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The present research provides data on the density (ρ), viscosity (η) and ability to absorb carbon dioxide of systems containing amine, molecular solvent (MS) and choline chloride (ChCl), with the investigation of the physical properties of both neat amine/MS/ChCl mixtures and their samples after complete CO2 saturation. The effect of the mixture composition was studied by varying amine from primary (monoethanolamine, MEA) to secondary (diethanolamine, DEA) and tertiary (triethanolamine, TEA) amine, and the degree of its substitution from a mono- (MEA, DEA and TEA) to a doubly-substituted (ethylenediamine, EDA) compound. The role of an MS was investigated via the exchange of ethylene glycol (EG) with water and dimethylsulfoxide (DMSO). In addition, the influence of the CO2 absorption promoters present in the ternary MEA/EG/ChCl mixture at an amount of 5 wt. % was also investigated. We show that an increase in ρ and η in the amine/EG/ChCl mixture affects the properties of neat amines. This suggests that in the studied ternary mixtures, the nature of the interspecies interactions is very similar to those in the previously studied MEA/EG/ChCl system. When EG was exchanged for H2O or DMSO, a decrease in ρ and an increase in η were observed. A comparison of the data with the corresponding properties of the systems composed of each pair of the mixture components indicates that the intensity and/or number of interspecies interactions in the present ternary mixtures were stronger than those in pure H2O, DMSO and MEA. While in the presence of promoters no significant changes in the studied properties were found, for the corresponding CO2-saturated samples, the ρ and η increased proportionally to the amount of absorbed gas. This was also the case for all the systems studied in the present research. The overall CO2 absorption of the EG-based mixtures decreased when going from primary to secondary and tertiary amines; it was 21% higher for the MEA/H2O/ChCl system compared to the mixtures containing EG and DMSO, which, in turn, showed similar absorption capacities. When the promoters were added to the MEA/EG/ChCl mixture, the highest capacity was found for the piperazine-containing system. [ABSTRACT FROM AUTHOR]

• Four novel DESs formed by chlorides of choline family and ethylene glycol in mole ratio 1: 2 were prepared. • Densities, viscosities, refractive indices and molar volumes of DESs were measured and obtained in a wide temperature range. • Solubilities of NH 3 were found to calculate the Henry's law constants and thermodynamics of absorption process. • NH 3 absorption capacity of DESs improved by 5–57% regarding to ethaline at same conditions if changing the HBA's structure. • 1H NMR and FTIR spectroscopy investigations found out the strong coupling between ammonia and hydroxyls of DESs. The current study deals with four novel deep eutectic solvents (DES) formed by choline-like chlorides (ChCl), namely ammonium salts with 2-hydroxyethyl and 2-(2-hydroxyethoxy)ethyl substituents, and ethylene glycol (EG) in mole ratio 1 : 2. Their thermophysical properties such as density (ρ), viscosity (η), refractive index (n D) were carefully investigated in a broad range of temperatures. The ammonia solubilities in considered DESs at T = (303.2–333.2) K and p = (100–636) kPa were measured and considering the slight deviation from ideality Krichevsky − Kasarnovsky equation were used for fitting the experimental data. Based on this, the Henry's law constants (H), partial molar volumes at infinite dilution of NH 3 in DESs (V N H 3 ∞), and then the changes of enthalpy (Δ s o l H °), Gibbs free energy (Δ s o l G °) and entropy (Δ s o l S °) during the NH 3 absorption process were obtained. For the investigated DESs an improvement of ammonia absorption capacity at 313.2 K and 101 kPa was found to be by 33 % (3.640 mol · kg−1) if changing one methyl to 2-hydroxyethyl group, by 57 % (4.295 mol · kg−1) if changing two methyl to two 2-hydroxyethyl groups, by 5 % (2.861 mol · kg−1) if changing one methyl to 2-(2-hydroxyethoxy)ethyl group, by 13 % (3.081 mol · kg−1) if changing two methyl to 2-hydroxyethyl and 2-(2-hydroxyethoxy)ethyl groups in HBA structure compared to the ethaline (ChCl : EG = 1 : 2; 2.729 mol · kg−1). This assumes occurring the gas capture via – most likely – hydrogen bonds interactions between the ammonia molecule(s) and the hydroxyalkyl fragments, while the ether's groups in HBA structure depress the positive effect of latter and hence decrease the general ammonia solubility in the considered DESs. Indeed, the strong linking emerging between hydroxyls of HBA and NH 3 leads to the deformation of solvent intrinsic structure, which was proven by 1H NMR and FTIR spectroscopy. [ABSTRACT FROM AUTHOR]