Selective oxidation of hydrogen sulfide to ammonium thiosulfate and sulfur over vanadium-bismuth oxide catalysts

摘要

The selective oxidation of hydrogen sulfide containing excess water and ammonia was studied over vanadium-bismuth mixed oxide catalysts. The investigation was focused on understanding the complex reaction steps and the roset of each metal oxide. Therefore, supported V_2O_5/TiO_2, V-Bi-O/TiO_2 catalysts and a mechanical mixture of V_2O_5 + Bi_2O_3 were tested in the reaction. Ammonia reacted either with H_2S or SO_2 produced from the oxidation of H_2S. Water vapor promoted the reaction of ammonia and SO_2. Strong synergistic phenomena in catalysts activity were observed for the mechanically mixed catalyst of V_2O_5 and Bi_2O_3. V-Bi-O/TiO_2 catalyst showed very high H_2S conversion without any considerable emission of SO_2. Temperature-programmed studies (TPR and TPO), XRD and Raman analyses revealed that the high catalytic performance of V-Bi-O/TiO_2 catalyst originated from the high redox capacity of the bismuth vanadate phase.