| 摘要 |
PROBLEM TO BE SOLVED: To reduce a consumption rate of reducer by making a condition of the same rate or more as reducer in oxidant after NOx is chemically absorbed on an absorption catalyst by making a condition having much oxidant with respect to reducer at the time of exhaust gas emission control, contact reacting absorbed NOx with reducer so as to reduce into N2. SOLUTION: In a NOx absorption catalyst 18 interposed in an exhaust emission control system, NOx, HC, and CO in exhaust gas are purified by a catalytic converter rhodium function at the time of stoichiometric operation, and NOx is purified by NOx absorption function at the time of a lean operation, and simultaneously, HC and CO are purified by a combustion function. At the time of a lean operation, it is judged that there is a NOx absorption function of the NOx absorption catalyst 18 or not. When it is judged that there is not an absorption function, an air-fuel ratio is rich-shifted for a predetennined period so as to regenerate the NOx absorption catalyst 18. The NOx absorption catalyst 18 including elements such as potassium, sodium, magnesium, strontium, and calcium as a part of component, is suitably used. |
