Systematic method of screening deep eutectic solvents as extractive solvents for m-cresol/cumene separation

Abstract

Deep eutectic solvents (DESs) have been widely applied as extractive solvents for the separation of phenolic compounds from low-temperature coal tar (LTCT). However, systematic study of screening suitable DESs from numerous candidates for this separation process is still scarce. In this work, a systematic method of screening promising DESs as extractive solvents is proposed for the separation of m-cresol/cumene, as a representative phenolic compound/neutral oil mixture in LTCT. Experimental data of DES-involved systems are collected from literature to validate the reliability of conductor-like screening model for real solvents (COSMO-RS), which serves as the foundation for thermodynamic calculation and process simulation. Then, the crucial influencing factors for DESs screening (i.e., salt and solvent, and the molar ratio) on the thermodynamic properties are investigated by COSMO-RS. After that, a systematic DESs screening method combining the calculation of infinite dilution thermodynamic properties, the estimation of melting point and viscosity, the calculation of liquid-liquid equilibria, and the evaluation of process performance is proposed. The results indicate that chlorocholine chloride (CChC): acetic acid (AA) (1:2) and choline chloride (ChCl): ethylene glycol (EG) (1:3) are identified as the optimum DESs for m-cresol/cumene separation. Finally, the high separation performances of CChC:AA (1:2) and ChCl:EG (1:3) are confirmed by extraction experiments.