Ag/MCM-41 as a highly efficient mesostructured catalyst for the chemoselective synthesis of methyl glycolate and ethylene glycol

Abstract

A novel highly efficient heterogeneous Ag/MCM-41 catalyst was prepared by ammonia-evaporation deposition-precipitation method and displayed outstanding methyl glycolate (MG) selectivity (up to 99%) and ethylene glycol (EG) selectivity (up to 99%) in the chemoselective gas-phase hydrogenation of dimethyloxalate (DMO). Systematic characterizations have been carried out to elucidate the bulk and surface physicochemical properties of the catalysts. It is shown that the silver loading, the calcination temperature, the surface hydroxyl group amount and the pretreatment atmosphere all have great influences on the catalytic performance of DMO hydrogenation reaction. The best catalytic performance could be achieved over the Ag/MCM-41 catalyst with 10wt.% silver loading after calcined at 673K. Much higher catalytic activity could be obtained via the MCM-41 supported silver catalyst with large amount of surface hydroxyl groups. The argon pretreated Ag/MCM-41 catalyst with less subsurface oxygen species exhibited much higher DMO conversion and MG selectivity compared with H2 and air pretreated samples. Under the optimized reaction conditions, 99% yield of MG and EG could be obtained over the optimized Ag/MCM-41 catalyst.