Exhaust gas purification system for an internal combustion engine.

摘要

A noble metal base catalyst (10) for decomposing a portion of NOx included in engine exhaust gas into intermediate products such as N2O and NO2 is installed in an exhaust conduit (6) of a lean burn engine (2). Further, an intermediate product decomposing means (12, 32, 46) for decomposing the intermediate products produced by the noble metal base catalyst (10) into N2 and O2 is installed downstream of the noble metal base catalyst (10). The noble metal base catalyst (10) has a high thermal durability, and the noble metal base catalyst (10) and the intermediate product decomposing means decompose (12, 32, 46) NOx into N2 and O2 without a large amount of HC.