An Overview of the Liquid-Liquid Equilibria of (Ionic Liquid plus Hydrocarbon) Binary Systems and Their Modeling by the Conductor-like Screening Model for Real Solvents

Ionic liquids (ILs), with their unique and tunable properties, are attracting the interest of both academia and refining companies as potential solvents for the extraction of specific compounds from hydrocarbons' streams. For such a purpose, the knowledge of the mutual solubilities between ionic liquids and hydrocarbons is required. Experimental measurements for all these systems are impracticable due to the large number of possible combinations of ionic liquids and hydrocarbons. Thus, a deeper understanding of the interactions taking place, and ruling the phase behavior, and the development of predictive models are essential issues to forecast a general picture of the liquid-liquid equilibria (LLE) between ionic liquids and hydrocarbons. In this work an overview of the mutual solubilities between ionic liquids and hydrocarbons is presented. A review of the experimental data available is reported, and the effect of various structural features of both the ionic liquids and the hydrocarbons through their mutual solubilities behavior is discussed. The capability of the Conductor-like Screening Model for Real Solvents (COSMO-RS) to predict the LLE of (IL + hydrocarbon) binary systems is further evaluated. More than 150 binary systems were investigated. It is shown that COSMO-RS allows a semiquantitative description of the LLE experimental data for the systems studied. Moreover, COSMO-RS majorly provides a correct qualitative trend of the phase behavior dependence of the ionic liquids and molecular compounds. Therefore, COSMO-RS can be a useful predictive tool with great potential in the screening of ionic liquids for specific extraction applications.