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This study developed two ionic solvents using chlorides from the choline (ChCl) family: ammonium salts with 2-hydroxyethyl groups, dimethyl-di(2-hydroxyethyl)-ammonium chloride (1) and methyl-tri(2-hydroxyethyl)-ammonium chloride (2) as the hydrogen bond acceptor (HBA) and glycerol (Gly) as the hydrogen bond donor (HBD) in a molar ratio of 1:2. The solubility of ammonia and carbon dioxide in these solvents and also solubility of carbon dioxide in glycelin (ChCl : Gly = 1:2) and pure glycerol were measured at temperatures ranging from 303.2 to 333.2 K and pressures from 100 to 813 kPa. From this, Henry’s law constants and the changes in thermodynamic functions during the absorption process were determined. We show that solubility of ammonia and carbon dioxide in these ionic solvents made from 2-hydroxyethyl-grafted hydrogen bond acceptors (HBAs) increases with the number of 2-hydroxyethyl groups compared to the glycelin comprising HBA with one 2-hydroxyethyl substituent only. Developed fluids also demonstrated catalytic activity in the cycloaddition of CO2to epichlorohydrin (ECH), producing chloropropylene carbonate (PC-Cl). Under reaction conditions of 100 °C, 650 kPa, and 2 mol % catalyst concentration, a 95% conversion of ECH was achieved within 6 h. The effect of various reaction conditions on the ECH conversion and PC-Cl yield was also investigated. Additionally, the densities (ρ) and viscosities (η) of both pure and gas-saturated fluids were measured, completing the comprehensive characterization of the ionic solvents.

The present study is concerned with a complex theoretical and experimental evaluation of the effect of various distribution coefficients on the hydrate crystallization process retrofitted with/without membrane in the process of the capture of carbon dioxide from flue gas (N2(83.13 mol.%)/CO2(16.87 mol.%)) at the low-pressure. A batch reactor with a stirrer was used to perform experiments under isothermal conditions of 275.5 K and initial pressure of 3.1 MPa, the aqueous solution with a TBAB concentration of 5.0 wt% in the presence of the 1500 ppm Tween-80 were tested. The following modes were studied: the pressure-dropping separation, separation at the constant pressure, and the continuous hydrate separation. The continuous hydrate separation with/without a membrane was modeled, and its experimental verification was carried out. It was shown that using a two-stage hydrate membrane technology with an increase in the distribution coefficient, the CO2capture cost per ton decreased and could reach 35 $/ton, with a 92 % CO2recovery and a CO2residue flow of 0.4 mol.%.

In the present paper, a systematic investigation of the influence of amine and salt concentration on the CO2absorption capacity (mCO2, moles of CO2absorbed by 1 kg of a solution) and amine efficiency (cCO2, moles of CO2absorbed by 1 mole of amine) of the ternary mixtures composed of monoethanolamine (MEA), ethylene glycol (EG), and choline chloride (ChCl) was carried out. We demonstrate that, in general, the presence of a fixed amount of ChCl in a mixed {MEA + EG} solvent cannot improve mCO2over an entire range of solvent composition and weakly decreases cCO2with the effect more pronounced for the mixtures containing greater amount of MEA. The influence of ChCl concentration on the above properties was analyzed for the mixtures with a fixed MEA/EG mole ratio but various ChCl concentrations. It was shown that a decrease in mCO2observed with an increase in ChCl, again, is rather caused by an overall decrease in MEA content in a mixture as its efficiency cCO2does not change when ChCl concentration increases. In addition, properties such as density (ρ) and viscosity (η) of the binary {MEA + EG} and ternary {MEA + EG + ChCl} mixtures were obtained within a wide range of temperatures for both neat and CO2-loaded samples. We show that regardless of the {MEA + EG} mixed solvent composition, the presence of ChCl increases both ρand η. For CO2-loaded samples, both properties increase significantly with a greater contribution for the mixtures containing greater amount of MEA.

Two new deep eutectic solvents (DESs) composed of urea (U) and salts of a choline family such as dimethyl-di(2-hydroxyethyl)-ammonium chloride [Me2COH2N]Cl and methyl-tri(2-hydroxyethyl)-ammonium chloride [MeCOH3N]Cl mixed in a 1:1 molar ratio were prepared. Their densities, viscosities, refractive indices, and properties related to the ammonia absorption were thoroughly investigated. We found that the obtained DESs show an absorption capacity of 2.078 and 2.632 molNH3·kg–1DESfor [Me2COH2N]Cl/U and [MeCOH3N]Cl/U, respectively, at 313.2 K and 101.3 kPa, which is approximately two times higher than for the choline chloride/urea (2:3) DES at the same conditions. Also, the obtained Henry’s law constants are of the same sequence; that is, they increase from [MeCOH3N]Cl/U to [Me2COH2N]Cl/U and finally to choline chloride/urea. The mentioned tendencies show good correlation with DES’s molar volume and its free volume, and also with the number of the CH2CH2OH substituents in a quaternary ammonium salt cation. This suggests that the gas capture occurs via the interactions (most likely H-bonding) between an NH3molecule(s) and the hydroxyalkyl fragments. Indeed, the results of 1H NMR and FTIR spectroscopy confirm strong coupling between ammonia and hydroxyls leading to a distortion of the inherent DES structure. This finding agrees well with the fact that an NH3dissolution process in the studied DESs is favored by an entropic contribution.