Increased NO
Exhaust purification system and methods for the reduction of emissions from an exhaust stream, including an upstream catalyst coupled with a passive NO x adsorber catalyst; means to contact the exhaust stream with ozone, to react NO in the exhaust stream with the ozone to produce NO 2 ; and an SCR catalyst.
1. An exhaust purification system for the reduction of emissions from an exhaust stream, comprising, in order:
a. an upstream catalyst coupled with a passive NO x adsorber catalyst;
b. means to contact the exhaust stream with ozone, to react NO in the exhaust stream with the ozone to produce NO 2 ;
c. an SCR catalyst.
2. The system of claim 1 , wherein the upstream catalyst comprises an oxidation catalyst and/or a cold start catalyst.
3. The system of claim 1 , wherein the passive NO x adsorber catalyst comprises a filter substrate.
4. The system of claim 1 , wherein the upstream catalyst and the passive NOx adsorber catalyst are included on a single substrate.
5. The system of claim 1 , further comprising a means for heating the exhaust gas upstream of the means to contact the exhaust stream with ozone.
6. The system of claim 1 , further comprising an SCRF catalyst located upstream of the SCR catalyst.
7. The system of any claim 1 , further comprising an ASC downstream of the SCR catalyst.
8. A method of reducing emissions from an exhaust stream, comprising:
a. contacting the exhaust stream with an upstream catalyst coupled with a passive NOx adsorber catalyst;
b. oxidizing NO to NO 2 by contacting the exhaust stream with ozone;
c. selectively catalytically reducing NO 2 to nitrogen by contacting the NO 2 produced from the oxidizing step with a reductant in the presence of an SCR catalyst.
9. The method of claim 8 , wherein the upstream catalyst comprises an oxidation catalyst and/or a cold start catalyst.
10. The method of claim 8 , wherein the passive NO x adsorber catalyst comprises a filter substrate.
11. The method of claim 8 , wherein the upstream catalyst and the passive NOx adsorber catalyst are included on a single substrate.
12. The method of claim 8 , further comprising heating the exhaust stream upstream of the SCR catalyst.
13. The method of claim 12 , wherein the exhaust stream is heated before contacting the exhaust stream with ozone.
14. The method of claim 8 , wherein the ozone is injected into the exhaust stream.
15. The method of claim 8 , wherein step c further comprises contacting the exhaust stream with an SCRF catalyst located upstream of the SCR catalyst.
16. The method of claim 8 , wherein about 20 wt % to about 80 wt % of the NO in the exhaust stream contacting the ozone is reacted with the ozone to produce NO 2 .
17. The method of claim 8 , wherein the exhaust stream comprises a NO 2 /NO x % value of about 20 wt % to about 70 wt % at initiation of step C.
18. The method of claim 8 , wherein step b is carried out at exhaust stream temperatures of 30° C. to 250° C.
19. The method of claim 8 , wherein NOx conversion of the method is higher than NOx conversion of a method which is equivalent except lacks step b.
20. The method of claim 13 , wherein NOx conversion of the method is higher than NOx conversion of a method which is equivalent except lacks step b and the heating step.