Computational Study on the Absorption Mechanisms of SO₂ by Ionic Liquids

Abstract

A density functional theory study was conducted to explore the absorption mechanisms of SO2 by ionic liquids (ILs), including task specific ILs 1,1,3,3‐tetramethylguanidinium lactate ([TMG][LAC]), and normal ILs 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIM][BF4]) and 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIM][PF6]). The strength of chemical absorption by [TMG][LAC] is stronger than physical absorption, and the physical absorption energy follows the order of [TMG][LAC] > [BMIM][BF4] > [BMIM][PF6]. Other than O⋅⋅⋅H hydrogen bonding, S⋅⋅⋅O interactions are important for [TMG][LAC] physical absorption of SO2, and S⋅⋅⋅F interactions are critical for SO2 absorption by [BMIM][BF4] or [BMIM][PF6]. Both anions and cations of ILs contribute to the physical absorption of SO2. [TMG]+ plays an important role in the chemical reaction between SO2 and [TMG][LAC]. The proton transfer reaction barrier between 1,1,3,3‐tetramethylguanidine and lactic acid is 1.176 kcal/mol.

A Computational Analysis of the Reaction of SO2 with Amino Acid Anions: Implications for Its Chemisorption in Biobased Ionic Liquids

“…In [ 38 ], it has been shown how aqueous solutions of AAILs are efficient absorbent media and how SO 2 can be regenerated after absorption by heating at 100 °C. In [ 39 ], a guanidium-based IL has been shown to undergo chemical reaction by means of its NH 2 group to yield an –NH–SO 2 structure.…”

Structural Arrangements of Guanidinium-Based Dicarboxylic Acid Ionic Liquids and Insights into Carbon Dioxide Uptake through Structural Voids

“…Considerable research on SO 2 absorption using [TMG]­[Lac] IL found that the high SO 2 absorption capacity was due to both physical and chemical absorption. [TMG]­[Lac] results showed that 1 mol of [TMG]­[Lac] absorbed one mol of SO 2 from a mixture of SO 2 and N 2 at 40 °C under ambient pressure. ,, Guanidinium-based ILs were synthesized by Shang et al. and demonstrated to be excellent SO 2 absorbers .…”

“…16,28,29 Guanidinium-based ILs were synthesized by Shang et al and demonstrated to be excellent SO 2 absorbers.…”