Efficient tuning of surface copper species of Cu/SiO2 catalyst for hydrogenation of dimethyl oxalate to ethylene glycol

Abstract

The chemoselective synthesis of ethylene glycol (EG) from the hydrogenation of dimethyl oxalate (DMO) derived from syngas is an attractive technology in the modern chemical industry. This work reported a novel hydrolysis precipitation (HP) method to efficiently tune the active copper species of Cu/SiO2 catalysts for DMO hydrogenation. Characterization techniques such as N2 physical adsorption, X-ray diffraction, H2 temperature programmed reduction, N2O titration, Fourier-transform infrared spectra, transmission electron microscopy, and X-ray photoelectron spectroscopy were employed to reveal the origin of the catalytic performances. Compared to the ammonia evaporation (AE) method, the HP method presented remarkable higher dispersion of copper species and large ratio of Cu+/(Cu++Cu0) on the catalyst surface, resulting in a superior catalytic performance in the hydrogenation of DMO to EG. Moreover, the amount of Cu0 and Cu+ sites on catalyst surface is dramatically affected by copper loading, and the catalyst with 30% copper showed the highest catalytic activity with a space time yield of 1.74gEG/(gcat·h) at 463K. Meanwhile, the positive correlation between Cu+ surface area and space time yield of EG suggests that the amount Cu+ is the key factor for hydrogenation of DMO to EG on the as-prepared Cu/SiO2 catalyst. The formation of more Cu+ species in the catalyst would enhance the activation of CO group in DMO and significantly improve the catalytic performances in DMO hydrogenation.