Growth model of oriented crystals of zeolite Si-ZSM-5

Abstract

A model for the growth of Si-ZSM-5 (silicalite-1) crystals from zeolite synthesis mixtures is proposed. Nucleation and crystal growth occur at the interface of gel particles and liquid, the only place where both the silicon source and template are present in abundance. In the extension of this model to growth on a support surface, a precursor gel layer plays an important role as an anchoring site for the template molecules. Orientation results from the preferential growth of the ac-plane of the crystallites in the plane of the substrate surface. The presence of alkali ions at this surface may adversely affect zeolite nucleation.