SYNTHESIS OF ULTRAFINE PARTICLES OF RARE EARTH OXIDES

稀土氧化物超细颗粒的合成

基本信息

批准号：
09450324
负责人：
ADACHI Gin-ya
金额：
$ 8.7万
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：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09450324/
关键词：
Rare earth oxides Ultrafine particles Reversed micelles Zirconia Catalysts Microemulsion Oxygen storage capacity Rare earth oxalates 固体触媒比表面積セリア-ジルコニア複合酸化物

项目摘要

This work deals with synthesis and characterization of ultrafine particles of rare earth-based oxides, especially focused on ceria and the ceria-zirconia systems which are applied as promoters in the automotive exhaust three-way catalysts.Cerium and yttrium oxide ultrafine particles were prepared using a reaction within reversed micelles, which was known as a microemulsion method. The ultrafine particles, which were obtained by mixing the W/O midroemulsions containing rare earth ions with those of ammonium hydroxide, were characterized by high-resolution electron microscope (HREM) observations. HREM micrographs showed that nanometer sized particles were prepared and their shapes were finiform. The smallest mean particle sizes of ceria and yttria obtained in this method were 2.6 and 4.0 nm, respectively. Those are the smallest among the values ever reported for ceria and yttria particles.Nanosize ceria-zirconia ultrafine particles were also prepared by the microemulsion method and were characterized by the HREM.The catalytic activities of the ceria-zirconia ultrafine particles impregnated on gamma -alumina powders for CO oxidation were compared with those of the conventional catalysts prepared by the co-precipitation method. Even after the heat treatment at 1273 K for 5 h in air, the Ce0.2Zr0.8O2/Al2O3 catalyst prepared by the microemulsion method showed a higher activity than that given by the conventional one. This finding suggests that the preparation method presented in this study is very useful to synthesize the catalysts of high activities and high heat resistance.

这项工作涉及稀土基氧化物超细颗粒的合成和表征，特别关注在汽车尾气三元催化剂中用作促进剂的二氧化铈和二氧化铈-氧化锆体系。使用以下方法制备了氧化铈和氧化钇超细颗粒反胶束内的反应，称为微乳液法。通过将含有稀土离子的W/O中间乳液与氢氧化铵混合而获得超细颗粒，并通过高分辨率电子显微镜（HREM）观察对其进行表征。 HREM 显微照片显示制备出纳米尺寸的颗粒，且其形状为丝状。该方法获得的二氧化铈和氧化钇的最小平均粒径分别为2.6和4.0 nm。这是迄今为止报道的二氧化铈和氧化钇颗粒中最小的值。还采用微乳液法制备了纳米尺寸二氧化锆-氧化锆超细颗粒，并通过高分辨电子显微镜进行了表征。γ-氧化铝浸渍二氧化铈-氧化锆超细颗粒的催化活性将用于CO氧化的粉末与共沉淀法制备的常规催化剂进行比较。即使在空气中1273 K下热处理5 h后，微乳液法制备的Ce0.2Zr0.8O2/Al2O3催化剂仍表现出比传统催化剂更高的活性。这一发现表明本研究提出的制备方法对于合成高活性和高耐热性的催化剂非常有用。