Thermal decomposition of cation exchange forms of zeolite A

Abstract

1. After partial dehydration of zeolites A(LiA, NaA, KA, RbA, CsA, CaA, MgA) (degree of dehydration 50–70%), there is a small compression of their cubic structures with the formation of metaphases, the volume of the cubic unit cells of which remains constant upon further dehydration, while the density decreases. 2. The greatest thermal stability, determined by the temperature interval of the process of amorphization of the metaphase, is possessed by metaphases of zeolites with rather large exchange cations (K, Rb, Cs). 3. The final products of crystallization of the amorphized phase formed as a result of thermal decomposition of the metaphase areβ-eucryptite and anorthite for LiA and CaA, respectively; a mixture of hexagonal and cubic kaliophilites for KA; aluminosilicates with the composition R2O·Al2O3·2SiO2, where R=Rb, Cs, possessing no natural analogs for RbA and CsA; and magnesium aluminate of undetermined composition for MgA.