WO1991015614A1 - Procede electrochimique de production d'acide chlorique a partir d'acide hypochloreux - Google Patents

Procede electrochimique de production d'acide chlorique a partir d'acide hypochloreux Download PDF

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Publication number
WO1991015614A1
WO1991015614A1 PCT/US1991/002182 US9102182W WO9115614A1 WO 1991015614 A1 WO1991015614 A1 WO 1991015614A1 US 9102182 W US9102182 W US 9102182W WO 9115614 A1 WO9115614 A1 WO 9115614A1
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WO
WIPO (PCT)
Prior art keywords
acid
chloric acid
solution
hypochlorous
anode
Prior art date
Application number
PCT/US1991/002182
Other languages
English (en)
Inventor
David W. Cawlfield
Jerry J. Kaczur
Ronald L. Dotson
Sudhir K. Mendiratta
Budd L. Duncan
Kenneth E. Woodard, Jr.
Original Assignee
Olin Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US07/502,206 external-priority patent/US5089095A/en
Priority claimed from US07/581,812 external-priority patent/US5108560A/en
Application filed by Olin Corporation filed Critical Olin Corporation
Publication of WO1991015614A1 publication Critical patent/WO1991015614A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/24—Halogens or compounds thereof
    • C25B1/26—Chlorine; Compounds thereof

Definitions

  • Chloric acid can be used in the formation of chlorine dioxide, a commercial bleaching and sanitizing agent.
  • Chloric acid is a known compound which has been made in laboratory preparations by the reaction of barium chlorate with sulfuric acid to precipitate barium sulfate and produce a dilute aqueous solution of chloric acid which was concentrated by evaporation of water under partial vacuum.
  • sodium chlorate is reacted with an acid such as hydrochloric acid or sulfuric acid to produce an aqueous solution of chloric acid containing sulfate or chloride ions as impurities.
  • commercial processes for producing chlorine dioxide form chloric acid as an intermediate.
  • U.S. Patent 3,810,969 issued May 14, 1974 to A.A. Schlumberger teaches a process for producing chloric acid of high purity by passing an aqueous solution containing from 0.2 gram mole to 11 gram moles per liter of an alkali metal chlorate such as sodium chlorate through a selected cationic exchange resin at a temperature from 5° to 40°C The process produces an aqueous solution containing from 0.2 gram mole to about 4.0 gram moles of HCIO-,.
  • Chloric acid however, up to the present time, has not been produced or available commercially because of the high manufacturing costs and/or the undesired impurities present in the solutions of HCIO- made by these reactions.
  • chloric acid can be produced efficiently at substantially reduced production costs using a process which can be operated commercially.
  • the chloric acid solutions produced are of high purity and are stable at ambient conditions.
  • a process for the production of chloric acid in high concentrations and substantially free of impurities such as. alkali metal ions, chloride ions and sulfate ions.
  • the process of the invention produces chloric acid in an electrolytic cell having an anode and a cathode, the process comprises feeding an aqueous solution of hypochlorous acid to the electrolytic cell, and electrolyzing the aqueous solution of hypochlorous acid solution to produce a chloric acid solution.
  • chloric acid is produced in an electrolytic cell having an anode compartment, a cathode compartment, and an cation exchange membrane separating the anode compartment from the cathode compartment, the process comprises feeding an aqueous solution of hypochlorous acid to the anode compartment, and electrolyzing the aqueous solution of hypochlorous acid solution to produce a chloric acid solution.
  • the process is represented by the following equation:
  • the novel process of the present invention employs as the starting material a concentrated solution of hypochlorous acid, HOC1.
  • One method of producing high purity concentrated HOC1 solutions is that in which gaseous mixtures, having high concentrations of hypochlorous acid vapors and chlorine monoxide gas and controlled amounts of water vapor are produced, for example, by the process described by J. P. Brennan et al in U.S. Patent No. 4,147,761. The gaseous mixture is then converted to a concentrated hypochlorous acid solution.
  • An additional process for producing high purity HOC1 solutions is that in which gaseous chlorine monoxide is dissolved in deionized water.
  • hypochlorous acid solution employed as the anolyte may be of any concentration, for practical reasons it is preferred to employ solutions which contain concentrations of from about 5 to about 60, and more preferably from about 5 to about 35 percent by weight of HOC1.
  • the solution is substantially free of ionic impurities such as chloride ions and alkali metal ions as well as metal ions such as nickel and copper, . among others.
  • the process of the invention is shown by the FIGURE which is a diagrammatic illustration of a system which can be employed.
  • the FIGURE shows an electrolytic cell 4 divided into anode compartment 10 and cathode compartment 30 by cation permeable ion exchange membrane 16.
  • Anode compartment 10 includes anode 12, and anode chamber 14 behind anode 12 for circulation of a coolant.
  • Cathode compartment 30 includes cathode 32, and cathode chamber 34 which aids in the disengagement of any catholyte gas produced.
  • the hypochlorite acid solution is pumped from container 40 to anode compartment 10 of electrolytic cell 4. Following electrolysis, the chloric acid solution produced is removed and passed through heat exchanger 50, and recovered. Spent catholyte from cathode compartment 30 is removed and returned to container 60.
  • Electrolytic cell designs for use in operating the process of the invention are those which minimize the anode to cathode gap to reduce electrical resistance.
  • the anode to membrane gap is maintained as narrow as possible but should be wide enough to prevent actual contact during cell operation. Maintenance of the anode to membrane gap can be accomplished, for example, by operating the cell with a higher pressure in the anode compartment than the cathode compartment, or by placing a fine non-conductive porous spacer between the anode and the membrane.
  • Suitable anode materials must be stable in an acidic and oxidative media.
  • anode material examples include platinum group metals, platinum group metal coated substrates, glassy carbon, fluorinated carbons, lead dioxide, noble metal oxides, and substrates coated with noble metal oxides.
  • the anode structure is preferably porous be"ing formed, for example, of a coated wire cloth or expanded mesh in a structure which allows the anolyte to flow in all three dimensions and promotes turbulence near the anode surface.
  • Materials which can be employed in the anode structures include platinum and platinum group metals, metal substrates coated with platinum or platinum group metals, lead dioxide and metal substrates coated with lead dioxide
  • Suitable metal substrates include valve metals such as titanium and niobium among others.
  • the anode is attached for example, by welding, to a back plate which is electrically and thermally conductive.
  • This back plate forms a wall of the anode chamber through which the coolant is circulated.
  • Suitable coolants include water, alcohol solutions, and glycol solutions.
  • the cathode is preferably in contact with the ion exchange membrane to minimize interference of hydrogen gas produced on the cathode with ionic conduction of hydrogen ions through the membrane to the cathode.
  • Any suitable materials which evolve hydrogen gas may be employed in the cathode such as stainless steel, nickel alloys, platinum group metals, metals plated with platinum group metals etc.
  • the cathode material should be insoluble in the acidic catholyte media while under current load, and preferably insoluble without cathodic protection.
  • any suitable electrolyte may be employed such as a mineral acid i.e., sulfuric acid, phosphoric acid, or hydrochloric acid , as well as chloric acid and/or perchloric acid.
  • the catholyte is a solid state acid such as a perfluorosulfonic acid resin (sold commercially by E.I. DuPont de Nemours & Company, Inc., under the trademark "NAFION").
  • a solid state acid such as a perfluorosulfonic acid resin (sold commercially by E.I. DuPont de Nemours & Company, Inc., under the trademark "NAFION").
  • the cation exchange membrane selected as a separator between the anode and cathode compartments is a chemically stable membrane which is substantially impervious to the hydrodynamic flow of the electrolytes and the passage of any gas products produced in the anode or cathode compartments.
  • Cation exchange membranes are well-known to contain fixed anionic groups that permit intrusion and exchange of cations, and exclude anions from an external source.
  • the resinous membrane or diaphragm has as a matrix, a cross-linked polymer, to which are attached charged groups such as —SO ⁇ .
  • the resins which can be used to produce the membranes include, for example, fluorocarbons, vinyl compounds, polyolefins, hydrocarbons, and copolymers thereof.
  • Preferred are cation exchange membranes such as those comprised of fluorocarbon polymers having a plurality of pendant sulfonic acid groups and/or phosphonic acid groups.
  • sulfonic acid group is meant to include compounds of sulfonic acid which when hydrolyzed produce sulfonic acid such as sulfonyl chloride and sulfonyl fluoride.
  • phosphonic acid group is meant to include compounds which when hydrolyzed produce phosphonic acid.
  • the process is operated to minimize the residence time of the chloric acid solution in the anolyte system. This can be achieved, for example, by limiting the size of the anode compartment with respect to width or length, etc. Residence times which are satisfactory are those which minimize decomposition of the hypochlorous acid by non-electrolytic reactions. Suitable residence times are typically less than about 8 hours, and preferably less than 2 hours.
  • the temperature of the chloric acid solution can be up to about 80 ⁇ C, and preferably from about 40° to about 80°C.
  • the chloric acid solution produced in the process of the invention includes mixtures of chloric acid and hypochlorous acid.
  • Concentrated chloric acid solutions are produced, for example, by evaporation of a portion of the water. Any residual hypochlorous acid is decomposed during the concentration.
  • the chloric acid solution is heated at temperatures above about 40°C. , for example at temperatures in the range of from about 40 to about 120 °C, preferably at from about 70 to about 120 °C. and more preferably at from about 95 to about 120 °C. It may be advantageous to employ a sealed reactor to decompose the hypochlorous acid at the autogenous pressures attained.
  • a dilute chloric acid solution can be concentrated by vacuum distillation at any suitable vacuum pressures such as those in the range of from about 0.01 to about 100 mm Hg.pressure
  • Chloric acid solutions can be produced by the novel process of the present invention in any concentrations desired up to about 45% by weight of HCIO-.. However, for commercial applications, preferred concentrations are those in the range of from about 10 to about 40% by weight of HCIO-.
  • a portion of the chloric acid solution produced is admixed with additional hypochlorous acid and the process operated continuously. This improves, for example, the conductivity of the anolyte.
  • An electrochemical cell of the type shown in Figure 1 was employed having an anode compartment and a cathode compartment separated by a cation exchange membrane.
  • the anode was formed from a platinum-clad niobium plate about .04" thick having an active surface area formed of a 10 x 10 square weave mesh.
  • the anode was spot-welded under an inert helium blanket to a platinum-clad niobium plate and placed within an anode spacer to form the anode compartment.
  • the anode compartment with the spacer was about 1/8 inch (0.3176 centimeters) wider than the anode, leaving a small gap adjacent- the cation exchange membrane through which the anolyte was force circulated.
  • the cathode was formed from a two layer Hastelloy®C-22 mesh structure having a very fine outer 100 mesh screen layer supported on a coarse inner (6 wires per inch) mesh layer.
  • the cathode was attached to a solid Hastelloy®C-22 backplate by spot welding and was placed within a cathode spacer to form a cathode compartment.
  • the cathode was in direct contact with the adjacent membrane in a zero-gap configuration.
  • hypochlorous acid containing 25% by weight of HOCl was continuously fed to the anode compartment as the anolyte at a flow rate of about 0.5 ml/min.
  • the catholyte compartment was initially filled with deionized water.
  • the deionized water was gradually acidified to a dilute hydrochloric acid of about 3% to about 5% concentration from the diffusion of a small amount of hypochlorous acid and/or chlorine gas from the anolyte compartment through the membrane.
  • the cell was operated at a current of 7.5 amps which was gradually increased to a final current of 10 amps.
  • the cell voltage was in
  • the electrolytic cell of Example 1 had the anode replaced with an anode formed from a platinum clad niobium plate with platinum clad mesh of the same size as in Example 1, but with a lead oxide coating.
  • the cell was operated for about eleven and one-half hours by continuously feeding as the anolyte an aqueous solution of hypochlorous acid containing 15% by weight of HOCl.
  • the cell operation was interrupted after about five and one-half hours and then restarted after about a sixteen and one-half hour interruption.
  • the anolyte feed rate was maintained at 0.77-0.78 ml/min during the periods of operation.
  • Chlo ic acid concentrations produced in the anolyte were in the range of from 8.812 to 10.406% by weight, with the concentration of HOCl being in the range of from 1.965 to 3.242% by weight
  • the electrolytic cell of Example 2 was employed with the same platinum cladding layer on the anode coated with lead oxide.
  • the anolyte solution an aqueous solution of hypochlorous acid containing about 15% by weight of HOCl, was continuously fed to the anode chamber at a rate maintained at about 0.77-0.78 ml/min.
  • the cell current was maintained in the range of about 6.0 to about 7.1 amps and the cell voltage varied from about 2.685 to about 2.789 volts.
  • the cell was operated for about 4 hours before operation was interrupted for about 17 hours and then resumed for an additional 4.5 hours.
  • Chloric acid concentrations produced in the anolyte were in the range of from about 5.961 to about 8.376% by weight, with the concentration of HOCl being in the range of from about 5.635 to about 8.211% by weight after the first three hours of operation.
  • the electrolytic cell of Example 1 was employed, except that the anode was formed from a porous felt metal structure of titanium metal ribbons coated with platinum metal.
  • the cell current was maintained at about 7.0 amps and cell voltages varied from about 2.750 to about 2.792 volts during about 7 hours of continuous operation.
  • Chloric acid was produced at a concentration in the range of from about 9.596 to about 11.547% by weight with the hypochlorous acid concentration being maintained at about 2.747 to about 3.014% by weight.
  • the yield of chloric acid was in the range of about 38.9 to about 48% at HOCl conversions of from about 81.1 to about 85.0%.
  • Current efficiencies were in the range of from about 62.1 to about 74.1%.
  • the electrolytic cell of Example 4 was operated for about 13 hours with one approximately 16 hour interruption after the first 6.5 hours of operation using an aqueous solution of hypochlorous acid containing about 20% by weight of HOCl as the anolyte.' After startup, the cell current was maintained in the range of about 7.0 to about 8.2 amps and cell voltages varied from about 2.662 to about 2.831. The yield of chloric acid having concentrations in the range of about 12.373 to about 17.208% by weight was from about 36.8 to about 47.2 percent. HOCl conversions of to HCIO- ranged from about 71.2 to about 90.3%. Current efficiencies of about 62.1 to about 74.1% were achieved.
  • the concentrations of chloric acid produced were in the range of from about 12.275 to about 17.208% by weight at yields of about 28.2 to about 47.2% at conversions of about 95.3 to about 100%.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

Abstract

Procédé de production d'acide chlorique dans une cellule électrolytique (1) comportant une anode et une cathode (32), consistant à alimenter la cellule électrolytique (4) en solution aqueuse d'acide hypochloreux, et à électrolyser la solution aqueuse d'acide hypochloreux afin de produire une solution d'acide chlorique. On produit des solutions d'acide chlorique présentant des concentrations situées dans la plage comprise entre 10 et 40 % en poids de HClO3.
PCT/US1991/002182 1990-03-30 1991-03-28 Procede electrochimique de production d'acide chlorique a partir d'acide hypochloreux WO1991015614A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US502,206 1990-03-30
US07/502,206 US5089095A (en) 1990-03-30 1990-03-30 Electrochemical process for producing chlorine dioxide from chloric acid
US581,812 1990-09-13
US07/581,812 US5108560A (en) 1990-03-30 1990-09-13 Electrochemical process for production of chloric acid from hypochlorous acid

Publications (1)

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WO1991015614A1 true WO1991015614A1 (fr) 1991-10-17

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5284553A (en) * 1990-08-22 1994-02-08 Sterling Canada, Inc. Chlorine dioxide generation from chloric acid
GR20130100562A (el) * 2013-10-03 2015-05-18 Θεοδωρος Ευσταθιου Καραβασιλης Κυτταρο ηλεκτρολυσης με κασετες ηλεκτροδιων

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4798715A (en) * 1988-02-05 1989-01-17 Eltech Systems Corporation Producing chlorine dioxide from chlorate salt

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4798715A (en) * 1988-02-05 1989-01-17 Eltech Systems Corporation Producing chlorine dioxide from chlorate salt

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY, Volume 5, p. 587,1979. *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5284553A (en) * 1990-08-22 1994-02-08 Sterling Canada, Inc. Chlorine dioxide generation from chloric acid
GR20130100562A (el) * 2013-10-03 2015-05-18 Θεοδωρος Ευσταθιου Καραβασιλης Κυτταρο ηλεκτρολυσης με κασετες ηλεκτροδιων

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AU7689691A (en) 1991-10-30

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