US4676971A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for removing chlorate from alkali metal hydroxide
Assignee: PPG Industries Inc
•
Filing: 1985-12-24
•
Granted: 1987-06-30
•
Expires: 2005-12-24
Abstract
Abstract A method is disclosed for reducing alkali metal chlorate impurities in an aqueous alkali metal hydroxide solution by heating a mixture of the alkali metal hydroxide solution with a hydroxycarboxylic acid or a salt thereof at temperature above about 125° C. and for a period of time sufficient to substantially eliminate the chlorate, the hydroxycarboxylic acid or salt thereof being substantially non-volatile at the heating temperature.
Inventors
- 👤 William H. Cooper
- 👤 Ana G. Brunet
- 👤 William F. Campbell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 16:27
CPC Classifications
C; C01; C01D; C01D1/00; C01D1/04; C01D1/28
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
105 words
A process for reducing chlorate concentration in a chlorate-containing aqueous alkali metal hydroxide solution, said process consisting of heating the alkali metal hydroxide solution in the presence of an effective amount of hydroxycarboxylic acid or sodium, potassium or ammonium salt thereof at a temperature of from at least 125° C. to about 190° C. for a time sufficient to substantially reduce the chlorate concentration in the alkali metal hydroxide solution, with the provisos that the hydroxycarboxylic acid or salt thereof is soluble in the alkali metal hydroxide solution and that the heating temperature is below the boiling point and decomposition temperature of the hydroxycarboxylic acid.
Claim 2
Dependent Claim
105 words
A process for reducing chlorate concentration in a chlorate-containing aqueous alkali metal hydroxide solution, said process consisting of heating the alkali metal hydroxide solution in the presence of an effective amount of hydroxycarboxylic acid or sodium, potassium or ammonium salt thereof at a temperature of from at least 125° C. to about 190° C. for a time sufficient to substantially reduce the chlorate concentration in the alkali metal hydroxide solution, with the provisos that the hydroxycarboxylic acid or salt thereof is soluble in the alkali metal hydroxide solution and that the heating temperature is below the boiling point and decomposition temperature of the hydroxycarboxylic acid.
Claim 3
Dependent Claim
27 words
The process of claim 1 wherein the hydroxycarboxylic acid is selected from the group consisting of monohydroxymonocarboxylic acid, monohydroxydicarboxylic acid, monohydroxytricarboxylic acid, dihydroxymonocarboxylic acid and dihydroxydicarboxylic acid.
Claim 4
Dependent Claim
33 words
The process of claim 2 wherein the monohydroxymonocarboxylic acid is selected from the group consisting of hydroxyethanoic acid, 2-hydroxybutanoic acid, 4-hydroxybutanoic acid, o-hydroxybenzoic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, hydroxy-(phenyl)ethanoic acid, and hydroxymethylbenzoic acid.
Claim 5
Dependent Claim
12 words
The process of claim 3 wherein the monohydroxymonocarboxylic acid is hydroxyethanoic acid.
Claim 6
Dependent Claim
13 words
The process of claim 2 wherein the monohydroxytricarboxylic acid salt is sodium citrate.
Claim 7
Dependent Claim
12 words
The process of claim 2 wherein the dihydroxydicarboxylic acid is 2,3-dihydroxybutanedioic acid.
Claim 8
Dependent Claim
13 words
The process of claim 2 wherein the dihydroxydicarboxylic acid salt is sodium tartrate.
Claim 9
Dependent Claim
27 words
The process of claim 1 wherein the effective amount of hydroxycarboxylic acid is at least six times the stoichiometric amount theoretically required to react with the chlorate.
Claim 10
Dependent Claim
14 words
The process of claim 1 wherein the temperature is at least about 140° C.
Claim 11
Dependent Claim
108 words
A process for reducing sodium chlorate concentration in a sodium chlorate-containing aqueous sodium hydroxide solution containing about 50 percent by weight sodium hydroxide, said process consisting of heating the sodium hydroxide solution in the presence of hydrocarboxylic acid or sodium, potassium or ammonium salt thereof at a temperature of from at least 125° C. to about 190° C. for a time sufficient to substantially reduce the sodium chlorate concentration in the sodium hydroxide solution, with the provisos that the hydroxycarboxylic acid or salt thereof is soluble in the sodium hydroxide solution and that the heating temperature is below the melting point and decomposition temperature of the hydroxycarboxylic acid.
Claim 12
Dependent Claim
108 words
A process for reducing sodium chlorate concentration in a sodium chlorate-containing aqueous sodium hydroxide solution containing about 50 percent by weight sodium hydroxide, said process consisting of heating the sodium hydroxide solution in the presence of hydrocarboxylic acid or sodium, potassium or ammonium salt thereof at a temperature of from at least 125° C. to about 190° C. for a time sufficient to substantially reduce the sodium chlorate concentration in the sodium hydroxide solution, with the provisos that the hydroxycarboxylic acid or salt thereof is soluble in the sodium hydroxide solution and that the heating temperature is below the melting point and decomposition temperature of the hydroxycarboxylic acid.
Claim 13
Dependent Claim
26 words
The process of claim 10 wherein the hydroxycarboxylic acid or salt thereof is selected from the group consisting of hydroxyethanoic acid, sodium citrate and sodium tartrate.
Claim 14
Dependent Claim
15 words
The process of claim 10 wherein the heating temperature is at least about 140° C.
Claim 15
Dependent Claim
28 words
The process of claim 10 wherein the effective amount of hydroxycarboxylic acid is at least six times the stoichiometric amount theoretically required to react with the sodium chlorate.
References Cited (Backward Citations)
US2404453A
Cited
US2617713A
Cited
US2562169A
Cited
US2610105A
Cited
US2823177A
Cited
US2790707A
Cited
US2889204A
Cited
US3325251A
Cited
US3301636A
Cited
GB1523979A
Cited
JPS5370998A
Cited
US4260494A
Cited
US4282178A
Cited
SU922070A1
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-06-29 | 1990-12-29 | 1991-06-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-06-29 | 1994-12-29 | 1995-06-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-06-29 | 1998-12-29 | 1999-06-30 | $7700.00 | Window Closed / Lapsed |