Supported Catalyst

We report the synthesis of silver (Ag) nano-spheres (NS) supported on zinc oxide (ZnO) nanorods through two step mechanism, using open vessel microwave reactor. Direct reduction of ZnO from zinc nitrates was followed by deposition precipitation of the silver on the ZnO nanorods. The supported Ag/ZnO nanoparticles were then characterized by electron microscopy, X-ray diffraction, FTIR, photoluminescence and UV–vis spectroscopy. The visible light photocatalytic activity of Ag/ZnO system was investigated using a test contaminant, methylene blue (MB). Almost complete removal of MB in about 60 min for doses higher than 0.5 g/L of the Ag/ZnO photocatalyst was achieved. This significant improvement in the photocatalytic efficiency of Ag/ZnO photocatalyst under visible light irradiation can be attributed to the presence of Ag nanoparticles on the ZnO nanoparticles which greatly enhances absorption in the visible range of solar spectrum enabled by surface plasmon resonance effect from Ag nanoparticles.

In this study, a novel continuous reactor has been developed to produce high quality methyl esters (biodiesel) from palm oil. A microporous TiO2/Al2O3 membrane was packed with potassium hydroxide catalyst supported on palm shell activated carbon. The central composite design (CCD) of response surface methodology (RSM) was employed to investigate the effects of reaction temperature, catalyst amount and cross flow circulation velocity on the production of biodiesel in the packed bed membrane reactor. The highest conversion of palm oil to biodiesel in the reactor was obtained at 70°C employing 157.04g catalyst per unit volume of the reactor and 0.21cm/s cross flow circulation velocity. The physical and chemical properties of the produced biodiesel were determined and compared with the standard specifications. High quality palm oil biodiesel was produced by combination of heterogeneous alkali transesterification and separation processes in the packed bed membrane reactor. © 2010 Elsevier Ltd.

http://ac.els-cdn.com/S0960852410014574/1-s2.0-S0960852410014574-main.pdf?_tid=74bcbdf2-025e-11e4-8ea3-00000aab0f27&acdnat=1404356723_f959262287254ffe4bce3abeee7084d9 
http://www.sciencedirect.com/science/article/pii/S0960852410014574

This work describes the synthesis and characterization of Pt/MgO (Pt/Mg(OH)2, calcined Pt/MgO and agglomerated Pt/MgO ) catalysts. The supports of the catalysts were obtained by thehydrolysis-precipitation method and the metallic phase of platinum was incorporated by impregnation. The characterization of the synthesized materials was made by means of DRX,FTIR, TGA-DTA and TPR techniques. The catalysts were applied to the hydrosilylation ofPhC≡CH with three different silanes (Ph3SiH, Ph2MeSiH and PhMe2SiH) as a model reaction.The activity of the proposed catalysts Pt/Mg(OH)2, calcined Pt/MgO and agglomerated Pt/MgOhad a reaction yield of 95 %. When the catalysts Pt/Mg(OH)2 and agglomerated Pt/MgO were used in the reaction with Ph3SiH, the selectivity to the trans isomer was favored (90%). Arelationship was found between the increase in the reaction time and the increase of the kineticvolume of the silane radicals. The present results were compared to the previously obtained results using as a catalyst Pt/MgO obtained by the sol-gel method.

Heterogeneous catalysts are promising for the transesterification reaction of vegetable oils to produce biodiesel. Unlike homogeneous, heterogeneous catalysts are environmentally benign and could be operated in continuous processes. Moreover they can be reused and ...

The ready availability of esters from natural sources makes them promising substrates for the sustainable production of key intermediates of the chemical industry. In this context, methods to selectively cleave the alkoxy or ester CO bond to obtain either alkane+acid or alcohol+aldehyde were investigated. Using Pd/Fe3O4 as the catalyst of choice and either 2-propanol — as indirect H source — or molecular hydrogen — as ample H source — the hydrogen coverage on the surface of the catalyst was controlled. This enabled selective cleavage of either the alkoxy CO bond or the ester CO bond in aromatic esters as shown for the hydrogenolysis of 2-phenylethylacetate as model substrate. Noteworthy, hydrogenation of the aromatic ring was not observed. Thus, an exceptionally high chemoselectivity of Pd/Fe3O4 to hydrogenolysis of the ester group is combined with the option to readily direct the regioselectivity.

Linear low-density polyethylene (LLDPE) is produced from an ethylene-only feed over a tandem catalyst system consisting of a phenoxy−imine titanium trimerization catalyst and a silylene-linked cyclopentadienyl/amido titanium polymerization catalyst cosupported on the same methylaluminoxane/ silica particles. The level of 1-hexene incorporation can be controlled by varying the ethylene pressure. P roduction of linear low-density polyethylene (LLDPE) by copolymerization of ethylene with an α-olefin is an important industrial process. 1 As currently practiced, ethylene is catalytically oligomerized to the α-olefin, principally 1-hexene or 1-octene, which is isolated and copolymerized with ethylene in a separate reactor, using a different catalytic system. 2 Orthogonal tandem catalysis, 3 where two independent catalysts operate together to perform consecutive transformations in a single reactor, offers the potential for a more efficient and economical process; a supported version would be of particular interest. Supported catalysts are widely used industrially in polyolefin synthesis, as they favor highly uniform particle morphology and free-flowing product without undesired " fines " (small polyethylene particles) and/or sticky ethylene copoly-mers with high 1-alkene content that adhere to reactor components, thus allowing for easy product isolation and preventing reactor fouling. 4 Several tandem catalyst systems for the synthesis of LLDPE have been reported 5 (to the best of our knowledge, none of these are in commercial use), including two supported systems. 5d,g In those examples, the two catalysts are on separate supports, 6 which can cause undesirable issues in an industrial process, such as catalyst segregation and inhomogeneity in the reactor over time. Supporting both catalysts on the same solid material would avoid such problems. It could also offer other potential advantages (e.g., more efficient tandem behavior resulting from proximity) as well as difficulties, such as reduced activity due to mutual interference; both of these have been observed with a covalently linked homogeneous tandem catalyst. 5f Here we report the first successful generation of a tandem LLDPE catalyst by cosupporting both trimerization and polymerization catalysts on the same silica particles. We previously reported that the ethylene trimerization precatalyst initially developed by Fujita et al., (FI)TiCl 3 (FI = (N-(5-methyl-3-(1-adamantyl)-salicylidene)-2′-(2″-methoxyphenyl)anilinato), 7 can be effectively used in a methylaluminoxane (MAO)/silica-supported form, called s-(FI)Ti. 8 A tandem catalyst with cosupported (Cp*SiNR)TiCl 2 (Cp*SiNR = (η 5-C 5 Me 4)Me 2 Si(η 1-NCMe 3), originally reported by Okuda et al. 9 and Dow Chemical Company, 10 as the copolymerization component, was generated by addition of a solution of the two catalysts to a toluene slurry of MAO/silica (Scheme 1). Co-supported systems with y/x = 1−10 were prepared in this manner. In all instances, the Al:Ti ratio (300:1) and the total titanium loading (0.018 mmol/g of MAO/silica) were kept the same. The cosupported catalyst systems thus obtained are yellow free-flowing, pyrophoric solids, highly sensitive toward air and moisture.

Heterogeneous catalysts are promising for the transesterification reaction of vegetable oils to produce biodiesel. Unlike homogeneous, heterogeneous catalysts are environmentally benign and could be operated in continuous processes. Moreover they can be reused and regenerated. However a high molar ratio of alcohol to oil, large amount of catalyst and high temperature and pressure are required when utilizing heterogeneous catalyst to produce biodiesel. In this paper, the catalytic activity of several solid base and acid catalysts, particularly metal oxides and supported metal oxides, was reviewed. Solid acid catalysts were able to do transesterification and esterification reactions simultaneously and convert oils with high amount of FFA (Free Fatty Acids). However, the reaction rate in the presence of solid base catalysts was faster. The catalyst efficiency depended on several factors such as specific surface area, pore size, pore volume and active site concentration. © 2009 Elsevier B.V. All rights reserved.

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http://www.sciencedirect.com/science/article/pii/S0378382009000629

In this review, we summarize the recent research progress on the preparation and catalytic performance of meso-and macroporous metal oxide or mixed metal oxide (including manganese oxides, cobalt oxides, iron oxides, chromium oxides, and perovskite-type oxides) catalysts and their supported transition metal and noble metal catalysts for the oxidative removal of typical volatile organic compounds (VOCs), which were prepared using the hard-templating and polyvinyl alcohol-protected reduction methods, respectively. Most of these porous catalysts performed well for the addressed reactions, which was associated with their surface areas, adsorbed oxygen species concentrations, lowtemperature reducibility, interactions between noble metal or metal oxide and support as well as porous structures. In addition, the perspectives for developing high-performance catalytic materials and novel VOCs removal technologies are also proposed.

In this study, a novel continuous reactor has been developed to produce high quality methyl esters (biodiesel) from palm oil. A microporous TiO2/Al2O3 membrane was packed with potassium hydroxide catalyst supported on palm shell activated carbon. The central composite design (CCD) of response surface methodology (RSM) was employed to investigate the effects of reaction temperature, catalyst amount and cross flow circulation velocity on the production of biodiesel in the packed bed membrane reactor. The highest conversion of palm oil to biodiesel in the reactor was obtained at 70°C employing 157.04g catalyst per unit volume of the reactor and 0.21cm/s cross flow circulation velocity. The physical and chemical properties of the produced biodiesel were determined and compared with the standard specifications. High quality palm oil biodiesel was produced by combination of heterogeneous alkali transesterification and separation processes in the packed bed membrane reactor. © 2010 Elsevier Ltd.

http://ac.els-cdn.com/S0960852410014574/1-s2.0-S0960852410014574-main.pdf?_tid=74bcbdf2-025e-11e4-8ea3-00000aab0f27&acdnat=1404356723_f959262287254ffe4bce3abeee7084d9 
http://www.sciencedirect.com/science/article/pii/S0960852410014574