JPS6045276B2 - Ion exchange membrane electrolyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion exchange membrane electrolyzer, and more particularly, to an ion exchange membrane electrolyzer having a specific ion exchange membrane and a specific electrode arrangement.

This invention relates to an electrolytic cell suitable for electrolyzing an aqueous alkali chloride solution. In recent years, from the viewpoint of pollution prevention, the method for obtaining caustic alkali and chlorine by electrolyzing an aqueous alkali chloride solution has been replaced by the diaphragm method instead of the mercury method, and a method using an ion exchange membrane for the purpose of obtaining even higher purity and highly concentrated caustic alkali. has been put into practical use.

On the other hand, in this type of electrolysis, it is imperative to reduce the electrolytic voltage as low as possible from the viewpoint of energy conservation, but in recent years, gas and liquid permeable porous holes have been added to one side of the fluorine-containing cation exchange membrane. The so-called SPE (Solid Poly
merElectmlyte) type alkali chloride electrolysis (for example, JP-A-53-52297, JP-A-52-78)
No. 788) is known.

This is a method that allows electrolysis to be carried out at a lower voltage than before because it can reduce the electrical resistance of the electrolytic solution and the electrical resistance caused by bubbles generated from hydrogen and chlorine gas, which were previously thought to be unavoidable in this type of technology. This is an excellent method. On the other hand, the present inventors conducted further research and, instead of bonding the above-mentioned electrode to the membrane surface as a porous layer, the present inventors attached a non-conductive porous layer, which does not itself have electrode activity, to the membrane surface. An electrolytic cell was developed in which the sliding voltage can be reduced almost in the same way as the electrolytic cell provided with the electrode porous layer by connecting the electrode to the porous layer and providing the electrode through the porous layer.

7 The electrolytic cell has a low sliding voltage, a wide range of selectivity as the electrode material does not come into direct contact with the membrane, and troubles due to gas generation at the interface between the membrane and the porous layer. It has an additional advantage over an electrolytic cell having a porous electrode layer in that it can prevent this.

By the way, when an ion exchange membrane having a porous layer on its surface that does not have electrode activity is used in a filter breath type electrolytic cell, it is generally sandwiched between two gaskets made of rubber or the like. incorporated into the frame.

In this way, a large number of battery case frames and ion exchange membranes are alternately arranged and overlapped with gaskets interposed therebetween, and are tightened from both ends to form a single body. In order to prevent leakage of the polar liquid, the clamping pressure is increased, and the contact area between the ion exchange membrane and the gasket is thereby strongly compressed. At the same time, the gasket, which is an elastic body, is deformed by the tightening pressure, and this deformation is also propagated to the ion exchange membrane. For this reason, the ion exchange membrane may break at its periphery. Therefore, in order to eliminate such difficulties,
It is effective to reinforce the contact area between the ion exchange membrane by reinforcing its periphery, or by controlling the deformation of the gasket. That is,
The present invention provides an electrolytic cell configured by alternately arranging a cell frame and an ion exchange membrane via a gasket, and partitioning an anode and a cathode with an ion exchange membrane, in which at least one of the anode and the cathode is The gasket is arranged through a gas and liquid permeable porous layer having no electrode activity formed on the surface of the ion exchange membrane, and the contact portion between the ion exchange membrane and the gasket has a reinforcing structure. The present invention provides a new ion-exchange membrane electrolytic cell.

In the present invention, the gas and liquid permeable porous layer formed on the ion exchange membrane surface may be made of either a conductive material or a non-conductive material as long as it does not act as an electrode, and may be made of either an inorganic material or an organic material. You may. However, it is preferable to use a material that has S corrosion resistance against the polar liquid and is hydrophilic. Preferred examples include metals, metal oxides, hydroxides, carbides, nitrides, or mixtures thereof, and hydrophilic polymers, particularly fluorine polymers for the anode side. others,
In addition to the following powder or granular materials, examples include materials previously formed as porous thin layers such as carbon vapor, fluororesin cloth, and nonwoven fabric. for example,
In the case of electrolysis of an aqueous alkali chloride solution, the porous layer on the anode side is selected from groups ■-A (preferably germanium, tin, and lead) of the periodic table, ■-groups B (preferably titanium, zirconium, and hafnium), and ■-B. Metals of the metal group (preferably niobium, tantalum), iron group metals (iron, cobalt, nickel), etc. alone or alloys, oxides, hydroxides, nitrides, or carbides are used.

For the porous layer on the cathode side, in addition to the materials used to form the porous layer on the anode side, silver, zirfuconium or its alloy, stainless steel, carbon, or tetrafluoroethylene resin treated to make it hydrophilic with potassium titanate, etc. is used. The constituent materials of the specific porous layer as described above are bonded and formed 7 as a porous layer on the surface of the ion exchange membrane by various means.

For example, a porous thin layer may be prepared in advance as described above and this may be attached to the ion exchange membrane surface, or the constituent material may be used as a paste or various dispersions by screen printing, spraying, transfer, or roll coating. It may be formed by coating with, etc. In the case of screen printing, transfer methods, etc.
The porous layer can be formed in various patterns such as a lattice shape or polka dot shape, or it can be formed as a dense porous layer such as a flat coating. Furthermore, particles or particle groups made of the material constituting the porous layer may be bonded to the ion exchange membrane surface independently of other particles or particle groups to form a porous layer as a whole. Generally, when forming a porous layer, the above material preferably has a particle size of 0.01 to 300μ, particularly 0.1 to 300μ.
It is used in the form of a 100μ powder.

The above materials may be used alone or in combination of two or more. For example, an inorganic material may be mixed with an organic material such as polytetrafluoroethylene modified by copolymerizing a small amount of an acid type monomer, or a fluorine-containing polymer for ion exchange membranes described below. When using a dispersion or paste containing powder or particles of the above materials, if necessary, a binder such as a fluorocarbon polymer such as polytetrafluoroethylene or polytrifluorochloroethylene, and further carboxymethyl cellulose, Thickeners such as celluloses such as methylcellulose and hydroxyethylcellulose, water-soluble substances such as polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, polymethylvinyl ether, tin, and polyacrylamide are used.

These binders or thickeners are preferably used in an amount of 0 to 5% by volume, particularly 0.5 to 3% by volume, based on the powder.
In addition, if necessary, a long-chain hydrocarbon, fluorinated hydrocarbon, etc. can be further added to facilitate the formation of a porous layer.

In any case, the content of the porous layer constituent material such as the particles in the formed porous layer is 0.001 to 50rn.
g/d1 is preferably about 0.01 to 30 rng/Clt. In this way, a porous layer with uniform thickness and high adhesion is formed on one or both surfaces of the ion exchange membrane, but it is preferable to press the porous layer against the membrane surface under pressure as necessary. preferable.

The pressure is preferably 100 to 300°C, particularly 110°C.
Under heating at ~250°C, preferably 1~1000k9
/Clil especially 5-500k9/C! It is preferable to use the word "blessed" under "i". By doing so, the ion exchange membrane and the porous layer can have a structure in which they are in even closer contact. The porous layer having no electrode activity thus formed on the ion exchange membrane surface preferably has an average pore diameter of 0.01 to 200μ, in order to obtain good gas and liquid permeability.
In particular, it should have a porosity of 0.1 to 100μ, a porosity of 10 to 99%, particularly 25 to 95%, and a thickness of preferably 0.
．． A suitable range is 0.1 to 200μ, particularly 0.1 to 100μ. When a porous layer having no electrode activity is formed on the surface of the ion exchange membrane, the electrode is placed through the porous layer.

As such an electrode, a porous electrode such as a mesh or expanded metal is used. As the electrode material, for example, a platinum group metal, a conductive oxide thereof, or a conductive reduced oxide thereof is used as an anode, while a platinum group metal, a conductive oxide thereof, or a conductive reduced oxide thereof is used as a cathode. Iron group metals are used. Examples of platinum group metals include platinum, rhodium, ruthenium, palladium, and iridium, and examples of iron group metals include iron, cobalt, nickel, Raney nickel, and stabilized Raney nickel. If a porous electrode is used, it can be formed from the material itself forming the anode or cathode. However, when platinum group metals or conductive oxides thereof are used, it is preferable to coat the surface of an expanded valve metal such as titanium or tantalum with these substances. Although these anodes or cathodes do not necessarily need to be placed in contact with the porous layer, preferably the electrodes are placed in contact with the porous layer. In addition, when only either the anode or the cathode is disposed via a porous layer having no electrode activity according to the present invention, the opposite electrode, the anode or the cathode, is
The porous electrode described above can be placed directly on the anode side or the cathode side of the ion exchange membrane.

In such a case, these electrodes may be provided in contact with the ion exchange membrane surface, or may be provided at intervals. The ion exchange membrane used in the present invention is made of a polymer containing a cation exchange group such as a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a phenolic hydroxyl group, and such a polymer includes a fluorine-containing polymer. It is particularly preferable to employ coalescence.

Examples of fluorine-containing polymers containing ion-exchange groups include combinations of vinyl monomers such as tetrafluoroethylene and chlorotrifluoroethylene with perfluorinated vinyl monomers having ion-exchange groups such as sulfonic acid, carboxylic acid, and phosphoric acid groups. Polymers are preferably used. Further, a film-like polymer of trifluorostyrene into which an ion exchange group such as a sulfonic acid group is introduced can also be used. Among these, it is particularly preferable to use polymers having the following polymerized j units (a) and (x), respectively, since highly pure caustic alkali can be obtained with relatively high current efficiency.

Here, X is F, sCl. ．． H or -CF3, X″
is x or CF3(CF2). n, m is 1 to 5, and Y is selected from the following.

X, y, z are all 0 to 10, and Z, R, are -
F or a perfluoroalkyl group having 1 to 10 carbon atoms.

In addition, A is -SOJM, -COOM or -SO2F, -CN, -CO which can be converted into these groups by hydrolysis.
F or -COOR, M is hydrogen or an alkali metal,
R represents an alkyl group having 1 to 10 carbon atoms. The cation exchange membrane used in the present invention has an ion exchange capacity of preferably 0.5 to 4.0 meq/g dry resin, particularly 0.8 to 2.0 meq/g dry resin. is preferable.

In order to provide such ion exchange capacity, the above (a) and (
The formation of an ion exchange membrane made of a copolymer consisting of polymerized units of (1), preferably 1 polymerized unit (1)
Suitably it is from 3 to 25 mol%, especially from 3 to 25 mol%.

The cation exchange membrane used in the present invention does not necessarily need to be formed from only one type of polymer, nor does it need to have only one type of ion exchange group.

For example, a laminated film of two types of polymers with a smaller ion exchange capacity on the cathode side than on the anode side, the cathode side has a weakly acidic exchange group such as a carboxylic acid group, and the anode side has a strong acidic exchange group such as a sulfonic acid group. An ion exchange membrane with a These ion exchange membranes are manufactured by various conventionally known methods, and these ion exchange membranes are manufactured by various methods. If necessary, it can be reinforced with a cloth, a woven fabric such as a net, a nonwoven fabric or a metal mesh, a porous body, etc., preferably made of a fluorine-containing polymer such as polytetrafluoroethylene.

Further, the thickness of the ion exchange membrane of the present invention is preferably 20
-500p1, preferably 50-400μ. The porous layers on the anode and cathode sides, which are preferably bonded to and formed on the surface of these ion exchange membranes, are made of
The form of the appropriate ion exchange group, for example, in the case of a carboxylic acid group, its ester type, and in the case of a sulfonic acid group, -S
In the O2F' type, bonding is achieved by the use of pressure and heat.

In the present invention, the contact portion between the gasket and the ion exchange membrane in which the specific porous layer is formed has a reinforcing structure.

There is no particular limitation on the means for reinforcing the structure, and any structure may be used as long as the periphery of the ion exchange membrane at the contact portion does not break due to the tightening pressure of the battery case frame. For example, a) means for reinforcing the peripheral edge of the ion-exchange membrane, i.e., means for applying or adhering high-strength resin, means for increasing the number of high-strength threads inserted into the peripheral edge, and means for reinforcing the peripheral edge of the ion-exchange membrane; Examples include means for increasing the thickness. Alternatively, reinforcing structures that suppress deformation of the gasket can be adopted, such as lining the gasket with a reinforcing cloth, bonding a reinforcing film with vulcanization adhesive, etc. As the conditions for electrolyzing, for example, an aqueous alkali chloride solution using the electrolytic cell of the present invention, the known conditions as described in the above-mentioned Japanese Patent Application Laid-Open No. Sho M-112398 can be adopted.

For example, in the anode chamber, preferably 2.5 to 5 normal (N)
An aqueous alkali chloride solution is supplied to the cathode chamber, and water or diluted alkali hydroxide is supplied to the cathode chamber, preferably at 80°C to 120°C.
℃ and a current density of 10 to 100 A/Dm2. In such a case, heavy metal ions such as calcium and magnesium in the aqueous alkali chloride solution cause deterioration of the ion exchange membrane, so it is preferable to keep them as small as possible. Furthermore, an acid such as hydrochloric acid can be added to the aqueous alkali chloride solution in order to prevent the generation of oxygen at the anode as much as possible.
The electrolytic cell in the present invention may be of a monopolar type or a bipolar type as long as it has the above configuration. In addition, the materials used to construct the electrolytic cell are those that are resistant to aqueous alkali chloride and chlorine, such as titanium, for the anode chamber, and those that are resistant to high concentrations of alkali hydroxide and hydrogen for the cathode chamber. Iron, stainless steel, or nickel are used. Further, in the present invention, when an ion exchange membrane with a porous layer attached is used, an electrode is arranged on the outside thereof. For example, in the case of the anode, expanded metal of valve metal coated with noble metal, its alloy or conductive oxide, and in the case of the cathode, iron, nickel or stainless steel net, mesh or expanded metal. It consists of Further, these electrodes are preferably brought into contact with the porous layer by pressing them against the porous layer. Although the above description has been made particularly as an electrolytic cell for an aqueous alkali chloride solution, it goes without saying that the electrolytic cell of the present invention can be similarly applied as an electrolytic cell for water, halogen acid, and alkali carbonate.

In addition, the electrolytic cell of the present invention can be used for electrolytic synthesis of various organic compounds,
For example, it is applicable to Kolbe reaction, oxidation reaction, reduction reaction, ring element dimerization reaction, etc. Next, the present invention will be explained in more detail using examples.

Example 1 10q of titanium oxide particles with a particle size of 5p or less in 100mt of water
1 and the surface of polytetrafluoroethylene with a particle size of 1 μ or less is mixed with tetrafluoroethylene and CF2=CFO (CF2)
A suspension containing 1v of particles coated with a copolymer of 3C00CH3 with an ion exchange capacity of 1.43 meq/g dry resin, thickness 140p was placed on a hot plate at 120 °C using a spray gun. It was sprayed onto both sides of an ion exchange membrane made of a copolymer of tetrafluoroethylene and CF2=CFO(CF2)3C00C113.

In this case, the speed of spraying was adjusted so that the water in the sprayed dispersion would dry within 1 inch after spraying.

Thereafter, the porous layer obtained by injection was heated to a temperature of 140'C.
After being pressed onto the ion exchange membrane at a molding pressure of 30k9/Cfl, the ion exchange membrane was hydrolyzed by immersion in a 25% by weight aqueous solution of caustic soda. Titanium oxide is on both sides of the ion exchange membrane at approximately 17F each! 9/d was included.
Next, on the anode side of the ion exchange membrane, an anode with a low chlorine overvoltage made of expanded titanium metal (minor axis 2.5 mm, major axis 5 wn) coated with a solid solution of ruthenium oxide, iridium oxide, and titanium oxide, and a cathode. SUS3O4 on the side
Expanded metal (minor axis 2.5 mm, major axis original i) was heated to 52% at 150°C in a 52% aqueous caustic solution. i
The cathode, which had been etched for 1 hour to have a low hydrogen overvoltage, was brought into pressure contact with the ion exchange membrane at a pressure of 0.01 k9/Cl.

As the cathode chamber frame gasket, a flat gasket with a thickness of 3W1 made of ethylene propylene rubber with a hardness of HS7O was used, and as the anode chamber frame gasket, a gasket with a thickness of 100 μm made of ethylene-tetrafluoroethylene copolymer was used.

The portion of the periphery of the ion exchange membrane that is in contact with the gasket is reinforced by laminating the same ion exchange membrane with a thickness of 140 μm into a frame shape using heat press. Therefore, only the peripheral part is 280μ
An ion exchange membrane having a thickness of 140 μm and a titanium oxide porous layer formed on both sides was used.
The battery case frame was tightened to give a surface pressure of 32 kg/C7ll. In the case of an ion-exchange membrane without peripheral edge reinforcement, when the surface pressure was increased significantly, the membrane broke at the gasket contact area, but with the membrane with peripheral edge reinforcement, the surface pressure increased to 50.
No breakage was observed even at about kg/Clg. While supplying a 5N aqueous sodium chloride solution to the anode chamber of the electrolytic cell as described above and water to the cathode chamber, the sodium chloride concentration in the anode chamber is maintained at 4N and the caustic soda concentration in the cathode chamber is maintained at 35% by weight. At the same time, electrolysis was carried out at 90° C. and 40 A/Dm2, and the following results were obtained. j Tank pressure (■)
Current efficiency (%) 3.

0293.2 Comparative Example 1 Electrolysis was carried out in the same manner as in Example 1 without attaching anything to both sides of the ion exchange membrane used in Example 1, and results below average were obtained.

Sliding voltage (V) Current efficiency (%) 3.
3693.3 Example 2 An ion exchange membrane in which porous titanium oxide layers similar to those in Example 1 were formed on both sides was used.

This ion exchange membrane has a thickness of 140 μm and has no peripheral edge reinforcement. As the cathode chamber frame gasket, a reinforced flat gasket was used, in which a 200 μm thick film of tetrafluoroethylene-hexafluoropropylene copolymer was vulcanized and adhered to the surface of an ethylene-propylene rubber gasket that contacted the ion exchange membrane.

Claims (1)

[Scope of Claims] 1. In an electrolytic cell configured by alternately arranging a cell frame and an ion exchange membrane with gaskets in between, and partitioning an anode and a cathode with an ion exchange membrane, at least one of the anode and the cathode is provided. One is disposed through a gas and liquid permeable porous layer having no electrode activity formed on the ion exchange membrane surface, and the contact portion between the ion exchange membrane and the gasket has an auxiliary structure. An ion-exchange membrane electrolyzer featuring: 2. The electrolytic cell according to claim 1, wherein the porous layer is made of a conductive or non-conductive inorganic or organic material that has corrosion resistance against polar liquid. 3 The porous layer has a porosity of 10-99% and a thickness of 0.01-99%
The electrolytic cell according to claim 1 or 2, which has a diameter of 200μ. 4. The electrolytic cell according to claim 1, wherein the ion exchange membrane is a fluorine ion exchange membrane having a carboxylic acid group, a sulfonic acid group, or a phosphoric acid group. 5. The electrolytic cell according to claim 1, wherein the reinforcing structure reinforces the peripheral edge of the ion exchange membrane that comes into contact with the gasket.