Catalyst structure for exhaust gas treatment
Provided is a new catalyst structure for exhaust gas treatment including an upper catalyst layer and a lower catalyst layer, in which the catalyst structure can sufficiently exhibit functions as a three way catalyst while maintaining gas diffusibility. Proposed is a catalyst structure including a substrate, an upper catalyst layer, and a lower catalyst layer, the catalyst structure having a first peak or a second peak at a pore volume diameter of 10 nm to 50 nm and a pore volume diameter of 50 nm to 100 nm, respectively, in the logarithmic differential pore volume distribution analyzed by a mercury intrusion porosimeter.
1. A catalyst structure for exhaust gas treatment comprising a substrate, an upper catalyst layer, and a lower catalyst layer, each of the upper catalyst layer and the lower catalyst layer comprising an inorganic porous material and a catalytically active component, wherein
the inorganic porous material of the upper catalyst layer comprises an oxide having a La-based apatite type structure represented by (LaA) 9.33-δ B 6 O 27.00-γ , where A is one or more elements selected from a group consisting of Ba, Pr, Y, Sr, Mg and Ce, B is one or more elements selected from a group consisting of Si, P and Fe, 0.3≤δ≤3.0 and 0.0<γ≤6.0, the catalytically active component of the upper catalyst layer comprises platinum, palladium, rhodium or iridium,
the inorganic porous material of the lower catalyst layer has an oxygen storage/release capacity function, the catalytically active component of the lower catalyst layer comprises platinum or palladium,
the inorganic porous material of the upper catalyst layer has a first peak having a highest peak height at a fine pore diameter of 70 nm to 99 nm in a logarithmic differential pore volume distribution of the inorganic porous material of the upper catalyst layer analyzed by a mercury intrusion porosimeter,
the inorganic porous material of the lower catalyst layer has a first peak having a highest peak height at a fine pore diameter of 10 nm to 51 nm in a logarithmic differential pore volume distribution of the inorganic porous material of the lower catalyst layer analyzed by the mercury intrusion porosimeter,
in a fine pore diameter range of 10 nm to 100 nm of a logarithmic differential pore volume distribution of the catalyst structure for exhaust gas treatment analyzed by the mercury intrusion porosimeter, a first peak having a highest peak height exists at a fine pore diameter of 10 nm to 50 nm and a second peak having a second highest peak height exists at a fine pore diameter of 50 nm to 100 nm, and
a difference between the fine pore diameter of the first peak and the fine pore diameter of the second peak is 20 nm to 60 nm.
2. The catalyst structure for exhaust gas treatment according to claim 1 , wherein a proportion of a layer thickness of the upper catalyst layer and a layer thicknesses of the lower catalyst layer is 60:180 to 100:120.
3. The catalyst structure for exhaust gas treatment according to claim 1 , wherein the oxide having the La-based apatite type structure occupies 50% by mass or more of the inorganic porous material included in the upper catalyst layer, and the inorganic porous material having the oxygen storage/release capacity function occupies 50% by mass or more of the inorganic porous material included in the lower catalyst layer.