Abstract
Zeolites are hydrated aluminosilicates containing alkali and alkaline-earth metal ions. Their framework structures are composed of an infinitely extending three-dimensional network of AlO4 and SiO4 tetrahedra, and characterized by intracrystalline void spaces such as cavities and channels surrounded with aluminosilicate network. The void spaces in zeolites are larger than those in other tectosilicates such as feldspars, and hence zeolites have more open, microporous structures. Such structural features yield various properties such as ion exchange, adsorption, molecular sieve and catalysis. In this paper, the properties of high silica zeolites, the basis on the development of acidity in zeolites, and the effects of molecular-shape selectivities in zeolite catalysts are described in connection with the compositions and structures of zeolites. In final, the catalytic conversion of methanol to hydrocarbons by use of zeolite ZSM-5 is briefly described.
