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

Abstract

We report a series of calculations to elucidate one possible mechanism of SO2 chemisorption in amino acid-based ionic liquids. Such systems have been successfully exploited as CO2 absorbents and, since SO2 is also a by-product of fossil fuels’ combustion, their ability in capturing SO2 has been assessed by recent experiments. This work is exclusively focused on evaluating the efficiency of the chemical trapping of SO2 by analyzing its reaction with the amino group of the amino acid. We have found that, overall, SO2 is less reactive than CO2, and that the specific amino acid side chain (either acid or basic) does not play a relevant role. We noticed that bimolecular absorption processes are quite unlikely to take place, a notable difference with CO2. The barriers along the reaction paths are found to be non-negligible, around 7–11 kcal/mol, and the thermodynamic of the reaction appears, from our models, unfavorable.

Cation functional group effect on SO2 absorption in amino acid ionic liquids

“…For example, Wang et al (2007) simulated the solubility of CO 2 and SO 2 in guanidium-based IL and Zhang et al (2020) investigated the stability effect of ILs during the CO 2 absorption process in the presence of SO 2 . Due to the ability of chemical removal of SO 2 by ILs, the chemical reaction of SO 2 gas has been taken into consideration through ab initio quantum computations ( Piacentini et al, 2022 ).…”

“…ILs also face toxicity, high viscosity, and high cost of production that limit their application in FGD technology. However, to enhance their efficiency, task-specific ILs, i.e., amino acid ionic liquids (AAILs) were proposed which are environmentally friendly, easily available, biodegradable, non-toxic, and due to having two amino and carboxylic groups, they are suitable for the desulfurization process ( Wang et al, 2020 ; Piacentini et al, 2022 ). An experimental investigation has shown that single-amino amino acids, especially glycine, have good absorption performance and gas saturation uptake increases to 0.461 g/g ( Wang et al, 2022b ).…”