**2. Ionic selection for water: ethanol and toluene: methylcyclohenene separation**

As it was mentioned above, ionic liquids show better performance than organic solvents in terms of vapor–liquid equilibrium. Therefore, the selection of the ionic liquids for a certain case study is based on the increase in relative volatility. The work of Ge et al. [23] shows an experimental selection of ionic liquids for water-ethanol separation. On the other hand, Gutierrez-Hernandez et al. [25] carried out a selection of ionic liquids for methylcyclohexane-toluene separation based on liquid-liquid extraction experiments. Nevertheless, the high viscosities of ionic liquids could limit the mass transfer in the ED column. **Table 1** contains experimentally determined relative volatilities and viscosities for both case studies.

It can be observed in **Table 1** that the selected ionic liquids for the separation of the waterethanol mixture, 1-ethyl-3-methylimidazolium chloride ([emim][Cl) and 1-ethyl-3-methylimidazolium acetate ([emim][OAc]) showed higher produced relative volatilities than the conventional organic solvent ethylene glycol (EG). For the second case, the ionic liquid


**Table 1.** Relative volatilities at a solvent-to-feed (S/F) ratio (mass basis) for different solvents and pure solvent viscosities (*η*) at *T* = 298.15 for both case studies.

1-hexyl-3-methylimidazolium tetracyanoborate ([hmim][TCB]) produced much higher relative volatilities than organic solvent. This is an indication that, a column with less separation stages or a less usage of solvent is expected to achieve a good separation. However, ionic liquids also show higher viscosity values than traditional solvents. Therefore, the mass transfer efficiency is expected to decrease.
