초록 ▼

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

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.

대표청구항 ▼

[ What is claimed is:] [16.] A process for purifying an exhaust gases from a lean burn engine, said process comprising:simultaneously removing carbon monoxide, hydrocarbons and nitrogen oxides by bringing said exhaust gas from a lean burn engine into contact with an exhaust gas purifying catalyst co

[ What is claimed is:] [16.] A process for purifying an exhaust gases from a lean burn engine, said process comprising:simultaneously removing carbon monoxide, hydrocarbons and nitrogen oxides by bringing said exhaust gas from a lean burn engine into contact with an exhaust gas purifying catalyst consisting essentially of;a porous support;a NO.sub.x storage component loaded on said porous support including at least one member selected from the group consisting of alkaline-earth metals, rare-earth elements and alkali metals;a noble metal catalyst ingredient loaded substantially exclusively on said porous support; andceria (CeO.sub.2) segregated from said noble metal catalyst ingredient,wherein a majority of said nitrogen oxides in said exhaust gas are adsorbed to said NO.sub.x storage component on said porous support under a lean burn atmosphere in which oxidizing concentrations are above a stoichiometric point that is required for oxidizing components to be oxidized in said exhaust gas, said exhaust gas is temporarily changed from lean burn to fuel-rich, and said adsorbed nitrogen oxides are released and chemically reduced by a reaction with said hydrocarbons and carbon monoxide in said exhaust gas under a stoichiometric atmosphere or a fuel-rich atmosphere in which oxygen concentrations are below said stoichiometric point.