Claims
- 1. Particulates consisting essentially of ceric oxide which have a specific surface of at least 190 m.sup.2 /g, measured after calcination of the ceric oxide for two hours or more at a temperature of from 350.degree. C. to 450.degree. C., and with a specific surface area of at least 15 m.sup.2 /g after calcination of the ceric oxide for two hours or more at a temperature of from 800.degree. C. to 900.degree. C.
- 2. The ceric oxide particulates as defined by claim 1, which have a spacific surface ranging from 190 to 280 m.sup.2 /g, measured after calcination at a temperature of from 350.degree. C. to 450.degree. C.
- 3. The cezic oxide particulates as defined by claim 2, which have a specific surface ranging from 200 to 280 m.sup.2 /g, measured after calcination at a temperature of from 350.degree. C. to 450.degree. C.
- 4. The ceric oxide particulates as defined, by claim 1, which have a specific surface of at least 15 m.sup.2 /g, measured after calcination at a temperature of from 800.degree. C. to 900.degree. C.
- 5. The ceric oxide particulates as defined by claim 4, which have a specific surface ranging from 20 to 100 m.sup.2 /g, measured after calcination at a temperature of 800.degree. C.
- 6. The ceric oxide particulates as defined by claim 1, said particulates retaining a specific surface ranging from 20 to 90 m.sup.2 /g after thermal treatment at a temperature of 800.degree. C.
- 7. The ceric oxide particulates as defined by claim 1, which have a pore volume ranging from 0.15 to 0.30 cm.sup.3 /g, measured after calcination at a temperature of from 350.degree. C. to 450.degree. C.
- 8. The ceric oxide particulates as defined by claim 7, having a mean pore diameter ranging from 2 nm to 10 nm.
- 9. The ceric oxide particulates as defined in claim 1, which have a pore volume ranging from 0.15 to 0.30 cm.sup.3 /g, measured after calcination at a temperature of 800.degree. C.
- 10. The ceric oxide particulates as defined by claim 9, having a mean pore diameter ranging from 10 nm to 20 nm.
- 11. The ceric oxide particulates as defined by claim 1, having a degree of crystallization higher than 80%.
- 12. The ceric oxide particulates as defined by claim 11, having a degree of crystallization higher than 90%.
- 13. Particulates consisting essentially of ceric oxide which have a specific surface of at least 190 m.sup.2 /g, measured after calcination of the ceric oxide for two hours or more at a temperature of from 350.degree. C. to 450.degree. C., and with a specific surface area of at least 15 m.sup.2 /g after calcination of the ceric oxide for two hours or more at a temperature of from 800.degree. C. to 900.degree. C., said ceric oxide particulates being prepared by a process comprising (a) suspending, in an aqueous solution of a decomposable base, a ceric hydroxide of the formula (I):
- Ce(M).sub.x (OH).sub.y (NO.sub.3).sub.z (I)
- wherein M is an alkali metal or a quaternary ammonium radical; x is a number ranging from 0.01 to 0.2; y is such that y=4-z+x; and z is a number ranging from 0.4 to 0.7; (b) heating the resulting suspension in a sealed reaction zone to a temperature and pressure respectively lower than its critical temperature and pressure; (c) cooling it and permitting it to return to atmospheric pressure; (d) separating the ceric hydroxide thus treated; and (e) calcining the separated ceric hydroxide for a time effective to produce a calcined ceric oxide product.
- 14. The ceric oxide particulates as defined by claim 13, which have a specific surface ranging from 190 to 280 m.sup.2 /g, measured after calcination at a temperature of from 350.degree. C. to 450.degree. C.
- 15. The ceric oxide particulates as defined by claim 13, which have a specific surface of at least 15 m.sup.2 /g, measured after calcination at a temperature of from 800.degree. C. to 900.degree. C.
- 16. The ceric oxide particulates as defined by claim 15, which have a specific surface ranging from 20 to 100 m.sup.2 /g, measured after calcination at a temperature of 800.degree. C.
- 17. The ceric oxide particulates as defined by claim 13, wherein said ceric hydroxide of formula (1) is prepared by reacting an aqueous solution of a cerium (IV) salt with a base to attain a degree of neutralization no greater than 3.0, and then heat treating the colloidal dispersion of a cerium (IV) compound thus formed, and separating therefrom the resulting ceric hydroxide precipitate.
- 18. The ceric oxide particulates as defined by claim 13, wherein said decomposable base comprises ammonia, urea, ammonium bicarbonate, ammonium carbonate, a primary, secondary, tertiary or quaternary amine, or mixtures thereof.
- 19. The ceric oxide particulates as defined by claim 13, said aqueous solution of a decomposable base having a concentration ranging from 1 to 10N.
- 20. The ceric oxide particulates as defined by claim 13, said process comprising autoclaving said aqueous suspension at a temperature ranging from 100.degree. to 350.degree. C.
- 21. The ceric oxide particulates as defined by claim 13, wherein the concentration of ceric hydroxide in the aqueous suspension, prior to said heat treatment (b), ranges from 0.1 mole to 4 moles/liter, expressed as CeO.sub.2.
Priority Claims (1)
Number |
Date |
Country |
Kind |
88 17069 |
Dec 1988 |
FRX |
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Parent Case Info
This application is a continuation, of application Ser. No. 08/462,320, filed Jun. 5, 1995, now abandoned which is a continuation of application Ser. No. 08/109,594, filed on Aug. 20, 1993, now abandoned which is a continuation of application Ser. No. 07/920,540, filed on Jul. 28, 1992, now U.S. Pat. No. 5,279,789, which is a continuation of application Ser. No. 07/456,378, filed on Dec. 26, 1989, now abandoned.
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Continuations (4)
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Date |
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462320 |
Jun 1995 |
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109594 |
Aug 1993 |
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920540 |
Jul 1992 |
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456378 |
Dec 1989 |
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