Pathway of the cycle between the oxidative adsorption of SO2 and the reductive decomposition of sulfate on the MgAl2−xFexO4 catalyst

Abstract The behaviors of the SO 2 oxidative adsorption and the reduction decomposition of formed sulfate over Mg–Fe–Al–O mixed spinel catalyst were studied by in situ IR, MR–GC–MS, Mossbauer spectroscopy and electrical conductivity measurement techniques. In the oxidative adsorption and/or reaction process, SO 2 and oxygen molecules are adsorbed on the lattice oxygen ions and oxygen vacancies, respectively. During the SO 2 adsorption and reaction, adsorbed sulfur species react with the lattice oxygen ions and form the sulfite-like species. When oxygen molecules are present in the feed mixture, sulfate is formed from the sulfite-like species reacting with the adsorbed oxygen ions. When the sulfated samples are reduced by hydrogen at 773 K, a large amount of H 2 S along with a small part of SO 2 is produced. Different iron species, Fe 3+ , Fe 2.5+ , Fe 2+ and Fe 0 are identified in the sulfated sample during the reduction process. In the half cycle of SO 2 oxidative adsorption and reaction, iron ions are directly involved in the formation of the mixed sulfate; in the half cycle of the reduction, due to the S–O–Fe bond being easily broken, the reducibility of the mixed sulfate hence is improved. A mechanism on the cycle between SO 2 oxidative adsorption and sulfate reductive decomposition is proposed.