Partial hydrogenation of dimethyl oxalate on Cu/SiO2 catalyst modified by sodium silicate

Abstract

Cu/SiO2 catalyst modified with Na2SiO3 was prepared by the ammonia evaporation impregnation method and applied in the partial hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG). The addition of Na2SiO3 led to a serious shrinkage of those accumulation pores in the catalyst, but hardly affect the structure of the mesopores bellow 8 nm. Moreover, the trace amount of Na2SiO3 enhanced the formation of copper phyllosilicate, which resulted in a minor increment in Cu+ species as well as a decrease of Cu0 species. An unexpected high MG yield of about 83% and MG selectivity of 99.8% was achieved over the Cu/SiO2 catalyst modified with 0.5% Na2SiO3 in the partial hydrogenation of DMO. The loss of some smaller accumulation pores due to the presence of Na2SiO3 dopant could be key reason for the higher selectivity, because the larger pores can ensure the fast transfer of MG to the external surface. Thus, the further hydrogenation of MG can be prevented. Moreover, the decrement of Cu0 species induced by doping of Na2SiO3 could be another reason for the higher selectivity to MG, since insufficient activated H2 could be provided for the further hydrogenation of MG.