Exhaust purification catalyst, exhaust emissin control device for internal combustion engine, and exhaust gas purification filter

Abstract

Provided are an exhaust purification catalyst which purifies an exhaust gas discharged from an internal combustion engine and in which high catalytic activity at a low temperature and high durability at a high temperature are compatible with each other, and an exhaust emission control device for the internal combustion engine in which the exhaust purification catalyst is used. The exhaust purification catalyst is a catalyst in which a noble metal particle is carried on a surface of a silicon carbide particle. The catalyst is a noble-metal-carrying silicon carbide particle ( 1 ) in which a noble metal particle ( 3 ) is carried on a surface of a silicon carbide particle ( 2 ) in a state of being coated with an oxide layer ( 4 ).

1 . An exhaust purification catalyst in which a noble metal particle is carried on a surface of a silicon carbide particle, wherein the noble metal particle is carried in a state of being coated with an oxide layer. 
     
     
         2 . The exhaust purification catalyst according to  claim 1 , wherein the oxide layer is formed from one or two compounds selected from a group consisting of amorphous SiO x  (provided that, 0<x≦3) and amorphous SiO y C z  (provided that, 0<y≦3 and 0<z≦3). 
     
     
         3 . The exhaust purification catalyst according to  claim 2 , wherein the oxide layer further contains one or two or more crystalline substances selected from a group consisting of SiO 2 , SiO, SiOC 3 , SiO 2 C 2 , and SiO 3 C. 
     
     
         4 . The exhaust purification catalyst according to  claim 1 , wherein an average primary particle size of the silicon carbide particle is 0.01 μm to 5 μm. 
     
     
         5 . The exhaust purification catalyst according to  claim 1 , wherein an average primary particle size of the noble metal particle is 1 nm to 50 nm. 
     
     
         6 . An exhaust emission control device for an internal combustion engine, which purifies an exhaust gas discharged from an internal combustion engine by using a catalyst disposed in an exhaust passage of the internal combustion engine, wherein at least one catalyst is the exhaust purification catalyst according to  claim 1 . 
     
     
         7 . An exhaust gas purification filter which purifies an exhaust gas by allowing particulate matter contained in the exhaust gas to pass through a filter base body formed from a porous substance to trap the particulate matter,
 wherein the filter base body includes,   a partition wall that is formed from a porous substance;   an inflow-side gas flow passage which is formed by the partition wall and in which an inflow-side end for an exhaust gas that contains particulate matter is opened; and   an outflow-side gas flow passage which is provided at a position different from that of the inflow-side gas flow passage of the filter base body and is formed by the partition wall and in which an outflow-side end for the exhaust gas is opened,   wherein a porous film having a pore size smaller than that of the partition wall is formed on a surface of the partition wall at least on an inflow-side gas flow passage side, and   the porous film contains silicon carbide particles and noble metal fine particles, and the noble metal particles, which are carried on the surface of the silicon carbide particles, are carried in a state of being coated with an oxide layer.   
     
     
         8 . The exhaust gas purification filter according to  claim 7 , wherein the oxide layer is formed from one or two compounds selected from a group consisting of amorphous SiO x  (provided that, 0<x≦3) and amorphous SiO y C z  (provided that, 0<y≦3 and 0<z≦3). 
     
     
         9 . The exhaust gas purification filter according to  claim 8 , wherein the oxide layer further contains one or two or more crystalline substances selected from a group consisting of SiO 2 , SiO, SiOC 3 , SiO 2 C 2 , and SiO 3 C. 
     
     
         10 . The exhaust gas purification filter according to  claim 7 , wherein an average primary particle size of the silicon carbide particles is 0.01 μm to 10 μm. 
     
     
         11 . The exhaust gas purification filter according to  claim 7 , wherein an average primary particle size of the noble metal particles is 1 nm to 50 nm. 
     
     
         12 . The exhaust gas purification filter according to  claim 7 , wherein an average pore size of the porous film is 0.05 μm to 3 μm, and an average porosity of the porous film is 50% to 90%. 
     
     
         13 . The exhaust purification catalyst according to  claim 2 , wherein an average primary particle size of the silicon carbide particle is 0.01 μm to 5 μm. 
     
     
         14 . The exhaust purification catalyst according to  claim 2 , wherein an average primary particle size of the noble metal particle is 1 nm to 50 nm. 
     
     
         15 . An exhaust emission control device for an internal combustion engine, which purifies an exhaust gas discharged from an internal combustion engine by using a catalyst disposed in an exhaust passage of the internal combustion engine, wherein at least one catalyst is the exhaust purification catalyst according to  claim 2 . 
     
     
         16 . The exhaust gas purification filter according to  claim 8 , wherein an average primary particle size of the silicon carbide particles is 0.01 μm to 10 μm. 
     
     
         17 . The exhaust gas purification filter according to  claim 8 , wherein an average primary particle size of the noble metal particles is 1 nm to 50 nm. 
     
     
         18 . The exhaust gas purification filter according to  claim 8 , wherein an average pore size of the porous film is 0.05 μm to 3 μm, and an average porosity of the porous film is 50% to 90%.