SCR catalyst
A copper-CHA zeolite catalyst for SCR of NO x is disclosed.
1. A catalyst composition comprising a copper-containing zeolite having a CHA framework, a molar silica-to-alumina ratio (SAR) of at least 40, and an atomic copper-to-aluminum ratio of at least 1.25, wherein the zeolite is essentially free of ion-exchanged copper and the zeolite is essentially free of framework transition metal.
2. The catalyst composition of claim 1 , wherein the copper-to-aluminum ratio is at least 1.5.
3. The catalyst composition of claim 1 , wherein the copper-to-aluminum ratio of at least 2.
4. The catalyst composition of claim 1 , wherein the SAR is 40 to 250.
5. The catalyst composition of claim 1 , wherein the SAR is about 45 to 85.
6. The catalyst composition of claim 1 , copper is present in an amount of about 3 to 5 weight percent, based on the total weight of the zeolite.
7. The catalyst composition of claim 1 , wherein the zeolite contains less than 1.5 weight percent copper oxide.
8. A catalyst article for treating exhaust gas comprising a catalyst composition according to claim 1 disposed on and/or within a substrate.
9. The catalyst article of claim 8 , wherein the substrate is a metal plate.
10. The catalyst article of claim 8 , wherein the substrate is a honeycomb.
11. The catalyst article of claim 10 , wherein the catalyst is a washcoat on the honeycomb.
12. The catalyst article of claim 10 , wherein the honeycomb is an extruded catalyst.
13. The catalyst article of claim 10 , wherein the honeycomb is a wall-flow filter.
14. The catalyst article of claim 10 , wherein the honeycomb is a flow-through honeycomb.
15. A catalyst composition comprising a washcoat slurry comprising a catalyst according to claim 1 and one or more binders.
16. A method for treating an exhaust gas comprising contacting a combustion exhaust gas containing NO x and/or NH 3 with a catalyst composition according to claim 1 to selectively reduce at least a portion of the NO x into N 2 and H 2 O and/or oxidize at least a portion of the NH 3 .
17. A system for treating an exhaust gas containing NOx, the system comprising a catalytic article according to claim 8 and a source of a reductant, wherein the reductant source is upstream of the catalytic article.
18. A catalyst composition comprising a copper-containing zeolite having a CHA framework, a molar silica-to-alumina ratio (SAR) of at least 40, and an atomic copper-to-aluminum ratio of at least 1.25, wherein the zeolite comprises a majority of in-situ copper compared to free copper oxides.
19. A catalyst composition comprising a copper-containing zeolite having a CHA framework, a molar silica-to-alumina ratio (SAR) of at least 40, and an atomic copper-to-aluminum ratio of at least 1.25, wherein the zeolite has a unit cell volume of about 2355 to about 2375 A 3 .