Role of heteroatoms in precursor formation of zeolites

摘要

The structures of amorphous precursors formed prior to the onset of crystallization of microporous aluminosilicates (mordenite) and zincosilicates (VPI-7) are determined employing high-energy X-ray diffraction (HEXRD) technique. Without heteroatoms, silicate ring size is distributed around 6 ring (6R). Aluminum incorporation promotes the formation of smaller rings (especially 4R), while zinc incorporation promotes the formation of 3R before their crystallizations. The ring statistics for the crystalline zeolites are formed in the corresponding amorphous precursors.