Small-angle neutron-scattering studies of the template-mediated crystallization of ZSM-5-type zeolite

Small-angle neutron-scattering scattering is a useful new approach to the study of zeolite crystallization from aluminosilicate gels and the action of template molecules. It has been applied to gels for synthesis of zeolite ZSM-5 using tetrapropylammonium ions as templates where the scattering length densities of the gel particles and their texture were determined by using contrast variation methods. Gels formulated from soluble silicate incorporate template molecules promptly into an amorphous {open_quotes}embryonic{close_quotes} structure, and crystallization ensues via a solid hydrogel transformation mechanism. Gels formulated from colloidal silica show different scattering behavior, and a liquid-phase transport mechanism is inferred. 8 refs., 4 figs., 2 tabs.