Some novel aspects of catalysis with solid acids - (Prof. N.R. Dhar Memorial Lecture, November 11, 1999)

Solid acids as catalysts are environmentally Friendly and highly versatile. These catalysts can be used in aqueous, polar and non-polar medium and eve n in the gas phase. Even superacidic catalysts have been developed. These c atalysts offer non-corrosive atmosphere. Special emphasis has been given to cationic ion exchange resins and acid treated clays as catalysts although the heterogenised heteropolyacids and zeolites do have their importance. A variety of industrially important reactions based on alkylation, etherifi cation, esterification, hydrolysis, oligomerisation etc, can be advantageou sly carried out with these catalyst and some of these are highlighted. Ofte n rate and selectivity with solid acids are superior to that realised with homogeneous catalysts and in many cases reactions that are not feasible wit h homogeneous catalysts occur with solid acids. A variety of organic transf ormations can be carried out. Solid acid catalysts can be used in Distillation Column Reactors and in Ext ractive Reaction modes and thus offer a number of advantages associated wit h capital and energy cost. Even impurity removal can be carried out in such reactors. Solid acid catalysts can also be exploited for separation of clo se boiling isomeric/non-isomeric substances.