US4372924A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Purification of alkali metal hydroxides
Assignee: Dow Chemical Co
•
Filing: 1980-05-27
•
Granted: 1983-02-08
•
Expires: 2000-05-27
Abstract
Abstract A method to purify an aqueous solution of an alkali metal hydroxide by countercurrently contacting the ammonia and hydroxide, in a volume ratio of about 0.6 to 1 to about 1 to 1, in a packed bed. The temperature in the lower portion of an extractor in which the process is carried out is controlled and maintained within a range of at least about 155° to about 170° F.
Inventors
- 👤 David L. Porter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 18:07
CPC Classifications
C; C01; C01D; C01D1/00; C01D1/04; C01D1/28; B; B01; B01J; B01J8/00; B01J8/02; B01J8/04; B01J8/0446; B01J8/0449; B01J8/0453
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
174 words
In a method to purify in liquid phases, an impure alkali metal hydroxide by countercurrently contacting an aqueous solution of the hydroxide with ammonia in a container having a first inlet for the impure hydroxide solution upwardly disposed from a second inlet for the ammonia, a first outlet for the purified hydroxide solution and a second outlet for the ammonia containing impurities extracted from the impure hydroxide solution, the improvement comprising (a) feeding an aqueous solution containing from about 40 to about 60 weight percent alkali metal hydroxide and at least a sodium chloride impurity into the first inlet; (b) feeding sufficient ammonia into the second inlet to provide an ammonia to alkali metal hydroxide volume ratio of about 0.6 to 1 to about 1 to 1; (c) countercurrently flowing the hydroxide and ammonia through a bed of a substantially inert, insoluble particulate material in the container; and (d) controlling the temperature of the purified hydroxide solution in the lower portion of the container within a range of about 155° to about 170° F.
Claim 2
Dependent Claim
174 words
In a method to purify in liquid phases, an impure alkali metal hydroxide by countercurrently contacting an aqueous solution of the hydroxide with ammonia in a container having a first inlet for the impure hydroxide solution upwardly disposed from a second inlet for the ammonia, a first outlet for the purified hydroxide solution and a second outlet for the ammonia containing impurities extracted from the impure hydroxide solution, the improvement comprising (a) feeding an aqueous solution containing from about 40 to about 60 weight percent alkali metal hydroxide and at least a sodium chloride impurity into the first inlet; (b) feeding sufficient ammonia into the second inlet to provide an ammonia to alkali metal hydroxide volume ratio of about 0.6 to 1 to about 1 to 1; (c) countercurrently flowing the hydroxide and ammonia through a bed of a substantially inert, insoluble particulate material in the container; and (d) controlling the temperature of the purified hydroxide solution in the lower portion of the container within a range of about 155° to about 170° F.
Claim 3
Dependent Claim
21 words
The improvement of claim 1 wherein the solution contains about 48 to about 52 weight percent of the alkali metal hydroxide.
Claim 4
Dependent Claim
31 words
The improvement of claim 1 wherein the ammonia fed into the container is at least about 90 weight percent pure and contains less than about 30 parts per million sodium chloride.
Claim 5
Dependent Claim
31 words
The improvement of claim 1 wherein the ammonia fed into the container is at least about 90 weight percent pure and contains less than about 10 parts per million sodium chloride.
Claim 6
Dependent Claim
17 words
The improvement of claims 1, 2, 3 or 4 wherein the alkali metal hydroxide is sodium hydroxide.
Claim 7
Dependent Claim
36 words
The improvement of claim 1 wherein the alkali metal hydroxide is sodium hydroxide containing less than about 1.2 weight percent sodium chloride and the purified hydroxide solution contains less than about 0.006 weight percent sodium chloride.
Claim 8
Dependent Claim
27 words
The improvement of claims 1 or 3 wherein the volume ratio of ammonia to alkali metal hydroxide is about 0.7 to 1 to about 0.8 to 1.
Claim 9
Dependent Claim
23 words
The improvement of claims 1, 3 or 4 wherein the temperature is controlled within the range of about 160° to about 165° F.
Claim 10
Dependent Claim
41 words
The improvement of claims 1, 3 or 4 wherein the temperature is controlled within the range of about 160° to about 165° F. and the ammonia to alkali metal hydroxide ratio is about 0.7 to 1 to about 0.8 to 1.
Claim 11
Dependent Claim
13 words
The improvement of claim 7 wherein the alkali metal hydroxide is sodium hydroxide.
Claim 12
Dependent Claim
13 words
The improvement of claim 8 wherein the alkali metal hydroxide is sodium hydroxide.
Claim 13
Dependent Claim
47 words
The improvement of claim 1 including before step (a), filling the container with ammonia and water to provide a liquid concentration within the container of about 75 weight percent ammonia and about 25 weight percent water and thereafter heating the contents of the container to operating temperature.
Claim 14
Dependent Claim
17 words
The improvement of claims 1, 3, 4 or 12 wherein the temperature is 158° to 167° F.
Claim 15
Dependent Claim
13 words
The improvement of claims 1 or 12 wherein the temperature is 162° F.
Claim 16
Dependent Claim
13 words
The improvement of claim 12 wherein the alkali metal hydroxide is sodium hydroxide.
Claim 17
Dependent Claim
28 words
The improvement of claim 13 wherein the alkali metal hydroxide is sodium hydroxide and the sodium hydroxide solution is agitated as said solution flows through the particulate material.
Claim 18
Dependent Claim
13 words
The improvement of claim 14 wherein the alkali metal hydroxide is sodium hydroxide.
References Cited (Backward Citations)
US2354823A
Cited
US2196594A
Cited
US2196595A
Cited
US2285300A
Cited
US2285299A
Cited
US2325339A
Cited
US2349596A
Cited
US2373257A
Cited
US2622009A
Cited
US2894732A
Cited
US3917811A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-02-07 | 1986-08-09 | 1987-02-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-02-07 | 1990-08-09 | 1991-02-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-02-07 | 1994-08-09 | 1995-02-08 | $7700.00 | Window Closed / Lapsed |