Study On The Design And Synthesis Of Nano MFI Structure Zeolite Supported Heteropoly Acids Catalysts In Oxidative Desulfurization Reactions

Oxidative desulfurization is a promising desulfurization technology.The development of catalysts with high activity and recyclability is the core issue of oxidative desulfurization technology.In this paper,zeolite/polyacid composite catalysts were designed and synthesized based on the concept of green economy,which can oxidize and remove organic sulfides from fuel under mild conditions.The specific process is as follows:First,three MFI zeolite catalysts were synthesized by hydrothermal method,and the catalytic performance of the catalyst was evaluated by oxidative removal experiments of simulated oils of thiophene(TH),benzothiophene(BT)and dibenzothiophene(DBT).BET results show that all three zeolites have microporous structure.The titanium silicalite(TS-1)exhibits the highest catalytic oxidation desulfurization activity among the three zeolites.The removal order of sulfide is TH(98.4%)>BT(37.4%)>DBT(32.9%).The removal effect of MFI zeolite on macromolecular organic sulfide is not ideal.Secondly,the supported POM-TS-1 composite catalyst was synthesized by using the optimized MIF-structured titanium silicate TS-1 as the carrier and Keggin-structured polyoxometalate(POM)as the active component.The results of FT-IR,XRD and ³¹P MAS-NMR show that the structure of POM in composite catalysts has not changed.The order of sulfide removal was TH(99.9%)>DBT(60%)>BT(49.1%).The introduction of polyacids improves the catalytic activity for the removal of macromolecular sulfides,which is the result of the shape selection of TS-1 zeolite,the diffusion effect of organic sulfur molecules and the combined effect of POM on the electron cloud density in the process of catalytic oxidation desulfurization.Thirdly,POM-TS-1 composite catalysts with different structure Mo-POM as active components were synthesized by impregnation method.The order of sulfide removal activity of different catalysts is Keggin Mo-H₂O₂-POM>Keggin Mo-POM>Dawson Mo-POM>Anderson Mo-POM>Mo-metal oxide.The formation of peroxide polyacid species is the reason for the better oxidation desulfurization activity of Keggin Mo-H₂O₂-POM catalysts.The optimum reaction conditions were as follows:catalyst 0.2 g,n(O):n(S)=10:1,temperature 60?.The order of sulfide removal was TH>DBT>BT.The catalyst has good recycling performance.It is a kind of catalyst with simple preparation method,high oxidation removal activity and green environmental.Finally,Fenton reagent and urea peroxide were used instead of hydrogen peroxide as oxidants for desulfurization reaction.Study on the influence of oxidation system on the results of catalytic oxidation desulfurization.The experimental results show that the oxidation system of Fenton and urea peroxide can effectively improve the utilization of hydrogen peroxide,which can be said to be an excellent oxidation system for desulfurization reaction.