Kuzmina O, Bordes E, Schmauck J, Hunt P A, Hallett J P, Welton T
Department of Chemistry, Imperial College London, SW7 2AZ, UK.
Phys Chem Chem Phys. 2016 Jun 28;18(24):16161-8. doi: 10.1039/c6cp02286c. Epub 2016 Jun 6.
The solubilities of the metal halides LiF, LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbCl, CsCl, CsI, were measured at temperatures ranging from 298.15 to 378.15 K in the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([C4C1im][OTf]). Li(+), Na(+) and K(+) salts with anions matching the ionic liquid have also been investigated to determine how well these cations dissolve in [C4C1im][OTf]. This study compares the influence of metal cation and halide anion on the solubility of salts within this ionic liquid. The highest solubility found was for iodide salts, and the lowest solubility for the three fluoride salts. There is no outstanding difference in the solubility of salts with matching anions in comparison to halide salts. The experimental data were correlated employing several phase equilibria models, including ideal mixtures, van't Hoff, the λh (Buchowski) equation, the modified Apelblat equation, and the non-random two-liquid model (NRTL). It was found that the van't Hoff model gave the best correlation results. On the basis of the experimental data the thermodynamic dissolution parameters (ΔH, ΔS, and ΔG) were determined for the studied systems together with computed gas phase metathesis parameters. Dissolution depends on the energy difference between enthalpies of fusion and dissolution of the solute salt. This demonstrates that overcoming the lattice energy of the solid matrix is the key to the solubility of inorganic salts in ionic liquids.
在离子液体1-丁基-3-甲基咪唑三氟甲磺酸盐（[C4C1im][OTf]）中，测定了金属卤化物LiF、LiCl、LiBr、LiI、NaF、NaCl、NaBr、NaI、KF、KCl、KBr、KI、RbCl、CsCl、CsI在298.15至378.15 K温度范围内的溶解度。还研究了阳离子与离子液体匹配的Li(+)、Na(+)和K(+)盐，以确定这些阳离子在[C4C1im][OTf]中的溶解情况。本研究比较了金属阳离子和卤化物阴离子对该离子液体中盐溶解度的影响。发现碘化物盐的溶解度最高，而三种氟化物盐的溶解度最低。与卤化物盐相比，阴离子匹配的盐在溶解度上没有显著差异。利用几种相平衡模型对实验数据进行了关联，包括理想混合物、范特霍夫方程、λh（布霍夫斯基）方程、修正的阿佩尔布拉特方程和非随机双液模型（NRTL）。发现范特霍夫模型给出了最佳的关联结果。根据实验数据，确定了所研究体系的热力学溶解参数（ΔH、ΔS和ΔG）以及计算得到的气相复分解参数。溶解取决于溶质盐的熔化焓和溶解焓之间的能量差。这表明克服固体基质的晶格能是无机盐在离子液体中溶解的关键。
