| 摘要 |
PROBLEM TO BE SOLVED: To improve the NOx cleaning performance (furthermore, hydrocarbon cleaning performance) and fuel consumption at the same time, and improve the durability, in an internal combustion engine in which a lean operation can be executed. SOLUTION: An iridium selective reduction catalyst (a first catalyst 28) containing iridium as an active seed and HC as reducing agent and for selectively reducing NOx in the lean atmosphere is arranged in an exhaust system, and the NOx adsorbing catalyst (a second catalyst 30) for adsorbing NOx in the lean atmosphere and for reducing the adsorbed NOx at a stoichiometric air-fuel ratio or rich air-fuel ratio less than the stoichiometric air-fuel ratio is arranged in the downstream of the first catalyst. Namely, cleaning performance is improved and fuel consumption performance and durability are improved by combining the catalysts having a different cleaning function. |
