MATGAS Research Center, Consejo Superior de Investigaciones Científicas (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Barcelona, Spain.
J Phys Chem B. 2012 Jul 5;116(26):7709-18. doi: 10.1021/jp303344f. Epub 2012 Jun 21.
In this work, the solubility of three common pollutants, SO(2), NH(3), and H(2)S, in ionic liquids (ILs) is studied using the soft-SAFT equation of state with relatively simple models. Three types of imidazolium ionic liquids with different anions are described in a transferable manner using the recently published molecular models (Andreu, J. S.; Vega, L. F. J. Phys. Chem. C 2007, 111, 16028; Llovell et al. J. Phys. Chem. B 2011, 115, 4387), whereas new models for SO(2), NH(3), and H(2)S are proposed here. Alkyl-imidazolium ionic liquids with the PF(6) and BF(4) anions are considered to be Lennard-Jones chainlike molecules with one associating site in each molecule describing the specific cation-anion interactions. Conversely, the cation and anion forming the imidazolium Tf(2)N ionic liquids are modeled as a single molecule with three associating sites, taking into account the delocalization of the anion electric charge due to the presence of oxygen groups surrounding the nitrogen of the anion. NH(3) is described with four associating sites: three sites of type H mimicking the hydrogen atoms and one site of type e representing the lone pair of electrons. H(2)S is modeled with three associating sites: two for the sites of type H for the hydrogen atoms and one site of type e for the electronegativity of the sulfur. SO(2) is modeled with two sites, representing the dipole moment of the molecule as an associative interaction. Soft-SAFT calculations with the three models for the pollutants provide very good agreement with the available phase equilibria, enthalpy of vaporization, and heat capacity experimental data. Then, binary mixtures of these compounds with imidazolium-based ionic liquids were calculated in an industrially relevant temperature range. Unlike association interactions between the ionic liquids and the pollutant gases have been explicitly accounted for using an advanced association scheme. A single temperature independent energy binary parameter is sufficient to describe every family of mixtures in good agreement with the available data in the literature. In addition, a vapor-liquid-liquid equilibrium (VLLE) region, never measured experimentally, has been identified for mixtures of hydrogen sulfide + imidazolium ionic liquids with the PF(6) anion at high H(2)S concentrations. This work illustrates that relatively simple models are able to capture the phase absorption diagram of different gases in ionic liquids, provided accurate models are available for the pure components as well as an accurate equation of state to model the behavior of complex systems.
在这项工作中，使用相对简单的模型，通过软 S-AFT 状态方程研究了三种常见污染物（SO2、NH3 和 H2S）在离子液体（ILs）中的溶解度。以可传递的方式用最近发表的分子模型（Andreu，JS；Vega，LFJ 物理化学 C 2007，111，16028；Llovell 等人 J 物理化学 B 2011，115，4387）描述了三种具有不同阴离子的咪唑基离子液体，而这里提出了新的 SO2、NH3 和 H2S 模型。具有[PF6]-和[BF4]-阴离子的烷基咪唑基离子液体被视为具有每个分子中一个缔合位点的 Lennard-Jones 链式分子，描述了特定的阳离子-阴离子相互作用。相反，形成咪唑基[Tf2N]-离子液体的阳离子和阴离子被建模为具有三个缔合位点的单个分子，考虑到由于阴离子周围的氧基团存在而导致阴离子电荷的离域。NH3 用四个缔合位点描述：三个 H 型位点模拟氢原子，一个 e 型位点代表孤对电子。H2S 用三个缔合位点建模：两个 H 型位点用于氢原子，一个 e 型位点用于硫的电负性。SO2 用两个位点建模，代表分子的偶极矩作为缔合相互作用。用三种污染物模型进行的软 S-AFT 计算与可用的相平衡、蒸发热和热容实验数据非常吻合。然后，在工业相关的温度范围内计算了这些化合物与基于咪唑的离子液体的二元混合物。与离子液体和污染物气体之间的缔合相互作用不同，已使用先进的缔合方案明确考虑到这一点。对于每一组混合物，仅需一个温度独立的能量二元参数即可以良好的一致性描述可用的文献数据。此外，在高 H2S 浓度下，从未实验测量过的混合物的氢硫化物+咪唑基离子液体与[PF6]-阴离子的汽液液平衡（VLLE）区域已被确定。这项工作表明，相对简单的模型能够捕获不同气体在离子液体中的相吸收图，只要为纯组分提供准确的模型以及用于模拟复杂系统行为的准确状态方程即可。
