Epoxidation of Propylene on a [Ag14O9] Cluster Representing Ag2O (001) Surface: A Density Functional Theory Study

Density functional theory calculations were employed to study partial oxidation of propylene on a [Ag14O9] cluster representing Ag2O (001) surface for which positive effect for ethylene oxide formation has been reported in our earlier work at the same level of theory (Fellah et al., Catal Lett 141: 762, 2011). Propylene oxide (PO), propanal, acetone and G-allyl radical formation reaction mechanisms were investigated. P-allyl formation path and two propylene adsorption paths resulting in PO formation are competing reactions on silver oxide (001) surface because of their comparable activation barriers (9, 8 and 9 kcal/mol, respectively) while P-allyl formation path is generally a more favorable path on Ag (111) surface as reported in previous theoretical literature. SO2 adsorption calculations indicate that silver oxide has lower Lewis basicity relative to oxygen atom adsorbed on silver. Calculations also showed that surface oxygen atom of Ag2O (001) has a higher spin density compared to that of oxygen atom adsorbed on Ag (111), which indicates that oxygen atom on Ag2O (001) cluster has a more radical character.