Exhaust gas purifcation 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 clam  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.  
     
     
         8 . A catalyst for purification of exhaust gas from an internal combustion engine, which comprises alumina, a rare earth element, at least one of Na, Sr, K, and at least one of Mg, Ti and Si.  
     
     
         9 . The catalyst according to  claim 8 , wherein the catalyst contains Mg and at least one of Ti and Si.  
     
     
         10 . The catalyst according to  claim 8 , wherein the rare earth element is supported on the alumina, at least two of Na, Sr, K, Mg, Ti and Si, and Mg are supported on the rare earth element.  
     
     
         11 . The catalyst according to  claim 10 , wherei the catalyst contains Mg, and at least two of Na, Sr, K, Mg, Ti and Si, at least one of Na, Sr and K, and at least one of Ti and Si.  
     
     
         12 . A method of manufacturing a catalyst for exhaust gas from an internal combination engine, which comprises: 
 coating alumina on a honeycomb base body;    coating Ce on the alumina; and    impregnating the Ce coating with at least one of Na, Sr and K, at least one of Mg, Ti and Si, at least two of Pt, Rh and Pd, at least one of Mg, Ti and Si, and Mg.