Yaotai Jiang

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

Efficient and reversible absorption of SO2 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 SO2 absorption, with the maximum absorption capacity of 0.625 g SO2 per g DES of LA–TEAC at 293.15 K under ambient pressure. The absorbed SO2 was easily released by bubbling N2 at 323.15 K and the regenerated DES was recycled five times without obvious loss of absorption performance. The solubility of SO2 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 SO2 absorption was also investigated. According to NMR and FTIR analyses, the absorption of SO2 in DES was a physical process. Moreover, all the DESs exhibited high selectivity for SO2/CO2. The present DESs are promising absorbents for SO2 because of their high absorption capacity and good reversibility.

Absorption of SO2 by renewable ionic liquid/polyethylene glycol binary mixture and thermodynamic analysis

Separation and removal of SO2 before atmospheric release of the flue gas is essential to combat acid rain formation. Traditional chemical absorbents and conventional ionic liquids (ILs) suffer from several shortcomings including waste, second pollution, high viscosity, poor biodegradability and low absorption capacity. In this work, two renewable ILs where both cation and anion come from biodegradable materials, 2-hydroxyethyl-trimethylammoniume levulinate ([Choline][LA]) and 2-hydroxyethyl-trimethylammoniume lactate ([Choline]L), were synthesized and mixed with polyethylene glycol 200 (PEG200) to form 40 w% ILs binary mixture as SO2 absorbents. Solubilities of SO2 in the above two mixtures were measured under the temperature range of 303.15–333.15 K and the pressure up to 1.2 bar, with the result of 6.97–7.24 mol kg−1 absorbents at 1.0 bar and 303.15 K. When the SO2 pressure is reduced to 0.039 bar, the solubilities are still 1.77–1.84 mol kg−1 absorbents. Reaction Equilibrium Thermodynamic Model (RETM) was used to analysis the thermodynamic behavior of SO2 in present ILs mixtures. The obtained absorption enthalpies are as low as −39.81 and −51.69 kJ mol−1 for the two binary mixtures, respectively. The two mixtures possess one or more improvements over commonly reported ILs in the aspects of biodegradability, absorption capacity, cost and energy consumption for regeneration of absorbents.

Investigation of furoate-based ionic liquid as efficient SO2 absorbent

A series of furoate anion-functionized ionic liquids (ILs) were synthesized and applied as new absorbents for SO2. Results showed that these ILs possessed satisfactory performance for SO2 absorption. At 293.15 K, the maximum absorption capacity was 0.69 and 0.24 g SO2 per g P4442[FA] under 1.0 and 0.1 bar, respectively. The SO2 enriched ILs were easily regenerated by bubbling N2 at 343.15 K and recycled five times without obvious loss of absorption performance. The influences of temperature, SO2 partial pressure, and water content in ILs on SO2 absorption performance were systematically explored. The absorption capacity of ILs is discussed from aspects of the structure of cations, anions, and the interaction of cation–anion. The absorption mechanism was analyzed using NMR and FTIR methods. The selectivities of SO2/CO2, SO2/N2 and SO2/O2 were studied and [P4442][FA] achieved relatively high selectivity for SO2 compared to other gases. Present furoate ILs demonstrate potential application as a SO2 absorbent owing to their good performance.