Carbon Supported Iron Fischer-Tropsch Nano-catalysts:Synthesis And Catalytic Performance

With the depletion of petroleum resources,looking for alternative energy has become a top priority of all tasks.According to the world energy distribution and China energy structure,the effective use of coal and natural gas will be the focus of development.Fischer-Tropsch synthesis has a pivotal position because it can transform coal and natural gas into high-quality oil.Although Fischer-Tropsch synthesis has a century history,there are still key issues with wide product distribution and low selectivity of target products.The key to solve the problem is to develop a new type of catalyst with excellent performance.Among the traditional catalysts,iron-based catalyst has the advantages of low price,high space-time yield,high water vapor conversion activity and wide operating temperature range,in addition,the carbon material has wide application in the field of catalysis due to the features of chemical inertia,high specific surface area,weak interaction with metal and easy to modify.Therefore,the paper centers on the preparation and catalytic performance of carbon supported iron Fischer-Tropsch catalysts.Carbon-coating iron catalyst with high metal loading is prepared by hydrothermal synthesis and high temperature carbonization procedure,the reaction conditions are optimized to determine the temperature of 250 oC,the pressure of 2 MPa,and H2/CO of 2.The composition and structure of catalyst is tunable by changing carbonization temperature,we find that catalytic performance is optimal,which is CH4 selectivity of 9% and C₅₊ selectivity of 54%,when carbonization temperature is 800 oC.Because iron species are reduced by carbon during carbonization period,the content of reduced iron species increases with higher carbonization temperature.Besides,the trace amount of alkali metal in the catalyst leads to the collaborative improvement of C₅₊ selectivity.Tubular carbon supported iron nano-catalyst is prepared with high temperature carbonization method.The precursor type,carbonization method and carbonization temperature are investigated,and catalytic performance is optimal when the catalyst is synthesized with FeCl3 and carbonized at 800 oC,which is that FTY is 234.3 ?molCO/s gFe and C₅₊ selectivity is 56%.The best performance is contributed by more reduced iron species,smallest iron particle size and largest CO adsorption content.In order to improve the selectivity,K promoter is introduced into the catalyst,then we investigate the introduction method and promoter content,it's concluded that C₅₊ selectivity can be increased to 66% with the catalyst including 0.1 wt% K prepared by incipient wetness impregnation method.