Effects of the reducing gas atmosphere on performance of FeCeNa catalyst for the hydrogenation of CO2 to olefins

Abstract

In this work, a series of FeCeNa catalyst were prepared and evaluated in the reducing gas atmosphere of CO and H2, respectively. The catalytic performance of hydrogenation of CO2 to olefins show the reducing gas atmosphere has an apparent effect on the CO2 conversion, CO selectivity, FTY and the ratio of O/P. In situ XRD, in situ XPS and TPSR were further carried out to investigate the effect of reducing gas atmosphere on the performance of FeCeNa catalyst for the hydrogenation of CO2 to olefins. When the reducing gas atmosphere of 3% Ce is switched from CO to H2, the catalyst has lower Fe3O4/FexCy, higher ratio of defect oxygen and higher CO2 desorption temperature. The adsorbed CO2 on the surface can react with the presence of H2 to produce higher ratio of the surface oxygen ions, which probably occupies the surface of the catalyst and inhibits the conversion of CO2 to CO and the transformation of CO to hydrocarbons. Besides, the surface Na/Fe ratio of 3% Ce decreases when the reducing gas atmosphere is switched from CO to H2, inhibiting the formation of olefins. Therefore, as for 3% Ce, switching the reducing gas atmosphere from CO to H2 can decrease the ratio of Fe3O4/FexCy, increase the ratio of defect oxygen and surface oxygen ion species, decrease the ratio of Na/Fe, and increase the CO2 desorption temperature, subsequently affect the RWGS and FT reaction, leading to the conversion of CO2 decreasing from 36% to 12%, the selectivity of CO increasing from 11% to 65%, the FTY decreasing from 1.37*10−6 molCO2/gFe•s to 0.13*10−6 molCO2/gFe•s and the ratio of O/P decreasing from 1.7 to 0.2.