Toyota Jidosha Kabushiki Kaisha

Cataler Industrial Co., Ltd.

Tuneyuki Tanizawa

Naoto Miyoshi

Koichi Kasahara

Syuji Tateishi

Kazunobu Ishibashi

A catalyst for purifying exhaust gases includes a heat resistant support, a porous layer coated on the heat resistant support, a noble metal catalyst ingredient loaded on the porous layer, and an NO.sub.x storage component including at least one member selected from the group consisting of alkaline-earth metals, rare-earth elements and alkali metals, and loaded on the porous layer. In the catalyst, the noble metal catalyst ingredient and the NO.sub.x storage component are disposed adjacent to each other, and are dispersed uniformly in the porous layer. In fuel-lean (i.e., oxygen-rich) atmospheres, NO present in exhaust gases is oxidized to NO.sub.2 by the noble metal catalyst ingredient, and at the same time the resulting NO.sub.2 is stored in the NO.sub.x storage component which is disposed adjacent to the nobel metal catalyst. In the stoichiometric or fuel-rich (i.e., oxygen-lean) atmospheres, the stored NO.sub.2 is released, and simultaneously urged to react with HC and CO present in exhaust gases by the action of the noble metal catalyst ingredient which is disposed adjacent to the NO.sub.x storage component. Hence, the catalyst is improved in terms of NO.sub.x purifying performance.

Catalyst for purifying exhaust gases

A catalyst for purifying exhaust gases includes a porous support, an NO.sub.x storage component including at least one member selected from the group consisting of alkaline-earth metals, rare-earth elements and alkali metals, and loaded on the porous support, a noble metal catalyst ingredient loaded on the porous support, and disposed adjacent to the NO.sub.x storage component, and ceria (CeO.sub.2) disposed away from the noble metal catalyst ingredient. By disposing the noble metal catalyst ingredient adjacent to the NO.sub.x storage component, the reduction reactions of NO.sub.x can be facilitated in fuel-rich (i.e., oxygen-lean) atmospheres without being interfered by the ceria. By disposing the ceria away from the noble metal catalyst ingredient, oxygen, which has been stored thereon in fuel-lean (i.e., oxygen-rich) atmospheres, can be released from the ceria at a controlled rate in a controlled amount in fuel-rich (i.e., oxygen-lean) atmospheres, and thereby the released oxygen can be inhibited from reacting with HC and CO in fuel-rich (i.e., oxygen-lean) atmospheres. Thus, the catalyst is improved in terms of NO.sub.x purifying performance.

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Tuneyuki Tanizawa