US3899403A
Expired / Lapsed
US
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Electrolytic method of making concentrated hydroxide solutions by sequential use of 3-compartment and 2-compartment electrolytic cells having separating compartment walls of particular cation-active permselective membranes
Assignee: Occidental Chemical Corp
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Filing: 1973-11-01
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Granted: 1975-08-12
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Expires: 1993-11-01
Abstract
Abstract A concentrated hydroxide solution containing over 250 g./l. of sodium hydroxide is made by a two-cell aqueous sodium chloride electrolysis process wherein, in a first cell, containing at least three (and preferably three) compartments, with a buffer compartment separated from adjoining anode and cathode compartments by walls of a cation-active permselective membrane, which is of a hydrolyzed copolymer of a perfluorinated hydrocarbon and fluorosulfonated perfluorovinyl ether or of a sulfostyrenated perfluorinated ethylene propylene polymer, a concentrated sodium hydroxide solution is made in the cathode compartment, a dilute sodium hydroxide solution is produced in a buffer compartment, to which compartment water is added during the electrolysis and chlorine is generated in the anode compartment, after which the dilute hydroxide is fed to the cathode compartment of a two-compartment electrolytic cell in which sodium chloride solution is electrolyzed in the anode compartment and concentrated sodium hydroxide solution, at a concentration of more than 250 g./l., is withdrawn from the cathode compartment. The caustic efficiency of the combined process is above 70%, which is normally unattainable using only a two-compartment membrane cell and yet, the sodium hydroxide solution resulting is at a high concentration.
Inventors
- 👤 Jr Edward H Cook
- 👤 Alvin T Emery
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 00:52
CPC Classifications
C; C25; C25B; C25B13/00; C25B13/02; C25B1/00; C25B1/01; C25B1/24; C25B1/26
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
288 words
A METHOD FOR ELECTROLYTICALLY MANUFACTURING A CONCENTRATED HYDROXIDE SOLUTION CONTAINING OVER 250 BUT LESS THAN 450 G./L. OF SODIUM HYDROXIDE OR EQUIVALENT HYDROXIDE WHICH COMPRISES MAKING CONCENTRATED AND DILUTE AQUEOUS HYDROXODE SOLUTIONS SIMULTANEOUSLY BY ELECTROLYZING AN AQUEOUS SOLUTION CONTAINING HALIDE IONS IN AN ELECTROLYTIC CELL HAVING AT LEAST THREE COMPARTMENTS THEREIN, AN ANODE, A CATHODE, T LEAST TWO CATION-ACTIVE PERMSELECTIVE MEMBRANES OF A POLYMERIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF A HYDROLYZED COPOLYMER OF A PERFLUORINATED HYDROARBON AND A FLUOROSULFONATED PERFLUOROVINYL ETHER AND A SULFOSTYRENATED PERFLUORINATED ETHYLENE PROPYLENE POLYMER, DEFINING ANODE AND CATHODE SIDE WALLS OF A BUFFER COMPARTMENT OF COMPARTMENTS BETWEEN ANODE AND CATHODE COMPARTMENTS, AND SUCH WALLS, WITH WALLS THEREABOUT, DEFINING ANODE AND CATHODE COMPARTMENTS, WHILE ADDING WATER TO THE BUFFER COMPARTMENT AT SUCH A RATE AS TO PRODUCE A DILUTE HYDROXIDE SOLUTION THEREIN AT THE SAME TIME THAT A MORE CONCENTRATED HYDROXIDE SOLUTION, CONTAINING OVER 250 BUT LESS THAN 450 G./L. OF SODIUM HYDROXIDE OR EQUIVALENT IS PRODUCED IN THE CATHODE COMPARTMENT, WHILE MAINTAINING A HIGH CAUSTIC EFFICIENCY, REMOVING THE DILUTE HYDROXIDE FROM THE BUFFER COMPARTMENT AND FEEDING IT TO THE CATHODE COMPARTMENT OF A TWO-COMPARTMENT ELECTROLYTIC CELL, HAVING ANODE AND CATHODE COMPARTMENTS SEPARATED BY A CATION-ACTIVE PERMSELECTIVE MEMBRANE OF A POLYMERIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF A HYDROLYZED COPOLYMER OF A PERFLUORINATED HYDROCARBON AND A FLUOROSULFONATED PERFLUOROVINYL ETHER, AND A SULFOSTYRENATED PERFLUORINATED ETHYLENE PROPYLENE POLYMER, IN WHICH CELL, IN THE ANODE COMPARTMENT THEREOF, AN AQUEOUS SOLUTION CONTAINING HALIDE IONS IS ELECTROLYZED, AND WITHDRAWING FROM THE CATHOLYTE COMPARTMENT OF THE TWO-COMPARTMENT CELL CONCENTRATED HYDROXIDE SOLUTION CONTAINING MORE THAN 250 BUT LESS THAN 450 G./L. OF SODIUM HYDROXIDE OR EQUIVALENT, SO THAT THE CATHODE COMPARTMENT EFFICIENCY OF THE COMBINED PROCESSES IS ABOVE 70%.
Claim 2
Independent Claim
288 words
A METHOD FOR ELECTROLYTICALLY MANUFACTURING A CONCENTRATED HYDROXIDE SOLUTION CONTAINING OVER 250 BUT LESS THAN 450 G./L. OF SODIUM HYDROXIDE OR EQUIVALENT HYDROXIDE WHICH COMPRISES MAKING CONCENTRATED AND DILUTE AQUEOUS HYDROXODE SOLUTIONS SIMULTANEOUSLY BY ELECTROLYZING AN AQUEOUS SOLUTION CONTAINING HALIDE IONS IN AN ELECTROLYTIC CELL HAVING AT LEAST THREE COMPARTMENTS THEREIN, AN ANODE, A CATHODE, T LEAST TWO CATION-ACTIVE PERMSELECTIVE MEMBRANES OF A POLYMERIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF A HYDROLYZED COPOLYMER OF A PERFLUORINATED HYDROARBON AND A FLUOROSULFONATED PERFLUOROVINYL ETHER AND A SULFOSTYRENATED PERFLUORINATED ETHYLENE PROPYLENE POLYMER, DEFINING ANODE AND CATHODE SIDE WALLS OF A BUFFER COMPARTMENT OF COMPARTMENTS BETWEEN ANODE AND CATHODE COMPARTMENTS, AND SUCH WALLS, WITH WALLS THEREABOUT, DEFINING ANODE AND CATHODE COMPARTMENTS, WHILE ADDING WATER TO THE BUFFER COMPARTMENT AT SUCH A RATE AS TO PRODUCE A DILUTE HYDROXIDE SOLUTION THEREIN AT THE SAME TIME THAT A MORE CONCENTRATED HYDROXIDE SOLUTION, CONTAINING OVER 250 BUT LESS THAN 450 G./L. OF SODIUM HYDROXIDE OR EQUIVALENT IS PRODUCED IN THE CATHODE COMPARTMENT, WHILE MAINTAINING A HIGH CAUSTIC EFFICIENCY, REMOVING THE DILUTE HYDROXIDE FROM THE BUFFER COMPARTMENT AND FEEDING IT TO THE CATHODE COMPARTMENT OF A TWO-COMPARTMENT ELECTROLYTIC CELL, HAVING ANODE AND CATHODE COMPARTMENTS SEPARATED BY A CATION-ACTIVE PERMSELECTIVE MEMBRANE OF A POLYMERIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF A HYDROLYZED COPOLYMER OF A PERFLUORINATED HYDROCARBON AND A FLUOROSULFONATED PERFLUOROVINYL ETHER, AND A SULFOSTYRENATED PERFLUORINATED ETHYLENE PROPYLENE POLYMER, IN WHICH CELL, IN THE ANODE COMPARTMENT THEREOF, AN AQUEOUS SOLUTION CONTAINING HALIDE IONS IS ELECTROLYZED, AND WITHDRAWING FROM THE CATHOLYTE COMPARTMENT OF THE TWO-COMPARTMENT CELL CONCENTRATED HYDROXIDE SOLUTION CONTAINING MORE THAN 250 BUT LESS THAN 450 G./L. OF SODIUM HYDROXIDE OR EQUIVALENT, SO THAT THE CATHODE COMPARTMENT EFFICIENCY OF THE COMBINED PROCESSES IS ABOVE 70%.
Claim 3
Dependent Claim
119 words
A method according to claim 1 wherein the electrolytic cells are three-compartment and two-compartment cells, the walls between the buffer compartment of the three-compartment cell and the anode and cathode compartments thereof and the wall between the anode and cathode compartments of the twocompartment cell are of a hydrolyzed copolymer of tetrafluoroethylene and a fluorosulfonated perfluorovinyl ether of the formula FSO2CF2CF2OCF(CF3)CF2OCF CF2, which copolymer has an equivalent weight of about 900 to 1,600, and the addition of water to the buffer compartment of the three-compartment cell is at such a rate that the dilute hydroxide removed from the buffer compartment and fed to the cathode compartment of the two-compartment electrolytic cell is at a concentration greater than 50 g./l.
Claim 4
Dependent Claim
137 words
A method according to claim 2 wherein sodium hydroxide, chlorine and hydrogen are made from an aqueous solution of sodium chloride, the concentrated sodium hydroxide solution removed from the cathode compartment of the three-compartment and two-compartment cells is at a concentration over 350 g./l. and the concentration of the sodium hydroxide solution withdrawn from the buffer compartment of the three-compartment cell and fed to the cathode compartment of the two-compartment cell is from 50 to 200 g./l., the permselective membranes are about 0.02 to 0.5 mm. thick, the concentration of sodium chloride in the anode compartments of the three-compartment and two-compartment cells is from about 200 to 320 g./l., the pH of the anolytes in both cells is about 1 to 5 and the temperatures of the anolytes, catholytes and buffer compartment solution are less than 105*C.
Claim 5
Dependent Claim
155 words
A method according to claim 3 wherein the permselective membranes are mounted on networks of a material selected from the group consisting of polytetrafluoroethylene, asbestos, perfluorinated ethylene propylene polymer, polypropylene, titanium, tantalum, niobium and noble metals, which networks have area percentages of openings therein from about 8 to 80%, the temperatures of the anolytes, catholytes and buffer compartment solution are in the range of 20* to 95*C, the surfaces of the cathodes are of a material selected from the group consisting of platinum, iridium, ruthenium, rhodium, graphite, iron and steel, the surfaces of the anodes are of a material selected from the group consisting of noble metals, noble metal alloys, noble metal oxides, mixtures of noble metal oxides with valve metal oxides, or mixture thereof, on a valve metal, the voltage is from about 2.3 to 6 volts and the current density is from about 0.5 to 4 amperes per square inch of electrode surface.
Claim 6
Dependent Claim
114 words
A method according to claim 4 wherein the networks are screens of cloths of polytetrafluoroethylene filaments having a thickness of 0.1 to 0.3 mm., the membrane walls are from 0.1 to 0.3 mm. thick, the polytetrafluoroethylene filament thickness is less than or equal to that of the membrane walls, the copolymer equivalent weight is from about 1,100 to 1,400, the cathodes are of steel, the anodes are of ruthenium oxide on titanium, the aqueous sodium chloride solution electrolytes are at a concentration of about 250 to 320 g./l., the pH of the anolyte is from 2 to 4 and the temperatures of the anolytes, catholytes and buffer compartment solution are from 65* to 95*C.
Claim 7
Dependent Claim
61 words
A method according to claim 5 wherein the aqueous solution of sodium hydroxide withdrawn from the buffer compartment of the three-compArtment cell is at a concentration of about 100 to 150 g./l., the concentrations of the catholytes withdrawn from the three-compartment and two-compartment cells are about 375 to 425 g./l. and the caustic efficiency of the combined process is over 75%.
Claim 8
Dependent Claim
98 words
A method according to claim 6 wherein a plurality of three-compartment and two-compartment cells is employed, the three-compartment cells operating at about 90% caustic efficiency or more and producing buffer compartment solution containing about 125 g./l. sodium hydroxide and the two-compartment cells operating at about 60% caustic efficiency or more, with the solution removed from the cathode compartment of both cells being at about 400 g./l. sodium hydroxide, the proportion of three-compartment cells to two-compartment cells is about 1.5 and the buffer compartment solution withdrawn from three three-compartment cells is fed to the catholytes of two two-compartment cells.
Claim 9
Dependent Claim
61 words
A method according to claim 3 wherein the aqueous solution of sodium hydroxide withdarwn from the buffer compartment of the three-compartment cell is at a concentration of about 100 to 150 g./l., the concentrations of the catholytes withdrawn from the three-compartment and two-compartment cells are about 375 to 425 g./l. and the caustic efficiency of the combined process is over 75%.
Claim 10
Dependent Claim
98 words
A method according to claim 3 wherein a plurality of three-compartment and two-compartment cells is employed, the three-compartment cells operating at about 90% caustic efficiency or more and producing buffer compartment solution containing about 125 g./l. sodium hydroxide and the two-compartment cells operating at about 60% caustic efficiency or more, with the solution removed from the cathode compartments of both cells being at about 400 g./l. sodium hydroxide, the proportion of three-compartment cells to two-compartment cells is about 1.5 and the buffer compartment solution withdrawn from three three-compartment cells is fed to the catholytes of two two-compartment cells.
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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) | 1978-08-11 | 1979-02-10 | 1979-08-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-11 | 1983-02-10 | 1983-08-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-11 | 1987-02-10 | 1987-08-12 | $7700.00 | Window Closed / Lapsed |