Exhaust gas purification catalyst and exhaust gas purification system using the exhaust gas purification catalyst

1. An exhaust gas purification catalyst comprising a substrate and a catalyst layer provided on the substrate, said catalyst having a first section located upstream along a flow direction of the exhaust gas and a second section located downstream from the first section, wherein

the catalyst layer in the first section comprises a first catalyst layer comprising palladium and a second catalyst layer comprising rhodium and covering the first catalyst layer;

a pore volume proportion is 12% or more and less than 18% wherein the pore volume proportion is a proportion of a total volume of the pores, which have a pore diameter of 0.06 μm to 30.0 μm as measured by mercury press-in method and existing in the substrate and the catalyst layer in the first section to a volume of the entire first section; and

a wash coat amount is 100 g/L to 190 g/L, wherein a wash coat amount is a mass per unit volume of the catalyst layer in the first section to the volume of the substrate existing in the first section.

2. The exhaust gas purification catalyst according to claim 1 , wherein said catalyst has a value of a1/a2 is 1.2 or more, wherein

when the first catalyst layer is divided into two equal portions along a thickness direction, a1 is defined as a mass of palladium existing on a surface side of the first catalyst layer, and a2 is defined as a mass of palladium existing on an opposite side to the surface side of the first catalyst layer when the first catalyst layer is divided into two equal portions along the thickness direction.

3. The exhaust gas purification catalyst according to claim 1 , wherein

a pore volume proportion is 8% to 25%, wherein the pore volume proportion is a proportion of a total volume of the pores, which have a pore diameter of 0.06 μm to 30.0 μm as measured by the mercury press-in method, existing in the substrate and the catalyst layer in the second section to a volume of the entire second section.

4. The exhaust gas purification catalyst according to claim 1 , wherein

the catalyst layer in the second section comprises a third catalyst layer comprising palladium and a fourth catalyst layer comprising rhodium and covering the third catalyst layer.

5. The exhaust gas purification catalyst according to claim 1 , wherein

the pore volume proportion of the substrate and the catalyst layer in the first section is not more than 90% of the pore volume proportion of the substrate and the catalyst layer in the second section.

6. The exhaust gas purification catalyst according to claim 1 , wherein

the wash coat amount which is the mass per unit volume of the catalyst layer in the second section relative to the volume of the substrate existing in the second section is 180 g/L to 300 g/L.

7. The exhaust gas purification catalyst according to claim 1 , wherein

the second catalyst layer has a through-hole having a width of 10 μm or more through which gas passes from a surface thereof to the first catalyst layer.

8. The exhaust gas purification catalyst according to claim 1 , wherein

a length of the flow direction of exhaust gas in the first section is 20% to 70% with respect to a length of the flow direction of exhaust gas in the substrate.

9. An exhaust gas purification system in which, in an exhaust path connected to an internal combustion engine, exhaust gas from the internal combustion engine is introduced into the exhaust gas purification catalyst according to claim 1 without passing through any other exhaust gas purification catalyst.