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

The addition of boron (B) as a promoter to the Ag/SiO 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/SiO catalyst (Ag-B/SiO) was inferior to incipient wetness impregnation introduction of the Ag/SiO catalyst (B/Ag/SiO). Moreover, the effects of B contents (0.5-5 wt %) on the physicochemical properties and catalytic performance of the B/Ag/SiO catalysts were investigated by XRF, N-physisorption, XRD, FTIR, TEM, EDX mapping, H-TPR, NH-TPD, XPS, and catalytic testing. The results indicated that both the catalytic activity and stability of the Ag/SiO catalyst were noticeably enhanced after the introduction of B. The B/Ag/SiO 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.