Formation mechanism of three-membered ring containing microporous zincosilicate RUB-17

Abstract

The crystallization process of RUB-17 (RSN-type), a zeolite-type zincosilicate, was studied in order to shed light on the zeolite crystallization mechanism. The sequence of crystallization events from the formation of the initial gel to the complete transformation into a zeolite-type material was investigated. Complementary methods, including XRD, TG/dTG, Raman, ²⁹Si MAS NMR, and SEM, that allowed studying both short and long-range order in the solids were used. The RSN-type structure contains 3-, 4-, 5- and 6-membered rings (MRs) that allowed elucidation of the formation of different building units in the course of zeolite formation. The set of experimental data revealed that the three-membered ring (3MR) was the unit preferentially formed during the induction period. At this stage of gel evolution, the presence of larger rings was not detected. The latter were observed only after the appearance of long-range order in the solid, proved by X-ray diffraction analysis. Hence, the formation of the RSN-type structure was related to the large 3MR population during the induction stage.