Highly selective catalytic oxidation of methane to methanol using Cu–Pd/anatase†

Abstract

Direct conversion of methane into high value-added products is of great practical significance. The synergistic effect in catalysts with dual-active components show potential to increase the methanol yield and selectivity. In this work, Cu–Pd/anatase is in situ generated and exhibits a relatively high methanol yield rate of ∼31 800 μmol g_cat⁻¹ h⁻¹ and near-exclusive selectivity of liquid products (methanol). The reaction mechanism behind the heterogeneous catalysis process has been investigated. It is confirmed that copper ions hold the ability to produce hydrogen peroxide which can be further promoted by anatase. Chlorine ions can promote the stable adsorption of CO and the formation of *CH₃ intermediates, facilitating high activity and selectivity for methanol production. Pd and Cu cooperatively dissociate methane, which promotes the formation of key configuration metal-CH₃. The ˙CH₃ intermediate desorption will be facilitated on Cu–Pd/anatase through the manner of electron regulation, which is proved by the combination of density functional theory calculations and in situ infrared spectroscopy. Methanol is formed when a ˙CH₃ is desorbed from a copper site and combines with a hydroxyl radical.