Highly stable Cu catalyst embedded in N-doped carbon microsphere for hydrogenation of dimethyl oxalate to methyl glycolate

Cu catalyst often subjects to low stability due to chemical state transformation during carbon-oxygen hydrogenation reaction. In the present work, the copper catalysts embedded in N-doped carbon microsphere (Cu@NC) were fabricated by one-pot hydrothermal method and applied in dimethyl oxalate (DMO) hydrogenation to methyl glycolate (MG). The optimized Cu@10NC catalyst exhibited an excellent stability with DMO conversion of 80.1% and MG selectivity of 80.3% during 220 h long-term evaluation under 1.9 MPa, 210 °C, H2/DMO molar ratio of 80 and WHSV of 0.8 gDMO·gCu-1·h-1, beneficial from the stable Cu+ ratio and confinement effect of carbon support during the reaction. The Cu dispersion and Cu+ proportion can be finely controlled by varying the N-doping content due to the enhanced interaction between Cu and carbon microspheres. Particularly, graphitic-N is primarily accountable for Cu dispersion, while pyridinic-N is dominantly responsible for the stabilization of Cu+ species.