Reversible Capture of SO₂ through Functionalized Ionic Liquids

Abstract

Emission of SO2 in flue gas from the combustion of fossil fuels leads to severe environmental problems. Exploration of green and efficient methods to capture SO2 is an interesting topic, especially at lower SO2 partial pressures. In this work, ionic liquids (ILs) 1-(2-diethylaminoethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Et2 NEMim][Tf2 N]) and 1-(2-diethylaminoethyl)-3-methylimidazolium tetrazolate ([Et2 NEMim][Tetz]) were synthesized. The performances of the two ILs to capture SO2 were studied under different conditions. It was demonstrated that the ILs were very efficient for SO2 absorption. The [Et2 NEMim][Tetz] IL designed in this work could absorb 0.47 g(SO2)g(IL)(-1) at 0.0101 MPa SO2 partial pressure, which is the highest capacity reported to date under the same conditions. The main reason for the large capacity was that both the cation and the anion could capture SO2 chemically. In addition, the IL could easily be regenerated, and the very high absorption capacity and rapid absorption/desorption rates were not changed over five repeated cycles.

π-Hole interaction: a theoretical insight into the mechanism of SO2 captured by [Et2NEMim][Tetz] ionic liquids

“…Therefore, a strong absorbed peak will appear at 1295 cm −1 , which arises from the interaction between SO 2 and the [Tetz] anion, while the peak at 1247 cm −1 is attributed to the interaction between SO 2 and the tertiary nitrogen of the cation. These results are also consistent with the experimental prediction that 1315 cm −1 is the interaction between SO 2 and the [Tetz] anion, while 1245 cm −1 is the interaction between SO 2 and the tertiary nitrogen on the cation [20,26,37].…”

“…The standard thermodynamic equilibrium constant (K 0 ) also shows that IL-5SO 2 is very low abundance in the products. Thus, the SO 2 absorption ratio at 20°C and 0.1 MPa does not extend beyond 5 mol SO2 mol IL −1 , which is consistent with experimental observations [26]. In order to find the best conditions for [Et 2 NEMim][Tetz] capture of SO 2 , the dependence of ΔG 0 on temperature and pressure were considered.…”

“…Thus, most of the absorbed SO 2 can be released by heating the ILs. The ΔG 0 and K 0 values at 80°C and 0.1 MPa are also listed in Table 4 [26].…”

“…and more researchers have reported the use of ILs to reversibly capture SO 2 and CO 2 by utilizing both physical and chemical interactions [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Very recently, Yang and Han et al [26] reported that two functionalized ILs, 1-(2-diethylaminoethyl)-3-methylimidazoliu bis (trifluoromethylsulfonyl)-imide ( A specific intermolecular interaction involving pnicogen, chalcogen and halogen atoms as acceptors of electron density, has been studied extensively in recent years [27][28][29][30][31]. As shown in Fig.…”

SO2-Induced Variations in the Viscosity of Ionic Liquids Investigated by in Situ Fourier Transform Infrared Spectroscopy and Simulation Calculations

“…To develop a new process based on ILs for gas separation, taking SO 2 as an example, a number of efforts have been spent in designing the novel functionalized ILs for higher absorption capacity of SO 2 and lower absorption enthalpy, and studying the mechanism between SO 2 and ILs by experimental methods and simulation calculations [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . Nevertheless, although the available studies on different aspects of ILs have increased almost exponentially, understanding deeply the physical properties of ILs is still a major point of discussion, which is essential for the design and scale-up of chemical processes in their applications.…”