US4562059A
Expired / Lapsed
US
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Method of preparing alumina
Assignee: Chiyoda Corp
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Filing: 1984-06-08
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Granted: 1985-12-31
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Expires: 2004-06-08
Abstract
Abstract An improved method of preparing alumina, including a first stage in which an alumina hydrogel is formed from seed aluminum hydroxide, and a second stage in which the alumina hydrogel is processed for conversion into alumina. The improvement is in the first stage, comprising the steps of: (a) providing an aqueous slurry containing seed aluminum hydroxide and (b) mixing a pH controlling agent with the aqueous slurry to adjust the pH of the aqueous slurry to a value less than 5 or more than 11 and to dissolve fine crystallites of aluminum hydroxide contained in the aqueous slurry, the pH controlling agent being substantially free of ions which can form a precipitate during the first step, and then (c) then mixing an alumina compound with the aqueous slurry to adjust the pH of the aqueous slurry to a value in the range of from 6 to 11 and to cause the seed aluminum hydroxide to grow, the steps (b) and (c) being repeated in sequence more than once so that the seed aluminum hydroxide is caused to grow into the alumina hydrogel.
Inventors
- 👤 Sachio Asaoka
- 👤 Takashi Sendo
- 👤 Munekazu Nakamura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 13:50
CPC Classifications
B; B82; B82Y; B82Y30/00; C; C01; C01F; C01F7/00; C01F7/02; C01F7/34; C01F7/04; C01F7/14; C01F7/141; C01P; C01P2004/00; C01P2004/60; C01P2004/64; C01P2006/00; C01P2006/14; C01P2006/16
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
175 words
In a method of preparing alumina, including forming an alumina hydrogel from seed aluminum hydroxide, and processing the alumina hydrogel for conversion into alumina, the improvement comprising the alumina hydrogel forming stage which comprises the steps of: (a) providing an aqueous slurry containing seed aluminum hydroxide, (b) mixing a pH controlling agent with the aqueous slurry to adjust the pH of the aqueous slurry to a value less than 5 or more than 11 and to dissolve fine crystallites of aluminum hydroxide contained in the aqueous slurry, said pH controlling agent being substantially free of aluminum salts, aluminates or ions which can form a precipitate during the alumina hydrogel forming stage, and (c) then mixing an aluminum compound with the aqueous slurry to adjust the pH of the aqueous slurry to value in the range of from 6 to 11 and to cause the seed aluminum hydroxide to grow, the steps (b) and (c) being repeated in sequence more than once so that the seed aluminum hydroxide is caused to grow into the alumina hydrogel.
Claim 2
Dependent Claim
175 words
In a method of preparing alumina, including forming an alumina hydrogel from seed aluminum hydroxide, and processing the alumina hydrogel for conversion into alumina, the improvement comprising the alumina hydrogel forming stage which comprises the steps of: (a) providing an aqueous slurry containing seed aluminum hydroxide, (b) mixing a pH controlling agent with the aqueous slurry to adjust the pH of the aqueous slurry to a value less than 5 or more than 11 and to dissolve fine crystallites of aluminum hydroxide contained in the aqueous slurry, said pH controlling agent being substantially free of aluminum salts, aluminates or ions which can form a precipitate during the alumina hydrogel forming stage, and (c) then mixing an aluminum compound with the aqueous slurry to adjust the pH of the aqueous slurry to value in the range of from 6 to 11 and to cause the seed aluminum hydroxide to grow, the steps (b) and (c) being repeated in sequence more than once so that the seed aluminum hydroxide is caused to grow into the alumina hydrogel.
Claim 3
Dependent Claim
23 words
A method as claimed in claim 1, wherein the alumina hydrogel forming step is performed at a temperature of at least 50° C.
Claim 4
Dependent Claim
19 words
A method as claimed in claim 1, wherein the steps (b) and (c) is conducted while agitating the slurry.
Claim 5
Dependent Claim
20 words
A method as claimed in claim 1, wherein the pH-control ling agent is sulfuric acid, nitric acid or hydrochloric acid.
Claim 6
Dependent Claim
14 words
A method as claimed in claim 4, wherein the aluminum compound is an aluminate.
Claim 7
Dependent Claim
24 words
A method as claimed in claim 5, wherein the pH-controlling agent is nitric acid and the aluminum compound is sodium aluminate or potassium aluminate.
Claim 8
Dependent Claim
17 words
A method as claimed in claim 1, wherein the pH-controlling agent is sodium hydroxide or potassium hydroxide.
Claim 9
Dependent Claim
15 words
A method as claimed in claim 7, wherein the aluminum compound is an aluminum salt.
Claim 10
Dependent Claim
19 words
A method as claimed in claim 8, wherein the aluminum salt is aluminum sulfate, aluminum nitrate or aluminum chloride.
Claim 11
Dependent Claim
27 words
A method as claimed in claim 1, wherein the step (a) includes mixing an aqueous solution containing aluminum sulfate with an aqueous solution of containing sodium aluminate.
Claim 12
Dependent Claim
21 words
A method as claimed in claim 1, wherein the pH-controlling agent is nitric acid and the aluminum compound is sodium aluminate.
References Cited (Backward Citations)
US4248852A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-12-30 | 1989-07-01 | 1989-12-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-12-30 | 1993-07-01 | 1993-12-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-12-30 | 1997-07-01 | 1997-12-31 | $7700.00 | Window Closed / Lapsed |