Andreu Jordi S, Vega Lourdes F
Consejo Superior de Investigaciones Cientificas (ICMAB-CSIC), Institut de Ciencia de Materials de Barcelona, Campus de la UAB, 08193 Bellaterra, Barcelona, Spain.
J Phys Chem B. 2008 Dec 4;112(48):15398-406. doi: 10.1021/jp807484g.
We present here a new model for the imidazolium-based ionic liquids (ILs) with the bis(trifluoromethylsulfonyl)imide anion Tf(2)N in the context of the soft-SAFT EoS. The model is used to predict the solubility of several compounds in these ILs, and results are compared to available experimental data. Since in the soft-SAFT EoS an associating site is used to represent a short-range and highly directional attractive force among molecules, we have used this feature to mimic the main interactions between the anion and the cation for the alkylimidazolium-[Tf(2)N] ILs. The members of the alkylimidazolium-[Tf(2)N] family are modeled as Lennard-Jones chains with three associating sites in each molecule (one "A" site and two "B" sites). An "A" site represents the nitrogen atom interactions with the cation, and a "B" site represents the delocalized charge due the oxygen molecules on the anion. Each type of associating site is identically defined, but only AB interactions between different IL molecules are allowed. Model parameters for the ionic liquids were estimated with experimental density data from different authors, following a similar approach taken in our previous work [Andreu and Vega, J. Phys. Chem. C 2007, 111, 16028]. The new set of parameters was used to study the solubility behavior of hydrogen, carbon dioxide, and xenon in these ILs over a wide range of temperature and pressure. It has been observed that no binary parameters are needed to correlate the solubility of hydrogen in [C(6)-mim][Tf(2)N] at different temperatures, and predictions up to 100 MPa are presented here. The model is able to correlate with very good agreement the experimental data for the systems [C(n)-mim][Tf(2)N] + CO(2) with only one temperature-independent mixture parameter, while two temperature-independent mixture parameters are needed to correlate the experimental solubility data for the systems IL + Xe, attaining an excellent agreement in a wide range of temperatures. The work presented here reinforces previous results, proving that a reasonable simple model for the IL within the framework of soft-SAFT is able to describe the physical absorption of different gases in ILs with good accuracy, in spite of the most complex nature of the anion, without the need of further parameters or terms. In addition, since these parameters do not depend on the particular conditions at which they were fitted, soft-SAFT is used then to analyze the solubility dependence of these gases in ILs, according to the anion nature and the alkyl chain length of the imidazolium cation by the use of the models developed within this approach.
在此，我们在软统计缔合流体理论（soft-SAFT）状态方程的框架下，提出了一种基于咪唑鎓的离子液体（ILs）与双（三氟甲基磺酰）亚胺阴离子[Tf₂N]⁻的新模型。该模型用于预测几种化合物在这些离子液体中的溶解度，并将结果与现有的实验数据进行比较。由于在软SAFT状态方程中，一个缔合位点用于表示分子间的短程且高度定向的吸引力，我们利用这一特性来模拟烷基咪唑鎓-[Tf₂N]离子液体中阴离子与阳离子之间的主要相互作用。烷基咪唑鎓-[Tf₂N]家族的成员被建模为每个分子中有三个缔合位点的 Lennard-Jones 链（一个“A”位点和两个“B”位点）。一个“A”位点表示氮原子与阳离子的相互作用，一个“B”位点表示由于阴离子上的氧分子产生的离域电荷。每种缔合位点的定义相同，但仅允许不同离子液体分子之间的 AB 相互作用。离子液体的模型参数是根据不同作者的实验密度数据估算的，采用了与我们之前的工作[安德鲁和维加，《物理化学杂志》C 2007 年，111 卷，16028 页]类似的方法。这组新参数用于研究氢气、二氧化碳和氙在这些离子液体中在很宽的温度和压力范围内的溶解度行为。已经观察到，在不同温度下关联氢气在[C₆ - mim][Tf₂N]中的溶解度不需要二元参数，此处给出了高达 100 MPa 的预测值。该模型仅用一个与温度无关的混合参数就能很好地关联[Cₙ - mim][Tf₂N] + CO₂体系的实验数据，而对于 IL + Xe 体系的实验溶解度数据关联则需要两个与温度无关的混合参数，在很宽的温度范围内都能达到极好的一致性。此处展示的工作强化了之前的结果，证明了在软 SAFT 框架内，一个合理简单的离子液体模型能够以良好的精度描述不同气体在离子液体中的物理吸收，尽管阴离子的性质最为复杂，且无需进一步的参数或项。此外，由于这些参数不依赖于它们被拟合时的特定条件，因此利用在此方法内开发的模型，软 SAFT 被用于根据阴离子性质和咪唑鎓阳离子的烷基链长度来分析这些气体在离子液体中的溶解度依赖性。
