FR2510143A1 - ION-EXCHANGING MEMBRANE ELECTROLYTIC DEVICE AND METHOD OF MANUFACTURING THE SAME - Google Patents

Abstract

THIS DEVICE INCLUDES A CATHODE, ANODE AND AN ION EXCHANGER MEMBRANE PLACED BETWEEN THEM. ACCORDING TO THE INVENTION, AT LEAST ONE OF THE ELECTRODES CONSTITUTED BY THE CATHODE AND THE ANODE IS FORMED OF A POREOUS ELECTRODE-PLATE PERMEABLE TO GAS AND LIQUID, WHICH IS INTIMATELY CONNECTED TO THE ION EXCHANGER MEMBRANE BY A POWDER OF ION EXCHANGE RESIN.

Description

The present invention relates to an electronic device

  lytic membrane using an ion exchange membrane and a method for

its manufacture.

  More specifically, the invention relates to an electrolytic device having an ion exchange membrane in the form of a diaphragm of solid polymeric electrolyte and wherein at least the cathode or the anode, formed by a gas-permeable porous plate and to the liquid, is intimately connected to the ion exchange membrane by a powdered ion exchange resin, as well as

  that a method for making this device.

  In recent times, save energy or resources, for example by reducing the consumption of electrical energy or by reducing the size of appliances,

  for example, has become a significant problem because of the increase in

  rapid cost of energy.

  For the electrolysis of aqueous solutions of sodium chloride and other substances, a cathode and anode separated by an interval of a diaphragm disposed between them have been used in the past. As an improvement, it has been proposed to adhere the cathode and the anode intimately to a cation exchange membrane, which decreases the electrical resistance due to the release of gas, resulting in a decrease of the electrolysis voltage (for example as described in Japanese Patent Applications (OPI)) 47 877/79 and 60 295/79) Various types of electrolytic processes using a so-called solid polymeric electrolyte are also known, see, for example, Japanese Patent Application Laid-Open No. 45,557 / 76 (corresponding to the United States patent). No. 3 489 670) and Japanese Patent Application (OPI) 78 788/77 (corresponding to

  U.S. Patent No. 4,039,409) concerning the elec-

  trolysis of water, Japanese Patent Application (OPI) 52 297/78 relates to

  Glauber salt electrolysis, Japanese patent applications

  (OPI) 95 996/79 and 97 581/79 concerning the hydrolysis of chlorinated

  as well as Japanese Patent Applications (OPI) 102 278/78, 93 690/79, 107 493/79, 112 398/79, 115 982/80 and 131 187/80 concerning

hydrolysis of sodium chloride.

  In an electrolytic device for a process

  using a solid polymeric electrolyte, an exchange membrane

  ion generator is used as an electrolyte diaphragm and

  electrocatalytic cathode and anode laminates are held against both sides of the diaphragm because they are directly connected to it.

  in such a device by contacting a power supply conductor

  with the electrocatalytic layer The distance between

  electrodes is thus reduced to the thickness of the diaphragm and, theo-

  There is no electrolytic solution between electri-

  Thus, since the losses due to the electrical resistance of the electrolytic solution between the electrodes and the release of bubbles are suppressed, the electrolysis voltage can be reduced accordingly. using a solid polymeric electrolyte are therefore suitable

  excellently to reduce energy consumption.

  However, in prior methods to electrodes

  intimately adhering to each other and those using electro-

  solid polymeric trolytes, by the progressive deflection of the ion exchange membrane during the electrolysis, and the formation of folds in the membrane, a gas such as hydrogen or chlorine accumulates in the spaces created by the separation or irregularity of shape of the ion exchange membrane, this

  which results in poor contact between the power supply

  of the electrocatalytic layer, or by a distribution

  irregular electric current on the electrolysis surface.

  This phenomenon poses a serious problem because it causes the rise

  fast electrolysis voltage.

  One method of solving this problem is to incorporate metal wires, mesh or porous plate as reinforcing elements in the ion exchange membrane and to use as adhesive a dispersion of polytetrafluoroethylene (for example as described in Japanese Patents (OPI 138 088/80, 139 842/80 and 141 580/80) However, the incorporation of

  reinforcement in the thin ion exchange membrane poses

  problems for the manufacture and properties of the membrane

  Moreover, since the adhesion of the electrode to the membrane remains inadequate

10143

  the electrode or each electrode may become detached from the membrane during a long electrolysis, in addition to the fact that

  the adhesive used increases the electrical resistance.

  The invention makes it possible to eliminate the problems described above.

  above. It provides an electrolytic device in which the adhesion between the ion exchange membrane and the cathode is excellent and by means of which the electrolysis can be carried out in a simple manner for a long time, without deformation of the

membrane.

  According to one embodiment, the electrolytic device comprises a cathode and an anode disposed on both sides of an ion exchange membrane, at least one of which is formed by a porous electrode plate permeable to gas and liquid, which is intimately connected to the membrane by an ion exchange resin of a powdery nature The invention also provides a method for

  to manufacture such an electrolytic device.

  The invention is based on the discovery that in the manufacture of

  cation of an electrolytic device with attachment of a plate

  porous electrode to an ion exchange membrane as described in Japanese Patent Application 169,406/79 of the Applicant

  or in Japanese Patent Applications (OPI) 131,187 / 80 and.

  138 088/80, a solid bond is obtained between the exchange membrane and

  ion generator and the electrode if one uses them as

  adhesive, a powdery ion exchange resin.

  The invention makes it possible to easily connect the membrane to the porous electrode plate and to obtain an intimate solid bond of high dimensional stability.

  not even if the electrolysis is continued for a long time.

  In addition, the deflection of the membrane or the formation of folds therein can be avoided without the necessity of using reinforcing elements, such as those discussed above, and it becomes possible to operate stably under

  a low voltage for a long time.

  The ion exchange resin used as an adhesive is similar to the resin used for the ion exchange membrane

  and does not alter the properties of the membrane forming the electrolyte.

  Such a resin has the additional advantage of producing an increase

  lesser of the electrical resistance.

  The membrane used in an electrolytic device according to the invention can be of different kinds and it is also possible to use a combination of several membranes, depending on the nature

of the electrolytic reaction.

  For the electrolysis of saline solutions, it is preferable to employ fluorine-containing cation exchange membranes having ion exchange groups such as carboxylic acid groups, sulfonic acid groups, hydrogenation groups, and the like. phosphoric acid or phenolic hydroxyl groups, etc., as described in Japanese Patent Applications (OPI) 131 187/80 and 138 088/80 already mentioned Other ion exchange membranes used for the implementation of the invention are described in United States Patent Nos. 3,134,697, 3,297,482,

  3,341,366, 3,432,353, 3,442,825, 3,489,670 and 4,039,409.

  At least one of the electrodes (cathode or anode) used

  in an electrolytic device according to the invention must be formed of a porous plate permeable to gas and liquid so that it

  can adhere intimately to the ion exchange membrane.

  porous electrode may be in various forms, for example as a net, sieve, woven material, mesh, perforated plate, porous sintered material, porous material having a spray applied coating, a porous material of portions of metal have been removed by etching, and so on. All these materials can be used as they are or as electrode substrates which are coated with

  active substance forming an electrode It is preferable that

  the electrode plate is approximately 10 to 99% and the size of the apertures is between approximately 1 μm and 5 mm, preferably between 100 μm and 1 mm, in order to facilitate the passage of the electrolytic solution. and the evacuation of unobstructed gases, without giving rise to the deformation of the exchange membrane

  ions by the penetration of portions of the membrane into the openings

tures of the electrode plate.

  The porous electrode plates can be made of various known materials and according to various known methods, depending on the electrolytic reaction for which the electrodes are to be used, and it is also possible to use the methods described in the documents already cited which are the application Japanese Patent Application (OPI) 131,187 / 80 and Japanese Patent Application 169,406/79 (corresponding to the United States Patent Application).

  of America No. 217,608 filed December 18, 1980).

  For example, in the electrolysis of a saline solution, it is possible to use, as cathodes, porous plates composed of iron, nickel, titanium, zirconium, niobium, or an alloy containing one of these metals. as the main component, Ti-Ta, Ti-Ta-Nb for example, platinum group metals, such as Pt, Ru, Ir, Rh or Pd, or oxides thereof, for example Ru O 2, Ir O 2, etc., other metals or metal compounds, such as W 03, Mo O 2, etc., and carbon, or combinations of these materials It is also possible to use, as cathodes, porous plates composed of iron, nickel, titanium and so on which are coated with an active cathode material by known means, for example by a thermodecomposition process, sintering of a powder, plating, spray coating etc. It is possible, for example, to use a plasma spray or metallization as described in evet

  Japanese (OPI) 40 676/73 and 46 581/76.

  As anodes, it is possible to use porous plates composed of platinum group metals, such as platinum, ruthenium, palladium, iridium, rhodium, etc., or their oxides, such as Ru 2> Pd O Ir O 23 Rh 203, etc., other metals, such as titanium, tantalum, tin or cobalt, or their oxides, such as Ti O 2,

  Ta 2 OV Sn O or combinations thereof, such as Ru O 2 -TiO O Ru O 2 -Ir O 2-

  It is also possible to use porous plates composed of titanium, tantalum, zirconium or their electrically conductive oxides, such as TiO 2 O x O <x <0.5. which are coated with an active substance forming anode by known methods, for example by a thermodecomposition process, by sintering, plating or a spray coating process, in particular as described in the United States patents

No. 3,711,385, 3,632,498.

  The porous electrode plate obtained is intimately

  to the ion exchange membrane previously described by means of

  of a powdery ion exchange resin.

  Suitable resins include known resins having sulfonic acid groups, sulfonamide groups or carboxylic acid groups, etc. as ion exchange groups, and it is also possible to use a powdery form, the resins used for the manufacture of membranes and mentioned in the docuixents cited above It is however preferable to use a resin, the same

  than that used for the membrane, which has the power to exchange

  ion generator of about 0.1 to 3 milliequivalents per gram of resin

  dry, in order to improve the intimate adhesion of the membrane to the elec-

  For example, if using Nafion NO 120 or NO 110 (Nafion is a trademark of du Pont de Nemours) for the ion exchange membrane, it is preferable to use a powder of the same resin or a

  powdery ion exchange resin such as Nafion N O 501 or 511.

  Although the particle size of the resin may be relatively freely selected, it is preferred that the average particle size be equal to or less than the average size of the apertures of the porous electrode plate. Generally, ion exchange resins will be used. dusts having an average particle size of about 0.5 to 1 mm When using such a resin as an adhesive, it easily penetrates the apertures of the porous electrode plate when assembled under heat and the pressure, with impregnation or fusion-of the resin in the plate, which makes join

  the membrane firmly and intimately to the electrode-plate.

  Different methods can be used to connect the porous electrode plate to the ion exchange membrane by means of the powdered ion exchange resin. The simplest method is to apply the powdered resin in a uniform thickness on one of the faces. of the electrode plate or the membrane and then to assemble the plate and the membrane by pressure and with heating of the assembly faces, preferably through the electrode, in order to melt the resin It is preferable that the temperature of the heating is between about 80 and 380 C and that the assembly pressure is between about 10 and 1000 kg / cm 2 The assembly under heat and pressure can be carried out in the air or, if desired, under a Inert atmosphere, under nitrogen or argon, for example. The assembly surface of the porous plate can also be pre-impregnated with the resin by mechanical introduction of the resin under pressure. u by applying a resin dispersion in a liquid, the resin may then be melted if desired by heating to form a layer of adhesive on the surface of the porous electrode plate, and then realize Another method is to deposit a powdery resin on one or both sides of the membrane during the manufacture of the membrane and to assemble the electrode plate together with the ion exchange membrane under pressure and heat. porous to the membrane under pressure and heat This last method has the advantage that the binding of the resin to the membrane and the bonding of the resin to the plate

  each electrode can be made under optimal conditions.

  males. In the case where the porous electrode plate consists of a porous electrically conductive substrate and an electrode active substance applied in the form of a coating on this substrate, it is possible to first connect the membrane intimately to the subtrate at of the resin, for example according to the method described above, and then cover the other side of the substrate with the active substance In this process, the application of the electrocatalytic substance should be carried out under conditions such that

  the ion exchange membrane is not likely to be broken; the opera-

  In particular, the method according to the invention is applicable not only to the provision of an inactive porous layer between the ion exchange membrane and the ion exchange membrane, but also to a vacuum metallization, a plating or an evaporation. electrode, as described in Japanese Patent Application No. 169,406 / 79 and Japanese Patent Application (OPI) 75,583 / 81,

  but also to the manufacture of analogous electrolytic cells.

  The following examples illustrate the invention without however

limit the scope.

EXAMPLE 1

  On a nickel sieve made of 0.5 mm diameter wires having a mesh aperture of about 0.7 mm and having an area of about 50 cm, a nickel powder of a size is applied. of 100 μm average particle by sintering for 10 min at 900 C in a-H 2 atmosphere to produce a porous cathode plate having a porous layer of a thickness of about 200 m and a porosity of about 80 % on the face to be connected to a membrane

ion exchange.

  Furthermore, a commercial ion exchange resin (Nafon No. 501), having an ion exchange capacity of about 0.8 milliequivalents / g of dry resin, is reduced to particles of a size

  average of 70 pu With the powder: thus obtained, it impregnates enough

  The porous cathode layer obtained as described above is additionally applied and a small quantity of powder, 5 g / m 2 for example, is applied to the surface of the layer. On the cathode layer thus prepared, an ion exchange membrane is provided. 120 Nafion then the membrane is adhered to the porous nickel cathode at 250 OC under a pressure of 10 kg / cm 2 The electrolytic cell is completed by placing an expandable gate 2 mm thick as anode to 3 mm of the membrane In order to allow a comparison, a similar cell is constructed in which the cathode, instead of being bonded to the membrane, is placed at 1.5 mm from it When electrolysis at 43%, after introduction of an aqueous solution of 10 'of Na OH in the cathode compartment and the anodic compartment Lnt, the electrolysis voltage of the cell having the cathode bonded to the membrane according to the invention is approximately 200 m V lower than

  the voltage of the cell where the cathode is not glued to the membrane.

  Moreover, after about 1000 h, no detachment of the cathode membrane is observed, so that the process can continue from

stably.

XAMPLE 2

  On a 0.1-μm thick laminated titanium grid having an opening coefficient of 60%, a titanium powder layer having an average particle size of about 50 microns was applied. Sintered the vacuum layer (10-5 Torr) at 0 ° C for 20 minutes to produce a porous plate having a thickness of about 50 μm and a porosity of about 80%. of a composite oxide of Ru and Ti in a weight ratio of metals of 60:40> by a conventional thermodecomposition process, which gives

a porous plate-anode.

  Next, the surface of this porous Nafion NO 500 anode in powder form (having an ion exchange capacity of about 0.8 milliequivalents / g of dry resin) is impregnated and has an average particle size of 20 days or less, and attaching a Nafion No. 315 ion exchange membrane to the surface thus prepared by pressing under 20 kg / cm 2 at 2500 C. Platinum black (specific surface area) is blended.

  m / g) and a dispersion of polytetrafluoroethylene according to

  weight ratio 100: 30 The mixture is applied to the other side of the membrane described above to form a cathodic layer

  and thus complete the electrolytic cell.

  In order to allow a comparison, we build a

  identical electrolytic cell except that the anode is connected directly

  membrane without the use of the resin powder

ion generator.

  During electrolysis at 80 ° C., after introduction of a

  4 N aqueous solution of NaCl in the anode compartment and

  duction of an aqueous solution of 20% of Na OH in the cathode compartment, the cell produced according to the invention operates from

  stably for 1000 hours or more at a voltage of

  average lysis of 3.3 V and no separation of the anode and the membrane is observed In the control cell, the anode is detached from the membrane> producing a rapid increase in the electrolysis voltage of 1 V or more, after 15 minutes already after

beginning of electrolysis.

EXAMPLE 3

  A porous nickel plate having a thickness of about 1 mm was laminated (Cermet NO 5, produced by Sumitomo Electric Inc.) to prepare a porous plate having a thickness of 0.3 mm and a porosity of 90%. plate of a thickness of about 1 μm deplatin by a heat-decomposition operation to produce a cathode The surface of this cathode is impregnated to a depth of about 0.2 mm with an ion exchange resin powder (Nafion No. 501) having an average particle size of 50 μm.

  porous cathode thus prepared and the whole is pressurized under atmospheric pressure.

  nitrogen at 3000 C at a pressure of 200 kg / m at the

  of the aluminum foil, it is found that a uniform layer of resin is intimately attached to one of the faces of the cathode plate

porous nickel.

  To this cathodic layer, an ion exchange membrane (Nafion No. 315) is fixed by pressing at 250 ° C. under 150 kg / m. As a cathode, a Ti gate coated with a RuO 2 -Ti composite oxide is used. O 2, according to the weight ratio 1: 1, which is placed at a distance of 2 mm from the membrane to complete the electrolytic cell. When electrolysis is carried out under the same conditions as in Example 2, a stable operation for 1000 h or more at an electrolysis voltage of about 3.3 V-and no separation of the porous cathode from

nickel and membrane.

  The invention is not limited to the embodiments described and those skilled in the art may make various modifications,

  However, sgns out of his frame.

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  A electrolytic device having a cathode, an anode and an ion-exchange membrane disposed therebetween, characterized in that at least one of the electrodes constituted by the cathode and the anode is formed of an electrode plate permeable porous gas and liquid, which is intimately connected to the membrane by a

  ion exchange resin powder.

  2 Device according to claim 1, characterized in that the membrane and the resin each have a heat exchanger

  ions of about 0.1 to 3 milliequivalents per gram of dry resin.

  3 Device according to claim 1, characterized in that it has a porous cathode plate intimately connected to the membrane

by means of the resin.

  4 Device according to claim 1 or 3, characterized in that the cathode is a porous plate prepared by (1) a sintering of a nickel powder or (2) sintering application of a

  nickel powder to a porous material based on nickel.

  Device according to claim 1 or 3, characterized in that the cathode is a porous plate prepared by plating a platinum group metal on (1) a porous nickel-based material

  or (2) a sintered product of nickel powder.

  6 Device according to claim 4, characterized in that the cathode is a porous plate prepared by plating a platinum group metal on (1) a porous nickel-based material or

  (2) a sintered product of nickel powder.

  7 Device according to claim 1, characterized in that it comprises a porous plate-anode intimately connected to the membrane

by the resin.

  8 Device according to claim 1 or 7, characterized in that the anode is a porous plate prepared by sintering a titanium powder or by sintering a titanium powder onto a titanium-based porous material and what said porous plate

  is further coated with an electrocatalytic metal oxide.

  9 Process for producing a posyped electrolytic device

  cathode, anode and ion exchange membrane placed

  between them, in particular according to any of the claims

  1 to 8, characterized in that it consists in producing a porous electrode plate permeable to gas and liquid so as to form at least one of the electrodes constituted by the cathode and the anode and to adhere this porous electrode plate to the ion exchange membrane by use

  under pressure and heat, a resin powder

ion generator.

  Process according to Claim 9, characterized in that it comprises an operation of adhering a membrane

  ion exchange material to an electrically conductive porous material

  electrode substrate using said powder of ion exchange resin under pressure and heat and to coat said electrode substrate with an active electrode material which is

permeable to gas and liquid.

  11 Process according to claim 9, characterized in that it comprises an operation which consists in applying the resin powder

  ion exchange at at least one of the faces of the exchange membrane -

  ions during the manufacture of this membrane.