Exhaust emission control apparatus for internal combustion engine

Abstract

One object of the present invention is to provide an exhaust emission control apparatus for an internal combustion engine that is capable of improving the NOx purification performance. An exhaust emission control apparatus being placed in an exhaust path of an internal combustion engine, comprising: an NOx retention material; ozone injection means for injecting ozone into an exhaust gas being positioned upstream from the NOx retention material; an HC adsorbent adsorbing HC contained in the exhaust gas; and a catalyst being placed in a region where desorbed NOx and desorbed HC contact each other. The HC adsorbent is prepared so as to desorb adsorbed HC at the same time as NOx being stored in the NOx retention material is desorbed.

1 . An exhaust emission control apparatus being placed in an exhaust path of an internal combustion engine, comprising:
 an NOx retention material;   ozone injection means for injecting ozone into an exhaust gas being positioned upstream from the NOx retention material;   an HC adsorbent adsorbing HC contained in the exhaust gas; and   a catalyst being placed in a region where desorbed NOx and desorbed HC contact each other;   wherein, said HC adsorbent is prepared so as to desorb adsorbed HC at the same time as NOx being stored in the NOx retention material is desorbed.   
   
   
       2 . The exhaust emission control apparatus according to  claim 1 , wherein the HC adsorbent and the NOx retention material are integrated with the catalyst. 
   
   
       3 . The exhaust emission control apparatus according to  claim 1 , wherein the NOx retention material is separated from the HC adsorbent,
 wherein the HC adsorbent is positioned upstream from the NOx retention material, and   wherein the ozone injection means injects ozone into the exhaust gas being positioned downstream from the NOx retention material.   
   
   
       4 . The exhaust emission control apparatus according to  claim 3 , wherein the NOx retention material is separated from the catalyst, and
 wherein the NOx retention material is positioned upstream from the catalyst.   
   
   
       5 . The exhaust emission control apparatus according to  claim 3 , wherein the NOx retention material is combined with the catalyst. 
   
   
       6 . The exhaust emission control apparatus according to  claim 1 , further comprising:
 control means for controlling the ozone injection means so that a molar quantity of ozone to be injected into the exhaust gas becomes greater than a molar quantity of nitrogen monoxide contained in the exhaust gas.   
   
   
       7 . The exhaust emission control apparatus according to  claim 6 , wherein the control means controls the ozone injection means so that the molar quantity of ozone to be injected into the exhaust gas becomes at least two times the molar quantity of nitrogen monoxide contained in the exhaust gas. 
   
   
       8 . An exhaust emission control apparatus being placed in an exhaust path of an internal combustion engine, comprising:
 an NOx retention material;   ozone injection device for injecting ozone into an exhaust gas being positioned upstream from the NOx retention material;   an HC adsorbent adsorbing HC contained in the exhaust gas; and   a catalyst being placed in a region where desorbed NOx and desorbed HC contact each other;   wherein, said HC adsorbent is prepared so as to desorb adsorbed HC at the same time as NOx being stored in the NOx retention material is desorbed.