Effect of EDTA-2Na modification on Fe-Co/Al2O3 for hydrogenation of carbon dioxide to lower olefins and gasoline

Abstract

Capturing and utilization of carbon dioxide (CO2) not only leads to effective use of carbon resources, but also alleviates environmental pollution caused by increasing concentration of CO2, thus making it a hot research topic in recent years. In this study, a series of highly dispersed iron-cobalt (Fe-Co) catalysts was prepared by ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) modification, which could efficiently convert CO2 into high value-added chemicals (C2-C4= and C5-C11). X-ray diffraction (XRD) analysis showed that the addition of a small amount of Co and EDTA-2Na contributed to enhance the sintering resistance of Fe species. During the calcination process, EDTA4− can be decomposed into small organic molecules with reducibility, thus promoting the reduction of iron species. The CO temperature-programmed desorption (CO-TPD) results showed that cobalt enhanced the adsorption and activation of intermediate CO on NaxFe-Co catalyst, thereby promoting the catalytic conversion of CO2. The complexation of EDTA promotes the synergistic effect of Fe-Co bimetals, enhances the chemical adsorption of CO2. Sodium in EDTA-2Na promotes the surface basicity of the catalysts, which is favored for improving the product distribution of hydrocarbons. At lower H2/CO2 (1/1) ratio, the EDTA-2Na modified Fe-Co/Al2O3 catalyst exhibited high conversion of CO2 (32.8 %) and excellent selectivity toward high value-added chemicals. The selectivity of by-product CO was only 8.1 %; and C2-C4= (32.5 %) and C5-C11 (46.3 %) accounted for ∼79 % selectivity among the hydrocarbons generated.