Active sites in CO2 hydrogenation over confined VOx-Rh catalysts.

Metal oxide-promoted Rh-based catalysts have been widely used for CO₂ hydrogenation, especially for the ethanol synthesis. However, this reaction usually suffers low CO₂ conversion and alcohols selectivity due to the formation of byproducts methane and CO. This paper describes an efficient vanadium oxide promoted Rh-based catalysts confined in mesopore MCM-41. The Rh-0.3VO_x/MCM-41 catalyst shows superior conversion (~12%) and ethanol selectivity (~24%) for CO₂ hydrogenation. The promoting effect can be attributed to the synergism of high Rh dispersion by the confinement effect of MCM-41 and the formation of VO_x-Rh interface sites. Experimental and theoretical results indicate the formation of til-CO at VO_x-Rh interface sites is easily dissociated into *CH_x, and then *CH_x can be inserted by CO to form CH₃CO*, followed by CH₃CO* hydrogenation to ethanol. [ABSTRACT FROM AUTHOR]