Phase equilibria of high pressure CO2 and deep eutectic solvents formed by quaternary ammonium salts and phenol

Phase equilibria of the binary systems of high pressure CO 2  +  deep eutectic solvents (DESs) formed by quaternary ammonium salts (QASs, including 2-hydroxy- N , N , N -trimethyl-ethanaminium chloride, ChCl; N , N , N -trimethyl-methanaminium chloride, TMAC; and N , N , N -triethyl-ethanaminium chloride, TEAC) and phenol were measured at temperatures from 313.15 K to 333.15 K, pressures from 1.71 MPa to 13.3 MPa and mole ratios of phenol to QAS from 2.00 to 4.00. It has been found that two-phase equilibrium exists at all the studied conditions. The solubility of phenol in the CO 2 phase and the solubility of CO 2 in the DES phase at different pressures, temperatures, mole ratios of phenol to QAS have been obtained. Both the solubility of phenol in the CO 2 phase and the solubility of CO 2 in the DES phase formed by ChCl and phenol shows the largest, while those in the DES phase formed by TEAC and phenol shows the smallest. This work provides phase equilibrium data for phenol extraction and QAS regeneration.