Catalyst for treating exhaust gas
Catalyst compositions and methods of preparation comprising: exchanging a rare earth element into a molecular sieve; incorporating a promoter metal into the molecular sieve; wherein the rare earth element exchanging step and the promoter metal incorporation step are performed as separate steps.
1. A method of preparing a catalyst composition comprising:
a. exchanging a rare earth element into a molecular sieve;
b. incorporating a promoter metal into the molecular sieve;
wherein the rare earth element exchanging step and the promoter metal incorporation step are performed as separate steps,
wherein the promoter metal comprises copper and the catalyst composition comprises an atomic Cu:Al of 0.2 to 0.45,
wherein the molecular sieve comprises CHA with a silica to alumina ratio (SAR) of 17 to about 23, and
wherein the catalyst composition comprises the rare earth element in an amount of about 0.5 to about 5 wt % of the catalyst composition.
2. The method claim 1 , wherein the rare earth element is exchanged into the molecular sieve before incorporating the promoter metal.
3. The method of claim 1 , wherein the promoter metal is incorporated into the molecular sieve before exchanging the rare earth element.
4. The method of claim 1 , wherein the rare earth element is exchanged into the molecular sieve by ion exchange.
5. The method of claim 1 , wherein the promoter metal is incorporated into the molecular sieve by ion exchange.
6. The method of claim 1 , wherein the catalyst composition comprises minimal surface CeO 2 .
7. The method of claim 1 , wherein the rare earth element comprises cerium.
8. The method of claim 1 , wherein the promoter metal comprises copper.
9. The method of claim 1 , wherein catalyst composition comprises the promoter metal in an amount of about 0.5 to about 6 wt % of the catalyst composition.
10. A catalyst composition prepared by the method of claim 1 .
11. A catalyst composition prepared according to the method of claim 1 .
12. The catalyst composition of claim 11 , wherein the molecular sieve comprises a small pore molecular sieve.
13. The catalyst composition of claim 11 , comprising the rare earth element in an amount of about 0.5 to about 5 wt % of the catalyst composition.
14. The catalyst composition of claim 11 , comprising the promoter metal in an amount of about 0.5 to about 6 wt % of the catalyst composition.
15. The catalyst composition of claim 11 , comprising minimal surface CeO 2 .