Study of the active phase of silver catalysts for ethylene epoxidation

An investigation of ethylene epoxidation on α-alumina-supported silver catalysts promoted by cesium found that cesium favored the formation of strongly adsorbed electrophilic oxygen. The reactant mixture (C2H4 and O2) modified the silver structure, favoring the formation of oxygen electrophilic species. In situ DRIFTS results demonstrated the formation of a thin film of silver for the cesium-promoted catalyst, decreasing the influence of the support. Similar in situ DRS profiles were observed for promoted and nonpromoted catalysts, indicating that the effect of cesium is due mainly to geometric rather than electronic effects. At iso-conversion conditions, Cs presence increased the yield toward ethylene oxide.