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

Abstract

A prepared FeZnNa@SiO2-C catalyst with graphitized carbon (C)-modified mesoporous SiO2 supports metal nanoparticles with the 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, could promote the absorption of CO2 and improved the conversion rate of CO2. Na as an alkaline substance can improve the absorption of more acidic CO2, which could increase the conversion rate of CO2 to 59.03%. Meanwhile, the addition of secondary metal Zn to 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, and facilitate the reduction of Fe2O3 and the formation of active Fe5C2 species. The formation of active Fe5C2 species was found in TEM and XRD, and the selectivity of the target product was 41.07%. The deep hydrogenation of olefins was inhibited, and the space–time yield (STY) of low olefins was raised again by inhibiting their deep hydrogenations, up to 0.0436. However, the corresponding STY did not increase infinitely with the increase of Na doping, and higher catalytic performance for CO2 hydrogenation could be exhibited when the Na doping reached 6.4%. Compared with Fe@SiO2-C catalyst, Na- and Zn-promoted Fe-based catalysts, prepared by the modified sol-gel method, can be used directly for highly efficient CO2 hydrogenation to low olefins and thus has a more promising application prospect in the future.

Recent Advances Hydrogenation of Carbon Dioxide to Light Olefins over Iron-Based Catalysts via the Fischer–Tropsch Synthesis

“…In recent years, the excessive use of fuels such as oil, coal, and natural gas has greatly contributed to the development of the economy and human society, but the increasing carbon dioxide emissions in the course of development have also brought about various environmental challenges, such as the greenhouse effect, ocean acidification, and climate anomaly. − Despite CO 2 being a greenhouse gas, CO 2 is a nontoxic carbon source that provides a fungible pathway to produce high-value-added products. , The direct conversion of CO 2 into value-added products is not only conducive to alleviating environmental issues caused by excessive CO 2 emission, but also realizes the resource utilization of CO 2 . − Therefore, CO 2 hydrogenation to value-added chemicals is an excellent way to reduce CO 2 concentrations and arouse the interest of researchers. − …”