Alternative Jet Fuels From Hydroisomerization Of Fischer-Tropsch Synthetic Kerosenes

Fischer-Tropsch synthesis is an important way of converting coal, natural gas andbiomass to synthetic liquid fuels. Recently, high oil price, energy supply security,global climate change have made Fischer-Tropsch reaction attractive. In this work,hydroisomerization of kerosene fraction of Fischer-Tropsch synthetic fuel was carriedout for changing molecular structure of fuel to produce alternative jet fuel with highselectivity.Bifunctional catalysts Pt/ZSM-22and Pt/SAPO-11were prepared by theimpregnation technique with0.5wt%Pt content. These experiments investigate theinfluence of reaction parameters such as temperature、pressure、liquid hourly spacevelocity and hydrogen to hydrocarbon volume ratio(VH2/Vfuel) on thehydroisomerization of kerosene fraction of FT synthetic fuel. The results show that:suitable operating conditions contribute to improving the activity and selectivity ofhydroisomerization. For Pt/ZSM-22, appropriate reaction conditions was:temperature278℃, pressure6MPa, LHSV of2.0h-1, hydrogen hydrocarbon ratio of1000; for Pt/SAPO-11, the optimum reaction conditions was: temperature355℃,pressure6MPa, LHSV of2.0h-1, hydrogen hydrocarbon ratio of1000.The further study about distribution of products and reaction mechanism wereconducted. It is found that: hydroisomerization is a sequential reaction,mono-branched isomers are primary product, while multi-branched isomers aresecondary reaction products, and cracking products are final product; mono-branchedisomers and multi-branched isomers have a certain relationship with the conversion;compared to Pt/ZSM-22, Pt/SAPO-11catalyst shows higher isomerization selectivity;the influence of chain length on distribution of isomers supports alkane isomerizationreaction follows pore mouth and key-lock mechanism.The experimental tested physical and chemical properties of hydroisomerizationproducts of FT synthetic kerosene on Pt/ZSM-22and Pt/SAPO-11, including density,boiling range, freezing point, flash point and viscosity. The results show that whenconversion reach47%both on Pt/SAPO-11and Pt/ZSM-22catalysts, the freezingpoint and other physical and chemical properties, meet the U.S. military standardMIL-DTL-83133G SPK alternative jet fuel requirments.