Epoxidation of ethylene over an Ag atom embedded B-vacancy defective boron-nitride nanosheet via a trimolecular Langmuir–Hinshelwood mechanism: A DFT investigation

The oxidation of ethylene (C 2 H 4 ) to produce value-added chemicals such as ethylene oxide is an important chemical process in industry. We investigated the oxidation of C 2 H 4 by O 2 catalyzed by an Ag-atom embedded boron-nitride nanosheet (Ag/ h -BN) using density functional theory calculations. The adsorption energies of O 2 and C 2 H 4 molecules on Ag/ h -BN are -0.85 and -1.21 eV, respectively, demonstrating that C 2 H 4 has a stronger tendency to interact with this surface. A trimolecular Langmuir-Hinshelwood mechanism involving the -CH 2 CH 2 OOCH 2 CH 2 - intermediate was found as the most efficient pathway for C 2 H 4 epoxidation. This intermediate is converted into two ethylene oxide molecules after passing over an activation barrier of 0.44 eV. The competing pathway to produce an acetaldehyde molecule has a very high activation barrier, indicating that C 2 H 4 epoxidation can occur selectively over Ag/ h -BN. These findings may be useful for modeling and designing high performance and selective single-metal catalysts for ethylene epoxidation.