| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a catalyst for purifying an exhaust gas excellent in NOx purifying performance, particularly excellent in the NOx purifying performance within lean limits, and a method and system therefor. <P>SOLUTION: The catalyst for purifying the exhaust gas comprises carrying a catalyst component containing rhodium, platinum and/or palladium, magnesium, calcium, strontium, barium, sodium, potassium, cesium and the like, and alumina on a honeycomb carrier, adsorbing NOx in a lean condition based on a theoretical air-fuel ratio and reducing the adsorbed NOx to N<SB>2</SB>in a stoichiometric amount of air condition and a fuel-rich condition. A plurality of catalyst coated layers containing the whole or a part of the catalyst component are provided, also rhodium is contained at least in the outermost surface layer of the catalyst coated layer, a rhodium content comprises 0.5 g or more against a liter of the catalyst, the rhodium content contained in the outermost surface layer comprises 80% or more of the whole rhodium content and the weight of the outermost surface layer of the catalyst coated layer comprises 40% or less of the whole weight of the catalyst coated layer. <P>COPYRIGHT: (C)2003,JPO |
