Exhaust system including SCRF catalyst with oxidation zone
Systems and methods of the present invention related to an exhaust gas purification system comprising: (a) a first injector for injecting ammonia or a compound decomposable to ammonia into the exhaust gas; (b) a diesel particulate filter including an inlet and an outlet, wherein the filter includes a selective catalyst reduction (SCR) catalyst and an oxidation catalyst; (c) a second injector for injecting ammonia or a compound decomposable to ammonia into the exhaust gas, located downstream of the filter; and (d) a downstream catalyst comprising a selective catalytic reduction catalyst, located downstream of the second injector.
1. An exhaust gas purification system comprising:
a. a first injector for injecting ammonia or a compound decomposable to ammonia into the exhaust gas;
b. a diesel particulate filter including an inlet and an outlet, wherein the filter includes a selective catalyst reduction (SCR) catalyst and an oxidation catalyst;
c. a second injector for injecting ammonia or a compound decomposable to ammonia into the exhaust gas, located downstream of the filter; and
d. a downstream catalyst comprising a selective catalytic reduction catalyst, located downstream of the second injector;
wherein the oxidation catalyst is coated on the outlet of the filter.
2. The exhaust gas purification system of claim 1 , wherein the oxidation catalyst comprises one or more platinum group metals.
3. The exhaust gas purification system of claim 1 , wherein the oxidation catalyst comprises platinum, palladium, or combinations thereof.
4. The exhaust gas purification system of claim 1 , wherein the selective catalytic reduction catalyst comprises a metal oxide based SCR catalyst formulation, a molecular sieve based SCR catalyst formulation, or mixtures thereof.
5. The exhaust gas purification system of claim 1 , wherein the downstream catalyst further comprises an ammonia oxidation catalyst.
6. The exhaust gas purification system of claim 1 , wherein the exhaust gas entering the downstream catalyst has a NO 2 :NO x ratio of more than 10%.
7. The exhaust gas purification system of claim 1 , further comprising an upstream catalyst located upstream of the filter, the upstream catalyst comprising a diesel oxidation catalyst, a NO x storage catalyst, or combinations thereof.
8. A method of purifying exhaust gas, comprising:
a. adding ammonia or a compound decomposable into ammonia into the exhaust gas by a first injector;
b. passing the exhaust gas through a diesel particulate filter including an inlet and an outlet, wherein the filter includes a selective catalytic reduction (SCR) catalyst and an oxidation catalyst;
c. adding ammonia or a compound decomposable into ammonia into the exhaust gas by a second injector, located downstream of the filter; and
d. passing the exhaust gas through a downstream catalyst comprising a selective reduction catalyst, located downstream of the second injector;
wherein the oxidation catalyst is coated on the outlet of the filter.
9. The method of claim 8 , wherein the oxidation catalyst comprises one or more platinum group metals.
10. The method of claim 8 , wherein the oxidation catalyst comprises platinum, palladium, or combinations thereof.
11. The method of claim 8 , wherein the selective catalytic reduction catalyst comprises a metal oxide based SCR catalyst formulation, a molecular sieve based SCR catalyst formulation, or mixtures thereof.
12. The method of claim 8 , wherein the downstream catalyst further comprises an ammonia oxidation catalyst.
13. The method of claim 8 , wherein the exhaust gas entering the downstream catalyst has a NO 2 :NO x ratio of more than 10%.
14. The method of claim 8 , further comprising an upstream catalyst located upstream of the filter, the upstream catalyst comprising a diesel oxidation catalyst, a NO x storage catalyst, or combinations thereof.
15. An exhaust gas purification system comprising:
a. a first injector for injecting ammonia or a compound decomposable to ammonia into the exhaust gas;
b. a diesel particulate filter including an inlet and an outlet, wherein the filter includes a selective catalyst reduction (SCR) catalyst and an oxidation catalyst;
c. a second injector for injecting ammonia or a compound decomposable to ammonia into the exhaust gas, located downstream of the filter; and
d. a downstream catalyst comprising a selective catalytic reduction catalyst, located downstream of the second injector;
wherein the downstream catalyst further comprises an ammonia oxidation catalyst.
16. A method of purifying exhaust gas, comprising:
a. adding ammonia or a compound decomposable into ammonia into the exhaust gas by a first injector;
b. passing the exhaust gas through a diesel particulate filter including an inlet and an outlet, wherein the filter includes a selective catalytic reduction (SCR) catalyst and an oxidation catalyst;
c. adding ammonia or a compound decomposable into ammonia into the exhaust gas by a second injector, located downstream of the filter; and
d. passing the exhaust gas through a downstream catalyst comprising a selective reduction catalyst, located downstream of the second injector;
wherein the downstream catalyst further comprises an ammonia oxidation catalyst.