Catalyst for purifying exhaust gases

Abstract

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.