Synthesis Of Surface Active Heteropolyacids-based Ionic Liquids And Catalytic Performancefor Desulfurization Of Fuel Oil

In recent years, fuel consumption has been increased with the rapid development ofsociety and technology. The emissions ofsulfur oxide (SOx) may have impact on humanhealth, which irreversibly generated byvehicle engines. Therefore, many countries legislatemore stringent environmental regulations to restrict the sulfur content in fuel oils. Reducingsulfur content of fuel oils has become an environmentally urgent subject worldwide. Atpresent, oxidative desulfurization (ODS) has attracted much attention owing to its specialadvantages such as mild reaction conditions, which is considered to be a promisingdesulfurization method with broad prospects of application. However,designing appropriatecatalysts is necessary.In this thesis, a series of surface active functional acidic heteropolyacids-based ionicliquids were prepared and characterized byinfrared spectrum(IR), nuclear magneticresonance(NMR), electrospray ionization mass spectrum(ESI-MS) and X-ray diffraction(XRD). It was found that their structures were consistent with the designed structures andtheir purities were all high.Thephysical and chemical properties of ionic liquids, including surface activity,thermal stability and solubility, were investigated by electrical conductivity measurementand thermogravimetricanalysis(TG). It was found that the carbon chain length of ionicliquidshad asignificant influence on both physical and chemical properties of ionic liquids.As the length of carbon chain increased, the critical micelle concentration (CMC) values ofionic liquids decreased, which indicated an increase of surface activity. In addition, thedecomposition temperatures of these ionic liquids were more than280°C. All of theseionic liquids exhibited excellent thermal stability.Deep desulfurization of dibenzothiophene model oil (DBT-Oil) catalyzed by a seriesof heteropolyacids-based ionic liquids was investigated in detail, using30%H2O2as theoxidant. Extractive catalytic oxidative desulfurization system exhibitedthe bestcatalyticactivity, using acetonitrile as the extractant and surface active heteropolyacids-based ionicliquids as the catalysts. In the extractive catalytic oxidative desulfurization system, thelength of carbon chain had obvious effect onthe removal of DBT from model oil. Among all these ionic liquids, hydrophobic functionalized ionic liquid with-SO3H group (C4-IL)exhibited the best catalytic performance, which was ascribed to its appropriate surfaceactivity. Under the optimal conditions ofn(H2O2):n(S):n(C4-IL)=6:1:0.02,V(CH3CN):V(DBT-Oil)=1:1,60°C, and60min, the removal of DBT was as high as100%.The ionic liquids still showed good catalytic activity after four cycles.Themechanism inextractive catalytic oxidative desulfurization system was also studied.