Catalyst for purifying exhaust gases.

摘要

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 NOx 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 NOx 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 NO2 by the noble metal catalyst ingredient, and at the same time the resulting NO2 is stored in the NOx storage component which is disposed adjacent to the nobel metal catalyst. In the stoichiometric or fuel-rich (i.e., oxygen-lean) atmospheres, the stored NO2 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 NOx storage component. Hence, the catalyst is improved in terms of NOx purifying performance.