Identifying the Predominant Active Copper Species in Methanol Oxidative Carbonylation: A Case for Cu+ or Cu0

A serial of Cu2O/activated carbon (AC) and Cu0/AC catalysts were prepared in situ and evaluated in methanol oxidative carbonylation to clarify the mechanistic differences between Cu2O and Cu0 active species. It was found that both species are catalytically active, but Cu2O exhibits significantly higher efficiency than Cu0. Feeding sequence studies reveal that, on Cu2O, co-adsorbed CH3O and CO react via the L–H mechanism to form CH3OCO intermediates, a favorable pathway for DMC formation; on Cu0, however, CH3OCO forms via the E–R mechanism between adsorbed CH3O and gaseous CO, which is less efficient. Moreover, deactivation is mainly due to copper oxidation, which is sequence-dependent but valence-independent. This study highlights Cu2O as the superior active center and offers fundamental understanding of copper valence-dependent catalysis in methanol oxidative carbonylation.