Abstract: Vinyl chloride selectivity during epoxidation on an atomic oxygen pre-adsorbed Ag(100) surface using density functional theory (DFT) with the periodic slab model was investigated. The reaction mechanism is a two-step process where chloroethylene oxametallacycle intermediate (OMMC) is first formed and then converted to the products. Because of the asymmetry of vinyl chloride, two competitive reaction pathways are evident. The reaction energies and the activation energies of the processes were determined by the DFT calculations. Compared with the reaction activity energy, in one pathway the formation of chloroethylene epoxide (CE) is more favorable than the formation of chloroacetaldehyde (CA) whereas in the other pathway, the formation of CA is more favorable than the formation of CE and acetyl chloride. To further understand the reason for the selectivity difference in these different paths the projected density of states of the C atom and the Ag atom involved in the OMMC was calculated.

Key words: vinyl chloride, density functional theory, selectivity epoxidation, silver, pre-adsorption, oxygen