Study On Catalyst For Selective Catalytic Reduction Of NO Under Lean-burn Condition

Energy crisis accelerates the development of lean-burn engine. However, traditionalthree-way catalyst is ineffective under lean-bum condition because of the significant incrementof NO_x(NO＞90%), oxygen and water vapour among the exhaust of lean-burn engine, therefore,a new type of catalyst that can efficiently remove NO in the presence of excessive oxygen andwater vapour becomes the current topic that many domestic and overseas scholars pay muchattention to.In this thesis preparations of two kinds of catalysts that can efficiently remove NO in thepresence of water vapour had been brought foward,â‘ Sn/γ-Al₂O₃ and Cu/γ-Al₂O₃ catalysts:Sn/γAl₂O₃ and Cu/γ-Al₂O₃ catalysts were respectively prepared by using NH₄HCO₃ andNH₃·H₂O as precipitators, NH₄Al(SO₄)₂ as aluminous salt.â‘¡Cu/ZrO₂/S₂O₈^2-/γ-Al₂O₃ catalyst:Cu/ZrO₂/S₂O₈^2-/γ-Al₂O₃ catalyst was prepared by modifying of S₂O₈^2- and Zr⁴⁺. Meanwhile, thestructure and property of catalysts had been investigated by using the catalysts performances andcharacterization. The results were showed as follows:1. NH₄HCO₃ and NH₃·H₂O as precipitators and NH₄aAl(SO₄)₂ as aluminous salt largened thespecific surface area and the pore volume, created a dual-peak structure with distribution of porediameter, increased the Lewis(L) acid amount and facilitated the reducibility of activitycomponent Sn⁴⁺, therefore, Sn/γ-Al₂O₃ catalyst had better catalytic performance. Cu/γ-Al₂O₃ hada marked increment of catalytic activity because of the above same reasons.2. The modification to supportγ-Al₂O₃ by addition of S₂O₈^2- increased acid amount,restrained the sinteration ofγ-Al₂O₃ support particles and the formation of CuAl₂O₄ spinelle,therefore, the catalytic activity had a marked improvement. The addition of Zr⁴⁺ enabled thecatalyst to further increase acid amount, restrain the sinteration ofγ-Al₂O₃ particles and theformation of CuAl₂O₄ spinelle and facilitate the reducibility of activity component Cu²⁺,accordingly, the catalytic activity got an increment again.