Roles of cerium oxide and the reducibility and recoverability of the surface oxygen species in the CeO₂/MgAl₂O₄ catalysts

The properties of surface oxygen species in the MgAl₂O₄ and CeO₂/MgAl₂O₄ catalysts were investigated by the temperature-programmed reduction (TPR) technique. Three different oxygen species existing on the surface of CeO₂/MgAl₂O₄ catalysts - surface adsorbed oxygen, surface lattice oxygen which was affected by the interaction between the supported cerium and carrier, and the oxygen species corresponding to the multilayer crystalline of CeO₂, were determined. The supported cerium oxide had different functions: it not only increased the amount of surface adsorbed oxygen, but also reduced the reduction temperature of surface lattice oxygen and improved the recoverability of the surface oxygen species. These roles of cerium oxide in the CeO₂/MgAl₂O₄ catalyst significantly affected on the SO₂ adsorption properties, in the both cases of gaseous oxygen absence and presence in the reaction stream, enhancing the De-SO₂ activity.