Simultaneously Enhanced Stability and Selectivity for Propene Epoxidation with H₂ and O₂ on Au Catalysts Supported on Nano-Crystalline Mesoporous TS-1

It is a challenging task to design efficient Au/Ti-containing catalysts for propene epoxidation with H2 and O2 that simultaneously achieve high catalytic stability and selectivity to propylene oxide (PO). This contribution first describes the synthesis of a nanocrystalline mesoporous titanium silicalite-1 (MTS-1) by dry-gel conversion that employs cheap triblock copolymers as template. Compared with TS-1, MTS-1 has a shortened reactant/product diffusion length as a result of smaller crystal size (<100 nm) and the presence of mesopores (ca. 3 nm). Surprisingly, this designed catalyst shows simultaneously improved PO selectivity over 95% as well as stability over 40 h, much better than the traditional Au/TS-1 catalyst. Moreover, the intrinsic reason for the enhanced performance is elucidated. The better mass transfer ability together with higher hydrophobicity of Au/MTS-1 results in lower coke weight and absence of refractory aromatic coke. In this way, the side reactions and deactivation caused by blocking of micropore are inhibited.