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Catalysts, Volume 8, Issue 2 (February 2018)

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Cover Story (view full-size image) (S)-Rivastigmine is a blockbuster drug heavily used for the treatment of mild to moderate dementia [...] Read more.
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Open AccessCommunication Composites of Laminar Nanostructured ZnO and VOx-Nanotubes Hybrid as Visible Light Active Photocatalysts
Catalysts 2018, 8(2), 93; https://doi.org/10.3390/catal8020093
Received: 15 January 2018 / Revised: 9 February 2018 / Accepted: 15 February 2018 / Published: 24 February 2018
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Abstract
A series of hybrid heterostructured nanocomposites of ZnO with V2O5 nanotubes (VOx-NTs) in different mixing ratios were synthesized, with the aim of reducing the recombination of photoinduced charge carriers and to optimize the absorption of visible light. The study was
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A series of hybrid heterostructured nanocomposites of ZnO with V2O5 nanotubes (VOx-NTs) in different mixing ratios were synthesized, with the aim of reducing the recombination of photoinduced charge carriers and to optimize the absorption of visible light. The study was focused on the use of heterostructured semiconductors that can extend light absorption to the visible range and enhance the photocatalytic performance of ZnO in the degradation of methylene blue as a model pollutant. The addition of VOx-NTs in the synthesis mixture led to a remarkable performance in the degradation of the model dye, with hybrid ZnO (stearic acid)/VOx-NTs at a ratio of 1:0.06 possessing the highest photocatalytic activity, about seven times faster than pristine zinc oxide. Diffuse reflectance spectroscopic measurements and experiments in the presence of different trapping elements allowed us to draw conclusions regarding the band positions and photocatalytic degradation mechanism. The photocatalytic activity measured in three subsequent cycles showed good reusability as no significant loss in efficiency of dye degradation was observed. Full article
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Open AccessReview A General Overview of Support Materials for Enzyme Immobilization: Characteristics, Properties, Practical Utility
Catalysts 2018, 8(2), 92; https://doi.org/10.3390/catal8020092
Received: 19 January 2018 / Revised: 12 February 2018 / Accepted: 21 February 2018 / Published: 24 February 2018
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Abstract
In recent years, enzyme immobilization has been presented as a powerful tool for the improvement of enzyme properties such as stability and reusability. However, the type of support material used plays a crucial role in the immobilization process due to the strong effect
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In recent years, enzyme immobilization has been presented as a powerful tool for the improvement of enzyme properties such as stability and reusability. However, the type of support material used plays a crucial role in the immobilization process due to the strong effect of these materials on the properties of the produced catalytic system. A large variety of inorganic and organic as well as hybrid and composite materials may be used as stable and efficient supports for biocatalysts. This review provides a general overview of the characteristics and properties of the materials applied for enzyme immobilization. For the purposes of this literature study, support materials are divided into two main groups, called Classic and New materials. The review will be useful in selection of appropriate support materials with tailored properties for the production of highly effective biocatalytic systems for use in various processes. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
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Open AccessReview The Design of MnOx Based Catalyst in Post-Plasma Catalysis Configuration for Toluene Abatement
Catalysts 2018, 8(2), 91; https://doi.org/10.3390/catal8020091
Received: 21 December 2017 / Revised: 9 February 2018 / Accepted: 11 February 2018 / Published: 23 February 2018
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Abstract
This review provides an overview of our present state of knowledge using manganese oxide (MnOx)-based catalysts for toluene abatement in PPC (Post plasma-catalysis) configuration. The context of this study is concisely sum-up. After briefly screening the main depollution methods, the principles
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This review provides an overview of our present state of knowledge using manganese oxide (MnOx)-based catalysts for toluene abatement in PPC (Post plasma-catalysis) configuration. The context of this study is concisely sum-up. After briefly screening the main depollution methods, the principles of PPC are exposed based on the coupling of two mature technologies such as NTP (Non thermal plasma) and catalysis. In that respect, the presentation of the abundant manganese oxides will be firstly given. Then in a second step the main features of MnOx allowing better performances in the reactions expected to occur in the abatement of toluene in PPC process are reviewed including ozone decomposition, toluene ozonation, CO oxidation and toluene total oxidation. Finally, in a last part the current status of the applications of PPC using MnOx on toluene abatement are discussed. In a first step, the selected variables of the hybrid process related to the experimental conditions of toluene abatement in air are identified. The selected variables are those expected to play a role in the performances of PPC system towards toluene abatement. Then the descriptors linked to the performances of the hybrid process in terms of efficiency are given and the effects of the variables on the experimental outcomes (descriptors) are discussed. The review would serve as a reference guide for the optimization of the PPC process using MnOx-based oxides for toluene abatement. Full article
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Open AccessReview Advances in Enantioselective C–H Activation/Mizoroki-Heck Reaction and Suzuki Reaction
Catalysts 2018, 8(2), 90; https://doi.org/10.3390/catal8020090
Received: 31 January 2018 / Revised: 14 February 2018 / Accepted: 15 February 2018 / Published: 23 February 2018
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Abstract
Traditional cross-coupling reactions, like Mizoroki-Heck Reaction and Suzuki Reaction, have revolutionized organic chemistry and are widely applied in modern organic synthesis. With the rapid development of C–H activation and asymmetric catalysis in recent years, enantioselective C–H activation/cross-coupling reactions have drawn much attention from
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Traditional cross-coupling reactions, like Mizoroki-Heck Reaction and Suzuki Reaction, have revolutionized organic chemistry and are widely applied in modern organic synthesis. With the rapid development of C–H activation and asymmetric catalysis in recent years, enantioselective C–H activation/cross-coupling reactions have drawn much attention from researchers. This review summarizes recent advances in enantioselective C–H activation/Mizoroki-Heck Reaction and Suzuki Reaction, with emphasis on the structures and functions of chiral ligands utilized in different reactions. Full article
(This article belongs to the Special Issue Catalyzed Mizoroki–Heck Reaction or C–H activation)
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Open AccessReview Catalysis and Downsizing in Mg-Based Hydrogen Storage Materials
Catalysts 2018, 8(2), 89; https://doi.org/10.3390/catal8020089
Received: 31 January 2018 / Revised: 31 January 2018 / Accepted: 15 February 2018 / Published: 23 February 2018
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Abstract
Magnesium (Mg)-based materials are promising candidates for hydrogen storage due to the low cost, high hydrogen storage capacity and abundant resources of magnesium for the realization of a hydrogen society. However, the sluggish kinetics and strong stability of the metal-hydrogen bonding of Mg-based
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Magnesium (Mg)-based materials are promising candidates for hydrogen storage due to the low cost, high hydrogen storage capacity and abundant resources of magnesium for the realization of a hydrogen society. However, the sluggish kinetics and strong stability of the metal-hydrogen bonding of Mg-based materials hinder their application, especially for onboard storage. Many researchers are devoted to overcoming these challenges by numerous methods. Here, this review summarizes some advances in the development of Mg-based hydrogen storage materials related to downsizing and catalysis. In particular, the focus is on how downsizing and catalysts affect the hydrogen storage capacity, kinetics and thermodynamics of Mg-based hydrogen storage materials. Finally, the future development and applications of Mg-based hydrogen storage materials is discussed. Full article
(This article belongs to the Special Issue Heterogeneous Catalysis & Hydrogen Storage)
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Open AccessArticle Ruthenium(II)-Arene Complexes of the Water-Soluble Ligand CAP as Catalysts for Homogeneous Transfer Hydrogenations in Aqueous Phase
Catalysts 2018, 8(2), 88; https://doi.org/10.3390/catal8020088
Received: 29 December 2017 / Revised: 14 February 2018 / Accepted: 15 February 2018 / Published: 22 February 2018
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Abstract
The neutral Ru(II) complex κP-[RuCl26-p-cymene)(CAP)] (1), and the two ionic complexes κP-[RuCl(η6-p-cymene)(MeCN)(CAP)]PF6 (2) and κP-[RuCl(η6-p-cymene)(CAP)2]PF6
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The neutral Ru(II) complex κP-[RuCl26-p-cymene)(CAP)] (1), and the two ionic complexes κP-[RuCl(η6-p-cymene)(MeCN)(CAP)]PF6 (2) and κP-[RuCl(η6-p-cymene)(CAP)2]PF6 (3), containing the water-soluble phosphine 1,4,7-triaza-9-phosphatricyclo[5.3.2.1]tridecane (CAP), were tested as catalysts for homogeneous hydrogenation of benzylidene acetone, selectively producing the saturated ketone as product. The catalytic tests were carried out in aqueous phase under transfer hydrogenation conditions, at mild temperatures using sodium formate as hydrogen source. Complex 3, which showed the highest stability under the reaction conditions applied, was also tested for C=N bond reduction from selected cyclic imines. Preliminary NMR studies run under pseudo-catalytic conditions starting from 3 showed the formation of κP-[RuH(η6-p-cymene)(CAP)2]PF6 (4) as the pivotal species in catalysis. Full article
(This article belongs to the Special Issue Homogeneous Catalysis and Mechanisms in Water and Biphasic Media)
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Open AccessArticle The H2-Treated TiO2 Supported Pt Catalysts Prepared by Strong Electrostatic Adsorption for Liquid-Phase Selective Hydrogenation
Catalysts 2018, 8(2), 87; https://doi.org/10.3390/catal8020087
Received: 15 January 2018 / Revised: 2 February 2018 / Accepted: 6 February 2018 / Published: 22 February 2018
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Abstract
The H2-treated TiO2 supported Pt catalysts were prepared by strong electrostatic adsorption method and tested in the liquid-phase selective hydrogenation of various organic compounds such as 3-nitrostyrene to vinylaniline (VA) and furfural to furfuryl alcohol (FA). A combination of high
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The H2-treated TiO2 supported Pt catalysts were prepared by strong electrostatic adsorption method and tested in the liquid-phase selective hydrogenation of various organic compounds such as 3-nitrostyrene to vinylaniline (VA) and furfural to furfuryl alcohol (FA). A combination of high Pt dispersion, strong interaction of Pt-TiOx, and the presence of low coordination Pt sites was necessary for high hydrogenation activity. However, while the selectivity of VA in 3-nitrostyrene hydrogenation did not depend much on the catalyst preparation method used, the selectivity of FA in furfural hydrogenation was much higher when the catalysts were prepared by SEA, comparing to those obtained by impregnation in which the solvent product was formed, due probably to the non-acidic conditions used during Pt loading by SEA method. Full article
(This article belongs to the Special Issue Active Sites in Catalytic Reaction)
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Open AccessFeature PaperArticle Improved Kinetic Data Acquisition Using An Optically Accessible Catalytic Plate Reactor with Spatially-Resolved Measurement Techniques. Case of Study: CO2 Methanation
Catalysts 2018, 8(2), 86; https://doi.org/10.3390/catal8020086
Received: 12 January 2018 / Revised: 15 February 2018 / Accepted: 19 February 2018 / Published: 21 February 2018
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Abstract
Modelling and optimization of chemical reactors require a good understanding of the reactions mechanism with the corresponding kinetic description. Therefore, high quality kinetic data are needed, which can be challenging to obtain, especially for fast and highly exothermic reactions such as the CO
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Modelling and optimization of chemical reactors require a good understanding of the reactions mechanism with the corresponding kinetic description. Therefore, high quality kinetic data are needed, which can be challenging to obtain, especially for fast and highly exothermic reactions such as the CO2 methanation. Traditionally, kinetic studies rely on measuring the exit gas composition (1 data point per species and experiment) using differential reactors with diluted catalyst beds and reactants to avoid temperature change. Therefore, an optically accessible catalytic channel reactor was designed, which allowed for the chance to gather spatially-resolved information on axial gas composition and catalyst surface temperature, specifically by means of a movable sampling capillary and shortwave infrared-thermography (SWIR), respectively. A catalyst coated plate was placed at the bottom of the channel, while a set of two quartz glass plates covers the top. In the current study 35 data points per gas species were collect for 1 experiment conducted under laminar flow conditions at 425 °C. Catalyst surface temperature determined via a SWIR camera was not influenced by polyatomic molecules partaking in the reaction and thus did not falsify the kinetic data. The catalyst mass distribution along the reactor axis was determined, enabling the development of a correct reactor model for kinetic parameter estimation and model discrimination. Full article
(This article belongs to the Special Issue Design Challenges for Catalytic and Photocatalytic Reactors)
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Open AccessArticle Influence of an Electronic Structure of N-TiO2 on Its Photocatalytic Activity towards Decomposition of Acetaldehyde under UV and Fluorescent Lamps Irradiation
Catalysts 2018, 8(2), 85; https://doi.org/10.3390/catal8020085
Received: 3 January 2018 / Revised: 15 February 2018 / Accepted: 17 February 2018 / Published: 20 February 2018
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Abstract
The electronic structure of N-TiO2 samples prepared by a sol-gel method was investigated by EPR (Electronic Paramagnetic Resonance) measurements and the energy-resolved distribution of electron traps. In EPR spectra, some of the resonance lines assigned to paramagnetic species of nitrogen and Ti
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The electronic structure of N-TiO2 samples prepared by a sol-gel method was investigated by EPR (Electronic Paramagnetic Resonance) measurements and the energy-resolved distribution of electron traps. In EPR spectra, some of the resonance lines assigned to paramagnetic species of nitrogen and Ti3+ were detected. Sample prepared at 300 °C revealed the highest intensity line of the nitrogen paramagnetic centers, whereas that prepared at 400 °C showed a paramagnetic line for Ti3+. Measurements of the electron trap distribution showed higher density of electron traps for sample prepared at 400 °C than that at 300 °C. Sample prepared at 300 °C, which revealed the highest amount of nitrogen built in the titania in the interstitial position was the most active under visible light. It was evidenced that photocatalytic decomposition of acetaldehyde was dependent strongly on the BET surface area and electrokinetic potential of the photocatalyst surface. The UV content in the fluorescent lamp affected the yield of acetaldehyde decomposition. Full article
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Open AccessArticle Immobilization Effects on the Catalytic Properties of Two Fusarium Verticillioides Lipases: Stability, Hydrolysis, Transesterification and Enantioselectivity Improvement
Catalysts 2018, 8(2), 84; https://doi.org/10.3390/catal8020084
Received: 15 December 2017 / Revised: 30 January 2018 / Accepted: 2 February 2018 / Published: 16 February 2018
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Abstract
Fusarium verticillioides lipases were purified in a “cascade” method using octadecyl Sepabeads and octyl Sepharose resins, which led to the isolation of two proteins with lipolytic activities. Lip 1 was purified after octyl Sepharose adsorption presenting 30.3 kDa and, Lip 2 presented 68.0
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Fusarium verticillioides lipases were purified in a “cascade” method using octadecyl Sepabeads and octyl Sepharose resins, which led to the isolation of two proteins with lipolytic activities. Lip 1 was purified after octyl Sepharose adsorption presenting 30.3 kDa and, Lip 2 presented 68.0 kDa after octadecyl adsorption. These immobilization processes resulted in an increase of 3-fold in activity of each immobilized enzyme. These enzymes presented optima of pH of 5.0 and 6.0, respectively and temperature at 40 °C. They were thermostable at 40 °C and both remained more than 50% of its activity at the pH range of 5.0 to 7.0, with 180 min of incubation. The sardine oil hydrolysis showed higher EPA/DHA ratio. Concerning the ethanolysis reaction, Lip 2 showed higher conversion (5.5%) and both lipases showed activity in the release of the S enantiomers from 2-O-butyryl-2-phenylacetic acid (mandelic butyrate acid) and HPBE hydrolysis. Lip 2 also demonstrated capacity of transesterification. These applications made these enzymes attractive for industrial application. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
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Open AccessArticle Aerobic Oxidation of Benzyl Alcohol on a Strontium-Based Gold Material: Remarkable Intrinsic Basicity and Reusable Catalyst
Catalysts 2018, 8(2), 83; https://doi.org/10.3390/catal8020083
Received: 5 January 2018 / Revised: 7 February 2018 / Accepted: 9 February 2018 / Published: 15 February 2018
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Abstract
The development of stable and active gold catalysts has arisen as a significant strategy for oxidation of alcohols. Nano-size PVA-stabilized gold nanoparticles immobilized on Sr(OH)2 by colloidal deposition presented high catalytic activity for benzyl alcohol oxidation. In 2.5 h, 2 bar of
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The development of stable and active gold catalysts has arisen as a significant strategy for oxidation of alcohols. Nano-size PVA-stabilized gold nanoparticles immobilized on Sr(OH)2 by colloidal deposition presented high catalytic activity for benzyl alcohol oxidation. In 2.5 h, 2 bar of O2 and without extra-base addition, the calcined support reached 54.6% (100 °C) and 67.4% (140 °C) of conversion, presenting the remarkable and unexplored intrinsic basicity that strontium-based materials retain. With sub-stoichiometric K2CO3 adding, under the same catalytic conditions, the catalyst conducted the reaction with similar activity, but with excellent reusability in the process, without any gold leaching. We investigated the influence that the support synthesis method and the solvent used for the NPs stabilization have on the oxidation activity. The produced materials were fully characterized by XPS, Rietveld refinement, and TEM. Full article
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Open AccessArticle Catalytic Fast Pyrolysis of Kraft Lignin over Hierarchical HZSM-5 and Hβ Zeolites
Catalysts 2018, 8(2), 82; https://doi.org/10.3390/catal8020082
Received: 25 January 2018 / Revised: 10 February 2018 / Accepted: 11 February 2018 / Published: 14 February 2018
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Abstract
The hierarchical HZSM-5 and Hβ zeolites were prepared by alkaline post-treatment methods adopting Na2CO3, TMAOH/NaOH mixture, and NaOH as desilication sources, respectively. More mesopores are produced over two kinds of zeolites, while the micropores portion is well preserved. The
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The hierarchical HZSM-5 and Hβ zeolites were prepared by alkaline post-treatment methods adopting Na2CO3, TMAOH/NaOH mixture, and NaOH as desilication sources, respectively. More mesopores are produced over two kinds of zeolites, while the micropores portion is well preserved. The mesopores formed in hierarchical Hβ zeolites were directly related to the basicity of the alkaline solution, indicating that Hβ zeolite is more sensitive to the alkaline post-treatment. The hierarchical HZSM-5 and Hβ zeolites are more active than the parent one for catalytic fast pyrolysis (CFP) of Kraft lignin. Hierarchical zeolites retained the function of acid catalysis, while additionally creating larger mesopores to ensure the entry of bulkier reactant molecules. The increase of the condensable volatiles yield can be attributed to the improvement of the mass transfer performance, which correlates well with the change of mesoporous surface area. In particular, the condensable volatiles yield for the optimized hierarchical Hβ reached approximately two times that of the parent Hβ zeolites. In contrast to the parent HZSM-5, the optimized hierarchical HZSM-5 zeolite significantly reduced the selectivity of oxygenates from 27.2% to 3.3%. Full article
(This article belongs to the Special Issue Catalytic Pyrolysis)
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Open AccessArticle Optimization of Biodiesel Production from Waste Cooking Oil Using Waste Eggshell as a Base Catalyst under a Microwave Heating System
Catalysts 2018, 8(2), 81; https://doi.org/10.3390/catal8020081
Received: 16 December 2017 / Revised: 26 January 2018 / Accepted: 30 January 2018 / Published: 14 February 2018
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Abstract
This paper intends to explore the most affordable and environmentally friendly method for the synthesis of biodiesel. Substitute fuel is presently a significant topic all over the world, attributable to the efforts of reducing global warming, which is the result arising from the
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This paper intends to explore the most affordable and environmentally friendly method for the synthesis of biodiesel. Substitute fuel is presently a significant topic all over the world, attributable to the efforts of reducing global warming, which is the result arising from the combustion of petroleum or petrol diesel fuel. Due to its advantages of being renewable and environmentally friendly, biodiesel production has the potential to become the major substitute of petrol diesel fuel. Biodiesel is non-toxic, biodegradable, is produced from renewable sources, and contributes a small amount of greenhouse gas (e.g., CO2 and SO2) emissions to the atmosphere. Research has established that one of the key obstacles to the commercialization of biodiesel is the high price of biodiesel production due to the shortage of suitable raw materials. However, waste-cooking-oil (WCO) is one of the most cost-effective sources of biodiesel synthesis, and can practically minimize the raw material cost. The research was carried out to produce biodiesel from waste cooking oil in order to reduce the cost, waste, and pollution associated with biodiesel production. The application of a microwave heating system towards enhancing the production of biodiesel from waste cooking oil has been given little consideration in the preceding research, particularly with the application of eggshell as a heterogeneous catalyst. However, the tentative results in this study show significant performance in terms of biodiesel production, as follows: (1) the increasing of the reaction time from 120 to 165 min considerably increased the biodiesel production, which declined with a further rise to 210 min; (2) the results of this study reveal that a methanol-to-oil molar ratio of nine is appropriate and can be used for the best production of biodiesel; (3) the production of biodiesel in this study demonstrated a significant increase in response to the further increasing of power; (4) a 120 min response time, a ratio of 9:1 methanol-to-oil molar fraction, 65 °C temperature; (5) and 5 wt % catalyst were found to be the most ideal reaction conditions during this study. In summary, recycled eggshell was re-used as a suitable catalyst to produce new biodiesel from waste cooking oil, applicable to diesel engines. Full article
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Open AccessReview Oriented Decoration in Metal-Functionalized Ordered Mesoporous Silicas and Their Catalytic Applications in the Oxidation of Aromatic Compounds
Catalysts 2018, 8(2), 80; https://doi.org/10.3390/catal8020080
Received: 22 December 2017 / Revised: 3 February 2018 / Accepted: 7 February 2018 / Published: 13 February 2018
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Abstract
Ordered mesoporous silicas (OMSs) attract considerable attention due to their advanced structural properties. However, for the pristine silica materials, the inert property greatly inhibits their catalytic applications. Thus, to contribute to the versatile surface of OMSs, different metal active sites, including acidic/basic sites
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Ordered mesoporous silicas (OMSs) attract considerable attention due to their advanced structural properties. However, for the pristine silica materials, the inert property greatly inhibits their catalytic applications. Thus, to contribute to the versatile surface of OMSs, different metal active sites, including acidic/basic sites and redox sites, have been introduced into specific locations (mesoporous channels and framework) of OMSs and the metal-functionalized ordered mesoporous silicas (MOMSs) show great potential in the catalytic applications. In this review, we first present the categories of metal active sites. Then, the synthesized processes of MOMSs are thoroughly discussed, in which the metal active sites would be introduced with the assistance of organic groups into the specific locations of OMSs. In addition, the structural morphologies of OMSs are elaborated and the catalytic applications of MOMSs in the oxidation of aromatic compounds are illustrated in detail. Finally, the prospects for the future development in this field are proposed. Full article
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Open AccessArticle Heterogeneous Catalysis by Tetraethylammonium Tetrachloroferrate of the Photooxidation of Toluene by Visible and Near-UV Light
Catalysts 2018, 8(2), 79; https://doi.org/10.3390/catal8020079
Received: 8 January 2018 / Revised: 8 February 2018 / Accepted: 11 February 2018 / Published: 13 February 2018
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Abstract
Titanium dioxide is the most extensively used heterogeneous catalyst for the photooxidation of toluene and other hydrocarbons, but it has low utility for the synthesis of benzyl alcohol, of which little is produced, or benzaldehyde, due to further oxidation to benzoic acid and
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Titanium dioxide is the most extensively used heterogeneous catalyst for the photooxidation of toluene and other hydrocarbons, but it has low utility for the synthesis of benzyl alcohol, of which little is produced, or benzaldehyde, due to further oxidation to benzoic acid and cresol, among other oxidation products, and eventually complete mineralization to CO2. Et4N[FeCl4] functions as a photocatalyst through the dissociation of chlorine atoms, which abstract hydrogen from toluene, and the photooxidation of toluene proceeds only as far as benzyl alcohol and benzaldehyde. Unlike TiO2, which requires ultraviolet (UV) irradiation, Et4N[FeCl4] catalyzes the photooxidation of toluene with visible light alone. Even under predominantly UV irradiation, the yield of benzyl alcohol plus benzaldehyde is greater with Et4N[FeCl4] than with TiO2. Et4N[FeCl4] photocatalysis yields benzyl chloride as a side product, but it can be minimized by restricting irradiation to wavelengths above 360 nm and by the use of long irradiation times. The photonic efficiency of oxidation in one experiment was found to be 0.042 mol/einstein at 365 nm. The use of sunlight as the irradiation source was explored. Full article
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