On the synergism between La₂O₂S and CoS₂ in the reduction of SO₂ to elemental sulfur by CO

In our study of the catalytic reduction of SO₂ to elemental sulfur by CO in the presence of La₂O₂S and CoS₂, a synergistic effect between the two sulfides was observed which not only increased the catalytic activity but also suppressed the formation of the side-product COS. It was also found that the crystal phase of CoS₂, which can be easily reduced by CO, could be retained when La₂O₂S coexisted even in small quantities. A mechanism was proposed based on the COS intermediate mechanism and the remote control concept.