US3654104A - Electrolysis of salt solution - Google Patents

Electrolysis of salt solution Download PDF

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Publication number
US3654104A
US3654104A US8825A US3654104DA US3654104A US 3654104 A US3654104 A US 3654104A US 8825 A US8825 A US 8825A US 3654104D A US3654104D A US 3654104DA US 3654104 A US3654104 A US 3654104A
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United States
Prior art keywords
compartment
solution
anode
cathode
exchange membrane
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Expired - Lifetime
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US8825A
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English (en)
Inventor
Mitsuo Yoshida
Hisao Kai
Tetsuo Yamane
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Asahi Kasei Corp
Asahi Chemical Industry Co Ltd
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Asahi Chemical Industry Co Ltd
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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
    • C25B1/24—Halogens or compounds thereof
    • C25B1/26—Chlorine; Compounds thereof
    • 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
    • C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
    • C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells

Definitions

  • An aqueous solution of alkali metal halide or hydrochloric acid is electrolyzed in an electrolytic cell consisting of at least one unit cell which comprises a cathode, an anode, a cation exchange membrane, and a neutral diaphragm having a water permeability of not more than 5 cc./ min. cm. under a pressure difference of 1 kg./cm.
  • cation exchange membrane and the neutral diaphragm are juxtaposed at a distance between the cathode and the anode to form an anode compartment between the anode and the neutral diaphragm, an intermediate compartment between the neutral diaphragm and the cation exchange membrane, and a cathode compartment between the cation exchange membrane and the cathode, by passing each compartment solution at a flow velocity of at least 3 cm./sec., While keeping an inside pressure of the intermediate compartment higher than that of the anode compartment.
  • This invention relates to a process for electrolysis of an aqueous electrolyte solution, and more particularly, it relates to a process for electrolyzing an aqueous solution of alkali metal halide or hydrochloric acid in a three-compartment electrolytic cell containing a neutral diaphragm and a cation exchange membrane.
  • the object of this invention is to overcome the abovesaid drawbacks of the heretofore-proposed methods for electrolyzing the aqueous electrolyte solution by using an ion exchange membrane and a neutral diaphragm. That is, the object of the present invention is to provide a method by which the electrolysis of alkali metal halide or hydrochloric acid may be carried out while maintaining the conditions at high current density under low voltages with high stability for a long period.
  • the electrolytic cell employed in this invention consists of at least one unit cell which comprises a cathode, an anode, a cation exchange membrane and a neutral diaphragm having a very low water permeability, Where the cation exchange membrane and the neutral diaphragm are juxtaposed at a distance between the cathode and the anode so that the cation exchange membrane and the neutral diaphragm may be at the cathode side and at the anode side respectively, to form an anode compartment defined by the anode and the neutral diaphragm, an intermediate compartment defined by the neutral diaphragm and the cation exchange membrane and a cathode compartment defined by the cation exchange membrane and the cathode.
  • an aqueous electrolyte solution is passed through the anode compartment and the intermediate compartment and a cathode solution through the cathode compartment at flow velocities of at least cm./ sec. respectively, while keeping an inside pressure of the intermediate compartment higher than an inside pressure of the anode compartment.
  • FIG. 1 shows a sectioned schematic view of the electro lytic cell used in this invention and a flow diagram showing an embodiment of the present invention.
  • FIG. 2 is the graph showing a relation between a flow velocity within an electrolytic cell and voltage of the cell of Example 3.
  • an electrolytic cell 19 consists of an anode 1, a cathode 2, a neutral diaphragm 3, and a cation exchange membrane 4, where the neutral diaphragm 3 and the cation exchange membrane 4 are juxtaposed at a distance from about 1 to 10 mm. between the anode 1 and the cathode 2 so that the neutral diaphragm may be at the anode side and the cation exchange membrane at the cathode side, whereby there are formed an anode compartment 9 by the anode 1 and the neutral diaphragm 3, an intermediate compartment 8 by the neutral diaphragm 3 and the cation exchange membrane 4 and a cathode compartment 13 by the cation exchange membrane 4 and the cathode 2.
  • the thickness of each compartment is usually several millimeters.
  • an electrolytic cell consisting only of one unit cell is shown for simplicity of illustration, but a practical electrolytic cell consists of a stack of a plurality of such unit cells.
  • the anode materials usually used in the conventional electro lytic cell for example, graphite, platinum, and titanium or tantalum plated with a noble metal such as platinum or rhodium.
  • the cathode materials usually used in the conventional electrolytic cell for example, iron, stainless steel, and nickel.
  • the neutral diaphragm 3 it is necessary that the neutral diaphragm 3 have a water permeability as low as possible, and it is desirable that the water permeability under a pressure difference of 1 kg./cm. be not more than 5 cc./min. cm. preferably not more than 2 cc./min. cm.
  • the neutral diaphragm having such properties may be easily manufactured by known methods, from an acidresistant and chlorine-resistant material, e.g.
  • a neutral diaphragm of blue asbestos is obtained by dispersing a binder such as a latex of polyvinylidene chloride (Saran), into an aqueous slurry of blue'asbestos, then subjecting the slurry to make a diaphragm and pressing the same, and if necessary, applying a suitable material such as divinylbenzene onto the surface of the resultant diaphragm; or thediaphragm of plastics may be obtained by mixing the plastics such as polytetrafluoroethylene, polyvinylidene chloride and polyethylene terephthalate with a plasticizer, then molding the mixture into film, and extracting the plasticizer out of the film.
  • a binder such as a latex of polyvinylidene chloride (Saran)
  • a suitable material such as divinylbenzene onto the surface of the resultant diaphragm
  • thediaphragm of plastics may be obtained by mixing the plastics such
  • cation exchange membrane 4 there may be employed any one which is prepared according to the Wellknown method, but among which there are preferably used those having the properties of a low alkali diffusion from the cathode compartment 13 to the intermediate compartment 8 and a good cation transport number.
  • the feed electrolyte solutions are alkali metal halides such as sodium chloride and potassium chloride, and hydrochloric acid.
  • alkali metal halides such as sodium chloride and potassium chloride
  • hydrochloric acid When the alkali metal halide is fed the products obtained are essentially a solution of the corresponding hydroxide, gaseous hydrogen anad chlorine.
  • hydrochloric acid When hydrochloric acid is fed the products are essentially gaseous hydrogen and chlorine.
  • each compartment solution is recycled between the tanks for recycle and the electrolytic cell.
  • A11 aqueous salt solution 5 to be electrolyzed is supplied to a tank 6 for recycle of an intermediate compartment solution.
  • the intermediate compartment solution is supplied from the tank 6 to the intermediate compartment 8 by means of a pump 17. Although a very small portion of the intermediate compartment solution sometimes passes from the intermediate compartment 8 to the anode compartment 9 through the neutral diaphragm 3, almost all of the intermediate compartment solution leaves the intermediate compartment and returns to the tank 6. A portion of the thus returned solution is supplied to a tank 7 for recycle of the anode compartment solution.
  • the anode compartment solution is supplied from the tank 7 to the anode compartment 9 by means of a pump 16, and returned again to the same tank 7, after the gas generated at the anode has been separated.
  • a portion of the returned anode compartment solution leaving the electrolytic cell is, after the residual anode gas being removed therefrom at an anode gas-removing apparatus 10, then admixed with the raw material salt and water, and supplied to the tank 6 as a solution 5 through an apparatus 11 for purifying an aqueous salt solution.
  • the cathode compartment solution I is likewise recycled between a tank 12 for recycle of the cathode compartment solution and the cathode compartment 13 by means of a pump 18, and after the gas generated at the cathode has been separated, a portion of the returned cathode compartment solution leaving the electrolytic cell is taken out of the electrolytic system as the product. To the tank 12 water 15 is supplied separately.
  • the pressure 'of the intermediate compartment 8 be higher than that of the anode compartment 9 within the electrolytic cell at said solution recycle. Furthermore, it isimportant for the operation of low voltage, as shown in the examples which follow, that the flow velocity of each compartment solution be at least 3 cm./ sec. By doing so, the transference of some amount of solution from the intermediate compartment-S to the anode compartment 9 through the neutral diaphragm 3 mayoccur.
  • the flow velocity of each compartment solution Within the electrolytic cell is adjusted to at least 3 cm./sec., whereby the distribution of solution flow may be improved, a fear of polarization of the cation exchange membrane 4 may be completely eliminated, and disengagement of the gases at the anode 1 and cathode 2 from the electrode surfaces'may be accelerated to keep a stable operation under a low voltage.
  • EXAMPLE 1 Electrolysis of sodium chloride by using a neutral diaphragm having a high water permeability which is not iucluded in the scope of this invention.
  • an electrolytic cell consisting of: as an anode a platinum-plated titanium electrode; as a cathode a stainless steel electrode; as a neutral diaphragm a polyester fabric having a water permeability as high as 20 cc./min. cm. under a pressure difference of 1 kg./ cm. and as a cation exchange membranea homogeneous membrane prepared by copolymerizing the phenyl ester of vinyl sulfonic acid, styrene and divinylbenzene as its principal constituents and hydrolyzing the thus obtained copolymer; an available area for current passage of the electrodes, the membranes and the diaphragm being 500 cm. (5 cm. x cm.); an interelectrode distance being.
  • the purified salt solution could not be supplied in time to the tank 6 for recycle of the intermediate compartment solution, and a portion of the returned anode compartment solution had to be supplied to the tank 6 for recycle of the intermediate compartment solution, resulting in contamination of chlorine gas into the intermediate compartment solution.
  • EXAMPLE 2 Electrolysis of sodium chloride by using a neutral diaphragm having a low water permeability.
  • Electric current was passed through the same electrolytic cell under the same conditions as in Example 1, except that there was used a neutral diaphragm of blue asbestos sheet whose surface had been treated with divinylbenzene for reducing its porosity and reinforced with a Saran net along the surface, having a water permeability as high as cc./min. cm. under a pressure difference of 1 kg./cm. and a flow velocity of each compartment solution was adjusted to 4 cm./sec. at the inlet of the electrolytic cell.
  • the intermediate compartment solution transferred to the anode compartment through the neutral diaphragm amounted to about 50 cc./min., and the returned intermediate compartment solution corresponded to a flow velocity of about 3.1 cm./sec.
  • EXAMPLE 3 The relation between the flow velocity in each compartment at the outlet and the voltage was determined in the same electrolytic cell under the same conditions as in Example 2, and one of the results is shown in FIG. 2.
  • the electrolytic conditions are given below:
  • EXAMPLE 4 An electrolytic cell consisting of 7 unit cells, each unit cell having an available area of 70 dm. (70 cm. x100 cm.) for current passage and all the unit cells being stacked in a filter press was used, where there was used as an anode a platinum-plated titanium electrode, as a cathode an iron electrode, as a neutral diaphragm a blue asbestos sheet incorporated with a polyester fabric as a core material and surface-treated with dinylbenzene for reducing its porosity, and as a cation exchange membrane a membrane of the vinyl sulfonic acid-divinylbenzene type. The interelectrode distance was 8 mm. There were used an aqueous ca.
  • EXAMPLE 5 In the same apparatus as employed in Example I, there were assembled the cation exchange membrane, which was prepared by polymerizing acrylic acid, divinylbenzene and styrene into a film shape and then saponifying the polymerizate with caustic soda, and the neutral membrane which was prepared by a paper-making process from an aqueous slurry of unravelled blue asbestos contaming Saran latex as a binder material and then followed by being pressed under a pressure of kg./cm. which had a water permeability of 2 cc./min. cm. under a pressure diiference of 1 kg./cm.
  • a saturated aqueous solution of potassium chloride was supplied into the intermediate and anode compartments, and an aqueous solution of 5 N-KOH was supplied into the cathode compartment, at the linear flow velocity of 4 cm./sec. at the inlet part of each compartment.
  • Electrolysis was carried out under the condition that the solution temperature and the DC. electric current were 60 C. and 75 a. (15 a./dm. respectively.
  • the pressure within the intermediate compartment was made higher by approx. 0.1 kg./cm. than that within the anode compartment.
  • Aqueous 10 N HCl solutions were fed into both the anode compartment and the intermediate compartment, and an aqueous 5 N HCl solution was fed into the cathode compartment, at the linear flow velocity of 4 cm./sec. at the inlet part of each compartment, at the temperature of 60 C. with a electric current density of 15 amp./dm.
  • the pressure within the intermediate compartment was made higher by approx. 0.05 kg./c1n. than that within the anode compartment.
  • a intermediate compartment solution transferred to the anode compartment through the neutral diaphragm amounted to approx. 22 cc./min.
  • the returned intermediate compartment solution corresponded to a flow velocity of approx. 3.6 cm./sec. and no contamination of chlorine gas into the intermediate solution was observed.
  • a cell voltage showed 3.20 volts and stable, and substantially no deterioration of the cation exchange membrane and the neutral diaphragm was observed.
  • aqueous solution to be electrolyzed is an aqueous alkali metal halide solution.
  • aqueous solution to be electrolyzed is an aqueous hydrochloric acid solution.

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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)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)
US8825A 1969-02-15 1970-02-05 Electrolysis of salt solution Expired - Lifetime US3654104A (en)

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JP44010766A JPS4820117B1 (enrdf_load_stackoverflow) 1969-02-15 1969-02-15

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JP (1) JPS4820117B1 (enrdf_load_stackoverflow)
CA (1) CA967507A (enrdf_load_stackoverflow)
DE (1) DE2006660B2 (enrdf_load_stackoverflow)
FR (1) FR2035402A5 (enrdf_load_stackoverflow)
GB (1) GB1270375A (enrdf_load_stackoverflow)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3761221A (en) * 1971-10-13 1973-09-25 F Stillions Combination combustible gas generator-burner
US3869364A (en) * 1973-01-05 1975-03-04 Vast Associates Inc J System for inhibiting attack on a ferrous anode electrode in an electrodialytic cell
US4131532A (en) * 1975-10-29 1978-12-26 Societe Generale De Constructions Electriques Et Mecaniques "Alsthom Et Cie" Electrochemical oxygen production device
US4137136A (en) * 1976-10-22 1979-01-30 Asahi Denka Kogyo Kabushiki Kaisha Method for electrolyzing alkali metal halide aqueous solution
US4191619A (en) * 1977-09-29 1980-03-04 Kernforschungsanlage Julich Gesellschaft Mit Beschrankter Process for conversion of materials in electrolytic solution
US4268366A (en) * 1979-04-23 1981-05-19 Occidental Research Corporation Method of concentrating alkali hydroxide in three compartment hybrid cells
US4880513A (en) * 1986-06-20 1989-11-14 The Graver Company Method and apparatus for generating acid and base regenerants and the use thereof to regenerate ion-exchange resins

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3761221A (en) * 1971-10-13 1973-09-25 F Stillions Combination combustible gas generator-burner
US3869364A (en) * 1973-01-05 1975-03-04 Vast Associates Inc J System for inhibiting attack on a ferrous anode electrode in an electrodialytic cell
US4131532A (en) * 1975-10-29 1978-12-26 Societe Generale De Constructions Electriques Et Mecaniques "Alsthom Et Cie" Electrochemical oxygen production device
US4137136A (en) * 1976-10-22 1979-01-30 Asahi Denka Kogyo Kabushiki Kaisha Method for electrolyzing alkali metal halide aqueous solution
US4191619A (en) * 1977-09-29 1980-03-04 Kernforschungsanlage Julich Gesellschaft Mit Beschrankter Process for conversion of materials in electrolytic solution
US4268366A (en) * 1979-04-23 1981-05-19 Occidental Research Corporation Method of concentrating alkali hydroxide in three compartment hybrid cells
US4880513A (en) * 1986-06-20 1989-11-14 The Graver Company Method and apparatus for generating acid and base regenerants and the use thereof to regenerate ion-exchange resins

Also Published As

Publication number Publication date
CA967507A (en) 1975-05-13
FR2035402A5 (enrdf_load_stackoverflow) 1970-12-18
GB1270375A (en) 1972-04-12
DE2006660A1 (de) 1970-08-20
DE2006660B2 (de) 1971-12-02
JPS4820117B1 (enrdf_load_stackoverflow) 1973-06-19

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