Hierarchical Ti-beta with a three-dimensional ordered mesoporosity for catalytic epoxidation of bulky cyclic olefins

摘要

The construction of hierarchical titanosilicate beta zeolites with desirably interconnected meso-/microporosity, controllable morphology and enhanced activity of catalytic oxidation is a pervasive challenge in the zeolite community. We report here in the synthesis of the hierarchical titanosilicate beta zeolite with a three-dimensionally ordered mesoporous-imprinted structure (3DOm-i Ti-beta) through the postsynthetic treatment of the parent 3DOm-i Al-beta by successive dealumination and titanation. The highly interconnected intracrystalline meso-/microporosity derived from the well-retained 3DOm-i structure led to both enhanced diffusion property and better accessibility of active sites to the bulky substrates, which was confirmed by the improved catalytic performances in the epoxidation of cyclic olefins (cyclohexene and cyclooctene) compared with the conventional solely microporous Ti-beta and TS-1. Moreover, the demonstrated that 3DOm-i Ti-beta catalyst exhibited not only a superior stability but also a facile recyclability by simple calcination in the epoxidation reaction.