Claims
- 1. A process for the production of spheroidal alumina shaped articles, which comprises dispersing an ungelled admixture of an alumina sol and hexamethylenetetramine, in the form of droplets, into a liquid forming medium which is but very slightly miscible with water, said medium being at a temperature of between about 50.degree. and 105.degree. C., next aging the alumina spheres thus shaped at a temperature greater than about 105.degree. C. at superatmospheric pressure, then secondarily aging said alumina spheres in a basic medium, and thence washing, drying and calcining said aged alumina spheres.
- 2. The process as defined by claim 1, wherein the alumina sol comprises a salt of the formula Al.sub.2 (OH).sub.6-a X.sub.a in which X is at least one anion selected from the group consisting of F.sup.-, Cl.sup.-, Br.sup.-, I.sup.-, NO.sub.3.sup.- or ClO.sub.4.sup.-.
- 3. The process as defined by claim 1, wherein the alumina sol comprises a salt of formula Al.sub.2 (OH).sub.6-a Cl.sub.a.
- 4. The process as defined by claim 1, wherein the alumina sol comprises from about 5 to 35% by weight of alumina, expressed as Al.sub.2 O.sub.3.
- 5. The process as defined by claim 4, wherein concentration of the alumina is between about 15 and 30% by weight.
- 6. The process as defined by claim 2, wherein the alumina sol displays an atomic ratio of Al/X ranging from 1.33 to 2.67.
- 7. The process as defined by claim 6, wherein the alumina sol displays an atomic ratio of Al/X ranging from 1.60 to 2.20.
- 8. The process as defined by claim 1, wherein the hexamethylenetetramine comprising the admixture is a 15 to 40% by weight concentrated solution.
- 9. The process as defined by claim 8, wherein hexamethylenetetramine solution has a concentration ranging from 30 to 45% by weight.
- 10. The process as defined by claim 1, wherein the admixture comprises a solution of hexamethylenetetramine, the same being mixed with the alumina sol in a volumetric ratio of hexamethylenetetramine/alumina sol ranging from 3:1 to 1:20.
- 11. The process as defined by claim 10, wherein the volumetric ratio is ranging from 1:1 to 1:5.
- 12. The process as defined by claim 10, wherein the concentration of aluminum in the admixture is ranging from about 6 to 12% by weight.
- 13. The process as defined by claim 12, wherein the concentration of aluminum in the admixture is ranging from about 7 to 11% by weight.
- 14. The process as defined by claim 3, wherein the hexamethylenetetramine/chlorine ratio is greater than 0.17.
- 15. The process as defined by claim 14, wherein the hexamethylenetetramine/chlorine ratio is ranging from 0.2 to 0.6.
- 16. The process as defined by claim 1, wherein the temperature of the forming medium is ranging from about 85.degree. to 95.degree. C.
- 17. The process as defined by claim 1, wherein the retention time of the droplets in the forming medium is ranging from 1 to second and 2 hours.
- 18. The process as defined by claim 1, wherein the alumina spheres are aged in a liquid which is but very slightly miscible with water at a temperature ranging from 105.degree. to 260.degree. C.
- 19. The process as defined by claim 18, wherein the spheres are aged at a temperature ranging from 120.degree. to 150.degree. C., under a pressure of from 2 to 10 atmospheres, and for a period of from 1 to 10 hours.
- 20. The process as defined by claim 2, wherein, upon termination of the initial aging step, the degree of neutralization of the acid anions contained in the initial sol is at least 68%.
- 21. The process as defined by claim 20, wherein the degree of neutralization is at least 80%.
- 22. The process as defined by claim 1, wherein the secondary aging of the spheres in the basic medium is performed at a temperature comprised between about 50.degree. and 100.degree. C., for a period of between about 1 and 10 hours, the pH of said basic medium, measured at 25.degree. C., being between about 6 and 11.
- 23. The process as defined by claim 22, wherein the spheres are aged in the basic medium at a temperature of between 70.degree. and 98.degree. C. and at a pH of between 8 and 10.
- 24. The process as defined in claim 1, wherein the basic medium comprises a medium selected from the group consisting of an ammoniacal solution, an amine solution and a sodium hydroxide solution.
- 25. The process as defined by claim 1, wherein the aged spheres are dried at a temperature of between about 90.degree. and 200.degree. C. for about 1 to 24 hours, and then calcined at a temperature of between about 425.degree. and 1000.degree. C. for from about 2 to 10 hours.
- 26. The process as defined by claim 1, wherein at least a portion of the alumina sol comprising the initial admixture has been replaced by a sol of an element selected from the group consisting of the elements of the Groups IB, IIIB, IVB, VB, VIB, IIIA, IVA, VA, VIA and VIII of the Periodic Table.
- 27. The process as defined by claim 1, wherein a salt of a metal selected from the group consisting of the metals of the Groups IB, IIB, IIIB, IVB, VB, IIA, IVA, VA, VIA, VIIA, VIII and VIB of the Periodic Table comprised the initial alumina sol.
- 28. The process as defined by claim 1, the initial alumina sol having admixed therewith a compound of a metal, or a metal itself, selected from the group consisting of the metals of the Groups IB, IIB, IVB, VB, VIIB, IIA, IIIA, IVA, VA, VIA, VIIA, VII or VIB of the Periodic Table.
- 29. The process as defined in claim 1, said forming medium being selected from the group consisting of gasoline, kerosene, dodecylbenzene, alcohol or organic solvent.
- 30. A process for the production of spheroidal alumina shaped articles, which comprises dispersing an ungelled admixture of an alumina sol and hexamethylenetetramine, in the form of droplets, into a liquid forming medium which is but very slightly miscible with water, said medium being at a temperature of between about 50.degree. and 105.degree. C., next aging the alumina spheres thus shaped in a medium having but slight miscibility with water at a temperature in the range of about 120.degree. to 150.degree. C. at superatmospheric pressure so that upon termination of said aging step the degree of neutralization of the acid anions contained in the initial sol is at least 68%, then secondarily aging said alumina spheres in a basic medium, and thence washing, drying and calcining said aged alumina spheres.
Priority Claims (1)
Number |
Date |
Country |
Kind |
77 23880 |
Aug 1977 |
FRX |
|
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of our copending application Ser. No. 929,772, filed July 31, 1978, now abandoned hereby expressly incorporated by reference in its entirety and relied upon.
US Referenced Citations (3)
Foreign Referenced Citations (2)
Number |
Date |
Country |
1042771 |
Nov 1953 |
FRX |
739396 |
Oct 1955 |
GBX |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
929772 |
Jul 1978 |
|