Au/uncalcined TS-1 catalysts for direct propene epoxidation with H2 and O2: Effects of Si/Ti molar ratio and Au loading

For direct propene epoxidation with H2/O2, TS-1 with blocked micropores (TS-1-B) is recognized as an attractive support for Au catalysts with enhanced stability and activity by suppressing the deactivation caused by micropore blocking. In this work, as a consecutive effort, effect of Si/Ti molar ratio of TS-1-B on catalytic performance is investigated. It is shown that the optimum Si/Ti molar ratio is 40. In other words, both lower and higher ratios are unfavorable for the formation of propylene oxide, which are possibly attributed to the presence of extra-framework Ti species and the difficult transmission of hydroperoxide species from Au surface to nearby Ti sites, respectively. Based on this, effect of Au loading on catalytic performance is further examined. When the Au loading is 0.13 wt%, the catalyst shows not only high PO formation rate of 158 gPO h−1 kgCat−1 comparable to the reported best activity without adding promoters, but also significantly enhanced stability at 200 °C over 30 h