Gas–liquid interactions in solution

Abstract

Two approaches are followed to understand how molecular interactions influence the macroscopic properties of solutions: (1) experiment, through the determination of gas solubility, and (2) computer simulation, used to evaluate microscopic properties (structural and energetic). Examples of application of these approaches are considered in order to explain the properties of solutions containing fluorinated fluids or ionic liquids. The molecular structures and interactions are described by force fields built from ab initio quantum chemical calculations. These models allow the determination of free energies from computer simulations by using appropriate energy routes provided by statistical mechanics. The macroscopic properties related to the process of dissolution of several gases are interpreted in terms of the molecular structure of the solutions and of the solute-solvent interactions.

Solubility of carbon dioxide and ethane in three ionic liquids based on the bis{(trifluoromethyl)sulfonyl}imide anion

“…(4) and (5) and constitute a reasonable approximation, for the case of gaseous solutes at low pressure, of the thermodynamic properties of solution [35]. The values for the partial molar Gibbs energy, enthalpy and entropy of solvation are given for the six investigated systems in Table 3.…”

“…From the temperature variation of K H , other thermodynamic properties of solvation can be calculated, which in the case of gaseous solutes at low pressures, can be approximated to the thermodynamic properties of solution [35]. The differences in enthalpy and entropy between the two standard states referred above (Δ solv H ∞ and Δ solv S ∞ , respectively) can be obtained by taking the corresponding partial derivatives of the Gibbs energy with respect to temperature:…”

Densities and refractive indices of imidazolium- and phosphonium-based ionic liquids: Effect of temperature, alkyl chain length, and anion

“…Even when comparing the different cations, the solubility of apolar gases like CF 4 also follow the values of the calculated free volumes as the solubility is lower in imidazolium-based ionic liquids (measured by Kumelan et al [65] and by Pison et al [66]) than in phosphoniumbased ionic liquids [38]. It is not, however, correct to make such comparisons as the mechanisms of solvation of some of these species, namely of CO 2 [67,68] in different ionic liquids are known to be controlled by electrostatic specific interactions and only to a minor extent by free volume effects [69].…”

Low pressure solubility and thermodynamics of solvation of oxygen, carbon dioxide, and carbon monoxide in fluorinated liquids

“…The relative importance of the entropic and enthalpic terms give pertinent information about the properties of the solutions, especially in very dilute solutes for which direct volumetric or calorimetric determinations are very difficult. The Gibbs free energy of solvation is also accessible by models of statistical thermodynamics and can be directly calculated by molecular simulation, and compared with experimental data provided a realistic intermolecular force field is available [7]. In that context, further objectives of this study include the understanding of the dependence of macroscopic thermodynamic properties of solution on the underlying molecular interactions [8].…”