Mazda Motor Corporation

Kazuo Misonoo

Masahiko Shigetsu

Takashi Takemoto

Satoshi Ichikawa

Hiroshi Yamada

Hiroshi Murakami

Kenji Okamoto

Kenichi Yamamoto

Hisaya Kawabata

Yuki Koda

Toshitsugu Ueoka

Taeko Shimizu

An inside layer including zeolite and an outside layer including alumina and Pd are formed in a layered shape on a carrier, and Ag and Bi are simultaneously allowed to be carried on the inside and outside layers through impregnation. Thus, production of an alloy through a reaction between Pd and Ag can be suppressed by Bi.

Oxidation catalyst

In the manufacturing process of the exhaust gas purifying catalyst (,), rhodium is supported by the base material using the rhodium carbonyl cluster solution in which rhodium carbonyl cluster is dissolved into methanol in the step of forming the upper catalytic layer (,) including rhodium and platinum as catalytic metals. By this, the dispersibility of rhodium in the base material is highly raised, and further rhodium is effectively restrained from being oxidized during the manufacturing process of the catalyst (,). Thus, according to the exhaust gas purifying catalyst (,) particularly, the purifying performance of NOx at both of lower exhaust gas temperature and higher exhaust gas temperature is highly improved.

Method of manufacturing catalyst

In the exhaust gas purifying catalyst (3), palladium is contained as a catalytic component and cerium oxide and (Ce, Pr) compound oxide is contained as a promoter. Now, the weight ratio of cerium oxide to (Ce, Pr) compound oxide is set between 9/1 and 7/3, and the ratio of praseodymium to cerium in the (Ce, Pr) compound oxide is set between 3 mol % and 50 mol %. In this way, because in this exhaust gas purifying catalyst (3), palladium with high low-temperature activity is used for a catalytic component, the exhaust gas purifying performance at low temperature is improved. And because cerium oxide and (Ce, Pr) compound oxide improves catalytic activity of palladium at high temperature, the exhaust gas purifying performance at high temperature, in particular, NOx purifying performance, is improved.

Catalyst for cleaning exhaust gas

An exhaust gas purifying catalyst is produced by, after contacting a ceria powder with a palladium solution and burning the ceria powder to support the palladium on the ceria powder, forming a coating layer of the ceria powder on a catalyst support and impregnating the coating layer with a solution of cerium and burning it to provide palladium oxide particles fixed around ceria particles and a ceria coating so as to cover the palladium particles.

Exhaust gas purifying catalyst and process of producing the same

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Hiroshima, Japan

Kazuo Misonoo