Mass Transfer in Extractive Distillation when Using Ionic Liquids as Solvents

Mass transfer efficiency study in extractive distillation with ionic liquids for the mixtures water-ethanol and toluene-methylcyclohexane has been carried out in this work. Ionic liquids for the separation of these mixtures overcome the performance of the common volatile organic solvents. However, these also showed higher viscosities. A rated-based analysis was performed in order to quantify the effect of the solvent viscosity and relative volatility on mass transfer efficiency. In addition to this, an experimental analysis of the mass transfer efficiency was carried out experimentally in an extractive distillation pilot plant. The results indicated that, high liquid viscosities of ionic liquids should not affect the mass transfer efficiency negatively if the produced relative volatilities are sufficiently higher than those produced by organic solvents. However, when the ionic liquid showed very high viscosities or this solvent was present in large concentrations inside the col- umn, the mass transfer efficiency decreases no matter how high the relative volatility is.