Thermal Properties Of Ionic Liquids For Extraction Separation And Absorpt Ion Refrigeration

Ionic liquid is a new kind of green solvent,which has many advantages,such as non-volatility,good chemical and thermal stability,adjustable,etc.These characteristics indicate that ionic liquid has the potential to be used as absorbent.In order to investigate the thermodynamic properties of liquid-liquid equilibrium and vapor-liquid equilibrium in the process of promoting extraction separation and absorption refrigeration of ionic liquids.Firstly,liquid-liquid equilibrium experiments were constructed for the separation of n-hexane and benzene by ionic liquids.The separation ability of[Emim]Et SO₄ and[Emim]NTF₂ ionic liquids was tested and compared with that of sulphoxane.For the working medium pair in the heat pump cycle,at the same temperature,the interaction between the absorber and the circulating agent makes the vapor pressure of the working pairs significantly lower than that of the pure refrigerant.The decrease of saturated vapor pressure is an important criterion to determine whether the mixed solution is suitable for working pairs.The working pairs of ionic liquid and water was constructed,and the binary systems of three kinds of ionic liquid（1-ethyl-3-methylimidazolium bromide[C₂mim]Br,1-propyl-3-methylimidazolium bromide[C₃mim]Br,1-butyl-3-methylimidazolium bromide[C₄mim]Br）and water and lithium bromide and water were determined.The equilibrium temperatures of four groups of binary systems under different pressures were measured.NRTL model was used to make correlation prediction for the data of ionic liquid system,in order to get the correlation parameter.Material Studio software was used to optimize the structure of the substances（H₂O,LiBr,and[C₂mim]Br,[C₃mim]Br,[C₄mim]Br）involved in the experiment,and the interaction force between the three ionic liquids and water was calculated and analyzed.The results show that the ability of anions to combine with water in ionic liquid is much higher than that of cations,which plays a decisive role in the decrease of vapor pressure.On the basis of the above work,the absorption heat pump model was built,and the calculation methods of the heat capacity and enthalpy of the working pairs in different states were put forward.The energy and heat of the whole system were also calculated.Finally,the COP of[C₂mim]Br/H₂O,[C₃mim]Br/H₂O and[C₄mim]Br/H₂O pair were calculated under the set conditions,and compared with the COP of LiBr/H₂O pair under approximate conditions.