Study On Catalytic Performance Of Fischer-Tropsch Synthesis Catalysts With Different Structural Promoters

Under the influence of the current crude oil price war,global crude oil production and prices fluctuate;crude oil is one of the important strategic materials,and China's dependence on external crude oil has been increasing year by year.Therefore,coal indirect liquefaction(CTL)technology has received widespread attention.CTL can provide high-quality synthetic oil and many valuable chemicals,thereby reducing or even replacing the use of crude oil.Fischer-Tropsch synthesis is the most critical step in CTL as a heterogeneous reaction.Fischer-Tropsch synthesis can convert carbon-containing substances such as coal,natural gas and biomass into synthesis gas(mainly H₂ and CO),which are converted into clean liquid fuels and high value-added chemical.Compared with other catalysts,the Fischer-Tropsch synthesis catalyst has the advantages of low price,high reactivity,and active water-gas shift reaction,and is particularly suitable for coal-based synthesis gas with low hydrocarbon ratio.Currently,iron-based catalysts have been widely used in the industry.The catalysts used in this work were prepared by co-precipitation,spray drying and equal volume impregnation methods.In this paper,the traditional Fe/Cu/Si O₂ iron-based catalyst is used as a reference,and Al,Ti,and Zr promoters are selected as structural promoter.Multiple characterization methods are used for the analysis of catalysts.N₂-physisorption,X-ray diffraction(XRD),temperature programming reduction(H₂-TPR),Scanning electron microscope(SEM),ammonia temperature programming desorption(NH₃-TPD)and M?ssbauer spectroscopy(MES)were conducted to characterize the phases,structure,morphology,reducibility and carbonization characteristics of the catalysts under industrial conditions.On this basis,the optimal calcination temperature of Fe Zr-Sol with high selectivity for low-carbon olefins was optimized.And the better performance of Al and Zr structure promoters are optimized in different proportions,in order to combine the advantages of the two catalysts to achieve better resultsBy studying the effects of different structural promoters on the performance of the Fischer-Tropsch synthesis of iron-based catalysts,it was found that the addition of different structural additives would have a significant effect on the catalyst.The results of N₂ physical adsorption showed that the specific surface area of the Fe Al-Sol and Fe Zr-Sol catalysts was significantly greater than that with the addition of Si and Ti,and the pore size distribution of the four catalysts are also very different.XRD and M?ssbauer spectroscopy show that catalysts with Al and Zr promoters are more easily reduced than traditional catalyst with Si promoter,and more iron carbide phases are generated after reduction.The H₂-TPR results show that due to the small interaction force between Zr and Fe,the temperature of the reduction peak is reduced.During the fixed-bed evaluation,the catalysts containing Zr and Al had higher activity,which also significantly improved the stability of the catalyst.However,Zr-containing catalysts have longer induction periods and better selectivity for lower olefins than other catalysts.Calcination temperature has different effects on different iron-based catalysts.Therefore,the calcination temperature of the Fe Zr catalyst in this paper was studied.It can be seen from the results of N₂ physical adsorption that the specific surface area shows a shape peak distribution,and the specific surface area reaches a maximum value at 500?.It is the easiest to be reduced,which generates more iron carbide phase,and the catalyst has the highest activity.