Tunable and facile preparation of chelate-based ionic liquids for highly efficient SO2 separation under low concentration in flue gas

Abstract

A strategy for facile preparation of chelate-based ionic liquids (ILs) by simple chelation was developed, where a series of chelate-based ILs with tunable functionalized anions (azole), cheap ligands (PEG400), and simple metal ions (Li+, Na+, and K+) were designed for SO2 capture under 2000 ppm in flue gas. Both the anion-tunable strategy and the fine-tuned strategy were used to explore the effect of anions, ligands, and metal ions. The experimental absorptions, spectroscopic investigations, and DFT calculations indicated that the process of SO2 capture was mostly based on the nucleophilic effect of electronegative N site toward SO2. Furthermore, the tuning of alkali metal ions was proved to have little influence on SO2 absorption. The ideal IL, [Na(PEG400)][Tetz], exhibited splendid available absorption capacity of SO2 (0.57 mol/mol), excellent selectivity (63 under 2000 ppm SO2/15% CO2), and outstanding reversibility, indicating good potential for industrial application.