Solubilities and thermodynamic properties of CO2 in choline-chloride based deep eutectic solvents

• Solubilities of carbon dioxide in three deep eutectic solvents (DESs) have been reported.
• The experimental data were reduced to Henry’s law constants.
• The Gibbs free energy, enthalpy, and entropy changes were calculated.
• Relationship between solubility and structure of DESs was developed.

The solubilities of CO2 in three kinds of deep eutectic solvents, (choline chloride + phenol), (choline chloride + diethylene glycol) and (choline chloride + triethylene glycol), were determined at temperatures ranging from 293.15 K to 323.15 K under pressures up to 600.0 kPa using isochoric saturation method. The mole ratios of choline chloride to phenol were selected as 1:2, 1:3 and 1:4, the others as 1:3 and 1:4. Henry’s constants and thermodynamic properties such as standard Gibbs free energy, enthalpy, and entropy changes of CO2 solvation were calculated from the correlation of solubility data. Results revealed that the solubility of CO2 increased with increasing pressure and decreased with increasing temperature. The enthalpies of solution were negative at all conditions.