Absorption and Oxidation of H2S in Caprolactam Tetrabutyl Ammonium Bromide Ionic Liquid

To explore environmentally benign solvents for absorbing and using H2S, a series of caprolactam tetrabutyl ammonium bromide ionic liquids were synthesized, the solubilities of H2S in which were measured at 303.2-363.2 K and atmospheric pressure. The solubility of H2S in the ionic liquid (1:1 mole ratio) was 5.40% at 303.2 K and ambient pressure, decreased sharply as temperature increased, and increased with the increasing mole ratio of caprolactam. The absorption and desorption of H2S were practically reversible in the ionic liquids, which was characterized by nuclear magnetic resonance. Using air, hydrogen sulfide could be oxidized to elemental S in the ionic liquids, which makes it easier to recycle hydrogen sulfide. Caprolactam tetrabutyl ammonium bromide ionic liquids would be useful for removing and reusing H2S in pollution control and could be regarded as the most potential absorbent and recoverer of H2S.