Research on separation of higher-rank phenols from coal tar: A combination of liquid-liquid extraction experiments and mechanism analysis

To separate higher-rank phenols from coal tar model compound, the quantum chemistry calculation, solvent power, and selectivity analysis evaluated the separation efficiency of polyols as solvents, and the liquid–liquid equilibrium data of toluene + {4-ethylphenol, 2-allylphenol, guaiacol, or 2-isopropylphenol} + ethylene glycol were measured in 303.2 K and 101.3 kPa. The distribution coefficient and separation factor were calculated to compare the efficiency of extracting different phenols using ethylene glycol. The molecular dynamics (MD) method investigated the mechanism of extraction of phenols by ethylene glycol, and the results are consistent with the experimental results, indicating that ethylene glycol can be used as an extractant for the extraction of higher-rank phenols from coal tar, and the extraction effect in the 4-ethylphenol-toluene system is the best. The non-bonded interaction energy, radial distribution function, and self-diffusion coefficient were discussed, which shows that the interaction force between phenols and ethylene glycol is mainly provided by electrostatic force.