Plate-like precursors formed in crystallization process of ferrierite from (Na, K)-aluminosilicate system

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.

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► Ferrierite showed rapid crystallization in comparison to mordenite.
► A 5R-rich plate-like precursor is observed in the crystallization of ferrierite.
► It is estimated that the crystallization of ferrierite would proceed through the stacking condensation of precursors.