| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control system applied to an internal combustion engine operated with exhaust atmosphere varying to be lean, stoichiometry or rich and with combustion atmosphere being in a lean state and excelling in emission controlling performance of NOx, HC and CO. <P>SOLUTION: The exhaust emission control system is applied to the internal combustion engine operated with the exhaust atmosphere varying to be lean, stoichiometry or rich and with the combustion atmosphere being in the lean state and comprises a first exhaust emission control catalyst adsorbing NOx in exhaust gas when the exhaust atmosphere is lean, releasing NOx and controlling its emission when the exhaust atmosphere is stoichiometry or rich and a second exhaust emission control catalyst arranged downstream of the first exhaust emission control catalyst and controlling emission of HC or the like in the exhaust gas when the exhaust atmosphere is rich, stoichiometry or lean, wherein the second exhaust emission control catalyst has an oxygen adsorption and discharge capacity in which a ratio of an oxygen discharge amount at catalyst temperature of 250-400°C to an oxygen discharge amount at catalyst temperature of 250-700°C is 0.04 or more. <P>COPYRIGHT: (C)2008,JPO&INPIT |
