Efficient removal of H₂S at high temperature using the ionic liquid solutions of [C₄mim]₃PMo₁₂O₄₀-An organic...

An innovative approach to H₂S capture and sulfur recovery via liquid redox at high temperature has been developed using [C₄mim]₃PMo₁₂O₄₀ at temperatures ranging from 80 to 180°C, which is superior to the conventional water-based system with an upper limit of working temperature normally below 60°C. The ionic liquids used as solvents include [C₄mim]Cl, [C₄mim]BF₄, [C₄mim]PF₆ and [C₄mim]NTf₂. Microscopic observation and turbidity measurement were used to investigate the dissolution of [C₄mim]₃PMo₁₂O₄₀ in the ionic liquids. Stabilization energy between H₂S and the anion of ionic liquid as well as H₂O was calculated to illustrate the interaction between H₂S and the solvents. The cavity theory can be adopted to illustrate the mechanism for H₂S absorption: the Cl^- ion with small radius can be incorporated into the cavities of [C₄mim]₃PMo₁₂O₄₀, and interact with H₂S strongly. The underlying mechanism for sulfur formation is the redox reaction between H₂S and PMo₁₂O₄₀^3-. H₂S can be oxidized to elemental sulfur and Mo⁶⁺ is partly reduced during absorption, according to UV-vis and FTIR spectra. The [C₄mim]₃PMo₁₂O₄₀-[C₄mim]Cl after reaction can be readily regenerated by air and thus enabling its efficient and repeatitive use. The absorbent of [C₄mim]₃PMo₁₂O₄₀-ionic liquid system provides a new approach for wet oxidation desulfurization at high temperature.