The role of cations in the interactions between anionic N-heterocycles and SO2

Chenchen Li,Dongmei Lu,Chao Wu

doi:10.1038/s41598-018-25432-6

Abstract

Our study shows that cation plays a more important role in the interactions between anionic N-heterocycles and SO2 than in the NHC-CO2 case. The adducts of NHC, SO2 and cation often exhibit multiple stable configurations with close energies rather than the only reported “CO2-sandwiched” planar NHC-CO2-cation structure. The structural diversity makes the models omitting cation inappropriate for predicting the SO2 capture products, which also leads to less clear trends of the cation effects than those observed in the CO2 case. The detailed cation effects are discussed in the text.

Highlights

As a key air pollutant, SO2 poses great danger to the environment
Since the two acid gases, CO2 and SO2, have a number of similarities in structure and property, we naturally wonder whether the interactions between SO2 and nitrogen-containing heterocycles (NHCs)-cation systems follow the same story line? in a recent simulation research, Ai group reported that for alkyl phosphonium tetrazolide-based ([Pnnnm][Tetz]) ionic liquids (ILs), compared with the binding between the anion ([Tetz]−) and SO2, the binding strength of the anion-cation pair with SO2 decreased sharply by about 58 kJ mol−1 and resulted in reduced SO2 absorption capacity[23], which was observed in the studies of Wang group and Wang group using different ILs8,24
After checking other NHC-cation-SO2 complexes, we found that multiple stable configurations are a common feature but the energy disparity among configurations is highly dependent on both the cation and anionic NHC

Summary

Introduction

As a key air pollutant, SO2 poses great danger to the environment. Traditional desulfurization scrubs flue gas with sorbent agents like limestone or lime, this technique is hampered by large amounts of useless or low-value by-products (e.g. calcium sulphite or sulfate). In a recent simulation research, Ai group reported that for alkyl phosphonium tetrazolide-based ([Pnnnm][Tetz]) ILs, compared with the binding between the anion ([Tetz]−) and SO2, the binding strength of the anion-cation pair with SO2 decreased sharply by about 58 kJ mol−1 and resulted in reduced SO2 absorption capacity[23], which was observed in the studies of Wang group and Wang group using different ILs8,24. In their calculations, SO2 did not insert in between the anion and cation pair like CO2 did. We concluded aspects about the cation effects and their influence on designing NHC-based ILs and porous materials for SO2 capture

Methods

Results

Conclusion