Claims
- 1. A ceric oxide which after calcination at a temperature in the range of from 350.degree. to 550+ C. has a specific surface of at least 85 m.sup.2 /g, a pore volume of at least 0.15 cm.sup.3 /g, and a median pore diameter greater than 50 .ANG..
- 2. The ceric oxide of claim 1, wherein the specific surface is at least 100 m.sup.2 /g after calcination at a temperature in the range of from 350.degree. to 500.degree. C.
- 3. The ceric oxide of claim 1, having a pore volume in the range of from 0.15 to 0.3 cm.sup.3 /g.
- 4. The ceric oxide of claim 1, having a purity greater than 99%.
- 5. The ceric oxide of claim 1, wherein the pore volume is greater than 0.15 cm.sup.3 /g, the median diameter of the pores is between 50 and 200 .ANG., and the ceric oxide has a monomodal pore distribution.
- 6. The ceric oxide of claim 5, having a specific surface of 100 to 150 m.sup.2 /g after calcination at a temperature in the range of from 350.degree. to 500.degree. C.
- 7. The ceric oxide of claim 6, having a specific surface of 100 to 150 m.sup.2 /g after calcination at a temperature in the range of from 400.degree. to 450.degree. C.
- 8. The ceric oxide of claim 5, wherein the median pore diameter is in the range of from 80 to 150 .ANG..
- 9. The ceric oxide of claim 5, having a uniform pore distribution, with the standard deviations el and e.sub.2 being in the range of from 1.0 to 2.0.
- 10. The ceric oxide of claim 1, having a dual population pore distribution, with the median diameter of the micropores being in the range of from 10 to 50 .ANG. and the median diameter of the mesopores being in the range of from 50 to 200 .ANG..
- 11. The ceric oxide of claim 10, wherein the specific surface is in the range of from 150 to 180 m.sup.2 /g after calcination at a temperature in the range of from 350.degree. to 500.degree. C.
- 12. The ceric oxide of claim 11, wherein the specific surface is in the range of from 150 to 180 m.sup.2 /g after calcination at a temperature in the range of from 400.degree. to 450.degree. C.
- 13. A process for the preparation of the ceric oxide of claim 1 and for calcining the ceric oxide, wherein the process comprises (i) destabilizing an aqueous colloidal dispersion of a cerium (IV) compound by combination with a base, (ii) separating the precipitate which results, (iii) drying the ceric oxide by subjecting it to a heat treatment, and (iv) calcining the ceric oxide.
- 14. The process of claim 13, wherein the aqueous colloidal dispersion of the cerium (IV) compound employed has the general Formula (I):
- Ce (M).sub.z (OH).sub.x (NO.sub.3).sub.y, pCeO.sub.2, nH.sub.2 O(I)
- wherein:
- M represents an alkaline metal or a quaternary ammonium radical;
- z ranges from 0 to 0.2;
- y ranges from 0 to 1.5;
- x is such that x=4-y+z;
- p ranges from 0 to 2.0; and
- n ranges from 0 to about 20.
- 15. The process of claim 14, wherein the concentration of the cerium (IV) compound in the colloidal dispersion is in the range of from 0.1 to 2.0 mole/liter.
- 16. The process of claim 15, wherein the concentration of the cerium (IV) compound in the colloidal dispersion is in the range of from 0.5 to 1 mole/liter.
- 17. The process of claim 14, wherein the proportion of cerium in colloidal form in said dispersion ranges from 99 to 100%.
- 18. The process of claim 14, wherein the colloids of the colloidal dispersion have a median hydrodynamic diameter ranging from 100 to 2,000 .ANG..
- 19. The process of claim 13, wherein the normality of the basic solution employed ranges from 0.1 to 11N.
- 20. The process of claim 19, wherein said normality range from 5 to 10N.
- 21. The process of claim 13, wherein the quantity of the base employed is such that the final pH of the dispersion is greater than 7.
- 22. The process of claim 21, wherein the final pH of the dispersion is greater than or equal to 9 and less than or equal to 10.
- 23. The process of claim 13, wherein the base is added to the aqueous colloidal dispersion of the cerium (IV) compound.
- 24. The process of claim 13, wherein the aqueous colloidal dispersion of the cerium (IV) compound is added to the base.
- 25. The process of claim 13, wherein the rate of addition of the base to the aqueous colloidal dispersion of the cerium (IV) compound ranges from 0.1 to 5 moles of OH.sup.- per mole of cerium (IV) per hour.
- 26. The process of claim 13, wherein the temperature of the mixture of the base and dispersion ranges from ambient temperature to about 60.degree. C.
- 27. The process of claim 13, wherein the reaction medium is further maintained under agitation for a period of time ranging from 1 minute to 24 hours.
- 28. The process of claim 13, wherein the separation is carried out by filtration, decantation, centrifugation or drainage.
- 29. The process of claim 13, wherein the precipitate is washed with water or an organic solvent.
- 30. The process of claim 13, wherein the heat treatment is carried out in air or under reduced pressure on the order of 1 to 100 mm mercury, at a temperature ranging from ambient to 100.degree. C., and for a period of time ranging from 2 to 48 hours.
- 31. A process for the preparation of a calcined ceric oxide comprising calcining the product produced by the process of claim 13 at a temperature ranging from 300.degree. to 800.degree. C. for a period of time ranging from 30 minutes to 10 hours.
- 32. The process of claim 31, wherein the calcination temperature ranges from 350.degree. to 450.degree. C.
- 33. The process of claim 31, wherein the duration of the calcination ranges from 4 to 8 hours.
- 34. A process for the preparation of the ceric oxide of claim 5, the process comprising (i) destabilizing an aqueous colloidal dispersion of a cerium (IV) compound by the addition of base thereto, (ii) separating the precipitate resulting therefrom, and (iii) calcining the separated precipitate, with said dispersion having been dispersed by a suspension in water of a cerium (IV) compound of the general Formula (II):
- Ce (OH).sub.x (NO.sub.3).sub.y, pCeO.sub.2, nH.sub.2 O (II)
- wherein:
- x is such that x=4-y;
- y ranges from 0.35 to 1.5;
- p is greater than or equal to 0 and less than or equal to 2.0; and
- n is greater than or equal to 0 and less than or equal to about 20;
- with the cerium (IV) compound having been prepared by a process which comprises (i) hydrolyzing an aqueous solution of a cerium (IV) salt in an acid medium wherein the molar ratio [H.sup.+ ]/[Ce.sup.IV eq.] is greater than or equal to 0 and less than or equal to 3; and (ii) separating the precipitate resulting therefrom.
- 35. The process of claim 34, wherein the cerium (IV) compound is obtained by a process which further comprises (iii) drying the precipitate by heat treating the separated precipitate.
- 36. The process of claim 34, wherein the hydrolysis (i), the mixing of the solution of the cerium (IV) salt and the hydrolysis medium is carried out simultaneously and continuously, the mixture is heated continuously to a temperature effective for hydrolysis, and the molar ratio [H.sup.+ ]/[Ce.sup.IV eq.] is greater than or equal to 0 and less than or equal to 3.
- 37. The process of claim 34, wherein the molar ratio [H.sup.+ ]/[Ce.sup.IV eq.] ranges from 0 to about 2.0.
- 38. The process of claim 34, wherein the hydrolysis (i), the solution of the cerium (IV) salt and the hydrolysis medium are initially mixed together under agitation and then heated to a temperature effective for hydrolysis, with the molar ratio [H.sup.+ ]/[Ce.sup.IV eq.] being greater than 0.75 and less than or equal to 3, regardless of the final concentration of cerium (IV), or the molar ratio of [H.sup.+ ]/[Ce.sup.IV eq.] is greater than or equal to 0 and less than or equal to 0.75 if the final equivalent concentration of cerium (IV) is greater than or equal to 0.4 mole/liter.
- 39. A process for the preparation of the ceric oxide of claim 10, the process comprising (i) destabilizing an aqueous colloidal dispersion of the cerium (IV) compound by the addition of a base thereto, (ii) separating the precipitate resulting therefrom, and (iii) calcining the separated precipitate, with the dispersion being prepared by a suspension in water of a cerium (IV) compound of the general Formula (II):
- Ce (OH).sub.x (NO.sub.3).sub.y pCeO.sub.2, nH.sub.2 O (II)
- wherein:
- x is such that x=4-y;
- y ranges from 0.35 to 1.5;
- p is greater than or equal to 0 and less than equal to 2.0; and
- n is greater than or equal to 0 and less than or equal to about 20;
- with the cerium (IV) compound having been prepared by a process which comprises (i) hydrolyzing an aqueous solution of a cerium (IV) salt in an acid medium, with the solution of the cerium (IV) salt and the hydrolysis medium being mixed under agitation and then heated to the reaction temperature, with the molar ratio [H.sup.+ ]/[Ce.sup.IV eq.] being greater than or equal to 0 and less than o equal to 0.75 and the final equivalent concentration of cerium (IV) being less than 0.4 mole/liter, and (ii) separating the precipitate resulting therefrom.
- 40. The process of claim 39, wherein the precipitate separated in (ii) is subjected to a heat treatment to dry the precipitate.
- 41. The process of claim 39, wherein the proportion of the aqueous solution of cerium (IV) salt and the hydrolysis medium is such that the final equivalent concentration of cerium (IV) ranges from 0.2 to 0.4 mole/liter.
- 42. The process of claim 34, wherein the aqueous solution of the cerium (IV) salt is an aqueous solution of ceric nitrate.
- 43. The process of claim 39, wherein the aqueous solution of the cerium (IV) salt is an aqueous solution of ceric nitrate.
- 44. The process of claim 34, wherein the acidity is introduced with nitric acid.
- 45. The process of claim 34, wherein the temperature of the hydrolysis medium ranges from about 70.degree. to about 120.degree. C.
- 46. The process of claim 39, wherein the temperature of the hydrolysis medium ranges from about 70.degree. to about 120.degree. C.
- 47. The process of claim 42, wherein the precipitate obtained after hydrolysis is separated and dried at a in the rang from 15.degree. C. to 100.degree. C.
- 48. The process of claim 47, wherein the temperature ranges from ambient temperature to about 50.degree. C.
- 49. A calcined ceric oxide having a specific surface of at least 85 m.sup.2 /g, a pore volume of at least 0.15 cm.sup.3 /g, and a median pore diameter greater than 50 .ANG..
Priority Claims (1)
Number |
Date |
Country |
Kind |
86 04347 |
Mar 1986 |
FRX |
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Parent Case Info
This application is a continuation of application Ser. No. 07/030,135, filed Mar. 26, 1987, now abandoned.
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Date |
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3761571 |
Woodhead |
Sep 1973 |
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4661330 |
Chane-Ching et al. |
Apr 1987 |
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4663137 |
Chane-Ching et al. |
May 1987 |
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4859432 |
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Aug 1989 |
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Foreign Referenced Citations (2)
Number |
Date |
Country |
2559755 |
Aug 1985 |
FRX |
145853 |
Jan 1981 |
DDX |
Non-Patent Literature Citations (1)
Entry |
Chemical Abstracts, vol. 96, 1961, 95:189463d, "Cerium Dioxide". |
Continuations (1)
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Number |
Date |
Country |
Parent |
30135 |
Mar 1987 |
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