Promoting effect of boron oxide on Ag/SiO2 catalyst for the hydrogenation of dimethyl oxalate to methyl glycolate

A highly active and stable catalyst for the hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG) had been developed. The Ag-B2O3/SiO2 catalysts were prepared by impregnation method with boric acid (H3BO3). The properties and the structures of the catalysts were fully characterized by BET, XRD, H2-TPR, NH3-TPD, FTIR, XPS and TEM. Compared with Ag/SiO2 catalyst, the Ag-B2O3/SiO2 catalyst exhibited significantly enhanced catalytic performance and high stability for the hydrogenation of DMO to MG under relatively milder reaction conditions (180 °C, 0.5 MPa). A high yield of 96.1% for MG was achieved over Ag-B2O3/SiO2 catalyst, while the yield of MG was only 54.3% over Ag/SiO2 catalyst. The excellent catalytic performance for Ag-B2O3/SiO2 catalyst was attributed to the introduction of B2O3. The addition of B2O3 to Ag/SiO2 catalyst favored the formation of highly dispersed Ag centers with electron-deficient state, which can strongly bind and activate the ester and acyl groups of DMO in the hydrogenation processes. Besides its effectiveness, the catalyst showed an excellent stability which can be performed for 264 h under the reaction conditions of 180 °C, 0.5 MPa H2 and the weight space velocity of 0.2 h−1.