| The combustion of sulfur compounds in fuel oil is one of the main factors that lead to environmental pollution,especially the more serious haze weather.Therefore,through the deep desulfurization of fuel,the maximum reduction of fuel sulfur content has always been the focus of global attention.At present,compared with the traditional hydrodesulfurization process with mature technology and industrial application,oxidative desulfurization technology can not only effectively remove aliphatic sulfides such as mercaptan and sulfide,but also realize the deep removal of thiophene sulfides and their derivatives with steric hindrance and high boiling point in the fuel under mild reaction conditions,it is a potential desulfurization technology.In this work,different oxidative desulfurization systems were designed and applied to the removal of thiophene sulfide in model oil.The main research work includes the following three parts:(1)Three kinds of tungstophosphoric acid based bis-imidazole ionic liquid catalysts[Cn(MIM)2]PW12O40(n=2,4,6)with different carbon chain lengths were designed and synthesized.The catalysts were characterized by 1H NMR,FT-IR,XRD and other methods,and were applied to extractive coupled catalytic oxidative desulfurization system(ECODS)with H2O2as oxidant and acetonitrile as extractant.The effects of different factors on desulfurization efficiency were investigated.The results showed that when[C2(MIM)2]PW12O40 was used as catalyst,the desulfurization efficiency was the highest.Under the optimal reaction conditions:V(oil)=5 m L,n(catalyst)/n(S)=0.025,n(O)/n(S)=6,t=60 min,T=50?,V(acetonitrile)=0.5 m L,the removal rate of Dibenzothiophene(DBT)could reach more than 98%.The good wettability of the catalyst in H2O2 and oil phase was the main factor affecting the desulfurization efficiency.When[C2(MIM)2]PW12O40 was recycled for 7 times,the desulfurization efficiency could still reach over 89%,and the catalyst structure was not destroyed.The only oxidation product of DBT was determined by gas chromatography-mass spectrometry(GC-MS),and the possible desulfurization mechanism was proposed.(2)A series of supported catalysts x%[C2(MIM)2]PW12O40/g-C3N4(x=3,10,30,50)were designed and synthesized,and applied to catalytic oxidative desulfurization system with H2O2 as oxidant.The catalyst were characterized by BET,SEM and other methods.The effects of different factors on desulfurization efficiency were investigated.The results showed that the desulfurization efficiency was the highest when 10%[C2(MIM)2]PW12O40/g-C3N4 was used as catalyst.Under the optimal reaction conditions:V(model oil)=5 m L,m(catalyst)=0.05 g,T=60?,t=60 min,n(O)/n(S)=4,the conversion rate of DBT could reach 99.6 4%.This was due to the good dispersion of the catalyst in H2O2 and oil phase and the rich electron W in the catalyst.In addition,10%[C2(MIM)2]PW12O40/g-C3N4 can be reused for 6 times without significant decrease in activity.The catalytic activity of the catalysts for different sulfides was DBT>4,6-dimethyldibenzothiophene(4,6-DMDBT)>benzothiophene(BT).(3)A series of bis-imidazole ionic liquid extractants[Cn(MIM)2](HSO4)2,[Cn(MIM)2](p-TSA)2,[Cn(MIM)2](TFA)2(n=2,4,6)with different acidity were designed and synthesized,and applied to the extractive coupled oxidative desulfurization system with H2O2 as oxidant.The extractants were characterized by UV-vis and other methods.The effects of different factors on desulfurization efficiency were investigated.The results showed that the desulfurization efficiency was the highest when[C4(MIM)2](p-TSA)2was used as extractant.Under the optimal reaction conditions:V(model oil)=5 m L,T=40?,t=40 min,n(O)/n(s)=6,m(extractant):m(oil)=1.5:1,the removal rate of DBT reached 98.35%,and its good extraction performance depends on the length of carbon chain in cation and the acidity of anion.The removal order of different sulfides by[C4(MIM)2](p-TSA)2 was DBT>4,6-DMDBT>BT,and the extraction performance of the[C4(MIM)2](p-TSA)2 which has been used for 6 times has been recovered after back extraction.Under the same reaction conditions,the removal rate of DBT could still reach 92.51%.In the process of extractive coupled oxidative desulfurization,the interaction between extractant and sulfide is the key factor for extractant to show high extraction performance.In this paper,through the construction of different oxidative desulfurization systems,the deep desulfurization technology based on different novel bis-imidazole ionic liquids with simple operation,mild conditions,high efficiency and economy was established,which provided a reference for the industrial application of real fuel desulfurization. |
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