文摘
Crystallization behaviors of zeolites ferrierite and mordenite in (Na, K)- and Na-aluminosilicate systems, respectively, are investigated. Aluminosilicate products are obtained by the hydrothermal treatment of reactant gel after various heating periods, and their properties are characterized by X-ray diffraction, field-emission scanning-electron microscopy, Raman spectroscopy, inductively coupled plasma-atomic emission spectroscopy, and solid-state 29Si MAS NMR spectroscopy. The results show that crystallization of ferrierite completed suddenly after a long induction period. The formation of a plate-like precursor rich in five-membered rings (5Rs) was observed, which was followed by the crystallization. On the other hand, the crystallization of mordenite proceeds over a long period and such unique precursors were not observed. In the case of ferrierite, it was suggested that the crystallization would proceed through stacking condensation of 5R-rich plate-like precursors.
