Effective absorption of SO2 by imidazole-based protic ionic liquids with multiple active sites: Thermodynamic and mechanical studies

In view of the environmental hazards caused by SO2, the development of efficient SO2 capture technology has important practical significance. In this work, a low-viscosity protic ionic liquids containing imidazole (Im), ether linkage, and tertiary amine structure was synthesized by acid-base neutralization of tris(3,6-dioxaheptyl)amine (TMEA) and Im for SO2 absorption. The results showed that the solubility of SO2 in [TMEA][Im] reached 12.754 mol kg(-1) at 298.2 K and 1 bar and the ideal selectivity of SO2/CO2 (1/1) is 141.7 at 1 bar. Furthermore, [TMEA][Im] can be reused and the SO2 absorption performance was not significantly reduced after five cycles. In addition, the absorption of low-concentration SO2 (2000 ppm) in [TMEA][Im] was also tested. Further spectroscopic research and thermodynamic analysis suggested that the high SO2 uptake by [TMEA][Im] was caused by the synergistic effect of physical and chemical absorption.