US3878072A — Electrolytic method for the manufacture of chlora…

Claim 1

Independent Claim 235 words

IN A PROCESS FOR ELECTROLYZING AN AQUEOUS ALKALI METAL CHLORIDE SOLUTION IN AN ELECTROLYTIC CELL HAVING AT LEAST THREE COMPARTMENTS THEREIN, AN ANODE, A CATHODE, AT LEAST ONE PERMSELECTIVE MEMBRANE OF A HYDROLYZED COPOLYMER OF A PERFLUORINATED HYDROCARBON AND A FLUORSULFONATED PERFLUOROVINYL ETHER, OR A SULFOSTYRENATED PERFLUORINATED ETHYLENE PROPYLENE POLYMER, THE CATHODE-SIDEWAL OF THE BUFFER COMPARTMENT BETWEEN THE ANODE AND CATHODE AND THE ANODE-SIDEWALL OF SAID COMPARTMENT BEING DEFINED BY SUCH PERMSELECTIVE MEMBRANE OR A POROUS DIAPHRAGM, SUCH WALLS, WITH WALLS THEREABOUT DEFINING AN ANODE AND CATHODE COMPARTMENT, THE IMPROVEMENT WHICH COMPRISES INTRODUCING AN AQUEOUS SOLUTION CONTAINING CHLORIDE AND CHLORATE INTO THE ANODE COMPARTMENT OF SUCH CELL, INTRODUCING WATER INTO THE BUFFER AND CATHODE COMPARTMENTS, PASSING ELECTRIC CURRENT BETWEEN THE ANODE AND CATHODE OF SAID CELL, FORMING HYDROXIDE IONS IN BOTH SAID BUFFER COMPARTMENT AND SAID CATHODE COMPARTMENTS AND CHOLRINE IN SAID ANODE COMPARTMENT, REACTING GASEOUS CHLORINE WITH THE CONTENTS OF SAID BUFFER COMPARTMENT AND/OR THE SOLUTIONS REMOVED THEREFROM, THE CONDITIONS OF SUCH REACTION BEING CONTROLLED TO PRODUCE HYPOCHLORITE OR CHLORATE AND CHLORIDE, CONVERTING THE HYPOCHLORITE, WHEN PRODUCED, TO CHLORATE AND CHLOR ATE AND CHLORIDE, FEEDING AT LEAST A PORTION OF THE CHLORATE AND CHLORIDE THUS PRODUCED TO THE ANODE COMPARTMENT FOR ELECTROLYSIS OF CHLORIDE THEREIN TO CHLORINE, WITH A RESULTING INCREASE IN THE PROPORTION OF CHLORATE TO CHLORIDE IN THE ANOYLTE, AND RECOVERING CHLORINE, CHLORATE AND SUBSTANTIALLY CHLORIDE FREE HYDROXIDE AS THE ELECTROLYSIS PRODUCTS.

Claim 2

Dependent Claim 235 words

IN A PROCESS FOR ELECTROLYZING AN AQUEOUS ALKALI METAL CHLORIDE SOLUTION IN AN ELECTROLYTIC CELL HAVING AT LEAST THREE COMPARTMENTS THEREIN, AN ANODE, A CATHODE, AT LEAST ONE PERMSELECTIVE MEMBRANE OF A HYDROLYZED COPOLYMER OF A PERFLUORINATED HYDROCARBON AND A FLUORSULFONATED PERFLUOROVINYL ETHER, OR A SULFOSTYRENATED PERFLUORINATED ETHYLENE PROPYLENE POLYMER, THE CATHODE-SIDEWAL OF THE BUFFER COMPARTMENT BETWEEN THE ANODE AND CATHODE AND THE ANODE-SIDEWALL OF SAID COMPARTMENT BEING DEFINED BY SUCH PERMSELECTIVE MEMBRANE OR A POROUS DIAPHRAGM, SUCH WALLS, WITH WALLS THEREABOUT DEFINING AN ANODE AND CATHODE COMPARTMENT, THE IMPROVEMENT WHICH COMPRISES INTRODUCING AN AQUEOUS SOLUTION CONTAINING CHLORIDE AND CHLORATE INTO THE ANODE COMPARTMENT OF SUCH CELL, INTRODUCING WATER INTO THE BUFFER AND CATHODE COMPARTMENTS, PASSING ELECTRIC CURRENT BETWEEN THE ANODE AND CATHODE OF SAID CELL, FORMING HYDROXIDE IONS IN BOTH SAID BUFFER COMPARTMENT AND SAID CATHODE COMPARTMENTS AND CHOLRINE IN SAID ANODE COMPARTMENT, REACTING GASEOUS CHLORINE WITH THE CONTENTS OF SAID BUFFER COMPARTMENT AND/OR THE SOLUTIONS REMOVED THEREFROM, THE CONDITIONS OF SUCH REACTION BEING CONTROLLED TO PRODUCE HYPOCHLORITE OR CHLORATE AND CHLORIDE, CONVERTING THE HYPOCHLORITE, WHEN PRODUCED, TO CHLORATE AND CHLOR ATE AND CHLORIDE, FEEDING AT LEAST A PORTION OF THE CHLORATE AND CHLORIDE THUS PRODUCED TO THE ANODE COMPARTMENT FOR ELECTROLYSIS OF CHLORIDE THEREIN TO CHLORINE, WITH A RESULTING INCREASE IN THE PROPORTION OF CHLORATE TO CHLORIDE IN THE ANOYLTE, AND RECOVERING CHLORINE, CHLORATE AND SUBSTANTIALLY CHLORIDE FREE HYDROXIDE AS THE ELECTROLYSIS PRODUCTS.

Claim 3

Dependent Claim 114 words

A method according to claim 1 wherein the permselective membranes define the buffer compartment walls common with other compartments and are of a hydrolyzed copolymer of tetrafluoroethylene and a sulfonated perfluorovinyl ether of the formula FSO2CF2CF2OCF(CF3)CF2OCF CF2, which copolymer has an equivalent weight of about 900 to 1,600, gaseous chlorine is reacted with solution removed from the buffer compartment, the pH of the aqueous buffer compartment solution is maintained in the range of about 8 to 11 and the pH of the anode compartment solution is maintained in the range of about 1 to 6, with the concentrations of chloride and chlorate in the anode compartment and the buffer compartment being about the same.

Claim 4

Dependent Claim 57 words

A method according to claim 2 wherein the aqueous solution electrolyzed is a water solution of sodium chloride and sodium chlorate, the hydroxide, chlorate and chloride produced are sodium hydroxide, sodium chlorate and sodium chloride, respectively, the membrane walls are of a thickness of about 0.02 to 0.5 mm. and a portion of the anolyte is recirculated.

Claim 5

Dependent Claim 124 words

A method according to claim 3 wherein the membranes are mounted on a network of material selected from the group consisting of polytetrafluoroethylene, asbestos, perfluorinated ethylene propylene polymer, polypropylene, titanium, tantalum, niobium and noble metals, which has an area percentage of openings therein from about 8 to 80%, the temperatures of the anolyte, catholyte and buffer compartment contents are from 20* to 105*C., the pH of the reaction medium in which buffer compartment takeoff solution is converted to chlorate by treatment with chlorine gas is from 6 to 7.5, sodium chloride and sodium chlorate are separated from at least a portion of the buffer compartment medium after the reaction with chlorine and the remaining liquor, after said separation, is fed to the anode compartment.

Claim 6

Dependent Claim 159 words

A method according to claim 4 wherein the membranes are from 0.1 to 0.3 mm. thick, the network is a screen or cloth of polytetrafluoroethylene filaments having a thickness of 0.01 to 0.3 mm. which is less than or equal to the thickness of the membrane mounted thereon and the area percentage of openings in the screen or cloth is from 10 to 70%, water is added to the catholyte, liquid sodium hydroxide solution is removed therefrom, solid sodium chloride and sodium chlorate are obtained by crystallization and separation operations, at least part of the chlorine gas produced in the anode compartment is reacted with contents removed from the buffer compartment to produce chlorate and chloride and at least a part of the solution resulting from such reacTion, together with the solution remaining after removal of solid sodium chloride and solid sodium chlorate therefrom and a portion of the anolyte are mixed together and fed to the anode compartment.

Claim 7

Dependent Claim 224 words

A method according to claim 5 wherein the surface of the cathode is of a material selected from the group consisting of platinum, iridium, ruthenium, rhodium, graphite, iron and steel and the surface of the anode is 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 and mixtures thereof, on a valve metal, the aqueous sodium chloride solution being electrolyzed is at a concentration of from 200 to 320 grams of NaCl per liter, the pH''s of the anolyte and buffer compartment solution are about 1 to 5, the temperature of the electrolyte in anode, buffer and cathode compartments is about 50* to 105*C., the voltage is from about 2.3 to 5 volts, the current density is from about 0.5 to 4 amperes per square inch of electrode surface, a composition of the same constitution as the feed to the anode compartment is fed to the buffer compartment and the mixture of recirculated anolyte, sodium chloride and sodium chlorate in solution, from reaction of the buffer compartment solution with chlorine, and a mother liquor remaining after removal of solid sodium chloride and solid sodium chlorate from such solution are blended together and saturated with sodium chloride before being fed to the anode compartment and the buffer compartment.

Claim 8

Dependent Claim 151 words

A method according to claim 6 wherein the equivalent weight of the membrane copolymer is from about 1,100 to 1,400, the cathode is of steel and the anode is of ruthenium oxide on titanium, the aqueous sodium chloride solution being electrolyzed is at a concentration of 250 to 300 grams per liter, the pH of the anolyte is from 2 to 4 the temperature of the electrolyte is from about 65* to 95*C. in anode, buffer and cathode compartments, the three solutions of claim 6 that are blended together are passed through a salt resaturator wherein solid sodium chloride is dissolved therein to saturate the combined solution with sodium chloride and the solution is fed to the anolyte and buffer compartments, with the proportion being fed to the anode compartment such that the acid content thereof prevents the sodium hydroxide therein from causing salting out of sodium chlorate in the cell.

Claim 9

Independent Claim 156 words

A method for electrolytically manufacturing a chlorate which comprises electrolyzing an aqueous solution containing chloride and chlorate ions in an electrolytic cell having at least three compartments therein, an anode, a cathode, at least one cation-active permselective membrane defining a cathode-side wall of a buffer compartment between the anode and cathode, an anode-side wall of said buffer compartment being defined by a cation-active permselective membrane or porous diaphragm, and such walls, with walls thereabouts, defining anode and cathode compartments, reacting gaseous chlorine with the contents of the buffer compartment and/or solution removed from it, regulating the rate of feed thereof and reaction conditions to produce hypochlorite or chlorate and chloride from hydroxide therein, converting the hypochlorite, when produced, to chlorate and chloride, feeding at least a portion of the chlorate and chloride produced thereby to the anode compartment and electrolyzing the chloride therein to chlorine, to increase the proportion of chlorate to chloride in the anolyte.

Claim 10

Independent Claim 156 words

A method for electrolytically manufacturing a chlorate which comprises electrolyzing an aqueous solution containing chloride and chlorate ions in an electrolytic cell having at least three compartments therein, an anode, a cathode, at least one cation-active permselective membrane defining a cathode-side wall of a buffer compartment between the anode and cathode, an anode-side wall of said buffer compartment being defined by a cation-active permselective membrane or porous diaphragm, and such walls, with walls thereabouts, defining anode and cathode compartments, reacting gaseous chlorine with the contents of the buffer compartment and/or solution removed from it, regulating the rate of feed thereof and reaction conditions to produce hypochlorite or chlorate and chloride from hydroxide therein, converting the hypochlorite, when produced, to chlorate and chloride, feeding at least a portion of the chlorate and chloride produced thereby to the anode compartment and electrolyzing the chloride therein to chlorine, to increase the proportion of chlorate to chloride in the anolyte.

Claim 11

Dependent Claim 66 words

A continuous method according to claim 8 wherein the electrolytic cell includes three compartments, anode, buffer and cathode compartments, the walls separating such compartments are of cation-active permselective membrane, and sodium chloride and sodium chlorate are charged to the anolyte compartment and sodium chlorate, chlorine, chlorine-free aqueous Sodium hydroxide solution and hydrogen are produced, the chlorate being produced from buffer compartment effluent external to the reactor.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1978-04-14	1978-10-14	1979-04-15	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1982-04-14	1982-10-14	1983-04-15	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1986-04-14	1986-10-14	1987-04-15	$7700.00	Window Closed / Lapsed

Electrolytic method for the manufacture of chlorates

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