Direct Conversion of Syngas to Ethanol over Rh-Fe/γ-Al2O3 Catalyst: Promotion Effect of Li

The influence of Li loading on the activity and selectivity of Rh-Fe/gamma-Al2O3 catalysts for the synthesis of ethanol from syngas was explored. The catalysts were characterized by means of XRD, N-2 adsorption, TPR, XPS, CO-TPD, and DRIFTS. Introduction of Li into Rh-Fe catalyst inhibited the Rh reducibility, which could stabilize oxidized Rh species. This led to the significant increase of Rh+/Rh-0 ratio over reduced catalysts, and then Rh+ became the major Rh species on the surface of reduced Li promoted catalyst. The enhanced Rh+ content improved the generation and stabilization of gem-dicarbonyls Rh+(CO)(2) species on Rh+ sites, which was indicated by CO adsorption behavior. It can be concluded that the addition of Li facilitated CO insertion ability and simultaneously suppressed CO dissociation ability. Lower hydrocarbons selectivity and higher ethanol selectivity were observed on Li modified Rh-Fe catalysts. The catalyst with 0.5 wt% Li exhibited the highest selectivity being 30.2% to ethanol. Graphical Abstract [GRAPHICS] .