The concept of eutectic solvents as a platform technology for a variety of applications including gas separation has become a popular approach. To date, the number of known deep eutectic solvents (DESs) is limited mainly to halide salts easily interacting with a hydrogen-bond donor (HBD) and resulting in the formation of a liquid phase. Actually, the DESs properties may be tuned by selecting the appropriate HBD, while the structure of the anion is not a decisive factor. However, the presence of other anions may be favorable for certain applications; therefore, expanding the range of deep eutectic solvents seems a relevant issue of chemistry and material science. In this study, we report the high absorption properties of the DES based on 1-butyl-3-methyl imidazolium methanesulfonate–urea toward ammonia. The structure features investigations have revealed the major contribution of C(2)-H to hydrogen bonding. To assess the possibility of selective separation, the solubility of ammonia and two acidic gases (H2S and CO2) in the absorbent has been measured. A superior gas sorption capacity was observed for ammonia, for which the Henry’s law constant was equal to 1.52 bar. The obtained results exceeded the solubility data reported in the literature for various ILs containing hydrogen-donating groups. The DESs demonstrated lower yet acceptable solubility toward hydrogen sulfide, whereas the solubility of CO2 was relatively poor. The thermostimulated desorption has demonstrated that the ability of gases to bind with DES molecules can be ranked as follows: NH3 > H2S > CO2. The physical sorption mechanism of ammonia, hydrogen sulfide, and carbon dioxide in the DES was proven by FTIR and thermal desorption analysis. The absorption was totally reversible, and the solubility of gases remains almost unchanged after three cycles.

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Herein, we studied the absorption of H 2 S and CO 2 by alkanolamine−protic ionic liquids binary mixtures based on 2-hydroxyethylammonium (MEA) or triethanolammonium cations and residues of 2hydroxy-5-sulfobenzoic acid or pyridine-3-carboxylic acid at various temperatures and partial gases pressures. It was found that absorbents based on the 2-hydroxyethylammonium cation, performed high absorption properties toward the H 2 S. The solubility of hydrogen sulfide, characterized by the Henry's Law constant, in MEA-based binary mixtures had the values comparable to the commercially available ionic liquids. The results of thermal desorption analysis demonstrated that the capture of acid gases in MEAbased absorbents occurred at two stages: through the dissolution in MEA component and in protic ionic liquid.

CO2 separation was found to be facilitated by transport membranes based on novel chitosan (CS)–poly(styrene) (PS) and chitosan (CS)–poly(acrylonitrile) (PAN) copolymer matrices doped with methylimidazolium based ionic liquids: [bmim][BF4], [bmim][PF6], and [bmim][Tf2N] (IL). CS plays the role of biodegradable film former and selectivity promoter. Copolymers were prepared implementing the latest achievements in radical copolymerization with chosen monomers, which enabled the achievement of outstanding mechanical strength values for the CS-based membranes (75–104 MPa for CS-PAN and 69–75 MPa for CS-PS). Ionic liquid (IL) doping affected the surface and mechanical properties of the membranes as well as the gas separation properties. The highest CO2 permeability 400 Barrers belongs to CS-b-PS/[bmim][BF4]. The highest selectivity α (CO2/N2) = 15.5 was achieved for CS-b-PAN/[bmim][BF4]. The operational temperature of the membranes is under 220 °C.

Pervaporation has been applied for tetrahydrofuran (THF) dehydration with novel composite membranes advanced by a thin selective layer composed of chitosan (CS) modified by copolymerization with vinyl monomers, acrylonitrile (AN) and styrene, in order to improve the chemical and mechanical stability of CS-based membranes. Composite membranes were developed by depositing a thin selective layer composed of CS copolymers onto a commercially-available porous support based on aromatic polysulfonamide (UPM-20®). The topography and morphology of the obtained materials were studied by atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). Thermal properties and stability were determined by coupled evolved gas analysis (EGA-MS). Transport properties were estimated in pervaporation dehydration of THF. The effect of operating parameters for the pervaporation dehydration of THF such as feed compositions and temperatures (295, 308 and 323 K) was evaluated. It was shown that CS modification with different vinyl monomers led to a difference in physical and transport properties. The composite membrane with the thin selective layer based on CS-PAN copolymer demonstrated optimal transport properties and exhibited the highest water content in the permeate with a reasonably high permeation flux.

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In the present paper, a systematic investigation of the influence of amine and salt concentration on the CO 2 absorption capacity (m CO 2 , moles of CO 2 absorbed by 1 kg of a solution) and amine efficiency (c CO 2 , moles of CO 2 absorbed 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 m CO 2 over an entire range of solvent composition and weakly decreases c CO 2 with 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 m CO 2 observed with an increase in ChCl, again, is rather caused by an overall decrease in MEA content in a mixture as its efficiency c CO 2 does 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 CO 2 -loaded samples. We show that regardless of the {MEA + EG} mixed solvent composition, the presence of ChCl increases both ρ and η. For CO 2loaded samples, both properties increase significantly with a greater contribution for the mixtures containing greater amount of MEA.

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