Liquid-liquid equilibria and mechanism analysis for separating phenol from coal tar containing toluene using 1,2-propanediol or 1,3-propanediol

Liquid-liquid equilibrium (LLE) data for the ternary systems of phenol + toluene + solvent were determined at 298.2, 308.2, and 318.2 K under 101.3 kPa, in which 1,2-propanediol (1,2-PDO) or 1,3-propanediol (1,3-PDO) was screened as the extracting agent. Two important indicators (distribution coefficient and separation factor) were calculated to evaluate the extraction performance of solvent for separating phenol from coal tar containing toluene. The separation factor was all greater than one, indicating that it is feasible to select 1,2-PDO or 1,3-PDO as extractants for separating phenol from coal tar containing toluene. Meanwhile, solvation free energy and interaction energy among the components were calculated to investigate the separation mechanism of phenol from coal tar containing toluene using 1,2-PDO or 1,3-PDO at a molecular level. Furthermore, NRTL and UNIQUAC thermodynamic models were utilized to correlate experimentally determined LLE data for phenol + toluene + solvent (1,2-PDO or 1,3-PDO) ternary systems at (298.2–318.2) K under 101.3 kPa, and the root-mean-square deviation value was used to evaluate the discrepancy between correlated and experimental values, yielding corresponding binary interaction parameters. In addition, graphical user interface method for topological analysis developed by Marcilla was used to corroborate the reliability of obtained binary interaction parameters.