Claims
- 1. A method of making a substantially phase-pure, thermally stable crystalline alumina composition comprising:
- about 85 wt. % to about 99 wt. % alumina;
- about 1 wt. % to about 15 wt. % modifying stabilizer selected from the group consisting of oxides of germanium (Ge), silicon (Si), phosphorus (P), arsenic (As), and mixtures thereof; and
- wherein said composition is substantially phase-pure and is thermally and hydrothermally phase-stable at temperatures up to about 1250.degree. C. and has a characteristic X-ray diffraction pattern which contains at least the following d-spacings and relative intensities:
- ______________________________________ d, .ANG. I/I.sub.0, %______________________________________ 2.770-2.795 15-49 2.712-2.738 15-49 2.580-2.608 15-49 2.440-2.467 31-84 2.295-2.315 15-49 2.268-2.290 15-49 2.148-2.162 0-14 1.979-1.996 50-84 1.941-1.950 31-49 1.400-1.407 50-84 1.388-1.394 85-100______________________________________
- and does not contain a resolved reflection centered at d=1.914 .ANG. or 2.881 .ANG., said method comprising:
- a) forming an aqueous suspension of an alumina precursor selected from the group consisting of boehmite and pseudo-boehmite with a water-soluble precursor of a modifying stabilizer, said stabilizer being selected from a group consisting of the oxides of germanium (Ge), silicon (Si), phosphorus (P), arsenic (As), and mixtures thereof;
- b) separating the water from the product of step (a) in a manner that results in the alumina precursor remaining thoroughly mixed with the modifying stabilizer precursor; and
- c) calcining the product of step (b).
- 2. The method of claim 1 which further comprises hydrothermally treating the product of step (c) by heating said product to a temperature of between about 800.degree. C. and about 1200.degree. C. in an atmosphere comprising between about 5 mol % and 30 mol % water in air and holding it in that temperature range for at least about 1 hour.
- 3. The method of claim 1 wherein SiO.sub.2 is the modifying stabilizer and the modifying-stabilizer precursor is selected from a group consisting of silicic acid, tetra ethyl ortho silicate and any tetra-alkyl ammonium silicate that has a solubility in water greater than about 1.0 wt. %.
- 4. The method of claim 1 wherein GeO.sub.2 is the modifying stabilizer and the modifying-stabilizer precursor is selected from the group consisting of tetraethylorthogermanate and any tetra-alkyl ammonium germanate that has a solubility in water greater than about 1.0 wt. %.
- 5. The method of claim 1 wherein P.sub.2 O.sub.5 is the modifying stabilizer and the modifying-stabilizer precursor is a phosphate.
- 6. The method of claim 1 wherein As.sub.2 O.sub.5 is the modifying stabilizer and the modifying-stabilizer precursor is an arsenate.
- 7. The method of claim 1 wherein a mixture of GeO.sub.2 and SiO.sub.2 is the modifying stabilizer.
- 8. The method of claim 1, wherein the modifying stabilizer is a mixture of GeO.sub.2 and SiO.sub.2, the precursor for GeO.sub.2 is a tetra-alkyl ammonium germanate that has a solubility in water greater than about 1 wt. %, and the precursor for SiO.sub.2 is a tetra methyl ammonium silicate.
- 9. The method of claim 1 wherein a mixture of GeO.sub.2 and P.sub.2 O.sub.5 is the modifying stabilizer.
- 10. The method of claim 1, wherein the modifying stabilizer is a mixture of GeO.sub.2 and P.sub.2 O.sub.5, the precursor for GeO.sub.2 is selected from a group consisting of any tetra-alkyl ammonium germanate that has a solubility in water greater than about 1 wt. %, and the precursor for P.sub.2 O.sub.5 is an ammonium phosphate.
- 11. The method of claim 1 wherein a mixture of P.sub.2 O.sub.5 and SiO.sub.2 is the modifying stabilizer.
- 12. The method of claim 1, wherein the modifying stabilizer is a mixture of P.sub.2 O.sub.5 and SiO.sub.2, the precursor for P.sub.2 O.sub.5 is an ammonium phosphate, and the precursor for SiO.sub.2 is selected from a group consisting of silicic acid and any tetra-alkyl ammonium silicate that has a solubility in water greater than about 1.0 wt. %.
- 13. The method of claim 1 wherein steam evaporation is used to separate the water from the product of step (a).
- 14. A method of making a substantially phase-pure, thermally stable crystalline alumina composition comprising:
- about 85 wt. % to about 99 wt. % alumina;
- about 1 wt. % to about 15 wt. % modifying stabilizer selected from the group consisting of oxides of germanium (Ge), silicon (Si), phosphorus (P), arsenic (As), and mixtures thereof; and
- wherein said composition is substantially phase-pure and is thermally and hydrothermally phase-stable at temperatures up to about 1250.degree. C. and has a characteristic X-ray diffraction pattern which contains at least the following d-spacings and relative intensities:
- ______________________________________ d, .ANG. I/I.sub.0 , %______________________________________ 2.770-2.795 15-49 2.712-2.738 15-49 2.580-2.608 15-49 2.440-2.467 31-84 2.295-2.315 15-49 2.268-2.290 15-49 2.148-2.162 0-14 1.979-1.996 50-84 1.941-1.950 31-49 1.400-1.407 50-84 1.388-1.394 85-100______________________________________
- and does not contain a resolved reflection centered at d=1.914 .ANG. or 2.881 .ANG., said method comprising:
- a) placing a mixture of an alumina precursor selected from the group consisting of boehmite and pseudo-boehmite and enough water to immerse the alumina precursor into an autoclave having a silica-containing glass lining;
- b) holding the mixture at atemperature of at least about 150.degree. C. and a pressure of at least 70 psig for at least two hours or until sufficient silica has leached out of the glass liner to form a stabilizing dopant within the alumina crystalline structure; and
- c) calcining the product of step (b).
- 15. A method of making substantially phase-pure and thermally stable crystalline alumina composition comprising:
- about 85 wt. % to about 99 wt. % alumina;
- about 1 wt. % to about 15 wt. % modifying stabilizer selected from the group consisting of oxides of germanium (Ge), silicon (Si), phosphorus (P), arsenic (As), and mixtures thereof; and
- wherein said composition is substantially phase-pure and is thermally and hydrothermally phase-stable at temperatures up to about 1250.degree. C. and has a characteristic X-ray diffraction pattern which contains at least the following d-spacings and relative intensities:
- ______________________________________ d, .ANG. I/I.sub.0 , %______________________________________ 2.770-2.795 15-49 2.712-2.738 15-49 2.580-2.608 15-49 2.440-2.467 31-84 2.295-2.315 15-49 2.268-2.290 15-49 2.148-2.162 0-14 1.979-1.996 50-84 1.941-1.950 31-49 1.400-1.407 50-84 1.388-1.394 85-100______________________________________
- and does not contain a resolved reflection centered at d=1.914 .ANG. or 2.881 .ANG., said method comprising:
- a) mixing an alumina precursor selected from the group consisting of boehmite and pseudo-boehmite with a modifying-stabilizer reagent enough water to immerse the alumina precursor and modifying-stabilizer reagent, said reagent being selected from a group consisting of silicic acid, and solutions of tetra-alkyl orthosilicate or tetra-alkyl orthogermanate in a solvent that is fully miscible with water;
- b) holding the product of step (a) at a temperature of at least about 150.degree. C. and a pressure of at least 70 psig for at least two hours; and
- c) calcining the product of step (b).
- 16. A catalyst support having a surface area greater than about 25 m.sup.2 /g that is stable against loss of surface area upon repeated and/or prolonged exposure to temperatures in excess of about 1050.degree. C. comprising a shaped body of the stabilized alumina composition made by the method of claim 1 and having an average particle size in the range of about 1 .mu. to about 50 .mu..
- 17. A catalyst support having a surface area greater than about 25 m.sup.2 /g that is stable against loss of surface area upon repeated and/or prolonged exposure to temperatures in excess of about 1050.degree. C. comprising a shaped body of the stabilized alumina composition made by the method of claim 14 and having an average particle size in the range of about 1 .mu. to about 50 .mu..
- 18. A catalyst support having a surface area greater than about 25 m.sup.2 /g that is stable against loss of surface area upon repeated and/or prolonged exposure to temperatures in excess of about 1050.degree. C. comprising a shaped body of the stabilized alumina composition made by the method of claim 15 and having an average particle size in the range of about 1 .mu. to about 50 .mu..
Parent Case Info
This application is a divisional application of application Ser. No. 08/778,668, filed Jan. 3, 1997, U.S. Pat. No. 5,877,106.
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