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  Subjects -> CHEMISTRY (Total: 881 journals)
    - ANALYTICAL CHEMISTRY (54 journals)
    - CHEMISTRY (616 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (28 journals)
    - INORGANIC CHEMISTRY (43 journals)
    - ORGANIC CHEMISTRY (48 journals)
    - PHYSICAL CHEMISTRY (71 journals)

CHEMISTRY (616 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     Hybrid Journal   (Followers: 43)
ACS Chemical Neuroscience     Hybrid Journal   (Followers: 21)
ACS Combinatorial Science     Hybrid Journal   (Followers: 23)
ACS Macro Letters     Hybrid Journal   (Followers: 25)
ACS Medicinal Chemistry Letters     Hybrid Journal   (Followers: 41)
ACS Nano     Hybrid Journal   (Followers: 280)
ACS Photonics     Hybrid Journal   (Followers: 14)
ACS Symposium Series     Full-text available via subscription  
ACS Synthetic Biology     Hybrid Journal   (Followers: 24)
Acta Chemica Iasi     Open Access   (Followers: 5)
Acta Chimica Slovaca     Open Access   (Followers: 2)
Acta Chimica Slovenica     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 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: 7)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 9)
Adsorption Science & Technology     Open Access   (Followers: 6)
Advanced Functional Materials     Hybrid Journal   (Followers: 57)
Advanced Science Focus     Free   (Followers: 5)
Advances in Chemical Engineering and Science     Open Access   (Followers: 67)
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: 24)
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: 16)
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: 44)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 3)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 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: 65)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 20)
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: 169)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 247)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 5)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 13)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Open Access   (Followers: 2)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 9)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 32)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 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     Hybrid Journal   (Followers: 359)
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     Hybrid Journal   (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: 133)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 87)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 2)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 1)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 6)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 70)
Catalysis for Sustainable Energy     Open Access   (Followers: 8)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 7)
Catalysis Science and Technology     Free   (Followers: 8)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 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: 20)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 74)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 26)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Hybrid Journal   (Followers: 22)
Chemical Reviews     Hybrid Journal   (Followers: 191)
Chemical Science     Open Access   (Followers: 25)
Chemical Technology     Open Access   (Followers: 26)
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: 159)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 16)
Chemistry and Materials Research     Open Access   (Followers: 21)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Open Access   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 43)
Chemistry of Materials     Hybrid Journal   (Followers: 259)
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: 12)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 11)
Chromatographia     Hybrid Journal   (Followers: 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: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 10)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 4)
Copernican Letters     Open Access   (Followers: 1)
Corrosion Series     Full-text available via subscription   (Followers: 6)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 6)
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  
Doklady Chemistry     Hybrid Journal  

        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  [203 journals]
  • Catalysts, Vol. 8, Pages 296: Performance of Ethane Dehydrogenation over
           PtSn Loaded onto a Calcined Mg(Al)O LDH with Three Mg:Al Molar Ratios
           Using a Novel Method

    • Authors: Shuqi Fang, Kang Bi, Qiao Zhang, Lingpeng Chen, Yongming Sun, Hongyu Huang, Longlong Ma, Chenguang Wang
      First page: 296
      Abstract: Layered double hydroxide (LDH) is a layered solid containing positively charged layers with negatively charged anions as an interchangeable interlayer. In this research, Mg(Al)O supports were synthesized with three different Mg:Al molar ratios, and bimetallic PtSn catalysts were loaded onto the supports via the anion exchange method. The properties of ethane dehydrogenation of the PtSn/Mg(Al)O catalysts were investigated. The results show that the structure and properties of the PtSn/Mg(Al)O catalysts were influenced by the Mg:Al molar ratio of the hydrotalcites, which consequently influenced the ethane dehydrogenation performance. When the Mg:Al ratio was 5:1, the ethane dehydrogenation performance was optimal, relative to the Mg:Al ratios of 2:1 and 10:1.
      Citation: Catalysts
      PubDate: 2018-07-24
      DOI: 10.3390/catal8080296
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 297: Propylsulfonic Acid Functionalized SBA-15
           Mesoporous Silica as Efficient Catalysts for the Acetalization of Glycerol
           

    • Authors: Ruiyun Li, Heyuan Song, Jing Chen
      First page: 297
      Abstract: As the main by-product obtained from biomass, glycerol could be converted into valuable chemicals. Tunable propylsulfonic acid functionalized SBA-15 and KIT-6 with different structural parameters have been prepared by different methods while using 3-mercaptopropyltrimethoxysilane (MPTMS) as the source of sulfur. The composition and structure of the synthesized catalysts have been well-characterized by N2 adsorption-desorption (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The catalytic performance of the prepared catalysts have been evaluated and compared in glycerol acetalization with formaldehyde to the mixture of 1,3-dioxane-5-ol and 1,3-dioxolane-4-methanol. Optimum reaction parameters were investigated to enhance the yield of products and control the distribution of glycerol formals. More than 90% yield of cyclic acetals were obtained with the ratio of two isomers 5R to 6R of 42:58.
      Citation: Catalysts
      PubDate: 2018-07-24
      DOI: 10.3390/catal8080297
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 298: Improvement of the Catalytic Efficiency of
           Butene Oligomerization Using Alkali Metal Hydroxide-Modified Hierarchical
           ZSM-5 Catalysts

    • Authors: Lei Zhang, Ming Ke, Zhaozheng Song, Yang Liu, Wenbo Shan, Qi Wang, Chengjie Xia, Changchun Li, Chunyu He
      First page: 298
      Abstract: Oligomerization of light olefin is an effective method to produce plentiful liquid fuels. However, oligomerization processes using microporous zeolites have severe problems due to steric hindrance. In this paper, oligomerization of butene using a series of new types of hierarchical HZSM-5 zeolite catalysts is studied. To obtain the modified HZSM-5 catalysts, HZSM-5 is treated with the same concentration of LiOH, NaOH, KOH, and CsOH aqueous solutions, respectively. It is demonstrated that the alkali treatment can effectively modify the acidity properties and hierarchical structure of the HZSM-5 catalyst, which is confirmed by X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Nitrogen Adsorption-desorption Measurements, Transmission Electron Microscopy Investigations (TEM), Ammonia Temperature-programmed Desorption Method (NH3-TPD), Pyridine FT-IR, and Thermogravimetric Analysis (TGA). The results show that hierarchical catalysts with interconnected open-mesopores, smaller crystal size, and suitable acidity can better prolong the catalyst lifetime during butene oligomerization. Particularly, the HZSM-5 catalysts treated with CsOH aqueous solution (ATHZ5-Cs) proved to be the most effective catalyst, resulting in approximately 99% conversion of butene and exhibiting C8+ selectivity of 85% within 12 h. Thus, an appropriate hierarchical catalyst can satisfy the oligomerization process and has the potential to be used as a substitute for the commercial ZSM-5 catalyst.
      Citation: Catalysts
      PubDate: 2018-07-25
      DOI: 10.3390/catal8080298
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 299: Physiochemical Characterization of
           α-Amylase as Crosslinked Enzyme Aggregates

    • Authors: Xiaodong Li, Zefen Yu, Zhaohui Bian, Jianping Xu, Li Zhang, Min Qiao
      First page: 299
      Abstract: Starch is promising candidate material for enhancing the catalytic activity of α-amylase during the crosslinking process. To help meet industrial needs, here we tested the influence of bovine serum albumin (BSA) and starch on the performance of crosslinked α-amylase aggregates (CLEA), α-amylase-prepared as CLEA with starch (CLEA-S), and BSA (CLEA-BSA). Our results showed that the activities of CLEA, CLEA-S, and CLEA-BSA were 1.1-, 1.0-, and 0.74-fold higher than the free α-amylase, respectively. The stability of the immobilized enzyme slightly changed. After immobilization, the enzyme increased its pH and temperature ranges with the optimal pH values of 5.5, 7.5, 5.5, respectively for CLEA, CLEA-S, and CLEA-BSA, and an upper temperature limit of 50 °C for all three immobilized forms. Among the three immobilized forms, the CLEA-S was the most thermostable, losing only 3% of its initial activity during 390 min incubation at 50 °C. Our microscopic observations of CLEA-S showed that porous structures were formed and such structures could help substance diffusion. In addition, there was excellent affinity between CLEA-S and the substrate. The results suggest that CLEA-S have great potential for industrial application, including for use in starch-based alcohol fermentation.
      Citation: Catalysts
      PubDate: 2018-07-26
      DOI: 10.3390/catal8080299
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 300: Co-, Cu- and Fe-Doped Ni/Al2O3 Catalysts for
           the Catalytic Decomposition of Methane into Hydrogen and Carbon Nanofibers
           

    • Authors: Daniel Torres, José Luis Pinilla, Isabel Suelves
      First page: 300
      Abstract: The catalytic decomposition of methane (CDM) process produces hydrogen in a single stage and avoids CO2 emission thanks to the formation of high added value carbon nanofilaments as a by-product. In this work, Ni monometallic and Ni–Co, Ni–Cu, and Ni–Fe bimetallic catalysts are tested in the CDM reaction for the obtention of fishbone carbon nanofibers (CNF). Catalysts, in which Al2O3 is used as textural promoter in their formulation, are based on Ni as main active phase for the carbon formation and on Co, Cu, or Fe as dopants in order to obtain alloys with improved catalytic behaviour. Characterization of bimetallic catalysts showed the formation of particles of Ni alloys with a bimodal size distribution. For the doping content studied (5 mol. %), only Cu formed an alloy with a lattice constant high enough to be able to favor the carbon diffusion through the catalytic particle against surface diffusion, resulting in higher carbon formations, longer activity times, and activity at 750 °C; whereas Ni, Ni–Co, and Ni–Fe catalysts were inactive. On the other hand, Fe also improved the undoped catalyst performance presenting a higher carbon formation at 700 °C and the obtention of narrow carbon nanofilaments from active Ni3Fe crystallites.
      Citation: Catalysts
      PubDate: 2018-07-27
      DOI: 10.3390/catal8080300
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 301: Three-Dimensional Heteroatom-Doped
           Nanocarbon for Metal-Free Oxygen Reduction Electrocatalysis: A Review

    • Authors: Dongbin Xiong, Xifei Li, Linlin Fan, Zhimin Bai
      First page: 301
      Abstract: The oxygen reduction reaction (ORR) at the cathode is a fundamental process and functions a pivotal role in fuel cells and metal–air batteries. However, the electrochemical performance of these technologies has been still challenged by the high cost, scarcity, and insufficient durability of the traditional Pt-based ORR electrocatalysts. Heteroatom-doped nanocarbon electrocatalysts with competitive activity, enhanced durability, and acceptable cost, have recently attracted increasing interest and hold great promise as substitute for precious-metal catalysts (e.g., Pt and Pt-based materials). More importantly, three-dimensional (3D) porous architecture appears to be necessary for achieving high catalytic ORR activity by providing high specific surface areas with more exposed active sites and large pore volumes for efficient mass transport of reactants to the electrocatalysts. In this review, recent progress on the design, fabrication, and performance of 3D heteroatom-doped nanocarbon catalysts is summarized, aiming to elucidate the effects of heteroatom doping and 3D structure on the ORR performance of nanocarbon catalysts, thus promoting the design of highly active nanocarbon-based ORR electrocatalysts.
      Citation: Catalysts
      PubDate: 2018-07-27
      DOI: 10.3390/catal8080301
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 302: Effect of Alkali-Doping on the Performance
           of Diatomite Supported Cu-Ni Bimetal Catalysts for Direct Synthesis of
           Dimethyl Carbonate

    • Authors: Dongmei Han, Yong Chen, Shuanjin Wang, Min Xiao, Yixin Lu, Yuezhong Meng
      First page: 302
      Abstract: Alkali-adopted Cu-Ni/diatomite catalysts were designed and used for the direct synthesis of dimethyl carbonate (DMC) from carbon dioxide and methanol. Alkali additives were introduced into Cu-Ni/diatomite catalyst as a promoter because of its lower work function (Ni > Cu > Li > Na > K > Cs) and stronger electron-donating ability. A series of alkali-promoted Cu-Ni/diatomite catalysts were prepared by wetness impregnation method with different kind and different loading of alkali. The synthesized catalysts were fully characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), temperature-programmed reduction (TPR), and NH3/CO2-TPD. The experimental results demonstrated that alkali adoption can significantly promote the catalytic activity of Cu–Ni bimetallic catalysts. Under the catalytic reaction conditions of 120 °C and 1.0 MPa; the highest CH3OH conversion of 9.22% with DMC selectivity of 85.9% has been achieved when using 15%(2Cu-Ni) 2%Cs2O/diatomite catalyst (CuO + NiO = 15 wt. %, atomic ratio of Cu/Ni = 2/1, Cs2O = 2 wt. %).
      Citation: Catalysts
      PubDate: 2018-07-27
      DOI: 10.3390/catal8080302
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 303: Plasma-Catalytic Mineralization of Toluene
           Adsorbed on CeO2

    • Authors: Zixian Jia, Xianjie Wang, Emeric Foucher, Frederic Thevenet, Antoine Rousseau
      First page: 303
      Abstract: In the context of coupling nonthermal plasmas with catalytic materials, CeO2 is used as adsorbent for toluene and combined with plasma for toluene oxidation. Two configurations are addressed for the regeneration of toluene saturated CeO2: (i) in plasma-catalysis (IPC); and (ii) post plasma-catalysis (PPC). As an advanced oxidation technique, the performances of toluene mineralization by the plasma-catalytic systems are evaluated and compared through the formation of CO2. First, the adsorption of 100 ppm of toluene onto CeO2 is characterized in detail. Total, reversible and irreversible adsorbed fractions are quantified. Specific attention is paid to the influence of relative humidity (RH): (i) on the adsorption of toluene on CeO2; and (ii) on the formation of ozone in IPC and PPC reactors. Then, the mineralization yield and the mineralization efficiency of adsorbed toluene are defined and investigated as a function of the specific input energy (SIE). Under these conditions, IPC and PPC reactors are compared. Interestingly, the highest mineralization yield and efficiency are achieved using the in-situ configuration operated with the lowest SIE, that is, lean conditions of ozone. Based on these results, the specific impact of RH on the IPC treatment of toluene adsorbed on CeO2 is addressed. Taking into account the impact of RH on toluene adsorption and ozone production, it is evidenced that the mineralization of toluene adsorbed on CeO2 is directly controlled by the amount of ozone produced by the discharge and decomposed on the surface of the coupling material. Results highlight the key role of ozone in the mineralization process and the possible detrimental effect of moisture.
      Citation: Catalysts
      PubDate: 2018-07-27
      DOI: 10.3390/catal8080303
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 304: Ionic Liquids as Bifunctional Cosolvents
           

    • Authors: Zhibo Zhang, Bao-hua Xu, Jianquan Luo, Nicolas Von Solms, Hongyan He, Yaqin Zhang, Manuel Pinelo, Suojiang Zhang
      First page: 304
      Abstract: Efficient CO2 conversion by formate dehydrogenase is limited by the low CO2 concentrations that can be reached in traditional buffers. The use of ionic liquids was proposed as a manner to increase CO2 concentration in the reaction system. It has been found, however, that the required cofactor (NADH) heavily degraded during the enzymatic reaction and that acidity was the main reason. Acidity, indeed, resulted in reduction of the conversion of CO2 into formic acid and contributed to overestimate the amount of formic acid produced when the progression of the reaction was followed by a decrease in NADH absorbance (method N). Stability of NADH and the mechanism of NADH degradation was investigated by UV, NMR and by DFT calculations. It was found that by selecting neutral–basic ionic liquids and by adjusting the concentration of the ionic liquid in the buffer, the concentration of NADH can be maintained in the reaction system with little loss. Conversion of CO2 to methanol in BmimBF4 (67.1%) was more than twice as compared with the conversion attained by the enzymatic reaction in phosphate buffer (24.3%).
      Citation: Catalysts
      PubDate: 2018-07-28
      DOI: 10.3390/catal8080304
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 305: Urea Activation by an External Brønsted
           Acid: Breaking Self-Association and Tuning Catalytic Performance

    • Authors: Isaac G. Sonsona, Eugenia Marqués-López, Marleen Häring, David Díaz Díaz, Raquel P. Herrera
      First page: 305
      Abstract: In this work, we hypothesize that Brønsted acids can activate urea-based catalysts by diminishing its self-assembly tendency. As a proof of concept, we used the asymmetric Friedel–Crafts alkylation of indoles with nitroalkenes as a benchmark reaction. The resulting 3-substituted indole derivatives were obtained with better results due to cooperative effects of the chiral urea and a Brønsted acid additive. Such synergy has been rationalized in terms of disassembly of the supramolecular catalyst aggregates, affording a more acidic and rigid catalytic complex.
      Citation: Catalysts
      PubDate: 2018-07-28
      DOI: 10.3390/catal8080305
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 306: Promotional Effect of Cerium and/or
           Zirconium Doping on Cu/ZSM-5 Catalysts for Selective Catalytic Reduction
           of NO by NH3

    • Authors: Ye Liu, Chonglin Song, Gang Lv, Chenyang Fan, Xiaodong Li
      First page: 306
      Abstract: The cerium and/or zirconium-doped Cu/ZSM-5 catalysts (CuCexZr1−xOy/ZSM-5) were prepared by ion exchange and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction by hydrogen (H2-TPR). Activities of the catalysts obtained on the selective catalytic reduction (SCR) of nitric oxide (NO) by ammonia were measured using temperature programmed reactions. Among all the catalysts tested, the CuCe0.75Zr0.25Oy/ZSM-5 catalyst presented the highest catalytic activity for the removal of NO, corresponding to the broadest active window of 175–468 °C. The cerium and zirconium addition enhanced the activity of catalysts, and the cerium-rich catalysts exhibited more excellent SCR activities as compared to the zirconium-rich catalysts. XRD and TEM results indicated that zirconium additions improved the copper dispersion and prevented copper crystallization. According to XPS and H2-TPR analysis, copper species were enriched on the ZSM-5 grain surfaces, and part of the copper ions were incorporated into the zirconium and/or cerium lattice. The strong interaction between copper species and cerium/zirconium improved the redox abilities of catalysts. Furthermore, the introduction of zirconium abates N2O formation in the tested temperature range.
      Citation: Catalysts
      PubDate: 2018-07-28
      DOI: 10.3390/catal8080306
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 307: Co-Aromatization of n-Butane and Methanol
           over PtSnK-Mo/ZSM-5 Zeolite Catalysts: The Promotion Effect of
           Ball-Milling

    • Authors: Kang Yang, Lingting Zhu, Jie Zhang, Xiuchun Huo, Weikun Lai, Yixin Lian, Weiping Fang
      First page: 307
      Abstract: The ball-milling (BM) method benefits the stabilization and dispersion of metallic particles for the preparation of the PtSnK–Mo/ZSM-5 catalyst. Based on the TPR, H2-TPD, XPS, and CO-FTIR results, the Pt–SnOx and MoOx species were formed separately on the BM sample. During the aromatization of cofeeding the n-butane with methanol, the yield of the aromatics is 59 wt.% at a n-butane conversion of 86% at 475 °C over the Pt Mo BM catalyst. The more weak acid sites also contribute to the aromatics formation with the less light alkanes formation. For the Pt Ga catalysts, the slow loss of activity suggests that the BM method can restrain the coke deposition on the Pt-SnOx species, because of a certain distance between the Pt–SnOx and GaOx species on the surface of ZSM-5.
      Citation: Catalysts
      PubDate: 2018-07-28
      DOI: 10.3390/catal8080307
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 308: Biocatalytic Approach to Chiral
           β-Nitroalcohols by Enantioselective Alcohol Dehydrogenase-Mediated
           Reduction of α-Nitroketones

    • Authors: Francesca Tentori, Elisabetta Brenna, Danilo Colombo, Michele Crotti, Francesco G. Gatti, Maria Chiara Ghezzi, Giuseppe Pedrocchi-Fantoni
      First page: 308
      Abstract: Chiral β-nitroalcohols are important building blocks in organic chemistry. The synthetic approach that is based on the enzyme-mediated reduction of α-nitroketones has been scarcely considered. In this work, the use of commercial alcohol dehydrogenases (ADHs) for the reduction of aromatic and aliphatic nitroketones is investigated. High conversions and enantioselectivities can be achieved with two specific ADHs, affording either the (S) or (R)-enantiomer of the corresponding nitroalcohols. The reaction conditions are carefully tuned to preserve the stability of the reduced product, and to avoid the hydrolytic degradation of the starting substrate. The further manipulation of the enantioenriched nitroalcohols into Boc-protected amminoalcohols is also described.
      Citation: Catalysts
      PubDate: 2018-07-29
      DOI: 10.3390/catal8080308
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 309: Highly Loaded and Dispersed Ni2P/Al2O3
           Catalyst with High Selectivity for Hydrogenation of Acetophenone

    • Authors: Junen Wang, Yanling Wang, Gaoli Chen, Zhanjun He
      First page: 309
      Abstract: Highly loaded and dispersed Ni2P/Al2O3 catalyst was prepared by the phosphidation of Ni/Al2O3 catalyst with Ni loading of 80 wt.% in liquid phase and compared with the Ni/Al2O3 catalyst for the hydrogenation of acetophenone. X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) etc. were used to characterize the textural and structural properties of the prepared catalysts. It was found that the Ni/Al2O3 and Ni2P/Al2O3 catalyst possessed high surface area, loading and dispersion. The Ni/Al2O3 catalyst had higher apparent activity while the Ni2P/Al2O3 catalyst had higher intrinsic activity for the hydrogenation of acetophenone (AP). Remarkably, the Ni2P/Al2O3 catalyst exhibited high selectivity to 1-phenylethanol, due to repulsion of the phosphorous (Pδ−) for phenyl group and attraction of the nickel (Niδ+) for oxygen atom of carbonyl group, leading to preferential hydrogenation of carbonyl group in acetophenone. The effect of the particle size of the catalyst on the chemical selectivity might be another reason for high selectivity on the Ni2P/Al2O3 catalyst.
      Citation: Catalysts
      PubDate: 2018-07-30
      DOI: 10.3390/catal8080309
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 310: Engineering Mesoporous NiO with Enriched
           Electrophilic Ni3+ and O− toward Efficient Oxygen Evolution

    • Authors: Xiu Liu, Zhi-Yuan Zhai, Zhou Chen, Li-Zhong Zhang, Xiu-Feng Zhao, Feng-Zhan Si, Jian-Hui Li
      First page: 310
      Abstract: Tremendous efforts have been devoted to develop low-cost and highly active electrocatalysts for oxygen evolution reaction (OER). Here, we report the synthesis of mesoporous nickel oxide by the template method and its application in the title reaction. The as-prepared mesoporous NiO possesses a large surface area, uniform mesopores, and rich surface electrophilic Ni3+ and O− species. The overpotential of meso-NiO in alkaline medium is 132 mV at 10 mA cm−1 and 410 mV at 50 mA cm−1, which is much smaller than that of the other types of NiO samples. The improvement in the OER activity can be ascribed to the synergy of the large surface area and uniform mesopores for better mass transfer and high density of Ni3+ and O− species favoring the nucleophilic attack by OH− to form a NiOOH intermediate. The reaction process and the role of electrophilic Ni3+ and O− were discussed in detail. This results are more conducive to the electrochemical decomposition of water to produce hydrogen fuel as a clean and renewable energy.
      Citation: Catalysts
      PubDate: 2018-07-30
      DOI: 10.3390/catal8080310
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 311: The Low Temperature Solvent-Free Aerobic
           Oxidation of Cyclohexene to Cyclohexane Diol over Highly Active
           Au/Graphite and Au/Graphene Catalysts

    • Authors: Owen Rogers, Samuel Pattisson, Joseph Macginley, Rebecca V. Engel, Keith Whiston, Stuart H. Taylor, Graham J. Hutchings
      First page: 311
      Abstract: The selectivity and activity of gold-catalysts supported on graphite and graphene have been compared in the oxidation of cyclohexene. These catalysts were prepared via impregnation and sol immobilisation methods, and tested using solventless and radical initiator-free reaction conditions. The selectivity of these catalysts has been directed towards cyclohexene epoxide using WO3 as a co-catalyst and further to cyclohexane diol by the addition of water, achieving a maximum selectivity of 17% to the diol. The sol immobilisation catalysts were more reproducible and far more active, however, selectivity towards the diol was lower than for the impregnation catalyst. The results suggest that formation of cyclohexane diol through solventless oxidation of cyclohexene is limited by a number of factors, such as the formation of an allylic hydroperoxyl species as well as the amount of in situ generated water.
      Citation: Catalysts
      PubDate: 2018-07-31
      DOI: 10.3390/catal8080311
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 312: Dehydrogenative Transformation of Alcoholic
           Substrates in Aqueous Media Catalyzed by an Iridium Complex Having a
           Functional Ligand with α-Hydroxypyridine and 4,5-Dihydro-1H-imidazol-2-yl
           Moieties

    • Authors: Masato Yoshida, Han Wang, Takuya Shimbayashi, Ken-ichi Fujita
      First page: 312
      Abstract: A new catalytic system that employs water as an environmentally friendly solvent for the dehydrogenative oxidation of alcohols and lactonization of diols has been developed. In this catalytic system, a water-soluble dicationic iridium complex having a functional ligand that comprises α-hydroxypyridine and 4,5-dihydro-1H-imidazol-2-yl moieties exhibits high catalytic performance. For example, the catalytic dehydrogenative oxidation of 1-phenylethanol in the presence of 0.25 mol % of the iridium catalyst and base under reflux in water proceeded to give acetophenone in 92% yield. Additionally, under similar reaction conditions, the iridium-catalyzed dehydrogenative lactonization of 1,2-benzenedimethanol gave phthalide in 98% yield.
      Citation: Catalysts
      PubDate: 2018-07-31
      DOI: 10.3390/catal8080312
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 313: Catalytic Transfer Hydrogenolysis as an
           Effective Tool for the Reductive Upgrading of Cellulose, Hemicellulose,
           Lignin, and Their Derived Molecules

    • Authors: Claudia Espro, Bianca Gumina, Tomasz Szumelda, Emilia Paone, Francesco Mauriello
      First page: 313
      Abstract: Lignocellulosic biomasses have a tremendous potential to cover the future demand of bio-based chemicals and materials, breaking down our historical dependence on petroleum resources. The development of green chemical technologies, together with the appropriate eco-politics, can make a decisive contribution to a cheap and effective conversion of lignocellulosic feedstocks into sustainable and renewable chemical building blocks. In this regard, the use of an indirect H-source for reducing the oxygen content in lignocellulosic biomasses and in their derived platform molecules is receiving increasing attention. In this contribution we highlight recent advances in the transfer hydrogenolysis of cellulose, hemicellulose, lignin, and of their derived model molecules promoted by heterogeneous catalysts for the sustainable production of biofuels and biochemicals.
      Citation: Catalysts
      PubDate: 2018-07-31
      DOI: 10.3390/catal8080313
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 314: A Comparative Review on the Catalytic
           Mechanism of Nonheme Iron Hydroxylases and Halogenases

    • Authors: Amy Timmins, Sam P. de Visser
      First page: 314
      Abstract: Enzymatic halogenation and haloperoxidation are unusual processes in biology; however, a range of halogenases and haloperoxidases exist that are able to transfer an aliphatic or aromatic C–H bond into C–Cl/C–Br. Haloperoxidases utilize hydrogen peroxide, and in a reaction with halides (Cl−/Br−), they react to form hypohalides (OCl−/OBr−) that subsequently react with substrate by halide transfer. There are three types of haloperoxidases, namely the iron-heme, nonheme vanadium, and flavin-dependent haloperoxidases that are reviewed here. In addition, there are the nonheme iron halogenases that show structural and functional similarity to the nonheme iron hydroxylases and form an iron(IV)-oxo active species from a reaction of molecular oxygen with α-ketoglutarate on an iron(II) center. They subsequently transfer a halide (Cl−/Br−) to an aliphatic C–H bond. We review the mechanism and function of nonheme iron halogenases and hydroxylases and show recent computational modelling studies of our group on the hectochlorin biosynthesis enzyme and prolyl-4-hydroxylase as examples of nonheme iron halogenases and hydroxylases. These studies have established the catalytic mechanism of these enzymes and show the importance of substrate and oxidant positioning on the stereo-, chemo- and regioselectivity of the reaction that takes place.
      Citation: Catalysts
      PubDate: 2018-07-31
      DOI: 10.3390/catal8080314
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 315: Interface-Active Metal Organic Frameworks
           for Knoevenagel Condensations in Water

    • Authors: Yanmei Zhang, Xiang Zhang, Rixia Bai, Xiyan Hou, Jun Li
      First page: 315
      Abstract: It is desirable but challenging to locate solid catalysts at the oil-water interface to stabilize “Pickering emulsions”, which is one of the promising ways to developefficient green chemical processes. Herein, water-stable metal organic framework ZIF-8 without any chemical modification was demonstrated to be an interface-active catalyst for Knoevenagel condensation in a biphasic system. Pickering emulsion formed under the reaction conditions due to its amphiphilic property, which was beneficial to the mass transfer and led to high catalytic performance. Moreover, it can be repeatedly applied for Knoevenagel condensation for at least six successive cycles without losing its catalytic activity and framework integrity.
      Citation: Catalysts
      PubDate: 2018-08-01
      DOI: 10.3390/catal8080315
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 316: Photocatalytic Water Disinfection under
           Solar Irradiation by d-Glucose-Modified Titania

    • Authors: Agata Markowska-Szczupak, Paulina Rokicka, Kunlei Wang, Maya Endo, Antoni Waldemar Morawski, Ewa Kowalska
      First page: 316
      Abstract: Modified titania photocatalysts were synthesized by the pressure method using titanium(IV) oxide from Grupa Azoty Zakłady Chemiczne “Police” S.A., Police, Poland, and d-glucose solution. Characterization of obtained composites was performed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), elemental analysis, and measurements of zeta potential and specific surface area (SSA). The possibility of using glucose-titania composites as photocatalysts for simulated solar-assisted disinfection against gram-negative Escherichia coli and gram-positive Stapchyloccocus epidermidis bacteria were examined in two reaction systems, i.e., for suspended and immobilized photocatalysts (on the concrete). It was found that an increase in the d-glucose concentration, i.e., higher carbon content, led to a decrease in antibacterial properties. The sample obtained from 1% of d-glucose solution at 100 °C (TiO2-1%-G-100) showed superior photocatalytic activity under UV-Vis irradiation toward both bacteria species. Water disinfection was more efficient for suspended photocatalyst than that for supported one, where complete disinfection was reached during 55–70 min and 120 min of irradiation, respectively. For the first time, it has been shown that titania modified with monosaccharides can be efficiently used for water disinfection, and the immobilization of photocatalyst on the concrete might be a prospective method for public water supplies.
      Citation: Catalysts
      PubDate: 2018-08-01
      DOI: 10.3390/catal8080316
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 317: Plasma Oxidation of H2S over
           Non-stoichiometric LaxMnO3 Perovskite Catalysts in a Dielectric Barrier
           Discharge Reactor

    • Authors: Kejie Xuan, Xinbo Zhu, Yuxiang Cai, Xin Tu
      First page: 317
      Abstract: In this work, plasma-catalytic removal of H2S over LaxMnO3 (x = 0.90, 0.95, 1, 1.05 and 1.10) has been studied in a coaxial dielectric barrier discharge (DBD) reactor. The non-stoichiometric effect of the LaxMnO3 catalysts on the removal of H2S and sulfur balance in the plasma-catalytic process has been investigated as a function of specific energy density (SED). The integration of the plasma with the LaxMnO3 catalysts significantly enhanced the reaction performance compared to the process using plasma alone. The highest H2S removal of 96.4% and sulfur balance of 90.5% were achieved over the La0.90MnO3 catalyst, while the major products included SO2 and SO3. The missing sulfur could be ascribed to the sulfur deposited on the catalyst surfaces. The non-stoichiometric LaxMnO3 catalyst exhibited larger specific surface areas and smaller crystallite sizes compared to the LaMnO3 catalyst. The non-stoichiometric effect changed their redox properties as the decreased La/Mn ratio favored the transformation of Mn3+ to Mn4+, which contributed to the generation of oxygen vacancies on the catalyst surfaces. The XPS and H2-TPR results confirmed that the Mn-rich catalysts showed the higher relative concentration of surface adsorbed oxygen (Oads) and lower reduction temperature compared to LaMnO3 catalyst. The reaction performance of the plasma-catalytic oxidation of H2S is closely related to the relative concentration of Oads formed on the catalyst surfaces and the reducibility of the catalysts.
      Citation: Catalysts
      PubDate: 2018-08-02
      DOI: 10.3390/catal8080317
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 318: Catalytic Copyrolysis of Cork Oak and Waste
           Plastic Films over HBeta

    • Authors: Young-Kwon Park, Boram Lee, Atsushi Watanabe, Hyung Won Lee, Ji Young Lee, Seungdo Kim, Tae Uk Han, Young-Min Kim
      First page: 318
      Abstract: The catalytic fast copyrolysis (CFCP) of cork oak (CoOak) and waste plastic films (WPFs) over HBeta(25) (SiO2/Al2O3: 25) was investigated using a thermogravimetric (TG) analyzer and a tandem micro reactor-gas chromatography/mass spectrometry (TMR-GC/MS) to determine the effectiveness of WPFs as the hydrogen donating cofeeding feedstock on the CFCP of biomass. By applying CFCP, the maximum decomposition temperatures of CoOak (373.4 °C) and WPFs (487.9 °C) were reduced to 364.5 °C for CoOak and 436.5 °C for WPFs due to the effective interaction between the pyrolysis intermediates of CoOak and WPFs over HBeta(25), which has strong acidity and an appropriate pore size. The experimental yields of aromatic hydrocarbons on the CFCP of CoOak and WPFs were higher than their calculated yields concluded from the yields obtained from the individual catalytic fast pyrolysis (CFP) of CoOak and WPFs. The coke amount produced from the CFP of CoOak and WPFs over HBeta(25) were also decreased by applying CFCP.
      Citation: Catalysts
      PubDate: 2018-08-03
      DOI: 10.3390/catal8080318
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 319: Investigation of Ni/SiO2 Fiber Catalysts
           Prepared by Different Methods on Hydrogen production from Ethanol Steam
           Reforming

    • Authors: Sareena Mhadmhan, Paweesuda Natewong, Natthawan Prasongthum, Chanatip Samart, Prasert Reubroycharoen
      First page: 319
      Abstract: Ni/SiO2 (Ni/SF) catalysts were prepared by electrospinning of the SF followed by impregnation. The performance of the Ni/SF catalysts for hydrogen production from ethanol steam reforming at various conditions was investigated in comparison with a conventional Ni/silica porous (Ni/SP) catalyst. The influence of the Ni/SF catalyst preparation methods on the catalytic activity and stability in ethanol steam reforming was also studied. The catalysts were prepared by three different preparation techniques: impregnation (IM), deposition precipitation (DP) and strong electrostatic adsorption (SEA). The Ni/SF catalyst exhibited higher performances and stability than the Ni/SP catalyst. The H2 yields of 55% and 47% were achieved at 600 °C using the Ni/SF and Ni/SP catalysts, respectively. The preparation methods had a significant effect on the catalytic activity and stability of the Ni/SF catalyst, where that prepared by the SEA method had a smaller Ni particle size and higher dispersion, and also exhibited the highest catalytic activity and stability compared to the Ni/SF catalysts prepared by IM and DP methods. The maximum H2 yield produced from the catalyst prepared by SEA was 65%, while that from the catalysts prepared by DP and IM were 60% and 55%, respectively, under the same conditions. The activity of the fiber catalysts prepared by SEA, DP and IM remained almost constant at all times during a 16 h stability test.
      Citation: Catalysts
      PubDate: 2018-08-04
      DOI: 10.3390/catal8080319
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 320: Investigation of Earth-Abundant Oxygen
           Reduction Electrocatalysts for the Cathode of Passive Air-Breathing Direct
           Formate Fuel Cells

    • Authors: Francisca E. R. Oliveira, Nelson A. Galiote, Fabio H. B. Lima
      First page: 320
      Abstract: The development of direct formate fuel cells encounters important obstacles related to the sluggish oxygen reduction reaction (ORR) and low tolerance to formate ions in Pt-based cathodes. In this study, electrocatalysts formed by earth-abundant elements were synthesized, and their activity and selectivity for the ORR were tested in alkaline electrolyte. The results showed that carbon-encapsulated iron-cobalt alloy nanoparticles and carbon-supported metal nitrides, characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD), do not present significant activity for the ORR, showing the same half-wave potential of Vulcan carbon. Contrarily, nitrogen-doped carbon, synthesized using imidazole as the nitrogen source, showed an increase in the half-wave potential, evidencing an influential role of nitrogen in the ORR electrocatalysis. The synthesis with the combination of Vulcan, imidazole, and iron or cobalt precursors resulted in the formation of nitrogen-coordinated iron (or cobalt) moieties, inserted in a carbon matrix, as revealed by X-ray absorption spectroscopy (XAS). Steady-state polarization curves for the ORR evidenced a synergistic effect between Fe and Co when these two metals were included in the synthesis (FeCo-N-C material), showing higher activity and higher limiting current density than the materials prepared only with Fe or Co. The FeCo-N-C material presented not only the highest activity for the ORR (approaching that of the state-of-the-art Pt/C) but also high tolerance to the presence of formate ions in the electrolyte. In addition, measurements with FeCo-N-C in the cathode of an passive air-breathing direct formate fuel cells, (natural diffusion of formate), showed peak power densities of 15.5 and 10.5 mW cm−2 using hydroxide and carbonate-based electrolytes, respectively, and high stability over 120 h of operation.
      Citation: Catalysts
      PubDate: 2018-08-06
      DOI: 10.3390/catal8080320
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 321: Laccase Activity as an Essential Factor in
           the Oligomerization of Rutin

    • Authors: Abel Muñiz-Mouro, Beatriz Gullón, Thelmo A. Lú-Chau, María Teresa Moreira, Juan M. Lema, Gemma Eibes
      First page: 321
      Abstract: The enzyme-mediated polymerization of bioactive phenolic compounds, such as the flavonoid rutin, has gained interest due to the enhanced physico-chemical and biological properties of the products, which increases their potential application as a nutraceutical. In this work, the influence of enzyme activity on rutin oligomerization was evaluated in reactions with low (1000 U/L) and high (10,000 U/L) initial laccase activities. For both reactions, high molecular weight oligomer fractions showed better properties compared to lower weight oligomers. Products of the reaction with low laccase activity exhibited thermal stability and antioxidant potential similar to control reaction, but led to higher inhibitory activity of xanthine oxidase and apparent aqueous solubility. Oligomers obtained in the reaction with high laccase activity showed better apparent aqueous solubility but decreased biological activities and stability. Their low antioxidant activity was correlated with a decreased phenolic content, which could be attributed to the formation of several bonds between rutin molecules.
      Citation: Catalysts
      PubDate: 2018-08-06
      DOI: 10.3390/catal8080321
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 322: Oxidative Steam Reforming of Raw Bio-Oil
           over Supported and Bulk Ni Catalysts for Hydrogen Production

    • Authors: Aitor Arandia, Aingeru Remiro, Verónica García, Pedro Castaño, Javier Bilbao, Ana G. Gayubo
      First page: 322
      Abstract: Several Ni catalysts of supported (on La2O3-αAl2O3, CeO2, and CeO2-ZrO2) or bulk types (Ni-La perovskites and NiAl2O4 spinel) have been tested in the oxidative steam reforming (OSR) of raw bio-oil, and special attention has been paid to the catalysts’ regenerability by means of studies on reaction-regeneration cycles. The experimental set-up consists of two units in series, for the separation of pyrolytic lignin in the first step (at 500 °C) and the on line OSR of the remaining oxygenates in a fluidized bed reactor at 700 °C. The spent catalysts have been characterized by N2 adsorption-desorption, X-ray diffraction and temperature programmed reduction, and temperature programmed oxidation (TPO). The results reveal that among the supported catalysts, the best balance between activity-H2 selectivity-stability corresponds to Ni/La2O3-αAl2O3, due to its smaller Ni0 particle size. Additionally, it is more selective to H2 than perovskite catalysts and more stable than both perovskites and the spinel catalyst. However, the activity of the bulk NiAl2O4 spinel catalyst can be completely recovered after regeneration by coke combustion at 850 °C because the spinel structure is completely recovered, which facilitates the dispersion of Ni in the reduction step prior to reaction. Consequently, this catalyst is suitable for the OSR at a higher scale in reaction-regeneration cycles.
      Citation: Catalysts
      PubDate: 2018-08-08
      DOI: 10.3390/catal8080322
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 323: Morphologically Tunable MnO2 Nanoparticles
           Fabrication, Modelling and Their Influences on Electrochemical Sensing
           Performance toward Dopamine

    • Authors: Quanguo He, Guangli Li, Xiaopeng Liu, Jun Liu, Peihong Deng, Dongchu Chen
      First page: 323
      Abstract: The morphology or shape of nanomaterials plays an important role in functional applications, especially in the electrochemical sensing performance of nanocomposites modified electrodes. Herein, the morphology-dependent electrochemical sensing properties of MnO2-reduced graphene oxide/glass carbon electrode (MnO2-RGO/GCE) toward dopamine detection were investigated. Firstly, various morphologies of nanoscale MnO2, including MnO2 nanowires (MnO2 NWs), MnO2 nanorods (MnO2 NRs), and MnO2 nanotubes (MnO2 NTs), were synthesized under different hydrothermal conditions. Then the corresponding MnO2-RGO/GCEs were fabricated via drop-casting and the subsequent electrochemical reduction method. The oxidation peak currents increase with the electrochemical activity area following the order of MnO2 NWs-RGO/GCE, MnO2 NTs-RGO/GCE, and MnO2 NRs-RGO/GCE. The spatial models for MnO2 NWs, MnO2 NTs, and MnO2 NRs are established and accordingly compared by their specific surface area, explaining well the evident difference in electrochemical responses. Therefore, the MnO2 NWs-RGO/GCE is selected for dopamine detection due to its better electrochemical sensing performance. The response peak current is found to be linear with dopamine concentration in the range of 8.0 × 10−8 mol/L–1.0 × 10−6 mol/L and 1.0 × 10−6 mol/L–8.0 × 10−5 mol/L with a lower detection limit of 1 × 10−9 mol/L (S/N = 3). Finally, MnO2 NWs-RGO/GCE is successfully used for the determination of dopamine injection samples, with a recovery of 99.6–103%. These findings are of great significance for understanding the relationship between unlimited nanoparticle structure manipulation and performance improvement.
      Citation: Catalysts
      PubDate: 2018-08-08
      DOI: 10.3390/catal8080323
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 324: Morphology-Controlled Nitrogen-Containing
           Polymers as Synthetic Precursors for Electrochemical Oxygen Reduction
           Fe/N/C Cathode Catalysts

    • Authors: Yuta Nabae
      First page: 324
      Abstract: Nitrogen-containing aromatic polymers such as polyimide are known for their high thermal stability. While they have been widely used in industry, their relevance to catalysis is still quite limited. In recent years, nitrogen-containing polymers have been explored as precursors of nitrogen-doped carbonaceous materials, which are particularly attractive as non-precious metal catalysts for oxygen reduction in fuel cells. The high thermal stability of nitrogen-containing polymers contributes to an effective control over the morphology of the resulting carbonaceous catalysts. This review article provides an overview of the recent progress on the research and development of Fe/N/C oxygen reduction catalysts prepared from morphology-controlled nitrogen-containing polymers.
      Citation: Catalysts
      PubDate: 2018-08-08
      DOI: 10.3390/catal8080324
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 325: Study of Extraction and Enzymatic Properties
           of Cell-Envelope Proteinases from a Novel Wild Lactobacillus plantarum
           LP69

    • Authors: He Chen, Jie Huang, Binyun Cao, Li Chen, Na Song, Ni Lei
      First page: 325
      Abstract: Lactobacilli cell-envelope proteinases (CEPs) have been widely used in the development of new streams of blockbuster nutraceuticals because of numerous biopharmaceutical potentials; thus, the development of viable methods for CEP extraction and the improvement of extraction efficiency will promote their full-scale application. In this study, CEP from a novel wild Lactobacillus plantarum LP69 was released from cells by incubating in calcium-free buffer. The extraction conditions of CEP were optimized by response surface methodology with the enzyme activity and specific activity as the detective marker. The optimal extraction conditions were: time of 80 min, temperature of 39 °C and buffer pH of 6.5. Under these conditions, enzyme activity and specific activity were (23.94 ± 0.86) U/mL and (1.37 ± 0.03) U/mg, respectively, which were well matched with the predicted values (22.12 U/mL and 1.36 U/mg). Optimal activity of the crude CEP occurred at pH 8.0 and 40 °C. It is a metallopeptidase, activated by Ca2+, inhibited by Zn2+ and ethylene-diamine-tetra-acetic acid, and a serine proteinase which is inhibited by phenylmethylsulfonyl fluoride. Kinetic studies showed that CEP from LP69 could hydrolyze whey protein, lactoglobulin and casein. Our study improves the extraction efficiency of CEPs from LP69, providing the reference for their industrial development.
      Citation: Catalysts
      PubDate: 2018-08-08
      DOI: 10.3390/catal8080325
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 326: Modification to L-H Kinetics Model and Its
           Application in the Investigation on Photodegradation of Gaseous Benzene by
           Nitrogen-Doped TiO2

    • Authors: Peng Sun, Jun Zhang, Wenxiu Liu, Qi Wang, Wenbin Cao
      First page: 326
      Abstract: In this paper, the Langmuir-Hinshelwood (L-H) model has been used to investigate the kinetics of photodegradation of gaseous benzene by nitrogen-doped TiO2 (N-TiO2) at 25 °C under visible light irradiation. Experimental results show that the photoreaction coefficient kpm increased from 3.992 × 10−6 mol·kg−1·s−1 to 11.55 × 10−6 mol·kg−1·s−1 along with increasing illumination intensity. However, the adsorption equilibrium constant KL decreased from 1139 to 597 m3·mol−1 when the illumination intensity increased from 36.7 × 104 lx to 75.1 × 104 lx, whereas it was 2761 m3·mol−1 in the absence of light. This is contrary to the fact that KL should be a constant if the temperature was fixed. This phenomenon can be attributed to the breaking of the adsorption-desorption equilibrium by photocatalytically decomposition. To compensate for the disequilibrium of the adsorption-desorption process, photoreaction coefficient kpm was introduced to the expression of KL and the compensation form was denoted as Km. KL is an indicator of the adsorption capacity of TiO2 while Km is only an indicator of the coverage ratio of TiO2 surface. The modified L-H model has been experimentally verified so it is expected to be used to predict the kinetics of the photocatalytic degradation of gaseous benzene.
      Citation: Catalysts
      PubDate: 2018-08-09
      DOI: 10.3390/catal8080326
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 327: Characteristics of Vanadium-Based Coal
           Gasification Slag and the NH3-Selective Catalytic Reduction of NO

    • Authors: Fang Han, Yanchun Gao, Qihuang Huo, Lina Han, Jiancheng Wang, Weiren Bao, Liping Chang
      First page: 327
      Abstract: In order to realize the resource utilization of coal gasification slag (CGS) and to effectively control the emission of nitrogen oxides (NOx) in coke oven gas, the effect of the reaction conditions and vanadium loading over the CGS catalysts was carried out for the selective catalytic reduction (SCR) of NO by NH3. The various vanadium loaded CGS catalysts were prepared using impregnation methods. The addition of 1% vanadium to the CGS catalyst (V1/CGS) significantly enhanced the NO conversion at a wide temperature range of 180–290 °C. The catalysts were characterized by N2 adsorption/desorption, X-ray photoelectron spectroscopy, H2-temperature programmed reduction, NH3-temperature programmed desorption, Inductively coupled plasma optical emission spectrometer (ICP-OES), thermo gravimetric analyses (TGA), Fourier Transform infrared spectroscopy (FTIR), Scanning electron microscope-Energy dispersive spectrometer (SEM-EDS), and X-ray powder diffraction (XRD). The experimental results show the following: That (1) the NO removal efficiency of the sample CGS3 was the best, and it could be up to 100% under the experimental conditions; (2) The NO removal efficiency of the catalysts was higher in the atmosphere with SO2 than that without SO2; (3) The XRD results indicated the active component of vanadium was homogeneously dispersed over CGS and the active component of catalyst was V2O5 according to the XPS results. In particular, the NH3-TPD spectra of the vanadium loaded CGS catalyst showed that vanadium produced more acid sites, and the Lewis acid sites on the vanadium species were the active sites for the catalytic reduction of NO at 240–290 °C.
      Citation: Catalysts
      PubDate: 2018-08-09
      DOI: 10.3390/catal8080327
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 328: NiFeOx as a Bifunctional Electrocatalyst for
           Oxygen Reduction (OR) and Evolution (OE) Reaction in Alkaline Media

    • Authors: Alagar Raj Paulraj, Yohannes Kiros, Mats Göthelid, Malin B. Johansson
      First page: 328
      Abstract: This article reports the two-step synthesis of NiFeOx nanomaterials and their characterization and bifunctional electrocatalytic activity measurements in alkaline electrolyte for metal-air batteries. The samples were mostly in layered double hydroxide at the initial temperature, but upon heat treatment, they were converted to NiFe2O4 phases. The electrochemical behaviour of the different samples was studied by linear sweep voltammetry and cyclic voltammetry on the glassy carbon electrode. The OER catalyst activity was observed for low mass loadings (0.125 mg cm−2), whereas high catalyst loading exhibited the best performance on the ORR side. The sample heat-treated at 250 °C delivered the highest bi-functional oxygen evolution and reduction reaction activity (OER/ORR) thanks to its thin-holey nanosheet-like structure with higher nickel oxidation state at 250 °C. This work further helps to develop low-cost electrocatalyst development for metal-air batteries.
      Citation: Catalysts
      PubDate: 2018-08-10
      DOI: 10.3390/catal8080328
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 329: Oxygen Reduction Reaction and Hydrogen
           Evolution Reaction Catalyzed by Pd–Ru Nanoparticles Encapsulated in
           Porous Carbon Nanosheets

    • Authors: Juntai Tian, Wen Wu, Zhenghua Tang, Yuan Wu, Robert Burns, Brandon Tichnell, Zhen Liu, Shaowei Chen
      First page: 329
      Abstract: Developing bi-functional electrocatalysts for both oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) is crucial for enhancing the energy transfer efficiency of metal–air batteries and fuel cells, as well as producing hydrogen with a high purity. Herein, a series of Pd–Ru alloyed nanoparticles encapsulated in porous carbon nanosheets (CNs) were synthesized and employed as a bifunctional electrocatalyst for both ORR and HER. The TEM measurements showed that Pd–Ru nanoparticles, with a size of approximately 1–5 nm, were uniformly dispersed on the carbon nanosheets. The crystal and electronic structures of the PdxRu100−x/CNs series were revealed by powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The as-prepared samples exhibited effective ORR activity in alkaline media and excellent HER activity in both alkaline and acid solutions. The Pd50Ru50/CNs sample displayed the best activity and stability among the series, which is comparable and superior to that of commercial 10% Pd/C. For ORR, the Pd50Ru50/CNs catalyst exhibited an onset potential of 0.903 V vs. RHE (Reversible Hydrogen Electrode) and 11.4% decrease of the current density after 30,000 s of continuous operation in stability test. For HER, the Pd50Ru50/CNs catalyst displayed an overpotential of 37.3 mV and 45.1 mV at 10 mA cm−2 in 0.1 M KOH and 0.5 M H2SO4, respectively. The strategy for encapsulating bimetallic alloys within porous carbon materials is promising for fabricating sustainable energy toward electrocatalysts with multiple electrocatalytic activities for energy related applications.
      Citation: Catalysts
      PubDate: 2018-08-11
      DOI: 10.3390/catal8080329
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 330: Constructing A Rational Kinetic Model of the
           Selective Propane Oxidation Over A Mixed Metal Oxide Catalyst

    • Authors: Christoph Sprung, Gregory S. Yablonsky, Robert Schlögl, Annette Trunschke
      First page: 330
      Abstract: This research presents a kinetic investigation of the selective oxidation of propane to acrylic acid over a MoVTeNb oxide (M1 phase) catalyst. The paper contains both an overview of the related literature, and original results with a focus on kinetic aspects. Two types of kinetic experiments were performed in a plug flow reactor, observing (i) steady-state conditions (partial pressure variations) and (ii) the catalyst evolution as a function of time-on-stream. For this, the catalyst was treated in reducing atmosphere, before re-oxidising it. These observations in long term behaviour were used to distinguish different catalytic routes, namely for the formation of propene, acetic acid, acrylic acid, carbon monoxide and carbon dioxide. A partial carbon balance was introduced, which is a ‘kinetic fingerprint’, that distinguishes one type of active site from another. Furthermore, an ‘active site’ was found to consist of one or more ‘active centres’. A rational mechanism was developed based on the theory of graphs and includes two time scales belonging to (i) the catalytic cycle and (ii) the catalyst evolution. Several different types of active sites exist, at least as many, as kinetically independent product molecules are formed over a catalyst surface.
      Citation: Catalysts
      PubDate: 2018-08-13
      DOI: 10.3390/catal8080330
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 331: Ru-(Mn-M)OX Solid Base Catalysts for the
           Upgrading of Xylitol to Glycols in Water

    • Authors: Maxime Rivière, Noémie Perret, Damien Delcroix, Amandine Cabiac, Catherine Pinel, Michèle Besson
      First page: 331
      Abstract: A series of Ru-(Mn-M)OX catalysts (M: Al, Ti, Zr, Zn) prepared by co-precipitation were investigated in the hydrogenolysis of xylitol in water to ethylene glycol, propylene glycol and glycerol at 200 °C and 60 bar of H2. The catalyst promoted with Al, Ru-(Mn-Al)OX, showed superior activity (57 h−1) and a high global selectivity to glycols and glycerol of 58% at 80% xylitol conversion. In comparison, the catalyst prepared by loading Ru on (Mn-Al)OX, Ru/(Mn-Al)OX was more active (111 h−1) but less selective (37%) than Ru-(Mn-Al)OX. Characterization of these catalysts by XRD, BET, CO2-TPD, NH3-TPD and TEM showed that Ru/(Mn-Al)OX contained highly dispersed and uniformly distributed Ru particles and fewer basic sites, which favored decarbonylation, epimerization and cascade decarbonylation reactions instead of retro-aldol reactions producing glycols. The hydrothermal stability of Ru-(Mn-Al)OX was improved by decreasing the xylitol/catalyst ratio, which decreased the formation of carboxylic acids and enabled recycling of the catalyst, with a very low deactivation.
      Citation: Catalysts
      PubDate: 2018-08-14
      DOI: 10.3390/catal8080331
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 332: Mixed-Oxide Catalysts with Spinel Structure
           for the Valorization of Biomass: The Chemical-Loop Reforming of Bioethanol
           

    • Authors: Olena Vozniuk, Tommaso Tabanelli, Nathalie Tanchoux, Jean-Marc M. Millet, Stefania Albonetti, Francesco Di Renzo, Fabrizio Cavani
      First page: 332
      Abstract: This short review reports on spinel-type mixed oxides as catalysts for the transformation of biomass-derived building blocks into chemicals and fuel additives. After an overview of the various methods reported in the literature for the synthesis of mixed oxides with spinel structure, the use of this class of materials for the chemical-loop reforming of bioalcohols is reviewed in detail. This reaction is aimed at the production of H2 with intrinsic separation of C-containing products, but also is a very versatile tool for investigating the solid-state chemistry of spinels.
      Citation: Catalysts
      PubDate: 2018-08-14
      DOI: 10.3390/catal8080332
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 333: Stabilization of Enzymes by Multipoint
           Covalent Attachment on Aldehyde-Supports: 2-Picoline Borane as an
           Alternative Reducing Agent

    • Authors: Alejandro H. Orrego, Maria Romero-Fernández, María del Carmen Millán-Linares, María del Mar Yust, José M. Guisán, Javier Rocha-Martin
      First page: 333
      Abstract: Enzyme immobilization by multipoint covalent attachment on supports activated with aliphatic aldehyde groups (e.g., glyoxyl agarose) has proven to be an excellent immobilization technique for enzyme stabilization. Borohydride reduction of immobilized enzymes is necessary to convert enzyme–support linkages into stable secondary amino groups and to convert the remaining aldehyde groups on the support into hydroxy groups. However, the use of borohydride can adversely affect the structure–activity of some immobilized enzymes. For this reason, 2-picoline borane is proposed here as an alternative milder reducing agent, especially, for those enzymes sensitive to borohydride reduction. The immobilization-stabilization parameters of five enzymes from different sources and nature (from monomeric to multimeric enzymes) were compared with those obtained by conventional methodology. The most interesting results were obtained for bacterial (R)-mandelate dehydrogenase (ManDH). Immobilized ManDH reduced with borohydride almost completely lost its catalytic activity (1.5% of expressed activity). In contrast, using 2-picoline borane and blocking the remaining aldehyde groups on the support with glycine allowed for a conjugate with a significant activity of 19.5%. This improved biocatalyst was 357-fold more stable than the soluble enzyme at 50 °C and pH 7. The results show that this alternative methodology can lead to more stable and active biocatalysts.
      Citation: Catalysts
      PubDate: 2018-08-15
      DOI: 10.3390/catal8080333
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 334: Magnetic Combined Cross-Linked Enzyme
           Aggregates of Ketoreductase and Alcohol Dehydrogenase: An Efficient and
           Stable Biocatalyst for Asymmetric Synthesis of (R)-3-Quinuclidinol with
           Regeneration of Coenzymes In Situ

    • Authors: Yuhan Chen, Qihua Jiang, Lili Sun, Qiang Li, Liping Zhou, Qian Chen, Shanshan Li, Mingan Yu, Wei Li
      First page: 334
      Abstract: Enzymes are biocatalysts. In this study, a novel biocatalyst consisting of magnetic combined cross-linked enzyme aggregates (combi-CLEAs) of 3-quinuclidinone reductase (QNR) and glucose dehydrogenase (GDH) for enantioselective synthesis of (R)-3-quinuclidinolwith regeneration of cofactors in situ was developed. The magnetic combi-CLEAs were fabricated with the use of ammonium sulfate as a precipitant and glutaraldehyde as a cross-linker for direct immobilization of QNR and GDH from E. coli BL(21) cell lysates onto amino-functionalized Fe3O4 nanoparticles. The physicochemical properties of the magnetic combi-CLEAs were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and magnetic measurements. Field emission scanning electron microscope (FE-SEM) images revealed a spherical structure with numerous pores which facilitate the movement of the substrates and coenzymes. Moreover, the magnetic combi-CLEAs exhibited improved operational and thermal stability, enhanced catalytic performance for transformation of 3-quinuclidinone (33 g/L) into (R)-3-quinuclidinol in 100% conversion yield and 100% enantiomeric excess (ee) after 3 h of reaction. The activity of the biocatalysts was preserved about 80% after 70 days storage and retained more than 40% of its initial activity after ten cycles. These results demonstrated that the magnetic combi-CLEAs, as cost-effective and environmentally friendly biocatalysts, were suitable for application in synthesis of (R)-3-quinuclidinol essential for the production of solifenacin and aclidinium with better performance than those currently available.
      Citation: Catalysts
      PubDate: 2018-08-15
      DOI: 10.3390/catal8080334
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 335: From a Sequential Chemo-Enzymatic Approach
           to a Continuous Process for HMF Production from Glucose

    • Authors: Alexandra Gimbernat, Marie Guehl, Nicolas Lopes Ferreira, Egon Heuson, Pascal Dhulster, Mickael Capron, Franck Dumeignil, Damien Delcroix, Jean Sébastien Girardon, Rénato Froidevaux
      First page: 335
      Abstract: Notably available from the cellulose contained in lignocellulosic biomass, glucose is a highly attractive substrate for eco-efficient processes towards high-value chemicals. A recent strategy for biomass valorization consists on combining biocatalysis and chemocatalysis to realise the so-called chemo-enzymatic or hybrid catalysis. Optimisation of the glucose conversion to 5-hydroxymethylfurfural (HMF) is the object of many research efforts. HMF can be produced by chemo-catalyzed fructose dehydration, while fructose can be selectively obtained from enzymatic glucose isomerization. Despite recent advances in HMF production, a fully integrated efficient process remains to be demonstrated. Our innovative approach consists on a continuous process involving enzymatic glucose isomerization, selective arylboronic-acid mediated fructose complexation/transportation, and chemical fructose dehydration to HMF. We designed a novel reactor based on two aqueous phases dynamically connected via an organic liquid membrane, which enabled substantial enhancement of glucose conversion (70%) while avoiding intermediate separation steps. Furthermore, in the as-combined steps, the use of an immobilized glucose isomerase and an acidic resin facilitates catalyst recycling.
      Citation: Catalysts
      PubDate: 2018-08-17
      DOI: 10.3390/catal8080335
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 336: Active Site of O2 and Its Improvement
           Mechanism over Ce-Ti Catalyst for NH3-SCR Reaction

    • Authors: Dong Jiang, Shule Zhang, Yiqing Zeng, Pengfei Wang, Qin Zhong
      First page: 336
      Abstract: The current study on Ce-Ti catalyst was mainly focused on the function of NH3 and NO adsorption sites. In our study, by comparing Ce-Ti (doped catalyst) to Ce/Ti (supported catalyst), the active site of O2 and its improvement mechanism over Ce-Ti catalyst for NH3-Selective catalytic reduction (SCR) reactions were investigated. For Ce-Ti catalyst, a cerium atom was confirmed entering a TiO2 crystal lattice by X-ray diffraction (XRD) and Raman; the structure of Ce-□-Ti (□ represents oxygen vacancy) in Ce-Ti catalyst was confirmed by X-ray photoelectron spectroscopy (XPS) and Photoluminescence spectra (PL spectra). The nature of this structure was characterized by electron paramagnetic resonance (EPR), Ammonia temperature-programmed desorption (NH3-TPD), hydrogen temperature-programmed reduction (H2-TPR), Nitric oxide temperature-programmed desorption (NO-TPD) and In situ DRIFT. The results indicated that oxygen vacancies had a promotive effect on the adsorption and activation of oxygen, and oxygen was converted to superoxide ions in large quantities. Also, because of adsorption and activation of NO and NH3, electrons were transferred to adsorbed oxygen via oxygen vacancies, which also promoted the formation of superoxide ions. We expected that our study could promote understanding of the active site of O2 and its improvement mechanism for doped catalyst.
      Citation: Catalysts
      PubDate: 2018-08-17
      DOI: 10.3390/catal8080336
      Issue No: Vol. 8, No. 8 (2018)
       
  • Catalysts, Vol. 8, Pages 337: Effects of Coordination Ability of
           Nitrogen-Containing Carboxylic Acid Ligands on Nieuwland Catalyst

    • Authors: Yanhe You, Juan Luo, Jianwei Xie, Jinli Zhang, Bin Dai
      First page: 337
      Abstract: This article investigated the effect of three nitrogen-containing carboxylic acid ligands for the Nieuwland catalyst system. The catalyst system containing 4.5% N-(2-acetamido) iminodiacetic acid exhibited improved catalytic activity with excellent performance. The yield of monovinylacetylene (MVA) was maintained at 36.7% after 24 h, which was increased by 17.1% relative to the Nieuwland catalyst system. Based on a variety of analyses on the crystals precipitated from the catalyst solutions, it can be inferred that the outstanding performance and lifetime of the catalysts were related to the abilities of these ligands to form strong coordination with Cu+ ions and stabilize them.
      Citation: Catalysts
      PubDate: 2018-08-17
      DOI: 10.3390/catal8080337
      Issue No: Vol. 8, No. 8 (2018)
       
  • 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 255: Development of Two Novel Processes for
           Hydrogenation of CO2 to Methanol over Cu/ZnO/Al2O3 Catalyst to Improve the
           Performance of Conventional Dual Type Methanol Synthesis Reactor

    • Authors: Behnaz Rahmatmand, Mohammad Reza Rahimpour, Peyman Keshavarz
      First page: 255
      Abstract: Conventional methanol synthesis process (CR configuration) consists of water-cooled and gas-cooled reactors in which methanol and water are condensed inside the gas-cooled reactor which deactivates the catalyst. In this study, two novel configurations (AW and ACW configurations) are represented to address this problem in which the gas-cooled reactor is replaced with adiabatic reactor. Moreover, a condenser is applied between adiabatic and water-cooled reactors in ACW configuration. Results show that temperature increases somewhat along the adiabatic reactor that prevents gas condensate formation. Besides, the adiabatic reactor maximum temperature is less than that of first reactor in CR configuration which prevents copper based catalyst thermal sintering. Moreover, a high cross section-to-length ratio of the adiabatic reactor leads to negligible pressure drop along the reactor and improvement in CO2 conversion to methanol that has positive environmental effects. Also, water mole fraction decreases along the reactors of AW and ACW configurations to prevent the deactivation of catalyst active sites. Eventually, methanol production rates by AW and ACW configurations are improved around 25.5% and 43.1% in comparison with CR configuration. So, novel AW and ACW configurations provide many benefits including improvement in catalyst activity and durability, CO2 conversion, and the methanol production rate.
      Citation: Catalysts
      PubDate: 2018-06-23
      DOI: 10.3390/catal8070255
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 256: DBD Plasma-ZrO2 Catalytic Decomposition of
           CO2 at Low Temperatures

    • Authors: Amin Zhou, Dong Chen, Cunhua Ma, Feng Yu, Bin Dai
      First page: 256
      Abstract: This study describes the decomposition of CO2 using Dielectric Barrier Discharge (DBD) plasma technology combined with the packing materials. A self-cooling coaxial cylinder DBD reactor that packed ZrO2 pellets or glass beads with a grain size of 1–2 mm was designed to decompose CO2. The control of the temperature of the reactor was achieved via passing the condensate water through the shell of the DBD reactor. Key factors, for instance discharge length, packing materials, beads size and discharge power, were investigated to evaluate the efficiency of CO2 decomposition. The results indicated that packing materials exhibited a prominent effect on CO2 decomposition, especially in the presence of ZrO2 pellets. Most encouragingly, a maximum decomposition rate of 49.1% (2-mm particle sizes) and 52.1% (1-mm particle sizes) was obtained with packing ZrO2 pellets and a 32.3% (2-mm particle sizes) and a 33.5% (1-mm particle sizes) decomposing rate with packing glass beads. In the meantime, CO selectivity was up to 95%. Furthermore, the energy efficiency was increased from 3.3%–7% before and after packing ZrO2 pellets into the DBD reactor. It was concluded that the packing ZrO2 simultaneously increases the key values, decomposition rate and energy efficiency, by a factor of two, which makes it very promising. The improved decomposition rate and energy efficiency can be attributed mainly to the stronger electric field and electron energy and the lower reaction temperature.
      Citation: Catalysts
      PubDate: 2018-06-23
      DOI: 10.3390/catal8070256
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 257: Hydrogen Production from Chemical Looping
           Reforming of Ethanol Using Ni/CeO2 Nanorod Oxygen Carrier

    • Authors: Lin Li, Bo Jiang, Dawei Tang, Zhouwei Zheng, Cong Zhao
      First page: 257
      Abstract: Chemical looping reforming (CLR) technique is a prospective option for hydrogen production. Improving oxygen mobility and sintering resistance are still the main challenges of the development of high-performance oxygen carriers (OCs) in the CLR process. This paper explores the performance of Ni/CeO2 nanorod (NR) as an OC in CLR of ethanol. Various characterization methods such as N2 adsorption-desorption, X-ray diffraction (XRD), Raman spectra, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (TPR), and H2 chemisorption were utilized to study the properties of fresh OCs. The characterization results show the Ni/CeO2-NR possesses high Ni dispersion, abundant oxygen vacancies, and strong metal-support interaction. The performance of prepared OCs was tested in a packed-bed reactor. H2 selectivity of 80% was achieved by Ni/CeO2-NR in 10-cycle stability test. The small particle size and abundant oxygen vacancies contributed to the water gas shift reaction, improving the catalytic activity. The covered interfacial Ni atoms closely anchored on the underlying surface oxygen vacancies on the (111) facets of CeO2-NR, enhancing the anti-sintering capability. Moreover, the strong oxygen mobility of CeO2-NR also effectively eliminated surface coke on the Ni particle surface.
      Citation: Catalysts
      PubDate: 2018-06-25
      DOI: 10.3390/catal8070257
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 258: Assessing the Potential of Co-Pt Bronze for
           Electrocatalysis in Acidic Media

    • Authors: Yuji Kamitaka, Noboru Taguchi, Yu Morimoto
      First page: 258
      Abstract: An electron-conducting mixed oxide, Co-Pt bronze was synthesized and examined as a candidate for a highly durable electrocatalyst for both the polymer electrolyte fuel cells and electrolyzers. The motivation of this study comes from the fact that this material has not been studied as an electrocatalyst in acidic media, although past studies showed a high electronic conductivity and a high corrosion resistance. Co-Pt bronze without metallic Pt was obtained by solid-state synthesis and hot aqua regia rinsing. The OER activity was found to be among the highest as a material without Ir and Ru in acidic media, and it showed extremely high electrochemical stability in the OER potential range. Its oxygen reduction reaction (ORR) was obtained after potential cycles down to the hydrogen region, which formed a thin Pt metallic layer over the oxide. While its specific activity was not more than that of pure platinum nanoparticles, its durability against the potential cycles was much higher.
      Citation: Catalysts
      PubDate: 2018-06-25
      DOI: 10.3390/catal8070258
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 259: Effect of Preparation Conditions on
           Structure and Activity of Sodium-Impregnated Oyster Shell Catalysts for
           Transesterification

    • Authors: Han Jin, Praveen Kolar, Steven W. Peretti, Jason A. Osborne, Jay J. Cheng
      First page: 259
      Abstract: The catalyst preparation technique plays a significant role in its activity and durability. The present research investigated sodium hydroxide and sodium chloride as the precursor chemicals for impregnation on waste oyster shells that were tested as heterogeneous base catalysts for transesterification of soybean oil. Effects of precursor concentration and calcination temperature on the surface structure and the activity of the catalysts were studied via the one-factor-at-a-time method. The optimal impregnation concentrations of sodium hydroxide and sodium chloride were determined to be 6 mol/L and 2.43 mol/L, respectively. The optimal calcination temperature was determined to be 800 °C for both sodium hydroxide and sodium chloride-impregnated catalysts. Analyses of the catalysts via X-ray Diffraction and X-ray photoelectron spectroscopy indicated that different active species were formed on the surface depending on the calcination temperature. Results obtained from this study could be used to fine-tune the procedure for the synthesis of transesterification catalysts from aquatic animal shells.
      Citation: Catalysts
      PubDate: 2018-06-26
      DOI: 10.3390/catal8070259
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 260: Influence of the Structure-Forming Agent on
           the Performance of Fe-N-C Catalysts

    • Authors: Sven Schardt, Natascha Weidler, W. David Z. Wallace, Ioanna Martinaiou, Robert W. Stark, Ulrike I. Kramm
      First page: 260
      Abstract: In this work, the influence of the structure-forming agent on the composition, morphology and oxygen reduction reaction (ORR) activity of Fe-N-C catalysts was investigated. As structure-forming agents (SFAs), dicyandiamide (DCDA) (nitrogen source) or oxalic acid (oxygen source) or mixtures thereof were used. For characterization, cyclic voltammetry and rotating disc electrode (RDE) experiments were performed in 0.1 M H2SO4. In addition to this, N2 sorption measurements and Raman spectroscopy were performed for the structural, and elemental analysis for chemical characterization. The role of metal, nitrogen and carbon sources within the synthesis of Fe-N-C catalysts has been pointed out before. Here, we show that the optimum in terms of ORR activity is achieved if both N- and O-containing SFAs are used in almost similar fractions. All catalysts display a redox couple, where its position depends on the fractions of SFAs. The SFA has also a strong impact on the morphology: Catalysts that were prepared with a larger fraction of N-containing SFA revealed a higher order in graphitization, indicated by bands in the 2nd order range of the Raman spectra. Nevertheless, the optimum in terms of ORR activity is obtained for the catalyst with highest D/G band ratio. Therefore, the results indicate that the presence of an additional oxygen-containing SFA is beneficial within the preparation.
      Citation: Catalysts
      PubDate: 2018-06-28
      DOI: 10.3390/catal8070260
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 261: Fast Pyrolysis of Sunflower Oil in the
           Presence of Microporous and Mesoporous Materials for Production of Bio-Oil
           

    • Authors: Aruzza M. M. Araújo, Gabriella S. M. Queiroz, Danielle O. Maia, Amanda D. Gondim, Luiz D. Souza, Valter J. Fernandes, Antonio S. Araujo
      First page: 261
      Abstract: The present work describes the study of micro (H-ZSM-5) and mesoporous (AL-MCM-41) structures, aiming at their application in the production of renewable fuels through the thermos-catalytic pyrolysis process both were synthesized hydrothermally and characterized by X-ray diffraction, thermal analysis, infrared spectroscopy, nitrogen adsorption, and surface acidity. The catalytic effect of the materials mentioned, as well as their mechanical mixtures in the proportions of H-ZSM-5 (75% wt) and AL-MCM-41 (25% wt); H-ZSM-5 (50% wt) and AL-MCM-41 (50% wt); H-ZSM-5 (25% wt) and AL-MCM-41 (75% wt) were used in the thermal and thermo-catalytic pyrolysis of sunflower oil. The products obtained in the presence of H-ZSM-5 (25% wt) and AL-MCM-41(75% wt) showed selectivity for the conversion of hydrocarbons between C11 and C16, which is near that of the petroleum-derived kerosene and diesel (>C16). On the other hand, the H-ZSM-5 (75% wt) and AL-MCM-41 (25% wt) material, in which the majoritarian catalyst is the microporous, with active sites and a higher surface acidity, indicates selectivity for light hydrocarbons (C5-C10), in the range of gasoline obtained by the conversion of mineral oil. The presence of catalysts (AL-MCM-41and H-ZSM-5) favors the deoxygenation of the pyrolysis products of sunflower oil by decarbonylation reaction.
      Citation: Catalysts
      PubDate: 2018-06-28
      DOI: 10.3390/catal8070261
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 262: Microwave, Ultrasound, and Mechanochemistry:
           Unconventional Tools that Are Used to Obtain “Smart” Catalysts for CO2
           Hydrogenation

    • Authors: Maela Manzoli, Barbara Bonelli
      First page: 262
      Abstract: The most recent progress obtained through the precise use of enabling technologies, namely microwave, ultrasound, and mechanochemistry, described in the literature for obtaining improved performance catalysts (and photocatalysts) for CO2 hydrogenation, are reviewed. In particular, the main advantages (and drawbacks) found in using the proposed methodologies will be discussed and compared by focusing on catalyst design and optimization of clean and efficient (green) synthetic processes. The role of microwaves as a possible activation tool used to improve the reaction yield will also be considered.
      Citation: Catalysts
      PubDate: 2018-06-28
      DOI: 10.3390/catal8070262
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 263: Geocatalytic Uptake of Ozone onto Natural
           Mineral Dust

    • Authors: Xianjie Wang, Manolis N. Romanias, Frédéric Thévenet, Antoine Rousseau
      First page: 263
      Abstract: Beyond tailored and synthetic catalysts sought out for ozone decomposition, mineral dusts provide naturally mixed metal oxide materials. The steady-state uptake of O3 evidenced across a wide concentration range signifies the catalytic decomposition of O3. The geocatalytic properties of such natural mineral dust open up new perspectives in atmospheric chemistry and catalytic processes.
      Citation: Catalysts
      PubDate: 2018-06-29
      DOI: 10.3390/catal8070263
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 264: Acid–Base Bifunctional Hf Nanohybrids
           Enable High Selectivity in the Catalytic Conversion of Ethyl Levulinate to
           γ-Valerolactone

    • Authors: Weibo Wu, Yan Li, Hu Li, Wenfeng Zhao, Song Yang
      First page: 264
      Abstract: The catalytic upgrading of bio-based platform molecules is a promising approach for biomass valorization. However, most solid catalysts are not thermally or chemically stable, and are difficult to prepare. In this study, a stable organic phosphonate–hafnium solid catalyst (PPOA–Hf) was synthesized, and acid–base bifunctional sites were found to play a cooperative role in the cascade transfer hydrogenation and cyclization of ethyl levulinate (EL) to γ-valerolactone (GVL). Under relatively mild reaction conditions of 160 °C for 6 h, EL was completely converted to GVL with a good yield of 85%. The apparent activation energy was calculated to be 53 kJ/mol, which was lower than other solid catalysts for the same reaction. In addition, the PPOA-Hf solid catalyst did not significantly decrease its activity after five recycles, and no evident leaching of Hf was observed, indicating its high stability and potential practical application.
      Citation: Catalysts
      PubDate: 2018-06-29
      DOI: 10.3390/catal8070264
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 265: A Contribution to the Experimental
           Microkinetic Approach of Gas/Solid Heterogeneous Catalysis: Measurement of
           the Individual Heats of Adsorption of Coadsorbed Species by Using the AEIR
           Method

    • Authors: Daniel Bianchi
      First page: 265
      Abstract: The two first surface elementary steps of a gas/solid catalytic reaction are the adsorption/desorption at least one of the reactants leading to its adsorption equilibrium which can be or not disturbed by the others surface elementary steps leading to the products. The variety of the sites of a conventional catalyst may lead to the formation of different coadsorbed species such as linear, bridged and threefold coordinated species for the adsorption of CO on supported metal particles. The aim of the present article is to summarize works performed in the last twenty years for the development and applications of an analytical method named Adsorption Equilibrium InfraRed spectroscopy (AEIR) for the measurement of the individual heats of adsorption of coadsorbed species and for the validation of mathematical expressions for their adsorption coefficients and adsorption models. The method uses the evolution of the IR bands characteristic of each of coadsorbed species during the increase in the adsorption temperature in isobaric conditions. The presentation shows that the versatility of AEIR leads to net advantages as compared to others conventional methods particularly in the context of the microkinetic approach of catalytic reactions.
      Citation: Catalysts
      PubDate: 2018-06-29
      DOI: 10.3390/catal8070265
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 266: Low-Temperature Activity and PdO-PdOx
           Transition in Methane Combustion by a PdO-PdOx/γ-Al2O3 Catalyst

    • Authors: Anil C. Banerjee, Jacqueline M. McGuire, Olivia Lawnick, Michael. J. Bozack
      First page: 266
      Abstract: The search to discover a suitable catalyst for complete combustion of methane at low temperature continues to be an active area of research. We prepared a 5 wt % PdO-PdOx/γ-Al2O3 catalyst by a modified Vortex-assisted Incipient Wetness Method. X-ray Photoelectron Spectroscopy showed that the original catalyst contained PdO (38%) and PdOx (62%) on the surface and indicated that PdOx originated from the interaction of PdO with the support. Scanning Transmission Electron Microscopy confirmed the catalyst had an average particle size of 10 nm and was well-dispersed in the support. The catalyst exhibited exceptional low-temperature activities with 90–94% methane conversion at 300–320 °C. The catalyst was active and stable after several catalytic runs with no signs of deactivation by steam in this narrow temperature range. However, the conversion decreased in the temperature range 325–400 °C. The surface composition changed to some extent after the reaction at 325 °C. A tentative mechanism proposes PdOx (Pd native oxide) as the active phase and migration of oxide ions from the support to PdO and then to PdOx during the catalytic oxidation. The high methane conversion at low temperature is attributed to the vortex method providing better dispersion, and to catalyst–support interaction producing the active phase of PdOx.
      Citation: Catalysts
      PubDate: 2018-06-29
      DOI: 10.3390/catal8070266
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 267: Removal of Methylene Blue from Water by
           BiFeO3/Carbon Fibre Nanocomposite and Its Photocatalytic Regeneration

    • Authors: Shuang Jiao, Yiming Zhao, Meng Bi, Shuyue Bi, Xiangman Li, Binsong Wang, Chensha Li, Yinmao Dong
      First page: 267
      Abstract: It is essential to prepare a highly efficient and reproducible adsorbent for purifying industrial dye wastewater. In this work, a novel and efficient BiFeO3/carbon fiber (CCT-BFO) nanocomposite adsorbent was prepared by the template method and through optimizing the preparation process. The morphology, physicochemical properties, and specific surface characteristics of the CCT-BFO were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) patterns, Fourier-transform infrared spectrometer (FTIR), and N2 adsorption-desorption isotherm. The CCT-BFO could efficiently remove the Methylene blue (MB) from aqueous solutions, and the adsorption performance is not easily influenced by the environment. The equilibrium adsorption data were fitted to the classical models very well; the maximum capacity of adsorption MB onto the CCT-BFO was higher than many other reported adsorbents and the data of the adsorption kinetics were described by a pseudo-second-order model. Furthermore, the CCT-BFO can be recycled by photocatalytic regeneration. And the constant adsorption capacity was almost retained after recycling five times.
      Citation: Catalysts
      PubDate: 2018-06-29
      DOI: 10.3390/catal8070267
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 268: Chiral Dirhodium(II) Carboxylates: New
           Insights into the Effect of Ligand Stereo-Purity on Catalyst Structure and
           Enantioselectivity

    • Authors: Frady G. Adly, Hannah Bollard, Michael G. Gardiner, Ashraf Ghanem
      First page: 268
      Abstract: The current report contributes to the understanding of the stereoselectivity of chiral dirhodium(II) carboxylate catalysts carrying N-protected tert-leucine ligands. Investigating the possible effect of ligand stereo-purity on catalyst structure and enantioselectivity was carried out. This was justified through a new X-ray crystal structure for Rh2(S,S,S,R-PTTL)4 diastereomer.
      Citation: Catalysts
      PubDate: 2018-06-30
      DOI: 10.3390/catal8070268
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 269: N,S Co-Doped Carbon Nanofibers Derived from
           Bacterial Cellulose/Poly(Methylene blue) Hybrids: Efficient
           Electrocatalyst for Oxygen Reduction Reaction

    • Authors: Jing Liu, Yi-Gang Ji, Bin Qiao, Fengqi Zhao, Hongxu Gao, Pei Chen, Zhongwei An, Xinbing Chen, Yu Chen
      First page: 269
      Abstract: Exploring inexpensive and highly efficient electrocatalyst to decrease the overpotential of oxygen reduction reaction (ORR) is one of the key issues for the commercialization of energy conversion and storage devices. Heteroatom-doped carbon materials have attracted increasing attention as promising electrocatalysts. Herein, we prepared a highly active electrocatalyst, nitrogen, sulfur co-doped carbon nanofibers (N/S-CNF), via in situ chemical oxidative polymerization of methylene blue on the bacterial cellulose nanofibers, followed by carbonization process. It was found that the type of nitrogen/sulfur source, methylene blue and poly(methylene blue), has significantly influence on the catalytic activity of the resultant carbon nanofibers. Benefiting from the porous structure and high surface area (729 m2/g) which favors mass transfer and exposing of active N and S atoms, the N/S-CNF displays high catalytic activity for the ORR in alkaline media with a half-wave potential of about 0.80 V, and better stability and stronger methanol tolerance than that of 20 wt % Pt/C, indicating great potential application in the field of alkaline fuel cell.
      Citation: Catalysts
      PubDate: 2018-06-30
      DOI: 10.3390/catal8070269
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 270: Oxidative Dehydrogenation of Liquefied
           Petroleum Gas on Copper, Zinc and Iron Oxide Impregnated on MFI Zeolite
           Assisted by Electric Power

    • Authors: Amin Alamdari, Ramin Karimzadeh
      First page: 270
      Abstract: Olefin was produced with a non-conventional method using an electric field exerted on zeolites. The lattice oxygen mobility increases with a decrease in band gap, leading to an increase in olefin yield. By impregnating the transition metal, an increase in carrier concentration occurs. The external electric field changes the Fermi level. In this research, HZSM-5 was placed in an external DC electric field with strength appropriate for studying its catalytic performance. The Fermi level changed with the metal type and the external electric field. The increase in permittivity with temperature extracts higher energy from the external electric field. In catalytic reactions assisted by the external DC electric field, at 510 °C, the yield was approximately equal to the yield in a conventional reaction at 650 °C. With regard to TGA, in the catalytic reaction assisted by the external DC electric field, the produced coke declined. The results showed that the maximum yield value (50.54%) and conversion (92.81%) were be obtained at 650 °C with an input electrical current of 12 mA, a gap distance of 10 mm and a metal loading of 4 wt. % over FeHZSM-5.
      Citation: Catalysts
      PubDate: 2018-06-30
      DOI: 10.3390/catal8070270
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 271: Organic Base-Catalyzed C–S Bond
           Construction from CO2: A New Route for the Synthesis of Benzothiazolones

    • Authors: Xiang Gao, Yuehua Deng, Changyu Lu, Lei Zhang, Xintao Wang, Bo Yu
      First page: 271
      Abstract: The synthesis of organosulfur compounds via the construction of C−S bonds using CO2 as a C1 resource is very interesting. Herein, a novel method of synthesizing benzothiazolones via the cyclocarbonylation of 2-aminothiophenols with CO2 was developed. A series of organic bases was investigated for the catalysis of cyclocarbonylation, and 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) displayed the best catalytic activity. Then, various reaction parameters such as CO2 pressure, temperature, amount of catalyst, and reaction time for the catalytic performance were studied. Finally, a series of benzothiazolones was synthesized under the optimal reaction conditions, and a possible catalytic mechanism was also proposed.
      Citation: Catalysts
      PubDate: 2018-06-30
      DOI: 10.3390/catal8070271
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 272: The Roles of Graphene and Ag in the Hybrid
           Ag@Ag2O-Graphene for Sulfamethoxazole Degradation

    • Authors: Li Zhou, Guoyan Zou, Huiping Deng
      First page: 272
      Abstract: Ag@Ag2O-graphene (Ag@Ag2O-G) with different concentrations of graphene was synthesized using a facile in situ precipitation method. The photocatalysts were characterized by field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (DRS). The antibioticsulfamethoxazole (SMX) degradationunder simulated solar light and visible light irradiationwas investigated to evaluate photocatalytic performance. The composite photocatalyst Ag@Ag2O-G with 2.5 wt% graphene presented the highest activity among all the prepared composite photocatalysts. The coupling of graphene and Ag0 increased the photocatalyticactivity and stability of pure Ag2O. Under higher SMX concentrations, the adsorption, not the photocatalytic ability, playeda crucial role during the SMX removal process. On the basis of the characterization and reactive oxygen species (ROS) scavenging experiments, a separation and transfer mechanism of photogenerated carriers was proposed. In the photocatalytic degradation of SMX, the major active species wereidentified as photogenerated holes; photogenerated electrons in the conduction band (CB) of Ag2O could not transfer to graphene through Ag0due to the more negative reduction potential of graphene. This is an important result regardinggraphene and Ag0 roles which isdifferent from that for the photocatalytic degradation of dyes. This researchmay provide new insights into photocatalytic processes for the degradation of non-dye pollutants bycomposite materials to guidethe design of highly efficient reaction systems.
      Citation: Catalysts
      PubDate: 2018-07-04
      DOI: 10.3390/catal8070272
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 273: Highly Efficient Electrocatalytic
           Carboxylation of 1-Phenylethyl Chloride at Cu Foam Cathode

    • Authors: La-Xia Wu, Qi-Long Sun, Man-Ping Yang, Ying-Guo Zhao, Ye-Bin Guan, Huan Wang, Jia-Xing Lu
      First page: 273
      Abstract: A simple and efficient electrocatalytic carboxylation of benzyl chloride with CO2 is described. The reaction operates under 1 atm CO2 and room temperature in an undivided cell with Cu foam cathode and Mg sacrificial anode without any additional catalyst. For the model compound 1-phenylethyl chloride, the influence of cathode material, solvent, charge, current density and temperature were investigated. Under optimized conditions, 99% yield of 2-phenylpropionic acid could be obtained. Moreover, reasonable yields were also achieved with other benzyl chlorides.
      Citation: Catalysts
      PubDate: 2018-07-06
      DOI: 10.3390/catal8070273
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 274: Biocatalytic Synthesis of Fungal
           β-Glucans

    • Authors: Lefki-Maria Papaspyridi, Anastasia Zerva, Evangelos Topakas
      First page: 274
      Abstract: Glucans are the dominant polysaccharide constituents of fungal cell walls. Remarkably, these major bioactive polysaccharides account for the beneficial effects that have been observed by many mushrooms of medicinal interest. Accordingly, the prevailing tendency is the use of bioactive mushroom β-glucans mainly in pharmaceutical industries or as food additives, since it seems that they can be involved in meeting the overall growing demand for food in the future, but also in medical and material sectors. β-(1,3)-Glucan synthase (GLS) is the responsible enzyme for the synthesis of these important polysaccharides, which is a member of the glycosyl transferase (GT) family. For optimizing the production of such natural polymers of great interest, the comprehension of the fungal synthetic mechanism, as well as the biochemical and molecular characteristics of the key enzyme GLS and its expression seem to be crucial. Overall, in this review article, the fungal β-glucans biosynthesis by GLS is summarized, while the in vitro synthesis of major polysaccharides is also discussed, catalyzed by glycoside hydrolases (GHs) and GTs. Possible future prospects of GLS in medicine and in developing other potential artificial composite materials with industrial applications are also summarized.
      Citation: Catalysts
      PubDate: 2018-07-06
      DOI: 10.3390/catal8070274
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 275: Cobalt and Nitrogen Co-Doped Graphene-Carbon
           Nanotube Aerogel as an Efficient Bifunctional Electrocatalyst for Oxygen
           Reduction and Evolution Reactions

    • Authors: Xiaochang Qiao, Jutao Jin, Hongbo Fan, Lifeng Cui, Shan Ji, Yingwei Li, Shijun Liao
      First page: 275
      Abstract: In this study, a low-cost and environmentally friendly method is developed to synthesize cobalt and nitrogen co-doped graphene-carbon nanotube aerogel (Co-N-GCA) as a bifunctional electrocatalyst for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). The as-prepared Co-N-GCA has a hierarchical meso- and macroporous structure with a high N doping level (8.92 at. %) and a large specific surface area (456 m2 g−1). In an alkaline medium, the catalyst exhibits superior ORR electrocatalytic activity with an onset potential 15 mV more positive than Pt/C, and its diffusion-limiting current density is 29% higher than that of commercial Pt/C. The obtained Co-N-GCA is also highly active toward the OER, with a small overpotential of 408 mV at a current density of 10 mA cm−2. Its overall oxygen electrode activity parameter (ΔE) is 0.821 V, which is comparable to most of the best nonprecious-metal catalysts reported previously. Furthermore, Co-N-GCA demonstrates superior durability in both the ORR and the OER, making it a promising noble-metal-free bifunctional catalyst in practical applications for energy conversion and storage.
      Citation: Catalysts
      PubDate: 2018-07-07
      DOI: 10.3390/catal8070275
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 276: Synthesis of Vinyl Chloride Monomer over
           

    • Authors: Xing Li, Haiyang Zhang, Baochang Man, Chuanming Zhang, Hui Dai, Bin Dai, Jinli Zhang
      First page: 276
      Abstract: A series of catalysts, including Ru/AC, Ф-P-Ru/AC, Ф-P-Ru/AC-HCl, and Ф-P-Ru/AC-HNO3, were prepared and evaluated for the hydrochlorination reaction of acetylene. The test results reveal that the Ф-P-Ru/AC-HNO3 catalyst shows superior catalytic performance with an initial acetylene conversion of 97.2% and a relative increment of 87.0% within 48 h in comparison with that of the traditional RuCl3 catalyst. The substitution of inorganic RuCl3 precursor by organic Ф-P-Ru complex species in the catalysts results in more active species and tends to confine them in the micro-pores; the modification of carbon support by nitric acid in Ф-P-Ru catalyst may produce an interaction between the functional groups on modified support and Ru species, which is favorable to anchor and then reduce the loss of active species during the reaction, further increasing the amount of dominating Ru species, and greatly improving the reactants adsorption ability on the catalysts, thus enhancing the performance of the resultant catalysts. The as-prepared Ф-P-Ru catalysts are shown to be promising mercury-free candidates for the synthesis of vinyl chloride monomer.
      Citation: Catalysts
      PubDate: 2018-07-09
      DOI: 10.3390/catal8070276
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 277: Cascade Strategy for the Tunable Catalytic
           Valorization of Levulinic Acid and γ-Valerolactone to
           2-Methyltetrahydrofuran and Alcohols

    • Authors: Domenico Licursi, Claudia Antonetti, Sara Fulignati, Michael Giannoni, Anna Maria Raspolli Galletti
      First page: 277
      Abstract: A cascade strategy for the catalytic valorization of aqueous solutions of levulinic acid as well as of γ-valerolactone to 2-methyltetrahydrofuran or to monoalcohols, 2-butanol and 2-pentanol, has been studied and optimized. Only commercial catalytic systems have been employed, adopting sustainable reaction conditions. For the first time, the combined use of ruthenium and rhenium catalysts supported on carbon, with niobium phosphate as acid co-catalyst, has been claimed for the hydrogenation of γ-valerolactone and levulinic acid, addressing the selectivity to 2-methyltetrahydrofuran. On the other hand, the use of zeolite HY with commercial Ru/C catalyst favors the selective production of 2-butanol, starting again from γ-valerolactone and levulinic acid, with selectivities up to 80 and 70 mol %, respectively. Both levulinic acid and γ-valerolactone hydrogenation reactions have been optimized, investigating the effect of the main reaction parameters, to properly tune the catalytic performances towards the desired products. The proper choice of both the catalytic system and the reaction conditions can smartly switch the process towards the selective production of 2-methyltetrahydrofuran or monoalcohols. The catalytic system [Ru/C + zeolite HY] at 200 °C and 3 MPa H2 is able to completely convert both γ-valerolactone and levulinic acid, with overall yields to monoalcohols of 100 mol % and 88.8 mol %, respectively.
      Citation: Catalysts
      PubDate: 2018-07-09
      DOI: 10.3390/catal8070277
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 278: Immobilization of an
           Endo-β-N-acetylglucosaminidase for the Release of Bioactive N-glycans

    • Authors: Joshua Cohen, Sercan Karav, Daniela Barile, Juliana de Moura Bell
      First page: 278
      Abstract: As more is learned about glycoproteins’ roles in human health and disease, the biological functionalities of N-linked glycans are becoming more relevant. Protein deglycosylation allows for the selective release of N-glycans and facilitates glycoproteomic investigation into their roles as prebiotics or anti-pathogenic factors. To increase throughput and enzyme reusability, this work evaluated several immobilization methods for an endo-β-N-acetylglucosaminidase recently discovered from the commensal Bifidobacterium infantis. Ribonuclease B was used as a model glycoprotein to compare N-glycans released by the free and immobilized enzyme. Amino-based covalent method showed the highest enzyme immobilization. Relative abundance of N-glycans and enzyme activity were determined using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Kinetic evaluation demonstrated that upon immobilization, both Vmax and the Km decreased. Optimal pH values of 5 and 7 were identified for the free and immobilized enzyme, respectively. Although a higher temperature (65 vs. 45 °C) favored rapid glycan release, the immobilized enzyme retained over 50% of its original activity after seven use cycles at 45 °C. In view of future applications in the dairy industry, we investigated the ability of this enzyme to deglycosylate whey proteins. The immobilized enzyme released a higher abundance of neutral glycans from whey proteins, while the free enzyme released more sialylated glycans, determined by nano-LC Chip Q-ToF MS.
      Citation: Catalysts
      PubDate: 2018-07-10
      DOI: 10.3390/catal8070278
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 279: Highly Active TiO2 Microspheres Formation in
           the Presence of Ethylammonium Nitrate Ionic Liquid

    • Authors: Anna Gołąbiewska, Micaela Checa-Suárez, Marta Paszkiewicz-Gawron, Wojciech Lisowski, Edyta Raczuk, Tomasz Klimczuk, Żaneta Polkowska, Ewelina Grabowska, Adriana Zaleska-Medynska, Justyna Łuczak
      First page: 279
      Abstract: Spherical microparticles of TiO2 were synthesized by the ionic liquid-assisted solvothermal method at different reaction times (3, 6, 12, and 24 h). The properties of the prepared photocatalysts were investigated by means of UV-VIS diffuse-reflectance spectroscopy (DRS), Brunauer–Emmett–Teller (BET) surface area measurements, scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicated that the efficiency of the phenol degradation was related to the time of the solvothermal synthesis, as determined for the TiO2_EAN(1:1)_24h sample. The microparticles of TiO2_EAN(1:1)_3h that formed during only 3 h of the synthesis time revealed a really high photoactivity under visible irradiation (75%). This value increased to 80% and 82% after 12 h and 24 h, respectively. The photoactivity increase was accompanied by the increase of the specific surface area, thus the poresize as well as the ability to absorb UV-VIS irradiation. The high efficiency of the phenol degradation of the ionic liquid (IL)–TiO2 photocatalysts was ascribed to the interaction between the surface of the TiO2 and ionic liquid components (carbon and nitrogen).
      Citation: Catalysts
      PubDate: 2018-07-11
      DOI: 10.3390/catal8070279
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 280: PdO/ZnO@mSiO2 Hybrid Nanocatalyst for
           Reduction of Nitroarenes

    • Authors: Jinwoo Kim, Aram Kim, Nallal Muthuchamy, Kang Hyun Park
      First page: 280
      Abstract: Development of a novel approach for synthesizing nanostructured catalysts and achieving further improvements in catalytic activity, effectiveness, and efficiency remains a major challenge. In this report, we describe the preparation of a nanostructured PdO/ZnO@mSiO2 hybrid nanocatalyst featuring well-dispersed PdO nanoparticles within hollow ZnO@mSiO2. The as-prepared PdO/ZnO@mSiO2 hybrid nanocatalyst exhibited good morphological features, derived from the controlled stepwise synthesis from Pd/PS@ZIF-8@mSiO2 (PS = polystyrene). The morphology, size, oxidation state, crystallinity, and thermal stability of the prepared PdO/ZnO@mSiO2 hybrid nanocatalyst were confirmed by a series of physicochemical techniques. The PdO/ZnO@mSiO2 hybrid nanocatalyst showed very high catalytic efficiency in the reduction of 4-nitrophenol and various nitroarenes under eco-friendly conditions. Therefore, the PdO/ZnO@mSiO2 hybrid nanocatalyst is a promising alternative catalyst for applications in environmental remediation.
      Citation: Catalysts
      PubDate: 2018-07-14
      DOI: 10.3390/catal8070280
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 281: Production of Structured Phosphatidylcholine
           with High Content of Myristic Acid by Lipase-Catalyzed Acidolysis and
           Interesterification

    • Authors: Anna Chojnacka, Witold Gładkowski
      First page: 281
      Abstract: Synthesis of structured phosphatidylcholine (PC) enriched with myristic acid (MA) was conducted by acidolysis and interesterification reactions using immobilized lipases as catalysts and two acyl donors: trimyristin (TMA) isolated from ground nutmeg, and myristic acid obtained by saponification of TMA. Screening experiments indicated that the most effective biocatalyst for interesterification was Rhizomucor miehei lipase (RML), whereas for acidolysis, the most active were Thermomyces lanuginosus lipase (TLL) and RML. The effect of the molar ratio of substrates (egg-yolk PC/acyl donor), enzyme loading, and different solvent on the incorporation of MA into PC and on PC recovery was studied. The maximal incorporation of MA (44 wt%) was achieved after 48 h of RML-catalyzed interesterification in hexane using substrates molar ratio (PC/trimyristin) 1/5 and 30% enzyme load. Comparable results were obtained in toluene with 1/3 substrates molar ratio. Interesterification of PC with trimyristin resulted in significantly higher MA incorporation than acidolysis with myristic acid, particularly in the reactions catalyzed by RML.
      Citation: Catalysts
      PubDate: 2018-07-14
      DOI: 10.3390/catal8070281
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 282: Magnetic Microreactors with Immobilized
           Enzymes—From Assemblage to Contemporary Applications

    • Authors: Elena Gkantzou, Michaela Patila, Haralambos Stamatis
      First page: 282
      Abstract: Microfluidics, as the technology for continuous flow processing in microscale, is being increasingly elaborated on in enzyme biotechnology and biocatalysis. Enzymatic microreactors are a precious tool for the investigation of catalytic properties and optimization of reaction parameters in a thriving and high-yielding way. The utilization of magnetic forces in the overall microfluidic system has reinforced enzymatic processes, paving the way for novel applications in a variety of research fields. In this review, we hold a discussion on how different magnetic particles combined with the appropriate biocatalyst under the proper system configuration may constitute a powerful microsystem and provide a highly explorable scope.
      Citation: Catalysts
      PubDate: 2018-07-14
      DOI: 10.3390/catal8070282
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 283: Effect of Y Modified Ceria Support in Mono
           and Bimetallic Pd–Au Catalysts for Complete Benzene Oxidation

    • Authors: Lyuba Ilieva, Anna Maria Venezia, Petya Petrova, Giuseppe Pantaleo, Leonarda Francesca Liotta, Rodolfo Zanella, Zbigniew Kaszkur, Tatyana Tabakova
      First page: 283
      Abstract: Mono metallic and bimetallic Pd (1 wt. %)–Au (3 wt. %) catalysts were prepared using two ceria supports doped with 1 wt. % Y2O3. Yttrium was added by impregnation or co-precipitation. The catalyst synthesis was carried out by deposition–precipitation method, with sequential deposition–precipitation of palladium over previously loaded gold in the case of the bimetallic samples. The obtained materials, characterized by X-ray powder diffraction (XRD), High resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction (TPR) techniques, were tested in the complete benzene oxidation (CBO). The results of the characterization analyses and the catalytic performance pointed to a close relationship between structural, redox, and catalytic properties of mono and bimetallic catalysts. Among the monometallic systems, Pd catalysts were more active as compared to the corresponding Au catalysts. The bimetallic systems exhibited the best combustion activity. In particular, over Pd–Au supported on Y-impregnated ceria, 100% of benzene conversion towards total oxidation at the temperature of 150 °C was obtained. Comparison of surface sensitive XPS results of fresh and spent catalysts ascertained the redox character of the reaction.
      Citation: Catalysts
      PubDate: 2018-07-16
      DOI: 10.3390/catal8070283
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 284: Photocatalytic Membrane Reactor (PMR) for
           Virus Removal in Drinking Water: Effect of Humic Acid

    • Authors: Rong Cheng, Liangjie Shen, Qi Wang, Shaoyu Xiang, Lei Shi, Xiang Zheng, Wenzhou Lv
      First page: 284
      Abstract: In the actual water environment, the health risk of waterborne viruses is evaluated to be 101–104 times higher at a similar level of exposure compared with bacteria and has aroused strong concern in many countries in the world. Photocatalytic membrane reactor (PMR), a new process for virus inactivation in water, has gradually become one of the main tools to inactivate pathogenic organisms in water. However, there is relatively little attention to the effect of natural organic matters (NOMs) on the PMR system, which actually exists in the water environment. In this paper, the TiO2-P25, a common type in sales and marketing, was selected as the photocatalyst, and humic acid was regarded as the representative substance of NOMs for investigating thoroughly the influence of humic acid on virus removal by the PMR system. It was found that competitive adsorption between the virus and humic acid occurred, which markedly reduced the amount of virus adsorbed on the surface of the photocatalyst. Moreover, with humic acid, the direct contact behavior between the virus and the photocatalyst was blocked to some extent, and the disinfection of phage f2 by the active free radicals produced by photocatalysis was furthermore badly affected. Meanwhile, the special structure of humic acid, which made humic acid be able to absorb light of 270–500 nm, led to the reduction of photocatalytic efficiency. Further experiments showed that when there was a certain concentration of humic acid in water, intermittent operation mode or higher membrane flux (>40 L/(m2·h)) was selected to partly alleviate the adverse effects of humic acid.
      Citation: Catalysts
      PubDate: 2018-07-16
      DOI: 10.3390/catal8070284
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 285: Ag/CeO2 Composites for Catalytic Abatement
           of CO, Soot and VOCs

    • Authors: M. V. Grabchenko, N. N. Mikheeva, G. V. Mamontov, M. A. Salaev, L. F. Liotta, O. V. Vodyankina
      First page: 285
      Abstract: Nowadays catalytic technologies are widely used to purify indoor and outdoor air from harmful compounds. Recently, Ag–CeO2 composites have found various applications in catalysis due to distinctive physical-chemical properties and relatively low costs as compared to those based on other noble metals. Currently, metal–support interaction is considered the key factor that determines high catalytic performance of silver–ceria composites. Despite thorough investigations, several questions remain debating. Among such issues, there are (1) morphology and size effects of both Ag and CeO2 particles, including their defective structure, (2) chemical and charge state of silver, (3) charge transfer between silver and ceria, (4) role of oxygen vacancies, (5) reducibility of support and the catalyst on the basis thereof. In this review, we consider recent advances and trends on the role of silver–ceria interactions in catalytic performance of Ag/CeO2 composites in low-temperature CO oxidation, soot oxidation, and volatile organic compounds (VOCs) abatement. Promising photo- and electrocatalytic applications of Ag/CeO2 composites are also discussed.
      Citation: Catalysts
      PubDate: 2018-07-16
      DOI: 10.3390/catal8070285
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 286: An Improved Method to Encapsulate Laccase
           from Trametes versicolor with Enhanced Stability and Catalytic Activity

    • Authors: Sitong Zhang, Zhuofu Wu, Guang Chen, Zhi Wang
      First page: 286
      Abstract: In this work, laccase from Trametes versicolor pretreated with copper ion solution was entrapped in copper alginate beads. The presence of laccase in copper alginate beads was verified by Fourier transform infrared (FTIR) spectroscopy. The alginate concentration used was optimized based on the specific activity and immobilization yield. After entrapment, laccase presents perfect pH stability and thermal stability with 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) as the substrate. Moreover, laccase in copper alginate beads exhibits good reusability during continuous batch operation for removing 2,4-dichlorophenol. More importantly, owing to the coupled effect of copper ion activation and copper alginate entrapment, the entrapped laccase shows a 3.0-fold and a 2.4-fold increase in specific activity and 2,4-DCP degradation rate compared with that of free laccase, respectively.
      Citation: Catalysts
      PubDate: 2018-07-17
      DOI: 10.3390/catal8070286
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 287: Immobilization of Prunus amygdalus
           Hydroxynitrile Lyase on Celite

    • Authors: Paula Bracco, Guzman Torrelo, Sander Noordam, Glenn de Jong, Ulf Hanefeld
      First page: 287
      Abstract: The hydroxynitrile lyase from Prunus amygdalus was immobilized on Celite R-633. The immobilized enzyme could successfully be utilized in buffer saturated MTBE and excellent conversions of benzaldehyde to R-mandelonitrile were observed. No leaching occurred. To achieve high enantioselectivities, the suppression of the undesired background reaction was essential. This could be achieved by high enzyme loadings and the tight packing of the immobilized enzymes. When the immobilized enzyme is loosely packed, both the enzyme catalysis and the background reaction accelerates and only a modest enantioselectivity is observed. The enzyme was recycled for up to ten times, with some loss of activity and also enantioselectivity after 5 cycles, independent of packing.
      Citation: Catalysts
      PubDate: 2018-07-17
      DOI: 10.3390/catal8070287
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 288: Air Regeneration of Ethanol-Laden Pellet
           NaY-SiO2 and Pt/NaY-SiO2: Effects of Air Flow Rate on Pt Morphology and
           Regeneration Efficiency

    • Authors: Cheng-Yang Yeh, Yi-Ting Chen, Nan-Yu Chen, Jen-Ray Chang
      First page: 288
      Abstract: Regeneration process and adsorbent performance were investigated by a fixed-bed adsorber at 300 °C. Surface species, zeolite structure, and Pt morphology were characterized by FT-IR, XRPD and EXAFS, respectively. Performance test results indicated that ethanol adsorption capacity of Pt/NaY-SiO2 is about 2.5 times that of NaY-SiO2. After regeneration, adsorption-capacity loss is 2.5 and 43%, respectively, for Pt/NaY-SiO2 regenerated at superficial velocity of 13.2 (PtR(HF)) and 5.3 cm/min (PtR(LF)); in contrast, it is 8 and 21%, respectively, for NaYR(HF) and NaYR(LF). The appearance of absorption bands in the CH stretching region (υCH) of the IR spectra characterizing the regenerated NaY-SiO2 suggested that the adsorption-capacity loss for NaY-SiO2 was mainly caused by the deposition of carbonaceous species formed in regeneration, which cannot be burned off readily at 300 °C. In contrast, no υCH bands have been observed for the IR spectra of PtR(HF) and PtR(LF), indicating that Pt helps to burn off carbonaceous species. However, Pt agglomeration was observed in TEM and EXAFS for Pt/NaY-SiO2(LF). The appearance of a υCO band at about 2085 cm−1 of the IR spectra characterizing PtR(LF) suggested that Pt agglomeration was induced by CO adsorption. The growth of Pt particles decreases the ethanol adsorbed on Pt together with the conversion of ethanol to ethoxides and aldehyde, leading to a decrease of adsorption capacity.
      Citation: Catalysts
      PubDate: 2018-07-17
      DOI: 10.3390/catal8070288
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 289: Optimization and in Silico Analysis of a
           Cold-Adapted Lipase from an Antarctic Pseudomonas sp. Strain AMS8 Reaction
           in Triton X-100 Reverse Micelles

    • Authors: Fatin Nur Fauzi Ana Abd. Jalil, Raja Noor Zaliha Raja Abd. Rahman, Abu Bakar Salleh, Mohd Shukuri Mohamad Ali
      First page: 289
      Abstract: A moderate yield of a purified enzyme can be achieved by using the simple technique of reverse micellar extraction (RME). RME is a liquid–liquid extraction method that uses a surfactant and an organic solvent to extract biomolecules. Instead of traditional chromatographic purification methods, which are tedious and expensive, RME using the nonionic surfactant Triton X-100 and toluene is used as an alternative purification technique to purify a recombinant cold-adapted lipase, AMS8. Various process parameters were optimized to maximize the activity recovery of the AMS8 lipase. The optimal conditions were found to be 50 mM sodium phosphate buffer, pH 7, 0.125 M NaCl, and 0.07 M Triton X-100 in toluene at 10 °C. Approximately 56% of the lipase activity was successfully recovered. Structural analysis of the lipase in a reverse micelle (RM) was performed using an in silico approach. The predicted model of AMS8 lipase was simulated in the Triton X-100/toluene reverse micelles from 5 to 40 °C. The lid 2 was slightly opened at 10 °C. However, the secondary structure of AMS8 was most affected in the non-catalytic domain compared to the catalytic domain, with an increased coil conformation. These results suggest that an AMS8 lipase can be extracted using Triton X-100/water/toluene micelles at low temperature. This RME approach will be an important tool for the downstream processing of recombinant cold-adapted lipases.
      Citation: Catalysts
      PubDate: 2018-07-18
      DOI: 10.3390/catal8070289
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 290: Enantioselective Bioreduction of Prochiral
           Pyrimidine Base Derivatives by Boni Protect Fungicide Containing Live
           Cells of Aureobasidium pullulans

    • Authors: Renata Kołodziejska, Renata Studzińska, Hanna Pawluk, Aleksandra Karczmarska-Wódzka, Alina Woźniak
      First page: 290
      Abstract: The enzymatic enantioselective bioreduction of prochiral 1-substituted-5-methyl-3-(2-oxo-2-phenylethyl)pyrimidine-2,4(1H,3H)-diones to corresponding chiral alcohols by Boni Protect fungicide containing live cells of Aureobasidium pullulans was studied. The microbe-catalyzed reduction of bulky-bulky ketones provides enantiomerically pure products (96–99% ee). In the presence of A. pullulans (Aureobasidium pullulans), one of the enantiotopic hydrides of the dihydropyridine ring coenzyme is selectively transferred to the si sides of the prochiral carbonyl group to give secondary alcohols with R configuration. The reactions were performed under various conditions in order to optimize the procedure with respect to time, solvent, and temperature. The present methodology demonstrates an alternative green way for the synthesis of chiral alcohols in a simple, economical, and eco-friendly biotransformation.
      Citation: Catalysts
      PubDate: 2018-07-18
      DOI: 10.3390/catal8070290
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 291: FeCrAlloy Monoliths Coated with Ni/Al2O3
           Applied to the Low-Temperature Production of Ethylene

    • Authors: Paula Brussino, Juan Pablo Bortolozzi, Oihane Sanz, Mario Montes, María Alicia Ulla, Ezequiel David Banús
      First page: 291
      Abstract: This paper investigates the oxidative dehydrogenation of ethane to produce ethylene at low temperatures (500 °C) in metallic structured substrates. To check this point, the FeCrAlloy® monoliths with different channel sizes (289–2360 cpsi) were prepared. The monoliths were coated with a Ni/Al2O3 catalyst (by washcoating of alumina and the latter nickel impregnation) and characterized by Scanning Electron Microscopy and Energy-Dispersive X-ray analysis (SEM-EDX), Temperature-Programmed Reduction (TPR), X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). The catalytic results showed that all monoliths coated with ~300 mg of catalyst presented similar ethane conversion (15%) at 450 °C. However, the lowest selectivity to ethylene was found for the monolith with the lower channel size and the higher geometric surface area, where a heterogeneous catalyst layer with Ni enriched islands was generated. Therefore, it can be said that the selectivity to ethylene is linked to the distribution of Ni species on the support (alumina). Nevertheless, in all cases the selectivity was high (above 70%). On the other hand, the stability in reaction tests of one of the coated monoliths was done. This structured catalyst proved to be more stable under reaction conditions than the powder catalyst, with an initial slight drop in the first 8 h but after that, constant activity for the 152 h left.
      Citation: Catalysts
      PubDate: 2018-07-19
      DOI: 10.3390/catal8070291
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 292: A Characterization Study of Reactive Sites
           in ALD-Synthesized WOx/ZrO2 Catalysts

    • Authors: Cong Wang, Xinyu Mao, Jennifer D. Lee, Tzia Ming Onn, Yu-Hao Yeh, Christopher B. Murray, Raymond J. Gorte
      First page: 292
      Abstract: A series of ZrO2-supported WOx catalysts were prepared using atomic layer deposition (ALD) with W(CO)6, and were then compared to a WOx/ZrO2 catalyst prepared via conventional impregnation. The types of sites present in these samples were characterized using temperature-programmed desorption/thermogravimetric analysis (TPD-TGA) measurements with 2-propanol and 2-propanamine. Weight changes showed that the WOx catalysts grew at a rate of 8.8 × 1017 W atoms/m2 per cycle. Scanning transmission electron microscopy/energy-dispersive spectroscopy (STEM-EDS) indicated that WOx was deposited uniformly, as did the 2-propanol TPD-TGA results, which showed that ZrO2 was completely covered after five ALD cycles. Furthermore, 2-propanamine TPD-TGA demonstrated the presence of three types of catalytic sites, the concentrations of which changed with the number of ALD cycles: dehydrogenation sites associated with ZrO2, Brønsted-acid sites associated with monolayer WOx clusters, and oxidation sites associated with higher WOx coverages. The Brønsted sites were not formed via ALD of WOx on SiO2. The reaction rates for 2-propanol dehydration were correlated with the concentration of Brønsted sites. While TPD-TGA of 2-propanamine did not differentiate the strength of Brønsted-acid sites, H–D exchange between D2O and either toluene or chlorobenzene indicated that the Brønsted sites in tungstated zirconia were much weaker than those in H-ZSM-5 zeolites.
      Citation: Catalysts
      PubDate: 2018-07-19
      DOI: 10.3390/catal8070292
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 293: Clarification of Active Sites at Interfaces
           between Silica Support and Nickel Active Components for Carbon Monoxide
           Methanation

    • Authors: Mengjuan Zhang, Panpan Li, Zhiqun Tian, Mingyuan Zhu, Fu Wang, Jiangbing Li, Bin Dai, Feng Yu, Hengshan Qiu, Hongwei Gao
      First page: 293
      Abstract: Identification of active site is critical for developing advanced heterogeneous catalysis. Here, a nickel/silica (Ni/SiO2) catalyst was prepared through an ammonia-evaporation method for CO methanation. The as-obtained Ni/SiO2 catalyst shows a CO conversion of 96.74% and a methane selectivity of 93.58% at 623 K with a weight hourly space velocity of 25,000 mL·g−1·h−1. After 150 h of continuous testing, the CO conversion still retains 96%, which indicates a high catalyst stability and long life. An in situ vacuum transmission infrared spectrum demonstrates that the main active sites locate at the interface between the metal Ni and the SiO2 at a wave number at 2060 cm−1 for the first time. The interesting discovery of the active site may offer a new insight for design and synthesis of methanation catalysts.
      Citation: Catalysts
      PubDate: 2018-07-20
      DOI: 10.3390/catal8070293
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 294: Influence of Transition Metal on the
           Hydrogen Evolution Reaction over Nano-Molybdenum-Carbide Catalyst

    • Authors: Meng Chen, Yufei Ma, Yanqiang Zhou, Changqing Liu, Yanlin Qin, Yanxiong Fang, Guoqing Guan, Xiumin Li, Zhaoshun Zhang, Tiejun Wang
      First page: 294
      Abstract: The highly efficient electrochemical hydrogen evolution reaction (HER) provides a promising way to solve energy and environment problems. In this work, various transition metals (Fe, Co, Ni, Cu, Ag, and Pt) were selected to support on molybdenum carbides by a simple organic-inorganic precursor carburization process. X-ray diffraction (XRD) analysis results indicated that the β-Mo2C phase was formed in all metal-doped samples. X-ray photoelectron spectroscopy analysis indicated that the binding energy of Mo2+ species (Mo2C) shifted to a lower value after metal was doped on the molybdenum carbide surface. Comparing with pure β-Mo2C, the electrocatalytic activity for HER was improved by transition metal doping on the surface. Remarkably, the catalytic activity improvement was more obvious when Pt was doped on molybdenum carbide (2% Pt-Mo2C). The 2% Pt-Mo2C required a η10 of 79 mV, and outperformed that of pure β-Mo2C (η10 = 410 mV) and other transition metal doped molybdenum carbides, with a small Tafel slope (55 mV/dec) and a low onset overpotential (32 mV) in 0.5 M H2SO4. Also, the 2% Pt-Mo2C catalyst demonstrated a high stability for the HER in 0.5 M H2SO4. This work highlights a feasible strategy to explore efficient electrocatalysts with low cost via engineering on the composition and nanostructure.
      Citation: Catalysts
      PubDate: 2018-07-22
      DOI: 10.3390/catal8070294
      Issue No: Vol. 8, No. 7 (2018)
       
  • Catalysts, Vol. 8, Pages 295: Molecular Rh(III) and Ir(III) Catalysts
           Immobilized on Bipyridine-Based Covalent Triazine Frameworks for the
           Hydrogenation of CO2 to Formate

    • Authors: Gunniya Hariyanandam Gunasekar, Kwangho Park, Hyeonseok Jeong, Kwang-Deog Jung, Kiyoung Park, Sungho Yoon
      First page: 295
      Abstract: The catalytic reactivity of molecular Rh(III)/Ir(III) catalysts immobilized on two- and three-dimensional Bipyridine-based Covalent Triazine Frameworks (bpy-CTF) for the hydrogenation of CO2 to formate has been described. The heterogenized Ir complex demonstrated superior catalytic efficiency over its Rh counterpart. The Ir catalyst immobilized on two-dimensional bpy-CTF showed an improved turnover frequency and turnover number compared to its three-dimensional counterpart. The two-dimensional Ir catalyst produced a maximum formate concentration of 1.8 M and maintained its catalytic efficiency over five consecutive runs with an average of 92% in each cycle. The reduced activity after recycling was studied by density functional theory calculations, and a plausible leaching pathway along with a rational catalyst design guidance have been proposed.
      Citation: Catalysts
      PubDate: 2018-07-22
      DOI: 10.3390/catal8070295
      Issue No: Vol. 8, No. 7 (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)
       
 
 
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