Thin-sheet monolithic-structured Pd–Au–CuOx/M-fiber (M = Ni, Al, SS, Cu) catalysts for gas-phase hydrogenation of dimethyl oxalate to ethylene glycol

A series of thin-sheet metal microfiber (including Cu, Al, Ni, and stainless-steel fiber) structured Pd–Au catalysts were prepared by a galvanic deposition method. Among these catalysts, the 0.1 Pd–0.5 Au/Cu-fiber catalyst delivers stable dimethyl oxalate (DMO) conversion of ∼99% and ethylene glycol (EG) selectivity of ∼93% within at least 200 h. However, the EG selectivity decreases from 87% to 60%, while the DMO conversion remains at ∼99% after 200 h on stream, which is derived from the decrease of the Cu+/Cu0 molar ratio on the catalyst surface. This work demonstrates that reserving Cu+ species is crucial to maintain good EG selectivity for DMO hydrogenation.