The rare earth elements modified FeK/Al2O3 catalysts for direct CO2 hydrogenation to liquid hydrocarbons

Abstract

The present work reports on the promoting effects of rare earth elements (La, Ce and Y) to FeK/Al2O3 catalysts on liquid hydrocarbons from CO2 hydrogenation. The addition of La, Ce and Y can both improve the selectivity of C5+ hydrocarbons and reduce the selectivity of CH4. The C5+ selectivity can enhance to about 60 % with CH4 selectivity of around 11 % at CO2 conversions above 20 %. N2 adsorption–desorption, in situ XRD, H2–TPR, CO2/H2–TPD, HRTEM and XPS are used to characterize the FeK/Al2O3 and FeK/M-Al2O3 (M = La, Ce, Y) catalysts. The results show that the introduction of rare earth elements into the FeK/Al2O3 catalyst obviously reduces the adsorption of H2, which suppresses the CH4 formation. On the other hand, rare earth elements also promote the adsorbed CO2 species, which leads to the enhanced liquid hydrocarbons selectivity. Finally, the tailored CO2/H2 ratio of CO2 and H2 adsorption on the catalyst surface can influence the catalyst activity and the product selectivity evidently.