Zeolites as Catalysts.I

Abstract

Zeolites are crystalline aluminosilicates of the general formula M_v(AlO₂)_x(SiO₂)_y ZH₂O in which M is either a monovalent or divalent cation. In the former case v is equal to x, whereas if M is divalent v is equal to one-half x. The cation can be exchanged reversibly without destroying the aluminosilicate framework. The water can also be removed without destroying the framework and can be replaced by other molecules whose molecular dimensions are smaller than the pore size of the cavities that are regularly distributed in the framework. The zeolites both occur naturally and can be made synthetically on either laboratory or industrial scale. In recent years they have assumed great technical importance as adsorbents and catalysts. They are also important from a structural point of view, since they represent the next degree of complexity of structure after that of large molecules.