EXHAUST GAS PURIFICATION CATALYST
An object of the present invention is to provide an exhaust gas purification catalyst capable of achieving both improvement of PM collection performance and suppression of pressure loss increase, and the present invention provides an exhaust gas purification catalyst ( 1 ) including: a wall-flow substrate; and at least one of a first catalyst layer ( 20 ) and a second catalyst layer ( 30 ), wherein the exhaust gas purification catalyst ( 1 ) satisfies the following formulae 1a and 2a: 1.3 × 10 - 3 ≤ Ra ( 1 a ) Xa × Ya ≤ 8. ( 2 a ) and/or satisfies the following formulae 1b and 2b: 1.3 × 10 - 3 ≤ Rb ( 1 b ) Xb × Yb ≤ 8. . ( 2 b )
1 . An exhaust gas purification catalyst comprising: a substrate extending in an exhaust gas flow direction; and at least one of a first catalyst layer and a second catalyst layer,
wherein the substrate comprises:
an inflow-side cell extending in the exhaust gas flow direction and having an open end on an exhaust gas inflow side thereof and a closed end on an exhaust gas outflow side thereof;
an outflow-side cell extending in the exhaust gas flow direction and having a closed end on an exhaust gas inflow side thereof and an open end on an exhaust gas outflow side thereof; and
a porous partition wall separating the inflow-side cell and the outflow-side cell from each other,
wherein the first catalyst layer is formed on an inflow-side cell side of the partition wall from an end on an exhaust gas inflow side of the partition wall along the exhaust gas flow direction,
wherein the second catalyst layer is formed on an outflow-side cell side of the partition wall from an end on an exhaust gas outflow side of the partition wall along a direction opposite to the exhaust gas flow direction, and
wherein the exhaust gas purification catalyst satisfies the following formulae 1a and 2a:
1.3
×
10
-
3
≤
Ra
(
1
a
)
Xa
×
Ya
≤
8.
(
2
a
)
wherein Ra represents a gas permeability (cm 3 /(cm 2 ·s·Pa)) of the first catalyst layer and the partition wall as determined using a permporometer, Xa represents a 50% flow pore diameter (μm) of the first catalyst layer and the partition wall as determined by a bubble point method using a permporometer, and Ya represents a 10% flow pore diameter (μm) of the first catalyst layer and the partition wall as determined by a bubble point method using a permporometer,
and/or satisfies the following formulae 1b and 2b:
1.3
×
10
-
3
≤
Rb
(
1
b
)
Xb
×
Yb
≤
8.
(
2
b
)
wherein Rb represents a gas permeability (cm 3 /(cm 2 ·s·Pa)) of the second catalyst layer and the partition wall as determined using a permporometer, Xb represents a 50% flow pore diameter (μm) of the second catalyst layer and the partition wall as determined by a bubble point method using a permporometer, and Yb represents a 10% flow pore diameter (μm) of the second catalyst layer and the partition wall as determined by a bubble point method using a permporometer.
2 . The exhaust gas purification catalyst as claimed in claim 1 , wherein the exhaust gas purification catalyst satisfies the following formula 3a:
2.
≤
Xa
×
Ya
(
3
a
)
and/or satisfies the following formula 3b:
2.
≤
Xb
×
Yb
.
(
3
b
)
3 . The exhaust gas purification catalyst as claimed in claim 1 , wherein the exhaust gas purification catalyst satisfies the following formula 4a:
0.6
≤
Xa
(
4
a
)
and/or satisfies the following formula 4b:
0
.
6
0
≤
Xb
.
(
4
b
)
4 . The exhaust gas purification catalyst as claimed in claim 1 , wherein the exhaust gas purification catalyst satisfies the following formula 5a
Ya
≤
5.
(
5
a
)
and/or satisfies the following formula 5b:
Yb
≤
5
.
0
0
(
5
b
)
5 . The exhaust gas purification catalyst as claimed in claim 1 - or 2 , wherein the first catalyst layer and the second catalyst layer each comprise a rod-shaped material and a non-rod-shaped material.
6 . The exhaust gas purification catalyst as claimed in claim 5 , wherein at least one of the rod-shaped material and the non-rod-shaped material comprises one or more selected from a Ce-based oxide and a Ce—Zr-based complex oxide.
7 . The exhaust gas purification catalyst as claimed in claim 5 , wherein a content of the rod-shaped material in the first catalyst layer is 4% by mass or more and 35% by mass or less, based on a mass of the first catalyst layer, and wherein a content of the rod-shaped material in the second catalyst layer is 4% by mass or more and 35% by mass or less, based on a mass of the second catalyst layer.
8 . The exhaust gas purification catalyst as claimed in claim 5 , wherein a content of the non-rod-shaped material in the first catalyst layer is 50% by mass or more and 95% by mass or less, based on a mass of the first catalyst layer, and wherein a content of the non-rod-shaped material in the second catalyst layer is 50% by mass or more and 95% by mass or less, based on a mass of the second catalyst layer.