Novel Guanidinium-Based Ionic Liquids for Highly Efficient SO₂ Capture

Abstract

The application of ionic liquids (ILs) for acidic gas absorption has long been an interesting and challenging issue. In this work, the ethyl sulfate ([C2OSO3](-)) anion has been introduced into the structure of guanidinium-based ILs to form two novel low-cost ethyl sulfate ILs, namely 2-ethyl-1,1,3,3-tetramethylguanidinium ethyl sulfate ([C2(2)(C1)2(C1)2(3)gu][C2OSO3]) and 2,2-diethyl-1,1,3,3-tetramethylguanidinium ethyl sulfate ([(C2)2(2)(C1)2(C1)2(3)gu][C2OSO3]). The ethyl sulfate ILs, together with 2-ethyl-1,1,3,3-tetramethylguanidinium bis(trifluoromethylsulfonyl)imide ([C2(2)(C1)2(C1)2(3)gu][NTf2]) and 2,2-diethyl-1,1,3,3-tetramethylguanidinium bis(trifluoromethylsulfonyl)imide ([(C2)2(2)(C1)2(C1)2(3)gu][NTf2]), are employed to evaluate the SO2 absorption and desorption performance. The recyclable ethyl sulfate ILs demonstrate high absorption capacities of SO2. At a low pressure of 0.1 bar and at 20 °C, 0.71 and 1.08 mol SO2 per mole of IL can be captured by [C2(2)(C1)2(C1)2(3)gu][C2OSO3] and [(C2)2(2)(C1)2(C1)2(3)gu][C2OSO3], respectively. The absorption enthalpy for SO2 absorption with [C2(2)(C1)2(C1)2(3)gu][C2OSO3] and [(C2)2(2)(C1)2(C1)2(3)gu][C2OSO3] are -3.98 and -3.43 kcal mol(-1), respectively. While those by [C2(2)(C1)2(C1)2(3)gu][NTf2] and [(C2)2(2)(C1)2(C1)2(3)gu][NTf2] turn out to be only 0.17 and 0.24 mol SO2 per mole of IL under the same conditions. It can be concluded that the guanidinium ethyl sulfate ILs show good performance for SO2 capture. Quantum chemistry calculations reveal nonbonded weak interactions between the ILs and SO2. The anionic moieties of the ILs play an important role in SO2 capture on the basis of the consistently experimental and computational results.

Guanidinium‐based dicarboxylic acid ionic liquids for SO2 capture

“…At a temperature of 40 ∘ C, the molar ratio of SO 2 to IL was about 0.4 at the SO 2 concentration of 2000 ppm for [TMG][PBE] . When SO 2 concentration was 2% by volume in mixed gas of N 2 and SO 2 , the equilibrium absorption of [TMG][PBE] was 0.72 mol SO 2 mol −1 of IL, which was higher than the value of 0.51 for [TMG]L at the same temperature reported by Ren et al 23 When the mixed gas of N 2 and SO 2 with SO 2 content of 8% by volume was absorbed by [TMG][PBE] at 1 bar pressure and 40 ∘ C, the equilibrium molar ratio of SO 2 to [TMG][PBE] was 1.45:1, which was more than the equilibrium absorption of [TMG]L under the same condition, 5 and far more than the saturated absorption of the [NTf 2 ]-based ILs at SO 2 pressure of 0.1 bar and 20 ∘ C. 7…”

“…Shang et al 6 also synthesized three guanidinium-based ionic liquids which had showed high SO 2 absorption rate. These ILs could absorb SO 2 by both physical and chemical interactions while physical absorption plays an important role at the temperature of 40 ∘ C. Lu et al 7 introduced the ethyl sulfate ([C 2 OSO 3 ] − ) anion into the structure of guanidinium-based ILs to form two novel low-cost ethyl sulfate ILs. These guanidinium ethyl sulfate ILs showed good performance for SO 2 capture.…”

Dual‐functionalized protic ionic liquids for efficient absorption of NH3 through synergistically physicochemical interaction

“…In recent years, ionic liquids (ILs) have been demonstrated to be promising media for the recovery of CO 2 , hydrogen sulfide (H 2 S), sulfur dioxide (SO 2 ) and NH 3 owing to their negligible volatility, excellent thermal stability, remarkable solubility and structure designability. Compared to the water scrubbing method, the goals of no waste water discharge, lower energy consumption and high purity NH 3 recovery can be achieved by using ILs.…”

pH-Responsive and Buffering Macromolecule Aqueous Absorbent and Mathematic Model-Based Feasibility Evaluation for SO2 Capture

“…Wu et al [15] first reported an IL-1,1,3,3-tetramethylguanidinium lactate ([TMG]L) for SO 2 absorption from a gas mixture of SO 2 and N 2 , and the result showed that 1 mol [TMG]L could selectively capture 0.978 mol SO 2 at 40 °C. Later, many other ILs, including hydroxyl ammonium ILs [16,17], ether-functionalized ILs [18][19][20], imidazolium-based ILs [21][22][23], guanidinium-based ILs [24][25][26], pyridinium-based ILs [27,28], anion-functionalized ILs [29,30], and, more recently, deep eutectic solvents [31][32][33], were investigated for SO 2 absorption.…”