SO2 Absorption/Desorption Characteristics of Two Novel Phosphate Ionic Liquids

Two kinds of phosphate ionic liquids were synthesized and their SO2 absorption performance was investigated. It was found that both ionic liquids could readily absorb SO2, and the absorption capacity could reach 2.8 and 2.7 mol SO2 per mole ILs, respectively, at ambient temperature and under normal pressure. Moreover, the cycle of SO2 absorption and desorption from ionic liquids was repeated for four times and no change in the absorption capacity was observed. FT-IR spectrum and 1H NMR were used to characterize the microstructure of SO2-absorbed ILs and ILs, analysis showed that both ionic liquids absorbed SO2 purely by physical absorption. Comparing with the previous reported ionic liquids such as [Bmim][PF6] and [Emim][BF4], the synthesized ionic liquids showed higher absorption capacity, due to the anion based phosphate (O˭P‒O) with the free electrons on the oxygen interacting with the Lewis acidic sulfur of SO2, and then showing a great affinity for SO2.