Alkaline earth modified activated carbon supported Cu catalysts with enhanced selectivity in the hydrogenation of dimethyl oxalate to methyl glycolate

Abstract

In this work, the effect of alkaline earth metal modification on the catalytic performance of activated carbon supported Cu was investigated. The experimental results showed that the introduction of Ca and Sr improved the selectivity of methyl glycolate (MG) during hydrogenation of dimethyl oxalate (DMO) in gas phase. The optimal loading amount of Ca was 0.1 wt%, and under the optimal conditions (temperature 240 °C, pressure 2 MPa, hydrogen-ester ratio of 80, feedstock 15% DMO methanol solution, and WLHSV_DMO = 0.9 h^-1) the selectivity of MG was as high as 94%, and the conversion of DMO was 97%. The optimal loading of Sr was 0.2 wt% with MG selectivity up to 89% and DMO conversion of 98%. The results of catalyst characterization showed that both Ca and Sr modifications were beneficial to further reduce the particle size of Cu, improve the dispersion of Cu, increase the basicity of the catalyst, and improve the stable presence of Cu⁺ during the reaction process. Cu⁺ was beneficial to the stabilization of the MG species, in which Cu⁺ accounted for more in the Ca-modified catalysts Cu⁺/(Cu⁺ + Cu⁰) = 0.65, and in the Sr-modified ones Cu⁺/(Cu⁺ + Cu⁰) = 0.51. Therefore, both Ca and Sr modified catalysts showed improvement in the selectivity of MG.