Device for purifying the exhaust gas of an internal combustion engine

Abstract

A device for purifying the exhaust gas of an internal combustion engine is disclosed. The device comprises a particulate filter arranged in the exhaust system, which carry a catalyst for absorbing and reducing NO x . The catalyst absorbs NO x when the air-fuel ratio in the surrounding atmosphere thereof is lean and releases the absorbed NO x to purify NO x by reduction when the air-fuel ratio is the stoichiometric or rich. The device further comprises a catalytic apparatus for purifying NO x arranged in the exhaust system upstream of the particulate filter, which has an oxidation function.

1 . A device for purifying the exhaust gas of an internal combustion engine comprising: 
 a particulate filter arranged in the exhaust system, which carry a catalyst for absorbing and reducing NO x , said catalyst absorbing NO x  when the air-fuel ratio in the surrounding atmosphere thereof is lean and releasing the absorbed NO x  to purify NO x  by reduction when said air-fuel ratio is the stoichiometric or rich; and    a catalytic apparatus for purifying NO x  arranged in the exhaust system upstream said particulate filter, which has an oxidation function.    
     
     
         2 . A device for purifying the exhaust gas of an internal combustion engine according to  claim 1 , further comprising bypassing means to make possible the exhaust gas bypass said particulate filter downstream said catalytic apparatus.  
     
     
         3 . A device for purifying the exhaust gas of an internal combustion engine according to  claim 2 , wherein said catalytic apparatus carries said catalyst for absorbing and reducing NO x , during the recovery process of the SO x  pollution of said catalytic apparatus, said bypassing means makes the exhaust gas bypass said particulate filter.  
     
     
         4 . A device for purifying the exhaust gas of an internal combustion engine according to  claim 2 , wherein said catalytic apparatus carries said catalyst for absorbing and reducing NO x , immediately after the finishing of the recovery process of the SO x  pollution of said catalytic apparatus, said bypassing means does not make the exhaust gas bypass said particulate filter and thus the exhaust gas passes through said particulate filter.  
     
     
         5 . A device for purifying the exhaust gas of an internal combustion engine comprising: 
 a particulate filter arranged in the exhaust system, which carries an oxidation catalyst; and    a catalytic apparatus for purifying NO x  arranged in the exhaust system upstream said particulate filter.    
     
     
         6 . A device for purifying the exhaust gas of an internal combustion engine according to  claim 5 , wherein said particulate filter carries an oxygen absorbing agent.