| 摘要 |
PROBLEM TO BE SOLVED: To satisfactorily purify NOX or SOX by NOX absorbent. SOLUTION: NOX absorbent 10 is disposed in an engine exhaust passage. When an air-fuel ratio of inflow exhaust is lean, the NOX absorbent 10 absorbs the NOX. When oxygen concentration in the inflow exhaust is lowered, the NOX absorbent 10 emits the absorbed NOX or SOX. The air-fuel ratio of the exhaust flowed into the absorbent 10 is temporally made to be rich so that the absorbent 10 emits the absorbed NOX or SOX. When the NOX or SOX is desired to be emitted from the absorbent 10, oxygen is made to be remained in the exhaust gas flowed in the absorbent 10 and the oxygen concentration in the exhaust gas is kept to be within a predetermined range.
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