CO₂Hydrogenation To Hydrocarbons Over Fe Supported On Ordered Mesoporous Carbons

With the rise of energy consumption due to rapid industrial development, a series of environmental and ecological problems have occurred as a result of the rapidly increasing CO2emissions associated with fossil fuels. It is important to explore sustainable energy development because of the depleting fossil fuels resources. Therefore it is necessary to study conversion and untilization of CO2, which has a strategic significance for environment and energy since we could transform CO2into high value-added products.Here, we synthesize some Fe-based catalysts supported on mesoporous carbon materials and the catalysts were examined for hydrogenation of CO2to hydrocarbons. The effects of interaction between carrier and catalysts or interaction between promoter and catalysts on the coversion of CO2and product distribution were analyzed.The mesoporous carbon materials as support were prepareded by removing the template agent of mesoporous polymeric material at defferent tempatures. Fe-based catalysts were synthesized by impregnation method and hydrogenation of CO2over the catalysts was conducted in a fixed bed down-flow reactor. The results indicate that the conversion of CO2on Fe catalysts loaded on mesoporous carbon after removing template agent at400℃could reach55.7%, with the selectivity of C2+at about51.0%and C2-C4=about16%under the pressure of3MPa, the reaction temperature of673K, the space velocity of1800h-1and the H2/CO2molar ratio of3. The conversion of CO2was kept at the same level while the product distribution was altered apparently when the mesoporous carbon was prepared by removing template agent at600℃. There are almost no olefins in the product while the content of C5+increased, and selectivity of C2+increased to62.5%. The performance of CO2hydrogenation reaction is almost the same with the mesoporous carbon prepared by removing template agent at600℃and800℃.Some Fe-based catalysts dopped with promoter were sythensized by co-incipient wetness impregnation method and the effects of promoters were examined using K, Cu, Mn, Ce, etc. for conversion of CO2to hydrocarbons over10%Fe/OMC-400. The effects of dopants are significant:K improved coversion of CO2to62.5%, selectivity of C2+to61.2%and the selectivity of C2-C4=increased13%. Mn improved coversion of CO2and selectivity of C2+as the same time the content of olifins decreased. The synergistic effect of Mn and K were studied and it can be seen that the synergistic effects of Mn-K weaken the interaction of Fe-K and Fe-Mn, respectively.The promoter copper increased the reducing capacity of catalysts and it is beneficial for reducing iron oxides to metallic iron. There is almost no olefin in the product of CO2hydrogenation to hydrocarbons over lOFe3Cu/OMC-400, while selectivity of C5+increased12%.The synergistic effect of Cu and K were studied and it can be seen that the selectivity of C5+rose over10Fe3Cu3K/OMC-400. Ce can promote the activity of hydrogenation such that the products were dominated by alkanes, without olifins. Mg can increase the reducibility and stability of catalysts, but decrease the selectivity of C2-C4.The promotion of Cs is less apparent than K, while there is more C5+and less CH4.