Patent US3904496A successfully refreshed from Google Patents.
US3904496A
Expired / Lapsed
US
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Electrolytic production of chlorine dioxide, chlorine, alkali metal hydroxide and hydrogen
Assignee: Occidental Chemical Corp
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Filing: 1974-01-02
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Granted: 1975-09-09
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Expires: 1994-01-02
Abstract
Abstract Chlorine dioxide, chlorine, alkali metal hydroxide and hydrogen are produced from hydrogen chloride, alkali metal chlorate, alkali metal chloride and water in a three compartment electrolytic cell in which a buffer compartment between the anode and cathode compartments is separated from the anode compartment by an anion-active permselective membrane and from the cathode compartment by a cation-active permselective membrane. Hydrogen chloride is fed to the anode compartment, aqueous alkali metal chlorate and chloride are fed to the buffer compartment and water is fed to the cathode compartment, with chlorine dioxide and chlorine being taken off from the anode compartment while hydrogen and alkali metal hydroxide substantially free of alkali metal chloride are produced in and removed from the cathode compartment. The products of the process are obtained in a single vessel in forms suitable for use in pulping wood and bleaching wood pulp without production of undesirable byproducts that create disposal problems or require further processing for conversion to useful products.
Inventors
- 👤 Cyril J Harke
- 👤 Jeffrey D Eng
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 04:47
CPC Classifications
C; C25; C25B; C25B1/00; C25B1/01; C25B1/34
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
149 words
A METHOD FOR ELECTROLYTICALLY PRODUCING CHLORINE, CHLORINE DIOXIDE, AQUEOUS ALKALI METAL HYDROXIDE SOLUTION SUBSTANTIALLY FREE OF ALKALI METAL CHLORIDE, AND HYDROGEN, WHICH COMPRISES FEEDING HYDROGEN CHLORIDE TO AN ANODE COMPARTMENT OF AN ELECTROLYTIC CELL, ALKALI METAL CHLORIDE AND ALKALI METAL CHLORATE TO A BUFFER COMPARTMENT OF SAID CELL AND WATER TO A CATHODE COMPARTMENT, THE ANODE AND BUFFER COMPARTMENTS BEING SEPARATED BY AN ANION-ACTIVFE PERMSELECTIVE MEMBRANE AND THE BUFFER AND CATHODE COMPARTMENTS BEING SEPARATED BY A CATION-ACTIVE PERMSELECTIVE MEMBRANE, SO THAT DURING ELECTROLYSIS CHLORATE AND CHLORIDE ANIONS PASS SELECTIVELY FROM THE BUFFER COMPARTMENT TO THE ANODE COMPARTMENT, WHERE THEY REACT AT THE ANODE WITH HYDROGEN CHLORIDE TO PRODUCE CHLORINE AND CHLORINE DIOXIDE, AND ALKALI METAL CATIONS DIFFUSE SELECTIVELY FROM THE BUFFER COMPARTMENT TO THE CATHODE COMPARTMENT, WHEREIN THEY REACT WITH WATER AT THE CATHODE TO PRODUCE HYDROGEN AND AQUEOUS ALKALI METAL HYDROXIDE SOLUTION SUBSTANTIALLY FREE OF ALKALI METAL CHLORIDE.
Claim 2
Independent Claim
149 words
A METHOD FOR ELECTROLYTICALLY PRODUCING CHLORINE, CHLORINE DIOXIDE, AQUEOUS ALKALI METAL HYDROXIDE SOLUTION SUBSTANTIALLY FREE OF ALKALI METAL CHLORIDE, AND HYDROGEN, WHICH COMPRISES FEEDING HYDROGEN CHLORIDE TO AN ANODE COMPARTMENT OF AN ELECTROLYTIC CELL, ALKALI METAL CHLORIDE AND ALKALI METAL CHLORATE TO A BUFFER COMPARTMENT OF SAID CELL AND WATER TO A CATHODE COMPARTMENT, THE ANODE AND BUFFER COMPARTMENTS BEING SEPARATED BY AN ANION-ACTIVFE PERMSELECTIVE MEMBRANE AND THE BUFFER AND CATHODE COMPARTMENTS BEING SEPARATED BY A CATION-ACTIVE PERMSELECTIVE MEMBRANE, SO THAT DURING ELECTROLYSIS CHLORATE AND CHLORIDE ANIONS PASS SELECTIVELY FROM THE BUFFER COMPARTMENT TO THE ANODE COMPARTMENT, WHERE THEY REACT AT THE ANODE WITH HYDROGEN CHLORIDE TO PRODUCE CHLORINE AND CHLORINE DIOXIDE, AND ALKALI METAL CATIONS DIFFUSE SELECTIVELY FROM THE BUFFER COMPARTMENT TO THE CATHODE COMPARTMENT, WHEREIN THEY REACT WITH WATER AT THE CATHODE TO PRODUCE HYDROGEN AND AQUEOUS ALKALI METAL HYDROXIDE SOLUTION SUBSTANTIALLY FREE OF ALKALI METAL CHLORIDE.
Claim 3
Dependent Claim
172 words
A method according to claim 1 wherein the alkali metal chloride, alkali metal chlorate and cations are sodium chloride, sodium chlorate and sodium cations, respectively, the chlorate and chloride salts are charged at about stoichiometrically equivalent rates, the anion-active membrane is a quaternary ammonium substituted fluorocarbon polymer or a quaternary ammonium substituted heterogeneous polyvinyl chloride base polymer and the cation-active membrane is selected from the group consisting of sulfostyrenated perfluorinated ethylene propylene copolymers, hydrolyzed copolymers of perfluorinated olefins and fluorosulfonated perfluorovinyl ethers and fluorinated polymers having pendant side chains containing sulfonyl groups which are attached to carbon atoms bearing at least one fluorine atom, with sulfonyl groups on one surface being in -(SO2NH)nM form where M is H, NH4, alkali metal or alkaline earth metal and n is the valence of M, and the sulfonyls of the polymer on the other membrane surface being in -(SO3)pY form wherein Y is a cation and p is the valence of the cation and when Y is H, M is also H, or being -SO2F.
Claim 4
Dependent Claim
135 words
A method according to claim 2 wherein the feed(s) to the buffer compartment solution is/are aqueous and about 1 to 6 Normal in sodium chloride and about 1 to 6 Normal in sodium chlorate, the temperature of electrolysis is below about 105*C., the concentration of aqueous sodium hydroxide produced at the cathode is about 60 to 300 g./l., the current efficiency is greater than about 85%, the caustic efficiency is greater than about 75% and the cation-active membrane is 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 or a perfluorinated copolymer of tetrafluoroethylene and FSO2CF2CF2OCF(CF3)CF2OCF CF2 in a molar ratio of about 7:1, wherein M and Y are both sodium and n and p are both 1.
Claim 5
Dependent Claim
101 words
A method according to claim 3 wherein the voltage of the cell is from about 2.5 to 4.0 volts, the current density is from about 0.5 to 4 amperes per square inch of electrode surface, the surfaces of the cathode are of a material selected from the group consisting of platinum, iridium, ruthenium, rhodium, graphite, iron and steel and the surfaces of the anode are of a material selected from the group consisting of noble metals, noble metal alloys, noble metal oxides, mixtures of noble metal oxides, valve metal oxides, mixtures of valve metal oxides and a valve metal, and graphite.
Claim 6
Dependent Claim
68 words
A method according to claim 4 wherein the permselective membranes are from about 0.02 to 0.5 mm. in thickness and are supported on a network of material selected from the group consisting of polytetrafluoroethylene, asbestos, perfluorinated ethylene-propylene copolymer, titanium, tantalum, niobium and noble metals, having an area percentage of openings therein of from about 8 to 80%, and the surfaces of the anode and cathode are of graphite.
Claim 7
Dependent Claim
98 words
A method according to claim 5 wherein the feed to the buffer compartment is an aqueous solution that contains about 2 to 4 gram-equivalents per liter of sodium chlorate and about 2 to 4 gram-equivalents per liter of sodium chloride, hydrogen chloride is fed to the anode compartment as an aqueous solution, the concentration of aqueous sodium hydroxide produced at the cathode is about 80 to 100 g./l., the current efficiency is greater than about 95%, the caustic efficiency is greater than about 85%, and the electrolysis is carried out at a temperature of about 65* to 95*C.
Claim 8
Dependent Claim
104 words
A method according to claim 6 wherein the surfaces of the anode and cathode are graphite of a density of about 1.68 to 1.78 g./ml., the hydrogen chloride feed solution contains about 9 to 10.4 gram-equivalents of hydrogen chloride per liter, the cation-active permselective membrane is the unmodified copolymer and has an equivalent weight of from about 1,100 to 1,400, the cation-active membrane and the anion-active membrane are about 0.1 to 0.3 mm. thick and the membranes are supported on cloths of polytetrafluoroethylene filaments having thicknesses of 0.01 to 0.3 mm. and having an area percentage of openings therein of about 10 to 70%.
Claim 9
Dependent Claim
18 words
A method according to claim 7 wherein the anion-active permselective membrane is a quaternary ammonium substituted fluorocarbon polymer.
Claim 10
Dependent Claim
20 words
A method according to claim 7 wherein the anion-active membrane is a quaternary ammonium substituted heterogeneous polyvinyl chloride based polymer.
Claim 11
Dependent Claim
44 words
A method accOrding to claim 5 wherein the chlorine and chlorine dioxide produced at the anode are separated and separated chlorine is reacted with hydrogen produced at the cathode to produce hydrogen chloride which is charged to the anode compartment as an aqueous solution.
References Cited (Backward Citations)
US3438879A
Cited
US3496077A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-08 | 1979-03-10 | 1979-09-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-08 | 1983-03-10 | 1983-09-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-08 | 1987-03-10 | 1987-09-09 | $7700.00 | Window Closed / Lapsed |