Design Of Carbon Supported Iron-based Catalyst And Its Catalytic Performance In CO Hydrogenation

Fischer-Tropsch process(FTS)is one of the important processes of carbon based energy conversion.The hydrocarbon products in this process are mainly straight chain hydrocarbons,and the primary products are rich in olefins.However,due to the limitation of Anderson-Schulz-Flory(ASF),olefin products lacks selectivity.Therefore,the regulation of FTS product distribution is of great research significance.The catalytic system currently studied is mainly based on Fe catalysts.Supported catalyst carriers can effectively disperse active components,stabilize active phases,and improve catalyst stability.The surface properties of carriers and their interactions with active components have a significant impact on catalytic performance.This paper designs and prepares Fe-based catalysts supported on carbon carriers with surface treatment and N atom doping.The influence of carbon carriers and their surface functional groups on CO hydrogenation is explored.Characterizations such as XRD,FT-IR,SEM,TEM,TG,CO-TPD,TPSR,Raman,in situ XRD,and in situ FT-IR are conducted.The influence and mechanism of carbon supported Fe-based catalysts and surface modification on the product distribution in FTS were studied.The main research content and results are as follows:(1)N-doped carbon support was obtained by thermal decomposition of phenolic resin and urea,which was then carbonized in inert atmosphere.Fe/CMS-N was obtained by impregnation method,and the catalyst without N doping was named Fe/CMS.The modified carbon support CMS-N-H2O2 was prepared by treating the carbon support in H2O2 for 4 h.The Fe/CMS-N-H2O2 catalyst was prepared by impregnation method.The obtained samples were used in CO hydrogenation.The findings demonstrate that the Fe active component is uniformly distributed on the surface of carbon,and that N doping increases the specific surface area,dispersity,and iron carbide creation.The catalysts before and after modification showed high CO hydrogenation activity.Due to an increase in surface hydroxyl groups,the Fe/CMS-N-H2O2 catalyst reduced the interaction between iron and support,which was advantageous for catalytic reduction,carburization and promoted chain growth.In CO hydrogenation,the CO conversion reaches 95%.The results show a light olefin selectivity of 36.46%,a CH4 selectivity of 14.23%,and an O/P ratio of 2.4.(2)Carbon spheres(CS)were prepared by hydrothermal method using sucrose and urea as raw materials.H2O2 and concentrated nitric acid were used to produce CS-H2O2 and CS-HNO3.Lastly,impregnation method was used to generate Fe/CS,Fe/CS-H2O2,and Fe/CS-HNO3 catalysts for CO hydrogenation reaction.The results show that the carbon carriers facilitate the reduction of the catalyst to the Fe5C2 phase.The pretreated Fe/CS-H2O2 and Fe/CS-HNO3 catalysts show an increase in surface-OH and enhanced CO adsorption capacity.On CS-H2O2 and CS-HNO3 catalysts,the carbon support weakens the interaction with iron active sites,improves the dispersity of active phase,promotes the carburization of Fe species,and improves the catalytic activity and olefin selectivity in CO hydrogenation.