Reaction temperature controlled selective hydrogenation of dimethyl oxalate to methyl glycolate and ethylene glycol over copper-hydroxyapatite catalysts

Copper based hydroxyapatite (HAP) supported (Cu/HAP) catalysts are synthesized by a facile ammonia-assisted one-pot synthesis (AAOPS) method and carefully studied on the selective hydrogenation of dimethyl oxalate (DMO). The Cu/HAP catalysts exhibit different catalytic performance compared with the conventional Cu/SiO2 ones. When the reaction temperatures are set at 483 K, the optimal Cu/HAP catalyst displays relatively high and stable catalytic performance with methyl glycolate (MG) as the main product. The yield to MG can reach 70% which is the highest value on the copper based catalysts till now. When the reaction temperature is risen to 513 K, the selectivity of the catalysts swifts to the ethylene glycol (EG), and the catalytic behavior is similar to the traditional Cu/SiO2 catalysts. It was found that the copper phosphate species play important roles in stabilizing the copper particles and the Cu+ species. Also, the abundant surface hydroxy groups on the catalysts are responsible for the distinct catalytic performance of the Cu/HAP catalysts.