Zirconia-based compositions for use in passive NOx adsorber devices

• US 10,500,562 B2
• Filed: 04/05/2018
• Issued: 12/10/2019
• Est. Priority Date: 04/05/2018
• Status: Active Grant

• Current Assignee: Magnesium Elektron Limited (Luxfer Holdings PLC), University Of Kentucky Research Foundation (University of Kentucky)
• Original Assignee: Magnesium Elektron Limited (Luxfer Holdings PLC)
• Inventors: Harris, Deborah Jayne, Scapens, David Alastair, Darab, John G., Crocker, Mark, Ji, Yaying
• Primary Examiner(s): Vanoy, Timothy C
• Application Number:
  US15/945,770
• Publication Number:
  US 20190308164A1
• Time in Patent Office: 614 Days
• CPC Class Codes: B01D 2253/1122 Metals
• CPC Class Codes: B01D 2253/25 Coated, impregnated or composite adsorbents
• CPC Class Codes: B01D 2255/1021 Platinum
• CPC Class Codes: B01D 2255/1023 Palladium
• CPC Class Codes: B01D 2255/2065 Cerium
• CPC Class Codes: B01D 2255/2066 Praseodymium
• CPC Class Codes: B01D 2255/20715 Zirconium
• CPC Class Codes: B01D 2255/2073 Manganese
• CPC Class Codes: B01D 2255/20738 Iron
• CPC Class Codes: B01D 2255/20776 Tungsten
• CPC Class Codes: B01D 2255/30 Silica
• CPC Class Codes: B01D 2255/407 Zr-Ce mixed oxides
• CPC Class Codes: B01D 2255/91 NOx-storage component incorporated in the catalyst
• CPC Class Codes: B01D 2257/404 Nitrogen oxides other than dinitrogen oxide
• CPC Class Codes: B01D 53/04 with stationary adsorbents B01D53/025 takes precedence
• CPC Class Codes: B01D 53/9413 Processes characterised by a specific catalyst
• CPC Class Codes: B01D 53/9418 for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
• CPC Class Codes: B01D 53/9422 for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)
• CPC Class Codes: B01D 53/9481 Catalyst preceded by an adsorption device without catalytic function for temporary storage of contaminants, e.g. during cold start
• CPC Class Codes: B01J 20/0225 Compounds of Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt
• CPC Class Codes: B01J 20/06 : comprising oxides or hydroxides of metals not provided for in group B01J20/04
• CPC Class Codes: B01J 20/3204 : Inorganic carriers, supports or substrates
• CPC Class Codes: B01J 20/3214 : characterised by the method for obtaining this coating or impregnating
• CPC Class Codes: B01J 20/3236 : containing metal, other than zeolites, e.g. oxides, hydroxides, sulphides or salts

Abstract

A passive NO_X adsorbent includes: palladium, platinum or a mixture thereof and a mixed or composite oxide including the following elements in percentage by weight, expressed in terms of oxide: 10-90% by weight zirconium and 0.1-50% by weight of least one of the following: a transition metal or a lanthanide series element other than Ce.

Although the passive NO_X adsorbent can include Ce in an amount ranging from 0.1 to 20% by weight expressed in terms of oxide, advantages are obtained particularly in the case of low-Ce or a substantially Ce-free passive NOx adsorbent.

Claims

1. A passive NO_X adsorbent comprising:

palladium, platinum or a mixture thereof and a mixed or composite oxide comprising the following elements in percentage by weight, expressed in terms of oxide;

10-90% by weight zirconium; and

0.1-50% by weight of least one of the following;

a lanthanide series element other than Ce, comprising Pr; and

a transition metal comprising at least one of the following metals selected from W, Mn, and Fe.

2. A passive NOx adsorbent according to claim 1 further comprising at least one of Y, La and Nd as said lanthanide series element other than Ce.

3. A passive NOx adsorbent according to claim 1, comprising Mn as said transition metal in an amount of 0.1 to 20% by weight and Pr as said lanthanide series element other than Ce in an amount of 0.5 to 30% by weight, wherein a total amount of Pr and Mn is not more than 50% by weight.

4. A passive NOx adsorbent according to claim 3 further comprising at least one of W and Fe as said transition metal.

5. A passive NOx adsorbent according to claim 3 further including at least one of Y, La and Nd as said lanthanide series element other than Ce.

6. A passive NOx adsorbent according to claim 3 further comprising an element from Group 14 of the Periodic Table in an amount ranging from 0.1 to 20% by weight expressed in terms of oxide.

7. A passive NOx adsorbent according to claim 1 comprising Ce in an amount ranging from 0.1% to not more than 20% by weight expressed in terms of oxide.

8. A passive NOx adsorbent according to claim 1 comprising Ce in an amount ranging from 0.5 to not more than 5% by weight expressed in terms of oxide.

9. A passive NOx adsorbent according to claim 1 with the proviso that the passive NOx adsorbent is substantially free of Ce.

10. A passive NOx adsorbent according to claim 1 with a minimum fresh NOx storage capacity of 7.5 μ

mol/g after 5 minutes at 120°

C.

11. A passive NOx adsorbent according to claim 1 with a minimum aged NOx storage capacity of 5 μ

mol/g after 5 minutes at 120°

C.

12. A passive NOx adsorbent according to claim 1 in which the mixed or composite oxide includes Mn as said at least one transition metal and optional Ce, with a minimum fresh NOx storage capacity of at least 40 μ

mol/g after 5 minutes at 120°

C.

13. A passive NOx adsorbent according to claim 1 in which the mixed or composite oxide includes Mn as said at least one transition metal and optional Ce, with a minimum aged NOx storage capacity of at least 19 μ

mol/g after 5 minutes at 120°

C.

14. A passive NOx adsorbent according to claim 1 in which the mixed or composite oxide includes Mn as said at least one transition metal, with a minimum fresh NOx storage capacity of at least 50 μ

mol/g after 5 minutes at 120°

C.

15. A passive NOx adsorbent according to claim 1 in which the mixed or composite oxide includes Mn as said at least one transition metal, with a minimum aged NOx storage capacity of at least 45 μ

mol/g after 5 minutes at 120°

C.

16. A passive NOx adsorbent according to claim 1 in combination with a Selective Catalytic Reduction catalyst.

17. A monolithic substrate supporting a washcoat, said washcoat comprising said passive NOx adsorbent according to claim 1.

18. A method for reducing nitrogen oxides (NOx) present in a lean gas stream comprising at least one of nitric oxide (NO) and nitrogen dioxide (NO₂), comprising the steps of:

(i) providing the passive NOx adsorbent according to claim 1 in the lean gas stream;

(ii) adsorbing NOx from the lean gas stream on or in the passive NOx adsorbent at a temperature below 200°

C.;

(iii) thermally net desorbing NO_X from the passive NOx adsorbent in the lean gas stream at 200°

C. and above;

(iv) catalytically reducing the NO_X on a downstream catalyst situated downstream of the passive NO_X adsorbent, with at least one of the following reductants;

a nitrogenous reductant, a hydrocarbon reductant, hydrogen and a mixture thereof.

19. A method according to claim 18 wherein the lean gas stream emanates from a gasoline fueled or diesel fueled engine.