| 摘要 |
PROBLEM TO BE SOLVED: To suppress the discharge of NOx in warming-up process immediately after cold starting of an engine. SOLUTION: A moisture trap 17 is provided in an exhaust passage, and a low temperature NOx trap catalyst 18 trapping NOx at a low temperature and emitting NOx at a high temperature is provided at the downstream. A high temperature NOx trap catalyst 19 is provided for trapping NOx in the exhaust in a lean atmosphere when activated. Immediately after cold starting, the low temperature NOx trap catalyst 18 entraps NOx in the exhaust. In a warm-up process, NOx desorption from the low temperature NOx trap catalyst 18 starts, and the NOx desorbed from the low temperature NOx trap catalyst 18 is entrapped with the high temperature NOx trap catalyst 19 because the high temperature NOx trap catalyst 19 has a function of trapping NOx in a low temperature state before activation. COPYRIGHT: (C)2004,JPO
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