Role of alkali metal in maintaining iron integrity during direct CO2 hydrogenation

Iron catalysts have been extensively investigated for the direct hydrogenation of CO2 into light olefins and longchain hydrocarbons. However, rapid catalyst deactivation is caused by the reoxidation of iron carbides to iron oxides by water. In this study, we developed a highly stable iron catalyst to produce high-yield liquid hydrocarbons (C5+). The presence of excess Na (20 wt%) as a promoter in the iron-aluminum oxide (FeAlOx) catalyst facilitated the formation of highly aggregated, highly crystalline metallic iron particles during reduction, which in turn produced large Ha<spacing diaeresis>gg carbide core-Fe3O4/AlOx shell particles during CO2 hydrogenation. Excess Na maintained the integrity of these core-shell particles over 2000 h on stream, resulting in a very low C5+ yield decay rate (0.005 % h- 1). Thus, Na was proposed to act as a structural promotor that maintains the integrity of iron domains during direct CO2 hydrogenation by suppressing particle pulverization and water reoxidation.