Studies on sulfate formation during the conversion of H2S and SO2 to sulfur over activated alumina

Abstract A mechanism for the conversion of H 2 S and SO 2 over alumina is proposed in which surface thiosulfate is formed and reacts with SO 2 and H 2 S via a series of oxy-anions to form sulfur and H 2 O. In addition to thiosulfate being a key species of the catalytic cycle, it is proposed that sulfate is also formed as part of the catalytic cycle but that its surface concentration is limited to some steady-state concentration by virtue of its reduction by H 2 S. The initial formation of thiosulfate and sulfate on alumina probably occurs by two mechanisms. One pathway involves interaction of either H 2 S or SO 2 with oxide sites on the alumina surface. Such oxide sites have been suggested by Sohlberg et al. to arise as a consequence of the interaction of vacant sites in the defect spinel structure of alumina with H 2 O [J. Phys. Chem. 100 (1996) 7550]. The other pathway, the first step of which has been referred to numerous times in the literature, likely involves the adsorption of SO 2 at Lewis acid–base sites, and reaction with H 2 S to form sulfur oxy-anions and eventually, sulfur and water.