Efficient removal of benzene from cyclohexane-benzene mixtures using deep eutectic solvents - COSMO-RS screening and experimental validation

- COSMO-RS is used to screen 40 DESs for the separation of benzene and cyclohexane.
- The screening results were validated experimentally for five DESs.
- The extraction efficiency can reach 97% after nine extraction cycles.
- The DESs were easily regenerated using rotary evaporation.
- NRTL model was successfully used to describe the ternary LLE data.

The separation of benzene and cyclohexane is considered one of the most challenging processes in the petrochemical industry. For this study, 40 deep eutectic solvents (DESs) were screened by using the COSMO-RS model. The screening was achieved based on a comparison of selectivity, capacity, and the performance index, all derived from the activity coefficient at infinite dilution. In addition, the sigma σ-profile and σ-potential of each component were used to analyse the interactions between the different species during the extraction process. After screening, five DESs were selected for experimental validation. The liquid-liquid extraction process was conducted, and the ternary diagrams were plotted for the selected DESs at 25 °C under atmospheric pressure. The NRTL model was successfully employed to correlate the experimental tie lines. The results revealed that COSMO-RS was a useful tool for screening potential DESs qualitatively. In addition, observations revealed strong agreement between NRTL and the experiment results, with a root mean square deviation of less than unity for all systems. The findings showed that the selected DESs are feasible for use as extracting solvents for this separation, whereby in all systems no trace of DES was found in the cyclohexane layer.