Post-treatment with ammonium hexafluorosilicate: An effective way to synthesize high silica MCM-22 zeolite

Ammonium hexafluorosilicate (AHFS) is an effective dealumination reagent for MCM-22 zeolite, and the Si/Al2 ratio range of MCM-22 was extended largely (SiO2/Al2O3 ∼ 300) by AHFS treatment. The physicochemical properties of the MCM-22 samples before and after dealumination were characterized by XRD, XRF, N2 adsorption and pyridine-IR measurements. Also, the samples were used as catalysts in C4 alkenes catalytic cracking to propene and the results showed that properly dealuminated MCM-22 (Si/Al2 ratio 58) exhibited higher activity, better stability and similar product distribution relative to the parent MCM-22 zeolite.