Exhaust gas purifying catalyst, metal oxide particle and production process thereof
AssigneeToyota Jidosha Kabushiki Kaisha
InventorsTakeshi Hirabayashi, Oji Kuno, Masahide Miura
Life of this patent
Estimating the term…
Abstract
In order to provide an exhaust gas purifying catalyst having improved heat resistance and OSC, a metal oxide particle, and a production process of the metal oxide particle, a metal oxide particle having a core (1) where the total molar number of alumina and silica is larger than the molar number of ceria, and a surface layer (2) where the molar number of ceria is larger than the total molar number of alumina and silica is provided. Further, an exhaust gas purifying catalyst comprising the metal oxide particle and a noble metal supported on the metal oxide particle; and a production process of the metal oxide particle are provided.
Claims8
An exhaust gas purifying catalyst comprising a metal oxide particle containing ceria and at least either one of alumina and silica, and a noble metal supported on said metal oxide particle,
- said metal oxide particle having a core where the total molar number of alumina and silica is larger than the molar number of ceria, and a surface layer where the molar number of ceria is larger than the total molar number of alumina and silica;
- wherein said metal oxide particle has a particle size of 500 nm or less;
- and
- wherein the molar ratio of (Al+Si):Ce in the metal oxide particle is from 1:0.5 to 0.5:1.
(canceled)
(canceled)
(canceled)
A process for producing a metal oxide particle having a core where the total molar number of alumina and silica is larger than the molar number of ceria, and a surface layer where the molar number of ceria is larger than the total molar number of alumina and silica, said process comprising:
- preparing a solution containing a ceria sol and a sol of at least either one of alumina and silica, wherein the isoelectric point of the ceria sol differs more than 3.5 from that of said at least one of alumina and silica sol,
- adjusting the pH of said solution to be closer to the isoelectric point of the sol of at least either one of alumina and silica than to the isoelectric point of the ceria sol, and to fall within and ±2.0 of the isoelectric point of alumina and/or silica sol, and
- aggregating the sol from said solution to produce an aggregate.
Dependencies are inferred from the claim text.