(465e) Capture of SO2 by Lactate-Based Ionic Liquids

Sulfur dioxide (SO₂), which is mainly emitted from the burning of fossil fuel, has caused serious environmental pollution. Up to date, flue gas desulfurization (FGD) is the most efficient way to control the emission of SO₂. Recently, the capture of SO₂ by ionic liquids (ILs) has drawn much attention all over the world for the unique properties of ILs. It is important to know how the cations and anions of the ILs influence the absorption and desorption behaviors of SO₂ for the design of new ILs with high thermal stability and high absorption capacities. In this work, we synthesized five kinds of ILs based on quaternary ammonium, imidazolium, guanidine and alkanolamines cations and lactate acid anion. They are tetraethylammonium lactate ([N₂₂₂₂]L), 1-butyl-3-methylimidazolium lactate ([Bmim]L), 1-hexyl-3-methylimidazolium lactate ([Hmim]L), 1,1,3,3-tetramethylguanidinium lactate ([TMG]L) and monoethanolaminium lactate ([MEA]L). The effect of cations on the absorption and desorption of SO₂ by these ILs was studied. It was found that the cations have significant influence on the absorption and desorption behaviors of SO₂ . The effect of cations on the SO₂ absorption capacities of the ILs follows the order: [N₂₂₂₂]⁺ > [Bmim]⁺  ~ [Hmim]⁺ > [TMG]⁺ > [MEA]⁺, and the effect of cations on the SO₂ desorption efficiency follows the order: [MEA]⁺ > [TMG]⁺ > [Hmim]⁺ > [Bmim]⁺ ≈ [N₂₂₂₂]⁺. The absorption and desorption of SO₂ by [Bmim]L were tested for five runs, and no obvious lose of SO₂ absorption capacity was found. The result suggests that the ILs based on lactate acid anion are excellent absorbents for the removal of SO₂from the flue gas.

The project is financially supported by the Natural Science Foundation of China (No. 21176020 and 20746001) and the Program for New Century Excellent Talents in University (NCET-08-0710)