Identification of Synergistic Actions between Cu0 and Cu+ Sites in Hydrogenation of Dimethyl Oxalate from Microkinetic Analysis

The kinetics of dimethyl oxalate (DMO) hydrogenation over Cu(111) and Cu 2 O(111) has been studied to understand the role of Cu 0 and Cu + sites in ethyl glycol (EG) production over Cu-based catalysts by the combination of density functional theory calculations and microkinetic analysis. The calculated results suggest that the presence of the Cu + sites would strengthen the binding of the reactants, products, and reaction intermediates to the substrate and thus promote the dissociation of DMO and H 2 . The Cu 0 sites are found to be beneficial to the hydrogenation of the acyl species whereas the Cu + sites are primarily responsible for the CH 3 OH formation. Microkinetic analysis indicates that the existence of the Cu + sites would increase the turnover frequency for the EG formation on Cu(111) by a factor of 20, under typical operating conditions. Hence, the excellent catalytic performance of the Cu-based catalysts in the hydrogenation of DMO to EG is attributed to the synergistic effect between the Cu 0 and Cu + sites, and a proper Cu 0 /Cu + molar ratio can dramatically improve the catalytic activity.