Investigation of a deep eutectic solvent formed by levulinic acid with quaternary ammonium salt as an efficient SO₂ absorbent

Abstract

Efficient and reversible absorption of SO 2 in six new deep eutectic solvents (DESs) composed of levulinic acid (LA) and quaternary ammonium salts (choline chloride, CC; choline acetyl chloride, CAC; tetraethylammonium chloride, TEAC; tetraethylammonium bromide, TEAB; tetrabutylammonium chloride, TBAC; tetrabutylammonium bromide, TBAB) was systematically investigated. The molar ratio of LA to quaternary ammonium salt was fixed at 3 : 1. The results showed that all DESs possessed satisfactory performance for SO 2 absorption, with the maximum absorption capacity of 0.625 g SO 2 per g DES of LA-TEAC at 293.15 K under ambient pressure. The absorbed SO 2 was easily released by bubbling N 2 at 323.15 K and the regenerated DES was recycled five times without obvious loss of absorption performance. The solubility of SO 2 in DES of LA-CC at T = 293. 15, 303.15, 313.15, and 323.15 K under subatmospheric pressures was also determined. The relative thermodynamic parameters, i.e., absorption enthalpy, absorption entropy, and absorption Gibbs free energy, were further calculated, giving results with small negative values. The influence of water content on the SO 2 absorption was also investigated. According to NMR and FTIR analyses, the absorption of SO 2 in DES was a physical process. Moreover, all the DESs exhibited high selectivity for SO 2 /CO 2 . The present DESs are promising absorbents for SO 2 because of their high absorption capacity and good reversibility.

Solubility and thermodynamic properties of SO 2 in three low volatile urea derivatives

“…A brief summary of the results is listed in Table 6. As can be seen from Table 6, the solubility of SO 2 in present solvents is similar to those in DESs of TEAC-LA (1:3) [15], ChCl-EG (1:2) and ChCl-thiourea (1:1) [14] and ChClglycerol (1:1) [13], NMP [17], and 1,1-[oxybis(2,1-ethanediyloxy-2,1-ethanediyl)]bis(imidazole) (Im 2 TEG) [23], but evidently higher than those in the ILs of 1,1,3,3-tetramethylguanidinium lactate ([TMG]L) and monoethanolaminium lactate ([MEA]L) [8], and Ndodecylimidazole (NDI) [23]. Obviously, the current solvents demonstrate lower absorption capacities than DMSO [16], NMI [17].…”

“…They are known as ''universal solvents" in the laboratory and industry owing to their large dipole moments (l TMU = 11.7 D, l DMI = 4.09 D, and l DMPU = 4.23 D at T = 298. 15 [26,27]. Moreover, they demonstrated strong dissolution ability for many substances.…”

“…Alternatively, deep eutectic solvents (DES), analogy of ILs, have recently emerged as new SO 2 absorbents. DESs, formed by choline chloride (ChCl) [13,14] and some quaternary ammonium salt [15], are also reported to capture SO 2 . However, due to their high viscosity as well as price, the industrial applications of ILs or DES are still in the cradle.…”

Quantum Chemistry Insight into the Interactions Between Deep Eutectic Solvents and SO2

“…Candidates for SO 2 capture solvents were determined after screening the available literature and shortlisting the most potential candidates for this task. After going through the literature [14,43,51,52,53], choline chloride (ChCl), 1-Butyl-3-methylimidazolium chloride (Bmim) and 1-Ethyl-3-methylimidazolium chloride (Emim) were selected as HBA and acetamide (Ac), citric acid (Ca), ethylene glycol (Eg), fructose (Ft), glycerol (Gy), lactic acid (La), levulinic acid (Lv), malic acid (Ma), phenylacetic acid (Pa) were selected as HBD. The selection of HBA was done based on the established know-how in literature as well as based on our previous studies.…”

Thermodynamic and molecular insights into the absorption of H2S, CO2, and CH4 in choline chloride plus urea mixtures

“…To date, DESs have been extensively studied for the absorption of CO 2 and SO 2 . In most cases, the studied DESs act as physical solvents for gases.…”