US3763005A - Electrolytic process for obtaining chlorine in a pure state and alkali metal phosphates in concentrated solution and a cell for accomplishing this process - Google Patents

Electrolytic process for obtaining chlorine in a pure state and alkali metal phosphates in concentrated solution and a cell for accomplishing this process Download PDF

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Publication number
US3763005A
US3763005A US00142672A US3763005DA US3763005A US 3763005 A US3763005 A US 3763005A US 00142672 A US00142672 A US 00142672A US 3763005D A US3763005D A US 3763005DA US 3763005 A US3763005 A US 3763005A
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United States
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alkali metal
cell
chlorine
process according
compartment
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US00142672A
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English (en)
Inventor
J Butre
F Pierrot
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Progil SARL
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Progil SARL
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    • 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
    • C25B1/14—Alkali metal compounds
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/30—Alkali metal phosphates
    • C01B25/301—Preparation from liquid orthophosphoric acid or from an acid solution or suspension of orthophosphates
    • C01B25/303—Preparation from liquid orthophosphoric acid or from an acid solution or suspension of orthophosphates with elimination of impurities
    • 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

  • the present invention relates to a process ofmanufacturing electrolytically in a cationic permselective membrane cell, pure chlorine, hydrogen and alkali metal phosphates in concentrated solution, from alkali metal chlorides and phosphoric acid obtained from attack on natural phosphate by the wet process. It relates also to electrolysis equipment for use in this process.
  • alkali metal chloride electrolysis in a cell having a permselective membrane of cationexchanger type gives rise to chlorine, hydrogen and a pure alkali metal hydroxide as compared to cells with diaphragms which act as percolators and which give chlorine, hydrogen and a diluted mixture of alkali metal hydroxides and chlorides.
  • the process accordingto the present invention comprises introducing in forced circulation into the anodic compartment an aqueous alkali metal chloride solution, while concentrated phosphoric acid or a concentrated alkali metal phosphate aqueous solution is fed in forced circulation into the cathodic compartment of an electrolysis cell, the cell having a cationic permselective membrane placed between the two electrodes and an anode which is of a porous nature in order to allow electrolyte percolation, and which presents an electrochemical activity only on the face opposite to the membrane.
  • This dilution may even be suppressed by a convenient choice of concentration ratio of the two liquid flows.
  • the permselective membrane is a strong acid cationexchanger-membrane the material of which is chosen from those polymers presenting a good resistance to chlorine and alkaline agents, especially perfluorinated polymers. Substitution resistance of such a membrane :in 0.6 N potassium chloride is between 0.2 and 8 ohm.cm according to the cases, and with a selectivity greater than percent.
  • the anodic compartment is divided into twodistinct portions; the properly anodic portion in which chlorine escapes on the side of the anode active face, and the portion between the anode and the membrane in which the electrolyte continuously sweeps the membrane, which is practically free from reaction products which escape on the active opposite face of the anode.
  • Percolation avoids an undesirable return of chlorine on the membrane, which could be a nuisance during a long operation.
  • the chlorine produced is not. contaminated with any other element; it is practically pure and contains a very small quantity of oxygen. There is no further-formation of oxidized derivatives of chlorine, especially chlora'tes.
  • the anode is a metal anode perforated with fine holes, made of a metal which may be titanium, tantalum, zirconium, niobium or, their alloys and covered only on one face with an active coating which may be platinum, iridium, palladium, ruthenium, osmium, rhodium, their alloys or their oxides.
  • the cathode is a metal cathode which may be perforated.
  • the solution of alkali metal chlorides preferably has a concentration near to saturation.
  • concentration near to saturation there may be used, in the case of sodium chloride solution, an industrial brine containing 300-315 g NaCl/l.
  • the solution may also be continuously resaturated; However it is possible to use solutions having a lower concentration for example down to 50 g/l.
  • the phosphoric acid used is the crude acid coming from treatment of natural phosphate by the wet process, and containing various cationic impurities. Since this acid is continuously introduced into the cathodic compartment, some of the metals present are reduced by the escaping hydrogen and precipitate in the from of phosphates in which the metal displays alow valency, which facilitates continuous filtration and a substantial recovery of P,O,, in the form of alkali metal phosphates. A complete removal of chromium and vanadium results, such products being especially troublesome in the further preparation of white alkali metal tripolyphosphates.
  • the P content of the solution may vary between 200 and 500 g/l.
  • the electrical energy used in the process according to the present invention is lower than that necessary for the production of the same quantity of chlorine in diaphragm cells. Electrical yield is greater than 99.5 percent.
  • Chlorine free from hydrogen contains less than 0.5 percent of oxygen.
  • the alkali metal phosphates produced contain less than 0.3 percent of the corresponding chloride.
  • brine containing the recycled salt thru line 8 and a fresh quantity of salt thru 9 arrives continuously in cell 10 thru line 11 between the membrane l2 and the anode 14.
  • Brine sweeps the membrane 12 which lets the sodium ions pass and electrolysis is conducted on the platinum covered active side 16 of the perforated titanium anode 14. Because of the circulation, very pure chlorine is removed at 18 at the same time as the unreacted brine. The mixture passes thru one or several degassers 20 which completely remove chlorine, which is sent to storage and brine is recycled thru 24 and a purifier 25. Phosphoric acid is fed continuously thru 26 into the cathodic compartment 28 consisting of a perforated nickel cathode 30. Because of the circulation, hydrogen, concentrated alkali metal phosphates and the precipitate of other metal phosphates are removed continuously thru 32, then pass into a degasser 34. Hydrogen is sent to storage thru 36, the precipitated phosphates are filtered at 38 and removed at 40 and pure alkali metal phosphates are obtained at 42 as a concentrated aqueous solution.
  • the cell described in this way is a monoelement cell.
  • Several monoelements may be mounted in series, according to techniques similar to that of filter-presses.
  • EXAMPLE 1 sodium chloride 304 gr. per liter sodium carbonate 0.3 gr. per liter sodium sulfate 7 gr. per liter Ca l.5 gr. per liter Mg 0.4 gr. per liter
  • a crude phosphoric acid coming from natural phosphate attach by the wet process and containing especially:
  • EXAMPLE 3 Temperature 60C. Voltage 4 volts Anolyte recycling rate 70% EXAMPLE 4
  • the solution arriving continuously under pressure into the anodic compartment of the cell used in the previous examples was potassium chloride of 340, g/l.
  • Anolyte concentration was maintained near 310 g/l. of sodium chloride.
  • a process of manufacturing chlorine in a pure state, hydrogen, and alkali metal phosphates in concentrated solution in an electrolysis cell said cell having a cationic permselective membrane separating an anode from a cathode and defining, respectiveiy, anodic and cathodic compartments, said anode being porous and presenting an electrochemical activity only on its face opposite from that nearest to said cationic permselective membrane, which process comprises introducing in forced circulation into the anodic compartment between the anode and said cationic permselective membrane an aqueous alkali metal chloride solution, at the same time introducing concentrated phosphoric acid or a concentrated alkali metal phosphate aqueous solution in forced circulation into the cathodic compartmerit, forcing anolite electrolyte to percolate through the porous anode thereby preventing chlorine from escaping into the space between said anode and said cationic permselective membrane.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
US00142672A 1970-05-15 1971-05-12 Electrolytic process for obtaining chlorine in a pure state and alkali metal phosphates in concentrated solution and a cell for accomplishing this process Expired - Lifetime US3763005A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7017742A FR2087342A5 (fr) 1970-05-15 1970-05-15

Publications (1)

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US3763005A true US3763005A (en) 1973-10-02

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US00142672A Expired - Lifetime US3763005A (en) 1970-05-15 1971-05-12 Electrolytic process for obtaining chlorine in a pure state and alkali metal phosphates in concentrated solution and a cell for accomplishing this process

Country Status (12)

Country Link
US (1) US3763005A (fr)
BE (1) BE767226A (fr)
CA (1) CA948150A (fr)
CS (1) CS172923B2 (fr)
DE (1) DE2124045C3 (fr)
ES (1) ES391040A1 (fr)
FR (1) FR2087342A5 (fr)
GB (1) GB1313441A (fr)
NL (1) NL7106594A (fr)
PL (1) PL81620B1 (fr)
RO (1) RO59453A (fr)
SU (1) SU467511A3 (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3974047A (en) * 1975-06-02 1976-08-10 The B. F. Goodrich Company Electrolytic cation exchange process for conjoint manufacture of chlorine and phosphate salts
US4086155A (en) * 1975-04-25 1978-04-25 Battelle Memorial Institute Electrolyzer with released gas
US4100050A (en) * 1973-11-29 1978-07-11 Hooker Chemicals & Plastics Corp. Coating metal anodes to decrease consumption rates
US4308122A (en) * 1978-12-04 1981-12-29 Hsa Reactors Limited Apparatus for waste treatment equipment
US4389287A (en) * 1980-01-31 1983-06-21 Skala Stephen F Withdrawal of molten alkali hydroxide through an electrode for depletion of water dissolved therein
CN102732906A (zh) * 2012-07-04 2012-10-17 四川大学 一种电解法制备磷酸二氢钾的方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE795460A (fr) * 1972-02-16 1973-08-16 Diamond Shamrock Corp Perfectionnements relatifs a des cuves electrolytiques

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4100050A (en) * 1973-11-29 1978-07-11 Hooker Chemicals & Plastics Corp. Coating metal anodes to decrease consumption rates
US4086155A (en) * 1975-04-25 1978-04-25 Battelle Memorial Institute Electrolyzer with released gas
US3974047A (en) * 1975-06-02 1976-08-10 The B. F. Goodrich Company Electrolytic cation exchange process for conjoint manufacture of chlorine and phosphate salts
US4326938A (en) * 1978-04-12 1982-04-27 Hsa Reactors Limited Planar carbon fiber electrode structure
US4308122A (en) * 1978-12-04 1981-12-29 Hsa Reactors Limited Apparatus for waste treatment equipment
US4389287A (en) * 1980-01-31 1983-06-21 Skala Stephen F Withdrawal of molten alkali hydroxide through an electrode for depletion of water dissolved therein
CN102732906A (zh) * 2012-07-04 2012-10-17 四川大学 一种电解法制备磷酸二氢钾的方法

Also Published As

Publication number Publication date
CS172923B2 (fr) 1977-01-28
SU467511A3 (ru) 1975-04-15
DE2124045C3 (de) 1973-11-22
DE2124045B2 (de) 1973-04-26
BE767226A (fr) 1971-11-16
GB1313441A (en) 1973-04-11
NL7106594A (fr) 1971-11-17
RO59453A (fr) 1976-03-15
PL81620B1 (fr) 1975-08-30
CA948150A (en) 1974-05-28
FR2087342A5 (fr) 1971-12-31
ES391040A1 (es) 1973-06-16
DE2124045A1 (de) 1971-11-25

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