DEVELOPMENT OF RARE EARTH BASED OXIDES FOR AUTOMOTIVE EXHAUST CATALYSTS

汽车尾气催化剂用稀土氧化物的开发

基本信息

批准号：
10555304
负责人：
ADACHI Gin-ya
金额：
$ 8.13万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10555304/
关键词：
Rare earth oxides Automotive exhaust catalysts Oxygen storage capacity Zirconia Rare earth oxalate Pyrochlore Hydrazine Chemical vapor transport 希土類シュウ塩酸マイクロエマルション微粒子逆ミセル

项目摘要

In this work we aimed development of rare-earth based oxides of high thermal stability and high catalytic activity. Especially we focused on ceria-zirconia mixed oxides which were applied as promoters in the automotive exhaust three-way catalysts.Nanosize Ceria and ceria-zirconia ultrafine particles prepared using a reaction within reversed micelles were characterized by HREM. The catalytic activities of the ceria-zirconia ultrafine particles supported on γ-alumina powders were higher than those given by the conventional catalysts prepared by the co-precipitation method, even after the heat treatment at 1273 K for 5 h in air.Ceria-zirconia solid solutions were also prepared by thermal decomposition of cerium zirconyl oxalate in an argon flow at 1273 K followed by oxidation at 673-873 K in air. The reduction behavior of the obtained powders was investigated and compared with the samples of high redox activity prepared by the conventional method. The ceria-zirconia samples prepared from the oxalate showed better reduction behavior, in spite of their very low surface areas. The reason for the behavior was attributed to both the appearance of a cubic phase with a different oxygen arrangement and the reduction by carbon formed in the sample preparation process.Surface modification of the ceria-zirconia solid solutions was carried out using formation and transport of volatile vapor complexes such as AlClィイD23ィエD2-CeClィイD23ィエD2 and AlClィイD23ィエD2-ZrClィイD24ィエD2, This process was named as "chemical filing." Reduction temperature of the sample after the chemical filing was lower than that of the fresh sample, and further decreased by a reduction/reoxidation cycle. The redox property of the chemically filed sample was maintained even after the redox cycles at high temperatures, indicating its durability compared to the solid solution prepared by a conventional procedure.

在这项工作中，我们的目标是开发具有高热稳定性和高催化活性的稀土基氧化物，特别是在汽车尾气三效催化剂中用作促进剂的氧化铈-氧化锆混合氧化物。纳米氧化铈和氧化铈-氧化锆。使用反胶束内反应制备的超细颗粒通过 HREM 表征了负载在 γ-氧化铝粉末上的氧化铈-氧化锆超细颗粒的催化活性。即使在空气中 1273 K 下热处理 5 h 后，其性能仍高于共沉淀法制备的常规催化剂。还通过在氩气流中热分解草酸锆锆制备了氧化铈-氧化锆固溶体。在 1273 K 下进行氧化，然后在空气中于 673-873 K 下进行氧化。研究了所得粉末的还原行为，并与高温样品进行了比较。尽管表面积非常低，但由草酸盐制备的二氧化铈-氧化锆样品表现出更好的氧化还原活性，其原因在于具有不同氧的立方相的出现。排列和样品制备过程中形成的碳的还原。利用挥发性蒸气复合物的形成和传输对二氧化铈-氧化锆固溶体进行表面改性，例如AlClD23D2-CeClD23D2和AlClD23D2-ZrClD24D2，该过程被命名为“化学填充”。化学填充后的样品的还原温度比新鲜样品的还原温度低，并且通过还原/再氧化循环进一步降低了氧化还原性能。即使在高温氧化还原循环后，化学填充的样品也能保持不变，这表明其与其他样品相比的耐久性至通过常规程序制备的固溶体。