Effect of TiO2 on catalytic performance of gold-titanium-catalyzed gas-phase epoxidation of propylene

Abstract

The gas-phase epoxidation of propylene with H2/O2 is a promising method to generate propylene oxide (PO). Au/TS-1 is preferred catalyst due to the synergistic effect between Au nanoparticles and framework Ti species. TS-1 with high Ti content are used as support for Au catalysts, which are expected to achieve fantastic catalytic performance. However, their actual catalytic properties are generally unsatisfactory. The reason for this phenomenon is that the role of TiO2 in Ti-containing support is unclear. Here, we found that increasing TiO2 content in Ti-containing supports offered improving isoelectric point (IEP), which could be responsible for the obviously enhanced Au loading. More Au nanoparticles inserted into the TS-1 micropore favors their cooperation with framework Ti sites to realize higher C3H6 conversion. Simultaneously, propanal generated via direct propylene oxidation catalyzed by Au/TiO2 leads to the decrease of PO selectivity. A volcanic-shaped relationship between TiO2 content and PO formation rate is emerged.