Boosting the Production of Light Olefins from CO2 Hydrogenation over Fe–Co Bimetallic Catalysts Derived from Layered Double Hydroxide

Abstract

CO2 hydrogenation to light olefins (C2–C4═) is especially attractive for the chemical utilization of CO2, and currently, effective catalysts are still under development. Herein, we report a succession of Fe–Co bimetallic catalysts derived from Fe–Co–Mg layered double hydroxides (LDHs) with different Fe/Co ratios [(c(Fe3+) + c(Co2+))/c(Mg2+) = 1] for converting CO2 to light olefins, which were also compared to MgO-supported Fe–Co prepared by the impregnation method. The best catalyst FeCo-9:1-LDH presented a high selectivity of C2–C4═ over 36% at a CO2 conversion higher than 40%. With ex/in situ characterization including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Mössbauer spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), we found that the Fe–Co–Mg LDH-derived catalyst (FeCo-9:1-LDH) is easily carburized to Co-modified iron carbide (Fe5C2), which is superior to the FeCo-9:1-I catalyst synthesized by impregnating Co and Fe onto MgO support. The former shows a higher CO2 conversion and higher C2–C4═ selectivity, while the latter produces more CH4. This work provides a series of catalysts for selective hydrogenation of CO2 to light olefins, as well as insights into the reaction pathway, favoring the rational design of CO2 hydrogenation catalysts.