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A new approach of CeO 2 and La 2 O 3 effects on the three‐way catalysts containing low precious metals
Author(s) -
Wang WenDong,
Lin PeiYan,
Fu YiLa,
Yu ShouMing,
Meng Ming,
Zhang XiaoPeng
Publication year - 2000
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.20000180504
Subject(s) - cerium , chemistry , lanthanum , catalysis , thermal stability , microporous material , dispersion (optics) , cerium oxide , lanthanum oxide , x ray photoelectron spectroscopy , doping , inorganic chemistry , aqueous solution , chemical engineering , organic chemistry , materials science , physics , optics , engineering , optoelectronics
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 CeO 2 and La 2 O 3 , were prepared with different precursor compounds and various doped manners. Crystal phases, dispersion of cerium and lanthanum, textural structure and thermal stability of the catalysts were investigated by XRD, XPS and pore parameters determination. The catalytic performance was studied by the measurements of CO, C 3 H 6 and NO conversions on dependence of temperature at stoichimetric number 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 mat the sample, in which CeO 2 and La 2 O 3 are doped with mixed oxide powders, possesses poor dispersion and less thermal stability, and the conversions of NO and C 3 H 6 are apparently lower man those of the samples aged at 850°C The main reason is due to the lanthanum enrichment on the surface. The precious metals and cerium may be covered and enveloped, and the PMs located on the internal microporous surface where no cerium and lanthanum exist, are easier to sinter and oxidize. For the sample doped with La(NO 3 ) 3 and Ce(NO 3 ) 3 aqueous solutions, high dispersion and thermal stable CeO 2 ‐La 2 O 3 solid solution on all the surface of microporous γ‐Al 2 O 3 is identified. The solid solution CeO 2 La 2 O 3 also possessed high dispersion in Ok sample doped with La 2 O 3 powder and Ce(NO 3 ) 3 aqueous solution. The last two aged samples keep higher NO conversion at S ≥1 region.