| 摘要 |
PROBLEM TO BE SOLVED: To provide an engine, capable of fully purifying surplus HCs, while effectively feeding the HC as the reducing agent to the catalyst purifying NOx in exhaust gas through reduction. SOLUTION: A first catalyst 3 and a second catalyst 4 are arranged at an exhaust passage 2 of an engine 1. The first catalyst 3 is structured, so that Pt is carried at HC absorbing carrier made of MFI the pore diameter of which is small, and the second catalyst 4 is structured so that Pt is carried at HC- absorbing carrier, made of a β-zeolite the pore diameter of which is large. At the first catalyst 3 on the upstream side, the HC absorbed in MFI and which molecular size is relatively small is oxidized, and NOx in the exhaust gas is reduced, by applying the absorbed HC. At the second catalyst on the downstream side, the HC, which is absorbed in a β-zeolite and of which the molecular size is relatively small, is oxidized and the remaining NOx is effectively reduced by applying the absorbed HC. |
