Extraction of {benzene, toluene, thiophene and 3-methylthiophene} from n-hexane: Liquid-liquid equilibrium measurements and interaction exploration

Abstract

In order to investigate the ability of N-methyl-2-pyrrolidone (NMP) to extract aromatics (benzene, toluene) and sulfides (3-methylthiophene, thiophene) from n-hexane, the liquid-liquid equilibrium (LLE) data of n-hexane + {benzene, toluene, thiophene or 3-methylthiophene} + NMP systems were determined at 293.15 K under 101.3 kPa. The Othmer-Tobias and Hand equations were applied to validate the reliability of the obtained LLE data, and the correlation coefficients (R2) are close to unity. It was found that sulfides could be successfully extracted from n-hexane by NMP solvent companying with the extraction of aromatics. However, the separation factors and distribution coefficients of the sulfides are greater than those of aromatics, indicating that the sulfides are more easily extracted by NMP. Furthermore, the separation energies of the sulfides are greater than that of aromatics, which is also a piece of evidence for easier separation of sulfides. In order to extend those results to other extraction processes involving those sulfides, aromatics and solvent, the binary interaction parameters of the NRTL and UNIQUAC thermodynamic models were calculated by correlating the LLE data. The RMSD values were all <0.0070, and a graphical user interface based on the Gibbs tangent plane test was also applied to validate the coherent consistency of the parameters. The results show that the obtained binary interaction parameters could be reliable adopted in the design and optimization of the related extraction/separation process in industry.