Rapid and Facile Synthesis of Highly Mesoporous SSZ-13 Zeolites from Interzeolite Conversion of Y Zeolite

The highly mesoporous SSZ-13 zeolites were successfully and rapidly synthesized via the conversion of Y zeolite using organosilane ([3-(trimethoxysilyl)propyl] octadecyldimethylammonium chloride, TPOAC) as a mesopore-directing agent. The morphologies and mesoporosities of hierarchical SSZ-13 zeolites significantly depend on the additive amounts of TPOAC in the synthesis system. Hierarchical SSZ-13-MT-2 zeolite, synthesized with a high molar proportion of TPOAC (x), exhibited aggregate particles assembled from nanocrystals approximately 20 nm in size, along with the largest external surface area and mesoporous volume, reaching 405.7 m2/g and 0.40 cm3/g, respectively. The crystallization evolution mechanism was discussed in detail, revealing that the rapid synthesis and formation of mesoporous structures in the hierarchical SSZ-13-MT-x samples can be attributed to a cooperative strategy involving the conversion from the Y zeolite to SSZ-13 along with the TPOAC-directed synthesis of mesoporous zeolites. Notably, the concentrations of Brønsted acid sites on the external surface of hierarchical SSZ-13-MT-x samples showed a linear correlation with the ratio of the external surface areas to total surface areas. Even at a high Si/Al ratio, the hierarchical SSZ-13-MT-2 sample demonstrated enhanced accessibility to Brønsted acid sites in the external surface. Furthermore, hierarchical SSZ-13-supported Pt catalysts exhibited the excellent catalytic performances in the naphthalene hydrogenation reaction. This facile synthetic strategy provides an alternative approach for preparing highly mesoporous zeolites.