Study On Solution Heat Of Acidic Ionic Liquids

Due to the unique properties,ionic liquids(ILs)have gathered a lot of attention in both academic and industrial communities.The pyridinium-based ILs,as a very typical ILs,not only has the characteristics of ionic liquids,but also has advantages including lower cost,lower toxicity and better adsorption capacity of sulfur dioxide.In addition,it is also believed that ILs with acidic groups may have better unique properties than those with non-acidic functionalized ionic liquids,especially,as catalyst.However,compared to the preparation and application of ionic liquids,the basic physical-chemical properties of ionic liquids are very scarce,especially that the thermochemical properties of ionic liquids are less studied.Thermodynamic data of ionic liquids is an important parameter for the industrialization and process design instruction.The lack of these basic data could hinder the rapid development of ionic liquid industrialization.Thus,the followings were reported in this paper:1.According to the literature,the calorimetric standard substance KCl is selected and used for calibrating the SRC-100 type solution-reaction calorimeter.The results are in good agreement with the findings in the literature.It indicates that the SRC-100 type solution-reaction calorimeter could meet the experimental requirements.2.Four kinds of ionic liquids were synthesized,including pyridinium-based ILs[CnPy]Br(n=2,3,4,5,6),acidic ionic liquids[CnPy][HSO4](n=2,3,4,5,6),[CnPy][TFA](n=2,3,5,6)and[Cnmim][H2PO4](n=3,4,5,6),and they are characterized by 1H-NMR spectroscopy.3.The solution enthalpy of eighteen kinds ionic liquids at different molarities are measured at 298.15±0.01 K,and the molar solution enthalpies are calculated.4.The molar heat of solution at infinite dilution,?sHm0,and Pitzer's parameters consist of ?(0)L MX,?(1)L MX ?C?L MX of the each ionic liquid are obtained in the basis of Pitzer theory of electrolyte solution.The experimental molar solution heat data are carried out for fitting using four parameter equations of Pitzer,and at the same time,the molar heat of solution at infinite dilution,?sHm0,are verified.5.By comparing the parameters of the solubility heat of the same series of ionic liquids,the linear equation is obtained through fitting.The average contribution per mole of methylene to the standard molar dilution molar solubility heat at infinite of the four kinds ionic liquids,including pyridinium-based ILs[CnPy]Br(n=2,3,4,5,6),acidic ionic liquids[CnPy][HSO4](n=2,3,4,5,6),[CnPy][TFA](n=2,3,5,6)and[Cnmim][H2PO4](n?3,4,5,6)are explored.Furthermore,it is also predicted molar dilution molar solubility heat at infinite of other kind ionic liquids and other physicochemical properties.6.Pitzer theory of electrolyte solution has been successfully applied to the dissolution process of ionic liquids,which means through established Pitzer equation,the parameters such as infinite dilute solution heat of ionic liquids can be calculated and the characteristic parameters of Pitzer equations are obtained at the same time.