CO-Mediated Deactivation Mechanism of SiO2-Supported Copper Catalysts during Dimethyl Oxalate Hydrogenation to Ethylene Glycol

Selective hydrogenation of dimethyl oxalate (DMO) derived from syngas to ethylene glycol (EG) over copper (Cu)-based catalysts is an important transformation of modern syngas chemical industry. Methanol, as a product or a solvent, can dissociate on the Cu surfaces by forming adsorbed CO under H-2 atmosphere at 473 K. A small amount of adsorbed CO accelerates Cu redox processes, thus inhibiting catalytic activity with a negative kinetic reaction order. The strong interaction between CO and Cu blocks active sites and disrupts the synergy of Cu+ and Cu-0 species, which are vital in DMO hydrogenation. The Ostwald ripening of Cu crystallites is induced by CO, resulting in aggregation of Cu crystallites. The imbalance of active species and crystallite aggregation lead to deactivation of the Cu catalysts during DMO hydrogenation to EG.