Screening of Double Solvents Based on Multi-Index Evaluation Method for the Selective Separation m-Cresol from Model Oil.

Abstract

Ionic liquid (IL) as an extractant is an effective method for separating oil–phenol mixtures. However, relatively high neutral oil entrainment can lead to oil loss and a remarkable reduction in phenol purity. To reduce the entrainment of neutral oil in the extraction process, a double-solvent extraction system composed of IL 1-ethyl-3-methyl imidazolium acetate ([C2mim][Ac]) and an organic solvent was investigated. The multi-index evaluation method was used to screen the conventional organic solvent. The double-solvent extraction experiments were employed to verify the accuracy of the COSMO-RS prediction. Eighteen organic solvents, the interaction energy with m-cresol and cumene (neutral oil), their extraction ability, and mutual solubility with [C2mim][Ac], were calculated by COSMO-RS. Alkane and cycloalkane were screened due to their strong interaction and low distribution coefficient with cumene, as well as the low mutual solubility with [C2mim][Ac]. The experimental results were in good agreement with the COSMO-RS prediction, and cyclopentane as an organic solvent had the lowest distribution coefficient and entrainment of cumene because of its strong nonpolarity and hydrogen-bond repulsive interaction, which was explained by the σ-profile and σ-potential analysis. When the cyclopentane-to-[C2mim][Ac] mass ratio increased from 0.0 to 3.0, the entrainment of cumene was evidently declined from 39.5 to 5.8% and the selectivity to m-cresol was improved from 378.0 to 1058.5.