Hydroxyl ammonium ionic liquids synthesized by water-bath microwave: synthesis and desulfurization.

Water-bath microwave method was used for hydroxyl ammonium ionic liquids (ILs) synthesis to study the removal of sulfur dioxide (SO(2)) from the flue gas. The results showed that the water-bath microwave method has some advantages of short reaction time and good yields. The synthesis of ethanolamine lactate ILs was fundamentally studied by an orthogonal experiment design (L(9)(3(4))). Based on statistic analysis, it is revealed that the molar ratio of ammonium/acid is the most significant variable, and the optimized preparation conditions are under 338 K, wave power of 300 W for 30 min with the molar ratio 1:1.1 (ethanolamine vs. lactic acid). At the same condition, the yield of the other ILs was over 90% except dimethyl ethanolamine-based ILs. Results showed that the solubility of SO(2) in ethanolamine lactate ILs was 0.51 (mole fraction), higher than others. Ethanolamine lactate ILs was a better absorbent for SO(2). The optimal temperature for the absorption and desorption process were 298 and 363 K, respectively. The optimal desorption time was 60 min. It was also found that water-bath microwave can improve the release of the absorbed SO(2) from ILs.