Small pore molecular sieve supported copper catalysts durable against lean/rich aging for the reduction of nitrogen oxides
View Patent ↗A method of using a catalyst comprises exposing a catalyst to at least one reactant in a chemical process. The catalyst comprises copper and a small pore molecular sieve having a maximum ring size of eight tetrahedral atoms. The chemical process undergoes at least one period of exposure to a reducing atmosphere. The catalyst has an initial activity and the catalyst has a final activity after the at least one period of exposure to the reducing atmosphere. The final activity is within 30% of the initial activity at a temperature between 200 and 500° C.
1. A system for treating exhaust gas comprising NOx absorber catalyst disposed upstream of an SCR catalyst, wherein said SCR catalyst comprises (i) copper and small-pore molecular sieve, and (ii) molecular sieve supported iron catalyst.
2. The system of claim 1 , wherein said small-pore molecular sieve has a CHA structure.
3. The system of claim 2 , wherein said small-pore molecular sieve has a silica-to-alumina ratio of about 8 to about 150.
4. The system of claim 2 , wherein said small pore molecular sieve is SSZ-13.
5. The system of claim 2 , wherein said small pore molecular sieve is SAPO-34.
6. The system of claim 1 , wherein said small-pore molecular sieve has a LEV structure.
7. The system of claim 1 , wherein said small-pore molecular sieve has an ERI structure.
8. The system of claim 1 , wherein said small-pore molecular sieve has a DDR structure.
9. The system of claim 1 , wherein said molecular sieve supported iron catalyst is selected from the group consisting of Fe/Ferrierite, Fe/ZSM-5, and Fe/Beta.
10. The system of claim 2 , wherein said molecular sieve supported iron catalyst is selected from the group consisting of Fe/Ferrierite, Fe/ZSM-5, and Fe/Beta.
11. The system of claim 3 , wherein said molecular sieve supported iron catalyst is selected from the group consisting of Fe/Ferrierite, Fe/ZSM-5, and Fe/Beta.
12. The system of claim 4 , wherein said molecular sieve supported iron catalyst is selected from the group consisting of Fe/Ferrierite, Fe/ZSM-5, and Fe/Beta.
13. The system of claim 5 , wherein said molecular sieve supported iron catalyst is selected from the group consisting of Fe/Ferrierite, Fe/ZSM-5, and Fe/Beta.
14. The system of claim 6 , wherein said molecular sieve supported iron catalyst is selected from the group consisting of Fe/Ferrierite, Fe/ZSM-5, and Fe/Beta.
15. The system of claim 7 , wherein said molecular sieve supported iron catalyst is selected from the group consisting of Fe/Ferrierite, Fe/ZSM-5, and Fe/Beta.
16. The system of claim 8 , wherein said molecular sieve supported iron catalyst is selected from the group consisting of Fe/Ferrierite, Fe/ZSM-5, and Fe/Beta.