Ether-functionalized ionic liquids as highly efficient SO2 absorbents

Abstract

Room temperature ionic liquids (RTILs), ether-functionalized imidazolium methanesulfonates, exhibit extremely high SO₂ solubility, at least 2 moles of SO₂ per mole of RTIL at 30 °C and at atmospheric pressure. The solubility of SO₂ in these RTILs increases with increasing number of tethered ether oxygen atoms and also with the pressure rise. FT-IR spectroscopic and quantum mechanical calculation results show that such high SO₂ solubility is originated from the combined interactions of SO₂ with methanesulfonate anion and ether oxygen atom or atoms on the imidazolium ring. The absorbed SO₂ gas can be readily and completely desorbed from the RTILs by heating at 100 °C in a N₂ flow, thereby allowing the RTILs to be reused up to 5 cycles without loss of their initial capacity.