Highly selective and stable Cu/SiO2 catalysts prepared with a green method for hydrogenation of diethyl oxalate into ethylene glycol

Abstract

Dimethyl oxalate (DMO) hydrogenation for ethylene glycol (EG) production is problematic due to environmental concerns and safety regulations. Therefore, development of improved methods for diethyl oxalate (DEO) hydrogenation based EG production is desirable. The objective of this research was to develop a cost-effective and environmentally benign approach for the synthesis of highly active and stable Cu/SiO2 catalysts for selective hydrogenation of diethyl oxalate (DEO) to ethylene glycol (EG). Here, ammonium carbonate is used to prepare Cu/SiO2 catalysts through deposition precipitation instead of the conventional pollution-producing evaporation process associated with the use of ammonia. The Cu/SiO2 catalysts prepared with the new method achieved 6.9–13.1% higher selectivity and showed better stability. The improved stability and selectivity resulted from increased chemical adsorption of DEO and H2 due to the high Cu2O concentration and Cu+/(Cu0+Cu+) ratio (reduced from ion-exchanged CuOSi units), and reduced carbon deposition on the Cu/SiO2 catalyst. The Cu2O reduced from CuOSi units in the Cu/SiO2 catalyst prepared by the new method was more stable than the Cu+ species reduced from copper phyllosilicate in the Cu/SiO2 catalyst prepared by the conventional method. Therefore, the new Cu/SiO2 catalyst preparation method appears most promising.