反气相色谱法表征离子液体1-己基-3-甲基咪唑四氟硼酸盐的热力学参数

采用反气相色谱法(IGC)表征了离子液体(IL)1-己基-3-甲基咪唑四氟硼酸盐(HMIM]BF₄)在343.15~373.15 K温度范围内的热力学参数.使用了一系列不同化学结构的探针分子测定HMIM]BF₄与溶剂之间的相互作用力.根据探针分子的保留时间计算得到探针分子与HMIM]BF₄之间的Flory-Huggins相互作用参数、摩尔吸附焓、无限稀释摩尔混合焓、摩尔蒸发焓、无限稀释活度系数以及HMIM]BF₄的溶解度参数.结果表明,n-C₆、n-C₇、n-C₈、n-C₉、乙醚、四氢呋喃、苯、环己烷为HMIM]BF₄的不良溶剂;甲苯、间二甲苯、甲醇、乙醇、二氯甲烷、四氯化碳、氯仿、丙酮、乙酸乙酯、乙酸甲酯为HMIM]BF₄的良溶剂.运用外推法得到了HMIM]BF₄在室温(298.15K)时的溶解度参数为23.70 (J·^-3)^0.5.实验结果证明反气相色谱法是一种简便准确的获得离子液体热力学参数的方法.获得的热力学参数体现了这种离子液体与探针分子之间的相互作用力.本研究为离子液体的进一步应用提供了参考.

Determination of the thermodynamic parameters of ionic liquid 1-hexyl-3-methylimidazolium tetrafluoroborate by inverse gas chromatography

Inverse gas chromatography (IGC) was used to characterize the thermodynamic properties of ionic liquid (IL) 1-hexyl-3-methylimidazolium tetrafluoroborate (HMIM]BF₄) in the temperature range from 343.15 K to 373.15 K. A series of solvents with different chemical natures were used to determine the HMIM]BF₄-solvent interactions. The thermodynamic parameters including Flory-Huggins interaction parameter, partial molar heats of sorption, mixing and evaporation as well as the activity coefficient at infinite dilution were obtained to judge the interactions between HMIM]BF₄ and the selected solvents. In addition, the solubility parameters of HMIM]BF₄ at different temperatures were determined. The results showed that among the selected solvents, n-C₆, n-C₇, n-C₈, n-C₉, diethyl ether, tetrahydrofuran, benzene and cyclohexane were poor solvents for HMIM]BF₄, while toluene, m-xylene, methanol, ethanol, dichloromethane, tetrachloromethane, chloroform, acetone, ethyl acetate and methyl acetate were the favorite ones. The solubility parameter of HMIM]BF₄ at room temperature (298.15 K) was 23.70 (J·^-3)^0.5, which was obtained by the linear extrapolation method. The experiment proved that IGC is a simple and accurate method to obtain the thermodynamic properties of ionic liquids. The obtained thermodynamic parameters revealed the strength of the interactions between the selected solvents and the ionic liquid, which could be used as a reference to the further applications of the ionic liquid.