Low-Temperature Hydrogenation of Methyl Acetate to Ethanol over a Manganese-Modified Cu/SiO2 Catalyst

One of the crucial steps in producing ethanol from syngas is the hydrogenation of methyl acetate (MA). There has been an increase in the use of reducible metal oxides as supports or additives in copper-based catalysts, which shows good performance in MA hydrogenation. However, a high temperature of 220-250 degrees C is generally required for MA hydrogenation, and the role of metal ion-oxygen vacancy (Mn+-O-v) defect structure in the catalyst is still controversial. Here, a series of manganese-modified Cu/SiO2 catalysts are prepared by the ammonia evaporation method followed by the ion-exchange process. At reaction temperatures as low as 180 degrees C, the optimal catalyst with a Cu/Mn ratio of 1.6 shows excellent activity and stability. Combined with various characterizations, MA-temperature-programmed desorption (TPD), and in situ MA adsorption Fourier transform infrared (FT-IR) spectroscopy experiments, it is evidenced that the surface Mn2+-O-v defect acts as one of the main active sites during the reaction, which can promote the adsorption and activation of C=O/C-O bonds in the MA molecules. The insights into the role of manganese species could give guidance to the further design of high-performance catalysts for the hydrogenation of the C=O/C-O bond.