Experimental Determination Of The Vapour Pressure And Standard Evaporation Enthalpy For Ionic Liquid And Estimation For Solubility Property

The ionic liquid,1-butyl-3-methyllimidazolium acetate[C4mim][OAc]has strong solubility and good catalytic properties,and 1-pentyl-3-methylimidazolium tetrafluoroborate[C5mim]BF4,a classic series of ionic liquid,is stable to air and water.The vapour pressures and standard vaporization enthalpies for[C4mim][OAc]and[C5mim][BF4]were determined using the thermogravimetric method,and hildebrand solubility parameters were estimated based on these values of the standard vaporization enthalpies,respectively.Firstly,ionic liquids 1-butyl-3-methyllimidazolium acetate[C4mim][OAc]was prepared by the neutralization method and characterized by 1H-NMR spectroscopy and differential scanning calorimetry(DSC).Secondly,vapour pressures for[C4mim][OAc]and[C5mim]BF4 were determined separately using the isothermal thermogravimetric analysis under the high purity nitrogen atmosphere.Since the vaporization and sublimation phenomenon under the conventional TGA conditions can be described by the Langmuir equation,According to the values of the rate of mass loss from the experiments,the standard vaporization enthalpies for[C4mim][OAc]and[C5mim]BF4 were calculated.In addition,they were compared with the results from quantum chemical calculation and discussed separately.according to the relationship between vaporization enthalpies and Hildebrand solubility parameter,we have calculated Hildebrand solubility parameters for[C4mim][OAc]and[C5mim]BF4.In terms of this parameter,the ionic liquids and traditional organic solvents are predicted to be miscible if the difference of their Hildebrand parameters is small,ideally zero,and it provides the theoretical guidance to know the miscibility system formed by the ionic liquids and traditional organic solvents.