Modeling the thermodynamic and physical properties of mixtures of room temperature molten salts (i.e. ionic liquids)

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Modeling the thermodynamic properties (including phase equilibria) and physical properties of multicomponent systems is of great industrial importance nowadays. The metallurgical and chemical industries commonly use thermochemical packages to simulate chemical reactions and phase equilibria for process development. In particular, "room temperature molten salts" (commonly referred to as "ionic liquids") have many potential applications (such as electrochemistry, and solvents and catalysts), and their mixtures have been studied relatively little in comparison with the pure liquids. The thermodynamic and phase equilibrium modeling of multicomponent salt systems consists in expanding the Gibbs energy of a phase as a function of temperature, pressure and composition, and finding a global energy minimum. Model parameters of the Gibbs energy functions are obtained by optimizing their values in order to best reproduce simultaneously the experimental data found in the literature (enthalpy, liquidus, etc.). Parameters form a database and the models are used to predict phase equilibria and thermodynamic properties in the multicomponent system. Models for the density, viscosity and electrical conductivity of multicomponent inorganic molten salts, all linked to the thermodynamic model that gives an estimation of the structure of the melt, were previously developed and applied successfully to inorganic electrolytes such as NaCl-KCl-MgCl2-CaCl2 and NaF-AlF3-CaF2-Al2O3-LiF-MgF2. The proposed project consists in developing models and databases of parameters for the prediction of phase equilibria (in particular, the liquidus temperature) and physical properties (mainly density and viscosity) of common-cation ternary mixtures of the type CX-CY-CZ (where C is a large organic cation, and X, Y and Z are three different inorganic anions), and then of common-anion ternary mixtures of the type C1X-C2X-C3X (where C1, C2 and C3 are three different organic cations, and X is an inorganic anion). The existing thermodynamic and physical property models will be adapted/modified accordingly, and they will be calibrated on measurements.