Controllable assembly of Fe3O4–Fe3C@MC by in situ doping of Mn for CO2 selective hydrogenation to light olefins

Abstract

Fe-based catalysts have shown the potential to convert CO₂ into light olefins, but their industrial processes are hindered by low selectivity and stability. Herein, efficient Mn in situ doped Fe-based catalysts anchored in mesoporous carbon were prepared by the solvent evaporation induced self-assembly (EISA) method, and the catalysts were tested in CO₂ hydrogenation reaction. The effect of different in situ doped promoters (Zr, Mn, and W) on the selectivity to light olefins was systematically studied, which shows that the promoters significantly affected the ratio of carbon species and hydrogen species adsorbed on the surface of active sites. The test results show that 20%Mn–1.2Fe@MC had the highest CO₂ conversion (59.58%) and light olefin selectivity (65.57%). The characterization results show that the in situ doped Mn not only affects the carbonization of FeO_x that regulates the ratio of FeO_x/FeC_x, but also improves the generation of Mn-doped Fe₃C NPs. The doping of Mn into Fe₃C creates a moderate electronic density environment that is beneficial to generating light olefins. Moreover, the Mn–C interaction suppresses the runoff of C from Fe₃C, which enhances the stability.