Controllable Synthesis Of ZSM-22 With Different Sizes And Morphologies And Their Performance On Production Of Bio-jet Fuel

Great concern have arisen on bio-jet fuel due to the high consumption of petrochemical resources,high carbon dioxide emission and the increasing demand for aviation fuel.The production of bio-jet fuel from biological deoxygenated oil has great application potential and development prospects.It is the key to develop high-performance catalysts on hydrocracking and hydroisomerization.In this paper,the controllable synthesis of ZSM-22 zeolites with different crystal sizes and aggregate morphologies had been achieved by optimized synthesis conditions and the intervention of growth regulators.The samples were characterized by XRD,SEM,N₂ physical adsorption,NH₃-TPD and Py-IR.Long-chain normal bioalkanes obtained by deoxygenation of Jatropha curcas oil were used as the raw material to evaluate the hydrocracking and isomerization performance of different H-ZSM-22 catalysts.On this basis,dual-functional catalysts Pt/ZSM-22 were prepared by loading of precious metal Pt.Their hydrocracking and isomerization performance were evaluated.The results indicated that:（1）Small size ZSM-22 zeolites with the average c-axis size below 350 nm were synthesized by aging,adding seeds,increasing the alkalinity,or adding organic bases of the initial gel.The ratio of length and diameter of the ZSM-22 grains decreased,while the opening ratio of the pore mouth with 10-membered ring increased greatly.Compared with the large-crystal sample,the specific surface area and the number of acid centers of the small-grained ZSM-22 samples also increased.The small crystal sample synthesized by increasing the alkalinity of the synthetic gel had stronger and more amount of strong acid sites.It had the maximum number of strong B acid at the pore mouths.H-ZSM-22 catalyst support with higher cracking and isomerization activity can be obtained with well-controlled on crystal size and modified on acidity.The conversion of long-chain normal paraffins can reach more than 80%.（2）ZSM-22 zeolites with different aggregate morphologies were synthesized by adding organic reagents,using different templates or post-processing methods.Different morphologies were achieved,like coarse clusters,long clusters,petal-like,long rods and ellipsoid.The sample synthesized with diethylamine as template was ellipsoidal.It had obvious mesoporous structure.After water boiling passivation or organic reagent swelling,the samples with larger aggregate widths and wider grain gaps were obtained.The ellipsoidal H-ZSM-22 catalyst with more acid amount had higher cracking and isomerization activity and the conversion of long-chain normal paraffins was over 90%.（3）After loading Pt,the Pt/ZSM-22 catalysts showed increased hydrogenation isomerization activity,increased iso/n-paraffin ratio of jet fuel product and reduced cracking selectivity.The conversion of the Pt/ZSM-22 catalysts prepared from the small size ZSM-22with small ratio of length and diameter,as well as ellipsoidal ZSM-22,was as high as 90%.Among them,the Pt/ZSM-22 supported by small size ZSM-22 presented excellent performance.The conversion of long-chain normal paraffins reached 97.79%,the yield of bio-jet fuel was as high as 50.25%with an iso/n-paraffin ratio of 7.55.