Solubilities and Thermodynamic Properties of Carbon Dioxide in Guaiacol-Based Deep Eutectic Solvents

In this work, the solubility data of CO2 in three kinds of guaiacol-based deep eutectic solvents (DESs) at 293.15, 303.15, 313.15, and 323.15 K and pressures below 600.0 kPa were determined. The DESs were prepared from guaiacol and quaternary ammonium salts (QASs, including choline chloride, acetylcholine chloride, and diethylamine hydrochloride) with a molar ratio of guaiacol to QAS of 3:1, 4:1, and 5:1. Henry’s law was used to correlate the solubility data, and the thermodynamic properties, such as standard Gibbs free energy, standard enthalpy, and standard entropy of these systems were derived. The solubility of CO2 increased with increasing molar ratio of guaiacol to QAS in each kind of DES. The dissolution enthalpies were negative at all conditions. The dissolution capacities of present DESs for CO2 were further compared with those of other DESs and several common ionic liquids.