Enhanced selective hydrogenation of glycolaldehyde to ethylene glycol over Cu0-Cu+ sites

Abstract

Selective hydrogenation of hydroxyaldehydes to polyalcohols is challenging due to the competitive hydrogenation of CO and CO. This study develops heterogeneous Cu catalysts for the selective synthesis of ethylene glycol via batch liquid-phase hydrogenation of glycolaldehyde. SiO2 supported Cu, fabricated by ammonia evaporation, enables to catalyze the CO bond hydrogenation with retaining the CO bond intact, yielding higher selective hydrogenation activity with ethylene glycol selectivity up to 99.8 % relative to MgO, Al2O3, CeO2, and TiO2 supports and Cu/SiO2 synthesized by deposition–precipitation and impregnation. Characterizations confirm that highly efficient 20Cu/SiO2-AE-623 K catalyst fabricated by ammonia evaporation is featured with larger Cu0 and Cu+ surface areas, of which the Cu+ species created from reducing copper phyllosilicate exhibit higher reactivity. A synergistic effect between Cu+ and Cu0 facilitates the selective adsorption/activation of glycolaldehyde on Cu+ sites and the dissociation of H2 on Cu0 sites, bringing a remarkable improvement in the selective hydrogenation performance.