CeO_2-ZrO_2-Al_2O_3的制备及其负载钯三效催化剂的催化性能

Preparation of CeO_2-ZrO_2-Al_2O_3 and Catalytic Performance of Palladium-Based Three-Way Catalyst

采用共沉淀法制备了一系列不同Al2O3含量的CeO2-ZrO2-Al2O3(CZA)氧化物,并用X射线衍射、激光拉曼光谱和N2吸附-脱附等手段进行了表征.以CZA为载体,采用浸渍法制得钯基催化剂.结果表明,当Al2O3含量为80%时,新鲜CZA样品中出现γ-Al2O3相.经600oC焙烧后,Al2O3在CZA样品中的溶域值略小于80%.经1000oC老化后,CZA样品中Al2O3含量为60%时,才开始出现微弱γ-Al2O3相,而其他氧化物物相结构稳定.添加Al2O3后材料比表面积和储氧量明显增大.随着Al2O3含量的增加,CZA样品的储氧量由336.2增至486.2μmol/g,表现出良好的抗高温老化性能.当Al2O3含量为40%时,新鲜催化剂对C3H8的起燃温度和完全转化温度分别为238和292oC,同时具有良好的温度特性和较宽的空燃比窗口.

CeO2-ZrO2-Al2O3 （CZA） samples with different alumina contents were prepared by the co-precipitation method. The CZA samples were characterized by X-ray diffraction （XRD）, Raman spectroscopy, N2 adsorption-desorption, and oxygen storage capacity （OSC） determination. XRD results showed that the samples with Al2O3 content lower than 80% could keep the single CeO2-ZrO2 cubic fluorite structure after calcination at 600 oC. However, when the Al2O3 content was up to 60%, the γ-Al2O3 phase was detected slightly in the aged samples. The results of N2 adsorption-desorption showed that the specific surface area and the OSC of fresh and aged CZA samples increased with the increase of Al2O3 content. The OSC of the aged sample increased from 336.2 to 486.2 μmol/g with the increase of Al2O3 content from 20% to 80%, indicating that the CZA composite oxide had good thermal stability. A series of Pd/CZA catalyst samples were prepared by impregnation, and the fresh Pd/CZA catalyst with 40% Al2O3 had high catalytic activity and broad working-window. Its light-off temperature was 238 oC, and full conversion temperature was 292 oC for C3H8.