Experimental and mechanism studies on the catalytic reduction of SO2 by CO over Fe2O3/γ-Al2O3 in the presence of H2O

The present research explored experimental and mechanism studies on the catalytic reduction of SO2 by carbon monoxide (CO) over Fe2O3/γ-Al2O3 to elemental sulfur in the presence of H2O. The varieties and concentrations of intermediates in the catalytic reduction at different temperatures were investigated. Carbonyl sulfide (COS) and H2S were formed as intermediates below 400 °C, while only H2S was observed at or above 400 °C. H2S resulted from the hydrolysis of COS over Fe2O3/γ-Al2O3 in the presence of H2O. When the temperature was below 400 °C, COS hydrolyzed partially, and reduction of SO2 by CO followed the intermediary mechanism of COS and the Claus reaction mechanism of H2S. However, COS hydrolyzed completely at or above 400 °C and the catalytic reaction only followed the Claus reaction mechanism of H2S. Moreover, XRD analysis indicated that in the catalytic reduction of SO2 by CO over Fe2O3/γ-Al2O3, Fe2O3 was initially reduced to Fe3O4 by CO, and then the oxygen of SO2 was accepted by the oxygen vacancy of Fe3O4 leading to the formation of elemental sulfur; finally, the active substance FeS2 formed, which suggests that the formation of Fe3O4 plays a key role in the initial reaction.