NOx storage catalyst with improved hydrothermal stability and NOx conversion

Patent metadata

Field	Value
Publication number	US-9610564-B2
Application number	US-201414204386-A
Country	US
Kind code	B2
Filing date	Mar 11, 2014
Priority date	Mar 13, 2013
Publication date	Apr 4, 2017
Grant date	Apr 4, 2017

Abstract

A lean NO x trap for the treatment of exhaust gas emissions, such as the oxidation of unburned hydrocarbons (HC), and carbon monoxide (CO), and the trapping and reduction of nitrogen oxides (NO x ) is disclosed. Nitrogen oxide storage catalysts can comprise a layer on a substrate including ceria-alumina particles having a ceria phase present in a weight percent of the composite in the range of about 20% to about 80% on an oxide basis, an alkaline earth metal component supported on the ceria-alumina particles, wherein the CeO 2 is present in the form of crystallites that are hydrothermally stable and have an average crystallite size less than 130 Å after aging at 950° C. for 5 hours in 2% O 2 and 10% steam in N 2 .

First claim

What is claimed is:

1. A nitrogen oxide storage catalyst comprising:
a layer on a substrate including ceria-alumina composite particles having a ceria phase present in a weight percent of the composite particles in the range of about 20% to about 80% on an oxide basis, a barium component supported on at least a portion of the ceria-alumina composite particles, wherein the CeO 2 is present in the form of crystallites that are hydrothermally stable and have an average crystallite size of less than 130 Å after aging at 950° C. for 5 hours in 2% O 2 and 10% steam in N 2 , the layer comprises a first washcoat layer on the substrate and a second washcoat layer on the first washcoat layer, wherein the second washcoat layer is substantially free of alkaline earth metal.

2. The nitrogen oxide storage catalyst of claim 1 , further comprising at least one platinum group metal selected from the group consisting of platinum, palladium, rhodium, iridium, and mixtures thereof, supported on the ceria-alumina composite particles.

3. The nitrogen oxide storage catalyst of claim 2 , wherein the platinum group metal is selected from platinum, palladium, rhodium, and mixtures thereof.

4. The nitrogen oxide storage catalyst of claim 1 , wherein the barium component is present in an amount in the range of about 5% to 30% by weight on an oxide basis of the first washcoat layer.

5. The nitrogen oxide storage catalyst of claim 1 , wherein the first washcoat layer comprises
ceria-alumina composite particles having the barium component supported thereon and
the second washcoat layer comprises ceria-alumina composite particles substantially free of the barium component.

6. The nitrogen oxide storage catalyst of claim 5 , wherein the barium component is present in an amount of in the range of about 5% to 30% by weight on an oxide basis of the first washcoat layer.

7. The nitrogen oxide storage catalyst of claim 5 , wherein the first washcoat layer is disposed on a honeycomb substrate.

8. The nitrogen oxide storage catalyst of claim 5 , wherein the composite particles of CeO 2 and Al 2 O 3 contains ceria in an amount in the range of about 30 to 70% by weight on an oxide basis.

9. The nitrogen oxide storage catalyst of claim 5 , wherein the composite particles of CeO 2 and Al 2 O 3 in the second washcoat layer contains ceria in an amount in the range of about 30 to 60% by weight on an oxide basis.

10. The nitrogen oxide storage catalyst of claim 5 , wherein the first washcoat layer and second washcoat layer further comprise at least one platinum group metal selected from the group consisting of platinum, palladium, rhodium, iridium and mixtures thereof, supported on the ceria-alumina particles.

11. The nitrogen oxide storage catalyst of claim 10 , wherein the platinum group metal in the second washcoat layer is selected from platinum, rhodium, and mixtures thereof.

12. The nitrogen oxide storage catalyst of claim 10 , wherein the platinum group metal in the first washcoat layer consists essentially of platinum and palladium.

13. The nitrogen oxide storage catalyst of claim 10 , wherein the platinum group metal in the first washcoat layer consists essentially of platinum.

14. The nitrogen oxide storage catalyst of claim 10 , wherein the platinum group metal in the first washcoat layer is selected from platinum, palladium, and mixtures thereof.

15. The nitrogen oxide storage catalyst of claim 14 , wherein the platinum group metal in the second washcoat layer consists essentially of platinum and rhodium.

16. The nitrogen oxide storage catalyst of claim 14 , wherein the platinum group metal in the second washcoat layer consists essentially of rhodium.

17. A system comprising the nitrogen oxide storage catalyst of claim 1 and a lean burn engine upstream from the nitrogen oxide storage catalyst.

18. The system of claim 17 further comprising a catalyst and, optionally, a particulate filter.

19. The system of claim 18 , wherein the catalyst is selected from a TWC catalyst, SCR catalyst, and diesel oxidation catalyst.

20. The nitrogen oxide storage catalyst of claim 1 , wherein the barium component is selected from the group consisting of barium oxide and barium carbonate.

Assignees

• Basf Corp

Inventors

• Xue Wen-Mei
• Wei Xinyi
• Hilgendorff Marcus
• Burk Patrick

Classifications

• B01J35/77

  Compounds characterised by their crystallite size · CPC title

• B01J35/45

  Nanoparticles · CPC title

• B01J35/70

  characterised by their crystalline properties, e.g. semi-crystalline (catalysts comprising carbon B01J21/18; molecular sieves B01J29/00) · CPC title

• B01D53/9422

  for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR) · CPC title

• B01D2255/102

  Platinum group metals · CPC title