SO₂ capture by 2-pyridineethanol through the formation of a zwitterionic liquid

In this work, we report the SO₂ capture by 2-pyridineethanol (2-PyEtOH). 2-PyEtOH exhibits a high SO₂ capacity, up to 1.16 g SO₂ per g solvent at 1.0 atm. The effect of temperature and pressure on the SO₂ absorption by 2-PyEtOH is investigated. It is found that 2-PyEtOH can capture 0.57 g SO₂ per g solvent even at a low SO₂ partial pressure of 0.10 atm. Interestingly, the absorbed SO₂ by 2-PyEtOH can be released at a low temperature of 50 °C, suggesting that 2-PyEtOH not only has a high capacity but also exhibits a regeneration process of low energy cost. Moreover, 2-PyEtOH also exhibits an excellent reversibility. The NMR and FTIR studies disclose that SO₂ reacts with the -OH group of 2-PyEtOH, resulting in the formation of a zwitterionic sulfite. We believe that the findings of this work will be very useful for the design of efficient absorbents for SO₂ capture.