Mixed-metal oxide catalysts containing iron for selective oxidation of hydrogen sulfide to sulfur

Abstract

Mixed-metal oxide catalysts consisting of iron-antimony and iron-tin were studied for the selective oxidation of hydrogen sulfide to sulfur. Catalytic properties of these catalysts changed significantly with the catalyst composition and catalytic synergistic phenomena were observed for the binary oxides within certain composition ranges. For iron-antimonate catalysts, FeSbO 4 catalyst having excess Fe 2O 3 (i.e., iron-rich catalysts) showed significantly better catalytic performances than the corresponding single oxide catalysts. For iron-tin catalysts, the maximum sulfur yield was obtained when iron and tin were in a molar ratio of one to one. A possible explanation for the catalytic synergistic behavior observed in H 2S oxidation was “remote control” mechanism, which assumed that mobile oxygen produced from Fe 2O 3, migrated to the surface of FeSbO 4 or SnO 2, created new active sites and improved the catalytic performances. For single iron oxide catalyst, large differences as to catalytic performance, surface area, and phase structure were found when the catalyst precursors (i.e., iron salts) were deposited in the media of different acids (nitric acid and oxalic acid).