采用共沉淀法制备了一系列不同Al_2O_3含量的CeO_2-ZrO_2-Al_2O_3(CZA)氧化物,并用X射线衍射、激光拉曼光谱和N_2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Al_2O_3含量为80%时,新鲜CZA样品中出现γ-Al_2O_3相.经600℃焙烧后,Al_2O_3在CZA样品中的溶域值略小于80%.经l000℃老化后,CZA样品中Al_2O_3含量为60%时,才开始出现微弱γ-Al_2O_3相,而其他氧化物物相结构稳定.添加Al_2O_3后材料比表面积和储氧量明显增大.随着Al_2O_3含量的增加,CZA样品的储氧量由336.2增至486.2 μmol/g,表现出良好的抗高温老化性能.当Al_2O_3含量为40%时,新鲜催化剂对C_3H_8的起燃温度和完全转化温度分别为238和292℃,同时具有良好的温度特性和较宽的空燃比窗口.
CeO_2-ZrO_2-Al_2O_3 (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, N_2 adsorption-desorption, and oxygen storage capacity (OSC) determination. XRD results showed that the samples with Al_2O_3 content lower than 80% could keep the single CeO_2-ZrO_2 cubic fluorite structure after calcination at 600 ℃. However, when the Al_2O_3 content was up to 60%, the γ-Al_2O_3 phase was detected slightly in the aged samples. The results of N_2 adsorption-desorption showed that the specific surface area and the OSC of fresh and aged CZA samples increased with the increase of Al_2O_3 content. The OSC of the aged sample increased from 336.2 to 486.2 μol/g with the increase of Al_2O_3 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% Al_2O_3 had high catalytic activity and broad working-window. Its light-off temperature was 238 ℃, and full conversion temperature was 292 ℃ for C_3H_8.
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