PLD50 with β-lactam antibiotic ampicillin was established as the optimal one in terms of exhibition and persistence of maximal lactonase activity of the enzyme.
      Citation: Catalysts
      PubDate: 2017-09-14
      DOI: 10.3390/catal7090271
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 272: The Catalytic Hydrogenation of Maleic
           Anhydride on CeO2−δ-Supported Transition Metal Catalysts

    • Authors: Xin Liao, Yin Zhang, Junqiu Guo, Lili Zhao, Martyn Hill, Zheng Jiang, Yongxiang Zhao
      First page: 272
      Abstract: The proper selection of transition metals and support is pivotal to the design of active and selective catalysts for maleic anhydride hydrogenation (MAH). Herein, the M/CeO2−δ (M = Co, Ni, Cu, respectively) catalysts with pre-optimised metal loading of 10 wt % were prepared via a wet impregnation method and well characterized to corroborate their MAH performance with the properties of metal, support and the M/CeO2−δ catalysts. The results revealed that the metal dispersion on the catalyst declines in the order of Ni/CeO2−δ > Co/CeO2−δ > Cu/CeO2−δ, similar to the apparent activity for maleic anhydride (MA) transformation to succinic anhydride (SA). The hydrogenolysis of SA to γ-butyrolactone (GBL) occurs on Ni/CeO2−δ and Co/CeO2−δ only when the MA → SA transformation completing. The Ni/CeO2−δ displays superior activity and selectivity to Co/CeO2−δ in both MA → SA and SA → GBL reactions, while the Cu/CeO2−δ and CeO2−δ are both inert for SA → GBL hydrogenolysis. The MA hydrogenation to SA follows the first order kinetic law on the Ni/CeO2−δ and Co/CeO2−δ catalysts yet a more complex kinetic characteristics observed on the Cu/CeO2−δ. The distinct catalytic hydrogenation behaviours of the M/CeO2−δ catalysts are assigned to the synergism of dispersion and electronic configuration of the transition metals and oxygen vacancies.
      Citation: Catalysts
      PubDate: 2017-09-14
      DOI: 10.3390/catal7090272
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 273: The Isomerization of Limonene over the
           Ti-SBA-15 Catalyst—The Influence of Reaction Time, Temperature, and
           Catalyst Content

    • Authors: Monika Retajczyk, Agnieszka Wróblewska
      First page: 273
      Abstract: The isomerization of limonene over the Ti-SBA-15 catalyst, which was prepared by the hydrothermal method, was studied. The main products of limonene isomerization were terpinolene, α-terpinene, γ-terpinene, and p-cymene—products with numerous applications. The amount of these products depended on reaction time, temperature, and catalyst content. These parameters changed in the following range: reaction time 30–1380 min, temperature 140–160 °C, and catalyst content 5–15 wt %. Finally, the most favorable conditions for the limonene isomerization process were established: a reaction time of 180 min, temperature of 160 °C, and amount of the catalyst 15 wt %. In order to obtain p-cymene (dehydroaromatization product), the most favorable conditions are similar but the reaction time should be 1380 min. The application of such conditions allowed us to obtain the highest amounts of the desired products in the shortest time.
      Citation: Catalysts
      PubDate: 2017-09-14
      DOI: 10.3390/catal7090273
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 274: Electrocarboxylation of Dichlorobenzenes on
           a Silver Electrode in DMF

    • Authors: Pei-Pei Luo, Ying-Tian Zhang, Bao-Li Chen, Shu-Xian Yu, Hua-Wei Zhou, Kong-Gang Qu, Yu-Xia Kong, Xian-Qiang Huang, Xian-Xi Zhang, Jia-Xing Lu
      First page: 274
      Abstract: Carbon dioxide (CO2) is the largest contributor to the greenhouse effect, and fixing and using this greenhouse gas in a facile manner is crucial. This work investigates the electrocarboxylation of dichlorobenzenes with the atmospheric pressure of CO2 in an undivided cell with an Ag cathode and an Mg sacrificial anode. The corresponding carboxylic acids and their derivatives, which are important industrial and fine chemicals, are obtained. To deeply understand this reaction, we investigate the influence of various reaction conditions, such as supporting electrolyte, current density, electric charge, and reaction temperature, on the electrocarboxylation yield by using 1,4-dichlorobenzene as the model compound. The electrochemical behavior of dichlorobenzenes is studied through cyclic voltammetry. The relation among the distinct electronic effects of dichlorobenzenes, the electrochemical characteristics of their reduction, and the distribution law of target products is also established.
      Citation: Catalysts
      PubDate: 2017-09-15
      DOI: 10.3390/catal7090274
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 275: Improving the Indigo Carmine Decolorization
           Ability of a Bacillus amyloliquefaciens Laccase by Site-Directed
           Mutagenesis

    • Authors: Jiayi Wang, Lei Lu, Fujuan Feng
      First page: 275
      Abstract: Indigo carmine is a typical recalcitrant dye which is widely used in textile dyeing processes. Laccases are versatile oxidases showing strong ability to eliminate hazardous dyes from wastewater. However, most laccases require the participation of mediators for efficient decolorization of indigo carmine. Here we describe the improvement of the decolorization ability of a bacterial laccase through site-directed mutagenesis. A D501G variant of Bacillus amyloliquefaciens laccase was constructed and overexpressed in Escherichia coli. The laccase activity in the culture supernatant achieved 3374 U·L−1 for the mutant. Compared with the wild-type enzyme, the D501G exhibited better stability and catalytic efficiency. It could decolorize more than 92% of indigo carmine without additional mediators in 5 h at pH 9.0, which was 3.5 times higher than the wild-type laccase. Isatin sulfonic acid was confirmed to be the main product of indigo carmine degradation by UV-vis and LC-MS analyses.
      Citation: Catalysts
      PubDate: 2017-09-15
      DOI: 10.3390/catal7090275
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 276: The Preparation of a Highly Efficient
           Ag3PO4/Ag/Bi2O2CO3 Photo-Catalyst and the Study of Its Photo-Catalytic
           Organic Synthesis Reaction Driven by Visible Light

    • Authors: Zhi Guo, Hui Xin, Jingjing Ma, Meifen Bai, Yan Wang, Jingyi Li
      First page: 276
      Abstract: Ag3PO4/Ag/Bi2O2CO3 composites were prepared by a hydrothermal and precipitation method. The morphology, structure, and valence state of the photo-catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface areas, and UV-vis diffuse reflectance spectra (UV-vis DRS). They were applied as heterogeneous catalysts in the synthesis of esters from aldehydes (or alcohols) and alcohols and the synthesis of imines from alcohols and amines under visible light irradiation. The photo-catalytic activities of the esterification reactions of aldehydes and alcohols were heavily dependent on the loading of Ag3PO4/Ag/Bi2O2CO3 as well as the intensity and wavelength of the visible light. Furthermore, their conversion under visible light irradiation was superior to that in the dark. Herein a reaction mechanism from aldehydes and alcohols to esters was proposed, and the Ag3PO4/Ag/Bi2O2CO3 catalysts could be used six times without a significant decrease in activity. Using these catalysts under visible light could motivate future studies to develop efficient recyclable photo-catalysts and facilitate many synthetic organic reactions.
      Citation: Catalysts
      PubDate: 2017-09-17
      DOI: 10.3390/catal7090276
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 277: A New Homo-Hexamer Mn-Containing Catalase
           from Geobacillus sp. WCH70

    • Authors: Hai-Chao Li, Qing Yu, Hui Wang, Xin-Yu Cao, Li Ma, Zheng-Qiang Li
      First page: 277
      Abstract: Catalase is an effective biocatalyst to degrade hydrogen peroxide to water and oxygen that can serve in textile effluent treatment to remove residual H2O2. Thermostable catalases are needed to withstand both the high temperature and pH of textile wastewater. We have cloned the Mn-containing catalase gene ACS24898.1 from Geobacillus sp. WCH70, which originated from thermophilic organisms, and expressed it in Escherichia coli in activated form. The recombinant protein has been purified to homogeneity and identified to be a new homo-hexamer Mn-containing catalase. The native molecular mass of the catalase has been measured to be 138 kDa by size-exclusion chromatography. The new enzyme has optimum catalyzed activity at pH 9.0 and a temperature of 75 °C. It is thermostable up to 70 °C for 8 h incubation and maintains 80% and 50% activity, respectively, at 80 °C after 5 h and 90 °C after 1 h. At 75 °C and pH 9.0, the Km is 67.26 mM for substrate H2O2 and the rate of reaction at H2O2 saturation, Vmax, is 75,300 U/mg. The thermophilic and alkaline preferred properties of this new Mn-catalase are valuable features in textile wastewater treatment.
      Citation: Catalysts
      PubDate: 2017-09-18
      DOI: 10.3390/catal7090277
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 278: S- and N-Doped Graphene Nanomaterials for
           the Oxygen Reduction Reaction

    • Authors: Luis Rivera, Sergio Fajardo, María Arévalo, Gonzalo García, Elena Pastor
      First page: 278
      Abstract: In the current work, heteroatom-doped graphene materials containing different atomic ratios of nitrogen and sulphur were employed as electrocatalysts for the oxygen reduction reaction (ORR) in acidic and alkaline media. To this end, the hydrothermal route and different chemical reducing agents were employed to synthesize the catalytic materials. The physicochemical characterization of the catalysts was performed by several techniques, such as X-ray diffraction, Raman spectroscopy and elemental analysis; meanwhile, the electrochemical performance of the materials toward the ORR was analyzed by linear sweep voltammetry (LSV), rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) techniques. The main results indicate that the ORR using heteroatom-doped graphene is a direct four-electron pathway, for which the catalytic activity is higher in alkaline than in acidic media. Indeed, a change of the reaction mechanism was observed with the insertion of N into the graphenic network, by the rate determining step changes from the first electrochemical step (formation of adsorbed OOH) on glassy carbon to the removal of adsorbed O (Oad) from the N-graphene surface. Moreover, the addition of sulphur atoms into the N-graphene structure increases the catalytic activity toward the ORR, as the desorption of Oad is accelerated.
      Citation: Catalysts
      PubDate: 2017-09-18
      DOI: 10.3390/catal7090278
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 279: Surface Oxidation of Supported Ni Particles
           and Its Impact on the Catalytic Performance during Dynamically Operated
           Methanation of CO2

    • Authors: Benjamin Mutz, Andreas Gänzler, Maarten Nachtegaal, Oliver Müller, Ronald Frahm, Wolfgang Kleist, Jan-Dierk Grunwaldt
      First page: 279
      Abstract: The methanation of CO2 within the power-to-gas concept was investigated under fluctuating reaction conditions to gather detailed insight into the structural dynamics of the catalyst. A 10 wt % Ni/Al2O3 catalyst with uniform 3.7 nm metal particles and a dispersion of 21% suitable to investigate structural changes also in a surface-sensitive way was prepared and characterized in detail. Operando quick-scanning X-ray absorption spectroscopy (XAS/QEXAFS) studies were performed to analyze the influence of 30 s and 300 s H2 interruptions during the methanation of CO2 in the presence of O2 impurities (technical CO2). These conditions represent the fluctuating supply of H2 from renewable energies for the decentralized methanation. Short-term H2 interruptions led to oxidation of the most reactive low-coordinated metallic Ni sites, which could not be re-reduced fully during the subsequent methanation cycle and accordingly caused deactivation. Detailed evaluation of the extended X-ray absorption fine structure (EXAFS) spectra showed surface oxidation/reduction processes, whereas the core of the Ni particles remained reduced. The 300-s H2 interruptions resulted in bulk oxidation already after the first cycle and a more pronounced deactivation. These results clearly show the importance and opportunities of investigating the structural dynamics of catalysts to identify their mechanism, especially in power-to-chemicals processes using renewable H2.
      Citation: Catalysts
      PubDate: 2017-09-18
      DOI: 10.3390/catal7090279
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 280: Halide-Enhanced Catalytic Activity of
           Palladium Nanoparticles Comes at the Expense of Catalyst Recovery

    • Authors: Azzedine Bouleghlimat, Mazin Othman, Louis Lagrave, Soichiro Matsuzawa, Yoshinobu Nakamura, Syuji Fujii, Niklaas Buurma
      First page: 280
      Abstract: In this communication, we present studies of the oxidative homocoupling of arylboronic acids catalyzed by immobilised palladium nanoparticles in aqueous solution. This reaction is of significant interest because it shares a key transmetallation step with the well-known Suzuki-Miyaura cross-coupling reaction. Additives can have significant effects on catalysis, both in terms of reaction mechanism and recovery of catalytic species, and our aim was to study the effect of added halides on catalytic efficiency and catalyst recovery. Using kinetic studies, we have shown that added halides (added as NaCl and NaBr) can increase the catalytic activity of the palladium nanoparticles more than 10-fold, allowing reactions to be completed in less than half a day at 30 °C. However, this increased activity comes at the expense of catalyst recovery. The results are in agreement with a reaction mechanism in which, under conditions involving high concentrations of chloride or bromide, palladium leaching plays an important role. Considering the evidence for analogous reactions occurring on the surface of palladium nanoparticles under different reaction conditions, we conclude that additives can exert a significant effect on the mechanism of reactions catalyzed by nanoparticles, including switching from a surface reaction to a solution reaction. The possibility of this switch in mechanism may also be the cause for the disagreement on this topic in the literature.
      Citation: Catalysts
      PubDate: 2017-09-19
      DOI: 10.3390/catal7090280
      Issue No: Vol. 7, No. 9 (2017)
       
  • Catalysts, Vol. 7, Pages 224: Photocatalytic Membrane Reactors (PMRs) in
           Water Treatment: Configurations and Influencing Factors

    • Authors: Xiang Zheng, Zhi-Peng Shen, Lei Shi, Rong Cheng, Dong-Hai Yuan
      First page: 224
      Abstract: The lack of access to clean water remains a severe issue all over the world. Coupling photocatalysis with the membrane separation process, which is known as a photocatalytic membrane reactor (PMR), is promising for water treatment. PMR has developed rapidly during the last few years, and this paper presents an overview of the progress in the configuration and operational parameters of PMRs. Two main configurations of PMRs (PMRs with immobilized photocatalyst; PMRs with suspended photocatalyst) are comprehensively described and characterized. Various influencing factors on the performance of PMRs, including photocatalyst, light source, water quality, aeration and membrane, are detailed. Moreover, a discussion on the current problems and development prospects of PMRs for practical application are presented.
      Citation: Catalysts
      PubDate: 2017-07-25
      DOI: 10.3390/catal7080224
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 225: Mesoporous ZSM-5 Zeolites in Acid Catalysis:
           Top-Down vs. Bottom-Up Approach

    • Authors: Pit Losch, Thomas Hoff, Joy Kolb, Claire Bernardon, Jean-Philippe Tessonnier, Benoît Louis
      First page: 225
      Abstract: A top-down desilication of Al-rich ZSM-5 zeolites and a bottom-up mesopores creating method were evaluated in this study. Three liquid–solid and one gas–solid heterogeneously-catalysed reactions were chosen to establish relationships between zeolites textural properties and their catalytic behavior in acid-catalysed model reactions that are influenced by shape selectivity: Diels-Alder cyclization between isoprene and methylacrylate, Methanol-to-Olefins (MTO) reaction, chlorination of iodobenzene with trichloroisocyanuric acid (TCCA), and Friedel-Crafts acylation of anisole by carboxylic acids with differing sizes. It is found amongst others that no optimal mesoporosity for all the different reactions can be easily obtained, but depending on the chosen application, a specific treatment has to be set to achieve high activity/selectivity and stability.
      Citation: Catalysts
      PubDate: 2017-07-26
      DOI: 10.3390/catal7080225
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 226: Renewable Hydrogen from Ethanol Reforming
           over CeO2-SiO2 Based Catalysts

    • Authors: Vincenzo Palma, Concetta Ruocco, Eugenio Meloni, Antonio Ricca
      First page: 226
      Abstract: In this research, a bimetallic Pt-Ni/CeO2-SiO2 catalyst, synthetized via wet impregnation, was successfully employed for the oxidative steam reforming of ethanol between 300 and 600 °C. The reaction performance of the Pt-Ni catalyst was investigated and compared with the Ni/CeO2-SiO2, Pt/CeO2-SiO2 as well as CeO2-SiO2 sample. The bimetallic catalyst displayed the best results in terms of hydrogen yield and by-products selectivity, thus highlighting the crucial role of active species (Pt and Ni) in promoting ethanol conversion and reaching the products distribution predicted by thermodynamics. The most promising sample, tested at 500 °C for more than 120 h, assured total conversion and no apparent deactivation, demonstrating the stability of the selected formulation. By changing contact time, the dependence of carbon formation rate on space velocity was also investigated.
      Citation: Catalysts
      PubDate: 2017-07-27
      DOI: 10.3390/catal7080226
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 227: Effect of Water Clustering on the Activity
           of Candida antarctica Lipase B in Organic Medium

    • Authors: Sindrila Dutta Banik, Mathias Nordblad, John Woodley, Günther Peters
      First page: 227
      Abstract: The effect of initial water activity of MTBE (methyl tert-butyl ether) medium on CALB (Candida antarctica lipase B) catalyzed esterification reaction is investigated using experimental methods and classical molecular dynamics (MD) simulations. The experimental kinetic studies show that the initial reaction rate of CALB-catalyzed esterification reaction between butyric acid and ethanol decreases with increasing initial water activity of the medium. The highest rate of esterification is observed at the lowest water activity studied. MD simulations were performed to gain a molecular insight on the effect of initial water activity on the rate of CALB-catalyzed reaction. Our results show that hydration has an insignificant effect on the structure and flexibility of CALB. Rather, it appears that water molecules bind to certain regions (“hot spots”) on the CALB surface and form clusters. The size of the water clusters at these hot spot regions gradually increase and expand with increasing water activity. Consequently, the surface area of CALB covered by the water molecules also increases. Specifically, our results indicate that a particular water cluster located close to the active site partially cover the binding pocket of substrate at high water activity. As a consequence, the effective concentration of substrate at the catalytic site decreases. Therefore, the reaction rate slows down with increasing water activity, which correlates well with the observed decrease in the experimentally determined initial reaction rate.
      Citation: Catalysts
      PubDate: 2017-07-29
      DOI: 10.3390/catal7080227
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 228: Direct Conversion of Propylene Oxide to
           3-Hydroxy Butyric Acid Using a Cobalt Carbonyl Ionic Liquid Catalyst

    • Authors: Senkuttuvan Rajendiran, Gyoosoon Park, Sungho Yoon
      First page: 228
      Abstract: The reported catalytic system demonstrates the possibility of efficient mass production of 3-hydroxybutyric acid (3-HBA) from inexpensive raw materials. The direct coupling of propylene oxide, water, and CO was catalyzed by 1-butyl-3-methylimidazolium cobalt tetracarbonyl ([Bmim][Co(CO)4]) ionic liquid to form 3-HBA with >99% conversion (49% selectivity) under mild conditions.
      Citation: Catalysts
      PubDate: 2017-07-30
      DOI: 10.3390/catal7080228
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 229: Fast and Large-Scale Anodizing Synthesis of
           Pine-Cone TiO2 for Solar-Driven Photocatalysis

    • Authors: Yan Liu, Yanzong Zhang, Lilin Wang, Gang Yang, Fei Shen, Shihuai Deng, Xiaohong Zhang, Yan He, Yaodong Hu, Xiaobo Chen
      First page: 229
      Abstract: Anodization has been widely used to synthesize nanostructured TiO2 films with promising photocatalytic performance for solar hydrogen production and pollution removal. However, it usually takes a few hours to obtain the right nanostructures even on a small scale (e.g., 10 mm × 20 mm). In order to attract interest for industrial applications, fast and large-scale fabrication is highly desirable. Herein, we demonstrate a fast and large-scale (e.g., 300 mm × 360 mm) synthesis of pine-cone TiO2 nanostructures within two min. The formation mechanism of pine-cone TiO2 is proposed. The pine-cone TiO2 possesses a strong solar absorption, and exhibits high photocatalytic activities in photo-oxidizing organic pollutants in wastewater and producing hydrogen from water under natural sunlight. Thus, this study demonstrates a promising method for fabricating TiO2 films towards practical photocatalytic applications.
      Citation: Catalysts
      PubDate: 2017-08-01
      DOI: 10.3390/catal7080229
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 230: Catalytic Performance of Fe(II)-Scorpionate
           Complexes towards Cyclohexane Oxidation in Organic, Ionic Liquid and/or
           Supercritical CO2 Media: A Comparative Study

    • Authors: Ana Ribeiro, Luísa Martins, Elisabete Alegria, Inês Matias, Tiago Duarte, Armando Pombeiro
      First page: 230
      Abstract: The catalytic activity of the iron(II) C-scorpionate complexes [FeCl2{HC(pz)3}] 1 (pz = pyrazol-1-yl) and [FeCl2{HOCH2C(pz)3}] 2, and of their precursor FeCl2·2H2O 3, towards cyclohexane oxidation with tert-butyl hydroperoxide was evaluated and compared in different media: acetonitrile, ionic liquids (1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], and 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, [bmim][FAP]), supercritical carbon dioxide (scCO2), and scCO2/[bmim][X] (X = PF6 or FAP) mixtures. The use of such alternative solvents led to efficient and selective protocols for the oxidation of cyclohexane. Moreover, tuning the alcohol/ketone selectivity was possible by choosing the suitable solvent.
      Citation: Catalysts
      PubDate: 2017-08-02
      DOI: 10.3390/catal7080230
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 231: Is Selective Heating of the Sulfonic Acid
           Catalyst AC-SO3H by Microwave Radiation Crucial in the Acid Hydrolysis of
           Cellulose to Glucose in Aqueous Media'

    • Authors: Satoshi Horikoshi, Takashi Minagawa, Shuntaro Tsubaki, Ayumu Onda, Nick Serpone
      First page: 231
      Abstract: Selective heating of microwave-absorbing solid catalysts in a heterogeneous medium may affect a chemical reaction; such selectivity cannot be achieved by conventional oil-bath or steam heating methods. Moreover, microwave methods are often misunderstood with respect to equipment and temperature measurements, so that additional experimentation is necessary. In this regard, the present study intended to clarify the effect of microwave selective heating on acid hydrolytic processes using a sulfonated activated carbon catalyst (AC-SO3H). The model reaction chosen was the acid hydrolysis of cellulose carried out in a Pyrex glass microwave reactor, with the process being monitored by examining the quantity of total sugar, reducing sugar, and glucose produced. Heat transfer from the catalyst to the aqueous solution through absorption of microwaves by the catalyst occurred as predicted from a simulation of heat transfer processes. The resulting experimental consequences are compared with those from the more uniform microwave conduction heating method by also performing the reaction in a SiC microwave reactor wherein microwaves are absorbed by SiC. Some inferences of the influence of microwave selective heating of carbon-based catalyst particles are reported. Under selective heating conditions (Pyrex glass reactor), the yield of glucose from the acid hydrolysis of cellulose was 56% upon microwave heating at 200 °C, nearly identical with the yield (55%) when the hydrolytic process was performed under mainly conventional heating conditions in the SiC reactor. Although the beneficial effect of catalyst selective heating was not reflected in the reaction efficiency, there were substantial changes in the state of adsorption of cellulose on the catalyst surface.
      Citation: Catalysts
      PubDate: 2017-08-08
      DOI: 10.3390/catal7080231
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 232: Functionalization of SSZ-13 and Fe-Beta with
           Copper by NH3 and NO Facilitated Solid-State Ion-Exchange

    • Authors: Alexander Shishkin, Soran Shwan, Torben Pingel, Eva Olsson, Anna Clemens, Per-Anders Carlsson, Hanna Härelind, Magnus Skoglundh
      First page: 232
      Abstract: We show that functionalization of SSZ-13 (CHA) and Fe-beta (*BEA) with copper using a recently reported solid-state ion-exchange method, facilitated by NH 3 and nitrogen oxides (NO), is a viable route to prepare Cu-SSZ-13 and (Cu + Fe)-beta catalysts, starting from H-SSZ-13 and Fe-beta, respectively. The physicochemical properties of the prepared catalysts are characterized by XRD, UV-Vis-spectroscopy and STEM-EDS, confirming that copper originally present in the physical mixture of CuO and H-SSZ-13, and CuO and Fe-beta, is inserted into the micropores of SSZ-13 and Fe-beta, respectively. Activity measurements in gas-flow reactor show that the samples are active for NO reduction by NH 3 -SCR over a broad temperature range, i.e., 150–500 ∘ C. For the Cu-SSZ-13 catalysts, which have a copper loading range of 0.5–4 wt. %, the sample prepared from the physical mixture with a CuO/SSZ-13 ratio corresponding to 2 wt. % Cu is the most active catalyst for NH 3 -SCR under the present reaction conditions. Furthermore, the (Cu + Fe)-beta catalyst shows higher NH 3 -SCR activity over a broader temperature range and especially at low temperature as compared to the Fe-beta and Cu-beta counterparts. The results encourage further elaboration on sequential ion-exchange procedures for bimetallic functionalization of zeolites.
      Citation: Catalysts
      PubDate: 2017-08-08
      DOI: 10.3390/catal7080232
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 233: Selective Alkylation of Benzene by Propane
           over Bifunctional Pd-Acid Catalysts

    • Authors: Abdullah Alotaibi, Sophie Hodgkiss, Elena Kozhevnikova, Ivan Kozhevnikov
      First page: 233
      Abstract: The alkylation of benzene by propane to yield isopropylbenzene (iPrPh) was studied using bifunctional Pd-acid catalysts, such as Pd-heteropoly acid and Pd-zeolite, in a fixed bed reactor at 300 °C and 1 bar pressure. Keggin-type tungstosilicic acid H4SiW12O40 (HSiW) and zeolite HZSM-5 were used as the acid components in these catalysts. The reaction occurred most efficiently over 2%Pd/25%HSiW/SiO2, giving iPrPh with up to 88% selectivity. The Pd-HSiW catalyst was more selective than the Pd-HZSM-5; the latter gave only 11–18% iPrPh selectivity. The reaction proceeded via a bifunctional mechanism including the dehydrogenation of propane to form propene on Pd sites, followed by the alkylation of benzene with the propene on acid sites. The effect of Pd loading in Pd-HSiW and Pd-HZSM-5 catalysts indicated that the first step reached quasi-equilibrium at 1.5–2% Pd loading and the second step became rate limiting. The addition of gold to Pd-HSiW enhanced the activity of this catalyst, although the Au-HSiW without Pd was inert.
      Citation: Catalysts
      PubDate: 2017-08-11
      DOI: 10.3390/catal7080233
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 234: Recent Progress on the Synthesis of
           Graphene-Based Nanostructures as Counter Electrodes in DSSCs Based on
           Iodine/Iodide Electrolytes

    • Authors: Dimitrios Tasis
      First page: 234
      Abstract: Graphene-based nanomaterials functionalized by different doping strategies have attracted great attention for energy conversion themes, due to their large specific surface area, high conductivity, and appreciable electrocatalytic properties. This mini-review presents an overview of the recent progress in the synthesis of graphene-based nanomaterials as counter electrodes for dye-sensitized solar cells based on iodine/iodide electrolytes, along with challenges and perspectives in this exciting field.
      Citation: Catalysts
      PubDate: 2017-08-14
      DOI: 10.3390/catal7080234
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 235: Efficient Catalytic Upgrading of Levulinic
           Acid into Alkyl Levulinates by Resin-Supported Acids and Flow Reactors

    • Authors: Valeria Trombettoni, Luca Bianchi, Ana Zupanic, Alessandro Porciello, Maurizio Cuomo, Oriana Piermatti, Assunta Marrocchi, Luigi Vaccaro
      First page: 235
      Abstract: Biomass-derived levulinic acid (LA) is an excellent substrate to obtain high-value esters that can be used as second-generation biofuels and biofuel additives. The present study focuses on the identification and definition of the key parameters crucial for the development of chemically and environmentally efficient protocols operating in continuous-flow for the preparation of structurally diverse alkyl levulinates via the esterification of LA. We have focused on the use of solid acid catalysts consisting of sulfonated cation exchange resins and considered different aliphatic alcohols to prepare levulinates 3 and 11–17 regioselectively, and in good to high yields (50–92%). Direct correlations between several reaction parameters and catalyst activity have been investigated and discussed to set proper flow reactors that allow minimal waste production during the workup procedure, enabling Environmental factor (E-factor) values as low as ca. 0.3, full recoverability and reusability of the catalysts, and the production of levulinates up to ca. 5 gxh−1 scale.
      Citation: Catalysts
      PubDate: 2017-08-15
      DOI: 10.3390/catal7080235
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 236: Heterogeneous Catalysis for Environmental
           Remediation

    • Authors: Xiaoguang Duan, Shaobin Wang
      First page: 236
      Abstract: The intensive human activities in chemical industry and environmental purification urge the development of advanced protocols for green production and waste management. [...]
      Citation: Catalysts
      PubDate: 2017-08-16
      DOI: 10.3390/catal7080236
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 237: Facile, One-Pot, Two-Step, Strategy for the
           Production of Potential Bio-Diesel Candidates from Fructose

    • Authors: Guo Qiu, Xincheng Wang, Chongpin Huang, Yingxia Li, Biaohua Chen
      First page: 237
      Abstract: The production of bio-diesel fuels from carbohydrates is a promising alternative to fossil fuels with regard to the growing severity of the environmental problem and energy crisis. Potential bio-diesel candidates or additives, such as 5-(hydroxymethyl)-2-(dimethoxymethyl) furan (HDMF), 2-(dimethoxymethyl)-5-(methoxymethyl) furan (DMMF), and 5-(methoxymethyl)-2-furaldehyde (MMF) could be produced from the alcoholic solutions of both 5-HMF and fructose in the presence of solid acid catalysts. In the present study, a readily prepared, silica, gel-supported nitric acid (SiO2-HNO3) catalyst was found to be exceptionally reactive for the production of HDMF from fructose. A DMSO-methanol biphasic solvent system was developed and HDMF, DMMF, and MMF were observed at 150 °C, with maximum yields of 34%, 34%, and 25%, respectively. Meanwhile, a maximum HDMF yield of 77% was obtained from 5-HMF in methanol. Moreover, a sequential, one-pot, two-step dehydration/acetalization process, involving the dehydration of fructose to 5-HMF in dimethylsulfoxide (DMSO) at 150 °C, and followed by adding a certain amount of methanol to react with the formed 5-HMF to HDMF at 100 °C, was developed to promote the yield of HDMF. The optimum yield of HDMF reached 70% with the complete conversion of fructose. The reaction mechanisms of dehydration and acetalization have been proposed for the conversion of 5-HMF to HDMF. The two-step design allows for facile catalyst recycling while supplying as a promising method for the production of biodiesel from complex carbohydrates.
      Citation: Catalysts
      PubDate: 2017-08-17
      DOI: 10.3390/catal7080237
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 238: Enzymatic Synthesis of S-Adenosylmethionine
           Using Immobilized Methionine Adenosyltransferase Variants on the 50-mM
           Scale

    • Authors: Weining Niu, Shanshan Cao, Menglin Yang, Le Xu
      First page: 238
      Abstract: S-adenosylmethionine (SAM), an important metabolite in all living organisms, has been widely used to treat various diseases. To develop a simple and efficient method to produce SAM, an engineered variant of the methionine adenosyltransferase (MAT) from Escherichia coli was investigated for its potential use in the enzymatic synthesis of SAM due to its significantly decreased product inhibition. The recombinant I303V MAT variant was successfully produced at a high level (~800 mg/L) with approximately four-fold higher specific activity than the wild-type MAT. The recombinant I303V MAT was covalently immobilized onto the amino resin and epoxy resin in order to obtain a robust biocatalyst to be used in industrial bioreactors. The immobilized preparation using amino resin exhibited the highest activity coupling yield (~84%), compared with approximately 3% for epoxy resin. The immobilized enzyme was more stable than the soluble enzyme under the reactive conditions, with a half-life of 229.5 h at 37 °C. The KmATP value (0.18 mM) of the immobilized enzyme was ca. two-fold lower than that of the soluble enzyme. Furthermore, the immobilized enzyme showed high operational stability during 10 consecutive 8 h batches, with the substrate adenosine triphosphate (ATP) conversion rate above 95% on the 50-mM scale.
      Citation: Catalysts
      PubDate: 2017-08-17
      DOI: 10.3390/catal7080238
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 239: The Differentiating Polarization Curve
           Technique for the Tafel Parameter Estimation

    • Authors: Osami Seri, Burapornpong Siree
      First page: 239
      Abstract: An experimentally obtained polarization curve for the hydrogen evolution reaction on silver in a 0.5 mol dm−3 solution was investigated using an electrochemical curve technique named the differential polarization method (DPM). The exchange current density estimated by the Tafel extrapolation method (TEM) and the DPM were compared and assessed from points of simple and more accurate handling. It is shown that the DPM has two advantages: (1) proper reading of the Tafel slope region and (2) elimination of the undesirable physical factors such as oxide film and solution resistance.
      Citation: Catalysts
      PubDate: 2017-08-17
      DOI: 10.3390/catal7080239
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 240: Enzymatic Oxyfunctionalization Driven by
           Photosynthetic Water-Splitting in the Cyanobacterium Synechocystis sp. PCC
           6803

    • Authors: Stefanie Böhmer, Katharina Köninger, Álvaro Gómez-Baraibar, Samiro Bojarra, Carolin Mügge, Sandy Schmidt, Marc Nowaczyk, Robert Kourist
      First page: 240
      Abstract: Photosynthetic water-splitting is a powerful force to drive selective redox reactions. The need of highly expensive redox partners such as NADPH and their regeneration is one of the main bottlenecks for the application of biocatalysis at an industrial scale. Recently, the possibility of using the photosystem of cyanobacteria to supply high amounts of reduced nicotinamide to a recombinant enoate reductase opened a new strategy for overcoming this hurdle. This paper presents the expansion of the photosynthetic regeneration system to a Baeyer–Villiger monooxygenase. Despite the potential of this strategy, this work also presents some of the encountered challenges as well as possible solutions, which will require further investigation. The successful enzymatic oxygenation shows that cyanobacterial whole-cell biocatalysis is an applicable approach that allows fuelling selective oxyfunctionalisation reactions at the expense of light and water. Yet, several hurdles such as side-reactions and the cell-density limitation, probably due to self-shading of the cells, will have to be overcome on the way to synthetic applications.
      Citation: Catalysts
      PubDate: 2017-08-17
      DOI: 10.3390/catal7080240
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 241: Improved H2 Production by Ethanol Steam
           Reforming over Sc2O3-Doped Co-ZnO Catalysts

    • Authors: Xuelian Liang, Xinping Shi, Fanfan Zhang, Yuyang Li, Hongbin Zhang, Youzhu Yuan
      First page: 241
      Abstract: H2 production by catalytically ethanol steam reforming (ESR) is an effective and prospective method for the application of fuel cells. However, the catalysts’ desirable activity and stability remains an unprecedented challenge. Herein, a type of Sc2O3-doped Co-ZnO catalyst was developed by a co-precipitation method. The so-constructed Co2Zn1Sc0.3 catalyst exhibited a superb catalytic performance compared with Co-ZnO, giving a STY(H2) as high as 1.099 mol·h−1·g-cat−1 (data taken 100 h after the reaction started). In comparison, the pristine Co-ZnO catalyst only afforded a STY(H2) of 0.684 mol·h−1·g-cat−1 under identical reaction conditions. Characterization results revealed that the Sc2O3 dopant strengthened the electronic interaction between Co species and ZnO, which was in favour of elevating the reduction temperature of Co oxides and boosting the dispersion of the Con+ (n = 1 or 2). The introduction of Sc2O3 induced the formation of O2− and OH−. All of these effects effectively inhibited the sintering of active Co species and markedly improved the activity and operating stability of the catalyst.
      Citation: Catalysts
      PubDate: 2017-08-18
      DOI: 10.3390/catal7080241
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 242: Galactooligosaccharide Production from
           Pantoea anthophila Strains Isolated from “Tejuino”, a Mexican
           Traditional Fermented Beverage

    • Authors: Claudia Yañez-Ñeco, Barbara Rodriguez-Colinas, Lorena Amaya-Delgado, Antonio Ballesteros, Anne Gschaedler, Francisco Plou, Javier Arrizon
      First page: 242
      Abstract: Two Pantoea anthophila bacterial strains were isolated from “tejuino”, a traditional Mexican beverage, and studied as β-galactosidase producers for galactooligosaccharides synthesis. Using 400 g/L of lactose, 50 °C, and 15 U/mL of β-galactosidase activity with ethanol-permeabilized cells, the maximum galactooligosaccharides (GOS) yield determined by High performance anion exchange chromatography with pulse amperometric detection (HPAEC-PAD) was 136 g/L (34% w/w of total sugars) at 96% of lactose conversion for Bac 55.2 and 145 g/L (36% w/w of total sugars) at 94% of lactose conversion for Bac 69.1. The main synthesized products were the disaccharides allolactose [Gal-β(1 → 6)-Glc] and 6-galactobiose [Gal-β(1 → 6)-Gal], as well as the trisaccharides 3′-galactosyl-lactose [Gal-β(1 → 3)-Gal-β(1 → 4)-Glc], 6-galactotriose [Gal-β(1 → 6)-Gal-β(1 → 6)-Gal], 3′-galactosyl-allolactose [Gal-β(1 → 3)-Gal-β(1 → 6)-Glc], and 6′-galactosyl-lactose [Gal-β(1 → 6)-Gal-β(1 → 4)-Glc]. The β-galactosidases present in both strains showed a high transgalactosylation activity and formed principally β(1 → 3) and β(1 → 6) linkages. Considering the stability and bifidogenic properties of GOS containing such types of bonds, P. anthophila strains Bac 55.2 and Bac 69.1 possess a high potential as novel biocatalysts for prebiotic industrial production.
      Citation: Catalysts
      PubDate: 2017-08-22
      DOI: 10.3390/catal7080242
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 243: Synthesis of NaOH-Modified TiOF2 and Its
           Enhanced Visible Light Photocatalytic Performance on RhB

    • Authors: Chentao Hou, Wenli Liu, Jiaming Zhu
      First page: 243
      Abstract: NaOH-modified TiOF2 was successfully prepared using a modified low-temperature hydrothermal method. Scanning electron microscopy shows that NaOH-modified TiOF2 displayed a complex network shape with network units of about 100 nm. The structures of NaOH-modified TiOF2 have not been reported elsewhere. The network shape permits the NaOH-modified TiOF2 a SBET of 36 m2∙g−1 and a pore diameter around 49 nm. X-ray diffraction characterization shows that TiOF2 and NaOH-modified TiOF2 are crystallized with a pure changed cubic phase which accords with the SEM results. Fourier transform infrared spectroscopy characterization shows that NaOH-modified TiOF2 has more O–H groups to supply more lone electron pairs to transfer from O of O–H to Ti and O of TiOF2. UV–vis diffuse reflectance spectroscopy (DRS) shows that the NaOH-modified TiOF2 sample has an adsorption plateau rising from 400 to 600 nm in comparison with TiOF2, and its band gap is 2.62 eV, lower than that of TiOF2. Due to the lower band gap, more O–H groups adsorption, network morphologies with larger surface area, and sensitization progress, the NaOH-modified TiOF2 exhibited much higher photocatalytic activity for Rhodamine B (RhB) degradation. In addition, considering the sensitization progress, O–H groups on TiOF2 not only accelerated the degradation rate of RhB, but also changed its degradation path. As a result, the NaOH-modified TiOF2 exhibited much higher photocatalytic activity for RhB degradation than the TiOF2 in references under visible light. This finding provides a new idea to enhance the photocatalytic performance by NaOH modification of the surface of TiOF2.
      Citation: Catalysts
      PubDate: 2017-08-22
      DOI: 10.3390/catal7080243
      Issue No: Vol. 7, No. 8 (2017)
       
  • Catalysts, Vol. 7, Pages 193: Chiral Catalyst Deactivation during the
           Asymmetric Hydrogenation of Acetophenone

    • Authors: Jose Ruelas-Leyva, Gustavo Fuentes
      First page: 193
      Abstract: Asymmetric hydrogenation in solution catalyzed by chiral catalysts is a powerful tool to obtain chiral secondary alcohols. It is possible to reach conversions and enantiomeric excesses close to 99%, but that frequently requires the use of non-optimal amounts of catalysts or long reaction times. That is in part caused by the lack of kinetic information needed for the design of large-scale reactors, including few reported details about catalyst deactivation. In this work, we present a kinetic model for the asymmetric hydrogenation in solution of acetophenone, a prochiral substrate, catalyzed by different bisphosphine-diamine Ru complexes. The experimental data was fitted with a first order model that includes first order deactivation of the catalyst and the presence of residual activity. The fit of the experimental data is very good, and an analysis of the kinetic and deactivation parameters gives further insight into the role of each ligand present in the Ru catalysts. This is the first report of a kinetic analysis of homogenous complexes’ catalysis including an analysis of their deactivation.
      PubDate: 2017-06-23
      DOI: 10.3390/catal7070193
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 194: Hydrothermal Carbonation Carbon-Coated CdS
           Nanocomposite with Enhanced Photocatalytic Activity and Stability

    • Authors: Yuanliang Ma, Zhongkun Zhao, Zhurui Shen, Qiang Cai, Huiming Ji, Leichao Meng
      First page: 194
      Abstract: Herein, a novel CdS nanocomposite is fabricated by a facile one-pot hydrothermal method assisted by glucose and polyvinylpyrrolidone (PVP). The as-prepared CdS is coated with a thin layer, which is determined to be hydrothermal carbonation carbon (HTCC) mainly containing semiconductive polyfuran. The as-prepared HTCC-coated CdS shows superior photocatalytic activity for the degradation of Rhodamine B (RhB) under visible light irradiation (λ ≥ 420 nm). The optimum sample (glucose content of 0.1 g) shows a degradation rate four-times that of pure CdS reference. Moreover, it also shows an improved stability, and the activity can be maintained at 96.2% after three cycles of recycling. The enhanced photocatalytic activity and stability of nanocomposite can mainly be attributed to: (i) The addition of PVP in the reaction solution can significantly increase the specific surface area of CdS and thus offer more active sites; (ii) The HTCC in the nanocomposite can expand the range of light absorption; (iii) The HTCC layer can form a heterojunction with CdS and improve the charge separation and transfer.
      PubDate: 2017-06-24
      DOI: 10.3390/catal7070194
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 195: Intramolecular Transfer of Pd Catalyst on
           Carbon–Carbon Triple Bond and Nitrogen–Nitrogen Double Bond in
           Suzuki–Miyaura Coupling Reaction

    • Authors: Takeru Kamigawara, Hajime Sugita, Koichiro Mikami, Yoshihiro Ohta, Tsutomu Yokozawa
      First page: 195
      Abstract: Intramolecular transfer of t-Bu3P-ligated Pd catalyst on a carbon–carbon triple bond (C≡C) and nitrogen–nitrogen double bond (N=N) was investigated and compared with the case of a carbon–carbon double bond (C=C), which is resistant to intramolecular transfer of the Pd catalyst. Suzuki–Miyaura coupling reaction of equimolar 4,4’-dibromotolan (1a) or 4,4’-dibromoazobenzene (1b) with 3-isobutoxyphenylboronic acid (2) was carried out in the presence of t-Bu3P-ligated Pd precatalyst 3 and KOH/18-crown-6 as a base at room temperature. In both cases, the diphenyl-substituted product was selectively obtained, indicating that the Pd catalyst walked from one benzene ring to the other through the C≡C or N=N bond after the first substitution with 2. Taking advantage of this finding, we conducted unstoichiometric Suzuki–Miyaura polycondensation of 1.3 equiv. of 1 and 1.0 equiv. of phenylenediboronic acid (ester) 6 in the presence of 3 and CsF/18-crown-6 as a base, obtaining high-molecular-weight conjugated polymer with a boronic acid (ester) moiety at both ends, contrary to the Flory principle.
      PubDate: 2017-06-23
      DOI: 10.3390/catal7070195
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 196: Selective Hydrogenolysis of Glycerol and
           Crude Glycerol (a By-Product or Waste Stream from the Biodiesel Industry)
           to 1,2-Propanediol over B2O3 Promoted Cu/Al2O3 Catalysts

    • Authors: Malaya Nanda, Zhongshun Yuan, Hengfu Shui, Chunbao Xu
      First page: 196
      Abstract: The performance of boron oxide (B2O3)-promoted Cu/Al2O3 catalyst in the selective hydrogenolysis of glycerol and crude glycerol (a by-product or waste stream from the biodiesel industry) to produce 1,2-propanediol (1,2-PDO) was investigated. The catalysts were characterized using N2-adsorption-desorption isotherm, Inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), ammonia temperature programmed desorption (NH3-TPD), thermogravimetric analysis (TGA), temperature programmed reduction (TPR), and transmission electron microscopy (TEM). Incorporation of B2O3 to Cu/Al2O3 was found to enhance the catalytic activity. At the optimum condition (250 °C, 6 MPa H2 pressure, 0.1 h−1 WHSV (weight hourly space velocity), and 5Cu-B/Al2O3 catalyst), 10 wt% aqueous solution of glycerol was converted into 1,2-PDO at 98 ± 2% glycerol conversion and 98 ± 2% selectivity. The effects of temperature, pressure, boron addition amount, and liquid hourly space velocity were studied. Different grades of glycerol (pharmaceutical, technical, or crude glycerol) were used in the process to investigate the stability and resistance to deactivation of the selected 5Cu-B/Al2O3 catalyst.
      PubDate: 2017-06-25
      DOI: 10.3390/catal7070196
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 197: The Effects of CeO2 Nanorods and CeO2
           Nanoflakes on Ni–S Alloys in Hydrogen Evolution Reactions in Alkaline
           Solutions

    • Authors: Meiqin Zhao, Yao Li, Haifeng Dong, Lixin Wang, Zhouhao Chen, Yazhou Wang, Zhiping Li, Meirong Xia, Guangjie Shao
      First page: 197
      Abstract: Composite coatings synthesized by different morphologies of CeO2 in supergravity devices are highly active in hydrogen evolution reactions (HERs). By adding CeO2 nanoflakes (CeO2 Nf) or CeO2 nanorods (CeO2 Nr), the change in the microstructures of composites becomes quite distinct. Moreover, most Ni–S alloys are attached on the surface of CeO2 and roughen it compare with pure CeO2. In order to make the expression more concise, this paper uses M instead of Ni–S. At a current density of 10 mA/cm2, overpotentials of Ni–S/CeO2 Nr (M–CeO2 Nr) and Ni–S/CeO2 Nf (M–CeO2 Nf) are 200 mV and 180 mV respectively, which is lower than that of Ni–S (M-0) coating (240 mV). The exchange current density (j0) values of M–CeO2 Nf and M–CeO2 Nr are 7.48 mA/cm2 and 7.40 mA/cm2, respectively, which are higher than that of M-0 (6.39 mA/cm2). Meanwhile, double-layer capacitances (Cdl) values of M–CeO2 Nf (6.4 mF/cm2) and M–CeO2 Nr (6 mF/cm2) are 21.3 times and 20 times of M-0 (0.3 mF/cm2), respectively
      PubDate: 2017-06-27
      DOI: 10.3390/catal7070197
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 198: Ordered PtSn/C Electrocatalyst: A High
           Performance Material for the Borohydride Electrooxidation Reaction

    • Authors: Francielle Bortoloti, Antonio Angelo
      First page: 198
      Abstract: This work used a rotating disc electrode and quasi-steady state polarization curves to investigate the sodium borohydride electrooxidation of ordered intermetallic PtSn/C in alkaline solution. Under similar experimental conditions, PtSn/C proved to be a better electrocatalyst than Pt in an overall process that involved eight electrons. Assays performed in the presence of thiourea and S2− species evidenced that a chemical hydrolysis step took place, followed by electrochemical oxidation of the generated H2. The results presented herein suggest that PtSn/C constitutes a promising electrode material for application in alkaline borohydride fuel cell.
      PubDate: 2017-06-29
      DOI: 10.3390/catal7070198
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 199: A Review on Selective Catalytic Reduction of
           NOx by NH3 over Mn–Based Catalysts at Low Temperatures: Catalysts,
           Mechanisms, Kinetics and DFT Calculations

    • Authors: Fengyu Gao, Xiaolong Tang, Honghong Yi, Shunzheng Zhao, Chenlu Li, Jingying Li, Yiran Shi, Xiaomi Meng
      First page: 199
      Abstract: It is a major challenge to develop the low–temperature catalysts (LTC, <250 °C) with excellent efficiency and stability for selective catalytic reduction (SCR) of NOx by NH3 from stationary sources. Mn-based LTC have been widely investigated due to its various valence states and excellent redox performance, while the poisoning by H2O or/and SO2 is one of the severe weaknesses. This paper reviews the latest research progress on Mn-based catalysts that are expected to break through the resistance, such as modified MnOx–CeO2, multi-metal oxides with special crystal or/and shape structures, modified TiO2 supporter, and novel carbon supporter (ACF, CNTs, GE), etc. The SCR mechanisms and promoting effects of redox cycle are described in detail. The reaction kinetics will be a benefit for the quantitative study of Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms. This paper also introduces the applications of quantum-chemical calculation using density functional theory to analyze the physic-chemical properties, explicates the reaction and poisoning mechanisms, and directs the design of functional catalysts on molecule levels. The intensive study of H2O/SO2 inhibition effects is by means of the combination analysis of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT), and the amplification of tolerance mechanisms will be helpful to design an excellent SCR catalyst.
      PubDate: 2017-06-29
      DOI: 10.3390/catal7070199
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 200: Activated Carbon Supported Mo-Ti-N Binary
           Transition Metal Nitride as Catalyst for Acetylene Hydrochlorination

    • Authors: Hui Dai, Mingyuan Zhu, Haiyang Zhang, Feng Yu, Chao Wang, Bin Dai
      First page: 200
      Abstract: Recently, many scientists have focused on the development of green industrial technology. However, the process of synthesizing vinyl chloride faces the problem of Hg pollution. Via a novel approach, we used two elements Mo and Ti to prepare an inexpensive and green binary transition metal nitride (BTMN) as the active ingredient in a catalyst with nano-sized particles and an excellent degree of activation, which was supported on activated carbon. When the Mo/Ti mole ratio was 3:1, the conversion of acetylene reached 89% and the selectivity exceeded 98.5%. The doping of Ti in Mo-based catalysts reduced the capacity of adsorption for acetylene and also increased the adsorption of hydrogen chloride. Most importantly, the performance of the BTMN excelled those of the individual transition metal nitrides, due to the synergistic activity between Mo and Ti. This will expand the new epoch of the employment of transition metal nitrides as catalysts in the hydrochlorination of acetylene reaction.
      PubDate: 2017-06-30
      DOI: 10.3390/catal7070200
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 201: Highly Effective Dual Transition Metal
           Macrocycle Based Electrocatalyst with Macro-/Mesoporous Structures for
           Oxygen Reduction Reaction

    • Authors: Xinxin Jin, Yan Xie, Jiahui Huang
      First page: 201
      Abstract: Metal macrocycle based non-noble metal electrocatalysts (NNMEs) with highly efficient oxygen reduction reaction (ORR) activity, good stability, and excellent resistance to the methanol cross-over effect have been regarded as one of the most important alternatives for Pt or Pt based alloys, which are widely used in fuel cells. However, the expensive price of most metal macrocycles hinder further investigation of such a family of NNMEs in large production for practical applications. Here, we introduce a simple strategy to synthesize metal macrocycle based porous carbon (MMPC) material with low cost and easy production of metal macrocycles (hemin (Hm) and vitamin B12 (VB12)) as raw materials by using a hard template of MgO. The pyrolysis of MMPC under the optimal temperature at 900 °C shows comparative ORR performance relative to commercial Pt/C, which could be attributed to the large surface area, macro-/mesoporous structure, the carbon layer encapsulating transition metal based oxides, as well as N-doped carbon species. In addition, MMPC (900) displays a better electrochemical property than 20 wt % Pt/C in terms of durability and tolerance to methanol in O2-saturated 0.1 M KOH media.
      PubDate: 2017-06-30
      DOI: 10.3390/catal7070201
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 202: High Active Zn/Mg-Modified Ni–P/Al2O3
           Catalysts Derived from ZnMgNiAl Layered Double Hydroxides for
           Hydrodesulfurization of Dibenzothiophene

    • Authors: Feng Li, Jinrong Liang, Wenxi Zhu, Hua Song, Keliang Wang, Cuiqin Li
      First page: 202
      Abstract: A series of ZnMgNiAl layered double hydroxides (LDHs) containing 20 wt.% Ni and different Zn/Mg molar ratios were prepared by a coprecipitation method, and then were introduced with H2PO4− via a microwave-hydrothermal method. With the resulting mixtures as the precursors, Zn/Mg-modified ZnMgNi–P/Al2O3 catalysts were prepared. The Zn/Mg molar ratio affected the formation of Ni2P and Ni12P5 in nickel phosphides. The ZnMgNi–P/Al2O3 catalyst with a Zn/Mg molar ratio of 3:1 exhibits the best dibenzothiophene hydrodesulfurization (HDS) activity. Compared with the Ni–P/Al2O3 catalyst prepared from the impregnation method, the ZnMgNi–P/Al2O3 catalyst shows a higher HDS activity (81.6% vs. 54.3%) and promotes the direct desulfurization of dibenzothiophene.
      PubDate: 2017-07-04
      DOI: 10.3390/catal7070202
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 203: Rapid Jatropha-Castor Biodiesel Production
           with Microwave Heating and a Heterogeneous Base Catalyst
           Nano-Ca(OH)2/Fe3O4

    • Authors: Ken-Lin Chang, Yuan-Chung Lin, Syu-Ruei Jhang, Way Lee Cheng, Shang-Cyuan Chen, Sung-Yuan Mao
      First page: 203
      Abstract: In this study, a nano-Ca(OH)2/Fe3O4 catalyst was used to produce biodiesel from a 1:1 mixed jatropha-castor oil. By loading Ca(OH)2 onto Fe3O4 nanoparticles, it increased the specific surface area by almost 40%, which improved the catalytic activity as it provided a larger area for the reactants to interact. The main purpose of mixing jatropha oil with castor oil was to lower the viscosity of the castor oil. The transesterification reaction was carried out at elevated temperature, using a microwave heating system. Moreover, it was shown that the preferred reaction conditions are using high temperature and short reaction duration. The optimized yield of methyl ester was 95%, achieved by using a catalyst with a Ca:Fe ratio of 7:1, temperature of 65 °C, methanol/oil ratio of 12:1, and reaction time of 35 min. The catalyst was shown to be reusable, easily recyclable, and its activity was very stable. Only 2% of the catalyst was lost, and the yield was 3% lower after ten successive applications. The solid, magnetic base catalyst could be easily separated from the reaction products, unlike homogeneous catalysts.
      PubDate: 2017-07-04
      DOI: 10.3390/catal7070203
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 204: Acidity-Reactivity Relationships in
           Catalytic Esterification over Ammonium Sulfate-Derived Sulfated Zirconia

    • Authors: Abdallah Rabee, Gamal Mekhemer, Amin Osatiashtiani, Mark Isaacs, Adam Lee, Karen Wilson, Mohamed Zaki
      First page: 204
      Abstract: New insight was gained into the acidity-reactivity relationships of sulfated zirconia (SZ) catalysts prepared via (NH4)2SO4 impregnation of Zr(OH)4 for propanoic acid esterification with methanol. A family of systematically related SZs was characterized by bulk and surface analyses including XRD, XPS, TGA-MS, N2 porosimetry, temperature-programmed propylamine decomposition, and FTIR of adsorbed pyridine, as well as methylbutynol (MBOH) as a reactive probe molecule. Increasing surface sulfation induces a transition from amphoteric character for the parent zirconia and low S loadings <1.7 wt %, evidenced by MBOH conversion to 3-hydroxy-3-methyl-2-butanone, methylbutyne and acetone, with higher S loadings resulting in strong Brønsted-Lewis acid pairs upon completion of the sulfate monolayer, which favored MBOH conversion to prenal. Catalytic activity for propanoic acid esterification directly correlated with acid strength determined from propylamine decomposition, coincident with the formation of Brønsted-Lewis acid pairs identified by MBOH reactive titration. Monodispersed bisulfate species are likely responsible for superacidity at intermediate sulfur loadings.
      PubDate: 2017-07-05
      DOI: 10.3390/catal7070204
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 205: DeNOx Abatement Modelling over Sonically
           Prepared Copper USY and ZSM5 Structured Catalysts

    • Authors: Przemysław J. Jodłowski, Łukasz Kuterasiński, Roman J. Jędrzejczyk, Damian Chlebda, Anna Gancarczyk, Sylwia Basąg, Lucjan Chmielarz
      First page: 205
      Abstract: Metallic supports play an important role as structured reactor internals. Due to their specific properties including enhanced heat and mass transport, high mechanical resistivity and elimination of local hot-spots, they are commonly used in gas exhaust abatement from stationary and automotive industries. In this study, the performance of three structured supports with deposited Cu/USY (Ultrastabilised Y—zeolite) for deNOx abatement were modelled. Based on kinetic and flow resistance experimental results, the one-dimensional (1D) model of structured reactor was developed. The performance of the structured reactors was compared by the length of the reactor necessary to achieve an arbitrary 90% NOx conversion. The performed simulations showed that the sonochemically prepared copper USY and ZSM-5 zeolites deposited on metallic supports may be successfully used as catalysts for deNOx process.
      PubDate: 2017-07-06
      DOI: 10.3390/catal7070205
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 206: Cerium Coordination Polymer Based Composite
           Mimicking Peroxidase for Detection of Nitroaniline

    • Authors: Xi Wang, Kunkun Zheng, Peijun Ji
      First page: 206
      Abstract: Cerium coordination polymer (CeCP) was synthesized with 1,3,5-benzenetricarboxylic acid as the ligand. By using the carboxyl groups on the surface of CeCP as the anchors, platinum nanoparticles were formed on CeCP forming the composite CeCP@Pt. The composite was characterized by measuring TEM images, and EDS and XPS spectra. CeCP@Pt was used to catalyze the oxidation of 3,3,5,5-tetramethylbenzidine in the presence of H2O2. The activity assay demonstrated that CeCP@Pt exhibited an activity similar to that of horseradish peroxidase, but with a much higher activity. CeCP@Pt was utilized to detect nitroaniline, being able to detect trace amount of nitroaniline (>3.125 × 10−4 mg/mL).
      PubDate: 2017-07-07
      DOI: 10.3390/catal7070206
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 207: Bimetallic Nanoparticles in Alternative
           Solvents for Catalytic Purposes

    • Authors: Trung Dang-Bao, Daniel Pla, Isabelle Favier, Montserrat Gómez
      First page: 207
      Abstract: Bimetallic nanoparticles represent attractive catalytic systems thanks to the synergy between both partners at the atomic level, mainly induced by electronic effects which in turn are associated with the corresponding structures (alloy, core-shell, hetero-dimer). This type of engineered material can trigger changes in the kinetics of catalyzed processes by variations on the electrophilicity/nucleophilicity of the metal centers involved and also promote cooperative effects to foster organic transformations, including multi-component and multi-step processes. Solvents become a crucial factor in the conception of catalytic processes, not only due to their environmental impact, but also because they can preserve the bimetallic structure during the catalytic reaction and therefore increase the catalyst life-time. In this frame, the present review focuses on the recent works described in the literature concerning the synthesis of bimetallic nanoparticles in non-conventional solvents, i.e., other than common volatile compounds, for catalytic applications.
      PubDate: 2017-07-07
      DOI: 10.3390/catal7070207
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 208: Newly Designed Ternary Metallic PtPdBi
           Hollow Catalyst with High Performance for Methanol and Ethanol Oxidation

    • Authors: Zhiping Xiong, Shumin Li, Hui Xu, Ke Zhang, Bo Yan, Yukou Du
      First page: 208
      Abstract: This paper reported the fabrication of ternary metallic PtPdBi hollow nanocatalyst through a facile, one-pot, wet-chemical method by adopting sodium borohydride and polyvinylpyrrolidone as reducing agent and surfactant directing agent, respectively. The hollow structure offers novel morphology and large surface areas, which are conducive to enhancing the electrocatalytic activity. The electrocatalytic properties of hollow PtPdBi nanocatalyst were investigated systematically in alkaline media through cyclic voltammetry and the as-prepared PtPdBi nanocatalyst displays greatly enhanced electrocatalytic activities towards methanol and ethanol oxidation. The calculated mass activities of PtPdBi electrocatalyst are 2.133 A mgPtPd−1 for methanol oxidation reaction and 5.256 A mgPtPd−1 for ethanol oxidation reaction, which are much better than that of commercial Pt/C and commercial Pd/C. The as-prepared hollow nanocatalyst may be a potential promising electrocatalyst in fuel cells and also may be extended to the applications of other desirable functions.
      Citation: Catalysts
      PubDate: 2017-07-10
      DOI: 10.3390/catal7070208
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 209: Low-Temperature Synthesis of
           Anatase/Rutile/Brookite TiO2 Nanoparticles on a Polymer Membrane for
           Photocatalysis

    • Authors: Kristina Fischer, Alina Gawel, David Rosen, Maria Krause, Amira Abdul Latif, Jan Griebel, Andrea Prager, Agnes Schulze
      First page: 209
      Abstract: Removing pollutants from water by using the photocatalyst TiO2 is a highly-promising method. A large amount of work has been done to increase the activity of TiO2, whereas the main two findings are increasing the surface area and applying mixed phase modifications (anatase, brookite, and rutile). Here, we present a method to directly synthesize non-agglomerated TiO2 nanoparticles with different crystal phase ratios via low temperature dissolution-precipitation (LTDRP) on a porous microfiltration membrane (polyethersulfone). The amount of hydrochloric acid and the temperature was varied between 0.1–1 M and 25–130 °C, respectively, while the concentration of titanium precursor (titanium(IV) isopropoxide) was kept unchanged. The TiO2 nanoparticles and the membrane were thoroughly characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), measuring the water contact angle and permeation flux, and examining the degradation of methylene blue. The mixed phase anatase/brookite with a main component being anatase exhibited the highest photocatalytic activity in removing methylene blue. Higher synthesis temperature induces enhanced crystallinity and, subsequently, the degradation rate of methylene blue was improved. Additionally, the photocatalytic activity remains high and unchanged for up to nine repeated cycles, i.e., full recovery of the photocatalytic properties is sustained.
      Citation: Catalysts
      PubDate: 2017-07-10
      DOI: 10.3390/catal7070209
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 210: Solventless Coupling of Epoxides and CO2 in
           Compressed Medium Catalysed by Fluorinated Metalloporphyrins

    • Authors: Rui Carrilho, Lucas Dias, Raquel Rivas, Mariette Pereira, Carmen Claver, Anna Masdeu-Bultó
      First page: 210
      Abstract: Metal complexes of meso-arylporphyrins (Cr(III), Fe(III), and Zn(II)) were evaluated in the coupling reaction of cyclohexene oxide (CHO) with CO2 in compressed medium, where the Cr complexes were demonstrated to be the most active systems, leading predominantly to copolymerisation products. It is noteworthy that no addition of solvent was required. To improve the catalytic activity, and to simultaneously increase the solubility in compressed CO2, a new fluorinated catalyst, tetrakis(4-trifluoromethylphenyl)porphyrinatochromium(III) chloride (CrCl-pCF3TPP), was applied to this reaction. The alternating copolymerisation of CHO with CO2, using the Cr(III) fluorinated porphyrin catalyst, required the use of a co-catalyst, bis(triphenylphosphine)iminium chloride (PPNCl), with the best yields of copolymers being obtained at 80 °C, and CO2 pressures in the range of 50–110 bar, over a period of 24 h, with a low catalyst/substrate molar ratio (0.07%). The polycarbonate’s structure was analysed by 1H NMR, 13C NMR, and MALDI-TOF spectroscopy, which demonstrated high carbonate incorporations (98–99%). Gel permeation chromatography revealed number-average molecular weights (Mn) in the range of 4800–12,800 and narrow molecular weight distributions (Mw/Mn ≤ 1.63).
      Citation: Catalysts
      PubDate: 2017-07-14
      DOI: 10.3390/catal7070210
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 211: Arenesulfonic Acid-Functionalized Bentonite
           as Catalyst in Glycerol Esterification with Acetic Acid

    • Authors: Maryam Tangestanifard, Hassan Ghaziaskar
      First page: 211
      Abstract: The present study is focused on the synthesis of arenesulfonic acid-functionalized bentonite as a catalyst to produce monoacetin, diacetin, and triacetin from glycerol and acetic acid using toluene as solvent and a water removing agent. The best conditions for the present reaction with acetic acid were an acetic acid:glycerol:toluene molar ratio of 7:1:1.4, 100 °C, and 0.074 wt % of catalyst (based on the total weight of glycerol). Under the reaction conditions, 96% glycerol conversion was achieved within 0.5 h from the start of the reaction. The maximum selectivity of 66% and 74% were achieved for diacetin and triacetin after 0.5 and 3 h of reaction, respectively, without formation of any byproduct. The arenesulfonic acid-functionalized bentonite was characterized by X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, N2 adsorption/desorption experiments (Brunauer, Emmett and Teller, BET, method), field emission scanning electron microscopy, and the surface acidity was determined by back titration. Without significant treatment, the catalyst was reusable for 5 consecutive runs.
      Citation: Catalysts
      PubDate: 2017-07-14
      DOI: 10.3390/catal7070211
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 212: In Silico Studies of Small Molecule
           Interactions with Enzymes Reveal Aspects of Catalytic Function

    • Authors: Rajni Verma, Katie Mitchell-Koch
      First page: 212
      Abstract: Small molecules, such as solvent, substrate, and cofactor molecules, are key players in enzyme catalysis. Computational methods are powerful tools for exploring the dynamics and thermodynamics of these small molecules as they participate in or contribute to enzymatic processes. In-depth knowledge of how small molecule interactions and dynamics influence protein conformational dynamics and function is critical for progress in the field of enzyme catalysis. Although numerous computational studies have focused on enzyme–substrate complexes to gain insight into catalytic mechanisms, transition states and reaction rates, the dynamics of solvents, substrates, and cofactors are generally less well studied. Also, solvent dynamics within the biomolecular solvation layer play an important part in enzyme catalysis, but a full understanding of its role is hampered by its complexity. Moreover, passive substrate transport has been identified in certain enzymes, and the underlying principles of molecular recognition are an area of active investigation. Enzymes are highly dynamic entities that undergo different conformational changes, which range from side chain rearrangement of a residue to larger-scale conformational dynamics involving domains. These events may happen nearby or far away from the catalytic site, and may occur on different time scales, yet many are related to biological and catalytic function. Computational studies, primarily molecular dynamics (MD) simulations, provide atomistic-level insight and site-specific information on small molecule interactions, and their role in conformational pre-reorganization and dynamics in enzyme catalysis. The review is focused on MD simulation studies of small molecule interactions and dynamics to characterize and comprehend protein dynamics and function in catalyzed reactions. Experimental and theoretical methods available to complement and expand insight from MD simulations are discussed briefly.
      Citation: Catalysts
      PubDate: 2017-07-14
      DOI: 10.3390/catal7070212
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 213: Pure and Fe-Doped Mesoporous Titania
           Catalyse the Oxidation of Acid Orange 7 by H2O2 under Different
           Illumination Conditions: Fe Doping Improves Photocatalytic Activity under
           Simulated Solar Light

    • Authors: Francesca Freyria, Matteo Compagnoni, Nicoletta Ditaranto, Ilenia Rossetti, Marco Piumetti, Gianguido Ramis, Barbara Bonelli
      First page: 213
      Abstract: A sample of mesoporous TiO2 (MT, specific surface area = 150 m2·g−1) and two samples of MT containing 2.5 wt.% Fe were prepared by either direct synthesis doping (Fe2.5-MTd) or impregnation (Fe2.5-MTi). Commercial TiO2 (Degussa P25, specific surface area = 56 m2 g−1) was used both as a benchmark and as a support for impregnation with either 0.8 or 2.5 wt.% Fe (Fe0.80-IT and Fe2.5-IT). The powders were characterized by X-ray diffraction, N2 isotherms at −196 °C, Energy Dispersive X-ray (EDX) Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Diffuse Reflectance (DR) ultra-violet (UV)-Vis and Mössbauer spectroscopies. Degradation of Acid Orange 7 (AO7) by H2O2 was the test reaction: effects of dark-conditions versus both UV and simulated solar light irradiation were considered. In dark conditions, AO7 conversion was higher with MT than with Degussa P25, whereas Fe-containing samples were active in a (slow) Fenton-like reaction. Under UV light, MT was as active as Degussa P25, and Fe doping enhanced the photocatalytic activity of Fe2.5-MTd; Fe-impregnated samples were also active, likely due to the occurrence of a photo-Fenton process. Interestingly, the Fe2.5-MTd sample showed the best performance under solar light, confirming the positive effect of Fe doping by direct synthesis with respect to impregnation.
      Citation: Catalysts
      PubDate: 2017-07-18
      DOI: 10.3390/catal7070213
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 214: Sulfur-Doped TiO2: Structure and Surface
           Properties

    • Authors: Sara Cravanzola, Federico Cesano, Fulvio Gaziano, Domenica Scarano
      First page: 214
      Abstract: A comprehensive study on the sulfur doping of TiO2, by means of H2S treatment at 673 K, has been performed in order to highlight the role of sulfur in affecting the properties of the system, as compared to the native TiO2. The focus of this study is to find a relationship among the surface, structure, and morphology properties, by means of a detailed chemical and physical characterization of the samples. In particular, transmission electron microscopy images provide a simple tool to have a direct and immediate evidence of the effects of H2S action on the TiO2 particles structure and surface defects. Furthermore, from spectroscopy analyses, the peculiar surface, optical properties, and methylene blue photodegradation test of S-doped TiO2 samples, as compared to pure TiO2, have been investigated and explained by the effects caused by the exchange of S species with O species and by the surface defects induced by the strong H2S treatment.
      Citation: Catalysts
      PubDate: 2017-07-18
      DOI: 10.3390/catal7070214
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 215: Mo(VI) Complexes Immobilized on SBA-15 as an
           Efficient Catalyst for 1-Octene Epoxidation

    • Authors: Jovita Moreno, Jose Iglesias, Juan Melero
      First page: 215
      Abstract: SBA-15 materials were functionalized through a post-synthetic methodology with molybdenum-Schiff bases to provide catalytic activity in epoxidation reactions. Thus, glycidoxypropyl functionalities were first attached to the surface of the mesostructured silica, followed by the reaction of the immobilized oxirane groups with 2-amino propyl pyridine. This reaction allowed the obtaining of (hydroxypropyl)-2-aminomethyl pyridine ligands, directly tethered to the surface of the mesoporous silica-based SBA-15, which resulted in excellent chelating ligands to immobilize dioxo molydenum species by a reaction with MoO2(acac)2. This investigation comprises a thorough characterization of the process for building the immobilized molybdenum-Schiff base complexes, as well as the use of the obtained materials in 1-octene oxidation in the presence of organic hydroperoxides. These materials displayed high intrinsic catalytic activity in the epoxidation of 1-octene with organic hydroperoxides under a wide variety of conditions, although both the reaction solvent as well as the nature of the organic hydroperoxide, exerted a dramatic influence on the catalytic activity of these heterogeneous oxidation catalysts. Thus, whereas nonpolar solvents provided good epoxide yields with high efficiency in the use of the oxidant, polar solvents depressed the catalytic activity of the supported Mo-Schiff bases. These results have been ascribed to the competition with the solvent, when polar, for binding to the metal sites, thus avoiding the formation of the hydroperoxo-metal cycle and the epoxidation of the olefin. The catalysts presented here show good reusability with low catalytic activity decay after the first reuse.
      Citation: Catalysts
      PubDate: 2017-07-18
      DOI: 10.3390/catal7070215
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 216: Highly ordered Nanomaterial Functionalized
           Copper Schiff Base Framework: Synthesis, Characterization, and Hydrogen
           Peroxide Decomposition Performance

    • Authors: Fatemeh Rajabi, María Pinilla-de Dios, Rafael Luque
      First page: 216
      Abstract: An immobilized copper Schiff base tridentate complex was prepared in three steps from SBA-15 supports. The immobilized copper nanocatalyst (heterogeneous catalyst) was characterized by Fourier transform infrared spectroscopy (FT-IR), cross polarization magic angle spinning (CP-MAS), 13-carbon nuclear magnetic resonance (13C-NMR), atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), and N2-physisorption. Moreover, morphological and structural features of the immobilized nanocatalyst were analyzed using transmission electron microscopy (TEM) and X-ray powder diffraction spectrometry (PXRD). After characterizing the nanocatalyst, the catalytic activity was determined in hydrogen peroxide (H2O2) decomposition. The high decomposition yield of H2O2 was obtained for low-loaded copper content materials at pH 7 and at room temperature. Furthermore, the nanocatalyst exhibited high activity and stability under the investigated conditions, and could be recovered and reused for at least five consecutive times without any significant loss in activity. No copper leaching was detected during the reaction by AAS measurements.
      Citation: Catalysts
      PubDate: 2017-07-19
      DOI: 10.3390/catal7070216
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 217: Co-Immobilization of Superoxide Dismutase
           with Catalase on Soft Microparticles Formed by Self-Assembly of
           Amphiphilic Poly(Aspartic Acid)

    • Authors: Siyu Mao, Rong Li, Wenchen Wang, Wei Feng, Peijun Ji
      First page: 217
      Abstract: Through genetic engineering technology, catalase (CAT) and superoxide dismutase (SOD) have been separately fused to an elastin-like polypeptide (ELP). Thus, the enzymes can be purified through phase transition. Hexadecylamine-modified poly(aspartic acid) (HPASP) is able to self-assemble, forming soft microparticles. The HPASP microparticles were used to co-immobilize SOD-ELP and CAT-ELP through amidation reaction. Circular dichroism (CD) confirmed that the secondary structures of the co-immobilized enzymes have been preserved. Fluorescence spectra showed that the co-immobilized enzymes exhibited a higher stability than the free enzymes. Dismutation of superoxide by superoxide dismutase (SOD) generates hydrogen peroxide. By using the co-immobilized enzymes (SOD-ELP/CAT-ELP@HPASP), the generated hydrogen peroxide of SOD-ELP can be decomposed in situ by CAT-ELP. Activity assay results demonstrated that the superoxide anion (•O2−) scavenging ability is 63.15 ± 0.75% for SOD-ELP/CAT-ELP@HPASP. The advantages of the approach of enzyme co-immobilization include the fact that the soft support HPASP itself is a polypeptide in nature, the stability of immobilized enzymes is improved, and a high activity has been achieved. Potentially SOD-ELP/CAT-ELP@HPASP can be applied in the cosmetic industry.
      Citation: Catalysts
      PubDate: 2017-07-19
      DOI: 10.3390/catal7070217
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 218: Catalytic Conversion of Carbohydrates to
           Furanic Derivatives in the Presence of Choline Chloride

    • Authors: François Jérôme, Karine De Oliveira Vigier
      First page: 218
      Abstract: The synthesis of furanic derivatives (5-hydroxymethylfurfural (HMF), furfural…) from carbohydrates is of high interest for a wide range of applications. These reactions are carried out in the presence of various solvents, and among them choline chloride can be used. It is a salt that can form a low melting mixture with a carbohydrate (fructose, glucose…) or a deep eutectic mixture with carboxylic acid. A review of the studies performed in the conversion of carbohydrates to furanic derivatives in the presence of choline chloride is presented here with the advantages and drawbacks of this solvent. Choline chloride can enhance the selectivity to HMF by stabilizing effect and allows the conversion of highly concentrated feed. However, the extraction of the products from these solvents still needs improvement.
      Citation: Catalysts
      PubDate: 2017-07-20
      DOI: 10.3390/catal7070218
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 219: Recyclable Fe3O4 Nanoparticles Catalysts for
           Aza-Michael Addition of Acryl Amides by Magnetic Field

    • Authors: Zhen-Xing Li, Dan Luo, Ming-Ming Li, Xiao-Fei Xing, Zheng-Zheng Ma, Hao Xu
      First page: 219
      Abstract: A nanostructure-based catalytic system has the advantages of both homogeneous and heterogeneous catalysis. It is of great significance to develop the sustainable and green process of homogeneous catalytic reaction. We report a novel, efficient and recyclable magnetic Fe3O4 nanoparticles-catalyzed aza-Michael addition reaction of acryl amides, and the magnetic nanoparticles catalysts can be recovered by external magnetic field. Both primary amine and secondary amine can react with various acryl amides providing a good output to target products successfully at room temperature. Further experiments reveal that the magnetic Fe3O4 nanoparticles-based catalyst shows excellent yields, which can be recycled 10 times, and, at the same time, it maintains a high catalytically activity. In this catalytic system, the tedious separation procedures are replaced by external magnetic field, which gives us a different direction for choosing a catalyst in a nanostructure-based catalytic system.
      Citation: Catalysts
      PubDate: 2017-07-20
      DOI: 10.3390/catal7070219
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 220: Electroreduction of CO2 into Ethanol over an
           Active Catalyst: Copper Supported on Titania

    • Authors: Jing Yuan, Li Liu, Rong-Rong Guo, Sheng Zeng, Huan Wang, Jia-Xing Lu
      First page: 220
      Abstract: A simple, inexpensive, and novel method was used to prepare electrocatalysts from Cu supported on titanium dioxide (Cu/TiO2). XRD, SEM, and TEM characterizations confirmed different loadings of Cu nanoparticles (NPs) on TiO2. Cyclic voltammetry tests indicated that Cu/TiO2 exhibited lower overpotential for CO2 reduction than that of Cu NPs. Moreover, 40 wt % Cu/TiO2 exhibited the highest faradaic efficiency for ethanol (FEethanol) of 27.4%, which is approximately 10-fold higher than that for Cu NPs (FEethanol = 2.7%). The 40 wt % Cu/TiO2 electrocatalyst exhibits a stable current density of 8.66 mA/cm2 over a 25 h stability test. The high efficiency towards CO2 electroreduction to ethanol may be attributed to the synergistic effect of Cu and TiO2 NPs. This work highlights the importance of compositional effect of NPs on their catalytic activities and provides a strategy for designing efficient catalysts for CO2 electroreduction in the future.
      Citation: Catalysts
      PubDate: 2017-07-20
      DOI: 10.3390/catal7070220
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 221: Conversion of Cellulose to Lactic Acid by
           Using ZrO2–Al2O3 Catalysts

    • Authors: Panya Wattanapaphawong, Osamu Sato, Koichi Sato, Naoki Mimura, Prasert Reubroycharoen, Aritomo Yamaguchi
      First page: 221
      Abstract: Lactic acid has a wide range of applications in many industries, both as an ingredient and as an intermediate. Here, we investigated the catalytic conversion of cellulose to lactic acid by using heterogeneous mixed-oxide catalysts containing ZrO2. Although pure ZrO2 has catalytic activity for the conversion of cellulose to lactic acid, the yield of lactic acid obtained is not satisfactory. In contrast, a series of ZrO2–Al2O3 catalysts containing various percentages of ZrO2 provided higher yields of lactic acid. The ZrO2–Al2O3 catalysts had more Lewis acid sites and far fewer base sites than ZrO2. This suggests that the Lewis acid sites on ZrO2–Al2O3 catalysts are more important than the base sites for the conversion of cellulose to lactic acid.
      Citation: Catalysts
      PubDate: 2017-07-21
      DOI: 10.3390/catal7070221
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 222: Solvent-Free Microwave-Induced Oxidation of
           Alcohols Catalyzed by Ferrite Magnetic Nanoparticles

    • Authors: Nuno Martins, Luísa Martins, Carlos Amorim, Vitor Amaral, Armando Pombeiro
      First page: 222
      Abstract: A series of first-row-transition-metal ferrite magnetic nanoparticles (NPs) MFe2O4 [M = Mn2+ (1), Fe2+ (2), Co2+ (3), Ni2+ (4), Cu2+ (5) or Zn2+ (6)] were prepared by the co-precipitation method and characterized by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscope - energy dispersive X-ray spectrometry (SEM-EDS), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). Those NPs were used as catalysts for the microwave-assisted oxidation of various alcohols in solvent-free medium. MnFe2O4 (1), CoFe2O4 (3) and CuFe2O4 (5) act as catalysts for the conversion of alcohols to the corresponding ketones or aldehydes with a yield range of 81 to 94% in 2 h at 120 °C using t-BuOOH as an oxidant. These catalysts can be readily isolated by using an external magnet and no significant loss of activity is observed when reused up to 10 consecutive runs. The effects of some parameters, such as temperature, time, type of oxidant and presence of organic radicals, on the oxidation reactions were also investigated. The presented literature overview highlights the advantages of our new 1–6 NPs catalytic systems in terms of efficiency and economy, mainly due the used microwave (MW) heating mode.
      Citation: Catalysts
      PubDate: 2017-07-24
      DOI: 10.3390/catal7070222
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 223: Synthesis and Evaluation of Ni Catalysts
           Supported on BaCe0.5Zr0.3−xY0.2NixO3−δ with Fused-Aggregate Network
           Structure for the Hydrogen Electrode of Solid Oxide Electrolysis Cell

    • Authors: Ryosuke Nishikawa, Katsuyoshi Kakinuma, Hanako Nishino, Manuel Brito, Srikanth Gopalan, Hiroyuki Uchida
      First page: 223
      Abstract: Nickel nanoparticles loaded on the electron–proton mixed conductor BaCe0.5Zr0.3−xY0.2NixO3−δ (Ni/BCZYN, x = 0 and 0.03) were synthesized for use in the hydrogen electrode of a proton-conducting solid oxide electrolysis cell (SOEC). The Ni nanoparticles, synthesized by an impregnation method, were from 45.8 nm to 84.1 nm in diameter, and were highly dispersed on the BCZYN. The BCZYN nanoparticles, fabricated by the flame oxide synthesis method, constructed a unique microstructure, the so-called “fused-aggregate network structure”. The BCZYN nanoparticles have capability of constructing a scaffold for the hydrogen electrode with both electronically conducting pathways and gas diffusion pathways. The catalytic activity on Ni/BCZYN (x = 0 and 0.03) catalyst layers (CLs) improved with the circumference length of the Ni nanoparticles. Moreover, the catalytic activity on the Ni/BCZYN (x = 0.03) CL was higher than that of the Ni/BCZYN (x = 0) CL. BCZYN (x = 0.03) possesses higher electronic conductivity than BCZYN (x = 0) due to the Ni doping, resulting in an enlarged effective reaction zone (ERZ). We conclude that the proton reduction reaction in the ERZ was the rate-determining step on the hydrogen electrode, and the reaction was enhanced by improving the electronic conductivity of the electron–proton mixed conductor BCZYN.
      Citation: Catalysts
      PubDate: 2017-07-24
      DOI: 10.3390/catal7070223
      Issue No: Vol. 7, No. 7 (2017)
       
  • Catalysts, Vol. 7, Pages 184: Catalytic Acetalization: An Efficient
           Strategy for High-Value Utilization of Biodiesel-Derived Glycerol

    • Authors: Suqun Sun, Min He, Yuanwei Dai, Xin Li, Zhijun Liu, Li Yao
      First page: 184
      Abstract: In this study, an efficient process for high value utilization of biodiesel-derived glycerol was proposed via a simple reaction of acetalization catalyzed by novel catalysts of ester sulfate-functionalized ionic liquids (ILs). The relationship between the IL structure and its catalytic activity was investigated. The effects of reaction conditions, and the substrate adaptability, were also carefully studied. The results demonstrate that ester sulfate-functionalized IL shows excellent catalytic activity on the acetalization of glycerol with aldehyde (ketone). Under the optimized condition, 87% glycerol conversion was obtained with 99% acetal selectivity when glycerol was condensed with cyclohexanone. In particular, 29% of product consists of six-membered compound, an important fine chemical and an excellent precursor in organic chemistry, because of the significant steric-hindrance effect of IL catalyst. Furthermore, the IL catalyst shows good recyclability where insignificant activity loss was exhibited even after six runs.
      PubDate: 2017-06-08
      DOI: 10.3390/catal7060184
      Issue No: Vol. 7, No. 6 (2017)
       
  • Catalysts, Vol. 7, Pages 185: Lipase-Catalyzed Synthesis of Indolyl
           4H-Chromenes via a Multicomponent Reaction in Ionic Liquid

    • Authors: Weian Zhang, Ziyuan Zhao, Zhi Wang, Chao Guo, Chunyu Wang, Rui Zhao, Lei Wang
      First page: 185
      Abstract: Synthesis of indolyl 4H-chromenes via a three-component reaction catalyzed by lipase in ionic liquidsis reported here for the first time. High yields (77–98%) were obtained when Mucor miehei lipase was used as the catalyst in [EMIM][BF4]. Furthermore, [EMIM][BF4] exhibited good reusability in this enzymatic reaction. This study affords a new example of lipase catalytic promiscuity and broadens the application range of ionic liquid in biocatalysis.
      PubDate: 2017-06-08
      DOI: 10.3390/catal7060185
      Issue No: Vol. 7, No. 6 (2017)
       
  • Catalysts, Vol. 7, Pages 186: Immobilized Palladium Nanoparticles on
           Zirconium Carboxy-Aminophosphonates Nanosheets as an Efficient Recoverable
           Heterogeneous Catalyst for Suzuki–Miyaura and Heck Coupling

    • Authors: Vadym Kozell, Tommaso Giannoni, Morena Nocchetti, Riccardo Vivani, Oriana Piermatti, Luigi Vaccaro
      First page: 186
      Abstract: Zirconium phosphate glycine diphosphonate nanosheets (ZPGly) have been used as support for the preparation of solid palladium nanoparticles, namely Pd@ZPGly. Thanks to the presence of carboxy-aminophosponate groups on the layer surface, ZPGly-based materials were able to stabilize a high amount of palladium (up to 22 wt %) also minimizing the amount of metal leached in the final products of representative important cross-coupling processes selected for proving the catalysts’ efficiency. The catalytic systems have been fully characterized and used in low amounts (0.1 mol %) in the Suzuki–Miyaura and Heck cross-couplings. Moreover, the protocols were optimized for the use of recoverable azeotropic mixtures (aq. EtOH 96% or aq. CH3CN 84%, respectively) and in the flow procedure allowing one to isolate the final pure products, without any purification step, with very low residual palladium content and with a very low waste production.
      PubDate: 2017-06-09
      DOI: 10.3390/catal7060186
      Issue No: Vol. 7, No. 6 (2017)
       
  • Catalysts, Vol. 7, Pages 187: Potential of Pervaporation and Vapor
           Separation with Water Selective Membranes for an Optimized Production of
           Biofuels—A Review

    • Authors: Catia Cannilla, Giuseppe Bonura, Francesco Frusteri
      First page: 187
      Abstract: The development of processes based on the integration of new technologies is of growing interest to industrial catalysis. Recently, significant efforts have been focused on the design of catalytic membrane reactors to improve process performance. In particular, the use of membranes, that allow a selective permeation of water from the reaction mixture, positively affects the reaction evolution by improving conversion for all reactions thermodynamically or kinetically limited by the presence of water. In this paper, how pervaporation (PV) and vapor permeation (VP) technologies can improve the catalytic performance of reactions of industrial interest is considered. Specifically, technological approaches proposed in the literature are discussed with the aim of highlighting advantages and problems encountered in order to address research towards the optimization of membrane reactor configurations for liquid biofuel production in large scale.
      PubDate: 2017-06-09
      DOI: 10.3390/catal7060187
      Issue No: Vol. 7, No. 6 (2017)
       
  • Catalysts, Vol. 7, Pages 188: Using Laccases in the Nanoflower to
           Synthesize Viniferin

    • Authors: Zhuofu Wu, Heng Li, XueJun Zhu, Shuai Li, Zhi Wang, Lei Wang, Zhengqiang Li, Guang Chen
      First page: 188
      Abstract: The laccase-incorporated nanoflower was fabricated and characterized by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). SEM images indicate that the laccase-incorporated nanoflower has a high surface area, which may facilitate the mass transfer of the substrate and the product. FTIR spectrums identify the existence of laccase in the nanoflowers. The novel immobilized laccase was used for the synthesis of viniferin. The reaction conditions had been optimized and the laccase-incorporated nanoflower can show its maximum specific activity (16.3 µmol/g/h) under the optimal reaction conditions. The specific activity of the laccase in the nanoflowers is enhanced about 2.2-fold compared with free laccase in solution without copper (II) ions. Furthermore, the laccase in the nanoflowers shows an increase in specific activity of ~180% compared with free laccase in a solution containing high concentrations (similar to the concentration in the flower) of copper (II) ions. The results also indicate that the laccase in the nanoflowers retain 93.2% of its initial specific activity even after ten continuous batches.
      PubDate: 2017-06-12
      DOI: 10.3390/catal7060188
      Issue No: Vol. 7, No. 6 (2017)
       
  • Catalysts, Vol. 7, Pages 189: Co3O4 Nanoparticle-Decorated N-Doped
           Mesoporous Carbon Nanofibers as an Efficient Catalyst for Oxygen Reduction
           Reaction

    • Authors: Hairong Xue, Tao Wang, Hao Gong, Hu Guo, Xiaoli Fan, Li Song, Wei Xia, Yaya Feng, Jianping He
      First page: 189
      Abstract: A low cost, durable, and efficient electrocatalyst for oxygen reduction reactions (ORR) is essential for high-performance fuel cells. Here, we fabricated Co3O4 nanoparticles (NPs) anchored on N-doped mesoporous carbon nanofibers (Co3O4/NMCF) by electrospinning combined with the simple heat treatment. Within this composite, carbon nanofibers possess a mesoporous structure, contributed to obtain a high surface area, which can facilitate the infiltration of electrolyte. Moreover, this one-dimensional (1D) carbon nanofiber also acts as a 1D conductive channel, effectively improving the transmission of electrons. In addition, the doping of the N element with high content combined with homogenously distributed Co3O4 NPs can significantly enhance the ORR electrocatalytic activity. Benefiting from the advantages of material and structure, the Co3O4/NMCF catalyst favors a four electron transfer process in alkaline media, exhibiting good ORR electrocatalytic activity, and its durability is much better than that of commercial Pt/C.
      PubDate: 2017-06-15
      DOI: 10.3390/catal7060189
      Issue No: Vol. 7, No. 6 (2017)
       
  • Catalysts, Vol. 7, Pages 190: Zirconium Phosphate Catalysts in the XXI
           Century: State of the Art from 2010 to Date

    • Authors: Monica Pica
      First page: 190
      Abstract: An overview on the developments of zirconium phosphate (ZrP) and its organic derivatives in heterogeneous catalysis in recent years is reported in the present review. Two basic aspects have been emphasized: first, the catalytic properties of zirconium phosphates were discussed, with particular attention to the effect of surface acidity and hydrophobic/hydrophilic character, textural properties, and particle morphology on the catalytic performances. Then, the use of zirconium phosphates as support for catalytic active species was reported, including organometallic complexes, metal ions, noble metal, and metal oxide nanoparticles. Zirconium phosphate plays, in those cases, a dual role, since it promotes the dispersion and stabilization of the catalysts, thanks to their interaction with the active sites on the surface of ZrP, and facilitates the recovery and reuse of the catalytic species due to their immobilization on the solid support.
      PubDate: 2017-06-19
      DOI: 10.3390/catal7060190
      Issue No: Vol. 7, No. 6 (2017)
       
  • Catalysts, Vol. 7, Pages 191: A Theoretical Insight into Enhanced
           Catalytic Activity of Au by Multiple Twin Nanoparticles

    • Authors: Kyoichi Sawabe, Taiki Koketsu, Junya Ohyama, Atsushi Satsuma
      First page: 191
      Abstract: Recently, it has been reported that the morphology of Au nanoparticles (NPs) affects the catalytic activity of CO oxidation; twin crystal NPs show higher activity for CO oxidation than single-crystal NPs. In this study, density functional calculations have been carried out to investigate the morphology effect of Au NPs using CO as a probe molecule. In the case of Au NPs with a size of more than 2 nm, CO adsorption energy on the Au NPs is mainly determined by a coordination number (CN) of adsorption sites. CO binding to a multiple twin NP with a size of about 1 nm is stronger than that on a single-crystal NP with the same size. A simple CN explanation cannot be applied to the enhancement of CO binding to the small multiple twin NP. This enhancement is related to a deformation of the NP structure before and after CO adsorption. It is suggested that the multiple twin NP with a size of less than 1 nm, which shows the deformation upon CO adsorption, contributes to the higher activity for CO oxidation.
      PubDate: 2017-06-19
      DOI: 10.3390/catal7060191
      Issue No: Vol. 7, No. 6 (2017)
       
  • Catalysts, Vol. 7, Pages 192: l-Amino Acid Production by a Immobilized
           Double-Racemase Hydantoinase Process: Improvement and Comparison with a
           Free Protein System

    • Authors: María Rodríguez-Alonso, Felipe Rodríguez-Vico, Francisco Las Heras-Vázquez, Josefa Clemente-Jiménez
      First page: 192
      Abstract: Protein immobilization is proving to be an environmentally friendly strategy for manufacturing biochemicals at high yields and low production costs. This work describes the optimization of the so-called “double-racemase hydantoinase process,” a system of four enzymes used to produce optically pure l-amino acids from a racemic mixture of hydantoins. The four proteins were immobilized separately, and, based on their specific activity, the optimal whole relation was determined. The first enzyme, d,l-hydantoinase, preferably hydrolyzes d-hydantoins from d,l-hydantoins to N-carbamoyl-d-amino acids. The remaining l-hydantoins are racemized by the second enzyme, hydantoin racemase, and continue supplying substrate d-hydantoins to the first enzyme. N-carbamoyl-d-amino acid is racemized in turn to N-carbamoyl-l-amino acid by the third enzyme, carbamoyl racemase. Finally, the N-carbamoyl-l-amino acid is transformed to l-amino acid by the fourth enzyme, l-carbamoylase. Therefore, the product of one enzyme is the substrate of another. Perfect coordination of the four activities is necessary to avoid the accumulation of reaction intermediates and to achieve an adequate rate for commercial purposes. The system has shown a broad pH optimum of 7–9, with a maximum activity at 8 and an optimal temperature of 60 °C. Comparison of the immobilized system with the free protein system showed that the reaction velocity increased for the production of norvaline, norleucine, ABA, and homophenylalanine, while it decreased for l-valine and remained unchanged for l-methionine.
      PubDate: 2017-06-20
      DOI: 10.3390/catal7060192
      Issue No: Vol. 7, No. 6 (2017)
       
  • Catalysts, Vol. 7, Pages 281: Hydroconversion of Waste Cooking Oil into
           Green Biofuel over Hierarchical USY-Supported NiMo Catalyst: A Comparative
           Study of Desilication and Dealumination

    • Authors: Zongwei Zhang, Qingfa Wang, Hao Chen, Xiangwen Zhang
      First page: 281
      Abstract: The hydroconversion of waste cooking oil into hydrocarbon fuel was investigated over the hierarchical USY zeolite-supported NiMo catalysts which were prepared by dealumination ((NH4)2SiF6)/desilication (NaOH). The physical and acidity properties of the hierarchical catalysts were characterized by X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET) infrared spectroscopy of adsorbed pyridine (Py-IR), ammonia temperature-programmed desorption (NH3-TPD), and H2 temperature-programmed reduction (H2-TPR). The Brønsted/Lewis (B/L) acid distribution was little affected by dealumination and the acid density decreased significantly. However, the highly-desilicated catalysts decreased the B/L ratio obviously. Therefore, many more Mo species in the NiMoO4− and MoO3 phases were produced in the AHFS-treated catalysts, while more high-valence-state Mo species in the NiMoO4− phase were formed in the NaOH-treated catalysts. The AHFS-treated catalysts showed higher catalytic activity and better DCO2 selectivity and selective cracking for jet fuel. The 42.3% selectivity of jet fuel and 13.5% selectivity of jet-range aromatics was achieved over the 8 wt % (NH4)2SiF6-treated catalyst with 67% DCO2 selectivity.
      Citation: Catalysts
      PubDate: 2017-09-22
      DOI: 10.3390/catal7100281
      Issue No: Vol. 7, No. 10 (2017)
       
  • Catalysts, Vol. 7, Pages 282: Active Site Mimicry of Glutathione
           Peroxidase by Glutathione Imprinted Selenium-Containing Trypsin

    • Authors: Yi Huang, Dan-Yang Ge, Hui Zong, Ju-Xin Yin, Xiao-Nan Qu, Shao-Wu Lv
      First page: 282
      Abstract: In order to overcome the instability of natural glutathione peroxidase (GPx), scientists endeavor to produce GPx mimics. The popular method first uses biological imprinting (BI) to produce the substrate binding sites and then employs chemical mutation (CM) to obtain the catalytic site. However, BICM has a drawback in that the catalytic site is not clear. Some researchers therefore tried to change the order of the method. These new GPx mimics were prepared by first producing the catalytic site through chemical mutation, and then employing biological imprinting to produce the substrate binding sites (CMBI). It has a clear catalytic site, but its determination of enzyme activity and kinetic analysis are still not elucidated. In this study, we used CMBI to synthesize a GPx mimic using trypsin as the imprinted molecule and GSSG as the template molecule and compared the enzyme activity of the four intermediates (Trypsin-SeO2H (TSeO2H), Trypsin-Se-SG (TSeSG), Imprinted Trypsin-Se-SG (ITSeSG), Cross-linked Imprinted Trypsin-Se-SG (CITSeSG), we analyzed the properties of intermediate products. All values are the means of at least four determinations, ITSeSG was produced from TSeSG through bio-imprinting, the activity of GPx mimics synthesized by CMBI was 5.7 times greater than native GPx, because of bio-imprinting make KmGSH value of the mimics decreased from 4.82 ± 0.27 mM (TSeSG) to 0.52 ± 0.05 mM (ITSeSG). This proves that bio-imprinting is the reason for increased substrate binding capability.
      Citation: Catalysts
      PubDate: 2017-09-22
      DOI: 10.3390/catal7100282
      Issue No: Vol. 7, No. 10 (2017)
       
  • Catalysts, Vol. 7, Pages 283: Reactive Magnetron Sputter Deposition of
           Bismuth Tungstate Coatings for Water Treatment Applications under Natural
           Sunlight

    • Authors: Marina Ratova, Rafaela Marcelino, Patterson de Souza, Camila Amorim, Peter Kelly
      First page: 283
      Abstract: Bismuth complex oxides, in particular, bismuth tungstate, have recently attracted attention as promising photocatalytic materials for water treatment processes. In the present work, photocatalytic bismuth tungstate films were prepared by pulsed direct current (DC) reactive magnetron sputtering of Bi and W targets in an Ar/O2 atmosphere onto spherically-shaped glass beads. The uniform coverage of the substrate was enabled by the use of oscillating bowl placed underneath the magnetrons. The atomic ratio of Bi/W was varied through the variation of the power applied to the magnetrons. The deposited coatings were analyzed by the scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy and atomic force microscopy. The photocatalytic properties of the films were studied via the methylene blue (MB) degradation process under artificial (fluorescent light) and natural (sunlight) irradiation, and compared to the photocatalytic performance of titanium dioxide coatings deposited onto identical substrates. The results showed that the photocatalytic performance of bismuth tungstate and bismuth oxide-coated beads was superior to that exhibited by TiO2-coated beads. Overall, reactive magnetron co-sputtering has been shown to be a promising technique for deposition of narrow band gap bismuth-based semiconducting oxides onto irregularly-shaped substrates for potential use in water treatment applications.
      Citation: Catalysts
      PubDate: 2017-09-23
      DOI: 10.3390/catal7100283
      Issue No: Vol. 7, No. 10 (2017)
       
 
 
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