Wide-ranging prediction of phase behavior in complex systems by CP-PC-SAFT with universal kij values. I. Mixtures of non-associating compounds with [C2mim][EtSO4], [C4mim][MeSO4], and [C2mim][MeSO3] ionic liquids

Abstract

This study shows that the inter-relations between critical constants can explain various phenomena occurring in the ionic liquids (IL) systems, such as the higher solubility of aromatic compounds and the differences between solubilities in the specific ILs. Indeed, as the critical constants get more remote, the systems become more asymmetric, increasing thus the immiscibility gaps. The Critical Point-based Perturbed-Chain Statistical Association Fluid Theory (CP-PC-SAFT) EoS rigorously obeys the Tc and Pc of ordinary substances. Moreover, its high precision in modelling the liquid phase properties yields realistic estimations of the imaginary critical constants of ILs. Such features attach an enhanced predictive capacity to this model, even while neglecting the complex chemical background of ILs. Although the substantial disagreements between different sources allow examining the general truthfulness of predictions rather their quantitative precision, it is demonstrated that using the universal value of k12 = 0.027 obtained for just one of the VLE datasets, CP-PC-SAFT realistically predicts various phase equilibria in mixtures of non-reacting gases, n-alkanes, aromatic hydrocarbons, ethers, ketones and haloalkanes with the considered ILs. The accuracies of these predictions are comparable with the widely implemented COSMO-RS approach. However, unlike it, CP-PC-SAFT can be applied for estimating high-pressure phase equilibria and it provides accurate predictions of volumetric data of mixtures in the particularly wide range of conditions.