Perparation Of Cu/La₂O₃-ZrO₂-Al₂O₃ Catalyst And Study On Catalytic Properties For Selective Reduction Of NO

With the significant increase of automobile quantity, the pollution caused by automobile exhaust has become more and more severe, especially for the NO_x, it not only will result in the formation of photochemistry smoke, acid rain and the human body breath endanger, but also will destroy the ecological environment, as well as bring the serious influence on the mankind's life and production. Lean-burn engine has the property of energy saving and enviromental protection, while the traditional three-way catalyst can't remove the nitric oxide effectively under lean-burn conditions. Thus to develop a kind of new catalyst which is suitable for the exhausted gas expelled by the lean-burn engine is becoming popularly in the catalytic field.Two kinds of catalysts have been prepared and studied in this thesis: The support Al₂O₃ was prepared by precipitation method with the aqueous solution of Al(NO₃)₃ dropping into the precipitant of (NH₄)₂CO₃ and then loaded with Cu²⁺ to make the Al₂O₃ catalylst. The composite support La₂O₃-ZrO₂-Al₂O₃ was prepared by coprecipitation method with the mixed aqueous solution of La(NO₃)₃, Al(NO₃)₃ and ZrOCl₂ dropping into the precipitant of (NH₄)₂CO₃ and then loaded with Cu²⁺ to make the Cu/La₂O₃-ZrO₂-Al₂O₃ catalylst. The relationship between the preparation method, the structure and the properties of the Cu/La₂O₃-ZrO₂-Al₂O₃ catalyst was also explored by means of SEM,XRD, BET, Py-IR, TG and TPR. The results are as follows:1. The catalyst Cu/Al₂O₃ that was prepared by precipitation and impregnant methods had higher activity for the selective reduction of NO with propylene in excess oxygen. The catalyst Cu/La₂O₃-ZrO₂-Al₂O₃ that was coprepared by precipitation and impregnant methods had higher activity than catalyst Cu/Al₂O₃.2. The support Al₂O₃ was prepared by Al(NO₃)₃ dropping into (NH₄)₂CO₃ could remarkably enlarge the surface area, the addition of La₂O₃ contributes mainly to the enhancement of the thermal stability, the addition of ZrO₂ could increase the amount of Lewis acidity and Bronsterd acidity. Consequently, the catalyst Cu/La₂O₃-ZrO₂-Al₂O₃ had higher activity for the selective reduction of NO with propylene in excess oxygen.3. Both Cu/Al₂O₃(I) and Cu/La₂O₃-ZrO₂-Al₂O₃ catalysts have a good hydrothermal stability, even with the present of 10% water vapor, the catalysts can also remain higher catalytic activity.