Selective Hydrogenation of Dimethyl Oxalate to Methyl Glycolate over Boron-Modified Ag/SiO2 Catalysts.

The addition of boron (B) as a promoter to the Ag/SiO2 catalyst for the selective hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG) was investigated. A comparison of the preparation method for incorporation of B found that the addition during the ammonia evaporation deposition-precipitation synthesis of the Ag/SiO2 catalyst (Ag-B/SiO2) was inferior to incipient wetness impregnation introduction of the Ag/SiO2 catalyst (B/Ag/SiO2). Moreover, the effects of B contents (0.5-5 wt %) on the physicochemical properties and catalytic performance of the B/Ag/SiO2 catalysts were investigated by XRF, N2-physisorption, XRD, FTIR, TEM, EDX mapping, H2-TPR, NH3-TPD, XPS, and catalytic testing. The results indicated that both the catalytic activity and stability of the Ag/SiO2 catalyst were noticeably enhanced after the introduction of B. The B/Ag/SiO2 catalyst with 1 wt % B showed the best catalytic performance of 100% DMO conversion and 88.3% MG selectivity, which could be attributed to the highest dispersion of the active metal and the smallest Ag particle size stabilized by the strong interaction between silver and boron species.