Physical Properties and NH3 Solubilities of Deep Eutectic Solvents Formed by Choline Chloride and Glycols

ABSTRACT In this study, deep eutectic solvents (DESs) formed by choline chloride (ChCl) and three glycols−ethylene glycol (EG), 1,3-propanediol (PD) and 1,4-butanediol (BD)−were investigated for NH3 absorption. The densities and viscosities of DESs at 298.2∼358.2 K and 101.3 kPa were measured first, and fitted to the linear equation and Vogel−Fulcher−Tammann equation respectively. The solubilities of NH3 in DESs at 298.2∼353.2 K and 0∼250.0 kPa were then measured by a well-established dual-chamber method. The effects of temperatures, pressures and liquid compositions on NH3 solubilities were examined, and the NH3 solubilities of DESs were compared with those of other solvents reported in the literature. Finally, the solubilities of NH3 were fitted to the Krichevsky−Kasarnovsky equation to calculate the Henry's constants and partial molar volumes at infinite dilution of NH3 in DESs, as well as the enthalpy changes, Gibbs free energy changes and entropy changes for NH3 absorption process.