Na Promoted FeZn@SiO2-C Catalysts for Sustainable Production of Low Olefins by CO2 Hydrogenation

Abstract

FeZnNa@SiO2-C catalyst with graphitized carbon (GC) modified mesoporous SiO2 support metal nanoparticles was prepared by sol-gel method. The effect of adding metal Na and Zn promoters as a dispersion on the CO2 hydrogenation to low olefins was systematically studied. The results showed that Zn-Na, as a combination, promoted the absorption of CO2 and improved the conversion rate of CO2. Na as an alkaline substance can improve the absorption of more acidic CO2, improving the conversion rate of CO2 to 59.03%. Meanwhiles, addition of secondary metal Zn into Fe-based catalysts to form a surface alloy could alter the adsorption of CO2 and the activation of C-O bonds, inhibit the subsequent hydrogenation of olefins to paraffins, facilitate the reduction of Fe2O3 and the formation of active Fe5C2 species. From TEM and XRD, the formation of active Fe5C2 species was found, the selectivity of the target product was 41.07%. The deep hydrogenation of olefins is inhibited, by inhibiting their deep hydrogenations, the STY of C2=-C4= was raised again, up to 0.0436. However, the corresponding STY does not increase infinitely with the increase of Na content, and when the Na content to 6.4%, which can be shown higher CO2 hydrogenation catalytic performance. Compared with Fe@SiO2-C catalyst, Na and Zn promoted Fe-based catalysts prepared by modified sol-gel method, can be used directly for highly efficient CO2 hydrogenation to low olefins and thus will be more promising in the future.