Measurement And Reasearch For Thermodynamic Properties Of Mixtures Containing Ionic Liquids

Ionic liquids (ILs) are a class of organic molten salts that are composed of cations and anions. As a new substance for replacement of tranditional volatile solvents, basic thermodynamic properties and wide application of ionic liquids are attractive to people and one of most popular researches. This work concentrates on the classical imidazolium-based ionic liquids, [BMIM][PF6] and [BMIM][BF4], and basic thermodynamic properties of binary systems composed by ionic liquids and organic solvents are measured and researched.Firstly, densities of mixtures of [BMIM][PF6] and [BMIM][BF4] with acetonitrile, benzene, 1-propanol are measured by a vibrating-tube densimeter. Densities measurements were used to compute the excess molar volumes, V E, which has been fitted to Redlich-Kister equation. The immiracible phenomena among mixtures are found obviously.To obtain further accurate data of solubility of mixtures containing ionic liquids, in this work an experimental device based on cloud point method was sets up and firstly integrating digital photograph system modified cloud point method. This new technology not only provided the solution to difficulty on observing directly cloud point, but also improved the accuracy of measuring data. 12 binary systems consisted of ionic liquids, [BMIM][PF6] and [BMIM][BF4], with 1-propanol, 1-butanol, 1-pentanol, benzene, toluene, and thiophene were measured in the experiment. The data of ionic liquids with alcohols were correlated by the nonrandom two-liquid (NRTL) equation. NRTL coefficients are correlated with temperature to improve results. The root-mean-square deviation of the mole fraction was less than 0.01 for the whole ionic liquids-alcohols systems. It is assumed that certain interactions took charge of systems through experimental data.For ionic liquids'application in fractional distillation, an experimental apparatus was constructed to the measurement of vapor pressure and vapor-liquid equilibrium data of 4 binary systems consisted of ionic liquids ([BMIM][PF6] and [BMIM][BF4]) and aromatic compounds were measured. Vapor pressure data of binary systems containing ionic liquids were correlated using NRTL equation, the average relative deviation was 1.14 % for the whole systems. The theory about interactions between ionic liquids and aromatic compounds can be compiled by experimental data.The melting points of ionic liquids are also very important basic data and have more to do with their applications. However, their applications are limited for not enough data. Melting points values of 161 ionic liquids were compiled and 30 simple groups and 3 characteristic factors were defined to construct a new thermodynamic model for predicting melting points of ionic liquids. The average relative deviation in this work was about 6.33 %. A random choice for 4 ionic liquids and comparison between calculated values and the values in the literature were made. The relative deviations for these ionic liquids are 6.12 %, 2.74 %, 1.38 %, and 4.6 %. Values can all be accepted for deviations were less than 6.33 %. The results shown that the melting points of ionic liquids determined by the method are accurate and the new model can be applied to predict the melting points of ionic liquids.