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
Polymerization of methyl methacrylate in toluene, at various temperatures with silica gel grade 955 supported \[C\-5Me\-5\]\-2SmMe(THF) was studied. This type of polymerization exhibits several characteristics. The PM...Polymerization of methyl methacrylate in toluene, at various temperatures with silica gel grade 955 supported \[C\-5Me\-5\]\-2SmMe(THF) was studied. This type of polymerization exhibits several characteristics. The PMMA obtained has higher number average molecular weight and wider molecular weight distribution compared with those obtained by solution polymerization with homogeneous catalyst system, although the polymerization activity is lower.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Polymerization of methyl methacrylate in toluene, at various temperatures with silica gel grade 955 supported \[C\-5Me\-5\]\-2SmMe(THF) was studied. This type of polymerization exhibits several characteristics. The PMMA obtained has higher number average molecular weight and wider molecular weight distribution compared with those obtained by solution polymerization with homogeneous catalyst system, although the polymerization activity is lower.
