Optimization of MOFs-induced strategy for preparing anatase-free hierarchical TS-1 towards 1-hexene epoxidation: TPAOH dosage regulation, silanization and stabilizing acidic sites

Abstract

Metal organic frameworks (MOFs)-induced synthetic strategy has been proven a convenient and efficient way for preparing anatase-free hierarchical TS-1 zeolite in our previous study. Here, to further enhance the catalytic performance on 1-hexene, the MOFs-induced hydrothermal synthesis route is optimized by adjusting the amount of tetrapropylammonium hydroxide (TPAOH) and performing different degrees of silanization treatment. A low TPAOH dosage can ensure the synthesized samples have abundant and dense active framework Ti at the expense of partial hierarchical structure. Further deep silanization treatment created mesoporous structure ranging between 20 and 30 nm without affecting the content or distribution of active titanium. The obtained anatase-free hierarchical TS-1 sample Sil-0.150 possesses excellent 1-hexene conversion of >38%. Based on detailed NH3-TPD and Py-IR tests, the presence of high-density Lewis acid sites (LAS) leads to a decreased epoxy product selectivity of 91.5%, and the optimized MOFs-induced synthesis strategy may open up new perspectives for the design and application of high-performance TS-1 catalysts in selective epoxidation reactions of various alkenes.