Theoretical insights into the removal pathways of adsorbed oxygen on the surface of χ-Fe5C2(5 1 0)

Abstract

Much attention has been paid to the direct preparation of light olefins from syngas by Fischer-Tropsch synthesis. The hydrogen coverage on the surface of χ-Fe5C2 (510) catalyst has a great influence on the activation pathway of CO and the coupling pathway of CC. The removal pathways of adsorbed O on the surface of the catalyst are also affected by the activation pathway of CO which changes due to the hydrogen coverage. At present, the removal pathways of adsorbed O are not clear. In this study, the removal pathways of adsorbed O on the surface of χ-Fe5C2 (510) with low and high hydrogen coverage are studied by density functional theory (DFT).It is found that the surface of χ-Fe5C2 (510) with high hydrogen coverage is more favorable for the reaction to occur and proceed. The formation pathways of H2O and CO2 are different under different hydrogen coverages. At low hydrogen coverage, CO2 is more likely to be generated by the combination of CO and OH followed by decomposition·H2O is more likely to be generated through the pathway of the combination of two OHs. At high hydrogen coverage, CO2 is more likely to be generated by the direct combination of CO and O·H2O is more inclined to be formed by the combination of OH and H. Through the study of the removal pathways of adsorbed O on the surface of χ-Fe5C2 (510), the formation mechanism of CO2 and H2O is clarified, and the effect of hydrogen coverage on the reaction mechanism is explored. It is hoped that it can help to improve the oxidation deactivation of the active components of the catalyst and the high selectivity of by-product CO2 in the reaction process.