Br?nsted acid catalysts have been used in a number of organic transformations. To overcome limi-tations, such as toxicity, volatility, high price and hazardous nature of the conventional methods, the catalysts are ads...Br?nsted acid catalysts have been used in a number of organic transformations. To overcome limi-tations, such as toxicity, volatility, high price and hazardous nature of the conventional methods, the catalysts are adsorbed on silica gel to give the benefits and advantages of ready availability, simple work-up procedure, long catalytic life, environment-friendliness, good to excellent yields and recy-clability. The uses of such catalysts have gained importance worldwide. This article describes some of the important silicated catalysts, namely, heteropolyacids, polyphosphoric acid, perchloric acid, fluoroboric acid, and silicated sulphuric acid. These catalysts have been used in a number of organic reactions to yield compounds that are important in the chemical and pharmaceutical industries. We summarize the beneficial effects of these catalysts and the reports that have been published on them in the past several years. In the present review, the description of the catalysts are introduced followed by a recent research history, and a comparison between the silica supported catalysts and other(polymer) supported catalysts. The article ends up giving the advantages of these catalytic systems over the conventional catalyst.展开更多
Microporous heteropolyoxometalates Cs\-\%x\%H\-\{5-\%x\%\}PW\-\{10\}V\-2O\-\{40\}/SiO\-2 were synthesized by a sol\|gel technique and characterized by IR, UV\|Vis, BET adsorption/desorption isotherm. The structural fr...Microporous heteropolyoxometalates Cs\-\%x\%H\-\{5-\%x\%\}PW\-\{10\}V\-2O\-\{40\}/SiO\-2 were synthesized by a sol\|gel technique and characterized by IR, UV\|Vis, BET adsorption/desorption isotherm. The structural frameworks of Cs\-\%x\%H\-\{5-\%x\%\}PW\-\{10\}V\-2O\-\{40\} are preserved within the silica networks. Cs\-\%x\%H\-\{5-\%x\%\}PW\-\{10\}V\-2O\-\{40\}/SiO\-2 are a kind of polyoxometalate\|silica gel hybrids with uniform micropores of ca. 0.65 nm. They show a high catalytic activity for oxidation reaction of benzyl alcohol by H\-2O\-2(30%) in liquid\|solid systems and product selectivity for benzaldehyde(>96%). The highest activity is observed at \%x\%=2.5 in Cs\-\%x\%H\-\{5-\%x\%\}PW\-\{10\}V\-2O\-\{40\}/SiO\-2 and little formation of benzoic acid and a more deeply oxidized product is observed.展开更多
Pd and /or Cu - La2O3/SiO2 catalysts were prepared by Pd and/or Cu supported on La2O3/SiO2 with impregnation The capacities of catalysts reduction and the performance of reaction were studied by H2-TPR and hydrogenati...Pd and /or Cu - La2O3/SiO2 catalysts were prepared by Pd and/or Cu supported on La2O3/SiO2 with impregnation The capacities of catalysts reduction and the performance of reaction were studied by H2-TPR and hydrogenation of CO2 The results of H2-TPR indicate that increasing the content of CuO is advantageous to the reduction of high dispersing CuO, but adding La2O3 hinder the reduction of high dispersing CuO It was found that Pd-Cu alloy formed while Pd, Cu impregnated on La2O3/SiO2 The results of hydrogenation of CO2 indicate that CO2 conversion is promoted by adding La2O3 increasing the content of CuO The thermal stablity of methanol formation was improved by adding La2O3 Aldehyde can be obtained when Pd-Cu were used as active components, and the production of methanol was related to the content of Pd loaded on the展开更多
基金supported by Mr. Gurpreet Singh, Assistant Professor, Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar
文摘Br?nsted acid catalysts have been used in a number of organic transformations. To overcome limi-tations, such as toxicity, volatility, high price and hazardous nature of the conventional methods, the catalysts are adsorbed on silica gel to give the benefits and advantages of ready availability, simple work-up procedure, long catalytic life, environment-friendliness, good to excellent yields and recy-clability. The uses of such catalysts have gained importance worldwide. This article describes some of the important silicated catalysts, namely, heteropolyacids, polyphosphoric acid, perchloric acid, fluoroboric acid, and silicated sulphuric acid. These catalysts have been used in a number of organic reactions to yield compounds that are important in the chemical and pharmaceutical industries. We summarize the beneficial effects of these catalysts and the reports that have been published on them in the past several years. In the present review, the description of the catalysts are introduced followed by a recent research history, and a comparison between the silica supported catalysts and other(polymer) supported catalysts. The article ends up giving the advantages of these catalytic systems over the conventional catalyst.
文摘Microporous heteropolyoxometalates Cs\-\%x\%H\-\{5-\%x\%\}PW\-\{10\}V\-2O\-\{40\}/SiO\-2 were synthesized by a sol\|gel technique and characterized by IR, UV\|Vis, BET adsorption/desorption isotherm. The structural frameworks of Cs\-\%x\%H\-\{5-\%x\%\}PW\-\{10\}V\-2O\-\{40\} are preserved within the silica networks. Cs\-\%x\%H\-\{5-\%x\%\}PW\-\{10\}V\-2O\-\{40\}/SiO\-2 are a kind of polyoxometalate\|silica gel hybrids with uniform micropores of ca. 0.65 nm. They show a high catalytic activity for oxidation reaction of benzyl alcohol by H\-2O\-2(30%) in liquid\|solid systems and product selectivity for benzaldehyde(>96%). The highest activity is observed at \%x\%=2.5 in Cs\-\%x\%H\-\{5-\%x\%\}PW\-\{10\}V\-2O\-\{40\}/SiO\-2 and little formation of benzoic acid and a more deeply oxidized product is observed.
文摘Pd and /or Cu - La2O3/SiO2 catalysts were prepared by Pd and/or Cu supported on La2O3/SiO2 with impregnation The capacities of catalysts reduction and the performance of reaction were studied by H2-TPR and hydrogenation of CO2 The results of H2-TPR indicate that increasing the content of CuO is advantageous to the reduction of high dispersing CuO, but adding La2O3 hinder the reduction of high dispersing CuO It was found that Pd-Cu alloy formed while Pd, Cu impregnated on La2O3/SiO2 The results of hydrogenation of CO2 indicate that CO2 conversion is promoted by adding La2O3 increasing the content of CuO The thermal stablity of methanol formation was improved by adding La2O3 Aldehyde can be obtained when Pd-Cu were used as active components, and the production of methanol was related to the content of Pd loaded on the
