Investigations of the crystallization of Y and ZSM-3 zeolites

Abstract

The crystallization of the structurally related zeolites Y and ZSM-3 was studied by kinetic experiments with a nucleation gel described in the literature for the synthesis of Y. Self crystallization of this gel resulted at the beginning in a hexagonal phase which changed to a cubic phase after longer crystallization times. The crystallization of Y-zeolite in an appropriate batch was initiated immediately by these gels. The crystallization of ZSM-3 in a Li-containing batch was supported by the initial hexagonal phase. For longer aged gels a preceding recrystallization of the nuclei took place as could be proved by adsorption measurements and studies of the product composition in dependence on the crystallization time. Experiments with different kinds of zeolites as nuclei showed that Y can be nucleated by a series of zeolites containing sixmembered rings via recrystallization processes. For ZSM-3 these processes are mostly too slow for an efficient nucleation.