Coated perovskite-based catalysts, catalyst combinations and methods of treating a gas stream
View Patent ↗One embodiment of the invention includes a method of treating a gas stream comprising flowing the gas stream over a hydrocarbon reduction and NO x reduction catalyst first, and thereafter flowing the gas over a perovskite and NO x trap material for NO x oxidation and storage. In one embodiment, the hydrocarbon reduction and NO x reduction catalyst may include palladium. In one embodiment, the perovskite catalyst may have the general formula ABO 3 , AA′BO 3 , ABB′O 3 , or AA′BB′O 3 . The perovskite catalyst may be the only catalyst or a second non-perovskite catalyst may include at least one of palladium, platinum, rhodium, ruthenium or a catalyst system including one or more of the same or alloys thereof. In one embodiment, the NO x trap material may include at least one of alkali metals, alkaline earth metals such as barium, calcium, potassium, or sodium.
1. A method comprising:
treating an exhaust steam including NO x comprising:
flowing the exhaust stream first over a hydrocarbon reduction and NO x reduction catalyst;
and thereafter flowing the exhaust stream over a perovskite catalyst and a NO x trap material for NO x oxidation and storage.
2. A method as set forth in claim 1 wherein the perovskite catalyst and NO x trap material comprises a layer on or over a support substrate, and wherein the hydrocarbon reduction and NO x reduction catalyst comprises a layer on or over the layer including the perovskite catalyst then NO x trap material.
3. A method as set forth in claim 1 wherein the hydrocarbon reduction and NO x reduction catalyst comprises a first layer or zone on or over a first portion of a substrate and wherein the perovskite catalyst and a NO x trap material comprise a layer or zone on or over a second portion of the substrate and wherein the hydrocarbon reduction and NO x reduction catalyst is not on the perovskite catalyst and NO x trap material.
4. A method as set forth in claim 1 wherein the hydrocarbon reduction and NO x reduction catalyst and the perovskite catalyst and NO x trap material are supported by a substrate.
5. A method as set forth in claim 4 wherein the substrate is substantially flat.
6. A method as set forth in claim 4 wherein the substrate comprises a bead or pellet.
7. A method as set forth in claim 4 wherein the substrate is constructed and arranged to have a ring, saddle, hollow cylinder or Raschig ring shape.
8. A method as set forth in claim 4 wherein the substrate is porous.
9. A method as set forth in claim 4 wherein the substrate is solid.
10. A method as set forth in claim 4 wherein the substrate comprises a gas flow through monolith having a plurality of through-holes formed therein.
11. A method as set forth in claim 10 wherein the monolith comprises a ceramic or metal material.
12. A method as set forth in claim 4 wherein the substrate comprises a wall flow filter.
13. A method as set forth in claim 1 wherein the perovskite catalyst and NO x trap material are constructed and arranged as a support substrate not carried by another substrate and wherein the hydrocarbon reduction and NO x reduction catalyst is coated on or over the substrate.
14. A method as set forth in claim 13 wherein the perovskite catalyst and NO x reduction material is porous.
15. A method as set forth in claim 1 wherein the perovskite catalyst has the general formula ABO 3 , AA′BO 3 , ABB′O 3 , or AA′BB′O 3 , wherein A comprises a rare earth metal from the Lanthanide Series and/or an alkaline-earth metal and wherein B comprises a transition metal.
16. A method as set forth in claim 15 , wherein said perovskite catalyst has the general formula AA′BO 3 ;
wherein A comprises a rare earth metal from the Lanthanide Series and/or an alkaline-earth metal;
wherein B comprises a transition metal; and
wherein A′ comprises a substitution of a promoter material for a portion of A.
17. A method as set forth in claim 15 , wherein said perovskite catalyst has the general formula ABB′O 3 ,
wherein A comprises a rare earth metal from the Lanthanide Series and/or an alkaline-earth metal;
wherein B comprises a transition metal; and
wherein B′ comprises a substitution of a promoter material for a portion of B.
18. A method as set forth in claim 15 , wherein said perovskite catalyst has the general formula AA′BB′O 3 ,
wherein A comprises a rare earth metal from the Lanthanide Series and/or an alkaline-earth metal;
wherein B comprises a transition metal;
wherein A′ comprises a substitution of a promoter material for a portion of A; and
wherein B′ comprises a substitution of a promoter material for a portion of B.
19. A method as set forth in of claim 18 , wherein A′ comprises Strontium.
20. A method as set forth in claim 15 , wherein A is Lanthanum.
21. A method as set forth in claim 15 , wherein B is Cobalt or Manganese or Iron.
22. A system for reducing NO x in a gas stream comprising:
a catalytic oxidation reactor comprising a first reaction zone comprising a hydrocarbon reduction and NO x reduction catalyst; and a second zone downstream of the first zone, the second zone comprising a perovskite catalyst and a NO x trap material for NO x oxidation and storage.
23. A system as set forth in claim 22 wherein the perovskite catalyst has the general formula ABO 3 , AA′BO 3 ABB′O 3 , or AA′BB′O 3 , wherein A comprises a rare earth metal from the Lanthanide Series and/or an alkaline-earth metal and wherein B comprises a transition metal.
24. The system of claim 22 , wherein said perovskite catalyst is of the general formula AA′BO 3 ;
wherein A comprises a rare earth metal from the Lanthanide Series and/or an alkaline-earth metal;
wherein B comprises a transition metal; and
wherein A′ comprises a substitution of a promoter material for a portion of A.
25. A system as set forth in claim 22 , wherein said perovskite catalyst is of the general formula ABB′O 3 ;
wherein A comprises a rare earth metal from the Lanthanide Series and/or an alkaline-earth metal;
wherein B comprises a transition metal; and
wherein B′ comprises a substitution of a promoter material for a portion of B.
26. A system as set forth in claim 22 , wherein said perovskite catalyst is of the general formula AA′BB′O 3 ;
wherein A comprises a rare earth metal from the Lanthanide Series and/or an alkaline-earth metal;
wherein B comprises a transition metal;
wherein A′ comprises a substitution of a promoter material for a portion of A; and
wherein B′ comprises a substitution of a promoter material for a portion of B.