Experimental Data of Fluid Phase Equilibria- Correlation and Prediction Models: A Review

The examples of phase equilibria in binary systems, solid/liquid (SLE), liquid/liquid (LLE), vapor/liquid (VLE), as well as liquid/liquid equilibria in ternary systems mainly containing ionic liquids (ILs), or the infragrance materials, or pharmaceuticals with molecular organic solvents, such as an alcohol, or water, or hydrocarbons, are presented. The most popular correlation methods of the experimental phase equilibrium data are presented, related to the excess Gibbs free energy models such as Wilson, universal-quasichemical, UNIQUAC and non-random two-liquid model, NRTL as well as several popular theories for the modeling of the phase equilibria and excess molar enthalpy, HE in binary or ternary mixtures are presented: the group contribution method (Mod. UNIFAC) and modified UNIFAC model for pharmaceuticals and lattice theory based on non-random hydrogen bonding (NRHB). The SLE, LLE, or VLE and HE of these systems may be described by the Perturbed-Chain Polar Statistical Associating Fluid Theory (PC-SAFT), or a Conductor-like Screening Model for Real Solvents (COSMO-RS). The examples of the application of ILs as extractants for the separation of aromatic hydrocarbons from alkanes, sulfur compounds from alkanes, alkenes from alkanes, ethylbenzene from styrene, butan-1-ol from water phase, or 2-phenylethanol (PEA) from water are discussed on the basis of previously published data. The first information about the selectivity of extrahent for separation can be obtained from the measurements of the limiting activity coefficient measurements by the gas–liquid chromatography technique. This review outlines the main research work carried out over the last few years on direct measurements of phase equilibria, or HE and limiting activity coefficients, the possibility of thermodynamic modeling with emphasis on recent research achievements and potential for future research.

Influence of temperature on thermodynamics for binary mixtures of short aliphatic protic ionic liquids

Two binary mixtures of protic ionic liquids comprising formate, acetate and propionate anions and 2-hydroxyethyl ammonium, bis(2-hydroxyethyl) ammonium and tris(2-hydroxyethyl) ammonium cations have been studied in terms of volumetric and acoustic properties as a function of temperature. The corresponding derived properties have been computed from the experimental data and fitted to temperature dependent Redlich?Kister and Redlich? ?Mayer equations; accurate results being obtained. Other properties such as intermolecular free length, acoustic impedance, geometrical volume, collision factor and isothermal coefficient of pressure excess molar enthalpy were computed due to their importance in the study of specific molecular interactions. The new experimental data were used to test the prediction capability of different models for density (Mchaweh?Nasrifar?Moshfeghian (MNM) model and the modified Heller temperature dependent equation (MHE)) and ultrasonic velocity (different empirical equations, collision factor theory (CFT) and free length theory (FLT)). The high non-ideality of these mixtures points to strong contractive behaviour at any temperature and composition. The obtained results indicate that ionic liquid interactions into mixture are stronger than in the ionic pure components for both mixtures at any studied condition. Despite the strong ion interaction, the tested models showed, at least, the qualitative prediction capability.