Vanadium-containing catalysts for the selective oxidation of H2S to elemental sulfur in the presence of excess water

Various vanadium-containing catalysts were searched for the commercial application in the selective oxidation of H₂S to elemental sulfur at low temperatures (less than 250°C) in the presence of excess (more than 35 vol.%) water. In the test of binary oxides, it was found that TiVO_x was the only catalyst that could sustain its activity without deactivation at 230°C. The best catalytic activity (85–90% sulfur yield) was obtained when VO_x/TiO₂ was incorporated with other metals such as Fe, Cr and Mo. Reaction occurred via redox mechanism and the reoxidation of reduced vanadium was the rate-limiting step. A long-term deactivation observed during the reaction was due to slower reoxidation of reduced vanadium by oxygen than the reduction by H₂S. Catalytic activities of VO_x/SiO₂, VO_x/TiO₂ and V–Fe–Cr–Mo–O_x/TiO₂ were well correlated with their redox properties that were observed by TPR/TPO and XPS measurements.