Plasma-catalytic Direct Oxidation of Methane to Methanol over Cu-MOR: Revealing the Zeolite-confined Cu 2+ Active Sites

Abstract

Efficient methane conversion to methanol remains a significant challenge in chemical industry. This study investigates the direct oxidation of methane to methanol under mild conditions, employing a synergy of non-thermal plasma and Cu-MOR (Copper-Mordenite) catalysts. Catalytic tests demonstrate that the Cu-MOR IE-3 catalyst (i.e., prepared by three cycles of ion exchange) exhibits superior catalytic performance (with 51% methanol selectivity and 7.9% methane conversion). Conversely, the Cu-MOR catalysts prepared via wetness impregnation tend to over-oxidize CH to CO and CO . Through systematic catalyst characterizations (XRD, TPR, UV-Vis, HRTEM, XPS), we elucidate that ion exchange mainly leads to the formation of zeolite-confined Cu species, while wetness impregnation predominantly results in CuO particles. Based on the catalytic performance, catalyst characterizations and in-situ FTIR spectra, we conclude that zeolite-confined Cu species serve as the active sites for plasma-catalytic direct oxidation of methane to methanol.