Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

Phenolic compounds (such as phenol, cresol and xylenol), which are basic materials for the organic chemical industry, are mainly produced from coal liquefaction oil, coal tar, petroleum, and biomass pyrolysis oil. It has been reported that the separation of phenols from oil with forming deep eutectic solvents based on quaternary ammonium salt is an efficient and environmentally friendly method. However, the phase equilibrium of quaternary ammonium salt + phenol + oil mixtures has not been reported in the literature. In this work, the phase equilibrium for separating phenol from model oil with choline chloride (ChCl), tetraethylammonium chloride (TEAC), and tetramethylammonium chloride (TMAC) was studied. Phase equilibria of three ternary systems of toluene + phenol + quaternary ammonium salt were measured at 25, 40 and 65 deg. C, and phase behaviors of the ternary systems were studied. Effects of temperature, type and dosage of quaternary ammonium salt on the equilibrium were investigated. The results show that low temperatures are beneficial to extraction of phenol and the phenol removal efficiency decreases with increasing temperature. For the quaternary ammonium salts, TEAC has the strongest ability to separate phenol, but the concentration of toluene entrained in the DES phase is the largest. Only TMAC is dissolved in the oil phase to a small extant, which can cause the loss of extractant. ChCl not only has high phenol removal efficiency, but also causes a small concentration of toluene entrained in the DES phase, which shows that ChCl is an efficient and environmentally friendly extractant.