UNIQUAC correlation of liquid–liquid equilibrium in systems involving ionic liquids: The DFT–PCM approach. Part II

Abstract

a b s t r a c tIn this work, new UNIQUAC structural parameters r and q for the ionic liquids were determined by quantum chemistry calculations performed with the Gaussian 03 and GAMESS 7.1 packages, including the density functional theory (DFT) for the optimization of the structures and the polarizable continuum method (PCM) for the calculation of molecular areas and volumes. Data liquid-liquid equilibrium (LLE) of 41 ternary systems involving 15 different ionic liquids, comprising 379 experimental tie-lines, was correlated by the UNIQUAC model for the activity coefficient. The results, expressed by deviations between experimental and calculated compositions, are very satisfactory, with deviation values about 1.93%.

(Liquid+liquid) equilibrium data for the system (propylene glycol+water+tetraoctyl ammonium 2-methyl-1-naphthoate)

“…The PCM in combination with the Density Functional Theory (DFT) to obtain the equilibrium geometry of the molecule provides a strong theoretical background for the prediction of the surface and volumetric parameters. Both quantum chemical computational approaches (PCM and COSMOtherm) have shown satisfactory results in the estimation of r and q values of alkylimidazolium ionic liquids and for its application in the UNIQUAC model [29,36,37]. The values of the van der Waals surface and volume, and the predicted molar volume for [TOA MNaph] are presented in table 1.…”

“…An alternative method to compute the UNIQUAC parameters r and q is the Polarizable Continuum Model (PCM) [28,29,37]. The PCM is a rigorous model based on quantum chemical calculations.…”

Liquid–liquid equilibria for ternary mixtures of water + 2-propanol + 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids at 298.15 K

“…The application of the UNIQUAC model for correlating the LLE data containing ILs, however, is narrower than that of the NRTL model for the former requires the structural volume (r) and surface area (q) parameters of ILs and the parameters are missing in the published papers for the new ILs [44]. The calculations of the values of r and q for some ILs by quantum chemistry approach have been reported and the validities of the calculated values applied to the UNIQUAC model were testified [44][45][46]. Therefore, the quantum chemistry approach was applied for determining the values of r and q for the studied ILs by Gaussian 09 in this work.…”

Separation of toluene from cyclic hydrocarbons using 1-butyl-3-methylimidazolium methylsulfate ionic liquid at T=298.15K and atmospheric pressure

“…Following a common procedure, the non-randomness parameter in the NRTL model, a, was set to different values between 0.1 and 0.4, and the best results were found for a values between 0.1 and 0.2. The required van der Waals parameters of the UNIQUAC model, r i , and q i , for the ionic liquid were taken from literature [44].…”