Au nanoparticles deposited on the external surfaces of TS-1: Enhanced stability and activity for direct propylene epoxidation with H2 and O2

Abstract

Au/TS-1 catalysts prepared by deposition–precipitation method are very promising for direct propylene epoxidation with H2 and O2. However, the catalysts usually suffer from rapid deactivation. In this work, calcined TS-1 with open micropores (TS-1-O) is first used to support Au catalysts, and then the used catalysts at different time-on-streams are characterized to understand the deactivation mechanism. The micropore blocking by carbonaceous deposits is found to be responsible for the deactivation. We therefore suggest a principle of catalyst design to improve the long term stability by depositing Au nanoparticles on the external surfaces of TS-1. For this purpose, uncalcined TS-1 with blocked micropores (TS-1-B) is used to support Au catalyst. As expected, the designed catalyst is not only very stable because of the elimination of pore blocking and the more accessible active sites, but also highly active with the PO formation rate of 125 gPO h−1 kgCat−1 for over 30 h.