Cost-efficient core-shell TS-1/silicalite-1 supported Au catalysts: Towards enhanced stability for propene epoxidation with H2 and O2

Designing cost-effective TS-1 with enhanced catalytic stability in direct propene epoxidation with H-2 and O-2 is attracting tremendous research interests. In this work, a novel hydrophobic TS-1/S-1 lamellar support with Ti-rich shell and Si-rich cores is first synthesized using trace amount of TPAOH template. The effect of TPAOH concentration on physico-chemical properties of catalyst is then investigated. Compared with conventional Au/TS-1, optimum Au/TS-1/S-1 catalyst exhibits fantastic catalytic stability for over 100 h and good PO formation rate of 126 g(PO)h(-1)kg(Ca)t(-1). Furthermore, the intrinsic reason for the enhanced stability is elucidated by TGA, XPS, Si-29 NMR and FT-IR. It is found that the coke weight for Au/TS-1/S-1 is only 0.99 wt%, much lower than 4.9 wt% for Au/TS-1 catalyst. The refractory aromatic coke is also not formed. On the one hand, this could be due to the unique core-shell structure and the presence of mesopores, which reduce the long diffusion path. On the other hand, it is because of enhanced hydrophobicity. This work sheds new light on the design and synthesis of highly effective and cost-efficient Au/Ti-containing catalysts.