Cerium oxide particles and method for production thereof

Patent metadata

Field	Value
Publication number	US-2019202710-A1
Application number	US-201716302481-A
Country	US
Kind code	A1
Filing date	May 17, 2017
Priority date	May 18, 2016
Publication date	Jul 4, 2019
Grant date	—

Abstract

The present invention relates to cerium oxide particles that have excellent heat resistance and/or pore volume 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 cocatalyst 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

1 . Cerium oxide particles having the following properties:
a specific surface area (SBET) comprised between 45 and 80 m 2 /g, after calcination at 900° C. for 5 hours, under air; and a specific surface area (SBET) comprised between 75 and 90 m 2 /g after calcination at 700° C. for 4 hours, under a gaseous atmosphere containing 10% by volume of O 2 , 10% by volume of H 2 O and the balance of N 2 .

2 . Cerium oxide particles according to claim 1 having the following properties:
a specific surface area (SBET) comprised between 55 and 80 m 2 /g after calcination at 900° C. for 5 hours, under air; and
a specific surface area (SBET) comprised between 75 and 90 m 2 /g after calcination at 700° C. for 4 hours, under a gaseous atmosphere containing 10% by volume of O 2 , 10% by volume of H 2 O and the balance of N 2

3 . Cerium oxide particles according to claim 1 , further comprising at least one metal oxide, other than cerium oxide, the metal being selected from the group consisting of (1) metallic elements in Group 4A in the periodic table, (2) metal elements in Group 4B in the periodic table, such as titanium and zirconium, (3) metal elements in Group 3A in the periodic table, (4) alkali metal elements, and (5) rare earth element (REE) or rare earth metal being selected from the fifteen lanthanides plus scandium and yttrium.

4 . Cerium oxide particles according to claim 1 , further comprising at least one metal oxide, other than cerium oxide, selected from the group consisting of: lanthanium oxide (La 2 O 3 ), praseodymium oxide (Pr 6 O 11 ), neodymium oxide (Nd 2 O 3 ) and yttrium oxide (Y 2 O 3 ).

5 . Cerium oxide particles according to claim 1 exhibiting a specific surface area (SBET) comprised between 30 and 60 m 2 /g after calcination at 900° C. for 24 hours, under air.

6 . Cerium oxide particles according to claim 1 exhibiting a specific surface area (SBET) comprised between 22 and 40 m 2 /g after calcination at 1000° C. for 5 hours, under air.

7 . Cerium oxide particles according to claim 1 exhibiting a total pore volume comprised between 0.8 and 4.0 ml/g after calcination at 400° C. for 10 hours, under air.

8 . Cerium oxide particles according to claim 1 exhibiting a total pore volume comprised between 0.70 and 1.9 ml/g after calcination at 900° C. for 24 hours, under air.

9 . Cerium oxide particles according to claim 1 exhibiting a pore volume of the pores having a pore size in the range of no more than 200 nm comprised between 0.27 and 0.9 ml/g after calcination at 400° C. for 10 hours, under air.

10 . Cerium oxide particles according to claim 1 exhibiting a pore volume of the pores having a pore size in the range of no more than 200 nm comprised between 0.23 and 0.65 ml/g after calcination at 900° C. for 24 hours, under air.

11 . Cerium oxide particles according to claim 1 exhibiting a total pore volume comprised between 1.5 and 4.0 ml/g after calcination at 400° C. for 10 hours, under air.

12 . Cerium oxide particles according to claim 11 exhibiting a total pore volume comprised between 1.5 and 3.8 ml/g after calcination at 900° C. for 24 hours, under air.

13 . Cerium oxide particles according to claim 11 exhibiting a pore volume of the pores having a pore size in the range of no more than 200 nm comprised between 0.3 and 1.5 ml/g after calcination at 400° C. for 10 hours, under air

14 . The cerium oxide particles according to claim 11 exhibiting a pore volume of the pores having a pore size in the range of no more than 200 nm comprised between 0.25 and 1.0 ml/g after calcination at 900° C. for 24 hours, under air.

15 . Cerium oxide particles according to claim 11 exhibiting a specific surface area (SBET) of at least 40 m 2 /g after calcination at 900° C. for 24 hours, under air.

16 . Cerium oxide particles according to claim 11 exhibiting a specific surface area (SBET) of at least 25 m 2 /g after calcination at 1000° C. for 5 hours, under air.

17 . Cerium oxide particles according to claim 1 , exhibiting an amount of NO x adsorbed higher than or equal to 22 μg NO x /g CeO 2 after calcination at 700° C. for 4 hours, under a gaseous atmosphere containing 10% by volume of O 2 , 10% by volume of H 2 O and the balance of N 2 .

18 . A method for preparing cerium oxide particles, the method comprising:
(a) providing a cerium salt solution comprising anions and cations, wherein between 90 and 100 mol % of the cerium cations are tetravalent cerium cations; (b) heating said cerium salt solution at a temperature comprised between 60 and 220° C. in order to obtain a suspension comprising a liquid medium and a precipitate; (c) decreasing the concentration of anions from the cerium salt present in the liquid medium between 10 and 90 mol %, in comparison with said anions comprised in the liquid medium in step (b); (d) heating the suspension obtained in step (c) at a temperature comprised between 100 and 300° C.; (e) optionally cooling the suspension obtained in step (d); (f) bringing said suspension into contact with a basic compound; (g) heating the suspension from step (f) at a temperature comprised between 60 and 300° C.; (h) optionally separating the precipitate from the liquid medium; (i) optionally adding an organic texturing agent to the suspension obtained in step (g) or the precipitate obtained in step (h); (j) optionally separating the precipitate from the liquid medium; and (k) calcining the precipitate obtained at the end of step (g) or obtained at step (h), (i) or (j) to obtain cerium oxide particles; said method comprising at least said step (h) and/or said step (j), wherein trivalent cerium (III) cations must be present in one of the steps before the precipitation step (f).

19 . The method according to claim 18 wherein the decrease of anions concentration in step (c) is obtained by addition of water to the suspension obtained in step (b) or by removing at least a part of the liquid medium from the suspension obtained in step (b) and then adding water to the medium.

20 . The method according to claim 18 , wherein the addition of an organic agent in step (i) is conducted and the organic texturing agent is selected from the group consisting of: anionic surfactants, nonionic surfactants, polyethylene glycols, carboxylic acids and their salts, and surfactants of the carboxymethylated fatty alcohol ethoxylate type.

21 . The method according to claim 18 , wherein the presence of cerium (III) cations is obtained by addition of a cerium (III) salt or by the addition of a reducing agent to reduce a part of the cerium (IV) cations already present.

22 . The method according to claim 21 wherein the source of trivalent cerium (III) cations is selected from the group consisting of nitrate, chloride, hydroxide, carbonate, and sulfate of cerium (III).

23 . The method according to claim 18 , wherein the temperature of heating in step (g) is in the range of from 90 to 200° C.

24 . The method according to claim 18 , wherein the cerium salt solution contains Ce IV , optionally Ce III , H + and NO 3 − .

25 - 27 . (canceled)

28 . A catalyst comprising cerium oxide particles according to claim 1 .

29 . The catalyst according to claim 28 wherein said catalyst is a co-catalyst comprising the cerium oxide particles, for purifying exhaust gas.

30 . A composition comprising cerium oxide particles accordin

Assignees

• Rhodia Operations

Inventors

• Ohtake Naotaka
• Ocampo Fabien
• Jorge Coelho Marques Rui Miguel

Classifications

• B01J37/031 Primary

  Precipitation · CPC title

• B01J37/08

  Heat treatment {(B01J37/0009, B01J37/0018 take precedence)} · CPC title

• C01P2006/16

  Pore diameter · CPC title

• C01P2006/14

  Pore volume · CPC title

• B01D2255/9207

  Specific surface · CPC title