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  Subjects -> CHEMISTRY (Total: 891 journals)
    - ANALYTICAL CHEMISTRY (55 journals)
    - CHEMISTRY (621 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (28 journals)
    - INORGANIC CHEMISTRY (45 journals)
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CHEMISTRY (621 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 14)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 43)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 21)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 26)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 41)
ACS Nano     Full-text available via subscription   (Followers: 274)
ACS Photonics     Full-text available via subscription   (Followers: 14)
ACS Symposium Series     Full-text available via subscription  
ACS Synthetic Biology     Full-text available via subscription   (Followers: 24)
Acta Chemica Iasi     Open Access   (Followers: 5)
Acta Chimica Slovaca     Open Access   (Followers: 2)
Acta Chimica Slovenica     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 7)
Acta Scientifica Naturalis     Open Access   (Followers: 3)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 6)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 9)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 6)
Advanced Functional Materials     Hybrid Journal   (Followers: 57)
Advanced Science Focus     Free   (Followers: 5)
Advances in Chemical Engineering and Science     Open Access   (Followers: 66)
Advances in Chemical Science     Open Access   (Followers: 18)
Advances in Chemistry     Open Access   (Followers: 21)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 19)
Advances in Drug Research     Full-text available via subscription   (Followers: 23)
Advances in Environmental Chemistry     Open Access   (Followers: 5)
Advances in Enzyme Research     Open Access   (Followers: 10)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 9)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 17)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 11)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 25)
Advances in Nanoparticles     Open Access   (Followers: 15)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 16)
Advances in Polymer Science     Hybrid Journal   (Followers: 43)
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: 6)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 3)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Al-Kimia : Jurnal Penelitian Sains Kimia     Open Access  
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 64)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 17)
American Journal of Chemistry     Open Access   (Followers: 30)
American Journal of Plant Physiology     Open Access   (Followers: 11)
American Mineralogist     Hybrid Journal   (Followers: 15)
Analyst     Full-text available via subscription   (Followers: 38)
Angewandte Chemie     Hybrid Journal   (Followers: 165)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 244)
Annales UMCS, Chemia     Open Access  
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 5)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 13)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal   (Followers: 2)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 9)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 31)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 2)
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  
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 350)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 10)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 2)
Biomacromolecules     Full-text available via subscription   (Followers: 21)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 7)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 5)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 128)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 84)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 2)
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: 2)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 6)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 71)
Catalysis for Sustainable Energy     Open Access   (Followers: 8)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 7)
Catalysis Science and Technology     Free   (Followers: 8)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 10)
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: 18)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 73)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 26)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 22)
Chemical Reviews     Full-text available via subscription   (Followers: 191)
Chemical Science     Open Access   (Followers: 24)
Chemical Technology     Open Access   (Followers: 24)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 56)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 24)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 7)
Chemistry & Biology     Full-text available via subscription   (Followers: 32)
Chemistry & Industry     Hybrid Journal   (Followers: 7)
Chemistry - A European Journal     Hybrid Journal   (Followers: 163)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 16)
Chemistry and Materials Research     Open Access   (Followers: 21)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 44)
Chemistry of Materials     Full-text available via subscription   (Followers: 254)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 19)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 1)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 4)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 14)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 11)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 11)
Chromatographia     Hybrid Journal   (Followers: 24)
Chromatography     Open Access   (Followers: 2)
Chromatography Research International     Open Access   (Followers: 6)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Cogent Chemistry     Open Access   (Followers: 1)
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 11)
Colloids and Interfaces     Open Access  
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 6)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 22)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Communications Chemistry     Open Access  
Composite Interfaces     Hybrid Journal   (Followers: 7)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 1)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 11)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 10)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 3)
Copernican Letters     Open Access   (Followers: 1)
Corrosion Series     Full-text available via subscription   (Followers: 6)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Croatica Chemica Acta     Open Access  
Crystal Structure Theory and Applications     Open Access   (Followers: 4)
CrystEngComm     Full-text available via subscription   (Followers: 13)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Chromatography     Hybrid Journal  
Current Green Chemistry     Hybrid Journal  
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Microwave Chemistry     Hybrid Journal  
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 14)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 69)
Current Trends in Biotechnology and Chemical Research     Open Access   (Followers: 3)
Dalton Transactions     Full-text available via subscription   (Followers: 23)
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  

        1 2 3 4 | Last

Journal Cover
Catalysts
Number of Followers: 10  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2073-4344
Published by MDPI Homepage  [202 journals]
  • Catalysts, Vol. 8, Pages 254: Recent Advances in ω-Transaminase-Mediated
           Biocatalysis for the Enantioselective Synthesis of Chiral Amines

    • Authors: Mahesh D. Patil, Gideon Grogan, Andreas Bommarius, Hyungdon Yun
      First page: 254
      Abstract: Chiral amines are important components of 40–45% of small molecule pharmaceuticals and many other industrially important fine chemicals and agrochemicals. Recent advances in synthetic applications of ω-transaminases for the production of chiral amines are reviewed herein. Although a new pool of potential ω-transaminases is being continuously screened and characterized from various microbial strains, their industrial application is limited by factors such as disfavored reaction equilibrium, poor substrate scope, and product inhibition. We present a closer look at recent developments in overcoming these challenges by various reaction engineering approaches. Furthermore, protein engineering techniques, which play a crucial role in improving the substrate scope of these biocatalysts and their operational stability, are also presented. Last, the incorporation of ω-transaminases in multi-enzymatic cascades, which significantly improves their synthetic applicability in the synthesis of complex chemical compounds, is detailed. This analysis of recent advances shows that ω-transaminases will continue to provide an efficient alternative to conventional catalysis for the synthesis of enantiomerically pure amines.
      Citation: Catalysts
      PubDate: 2018-06-21
      DOI: 10.3390/catal8070254
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 222: Degradation and Loss of Antibacterial
           Activity of Commercial Amoxicillin with TiO2/WO3-Assisted Solar
           Photocatalysis

    • Authors: Augusto Arce-Sarria, Fiderman Machuca-Martínez, Ciro Bustillo-Lecompte, Aracely Hernández-Ramírez, José Colina-Márquez
      First page: 222
      Abstract: In this study, a TiO2 catalyst, modified with tungsten oxide (WO3), was synthesized to reduce its bandgap energy (Eg) and to improve its photocatalytic performance. For the catalyst evaluation, the effect of the calcination temperature on the solar photocatalytic degradation was analyzed. The experimental runs were carried out in a CPC (compound parabolic collector) pilot-scale solar reactor, following a multilevel factorial experimental design, which allowed analysis of the effect of the calcination temperature, the initial concentration of amoxicillin, and the catalyst load on the amoxicillin removal. The most favorable calcination temperature for the catalyst performance, concerning the removal of amoxicillin, was 700 °C; because it was the only sample that showed the rutile phase in its crystalline structure. Regarding the loss of the antibiotic activity, the inhibition tests showed that the treated solution of amoxicillin exhibited lower antibacterial activity. The highest amoxicillin removal achieved in these experiments was 64.4% with 100 ppm of amoxicillin concentration, 700 °C of calcination temperature, and 0.1 g L−1 of catalyst load. Nonetheless, the modified TiO2/WO3 underperformed compared to the commercial TiO2 P25, due to its low specific surface and the particles sintering during the sol-gel synthesis.
      Citation: Catalysts
      PubDate: 2018-05-23
      DOI: 10.3390/catal8060222
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 223: Dioxygen Activation by Laccases: Green
           Chemistry for Fine Chemical Synthesis

    • Authors: Cynthia Romero-Guido, Antonino Baez, Eduardo Torres
      First page: 223
      Abstract: Laccases are enzymes with attractive features for the synthesis of fine chemicals. The friendly reaction conditions of laccases and their high conversion and selectivity make them particularly suitable for green methods of synthesis. In addition, laccases are enzymes with broad substrate variability, ease of production, and no need of cofactors or aggressive oxidizing agents. Among molecules oxidized by laccases are polycyclic aromatic hydrocarbons, azo dyes, pesticides, phenols, and pharmaceuticals. This article reviews the laccase-mediated oxidation of fine chemicals for the production of biologically active compounds. The main aspects of the enzymatic oxidation are summarized; potentials and limitations are identified and proposals to develop more robust catalysts are analyzed.
      Citation: Catalysts
      PubDate: 2018-05-24
      DOI: 10.3390/catal8060223
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 224: Exploring Basic Components Effect on the
           Catalytic Efficiency of Chevron-Phillips Catalyst in Ethylene
           Trimerization

    • Authors: Ebtehal Naji-Rad, Martí Gimferrer, Naeimeh Bahri-Laleh, Mehdi Nekoomanesh-Haghighi, Roghieh Jamjah, Albert Poater
      First page: 224
      Abstract: In the present work, the effect of basic components on the energy pathway of ethylene oligomerization using the landmark Chevron-Phillips catalyst has been explored in detail, using density functional theory (DFT). Studied factors were chosen considering the main components of the Chevron-Phillips catalyst, i.e., ligand, cocatalyst, and halocarbon compounds, comprising (i) the type of alkyl substituents in pyrrole ligand, i.e., methyl, iso-propyl, tert-butyl, and phenyl, as well as the simple hydrogen and the electron withdrawing fluoro and trifluoromethyl; (ii) the number of Cl atoms in Al compounds (as AlMe2Cl, AlMeCl2 and AlCl3), which indicate the halocarbon level, and (iii) cocatalyst type, i.e., alkylboron, alkylaluminium, or alkylgallium. Besides the main ingredients, the solvent effect (using toluene or methylcyclohexane) on the oligomerization pathway was also explored. In this regard, the full catalytic cycles for the main product (1-hexene) formation, as well as side reactions, i.e., 1-butene release and chromacyclononane formation, were calculated on the basis of the metallacycle-based mechanism. According to the obtained results, a modification on the Chevron-Phillips catalyst system, which demonstrates higher 1-hexene selectivity and activity, is suggested.
      Citation: Catalysts
      PubDate: 2018-05-24
      DOI: 10.3390/catal8060224
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 225: Electrocatalytic Performance of Carbon
           Supported WO3-Containing Pd–W Nanoalloys for Oxygen Reduction Reaction
           in Alkaline Media

    • Authors: Nan Cui, Wenpeng Li, Zengfeng Guo, Xun Xu, Hongxia Zhao
      First page: 225
      Abstract: In this paper, we report that WOx containing nanoalloys exhibit stable electrocatalytic performance in alkaline media, though bulk WO3 is easy to dissolve in NaOH solution. Carbon supported oxide-rich Pd–W alloy nanoparticles (PdW/C) with different Pd:W atom ratios were prepared by the reduction–oxidation method. Among the catalysts, the oxide-rich Pd0.8W0.2/C (Pd/W = 8:2, atom ratio) exhibits the highest catalytic activity for the oxygen reduction reaction. The X-ray photoelectron spectroscopy data shows that ~40% of Pd atoms and ~60% of the W atoms are in their oxide form. The Pd 3d5/2 binding energy of the oxide-rich Pd–W nanoalloys is higher than that of Pd/C, indicating the electronic structure of Pd is affected by the strong interaction between Pd and W/WO3. Compare to Pd/C, the onset potential of the oxygen reduction reaction at the oxide-rich Pd0.8W0.2/C shifts to a higher potential. The current density (mA·mg Pd−1) at the oxide-rich Pd0.8W0.2/C is ~1.6 times of that at Pd/C. The oxide-rich Pd0.8W0.2/C also exhibits higher catalytic stability than Pd/C, which demonstrates that it is a prospective candidate for the cathode of fuel cells operating with alkaline electrolyte.
      Citation: Catalysts
      PubDate: 2018-05-24
      DOI: 10.3390/catal8060225
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 226: Molecular Orientations Change Reaction
           Kinetics and Mechanism: A Review on Catalytic Alcohol Oxidation in Gas
           Phase and Liquid Phase on Size-Controlled Pt Nanoparticles

    • Authors: Fudong Liu, Hailiang Wang, Andras Sapi, Hironori Tatsumi, Danylo Zherebetskyy, Hui-Ling Han, Lindsay M. Carl, Gabor A. Somorjai
      First page: 226
      Abstract: Catalytic oxidation of alcohols is an essential process for energy conversion, production of fine chemicals and pharmaceutical intermediates. Although it has been broadly utilized in industry, the basic understanding for catalytic alcohol oxidations at a molecular level, especially under both gas and liquid phases, is still lacking. In this paper, we systematically summarized our work on catalytic alcohol oxidation over size-controlled Pt nanoparticles. The studied alcohols included methanol, ethanol, 1-propanol, 2-propanol, and 2-butanol. The turnover rates of different alcohols on Pt nanoparticles and also the apparent activation energy in gas and liquid phase reactions were compared. The Pt nanoparticle size dependence of reaction rates and product selectivity was also carefully examined. Water showed very distinct effects for gas and liquid phase alcohol oxidations, either as an inhibitor or as a promoter depending on alcohol type and reaction phase. A deep understanding of different alcohol molecular orientations on Pt surface in gas and liquid phase reactions was established using sum-frequency generation spectroscopy analysis for in situ alcohol oxidations, as well as density functional theory calculation. This approach can not only explain the entirely different behaviors of alcohol oxidations in gas and liquid phases, but can also provide guidance for future catalyst/process design.
      Citation: Catalysts
      PubDate: 2018-05-27
      DOI: 10.3390/catal8060226
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 227: Photocatalytic Behavior of Strontium
           Aluminates Co-Doped with Europium and Dysprosium Synthesized by
           Hydrothermal Reaction in Degradation of Methylene Blue

    • Authors: Byung-Geon Park
      First page: 227
      Abstract: Strontium aluminates co-doped with europium and dysprosium were prepared by a hydrothermal reaction through a sintering process at lower temperatures. The physicochemical properties of the strontium aluminates co-doped with europium and dysprosium were characterized and compared with those of strontium aluminates prepared by a sol–gel method. The photocatalytic properties of the strontium aluminates co-doped with europium and dysprosium were evaluated through the photocatalytic decomposition of methylene blue dye. The strontium aluminates co-doped with europium and dysprosium prepared by the hydrothermal reaction exhibited good phosphorescence and photocatalytic activities that were similar to those prepared by the sol–gel method. The photocatalytic activity of these catalysts for methylene blue degradation was higher than that of the titanium dioxide (TiO2) photocatalyst.
      Citation: Catalysts
      PubDate: 2018-05-28
      DOI: 10.3390/catal8060227
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 228: On the Impact of the Preparation Method on
           the Surface Basicity of Mg–Zr Mixed Oxide Catalysts for Tributyrin
           Transesterification

    • Authors: Abdallah I. M. Rabee, Jinesh C. Manayil, Mark A. Isaacs, Christopher M. A. Parlett, Lee J. Durndell, Mohamed I. Zaki, Adam F. Lee, Karen Wilson
      First page: 228
      Abstract: Mixed metal oxides are promising heterogeneous catalysts for biofuel production from lipids via alcoholysis, however, the impact of solid acidity and/or basicity on reactivity is comparatively poorly understood. Two systematically related families of MgO–ZrO2 mixed oxide catalysts were therefore prepared by different synthetic routes to elucidate the impact of surface acid-base properties on catalytic performance in the transesterification of tributyrin with methanol. The resulting materials were characterized by TGA-MS, ICP-OES, N2 porosimetry, XRD, TEM, XPS, DRIFTS, and CO2-temperature-programmed desorption (TPD). MgO–ZrO2 catalysts prepared by both non-aqueous impregnation and citric acid-mediated sol–gel routes exhibit excellent activity and stability. The citrate routes favor highly dispersed MgO and concomitant Lewis acid-base pair formation at the interface with zirconia. However, for both the citrate and impregnation routes, tributyrin transesterification occurs over a common, strongly basic MgO active site.
      Citation: Catalysts
      PubDate: 2018-05-28
      DOI: 10.3390/catal8060228
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 229: Gallium-Promoted Ni Catalyst Supported on
           MCM-41 for Dry Reforming of Methane

    • Authors: Ahmed S. Al-Fatesh, Ahmed A. Ibrahim, Jehad K. Abu-Dahrieh, Abdulrahman S. Al-Awadi, Ahmed Mohamed El-Toni, Anis H. Fakeeha, Ahmed E. Abasaeed
      First page: 229
      Abstract: The stability and catalytic activity of mesoporous Ni/MCM-41 promoted with a Ga loading of (0.0, 1.0, 1.5, 2.0, 2.5, and 3.0 wt %) as an innovative catalyst was examined for syngas production via CO2 reforming of CH4. The objective of present work was to develop a potential catalyst for CO2 reforming of methane. For this purpose different loadings of gallium were used to promote 5% nickel catalyst supported on MCM-41. An incipient wetness impregnation method was used for preparing the catalysts and investigated at 800 °C. Physicochemical characterization techniques—including BET, XRD, TPD, TPR, TEM, and TGA—were used to characterize the catalysts. The addition of small amounts of Ga resulted in higher surface areas with a maximum surface area of 1036 m2/g for 2.5% Ga. The incorporation of Ga to the catalyst decreased the medium and strong basic sites and reduced the amount of carbon deposited. There was no weight loss for 3%Ga+5%Ni/MCM-41. The 2% Ga loading showed the highest CH4 conversion of 88.2% and optimum stability, with an activity loss of only 1.58%. The Ga promoter raised the H2/CO ratio from 0.9 to unity.
      Citation: Catalysts
      PubDate: 2018-06-01
      DOI: 10.3390/catal8060229
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 230: MgO-Templated Mesoporous Carbon as a
           Catalyst Support for Polymer Electrolyte Fuel Cells

    • Authors: Yuji Kamitaka, Tomohiro Takeshita, Yu Morimoto
      First page: 230
      Abstract: An MgO-templated mesoporous carbon, CNovel®, was employed as a catalyst support for the cathode of polymer electrolyte fuel cells (PEFCs) after modifying its dimensional, crystalline, surface and porous structures and the electrochemical oxygen reduction reaction (ORR) activities were examined by the thin-film rotating disk electrode (RDE) method and as well as the membrane electrode assembly (MEA) method. Although the catalytic activity of Pt on CNovel® was comparable with that on a non-porous carbon, Vulcan®, in the RDE configuration without Nafion®, Pt/CNovel showed a considerably higher activity than Pt/Vulcan in the MEA condition with Nafion®. The mechanism inducing this difference was discussed from the results of electrochemical surface area and sulfonic coverage measurements which suggested that Pt particles on inside pores of CNovel® are not covered with Nafion® ionomer while protons can still reach those Pt particles through water network. The MEA performance in the middle and high current-density regions was drastically improved by heat-treatment in air, which modified the pore structure to through-pored ones.
      Citation: Catalysts
      PubDate: 2018-06-01
      DOI: 10.3390/catal8060230
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 231: Ammonia Concentration Distribution
           Measurements on Selective Catalytic Reduction Catalysts

    • Authors: Rafal Sala, Jakub Dzida, Jaroslaw Krasowski
      First page: 231
      Abstract: This work presents the methodology and accurate evaluation of ammonia concentration distribution measurements at the selective catalytic reduction (SCR) catalyst outlet cross-section. The uniformity of ammonia concentration is a crucial factor influencing overall SCR effectiveness, and it contributes to the necessity of employing a reliable test method. The aftertreatment system design (mainly its geometrical features) can be evaluated in detail. The ammonia concentration is measured at the SCR catalyst outlet at grid points covering from the center to the outer edges of the catalyst. Its execution requires the introduction of a probe hovering over the back face of the SCR. To obtain the expected accuracy, it is necessary to measure a sufficient number of points in a reasonable timeframe. In order to achieve that, a fully automatic sampling device was developed. Sample results are presented showing the capabilities of the created test stand and its importance for the design development and validation stages of SCR-based engine aftertreatment.
      Citation: Catalysts
      PubDate: 2018-06-01
      DOI: 10.3390/catal8060231
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 232: Nitrogen-Doped Porous Carbon Derived from
           Bamboo Shoot as Solid Base Catalyst for Knoevenagel Condensation and
           Transesterification Reactions

    • Authors: Bingbing Mi, Xiufang Chen, Changle Jiang, Jingxin Wang, Xiujuan Chen, Bo Zhang, Xianmiao Liu, Zhijia Liu, Benhua Fei
      First page: 232
      Abstract: Highly porous nitrogen-doped carbons derived from bamboo shoots (BSNCs) were prepared through an in-situ synthesis method. The results showed that BSNCs had a large specific surface area, a relatively high nitrogen content and hierarchically porous structures. The catalytic properties of BSNCs were evaluated based on Knoevenagel condensation and transesterification reactions. Deprotonated BSNC-700 exhibited high efficiency for the model reactions as a solid base catalyst, and the superior sample deprotonated in tBuOK solution with a concentration of 0.1 increased the conversion rate from 16.1% to 76.0% for Knoevenagel condensation. The two reactions proceeded smoothly in the presence of deprotonated BSNC-700. The results also showed that the catalyst could be recycled for several times for Knoevenagel condensation. The results from this research will provide a guideline to develop bamboo shoot as a precursor to fabricate a superb solid base catalyst.
      Citation: Catalysts
      PubDate: 2018-06-04
      DOI: 10.3390/catal8060232
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 233: Electrochemical Biosensor for the
           Determination of Amlodipine Besylate Based on Gelatin–Polyaniline Iron
           Oxide Biocomposite Film

    • Authors: Elbahi Djaalab, Mohamed El Hadi SAMAR, Saida Zougar, Rochdi Kherrat
      First page: 233
      Abstract: In the present study, a new biosensor based on lipase from Candida rugosa (CRL) was developed for amlodipine besylate drug (AMD) with biodegradable material using a mixture of polyaniline iron oxide and gelatin. Polyaniline/Fe2O3 (PANI@Fe2O3) was prepared by a chemical polymerization method in a medium of ammonium persulfate as an oxidant and characterized by employing Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR), and Ultra-violet (UV) spectroscopy. The purified enzyme was entrapped in the biocomposite matrix film with the aid of a glutaraldehyde cross-linking reagent to establish the immobilization of the lipase. The principle of the biosensor is based on the electrochemical properties of amlodipine besylate (AMD), which were studied for the first time using the cyclic voltammetric method. The cathodic behavior of AMD was measured on the irreversible reduction signal at −0.185 V versus Ag/AgCl at pH 7.4 and 30 °C in a phosphate alkaline buffer.
      Citation: Catalysts
      PubDate: 2018-06-04
      DOI: 10.3390/catal8060233
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 234: Immobilization of an Antarctic Pseudomonas
           AMS8 Lipase for Low Temperature Ethyl Hexanoate Synthesis

    • Authors: Nurshakila Musa, Wahhida Latip, Raja Noor Zaliha Abd Rahman, Abu Bakar Salleh, Mohd Shukuri Mohamad Ali
      First page: 234
      Abstract: The demand for synthetic flavor ester is high, especially in the food, beverage, and cosmetic and pharmaceutical industries. It is derived from the reaction between a short-chain fatty acid and alcohol. Lipases from Antarctic bacteria have gained huge interest in the industry due to its ability react at low temperatures. The use of immobilization enzymes is one of the methods that can improve the stability of the enzyme. The current work encompasses the low temperature enzymatic synthesis of ethyl hexanoate by direct esterification of ethanol with hexanoic acid in a toluene and solvent-free system. The effects of various reaction parameters such as the organic solvent, temperature, time, substrate, substrate ratio and concentration, enzyme concentration on ethyl hexanoate synthesis were tested. Several matrices were used for immobilization and comparisons of the efficiency of immobilized enzyme with free enzyme in the synthesis of flavor ester were conducted. Ester production was optimally synthesized at 20 °C in both systems— immobilized and free enzyme. A 69% ester conversion rate was achieved after a two-hour incubation in toluene, compared to 47% in a solvent-free system for free enzyme. Immobilized AMS8 lipase showed a higher conversion of ester in toluene with respect to free-solvents, from 80% to 59%, respectively. Immobilized enzymes showed enhancement to the stability of the enzyme in the presence of the organic solvent. The development of AMS8 lipase as an immobilized biocatalyst demonstrates great potential as a cost-effective enzyme for biocatalysis and biotransformation in the food industry.
      Citation: Catalysts
      PubDate: 2018-06-04
      DOI: 10.3390/catal8060234
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 235: Prickly Pear-Like Three-Dimensional Porous
           MoS2: Synthesis, Characterization and Advanced Hydrogen Evolution Reaction
           

    • Authors: Huiting Lu, Xin Chen, Wenhao Dai, Kai Zhang, Conghui Liu, Haifeng Dong
      First page: 235
      Abstract: Herein, we hydrothermally synthesize a type of prickly pear-like three-dimensional (3D) porous MoS2 (ZT-MoS2), using a zinc oxide (ZnO) rod deposited on quartz glass substrates, as a template for an advanced hydrogen evolution reaction (HER) catalyst. Microscopic and spectroscopic tools comprehensively characterize the morphology of the ZT-MoS2 nanostructure, which exhibits adequate edge active sites and defects, as well as a high component of active octahedral MoS2 (1T-MoS2). Electrochemical characterizations reveal the good HER performance of the ZT-MoS2 that presents a good overpotential of 110 mV, and a Tafel slope of 63 mV·dec−1, superior to most of the previously reported MoS2-based HER catalysts. This work contributes to the design and fabrication of 3D MoS2 with enhanced HER performance, which holds great promise for fuel cells and energy conversion.
      Citation: Catalysts
      PubDate: 2018-06-04
      DOI: 10.3390/catal8060235
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 236: Studied Localized Surface Plasmon Resonance
           Effects of Au Nanoparticles on TiO2 by FDTD Simulations

    • Authors: Guo-Ying Yao, Qing-Lu Liu, Zong-Yan Zhao
      First page: 236
      Abstract: Localized surface plasmon resonance (LSPR) plays a significant role in the fields of photocatalysis and solar cells. It can not only broaden the spectral response range of materials, but also improve the separation probability of photo-generated electron-hole pairs through local field enhancement or hot electron injection. In this article, the LSPR effects of Au/TiO2 composite photocatalyst, with different sizes and shapes, have been simulated by the finite difference time domain (FDTD) method. The variation tendency of the resonance-absorption peaks and the intensity of enhanced local enhanced electric field were systematically compared and emphasized. When the location of Au nanosphere is gradually immersed into the TiO2 substrate, the local enhanced electric field of the boundary is gradually enhanced. When Au nanoshperes are covered by TiO2 at 100 nm depths, the local enhanced electric field intensities reach the maximum value. However, when Au nanorods are loaded on the surface of the TiO2 substrate, the intensity of the corresponding enhanced local enhanced electric field is the maximum. Au nanospheres produce two strong absorption peaks in the visible light region, which are induced by the LSPR effect and interband transitions between Au nanoparticles and the TiO2 substrate. For the LSPR resonance-absorption peaks, the corresponding position is red-shifted by about 100 nm, as the location of Au nanospheres are gradually immersed into the TiO2 substrate. On the other hand, the size change of the Au nanorods do not lead to a similar variation of the LSPR resonance-absorption peaks, except to change the length-diameter ratio. Meanwhile, the LSPR effects are obviously interfered with by the interband transitions between the Au nanorods and TiO2 substrate. At the end of this article, three photo-generated carrier separation mechanisms are proposed. Among them, the existence of direct electron transfer between Au nanoparticles and the TiO2 substrate leads to the enhanced local enhanced electric field at the boundaries, which is favorable for the improvement of photocatalytic performance of TiO2. These findings could explain the underlying mechanism of some experimental observations in published experimental works, and helpful to design highly efficient composite photocatalysts that contain noble metal co-catalyst nanoparticles.
      Citation: Catalysts
      PubDate: 2018-06-05
      DOI: 10.3390/catal8060236
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 237: Electrochemically Obtained TiO2/CuxOy
           Nanotube Arrays Presenting a Photocatalytic Response in Processes of
           Pollutants Degradation and Bacteria Inactivation in Aqueous Phase

    • Authors: Magda Kozak, Paweł Mazierski, Joanna Żebrowska, Marek Kobylański, Tomasz Klimczuk, Wojciech Lisowski, Grzegorz Trykowski, Grzegorz Nowaczyk, Adriana Zaleska-Medynska
      First page: 237
      Abstract: TiO2/CuxOy nanotube (NT) arrays were synthesized using the anodization method in the presence of ethylene glycol and different parameters applied. The presence, morphology, and chemical character of the obtained structures was characterized using a variety of methods—SEM (scanning electron microscopy), XPS (X-ray photoelectron spectroscopy), XRD (X-ray crystallography), PL (photoluminescence), and EDX (energy-dispersive X-ray spectroscopy). A p-n mixed oxide heterojunction of Ti-Cu was created with a proved response to the visible light range and the stable form that were in contact with Ti. TiO2/CuxOy NTs presented the appearance of both Cu2O (mainly) and CuO components influencing the dimensions of the NTs (1.1–1.3 µm). Additionally, changes in voltage have been proven to affect the NTs’ length, which reached a value of 3.5 µm for Ti90Cu10_50V. Degradation of phenol in the aqueous phase was observed in 16% of Ti85Cu15_30V after 1 h of visible light irradiation (λ > 420 nm). Scavenger tests for phenol degradation process in presence of NT samples exposed the responsibility of superoxide radicals for degradation of organic compounds in Vis light region. Inactivation of bacteria strains Escherichia coli (E. coli), Bacillus subtilis (B. subtilis), and Clostridium sp. in presence of obtained TiO2/CuxOy NT photocatalysts, and Vis light has been studied showing a great improvement in inactivation efficiency with a response rate of 97% inactivation for E. coli and 98% for Clostridium sp. in 60 min. Evidently, TEM (transmission electron microscopy) images confirmed the bacteria cells’ damage.
      Citation: Catalysts
      PubDate: 2018-06-05
      DOI: 10.3390/catal8060237
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 238: Industrial Applications of Enzymes: Recent
           Advances, Techniques, and Outlooks

    • Authors: Jordan Chapman, Ahmed E. Ismail, Cerasela Zoica Dinu
      First page: 238
      Abstract: Enzymes as industrial biocatalysts offer numerous advantages over traditional chemical processes with respect to sustainability and process efficiency. Enzyme catalysis has been scaled up for commercial processes in the pharmaceutical, food and beverage industries, although further enhancements in stability and biocatalyst functionality are required for optimal biocatalytic processes in the energy sector for biofuel production and in natural gas conversion. The technical barriers associated with the implementation of immobilized enzymes suggest that a multidisciplinary approach is necessary for the development of immobilized biocatalysts applicable in such industrial-scale processes. Specifically, the overlap of technical expertise in enzyme immobilization, protein and process engineering will define the next generation of immobilized biocatalysts and the successful scale-up of their induced processes. This review discusses how biocatalysis has been successfully deployed, how enzyme immobilization can improve industrial processes, as well as focuses on the analysis tools critical for the multi-scale implementation of enzyme immobilization for increased product yield at maximum market profitability and minimum logistical burden on the environment and user.
      Citation: Catalysts
      PubDate: 2018-06-05
      DOI: 10.3390/catal8060238
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 239: A Novel High-Activity Zn-Co Catalyst for
           Acetylene Acetoxylation

    • Authors: Peijie He, Liuhua Huang, Xueyi Wu, Zhuang Xu, Mingyuan Zhu, Xugen Wang, Bin Dai
      First page: 239
      Abstract: In this paper, Zn(OAc)2/AC and Zn-Co/AC catalysts were prepared and applied in an acetylene acetoxylation reaction. Compared with monometallic Zn(OAc)2/AC catalyst, which is widely applied in industry, the Zn-Co catalysts exhibited excellent catalytic performance. Transmission electron microscopy results displayed that the addition of cobalt improved the dispersity of zinc acetate particles and inhibited catalyst sintering on the catalyst surface. X-ray photoelectron spectra suggested that the Co additive changed the electron density of zinc acetate probably because of the interaction between Zn and Co species. Temperature programmed desorption analysis demonstrated Co additive strengthened the adsorption of acetic acid and weakened the adsorption of acetylene.
      Citation: Catalysts
      PubDate: 2018-06-06
      DOI: 10.3390/catal8060239
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 240: Synergistic Effect of Cu2O and Urea as
           Modifiers of TiO2 for Enhanced Visible Light Activity

    • Authors: Marcin Janczarek, Kunlei Wang, Ewa Kowalska
      First page: 240
      Abstract: Low cost compounds, i.e., Cu2O and urea, were used as TiO2 modifiers to introduce visible light activity. Simple and cheap methods were applied to synthesize an efficient and stable nanocomposite photocatalytic material. First, the core-shell structure TiO2–polytriazine derivatives were prepared. Thereafter, Cu2O was added as the second semiconductor to form a dual heterojunction system. Enhanced visible light activity was found for the above-mentioned nanocomposite, confirming a synergistic effect of Cu2O and urea (via polytriazine derivatives on titania surface). Two possible mechanisms of visible light activity of the considered material were proposed regarding the type II heterojunction and Z-scheme through the essential improvement of the charge separation effect.
      Citation: Catalysts
      PubDate: 2018-06-06
      DOI: 10.3390/catal8060240
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 241: The Promoting Effect of Ce on the
           Performance of Au/CexZr1−xO2 for γ-Valerolactone Production from
           Biomass-Based Levulinic Acid and Formic Acid

    • Authors: Xiaoling Li, Jianmei Li, Xudong Liu, Qi Tian, Changwei Hu
      First page: 241
      Abstract: The production of γ-valerolactone (GVL) directly from biomass-based levulinic acid (LA) and formic acid (FA) without extra hydrogen source is attractive but challenging, due to the requirement of a highly active and stable catalyst. In present work, Au/CexZr1−xO2 with various Ce/Zr ratios were prepared as the catalyst for GVL production from LA with the equivalent molar FA, and characterized by XRD, Raman-spectra, BET, NH3-TPD, TEM and XPS. It was found that the doped Ce in Au/CexZr1−xO2 catalyst could improve the reduction of Au3+ to metallic Au0, and also promoted the dispersion of Au0, yielding uniform Au0 nanoparticles with a small average particle size of about 2.4 nm, thus enhancing both the decomposition of FA to CO-free H2 and the hydrogenation of LA. Meanwhile, a certain amount of doped Ce (x ≤ 0.4) could facilitate the formation of tetragonal phase (the most desired structure on LA conversion to GVL), and increase the amount of weak and medium-strength acidic sites of catalyst, thereby promoting the dehydration reaction of the intermediate derived from LA hydrogenation. Au/Ce0.4Zr0.6O2 catalyst exhibited the best catalytic activity, achieving 90.8% of LA conversion and 83.5% of GVL yield (TON = 2047.8), with good recyclability, and the activity showed no obvious change after 5 runs.
      Citation: Catalysts
      PubDate: 2018-06-07
      DOI: 10.3390/catal8060241
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 242: The Synthetic Potential of Fungal Feruloyl
           Esterases: A Correlation with Current Classification Systems and Predicted
           Structural Properties

    • Authors: Io Antonopoulou, Adiphol Dilokpimol, Laura Iancu, Miia R. Mäkelä, Simona Varriale, Gabriella Cerullo, Silvia Hüttner, Stefan Uthoff, Peter Jütten, Alexander Piechot, Alexander Steinbüchel, Lisbeth Olsson, Vincenza Faraco, Kristiina S. Hildén, Ronald P. de Vries, Ulrika Rova, Paul Christakopoulos
      First page: 242
      Abstract: Twenty-eight fungal feruloyl esterases (FAEs) were evaluated for their synthetic abilities in a ternary system of n-hexane: t-butanol: 100 mM MOPS-NaOH pH 6.0 forming detergentless microemulsions. Five main derivatives were synthesized, namely prenyl ferulate, prenyl caffeate, butyl ferulate, glyceryl ferulate, and l-arabinose ferulate, offering, in general, higher yields when more hydrophilic alcohol substitutions were used. Acetyl xylan esterase-related FAEs belonging to phylogenetic subfamilies (SF) 5 and 6 showed increased synthetic yields among tested enzymes. In particular, it was shown that FAEs belonging to SF6 generally transesterified aliphatic alcohols more efficiently while SF5 members preferred bulkier l-arabinose. Predicted surface properties and structural characteristics were correlated with the synthetic potential of selected tannase-related, acetyl-xylan-related, and lipase-related FAEs (SF1-2, -6, -7 members) based on homology modeling and small molecular docking simulations.
      Citation: Catalysts
      PubDate: 2018-06-07
      DOI: 10.3390/catal8060242
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 243: An Iron-Based Catalyst with Multiple Active
           Components Synergetically Improved Electrochemical Performance for Oxygen
           Reduction Reaction

    • Authors: Jian Zhang, Xiaoming Song, Ping Li, Shuai Wang, Zexing Wu, Xien Liu
      First page: 243
      Abstract: Lack of highly active and stable non-precious metal catalysts (NPMCs) as an alternative to Pt for oxygen reduction reaction (ORR) in the application of zinc-air batteries and proton-exchange membrane fuel cells (PEMFCs) significantly hinders the commercialization of these energy devices. Herein, we synthesize a new type of catalyst composed of nitrogen-coordinated and carbon-embedded metal (Fe-N/Fe3C/Fe/C) by pyrolyzing a precursor at 800 °C under argon atmosphere, and the precursor is obtained by heating a mixture of the tri (dipyrido [3,2-a:2′,3′-c] phenazinyl) phenylene and FeSO4 at 160 °C in a Teflon-lined stainless autoclave. The resultant Fe-N/Fe3C/Fe/C-800 exhibits the highest activity for the ORR with onset and half-wave potentials of 1.00 and 0.82 V in 0.1 M KOH, respectively. Furthermore, it also shows a potential ORR activity in 0.1 M HClO4, which is promising for the application in commercial PEMFCs. Most importantly, Fe-N/Fe3C/Fe/C-800 exhibits a comparable electrochemical performance to Pt/C for the application in zinc-air battery. The specific capacity approaches 700 mAh·g−1, and the maximum power density is also comparable to that of Pt/C at the current density of 200 mA·cm−2. The work opens up a simple strategy to prepare ORR electrocatalyts for zinc-air battery and PEMFCs.
      Citation: Catalysts
      PubDate: 2018-06-07
      DOI: 10.3390/catal8060243
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 244: Theoretical Study of the Mechanism for CO2
           Hydrogenation to Methanol Catalyzed by trans-RuH2(CO)(dpa)

    • Authors: Jinxia Zhou, Liangliang Huang, Wei Yan, Jun Li, Chang Liu, Xiaohua Lu
      First page: 244
      Abstract: In this work, the reaction mechanism for the conversion of CO2 and H2 to methanol has been researched by density functional theory (DFT). The production of methanol from CO2 and H2 is catalyzed by a univocal bifunctional pincer-type complex trans-RuH2(CO)(dpa) (dpa = bis-(2-diphenylphosphinoethyl)amine). The reaction mechanism includes three continuous catalytic processes: (1) CO2 is converted to formic acid; (2) formic acid is converted to formaldehyde and water; (3) formaldehyde is converted to methanol. By computing the catalytic processes, we have shown that the rate-limiting step in the whole process is the direct cleavage of H2. The calculated largest free energy barrier is 21.6 kcal/mol. However, with the help of water, the free energy barrier can be lowered to 12.7 kcal/mol, which suggests viability of trans-RuH2(CO)(dpa) as a catalyst for the direct conversion of CO2 and H2 to methanol.
      Citation: Catalysts
      PubDate: 2018-06-11
      DOI: 10.3390/catal8060244
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 245: Carbon Supported Multi-Branch
           Nitrogen-Containing Polymers as Oxygen Reduction Catalysts

    • Authors: Ya Chu, Lin Gu, Xiuping Ju, Hongmei Du, Jinsheng Zhao, Konggang Qu
      First page: 245
      Abstract: A composite catalyst was obtained by covalently linking G4-NH2 dendrimers and 1,10-phenanthroline-5-carboxylic acid on the surface of carbon powder, and the composite was named as PMPhen/C. In order to improve the catalytic performance of the composite, copper ions (II) were introduced to PMPhen/C by complex to form the PMPhen-Cu/C catalyst. Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were applied to investigate the surface microstructure and elemental compositions of the catalysts. The results from electrochemical analysis show that PMPhen/C reduced oxygen to hydrogen peroxide (H2O2) through a two-electron transfer process. PMPhen-Cu/C could reduce oxygen to water through a four-electron pathway. Except the slightly lower initial reduction potential, PMPhen-Cu/C has a comparable oxygen reduction ability (ORR) to that of the commercially available Pt/C catalyst, which makes it a potential candidate as the cathodic catalyst in some fuel cells running in neutral medium, such as a microbial fuel cell.
      Citation: Catalysts
      PubDate: 2018-06-12
      DOI: 10.3390/catal8060245
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 246: Synthesis of Sulfur-Resistant TiO2-CeO2
           Composite and Its Catalytic Performance in the Oxidation of a Soluble
           Organic Fraction from Diesel Exhaust

    • Authors: Na Zhang, Zhengzheng Yang, Zhi Chen, Yunxiang Li, Yunwen Liao, Youping Li, Maochu Gong, Yaoqiang Chen
      First page: 246
      Abstract: Sulfur poisoning is one of the most important factors deteriorating the purification efficiency of diesel exhaust after-treatment system, thus improving the sulfur resistibility of catalysts is imperative. Herein, ceria oxygen storage material was introduced into a sulfur-resistant titania by a co-precipitation method, and the sulfur resistibility and catalytic activity of prepared TiO2-CeO2 composite in the oxidation of diesel soluble organic fraction (SOF) were studied. Catalytic performance testing results show that the CeO2 modification significantly improves the catalytic SOF purification efficiency of TiO2-CeO2 catalyst. SO2 uptake and energy-dispersive X-ray (EDX) results suggest that the ceria doping does not debase the excellent sulfur resistibility of bare TiO2, the prepared TiO2-CeO2 catalyst exhibits obviously better sulfur resistibility than the CeO2 and commercial CeO2-ZrO2-Al2O3. X-ray powder diffraction (XRD) and Raman spectra indicate that cerium ions can enter into the TiO2 lattice and not form complete CeO2 crystals. X-ray photoelectron spectroscopy (XPS), H2-temperature programmed reduction (H2-TPR) and oxygen storage capacity (OSC) testing results imply that the addition of CeO2 in TiO2-CeO2 catalyst can significantly enhance the surface oxygen concentration and oxygen storage capacity of TiO2-CeO2.
      Citation: Catalysts
      PubDate: 2018-06-14
      DOI: 10.3390/catal8060246
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 247: Simulating Real World Soot-Catalyst Contact
           Conditions for Lab-Scale Catalytic Soot Oxidation Studies

    • Authors: Changsheng Su, Yujun Wang, Ashok Kumar, Paul J. McGinn
      First page: 247
      Abstract: In diesel soot oxidation studies, both well-defined model soot and a reliable means to simulate realistic contact conditions with catalysts are crucial. This study is the first attempt in the field to establish a lab-scale continuous flame soot deposition method in simulating the “contact condition” of soot and a structured diesel particulate filter (DPF) catalyst. The properties of this flame soot were examined by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM) for structure analysis, Brunauer-Emmett-Teller (BET) for surface area analysis, and thermogravimetric analysis (TGA) for reactivity and kinetics analysis. For validation purposes, catalytic oxidation of Tiki® soot using the simulated contact condition was conducted to compare with the diesel particulates collected from a real diesel engine exhaust system. It was found that the flame soot is more uniform and controllable than similar samples of collected diesel particulates. The change in T50 due to the presence of the catalyst is very similar in both cases, implying that the flame deposit method is able to produce comparably realistic contact conditions to that resulting from the real exhaust system. Comparing against the expensive engine testing, this novel method allows researchers to quickly set up a procedure in the laboratory scale to reveal the catalytic soot oxidation properties in a comparable loose contact condition.
      Citation: Catalysts
      PubDate: 2018-06-14
      DOI: 10.3390/catal8060247
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 248: Mode Transition of Filaments in Packed-Bed
           Dielectric Barrier Discharges

    • Authors: Mingxiang Gao, Ya Zhang, Hongyu Wang, Bin Guo, Quanzhi Zhang, Annemie Bogaerts
      First page: 248
      Abstract: We investigated the mode transition from volume to surface discharge in a packed bed dielectric barrier discharge reactor by a two-dimensional particle-in-cell/Monte Carlo collision method. The calculations are performed at atmospheric pressure for various driving voltages and for gas mixtures with different N2 and O2 compositions. Our results reveal that both a change of the driving voltage and gas mixture can induce mode transition. Upon increasing voltage, a mode transition from hybrid (volume+surface) discharge to pure surface discharge occurs, because the charged species can escape much more easily to the beads and charge the bead surface due to the strong electric field at high driving voltage. This significant surface charging will further enhance the tangential component of the electric field along the dielectric bead surface, yielding surface ionization waves (SIWs). The SIWs will give rise to a high concentration of reactive species on the surface, and thus possibly enhance the surface activity of the beads, which might be of interest for plasma catalysis. Indeed, electron impact excitation and ionization mainly take place near the bead surface. In addition, the propagation speed of SIWs becomes faster with increasing N2 content in the gas mixture, and slower with increasing O2 content, due to the loss of electrons by attachment to O2 molecules. Indeed, the negative O2− ion density produced by electron impact attachment is much higher than the electron and positive O2+ ion density. The different ionization rates between N2 and O2 gases will create different amounts of electrons and ions on the dielectric bead surface, which might also have effects in plasma catalysis.
      Citation: Catalysts
      PubDate: 2018-06-15
      DOI: 10.3390/catal8060248
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 249: Enzymatic Synthesis of Thioesters from
           Thiols and Vinyl Esters in a Continuous-Flow Microreactor

    • Authors: Nani Zhou, Le Shen, Zhen Dong, Jiahong Shen, Lihua Du, Xiping Luo
      First page: 249
      Abstract: The preparation of thioesters through the lipase-catalysed transesterification reaction of thiols with vinyl carboxyl esters is described. The reactions were carried out by Lipase TL IM from Thermomyces lanuginosus as a catalyst and performed under a continuous flow microreactor. We first found that lipase TL IM can be used in the reaction of thioester synthesis with high efficiency. Various reaction parameters were investigated including substrate molar ratio, reaction time, and temperature. Maximum conversion (96%) was obtained under the optimal condition of a substrate molar ratio of 1:2 (4-methylbenzyl mercaptan:vinyl esters) at 50 °C for about 30 min. Compared with other methods, the salient features of this work include mild reaction conditions (50 °C), short reaction times (30 min), high yields, and environment-friendliness.
      Citation: Catalysts
      PubDate: 2018-06-16
      DOI: 10.3390/catal8060249
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 250: Diastereoselective Synthesis of 7,8-Carvone
           Epoxides

    • Authors: Sofia Pombal, Ignacio E. Tobal, Alejandro M. Roncero, Jesus M. Rodilla, Narciso M. Garrido, Francisca Sanz, Alberto Esteban, Jaime Tostado, Rosalina F. Moro, Maria Jose Sexmero, Pablo G. Jambrina, David Diez
      First page: 250
      Abstract: The synthesis of the two 7,8-epoxides of carvone has been attained using organocatalysis in a two-step synthetic route through a bromoester intermediate. Among the different reaction conditions tested for the bromination reaction, moderate yields and diastereoselection are achieved using proline, quinidine, and diphenylprolinol, yielding the corresponding bromoesters that were transformed separately into their epoxides, obtaining the enantiopure products.
      Citation: Catalysts
      PubDate: 2018-06-19
      DOI: 10.3390/catal8060250
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 251: An Efficient Photocatalyst for Fast
           Reduction of Cr(VI) by Ultra-Trace Silver Enhanced Titania in Aqueous
           Solution

    • Authors: Shengyan Pu, Yaqi Hou, Hongyu Chen, Daili Deng, Zeng Yang, Shengyang Xue, Rongxin Zhu, Zenghui Diao, Wei Chu
      First page: 251
      Abstract: For the purpose of establishing a simple route to prepare a metal-semiconductor hybrid catalyst efficiently and reduce its cost through precise doping noble metals. In this study, ultra-trace silver doped TiO2 photocatalysts were fabricated via a “green” ultrasonic impregnation-assisted photoreduction strategy in an ethanol system, and its photocatalytic performance was systematically investigated by utilizing Cr(VI) as the model contaminant. A schottky energy barrier was constructed in Ag@TiO2, which served as a recombination center and possessed superior photocatalytic activity for Cr(VI) reduction. The obtained catalysts exhibited a significant e−/h+ separation efficiency which directly led to an obvious photocatalytic property enhancement. Then, the resultant Ag@TiO2 (0.06 wt %, 30 min irradiation) showed about 2.5 times the activity as that of commercial P25 NPs for Cr(VI) degradation. Moreover, after five cycles, it still maintained considerably high catalytic ability (62%). This work provides a deep insight into preparation techniques of metal-semiconductor photocatalyst and broadens their application prospect.
      Citation: Catalysts
      PubDate: 2018-06-19
      DOI: 10.3390/catal8060251
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 252: Ti-Doped Pd-Au Catalysts for One-Pot
           Hydrogenation and Ring Opening of Furfural

    • Authors: Nandan Shreehari Date, Valeria La Parola, Chandrashekhar Vasant Rode, Maria Luisa Testa
      First page: 252
      Abstract: Pd-Au bimetallic catalysts with different Pd/Au atomic ratios, supported on ordered structured silica (Hexagonal mesoporous silica—HMS, or Santa Barbara Amorphous-15—SBA-15) were evaluated for one-pot hydrogenation of furfural to 1,2-pentanediol. The surface and structural properties of the catalysts were deeply investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), N2 adsorption isotherms (BET), Infrared spectroscopy (IR), and acid capacity measurements. XPS studies revealed that Ti doped supports had higher dispersion of the active phase, particularly in the case of Pd-Au materials in which Ti played an important role in stabilizing the metallic species. Among the various process conditions studied, such as temperature (160 °C), catalyst amount (10% w/w), and reaction time (5 h), H2 pressure (500 psi) was found to improve the 1,2-pentanediol selectivity. The SBA silica bimetallic Ti-doped system showed the best performance in terms of stability and reusability, after multiple cycles. Under specific reaction conditions, the synergism between Pd-Au alloy and Ti doping of the support allowed the ring opening pathway towards the formation of 1,2-pentanediol in furfural hydrogenation.
      Citation: Catalysts
      PubDate: 2018-06-20
      DOI: 10.3390/catal8060252
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 253: Desilicated ZSM-5 Zeolites for the
           Production of Renewable p-Xylene via Diels–Alder Cycloaddition of
           Dimethylfuran and Ethylene

    • Authors: Joel McGlone, Peter Priecel, Luigi Da Vià, Liqaa Majdal, Jose A. Lopez-Sanchez
      First page: 253
      Abstract: The selective production of p-xylene and other aromatics starting from sugars and bioderived ethylene offers great promise and can eliminate the need for separation of xylene isomers, as well as decreasing dependency on fossil resources and CO2 emissions. Although the reaction is known, the microporosity of traditional commercial zeolites appears to be a limiting factor. In this work, we demonstrate for the first time that simply desilication of microporous commercial zeolites by a simple NaOH treatment can greatly enhance conversion and selectivity. The [4 + 2] Diels–Alder cycloaddition of 2,5-dimethylfuran with ethylene in a pressurised reactor was investigated using a series of H-ZSM-5 catalysts with SiO2/Al2O3 ratios 30 and 80 with increasing pore size induced by desilication. X-ray diffraction, scanning electron microscopy, 27Al magic-angle spinning nuclear magnetic resonance, temperature programmed desorption of ammonia, and nitrogen physisorption measurements were used to characterise the catalysts. The enhancement of conversion was observed for all desilicated samples compared to the untreated zeolite, and increases in temperature and ethylene pressure significantly improved both dimethylfuran conversion and selectivity to p-xylene due to the easier desorption from the zeolite’s surface and the augmented cycloaddition rate, respectively. A compromise between acidity and mesoporosity was found to be the key to enhancing the activity and maximising the selectivity in the production of p-xylene from 2,5-dimethylfuran.
      Citation: Catalysts
      PubDate: 2018-06-20
      DOI: 10.3390/catal8060253
      Issue No: Vol. 8, No. 6 (2018)
       
  • Catalysts, Vol. 8, Pages 172: Selective Hydrogenation of Benzene to
           Cyclohexene over Monometallic Ru Catalysts: Investigation of ZnO and ZnSO4
           as Reaction Additives as Well as Particle Size Effect

    • Authors: Haijie Sun, Zhihao Chen, Chenggang Li, Lingxia Chen, Yan Li, Zhikun Peng, Zhongyi Liu, Shouchang Liu
      First page: 172
      Abstract: Monometallic Ru catalysts with different particle size were prepared via a precipitation method and reduced at different temperatures. In addition, their catalytic activity towards cyclohexene formation from selective hydrogenation of benzene was investigated. With the utilization of ZnO and ZnSO4 as reaction additives, (Zn(OH)2)3(ZnSO4)(H2O)3 could be generated and chemisorbed on the Ru surface, which played a crucial role on increasing the selectivity to cyclohexene and retarding the catalytic activity towards benzene conversion. Interestingly, without addition of ZnO and ZnSO4, no cyclohexene was observed over all tested Ru catalysts with different particle sizes. This suggested that particle size plays no role in cyclohexene synthesis from selective hydrogenation of benzene over the pure monometallic Ru catalysts in the absence of ZnO and ZnSO4. On the other hand, when both ZnO and ZnSO4 were applied, surface n(Zn2+)/n(Ru) molar ratio increased with increasing particle size of the monometallic Ru catalysts after catalytic experiments, demonstrating that the content of chemisorbed (Zn(OH)2)3(ZnSO4)(H2O)3 on Ru catalysts surface is enhanced under such a circumstance. More importantly, the maximum cyclohexene yield obtained over monometallic Ru catalysts showed a volcanic-type variation with increasing particle size of Ru from 3.6 nm to 5.6 nm. When the particle size of the monometallic Ru catalyst was 4.7 nm, the highest cyclohexene yield of 60.4% was achieved with an optimum n(ZnO)/n(Ru) ratio of 0.19:1 in the presence of 0.62 mol·dm−3 ZnSO4 within 25 min of catalytic experiments at 423 K under 5.0 MPa of H2. In addition, no decrease of catalytic activity towards cyclohexene generation was observed over this catalyst after 10 catalytic experiments without any regeneration.
      Citation: Catalysts
      PubDate: 2018-04-24
      DOI: 10.3390/catal8050172
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 173: Numerical Investigations of the Influencing
           Factors on a Rotary Regenerator-Type Catalytic Combustion Reactor

    • Authors: Zhenkun Sang, Zemin Bo, Xiaojing Lv, Yiwu Weng
      First page: 173
      Abstract: Ultra-low calorific value gas (ULCVG) not only poses a problem for environmental pollution, but also createsa waste of energy resources if not utilized. A novel reactor, a rotary regenerator-type catalytic combustion reactor (RRCCR), which integrates the functions of a regenerator and combustor into one component, is proposed for the elimination and utilization of ULCVG. Compared to reversal-flow reactor, the operation of the RRCCR is achieved by incremental rotation rather than by valve control, and it has many outstanding characteristics, such as a compact structure, flexible application, and limited energy for circulation. Due to the effects of the variation of the gas flow and concentration on the performance of the reactor, different inlet velocities and concentrations are analyzed by numerical investigations. The results reveal that the two factors have a major impact on the performance of the reactor. The performance of the reactor is more sensitive to the increase of velocity and the decrease of methane concentration. When the inlet concentration (2%vol.) is reduced by 50%, to maintain the methane conversion over 90%, the inlet velocity can be reduced by more than three times. Finally, the highly-efficient and stable operating envelope of the reactor is drawn.
      Citation: Catalysts
      PubDate: 2018-04-24
      DOI: 10.3390/catal8050173
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 174: Techniques for Preparation of Cross-Linked
           Enzyme Aggregates and Their Applications in Bioconversions

    • Authors: Hiroshi Yamaguchi, Yuhei Kiyota, Masaya Miyazaki
      First page: 174
      Abstract: Enzymes are biocatalysts. They are useful in environmentally friendly production processes and have high potential for industrial applications. However, because of problems with operational stability, cost, and catalytic efficiency, many enzymatic processes have limited applications. The use of cross-linked enzyme aggregates (CLEAs) has been introduced as an effective carrier-free immobilization method. This immobilization method is attractive because it is simple and robust, and unpurified enzymes can be used. Coimmobilization of different enzymes can be achieved. CLEAs generally show high catalytic activities, good storage and operational stabilities, and good reusability. In this review, we summarize techniques for the preparation of CLEAs for use as biocatalysts. Some important applications of these techniques in chemical synthesis and environmental applications are also included. CLEAs provide feasible and efficient techniques for improving the properties of immobilized enzymes for use in industrial applications.
      Citation: Catalysts
      PubDate: 2018-04-24
      DOI: 10.3390/catal8050174
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 175: Nb-Modified Ce/Ti Oxide Catalyst for the
           Selective Catalytic Reduction of NO with NH3 at Low Temperature

    • Authors: Jawaher Mosrati, Hanan Atia, Reinhard Eckelt, Henrik Lund, Giovanni Agostini, Ursula Bentrup, Nils Rockstroh, Sonja Keller, Udo Armbruster, Mourad Mhamdi
      First page: 175
      Abstract: Recently, great attention has been paid to Ceria-based materials for selective catalytic reduction (SCR) with NH3 owing to their unique redox, oxygen storage, and acid-base properties. Two series of bimetallic catalysts issued from Titania modified by Ce and Nb were prepared by the one-step sol-gel method (SG) and by the sol-gel route followed by impregnation (WI). The resulting core-shell and bulk catalysts were tested in NH3-SCR of NOx. The impregnated Nb5/Ce40/Ti100 (WI) catalyst displayed 95% NOx conversion at 200 °C (GHSV = 60,000 mL·g−1·h−1, 1000 ppm NOx, 1000 ppm NH3, 5% O2/He) without forming N2O. The catalysts were characterized by various methods including ICP-OES, N2-physisorption, XRD, Raman, NH3-TPD, DRIFTS, XPS, and H2-TPR. The results showed that the introduction of Nb decreases the surface area and strengthens the surface acidity. This behavior can be explained by the strong interaction between Ceria and Titania which generates Ce-O-Ti units, as well as a high concentration of amorphous or highly dispersed Niobia. This should be the reason for the excellent performance of the catalyst prepared by the sol-gel method followed by impregnation. Furthermore, Nb5/Ce40/Ti100 (WI) has the largest NH3 adsorption capacity, which is helpful to promote the NH3-SCR reaction. The long-term stability and the effect of H2O on the catalysts were also evaluated.
      Citation: Catalysts
      PubDate: 2018-04-26
      DOI: 10.3390/catal8050175
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 176: Immobilization of Planococcus sp. S5 Strain
           on the Loofah Sponge and Its Application in Naproxen Removal

    • Authors: Anna Dzionek, Danuta Wojcieszyńska, Katarzyna Hupert-Kocurek, Małgorzata Adamczyk-Habrajska, Urszula Guzik
      First page: 176
      Abstract: Planococcus sp. S5, a Gram-positive bacterium isolated from the activated sludge is known to degrade naproxen in the presence of an additional carbon source. Due to the possible toxicity of naproxen and intermediates of its degradation, the whole cells of S5 strain were immobilized onto loofah sponge. The immobilized cells degraded 6, 9, 12 or 15 mg/L of naproxen faster than the free cells. Planococcus sp. cells immobilized onto the loofah sponge were able to degrade naproxen efficiently for 55 days without significant damage and disintegration of the carrier. Analysis of the activity of enzymes involved in naproxen degradation showed that stabilization of S5 cells in exopolysaccharide (EPS) resulted in a significant increase of their activity. Changes in the structure of biofilm formed on the loofah sponge cubes during degradation of naproxen were observed. Developed biocatalyst system showed high resistance to naproxen and its intermediates and degraded higher concentrations of the drug in comparison to the free cells.
      Citation: Catalysts
      PubDate: 2018-04-26
      DOI: 10.3390/catal8050176
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 177: Heterogeneous Biocatalysts Prepared by
           Immuring Enzymatic Active Components inside Silica Xerogel and
           Nanocarbons-In-Silica Composites

    • Authors: Galina Kovalenko, Larisa Perminova, Anatoly Beklemishev, Valentin Parmon
      First page: 177
      Abstract: Proprietary results on preparation and studies of whole-cell and lysates-based heterogeneous biocatalysts with different enzymatic activity were reviewed. A peculiar method was developed for preparing these biocatalysts by immuring (entrapping) enzymatic active components (EAC) inside silica (SiO2) xerogel and nanocarbons-in-silica composites. Properties of the multi-component composite biocatalysts such as enzymatic activity and operational stability were compared. The effect of the inclusion of nanocarbons such as nanotubes, nanofibers, and onion-like nanospheres with various texture, nanostructure and dispersion were thoroughly studied. With invertase-active biocatalysts, the direct correlation between an increase in the enzymatic activity of the nanocarbons-in-silica biocatalyst and efficiency of EAC adhesion on nanocarbons was observed. The steady-state invertase activity of the baker yeast lysates-based biocatalysts was determined to increase by a factor of 5–6 after inclusion of the multi-walled carbon nanotubes inside SiO2-xerogel. With lipase-active biocatalysts, the effect of the included nanocarbons on the biocatalytic properties depended significantly on the reaction type. In interesterification of oil-fat blends, the biocatalysts without any included nanocarbons demonstrated the maximal lipase activity. In esterification of fatty acids with aliphatic alcohols, the activity of the biocatalysts increased by a factor of 1.5–2 after inclusion of the aggregated multi-walled carbon nanotubes (CNTs) inside SiO2-xerogel. In the low-temperature synthesis of isopentyl esters of butyric (C4:0), capric (C10:0), and srearic (C18:0) fatty acids, the lipase-active composite CNTs-in-silica biocatalysts operated without loss of activity for more than thousand hours.
      Citation: Catalysts
      PubDate: 2018-04-26
      DOI: 10.3390/catal8050177
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 178: A Simple Route in Fabricating
           Carbon-Modified Titania Films with Glucose and Their
           Visible-Light-Responsive Photocatalytic Activity

    • Authors: Shih-Hsun Chen, Yu-Cheng Hsiao, Yu-Jia Chiu, Yao-Hsuan Tseng
      First page: 178
      Abstract: Carbon-modified titania (C–TiO2) films were easily prepared by using an impregnation process with a glucose-containing TiO2 sol. Through controlling calcination conditions, the as-obtained C–TiO2 products exhibited highly photocatalytic activity for the degradation of gaseous NOx under visible light and ultraviolet illumination. The effects of carbon content and calcination temperature on the photocatalytic performances and their photochemical and physical properties were investigated. Carbonaceous species on the TiO2 surface enhanced the visible-light absorption of TiO2 films; however, an excessive amount of carbon on the TiO2 surface reduced its photocatalytic ability due to the serious coverage effect on active sites. The results show that a suitable glucose addition is about 50–100% of the weight of TiO2 content and the optimized calcination temperature is 300 °C, which leads to better photocatalytic activity under ultraviolet and visible- light irradiations. Accordingly, the simple-prepared C–TiO2 films functioned as visible-light-responsive catalysts, allowing for a feasible producing route for real applications.
      Citation: Catalysts
      PubDate: 2018-04-27
      DOI: 10.3390/catal8050178
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 179: Photocatalytic Degradation of Commercial
           Acetaminophen: Evaluation, Modeling, and Scaling-Up of Photoreactors

    • Authors: Déyler Castilla-Caballero, Fiderman Machuca-Martínez, Ciro Bustillo-Lecompte, José Colina-Márquez
      First page: 179
      Abstract: In this work, the performance of a pilot-scale solar CPC reactor was evaluated for the degradation of commercial acetaminophen, using TiO2 P25 as a catalyst. The statistical Taguchi’s method was used to estimate the combination of initial pH and catalyst load while tackling the variability of the solar radiation intensity under tropical weather conditions through the estimation of the signal-to-noise ratios (S/N) of the controllable variables. Moreover, a kinetic law that included the explicit dependence on the local volumetric rate of photon absorption (LVRPA) was used. The radiant field was estimated by joining the Six Flux Model (SFM) with a solar emission model based on clarity index (KC), whereas the mass balance was coupled to the hydrodynamic equations, corresponding to the turbulent regime. For scaling-up purposes, the ratio of the total area-to-total-pollutant volume (AT/VT) was varied for observing the effect of this parameter on the overall plant performance. The Taguchi’s experimental design results showed that the best combination of initial pH and catalyst load was 9 and 0.6 g L−1, respectively. Also, full-scale plants would require far fewer ratios of AT/VT than for pilot or intermediate-scale ones. This information may be beneficial for reducing assembling costs of photocatalytic reactors scaling-up.
      Citation: Catalysts
      PubDate: 2018-04-28
      DOI: 10.3390/catal8050179
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 180: Rapid Immobilization of Cellulase onto
           Graphene Oxide with a Hydrophobic Spacer

    • Authors: Jian Gao, Chun-Liu Lu, Yue Wang, Shuang-Shuang Wang, Jia-Jia Shen, Jiu-Xun Zhang, Ye-Wang Zhang
      First page: 180
      Abstract: A rapid immobilization method for cellulase was developed. Functional graphene oxide was synthesized and grafted with hydrophobic spacer P-β-sulfuric acid ester ethyl sulfone aniline (SESA) though etherification and diazotization. The functionalized graphene oxide was characterized by Fourier-transform infrared spectroscopy and was used as the carrier for the immobilization of cellulase via covalent binding. The immobilization of cellulase was finished in a very short time (10 min) and very high immobilization yield and efficiency of above 90% were achieved after optimization. When compared with the free cellulase, thermal and operational stabilities of the immobilized cellulase were improved significantly. At 50 °C, the half-life of the immobilized cellulase (533 min) was six-fold higher than that of the free cellulase (89 min). Additionally, the affinity between immobilized cellulase (Km = 2.19 g·L−1) and substrate was more favorable than that of free cellulase (Km = 3.84 g·L−1), suggesting the immobilized cellulase has higher catalytic efficiency. The possible immobilization mechanism was proposed. The results strongly indicate that the immobilization is highly efficient and has great potential for the immobilization of other enzymes.
      Citation: Catalysts
      PubDate: 2018-04-28
      DOI: 10.3390/catal8050180
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 181: An Overview on the N-Heterocyclic
           Carbene-Catalyzed Aza-Benzoin Condensation Reaction

    • Authors: Domenico Albanese, Nicoletta Gaggero
      First page: 181
      Abstract: The N-heterocyclic carbene(NHCs)-catalyzed aza-benzoin condensation reaction is an efficient, single step strategy which employs easily available substrates, such as aldehydes and imines, to provide α-amino ketones. The multifunctionality and high reactivity of α-amino ketones makes these structures attractive for medicinal chemistry and as precursors of a variety of amine derivatives. The different electrophilic characteristics of aldehydes and imines ensure a high regioselective reaction. Enantiomerically-enriched α-amino ketones have been synthesized through stereoselective couplings promoted by chiral N-heterocyclic carbenes. One-pot domino procedures, including an aza-benzoin step, allow valuable complex molecules to be accessed.
      Citation: Catalysts
      PubDate: 2018-04-28
      DOI: 10.3390/catal8050181
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 182: Hydrogenation of m-Chloronitrobenzene over
           Different Morphologies Ni/TiO2 without Addition of Molecular Hydrogen

    • Authors: Feng Li, Jinrong Liang, Wenxi Zhu, Hua Song, Keliang Wang, Cuiqin Li
      First page: 182
      Abstract: Ni/TiO2 catalysts with different morphologies (granular, sheet, tubular and spherical) were prepared. Hydrogen was generated from ethanol aqueous-phase reforming over Ni/TiO2 in a water-ethanol-m-chloronitrobenzene reaction system and directly applied into m-chloronitrobenzene catalytic hydrogenation. Thereby, in-situ liquid-phase hydrogenation of m-chloronitrobenzene over Ni/TiO2 without addition of molecular hydrogen was successful. Compared with granular, sheet and spherical Ni/TiO2, the nanotubular Ni/TiO2 prepared from one-step hydrothermal reaction had larger specific surface area, smaller and uniformly-distributed pore sizes and more Lewis acid sites. In-situ liquid-phase hydrogenation of m-chloronitrobenzene experiments showed the nanotubular Ni/TiO2 had the highest catalytic activity, which was ascribed to both catalyst morphology and acid sites. Firstly, the nanotubular structure endowed the catalysts with a nanoscale confinement effect and thereby high catalytic performance. Secondly, the Lewis acid sites not only accelerated water–gas shift reaction, enhancing the ethanol aqueous-phase reforming activity for hydrogen generation, but also promoted the adsorption and hydrogenation of –NO2 on the active sites of the catalysts.
      Citation: Catalysts
      PubDate: 2018-04-29
      DOI: 10.3390/catal8050182
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 183: Preferential CO Oxidation in H2 over
           Au/La2O3/Al2O3 Catalysts: The Effect of the Catalyst Reduction Method

    • Authors: Pandian Lakshmanan, Eun Duck Park
      First page: 183
      Abstract: We investigated the influence of the reduction method on the preferential oxidation of CO in H2 (CO-PROX) over Au/La2O3/Al2O3 catalysts. An Au/La2O3/Al2O3 sample, prepared using deposition–precipitation with urea, was reduced by chemical reduction with NaBH4 or glycerol. Several techniques, such as diffuse-reflectance infrared Fourier-transform spectroscopy after CO adsorption (CO-DRIFTS), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) were used to characterize the catalysts. Additionally, the catalysts were examined by in situ DRIFTS during methanol decomposition. The results reveal that the reduction method affects the average particle size and electronic state of gold, as well as the characteristics of the CO–Au0 interactions. The best CO-PROX performance was observed for the catalyst chemically reduced using NaBH4 with a NaBH4/Au molar ratio of 35. This catalyst contained gold particles with size of ~4 nm, for which the XPS binding energy was lower than that of metallic gold.
      Citation: Catalysts
      PubDate: 2018-04-30
      DOI: 10.3390/catal8050183
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 184: One-Pot, One-Step Production of Dietary
           Nucleotides by Magnetic Biocatalysts

    • Authors: Jon del Arco, Sara Martínez-Pascual, Vicente Javier Clemente-Suárez, Octavio Jorge Corral, Justin Jordaan, Daniel Hormigo, Almudena Perona, Jesús Fernández-Lucas
      First page: 184
      Abstract: The enzymatic synthesis of nucleotides offers several advantages over traditional multistep chemical methods, such as stereoselectivity, regioselectivity, enantioselectivity, simple downstream processing, and the use of mild reaction conditions. However, in order to scale up these bioprocesses, several drawbacks, such as the low enzyme stability and recycling, must be considered. Enzyme immobilization may overcome these cost-related problems by enhancing protein stability and facilitating the separation of products. In this regard, tetrameric hypoxanthine–guanine–xanthine phosphoribosyltransferase (HGXPRT) from Thermus thermophilus HB8 was covalently immobilized onto glutaraldehyde-activated MagReSyn®Amine magnetic iron oxide porous microparticles (MTtHGXPRT). In this context, two different strategies were followed: (a) an enzyme immobilization through its N-terminus residues at pH 8.5 (derivatives MTtHGXPRT1-3); and (b) a multipoint covalent immobilization through the surface lysine residues at pH 10 (derivatives MTtHGXPRT4-5). The immobilized derivatives of MTtHGXPRT3 (activity 1581 international units per gram of support, IU/g; retained activity 29%) and MTtHGXPRT5 (activity 1108 IU/g; retained activity 23%) displayed the best wet biocatalyst activity, and retained activity values in the enzymatic synthesis of inosine-5′-monophosphate (IMP). In addition, the dependence of the activities and stabilities of both derivatives on pH and temperature was tested, as well as their reusability potential. Taking these results into account, MTtHGXPRT3 was chosen as the best biocatalyst (negligible loss of activity at 60 °C during 24 h; reusable up to seven cycles). Finally, as proof of concept, the enzymatic production of dietary nucleotides from high concentrations of low soluble bases was achieved.
      Citation: Catalysts
      PubDate: 2018-04-30
      DOI: 10.3390/catal8050184
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 185: Pyrene-Based Conjugated Polymer/Bi2MoO6
           Z-Scheme Hybrids: Facile Construction and Sustainable Enhanced
           Photocatalytic Performance in Ciprofloxacin and Cr(VI) Removal under
           Visible Light Irradiation

    • Authors: Xianglong Yang, Yonggang Xiang, Xuepeng Wang, Shu Li, Hao Chen, Xing Ding
      First page: 185
      Abstract: The search for appropriate materials with favorable staggered energy band arrangements is important and is a great challenge in order to fabricate Z-scheme photocatalysts with high activity in visible light. In this study, we demonstrated a facile and feasible strategy to construct highly active organic–inorganic Z-scheme hybrids (P-BMO) with linear pyrene-based conjugated polymer (P17-E) and Bi2MoO6, via an in-situ palladium-catalyzed cross-coupling reaction. The characterization results revealed C-O chemical bond formed at the heterointerface between P17-E and Bi2MoO6 after in-situ polycondensation and endowed the hybrids with observably improved photogenerated carries transfer capabilities. Visible, light-driven photocatalytic removal of ciprofloxacin and Cr(VI) were significantly enhanced after the incorporation of P17-E into Bi2MoO6, whether with the morphology of nanosheets, nanobelts, or microspheres. Moreover, these P-BMO hybrids were also found to exhibit excellent sustainable photocatalytic performance after four runs of photocatalytic evaluation tests, suggesting their high activity and stability. To better eliminate the redox ability enhancement of P-BMO, a reasonable Z-scheme electrons transferring mechanism between P17-E and Bi2MoO6 was proposed and proved by the determination of •O2– and •OH and Pt nanoparticles photodeposition experiments. This work might provide a viable source and insight into the design of Z-scheme photocatalysts with excellent redox ability for environmental remediation.
      Citation: Catalysts
      PubDate: 2018-05-01
      DOI: 10.3390/catal8050185
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 186: Dehydrogenation Catalysts for Synthesis of
           O-Phenylphenol via Cu/Ni/Mg/Al Hydrotalcite-Like Compounds as Precursors

    • Authors: Jilong Wang, Tianchi Zhang, Kai Li, Yanan Cao, Yongping Zeng
      First page: 186
      Abstract: A series of copper containing catalysts were prepared by calcination of Cu/Ni/Mg/Al hydrotalcite-like precursors, using the coprecipitation method. The materials were characterized and show a well-crystallized layered structure of hydrotalcite with smaller Cu0 particles. We also studied their catalytic performance for conversion of 2-(1-cyclohexenyl) cyclohexanone into o-phenylphenol. The catalysts containing Ni showed higher catalytic activity; the optimum stability occurred when the Ni2+:(Ni2+ + Cu2+) atomic ratio was 0.4. The combination of Cu and Ni can greatly improve the stability and activities of the catalyst.
      Citation: Catalysts
      PubDate: 2018-05-02
      DOI: 10.3390/catal8050186
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 187: Intrinsic Catalytic Activity of
           Gold/Multi-Walled Carbon Nanotubes Composites in Squaric Acid-Iron(II/III)
           System

    • Authors: Yanxia Li, Cheng Jiang, Shengheng Lin, Jiajia Lai, Liyun Zheng, Pengjun Xu
      First page: 187
      Abstract: In this paper, gold/multi-walled carbon nanotube (Au/MWCNTs) composites were prepared via in situ reductions. The synthesized materials could effectively catalyze the system of square acid (SQA)-iron(II/III) to produce a significant color reaction. By designing the orthogonal test of three-factor and three-level, the three factors of sodium formate solution concentration, ultrasonic time and synthesis reaction time were optimized in the process of Au/MWCNTs preparation. Results showed that the Au/MWCNTs had the best catalytic activity under the conditions of sodium formate solution concentration of 400 mmol/L, ultrasonic for 30 min and reaction for 4 h. In a subsequent comparison with H2O2, it found that the catalytic performance of 1 mg of Au/MWCNTs composite was equivalent to that of H2O2 with the concentration of 0.28 mmol/L. It demonstrated that the prepared Au/MWCNTs composites had good catalytic activity, stable color and low background noise, indicating a good prospect in various fields including that of catalytic reaction, sensing analysis, and nanomaterials labeling.
      Citation: Catalysts
      PubDate: 2018-05-02
      DOI: 10.3390/catal8050187
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 188: One-Pot Synthesis of N,N′-dialkylureas via
           Carbonylation of Amines with CO2 Applying Y0.08Zr0.92O1.96 Mixed Oxide
           (YSZ-8) as a Heterogeneous Catalyst

    • Authors: Dalei Sun, Kaihong Xie, Yanxiong Fang, Xianghua Yang
      First page: 188
      Abstract: One-pot synthesis of N,N′-dialkylureas were successfully achieved from catalytic carbonylation of aliphatic primary amines with CO2 as the carbon source and Y0.08Zr0.92O1.96 mixed oxide (Yttria-stabilized zirconia, YSZ-8) as the heterogeneous catalyst. The yield of the target product was obtained up to 80.60% from a 48 h reaction with an aliphatic primary amine and 3.0 MPa CO2 in N-methyl-2-pirrolidinone at 160 °C. A multi-pronged mechanistic study was carried out where factors that might influence the reaction efficiency were studied, including catalyst structure, substrates basicity, CO2 pressure, solvent polarity and reaction time. The presence of oxygen vacancies in YSZ-8 was found to be essential for the carbonylation process by creating additional reduction potential for the activation of CO2 which would lead to the key intermediate species.
      Citation: Catalysts
      PubDate: 2018-05-02
      DOI: 10.3390/catal8050188
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 189: Preparation of RGO-P25 Nanocomposites for
           the Photocatalytic Degradation of Ammonia in Livestock Farms

    • Authors: Shihua Pu, Dingbiao Long, Zuohua Liu, Feiyun Yang, Jiaming Zhu
      First page: 189
      Abstract: In this paper, the Hummer’s method was used to prepare the compound catalyst of reduced graphene and TiO2 (RGO-P25), and the sand core plate was used as the carrier to provide the theoretical basis for the application of animal environmental purification by exploring the degradation of ammonia in RGO-P25. Characterization results show that the band gap of P25 is reduced from 3.14 eV to 2.96 eV after the combination of RGO, and the recombination rate of the photogenerated electrons and holes also decreased significantly, both resulting in the improvement of ammonia degradation by composite catalysts. Experimental results show that the carrier (sand core plate) and RGO-P25 are effectively stabilized with Si–O–Ti, but the blank core plate carrier could not degrade the ammonia, and its adsorption is not obvious, only 5% ± 1%, under 300 W ultraviolet lamp irradiation, the degradation rates of P25, RGO and RGO-P25 for ammonia at initial concentrations of 119–124 ppm were 72.25%, 81.66% and 93.64%, respectively. P25 dispersed through RGO can effectively adsorb ammonia on the surface to provide a reaction environment and thereby improve its photocatalytic efficiency, thus, endowing the RGO-P25 composites with higher photocatalytic degradation performance than RGO or P25 individually.
      Citation: Catalysts
      PubDate: 2018-05-03
      DOI: 10.3390/catal8050189
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 190: The Activation of Methane on Ru, Rh, and Pd
           Decorated Carbon Nanotube and Boron Nitride Nanotube: A DFT Study

    • Authors: Bundet Boekfa, Piti Treesukol, Yuwanda Injongkol, Thana Maihom, Phornphimon Maitarad, Jumras Limtrakul
      First page: 190
      Abstract: Methane decomposition catalyzed by an Ru, Rh, or Pd atom supported on a carbon or boron nitride nanotubes was analyzed by means of the density functional theory with the M06-L hybrid functional. The results suggested that the dissociative reaction of methane was a single-step mechanism. Based on the calculated activation energy, the Ru-decorated carbon nanotube showed superior catalytic activity with an activation barrier of 14.5 kcal mol−1, followed by the Rh-decorated carbon nanotube (18.1 kcal mol−1) and the Pd-decorated carbon nanotube (25.6 kcal mol−1). The catalytic performances of metals supported on a boron nitride nanotube were better than those on a carbon nanotube. The total activation barrier for the Ru, Rh, and Pd atoms on boron nitride nanotube was 10.2, 14.0, and 20.5 kcal mol−1, respectively. Dissociative adsorption complexes on the Ru–boron nitride nanotube were the most stable. The anionic state of the supported metal atom was responsible for decreasing the activation energy of methane decomposition. Our finding provides a crucial point for further investigation.
      Citation: Catalysts
      PubDate: 2018-05-04
      DOI: 10.3390/catal8050190
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 191: Optimization of Charcoal Production Process
           from Woody Biomass Waste: Effect of Ni-Containing Catalysts on Pyrolysis
           Vapors

    • Authors: Jon Solar, Blanca Maria Caballero, Isabel De Marco, Alexander López-Urionabarrenechea, Naia Gastelu
      First page: 191
      Abstract: Woody biomass waste (Pinus radiata) coming from forestry activities has been pyrolyzed with the aim of obtaining charcoal and, at the same time, a hydrogen-rich gas fraction. The pyrolysis has been carried out in a laboratory scale continuous screw reactor, where carbonization takes place, connected to a vapor treatment reactor, at which the carbonization vapors are thermo-catalytically treated. Different peak temperatures have been studied in the carbonization process (500–900 °C), while the presence of different Ni-containing catalysts in the vapor treatment has been analyzed. Low temperature pyrolysis produces high liquid and solid yields, however, increasing the temperature progressively up to 900 °C drastically increases gas yield. The amount of nickel affects the vapors treatment phase, enhancing even further the production of interesting products such as hydrogen and reducing the generated liquids to very low yields. The gases obtained at very high temperatures (700–900 °C) in the presence of Ni-containing catalysts are rich in H2 and CO, which makes them valuable for energy production, as hydrogen source, producer gas or reducing agent.
      Citation: Catalysts
      PubDate: 2018-05-04
      DOI: 10.3390/catal8050191
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 192: Controlling Redox Enzyme Orientation at
           Planar Electrodes

    • Authors: Vivek Pratap Hitaishi, Romain Clement, Nicolas Bourassin, Marc Baaden, Anne de Poulpiquet, Sophie Sacquin-Mora, Alexandre Ciaccafava, Elisabeth Lojou
      First page: 192
      Abstract: Redox enzymes, which catalyze reactions involving electron transfers in living organisms, are very promising components of biotechnological devices, and can be envisioned for sensing applications as well as for energy conversion. In this context, one of the most significant challenges is to achieve efficient direct electron transfer by tunneling between enzymes and conductive surfaces. Based on various examples of bioelectrochemical studies described in the recent literature, this review discusses the issue of enzyme immobilization at planar electrode interfaces. The fundamental importance of controlling enzyme orientation, how to obtain such orientation, and how it can be verified experimentally or by modeling are the three main directions explored. Since redox enzymes are sizable proteins with anisotropic properties, achieving their functional immobilization requires a specific and controlled orientation on the electrode surface. All the factors influenced by this orientation are described, ranging from electronic conductivity to efficiency of substrate supply. The specificities of the enzymatic molecule, surface properties, and dipole moment, which in turn influence the orientation, are introduced. Various ways of ensuring functional immobilization through tuning of both the enzyme and the electrode surface are then described. Finally, the review deals with analytical techniques that have enabled characterization and quantification of successful achievement of the desired orientation. The rich contributions of electrochemistry, spectroscopy (especially infrared spectroscopy), modeling, and microscopy are featured, along with their limitations.
      Citation: Catalysts
      PubDate: 2018-05-04
      DOI: 10.3390/catal8050192
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 193: Selective Conversion of Furfural to
           Cyclopentanone or Cyclopentanol Using Co-Ni Catalyst in Water

    • Authors: Yaru Li, Xingcui Guo, Daosheng Liu, Xindong Mu, Xiufang Chen, Yan Shi
      First page: 193
      Abstract: Co-Ni catalysts, prepared by a typical wetness impregnation method, can selectively convert furfural (FFA) to cyclopentanone (CPO) or cyclopentanol (CPL) in water, respectively. The catalytic performance depends strongly on the support. It is also strongly influenced by the Co-Ni loadings of the catalyst. The 10%Co-10%Ni/TiO2 catalyst showed the highest selectivity toward CPO (53.3%) with almost complete FFA conversion, and the main product was CPL (45.4%) over 20%Co/TiO2 at the optimized conditions (150 °C, 4 MPa H2, 4 h). The surface morphology, surface area, composition and reducibility properties of these catalysts were fully characterized by XRD, H2-TPR, ICP-AES and SEM. The factors that influenced the activity of catalysts were also investigated in detail. Additionally, the stability of catalyst for the hydrogenative rearrangement of FFA was studied.
      Citation: Catalysts
      PubDate: 2018-05-04
      DOI: 10.3390/catal8050193
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 194: Palladium-Catalyzed Isomerization-Coupling
           Reactions of Allyl Chloride with Amines to Generate Functionalized
           Phosphorus Derivatives

    • Authors: Jing-Hong Wen, Qiang Li, Shao-Zhen Nie, Jing-Jing Ye, Qing Xu, Chang-Qiu Zhao
      First page: 194
      Abstract: A Pd-catalyzed isomerization-coupling reaction of P-containing allyl chloride with amine afforded imine or enamine that was converted to various functionalized phosphorus derivatives via hydrolysis, reduction, or Stork reactions. The reaction was confirmed to proceed via an isomerization of a starting material and a coupling of the resulting vinyl chloride with amine.
      Citation: Catalysts
      PubDate: 2018-05-05
      DOI: 10.3390/catal8050194
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 195: Metal-Free Organocatalysis

    • Authors: Aurelio G. Csákÿ
      First page: 195
      Abstract: Fostering research in fundamental organic transformations is of utmost importance for the development of science.[...]
      Citation: Catalysts
      PubDate: 2018-05-06
      DOI: 10.3390/catal8050195
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 196: Recent Progress in Nitrogen-Doped Metal-Free
           Electrocatalysts for Oxygen Reduction Reaction

    • Authors: Zexing Wu, Min Song, Jie Wang, Xien Liu
      First page: 196
      Abstract: Electrocatalysis for the oxygen reduction reaction (ORR) at the cathode plays a critical role in fuel cells and metal-air batteries. However, the high-cost and sluggish kinetics of the catalytic reaction have hindered its development. Therefore, developing efficient catalysts to address these issues is of vital significance. In this work, we summarized the recent progress of nitrogen (N)-doped metal-free catalysts for the ORR, owing to their high catalytic activity (comparable to Pt/C) and cost-effectiveness. The synthetic strategy and the morphology structure to catalytic performance are mainly discussed. Furthermore, the design of N-doped nanomaterials with other heteroatoms in aiming to further enhance the ORR performance is also reviewed. At the end of the review, we provide a brief summary of the N-doped carbon-based catalysts in enhancing the ORR performance and give future perspectives for their further development.
      Citation: Catalysts
      PubDate: 2018-05-07
      DOI: 10.3390/catal8050196
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 197: Isolation, Characterization, and
           Environmental Application of Bio-Based Materials as Auxiliaries in
           Photocatalytic Processes

    • Authors: Davide Palma, Alessandra Bianco Prevot, Luisella Celi, Maria Martin, Debora Fabbri, Giuliana Magnacca, Michele R. Chierotti, Roberto Nisticò
      First page: 197
      Abstract: Sustainable alternative substrates for advanced applications represent an increasing field of research that attracts the attention of worldwide experts (in accordance with green chemistry principles). In this context, bio-based substances (BBS) isolated from urban composted biowaste were purified and characterized. Additionally, these materials were tested as auxiliaries in advanced oxidizing photocatalytic processes for the abatement of organic contaminants in aqueous medium. Results highlighted the capability of these substances to enhance efficiency in water remediation treatments under mild conditions, favoring the entire light-driven photocatalytic process.
      Citation: Catalysts
      PubDate: 2018-05-08
      DOI: 10.3390/catal8050197
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 198: Metal-Carbon-CNF Composites Obtained by
           Catalytic Pyrolysis of Urban Plastic Residues as Electro-Catalysts for the
           Reduction of CO2

    • Authors: Jesica Castelo-Quibén, Abdelhakim Elmouwahidi, Francisco J. Maldonado-Hódar, Francisco Carrasco-Marín, Agustín F. Pérez-Cadenas
      First page: 198
      Abstract: Metal–carbon–carbon nanofibers composites obtained by catalytic pyrolysis of urban plastic residues have been prepared using Fe, Co or Ni as pyrolitic catalysts. The composite materials have been fully characterized from a textural and chemical point of view. The proportion of carbon nanofibers and the final content of carbon phases depend on the used pyrolitic metal with Ni being the most active pyrolitic catalysts. The composites show the electro-catalyst activity in the CO2 reduction to hydrocarbons, favoring all the formation of C1 to C4 hydrocarbons. The tendency of this activity is in accordance with the apparent faradaic efficiencies and the linear sweep voltammetries. The cobalt-based composite shows high selectivity to C3 hydrocarbons within this group of compounds.
      Citation: Catalysts
      PubDate: 2018-05-09
      DOI: 10.3390/catal8050198
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 199: Effect of Mesoporous Chitosan Action and
           Coordination on the Catalytic Activity of Mesoporous Chitosan-Grafted
           Cobalt Tetrakis(p-Sulfophenyl)Porphyrin for Ethylbenzene Oxidation

    • Authors: Guan Huang, Lin Qiang Mo, Yan Xun Wei, Hong Zhou, Yong An Guo, Su Juan Wei
      First page: 199
      Abstract: To simulate the active site cavity structure function and axial coordination of cytochrome P-450 enzymes, mesoporous chitosan(mesp-CTS) was used as a scaffold for a meso-sized cavity to immobilize cobalt tetrakis(p-sulphophenyl)porphyrin chloride(Co TPPS). Immobilization was achieved via an acid–base reaction and axial coordination of the H2N-C group to the Co ion in Co TPPS, thus forming the biomimetic catalyst Co TPPS/mesp-CTS. Several approaches, including scanning electron microscopy (SEM), the Brunauer–Emmett–Teller (BET)technique, Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, thermogravimetric and differential scanning calorimetry (TG-DSC), and X-ray photoelectron spectroscopy (XPS), were used to characterize the grafted catalyst. The catalytic performance of Co TPPS/mesp-CTS in ethylbenzene oxidation without any solvents and additives was investigated. The results showed that only 0.96 × 10 mol of Co TPPS grafted onto mesp-CTS could be recycled three times for 200 mL of ethylbenzene oxidation, with an average yield of 44.6% and selectivity of 68.8%. The highly efficient catalysis can be attributed to promotion by mesp-CTS, including the effect of the mesoporous structure and the axial coordination to the Co ion in Co TPPS. This biomimetic methodology provides a method for clean production of acetophenone via ethylbenzene oxidation.
      Citation: Catalysts
      PubDate: 2018-05-10
      DOI: 10.3390/catal8050199
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 200: Improvement Effect of Ni to Pd-Ni/SBA-15
           Catalyst for Selective Hydrogenation of Cinnamaldehyde to
           Hydrocinnamaldehyde

    • Authors: Shiying Han, Yunfei Liu, Jiang Li, Rui Li, Fulong Yuan, Yujun Zhu
      First page: 200
      Abstract: A series of Pd-Ni bimetallic catalysts supported on SBA-15 (0.2%Pd-x%Ni/SBA-15, x = 0.4, 0.7, and 1.2) were prepared through the impregnation method combined with the NaBH4 reduction method. X-ray diffraction (XRD), N2 adsorption-desorption, X-ray photoemission spectroscopy (XPS) and transmission electron microscope (TEM) were used to characterize the prepared catalysts. All the synthesized catalysts were evaluated for the liquid-phase hydrogenation of cinnamaldehyde (CAL). The addition of Ni obviously enhanced the CAL conversion and selectivity of C=C hydrogenation to hydrocinnamaldehyde (HALD) over the 0.2%Pd-x%Ni/SBA-15 catalysts. Meanwhile, 0.2%Pd-1.2%Ni/SBA-15 showed the best performance with 96.3% conversion and 87.8% selectivity toward HALD. This improvement was attributed to the synergistic effect between the Pd and Ni nanoparticles, enhancing the dispersion of Pd metal particles and increasing the content of surface Pd0 species. In addition, the influences of a few reaction factors including H2 pressure, reaction temperature, and reaction time were studied over 0.2%Pd-1.2%Ni/SBA-15.
      Citation: Catalysts
      PubDate: 2018-05-11
      DOI: 10.3390/catal8050200
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 201: Immobilization of the β-fructofuranosidase
           from Xanthophyllomyces dendrorhous by Entrapment in Polyvinyl Alcohol and
           Its Application to Neo-Fructooligosaccharides Production

    • Authors: Noa Míguez, María Gimeno-Pérez, David Fernández-Polo, Fadia Cervantes, Antonio Ballesteros, María Fernández-Lobato, María Ribeiro, Francisco Plou
      First page: 201
      Abstract: The β-fructofuranosidase (Xd-INV) from the basidiomycota yeast Xanthophyllomyces dendrorhous (formerly Phaffia rhodozyma) is unique in its ability to synthesize neo- fructooligosaccharides (neo-FOS). In order to facilitate its industrial application, the recombinant enzyme expressed in Pichia pastoris (pXd-INV) was immobilized by entrapment in polyvinyl alcohol (PVA) hydrogels. The encapsulation efficiency exceeded 80%. The PVA lenticular particles of immobilized pXd-INV were stable up to approximately 40 °C. Using 600 g/L sucrose, the immobilized biocatalyst synthesized 18.9% (w/w) FOS (59.1 g/L of neokestose, 30.2 g/L of 1-kestose, 11.6 g/L of neonystose and 12.6 g/L of blastose). The operational stability of PVA-immobilized biocatalyst was assayed in a batch reactor at 30 °C. The enzyme preserved its initial activity during at least 7 cycles of 26 h.
      Citation: Catalysts
      PubDate: 2018-05-11
      DOI: 10.3390/catal8050201
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 202: Solid-Supported Palladium Catalysts in
           Sonogashira Reactions: Recent Developments

    • Authors: Diego A. Alonso, Alejandro Baeza, Rafael Chinchilla, Cecilia Gómez, Gabriela Guillena, Isidro M. Pastor, Diego J. Ramón
      First page: 202
      Abstract: The Sonogashira cross-coupling reaction is the most frequently employed synthetic procedure for the preparation of arylated alkynes, which are important conjugated compounds with multiple applications. Despite of their rather high price, this reaction is usually catalyzed by palladium species, making the recovery and reuse of the catalyst an interesting topic, mainly for industrial purposes. Easy recycle can be achieved anchoring the palladium catalyst to a separable support. This review shows recent developments in the use of palladium species anchored to different solid supports as recoverable catalysts for Sonogashira cross-coupling reactions.
      Citation: Catalysts
      PubDate: 2018-05-11
      DOI: 10.3390/catal8050202
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 203: Ru–Pd Bimetallic Catalysts Supported on
           CeO2-MnOX Oxides as Efficient Systems for H2 Purification through CO
           Preferential Oxidation

    • Authors: Roberto Fiorenza, Luca Spitaleri, Antonino Gulino, Salvatore Scirè
      First page: 203
      Abstract: The catalytic performances of Ru/ceria-based catalysts in the CO preferential oxidation (CO-PROX) reaction are discussed here. Specifically, the effect of the addition of different oxides to Ru/CeO2 has been assessed. The Ru/CeO2-MnOx system showed the best performance in the 80–120 °C temperature range, advantageous for polymer-electrolyte membrane fuel cell (PEMFC) applications. Furthermore, the influence of the addition of different metals to this mixed oxide system has been evaluated. The bimetallic Ru–Pd/CeO2-MnOx catalyst exhibited the highest yield to CO2 (75%) at 120 °C whereas the monometallic Ru/CeO2-MnOx sample was that one with the highest CO2 yield (60%) at 100 °C. The characterization data (H2-temperature programmed reduction (H2-TPR), X-ray diffraction (XRD), N2 adsorption-desorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), X-ray photoelectron spectroscopy (XPS)) pointed out that the co-presence of manganese oxide and ruthenium enhances the mobility/reactivity of surface ceria oxygens accounting for the good CO-PROX performance of this system. Reducible oxides as CeO2 and MnOx, in fact, play two important functions, namely weakening the CO adsorption on the metal active sites and providing additional sites for adsorption/activation of O2, thus changing the mechanism from competitive Langmuir–Hinshelwood into non-competitive one-step dual site Langmuir–Hinshelwood/Mars–van Krevelen. As confirmed by H2-TPR and XPS measurements, these features are boosted by the simultaneous presence of ruthenium and palladium. The strong reciprocal interaction of these metals between them and with the CeO2-MnOx support was assumed to be responsible of the promoted reducibility/reactivity of CeO2 oxygens, thus resulting in the best CO-PROX efficiency at low temperature of the Ru-Pd/CeO2-MnOx catalyst. The higher selectivity to CO2 found on the Ru–Pd system, which reduces the undesired H2 consumption, represents a promising result of this research, being one of the key aims of the design of CO-PROX catalysts.
      Citation: Catalysts
      PubDate: 2018-05-12
      DOI: 10.3390/catal8050203
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 204: A Demonstration of Pt L3-Edge EXAFS Free
           from Au L3-Edge Using Log–Spiral Bent Crystal Laue Analyzers

    • Authors: Yuki Wakisaka, Daiki Kido, Hiromitsu Uehara, Qiuyi Yuan, Satoru Takakusagi, Yohei Uemura, Toshihiko Yokoyama, Takahiro Wada, Motohiro Uo, Tomohiro Sakata, Oki Sekizawa, Tomoya Uruga, Yasuhiro Iwasawa, Kiyotaka Asakura
      First page: 204
      Abstract: Pt-Au nanostructures are important and well-studied fuel cell catalysts for their promising catalytic performance. However, a detailed quantitative local structure analysis, using extended X-ray absorption fine structure (EXAFS) spectroscopy, have been inhibited by interference between Pt and Au L3-edges. In this paper, Pt L3-edge XAFS analysis, free of Au L3 edge, is demonstrated for a Pt-Au reference sample using a low-cost log–spiral bent crystal Laue analyzer (BCLA). This method facilitates the EXAFS structural analysis of Pt-Au catalysts, which are important to improve fuel cell catalysts.
      Citation: Catalysts
      PubDate: 2018-05-13
      DOI: 10.3390/catal8050204
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 205: Artificial Biocatalytic Linear Cascades to
           Access Hydroxy Acids, Lactones, and α- and β-Amino Acids

    • Authors: Joerg H. Schrittwieser, Stefan Velikogne, Wolfgang Kroutil
      First page: 205
      Abstract: α-, β-, and ω-Hydroxy acids, amino acids, and lactones represent common building blocks and intermediates for various target molecules. This review summarizes artificial cascades published during the last 10 years leading to these products. Renewables as well as compounds originating from fossil resources have been employed as starting material. The review provides an inspiration for new cascade designs and may be the basis to design variations of these cascades starting either from alternative substrates or extending them to even more sophisticated products.
      Citation: Catalysts
      PubDate: 2018-05-14
      DOI: 10.3390/catal8050205
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 206: Total Synthesis and Biological Evaluation of
           Phaeosphaerides

    • Authors: Kenichi Kobayashi, Kosaku Tanaka, Hiroshi Kogen
      First page: 206
      Abstract: This article reviews studies regarding the total synthesis of phaeosphaerides A and B, nitrogen-containing bicyclic natural products isolated from an endophytic fungus. Numerous synthetic efforts and an X-ray crystal structure analysis of phaeosphaeride A have enabled revision of its originally proposed structure. In addition, a successful protic acid-mediated transformation of phaeosphaeride A to phaeosphaeride B revealed the hypothetical biosynthesis of phaeosphaeride B from phaeosphaeride A. Structure–activity relationship studies of phaeosphaeride derivatives are also discussed.
      Citation: Catalysts
      PubDate: 2018-05-14
      DOI: 10.3390/catal8050206
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 207: Fe Oxides Loaded on Carbon Cloth by
           Hydrothermal Process as an Effective and Reusable Heterogenous Fenton
           Catalyst

    • Authors: Honghui Yang, Bofang Shi, Silan Wang
      First page: 207
      Abstract: Iron based heterogeneous Fenton catalysts are attracting much attention for its economic and environmental friendly characteristics. In this study, iron oxides loaded carbon cloth (assigned as Fe@CC) was prepared using hydrothermal hydrolysis of Fe(NO3)3. The specific surface area of Fe@CC determined by N2 adsorption–desorption Brunauer–Emmett–Teller method was up to 1325.5 m2/g, which increased by 81.8% compared with that of native carbon cloth mainly due to the loading of iron oxide. XPS (X-ray photoelectron spectroscopy) spectra confirmed that the iron oxide on the carbon surface included mainly FeOOH. Its heterogeneous Fenton-like activity was determined using Acid Red G as a model substrate for degradation. Fe@CC maintained high and relatively stable activity during 11 tests, and it showed high COD (Chemical Oxygen Demand) removal efficiency and high apparent H2O2 utilization efficiency. The homogeneous Fenton reaction using the amount of leached Fe(III) suggested that the surficial reaction on Fe@CC was dominant. The stability and the mechanism for gradual decrease of activity during the first 4 tests were also discussed.
      Citation: Catalysts
      PubDate: 2018-05-15
      DOI: 10.3390/catal8050207
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 208: Cross-Linked Enzyme Aggregates of Feruloyl
           Esterase Preparations from Thermothelomyces thermophila and Talaromyces
           wortmannii

    • Authors: Anastasia Zerva, Io Antonopoulou, Josefine Enman, Laura Iancu, Ulrika Rova, Paul Christakopoulos
      First page: 208
      Abstract: Cross-linked enzyme aggregates (CLEA®) technology is a well-established method in the current literature for the low-cost and effective immobilization of several enzymes. The main advantage of this particular method is the simplicity of the process, since it consists of only two steps. However, CLEA immobilization must be carefully designed for each desired enzyme, since the optimum conditions for enzymes can vary significantly, according to their physicochemical properties. In the present study, an investigation of the optimum CLEA immobilization conditions was carried out for eight feruloyl esterase preparations. Feruloyl esterases are a very important enzyme group in the valorization of lignocellulosic biomass, since they act in a synergistic way with other enzymes for the breakdown of plant biomass. Specifically, we investigated the type and concentration of precipitant and the crosslinker concentration, for retaining optimal activity. FAE68 was found to be the most promising enzyme for CLEA immobilization, since in this case, the maximum retained activity, over 98%, was observed. Subsequently, we examined the operational stability and the stability in organic solvents for the obtained CLEA preparations, as well as their structure. Overall, our results support that the maximum activity retaining and the stability properties of the final CLEAs can vary greatly in different FAE preparations. Nevertheless, some of the examined FAEs show a significant potential for further applications in harsh industrial conditions.
      Citation: Catalysts
      PubDate: 2018-05-15
      DOI: 10.3390/catal8050208
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 209: Improved CO-PROX Performance of CuO/CeO2
           Catalysts by Using Nanometric Ceria as Support

    • Authors: Almerinda Di Benedetto, Gianluca Landi, Luciana Lisi
      First page: 209
      Abstract: Despite of the huge number of papers about the catalytic preferential oxidation of CO (CO-PROX) for the purification of H2 streams, there is still a need for more effective catalysts in order to reduce the large required catalyst volume of CO-PROX unity. In this work, large surface area nanometric ceria was used as support for CuO/CeO2 catalysts with CuO load up to 10 wt % easily dispersed by wet impregnation. Catalysts were characterized by ICP-MS, XRD, SEM/EDS, N2 physisorption, H2 temperature programmed reduction (TPR), and CO2 temperature programmed desorption (TPD) and tested under different reaction conditions (including under feed containing inhibiting species such as CO2 and H2O). Catalytic tests revealed that our samples show high activity and selectivity even under stringent reaction conditions; moreover, they result among the most active catalysts when compared to those reported in the scientific literature. The high activity can be related to the enhanced amount of highly dispersed copper sites in strong interaction with ceria related to the nature of the nanometric support, as evidenced by the characterization techniques. Despite the high concentration of active copper sites, catalytic performance is limited by CO2 desorption from ceria in the neighborhood of copper sites, which prevents a further improvement. This suggests that new catalyst formulations should also provide a lower affinity towards CO2.
      Citation: Catalysts
      PubDate: 2018-05-15
      DOI: 10.3390/catal8050209
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 210: Synthesis, Characterization of Nanosized
           ZnCr2O4 and Its Photocatalytic Performance in the Degradation of Humic
           Acid from Drinking Water

    • Authors: Raluca Dumitru, Florica Manea, Cornelia Păcurariu, Lavinia Lupa, Aniela Pop, Adrian Cioablă, Adrian Surdu, Adelina Ianculescu
      First page: 210
      Abstract: Zinc chromite (ZnCr2O4) has been synthesized by the thermolysis of a new Zn(II)-Cr(III) oxalate coordination compound, namely [Cr2Zn(C2O4)4(OH2)6]·4H2O. The coordination compound has been characterized by chemical analysis, infrared spectroscopy (IR), and thermal analysis. The zinc chromite obtained after a heating treatment of the coordination compound at 450 °C for 1 h has been investigated by XRD, FE-SEM, TEM/HR-TEM coupled with selected area electron diffraction (SAED) measurements. The photocatalytic performance of nanosized zinc chromite was assessed for the degradation and mineralization of humic acid (HA) from a drinking water source, envisaging the development of the advanced oxidation process for drinking water treatment technology. A mineralization efficiency of 60% was achieved after 180 min of 50 mg L−1 HA photocatalysis using zinc chromite under UV irradiation, in comparison with 7% efficiency reached by photolysis.
      Citation: Catalysts
      PubDate: 2018-05-15
      DOI: 10.3390/catal8050210
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 211: Catalytic Ozonation of Toluene Using Chilean
           Natural Zeolite: The Key Role of Brønsted and Lewis Acid Sites

    • Authors: Serguei Alejandro-Martín, Héctor Valdés, Marie-Hélène Manero, Claudio A. Zaror
      First page: 211
      Abstract: The influence of surface physical-chemical characteristics of Chilean natural zeolite on the catalytic ozonation of toluene is presented in this article. Surface characteristics of natural zeolite were modified by acid treatment with hydrochloric acid and ion-exchange with ammonium sulphate. Prior to catalytic ozonation assays, natural and chemically modified zeolite samples were thermally treated at 623 and 823 K in order to enhance Brønsted and Lewis acid sites formation, respectively. Natural and modified zeolite samples were characterised by N2 adsorption at 77 K, elemental analysis, X-ray fluorescence, and Fourier transform infrared (FTIR) spectroscopy, using pyridine as a probe molecule. The highest values of the reaction rate of toluene oxidation were observed when NH4Z1 and 2NH4Z1 zeolite samples were used. Those samples registered the highest density values of Lewis acid sites compared to other samples used here. Results indicate that the presence of strong Lewis acid sites at the 2NH4Z1 zeolite surface causes an increase in the reaction rate of toluene oxidation, confirming the role of Lewis acid sites during the catalytic ozonation of toluene at room temperature. Lewis acid sites decompose gaseous ozone into atomic oxygen, which reacts with the adsorbed toluene at Brønsted acid sites. On the other hand, no significant contribution of Brønsted acid sites on the reaction rate was registered when NH4Z1 and 2NH4Z1 zeolite samples were used.
      Citation: Catalysts
      PubDate: 2018-05-17
      DOI: 10.3390/catal8050211
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 212: Nanostructured Oxides Synthesised via
           scCO2-Assisted Sol-Gel Methods and Their Application in Catalysis

    • Authors: Yehan Tao, Paolo P. Pescarmona
      First page: 212
      Abstract: Nanostructured metal oxides and silicates are increasingly applied in catalysis, either as supports or as active species in heterogeneous catalysts, owing to the physicochemical properties that typically distinguish them from bulk oxides, such as higher surface area and a larger fraction of coordinatively unsaturated sites at their surface. Among the different synthetic routes for preparing these oxides, sol-gel is a relatively facile and efficient method. The use of supercritical CO2 (scCO2) in the sol-gel process can be functional to the formation of nanostructured materials. The physical properties of the scCO2 medium can be controlled by adjusting the processing temperature and the pressure of CO2, thus enabling the synthesis conditions to be tuned. This paper provides a review of the studies on the synthesis of oxide nanomaterials via scCO2-assisted sol-gel methods and their catalytic applications. The advantages brought about by scCO2 in the synthesis of oxides are described, and the performance of oxide-based catalysts prepared by scCO2 routes is compared to their counterparts prepared via non-scCO2-assisted methods.
      Citation: Catalysts
      PubDate: 2018-05-17
      DOI: 10.3390/catal8050212
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 213: The Role of Pulse Voltage Amplitude on
           Chemical Processes Induced by Streamer Discharge at Water Surface

    • Authors: Ruma, Hamid Hosano, Takashi Sakugawa, Hidenori Akiyama
      First page: 213
      Abstract: The paper reports the effects of pulse voltage amplitude on streamer discharge propagation at water surface. The subsequent chemical processes in a reactor following the surface discharges with different voltages are presented. A pulsed power modulator (PPM) system equipped with a control unit was employed to generate 0–25 kV pulses at 500 Hz. A point-plane electrode configuration was used for experiments, with the point electrode placed with 1 mm gap from the water surface in atmospheric air, and plane ground submerged with 30 mm gap in water. The streamer length at water surface was significantly influenced by the pulse voltage amplitude. Colorimetric measurement of hydrogen peroxide (H2O2) and treatment of indigo carmine organic dye solution were carried out to elucidate the chemical processes produced at various pulse voltages. The experimental results reveal that the applied voltage is a factor that greatly affects water surface discharges and their chemical processes.
      Citation: Catalysts
      PubDate: 2018-05-17
      DOI: 10.3390/catal8050213
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 214: Host-Guest Engineering of Layered Double
           Hydroxides towards Efficient Oxygen Evolution Reaction: Recent Advances
           and Perspectives

    • Authors: Jianming Li, Shan Jiang, Mingfei Shao, Min Wei
      First page: 214
      Abstract: Electrochemical water splitting has great potential in the storage of intermittent energy from the sun, wind, or other renewable sources for sustainable clean energy applications. However, the anodic oxygen evolution reaction (OER) usually determines the efficiency of practical water electrolysis due to its sluggish four-electron process. Layered double hydroxides (LDHs) have attracted increasing attention as one of the ideal and promising electrocatalysts for water oxidation due to their excellent activity, high stability in basic conditions, as well as their earth-abundant compositions. In this review, we discuss the recent progress on LDH-based OER electrocatalysts in terms of active sites, host-guest engineering, and catalytic performances. Moreover, further developments and challenges in developing promising electrocatalysts based on LDHs are discussed from the viewpoint of molecular design and engineering.
      Citation: Catalysts
      PubDate: 2018-05-17
      DOI: 10.3390/catal8050214
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 215: The Pros and Cons of Polydopamine-Sensitized
           Titanium Oxide for the Photoreduction of CO2

    • Authors: Tongyao Wang, Ming Xia, Xueqian Kong
      First page: 215
      Abstract: Photocatalytic reduction of CO2 into fuels is a promising route to reduce greenhouse gas emission, and it demands high-performance photocatalysts that can use visible light in the solar spectrum. Due to its broadband light adsorption, polydopamine (PDA) is considered as a promising photo-sensitization material for semiconductor photocatalysts. In this work, titanium oxides have been coated with PDA through an in-situ oxidation polymerization method to pursue CO2 reduction under visible light. We have shown that the surface coated PDA with a thickness of around 1 nm can enhance the photocatalytic performance of anatase under visible light to reduce CO2 into CO. Assisted with additional UV-vis adsorption and photoluminescence characterizations, we confirmed the sensitization effect of PDA on anatase. Furthermore, our study shows that thicker PDA coating might not be favorable, as PDA could decompose under both visible and UV-vis light irradiations. 13C solid-state nuclear magnetic resonance showed structural differences between thin and thick PDA coatings and revealed compositional changes of PDA after light irradiation.
      Citation: Catalysts
      PubDate: 2018-05-17
      DOI: 10.3390/catal8050215
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 216: Biocatalysis and Biotransformations

    • Authors: Manuel Ferrer
      First page: 216
      Abstract: n/a
      Citation: Catalysts
      PubDate: 2018-05-17
      DOI: 10.3390/catal8050216
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 217: Deep Eutectic Mixtures as Reaction Media for
           the Enantioselective Organocatalyzed α-Amination of 1,3-Dicarbonyl
           Compounds

    • Authors: Diego Ros Ñíguez, Pegah Khazaeli, Diego A. Alonso, Gabriela Guillena
      First page: 217
      Abstract: The enantioselective α-amination of 1,3-dicarbonyl compounds has been performed using deep eutectic solvents (DES) as a reaction media and chiral 2-amino benzimidazole-derived compounds as a catalytic system. With this procedure, the use of toxic volatile organic compounds (VOCs) as reaction media is avoided. Furthermore, highly functionalized chiral molecules, which are important intermediates for the natural product synthesis, are synthetized by an efficient and stereoselective protocol. Moreover, the reaction can be done on a preparative scale, with the recycling of the catalytic system being possible for at least five consecutive reaction runs. This procedure represents a cheap, simple, clean, and scalable method that meets most of the principles to be considered a green and sustainable process.
      Citation: Catalysts
      PubDate: 2018-05-18
      DOI: 10.3390/catal8050217
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 218: Activation of Persulfate Using an Industrial
           Iron-Rich Sludge as an Efficient Nanocatalyst for Landfill Leachate
           Treatment

    • Authors: Alaa Mohamad Soubh, Majid Baghdadi, Mohammad Ali Abdoli, Behnoush Aminzadeh
      First page: 218
      Abstract: In this research, the performance of nanomaterials obtained from the converter sludge (CS) of Esfahan Steel Company, Iran was investigated for the activation of persulfate (PS). The experiments were conducted on real and synthetic leachates. CS showed high catalytic activity for removal of chemical oxygen demand COD and NH3 because of its high iron oxide content. The effects of pH, CS dosage, and PS/COD ratio, temperature, and reaction time on the removal of COD and NH3 were evaluated to optimize operational conditions (pH 2, CS dosage: 1.2 g L−1, PS/COD: 4, and reaction time: 60 min). Maximum COD and NH3 removal efficiencies were 73.56 and 63.87%, respectively. Finally, the optimized process was applied for treatment of a real leachate sample. Although the treated leachate was not suitable to discharge into the environment, an increase in the 5-day biochemical oxygen demand (BOD5) and biodegradability (BOD5/COD) of leachate after treatment indicated that the effluent can be biologically treated. As a consequence, it can be combined with sewage or can be returned to the landfill.
      Citation: Catalysts
      PubDate: 2018-05-20
      DOI: 10.3390/catal8050218
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 219: Catalytic Ozonation by Iron Coated Pumice
           for the Degradation of Natural Organic Matters

    • Authors: Alper Alver, Ahmet Kılıç
      First page: 219
      Abstract: The use of iron-coated pumice (ICP) in heterogeneous catalytic ozonation significantly enhanced the removal efficiency of natural organic matters (NOMs) in water, due to the synergistic effect of hybrid processes when compared to sole ozonation and adsorption. Multiple characterization analyses (BET, TEM, XRD, DLS, FT-IR, and pHPZC) were employed for a systematic investigation of the catalyst surface properties. This analysis indicated that the ICP crystal structure was α-FeOOH, the surface hydroxyl group of ICP was significantly increased after coating, the particle size of ICP was about 200–250 nm, the BET surface area of ICP was about 10.56 m2 g−1, the pHPZC value of ICP was about 7.13, and that enhancement by iron loading was observed in the FT-IR spectra. The contribution of surface adsorption, hydroxyl radicals, and sole ozonation to catalytic ozonation was determined as 21.29%, 66.22%, and 12.49%, respectively. The reaction kinetic analysis with tert-Butyl alcohol (TBA) was used as a radical scavenger, confirming that surface ferrous iron loading promoted the role of the hydroxyl radicals. The phosphate was used as an inorganic probe, and significantly inhibited the removal efficiency of catalytic NOM ozonation. This is an indication that the reactions which occur are more dominant in the solution phase.
      Citation: Catalysts
      PubDate: 2018-05-21
      DOI: 10.3390/catal8050219
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 220: Effects of Synthesis on the Structural
           Properties and Methane Partial Oxidation Activity of Ni/CeO2 Catalyst

    • Authors: Valeria La Parola, Giuseppe Pantaleo, Anna Venezia
      First page: 220
      Abstract: Nickel catalysts supported on homemade CeO2 oxide were prepared by two procedures intending to achieve different degree of metal-support interaction. One method consisted of a co-precipitation that was assisted by microwave; the other method was based on a modified wetness impregnation in the presence of the organic complexing ligand, nitrilotriacetic acid (NTA). The support and catalysts were characterized by temperature programmed reduction (TPR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. Significant differences in the structure, in redox properties and in the elemental surface composition emerged. The catalytic behavior in the partial oxidation of methane was tested at atmospheric pressure, in a range of temperature between 400–800 °C, using diluted feed gas mixture with CH4/O2 = 2 and GHSV= 60,000 mL g−1 h−1. Moreover, the effect of the catalyst reduction pretreatment was investigated. The better catalytic performance of the microwave-assisted sample as compared to the NTA prepared sample was attributed to the stronger interaction of nickel with CeO2. Indeed, according to the structural and reducibility results, an adequate electronic contact between the metal and the support favors the formation of oxygen vacancies of ceria and inhibits the sintering of the catalyst active species, with an improvement of the catalytic performance.
      Citation: Catalysts
      PubDate: 2018-05-21
      DOI: 10.3390/catal8050220
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 221: Selective Reduction of Ketones and Aldehydes
           in Continuous-Flow Microreactor—Kinetic Studies

    • Authors: Katarzyna Maresz, Agnieszka Ciemięga, Julita Mrowiec-Białoń
      First page: 221
      Abstract: In this work, the kinetics of Meerwein–Ponndorf–Verley chemoselective reduction of carbonyl compounds was studied in monolithic continuous-flow microreactors. To the best of our knowledge, this is the first report on the MPV reaction kinetics performed in a flow process. The microreactors are a very attractive alternative to the batch reactors conventionally used in this process. The proposed micro-flow system for synthesis of unsaturated secondary alcohols proved to be very efficient and easily controlled. The microreactors had reactive cores made of zirconium-functionalized silica monoliths of excellent catalytic properties and flow characteristics. The catalytic experiments were carried out with the use of 2-butanol as a hydrogen donor. Herein, we present the kinetic parameters of cyclohexanone reduction in a flow reactor and data on the reaction rate for several important ketones and aldehydes. The lack of diffusion constraints in the microreactors was demonstrated. Our results were compared with those from other authors and demonstrate the great potential of microreactor applications in fine chemical and complex intermediate manufacturing.
      Citation: Catalysts
      PubDate: 2018-05-22
      DOI: 10.3390/catal8050221
      Issue No: Vol. 8, No. 5 (2018)
       
  • Catalysts, Vol. 8, Pages 154: Preparation of Stable Cross-Linked Enzyme
           Aggregates (CLEAs) of a Ureibacillus thermosphaericus Esterase for
           Application in Malathion Removal from Wastewater

    • Authors: Yuliya Samoylova, Ksenia Sorokina, Alexander Piligaev, Valentin Parmon
      First page: 154
      Abstract: In this study, the active and stable cross-linked enzyme aggregates (CLEAs) of the thermostable esterase estUT1 of the bacterium Ureibacillus thermosphaericus were prepared for application in malathion removal from municipal wastewater. Co-expression of esterase with an E. coli chaperone team (KJE, ClpB, and ELS) increased the activity of the soluble enzyme fraction up to 200.7 ± 15.5 U mg−1. Response surface methodology (RSM) was used to optimize the preparation of the CLEA-estUT1 biocatalyst to maximize its activity and minimize enzyme loss. CLEA-estUT1 with the highest activity of 29.4 ± 0.5 U mg−1 (90.6 ± 2.7% of the recovered activity) was prepared with 65.1% (w/v) ammonium sulfate, 120.6 mM glutaraldehyde, and 0.2 mM bovine serum albumin at 5.1 h of cross-linking. The biocatalyst has maximal activity at 80 °С and pH 8.0. Analysis of the properties of CLEA-estUT1 and free enzyme at 50–80 °C and pH 5.0–10.0 showed higher stability of the biocatalyst. CLEA-estUT1 showed marked tolerance against a number of chemicals and high operational stability and activity in the reaction of malathion hydrolysis in wastewater (up to 99.5 ± 1.4%). After 25 cycles of malathion hydrolysis at 37 °С, it retained 55.2 ± 1.1% of the initial activity. The high stability and reusability of CLEA-estUT1 make it applicable for the degradation of insecticides.
      Citation: Catalysts
      PubDate: 2018-04-11
      DOI: 10.3390/catal8040154
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 156: The Effects of Coordinated Molecules of Two
           Gly-Schiff Base Copper Complexes on Their Oxygen Reduction Reaction
           Performance

    • Authors: Zhe Ma, Ya Chu, Chonggang Fu, Hongmei Du, Xianqiang Huang, Jinsheng Zhao
      First page: 156
      Abstract: In this study, two simple Schiff base copper complexes [Cu(H2O)2(HL)]·2H2O (Complex 1) (H3L = 2-OH-4-(OH)-C6H2CH=NCH2CO2H) and [Cu(py)2(HL)] (Complex 2) (Py = pyridine) were initially achieved and authenticated by single-crystal X-ray structure analyses (SXRD), powder X-ray diffraction analyses (PXRD), FT-IR spectroscopy, and elemental analyses. The SXRD reveals that the Cu2+ center in Complex 1 exhibited a distorted square pyramidal geometry, which is constructed based on phenolate oxygen, water molecules, carboxylate oxygen, and imine nitrogen from a deprotonated H3L ligand in an NO4 fashion. The Cu2+ atom in Complex 2 had distorted square pyramidal geometry, and was coordinated with two pyridine molecules and one Gly-Schiff base ligand, exhibiting an N3O2 binding set. Additionally, the free water molecules in Complex 1 linked independent copper complexes by intermolecular hydrogen bond to form a 2D framework. However, the one-dimensional chain supramolecular structure of Complex 2 was formed by the intermolecular O–H…O hydrogen bonds. The oxygen reduction performance of the two complexes was analyzed by cyclic voltammetry (CV) and the rotating disk electrode (RDE) method. Both complexes could catalyze the conversion of oxygen to water through a predominant four-electron pathway, and the Cu–NxOy moieties might be the functional moieties for the catalytic activity. The catalytic pathways and underlying mechanisms are also discussed in detail, from which the structure–activity relationship of the complexes was obtained.
      Citation: Catalysts
      PubDate: 2018-04-12
      DOI: 10.3390/catal8040156
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 157: Catalytic Role of H2O Molecules in Oxidation
           of CH3OH in Water

    • Authors: Satoshi Inaba
      First page: 157
      Abstract: We have examined the catalytic role of H2O molecules in the oxidation of CH3OH in water by quantum chemical simulations. A CH3OH is decomposed into molecules, a formaldehyde and an H2, in water, while it is converted into radicals in a gas phase reaction at a high temperature. H2O molecules located near a CH3OH form a first hydration shell and act as catalyst for the oxidation of CH3OH in water. The oxidation process of a CH3OH in water begins when a proton is delivered to a neighbor H2O molecule from a hydroxyl of a CH3OH. The H2O molecule transfers an extra proton to a second H2O molecule, a proton of which is combined with a proton detached from the methyl of the CH3OH, forming an H2. The energy barrier to decompose a CH3OH is significantly reduced by the catalyst of H2O molecules in water. A cluster of H2O molecules arise in water as an enclosed chain of hydrogen bonds between H2O molecules. A proton is transferred with less energy between H2O molecules within a cluster of H2O molecules. A cluster of five H2O molecules further reduces the energy barrier. The calculated oxidation rate of CH3OH with the transition state theory agrees well with that determined by experiments.
      Citation: Catalysts
      PubDate: 2018-04-12
      DOI: 10.3390/catal8040157
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 158: Binary Nitrogen Precursor-Derived Porous
           Fe-N-S/C Catalyst for Efficient Oxygen Reduction Reaction in a Zn-Air
           Battery

    • Authors: Xiao Liu, Chi Chen, Qingqing Cheng, Liangliang Zou, Zhiqing Zou, Hui Yang
      First page: 158
      Abstract: It is still a challenge to synthesize non-precious-metal catalysts with high activity and stability for the oxygen reduction reaction (ORR) to replace the state-of-the art Pt/C catalyst. Herein, a Fe, N, S co-doped porous carbon (Fe-NS/PC) is developed by using g-C3N4 and 2,4,6-tri(2-pyridyl)-1,3,5-triazine (TPTZ) as binary nitrogen precursors. The interaction of binary nitrogen precursors not only leads to the formation of more micropores, but also increases the doping amount of both iron and nitrogen dispersed in the carbon matrix. After a second heat-treatment, the best Fe/NS/C-g-C3N4/TPTZ-1000 catalyst exhibits excellent ORR performance with an onset potential of 1.0 V vs. reversible hydrogen electrode (RHE) and a half-wave potential of 0.868 V (RHE) in alkaline medium. The long-term durability is even superior to the commercial Pt/C catalyst. In the meantime, an assembled Zn-air battery with Fe/NS/C-g-C3N4/TPTZ-1000 as the cathode shows a maximal power density of 225 mW·cm−2 and excellent durability, demonstrating the great potential of practical applications in energy conversion devices.
      Citation: Catalysts
      PubDate: 2018-04-13
      DOI: 10.3390/catal8040158
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 159: Immobilization of Enterobacter aerogenes by
           a Trimetric Autotransporter Adhesin, AtaA, and Its Application to
           Biohydrogen Production

    • Authors: Hajime Nakatani, Nan Ding, Yuki Ohara, Katsutoshi Hori
      First page: 159
      Abstract: Biological hydrogen production by microbial cells has been extensively researched as an energy-efficient and environmentally-friendly process. In this study, we propose a fast, easy method for immobilizing Enterobacter aerogenes by expressing ataA, which encodes the adhesive protein of Acinetobacter sp. Tol 5. AtaA protein on the E. aerogenes cells carrying the ataA gene was demonstrated by immunoblotting and flow cytometry. The AtaA-producing cells exhibited stronger adherence and auto-agglutination characteristics than wild-type cells, and were successfully immobilized (at approximately 2.5 mg/cm3) on polyurethane foam. Hydrogen production from the cell-immobilized polyurethane foams was monitored in repetitive batch reactions and flow reactor studies. The total hydrogen production in triple-repetitive batch reactions reached 0.6 mol/mol glucose, and the hydrogen production rate in the flow reactor was 42 mL·h−1·L−1. The AtaA production achieved simple and immediate immobilization of E. aerogenes on the foam, enabling repetitive and continuous hydrogen production. This report newly demonstrates the production of AtaA on the cell surfaces of bacterial genera other than Acinetobacter, and can simplify and accelerate the immobilization of whole-cell catalysts.
      Citation: Catalysts
      PubDate: 2018-04-16
      DOI: 10.3390/catal8040159
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 160: Catalytic Activities of Noble Metal
           Phosphides for Hydrogenation and Hydrodesulfurization Reactions

    • Authors: Yasuharu Kanda, Kota Kawanishi, Taiki Tsujino, Ahmad MFM Al-otaibi, Yoshio Uemichi
      First page: 160
      Abstract: In this work, the development of a highly active noble metal phosphide (NMXPY)-based hydrodesulfurization (HDS) catalyst with a high hydrogenating ability for heavy oils was studied. NMXPY catalysts were obtained by reduction of P-added noble metals (NM-P, NM: Rh, Pd, Ru) supported on SiO2. The order of activities for the hydrogenation of biphenyl was Rh-P > NiMoS > Pd-P > Ru-P. This order was almost the same as that of the catalytic activities for the HDS of dibenzothiophene. In the HDS of 4,6-dimethyldibenzothiophene (4,6-DMDBT), the HDS activity of the Rh-P catalyst increased with increasing reaction temperature, but the maximum HDS activity for the NiMoS catalyst was observed at 270 °C. The Rh-P catalyst yielded fully hydrogenated products with high selectivity compared with the NiMoS catalyst. Furthermore, XRD analysis of the spent Rh-P catalysts revealed that the Rh2P phase possessed high sulfur tolerance and resistance to sintering.
      Citation: Catalysts
      PubDate: 2018-04-17
      DOI: 10.3390/catal8040160
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 161: A Comparative Study of Gold Impregnation
           Methods for Obtaining Metal/Semiconductor Nanophotocatalysts: Direct
           Turkevich, Inverse Turkevich, and Progressive Heating Methods

    • Authors: Mayra Matamoros-Ambrocio, María de Lourdes Ruiz-Peralta, Ernesto Chigo-Anota, Jesús García-Serrano, Armando Pérez-Centeno, Manuel Sánchez-Cantú, Efraín Rubio-Rosas, Alejandro Escobedo-Morales
      First page: 161
      Abstract: ZnO nanostructures decorated with gold nanoparticles (Au-NPs) were synthesized by thermal decomposition of ZnO2 powders and their subsequent impregnation of metal nanoparticles using either the Direct Turkevich Method, the Inverse Turkevich Method, or the Progressive Heating Method. It was found that the impregnation approach influences the resulting microstructure and photocatalytic activity of the obtained materials. While the Direct Turkevich approach gave the highest yield of metal loading, the smallest Au-NPs were obtained by Inverse Turkevich and the Progressive Heating Method. The photocatalytic activity of the pristine support and gold-loaded samples was studied in the decolorization of Rhodamine B solutions using UV- and pure visible-light illumination. All Au-NPs/ZnO samples showed higher photocatalytic activity than the bare support when UV-light was used. This effect is attributed to a charge carrier separation due to electron transfer from ZnO to the metal nanoparticles and the built-in electric field at the interfaces. Contrarily to most reports, visible-light sensitization using plasmonic nanoparticles was not observed. The experimental evidence points against hot-electron injection from Au-NPs to the semiconductor component. This behavior is associated with the height of the Schottky barrier at the metal-semiconductor junctions. The differences in the photocatalytic performance among the samples under UV- and visible-light are explained in terms of the characteristics of the Au-NPs driven by the growth mechanism involved in each impregnation method and the physicochemical properties of the generated interfaces.
      Citation: Catalysts
      PubDate: 2018-04-18
      DOI: 10.3390/catal8040161
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 162: Mobility of NH3-Solvated CuII Ions in
           Cu-SSZ-13 and Cu-ZSM-5 NH3-SCR Catalysts: A Comparative Impedance
           Spectroscopy Study

    • Authors: Valentina Rizzotto, Peirong Chen, Ulrich Simon
      First page: 162
      Abstract: The mobility of NH3-solvated Cu ions within the zeolite framework has been recently identified as a key factor for the kinetics of the selective catalytic reduction of NOx with NH3 (NH3-SCR) over Cu-zeolite catalysts at low temperatures. Here, we utilize in situ impedance spectroscopy to explore the mobility of NH3-solvated CuII ions, i.e., CuII(NH3)n, in Cu-SSZ-13 and Cu-ZSM-5 zeolites with varied Cu ion exchange levels, and observed that both the zeolite framework (CHA or MFI) and the Cu exchange level influence the high-frequency dielectric relaxation processes that are associated with the short-range (local) motion of CuII(NH3)n. Our results suggest that the local motion of CuII(NH3)n species is favored within the CHA framework due to the unique cage structure, and thereby contribute to the overall ion conductivity at high frequencies, which, on the contrary, is not observed for ZSM-5, where NH3-solvated Cu2+ ions do not experience a comparable constrained space for local motion. This study sheds new light on the mobility of Cu active sites under NH3-SCR related reaction conditions and may contribute to an advanced understanding of the underlying mechanism.
      Citation: Catalysts
      PubDate: 2018-04-18
      DOI: 10.3390/catal8040162
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 163: An Overview on Zeolite Shaping Technology
           and Solutions to Overcome Diffusion Limitations

    • Authors: Rogéria Bingre, Benoît Louis, Patrick Nguyen
      First page: 163
      Abstract: Synthetic zeolites are widely used as catalysts/carriers for many petrochemical reactions and in refining processes. These materials are usually synthesized in a powder form and must be shaped prior to use in industrial reactors. This review presents the state-of-the-art of the zeolite shaping technology describing the main modifications induced by the interactions between the zeolite and the binder. Additionally, a strategy is presented to overcome the diffusion limitations associated to the microporous structure of zeolites, consisting in the introduction of hierarchical porosity in the binder. Several developments in the field of hierarchical aluminas are summarized in this article, highlighting the possibility to design different ordered/disordered mesoporous and macroporous structures.
      Citation: Catalysts
      PubDate: 2018-04-18
      DOI: 10.3390/catal8040163
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 164: Surface Reduced CeO2 Nanowires for Direct
           Conversion of CO2 and Methanol to Dimethyl Carbonate: Catalytic
           Performance and Role of Oxygen Vacancy

    • Authors: Zhongwei Fu, Yuehong Yu, Zhen Li, Dongmei Han, Shuanjin Wang, Min Xiao, Yuezhong Meng
      First page: 164
      Abstract: Ultralong 1D CeO2 nanowires were synthesized via an advanced solvothermal method, surface reduced under H2 atmosphere, and first applied in direct synthesis of dimethyl carbonate (DMC) from CO2 and CH3OH. The micro morphologies, physical parameters of nanowires were fully investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption, X-ray photoelectron spectrum (XPS), and temperature-programmed desorption of ammonia/carbon dioxide (NH3-TPD/CO2-TPD). The effects of surface oxygen vacancy and acidic/alkaline sites on the catalytic activity was explored. After reduction, the acidic/alkaline sites of CeO2 nanowires can be dramatically improved and evidently raised the catalytic performance. CeO2 nanowires reduced at 500 °C (CeO2_NW_500) exhibited notably superior activity with DMC yield of 16.85 mmol gcat−1. Furthermore, kinetic insights of initial rate were carried out and the apparent activation energy barrier of CeO2_NW_500 catalyst was found to be 41.9 kJ/mol, much tiny than that of CeO2_NW catalyst (74.7 KJ/mol).
      Citation: Catalysts
      PubDate: 2018-04-19
      DOI: 10.3390/catal8040164
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 165: Asymmetric Ketone Reduction by Immobilized
           Rhodotorula mucilaginosa

    • Authors: Hui Liu, Wen-Di Duan, Fayene Zeferino Ribeiro de Souza, Lan Liu, Bi-Shuang Chen
      First page: 165
      Abstract: In our previous study, Rhodotorula mucilaginosa (R. mucilaginosa) was selected via high throughput screening as a very active and selective whole-cell biocatalyst for the asymmetric reduction of ketones. In this study, the reduction of ketones to the desired chiral alcohols by immobilized cells of this strain was investigated. Characterization with Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) showed that whole R. mucilaginosa cells were successfully immobilized on support matrices composed of agar, calcium alginate, PVA-alginate and chitosan. The immobilized cells were applied to the enantioselective reduction of fourteen different aromatic ketones. Good to excellent results were achieved with R. mucilaginosa cells immobilized on agar and calcium alginate. The immobilized cells on the selected support matrix composed of agar exhibited a significant increase in pH tolerance at pH 3.5–9 and demonstrated highly improved thermal stability compared to free cells. The cells immobilized on agar retained 90% activity after 60 days storage at 4 °C and retained almost 100% activity after 6 reuse cycles. In addition, the immobilization procedures are very simple and cause minimal pollution. These results suggest that the application of immobilized R. mucilaginosa can be practical on an industrial scale to produce chiral alcohols.
      Citation: Catalysts
      PubDate: 2018-04-19
      DOI: 10.3390/catal8040165
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 166: Applications of Immobilized Bio-Catalyst in
           Metal-Organic Frameworks

    • Authors: Qi Wang, Xizhen Lian, Yu Fang, Hong-Cai Zhou
      First page: 166
      Abstract: Immobilization of bio-catalysts in solid porous materials has attracted much attention in the last few decades due to its vast application potential in ex vivo catalysis. Despite the high efficiency and selectivity of enzymatic catalytic processes, enzymes may suffer from denaturation under industrial production conditions, which, in turn, diminish their catalytic performances and long-term recyclability. Metal-organic frameworks (MOFs), as a growing type of hybrid materials, have been identified as promising platforms for enzyme immobilization owing to their enormous structural and functional tunability, and extraordinary porosity. This review mainly focuses on the applications of enzyme@MOFs hybrid materials in catalysis, sensing, and detection. The improvements of catalytic activity and robustness of encapsulated enzymes over the free counterpart are discussed in detail.
      Citation: Catalysts
      PubDate: 2018-04-20
      DOI: 10.3390/catal8040166
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 167: Unprecedented Proline-Based Heterogeneous
           Organocatalyst for Selective Production of Vanillin

    • Authors: Farveh Saberi, Daily Rodriguez-Padrón, Araceli Garcia, Hamid Reza Shaterian, Rafael Luque
      First page: 167
      Abstract: An organocatalytic system based on an unprecedented proline analogue and iron oxide magnetic nanoparticles (Prn/Fe2O3@SiO2) was designed and employed in vanillin production from isoeugenol and vanillyl alcohol. Full characterization of the obtained catalyst revealed the successful functionalization of the nanoparticle surface with the organic moieties. The activity of the magnetic bifunctional material was compared with its proton-unexchanged counterpart. Interestingly, the oxidation of isoeugenol resulted in being highly dependent on the acidic functionalities of the organocatalyst. Nonetheless, the catalytic performance of the proton-unexchanged catalyst suggested that the acidic and basic sites of the Prn/Fe2O3@SiO2 exhibited a synergic effect, giving rise to higher conversion and selectivity. The presence of bifunctional groups in the proline analogue, together with the magnetic properties of the iron oxide nanoparticles, could lead to high efficiency, versatility, recoverability, and reusability.
      Citation: Catalysts
      PubDate: 2018-04-20
      DOI: 10.3390/catal8040167
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 168: Co-Immobilization of Ketoreductase and
           Glucose Dehydrogenase

    • Authors: Tatiana Petrovičová, Kristína Markošová, Zuzana Hegyi, Ioulia Smonou, Michal Rosenberg, Martin Rebroš
      First page: 168
      Abstract: A two-enzyme system composed of immobilized ketoreductase (Hansenula polymorpha) and glucose dehydrogenase (Bacillus megaterium) was developed for the asymmetric reduction of keto esters to optically active hydroxy esters via immobilization in polyvinyl alcohol (PVA) gel particles. The concentration of enzymes was optimized, and the final particles were used 18 times in a row in a batch mode to achieve minimal loss of activity and complete conversion of the model substrate, β-ketoester ethyl-2-methylacetoacetate. Excellent stability was also achieved using new storage conditions of PVA particles, with 80% of activity being retained after almost 10 months.
      Citation: Catalysts
      PubDate: 2018-04-20
      DOI: 10.3390/catal8040168
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 169: A Biorefinery Cascade Conversion of
           Hemicellulose-Free Eucalyptus Globulus Wood: Production of Concentrated
           Levulinic Acid Solutions for γ-Valerolactone Sustainable Preparation

    • Authors: Sandra Rivas, Anna Maria Raspolli Galletti, Claudia Antonetti, Domenico Licursi, Valentín Santos, Juan Carlos Parajó
      First page: 169
      Abstract: Eucalyptus globulus wood samples were subjected to preliminary aqueous processing to remove water-soluble extractives and hemicelluloses, and the resulting solid (mainly made up of cellulose and lignin) was employed as a substrate for converting the cellulosic fraction into mixtures of levulinic and formic acid through a sulfuric acid-catalyzed reaction. These runs were carried out in a microwave-heated reactor at different temperatures and reaction times, operating in single-batch or cross-flow modes, in order to identify the most favorable operational conditions. Selected liquid phases deriving from these experiments, which resulted in concentrated levulinic acid up to 408 mmol/L, were then employed for γ-valerolactone production by levulinc acid hydrogenation in the presence of the commercial 5% Ru/C catalyst. In order to assess the effects of the main reaction parameters, hydrogenation experiments were performed at different temperatures, reaction times, amounts of ruthenium catalyst and hydrogen pressure. Yields of γ-valerolactone in the range of 85–90 mol % were obtained from the hydrogenation of the wood-derived solutions containing levulinic acid, obtained by single-batch operation or by the cross-flow process. The negative effect of co-produced formic acid present in crude levulinic acid solutions was evidenced and counteracted efficiently by allowing the preliminary thermal decomposition of formic acid itself.
      Citation: Catalysts
      PubDate: 2018-04-21
      DOI: 10.3390/catal8040169
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 170: Maltose Production Using Starch from Cassava
           Bagasse Catalyzed by Cross-Linked β-Amylase Aggregates

    • Authors: Rafael Araujo-Silva, Agnes Cristina Oliveira Mafra, Mayerlenis Jimenez Rojas, Willian Kopp, Roberto de Campos Giordano, Roberto Fernandez-Lafuente, Paulo Waldir Tardioli
      First page: 170
      Abstract: Barley β-amylase was immobilized using different techniques. The highest global yield was obtained using the cross-linked enzyme aggregates (CLEA) technique, employing bovine serum albumin (BSA) or soy protein isolate (SPI) as feeder proteins to reduce diffusion problems. The CLEAs produced using BSA or SPI showed 82.7 ± 5.8 and 53.3 ± 2.4% global yield, respectively, and a stabilization effect was observed upon immobilization at neutral pH value, e.g., after 12 h at 55 °C, the free β-amylase is fully inactivated, while CLEAs retained 25 and 15% of activity (using BSA and SPI, respectively). CLEA using SPI was selected because of its easier recovery, being chosen to convert the residual starch contained in cassava bagasse into maltose. This biocatalyst permitted to reach almost 70% of maltose conversion in 4 h using 30.0 g/L bagasse starch solution (Dextrose Equivalent of 15.88) and 1.2 U of biocatalyst per gram of starch at pH 7.0 and 40 °C. After 4 reuses (batches of 12 h) the CLEA using SPI maintained 25.50 ± 0.01% of conversion due to the difficulty of recovering.
      Citation: Catalysts
      PubDate: 2018-04-21
      DOI: 10.3390/catal8040170
      Issue No: Vol. 8, No. 4 (2018)
       
  • Catalysts, Vol. 8, Pages 171: CuO Nanoparticles Supported on TiO2 with
           High Efficiency for CO2 Electrochemical Reduction to Ethanol

    • Authors: Jing Yuan, Jing-Jie Zhang, Man-Ping Yang, Wang-Jun Meng, Huan Wang, Jia-Xing Lu
      First page: 171
      Abstract: Non-noble metal oxides consisting of CuO and TiO2 (CuO/TiO2 catalyst) for CO2 reduction were fabricated using a simple hydrothermal method. The designed catalysts of CuO could be in situ reduced to a metallic Cu-forming Cu/TiO2 catalyst, which could efficiently catalyze CO2 reduction to multi-carbon oxygenates (ethanol, acetone, and n-propanol) with a maximum overall faradaic efficiency of 47.4% at a potential of −0.85 V vs. reversible hydrogen electrode (RHE) in 0.5 M KHCO3 solution. The catalytic activity for CO2 electroreduction strongly depends on the CuO contents of the catalysts as-prepared, resulting in different electrochemistry surface areas. The significantly improved CO2 catalytic activity of CuO/TiO2 might be due to the strong CO2 adsorption ability.
      Citation: Catalysts
      PubDate: 2018-04-21
      DOI: 10.3390/catal8040171
      Issue No: Vol. 8, No. 4 (2018)
       
 
 
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