Re- and Cs-Copromoted Silver Catalysts for Ethylene Epoxidation: A Theoretical Study

Resumo

The effect of Re- and Cs-copromotion of Ag catalysts for ethylene epoxidation is studied computationally using density functional theory approach. The models reflecting Re involvement in the form of oxyanion and as a component of Ag-Re alloys are considered. The synergistic effect of Cs and Re is caused by the formation of the CsReO_x species, with Cs stabilizing the Re oxyanion to promote ethylene epoxidation over the Ag catalysts. The role of Re is proposed to be related to altering the electron density distribution, compensating oxygen vacancies, covering non-selective sites, and providing the optimal retention time for initial compounds, products, and oxametallacycles on the catalyst surface.