Partial oxidation of propylene with H2 and O2 over Au supported on ZrO2 with different structural and surface properties

Abstract

Various ZrO2 with pure tetragonal, monoclinic, and mixed phases were used as carriers of gold nanoparticles for an exploration to production of propylene oxide (PO) in co-presence of propylene with H2 and O2. Catalysts with similar gold dispersion (2–5 nm gold particles) were prepared by a deposition–precipitation method. 100% selectivity to PO was obtained for the first time over non-titanium-supported Au catalysts on both tetragonal and monoclinic ZrO2 supports, which needs a good match of nanogold and active sites (quite possible hydroxyls connected with Zr4+). However, Au/tetragonal ZrO2 benefits PO formation that could be accelerated by hydroxyl groups while Au/monoclinic ZrO2 generates more acrolein and suppresses CO2 formation. The active sites for the production of PO are speculated to be Au and Zr-O rectangular pyramids in ZrO2, similar to that on TiO2 and acrolein appears on the Au near oxygen vacancies.