Probing the promotional roles of cerium in the structure and performance of Cu/SiO2 catalysts for ethanol production

Abstract

In this contribution, the efficient hydrogenation of dimethyl oxalate (DMO) to ethanol was achieved over a series of cerium promoted Cu/SiO₂ (xCe-Cu/SiO₂) catalysts prepared by a urea-assisted gelation approach. As a promoter, Ce played a crucial role in improving the structure, properties and catalytic performance of the Cu/SiO₂ catalysts. The structure and chemical properties of the synthesized catalysts were characterized by XRD, FT-IR, in situ XRD, TEM, STEM-EDX mapping, N₂O titration, H₂-TPR, H₂-TPD, XPS, XAES, etc. The characterization results disclosed that the addition of a Ce promoter to the Cu/SiO₂ catalysts remarkably increased the Cu dispersion and retarded the sintering of small-sized Cu species. The strong interaction between the Ce promoter and Cu species substantially changed the redox properties of xCe-Cu/SiO₂ catalysts and made the Cu²⁺ species easy to reduce. In addition, the activation ability of H₂ species was significantly improved in the xCe-Cu/SiO₂ catalysts, as evidenced by H₂-TPD studies. Among these synthesized catalysts, the 1Ce-Cu/SiO₂ catalyst with a 1.0 wt% Ce loading exhibited the highest catalytic activity (100% DMO conversion), ethanol selectivity (91.8%) and stability. This enhancement of catalytic activity, ethanol selectivity and stability is very promising for the development of an alternative route for the production of ethanol by hydrogenation of DMO from syngas.