Composite catalyst for purification of exhaust gas

Details Composite catalyst for purification of exhaust gas Composite catalyst for purification of exhaust gas

1998-11-24

2001-07-17

Bell, Mark L. (Department: 1755)

Catalyst, solid sorbent, or support therefor: product or process

Catalyst or precursor therefor

Metal, metal oxide or metal hydroxide

C502S303000, C502S326000, C502S525000, C502S527120, C502S527150, C502S527160, C502S527170, C502S527190, C428S469000, C428S472000

Reexamination Certificate

active

06261990

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a composite catalyst for the purification of exhaust gas.
As a catalyst for the purification of exhaust gas, particularly NOx (nitrogen oxide), there has heretofore been known an Ir (iridium) catalyst (see U.S. Pat. No. 5,326,735 and U.S. Pat. No. 5,487,268).
The conventional Ir catalyst exhibits a relatively high capacity of purifying NOx in an atmosphere of excess oxygen but is disadvantageous in that it has a low durability.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a composite catalyst for the purification of exhaust gas which exhibits a high capacity of purifying NOx and an excellent durability in an atmosphere of excess oxygen.
In order to accomplish the foregoing object, the present invention provides a composite catalyst for the purification of exhaust gas comprising a first catalyst part containing an Ir catalyst and a second catalyst part covering the first catalyst part and containing a perovskite type composite oxide.
In the foregoing arrangement, the perovskite type composite oxide in the second catalyst part contributes mainly to oxidation reaction such as NO+O
2
→NO
2
in an atmosphere of excess oxygen while the Ir catalyst in the first catalyst part contributes mainly to reduction reaction with HC (hydrocarbons including saturated or unsaturated hydrocarbons) as a reducing agent such as NO
2
+HC+O
2
→N
2
+CO
2
+H
2
O (typical equation) in an atmosphere of excess oxygen. In other words, the use of perovskite type composite oxide allows NO
2
to be positively supplied into the Ir catalyst and the Ir catalyst to efficiently reduce NO
2
to N
2
. Thus, the composite catalyst exhibits a high capacity of purifying NOx in an atmosphere of excess oxygen.
On the other hand, when the Ir catalyst is directly exposed to an atmosphere of excess oxygen at elevated temperatures, Ir becomes an oxide which can be easily vaporized. This causes deterioration of the durability of the Ir catalyst. In order to overcome these difficulties, the first catalyst part having an Ir catalyst is covered by a second catalyst part. This second catalyst part inhibits evaporation of the Ir oxide, making it possible to drastically enhance the-durability of the Ir catalyst.


REFERENCES:
patent: 3884837 (1975-05-01), Remeika et al.
patent: 3900428 (1975-08-01), Mai et al.
patent: 3905918 (1975-09-01), Mai et al.
patent: 4126580 (1978-11-01), Lauder
patent: 4134852 (1979-01-01), Volin
patent: 4140655 (1979-02-01), Chabot et al.
patent: 4151123 (1979-04-01), McCann, III
patent: 4426319 (1984-01-01), Blanchard et al.
patent: 4426320 (1984-01-01), Ernest et al.
patent: 4710487 (1987-12-01), Koch
patent: 4812300 (1989-03-01), Quinlan et al.
patent: 4849398 (1989-07-01), Takada et al.
patent: 4861802 (1989-08-01), McCann
patent: 4868148 (1989-09-01), Henk et al.
patent: 4923842 (1990-05-01), Summers
patent: 5149516 (1992-09-01), Han et al.
patent: 5185311 (1993-02-01), Tabata et al.
patent: 5326735 (1994-07-01), Itoh et al.
patent: 5439865 (1995-08-01), Abe et al.
patent: 5487268 (1996-01-01), Itoh et al.
patent: 5559073 (1996-09-01), Hu et al.
patent: 5628975 (1997-05-01), Horiuchi et al.
patent: 5691263 (1997-11-01), Park et al.
patent: 0513413A1 (1992-11-01), None
patent: 0577879A1 (1994-01-01), None
patent: 5-38420 (1993-02-01), None
patent: 6-31173 (1994-02-01), None
patent: 8-1006 (1996-01-01), None
patent: 2598717 (1997-01-01), None
patent: WO 90/08589 (1990-08-01), None

Affiliated with

Also associated with

Rating

Composite catalyst for purification of exhaust gas does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Composite catalyst for purification of exhaust gas, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Composite catalyst for purification of exhaust gas will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2493935