Preparation Of Tungsten-containing Catalyst By Ionic Liquid Modification And Its Application In Fuel Oxidative Desulfurization

The combustion of sulphide in fuel products will produce sulphur oxides and cause environmental problems including acid rain and photochemical smog,which seriously affect people's physical and mental health.Therefore,it is urgent to reduce the sulfide content of fuel products.Among series of desulfurization technologies,oxidative desulfurization?ODS?has been attraced much attentiondue to the advantages of mild operating conditions,low cost,and high desulfurization efficiency.Thetransition-metal compound based on tungsten?W?can be used in catalytic oxidative desulfurization,for example,tungsten trioxide?WO₃?,phosphotungstic acid?HPW?and tungste ionic liquids all possess high catalytic performance.However,the industrial applications of these tungsten oxides are limited due to the small specific surface and higher cost of tungsten oxide.It is urgent to achieve the industrial application of tungsten-based catalysts.From now on,supported catalysts can not only reduce the amount of active components,but also obtain the excellent properties of the carrier itself,which are widely used in heterogeneous catalytic reactions.Therefore,catalytic oxidation desulfurization with supported tungsten-based catalysts has become a hot spot of current research.In this work,WO₃-SiO₂ with different loadings catalysts were prepared by sol-gel method using tungstic acid,ammonium metatungstate and ionic liquid as tungsten source.Then,the morphology and structure of the catalysts were characterized by a series of characterization instruments and techniques including TEM,XRD,FT-IR,Raman.The results showed that the WO₃-SiO₂ synthesized with ionic liquid possessed more monoclinic WO₃,butthere was an agglomerate of W active component in WO₃-SiO₂ when the tungsten loading was higher than 0.1.Then,hydrogen peroxide?H₂O₂?-extraction-oxidation desulfurization system was established with acetonitrile as extractant and H₂O₂ as oxidant,And the oxidative desulfurization performance and the optimal rection conditions of WO₃-SiO₂were futher investigated.The results showed that the WO₃-SiO₂ synthesized with ionic liquid exhibited the highest catalytic performance than other tungsten source.With the optimal reaction condition of T= 50 ?,O/S= 3,m?catalyst?= 0.O₃ g,the removal rate of dibenzothiophene?DBT?in model oil could reach 94.73%after 60 minutes.The analysis of oxidative desulfurization mechanism showed thatDBT was oxidized to polar dibenzothiophene sulfone and extracted into acetonitrile phase duringthe reaction process.Herein,the enhancement of catalytic oxidative activity of prepared catalyst mainly attributed to the continuous extraction-oxidation.Different WO₃ forms of CNT-WO₃ were prepared by conventional impregnation method and[C₁₆mim]Cl modified precipitation method.Then,the carbon nanotube?CNT?and CNT-WO₃ were characterized by FT-IR,Raman,XRD,Uv-vis,TEM and testd in oxidative desulfurization system The study on characterization and oxidative desulfurization performance of different types of CNTs showed that the degree of graphitization and the polarity of carbon nanotubes?CNTs?possiblily influence the performance of oxidative desulfurization.Furthermore,the acidification of CNTs could promote the oxidative desulfurization rate by increasing the polarity of CNTs.The characterization and desulfurization performance of CNT-WO₃ showed that the content of monoclinic WO₃and the desulfurization rateincreased with W loadingincreasing.Moreover,the WO₃ form changed from tetrahedral WO₃ to octahedral WO₃,which indicated that monoclinic WO₃,tetrahedral WO₃,and octahedral WO₃ were active components of oxidative desulfurization.The characterization and desulfurization test results of CNT-WO₃ modified by[C₁₆mim]Cl showed that the WO₃ form changed in the order of monoclinic WO₃,tetragonal WO₃,tetrahedral WO₃,and the oxidative desulfurization rate increased from 28.60%to 66.39%and 87.07%with adding the amount of[C₁₆mim]Cl.Therefore,it can be concluded that catalytic oxidation desulfurization performance ranked in the order of tetrahedral WO₃>tetragonal WO₃>monoclinic WO₃in supported WO₃catalysts.Different W active component of WO₃,HPW,1-hexadecyl-3-methyl-imidazoliumphosp--hotungstate([C₁₆mim]₃PW₁₂O₄₀)were supportedon TiO₂ by sol-gel method.And the morphologies and structures of the catalysts were characterized by TEM,XRD,FT-IR,and BET.The results showed that the W active components were agglomerated on TiO₂-WO₃.On the contrary,the active components of tungsten were homodispersed on TiO₂-HPW.Moreover,TiO₂-HPW possessed more microporous structure and exhibited higher catalytic oxidation performance than TiO₂-WO₃ and TiO₂-[C₁₆mim]₃PW₁₂O₄₀.When the molar ratio of tungsten to titanium was 0.06,The TiO₂-HPW could achieve the highest desulfurization rate of 98.31%underthe reaction conditions of 50 ?,O/S = 3,and catalyst?catalyst?= 0.O₂ g.Compared with WO₃-SiO₂ and CNT-WO₃,TiO₂-HPW showed higher oxidative desulfurization activity with lower loading of W components and better recovery performance.