Trifluoroacetic Acid Ionic Liquids:Synthesis,Propertiesand And Application In Desulfurization Of Fuel Oil

More strict regulations for the standards have been made for production of the fuel oil owing to the pollution from burning fuel oil becoming more and more harmful for environment and human beings.The sulfur content of fuel oil has become the attention focus of countries,as a major indicator of fuel standards.It has become the general trend that producing low sulfur,even zero sulfur,content fuel oil for petrochemical industry.At present,in the various processes of desulfurization,the oxidation-extraction desulfurization with ionic liquid attracts extensive attention worldwide owing to its mild reaction conditions,simple operation,non-volatile solvent and higher desulfurization rate.In this paper,a series of 1-alkyl-3-methylimidazolium trifluoroacetic acid ionic liquids,[C₂mim]TFA,[C₃mim]TFA,[C₄mim]TFA,[C₅mim]TFA and[C₆mim]TFA were synthesized by adopting the traditional two-step method,and the ionic liquids were characterized and verified by 1H-NMR.The densities and surface tension of 1-alkyl-3-methylimidazolium trifluoroacetic acid ionic liquids were measured,and physicochemical properties of ILs were obtained by calculation,such as the standard entropy,surface entropy,surface energy,lattice energy,molar enthalpies of vaporization etc.This paper verified the interstice model of ILs.The parameters of interstice model and the coefficients of thermal expansion of the ILs were calculated,and were in good agreement with the experiment values,which means the interstice model is reasonable.The experiment of oxidation-extraction desulfurization were conducted with the synthesized ionic liquid[C₄mim]TFA and model oil.After the optimized condition experiment,the mass ratio between model oil and IL,the amount of H2O2,temperature,reaction time,were confirmed.The orthogonal experiment analysis,and the best technological parameters were determined as:the mass ratio between model oil and IL was 40:1?mL?,the amount of oxidant was 1 mL,temperature was 60?,time was 60 mim.Through simple treatment,the ILs were recycled for 10 times and the desulfurization results were even excellent.At last,this paper studied the desulfurization performance of the homologs of 1-alkyl-3-methylimidazolium trifluoroacetic acid ionic liquids[Cnmim]TFA?n=2,3,4,5?.It showed that[C₄mim]TFA has the best desulfurization results among them,and with the length change of carbon chain in imidazolium molecular.[C₂mim]TFA,[C₃mim]TFA and[C₅mim]TFA have poor desulfurization performance relatively.It appears that the desulfurization performance of ILs doesn't only depends on the type of anion,but also on the cation structure.This paper not only studied the physicochemical properties of 1-alkyl-3-methylimidazolium trifluoroacetic acid ionic liquids,but also put forward a new method which made 1-alkyl-3-methylimidazolium trifluoroacetic acid ionic liquids as catalysts and extraction agent of oxidation-extraction desulfurization.It provided new scientific basis of theoretical and applied research.