Activity of Ethylene Epoxidation over High Surface Area Alumina Support Au-Ag Catalysts

Abstract

In this study, the effect of gold-added silver catalyst supported on high surface area alumina on the ethylene epoxidation activity was investigated. An addition of Au with a small amount was found to create Au–Ag bimetallic which favors the ethylene epoxidation reaction. Gold as a diluting agent on silver surface resulting in destroying multiple Ag sites which favor atomic oxygen adsorption. As a result, adding gold simply creates new adsorption sites for molecular oxygen which is responsible for the ethylene epoxidation reaction. However, at high gold loadings of Ag/Al2O3 catalyst, the formation of Au–Ag alloys was found resulting in decreasing the ethylene epoxidation activity since the Au–Ag alloy favors a complete oxidation reaction. For the ethylene epoxidation reaction, the optimum Ag to Au ratio was 13.18 wt% to 0.63 wt% in the optimum temperature range of 510–520 K.