Ag-(Mo-W)/ZrO2 catalysts for the production of propylene oxide: Effect of pH in the preparation of ZrO2 support

Abstract Direct oxidation of propylene to propylene oxide was carried out over Ag-(Mo-W)/ZrO 2 (pH X) catalysts prepared by changing the pH of Zr precursor solution from 3 to 14 while preparing the ZrO 2 support. It was found that the fraction of monoclinic phase and the ratio of acidity to basicity in the catalysts showed a volcano-shaped trend with respect to pH of Zr precursor solution. Such characteristics were well correlated with the selectivity of reaction towards propylene oxide. Ag-(Mo-W)/ZrO 2 (pH 10) with the highest fraction of monoclinic phase of ZrO 2 and ratio of surface acidity to basicity showed the highest selectivity (68%) for propylene oxide.