Synthesis,Characterization And Properties Of Ether Amino Acid Functionalized Ionic Liquids

Thanks to the modifiability of anions and cations,functionalized ionic liquids can be prepared by flexible design.Based on the unique contribution of ether groups to low viscosity and high conductivity,as well as the advantages of biodegradability of amino acids,a variety of ether amino acid functionalized ionic liquids1-alkyl-3-methylimidazoliumthreonine[C_nMim][Thr]?n=2-6?,1-?2-alkoxyethyl?-3-methylimidazolium chloride[C_nOC₂Mim][Cl]?n=1,2?,1-?2-alkoxyethyl?-3-methylimidazolium threonine[C_nOC₂Mim][Thr]?n=1,2?,1-?2-alkoxyethyl?-3-methylimidazolium alanine[C_nOC₂Mim][Ala]?n=1,2?,1-?2-alkoxyethyl?-3-methylimidazolium bromide[C_nOC₂Mim][Br]?n=1,2?and1-?2-alkoxyethyl?-3-methylimidazolium alanine[C_nOC₂Mim][Gly]?n=1,2?with different anion and anion were synthesized.The products were characterized by ¹H NMR,¹³C NMR,TG and Elemental Analysis.The purities of these products were more than 99%,which met the requirements for determination of physicochemical properties.The density,surface tension,refractive index and viscosity of ionic liquids[C_nMim][Thr]?n=2-6?,[C_nOC₂Mim][Cl]?n=1,2?,[C₂OC₂Mim][Br],[C_nOC₂Mim][Thr]?n=1,2?,[C_nOC₂Mim][Ala]?n=1,2?and[C_nOC₂Mim][Gly]?n=1,2?were measured in different temperature ranges.The contribution of methylene group and ether oxygen atom to the molecular volume,standard entropy and lattice energy in the volume properties were calculated and discussed respectively by using the measured data.Moreover,the change rules of surface entropy,surface energy,speed of sound,thermal expansion coefficient,molar polarization and molar susceptibility in the surface properties and polarization properties were calculated.Using Eyring's viscosity equation and thermodynamic formula,the viscous flow activation Gibbs free energy?G^?,the viscous flow activation enthalpy?H^?and the viscous flow activation entropy?S^?of ionic liquids at different temperatures were calculated.It is concluded that the resistance of viscous flow of ionic liquid mainly comes from the effect of enthalpy.The definition of the molar surface Gibbs free energy was substituted into the Lorentz-Lorenz relationship,an equation for predicting surface tensions of ionic liquids was obtained,and the predicted values are highly correlated with the experimental data.In addition,combining the vaporisation enthalpy model with Glasser's lattice energy theory,a method of predicting the ion pair association enthalpy in the gas phase was proposed by using thermodynamic cycle,which helps to understand the interaction mode between anions and cations in ionic liquids.More importantly,a semi-empirical method for estimating the heat capacity difference between the vapour phase and the liquid phase?_l^gC⁰_p,m of ionic liquids was proposed.Compared with the traditional Verevkin method and the?_l^gC⁰_p,m empirical value(-110 J·K^-1·mol^-1),the order of magnitude is basically the same.An equation of the polarity coefficient P was proposed,and it is also applied to molecular liquids.The change trend of the polarity coefficient P value is positively correlated with the change of the dielectric constant value,indicating that the polarity coefficient P can be used not only as the scale of ionic liquids polarity,but also molecular liquid polarity,which shows excellent universality.Combined the molar surface Gibbs free energy with the traditional E?tv?s empirical equation,the molar surface entropy was obtained.The thermodynamic function can be used to characterize the polarity of ionic liquids.Specifically,the larger molar surface entropy,the worse the order of the ionic liquids surface,and the surface order of ionic liquids is one of the important factors determining the polarity.This innovative ionic liquids polarity characterization approach has great academic value.Based on systematic research,further investigates the application of ionic liquids in extractiving oxidative desulfurization.Due to the high selectivity and structural stability of ionic liquids for thiophene sulfides,the removal efficiency of ionic liquids[C₂OC₂Mim][Thr],[C₂OC₂Mim][Gly],and[C₂OC₂Mim][Cl]as extractants for sulfur-containing substrates in model oil was investigated.The results show that these three ionic liquids have excellent single extraction desulfurization efficiency?52-56%?for DBT,and exhibit more excellent desulfurization ability than conventional ionic liquids?15-20%?.The optimal operating conditions for desulfurization were determined by optimizing experimental parameters:the volume of extractant was 3mL,the amount of catalyst was 0.05 g,the oxygen-sulfur ratio was 4 and the temperature was 55°C.The comparison of two kinds of sulfur compounds in fuel oil shows that the desulfurization system has excellent desulfurization effect,which lays a foundation for the further industrial application of ionic liquids.