Enhanced selective hydrogenation of dimethyl oxalate to methyl glycolate through Cu-Ag bimetallic catalysts encapsulated in amino-functionalized mesoporous silica nanospheres

Semi-hydrogenation of syngas-based dimethyl oxalate (DMO) to valuable methyl glycolate (MG) intermediate has attracted considerable attention recently, while the yield of MG remains a challenge due to thermodynamically favorable continuous hydrogenation of DMO to ethylene glycol (EG). Silver catalysts were reported to be effective but suffered from low stability. Herein, we precisely designed an amino-functionalized mesoporous silica (NH 2 -MS) nanospheres-encapsulated Cu-Ag bimetallic catalyst (CuAg@NH 2 -MS) by a hybrid strategy of EDTA-modification and vacuum-impregnation. The designed bimetallic catalyst exhibited the best compromise between conversion and selectivity with a high MG yield of ∼96.3%, outperforming the unmodified CuAg@MS and mono-metallic Cu@NH 2 -MS and Ag@NH 2 -MS catalysts. Transmission electron microscope analysis revealed that amino-functionalization can effectively disperse and stabilize Cu-Ag nanoparticles. Hydrogen temperature-programmed reduction and X-ray photoelectron spectroscopy confirmed enhanced electron transfer between Cu and Ag species, as well as between Cu-Ag nanoparticles and the NH 2 -MS support. The highly dispersed active metals and enhanced electron interaction ultimately enabled a high MG yield by breaking the trade-off between DMO hydrogenation activity and MG selectivity. This robust catalyst also exhibited remarkable stability in continuous operation for 300 h in a fixed bed reactor. This work will facilitate precise construction of stable metal nano-catalysts for efficient catalytic selective hydrogenation.