Device for cleaning exhaust gas of internal combustion engine

Abstract

The device for cleaning exhaust gas of the internal combustion engine includes means provided in an exhaust gas passage ( 15 ) of the internal combustion engine ( 10 ), such as a NOx catalyst ( 20 ), a SOx trap catalyst ( 30 ) provided at a position upstream from the exhaust gas cleaning means, and means ( 40, 41 ) for feeding ozone to a position upstream from the SOx trap catalyst. SOx in the exhaust gas is absorbed by the SOx trap catalyst before reaching the NOx catalyst. Particularly, it is possible to oxidize SOx in the exhaust gas by ozone as oxidizing gas to be an easily decomposable state, whereby SOx is absorbable even at a low temperature. Preferably, the SOx trap catalyst has no active points consisting of precious metal. In such a case, the SOx trap catalyst is prevented from being sulfur-poisoned whereby the deterioration of the SOx absorbing ability is avoidable.

1 . A device for cleaning exhaust gas of an internal combustion engine, comprising
 means provided in an exhaust gas passage of the internal combustion engine, for cleaning exhaust gas discharged from a combustion chamber,   a SOx trap catalyst provided in said exhaust gas passage at a position upstream from said exhaust gas cleaning means, for absorbing SOx in the exhaust gas, and   means for feeding ozone to said exhaust gas passage at a position upstream from said SOx trap catalyst, wherein   said exhaust gas cleaning means cleans at least one of HC, CO and NOx components in the exhaust gas at a cleaning rate higher than that of said SOx trap catalyst.   
     
     
         2 . A device for cleaning exhaust gas of an internal combustion engine as defined by  claim 1 , wherein said SOx trap catalyst contains alkali metal element, alkaline earth metal element or rare earth element. 
     
     
         3 . A device for cleaning exhaust gas of an internal combustion engine as defined by  claim 1 , wherein said exhaust gas cleaning device comprises a NOx catalyst of a storage reduction type, and said NOx catalyst of a storage reduction type carries more precious metal than in said SOx trap catalyst. 
     
     
         4 . A device for cleaning exhaust gas of an internal combustion engine as defined by  claim 1 , wherein said SOx trap catalyst has no active points consisting of precious metal.