Reserch On The Modification And Sulfur Poisoning Of V₂O₅/TiO₂ Catalysts For NH₃-SCR Reaction

Nowadays,the selective catalytic reduction of NO with NH₃?NH₃-SCR?is a widely used deNO_x technology,in which the catalyst is the key factor.V₂O₅-WO₃/TiO₂ catalyst,a well-known commercial catalyst,has been applied owing to its high catalytic activity at 300-450°C and stability.However,this catalyst still exhibits some drawbacks,such as a relatively low sulfur tolerance in high-SO₂ concentration atmospheres,low NH₃-SCR activity at low temperatures and a high cost of tungsten oxide as additive.In order to resovle these problems,modification of V₂O₅/TiO₂ catalyst was performed,and the mechanisms of sulfur poisoning were explored based on characterizations of the structural,surface acidic and redox properties.On the aspect of catalyst modification,BaSO₄ was doped to the V₂O₅/TiO₂.The V₂O₅-BaSO₄/TiO₂ catalyst presnted higher SO₂ resistance espically at high temperatures than V₂O₅-WO₃/TiO₂ after the sulfur poisoning treatment at350°C for 3 h.Besides,the replace of WO₃ by BaSO₄ could reduce the cost of catalyst effectively.Meanwhile,Sb₂O₃ was doped to the V₂O₅/TiO₂ to prepare a low-temperture catalyst.The prepared V₂O₅-Sb₂O₃/TiO₂ showed higher catalytic performance and SO₂ resistance.Both of the above two desgined catalysts have good commercial application potential in the future.On the aspect of sulfur-poisoning mechanism study,the introductionof BaSO₄ was found to contribute to the formation of the readily decomposable sulfate species on the catalyst surface,which not only increased the strong acid sites,but also protected the redox cycle of active vanadium oxide to some extent.The modification of Sb₂O₃decreased the deposition of NH₄HSO₄ on the catalyst surface,which was the main deactiviction of the sulfatd catalyst at low temperatures.The lower SO₂ oxidation activity and higher reactivity of NH₄HSO₄ with NO were the key factors for the low deposition of NH₄HSO₄.The above mechanism studies would have a significant effect for the development of V-based catalysts with high sulfur tolereance.