Inorganic Nonmetallic Acid(SO₄^2-/PO₄（3-）) Modified Of CeO₂ Catalyst For Denitration Performance

Nitrogen oxide species（NO_x）is one of the main air pollution.The selective catalytic reduction by ammonia is being considered as the most useful and commercialized approach for removing NO_x.The commercialized catalyst is V₂O₅-WO₃（MoO₃）/TiO₂ catalyst,which exhibits a superior deNO_x performance at 300-400?C,the toxicity of V₂O₅ and low N₂ selectivity restrain their further commercial application.Therefore,it is necessary to develop an environment-friendly non-vanadium-based SCR catalysts.（1）A series of CeO₂ prepared with H₂SO₄、H₃PO₄ and H₂SO₄-H₃PO₄ were investigated by one-pot method.The sulfates contributed to the improvement of Br?nsted（B）acid sites while phosphates were prone to the enhancement of Lewis（L）acid sites.Besides.the nitrates adsorbed on the CeO₂ and NH₃ contacted with the sulfates,which followed the L-H mechanism at 200°C on C-P-S and C-S.The adsorption and activation of NO and NH₃ over C-P were the same active sites,which obeyed to E-R mechanism at 200°C.C-P showed the excellent redox ability.C-S showed less amounts of surface acidity,causing the poor low-temperature SCR activity.C-P-S possessed the best catalytic activity because of the appropriate surface acidity and redox property.（2）A series of CeO₂ modified by Fe species was synthesized via one-pot method.The characterization revealed that an interaction existed among Fe,sulfates and Ce species.The excellent SCR performance was associated with a remarkable increase in chemisorbed oxygen,the ratio of Ce³⁺/(Ce⁴⁺+Ce³⁺)and Fe³⁺/(Fe³⁺+Fe²⁺).Importantly,the introduction of iron oxides and sulfates into the CeO₂ increased the surface acidity and redox property,resulting in the improvement of the SCR performance.Furthermore,with the increase of calcination temperature,the interaction among Fe,sulfates and Ce species was weakened,which result in the decrease of chemisorbed oxygen、Ce³⁺and Fe³⁺.The surface acidity and redox property were also weakened,which was responsible for the SCR performance.