Dynamic redox cycle of Cu-0 and Cu+ over Cu/SiO2 catalyst in ester hydrogenation

Esters (methyl acetate, ethyl acetate, dimethyl oxalate) can oxidize Cu-0 of the reduced Cu/SiO2 catalyst to Cu+ and the obtained Cu+ can be reduced back to Cu-0 by H-2 under reaction conditions. Cu-0 and Cu+ are in a dynamic cycle during ester hydrogenation. The ratio of Cu+/Cu-0 in the presence of esters under reaction conditions is probably different from that in the absence of esters under characterization conditions. The effect of the dynamic cycle on the Cu+/Cu-0 ratio should be taken into consideration when establishing the relationship between the Cu+/Cu-0 ratio and reaction performance.