Mesoporous/Microporous Titanium Silicalite with Controllable Pore Diameter for Cyclohexene Epoxidation

A mesoporous/microporous titanium silicalite with controllable pore diameter was synthesized in an easy and new route by using cetyltrimethylammonium bromide (CTAB) as a mesoporous template and tetrapropylammonium hydroxide (TPAOH) as a microporous template. This route leads to the formation of mesopores prior to the crystallization of microporous MFI topology. The porosity formation sequence makes the two types of channels, which are micropores with MFI topology and mesopores with wormlike morphology, distribute homogeneously. The pore diameter of the mesopores can be adjusted from the maximum center of 2.6 nm to that of 6.9 nm by tuning the molar ratio of CTAB to silicon from 0.125 to 0.20. The mesoporous/microporous titanium silicalite catalysts were evaluated in the epoxidation of cyclohexene, and showed excellent catalytic activities, with respect to the conventional microporous TS-1, because of the enhanced diffusion property in the mesopores and higher titanium content near the external surface of the former.