Exhaust Gas Purification Apparatus of Internal Combustion Engine and Catalyst for Purifying Exhaust Gas of Internal Combustion Engine

Abstract

An exhaust gas purification apparatus for use in an internal combustion engine comprises an exhaust gas duct connected to the engine through which exhaust gas containing NO x gas passes, and a catalyst disposed in the exhaust gas duct such that it contacts the exhaust gas. The catalyst chemically adsorbs NO x when a stoichiometric amount of a gaseous oxidizing agent present in the exhaust gas is larger than that of a gaseous reducing agent present in the exhaust gas for reducing NO x , adsorbed NO x is catalytically reduced in the presence of a reducing agent when the stoichiometric amount of the oxidizing agent is not larger that of the reducing agent.

1 . An exhaust gas purification apparatus using a catalyst, wherein the catalyst comprising alumina and as catalytic components at least two of Rh, Pt and Pd, at least one of Ce, La and Y, at least one of Na, K and Sr.  
   
   
       2 . The apparatus according to  claim 1 , which further contains Mg.  
   
   
       3 . The apparatus according to  claim 2 , wherein the catalyst is supported on a honeycomb base body, an amount of catalytic components being 18 to 36 g/L of the honeycomb structure.  
   
   
       4 . The apparatus according to  claim 3 , wherein an amount of at least one of the Na, Sr and K is larger than that of at least one of Mg, Ti and Si.  
   
   
       5 . The apparatus according to  claim 1 , which further contains at least one of Ti and Si and Mg.  
   
   
       6 . The apparatus according to  claim 5 , wherein the catalyst is supported on a honeycomb base body, an amount of Mg being 2 to 4 g/L of the honeycomb structure.  
   
   
       7 . The apparatus according to  claim 1 , wherein the catalyst contains Ce, Rh, Pt, Mg, Na and Ti.