Liquid-liquid Equilibrium And Simulation On Azeotrope Containing Lower Alcohols With Ionicl Iquids

As a new type of green solvent,ionic liquid can be used as an excellent substitute for traditional organic solvent for its unique physical and chemical properties such as designability,wide liquid and nonvolatile.The theoretical study of ionic liquids is the prerequisite for practical application,and the basic physical properties of ionic liquids are of great importance to theoretical research.In order to accumulate the basic and abundant data,the quantum chemistry calculations were used to calculate the volume parameters r and the surface area parameters q for the molecular structure of the ionic liquids in this paper.Then the molecular structures of the ionic liquids were optimized by the Restricted Hartree Fock method and the Density Functional Theory.The volume and surface area of the optimal molecular structure were calculated by using the Polarizable Continuum Model.The structural parameters r and q of 12 kinds of ionic liquids were obtained.According to the parameters,the UNIQUAC model was used to correlate the liquid-liquid equilibrium data of the ionic liquid systems in the literatures,and the corresponding systems model parameters were obtained.The global average deviation is 0.0117,which indicates that the calculated r and q values of the ionic liquids in this paper can help the UNIQUAC model to correlate the liquid-liquid equilibrium data better.Our research studied the separation of azeotropes containing lower alcohol liquor using imidazole ionic liquids as solvent to handle the difficult problem in separating azeotropes.In this paper,liquid-liquid equilibrium of imidazole ionic liquids was studied.The extraction feasibility of ionic liquids on the azeotrope was revealled.For the alcohol-water azeotrope systems,the ionic liquids based on 1-alkyl-3-methylimidazole bistrifluoromethanesulfonimide([Cnmim][NTf2])were used as the extractants.The liquid-liquid phase equilibrium experiments were carried out for three systems about water-alcohol-[Cnmim][NTf2].The ionic liquid [Hmim][OTf] was used as the extractant for the alcohol-heptane azeotropes,and the liquid-liquid equilibrium of the three systems of heptane-alcohol-[Hmim][OTf] were studied.The distribution ratios and separation factors were calculated and the extraction abilities of the ionic liquids were compared with other ionic liquids in the literatures.Influences of ionic liquids with different length of alkyl chain and alcohols with different structure on the liquid-liquid equilibria were investigated.The NRTL and UNIQUAC models were used to correlate the liquid-liquid equilibrium experimental data for six ternary systems involving ionic liquid.The NRTL and UNIQUAC model parameters were obtained by using the calculated r and q values of ionic liquids.The UNIFAC model was used to predict the phase behavior of heptane-alcohol-[Hmim][OTf] and the results with experimental results were compared.The predictive ability of the UNIFAC model to the ionic liquid systems was evaluated.The experimental results demonstrate the feasibilities of the ionic liquids for the separation of the azeotropes containing lower alcohol.The presented ionic liquids structure parameters,experimental data and thermodynamic model parameters can be used for the liquid-liquid equilibrium calculation and the design of the related processes.