A significantly enhanced Cu+/Cu0 catalytic active structure via the electronic effect of K for methyl glycolate synthesis

An enhanced Cu + /Cu 0 catalytic structure via the electronic effect of K was fabricated; • The proper amount of K could regulate the ratio of Cu + /Cu 0 and promote Cu dispersion; • Both the enhanced Cu + /Cu 0 ratio and the smaller Cu size promote the generation of MG; • The increased basic sites by the K doping remarkably increase the ethers by-products; • The deactivation was caused by the boosted Cu + ratio and the coated active sites by K. In this work, the CuZr 2 catalysts with significantly enhanced Cu + /Cu 0 catalytic active structures via the electronic effect of K were synthesized by the means of citrate complexation and used for dimethyl oxalate (DMO) hydrogenation to methyl glycolate (MG). The CuZr 2 –1.0 K sample exhibited the most outstanding performance, achieving a DMO conversion of 93.4% and MG selectivity of 85.8%. And the role of K in Cu-based catalysts for DMO hydrogenation is universal. The reduction of the catalyst was inhibited after potassium addition, lowering the Cu 0 content, thus leading to a decrease in the H 2 adsorption capacity of the catalyst, and accordingly, its activity decreased. The results showed that the ratio of Cu + /Cu 0 increased after K doping, and the adsorption strength of the catalyst for H 2 was weakened, which inhibited the deep hydrogenation of DMO. Simultaneously, the smaller size of metallic Cu via the appropriate amount of K doping facilitated the desorption of MG. Therefore, the selectivity for the target product MG was remarkably improved. However, the basic sites on the catalyst surface could increase after K doping, which would lead to an increase in the ether by-products. As the reaction proceeded, the ability of the catalyst to adsorb and activate H 2 was diminished due to the significantly increased surface K content and Cu + ratio, leading to the deactivation of the K-doped catalyst. This study provides a potential pathway for alkali metals to regulate the electronic structure of Cu-based catalysts and apply them to the hydrogenation of DMO to MG. Download: Download high-res image (258KB) Download: Download full-size image