EXHAUST GAS PURIFICATION CATALYST

Abstract

A catalytic matter comprises alumina particles. A compound oxide is loaded on surfaces of the alumina particles. The compound oxide contains cerium, zirconium, and lanthanum, but not aluminum. A catalytic metal is loaded on the surfaces of the alumina particles. The catalytic matter may be manufactured by preparing a first acidic solution containing aluminum, adding a first basic solution to the first acidic solution, thereby obtaining a second basic solution and precipitating a first hydroxide in the second basic solution, preparing a second acidic solution containing cerium, zirconium and lanthanum, adding the second acidic solution to the first hydroxide, thereby precipitating a second hydroxide on the first hydroxide, drying the first and second hydroxides to obtain an oxide matter, and loading a catalytic metal on the oxide matter. By loading the compound oxide containing cerium as an oxygen storage material on the alumina particle surfaces, the amount of the oxygen storage material on the surfaces of alumina particles may be increased, and the catalytic metal may loaded on or in the proximity of the oxygen storage material. Therefore, the catalytic metal may be supplied with sufficient amount of active oxygen to purify the exhaust gas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by reading examples of embodiments in which the invention is used to advantage, referred to herein as the Detailed Description, with reference to the drawings wherein:

FIG. 1 is a schematic view showing a structure of a La contained alumina particle and a compound oxide;

FIG. 2 is a photograph taken by a transmission electron microscope (TEM) and showing a surface of a La contained alumina particle and a compound oxide containing Ce, Z, Y, and La;

FIG. 3 is a schematic view of an apparatus measuring oxygen concentration in model gas upstream and downstream of a catalyst specimen;

FIG. 4 is a graph showing oxygen concentration measured by the apparatus of FIG. 3 and translated into an air fuel ratio, and a difference of the air fuel ratio between upstream and downstream of the catalyst specimen;

FIG. 5 is a graph showing oxygen release amount versus weight percent of La₂O₃ contained in Ce—Zr—Y—La compound oxide with respect to a total weight of La₂O₃ contained in the catalytic matter; and

FIG. 6 is a graph showing NOx conversion rate at 500° C. (NOx C500) and HC light-off temperature (HC T50) versus weight percent of La₂O₃ contained in Ce—Zr—Y—La compound oxide with respect to the total weight of La₂O₃ contained in the catalytic matter.

Claims

1. Catalytic matter comprising: alumina particles;a compound oxide which is loaded on surfaces of said alumina particles, and contains cerium, zirconium, and lanthanum, but not aluminum; anda catalytic metal loaded on said alumina particles.

2. The catalytic matter as described in claim 1, wherein said alumina particles consist of a compound oxide containing lanthanum.

3. The catalytic matter as described in claim 1, wherein weight of lanthanum oxide contained in said compound oxide is 1% or greater of total weight of lanthanum oxide contained in said catalytic matter.

4. The catalytic matter as described in claim 3, wherein the weight of lanthanum oxide contained in said compound oxide is between 1 and 50% of the total weight of lanthanum oxide contained in said catalytic matter.

5. The catalytic matter as described in claim 4, wherein the weight of lanthanum oxide contained in said compound oxide is between 7 and 40% of the total weight of lanthanum oxide contained in said catalytic matter.

6. The catalytic matter as described in claim 3, wherein the weight of lanthanum oxide contained in said compound oxide is 75% or greater of the total weight of lanthanum oxide contained in said catalytic matter.

7. The catalytic matter as described in claim 1, wherein said oxygen storage material of said compound oxide further contains yttrium.

8. The catalytic matter as described in claim 1, wherein said catalytic metal comprises rhodium.

9. A catalyst converter for purifying exhaust gas from an internal combustion engine, having a carrier, and a catalyst layer positioned above said carrier, said catalyst layer comprising: a substrate made of alumina;an oxygen storage material loaded on said substrate, said oxygen storage material being made of a compound oxide containing cerium, zirconium, and lanthanum, but not aluminum; anda catalytic metal loaded on said substrate.

10. The catalytic converter as described in claim 9, wherein said substrate comprises a compound oxide containing lanthanum.

11. The catalytic converter as described in claim 9, wherein weight of lanthanum oxide contained in said compound oxide is 1% or greater of total weight of lanthanum oxide contained in said substrate and said oxygen storage material.

12. The catalyst converter as described in claim 9, wherein said oxygen storage material of said compound oxide further contains yttrium.

13. A method of manufacturing catalytic matter comprising: preparing a first salt solution containing aluminum;adding a first basic solution to said first salt solution, thereby obtaining a second basic solution and precipitating a first hydroxide in said second basic solution;preparing a second salt solution containing cerium, zirconium and lanthanum;adding said second salt solution to said first hydroxide, thereby precipitating a second hydroxide on said first hydroxide;drying said first and second hydroxides to obtain a first oxide; andloading a catalytic metal on said first oxide.

14. The method as described in claim 13, further comprising: preparing a slurry containing said first oxide and said catalytic metal loaded thereon; andcoating said slurry on a carrier, thereby obtaining a catalyst brick.

15. The method as described in claim 13, wherein said first acidic solution is prepared by dissolving an aluminum nitrate hydrate into water.

16. The method as described in claim 15, wherein said first acidic solution is prepared by further dissolving a lanthanum nitrate hydrate into water.

17. The method as described in claim 15, wherein said first acidic solution is ammonia water.

18. The method as described in claim 17, wherein said second acidic solution is prepared by dissolving a cerium nitrate hydrate, a zirconium nitrate hydrate, and a lanthanum nitrate hydrate into water.

19. The method as described in claim 13, wherein said first and second hydroxides are dried to obtain said first oxide by: dehydrating a slurry containing said first and second hydroxides;drying said slurry at a temperature higher than a room temperature, thereby obtaining dried matter;crushing said dried matter; andcalcining said crushed matter, thereby obtaining oxide particles.

20. The method as described in claim 13, wherein said catalytic metal is loaded on said first oxide by: preparing a slurry containing said first oxide;preparing a salt solution containing said catalytic metal;mixing said slurry and said salt solution, thereby obtaining mixed matter; anddehydrating said mixed matter; andcalcining said dehydrated mixed matter.