Treatment system for gasoline engine exhaust gas

1. A treatment system for a gasoline engine exhaust gas stream comprising a particulate filter, said particulate filter comprising:

a particulate filter substrate,

an inlet layer disposed on the exhaust gas inlet surface of the filter substrate,

an outlet layer disposed on the exhaust gas outlet surface of the filter substrate, wherein the inlet layer comprises Rh and Pd and the outlet layer comprises Rh, or Rh and a zeolite, and

wherein said system further comprises a three-way conversion (TWC) catalyst and/or an NOx-trap which is in fluid communication with the particular filter.

2. The treatment system according to claim 1 , wherein the outlet layer further comprises Pd.

3. The treatment system according to claim 1 , wherein the zeolite is selected from the group consisting of faujasite, chabazite, clinoptilolite, mordenite, silicalite, zeolite X, zeolite Y, ultrastable zeolite Y, ZSM-5 zeolite, ZSM-12 zeolite, SSZ-3 zeolite, SAPO 5 zeolite, offretite, beta zeolite, and mixtures thereof.

4. The treatment system according to claim 1 , wherein the inlet layer, the outlet layer, or both independently further comprises a metal oxide support material, said support material preferably being selected from the group consisting of alumina, zirconia, zirconia-alumina, baria-alumina, lanthana-alumina, lanthana-zirconia-alumina, and mixtures thereof.

5. The treatment system according to claim 4 , wherein the metal oxide support material comprises gamma-alumina that is doped with a refractory metal, a rare-earth metal, or both.

6. The treatment system according to claim 4 , wherein the metal oxide support is doped with lanthanum, zirconium, or both.

7. The treatment system according to claim 1 , wherein the inlet layer, the outlet layer, or both independently further comprises an oxygen storage component (OSC) selected from the group consisting of zirconia, ceria, baria, lanthana, praseodymia, neodymia, and mixtures thereof.

8. The treatment system according to claim 7 , wherein the OSC comprises a ceria-zirconia composite.

9. The treatment system according to claim 1 , wherein the inlet layer, the outlet layer, or both independently further comprises an NO x -trap component selected from the group consisting of alkali metal oxides, alkaline earth metal oxides, rare-earth metal oxides, and mixtures thereof.

10. The treatment system according to claim 9 , wherein the NO x -trap component comprises barium oxide, strontium oxide, or both.

11. The treatment system according to claim 1 , wherein the particulate filter substrate is a flow-through monolith, preferably a wall-flow filter, wherein the wall-flow filter preferably has a honeycomb structure.

12. The treatment system according to claim 1 , wherein the TWC catalyst is located upstream of the particulate filter.

13. The treatment system according to claim 12 , wherein the TWC catalyst comprises Rh, Pd, or both; a metal oxide support material being selected from the group consisting of alumina, zirconia, zirconia-alumina, baria-alumina, lanthana-alumina, lanthana-zirconia-alumina, and mixtures thereof; and an OSC, being selected from the group consisting of zirconia, ceria, baria, lanthana, praseodymia, neodymia, and mixtures thereof.

14. The treatment system according to claim 1 , wherein the NO x -trap is located upstream of the particulate filter.

15. The treatment system according to claim 14 , wherein the NO x -trap comprises a compound selected from the group consisting of alkali metal-, alkaline earth metal-, rare-earth metal oxides, and mixtures thereof.

16. The treatment system according to claim 15 , wherein the NO x -trap comprises barium oxide, strontium oxide, or both.

17. The treatment system according to claim 1 , said system further comprising:

a gasoline engine, and

an exhaust gas conduit in communication with the engine,

wherein the particulate filter substrate and the TWC catalyst and/or NO x -trap are disposed within the exhaust gas conduit.

18. The treatment system according to claim 17 , wherein the gasoline engine is a gasoline direct injection engine.

19. A method for the treatment of gasoline engine exhaust gas comprising:

(i) providing a treatment system according to claim 1 , and

(ii) conducting a gasoline engine exhaust gas stream through the treatment system.

20. The method according to claim 19 , wherein the exhaust gas stream comprises hydrocarbons (HC), CO, NO x , and soot in an HC:CO:NO x :soot weight ratios of (2.5-7.0):(0.5-3.0):(1.0-4.7):(0.00005-0.01).

21. A treatment system for a gasoline engine exhaust gas stream comprising a particulate filter, said particulate filter comprising:

a particulate filter substrate,

an inlet layer disposed on the exhaust gas inlet surface of the filter substrate, and

an outlet layer disposed on the exhaust gas outlet surface of the filter substrate, wherein the inlet layer comprises Rh, Pd, or both and the outlet layer comprises Rh, Pd, and a zeolite, and

wherein said system further comprises a three-way conversion (TWC) catalyst and/or an NO x -trap which is in fluid communication with the particulate filter.

22. A treatment system for a gasoline engine exhaust gas stream comprising a particulate filter, said particulate filter comprising:

a particulate filter substrate,

an inlet layer disposed on the exhaust gas inlet surface of the filter substrate, and

an outlet layer disposed on the exhaust gas outlet surface of the filter substrate, wherein the inlet layer comprises Rh and Pd and the outlet layer comprises Rh, a zeolite, or both, wherein the inlet layer, the outlet layer or both further comprise Pt, and

wherein said system further comprises a three-way conversion (TWC) catalyst and/or an NO x -trap which is in fluid communication with the particulate filter.