Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Patent
1994-08-29
1998-05-19
Caldarola, Glenn
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
502327, 502328, 502333, 502334, 502340, 502341, 502349, 4232135, B01J 2300, B01J 802
Patent
active
057535809
ABSTRACT:
A bottom washcoat layer 2 and a top washcoat layer 3 including alumina (Al.sub.2 O.sub.3) are sequentially laminated onto the surface of a monolith carrier 1. Cerium, zirconium and palladium are carried in the bottom washcoat layer 2, and platinum, rhodium, barium and cerium are carried in the top washcoat layer 3. The cerium content in the top washcoat layer 3 is set smaller than that in the bottom washcoat layer 2. This causes the hydrocarbon conversion performance of rhodium and the nitrogen conversion performance of platinum in the top washcoat layer 3 to be balanced properly, while maintaining the hydrocarbon conversion performance of palladium in the bottom washcoat layer, thereby providing an improved exhaust gas purification performance as a whole. In addition, platinum and palladium carried in separate washcoat layers make it possible to inhibit the formation of a platinum-palladium alloy under high temperature conditions to prevent a reduction in exhaust gas purification effect. Further, the heat deterioration of cerium can be inhibited by zirconium, and the alumina surface area can be stabilized by barium, thereby providing an improved durability of the catalyst under high temperature conditions.
REFERENCES:
patent: 5019546 (1991-05-01), Murakami et al.
patent: 5254519 (1993-10-01), Wan et al.
patent: 5376610 (1994-12-01), Takahata et al.
Hayashi Tadayoshi
Kikuchi Shin-ichi
Bullock In Suk
Caldarola Glenn
Honda Giken Kogyo Kabushiki Kaisha
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