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

To explore environmentally benign solvents for absorbing and using H 2 S, a series of caprolactam tetrabutyl ammonium bromide ionic liquids were synthesized, the solubilities of H 2 S in which were measured at 303.2−363.2 K and atmospheric pressure. The solubility of H 2 S 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 H 2 S 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 H 2 S in pollution control and could be regarded as the most potential absorbent and recoverer of H 2 S.