Absorption of SO2 in Furoate Ionic Liquids/PEG200 Mixtures and Thermodynamic Analysis

Carboxylate ionic liquid (IL) and polyethylene glycol 200 (PEG200) mixtures are suitable for the absorption of acidic SO2 because of their unique properties. In the present work, tetraethylammonium furoate ([N2222][FA]) and choline furoate ([Ch][FA]) were blended with PEG200 to form 40 wt % ILs/PEG200 mixtures as SO2 absorbents. The solubilities of SO2 in these two ILs/PEG200 mixtures were measured at T = (303.15, 313.15, 323.15, and 333.15) K and pressure up to 1.2 bar. [N2222][FA]/PEG200 demonstrated the high SO2 absorption capacity of 7.224 mol per kg absorbent at 303.15 K and 1.0 bar. The chemisorption mechanism of SO2 by mixture was studied by Fourier transform infrared and nuclear magnetic resonance spectra, and the influence of cations on the SO2 absorption capacity was analyzed. Furthermore, the reaction equilibrium thermodynamic model was used to correlate the experimental data, and Henry’s law constant (H), reaction equilibrium constant (K0), and thermodynamic properties (ΔrGm0, ΔrHm0, and ΔrSm0) were derived. The absorption enthalpies of the two binary mixtures are −46.39 and −23.07 kJ·mol–1 for the two mixtures, respectively. Considering the low cost, biodegradability of the materials, high capacity, and low absorption enthalpy, the [N2222][FA]/PEG200 mixture was regarded to be an attractive and promising alternative to pure ILs and ordinary solvent as a desulfurizer.