The Synthesis Of Novel Ionic Liquid And Their Application In Deep Desulfurization Of Fuel Oil

The existence of organic sulfur compounds in fuel oil has become an important factor causing the formation of haze weather which leads to increasingly serious environmental pollution problems.As a result,governments around the world have strengthened their environmental awareness and have set more stringent standards of sulfur content for gasoline and diesel.Among them,thiophene and its derivatives are often difficult to remove due to the higher boiling point and larger steric hindrance.Therefore,the ultra-deep desulfurization of fuel oil has become a global problem to be solved.This paper first proposed the synthesis of a series of protic ionic liquids(PILs)through the exothermic neutralization reaction of base and acid for the extraction desulfurization of sulfides in fuel.The DBU due to the larger volume is chosen as the cation of ionic liquid and the specific group(amidine)and structure(two heterocyclic rings)in DBU can enhance the interaction between[DBU]+and the sulfur on thiophene.Besides,due to its relatively large molecular structure,the planar structure between anions and cations leads to a "?-? stacking" structure,which is beneficial to the insertion of more sulfide molecules into the structure of ionic liquids to form a liquid phase inclusion.Therefore,the extraction desulfurization efficiency can be effectively improved.In this paper,a series of novel PILs were synthesized and the anions were generated from formic acid,acetic acid,propionic acid,butyric acid and phenol.All these PILs were used for the extraction desulfurization of dibenzothiophene(DBT),benzothiophene(BT)and 4,6-dimethyldibenzothiophene(DMDBT)in model oil.The extraction efficiency sequence of DBT was[DBU](82.55%)>[NFM](61.03%)>[NMIM](43.95%)>[NMM](32.95%)while PIL anion was formate.Therefore,the[DBU]+protic ionic liquid showed the best extraction desulfurization efficiency,which could remove more than 80%DBT and BT in one cycle.The extraction efficiencies of[DBU][Pr]were 98.33%for DBT and 98.67%for BT after three extraction cycles.The value for DMDBT was 99.38%after five cycles.Finally,the interaction energies of these PILs with three aromatic sulfur compounds were studied through quantum chemistry calculation,and the mechanism of extraction desulfurization was also studied.In order to achieve more economical and efficient ultra-deep desulfurization of fuel oil,this paper develops an oxidation/extraction"one-pot" ultra-deep desulfurization process based on acidic functional ionic liquids.Bronsted acid(TsOH,TFA,HCOOH,H2SO4)anions with lower pKa values are designed to form strong acidic sites by providing hydrogen ions(H+)or protons to interact with cations,then which interact with oxidants such as H2O2 to show excellent catalytic performance.The extraction performance of the ionic liquids can be adjusted by the interaction between the cations and the aromatic sulfides.Therefore,DBU,NMM,NFM were selected as cations to synthesize acidic ionic liquids[DBU][HCOO],[NMM][HCOO],[NFM][HCOO],[NFM][HS04],[NFM][Tos]and[NFM][TFA],which were used as catalysts and extractants for catalytic oxidation/extraction "one-pot"desulfurization process.It was found that the[NFM]+ ionic liquids had the best desulfurization performance,and the acidity of ILs was positively correlated with the desulfurization efficiency,while the acidity of anions was not completely consistent with the acidity of ILs.The structure of[NFM][TFA]was determined by DFT.The desulfurization efficiency of DBT for different desulfurization systems was studied,and the desulfurization process conditions were also optimized.Under the optimal reaction conditions,the desulfurization efficiencies of[NFM][TFA]for DMDBT and DBT could reach 99.82%and 99.67%within 30 min,respectively.For BT,the desulfurization efficiency was 93.31%at 180 min,and the order of reactive activity for different sulfides was DMDBT>DBT>BT.After 5 cycles,the desulfurization efficiency of[NFM][TFA]was no significant change.In addition,the kinetics and thermodynamics of desulfurization process were explored,and the desulfurization efficiency of[NFM][TFA]for real diesel was also investigated.Finally,the possible pathways of catalytic oxidative reaction for sulfides by acidic ionic liquid[NFM][TFA]were studied,and the catalytic mechanism of IL and H2O2 was revealed.By constructing different desulfurization process routes,the paper established an ultra-deep desulfurization technology based on different new ionic liquids,which is easy to operate,efficient and economical,and this provides guidance for the industrial application of desulfurization of real oil.