Histidine-derivate modified Cu/SiO2 catalyst for selective hydrogenation of dimethyl oxalate to methyl glycolate

Abstract

Cu-based catalysts are extensively employed in dimethyl oxalate (DMO) hydrogenation, but it is rather challenging to obtain methyl glycolate (MG) over traditional Cu-based catalysts with high selectivity at high DMO conversion. Herein, the physicochemical properties of the typical Cu/SiO₂ catalyst and its corresponding catalytic performance toward DMO hydrogenation were tuned by surface modification with a biological template (histidine). On the premise of near-total conversion of DMO, the MG selectivity substantially increased from 15.7 % to 82.9 % when the typical Cu/SiO₂ catalyst was modified by 7 wt% histidine, which was fairly impressive among the reported results up to now. Furthermore, comprehensive characterization and kinetic study disclosed the underlying mechanism. After thermal treatment, histidine retains its skeleton framework (imidazole), the emerging Cu–N interaction weakened the Cu-silica interaction, leading to the reduction in percentage of Cu⁺ and increase in electron density on the Cu/SiO₂ catalyst. As a result, the adsorption and activation ability toward MG were obviously suppressed, which was proved as the critical step for selective hydrogenation of DMO toward MG.