Reduction of sulfur dioxide and surface sulfate on γ-alumina

The desorption and reduction of SO_2 adsorbed on γ-Al_2O_3 and the reduction of surface sulfate on γ-Al_2O_3 have been investigated by microreactor experiments and thermogravimetric analysis (TGA). Temperature-programmed desorption (TPD) of adsorbed SO_2 showed one broad desorption peak. Temperature-programmed reduction (TPR) resulted in the desorption of SO_2 and the production of H_2S and elemental sulfur, the latter two products increasing with increasing pressure of hydrogen. The reduction of surface sulfate is very slow below 550ºC with the main reduction product being SO_2. A small amount of H_2S was produced at higher temperatures, probably from the reduction of elemental sulfur by hydrogen. The reduction experiments showed that surface sulfate formed on strong surface sites yielded H_2S or S (el) upon reduction, while sulfate formed on weak sites released SO_2 upon reduction