Catalyst and method of preparation

Patent metadata

Field	Value
Publication number	US-10537879-B2
Application number	US-201715468505-A
Country	US
Kind code	B2
Filing date	Mar 24, 2017
Priority date	Mar 4, 2011
Publication date	Jan 21, 2020
Grant date	Jan 21, 2020

Abstract

A method of making a supported catalytic species comprising an alloy of at least two metals, comprises the steps of:
(i) combining a particulate support material, a solution of a first metal compound, a solution of a second metal compound, and a solution of an alkaline precipitating agent to form a slurry mixture; (ii) agitating the resultant mixture; and (iii) contacting the solids with a reducing agent, wherein the first metal in the first metal compound and the second metal in the second metal compound is each independently selected from the group consisting of gold, palladium, platinum, rhodium, iridium, silver, osmium and ruthenium; and wherein the first metal is not the same as the second metal.

First claim

The invention claimed is:

1. A method of making a supported catalytic species comprising an alloy of at least two metals, the method comprising the steps of:
(i) preparing an initial slurry mixture comprising a particulate support material and a solution of a first metal compound, a second metal compound, and an alkaline precipitating agent, wherein the initial slurry mixture has a pH in a range of from 6 to 9; then
(ii) agitating the initial slurry mixture for a time sufficient to form an agitated slurry mixture comprising the particulate support material, comprising hydrolyzed metal solids deposited thereon and formed from the reaction of the alkaline precipitating agent and the first and second metal compounds, and an associated liquid, while maintaining the agitated slurry mixture at a pH in a range of from 6 to 9; and then
(iii) contacting the hydrolyzed metal solids deposited on the particulate support material with a reducing agent to form the supported catalytic species, such that the first and second metals have been reduced to form a first reduced metal and a second reduced metal, respectively, and both are supported on the particulate support material;
wherein the first metal in the first metal compound and the second metal in the second metal compound is each independently gold, palladium, platinum, rhodium, iridium, silver, osmium or ruthenium; and
the first metal is not the same as the second metal.

2. A method according to claim 1 , wherein the first metal is selected from gold, platinum and rhodium and the second metal is palladium.

3. A method according to claim 2 , wherein the first metal is gold and the second metal is palladium.

4. A method according to claim 2 , wherein the first metal is platinum and the second metal is palladium.

5. A method according to claim 1 , wherein the reducing agent comprises hydrazine.

6. The method of claim 1 , wherein at least 80 wt % of the first reduced metal on the particulate support material and at least 80 wt % of the second metal on the particulate support material is in the form of an alloy.

7. The method of claim 3 , wherein 70% or more of the gold and 70% or more of the palladium are present in the form of an alloy of palladium and gold, the average metal crystallite size of the alloy is <15 nm after ageing in air for 48 hours at 750° C. and the catalyst particle contains a total of from 0.1-10% by weight of palladium and gold.

8. A method of preparing a catalyzed substrate, the method comprising the steps of:
(i) preparing a first supported catalytic species according to claim 1 , and further
(ii) separating and washing the first supported catalytic species;
(iii) preparing a washcoat by forming a slurry of the first supported catalytic species; and
(iv) contacting the washcoat with a substrate.

9. A method according to claim 8 which does not include a drying or calcining step between steps (ii) and step (iii).

10. A method according to claim 8 , wherein step (iii) comprises preparing a washcoat by forming a slurry of the first supported catalytic species and one or more second supported catalytic species different from the first supported catalytic species.

11. The method of claim 1 , wherein the particulate metal support comprises alumina, silica, aluminosilicate, titania, zirconia, ceria, carbon or a mixture or a composite thereof.

12. The method of claim 1 , wherein the particulate metal support comprises alumina, silica, zirconia, ceria, or a mixture or a composite thereof.

13. The method of claim 1 , wherein the initial slurry mixture has a solids content of less than 25 wt %.

14. The method of claim 1 , wherein the alkaline precipitating agent comprises a metal carbonate, bicarbonates, or hydroxide.

15. The method of claim 1 , wherein the alkaline precipitating agent is an aqueous solution of potassium carbonate or potassium bicarbonate.

16. The method of claim 1 , wherein the hydrolyzed metal solids are separated from the agitated slurry mixture before contacting with the hydrolyzed metal solids with the reducing agent.

17. The method of claim 1 further comprising drying, calcining, and/or ageing the supported catalytic species.

18. The method of claim 17 , wherein the reduced first and second metals that are supported on the particulate support material are in the form of an alloy.

19. The method of claim 3 , wherein the slurry mixture has an initial pH, before agitating, in a range of from 6 to 7.

20. The method of claim 3 , wherein the agitated slurry of hydrolyzed metal solids is maintained during agitation to have a pH in a range of from 7 and 8.

21. The method of claim 1 , comprising the steps of:
(i) preparing an initial slurry mixture comprising:
(a) a particulate support material comprising alumina, silica-alumina, ceria or ceria-zirconia, and
(b) a solution comprising a gold compound, a palladium compound, and an alkaline precipitating agent comprising potassium carbonate or potassium bicarbonate, the initial slurry mixture having a pH in a range of from 6 to 7; then

(ii) agitating the initial slurry mixture for a time sufficient to form hydrolyzed gold and/or palladium solids deposited on the particulate support material, while maintaining the agitated slurry mixture at a pH in a range of from 7 to 8; then
(iii) optionally separating the particulate support material, comprising the hydrolyzed gold and/or palladium solids deposited thereon and formed from the reaction of the alkaline precipitating agent and the gold and palladium compounds from the agitated slurry mixture; and then
(iii) contacting the hydrolyzed gold and/or palladium solids with hydrazine to form the supported catalytic species.

22. The method of claim 1 , comprising the steps of:
(i) preparing an initial slurry mixture comprising:
(a) a particulate support material comprising alumina, silica-alumina, ceria or ceria-zirconia,
(b) a solution comprising a platinum compound, a palladium compound, and an alkaline precipitating agent comprising potassium carbonate or potassium bicarbonate,

the initial slurry mixture having a pH in a range of from 8 to 9 when the particulate support is alumina; then
(ii) agitating the initial slurry mixture for a time sufficient to form hydrolyzed platinum and/or palladium solids, while maintaining the agitated slurry mixture at a pH in a range of from 7 to 8; then
(iii) optionally separating the particulate support material, comprising the hydrolyzed platinum and/or palladium solids deposited thereon and formed from the reaction of the alkaline precipitating agent and the platinum and palladium compounds from the agitated slurry mixture; and then
(iii) contacting the hydrolyzed platinum and/or palladium solids with hydrazine.

23. The method of claim 21 , wherein the initial slurry mixture has a solids content of less than 25 wt %.

24. The method of claim 22 , wherein the initial slurry mixture has a solids content of less than 25 wt %.

Assignees

• Johnson Matthey Plc

Inventors

• Bergeal David
• Chiffey Andrew Francis
• Johnston Peter
• Moreau Francois
• Phillips Paul Richard

Classifications

• B01J23/42

  Platinum · CPC title

• B01J37/03

  Precipitation; Co-precipitation · CPC title

• B01J23/464

  Rhodium · CPC title

• B22F9/24

  starting from liquid metal compounds, e.g. solutions · CPC title

• B01J37/035 Primary

  Precipitation on carriers · CPC title