Study On The Synthety Of Functional Ionic Liquid And Use For Deep Desulfurization

As we all know,the sulfur oxides(SOx)as the major source of air pollution and ozone depletion were released by the combustion of fuel oils.Besides,it is very difficult to remove dibenzothiophene(DBT)with two alkyl substituents at the 4-and 6-positions respectively and its derivatives owing to no suitable catalyst and the steric hindrance by traditional hydrodesulfurization(HDS).However,the ILs with the unique physicochemical properties,conform to the current concept of environmental friendly.In addition,the ILs have strong complexation ability to aromatic sulfur compounds and immiscibility with fuel oils.Therefore,the ionic liquids(ILs)as desirable extractants in EDS have been wildly used to remove sulfur compounds.Four benzyl-based ionic liquids(ILs)were synthetized and used for deep desulfurization for model oil and real diesel fuel.The removal efficiencies of benzothiophene(BT)and dibenzothiophene(DBT)with N-benzyl-N-methylimidazolium-based ILs([Bzmim][NTf2]and[Bzmim][SCN])as extractants are higher than that with N-benzyl-N-methylmorpholine-based ILs([Bzmp][NTf2]and[Bzmp][SCN])as extractants.The desulfurization capability follows Nernst's Law.The removal efficiency of DBT with[Bzmim][SCN]as extractant could reach up to 99.2%after four-stage cross-current extractions.A reactive extraction mathematical model for desulfurization was established.An oxidation-extraction two-step deep desulfurization method was developed based on the detailed studies on oxidation mechanism.DBT was first oxidized by H2O2 with CH3COOH as catalyst and then the unoxidized DBT and uncrystallized dibenzothiophene sulfoxide(DBTO2)in model oil were extracted by[Bzmim][NTf2],and finally the removal efficiency reached up to 98.4%.Besides,the removal of 4,6-DMDBT was investigated with synthesized ILs and the removal efficiency was approximately 96.4%after oxidation and one-stage extraction processes.Moreover,the oxidation-extraction two-step deep desulfurization method was also effective for removing sulfur compounds from real diesel fuel.The removal efficiency of sulfur compounds reached up to 96%after oxidation and three-stage cross-current extraction processes with fresh[Bzmim][NTf2]as extractant.A highly removal efficiency for extractive desulfurization(EDS)system with imidazole anion-based ionic liquids(ILs)has been developed.The imidazole anion-based ILs as extractants([DBU][Im]?[TMG][Im])are composed by organic base as cations with strong alkaline and imidazole based weak proton donors as anion,which have apparently high affinities with sulfur compounds.In particularly,the[DBU][Im]as extractant in term of structure,not only provides the imidazolium ring,but also the structure of DBU could provide the extra heterocyclic aromatic ring.Thus,the cations and anions could increase the ?-? interactions with sulfur compounds together so that the removal efficiency of sulfur compounds could be improved followed.The removal efficiencies of DBT,4,6-DMDBT and BT with[DBU][Im]and[TMG][Im]as extractants under the IL:model oil(w/w)=1:1 at room temperature are 79.2%/69.4%,68.4%/57.7%and 61.2%/54.4%,respectively.The equilibrium between two phases was attained completely after only about 10min.After five multi-stage cross-current extraction under the[DBU][Im]:model oil(w/w)= 1:3,the content of DBT in the model oil decreased to 5ppm(<10ppm).Furthermore,the oxidation-extraction two-step deep desulfurization method was applied in the model oil system and real diesel fuel.The removal efficiency of DBT and 4,6-DMDBT in model oil could reach up to 98.2%,99.9%respectively,while the sulfur removal in real diesel fuel could reach up to 97.0%by three-stage cross-current extraction processes under the extraction condition of diesel fuel/IL(w/w)= 1:2.In conclusion,the structure of benzyl,DBU,TMG can improve the the sulfur removal,I hope the study can be used to guide ionic liquid industrial application.