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

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 PMo12O403-. 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.