Cerium oxide particles and method for production thereof

Patent metadata

Field	Value
Publication number	US-10160658-B2
Application number	US-201515526610-A
Country	US
Kind code	B2
Filing date	Nov 10, 2015
Priority date	Nov 12, 2014
Publication date	Dec 25, 2018
Grant date	Dec 25, 2018

Abstract

The present invention relates to cerium oxide particles that have excellent heat resistance especially useful for catalysts, functional ceramics, solid electrolyte for fuel cells, polishing, ultraviolet absorbers and the like, and particularly suitable for use as a catalyst or co-catalyst material, for instance in catalysis for purifying vehicle exhaust gas. The present invention also relates to a method for preparing such cerium oxide particles, and a catalyst, such as for purifying exhaust gas, utilizing these cerium oxide particles.

First claim

The invention claimed is:

1. A method for preparing cerium oxide particles, the method comprising:
heating a cerium salt solution at a temperature comprised between 60 and 220° C. to obtain an initial suspension comprising a liquid medium and a precipitate, wherein the cerium salt solution comprises anions and cations and wherein between 90 and 100 mol % of the cations are tetravalent cerium cations;
decreasing the concentration of anions in the initial suspension between 10 and 90 mol %, thus forming a modified suspension;
heating the modified suspension at a temperature comprised between 100 and 300° C., to form a heated suspension;
optionally cooling the heated suspension;
bringing said heated suspension, optionally cooled, into contact with a basic compound, thus forming a basic suspension;
optionally separating a first precipitate from the liquid medium of the basic suspension;
adding an organic texturing agent to the basic suspension, thus forming a textured suspension, or to the first precipitate, thus forming a textured first precipitate;
optionally separating a second precipitate from the liquid medium of the textured suspension; and
calcining the textured first precipitate or the second precipitate to obtain cerium oxide particles;
wherein at least one of the optional separating steps is performed in the method.

2. The method according to claim 1 wherein the cerium salt solution is selected from the group consisting of: cerium nitrate solution, cerium ammonium nitrate solution, cerium sulfate solution and cerium ammonium sulfate solution.

3. The method according to claim 1 wherein the cerium salt solution has a cerium concentration comprised between 5 and 150 g/L in terms of cerium oxide.

4. The method according to claim 1 wherein decreasing the concentration of anions in the initial suspension comprises adding water to the initial suspension.

5. The method according to claim 1 wherein decreasing the concentration of anions in the initial suspension comprises removing at least a part of the liquid medium from the initial suspension and then adding water to the medium.

6. The method according to claim 1 wherein the organic texturing agent is selected from the group consisting of: anionic surfactants, nonionic surfactants, polyethylene glycols, carboxylic acids and their salts, and carboxymethylated fatty alcohol ethoxylate surfactants.

7. Cerium oxide particles having the following properties:
a specific surface area (SBET) comprised between 80 and 120 m 2 /g after calcination at 800° C. for 2 hours, under air;
a specific surface area (SBET) comprised between 55 and 80 m 2 /g after calcination at 900° C. for 5 hours, under air;
a total pore volume comprised between 0.9 and 1.6 ml/g after calcination at 800° C. for 2 hours, under air; and
a total pore volume comprised between 0.85 and 1.5 ml/g after calcination at 900° C. for 5 hours, under air.

8. Cerium oxide particles according to claim 7 wherein said particles have an S1/S2 ratio comprised between 0.5 and 0.7 taken after calcination at 800° C. for 2 hours,
wherein S1 is the area defined by a baseline and a TPR curve in a temperature range of 200 to 600° C. and S2 is the area defined by said baseline and said TPR curve in a temperature range of 600 to 1000° C.,
wherein the baseline is a line segment drawn from a point on the TPR curve corresponding to 200° C., parallel to the temperature axis, up to 1000° C., and
wherein the TPR curve is the result of temperature programmed reduction of said particles using a temperature programmed desorption analyzer with a carrier gas containing 90% argon and 10% hydrogen at a gas flow rate of 30 ml/min and at a heating rate of 13.3° C./min.

9. Cerium oxide particles according to claim 8 wherein said particles have an S1/S2 ratio comprised between 0.3 and 0.5 taken after calcination at 900° C. for 5 hours.

10. Cerium oxide particles according to claim 7 wherein said cerium oxide particles comprise at least one rare earth element oxide, other than cerium oxide.

11. A catalyst comprising at least cerium oxide particles according to claim 7 .

12. The catalyst according to claim 11 wherein said catalyst is a co-catalyst comprising the cerium oxide particles, for purifying exhaust gas.

13. A composition comprising at least cerium oxide particles according to claim 7 .

14. Composition according to claim 13 , wherein said composition is a suspension comprising at least a liquid medium and the cerium oxide particles.

15. A method of removing a portion of a substrate, comprising:
providing at least a composition comprising cerium oxide particles according to claim 7 ,
contacting at least the composition with the substrate to be polished, and
polishing the substrate.

16. Cerium oxide particles according to claim 7 wherein said particles have:
a S1/S2 ratio comprised between 0.5 and 0.7 taken after calcination at 800° C. for 2 hours, and
a S1/S2 ratio comprised between 0.3 and 0.5 taken after calcination at 900° C. for 5 hours,
wherein S1 is the area defined by a baseline and a TPR curve in a temperature range of 200 to 600° C. and S2 is the area defined by said baseline and said TPR curve in a temperature range of 600 to 1000° C.,
wherein the baseline is a line segment drawn from a point on the TPR curve corresponding to 200° C., parallel to the temperature axis, up to 1000° C., and

wherein the TPR curve is the result of temperature programmed reduction of said particles using a temperature programmed desorption analyzer with a carrier gas containing 90% argon and 10% hydrogen at a gas flow rate of 30 ml/min and at a heating rate of 13.3° C./min.

17. Cerium oxide particles according to claim 16 wherein said cerium oxide particles comprise at least one rare earth element oxide, other than cerium oxide.

Assignees

• Rhodia Operations

Inventors

• Ohtake Naotaka
• Okazumi Mitsuhiro
• Ocampo Fabien

Classifications

• B01J20/06 Primary

  comprising oxides or hydroxides of metals not provided for in group B01J20/04 · CPC title

• C01F17/206

  oxide or hydroxide being the only anion · CPC title

• C01P2006/14

  Pore volume · CPC title

• B01J20/28059

  being less than 100 m2/g · CPC title

• B01J20/28069

  Pore volume, e.g. total pore volume, mesopore volume, micropore volume · CPC title