Study On The Performance Of Sn-Ce-PO Catalysts For The Selective Reduction Of Nitrogen Oxides With Ammonia

With the development of industrial society,all kinds of factories have appeared rapidly.Excessive emission of nitrogen oxides has caused serious harm to human and environment.Selective catalytic reduction of NOx by Ammonia(NH3-SCR)has become an efficient denitration method in many flue gas desolation technologies.In the industry,the earliest V2O5-WO3/TiO2 catalyst has the disadvantages of narrow operating temperature window,poor sulfur resistance ability and V has the biological toxicity.Therefore,the research and development of V-free NH3-SCR catalyst has very important practical significance.In this paper,CePO4 catalysts with different crystal phases,SnxCe-P-Oy(x=0.1,0.2,0.3,0.4)and Sn0.2-Ce-Px-Oy(x=0.8,0.6,0.4,0.2)were prepared by co-precipitation method and hydrothermal method,respectively.Their catalytic performance in the denitration of NH3-SCR was tested.XRD,N2 adsorptio-desorption test,NH3-TPD,H2-TPR,XPS,in situ DRIFTS and other characterization methods were used to investigate the relationship between the physical and chemical properties of the catalysts and catalytic denitration performance.The NO conversion and N₂ selectivity of hexagonal CePO4-H catalysts at 300-500? are greater than 95%and 100%.It also exhibits excellent stability and H₂O+SO₂ resistance.Mainly because it has more Br?nsted acid sites.Sn_0.2-Ce-P-Oy catalyst can achieve more than 90%conversion at 240-450? and maintain 100%N₂ selectivity throughout the operating temperature window.Catalytic performance is almost unaffected by 100 ppm SO₂ at 270 ?.The excellent performance is attributed to the increased variety of acid sites and appropriate oxidation capacity.Sn_0.2-Ce-P_0.4-Oy catalyst achieved 100%conversion at 210-450? and maintained more than 90%N₂ selectivity throughout the activity temperature window.Catalytic activity was barely affected by 100 ppm SO₂ and 5%H₂O at 240?.These are due to the interaction between Sn and Ce(2Ce₄++Sn₂+(?)₂Ce₃++Sn₄+),promoted the catalyst with more acid,surface adsorption oxygen and appropriate oxidation capacity.The surface acid sites and the adsorbed species of nitrogen oxides on the catalysts were studied in detail by in situ DRIFTS,the changes of the adsorbed species on the surface during the reaction process were analyzed,and the corresponding reaction mechanism was proposed.