Separation of m-cresol from model oil by pyridinium-based ionic liquids: COSMO-RS screening, experimental study, and process simulation

Abstract

The separation of phenolic compounds from low-temperature coal tar is conducive to the rational utilization of resources and environmental protection. In this work, pyridinium-based ionic liquids (ILs) were used as extractants for m-cresol/cumene separation. 70 pyridinium-based ILs formed by 10 cations and 7 anions were screened combining the calculation of the extraction ability of ILs for m-cresol and the mutual solubility of ILs with cumene by COSMO-RS model. The influences of cation and anion structures were studied and further explored by σ-profile and σ-potential. Among 70 ILs, the IL 1-ethyl-pyridinium dicyanamide ([C2py][N(CN)2]) was finally identified. Then [C2py][N(CN)2] was synthesized and used to separate m-cresol from model oil. The influences of stirring time, temperature, IL: model oil mass ratio, and initial m-cresol content on the separation performance of [C2py][N(CN)2] were investigated. The regeneration of [C2py][N(CN)2] was carried out and was characterized by FT-IR. The formation of hydrogen bond between [C2py][N(CN)2] and m-cresol was confirmed by FT-IR. Moreover, the process simulation and optimization were investigated by Aspen Plus based on the NRTL model. For the separation process using [C2py][N(CN)2], products with high recovery ratio (99.97% for m-cresol and 99.99% for cumene) and high mass purity (99.97 wt% for m-cresol and 99.80 wt% for cumene) were obtained. The simulation results could provide a guidance for industrial application.