Exhaust treatment system for ammonia-fueled vehicles

1. An emission treatment system for NO x abatement in an exhaust stream of an ammonia-fueled engine, the emission treatment system comprising:

a selective catalytic reduction (SCR) catalyst disposed on a substrate in fluid communication with the exhaust stream of the ammonia-fueled engine; and

an oxidation catalyst disposed on a substrate positioned upstream and/or downstream of the SCR catalyst and in fluid communication with the exhaust stream and the SCR catalyst, wherein the oxidation catalyst is a diesel oxidation catalyst (DOC).

2. The emission treatment system of claim 1 , wherein the oxidation catalyst comprises a refractory metal oxide support impregnated with a platinum group metal (PGM).

3. The emission treatment system of claim 2 , wherein the PGM comprises platinum, palladium, or a combination thereof.

4. The emission treatment system of claim 2 , wherein the oxidation catalyst further comprises a refractory metal oxide support impregnated with a non-PGM transition metal, an alkaline earth metal, or a combination thereof.

5. The emission treatment system of claim 4 , wherein the non-PGM transition metal comprises manganese.

6. The emission treatment system of claim 4 , wherein the alkaline earth metal comprises barium.

7. The emission treatment system of claim 1 , wherein the SCR catalyst comprises a metal-promoted molecular sieve, a vanadia-based composition, or a combination thereof.

8. The emission treatment system of claim 1 , wherein the SCR catalyst and the oxidation catalysts are present in the form of an SCR/AMOx catalyst.

9. The emission treatment system of claim 1 , wherein the SCR catalyst is a copper-, an iron-, or a manganese-containing zeolite.

10. The emission treatment system of claim 9 , wherein the zeolite has a framework type chosen from LEV, CHA, AEI, MEI, FER, or a combination thereof.

11. The emission treatment system of claim 10 , further comprising one or more adsorption components chosen from a low-temperature NO x adsorber (LT-NA), a low temperature ammonia adsorber (LT-AA), a low temperature water vapor adsorber (LT-WA), or a combination thereof.

12. The emission treatment system of claim 11 , wherein the one or more adsorption components are arranged in any order and combination.

13. The emission treatment system of claim 11 , wherein each of the one or more adsorption components is disposed on a substrate, positioned upstream or downstream of the SCR catalyst, and in fluid communication with the exhaust stream and the SCR catalyst.

14. The emission treatment system of claim 11 , wherein each of the one or more adsorption components are disposed on the same substrate as a mixture, in a zoned configuration, or in a layered configuration.

15. The emission treatment system of claim 11 , wherein one or more of the SCR catalyst, the oxidation catalyst, and the one or more adsorption components are disposed on the same substrate, as a mixture, in a zoned configuration, or in a layered configuration.

16. The emission treatment system of claim 11 , wherein the one or more adsorption components and a DOC are disposed on the same substrate as a mixture, in a zoned configuration, or in a layered configuration.

17. The emission treatment system of claim 11 , wherein the LT-NA is present and comprises a molecular sieve, impregnated with at least one platinum group metal component, or a metal organic framework (MOF).

18. The emission treatment system of claim 11 , wherein the LT-AA is present and comprises a molecular sieve or a MOF.

19. The emission treatment system of claim 11 , wherein the LT-WA is present and chosen from molecular sieves, clays, activated charcoal, activated alumina, silica, calcium sulfate, calcium chloride, a MOF, and combinations thereof.

20. The emission treatment system of claim 11 , wherein one or more of the SCR catalyst, the one or more adsorption components, and the oxidation catalyst are disposed on a flow-through substrate in the form of a honeycomb having a plurality of longitudinally-extending gas flow passages extending from an inlet to an outlet, and/or wherein one or more of the SCR catalyst, the one or more adsorption components, and the oxidation catalyst are disposed on a wall-flow substrate or optionally on a metal substrate with flow-through channels wherein a part of the exhaust gas is in fluid communication between channels.

21. The emission treatment system of claim 1 , further comprising one or more additional SCR catalysts, one or more additional oxidation catalysts, or combinations thereof.

22. The emission treatment system of claim 21 , comprising, in order, beginning with the emission treatment component closest to the engine, one of the following arrangements:

(a) Adsorption component(s), DOC, SCR catalyst, and AMOx;

(b) SCR, Adsorption component(s), DOC, and AMOx;

(c) Adsorption component(s), SCR catalyst, DOC, SCR catalyst, and AMOx;

(d) Adsorption component(s), SCR catalyst, and AMOx;

(e) Adsorption component(s), DOC, and SCR catalyst;

(f) SCR catalyst, AMOx, and adsorption component(s);

(f) SCR catalyst and AMOx; or

(g) DOC and SCR catalyst.

23. The emission treatment system for NO x abatement in an exhaust stream of an ammonia-fueled engine according to claim 1 , further comprising:

one or more adsorption components disposed on a substrate positioned upstream of the SCR catalyst and in fluid communication with the exhaust stream and the SCR catalyst, the adsorption components being chosen from low temperature NO x adsorbers (LT-NA), low temperature ammonia adsorbers (LT-AA), low temperature water vapor adsorbers (LT-WA), and combinations thereof.

24. A method for abating NO x in an exhaust stream from an ammonia-fueled engine, the method comprising contacting the exhaust gas stream with the emission treatment system of claim 1 .