Exhasut gas purifying catalyst

Abstract

An exhaust gas purifying catalyst comprises a substrate having a through hole serving as a passage for exhaust gas; and a catalyst coating layer formed on an internal surface of the through hole. The catalyst coating layer contains: a component (i): a precious metal; and a component (ii): at least one of a Zr oxide, a Ce oxide and a ZrCe mixed oxide. On an upstream portion of the passage, an oxide equivalent weight of Zr is within a range of 51-100 wt % of an oxide equivalent weight of Zr and Ce contained in the component (ii). On a downstream portion of the passage, the component (ii) includes at least one of a Ce oxide and a ZrCe mixed oxide in which an oxide equivalent weight of Ce is within a range of 58-100 wt % of an oxide equivalent weight of Zr and Ce contained in the ZrCe mixed oxide.

1 . An exhaust gas purifying catalyst comprising:
 a substrate having a through hole penetrating the substrate in an axial direction; and   a catalyst coating layer formed on an internal surface of the through hole, the catalyst coating layer containing:
 a component (i): a precious metal; and 
 a component (ii): at least one of a group consisting of a Zr oxide, a Ce oxide and a ZrCe mixed oxide, 
   wherein the through hole forms a passage for an exhaust gas, and   an oxide equivalent weight of Zr in an upstream portion of the passage is greater than an oxide equivalent content of Ce in the upstream portion of the passage, and an oxide equivalent content of Ce in a downstream portion of the passage is greater than the oxide equivalent content of Ce in the upstream portion of the passage.   
     
     
         2 . The exhaust gas purifying catalyst according to  claim 1 , wherein an axial length of the area A along the passage is 10 to 50% of an entire axial length of the passage. 
     
     
         3 . The exhaust gas purifying catalyst according to clain, wherein a proportion between a weight of the precious metal contained in the catalyst coating layer formed in the area A and a weight of the precious metal contained in the catalyst coating layer formed in the area B is within a range of 2:1 to 10:1. 
     
     
         4 . The exhaust gas purifying catalyst according to  claim 1 , wherein the precious metal contained in the catalyst coating layer formed in the area A includes at least one of Pd and Rh. 
     
     
         5 . The exhaust gas purifying catalyst according to  claim 4 , wherein the precious metal contained in the catalyst coating layer formed in the area A further includes Pt. 
     
     
         6 . The exhaust gas purifying catalyst according to  claim 1 , wherein the precious metal contained in the catalyst coating layer formed in the area B includes at least one of Pt, Pd and Rh.