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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.

本研究旨在开发高热稳定性和高催化活性的稀土基氧化物。重点研究了铈锆复合氧化物作为汽车尾气三效催化剂助剂的应用，并采用反胶束反应法制备了纳米级铈和铈锆超细颗粒，用高分辨电子显微镜对其进行了表征。结果表明，以γ-Al 2 O3为载体的CeO 2-ZrO 2超微粒子的催化活性高于共沉淀法制备的催化剂，即使在1273 K下在空气中热处理5 h后也是如此。还通过在1273 K下在氩气流中热分解草酸氧锆铈，然后在673 K下氧化来制备氧化铈-氧化锆固溶体。873 K的空气。研究了所得粉体的还原行为，并与传统方法制备的高氧化还原活性样品进行了比较。由草酸盐制备的氧化铈-氧化锆样品显示出更好的还原行为，尽管它们的非常低的表面积。氧化铈-氧化锆固溶体的表面改性是利用挥发性气相复合物如AlCl_xD_23_xD_2-CeCl_xD_23_xD_2和AlCl_xD_23_xD_2-ZrCl_xD_24_xD_2的形成和迁移进行的，这一过程被称为“化学锉削”。“化学填充后样品的还原温度低于新鲜样品的还原温度，并通过还原/再氧化循环进一步降低。的氧化还原性质的化学字段的样品保持，即使在高温下的氧化还原循环后，表明其耐久性相比，通过常规程序制备的固溶体。