Exhaust gas treatment system for an internal combustion engine

Abstract

An exhaust gas treatment system for an internal combustion engine reduces the amount of NOx in exhaust gas flowing through an exhaust passage of the engine. The system has a plasma generator including two electrodes spaced away from each other in the exhaust passage, a high-frequency power supply connected to one of the electrodes, and a NOx absorber provided between the electrodes.

1 . An exhaust gas treatment system for an internal combustion engine, the system for reducing the amount of NOx in exhaust gas flowing through an exhaust passage of the engine, comprising:
 a plasma generator including;
 two electrodes spaced away from each other in the exhaust passage; 
 a high-frequency power supply connected to one of the electrodes; and 
 a NOx absorber provided between the electrodes. 
   
   
   
       2 . The exhaust gas treatment system according to  claim 1 , wherein a plurality of plasma generators is provided in series in the exhaust passage, and the plasma generators are operated at different timings from each other. 
   
   
       3 . The exhaust gas treatment system according to  claim 2 , further comprising a controller that monitors engine load and changes the number of plasma generators to be operated depending on the engine load. 
   
   
       4 . The exhaust gas treatment system according to  claim 1 , wherein the energy for discharge between the electrodes is set in a range of 642 to 942 kJ/mol. 
   
   
       5 . The exhaust gas treatment system according to  claim 1 , wherein the NOx absorber contains a material that allows physisorprtion of NOx thereon. 
   
   
       6 . The exhaust gas treatment system according to  claim 5 , wherein the material is selected from the group consisting of:
 alkali metals;   alkali earth metals;   lanthanoids;   oxides of the alkali metals, the alkali earth metals or the lanthanoids;   compounds of either the alkali metals, the alkali earth metals or the lanthanoids with elements other than the alkali metals, the alkali earth metals and the lanthanoids; and   oxides of the compounds.