Zirconia-based compositions for use in passive NOx adsorber devices

Patent metadata

Field	Value
Publication number	US-10500562-B2
Application number	US-201815945770-A
Country	US
Kind code	B2
Filing date	Apr 5, 2018
Priority date	Apr 5, 2018
Publication date	Dec 10, 2019
Grant date	Dec 10, 2019

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.

First claim

What is claimed is:

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 μmol/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 μmol/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 μmol/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 μmol/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 μmol/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 μmol/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 (NO 2 ), 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.

Assignees

• Magnesium Elektron Ltd
• Univ Kentucky Res Found

Inventors

• Harris Deborah Jayne
• Scapens David Alastair
• Darab John G
• Crocker Mark
• Ji Yaying

Classifications

• B01D2255/1021

  Platinum · CPC title

• B01D2255/2073

  Manganese · CPC title

• B01J20/0225 Primary

  Compounds of Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt · CPC title

• B01D2255/407

  Zr-Ce mixed oxides · CPC title

• B01D2255/20738

  Iron · CPC title