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Structural analysis of precursors species yielding of three-membered ring zincosilicate zeolite RUB-17 (RSN)

Currently, in zeolite science the preparation of zeolites and zeolite-like materials with large pore volume and extra-large pores is one of the major topics. The topological studies have revealed a linear correlation between the zeolite framework density and the size of building units, i.e., the smallest rings in the frameworks (3- and 4-membered) usually constitute the most open structures. In order to increase the flexibility of the T–O–T angle in zeolite frameworks and as a consequence promote the formation of three- and four-membered rings, cations as Ge and Zn, able to substitute Si and/or Al in zeolite frameworks, have been introduced in zeolite synthesis. The objective of present study is to shed light in the formation of a material containing large number of three-member rings in the structure (RSN-type). The chemical composition of the starting reaction mixture was 1.0TEOS:0.1ZnO:0.5NaOH:0.5KOH:0.08TEAOH:44H2O. The hydrothermal treatment was performed at 180 °C. Several complementary techniques were employed in order to study the formation processes taking place during the synthesis of RUB-17 and to characterize the final product itself. The crystallization process was monitored by powder X-ray diffraction as well as by Raman and NMR spectroscopy. In addition, methods such as TG/DSC, N2 adsorption and chemical analysis have been applied for obtaining additional information to understand better the course of the RUB-17 crystallization process. The physicochemical characterization was completed with theoretical calculations. The correlation of the results of the applied methods allowed following the formation of 3MR in defined periods of the reaction. The performed study provided a new insight on the mechanism of formation of 3MR and the overall course of zeolite crystallization process.

zincosilicate; microporous materials; three-member rings

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