Kiyomi Okabe

CO2 hydrogenation to ethanol over promoted Rh/SiO2 catalysts

Abstract Hydrogenation of CO2 to ethanol was carried out over Rh/SiO2 based catalysts. The main product over the unpromoted catalysts was methane. By adding various metal oxide promoters to the catalysts, CO2 conversion and selectivity to alcohols (methanol and ethanol) increased. Among the promoters, Li salts showed the most prominent effect on ethanol production. Reaction conditions were optimized for ethanol formation over Rh-Li/SiO2 catalysts. An ethanol selectivity of 15.5% and a CO2 conversion of 7.0% were obtained at P = 5 MPa and T= 513 K in a flow of H2-CO2 premixed gas (H2/CO2 = 3) with a flow-rate of 100 cm3/min. By in situ FT-IR analysis of the adsorbed species on the catalysts, the reaction was suggested to proceed via CO intermediate(s).

Ethanol synthesis by catalytic hydrogenation of CO2 over Rh FeSiO2 catalysts

Ethanol synthesis by catalytic hydrogenation of CO2 was carried out over Rh FeSiO2 catalysts prepared by coimpregnation. The added amount of Fe influenced ethanol selectivity as well as CO2 conversion in the range FeRh = 0–3. Product selectivity was correlated with %Fe0 evaluated by XPS. The ethanol selectivity was correlated with the amount of bridged-CO adsorbed species evaluated by in situ FT-IR. It has been suggested that Fe changed the electronic states of Rh and that Fe0 promoted methanation and prevented ethanol formation, as well as CO and methanol formation. An ethanol selectivity of 16.0% and a CO2 conversion of 26.7% were obtained at 5 MPa and 533 K in a flow of H2 CO2 premixed gas (H2CO2 = 3) with a flow rate of 100 cm3/min over 5 wt% Rh Fe(1 : 2)SiO2 catalysts.