The Surface Atomic Oxyradical Mechanism for Ag-Catalyzed Olefin Epoxidationl

We report comprehensive, quantitative, ab initio theoretical estimates for the energetics involved in the Ag-catalyzed epoxidation of olefins. From these estimates, a detailed mechanism is proposed. This mechanism (based on theoretical quantum chemical studies of the interaction of atomic and molecular adsorbates with clusters of Ag atoms) proposes that a surface atomic oxyradical anion is the active oxygen species for forming epoxide. This mechanism explains the role of electronegative (Cl-) and electropositive (Cs’) promoters and explains why selectivity (toward epoxide) is far higher for ethylene than for propene and other higher olefins. Recent experiments which suggested OZ(adj as the active species are reinterpreted within the context of this new atomic oxygen radical mechanism.