US4384937A
Expired / Lapsed
US
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Production of chromic acid in a three-compartment cell
Assignee: Diamond Shamrock Chemicals Co
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Filing: 1979-05-29
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Granted: 1983-05-24
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Expires: 1999-05-29
Abstract
Abstract Chromic acid is now efficiently prepared in a process using dichromate, such as the dichromate typically available as an intermediate in the chromic acid production from chrome ore. In the process, the dichromate is introduced into the center compartment of a three-compartment electrolytic cell and dichromate-containing center compartment electrolyte flows through a porous diaphragm into the anode compartment of the cell. Electrolyte is introduced to the cell cathode compartment which is separated from the center compartment by a substantially hydraulically impermeable cation-exchange membrane means. During electrolysis, chromic acid is prepared in the anolyte and alkali product is produced in the catholyte.
Inventors
- 👤 Nicholas Shuster
- 👤 Andrew D. Babinsky
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 17:30
CPC Classifications
C; C25; C25B; C25B1/00; C25B1/01; C25B1/22
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
203 words
An electrolytic cell for the production of chromic acid from sodium dichromate, which cell comprises: (A) an anode compartment in juxtaposition with a center compartment of said cell and containing an anode, said anode compartment further containing aqueous chromic-acid-containing anolyte at elevated temperature but below boiling condition, said anolyte containing dichromate and having an anolyte ratio below 31.95 percent; (B) a center compartment containing aqueous dichromate-containing electrolyte at elevated temperature but below boiling condition, which electrolyte comprises 0-100 grams per liter of alkali product, 0-100 grams per liter of chromic acid and below about 1600 grams per liter of dichromate, with the total of the hexavalent chromium in said electrolyte, expressed as Cr +6 , being above about 100 grams per liter, and with any reduced forms of chromium, if such exist, being present at substantially below about 2 percent of said hexavalent chromium, and wherein said compartment is separated at least in part from cell anolyte by porous diaphragm means and at least partially from cell catholyte by substantially hydraulically impermeable cation-exchange membrane means; and (C) a cathode compartment in juxtaposition with said center compartment, said cathode compartment having a cathode and containing aqueous catholyte at elevated temperature but below boiling condition.
Claim 2
Dependent Claim
203 words
An electrolytic cell for the production of chromic acid from sodium dichromate, which cell comprises: (A) an anode compartment in juxtaposition with a center compartment of said cell and containing an anode, said anode compartment further containing aqueous chromic-acid-containing anolyte at elevated temperature but below boiling condition, said anolyte containing dichromate and having an anolyte ratio below 31.95 percent; (B) a center compartment containing aqueous dichromate-containing electrolyte at elevated temperature but below boiling condition, which electrolyte comprises 0-100 grams per liter of alkali product, 0-100 grams per liter of chromic acid and below about 1600 grams per liter of dichromate, with the total of the hexavalent chromium in said electrolyte, expressed as Cr +6 , being above about 100 grams per liter, and with any reduced forms of chromium, if such exist, being present at substantially below about 2 percent of said hexavalent chromium, and wherein said compartment is separated at least in part from cell anolyte by porous diaphragm means and at least partially from cell catholyte by substantially hydraulically impermeable cation-exchange membrane means; and (C) a cathode compartment in juxtaposition with said center compartment, said cathode compartment having a cathode and containing aqueous catholyte at elevated temperature but below boiling condition.
Claim 3
Dependent Claim
29 words
The electrolyte cell of claim 1 wherein said chromic-acid-containing anolyte of said anode compartment also contains sodium dichromate and has an anolyte ratio between about 3 and 20.8 percent.
Claim 4
Dependent Claim
33 words
The electrolyte cell of claim 1 wherein the anode is a metal anode wherein the metal is selected from the group consisting of lead, lead alloys and valve metals bearing a noble-metal-containing coating.
Claim 5
Dependent Claim
67 words
The electrolytic cell of claim 1 wherein said anolyte, catholyte and dichromate-containing electrolyte are all at elevated temperature maintained within the range from about 40° C. to about 95° C., and said dichromate-containing center compartment electrolyte is under a hydrostatic pressure maintained within the range from about 0 psig to about 2 psig, thereby enhancing flow of said electrolyte from said center compartment through the porous diaphragm.
Claim 6
Dependent Claim
34 words
The electrolytic cell of claim 1 wherein chromic acid is present in said anolyte in a concentration below about 1200 grams per liter and said anolyte is substantially free from reduced forms of chromium.
Claim 7
Dependent Claim
35 words
The electrolyte cell of claim 1 further characterized by having vent means for removing gas generated at the anode, and outlet means, separated from said vent means, for withdrawing chromic-acid-containing anolyte from said anode compartment.
Claim 8
Dependent Claim
20 words
The electrolytic cell of claim 1 wherein the dichromate inlet means to said anode compartment comprises said porous diaphragm means.
Claim 9
Dependent Claim
17 words
The electrolytic cell of claim 1 wherein said dichromate-containing electrolyte of said center compartment contains sodium dichromate.
Claim 10
Dependent Claim
58 words
The electrolytic cell of claim 1 wherein said porous diaphragm means comprises fluorocarbon polymer substance and said membrane means comprises a film of a polymer, chemically resistant to the catholyte and center compartment dichromate-containing electrolyte of said cell, and containing hydrophilic, ion-exchange groups selected from the group consisting of sulfonic groups, carboxylic groups, sulfonamide groups, and mixtures thereof.
Claim 11
Dependent Claim
34 words
The electrolytic cell of claim 1 further characterized by containing inlet means for introducing dichromate to said center compartment, and center compartment outlet means for withdrawing solution, depleted in dichromate, from said electrolytic cell.
Claim 12
Dependent Claim
20 words
The electrolytic cell of claim 10 wherein the dichromate introduuced to said center compartment is substantially free from chromic acid.
Claim 13
Dependent Claim
30 words
The electrolytic cell of claim 10 wherein the dichromate introduced to said center compartment is selected from the group consisting of sodium dichromate, potassium dichromate, ammonium dichromate and mixtures thereof.
Claim 14
Dependent Claim
56 words
The electrolytic cell of claim 1 further characterized by having materials in contact with said center compartment electrolyte selected from the group consisting of titanium, fluorocarbon polymer substance, polymer film containing hydrophilic ion-exchange groups, tantalum and glass, and materials in contact with said anolyte selected from the group consisting of glass, ceramic and fluorocarbon polymer substance.
Claim 15
Dependent Claim
20 words
The electrolytic cell of claim 1 wherein said catholyte contains less than about 600 grams per liter of alkali product.
Claim 16
Dependent Claim
36 words
The electrolytic cell of claim 1 further characterized by having vent means for removing gas generated at the cathode, and having outlet means for withdrawing alkali-product-containing catholyte, while further having inlet means to said cathode compartment.
Claim 17
Dependent Claim
50 words
The electrolytic cell of claim 15 wherein the alkali product concentration in said cathode compartment is at least partially controlled during electrolysis by water addition thereto through said inlet means, or by addition to catholyte being recirculated outside said cell, whereby said recirculating catholyte is introduced through said inlet means.
Claim 18
Dependent Claim
41 words
The electrolytic cell of claim 15 further characterized by introducing carbon dioxide into the catholyte through said inlet means, or by introducing carbon dioxide into catholyte being recirculated outside the cell, whereby said recirculating catholyte is introduced through said inlet means.
Claim 19
Dependent Claim
18 words
The electrolytic cell of claim 17 wherein carbonate product is withdrawn from said cell or from recirculating catholyte.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-05-23 | 1986-11-22 | 1987-05-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-05-23 | 1990-11-22 | 1991-05-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-05-23 | 1994-11-22 | 1995-05-24 | $7700.00 | Window Closed / Lapsed |