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Catalysts, Volume 7, Issue 3 (March 2017)

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Cover Story Density functional theory (DFT) calculations have been used to explore the catalytic potential in [...] Read more.
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Research

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Open AccessArticle Organocatalytic Enantioselective Epoxidation of Some Aryl-Substituted Vinylidenebisphosphonate Esters: On the Way to Chiral Anti-Osteoporosis Drugs
Catalysts 2017, 7(3), 90; doi:10.3390/catal7030090
Received: 18 January 2017 / Revised: 7 March 2017 / Accepted: 13 March 2017 / Published: 20 March 2017
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Abstract
The synthesis of a new class of epoxide derivatives from prochiral vinylidene bisphosphonate (VBP) precursors is reported using hydrogen peroxide as the terminal oxidant. The reaction is carried out using a series of possible organic activators having a basic character, with the best
[...] Read more.
The synthesis of a new class of epoxide derivatives from prochiral vinylidene bisphosphonate (VBP) precursors is reported using hydrogen peroxide as the terminal oxidant. The reaction is carried out using a series of possible organic activators having a basic character, with the best results being observed using quinine and sparteine. These activators not only provide from good to excellent epoxide yields with a large variety of VBPs, but also interesting enantioselectivities in the 67%–96% ee range, at least in the case of the Ph and m-MeO–Ph VBP derivatives, opening the way to a number of chiral anti-osteoporosis potentially active pharmaceutical ingredients. Full article
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Open AccessArticle Stabilization of a Lipolytic Enzyme for Commercial Application
Catalysts 2017, 7(3), 91; doi:10.3390/catal7030091
Received: 26 January 2017 / Revised: 6 March 2017 / Accepted: 10 March 2017 / Published: 21 March 2017
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Abstract
Thermomyces lanouginosa lipase has been used to develop improved methods for carrier-free immobilization, the Cross-Linked Enzyme Aggregates (CLEAs), for its application in detergent products. An activator step has been introduced to the CLEAs preparation process with the addition of Tween 80 as activator
[...] Read more.
Thermomyces lanouginosa lipase has been used to develop improved methods for carrier-free immobilization, the Cross-Linked Enzyme Aggregates (CLEAs), for its application in detergent products. An activator step has been introduced to the CLEAs preparation process with the addition of Tween 80 as activator molecule, in order to obtain a higher number of the individual lipase molecules in the ”open lid” conformation prior to the cross-linking step. A terminator step has been introduced to quench the cross-linking reaction at an optimal time by treatment with an amine buffer in order to obtain smaller and more homogenous cross-linked particles. This improved immobilization method has been compared to a commercially available enzyme and has been shown to be made up of smaller and more homogenous particles with an average diameter of 1.85 ± 0.28 µm which are 129.7% more active than the free enzyme. The CLEAs produced show improved features for commercial applications such as an improved wash performance comparable with the free enzyme, improved stability to proteolysis and a higher activity after long-term storage. Full article
(This article belongs to the Special Issue Immobilized Enzymes: Strategies for Enzyme Stabilization)
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Open AccessArticle Synthesis of Renewable Diesel Range Alkanes by Hydrodeoxygenation of Palmitic Acid over 5% Ni/CNTs under Mild Conditions
Catalysts 2017, 7(3), 81; doi:10.3390/catal7030081
Received: 13 February 2017 / Revised: 5 March 2017 / Accepted: 7 March 2017 / Published: 9 March 2017
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Abstract
Recently, the catalytic upgrading of bio-oil to renewable diesel has been attracting more and more attention. In the current paper, carbon nanotube (CNT)-supported nickel catalysts, namely, 5% Ni/CNTs, were prepared for liquid hydrocarbon production through the deoxygenation of palmitic acid, the model compound
[...] Read more.
Recently, the catalytic upgrading of bio-oil to renewable diesel has been attracting more and more attention. In the current paper, carbon nanotube (CNT)-supported nickel catalysts, namely, 5% Ni/CNTs, were prepared for liquid hydrocarbon production through the deoxygenation of palmitic acid, the model compound of bio-oil under a mild condition of 240 °C reaction temperature and 2 MPa H2 pressure. The experimental results revealed that the main reaction product was pentadecane (yield of 89.64%) at an optimum palmitic acid conversion of 97.25% via the hydrodecarbonylation (HDC) process. The deoxygenation mechanism for palmitic acid conversion was also investigated. This study provides technical parameters and a theoretical basis for further industrialization in the bio-oil upgrading process. Full article
(This article belongs to the Special Issue Catalytic Sustainable Processes in Biorefineries)
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Open AccessArticle Comparison of Efficiencies and Mechanisms of Catalytic Ozonation of Recalcitrant Petroleum Refinery Wastewater by Ce, Mg, and Ce-Mg Oxides Loaded Al2O3
Catalysts 2017, 7(3), 72; doi:10.3390/catal7030072
Received: 21 December 2016 / Revised: 18 February 2017 / Accepted: 21 February 2017 / Published: 24 February 2017
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Abstract
The use of catalytic ozonation processes (COPs) for the advanced treatment of recalcitrant petroleum refinery wastewater (RPRW) is rapidly expanding. In this study, magnesium (Mg), cerium (Ce), and Mg-Ce oxide-loaded alumina (Al2O3) were developed as cost efficient catalysts for
[...] Read more.
The use of catalytic ozonation processes (COPs) for the advanced treatment of recalcitrant petroleum refinery wastewater (RPRW) is rapidly expanding. In this study, magnesium (Mg), cerium (Ce), and Mg-Ce oxide-loaded alumina (Al2O3) were developed as cost efficient catalysts for ozonation treatment of RPRW, having performance metrics that meet new discharge standards. Interactions between the metal oxides and the Al2O3 support influence the catalytic properties, as well as the efficiency and mechanism. Mg-Ce/Al2O3 (Mg-Ce/Al2O3-COP) reduced the chemical oxygen demand by 4.7%, 4.1%, 6.0%, and 17.5% relative to Mg/Al2O3-COP, Ce/Al2O3-COP, Al2O3-COP, and single ozonation, respectively. The loaded composite metal oxides significantly increased the hydroxyl radical-mediated oxidation. Surface hydroxyl groups (–OHs) are the dominant catalytic active sites on Al2O3. These active surface –OHs along with the deposited metal oxides (Mg2+ and/or Ce4+) increased the catalytic activity. The Mg-Ce/Al2O3 catalyst can be economically produced, has high efficiency, and is stable under acidic and alkaline conditions. Full article
(This article belongs to the Special Issue Heterogeneous Catalysis for Environmental Remediation)
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Open AccessArticle Catalytic Transfer Hydrogenation of Biobased HMF to 2,5-Bis-(Hydroxymethyl)Furan over Ru/Co3O4
Catalysts 2017, 7(3), 92; doi:10.3390/catal7030092
Received: 4 March 2017 / Revised: 15 March 2017 / Accepted: 16 March 2017 / Published: 21 March 2017
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Abstract
2,5-Bis-(hydroxymethyl)furan (BHMF) is an important biomass-based platform chemical that can be derived from the hydrogenation of biomass-based 5-hydroxymethylfurfural (HMF). In this paper, the formation of BHMF from HMF via the catalytic transfer hydrogenation (CTH) process, using isopropanol as the hydrogen source and Ru/Co
[...] Read more.
2,5-Bis-(hydroxymethyl)furan (BHMF) is an important biomass-based platform chemical that can be derived from the hydrogenation of biomass-based 5-hydroxymethylfurfural (HMF). In this paper, the formation of BHMF from HMF via the catalytic transfer hydrogenation (CTH) process, using isopropanol as the hydrogen source and Ru/Co3O4 as the catalyst, was studied. The results revealed that the Ru/Co3O4 catalyst displayed a high catalytic efficiency, and that a BHMF yield of up to 82% was obtained at 190 °C in 6 h. Moreover, it was found that the recovered Ru/Co3O4 exhibited a similar catalytic activity to the pristine Ru/Co3O4 catalyst. These results supported the conclusion that the present CTH process is an attractive green route for the synthesis of BHMF from biomass-based HMF. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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Open AccessArticle Biotemplated Mesoporous TiO2/SiO2 Composite Derived from Aquatic Plant Leaves for Efficient Dye Degradation
Catalysts 2017, 7(3), 82; doi:10.3390/catal7030082
Received: 10 January 2017 / Accepted: 7 March 2017 / Published: 9 March 2017
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Abstract
The biotemplating technique is an environmental-protective high-efficiency new technology by which the resulting TiO2 may simultaneously attain the duplication of structure and self-doping elements from biotemplate materials, which is highly desirable for photocatalytic applications. In this paper, aquatic plant leaves—including reed, water hyacinth,
[...] Read more.
The biotemplating technique is an environmental-protective high-efficiency new technology by which the resulting TiO2 may simultaneously attain the duplication of structure and self-doping elements from biotemplate materials, which is highly desirable for photocatalytic applications. In this paper, aquatic plant leaves—including reed, water hyacinth, and duckweed—were used as both templates and silicon precursors to successfully synthesize biomorphic TiO2/SiO2 composite with mesoporous structures. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption–desorption, and UV–visible diffuse reflectance spectra were applied to characterize the microstructures of the samples. The results show that all TiO2/SiO2 composites are mainly composed of an anatase phase with mesoporous structure and possess high specific surface area. Compared with commercial Degussa P25 TiO2, all TiO2/SiO2 samples display intensive light-harvesting efficiency, particularly in the visible light range. The activities were evaluated by using gentian violet as a target for photocatalytic degradation experiments under simulated solar irradiation. The TiO2/SiO2 samples templated by reed and water hyacinth leaves exhibit high activity, while the TiO2/SiO2 samples obtained from duckweed are inferior to P25 in the degradation of gentian violet. A synergistic effect of SiO2 incorporation and structural construction through biotemplating is proposed to be beneficial to photocatalytic activity. Full article
(This article belongs to the Special Issue Heterogeneous Catalysis for Environmental Remediation)
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Open AccessArticle Catalytic Dehydration of Glycerol to Acrolein over a Catalyst of Pd/LaY Zeolite and Comparison with the Chemical Equilibrium
Catalysts 2017, 7(3), 73; doi:10.3390/catal7030073
Received: 9 December 2016 / Revised: 26 January 2017 / Accepted: 13 February 2017 / Published: 25 February 2017
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Abstract
Glycerol dehydration to acrolein was studied with three catalysts using zeolite-Y. This zeolite in its protonic form (HY), with La (LaY) and Pd with La (Pd/LaY), was characterized by X-ray diffraction (XRD), Fourier-transform-infrared spectroscopy (FTIR) with pyridine, BET, Scanning Electron Microscope (SEM)–Energy-Dispersive Spectroscopy
[...] Read more.
Glycerol dehydration to acrolein was studied with three catalysts using zeolite-Y. This zeolite in its protonic form (HY), with La (LaY) and Pd with La (Pd/LaY), was characterized by X-ray diffraction (XRD), Fourier-transform-infrared spectroscopy (FTIR) with pyridine, BET, Scanning Electron Microscope (SEM)–Energy-Dispersive Spectroscopy X-ray (EDS) and the catalytic activity tests were carried out under H2 atmosphere. It was found that La ions exchanged in the zeolite-Y resulted in the improvement of both glycerol conversion and yield to acrolein, also a relatively constant glycerol conversion was achieved up to three hours, due to the presence of Pd on the catalyst and H2 in the feed. The comparison of the calculated and experimental yields obtained from the catalytic tests of the Pd/LaY catalyst indicates a greater activity for the reaction to acrolein than for the reaction to acetol. The calculated equilibrium yields of the dehydration reaction from glycerol to acrolein, acetol, ethanal, methanol, and water and the experimental yields of a Pd/LaY catalyst were compared. Thermodynamically, a complete conversion of glycerol can be achieved since the general system remains exothermic and promotes the path to acetol below 480 K. Above this temperature the system consumes energy and favors the production of acrolein, reaching its maximum concentration at 600 K. Full article
(This article belongs to the Special Issue Catalysis of Biomass-Derived Molecules)
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Open AccessArticle Graphene Oxide-Supported Oxime Palladacycles as Efficient Catalysts for the Suzuki–Miyaura Cross-Coupling Reaction of Aryl Bromides at Room Temperature under Aqueous Conditions
Catalysts 2017, 7(3), 94; doi:10.3390/catal7030094
Received: 25 January 2017 / Revised: 13 February 2017 / Accepted: 16 March 2017 / Published: 22 March 2017
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Abstract
Palladacycles are highly efficient precatalysts in cross-coupling reactions whose immobilization on carbonaceous materials has been hardly studied. Herein, we report a detailed study on the synthesis and characterization of new oxime palladacycle-graphene oxide non-covalent materials along with their catalytic activity in the Suzuki–Miyaura
[...] Read more.
Palladacycles are highly efficient precatalysts in cross-coupling reactions whose immobilization on carbonaceous materials has been hardly studied. Herein, we report a detailed study on the synthesis and characterization of new oxime palladacycle-graphene oxide non-covalent materials along with their catalytic activity in the Suzuki–Miyaura reaction. Catalyst 1-GO, which has been fully characterized by ICP, XPS, TGA, and UV-Vis analyses has been demonstrated to be an efficient catalyst for the Suzuki–Miyaura coupling between aryl bromides and arylboronic acids using very low catalyst loadings (0.002 mol % of Pd) at room temperature under aqueous conditions. Full article
(This article belongs to the Special Issue Suzuki–Miyaura Cross-Coupling Reaction and Potential Applications)
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Open AccessArticle Solvent-Free Biginelli Reactions Catalyzed by Hierarchical Zeolite Utilizing a Ball Mill Technique: A Green Sustainable Process
Catalysts 2017, 7(3), 84; doi:10.3390/catal7030084
Received: 3 February 2017 / Revised: 27 February 2017 / Accepted: 6 March 2017 / Published: 13 March 2017
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Abstract
A sustainable, green one-pot process for the synthesis of dihydropyrimidinones (DHPMs) derivatives by a three-component reaction of β-ketoester derivatives, aldehyde and urea or thiourea over the alkali-treated H-ZSM-5 zeolite under ball-milling was developed. Isolation of the product with ethyl acetate shadowed by vanishing
[...] Read more.
A sustainable, green one-pot process for the synthesis of dihydropyrimidinones (DHPMs) derivatives by a three-component reaction of β-ketoester derivatives, aldehyde and urea or thiourea over the alkali-treated H-ZSM-5 zeolite under ball-milling was developed. Isolation of the product with ethyl acetate shadowed by vanishing of solvent was applied. The hierachical zeolite catalyst (MFI27_6) showed high yield (86%–96%) of DHPMs in a very short time (10–30 min). The recyclability of the catalyst for the subsequent reactions was examined in four subsequent runs. The catalyst was shown to be robust without a detectable reduction in catalytic activity, and high yields of products showed the efficient protocol of the Biginelli reactions. Full article
(This article belongs to the Special Issue Enabling Technologies toward Green Catalysis)
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Open AccessArticle Highly Selective Solid Acid Catalyst H1−xTi2(PO4)3−x(SO4)x for Non-Oxidative Dehydrogenation of Methanol and Ethanol
Catalysts 2017, 7(3), 95; doi:10.3390/catal7030095
Received: 21 February 2017 / Revised: 13 March 2017 / Accepted: 16 March 2017 / Published: 22 March 2017
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Abstract
The conversion of alcohols towards aldehydes in the presence of catalysts by non-oxidative dehydrogenation requires special importance from the perspective of green chemistry. Sodium (Na) super ionic conductor (NASICON)-type hydrogen titanium phosphate sulfate (HTPS; H1−xTi2(PO4)3−
[...] Read more.
The conversion of alcohols towards aldehydes in the presence of catalysts by non-oxidative dehydrogenation requires special importance from the perspective of green chemistry. Sodium (Na) super ionic conductor (NASICON)-type hydrogen titanium phosphate sulfate (HTPS; H1−xTi2(PO4)3−x(SO4)x, x = 0.5–1) catalysts were synthesized by the sol-gel method, characterized by N2 gas sorption, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), NH3 temperature-programmed desorption (NH3-TPD), ultraviolet–visible (UV-VIS) spectroscopy, and their catalytic properties were studied for the non-oxidative dehydrogenation of methanol and ethanol. The ethanol is more reactive than methanol, with the conversion for ethanol exceeding 95% as compared to methanol, where the conversion has a maximum value at 55%. The selectivity to formaldehyde is almost 100% in methanol conversion, while the selectivity to acetaldehyde decreases from 56% to 43% in ethanol conversion, when the reaction temperature is increased from 250 to 400 °C. Full article
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Open AccessArticle Effect of Different Nano-Sized Silica Sols as Supports on the Structure and Properties of Cu/SiO2 for Hydrogenation of Dimethyl Oxalate
Catalysts 2017, 7(3), 75; doi:10.3390/catal7030075
Received: 6 January 2017 / Revised: 15 February 2017 / Accepted: 20 February 2017 / Published: 25 February 2017
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Abstract
Cu/x-SiO2 catalysts with 4, 10, and 20 nm silica sols as supports was produced by ammonia evaporation method and characterized. Different nano-sized silica sols as supports significantly affected the structure and catalytic properties of the copper catalysts for ethylene glycol
[...] Read more.
Cu/x-SiO2 catalysts with 4, 10, and 20 nm silica sols as supports was produced by ammonia evaporation method and characterized. Different nano-sized silica sols as supports significantly affected the structure and catalytic properties of the copper catalysts for ethylene glycol synthesis from dimethyl oxalate. Compared with Cu/20-SiO2 and Cu/4-SiO2 catalysts, the catalytic performance and stability of Cu/10-SiO2 catalyst were greatly enhanced. The Cu/10-SiO2 catalyst showed 99.9% conversion with 94% EG selectivity and a lifetime of over 3080 h if it is calculated by industrial weight liquid hourly space velocity (WLHSV) of 0.5 h−1. The Cu/10-SiO2 catalyst has one of the longest lifetimes among the catalysts and is a good alternative catalyst for this reaction. Improvement in the catalytic performance and stability of Cu/10-SiO2 is attributed to the proper SBET, Dp and larger dispersion of copper. In addition, the supports of Cu/10-SiO2 catalyst have smaller particles than that of Cu/20-SiO2; thus, the migration and growth of copper species in catalysts are restrained during the reaction. Full article
(This article belongs to the Special Issue Mesostructured Materials and Their Catalytic Applications)
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Open AccessFeature PaperArticle Suzuki-Miyaura C-C Coupling Reactions Catalyzed by Supported Pd Nanoparticles for the Preparation of Fluorinated Biphenyl Derivatives
Catalysts 2017, 7(3), 76; doi:10.3390/catal7030076
Received: 20 December 2016 / Revised: 23 February 2017 / Accepted: 24 February 2017 / Published: 28 February 2017
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Abstract
Heterogeneous recyclable catalysts in Suzuki-Miyaura C-C coupling reactions are of great interest in green chemistry as reusable alternatives to homogeneous Pd complexes. Considering the interesting properties of fluorinated compounds for the pharmaceutical industry, as precursors of novel materials, and also as components of
[...] Read more.
Heterogeneous recyclable catalysts in Suzuki-Miyaura C-C coupling reactions are of great interest in green chemistry as reusable alternatives to homogeneous Pd complexes. Considering the interesting properties of fluorinated compounds for the pharmaceutical industry, as precursors of novel materials, and also as components of liquid crystalline media, this present study describes the preparation of different fluorinated biphenyl derivatives by Suzuki-Miyaura coupling reactions catalyzed by a heterogeneous system (G-COOH-Pd-10) based on Pd nanoparticles supported onto COOH-modified graphene. The catalytic activity of the hybrid material G-COOH-Pd-10 has been tested in Suzuki-Miyaura C–C coupling reactions observing excellent versatility and good conversion rates in the reactions of phenylboronic acid, 4-vinylphenylboronic acid, 4-carboxyphenylboronic acid, and 4-fluorophenylboronic acid with 1-bromo-4-fluorobenzene. In addition, the influence of the arylbromide has been studied by carrying out reactions of 4-fluorophenylboronic acid with 1-bromo-2-fluorobenzene, 1-bromo-3-fluorobenzene, 1-bromo-4-fluorobenzene, 2-bromo-5-fluorotoluene, and 2-bromo-4-fluorotoluene. Finally, catalyst recyclability tests show a good degree of reusability of the system based on G-COOH-Pd-10 as the decrease in catalytic activity after five consecutive catalytic cycles in the reaction of 1-bromo-4-fluorobenzene with 4-florophenylboronic acid at 48 hours of reaction is lower than 8% while in the case of reactions at three hours the recyclability of the systems is much lower. Full article
(This article belongs to the Special Issue Suzuki–Miyaura Cross-Coupling Reaction and Potential Applications)
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Open AccessArticle Dendrimer-Stabilized Ru Nanoparticles Immobilized in Organo-Silica Materials for Hydrogenation of Phenols
Catalysts 2017, 7(3), 86; doi:10.3390/catal7030086
Received: 14 November 2016 / Revised: 25 January 2017 / Accepted: 2 March 2017 / Published: 14 March 2017
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Abstract
New hybrid catalysts based on Ru nanoparticles, encapsulated into poly(propylene imine dendrimers), immobilized into silica pores, were synthesized and examined for the hydrogenation of alkyl-substituted phenols. The corresponding alkyl-substituted cyclohexanols were presented as the major reaction products, while incomplete hydrogenation products appeared to
[...] Read more.
New hybrid catalysts based on Ru nanoparticles, encapsulated into poly(propylene imine dendrimers), immobilized into silica pores, were synthesized and examined for the hydrogenation of alkyl-substituted phenols. The corresponding alkyl-substituted cyclohexanols were presented as the major reaction products, while incomplete hydrogenation products appeared to be minor. A competition between the sterical factors of dendrimer-containing carriers and the electronic factors of substrate substituents influenced the hydrogenation rate of the alkyl-substituted phenols. The carrier structure was found to have a significant influence on both the physical and chemical properties of the catalysts and their hydrogenation activity. The synthesized hybrid catalysts appeared to be stable after recycling and could be re-used several times without significant loss of activity. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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Open AccessArticle Polymerization of Alkylsilanes on ZIF-8 to Hierarchical Siloxane Microspheres and Microflowers
Catalysts 2017, 7(3), 77; doi:10.3390/catal7030077
Received: 6 December 2016 / Revised: 28 February 2017 / Accepted: 1 March 2017 / Published: 3 March 2017
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Abstract
The use of metal-organic frameworks (MOFs) in the polymerization field remains comparatively rare up to now, let alone studies on the fabrication of polymer microstructures through a MOFs-catalyzed assembly process. Zeolitic imidazolate framework-8 (ZIF-8), a well-known MOF for its chemical and thermal stabilities,
[...] Read more.
The use of metal-organic frameworks (MOFs) in the polymerization field remains comparatively rare up to now, let alone studies on the fabrication of polymer microstructures through a MOFs-catalyzed assembly process. Zeolitic imidazolate framework-8 (ZIF-8), a well-known MOF for its chemical and thermal stabilities, was used to induce a polymerization reaction of saturated alkylsilanes for the first time. The reaction temperature was found to be critical for morphology control of the polymerized ZIF-siloxane composites. The polymerization of alkylsilanes by ZIF-8 at room temperature resulted in siloxane microspheres while rose petal-like microstructures were obtained at higher temperature. The effects of the reaction time on the structures of the polymerization products were also investigated and the polymerization reaction process was proposed. This work expands the field of MOFs’ applications and develops a reasonable method for the multidimensional assembly of MOFs building blocks into required structures or platforms for designing new kinds of hierarchical morphologies, which to our knowledge has not been previously investigated. Full article
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Open AccessArticle The Role of Ruthenium in CO2 Capture and Catalytic Conversion to Fuel by Dual Function Materials (DFM)
Catalysts 2017, 7(3), 88; doi:10.3390/catal7030088
Received: 7 February 2017 / Revised: 5 March 2017 / Accepted: 14 March 2017 / Published: 17 March 2017
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Abstract
Development of sustainable energy technologies and reduction of carbon dioxide in the atmosphere are the two effective strategies in dealing with current environmental issues. Herein we report a Dual Function Material (DFM) consisting of supported sodium carbonate in intimate contact with dispersed Ru
[...] Read more.
Development of sustainable energy technologies and reduction of carbon dioxide in the atmosphere are the two effective strategies in dealing with current environmental issues. Herein we report a Dual Function Material (DFM) consisting of supported sodium carbonate in intimate contact with dispersed Ru as a promising catalytic solution for combining both approaches. The Ru-Na2CO3 DFM deposited on Al2O3 captures CO2 from a flue gas and catalytically converts it to synthetic natural gas (i.e., methane) using H2 generated from renewable sources. The Ru in the DFM, in combination with H2, catalytically hydrogenates both adsorbed CO2 and the bulk Na2CO3, forming methane. The depleted sites adsorb CO2 through a carbonate reformation process and in addition adsorb CO2 on its surface. This material functions well in O2- and H2O-containing flue gas where the favorable Ru redox property allows RuOx, formed during flue gas exposure, to be reduced during the hydrogenation cycle. As a combined CO2 capture and utilization scheme, this technology overcomes many of the limitations of the conventional liquid amine-based CO2 sorbent technology. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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Open AccessArticle Two-Dimensional Layered Double Hydroxide Derived from Vermiculite Waste Water Supported Highly Dispersed Ni Nanoparticles for CO Methanation
Catalysts 2017, 7(3), 79; doi:10.3390/catal7030079
Received: 9 December 2016 / Accepted: 1 March 2017 / Published: 7 March 2017
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Abstract
Expanded multilayered vermiculite (VMT) was successfully used as catalyst support and Ni/VMT synthesized by microwave irradiation assisted synthesis (MIAS) exhibited excellent performance in our previous work. We also developed a two-dimensional porous SiO2 nanomesh (2D VMT-SiO2) by mixed-acid etching of VMT. Compared with
[...] Read more.
Expanded multilayered vermiculite (VMT) was successfully used as catalyst support and Ni/VMT synthesized by microwave irradiation assisted synthesis (MIAS) exhibited excellent performance in our previous work. We also developed a two-dimensional porous SiO2 nanomesh (2D VMT-SiO2) by mixed-acid etching of VMT. Compared with three-dimensional (3D) MCM-41, 2D VMT-SiO2 as a catalyst support provided a superior position for implantation of NiO species and the as-obtained catalyst exhibited excellent performance. In this paper, we successfully synthesized a layered double hydroxide (LDH) using the spent liquor after mixed-acid etching of VMT, which mainly contained Mg2+ and Al3+. The as-calcined layered double oxide (LDO) was used as a catalyst support for CO methanation. Compared with Ni/MgAl-LDO, Ni/VMT-LDO had smaller active component particles; therefore, in this study, it exhibited excellent catalytic performance over the whole temperature range of 250–500 °C. Ni/VMT-LDO achieved the best activity with 87.88% CO conversion, 89.97% CH4 selectivity, and 12.47 × 10−2·s−1 turn over frequency (TOF) at 400 °C under a gas hourly space velocity of 20,000 mL/g/h. This study demonstrated that VMT-LDO as a catalyst support provided an efficient way to develop high-performance catalysts for synthetic natural gas (SNG) from syngas. Full article
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Review

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Open AccessReview Electrocatalysts Prepared by Galvanic Replacement
Catalysts 2017, 7(3), 80; doi:10.3390/catal7030080
Received: 28 December 2016 / Revised: 1 March 2017 / Accepted: 2 March 2017 / Published: 8 March 2017
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Abstract
Galvanic replacement is the spontaneous replacement of surface layers of a metal, M, by a more noble metal, Mnoble, when the former is treated with a solution containing the latter in ionic form, according to the general replacement reaction: nM
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Galvanic replacement is the spontaneous replacement of surface layers of a metal, M, by a more noble metal, Mnoble, when the former is treated with a solution containing the latter in ionic form, according to the general replacement reaction: nM + mMnoblen+nMm+ + mMnoble. The reaction is driven by the difference in the equilibrium potential of the two metal/metal ion redox couples and, to avoid parasitic cathodic processes such as oxygen reduction and (in some cases) hydrogen evolution too, both oxygen levels and the pH must be optimized. The resulting bimetallic material can in principle have a Mnoble-rich shell and M-rich core (denoted as Mnoble(M)) leading to a possible decrease in noble metal loading and the modification of its properties by the underlying metal M. This paper reviews a number of bimetallic or ternary electrocatalytic materials prepared by galvanic replacement for fuel cell, electrolysis and electrosynthesis reactions. These include oxygen reduction, methanol, formic acid and ethanol oxidation, hydrogen evolution and oxidation, oxygen evolution, borohydride oxidation, and halide reduction. Methods for depositing the precursor metal M on the support material (electrodeposition, electroless deposition, photodeposition) as well as the various options for the support are also reviewed. Full article
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Open AccessFeature PaperReview Review of Heterogeneous Catalysts for Catalytically Upgrading Vegetable Oils into Hydrocarbon Biofuels
Catalysts 2017, 7(3), 83; doi:10.3390/catal7030083
Received: 29 December 2016 / Revised: 24 February 2017 / Accepted: 7 March 2017 / Published: 11 March 2017
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Abstract
To address the issues of greenhouse gas emissions associated with fossil fuels, vegetable oilseeds, especially non-food oilseeds, are used as an alternative fuel resource. Vegetable oil derived from these oilseeds can be upgraded into hydrocarbon biofuel. Catalytic cracking and hydroprocessing are two of
[...] Read more.
To address the issues of greenhouse gas emissions associated with fossil fuels, vegetable oilseeds, especially non-food oilseeds, are used as an alternative fuel resource. Vegetable oil derived from these oilseeds can be upgraded into hydrocarbon biofuel. Catalytic cracking and hydroprocessing are two of the most promising pathways for converting vegetable oil to hydrocarbon biofuel. Heterogeneous catalysts play a critical role in those processes. The present review summarizes current progresses and remaining challenges of vegetable oil upgrading to biofuel. The catalyst properties, applications, deactivation, and regeneration are reviewed. A comparison of catalysts used in vegetable oil and bio-oil upgrading is also carried out. Some suggestions for heterogeneous catalysts applied in vegetable oil upgrading to improve the yield and quality of hydrocarbon biofuel are provided for further research in the future. Full article
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Open AccessReview Photocatalytic Water Oxidation on ZnO: A Review
Catalysts 2017, 7(3), 93; doi:10.3390/catal7030093
Received: 16 December 2016 / Revised: 27 February 2017 / Accepted: 2 March 2017 / Published: 21 March 2017
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Abstract
The investigation of the water oxidation mechanism on photocatalytic semiconductor surfaces has gained much attention for its potential to unlock the technological limitations of producing H2 from carbon-free sources, i.e., H2O. This review seeks to highlight the available scientific and
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The investigation of the water oxidation mechanism on photocatalytic semiconductor surfaces has gained much attention for its potential to unlock the technological limitations of producing H2 from carbon-free sources, i.e., H2O. This review seeks to highlight the available scientific and fundamental understanding towards the water oxidation mechanism on ZnO surfaces, as well as present a summary on the modification strategies carried out to increase the photocatalytic response of ZnO. Full article
(This article belongs to the Special Issue Water Oxidation Catalysis)
Open AccessReview The Suzuki–Miyaura Cross-Coupling as a Versatile Tool for Peptide Diversification and Cyclization
Catalysts 2017, 7(3), 74; doi:10.3390/catal7030074
Received: 25 January 2017 / Revised: 20 February 2017 / Accepted: 21 February 2017 / Published: 25 February 2017
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Abstract
The (site-selective) derivatization of amino acids and peptides represents an attractive field with potential applications in the establishment of structure–activity relationships and labeling of bioactive compounds. In this respect, bioorthogonal cross-coupling reactions provide valuable means for ready access to peptide analogues with diversified
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The (site-selective) derivatization of amino acids and peptides represents an attractive field with potential applications in the establishment of structure–activity relationships and labeling of bioactive compounds. In this respect, bioorthogonal cross-coupling reactions provide valuable means for ready access to peptide analogues with diversified structure and function. Due to the complex and chiral nature of peptides, mild reaction conditions are preferred; hence, a suitable cross-coupling reaction is required for the chemical modification of these challenging substrates. The Suzuki reaction, involving organoboron species, is appropriate given the stability and environmentally benign nature of these reactants and their amenability to be applied in (partial) aqueous reaction conditions, an expected requirement upon the derivatization of peptides. Concerning the halogenated reaction partner, residues bearing halogen moieties can either be introduced directly as halogenated amino acids during solid-phase peptide synthesis (SPPS) or genetically encoded into larger proteins. A reversed approach building in boron in the peptidic backbone is also possible. Furthermore, based on this complementarity, cyclic peptides can be prepared by halogenation, and borylation of two amino acid side chains present within the same peptidic substrate. Here, the Suzuki–Miyaura reaction is a tool to induce the desired cyclization. In this review, we discuss diverse amino acid and peptide-based applications explored by means of this extremely versatile cross-coupling reaction. With the advent of peptide-based drugs, versatile bioorthogonal conversions on these substrates have become highly valuable. Full article
(This article belongs to the Special Issue Suzuki–Miyaura Cross-Coupling Reaction and Potential Applications)
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Open AccessReview Recent Advancements in Stereoselective Olefin Metathesis Using Ruthenium Catalysts
Catalysts 2017, 7(3), 87; doi:10.3390/catal7030087
Received: 4 February 2017 / Revised: 7 March 2017 / Accepted: 9 March 2017 / Published: 14 March 2017
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Abstract
Olefin metathesis is a prevailing method for the construction of organic molecules. Recent advancements in olefin metathesis have focused on stereoselective transformations. Ruthenium olefin metathesis catalysts have had a particularly pronounced impact in the area of stereoselective olefin metathesis. The development of three
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Olefin metathesis is a prevailing method for the construction of organic molecules. Recent advancements in olefin metathesis have focused on stereoselective transformations. Ruthenium olefin metathesis catalysts have had a particularly pronounced impact in the area of stereoselective olefin metathesis. The development of three categories of Z-selective olefin metathesis catalysts has made Z-olefins easily accessible to both laboratory and industrial chemists. Further design enhancements to asymmetric olefin metathesis catalysts have streamlined the construction of complex molecules. The understanding gained in these areas has extended to the employment of ruthenium catalysts to stereoretentive olefin metathesis, the first example of a kinetically E-selective process. These advancements, as well as synthetic applications of the newly developed catalysts, are discussed. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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Open AccessReview Upgrading Lignocellulosic Biomasses: Hydrogenolysis of Platform Derived Molecules Promoted by Heterogeneous Pd-Fe Catalysts
Catalysts 2017, 7(3), 78; doi:10.3390/catal7030078
Received: 30 December 2016 / Revised: 16 February 2017 / Accepted: 1 March 2017 / Published: 7 March 2017
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Abstract
This review provides an overview of heterogeneous bimetallic Pd-Fe catalysts in the C–C and C–O cleavage of platform molecules such as C2–C6 polyols, furfural, phenol derivatives and aromatic ethers that are all easily obtainable from renewable cellulose, hemicellulose and lignin (the major components
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This review provides an overview of heterogeneous bimetallic Pd-Fe catalysts in the C–C and C–O cleavage of platform molecules such as C2–C6 polyols, furfural, phenol derivatives and aromatic ethers that are all easily obtainable from renewable cellulose, hemicellulose and lignin (the major components of lignocellulosic biomasses). The interaction between palladium and iron affords bimetallic Pd-Fe sites (ensemble or alloy) that were found to be very active in several sustainable reactions including hydrogenolysis, catalytic transfer hydrogenolysis (CTH) and aqueous phase reforming (APR) that will be highlighted. This contribution concentrates also on the different synthetic strategies (incipient wetness impregnation, deposition-precipitaion, co-precipitaion) adopted for the preparation of heterogeneous Pd-Fe systems as well as on the main characterization techniques used (XRD, TEM, H2-TPR, XPS and EXAFS) in order to elucidate the key factors that influence the unique catalytic performances observed. Full article
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Open AccessReview Pd/C Catalysis under Microwave Dielectric Heating
Catalysts 2017, 7(3), 89; doi:10.3390/catal7030089
Received: 16 December 2016 / Revised: 10 March 2017 / Accepted: 16 March 2017 / Published: 20 March 2017
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Abstract
Microwave-assisted organic synthesis (MAOS) provides a novel and efficient means of achieving heat organic reactions. Nevertheless, the potential arcing phenomena via microwave (MW) interaction with solid metal catalysts has limited its use by organic chemists. As arcing phenomena are now better understood, new
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Microwave-assisted organic synthesis (MAOS) provides a novel and efficient means of achieving heat organic reactions. Nevertheless, the potential arcing phenomena via microwave (MW) interaction with solid metal catalysts has limited its use by organic chemists. As arcing phenomena are now better understood, new applications of Pd/C-catalyzed reactions under MW dielectric heating are now possible. In this review, the state of the art, benefits, and challenges of coupling MW heating with heterogeneous Pd/C catalysis are discussed to inform organic chemists about their use with one of the most popular heterogeneous catalysts. Full article
(This article belongs to the Special Issue Enabling Technologies toward Green Catalysis)
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Open AccessLetter Olefin Metathesis with Ru-Based Catalysts Exchanging the Typical N-Heterocyclic Carbenes by a Phosphine–Phosphonium Ylide
Catalysts 2017, 7(3), 85; doi:10.3390/catal7030085
Received: 2 February 2017 / Revised: 1 March 2017 / Accepted: 9 March 2017 / Published: 14 March 2017
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Abstract
Density functional theory (DFT) calculations have been used to describe the first turnover of an olefin metathesis reaction calling for a new in silico family of homogenous Ru-based catalysts bearing a phosphine–phosphonium ylide ligand, with ethylene as a substrate. Equal to conventional Ru-based
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Density functional theory (DFT) calculations have been used to describe the first turnover of an olefin metathesis reaction calling for a new in silico family of homogenous Ru-based catalysts bearing a phosphine–phosphonium ylide ligand, with ethylene as a substrate. Equal to conventional Ru-based catalysts bearing an N-heterocyclic carbene (NHC) ligand, the activation of these congeners occurs through a dissociative mechanism, with a more exothermic first phosphine dissociation step. In spite of a stronger electron-donating ability of a phosphonium ylide C-ligand with respect to a diaminocarbene analogue, upper energy barriers were calculated to be on average ca. 5 kcal/mol higher than those of Ru–NHC standards. Overall, the study also highlights advantages of bidentate ligands over classical monodentate NHC and phosphine ligands, with a particular preference for the cis attack of the olefin. The new generation of catalysts is constituted by cationic complexes potentially soluble in water, to be compared with the typical neutral Ru–NHC ones. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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