Exhaust gas purifying catalyst and process for producing the same
First Claim
1. An exhaust gas purifying catalyst sequentially comprising on alumina grains:
- (a) at least one rare earth element oxide,(b) rhodium, and(c) at least one of platinum and palladium.
1 Assignment
0 Petitions
Accused Products
Abstract
An exhaust gas purifying catalyst for oxidizing HC and CO and for reducing NOx is provided, which comprises at least one oxide of rare earth element, rhodium, and at least one of platinum and palladium loaded on alumina grains. The major amount of rhodium is dispersed on the oxide of rare earth element. Thus, the rhodium solidification into the alumina grains is prevented. Further, when cerium oxide accompanying lanthanum oxide, neodymium oxide or a mixture thereof is used as the oxide of rare earth element, the sintering of cerium oxide or palladium at a high temperature is suppressed since it forms a complex oxide with lanthanum oxide, neodymium oxide or a mixture thereof. Additionally, when stabilized alumina grains in which a rare earth element and an alkali earth element are present in a solid solution state are used, the deterioration of NOx purifying activity of the catalyst at a high temperature is suppressed. The exhaust gas purifying catalyst of this invention has high durability as well as high activity at a high temperature.
46 Citations
17 Claims
-
1. An exhaust gas purifying catalyst sequentially comprising on alumina grains:
-
(a) at least one rare earth element oxide, (b) rhodium, and (c) at least one of platinum and palladium. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
-
-
14. A process for producing an exhaust gas purifying catalyst comprising the steps of:
-
coating alumina grains on a catalyst support; loading at least one rare earth element oxide on the alumina grains; loading rhodium on said rare earth element oxide; and loading at least one of platinum and palladium thereon. - View Dependent Claims (15, 16)
-
-
17. A process for producing an exhaust gas purifying catalyst comprising the steps of:
-
coating a catalyst support with alumina grains by immersing the catalyst support in a slurry of the alumina grains; loading at least one rare earth element oxide on the alumina grains by immersing the thus-coated catalyst support in an aqueous solution containing at least one rare earth element, drying the resulting catalyst support and then calcining it; loading rhodium on said rare earth element oxide by immersing the thus-obtained catalyst support in an aqueous solution containing rhodium, drying the resulting catalyst support and then calcining it; and loading at least one of platinum and palladium thereon by immersing the thus-calcined catalyst support in an aqueous solution containing at least one of said platinum and said palladium, drying the thus-prepared catalyst support and calcining it.
-
Specification