Patent ID: 6192675
Filing Date: 2001-02-27
Classification: B01D,F01N,F02B,Y02T

Abstract:
An exhaust gas purification device for an internal combustion engine operated at a lean operating air-fuel ratio comprising:a plurality of selective reduction catalysts disposed in series in the exhaust gas passage of the engine, wherein each of the selective reduction catalysts is capable of reducing NO.sub.x in the exhaust gas of the engine by selectively reacting NO.sub.x with a reducing agent in the exhaust gas even if the air-fuel ratio of the exhaust gas is lean;reducing agent supply means for supplying the reducing agent to the exhaust gas in the exhaust gas passage upstream of a first selective reduction catalyst disposed on the most upstream side in the selective reduction catalysts so that the exhaust gas containing the reducing agent is always supplied to the first selective reduction catalyst during operation of the engine; andbypass passage means for bypassing at least the first catalyst in such a manner that, during operation of the engine, a part of the exhaust gas containing the reducing agent always directly flows into selective reduction catalysts downstream of the first catalyst without flowing through the first catalyst.