A new approach of CeO2 and La2O3 effects on the three-way catalysts containing low precious metals

• 来源期刊: 中国化学(英文版)
• 年，卷（期）: 2000,（5）
• 页码范围: 673-682
• 页数: 10页
• 语种: 英文

摘要

A series of three-way catalysts (TWCs), containing a small amount of precious metals ( PMs, including Pt, Pd and Rh ) and a large amount of promoters CeO2 and La2O3, were pre pared with different precursor compotmds and various doped mtaners. Crystal phases, dispersion of cerium and lan thamun, textural structure and thermal stability of the cata lysts were investigated by XRD, XPS and pore parameters de termination. The catalytic performance was studied by the measurements of CO, C3H6 and NO conversions on depen dence of temperature at stoichimetric nunber point (S = 1.00), and from S=0.75 to 1.30 at 280℃C or 340℃C for fresh or aged samples, respectively. The correlation between the catalytic performance and the characteristics of fresh and aged samples were discussed. The results show that the sampie, in which CeO2 and La2Os are doped with mixed oxide powders, possesses poor dispersion and less thermal stability, and the conversions of NO and C3H6 are apparently lower than those of the samples aged at 850℃C. The main reason is due to the ianthamum enriclument on the surface. The precious metals and cerium may be covered and enveloped, and the PMs lo cated on the internal microporous su-face where no cerium and lanthanum exist, are easier to sinter and oxidize. For the sample doped with La(NO3)3 and Ce(NO3)3 aqueous solu tions, high dispersion and thermal stable CeO2-La2O3 solid so lution on all the surface of microporous γ-Al2O3 is identified. The solid solution CeO2-La2O3 also possessed high dispersion in the sample doped with La2O3 powder and Ce(NO3)3 aque ous soltion The last two aged samples keep higher NO eon version at S＞1 region.