Subjects -> CHEMISTRY (Total: 986 journals)
    - ANALYTICAL CHEMISTRY (58 journals)
    - CHEMISTRY (715 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (28 journals)
    - INORGANIC CHEMISTRY (44 journals)
    - ORGANIC CHEMISTRY (48 journals)
    - PHYSICAL CHEMISTRY (71 journals)

CHEMISTRY (715 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 19)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 34)
ACS Applied Polymer Materials     Hybrid Journal   (Followers: 2)
ACS Catalysis     Hybrid Journal   (Followers: 60)
ACS Chemical Neuroscience     Hybrid Journal   (Followers: 23)
ACS Combinatorial Science     Hybrid Journal   (Followers: 23)
ACS Macro Letters     Hybrid Journal   (Followers: 30)
ACS Medicinal Chemistry Letters     Hybrid Journal   (Followers: 48)
ACS Nano     Hybrid Journal   (Followers: 416)
ACS Photonics     Hybrid Journal   (Followers: 17)
ACS Symposium Series     Full-text available via subscription   (Followers: 3)
ACS Synthetic Biology     Hybrid Journal   (Followers: 31)
Acta Chemica Iasi     Open Access   (Followers: 8)
Acta Chimica Slovaca     Open Access   (Followers: 4)
Acta Chimica Slovenica     Open Access   (Followers: 2)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access   (Followers: 1)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 9)
Acta Scientifica Naturalis     Open Access   (Followers: 3)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 9)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 11)
Adsorption Science & Technology     Open Access   (Followers: 8)
Advanced Electronic Materials     Hybrid Journal   (Followers: 3)
Advanced Functional Materials     Hybrid Journal   (Followers: 72)
Advanced Science Focus     Free   (Followers: 6)
Advanced Theory and Simulations     Hybrid Journal   (Followers: 1)
Advanced Therapeutics     Hybrid Journal   (Followers: 1)
Advances in Chemical Engineering and Science     Open Access   (Followers: 94)
Advances in Chemical Science     Open Access   (Followers: 37)
Advances in Chemistry     Open Access   (Followers: 31)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 21)
Advances in Drug Research     Full-text available via subscription   (Followers: 26)
Advances in Environmental Chemistry     Open Access   (Followers: 10)
Advances in Enzyme Research     Open Access   (Followers: 12)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 9)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 17)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 11)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 31)
Advances in Nanoparticles     Open Access   (Followers: 19)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 19)
Advances in Polymer Science     Hybrid Journal   (Followers: 49)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 7)
Advances in Science and Technology     Full-text available via subscription   (Followers: 15)
Aerosol Science and Engineering     Hybrid Journal  
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 5)
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  
Alchemy : Journal of Chemistry     Open Access   (Followers: 4)
Alchemy : Jurnal Penelitian Kimia     Open Access   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
Alotrop     Open Access  
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 69)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 22)
American Journal of Chemistry     Open Access   (Followers: 36)
American Journal of Plant Physiology     Open Access   (Followers: 13)
American Mineralogist     Hybrid Journal   (Followers: 15)
Anadolu University Journal of Science and Technology A : Applied Sciences and Engineering     Open Access  
Analyst     Full-text available via subscription   (Followers: 38)
Angewandte Chemie     Hybrid Journal   (Followers: 203)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 318)
Annales Universitatis Mariae Curie-Sklodowska, sectio AA – Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 5)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 5)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 8)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 15)
Antiviral Chemistry and Chemotherapy     Open Access   (Followers: 2)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 10)
Applied Spectroscopy     Full-text available via subscription   (Followers: 26)
Applied Surface Science     Hybrid Journal   (Followers: 33)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Applied Chemistry Research     Open Access   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 3)
Asian Journal of Chemical Sciences     Open Access   (Followers: 1)
Asian Journal of Chemistry and Pharmaceutical Sciences     Open Access   (Followers: 2)
Asian Journal of Physical and Chemical Sciences     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 7)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 4)
Avances en Quimica     Open Access  
Biochemical Pharmacology     Hybrid Journal   (Followers: 11)
Biochemistry     Hybrid Journal   (Followers: 446)
Biochemistry Insights     Open Access   (Followers: 7)
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: 3)
Biomacromolecules     Hybrid Journal   (Followers: 24)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 11)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 6)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 200)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 88)
Bioorganic Chemistry     Hybrid Journal   (Followers: 9)
Biopolymers     Hybrid Journal   (Followers: 17)
Biosensors     Open Access   (Followers: 3)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of Institute of Chemistry and Chemical Technology, Mongolian Academy of Sciences     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: 26)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 4)
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: 12)
Canadian Mineralogist     Full-text available via subscription   (Followers: 7)
Carbohydrate Research     Hybrid Journal   (Followers: 23)
Carbon     Hybrid Journal   (Followers: 74)
Catalysis for Sustainable Energy     Open Access   (Followers: 10)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 9)
Catalysis Science and Technology     Hybrid Journal   (Followers: 11)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 14)
Cellulose     Hybrid Journal   (Followers: 13)
Cereal Chemistry     Full-text available via subscription   (Followers: 5)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 2)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 23)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 81)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 27)
Chemical Physics Letters : X     Open Access   (Followers: 2)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Hybrid Journal   (Followers: 24)
Chemical Reviews     Hybrid Journal   (Followers: 246)
Chemical Science     Open Access   (Followers: 36)
Chemical Science International Journal     Open Access   (Followers: 1)
Chemical Technology     Open Access   (Followers: 54)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 56)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 21)
ChemInform     Hybrid Journal   (Followers: 9)
Chemistry     Open Access  
Chemistry & Biodiversity     Hybrid Journal   (Followers: 7)
Chemistry & Biology     Full-text available via subscription   (Followers: 31)
Chemistry & Industry     Full-text available via subscription   (Followers: 8)
Chemistry - A European Journal     Hybrid Journal   (Followers: 209)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 19)
Chemistry Africa : A Journal of the Tunisian Chemical Society     Hybrid Journal  
Chemistry and Materials Research     Open Access   (Followers: 24)
Chemistry Central Journal     Open Access   (Followers: 5)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry Education Review     Open Access   (Followers: 2)
Chemistry in Education     Open Access   (Followers: 8)
Chemistry International     Open Access   (Followers: 3)
Chemistry Letters     Full-text available via subscription   (Followers: 47)
Chemistry of Heterocyclic Compounds     Hybrid Journal   (Followers: 4)
Chemistry of Materials     Hybrid Journal   (Followers: 308)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 10)
Chemistry World     Full-text available via subscription   (Followers: 21)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 1)
ChemistrySelect     Hybrid Journal  
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
ChemNanoMat     Hybrid Journal   (Followers: 1)
Chemoecology     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access   (Followers: 1)
ChemPhotoChem     Hybrid Journal  
ChemPhysChem     Hybrid Journal   (Followers: 12)
ChemPlusChem     Hybrid Journal   (Followers: 2)
Chempublish Journal     Open Access   (Followers: 1)
ChemSystemsChem     Hybrid Journal   (Followers: 1)
ChemTexts     Hybrid Journal   (Followers: 1)
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: 12)
Chromatographia     Hybrid Journal   (Followers: 22)
Chromatography     Open Access   (Followers: 3)
Chromatography Research International     Open Access   (Followers: 5)
Ciencia     Open Access   (Followers: 1)
Clay Minerals     Hybrid Journal   (Followers: 9)
Cogent Chemistry     Open Access   (Followers: 3)
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 12)
Colloids and Interfaces     Open Access  
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 7)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 23)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Communications Chemistry     Open Access   (Followers: 2)
Communications Materials     Open Access   (Followers: 3)
Composite Interfaces     Hybrid Journal   (Followers: 9)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 2)

        1 2 3 4 | Last

Similar Journals
Journal Cover
Catalysts
Number of Followers: 14  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2073-4344
Published by MDPI Homepage  [230 journals]
  • Catalysts, Vol. 10, Pages 594: Transition Metal Sulfides- and Noble
           Metal-Based Catalysts for N-Hexadecane Hydroisomerization: A Study of
           Poisons Tolerance

    • Authors: Pimerzin, Savinov, Vutolkina, Makova, Glotov, Vinokurov, Pimerzin
      First page: 594
      Abstract: Bifunctional catalysts on the base of transition metal sulfides (CoMoS and NiWS) and platinum as noble metal were synthesized via wetness impregnation of freshly synthesized Al2O3-SAPO-11 composites, supported with favorable acidic properties. The physical-chemical properties of the prepared materials were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), low-temperature N2 adsorption and high resolution transmission electron microscopy (HR TEM) methods. Catalytic properties were studied in n-hexadecane isomerization using a fixed-bed flow reactor. The catalytic poisons tolerance of transition metal sulfides (TMS)- and Pt-catalysts has been studied for sulfur and nitrogen, with the amount of 10–100 ppm addition to feedstock. TMS-catalysts show good stability during sulfur-containing feedstock processing, whereas Pt-catalyst loses much of its isomerization activity. Nitrogen-containing compounds in the feedstock has a significant impact on the catalytic activity of both TMS and Pt-based catalysts.
      Citation: Catalysts
      PubDate: 2020-05-26
      DOI: 10.3390/catal10060594
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 595: Hepatoprotective Effects of Pleurotus
           Ostreatus Protein Hydrolysates Yielded by Pepsin Hydrolysis

    • Authors: Zhang, Lu, Feng, Liu, Li, Hao, Wang, Dong, Wang
      First page: 595
      Abstract: Pleurotus ostreatus protein extract (POPE) was prepared by the alkali precipitation method with 0.3% (w/v) NaOH. POPEP-III with a MW of 3000–5000 Da was acquired by pepsin enenzymatic hydrolysis. POPEP-III displayed noteworthy effects of 1,1-diphenyl-2-picrylhydrazyl DPPH and H2O2 scavenging activities, Fe2+ chelating ability, lipid peroxidation inhibition capacity, and metal reducing power. The administration of POPEP-III in mice significantly prevented prior CCl4-induced strengthen serum ALT and AST activities, changing from 365.44 ± 36.87 IU/L to 220.23 ± 22.27 IU/L and 352.52 IU/L to 206.75 ± 17.26 IU/L, respectively (p < 0.001), and suppressed hepatic malondialdehyde (MDA) formation from 15.28 ± 3.47 nmol/mg prot to 10.04 ± 2.06 nmol/mg prot (p < 0.001). Mice treated with POPEP-III demonstrated augmented activities of superoxide dismutase (SOD) in the liver, from 187.49 ± 19.81 U/mg prot to 233.35 ± 34.23 U/mg prot, and of glutathione peroxidase (GSH-Px), from 84.01 ± 14.54 U/mg prot to 115.9 ± 16.57 U/mg prot (p < 0.05). POPEP-III also prevented CCl4-induced oxidative liver histological alteration. The results suggest that POPEP-III can protect the liver from CCl4-induced oxidative damage.
      Citation: Catalysts
      PubDate: 2020-05-26
      DOI: 10.3390/catal10060595
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 596: Preparation of PP/2D-Nanosheet Composites
           Using MoS2/MgCl2- and BN/MgCl2-Bisupported Ziegler–Natta Catalysts

    • Authors: He-xin Zhang, Byeong-Gwang Shin, Dong-Eun Lee, Keun-Byoung Yoon
      First page: 596
      Abstract: Polypropylene/molybdenum disulfied (PP/MoS2) and Polypropylene/hexagonal boron nitride (PP/hBN) nanocomposites with varying concentration (0–6 wt %) were fabricated via in situ polymerization using two-dimensional (2D)-nanosheet/MgCl2-supported Ti-based Ziegler–Natta catalysts, which was prepared through a novel coagglomeration method. For catalyst preparation and interfacial interaction, MoS2 and hBN were modified with octadecylamine (ODA) and octyltriethoxysilane (OTES), respectively. Compared with those of pristine PP, thermal stability of composites was 70 °C higher and also tensile strength and Young’s modulus of the composites were up to 35% and 60% higher (even at small filler contents), respectively. The alkyl-modified 2D nanofillers were characterized by strong interfacial interactions between the nanofiller and the polymer matrix. The coagglomeration method employed in this work allows easy introduction and content manipulation of various 2D-nanosheets for the preparation of 2D-nanosheet/MgCl2-supported Ti-based Ziegler–Natta catalysts.
      Citation: Catalysts
      PubDate: 2020-05-27
      DOI: 10.3390/catal10060596
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 597: CO Tolerance and Stability of Graphene and
           N-Doped Graphene Supported Pt Anode Electrocatalysts for Polymer
           Electrolyte Membrane Fuel Cells

    • Authors: Martin González-Hernández, Ermete Antolini, Joelma Perez
      First page: 597
      Abstract: Pt electrocatalysts supported on pristine graphene nanosheets (GNS) and nitrogen-doped graphene nanoplatelets (N-GNP) were prepared through the ethylene glycol process, and a comparison of their CO tolerance and stability as anode materials in polymer electrolyte membrane fuel cells (PEMFCs) with those of the conventional carbon (C)-supported Pt was made. Repetitive potential cycling in a half cell showed that Pt/GNS catalysts have the highest stability, in terms of the highest sintering resistance (lowest particle growth) and the lowest electrochemically active surface area loss. By tests in PEMFCs, the Pt/N-GNP catalyst showed the highest CO tolerance, while the poisoning resistance of Pt/GNS was lower than that of Pt/C. The higher CO tolerance of Pt/N-GNP than that of Pt/GNS was ascribed to the presence of a defect in graphene, generated by N-doping, decreasing CO adsorption energy.
      Citation: Catalysts
      PubDate: 2020-05-27
      DOI: 10.3390/catal10060597
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 598: A Review on the Pathways of the Improved
           Structural Characteristics and Photocatalytic Performance of Titanium
           Dioxide (TiO2) Thin Films Fabricated by the Magnetron-Sputtering Technique
           

    • Authors: Yu-Hsiang Wang, Kazi Hasibur Rahman, Chih-Chao Wu, Kuan-Chung Chen
      First page: 598
      Abstract: Titanium dioxide (TiO2) thin films are used for a broad range of applications such as wastewater treatment, photocatalytic degradation activity, water splitting, antibacterial and also in biomedical applications. There is a wide range of synthesis techniques for the deposition of TiO2 thin films, such as chemical vapor deposition (CVD) and physical vapor deposition (PVD), both of which are well known deposition methods. Layer by layer deposition with good homogeneity, even thickness and good adhesive nature is possible by using the PVD technique, with the products being used for photocatalytic applications. This review studies the effects of magnetron sputtering conditions on TiO2 films. This innovative technique can enhance the photocatalytic activity by increasing the thickness of the film higher than any other methods. The main purpose of this article is to review the effects of DC and RF magnetron sputtering conditions on the preparation of TiO2 thin films for photocatalysis. The characteristics of TiO2 films (i.e., structure, composition, and crystallinity) are affected significantly by the substrate type, the sputtering power, the distance between substrate and target, working pressure, argon/oxygen ratio, deposition time, substrate temperature, dopant types, and finally the annealing treatment. The photocatalytic activity and optical properties, including the degree of crystallinity, band gap (Eg), refractive index (n), transmittance (T), and extinction coefficient (k), of TiO2 films are dependent on the above- mentioned film characteristics. Optimal TiO2 films should have a small particle size, a strong degree of crystallinity, a low band gap, a low contact angle, a high refractive index, transmittance, and extinction coefficient. Finally, metallic and nonmetallic dopants can be added to enhance the photocatalytic activity of TiO2 films by narrowing the band gap.
      Citation: Catalysts
      PubDate: 2020-05-27
      DOI: 10.3390/catal10060598
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 599: Specialized Olefin Metathesis Catalysts
           Featuring Unsymmetrical N-Heterocyclic Carbene Ligands Bearing
           N-(Fluoren-9-yl) Arm

    • Authors: Phillip I. Jolly, Anna Marczyk, Paweł Małecki, Damian Trzybiński, Krzysztof Woźniak, Anna Kajetanowicz, Karol Grela
      First page: 599
      Abstract: Beneficial structural motifs from two known state-of-the-art olefin metathesis catalysts types, bearing unsymmetrical N-heterocyclic carbenes (uNHCs), were combined into a new hybridized design thereby translating the complementary beneficial reactivity demonstrated by their ‘parent’ complexes to the new N-fluorene derived olefin metathesis catalysts. Two chelating 2-iso-propoxy-benzylidene (Hoveyda-type) and two 3-phenyl-1H-inden-1-ylidene (indenylidene-type) complexes were successfully prepared by in situ generation of either the N′-mesityl (Mes) or N′-diisopropylphenyl (Dipp) derived uNHCs taking advantage of the thermal decomposition of the corresponding 2-(penta-fluorophenyl)-imidazolidines (NHC adducts). The new fluorene-derived catalysts mediate challenging olefin metathesis processes, such as α-olefin self-metathesis, with high selectivity and conversion.
      Citation: Catalysts
      PubDate: 2020-05-27
      DOI: 10.3390/catal10060599
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 600: A Colorimetric Aptamer Sensor Based on the
           Enhanced Peroxidase Activity of Functionalized Graphene/Fe3O4-AuNPs for
           Detection of Lead (II) Ions

    • Authors: Zui Tao, You Zhou, Nuo Duan, Zhouping Wang
      First page: 600
      Abstract: Lead (II) is regarded as one of the most hazardous heavy metals, and lead contamination has a serious impact on food chains, human health, and the environment. Herein, a colorimetric aptasensor based on the graphene/Fe3O4-AuNPs composites with enhanced peroxidase-like activity has been developed to monitor lead ions (Pb2+). In short, graphene/Fe3O4-AuNPs were fabricated and acted as an enzyme mimetic, so the color change could be observed by chromogenic reaction. The aptamer of Pb2+ was decorated on the surface of the amine magnetic beads by streptavidin–biotin interaction, and the complementary strands of the aptamer and target Pb2+ competed for the binding Pb2+ aptamer. In the presence of Pb2+, aptamers bonded the metal ions and were removed from the system by magnetic separation; the free cDNA was adsorbed onto the surface of the graphene/Fe3O4-AuNPs composites, thus inhibiting the catalytic activity and the color reaction. The absorbance of the reaction solution at 652 nm had a clear linear correlation with the Pb2+ concentration in the range of 1–300 ng/mL, and the limit of detection was 0.63 ng/mL. This assay is simple and convenient in operation, has good selectivity, and has been used to test tap water samples, which proves that it is capable for the routine monitoring of Pb2+.
      Citation: Catalysts
      PubDate: 2020-05-29
      DOI: 10.3390/catal10060600
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 601: CO2 Methanation over Rh/CeO2 Studied with
           

    • Authors: Felix Hemmingsson, Andreas Schaefer, Magnus Skoglundh, Per-Anders Carlsson
      First page: 601
      Abstract: Methane is a well-established fuel molecule whose production from CO 2 through methanation garners increasing interest as an energy storage solution. While often produced with Ni based catalysts, other metals are of interest thanks to higher robustness and activity-selectivity numbers. The Rh/CeO 2 catalyst has shown appreciable properties for CO 2 methanation and its structural dynamics has been studied in situ. However, the reaction pathway is unknown. Here, we present infrared modulation excitation spectroscopy measurements with phase sensitive detection of a Rh/CeO 2 catalyst adsorbate composition during H 2 pulsing (0–2 vol.%) to a constant CO 2 (0.5 vol.%) feed. Various carbonyl (CO) and carbonate (b-CO 3 /p-CO 3 ) ad-species clearly respond to the hydrogen stimulus, making them potential reaction intermediates. The different CO ad-species are likely intermediates for product CO and CH 4 but their individual contributions to the respective formations are not unambiguously ascertained. As for the carbonate dynamics, it might be linked to the reduction/oxidation of the CeO 2 surface upon H 2 pulsing. Formate (HCOO) ad-species are clearly visible but appear to be, if not spectators, linked to slow side reactions possibly also affected by CeO 2 redox processes.
      Citation: Catalysts
      PubDate: 2020-05-29
      DOI: 10.3390/catal10060601
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 602: Catalytic Pyrolysis of Tetra Pak over
           Acidic Catalysts

    • Authors: Muhammad Zain Siddiqui, Tae Uk Han, Young-Kwon Park, Young-Min Kim, Seungdo Kim
      First page: 602
      Abstract: The thermal and catalytic pyrolysis of two kinds of Tetra Pak waste (TP-1 and TP-2) over three different acidic catalysts—HZSM-5(SiO2/Al2O3, 30), HBeta (38), and Al-MCM-41(20)—were investigated in this study. Tetra Pak (TP) wastes consist of composite material comprising kraft paper, polyethylene (PE) film, and aluminum foil. Thermal decomposition behaviors during the pyrolysis of TPs were monitored using a thermogravimetric (TG) analyzer and tandem micro reactor-gas chromatography/mass spectrometry (TMR-GC/MS). Neither the interaction between the non-catalytic pyrolysis intermediates of kraft paper and PE, nor the effect of aluminum foil have been monitored during the non-catalytic TG analysis of TPs. The maximum decomposition temperatures of PE in TP-1 shifted from 465 °C to 432 °C by HBeta(38), 439 °C by HZSM-5(30), and 449 °C by Al-MCM-41(20), respectively. The results of the TMR-GC/MS analysis indicate that the non-catalytic pyrolysis of TPs results in the formation of large amounts of furans and heavy hydrocarbons and they are converted efficiently to aromatic hydrocarbons over the acidic catalysts. Among the three catalysts, HZSM-5(30) produced the largest amount of aromatic hydrocarbons, followed by HBeta(38) and Al-MCM-41(20) owing to their different acidity and pore size. Compared to TP-1, TP-2 produced a larger amount of aromatic hydrocarbons via catalytic pyrolysis because of its relatively larger PE content. The synergistic formation of aromatic hydrocarbons was also enhanced during the catalytic pyrolysis of TPs due to the effective role of PE as hydrogen donor to kraft paper. In terms of their catalytic effectiveness, HZSM-5(30) had a longer lifetime than HBeta(38).
      Citation: Catalysts
      PubDate: 2020-05-29
      DOI: 10.3390/catal10060602
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 603: Thermal Post-Treatments to Enhance the
           Water Stability of NH2-MIL-125(Ti)

    • Authors: Almudena Gómez-Avilés, Virginia Muelas-Ramos, Jorge Bedia, Juan Jose Rodriguez, Carolina Belver
      First page: 603
      Abstract: NH2-MIL-125(Ti) is a metal organic framework (MOF) based on Ti-oxo-clusters widely investigated in water-related applications. Such applications require MOFs with an excellent stability in the aqueous phase, but, despite this, the extent of MOFs’ degradation in water is still not yet fully understood. In this study, we report a quantitative study of the water stability of NH2-MIL-125(Ti), analyzing the ligand release along the contact time in water. This study demonstrates that NH2-MIL-125(Ti) easily leached out over time while maintaining its structure. The effect of different thermal treatments applied to NH2-MIL-125(Ti) was investigated to enhance its water stability. The structural and textural properties of those modified MOFs were studied in detail and those maintaining the NH2-MIL-125(Ti) properties were exposed to aqueous medium. The analysis of the released ligand concentration in the filtrate can provide information on the water stability of this material.
      Citation: Catalysts
      PubDate: 2020-05-29
      DOI: 10.3390/catal10060603
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 604: Biochemical Degradation of Chitosan over
           Immobilized Cellulase and Supported Fenton Catalysts

    • Authors: Huawei Geng, Zonggang Mou, Ziyong Liu, Fuli Li, Cheng Yang
      First page: 604
      Abstract: This paper describes the application of Fe-MCM-48 (Mobil Composition of Matter No.48) and cellulase-MCM-48 catalysts for the depolymerization of chitosan. The results show that H2O2 is a good oxidant for the depolymerization of chitosan in the presence of Fe-MCM-48. The average polymerization degree of the product decreased to 6.1, and decreased to 29.2 when cellulase-MCM-48 was used as a catalyst, because the effect of the enzyme was affected by the molecular structure of chitosan. When both materials were used for depolymerization, the average degree of polymerization sharply decreased to 3.8. The results show that the two degradation methods can promote each other to obtain oligosaccharides with a lower degree of polymerization. This provides a new method for the controllable degradation of chitosan and lays a good foundation for the industrial production of chitosan oligosaccharides with a low degree of polymerization.
      Citation: Catalysts
      PubDate: 2020-05-29
      DOI: 10.3390/catal10060604
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 605: One Pot Use of Combilipases for Full
           Modification of Oils and Fats: Multifunctional and Heterogeneous
           Substrates

    • Authors: Sara Arana-Peña, Diego Carballares, Ángel Berenguer-Murcia, Andrés R. Alcántara, Rafael C. Rodrigues, Roberto Fernandez-Lafuente
      First page: 605
      Abstract: Lipases are among the most utilized enzymes in biocatalysis. In many instances, the main reason for their use is their high specificity or selectivity. However, when full modification of a multifunctional and heterogeneous substrate is pursued, enzyme selectivity and specificity become a problem. This is the case of hydrolysis of oils and fats to produce free fatty acids or their alcoholysis to produce biodiesel, which can be considered cascade reactions. In these cases, to the original heterogeneity of the substrate, the presence of intermediate products, such as diglycerides or monoglycerides, can be an additional drawback. Using these heterogeneous substrates, enzyme specificity can promote that some substrates (initial substrates or intermediate products) may not be recognized as such (in the worst case scenario they may be acting as inhibitors) by the enzyme, causing yields and reaction rates to drop. To solve this situation, a mixture of lipases with different specificity, selectivity and differently affected by the reaction conditions can offer much better results than the use of a single lipase exhibiting a very high initial activity or even the best global reaction course. This mixture of lipases from different sources has been called “combilipases” and is becoming increasingly popular. They include the use of liquid lipase formulations or immobilized lipases. In some instances, the lipases have been coimmobilized. Some discussion is offered regarding the problems that this coimmobilization may give rise to, and some strategies to solve some of these problems are proposed. The use of combilipases in the future may be extended to other processes and enzymes.
      Citation: Catalysts
      PubDate: 2020-05-29
      DOI: 10.3390/catal10060605
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 606: A Novel Catalytic Micro-Combustor Inspired
           by the Nasal Geometry of Reindeer: CFD Modeling and Simulation

    • Authors: Valeria Di Sarli, Marco Trofa, Almerinda Di Benedetto
      First page: 606
      Abstract: A three-dimensional CFD model of a novel configuration of catalytic micro-combustor inspired by the nasal geometry of reindeer was developed using the commercial code ANSYS Fluent 19.0. The thermal behavior of this nature-inspired (NI) configuration was investigated through simulations of lean propane/air combustion performed at different values of residence time (i.e., inlet gas velocity) and (external convective) heat transfer coefficient. Simulations at the same conditions were also run for a standard parallel-channel (PC) configuration of equivalent dimensions. Numerical results show that the operating window of stable combustion is wider in the case of the NI configuration. In particular, the blow-out behavior is substantially the same for the two configurations. Conversely, the extinction behavior, which is dominated by competition between the heat losses towards the external environment and the heat produced by combustion, differs. The NI configuration exhibits a greater ability than the PC configuration to keep the heat generated by combustion trapped inside the micro-reactor. As a consequence, extinction occurs at higher values of residence time and heat transfer coefficient for this novel configuration.
      Citation: Catalysts
      PubDate: 2020-05-31
      DOI: 10.3390/catal10060606
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 607: VOC Removal from Manure Gaseous Emissions
           with UV Photolysis and UV-TiO2 Photocatalysis

    • Authors: Xiuyan Yang, Jacek A. Koziel, Yael Laor, Wenda Zhu, J. (Hans) van Leeuwen, William S. Jenks, Steven J. Hoff, Jeffrey Zimmerman, Shicheng Zhang, Uzi Ravid, Robert Armon
      First page: 607
      Abstract: Control of gaseous emissions from livestock operations is needed to ensure compliance with environmental regulations and sustainability of the industry. The focus of this research was to mitigate livestock odor emissions with UV light. Effects of the UV dose, wavelength, TiO2 catalyst, air temperature, and relative humidity were tested at lab scale on a synthetic mixture of nine odorous volatile organic compounds (VOCs) and real poultry manure offgas. Results show that it was feasible to control odorous VOCs with both photolysis and photocatalysis (synthetic VOCs mixture) and with photocatalysis (manure offgas). The treatment effectiveness R (defined as % conversion), was proportional to the light intensity for synthetic VOCs mixtures and followed an order of UV185+254 + TiO2 > UV254 + TiO2 > UV185+254; no catalyst > UV254; no catalyst. VOC conversion R > 80% was achieved when light energy was >~60 J L−1. The use of deep UV (UV185+254) improved the R, particularly when photolysis was the primary treatment. Odor removal up to ~80% was also observed for a synthetic VOCs mixture, and actual poultry manure offgas. Scale-up studies are warranted.
      Citation: Catalysts
      PubDate: 2020-06-01
      DOI: 10.3390/catal10060607
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 608: Highly Efficient and Reusable Alkyne
           Hydrosilylation Catalysts Based on Rhodium Complexes Ligated by
           Imidazolium-Substituted Phosphine

    • Authors: Olga Bartlewicz, Magdalena Jankowska-Wajda, Hieronim Maciejewski
      First page: 608
      Abstract: Rhodium complexes ligated by imidazolium-substituted phosphine were used as catalysts in the hydrosilylation of alkynes (1-heptyne, 1-octyne, and phenylacetylene) with 1,1,1,3,5,5,5-heptamethyltrisiloxane (HMTS) or triethylsilane (TES). In all cases, the above complexes showed higher activity and selectivity compared to their precursors ([Rh(PPh3)3Cl] and [{Rh(µ-Cl)(cod)}2]). In the reactions with aliphatic alkynes (both when HMTS and TES were used as hydrosilylating agents), β(Z) isomer was mainly formed, but, in the reaction of phenylacetylene with TES, the β(E) product was formed. The catalysts are very durable, stable in air and first and foremost insoluble in the reactants which facilitated their isolation and permitted their multiple use in subsequent catalytic runs. They make a very good alternative to the commonly used homogeneous catalysts.
      Citation: Catalysts
      PubDate: 2020-06-01
      DOI: 10.3390/catal10060608
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 609: Valorization of Biodiesel Byproduct Crude
           Glycerol for the Production of Bioenergy and Biochemicals

    • Authors: Niravkumar Mahendrasinh Kosamia, Mahdieh Samavi, Bijaya Kumar Uprety, Sudip Kumar Rakshit
      First page: 609
      Abstract: The rapid growth of global biodiesel production requires simultaneous effective utilization of glycerol obtained as a by-product of the transesterification process. Accumulation of the byproduct glycerol from biodiesel industries can lead to considerable environment issues. Hence, there is extensive research focus on the transformation of crude glycerol into value-added products. This paper makes an overview of the nature of crude glycerol and ongoing research on its conversion to value-added products. Both chemical and biological routes of glycerol valorization will be presented. Details of crude glycerol conversion into microbial lipid and subsequent products will also be highlighted.
      Citation: Catalysts
      PubDate: 2020-06-01
      DOI: 10.3390/catal10060609
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 610: A Kinetic Study on the Efficient Formation
           of High-Valent Mn(TPPS)-oxo Complexes by Various Oxidants

    • Authors: Magdalena Procner, Łukasz Orzel, Grażyna Stochel, Rudi van Eldik
      First page: 610
      Abstract: New, more efficient methods of wastewater treatment, which will limit the harmful effects of textile dyes on the natural environment, are still being sought. Significant research work suggests that catalysts based on transition metal complexes can be used in efficient and environmentally friendly processes. In this context, a number of compounds containing manganese have been investigated. A suitable catalyst should have the capacity to activate a selected oxidant or group of oxidants, in order to be used in industrial oxidation reactions. In the present study we investigated the ability of MnIII(TPPS), where TPPS = 5,10,15,20-tetrakis(4-sulphonatophenyl)-21H,23H-porphyrine, to activate five different oxidants, namely hydrogen peroxide, peracetic acid, sodium hypochlorite, potassium peroxomonosulfate and sodium perborate, via the formation of high valent Mn(TPPS)-oxo complexes. Kinetic and spectroscopic data showed that the oxidation process is highly pH dependent and is strongly accelerated by the presence of carbonate in the reaction mixture for three of the five oxidizing agents. The highest efficiency for the oxidation of MnIII(TPPS) to high-valent Mn(TPPS)-oxo complexes, was found for peracetic acid at pH ≈ 11 in 0.5 M carbonate solution, which is at least an order of magnitude higher than the rate constants found for the other tested oxidants under similar conditions.
      Citation: Catalysts
      PubDate: 2020-06-01
      DOI: 10.3390/catal10060610
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 611: Industrial Textile Wastewater Ozone
           Treatment: Catalyst Selection

    • Authors: Lucyna Bilińska, Kazimierz Blus, Magdalena Bilińska, Marta Gmurek
      First page: 611
      Abstract: One of the recent trends in textile wastewater treatment has become catalytic ozonation. The necessity of effective color removal in a short treatment time is a standard during industrial implementation. At the same time, efficient chemical oxygen demand (COD), total organic carbon (TOC), and toxic by-product removal are highly expected. This study presents the results of a catalytic ozonation treatment. Three types of catalysts: a metal oxide (TiO2 as P25 by Degussa), activated carbon (nano-powder by Sigma, AC), and metal particles (platinum, 1% wt. supported on AC matrix by Sigma, Pt–AC) have been applied. The investigations were conducted for real industrial wastewater originated in textile dyeing with Reactive Black 5 dye (RB5). The experiments ran for the raw wastewater (without pretreatment), exposed blocking of the catalytic action by all used catalysts. The catalytic effect could be observed when catalytic ozonation was used as a polishing step after electrocoagulation (EC). Although the catalytic effect could be observe for all catalysts then, especially in the removal of colorless by-products, the AC was exposed as the most effective. This contributed to 35% and 40% of TOC and COD removal. While only 18% and 23% of TOC and COD were removed in the same process without AC. The decrease in toxicity was 30%. The results of the study revealed the complexity of the issue and resulted in an extensive discussion devoted to the basis of the catalytic activity of each catalyst.
      Citation: Catalysts
      PubDate: 2020-06-01
      DOI: 10.3390/catal10060611
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 612: Toxicity Reduction of Industrial and
           Municipal Wastewater by Advanced Oxidation Processes (Photo-Fenton,
           UVC/H2O2, Electro-Fenton and Galvanic Fenton): A Review

    • Authors: Juan José Rueda-Márquez, Irina Levchuk, Manuel Manzano, Mika Sillanpää
      First page: 612
      Abstract: The application of Fenton-based advanced oxidation processes (AOPs), such as photo-Fenton or electro-Fenton for wastewater treatment have been extensively studied in recent decades due to its high efficiency for the decomposition of persistent organic pollutants. Usually Fenton-based AOPs are used for the degradation of targeted pollutant or group of pollutants, which often leads to the formation of toxic by-products possessing a potential environmental risk. In this work, we have collected and reviewed recent findings regarding the feasibility of Fenton-based AOPs (photo-Fenton, UVC/H2O2, electro-Fenton and galvanic Fenton) for the detoxification of real municipal and industrial wastewaters. More specifically, operational conditions, relevance and suitability of different bioassays for the toxicity assessment of various wastewater types, cost estimation, all of which compose current challenges for the application of these AOPs for real wastewater detoxification are discussed.
      Citation: Catalysts
      PubDate: 2020-06-01
      DOI: 10.3390/catal10060612
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 613: Highly Active Transition Metal-Promoted
           CuCeMgAlO Mixed Oxide Catalysts Obtained from Multicationic LDH Precursors
           for the Total Oxidation of Methane

    • Authors: Hussein Mahdi S. Al-Aani, Mihaela M. Trandafir, Ioana Fechete, Lucia N. Leonat, Mihaela Badea, Cătălin Negrilă, Ionel Popescu, Mihaela Florea, Ioan-Cezar Marcu
      First page: 613
      Abstract: To improve the catalytic performance of an active layered double hydroxide (LDH)-derived CuCeMgAlO mixed oxide catalyst in the total oxidation of methane, it was promoted with different transition-metal cations. Thus, two series of multicationic mixed oxides were prepared by the thermal decomposition at 750 °C of their corresponding LDH precursors synthesized by coprecipitation at constant pH of 10 under ambient atmosphere. The first series of catalysts consisted of four M(3)CuCeMgAlO mixed oxides containing 3 at.% M (M = Mn, Fe, Co, Ni), 15 at.% Cu, 10 at.% Ce (at.% with respect to cations), and with Mg/Al atomic ratio fixed to 3. The second series consisted of four Co(x)CuCeMgAlO mixed oxides with x = 1, 3, 6, and 9 at.% Co, while keeping constant the Cu and Ce contents and the Mg/Al atomic ratio. All the mixed oxides were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with X-ray energy dispersion analysis (EDX), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption at −196 °C, temperature-programmed reduction under hydrogen (H2-TPR), and diffuse reflectance UV-VIS spectroscopy (DR UV-VIS), while thermogravimetric and differential thermal analyses (TG-DTG-DTA) together with XRD were used for the LDH precursors. The catalysts were evaluated in the total oxidation of methane, a test reaction for volatile organic compounds (VOC) abatement. Their catalytic performance was explained in correlation with their physicochemical properties and was compared with that of a reference Pd/Al2O3 catalyst. Among the mixed oxides studied, Co(3)CuCeMgAlO was found to be the most active catalyst, with a temperature corresponding to 50% methane conversion (T50) of 438 °C, which was only 19 °C higher than that of a reference Pd/Al2O3 catalyst. On the other hand, this T50 value was ca. 25 °C lower than that observed for the unpromoted CuCeMgAlO system, accounting for the improved performance of the Co-promoted catalyst, which also showed a good stability on stream.
      Citation: Catalysts
      PubDate: 2020-06-01
      DOI: 10.3390/catal10060613
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 614: Morphological and Optical Properties of
           Cobalt Ion- Modified ZnO Nanowires

    • Authors: Seok Cheol Choi, Do Kyung Lee, Sang Ho Sohn
      First page: 614
      Abstract: In this study, we prepared cobalt (Co) ion-modified ZnO nanowires using hydrothermal synthesis with zinc acetate dehydrate and Co (II) acetate hydrate precursors in ethanol solutions. Their morphological and optical properties were investigated with varying Co precursor concentration. The morphological changes of the ZnO nanowires depended positively on the concentration of the Co precursor. The ZnO nanowires showed modified crystal orientations and nanostructure shapes depending on the Co concentration in the solutions. Variations in the optical properties of the Co ion-modified ZnO nanowires could be explained by the interaction of the Co ions with the band electrons, oxygen vacancies, and zinc interstitials. The overall growth and characteristics of ZnO nanowires synthesized in solutions containing low levels of Co ions were related to Co doping into the ZnO bulks. In solutions containing high levels of Co ions, these were additionally related to the Co oxide cluster.
      Citation: Catalysts
      PubDate: 2020-06-01
      DOI: 10.3390/catal10060614
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 615: High Yield to 1-Propanol from Crude
           Glycerol Using Two Reaction Steps with Ni Catalysts

    • Authors: Martín N. Gatti, Julieta L. Cerioni, Francisco Pompeo, Gerardo F. Santori, Nora N. Nichio
      First page: 615
      Abstract: The objective of the present work is to achieve high yield to 1-propanol (1-POH) by crude glycerol hydrogenolysis in liquid phase and find an alternative to the use of noble metals by employing Ni catalysts. Two Ni catalysts with different supports, alumina (γ-Al2O3), and a phosphorous-impregnated carbon composite (CS-P) were studied and characterized in order to determine their acid properties and metallic phases. With the Ni/γ-Al2O3 catalyst, which presented small particles of metallic Ni interacting with the acid sites of the support, it was possible to obtain a complete conversion of crude glycerol with high selectivity towards 1,2-propylene glycol (1,2 PG) (87%) at 220 °C whereas with the Ni/CS-P catalyst, the presence of AlPOx species and the Ni2P metallic phase supplied acidity to the catalyst, which promoted the C-O bond cleavage reaction of the secondary carbon of 1,2 PG to obtain 1-POH with very high selectivity (71%) at 260 °C. It was found that the employment of two consecutive reaction stages (first with Ni/ γ-Al2O3 at 220 °C and then with Ni/CS-P at 260 °C) allows reaching levels of selectivity and a yield to 1-POH (79%) comparable to noble metal-based catalysts.
      Citation: Catalysts
      PubDate: 2020-06-02
      DOI: 10.3390/catal10060615
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 616: Effect of Ultrasound-Assisted Blanching on
           Myrosinase Activity and Sulforaphane Content in Broccoli Florets

    • Authors: Andrea Mahn, Julián Quintero, Noelia Castillo, Raidel Comett
      First page: 616
      Abstract: Sulforaphane (SFN) is a health-promoting compound occurring in broccoli. It is formed by action of myrosinase in a two-step reaction that also yields undesirable compounds such as nitriles and isothionitriles. Different techniques affecting enzyme activity and tissue integrity were proposed to increase SFN content in the edible parts and discards of broccoli. Ultrasound processing is an emerging technology that produces these effects in foods, but has been poorly explored in broccoli so far. The aim of this work was to study the effect of ultrasound-assisted blanching on myrosinase activity and SFN content in broccoli florets. Myrosinase showed first-order inactivation kinetics in blanching at different temperatures with and without ultrasound processing. The inactivation rate was faster using ultrasound, with kinetic constants two orders of magnitude higher than without ultrasound. The activation energy (Ea) in traditional blanching (57.3 kJ mol−1) was higher than in ultrasound-assisted blanching (15.8 kJ mol−1). Accordingly, ultrasound accelerates myrosinase inactivation. The blanching time and temperature significantly affected myrosinase activity and SFN content. At 60 °C and 4 min of ultrasound-assisted blanching, myrosinase activity was minimum and SFN content was the highest. These findings may help to design SFN enrichment processes and will contribute to the valorization of agro-industrial wastes.
      Citation: Catalysts
      PubDate: 2020-06-02
      DOI: 10.3390/catal10060616
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 617: XPS Studies of the Initial Oxidation of
           Polycrystalline Rh Surface

    • Authors: Marek Trzcinski, Grażyna Balcerowska-Czerniak, Antoni Bukaluk
      First page: 617
      Abstract: Increased interest in the oxidation process of polycrystalline rhodium, observed in recent years, is the result of its application in exhaust catalytic converters. However, most studies have involved sample surfaces with low Miller indices. In our research, we investigated polycrystalline rhodium foil containing crystallographically different, highly stepped, µm-sized crystallites. These crystallites were exposed to identical oxidizing conditions. To determine crystallographic orientation, the electron backscattering diffraction (EBSD) method was used. To investigate the initial stages of oxidation on the individual crystallites of Rh, X-ray photoelectron spectroscopy (XPS) studies were performed. The results obtained for the individual crystallites were compared and analyzed using chemical state quantification of XPS data and multivariate statistical analysis (MVA).
      Citation: Catalysts
      PubDate: 2020-06-02
      DOI: 10.3390/catal10060617
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 618: Organocatalytic Asymmetric Michael Addition
           of Ketones to α, β-Unsaturated Nitro Compounds

    • Authors: Jae Ho Shim, Si Hun Nam, Byeong-Seon Kim, Deok-Chan Ha
      First page: 618
      Abstract: An organic catalyst “(R, R)-1,2-diphenylethylenediamine(DPEN) derivative’’ was devel-oped as a chiral bifunctional organocatalyst and applied for asymmetric Michael additions of aromatic ketones to trans-β-nitroalkene compounds under neutral conditions. The isopropyl-subs-tituted thiourea catalyst in neutral condition provides high chemical yield and enantioselectivities (ee) (up to 96% yield, 98% ee).
      Citation: Catalysts
      PubDate: 2020-06-02
      DOI: 10.3390/catal10060618
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 619: Study of the Effect of Activated Carbon
           Cathode Configuration on the Performance of a Membrane-Less Microbial Fuel
           Cell

    • Authors: M. L. Jiménez González, Carlos Hernández Benítez, Zabdiel Abisai Juarez, Evelyn Zamudio Pérez, Víctor Ángel Ramírez Coutiño, Irma Robles, Luis A. Godínez, Francisco J. Rodríguez-Valadez
      First page: 619
      Abstract: In this paper, the effect of cathode configuration on the performance of a membrane-less microbial fuel cell (MFC) was evaluated using three different arrangements: an activated carbon bed exposed to air (MFCE), a wetland immersed in an activated carbon bed (MFCW) and a cathode connected to an aeration tower featuring a water recirculation device (MFCT). To evaluate the MFC performance, the efficiency of the organic matter removal, the generated voltage, the power density and the internal resistance of the systems were properly assessed. The experimental results showed that while the COD removal efficiency was in all cases over 60% (after 40 days), the MFCT arrangement showed the best performance since the average removal value was 82%, compared to close to 70% for MFCE and MFCW. Statistical analysis of the COD removal efficiency confirmed that the performance of MCFT is substantially better than that of MFCE and MFCW. In regard to the other parameters surveyed, no significant influence of the different cathode arrangements explored could be found.
      Citation: Catalysts
      PubDate: 2020-06-02
      DOI: 10.3390/catal10060619
      Issue No: Vol. 10, No. 6 (2020)
       
  • Catalysts, Vol. 10, Pages 520: Hydrothermal Synthesis of rGO-TiO2
           Composites as High-Performance UV Photocatalysts for Ethylparaben
           Degradation

    • Authors: Miller Ruidíaz-Martínez, Miguel A. Álvarez, María Victoria López-Ramón, Guillermo Cruz-Quesada, José Rivera-Utrilla, Manuel Sánchez-Polo
      First page: 520
      Abstract: A series of reduced graphene oxide-TiO2 composites (rGO-TiO2) were prepared by hydrothermal treatment using graphite and titanium isopropoxide as raw materials. The structural, surface, electronic, and optical properties of the prepared composites were extensively characterized by N2 adsorption, FTIR, XRD, XPS, Raman spectroscopy, and DRS. GO was found to be effectively reduced and TiO2 to be in pure anatase phase in all composites obtained. Finally, experiments were performed to evaluate the effectiveness of these new materials as photocatalysts in the degradation of ethylparaben (EtP) by UV radiation. According to the band-gap energies obtained (ranging between 3.09 eV for 4% rGO-TiO2 to 2.55 eV for 30% rGO-TiO2), the rGO-TiO2 composites behave as semiconductor materials. The photocatalytic activity is highest with a rGO content of 7 wt% (7% rGO-TiO2), being higher than observed for pure TiO2 (Eg = 3.20 eV) and achieving 98.6% EtP degradation after only 40 min of treatment. However, the degradation yield decreases with higher percentages of rGO. Comparison with rGO-P25 composites showed that a better photocatalytic performance in EtP degradation is obtained with synthesized TiO2 (rGO-TiO2), probably due to the presence of the rutile phase (14.1 wt %) in commercial P25.
      Citation: Catalysts
      PubDate: 2020-05-08
      DOI: 10.3390/catal10050520
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 521: Removal of Hydrogen Sulfide From Various
           Industrial Gases: A Review of The Most Promising Adsorbing Materials

    • Authors: Amvrosios G. Georgiadis, Nikolaos D. Charisiou, Maria A. Goula
      First page: 521
      Abstract: The separation of hydrogen sulfide (H2S) from gas streams has significant economic and environmental repercussions for the oil and gas industries. The present work reviews H2S separation via nonreactive and reactive adsorption from various industrial gases, focusing on the most commonly used materials i.e., natural or synthetic zeolites, activated carbons, and metal oxides. In respect to cation-exchanged zeolites, attention should also be paid to parameters such as structural and performance regenerability, low adsorption temperatures, and thermal conductivities, in order to create more efficient materials in terms of H2S adsorption. Although in the literature it is reported that activated carbons can generally achieve higher adsorption capacities than zeolites and metal oxides, they exhibit poor regeneration potential. Future work should mainly focus on finding the optimum temperature, solvent concentration, and regeneration time in order to increase regeneration efficiency. Metal oxides have also been extensively used as adsorbents for hydrogen sulfide capture. Among these materials, ZnO and Cu–Zn–O have been studied the most, as they seem to offer improved H2S adsorption capacities. However, there is a clear lack of understanding in relation to the basic sulfidation mechanisms. The elucidation of these reaction mechanisms will be a toilsome but necessary undertaking in order to design materials with high regenerative capacity and structural reversibility.
      Citation: Catalysts
      PubDate: 2020-05-08
      DOI: 10.3390/catal10050521
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 522: New Phosphorous-Based [FeFe]-Hydrogenase
           Models

    • Authors: Florian Wittkamp, Esma Birsen Boydas, Michael Roemelt, Ulf-Peter Apfel
      First page: 522
      Abstract: [FeFe]-hydrogenases have attracted research for more than twenty years as paragons for the design of new catalysts for the hydrogen evolution reaction (HER). The bridging dithiolate comprising a secondary amine as bridgehead is the key element for the reactivity of native [FeFe]-hydrogenases and was therefore the midpoint of hundreds of biomimetic hydrogenase models. However, within those mimics, phosphorous is barely seen as a central element in the azadithiolato bridge despite being the direct heavier homologue of nitrogen. We herein synthesized three new phosphorous based [FeFe]-hydrogenase models by reacting dithiols (HSCH2)2P(O)R (R = Me, OEt, OPh) with Fe3(CO)12. All synthesized mimics show catalytic reactivity regarding HER and change their mechanisms depending on the strength of the used acid. In all presented mimics, the oxide is the center of reactivity, independent of the nature of the bridgehead. However, the phosphorous atom might be reduced by the methods we present herein to alter the reactivity of the model compounds towards protons and oxygen.
      Citation: Catalysts
      PubDate: 2020-05-08
      DOI: 10.3390/catal10050522
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 523: Three-Dimensional Mesoporous Ni-CeO2
           Catalysts with Ni Embedded in the Pore Walls for CO2 Methanation

    • Authors: Luhui Wang, Junang Hu, Hui Liu, Qinhong Wei, Dandan Gong, Liuye Mo, Hengcong Tao, Chengyang Zhang
      First page: 523
      Abstract: Mesoporous Ni-based catalysts with Ni confined in nanochannels are widely used in CO2 methanation. However, when Ni loadings are high, the nanochannels are easily blocked by nickel particles, which reduces the catalytic performance. In this work, three-dimensional mesoporous Ni-CeO2-CSC catalysts with high Ni loadings (20−80 wt %) were prepared using a colloidal solution combustion method, and characterized by nitrogen adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and H2 temperature programmed reduction (H2-TPR). Among the catalysts with different Ni loadings, the 50% Ni-CeO2-CSC with 50 wt % Ni loading exhibited the best catalytic performance in CO2 methanation. Furthermore, the 50% Ni-CeO2-CSC catalyst was stable for 50 h at 300° and 350 °C in CO2 methanation. The characterization results illustrate that the 50% Ni-CeO2-CSC catalyst has Ni particles smaller than 5 nm embedded in the pore walls, and the Ni particles interact with CeO2. On the contrary, the 50% Ni-CeO2-CP catalyst, prepared using the traditional coprecipitation method, is less active and selective for CO2 methanation due to the larger size of the Ni and CeO2 particles. The special three-dimensional mesoporous embedded structure in the 50% Ni-CeO2-CSC can provide more metal–oxide interface and stabilize small Ni particles in pore walls, which makes the catalyst more active and stable in CO2 methanation.
      Citation: Catalysts
      PubDate: 2020-05-08
      DOI: 10.3390/catal10050523
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 524: Ir-Sn-Sb-O Electrocatalyst for Oxygen
           Evolution Reaction: Physicochemical Characterization and Performance in
           Water Electrolysis Single Cell with Solid Polymer Electrolyte

    • Authors: Nicté J. Pérez-Viramontes, Virginia H. Collins-Martínez, Ismailia L. Escalante-García, José R. Flores-Hernández, Marisol Galván-Valencia, Sergio M. Durón-Torres
      First page: 524
      Abstract: Mixed oxide Ir-Sn-Sb-O electrocatalyst was synthesized using thermal decomposition from chloride precursors in ethanol. Our previous results showed that Ir-Sn-Sb-O possesses electrocatalytic activity for an oxygen evolution reaction (OER) in acidic media. In the present work, the physicochemical characterization and performance of Ir-Sn-Sb-O in an electrolysis cell are reported. IrO2 supported on antimony doped tin oxide (ATO) was also considered in this study as a reference catalyst. Scanning electron microscopy (SEM) images indicated that Ir-Sn-Sb-O has a mixed morphology with nanometric size. Energy dispersive X-ray spectroscopy (EDS) showed a heterogeneous atomic distribution. Transmission electron microscopy (TEM) analysis resulted in particle sizes of IrO2 and ATO between 3 to >10 nm, while the Ir-Sn-Sb-O catalyst presented non-uniform particle sizes from 3 to 50 nm. X-ray diffraction (XRD) measurements indicated that synthesized mixed oxide consists of IrO2, IrOx, doped SnO2 phases and metallic Ir. The Ir-Sn-Sb-O mixed composition was corroborated by temperature programmed reduction (TPR) measurements. The performance of Ir-Sn-Sb-O in a single cell electrolyser showed better results for hydrogen production than IrO2/ATO using a mechanical mixture. Ir-Sn-Sb-O demonstrated an onset potential for water electrolysis close to 1.45 V on Ir-Sn-Sb-O and a current density near to 260 mA mg−1 at 1.8 V. The results suggest that the mixed oxide Ir-Sn-Sb-O has favorable properties for further applications in water electrolysers.
      Citation: Catalysts
      PubDate: 2020-05-08
      DOI: 10.3390/catal10050524
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 525: Enhanced Photoelectrochemical Water
           Splitting at Hematite Photoanodes by Effect of a NiFe-Oxide co-Catalyst

    • Authors: Vecchio, Trocino, Zignani, Baglio, Carbone, Garcia, Contreras, Gómez, Aricò
      First page: 525
      Abstract: Tandem photoelectrochemical cells (PECs), made up of a solid electrolyte membrane between two low-cost photoelectrodes, were investigated to produce “green” hydrogen by exploiting renewable solar energy. The assembly of the PEC consisted of an anionic solid polymer electrolyte membrane (gas separator) clamped between an n-type Fe2O3 photoanode and a p-type CuO photocathode. The semiconductors were deposited on fluorine-doped tin oxide (FTO) transparent substrates and the cell was investigated with the hematite surface directly exposed to a solar simulator. Ionomer dispersions obtained from the dissolution of commercial polymers in the appropriate solvents were employed as an ionic interface with the photoelectrodes. Thus, the overall photoelectrochemical water splitting occurred in two membrane-separated compartments, i.e., the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. A cost-effective NiFeOx co-catalyst was deposited on the hematite photoanode surface and investigated as a surface catalytic enhancer in order to improve the OER kinetics, this reaction being the rate-determining step of the entire process. The co-catalyst was compared with other well-known OER electrocatalysts such as La0.6Sr0.4Fe0.8CoO3 (LSFCO) perovskite and IrRuOx. The Ni-Fe oxide was the most promising co-catalyst for the oxygen evolution in the anionic environment in terms of an enhanced PEC photocurrent and efficiency. The materials were physico-chemically characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM).
      Citation: Catalysts
      PubDate: 2020-05-09
      DOI: 10.3390/catal10050525
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 526: Nanostructured Magnéli-Phase W18O49 Thin
           Films for Photoelectrochemical Water Splitting

    • Authors: A. K. Mohamedkhair, Q. A. Drmosh, Mohammad Qamar, Z. H. Yamani
      First page: 526
      Abstract: Converting water into hydrogen through the photo-electrochemical (PEC) process is one of the most exciting approaches in this field, and there is a quest to design or search for new electro-photo-catalytic materials. In this work, simple steps for fabrication and transformation of metallic tungsten thin film into the photo-active Magnéli-phase (W18O49) of tungsten oxide thin film is demonstrated. The post-annealing temperature has a significant impact on the phase evolution of tungsten film into W18O49. The film thickness of W18O49 is controlled by controlling the sputtering time (or deposition time) of W film. The PEC performance of the as-prepared electrodes is evaluated by monitoring the water oxidation reaction under visible radiation. The PEC findings reveal a correlation between PEC performance and phase, morphology, and thickness of the film. The as-derived W18O49 can efficiently catalyze the water oxidation reaction at neutral solution pH, generating 0.6 and 1.4 mA cm−1 photo-current at 0.6 and 0.8 V vs. Saturated calomel electrode (SCE), respectively, in addition to excellent stability. The electrical conductivity and the charge transfer kinetics are investigated employing the electrochemical impedance spectroscopic (EIS) technique.
      Citation: Catalysts
      PubDate: 2020-05-10
      DOI: 10.3390/catal10050526
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 527: A DFT Insight into the Tuning Effect of
           Potassium Promoter on the Formation of Carbon Atoms via Carburization
           Gases Dissociation on Iron-Based Catalysts

    • Authors: Gong, Cao, Sun, Cui, Gao, Hao
      First page: 527
      Abstract: The research of the formation mechanism of iron carbides is significant to design the high-performance catalysts for the Fischer–Tropsch synthesis (FTS) process. In this paper, the effect of potassium promoter on the formation of atomic carbon via carburization gases dissociation on the iron-based catalyst, the C2H4, C2H2 and CO/H2 adsorption energies and dissociation paths as well as the rate constants of the corresponding elementary steps are investigated by DFT on the Fe(110), Fe(110)-K2O, Fe(211) and Fe(211)-K2O surfaces. The calculation results demonstrated that the K2O promoter can modify the capabilities of surface C formation via the thermodynamic method as well as the kinetical method. The K2O promoter can increase the CO adsorption energy while decreasing the C2H4 adsorption energy both on Fe(110) and Fe(211) surfaces. Kinetically, via tuning the catalyst surfaces from Fe(110) to Fe(211), the K2O promoter can inhibit the ability of C2H4/C2H2 dissociation to atomic carbon, while enhancing the ability of CO/H2 decomposition to atomic carbon. The C2H4/C2H2 dissociation rate constants on Fe(211) and Fe(211)-K2O are about 107 times slower than that on Fe(110) and Fe(110)-K2O, whereas the dissociation rate constants of CO/H2 on Fe(211) are about 106 times faster than that on Fe(110), and about 107 times faster on Fe(211)-K2O than on Fe(110)-K2O.
      Citation: Catalysts
      PubDate: 2020-05-10
      DOI: 10.3390/catal10050527
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 528: Comparative Study of ZnO Thin Films Doped
           with Transition Metals (Cu and Co) for Methylene Blue Photodegradation
           under Visible Irradiation

    • Authors: William Vallejo, Alvaro Cantillo, Briggitte Salazar, Carlos Diaz-Uribe, Wilkendry Ramos, Eduard Romero, Mikel Hurtado
      First page: 528
      Abstract: We synthesized and characterized both Co-doped ZnO (ZnO:Co) and Cu-doped ZnO (ZnO:Cu) thin films. The catalysts’ synthesis was carried out by the sol–gel method while the doctor blade technique was used for thin film deposition. The physicochemical characterization of the catalysts was carried out by Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffraction, and diffuse reflectance measurements. The photocatalytic activity was studied under visible irradiation in aqueous solution, and kinetic parameters were determined by pseudo-first-order fitting. The Raman spectra results evinced the doping process and suggested the formation of heterojunctions for both dopants. The structural diffraction patterns indicated that the catalysts were polycrystalline and demonstrated the presence of a ZnO wurtzite crystalline phase. The SEM analysis showed that the morphological properties changed significantly, the micro-aggregates disappeared, and agglomeration was reduced after modification of ZnO. The ZnO optical bandgap (3.22 eV) reduced after the doping process, these being ZnO:Co (2.39 eV) and ZnO:Co (3.01 eV). Finally, the kinetic results of methylene blue photodegradation reached 62.6% for ZnO:Co thin films and 42.5% for ZnO:Cu thin films.
      Citation: Catalysts
      PubDate: 2020-05-11
      DOI: 10.3390/catal10050528
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 529: New Trends in Enantioselective
           Cross-Dehydrogenative Coupling

    • Authors: Ana Maria Faisca Phillips, Maria de Fátima C. Guedes da Silva, Armando J. L. Pombeiro
      First page: 529
      Abstract: The development of cross-dehydrogenative coupling in recent years has simplified the synthesis of many materials, as a result of facile C–H activation, which, together with its greater atom economy and environmental friendliness, has made an impact on modern organic chemistry. Indeed, many C–C and C–X (X = N, O, P, S, B, or Si) coupling reactions can now be performed directly between two C–H bonds or a C–H and an X–H bond, simply by adding catalytic amounts of a metal salt to a mixture of the two and an oxidant to accept the two hydrogen atoms released. Chiral organocatalysts or chiral ligands have been joined to promote enantioselective processes, resulting in the development of efficient reaction cascades that provide products in high yields and high levels of asymmetric induction through cooperative catalysis. In recent years, photochemical oxidation and electrochemistry have widened even more the scope of cross-dehydrogenative coupling (CDC). In this review, we summarized the recent literature in this subject, hoping that it will inspire many new synthetic strategies.
      Citation: Catalysts
      PubDate: 2020-05-11
      DOI: 10.3390/catal10050529
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 530: The Potential Use of Core-Shell Structured
           Spheres in a Packed-Bed DBD Plasma Reactor for CO2 Conversion

    • Authors: Uytdenhouwen, Meynen, Cool, Bogaerts
      First page: 530
      Abstract: This work proposes to use core-shell structured spheres to evaluate whether it allows to individually optimize bulk and surface effects of a packing material, in order to optimize conversion and energy efficiency. Different core-shell materials have been prepared by spray coating, using dense spheres (as core) and powders (as shell) of SiO2, Al2O3, and BaTiO3. The materials are investigated for their performance in CO2 dissociation and compared against a benchmark consisting of a packed-bed reactor with the pure dense spheres, as well as an empty reactor. The results in terms of CO2 conversion and energy efficiency show various interactions between the core and shell material, depending on their combination. Al2O3 was found as the best core material under the applied conditions here, followed by BaTiO3 and SiO2, in agreement with their behaviour for the pure spheres. Applying a thin shell layer on the cores showed equal performance between the different shell materials. Increasing the layer thickness shifts this behaviour, and strong combination effects were observed depending on the specific material. Therefore, this method of core-shell spheres has the potential to allow tuning of the packing properties more closely to the application by designing an optimal combination of core and shell.
      Citation: Catalysts
      PubDate: 2020-05-11
      DOI: 10.3390/catal10050530
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 531: Photocatalytic Activities of PET Filaments
           Deposited with N-Doped TiO2 Nanoparticles Sensitized with Disperse Blue
           Dyes

    • Authors: Hui Zhang, Ye Han, Limeng Yang, Xiaoling Guo, Hailiang Wu, Ningtao Mao
      First page: 531
      Abstract: In this study, the enhanced photocatalytic activities of polyethylene terephthalate (PET) filaments deposited with N-doped Titanium dioxide (TiO2) nanoparticles sensitized with water insoluble disperse blue SE–2R dye were investigated. The PET filaments were loaded with two types of N-doped TiO2 nanoparticles, one with and the other without being sensitized with disperse blue SE–2R dye, in one-pot hydrothermal process respectively. The differences in photocatalytic activities between the N-doped TiO2 and the dye-sensitized N-doped TiO2 nanoparticles when exposed to both UV rays and visible lights were analyzed and compared by using their photodegradations of methylene blue (MB) dye. It was demonstrated that the disperse blue dye facilitated the electron–hole separation in N-doped TiO2 nanoparticles faster under UV irradiation than that under visible light irradiation. The enhanced photocatalytic activity of the PET filaments loaded with dye-sensitized N-doped TiO2 nanoparticles exposure to UV irradiation, in comparison with that under visible light irradiation, was attributed to both improved light absorption capacity and high separation efficiency of photo-generated electron–hole pairs. Furthermore, the conduction band and band gap of the PET filaments deposited with N-doped TiO2 nanoparticles sensitized with disperse blue SE–2R dye were influenced by the wavelength of light sources, while its valence band was not affected. The PET filaments deposited with dye-sensitized N-doped TiO2 nanoparticles have a potential application to degrade organic pollutants.
      Citation: Catalysts
      PubDate: 2020-05-11
      DOI: 10.3390/catal10050531
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 532: Shape-Selective Mesoscale
           Nanoarchitectures: Preparation and Photocatalytic Performance

    • Authors: Simona E. Hunyadi Murph, Katie Heruox
      First page: 532
      Abstract: We create ordered arrays of shape-selective gold-titania composite nanomaterials at the mesoscale (100 µm to 5 mm) by a combination of both bottom-up and top-down approaches for exquisite control of the size, shape, and arrangement of nanomaterials. Lithographic techniques along with wet chemical synthetic methods were combined to create these composite nanomaterials. The photocatalytic activity of these TiO2, TiO2-Au and SiO2-TiO2-Au nano-composite mesoscale materials was monitored by the photodegradation of a model analyte, methyl orange, under UV and visible (Vis) illumination. Bare TiO2- and SiO2-TiO2-coated pillar arrays showed significant activity toward methyl orange in UV light with degradation rates on the order of 10−4–10−3 min−1. The photocatalytic activity of these arrays was also found to depend on the nanoparticle shape, in which particles with more edges and corners were found to be more reactive than spherical particles (i.e., the photocatalytic activity decreased as follows: diamonds > squares > triangles > spheres). SiO2-TiO2-Au nano-composite pillar arrays were tested in both UV and Vis light and showed increased activity in Vis light but decreased activity in UV light as compared to the bare semiconductor arrays. Additionally, the Au nanorod-functionalized nanoarrays exhibit a strong shape-dependence in their photocatalytic activity toward methyl orange degradation in Vis light.
      Citation: Catalysts
      PubDate: 2020-05-12
      DOI: 10.3390/catal10050532
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 533: The Study of Reverse Water Gas Shift
           Reaction Activity over Different Interfaces: The Design of Cu-Plate ZnO
           Model Catalysts

    • Authors: Wen, Huang, Sun, Liang, Zhang, Zhang, Fu, Wu, Chen, Ye
      First page: 533
      Abstract: CO2 hydrogenation to methanol is one of the main and valuable catalytic reactions applied on Cu/ZnO-based catalysts; the interface formed through Zn migration from ZnO support to the surface of Cu nanoparticle (ZnOx-Cu NP-ZnO) has been reported to account for methanol synthesis from CO2 hydrogenation. However, the accompanied reverse water gas shift (RWGS) reaction significantly decreases methanol selectivity and deactivates catalysts soon. Inhibition of RWGS is thus of great importance to afford high yield of methanol. The clear understanding of the reactivity of RWGS reaction on both the direct contact Cu-ZnO interface and ZnOx-Cu NP-ZnO interface is essential to reveal the low methanol selectivity in CO2 hydrogenation to methanol and look for efficient catalysts for RWGS reaction. Cu doped plate ZnO (ZnO:XCu) model catalysts were prepared through a hydrothermal method to simulate direct contact Cu-ZnO interface and plate ZnO supported 1 wt % Cu (1Cu/ZnO) catalyst was prepared by wet impregnation for comparison in RWGS reaction. Electron paramagnetic resonance (EPR), XRD, SEM, Raman, hydrogen temperature-programmed reduction (H2-TPR) and CO2 temperature-programmed desorption (CO2-TPD) were employed to characterize these catalysts. The characterization results confirmed that Cu incorporated into ZnO lattice and finally formed direct contact Cu-ZnO interface after H2 reduction. The catalytic performance revealed that direct contact Cu-ZnO interface displays inferior RWGS reaction reactivity at reaction temperature lower than 500 °C, compared with the ZnOx-Cu NP-ZnO interface; however, it is more stable at reaction temperature higher than 500 °C, enables ZnO:XCu model catalysts superior catalytic activity to that of 1Cu/ZnO. This finding will facilitate the designing of robust and efficient catalysts for both CO2 hydrogenation to methanol and RWGS reactions.
      Citation: Catalysts
      PubDate: 2020-05-12
      DOI: 10.3390/catal10050533
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 534: Suppression of Hydrophobic Recovery in
           Photo-Initiated Chemical Vapor Deposition

    • Authors: Alessio Aufoujal, Ulrich Legrand, Jean-Luc Meunier, Jason Robert Tavares
      First page: 534
      Abstract: Photo-initiated chemical vapor deposition (PICVD) functionalizes carbon nanotube (CNT)-enhanced porous substrates with a highly polar polymeric nanometric film, rendering them super-hydrophilic. Despite its ability to generate fully wettable surfaces at low temperatures and atmospheric pressure, PICVD coatings normally undergo hydrophobic recovery. This is a process by which a percentage of oxygenated functional group diffuse/re-arrange from the top layer of the deposited film towards the bulk of the substrate, taking the induced hydrophilic property of the material with them. Thus, hydrophilicity decreases over time. To address this, a vertical chemical gradient (VCG) can be deposited onto the CNT-substrate. The VCG consists of a first, thicker highly cross-linked layer followed by a second, thinner highly functionalized layer. In this article, we show, through water contact angle and XPS measurements, that the increased cross-linking density of the first layer can reduce the mobility of polar functional groups, forcing them to remain at the topmost layer of the PICVD coating and to suppress hydrophobic recovery. We show that employing a bi-layer VCG suppresses hydrophobic recovery for five days and reduces its effect afterwards (contact angle stabilizes to 42 ± 1° instead of 125 ± 3°).
      Citation: Catalysts
      PubDate: 2020-05-12
      DOI: 10.3390/catal10050534
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 535: Pyridyl-Anchored Type BODIPY
           Sensitizer-TiO2 Photocatalyst for Enhanced Visible Light-Driven
           Photocatalytic Hydrogen Production

    • Authors: Xiao-Feng Shen, Motonori Watanabe, Atsushi Takagaki, Jun Tae Song, Tatsumi Ishihara
      First page: 535
      Abstract: Dye-sensitized photocatalytic hydrogen production using a boron-dipyrromethene (BODIPY) organic material having a pyridyl group at the anchor site was investigated. Phenyl, carbazole, and phenothiazine derivatives were introduced into BODIPY dyes, and their photocatalytic activities were examined. Identification was performed by nuclear magnetic resonance (NMR), infrared (IR), mass (MS) spectra, and absorption spectra, and catalyst evaluation was performed by using visible-light irradiation and photocatalytic hydrogen production and photocurrent. These dyes have strong absorption at 600–700 nm, suggesting that they are promising as photosensitizers. When the photocatalytic activity was examined, stable catalytic performance was demonstrated, and the activity of the Pt-TiO2 photocatalyst carrying a dye having a carbazole group was 249 μmol/gcat·h. Photocurrent measurements suggest that dye-sensitized photocatalytic activity is occurring. This result suggests that BODIPY organic materials with pyridyl groups as anchor sites are useful as novel dye-sensitized photocatalysts.
      Citation: Catalysts
      PubDate: 2020-05-12
      DOI: 10.3390/catal10050535
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 536: Biocatalysis of Industrial Kraft Pulps:
           Similarities and Differences between Hardwood and Softwood Pulps in
           Hydrolysis by Enzyme Complex of Penicillium verruculosum

    • Authors: Andrey S. Aksenov, Irina V. Tyshkunova, Daria N. Poshina, Anastasia A. Guryanova, Dmitry G. Chukhchin, Igor G. Sinelnikov, Konstantin Y. Terentyev, Yury A. Skorik, Evgeniy V. Novozhilov, Arkady P. Synitsyn
      First page: 536
      Abstract: Kraft pulp enzymatic hydrolysis is a promising method of woody biomass bioconversion. The influence of composition and structure of kraft fibers on their hydrolysis efficiency was evaluated while using four substrates, unbleached hardwood pulp (UHP), unbleached softwood pulp (USP), bleached hardwood pulp (BHP), and bleached softwood pulp (BSP). Hydrolysis was carried out with Penicillium verruculosum enzyme complex at a dosage of 10 filter paper units (FPU)/g pulp. The changes in fiber morphology and structure were visualized while using optical and electron microscopy. Fiber cutting and swelling and quick xylan destruction were the main processes at the beginning of hydrolysis. The negative effect of lignin content was more pronounced for USP. Drying decreased the sugar yield of dissolved hydrolysis products for all kraft pulps. Fiber morphology, different xylan and mannan content, and hemicelluloses localization in kraft fibers deeply affected the hydrolyzability of bleached pulps. The introduction of additional xylobiase, mannanase, and cellobiohydrolase activities to enzyme mixture will further improve the hydrolysis of bleached pulps. A high efficiency of never-dried bleached pulp bioconversion was shown. At 10% substrate concentration, hydrolysates with more than 50 g/L sugar concentration were obtained. The bioconversion of never-dried BHP and BSP could be integrated into working kraft pulp mills.
      Citation: Catalysts
      PubDate: 2020-05-13
      DOI: 10.3390/catal10050536
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 537: Ruthenium Catalysts Templated on Mesoporous
           MCM-41 Type Silica and Natural Clay Nanotubes for Hydrogenation of Benzene
           to Cyclohexane

    • Authors: Aleksandr Glotov, Anna Vutolkina, Aleksey Pimerzin, Vladimir Nedolivko, Gleb Zasypalov, Valentine Stytsenko, Eduard Karakhanov, Vladimir Vinokurov
      First page: 537
      Abstract: Mesoporous ruthenium catalysts (0.74–3.06 wt%) based on ordered Mobil Composition of Matter No. 41 (MCM-41) silica arrays on aluminosilicate halloysite nanotubes (HNTs), as well as HNT-based counterparts, were synthesized and tested in benzene hydrogenation. The structure of HNT core-shell silica composite-supported Ru catalysts were investigated by transmission electron microscopy (TEM), X-ray fluorescence (XRF) and temperature-programmed reduction (TPR-H2). The textural characteristics were specified by low-temperature nitrogen adsorption/desorption. The catalytic evaluation of Ru nanoparticles supported on both the pristine HNTs and MCM-41/HNT composite in benzene hydrogenation was carried out in a Parr multiple reactor system with batch stirred reactors (autoclaves) at 80 °C, a hydrogen pressure of 3.0 MPa and a hydrogen/benzene molar ratio of 3.3. Due to its hierarchical structure and high specific surface area, the MCM-41/HNT composite provided the uniform distribution and stabilization of Ru nanoparticles (NPs) resulted in the higher specific activity and stability as compared with the HNT-based counterpart. The highest specific activity (5594 h−1) along with deep benzene hydrogenation to cyclohexane was achieved for the Ru/MCM-41/HNT catalyst with a low metal content.
      Citation: Catalysts
      PubDate: 2020-05-13
      DOI: 10.3390/catal10050537
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 538: Enzymatic Synthesis of O-Methylated
           Phenophospholipids by Lipase-Catalyzed Acidolysis of Egg-Yolk
           Phosphatidylcholine with Anisic and Veratric Acids

    • Authors: Marta Okulus, Anna Gliszczyńska
      First page: 538
      Abstract: Lipase-catalyzed acidolysis reactions of egg-yolk phosphatidylcholine (PC) with anisic (ANISA) and veratric (VERA) acids were investigated to develop a biotechnological method for the production of corresponding biologically active O-methylated phenophospholipids. Screening experiments with four commercially available immobilized lipases indicated that the most effective biocatalyst for the incorporation of ANISA into phospholipids was Novozym 435. None of the tested enzymes were able to catalyze the synthesis of PC structured with VERA. The effects of different solvents, substrate molar ratios, temperature, enzyme loading, and time of the reaction on the process of incorporation of ANISA into the phospholipids were evaluated in the next step of the study. The mixture of toluene/chloroform in the ratio 9:1 (v/v) significantly increased the incorporation of ANISA into PC. The acidolysis reaction was carried out using the selected binary solvent system, 1/15 substrate molar ratio PC/ANISA, 30% (w/w) enzyme load, and temperature of 50 °C afforded after 72 h anisoylated lysophosphatidylcholine (ANISA-LPC) and anisoylated phosphatidylcholine (ANISA-PC) in isolated yields of 28.5% and 2.5% (w/w), respectively. This is the first study reporting the production of ANISA-LPC and ANISA-PC via a one-step enzymatic method, which is an environmentally friendly alternative to the chemical synthesis of these biologically active compounds.
      Citation: Catalysts
      PubDate: 2020-05-13
      DOI: 10.3390/catal10050538
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 539: Enhanced Hydrogen Production from Ethanol
           Photoreforming by Site-Specific Deposition of Au on Cu2O/TiO2 p-n Junction
           

    • Authors: Lan Luo, Tingting Zhang, Xin Zhang, Rongping Yun, Yanjun Lin, Bing Zhang, Xu Xiang
      First page: 539
      Abstract: Hydrogen production by photoreforming of biomass-derived ethanol is a renewable way of obtaining clean fuel. We developed a site-specific deposition strategy to construct supported Au catalysts by rationally constructing Ti3+ defects inTiO2 nanorods and Cu2O-TiO2 p-n junction across the interface of two components. The Au nanoparticles (~2.5 nm) were selectively anchored onto either TiO2 nanorods (Au@TiO2/Cu2O) or Cu2O nanocubes (Au@Cu2O/TiO2) or both TiO2 and Cu2O (Au@TiO2/Cu2O@Au) with the same Au loading. The electronic structure of supported Au species was changed by forming Au@TiO2 interface due to the adjacent Ti3+ defects and the associated oxygen vacancies while unchanged in Au@Cu2O/TiO2 catalyst. The p-n junction of TiO2/Cu2O promoted charge separation and transfer across the junction. During ethanol photoreforming, Au@TiO2/Cu2O catalyst possessing both the Au@TiO2 interface and the p-n junction showed the highest H2 production rate of 8548 μmol gcat−1 h−1 under simulated solar light, apparently superior to both Au@TiO2 and Au@Cu2O/TiO2 catalyst. The acetaldehyde was produced in liquid phase at an almost stoichiometric rate, and C−C cleavage of ethanol molecules to form CH4 or CO2 was greatly inhibited. Extensive spectroscopic results support the claim that Au adjacent to surface Ti3+ defects could be active sites for H2 production and p-n junction of TiO2/Cu2O facilitates photo-generated charge transfer and further dehydrogenation of ethanol to acetaldehyde during the photoreforming.
      Citation: Catalysts
      PubDate: 2020-05-13
      DOI: 10.3390/catal10050539
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 540: Photocatalytic Oxidative Degradation of
           Carbamazepine by TiO2 Irradiated by UV Light Emitting Diode

    • Authors: Zhilin Ran, Yuanhang Fang, Jian Sun, Cong Ma, Shaofeng Li
      First page: 540
      Abstract: Here, ultraviolet light-emitting diodes (UV-LED) combined with TiO2 was used to investigate the feasibility of carbamazepine (CBZ) degradation. The effects of various factors, like crystal form of the catalyst (anatase, rutile, and mixed phase), mass concentration of TiO2, wavelength and irradiation intensity of the UV-LED light source, pH of the reaction system, and coexisting anions and cations, on the photocatalytic degradation of CBZ were studied. The mixed-phase (2.8 g/L) showed the best degradation efficiency at 365 nm among three kinds of TiO2, wherein CBZ (21.1 µM) was completely oxidized within 1 hour. The results of batch experiments showed that: i) CBZ degradation efficiency under UV-LED light at 365 nm was higher than 275 nm, due to stronger penetrability of 365 nm light in solution. ii) The degradation efficiency increased with increase in irradiation intensity and pH, whereas it decreased with increase in initial CBZ concentration. iii) The optimal amount of mixed-phase TiO2 catalyst was 2.8 g/L and excessive catalyst decreased the rate. iv) The co-existence of CO32−, HCO3−, and Fe3+ ions in water significantly accelerated the degradation rate of photocatalytic CBZ, whereas Cu2+ ions strongly inhibited the degradation process of CBZ. ·OH was found to be the main active species in the UV-LED photocatalytic degradation of CBZ. UV-LED is more environmentally friendly, energy efficient, and safer, whereas commercial TiO2 is economical and readily available. Therefore, this study provides a practically viable reference method for the degradation of pharmaceuticals and personal care products (PPCPs).
      Citation: Catalysts
      PubDate: 2020-05-13
      DOI: 10.3390/catal10050540
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 541: Biomorphic Fibrous TiO2 Photocatalyst
           Obtained by Hydrothermal Impregnation of Short Flax Fibers with Titanium
           Polyhydroxocomplexes

    • Authors: Mikhail F. Butman, Nataliya E. Kochkina, Nikolay L. Ovchinnikov, Nikolay V. Zinenko, Dmitry N. Sergeev, Michael Müller
      First page: 541
      Abstract: A biomimetic solution technology for producing a photocatalytic material in the form of biomorphic titanium oxide fibers with a hierarchical structure using short flax fiber as a biotemplate is proposed. The impregnation of flax fibers intensified under hydrothermal conditions with a precursor was performed in an autoclave to activate the nucleation of the photoactive TiO2 phases. The interaction between precursor and flax fibers was studied by using infrared spectroscopy (IR) and differential scanning calorimetry/thermogravimetry analysis (DSC/TG). The morphology, structure, and textural properties of the TiO2 fibers obtained at annealing temperatures of 500–700 °C were determined by X-ray diffraction analysis, scanning electron microscopy, and nitrogen adsorption/desorption. It is shown that the annealing temperature of the impregnated biotemplates significantly affects the phase composition, crystallite size, and porous structure of TiO2 fiber samples. The photocatalytic activity of the obtained fibrous TiO2 materials was evaluated by using the decomposition of the cationic dye Rhodamine B in an aqueous solution (concentration 12 mg/L) under the influence of ultraviolet radiation (UV). The maximum photodegradation efficiency of the Rhodamine B was observed for TiO2 fibers annealed at 600 °C and containing 40% anatase and 60% rutile. This sample ensured 100% degradation of the dye in 20 min, and this amount significantly exceeds the photocatalytic activity of the commercial Degussa P25 photocatalyst and TiO2 samples obtained previously under hydrothermal conditions by the sol-gel method.
      Citation: Catalysts
      PubDate: 2020-05-13
      DOI: 10.3390/catal10050541
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 542: Preparation of Metal Oxides Containing ppm
           Levels of Pd as Catalysts for the Reduction of Nitroarene and Evaluation
           of Their Catalytic Activity by the Fluorescence-Based High-Throughput
           Screening Method

    • Authors: Taeho Lim, Min Su Han
      First page: 542
      Abstract: Herein, an easily accessible and efficient green method for the reduction of nitroarene compounds was developed using metal oxide catalysts. Heterogeneous metal oxides with or without Pd were prepared by a simple and scalable co-precipitation method and used for the reduction of nitroarenes. A fluorescence-based high-throughput screening (HTS) method was also developed for the rapid analysis of the reaction conditions. The catalytic activity of the metal oxides and reaction conditions were rapidly screened by the fluorescence-based HTS method, and Pd/CuO showed the highest catalytic activity under mild reaction conditions. After identifying the optimal reaction conditions, various nitroarenes were reduced to the corresponding aniline derivatives by Pd/CuO (0.005 mol% of Pd) under these conditions. Furthermore, the Pd/CuO catalyst was used for the one-pot Suzuki–Miyaura cross-coupling/reduction reaction. A gram-scale reaction (20 mmol) was successfully performed using the present method, and Pd/CuO showed high reusability without a loss of catalytic activity for five cycles.
      Citation: Catalysts
      PubDate: 2020-05-13
      DOI: 10.3390/catal10050542
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 543: Insights into the Mechanism of Ethionamide
           Resistance in Mycobacterium tuberculosis through an in silico Structural
           Evaluation of EthA and Mutants Identified in Clinical Isolates

    • Authors: Vinicius Carius de Souza, Deborah Antunes, Lucianna H.S. Santos, Priscila Vanessa Zabala Capriles Goliatt, Ernesto Raul Caffarena, Ana Carolina Ramos Guimarães, Teca Calcagno Galvão
      First page: 543
      Abstract: Mutation in the ethionamide (ETH) activating enzyme, EthA, is the main factor determining resistance to this drug, used to treat TB patients infected with MDR and XDR Mycobacterium tuberculosis isolates. Many mutations in EthA of ETH resistant (ETH-R) isolates have been described but their roles in resistance remain uncharacterized, partly because structural studies on the enzyme are lacking. Thus, we took a two-tier approach to evaluate two mutations (Y50C and T453I) found in ETH-R clinical isolates. First, we used a combination of comparative modeling, molecular docking, and molecular dynamics to build an EthA model in complex with ETH that has hallmark features of structurally characterized homologs. Second, we used free energy computational calculations for the reliable prediction of relative free energies between the wild type and mutant enzymes. The ΔΔG values for Y50C and T453I mutant enzymes in complex with FADH2-NADP-ETH were 3.34 (+/−0.55) and 8.11 (+/−0.51) kcal/mol, respectively, compared to the wild type complex. The positive ΔΔG values indicate that the wild type complex is more stable than the mutants, with the T453I complex being the least stable. These are the first results shedding light on the molecular basis of ETH resistance, namely reduced complex stability of mutant EthA.
      Citation: Catalysts
      PubDate: 2020-05-14
      DOI: 10.3390/catal10050543
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 544: A Facile and Scalable Approach to Ultrathin
           NixMg1−xO Solid Solution Nanoplates and Their Performance for Carbon
           Dioxide Reforming of Methane

    • Authors: Guoqiang Zhang, Zhiyun Zhang, Yunqiang Wang, Yanqiu Liu, Qiping Kang
      First page: 544
      Abstract: Carbon dioxide reforming of methane (CRM) represents a promising method that can effectively convert CH4 and CO2 into valuable energy resources. Herein, ultrathin NixMg1−xO nanoplate catalysts were synthesized using a scalable and facile process involving a one-pot, co-precipitation method in the absence of surfactants. This approach resulted in the synthesis of planar NixMg1−xO catalysts that were much thinner (˂8 nm) with larger specific surface area (>120 m2/g) in comparison to NixMg1−xO catalysts prepared by conventional methods. The ultrathin NixMg1−xO nanoplate catalysts exhibited high thermal stability, catalytic activity, and durability for CRM. Especially, these novel catalysts exhibited excellent anti-coking behavior with a low carbon deposition of 2.1 wt.% after 36 h of continuous reaction compared with the conventional catalysts, under the reaction conditions of the present study. The improved performance of the thin NixMg1−xO nanoplate catalysts was attributed to the high specific surface area and the interaction between metallic nickel nanocatalysts and the solid solution substrates to stabilize the Ni nanoparticles.
      Citation: Catalysts
      PubDate: 2020-05-14
      DOI: 10.3390/catal10050544
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 545: Comparison of Ga2O3 and TiO2 Nanostructures
           for Photocatalytic Degradation of Volatile Organic Compounds

    • Authors: Yoo, Ryou, Lee, Cho, Cho, Hwang
      First page: 545
      Abstract: The photocatalytic degradation of formaldehyde, acetaldehyde, toluene, and styrene are compared using monoclinic Ga2O3 and anatase TiO2 nanostructures under ultraviolet-C irradiation. These Ga2O3 and TiO2 photocatalysts are characterized using a field emission scanning electron microscope, a powder X-ray diffraction system, the Brunauer–Emmett–Teller method, and a Fourier transform infrared spectrometer. The Ga2O3 shows a higher reaction rate constant (k, min-1) than TiO2 by a factor of 7.1 for toluene, 8.1 for styrene, 3.1 for formaldehyde, and 2.0 for acetaldehyde. The results demonstrate that the photocatalytic activity ratio of the Ga2O3 over the TiO2 becomes more prominent toward the aromatic compounds compared with the nonaromatic compounds. Highly energetic photo-generated carriers on the conduction/valence band-edge of the Ga2O3, in comparison with that of the TiO2, result in superior photocatalytic activity, in particular on aromatic volatile organic compounds (VOCs) with a high bond dissociation energy.
      Citation: Catalysts
      PubDate: 2020-05-14
      DOI: 10.3390/catal10050545
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 546: Synthesis of Conducting Bifunctional
           Polyaniline@Mn-TiO2 Nanocomposites for Supercapacitor Electrode and
           Visible Light Driven Photocatalysis

    • Authors: Milan Babu Poudel, Changho Yu, Han Joo Kim
      First page: 546
      Abstract: We report a polyaniline-wrapped, manganese-doped titanium oxide (PANi/Mn-TiO2) nanoparticle composite for supercapacitor electrode and photocatalytic degradation. The PANi/Mn-TiO2 nanoparticles were synthesized using a solvothermal process, followed by oxidative polymerization of aniline. The structural properties of studied materials were confirmed by XRD, FTIR, HRTEM, FESEM, and UV visible spectroscopy. The as-prepared PANi/Mn-TiO2 nanoparticles revealed admirable electrochemical performance with a specific capacitance of 635.87 F g−1 at a current density of 1 A g−1 with a notable life cycle retention of 91% after 5000 charge/discharge cycles. Furthermore, the asymmetric cell with PANi/Mn-TiO2 as a positive electrode exhibited energy density of 18.66 W h kg−1 with excellent stability. Moreover, the PANi/Mn-TiO2 had promising photocatalytic activity for methylene blue degradation. The improved performance of PANi/Mn-TiO2 nanoparticles is attributed to the well-built synergetic effect of components that lead to significant reduction of band gap energy and charge transfer resistance, as revealed by UV visible spectroscopy and electrochemical impedance spectroscopy.
      Citation: Catalysts
      PubDate: 2020-05-14
      DOI: 10.3390/catal10050546
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 547: Efficient N, Fe Co-Doped TiO2 Active under
           Cost-Effective Visible LED Light: From Powders to Films

    • Authors: Sigrid Douven, Julien G. Mahy, Cédric Wolfs, Charles Reyserhove, Dirk Poelman, François Devred, Eric M. Gaigneaux, Stéphanie D. Lambert
      First page: 547
      Abstract: An eco-friendly photocatalytic coating, active under a cost-effective near-visible LED system, was synthesized without any calcination step for the removal of organic pollutants. Three types of doping (Fe, N and Fe + N), with different dopant/Ti molar ratios, were investigated and compared with undoped TiO2 and the commercial P25 photocatalyst. Nano-crystalline anatase-brookite particles were successfully produced with the aqueous sol-gel process, also at a larger scale. All samples displayed a higher visible absorption and specific surface area than P25. Photoactivity of the catalyst powders was evaluated through the degradation of p-nitrophenol in water under visible light (>400 nm). As intended, all samples were more performant than P25. The N-doping, the Fe-doping and their combination promoted the activity under visible light. Films, coated on three different substrates, were then compared. Finally, the photoactivity of a film, produced from the optimal N-Fe co-doped colloid, was evaluated on the degradation of (i) p-nitrophenol under UV-A light (365 nm) and (ii) rhodamine B under LED visible light (395 nm), and compared to undoped TiO2 film. The higher enhancement is obtained under the longer wavelength (395 nm). The possibility of producing photocatalytic films without any calcination step and active under low-energy LED light constitutes a step forward for an industrial development.
      Citation: Catalysts
      PubDate: 2020-05-14
      DOI: 10.3390/catal10050547
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 548: Simulation and Optimization of the CWPO
           Process by Combination of Aspen Plus and 6-Factor Doehlert Matrix: Towards
           Autothermal Operation

    • Authors: Jose L. Diaz de Tuesta, Asunción Quintanilla, Daniel Moreno, Víctor R. Ferro, Jose A. Casas
      First page: 548
      Abstract: This work aims to present an industrial perspective on Catalytic Wet Peroxide Oxidation (CWPO) technology. Herein, process simulation and experimental design have been coupled to study the optimal process conditions to ensure high-performance oxidation, minimum H2O2 consumption and maximum energetic efficiency in an industrial scale CWPO unit. The CWPO of phenol in the presence of carbon black catalysts was studied as a model process in the Aspen Plus® v11 simulator. The kinetic model implemented, based on 30 kinetic equations with 11 organic compounds and H2O2 involvement, was valid to describe the complex reaction network and to reproduce the experimental results. The computer experiments were designed on a six-factor Doehlert Matrix in order to describe the influence of the operating conditions (i.e., the different process temperatures, inlet chemical oxygen demands, doses of H2O2 and space time) on each selected output response (conversion, efficiency of H2O2 consumption and energetic efficiency) by a quadratic model. The optimization of the WPO performance by a multi-criteria function highlighted the inlet chemical oxygen demand as the most influential operating condition. It needed to have values between 9.5 and 24 g L−1 for autothermal operation to be sustained under mild operating conditions (reaction temperature: 93–130 °C and pressure: 1–4 atm) and with a stoichiometric dose of H2O2.
      Citation: Catalysts
      PubDate: 2020-05-15
      DOI: 10.3390/catal10050548
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 549: Fabrication of ZnO-Fe-MXene Based
           Nanocomposites for Efficient CO2 Reduction

    • Authors: Karthik Kannan, Mostafa H. Sliem, Aboubakr M. Abdullah, Kishor Kumar Sadasivuni, Bijandra Kumar
      First page: 549
      Abstract: A ZnO-Fe-MXene nanocomposite was fabricated and examined with diverse spectroscopic techniques. The hexagonal structure of ZnO, MXene, and ZnO-Fe-MXene nanocomposites were validated through XRD. FTIR showed the characteristic vibrational frequencies of ZnO and MXene. The micrographs of the SEM showed nanoparticles with a flower-like structure. The electrocatalytic reduction efficiency of ZnO-Fe-MXene nanocomposite was analyzed through cyclic voltammetry and electrochemical impedance spectroscopy methods. The ZnO-Fe-MXene electrode was confirmed to have a high current density of 18.75 mA/cm2 under a CO2 atmosphere. Nyquist plots also illustrated a decrease in the impedance of the ZnO-Fe-MXene layer, indicating fast charge transfer between the Zn and MXene layers. Additionally, this electrochemical study highlights new features of ZnO-Fe-MXene for CO2 reduction.
      Citation: Catalysts
      PubDate: 2020-05-15
      DOI: 10.3390/catal10050549
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 550: Structure, Acidity, and Redox Aspects of
           VOx/ZrO2/SiO2 Catalysts for the n-Butane Oxidative Dehydrogenation

    • Authors: Sánchez-García, Handy, Ávila-Hernández, Rodríguez, García-Alamilla, Cardenas-Galindo
      First page: 550
      Abstract: ZrOx/SiO2 and VOx/ZrOx/SiO2 catalysts (5 wt %–25 wt % Zr, 4 wt % V) were prepared by grafting zirconium and vanadium alkoxides on Aerosil 380. All samples were characterized by temperature programmed reduction, N2 physisorption, X-ray diffraction, Raman spectroscopy, and ammonia adsorption microcalorimetry. Tetragonal ZrO2 and zircon (ZrSiO4) were present at 25 wt % Zr, but only amorphous zirconia overlayer existed for lower loadings. At lower Zr loadings (5 wt %–10 wt % Zr), exposed silica surface leads to V2O5 crystallites and isolated VO4 species, although V reducibility behavior changes, from being similar to VOx/SiO2 (5 wt % Zr) to showing VOx/ZrO2 behavior at 10 wt % Zr, and a diminished total amount of reducible V. Highly acidic ZrO2 sites are covered by the vanadium grafting, forming weaker sites (60–100 kJ/mol NH3 adsorption strength). Catalytic conversion and selectivity for the oxidative dehydrogenation of n-butane (673 K, n-C4/O2 = 2.2) over VOx/ZrOx/SiO2 show that 1,3-butadiene is favored over cis-2-butene and trans-2-butene, although there is some selectivity to the 2-butenes when VOx/ZrO2 behavior is evident. At low Zr loadings, butadiene formed during reaction acts as the diene species in a Diels–Alder reaction and gives rise to a cyclic compound that undergoes further dehydrogenation to produce benzaldehyde.
      Citation: Catalysts
      PubDate: 2020-05-15
      DOI: 10.3390/catal10050550
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 551: In-Depth Structural and Optical Analysis of
           Ce-modified ZnO Nanopowders with Enhanced Photocatalytic Activity Prepared
           by Microwave-Assisted Hydrothermal Method

    • Authors: Bazta, Urbieta, Trasobares, Piqueras, Fernández, Addou, Calvino, Hungría
      First page: 551
      Abstract: Pure and Ce-modified ZnO nanosheet-like polycrystalline samples were successfully synthesized by a simple and fast microwave-based process and tested as photocatalytic materials in environmental remediation processes. In an attempt to clarify the actual relationships between functionality and atomic scale structure, an in-depth characterization study of these materials using a battery of complementary techniques was performed. X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-Ray spectroscopy-scanning transmission electron microscopy (STEM-XEDS), photoluminescence spectroscopy (PL) and UV–Visible absorption spectroscopy were used to evaluate the effect of Ce ions on the structural, morphological, optical and photocatalytic properties of the prepared ZnO nanostructures. The XRD results showed that the obtained photocatalysts were composed of hexagonal, wurtzite type crystallites in the 34–44 nm size range. The SEM and TEM showed nanosheet-shaped crystallites, a significant fraction of them in contact with bundles of randomly oriented and much smaller nanoparticles of a mixed cerium–zinc phase with a composition close to Ce0.68Zn0.32Ox. Importantly, in clear contrast to the prevailing proposals regarding this type of materials, the STEM-XEDS characterization of the photocatalyst samples revealed that Ce did not incorporate into the ZnO crystal lattice as a dopant but that a heterojunction formed between the ZnO nanosheets and the Ce–Zn mixed oxide phase nanoparticles instead. These two relevant compositional features could in fact be established thanks to the particular morphology obtained by the use of the microwave-assisted hydrothermal synthesis. The optical study revealed that in the ZnO:Ce samples optical band gap was found to decrease to 3.17 eV in the samples with the highest Ce content. It was also found that the ZnO:Ce (2 at.%) sample exhibited the highest photocatalytic activity for the degradation of methylene blue (MB), when compared to both the pure ZnO and commercial TiO2-P25 under simulated sunlight irradiation. The kinetics of MB photodegradation in the presence of the different photocatalysts could be properly described using a Langmuir–Hinshelwood (LH) model, for which the ZnO:Ce (2 at.%) sample exhibited the highest value of effective kinetic constant.
      Citation: Catalysts
      PubDate: 2020-05-15
      DOI: 10.3390/catal10050551
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 552: Deactivation of a Vanadium-Based SCR
           Catalyst Used in a Biogas-Powered Euro VI Heavy-Duty Engine Installation

    • Authors: Johanna Englund, Sandra Dahlin, Andreas Schaefer, Kunpeng Xie, Lennart Andersson, Soran Shwan, Per-Anders Carlsson, Lars J. Pettersson, Magnus Skoglundh
      First page: 552
      Abstract: We have investigated how the exhaust gases from a heavy-duty Euro VI engine, powered with biogas impact a vanadium-based selective catalytic reduction (SCR) catalyst in terms of performance. A full Euro VI emission control system was used and the accumulation of catalyst poisons from the combustion was investigated for the up-stream particulate filter as well as the SCR catalyst. The NO x reduction performance in terms of standard, fast and NO 2 -rich SCR was evaluated before and after exposure to exhaust from a biogas-powered engine for 900 h. The SCR catalyst retains a significant part of its activity towards NO x reduction after exposure to biogas exhaust, likely due to capture of catalyst poisons on the up-stream components where the deactivation of the oxidation catalyst is especially profound. At lower temperatures some deactivation of the first part of the SCR catalyst was observed which could be explained by a considerably higher surface V 4 + /V 5 + ratio for this sample compared to the other samples. The higher value indicates that the reoxidation of V 4 + to V 5 + is partially hindered, blocking the redox cycle for parts of the active sites.
      Citation: Catalysts
      PubDate: 2020-05-16
      DOI: 10.3390/catal10050552
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 553: The Impact of Reduction Temperature and
           Nanoparticles Size on the Catalytic Activity of Cobalt-Containing BEA
           Zeolite in Fischer–Tropsch Synthesis

    • Authors: Karolina A. Chalupka, Jacek Grams, Pawel Mierczynski, Malgorzata I. Szynkowska, Jacek Rynkowski, Thomas Onfroy, Sandra Casale, Stanislaw Dzwigaj
      First page: 553
      Abstract: A goal of this work was to investigate the influence of the preparation procedure and activation conditions (reduction temperature and reducing medium: pure hydrogen (100% H2) or hydrogen-argon mixture (5% H2-95% Ar)) on the activity of Co-containing BEA zeolites in Fischer–Tropsch synthesis. Therefore, a series of CoBEA zeolites were obtained by a conventional wet impregnation (Co5.0AlBEA) and a two-step postsynthesis preparation procedure involving dealumination and impregnation steps (Co5.0SiBEA). Both types of zeolites were calcined in air at 500 °C for 3 h and then reduced at 500, 800 and 900 °C for 1 h in 100 % H2 and in 5% H2–95% Ar mixture flow. The obtained Red-C-Co5.0AlBEA and Red-C-Co5.0SiBEA catalysts with various physicochemical properties were tested in Fischer–Tropsch reaction. Among the studied catalysts, Red-C-Co5.0SiBEA reduced at 500 °C in pure hydrogen was the most active, presenting selectivity to liquid products of 91% containing mainly C7–C16 n-alkanes and isoalkanes as well as small amount of olefins, with CO conversion of about 11%. The Red-C-Co5.0AlBEA catalysts were not active in the Fischer–Tropsch synthesis. It showed that removal of aluminum from the BEA zeolite in the first step of postsynthesis preparation procedure played a key role in the preparation of efficient catalysts for Fischer–Tropsch synthesis. An increase of the reduction temperature from 500 to 800 and 900 °C resulted in two times lower CO conversion and a drop of the selectivity towards liquid products (up to 62%–88%). The identified main liquid products were n-alkanes and isoalkanes. The higher activity of Red-C-Co5.0SiBEA catalysts can be assigned to good dispersion of cobalt nanoparticles and thus a smaller cobalt nanoparticles size than in the case of Red-C-Co5.0AlBEA catalyst.
      Citation: Catalysts
      PubDate: 2020-05-16
      DOI: 10.3390/catal10050553
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 554: Study of Catalysts’ Influence on
           Photocatalysis/Photodegradation of Olive Oil Mill Wastewater.
           Determination of the Optimum Working Conditions

    • Authors: Hodaifa, Agabo García, Borja
      First page: 554
      Abstract: The high production of raw olive oil mill wastewater (OMW) is a current environmental problem due to its high organic load and phenol compounds. In this work, photo-Fenton reaction as an advanced oxidation process has been chosen for OMW treatment. In this sense, different iron salts (FeCl3, Fe2(SO4)3, FeSO4·7H2O, and Fe(ClO4)3) as catalysts were used in order to compare their effects on treatment. For each catalyst, different H2O2 concentrations (2.5, 5.0, 7.5, 10.0, 15.0, 20.0, and 30.0%, w/v) as oxidizing agents were tested. The common experimental conditions were temperature 20 °C, the catalyst/H2O2 ratio = 0.03, pH = 3, and ultraviolet light. The Lagergren kinetic model, in cases of total organic carbon removal, for the best H2O2 concentration per catalyst was used. During the experiments, the water quality was determined by measuring the removal percentages on chemical oxygen demand, total carbon, total organic carbon, total nitrogen, total phenolic compounds, total iron, turbidity and electric conductivity. The best catalyst was FeCl3 and the optimum H2O2 concentration was 7.5% (w/v). At these optimal conditions, the removal percentages for chemical oxygen demand, total phenolic compounds, total carbon, total organic carbon and total nitrogen were 60.3%, 88.4%, 70.1%, 63.2% and 51.5%, respectively.
      Citation: Catalysts
      PubDate: 2020-05-17
      DOI: 10.3390/catal10050554
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 555: An Evolutionary Marker of the Ribokinase
           Superfamily Is Responsible for Zinc-Mediated Regulation of Human Pyridoxal
           Kinase

    • Authors: César A. Ramírez-Sarmiento, Felipe Engelberger, Victoria Guixé
      First page: 555
      Abstract: The ribokinase superfamily catalyzes the phosphorylation of a vast diversity of substrates, and its members are characterized by the conservation of a common structural fold along with highly conserved sequence motifs responsible for phosphoryl transfer (GXGD) and stabilization of the metal-nucleotide complex (NXXE). Recently, a third motif (HXE) exclusive from ADP-dependent enzymes was identified, with its glutamic acid participating in water-mediated interactions with the metal-nucleotide complex and in stabilization of the ternary complex during catalysis. In this work, we bioinformatically determine that the aspartic acid of another motif (DPV), exclusively found in hydroxyethyl thiazole (THZK), hydroxymethyl pyrimidine (HMPK) and pyridoxal kinases (PLK), is structurally equivalent to the acidic residue in the HXE motif. Moreover, this residue is highly conserved among all ribokinase superfamily members. To determine whether the functional role of the DPV motif is similar to the HXE motif, we employed molecular dynamics simulations using crystal structures of phosphoryl donor substrate-complexed THZK and PLK, showing that its aspartic acid participated in water-mediated or direct interactions with the divalent metal of the metal-nucleotide complex. Lastly, enzyme kinetic assays on human PLK, an enzyme that utilizes zinc, showed that site-directed mutagenesis of the aspartic acid from the DPV motif abolishes the inhibition of this enzyme by increasing free zinc concentrations. Altogether, our results highlight that the DPV and HXE motifs are evolutionary markers of the functional and structural divergence of the ribokinase superfamily and evidence the role of the DPV motif in the interaction with both free and nucleotide-complexed divalent metals in the binding site of these enzymes.
      Citation: Catalysts
      PubDate: 2020-05-18
      DOI: 10.3390/catal10050555
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 556: Surface Engineering of WO3/BiVO4 to Boost
           Solar Water-Splitting

    • Authors: Yuncheng Cao, Zheng Xing, Bobo Wang, Wei Tang, Rong Wu, Jiangyu Li, Ming Ma
      First page: 556
      Abstract: Single-phase photoanodes often suffer inferior charge transport, which can be mitigated by constructing efficient heterojunctions. Thus, we have fabricated a fluorine-doped tin oxide (FTO)/WO3/BiVO4 heterojunction using hydrothermal and spin-coating methods. Surface engineering was exploited to further accelerate the reaction kinetics, which was achieved via post-modification with NaOH solution. This treatment alters the surface chemical state of the BiVO4 nanoparticles, leading to enhanced charge transport and surface water oxidation processes. As a result, the optimized sample can produce a photocurrent more than two times that of WO3. The simple post-treatment provides a viable and cost-effective strategy for promoting the photoelectric properties of photoanodes.
      Citation: Catalysts
      PubDate: 2020-05-18
      DOI: 10.3390/catal10050556
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 557: Mechanistic Insights into Visible
           Light-Induced Direct Hydroxylation of Benzene to Phenol with Air and Water
           over Pt-Modified WO3 Photocatalyst

    • Authors: Yuya Kurikawa, Masahiro Togo, Michihisa Murata, Yasuaki Matsuda, Yoshihisa Sakata, Hisayoshi Kobayashi, Shinya Higashimoto
      First page: 557
      Abstract: Activation of C(sp2)-H in aromatic molecules such as benzene is one of the challenging reactions. The tungsten trioxide supported Pt nanoparticles (Pt-WO3) exhibited hydroxylation of benzene in the presence of air and H2O under visible-light (420 < λ < 540 nm) irradiation. The photocatalytic activities (yields and selectivity of phenol) were studied under several experimental conditions. Furthermore, investigations of mechanistic insight into hydroxylation of benzene have been carried out by analyses with apparent quantum yields (AQY), an H218O isotope-labeling experiment, kinetic isotope effects (KIE), electrochemical measurements and density functional theory (DFT) calculations. It was proposed that dissociation of the O–H bond in H2O is the rate-determining step. Furthermore, the substitution of the OH derived from H2O with H abstracted from benzene by photo-formed H2O2 indicated a mechanism involving a push-pull process for the hydroxylation of benzene into phenol.
      Citation: Catalysts
      PubDate: 2020-05-18
      DOI: 10.3390/catal10050557
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 558: Interaction of SO2 with the Platinum (001),
           (011), and (111) Surfaces: A DFT Study

    • Authors: Ungerer, Santos-Carballal, Cadi-Essadek, van Sittert, de Leeuw
      First page: 558
      Abstract: Given the importance of SO2 as a pollutant species in the environment and its role in the hybrid sulphur (HyS) cycle for hydrogen production, we carried out a density functional theory study of its interaction with the Pt (001), (011), and (111) surfaces. First, we investigated the adsorption of a single SO2 molecule on the three Pt surfaces. On both the (001) and (111) surfaces, the SO2 had a S,O-bonded geometry, while on the (011) surface, it had a co-pyramidal and bridge geometry. The largest adsorption energy was obtained on the (001) surface (Eads = −2.47 eV), followed by the (011) surface (Eads = −2.39 and −2.28 eV for co-pyramidal and bridge geometries, respectively) and the (111) surface (Eads = −1.85 eV). When the surface coverage was increased up to a monolayer, we noted an increase of Eads/SO2 for all the surfaces, but the (001) surface remained the most favourable overall for SO2 adsorption. On the (111) surface, we found that when the surface coverage was θ > 0.78, two neighbouring SO2 molecules reacted to form SO and SO3. Considering the experimental conditions, we observed that the highest coverage in terms of the number of SO2 molecules per metal surface area was (111) > (001) > (011). As expected, when the temperature increased, the surface coverage decreased on all the surfaces, and gradual desorption of SO2 would occur above 500 K. Total desorption occurred at temperatures higher than 700 K for the (011) and (111) surfaces. It was seen that at 0 and 800 K, only the (001) and (111) surfaces were expressed in the morphology, but at 298 and 400 K, the (011) surface was present as well. Taking into account these data and those from a previous paper on water adsorption on Pt, it was evident that at temperatures between 400 and 450 K, where the HyS cycle operates, most of the water would desorb from the surface, thereby increasing the SO2 concentration, which in turn may lead to sulphur poisoning of the catalyst.
      Citation: Catalysts
      PubDate: 2020-05-18
      DOI: 10.3390/catal10050558
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 559: Oxidative Dehydrogenation of Methane When
           Using TiO2- or WO3-Doped Sm2O3 in the Presence of Active Oxygen Excited
           with UV-LED

    • Authors: Sugiyama, Hayashi, Okitsu, Shimoda, Katoh, Furube, Kato, Ninomiya
      First page: 559
      Abstract: There are active oxygen species that contribute to oxidative coupling or the partial oxidation during the oxidative dehydrogenation of methane when using solid oxide catalysts, and those species have not been definitively identified. In the present study, we clarify which of the active oxygen species affect the oxidative dehydrogenation of methane by employing photo-catalysts such as TiO2 or WO3, which generate active oxygen from UV-LED irradiation conditions under an oxygen flow. These photo-catalysts were studied in combination with Sm2O3, which is a methane oxidation coupling catalyst. For this purpose, we constructed a reaction system that could directly irradiate UV-LED to a solid catalyst via a normal fixed-bed continuous-flow reactor operated at atmospheric pressure. Binary catalysts prepared from TiO2 or WO3 were either supported on or kneaded with Sm2O3 in the present study. UV-LED irradiation clearly improved the partial oxidation from methane to CO and/or slightly improved the oxidative coupling route from methane to ethylene when binary catalysts consisting of Sm2O3 and TiO2 are used, while negligible UV-LED effects were detected when using Sm2O3 and WO3. These results indicate that with UV-LED irradiation the active oxygen of O2- from TiO2 certainly contributes to the activation of methane during the oxidative dehydrogenation of methane when using Sm2O3, while the active oxygen of H2O2 from WO3 under the same conditions afforded only negligible effects on the activation of methane.
      Citation: Catalysts
      PubDate: 2020-05-18
      DOI: 10.3390/catal10050559
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 560: TiO2 and Active Coated Glass
           Photodegradation of Ibuprofen

    • Authors: Khalaf, Shoqeir, Lelario, Scrano, Bufo, Karaman
      First page: 560
      Abstract: Commercial non-steroidal anti-inflammatory drugs (NSAIDs) are considered as toxic to the environment since they induce side effects when consumed by humans or aquatic life. Ibuprofen is a member of the NSAID family and is widely used as an anti-inflammatory and painkiller agent.Photolysis is a potentially important method of degradation for several emerging contaminants, and individual compounds can undergo photolysis to various degrees, depending on their chemical structure. The efficiency oftitanium dioxide (TiO2) and photocatalysis was investigated for the removal of ibuprofen from the aquatic environment, and the performance of these different processes was evaluated. In heterogeneous photocatalysis, two experiments were carried out using TiO2 as (i) dispersed powder, and (ii) TiO2 immobilized on the active surface of commercial coated glass.The kinetics of each photoreaction was determined, and the identification of the photoproducts was carried out by liquid chromatography coupled with Fourier-transform ion cyclotron resonance mass spectrometry (LC-FTICR MS). The overall results suggest that the TiO2 active thin layer immobilized on the glass substrate can avoid recovery problems related to the use of TiO2 powder in heterogeneous photocatalysis and may be a promising tool toward protecting the environment from emerging contaminants such as ibuprofen and its derivatives.
      Citation: Catalysts
      PubDate: 2020-05-18
      DOI: 10.3390/catal10050560
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 561: Contrasting Effects of Potassium Addition
           on M3O4 (M = Co, Fe, and Mn) Oxides during Direct NO Decomposition
           Catalysis

    • Authors: Torin C. Peck, Charles A. Roberts, Gunugunuri K. Reddy
      First page: 561
      Abstract: While the promotional effect of potassium on Co3O4 NO decomposition catalytic performance is established in the literature, it remains unknown if K is also a promoter of NO decomposition over similar simple first-row transition metal spinels like Mn3O4 and Fe3O4. Thus, potassium was impregnated (0.9–3.0 wt.%) on Co3O4, Mn3O4, and Fe3O4 and evaluated for NO decomposition reactivity from 400–650 °C. The activity of Co3O4 was strongly dependent on the amount of potassium present, with a maximum of ~0.18 [(µmol NO to N2) g−1 s−1] at 0.9 wt.% K. Without potassium, Fe3O4 exhibited deactivation with time-on-stream due to a non-catalytic chemical reaction with NO forming α-Fe2O3 (hematite), which is inactive for NO decomposition. Potassium addition led to some stabilization of Fe3O4, however, γ-Fe2O3 (maghemite) and a potassium–iron mixed oxide were also formed, and catalytic activity was only observed at 650 °C and was ~50× lower than 0.9 wt.% K on Co3O4. The addition of K to Mn3O4 led to formation of potassium–manganese mixed oxide phases, which became more prevalent after reaction and were nearly inactive for NO decomposition. Characterization of fresh and spent catalysts by scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDX), in situ NO adsorption Fourier transform infrared spectroscopy, temperature programmed desorption techniques, X-ray powder diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) revealed the unique potassium promotion of Co3O4 for NO decomposition arises not only from modification of the interaction of the catalyst surface with NOx (increased potassium-nitrite formation), but also from an improved ability to desorb oxygen as product O2 while maintaining the integrity and purity of the spinel phase.
      Citation: Catalysts
      PubDate: 2020-05-19
      DOI: 10.3390/catal10050561
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 562: α-Functionalization of Imines via Visible
           Light Photoredox Catalysis

    • Authors: Alberto F. Garrido-Castro, M. Carmen Maestro, José Alemán
      First page: 562
      Abstract: The innate electrophilicity of imine building blocks has been exploited in organic synthetic chemistry for decades. Inspired by the resurgence in photocatalysis, imine reactivity has now been redesigned through the generation of unconventional and versatile radical intermediates under mild reaction conditions. While novel photocatalytic approaches have broadened the range and applicability of conventional radical additions to imine acceptors, the possibility to use these imines as latent nucleophiles via single-electron reduction has also been uncovered. Thus, multiple research programs have converged on this issue, delivering creative and practical strategies to achieve racemic and asymmetric a-functionalizations of imines under visible light photoredox catalysis.
      Citation: Catalysts
      PubDate: 2020-05-19
      DOI: 10.3390/catal10050562
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 563: Synthesis and Evaluation of PtNi
           Electrocatalysts for CO and Methanol Oxidation in Low Temperature Fuel
           Cells

    • Authors: Griselda Caballero-Manrique, Julia Garcia-Cardona, Enric Brillas, Juan A. Jaén, John Manuel Sánchez, Pere L. Cabot
      First page: 563
      Abstract: Pt(Ni)/C and PtRu(Ni)/C catalysts were synthesized by electroless deposition of Ni on a carbon dispersion followed by sequenced Pt deposition and spontaneous deposition of Ru species. The structural analyses of the catalysts with 88:12 and 98:2 Pt:Ni atomic ratios pointed out to the formation of small hexagonal Ni crystallites covered by thin cubic Pt surface structures with no evidence about PtNi alloy formation. The onset potentials for CO oxidation on Pt(Ni)/C and PtRu(Ni)/C were about 0.10 and 0.24 V more negative than those of Pt/C, thus indicating their better CO tolerance. The surface Ru species appeared to have the major effect by facilitating the CO removal by the bifunctional mechanism. The onset potential for the methanol oxidation reaction (MOR) of Pt(Ni)/C was about 0.15 V lower than that of Pt/C. The mass and specific activities together with the exchange current densities of the Pt(Ni)/C catalysts were also higher than those of Pt/C, making in evidence their higher activity in front of the MOR. The Tafel slopes for the MOR on Pt(Ni)/C suggested different reaction mechanism than on Pt/C. The electronic (ligand) effect of Ni on Pt was considered the main reason to explain the higher activity of Pt(Ni)/C in front of the CO oxidation and the MOR.
      Citation: Catalysts
      PubDate: 2020-05-19
      DOI: 10.3390/catal10050563
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 564: Pt/Re/CeO2 Based Catalysts for
           CO-Water–Gas Shift Reaction: From Powders to Structured Catalyst

    • Authors: Vincenzo Palma, Fausto Gallucci, Pluton Pullumbi, Concetta Ruocco, Eugenio Meloni, Marco Martino
      First page: 564
      Abstract: This work focuses on the development of a Pt/Re/CeO2-based structured catalyst for a single stage water–gas shift process. In the first part of the work, the activity in water–gas shift reactions was evaluated for three Pt/Re/CeO2-based powder catalysts, with Pt/Re ratio equal to 1/1, 1/2 ad 2/1 and total loading ≈ 1 wt%. The catalysts were prepared by sequential dry impregnation of commercial ceria, with the salts precursors of rhenium and platinum; the activity tests were carried out by feeding a reacting mixture with a variable CO/H2O ratio, equal to 7/14, 7/20 and 7/24, and the kinetic parameters were determined. The model which better described the experimental results involves the water–gas shift (WGS) reaction and CO as well as CO2 methanation. The preliminary tests showed that the catalyst with the Pt/Re ratio equal to 2/1 had the best performance, and this was selected for further investigations. In the second part of the work, a structured catalyst, obtained by coating a commercial aluminum alloy foam with the chosen catalytic formulation, was prepared and tested in different reaction conditions. The results demonstrated that a single stage water–gas shift process is achievable, obtaining a hydrogen production rate of 18.7 mmol/min at 685 K, at τ = 53 ms, by feeding a simulated reformate gas mixture (37.61 vol% H2, 9.31 vol% CO2, 9.31 vol% CO, 42.19 vol% H2O, 1.37 vol% CH4).
      Citation: Catalysts
      PubDate: 2020-05-19
      DOI: 10.3390/catal10050564
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 565: Synthesis of DHA/EPA Ethyl Esters via
           Lipase-Catalyzed Acidolysis Using Novozym® 435: A Kinetic Study

    • Authors: Chia-Hung Kuo, Chun-Yung Huang, Chien-Liang Lee, Wen-Cheng Kuo, Shu-Ling Hsieh, Chwen-Jen Shieh
      First page: 565
      Abstract: DHA/EPA ethyl ester is mainly used in the treatment of arteriosclerosis and hyperlipidemia. In this study, DHA+EPA ethyl ester was synthesized via lipase-catalyzed acidolysis of ethyl acetate (EA) with DHA+EPA concentrate in n-hexane using Novozym® 435. The DHA+EPA concentrate (in free fatty acid form), contained 54.4% DHA and 16.8% EPA, was used as raw material. A central composite design combined with response surface methodology (RSM) was used to evaluate the relationship between substrate concentrations and initial rate of DHA+EPA ethyl ester production. The results indicated that the reaction followed the ordered mechanism and as such, the ordered mechanism model was used to estimate the maximum reaction rate (Vmax) and kinetic constants. The ordered mechanism model was also combined with the batch reaction equation to simulate and predict the conversion of DHA+EPA ethyl ester in lipase-catalyzed acidolysis. The integral equation showed a good predictive relationship between the simulated and experimental results. 88–94% conversion yields were obtained from 100–400 mM DHA+EPA concentrate at a constant enzyme activity of 200 U, substrate ratio of 1:1 (DHA+EPA: EA), and reaction time of 300 min.
      Citation: Catalysts
      PubDate: 2020-05-19
      DOI: 10.3390/catal10050565
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 566: Promoting Effect of Ti Species in
           MnOx-FeOx/Silicalite-1 for the Low-Temperature NH3-SCR Reaction

    • Authors: Jialiang Gu, Rudi Duan, Weibin Chen, Yan Chen, Lili Liu, Xidong Wang
      First page: 566
      Abstract: Manganese and iron oxides catalysts supported on silicalite-1 and titanium silicalite-1 (TS-1) are synthesized by the wet impregnation method for the selective catalytic reduction (SCR) of NOx with NH3 (NH3-SCR), respectively. The optimized catalyst demonstrates an increased NOx conversion efficiency of 20% below 150 °C, with a space velocity of 18,000 h−1, which can be attributed to the incorporation of Ti species. The presence of Ti species enhances surface acidity and redox ability of the catalyst without changing the structure of supporter. Moreover, further researches based on in situ NH3 adsorption reveal that Lewis acid sites linked to Mn4+ on the surface have a huge influence on the improvement of denitration efficiency of the catalyst at low temperatures.
      Citation: Catalysts
      PubDate: 2020-05-19
      DOI: 10.3390/catal10050566
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 567: CO2 Conversion to Methanol over Novel
           Carbon Nanofiber-Based Cu/ZrO2 Catalysts—A Kinetics Study

    • Authors: Israf Ud Din, Maizatul S. Shaharun, Abdul Naeem, Mshari A. Alotaibi, Abdulrahman I. Alharthi, Qazi Nasir
      First page: 567
      Abstract: Ongoing industrialization has deteriorated the global environment. Global warming is a human-induced issue affecting the environment. The alarming increase in CO2 emissions is among the major contributors to global warming. The conversion of CO2 to methanol is an economically viable and environmentally friendly solution to mitigate its concentration. Here, hydrogenation of CO2 was studied over carbon nanofiber-based Cu/ZrO2 catalysts. Kinetics investigations were carried out for the reaction. Overall, kinetics data indicated that CO2 conversion follows a pseudo-first-order reaction. The kinetics studies were further modeled by using an artificial neural network, which supported the experimental kinetics study.
      Citation: Catalysts
      PubDate: 2020-05-19
      DOI: 10.3390/catal10050567
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 568: Enantioselective Epoxidation by
           Flavoprotein Monooxygenases Supported by Organic Solvents

    • Authors: Daniel Eggerichs, Carolin Mügge, Julia Mayweg, Ulf-Peter Apfel, Dirk Tischler
      First page: 568
      Abstract: Styrene and indole monooxygenases (SMO and IMO) are two-component flavoprotein monooxygenases composed of a nicotinamide adenine dinucleotide (NADH)-dependent flavin adenine dinucleotide (FAD)-reductase (StyB or IndB) and a monooxygenase (StyA or IndA). The latter uses reduced FAD to activate oxygen and to oxygenate the substrate while releasing water. We circumvented the need for the reductase by direct FAD reduction in solution using the NAD(P)H-mimic 1-benzyl-1,4-dihydronicotinamide (BNAH) to fuel monooxygenases without NADH requirement. Herein, we report on the hitherto unknown solvent tolerance for the indole monooxygenase from Gemmobacter nectariphilus DSM15620 (GnIndA) and the styrene monooxygenase from Gordonia rubripertincta CWB2 (GrStyA). These enzymes were shown to convert bulky and rather hydrophobic styrene derivatives in the presence of organic cosolvents. Subsequently, BNAH-driven biotransformation was furthermore optimized with regard to the applied cosolvent and its concentration as well as FAD and BNAH concentration. We herein demonstrate that GnIndA and GrStyA enable selective epoxidations of allylic double bonds (up to 217 mU mg−1) in the presence of organic solvents such as tetrahydrofuran, acetonitrile, or several alcohols. Notably, GnIndA was found to resist methanol concentrations up to 25 vol.%. Furthermore, a diverse substrate preference was determined for both enzymes, making their distinct use very interesting. In general, our results seem representative for many IMOs as was corroborated by in silico mutagenetic studies.
      Citation: Catalysts
      PubDate: 2020-05-19
      DOI: 10.3390/catal10050568
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 569: NiO, Fe2O3, and MoO3 Supported over SiO2
           Nanocatalysts for Asphaltene Adsorption and Catalytic Decomposition:
           Optimization through a Simplex–Centroid Mixture Design of Experiments

    • Authors: Daniela Arias-Madrid, Oscar E. Medina, Jaime Gallego, Sócrates Acevedo, Alexander A. Correa-Espinal, Farid B. Cortés, Camilo A. Franco
      First page: 569
      Abstract: The main objective of this study was to evaluate the effect of functionalized silica nanoparticles with Fe2O3, NiO, and MoO3 metal oxides on the decomposition of asphaltenes, through an experimental simplex–centroid mixture design for surface area, asphaltene adsorption, and activation energy. The experimental nanoparticle surface area was measured by adsorption of N2. Adsorption isotherms, and the subsequent oxidation process of asphaltenes, were performed through batch adsorption experiments and thermogravimetric analysis, respectively. Among the monometallic systems, the presence of iron increased the affinity between the nanoparticle and the asphaltenes, and a higher metal oxide load increased the adsorptive capacity of the system. For the pairings evaluated, there was better synergy between iron and nickel, with the participation of the former being slightly superior. In the mixture design that included three transition elements, the participation of molybdenum was not significant, and the adsorption of asphaltenes was dominated by the active sites formed by the other two transition element oxides. The mixture design created to minimize the activation energy showed that the interaction of the three transition elements is important and can be evidenced in the interaction coefficients.
      Citation: Catalysts
      PubDate: 2020-05-19
      DOI: 10.3390/catal10050569
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 570: Critical Issues and Guidelines to Improve
           the Performance of Photocatalytic Polymeric Membranes

    • Authors: Marta Romay, Nazely Diban, Maria J. Rivero, Ane Urtiaga, Inmaculada Ortiz
      First page: 570
      Abstract: Photocatalytic membrane reactors (PMR), with immobilized photocatalysts, play an important role in process intensification strategies; this approach offers a simple solution to the typical catalyst recovery problem of photocatalytic processes and, by simultaneous filtration and photocatalysis of the aqueous streams, facilitates clean water production in a single unit. The synthesis of polymer photocatalytic membranes has been widely explored, while studies focused on ceramic photocatalytic membranes represent a minority. However, previous reports have identified that the successful synthesis of polymeric photocatalytic membranes still faces certain challenges that demand further research, e.g., (i) reduced photocatalytic activity, (ii) photocatalyst stability, and (iii) membrane aging, to achieve technological competitiveness with respect to suspended photocatalytic systems. The novelty of this review is to go a step further to preceding literature by first, critically analyzing the factors behind these major limitations and second, establishing useful guidelines. This information will help researchers in the field in the selection of the membrane materials and synthesis methodology for a better performance of polymeric photocatalytic membranes with targeted functionality; special attention is focused on factors affecting membrane aging and photocatalyst stability.
      Citation: Catalysts
      PubDate: 2020-05-19
      DOI: 10.3390/catal10050570
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 571: Pd-Catalyzed Intermolecular Dehydrogenative
           Heck Reactions of Five-Membered Heteroarenes

    • Authors: Jean Le Bras, Jacques Muzart
      First page: 571
      Abstract: The Pd-mediated cross-coupling of (hetero)arenes with alkenes may be an effective method for the formation of a C–C bond from two C–H bonds. Discovered by Fujiwara and co-workers in 1967, this reaction led to a number of reports that we firstly highlighted in 2011 (review with references till June 2010) and for which, we retained the name “dehydrogenative Heck reaction”. The topic, especially the reactions of five-membered heteroarenes, has been the subject of intensive research over the last ten years. The present review is limited to these dehydrogenative Heck reactions published since 2010, underlining the progress of the procedures.
      Citation: Catalysts
      PubDate: 2020-05-19
      DOI: 10.3390/catal10050571
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 572: Identification of Main Active Sites and the
           Role of NO2 on NOx Reduction with CH4 over In/BEA Catalyst: A
           Computational Study

    • Authors: Erhao Gao, Hua Pan, Li Wang, Yao Shi, Jun Chen
      First page: 572
      Abstract: The main active sites and the catalytic process in selective catalytic reduction of NOx by CH4 (CH4-SCR) on In/BEA catalyst were investigated by density functional theory (DFT) using a periodic model. The [InO]+ and [InOH]2+ moieties were constructed in the channel of periodic BEA zeolite representing the Lewis and Brønsted acid sites. The electronic structures [InO]+ and [InOH]2+ were analyzed, and it was found that the [InO]+ group were the main active sites for CH4 activation and NO/NO2 adsorption in the CH4-SCR process. CH4 molecules could be activated on the O site of the [InO]+ group in In/BEA, which was resulted from the strong interactions between the C-p orbital of the CH4 molecule and the O-p orbital of the [InO]+ group. CH4 activation was the initial step in CH4-SCR on In/BEA catalyst. NO2 molecules were essential in the SCR process, and they could be produced by NO reacting with gaseous O2 or the O atom of the [InO]+ group. The presence of NO2 could facilitate the key intermediate nitromethane (CH3NO2) formation and lower the reaction barrier in the SCR process.
      Citation: Catalysts
      PubDate: 2020-05-19
      DOI: 10.3390/catal10050572
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 573: Solar Degradation of Sulfamethazine Using
           rGO/Bi Composite Photocatalysts

    • Authors: María Fernández-Perales, Marisa Rozalen, Manuel Sánchez-Polo, José Rivera-Utrilla, María Victoria López-Ramón, Miguel A. Álvarez
      First page: 573
      Abstract: Heterogeneous photocatalysts for water decontamination were obtained by the optimized synthesis of bismuth-functionalized reduced graphene oxide (rGO/Bi) using the Hummer method and microwave treatment. Sulfamethazine (SMZ) was used as model pollutant to evaluate the photocatalytic efficacy. Photocatalysts were characterized by VP-SEM, HRTEM, XDR, XPS, RAMAN, and FTIR analyses, which confirmed the effective reduction of GO to rGO and the presence of bismuth as a crystalline phase of Bi2O3 polydispersed on the surface. Their performance was influenced by the rGO/Bi ratio, microwave temperature, and treatment time. The as-obtained 5%rGO/Bi composite had the highest photocatalytic activity for SMZ degradation under visible light irradiation (λ > 400 nm), achieving 100% degradation after only 2 h of treatment. The degradation yield decreased with higher percentages of rGO. Accordingly, the rGO/Bi catalysts efficiently removed SMZ, showing a high photocatalytic activity, and remained unchanged after three treatment cycles; furthermore, cytotoxicity tests demonstrated the nontoxicity of the aqueous medium after SMZ degradation. These findings support the potential value of these novel composites as photocatalysts to selectively remove pollutants in water treatment plants.
      Citation: Catalysts
      PubDate: 2020-05-20
      DOI: 10.3390/catal10050573
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 574: Adsorption and Photocatalytic Study of
           Phenol Using Composites of Activated Carbon Prepared from Onion Leaves
           (Allium fistulosum) and Metallic Oxides (ZnO and TiO2)

    • Authors: Diego Felipe Hernández-Barreto, Jenny Paola Rodriguez-Estupiñán, Juan Carlos Moreno-Piraján, Rocío Sierra Ramírez, Liliana Giraldo
      First page: 574
      Abstract: The aim of this study was to evaluate and compare the adsorption and photocatalytic activity of activated carbon-based photocatalysts. Titanium dioxide (TiO2) and zinc oxide (ZnO) were chosen as semiconductors to prepare composites with activated carbon by the wet impregnation method. Activated carbon was prepared using as starting material onion leaves (Allium fistulosum) and as activating agent phosphoric acid (H3PO4). Photooxidation and batch adsorption of phenol was studied to compare the efficiency of the materials prepared. The results showed that the composite AC–TiO2 has a greater photocatalytic activity and a better adsorption capacity compared to AC–ZnO composite.
      Citation: Catalysts
      PubDate: 2020-05-20
      DOI: 10.3390/catal10050574
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 575: Trimesoyl Chloride-Melamine Copolymer-TiO2
           Nanocomposites as High-Performance Visible-Light Photocatalysts for
           Volatile Organic Compound Degradation

    • Authors: Luqian Zhang, Chen Wang, Jing Sun, Zhengkai An
      First page: 575
      Abstract: Benzene is a typical volatile organic compound (VOC) and is found widely in industrial waste gases. In this study, trimesoyl chloride-melamine copolymer (TMP)-TiO2 nanocomposites with excellent photocatalytic efficiency in visible-light degradation of gas-phase benzene were synthesized via an in situ hydrothermal synthesis. The optimal conditions for TMP-TiO2 nanocomposite synthesis were determined by orthogonal experiments. The structural, physiochemical, and optoelectronic properties of the samples were studied by various analytical techniques. Ultraviolet-visible diffuse reflectance spectroscopy and surface photovoltage spectra showed that the positions of the light-absorbance edges of the TMP-TiO2 nanocomposites were sharply red-shifted to the visible region relative to those of unmodified TiO2. The most efficient TMP-TiO2 nanocomposite was used for photocatalytic oxidative degradation of gas-phase benzene (initial concentration 230 mg m−3) under visible-light irradiation (380–800 nm); the degradation rate was 100% within 180 min. Under the same reaction conditions, the degradation rates of unmodified TiO2 (hydrothermally synthesized TiO2) and commercial material Degussa P25 were 19% and 23.6%, respectively. This is because the Ti–O–N and Ti–O–C bonds in TMP-modified TiO2 reduce the band gap of TMP-TiO2. The amide bonds in the TMP decrease the TiO2 nanoparticle size and thus increased the specific surface area. The conjugated structures in the TMP provide abundant active sites for trapping photogenerated electrons and promote the separation and transfer of photogenerated electrons and holes.
      Citation: Catalysts
      PubDate: 2020-05-20
      DOI: 10.3390/catal10050575
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 576: Catalytic Applications of CeO2-Based
           Materials

    • Authors: Antonio Vita
      First page: 576
      Abstract: Among the metal-oxides, ceria represents one of the most promising materials for chemical transformations mainly for environmental applications and energy conversion systems [...]
      Citation: Catalysts
      PubDate: 2020-05-20
      DOI: 10.3390/catal10050576
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 577: New Experiment of Diesel Exhaust Treatment
           by Atmospheric Pressure Plasma–Wood Fiber Combination

    • Authors: Xiurong Guo, Khanh Hop Ha, Danfeng Du
      First page: 577
      Abstract: Herein, a novel process of diesel exhaust purification by non-thermal plasma combined with wood fiber has been investigated to understand the effect of purification efficiency on the emission. The dielectric barrier discharge (DBD) and wood fiber (WF) improved removal efficiency of nitrogen oxide (NOx) owing to the positive activity of oxygen-containing functional groups (such as O–H groups or C–O groups) on the wood surface, which promoted the removal of NOx by 10%–13%. The mechanism to remove NOx in the presence of wood fibers was also deduced through FTIR spectra. When carbon black was loaded on the wood fiber, there was simultaneous removal of carbon soot and NOX. Although complete purification was not achieved, a high purification efficiency was obtained under the conditions of room temperature and no catalysts. These advantages highlight the importance of use of wood and non-thermal plasma (NTP), and this research work opens new avenues in the field of emissions treatment.
      Citation: Catalysts
      PubDate: 2020-05-21
      DOI: 10.3390/catal10050577
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 578: POM@MOF Hybrids: Synthesis and Applications

    • Authors: Jiamin Sun, Sara Abednatanzi, Pascal Van Der Voort, Ying-Ya Liu, Karen Leus
      First page: 578
      Abstract: The hybrid materials that are created by supporting or incorporating polyoxometalates (POMs) into/onto metal–organic frameworks (MOFs) have a unique set of properties. They combine the strong acidity, oxygen-rich surface, and redox capability of POMs, while overcoming their drawbacks, such as difficult handling, a low surface area, and a high solubility. MOFs are ideal hosts because of their high surface area, long-range ordered structure, and high tunability in terms of the pore size and channels. In some cases, MOFs add an extra dimension to the functionality of hybrids. This review summarizes the recent developments in the field of POM@MOF hybrids. The most common applied synthesis strategies are discussed, together with major applications, such as their use in catalysis (organocatalysis, electrocatalysis, and photocatalysis). The more than 100 papers on this topic have been systematically summarized in a handy table, which covers almost all of the work conducted in this field up to now.
      Citation: Catalysts
      PubDate: 2020-05-21
      DOI: 10.3390/catal10050578
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 579: One-Step Synthesis of b-N-TiO2/C
           Nanocomposites with High Visible Light Photocatalytic Activity to Degrade
           Microcystis aeruginosa

    • Authors: Xu Zhang, Min Cai, Naxin Cui, Guifa Chen, Guoyan Zou, Li Zhou
      First page: 579
      Abstract: Black TiO2 with doped nitrogen and modified carbon (b-N-TiO2/C) were successfully prepared by sol-gel method in the presence of urea as a source of nitrogen and carbon. The photocatalysts were characterized by field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman, electron paramagnetic resonance (EPR), and UV-vis diffuse reflectance spectra (DRS). The doped nitrogen, introduced defects, and modified carbon played a synergistic role in enhancing photocatalytic activity of b-N-TiO2/C for the degradation of chlorophyll-a in algae cells. The sample, with a proper amount of phase composition and oxygen vacancies, showed the highest efficiency to degrade chlorophyll-a, and the addition of H2O2 promoted this photocatalysis degradation. Based on the trapping experiments and electron spin resonance (ESR) signals, a photocatalytic mechanism of b-N-TiO2/C was proposed. In the photocatalytic degradation of chlorophyll-a, the major reactive species were identified as OH and O2-. This research may provide new insights into the photocatalytic inactivation of algae cells by composite photocatalysts.
      Citation: Catalysts
      PubDate: 2020-05-21
      DOI: 10.3390/catal10050579
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 580: Room-Temperature Nitrophenol Reduction over
           Ag–CeO2 Catalysts: The Role of Catalyst Preparation Method

    • Authors: Mariia Chernykh, Natalia Mikheeva, Vladimir Zaikovskii, Mikhail Salaev, Leonarda F. Liotta, Grigory Mamontov
      First page: 580
      Abstract: Ag–CeO2 catalysts (20 mol % Ag) were synthesized using different techniques (co-precipitation, impregnation, and impregnation of pre-reduced ceria), characterized by XRD, N2 sorption, TEM, H2-TPR methods, and probed in room-temperature p-nitrophenol reduction into p-aminophenol in aqueous solution at atmospheric pressure. The catalyst preparation method was found to determine the textural characteristics, the oxidation state and distribution of silver and, hence, the catalytic activity in the p-nitrophenol reduction. The impregnation technique was the most favorable for the formation over the ceria surface of highly dispersed silver species that are active in the p-nitrophenol reduction (the first-order rate constant k = 0.656 min−1).
      Citation: Catalysts
      PubDate: 2020-05-21
      DOI: 10.3390/catal10050580
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 581: Sustainable Catalytic Conversion of Biomass
           for the Production of Biofuels and Bioproducts

    • Authors: Gabriel Morales, Jose Iglesias, Juan A. Melero
      First page: 581
      Abstract: Biomass, in its many forms—oils and fats, lignocellulose, algae, etc [...]
      Citation: Catalysts
      PubDate: 2020-05-22
      DOI: 10.3390/catal10050581
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 582: High Temperature Water Gas Shift Reactivity
           of Novel Perovskite Catalysts

    • Authors: Janko Popovic, Lorenz Lindenthal, Raffael Rameshan, Thomas Ruh, Andreas Nenning, Stefan Löffler, Alexander Karl Opitz, Christoph Rameshan
      First page: 582
      Abstract: High temperature water-gas shift (HT-WGS) is an industrially highly relevant reaction. Moreover, climate change and the resulting necessary search for sustainable energy sources are making WGS and reverse-WGS catalytic key reactions for synthetic fuel production. Hence, extensive research has been done to develop improved or novel catalysts. An extremely promising material class for novel highly active HT-WGS catalysts with superior thermal stability are perovskite-type oxides. With their large compositional flexibility, they enable new options for rational catalyst design. Particularly, both cation sites (A and B in ABO3) can be doped with promoters or catalytically active elements. Additionally, B-site dopants are able to migrate to the surface under reducing conditions (a process called exsolution), forming catalytically active nanoparticles and creating an interface that can strongly boost catalytic performance. In this study, we varied A-site composition and B-site doping (Ni, Co), thus comparing six novel perovskites and testing them for their HT-WGS activity: La0.9Ca0.1FeO3-δ, La0.6Ca0.4FeO3-δ, Nd0.9Ca0.1FeO3-δ, Nd0.6Ca0.4FeO3-δ, Nd0.6Ca0.4Fe0.9Ni0.1O3-δ and Nd0.6Ca0.4Fe0.9Co0.1O3-δ. Cobalt and Nickel doping resulted in the highest activity observed in our study, highlighting that doped perovskites are promising novel HT-WGS catalysts. The effect of the compositional variations is discussed considering the kinetics of the two partial reactions of WGS-CO oxidation and water splitting.
      Citation: Catalysts
      PubDate: 2020-05-22
      DOI: 10.3390/catal10050582
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 583: The Effect of CO Partial Pressure on
           Important Kinetic Parameters of Methanation Reaction on Co-Based FTS
           Catalyst Studied by SSITKA-MS and Operando DRIFTS-MS Techniques

    • Authors: Michalis A. Vasiliades, Konstantina K. Kyprianou, Nilenindran S. Govender, Ashriti Govender, Renier Crous, Denzil Moodley, Angelos M. Efstathiou
      First page: 583
      Abstract: A 20 wt% Co-0.05 wt% Pt/γ-Al2O3 catalyst was investigated to obtain a fundamental understanding of the effect of CO partial pressure (constant H2 partial pressure) on important kinetic parameters of the methanation reaction (x vol% CO/25 vol% H2, x = 3, 5 and 7) by performing advanced transient isotopic and operando diffuse reflectance infrared Fourier transform spectroscopy – mass spectrometry (DRIFTS-MS) experiments. Steady State Isotopic Transient Kinetic Analysis (SSITKA) experiments conducted at 1.2 bar, 230 °C after 5 h in CO/H2 revealed that the surface coverages, θCO and θCHx and the mean residence times, τCO, and τCHx (s) of the reversibly adsorbed CO-s and active CHx-s (Cα) intermediates leading to CH4, respectively, increased with increasing CO partial pressure. On the contrary, the apparent activity (keff, s−1) of CHx-s intermediates, turnover frequency (TOF, s−1) of methanation reaction, and the CH4-selectivity (SCH4, %) were found to decrease. Transient isothermal hydrogenation (TIH) following the SSITKA step-gas switch provided important information regarding the reactivity and concentration of active (Cα) and inactive -CxHy (Cβ) carbonaceous species formed after 5 h in the CO/H2 reaction. The latter Cβ species were readily hydrogenated at 230 °C in 50%H2/Ar. The surface coverage of Cβ was found to vary only slightly with increasing CO partial pressure. Temperature-programmed hydrogenation (TPH) following SSITKA and TIH revealed that other types of inactive carbonaceous species (Cγ) were formed during Fischer-Tropsch Synthesis (FTS) and hydrogenated at elevated temperatures (250–550 °C). The amount of Cγ was found to significantly increase with increasing CO partial pressure. All carbonaceous species hydrogenated during TIH and TPH revealed large differences in their kinetics of hydrogenation with respect to the CO partial pressure in the CO/H2 reaction mixture. Operando DRIFTS-MS transient isothermal hydrogenation of adsorbed CO-s formed after 2 h in 5 vol% CO/25 vol% H2/Ar at 200 °C coupled with kinetic modeling (H-assisted CO hydrogenation) provided information regarding the relative reactivity (keff) for CH4 formation of the two kinds of linear-type adsorbed CO-s on the cobalt surface.
      Citation: Catalysts
      PubDate: 2020-05-22
      DOI: 10.3390/catal10050583
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 584: Hydrogenation and Hydrodeoxygenation of
           Oxygen-Substituted Aromatics over Rh/silica: Catechol, Resorcinol and
           Hydroquinone

    • Authors: Kathleen Kirkwood, S. David Jackson
      First page: 584
      Abstract: The hydrogenation and hydrodeoxygenation (HDO) of dihydroxybenzene isomers, catechol (1,2-dihydroxybenzene), resorcinol (1,3-dihydroxybenzene) and hydroquinone (1,4-dihydroxybenzene) was studied in the liquid phase over a Rh/silica catalyst at 303–343 K and 3 barg hydrogen pressure. The following order of reactivity, resorcinol > catechol > hydroquinone (meta > ortho > para) was obtained. Kinetic analysis revealed that catechol had a negative order of reaction whereas both hydroquinone and resorcinol gave positive half-order suggesting that catechol is more strongly adsorbed. Activation energies of ~30 kJ·mol−1 were determined for catechol and hydroquinone, while resorcinol gave a value of 41 kJ·mol−1. Resorcinol, and similarly hydroquinone, gave higher yields of the hydrogenolysis products (cyclohexanol, cyclohexanone and cyclohexane) with a cumulative yield of ~40%. In contrast catechol favoured hydrogenation, specifically to cis-1,2-dihydroxycyclohexane. It is proposed that cis-isomers are formed from hydrogenation of dihydroxycyclohexenes and high selectivity to cis-1,2-dihydroxycyclohexane can be explained by the enhanced stability of 1,2-dihydroxycyclohex-1-ene relative to other cyclohexene intermediates of catechol, resorcinol or hydroquinone. Trans-isomers are not formed by isomerisation of the equivalent cis-dihydroxycyclohexane but by direct hydrogenation of 2/3/4-hydroxycyclohexanone. The higher selectivity to HDO for resorcinol and hydroquinone may relate to the reactive surface cyclohexenes that have a C=C double bond β-γ to a hydroxyl group aiding hydrogenolysis. Using deuterium instead of hydrogen revealed that each isomer had a unique kinetic isotope effect and that HDO to cyclohexane was dramatically affected. The delay in the production of cyclohexane suggest that deuterium acted as an inhibitor and may have blocked the specific HDO site that results in cyclohexane formation. Carbon deposition was detected by temperature programmed oxidation (TPO) and revealed three surface species.
      Citation: Catalysts
      PubDate: 2020-05-22
      DOI: 10.3390/catal10050584
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 585: Effects of Long-Term Supplementation with
           Aluminum or Selenium on the Activities of Antioxidant Enzymes in Mouse
           Brain and Liver

    • Authors: Ilona Sadauskiene, Arunas Liekis, Inga Staneviciene, Rima Naginiene, Leonid Ivanov
      First page: 585
      Abstract: The aim of this study was to investigate the effects of aluminum (Al) or selenium (Se) on the “primary” antioxidant defense system enzymes (superoxide dismutase, catalase, and glutathione reductase) in cells of mouse brain and liver after long-term (8-week) exposure to drinking water supplemented with AlCl3 (50 mg or 100 mg Al/L in drinking water) or Na2SeO3 (0.2 mg or 0.4 mg Se/L in drinking water). Results have shown that a high dose of Se increased the activities of superoxide dismutase and catalase in mouse brain and liver. Exposure to a low dose of Se resulted in an increase in catalase activity in mouse brain, but did not show any statistically significant changes in superoxide dismutase activity in both organs. Meanwhile, the administration of both doses of Al caused no changes in activities of these enzymes in mouse brain and liver. The greatest sensitivity to the effect of Al or Se was exhibited by glutathione reductase. Exposure to both doses of Al or Se resulted in statistically significant increase in glutathione reductase activity in both brain and liver. It was concluded that 8-week exposure to Se caused a statistically significant increase in superoxide dismutase, catalase and glutathione reductase activities in mouse brain and/or liver, however, these changes were dependent on the used dose. The exposure to both Al doses caused a statistically significant increase only in glutathione reductase activity of both organs.
      Citation: Catalysts
      PubDate: 2020-05-23
      DOI: 10.3390/catal10050585
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 586: Synthesis of Titanium Dioxide via
           Surfactant-Assisted Microwave Method for Photocatalytic and Dye-Sensitized
           Solar Cells Applications

    • Authors: Kubiak, Bielan, Bartkowiak, Gabała, Piasecki, Zalas, Zielińska-Jurek, Janczarek, Siwińska-Ciesielczyk, Jesionowski
      First page: 586
      Abstract: Keywords: titania; nanoparticles; surfactants; microwave method; photocatalysis; DSSC
      Citation: Catalysts
      PubDate: 2020-05-23
      DOI: 10.3390/catal10050586
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 587: Particle Number Emissions of a Diesel
           Vehicle during and between Regeneration Events

    • Authors: Barouch Giechaskiel
      First page: 587
      Abstract: All modern diesel vehicles in Europe are equipped with diesel particulate filters (DPFs) and their particle number (PN) emissions at the tailpipe are close to ambient air levels. After the Dieselgate scandal for high NOx emissions of diesel vehicles on the road, the high PN emissions during regeneration events are on the focus. The PN emissions of a diesel vehicle on the road and in the laboratory with or without regeneration events were measured using systems with evaporation tubes and catalytic strippers and counters with lower sizes of 23, 10 and 4 nm. The tests showed significant PN levels only during engine cold starts with a big fraction of sub-23 nm particles during the first minute. After the first seconds the sub-23 nm fraction was negligible. Urea injection at the selective catalytic reduction (SCR) for NOx system did not affect the PN levels and the sub-23 nm fraction. The emissions during regeneration events were higher than the PN limit, but rapidly decreased 2-3 orders of magnitude below the limit after the regeneration. Artificially high sub-10 nm levels were seen during the regeneration (volatile artifact) at the system with the evaporation tube. The regenerations were forced every 100–350 km and the overall emissions including the regeneration events were two to four times lower than the current laboratory PN limit. The results of this study confirmed the efficiency of DPFs under laboratory and on-road driving conditions.
      Citation: Catalysts
      PubDate: 2020-05-23
      DOI: 10.3390/catal10050587
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 588: Development and Optimization of
           Lipase-Catalyzed Synthesis of Phospholipids Containing
           3,4-Dimethoxycinnamic Acid by Response Surface Methodology

    • Authors: Magdalena Rychlicka, Natalia Niezgoda, Anna Gliszczyńska
      First page: 588
      Abstract: The interesterification reaction of egg-yolk phosphatidylcholine (PC) with ethyl ester of 3,4-dimethoxycinnamic acid (E3,4DMCA) catalyzed by Novozym 435 in hexane as a reaction medium was shown to be an effective method for the synthesis of corresponding structured O-methylated phenophospholipids. The effects of substrate molar ratios, time of the reaction and enzyme load on the process of incorporation of 3,4DMCA into PC were evaluated by using the experimental factorial design of three factors and three levels. The results showed that a substrate molar ratio is a crucial variable for the maximization of the synthesis of 3,4-dimethoxycinnamoylated phospholipids. Under optimized parameters of 1/10 substrate molar ratio PC/E3,4DMCA, enzyme load 30% (w/w), hexane as a medium and incubation time of 3 days, the incorporation of aromatic acid into phospholipid fraction reached 21 mol%. The modified phosphatidylcholine (3,4DMCA-PC) and modified lysophosphatidylcholine (3,4DMCA-LPC) were obtained in isolated yields of 3.5% and 27.5% (w/w), respectively. The developed method of phosphatidylcholine interesterification is the first described in the literature dealing with 3,4DMCA and allows us to obtain new O-methylated phenophospholipids with potential applications as food additives or nutraceuticals with pro-health activity.
      Citation: Catalysts
      PubDate: 2020-05-24
      DOI: 10.3390/catal10050588
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 589: CuII- and CoII-Based MOFs:
           {[La2Cu3(µ-H2O)(ODA)6(H2O)3]∙3H2O}n and
           {[La2Co3(ODA)6(H2O)6]∙12H2O}n. The Relevance of Physicochemical
           Properties on the Catalytic Aerobic Oxidation of Cyclohexene

    • Authors: Luis Santibáñez, Néstor Escalona, Julia Torres, Carlos Kremer, Patricio Cancino, Evgenia Spodine
      First page: 589
      Abstract: The aerobic oxidation of cyclohexene was done using the heterometallic metal organic frameworks (MOFs) {[La2Cu3(μ-H2O)(ODA)6(H2O)3]⋅3H2O}n (LaCuODA)) (1) and {[La2Co3(ODA)6(H2O)6]∙12H2O}n (LaCoODA) (2) as catalysts, in solvent free conditions (ODA, oxydiacetic acid). After 24 h of reaction, the catalytic system showed that LaCoODA had a better catalytic performance than that of LaCuODA (conversion 85% and 67%). The structures of both catalysts were very similar, showing channels running along the c axis. The physicochemical properties of both MOFs were determined to understand the catalytic performance. The Langmuir surface area of LaCoODA was shown to be greater than that of LaCuODA, while the acid strength and acid sites were greater for LaCuODA. On the other hand, the redox potential of the active sites was related to CoII/CoIII in LaCoODA and CuII/CuI in LaCuODA. Therefore, it is concluded that the Langmuir surface area and the redox potentials were more important than the acid strength and acid sites of the studied MOFs, in terms of the referred catalytic performance. Finally, the reaction conditions were also shown to play an important role in the catalytic performance of the studied systems. Especially, the type of oxidant and the way to supply it to the reaction medium influenced the catalytic results.
      Citation: Catalysts
      PubDate: 2020-05-25
      DOI: 10.3390/catal10050589
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 590: Higher Activity of Ni/g-Al2O3 over
           Fe/g-Al2O3 and Ru/g-Al2O3 for Catalytic Ammonia Synthesis in Nonthermal
           Atmospheric-Pressure Plasma of N2 and H2

    • Authors: Masakazu Iwamoto, Masataka Horikoshi, Ryu Hashimoto, Kaori Shimano, Tomiko Sawaguchi, Harunobu Teduka, Masahiko Matsukata
      First page: 590
      Abstract: Developing a novel ammonia synthesis process from N2 and H2 is of interest to the catalysis and hydrogen research communities. g-Alumina-supported nickel was determined capable of serving as an efficient catalyst for ammonia synthesis using nonthermal plasma under atmospheric pressure without heating. The catalytic activity was almost unrelated to the crystal structure and the surface area of the alumina carrier. The activity of Ni/Al2O3 was quantitatively compared with that of Fe/Al2O3 and Ru/Al2O3, which contained active metals for the conventional Haber–Bosch process. The activity sequence was Ni/Al2O3 > Al2O3 > Fe/Al2O3 > no additive > Ru/Al2O3, surprisingly indicating that the loading of Fe and Ru decreased the activity of Al2O3. The catalytic activity of Ni/Al2O3 was dependent on the amount of loaded Ni, the calcination temperature, and the reaction time. XRD, visual, and XPS observations of the catalysts before the plasma reaction indicated the generation of NiO and NiAl2O4 on Al2O3, the latter of which was generated upon high-temperature calcination. The NiO species was readily reduced to Ni metal in the plasma reaction, whereas the NiAl2O4 species was difficult to reduce. The catalytic behavior could be attributed to the production of fine Ni metal particles that served as active sites. The PN2/PH2 ratio dependence and rate constants of formation and decomposition of ammonia were finally determined for 5.0 wt % Ni/Al2O3 calcined at 773 K. The ammonia yield was 6.3% at an applied voltage of 6.0 kV, a residence time of reactant gases of 0.12 min, and PH2/PN2 = 1.
      Citation: Catalysts
      PubDate: 2020-05-25
      DOI: 10.3390/catal10050590
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 591: ADMET Polymerization of Dimeric Cinchona
           Squaramides for the Preparation of a Highly Enantioselective Polymeric
           Organocatalyst

    • Authors: Mohammad Shahid Ullah, Sadia Afrin Chhanda, Shinichi Itsuno
      First page: 591
      Abstract: Under the acyclic diene metathesis (ADMET) reaction condition, the C3-vinyl groups of cinchona alkaloids readily react with each other to form a C-C bond. A novel type of cinchona alkaloid polymers was synthesized from dimeric cinchona squaramides using the Hoveyda-Grubbs’ second-generation catalysts (HG2) by means of ADMET reaction. The chiral polymers, containing cinchona squaramide moieties in their main chains, were subsequently employed as catalysts for the enantioselective Michael reaction to give the corresponding chiral adducts in high yields with excellent enantioselectivity and diastereoselectivity. Both enantiomers from the asymmetric Michael reaction were distinctively prepared while using the polymeric catalysts, possessing pseudoenantiomeric structures. The catalysts were readily recovered from the reaction mixture and recycled several times due to the insolubility of the cinchona-based squaramide polymers.
      Citation: Catalysts
      PubDate: 2020-05-25
      DOI: 10.3390/catal10050591
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 592: Bimetallic Metal-Organic Framework Mediated
           Synthesis of Ni-Co Catalysts for the Dry Reforming of Methane

    • Authors: Il Son Khan, Adrian Ramirez, Genrikh Shterk, Luis Garzón-Tovar, Jorge Gascon
      First page: 592
      Abstract: Dry reforming of methane (DRM) involves the conversion of CO2 and CH4, the most important greenhouse gases, into syngas, a stoichiometric mixture of H2 and CO that can be further processed via Fischer–Tropsch chemistry into a wide variety of products. However, the devolvement of the coke resistant catalyst, especially at high pressures, is still hampering commercial applications. One of the relatively new approaches for the synthesis of metal nanoparticle based catalysts comprises the use of metal-organic frameworks (MOFs) as catalyst precursors. In this work we have explored MOF-74/CPO-27 MOFs as precursors for the synthesis of Ni, Co and bimetallic Ni-Co metal nanoparticles. Our results show that the bimetallic system produced through pyrolysis of a Ni-Co@CMOF-74 precursor displays the best activity at moderate pressures, with stable performance during at least 10 h at 700 °C, 5 bar and 33 L·h−1·g−1.
      Citation: Catalysts
      PubDate: 2020-05-25
      DOI: 10.3390/catal10050592
      Issue No: Vol. 10, No. 5 (2020)
       
  • Catalysts, Vol. 10, Pages 593: Effective Interactions of Ag Nanoparticles
           on the Surface of SBA-15 in Performing Deep Desulfurization of Real Diesel
           Fuel

    • Authors: Clenildo de Longe, Rafael Viana Sales, Anne Beatriz Figueira Câmara, Heloise Oliveira Medeiros de Araújo Moura, Enrique Rodríguez-Castellón, Sibele Berenice Castellã Pergher, Leila Maria Aguilera Campos, Maritza Montoya Urbina, Luciene Santos de Carvalho
      First page: 593
      Abstract: SBA-15 materials as-synthesized and impregnated with Ag nanoparticles were applied to perform adsorptive desulfurization of real diesel fuel. High-angle annular dark-field scanning transmission electron microscopy and field-emission scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (HAADF-STEM-EDX and FESEM-EDX) and X-ray photoelectron spectroscopy (XPS) results confirmed that there is uniform distribution of Ag nanodomains on the surface and in the channels of a 2AgSBA-15 (2% Ag) sample. The interaction between sulfur compounds and adsorbent mainly occurred via π-complexation mechanisms, as observed via XPS and equilibrium data. The kinetic results for 2AgSBA-15 were better fitted to the pseudo-second-order model (R2 > 0.9999), indicating that the determining step of the adsorptive process is chemisorption, whereas the equilibrium results were better fitted to the Langmuir model (R2 > 0.9994), thus indicating that the adsorption occurs on the adsorbent surface monolayer with significant adsorption capacity (qm = 20.30 mgS/g), approximately two times greater than that observed for pure SBA-15. The mean desulfurization reached by the adsorbents was up to 86.8% for six recycling steps.
      Citation: Catalysts
      PubDate: 2020-05-25
      DOI: 10.3390/catal10050593
      Issue No: Vol. 10, No. 5 (2020)
       
 
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