Ether-functionalized ionic liquids as highly efficient SO2 absorbents

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 degrees 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 degrees C in a N-2 flow, thereby allowing the RTILs to be reused up to 5 cycles without loss of their initial capacity.