SELECTIVE OXIDATION OF H_2S USING CeO_2-TiO_2 CATALYSTS SYNTHESIZED BY SOL-GEL METHOD

摘要

Hydrogen sulfide (H_2S), which is highly odorous and toxic, commonly accompanies fuels in oil and gas refinery processes. Since, more stringent fuel-regulations and increasing environmental concerns have been issued, reducing H_2S along with SO_2 became one of the leading issues in emission reduction. TiO_2 has been considered as a good catalyst and support in selective oxidation of hydrogen sulfide. Sol-gel method for preparation of the catalyst improved the catalytic activity compare to other methods. On the other hand, CeO_2has good redox property and high mobility of capping oxygen. In the present work, CeO_2-TiO_2 catalysts were synthesized by using sol-gel method, and their catalytic performance has been investigated for the selective oxidation of H_2S to elemental sulfur. The obtained catalysts were characterized by X-ray diffraction (XRD), surface area measurements (BET), and X-ray photoelectron spectroscopy (XPS). CeO_2-TiO_2 catalysts with the higher proportion of TiO_2 show very good conversion of H_2S without any considerable emission of SO_2. Conversion of hydrogen sulfide decreased with the increase of CeO_2 content. Catalysts with more Ce~(3+)/Ce~(4+) showed higher reactivity, since Ce~(3+) can increase the vacancies and the unsaturated chemical bonds on the surface which play an important role in oxidation reaction.