Study On The Aromatization Reaction Of Methanol And Olefin On ZSM-5 Zeolite

According to national VI standards,it is required to reduce olefin content of FCC gasoline which is regard as main gasoline source in our country.The conversion of olefin to aromatics is one of the main methods of gasoline modification for improving octane number.In this paper,ZSM-5 zeolites were used to prepare two aromatization catalysts,where one is HZSM-5 with abundant B acid center and the other is Zn Na ZSM-5 with rich Zn-L acid center.A series of zeolite catalysts containing different acid centers using for alkene aromatization were prepared by the method of mechanical mixing.The catalysts performance was also investigated for aromatization via the coupling of olefin and alcohol.The reaction pathways of aromatization were researched over ZSM-5 zeolites catalysts containing different acid sites,where methanol,1-octene and cyclohexene were used as model compounds.Three different model compounds on zeolite catalysts with both B acid and Zn-L acid exhibited excellent aromatic selectivity.As the content of Zn Na ZSM-5 in the mixed catalyst increased gradually,the proportion of heavy aromatics in the products of three different raw materials would gradually increase.With the decrease of B-acid,the cracking depth became lower.More abundant gro wth chain olefins as aromatization precursor would have a higher probability of generating heavy aromatics,among which the cyclohexene has the highest aromatic selectivity,and1-octene was more selective than methanol in the reaction with high carbon number,and the selectivity of C₄⁼and C₅⁺was much higher than methanol.The by-products of methanol reaction were mainly alkenes with low carbon number.The alfin coupling aromatization was studied by the reaction of methanol and different alkenes.In the coupling reaction of methanol and 1-octene,the aromatics selectivity on four catalysts containing B-acid was improved to a certain extent,in the meanwhile BTX was the main product.The products of coupling reaction between methanol and cyclohexene were analyzed.The addition of methanol improved the selectivity of polymethyl aromatics,and the presence of methylation reaction could optimize the composition of aromatics.When the methanol was coupled with olefin during aromatization,more toluene,xylene and polymethyl aromatics would be generated.The addition of methanol promoted the methylation reaction,which could optimize the distribution of aromatics.The effects of alfin coupling ratio and temperature on the reaction were investigated.The optimum reaction conditions were obtained by comb ining five different mixing ratios and different reaction temperatures.