Preparation of anatase-free hierarchical titanosilicalite-1 in favor of allyl chloride epoxidation

Abstract The exploration of highly efficient titanium silicalite-1 (TS-1) zeolite based on small crystal size and controllable coordination state of Ti species is of great importance in promoting the industrial application of TS-1. Herein, hierarchical small-crystal TS-1 free of anatase has been hydrothermally prepared via a glycine-assisted strategy in a tetrapropylammonium bromide (TPABr)-ethanolamine system. Under the synergistic effect of the glycine and seed, a 1 μm in sized microporous TS-1 zeolite was prepared with all Ti species existed in the form of framework Ti. By density functional theory (DFT) calculations, it was found that the self-condensation of Ti(OH)4 to TiO2 could be hindered in the presence of glycine. Furthermore, the TS-1 zeolite was alkaline etched to prepare hierarchical TS-1 free of anatase. The desilication could be slowed down and the framework Ti was basically preserved, when the glycine was present during post-synthesis treatment. The resultant hierarchical TS-1 exhibited a superior catalytic performance in the epoxidation of allyl chloride, that the H2O2 conversion and H2O2 utilization reached 99.3% and 99.7%, respectively. This preparation could simultaneously control over crystal size and coordination state of Ti species and also provide a practical strategy for exploring highly efficient zeolite catalyst.