采用共沉淀法制备了一系列Nd2O3含量为0~13wt%的CeO2-ZrO2-A12O3(CZA)复合氧化物, 并通过X射线衍射(XRD)、低温N2吸附–脱附、氧脉冲吸附(OSC)、H2–程序升温还原(H2-TPR)及扫描电子显微镜(SEM)等方法对所制备的材料进行了表征. 研究结果表明, Nd2O3在CZA固溶体中的溶解限约为10wt%, 过量Nd的添加会出现分相形成Nd0.5Ce0.5O1.75氧化物. 掺杂适量Nd能有效抑制氧化物晶粒的长大, 提高材料的热稳定性和氧化还原性能. Nd2O3的掺杂量为10wt%时, 样品的织构稳定性最好, 1000℃老化5 h后, 比表面积和孔容分别达97.14 m2/g和 0.44 mL/g. Nd2O3的掺杂量为7wt%时, 样品有高的储氧量, 经600℃和1000℃焙烧后储氧量分别为938.01 μmol/g和821.72 μmol/g; 体相氧的移动能力最强, 还原性能最佳, 老化后还原峰温由465℃升高到483℃. SEM结果表明, 所制备的材料均为球形颗粒, Nd2O3的添加可以有效阻止高温焙烧过程中粒子的团聚.
A series of CeO2-ZrO2-Al2O3 (CZA) mixed oxides with Nd2O3 contents 0–13wt% were prepared by co-precipitation method and characterized by X-ray diffraction (XRD), N2 adsorption-desorption at low temperature, oxygen pulsing technique (OSC), H2-temperature programmed reduction (H2-TPR) and scanning electrical microscope (SEM). The results show that the solubility limit of Nd2O3 in the CZA solid solution is about 10wt%. With excessive Nd dopant, the single phase will separate resulting in the formation of Nd0.5Ce0.5O1.75 phase. Furthermore, the proper addition of Nd to CZA solid solution effectively restrains the sintering of oxide particles and greatly improves the thermal stability and redox property of the materials. When the doping amount of Nd2O3 in CZA solid solution is 10wt%, the sample has the best textural stability i.e. after calcination at 1000℃ for 5 h, the specific surface area and pore volume achieve 97.14 m2/g and 0.44 mL/g, respectively. For the CZA sample prepared with 7wt% Nd2O3 in CZA solid solution, the OSC is the highest in all samples, reaching 938.01 μmol/g and 821.72 μmol/g after calcination at 600℃ and 1000℃, respectively. Meanwhile, the mobility of bulk oxygen is the strongest and the sample has optimal reducibility at low temperature. After aging, the reduction peak temperature can be increased from 465℃ to 483℃. SEM image shows that all the prepared CZA samples have spherical particles and Nd2O3 can effectively prevent the agglomeration of particles in the process of high-temperature calcination.
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