JP2022152820A - Electrolytic cell of two chamber process for brine electrolysis using gas diffusion electrode, and utilization thereof - Google Patents

Abstract

To provide an easily assemblable electrolytic cell of a two chamber process for brine electrolysis using a gas diffusion electrode and the like.SOLUTION: In an electrolytic cell of a two chamber process for brine electrolysis using a gas diffusion electrode, a cathode electrode is a gas diffusion electrode composed of only two layers of a hydrophilic and conductive electrode support layer and a conductive reaction layer arranged on one surface side of the electrode support layer and containing a hydrophilic catalyst and a hydrophobic resin. In a cathode chamber, the electrode support layer is arranged so as to come into contact with an ion exchange membrane on a surface opposite to the surface on which the reaction layer is arranged.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an electrolytic cell for a two-chamber method of gas diffusion electrode salt electrolysis and its application technology.

Sodium hydroxide and chlorine have conventionally been produced by electrolyzing a saline solution using an ion-exchange membrane and a metal electrode as a cathode. However, since the electrolysis of saline water requires a large amount of electric power, in recent years, with the expectation of significant energy savings, a method of reducing oxygen using a gas diffusion electrode as a cathode electrode has been investigated.

In the method of reducing oxygen using gas diffusion electrodes, in addition to the three-chamber method in which the electrolytic cell is divided into three chambers, an anode chamber, a catholyte chamber, and a cathode gas chamber, an anode, an ion-exchange membrane, and a gas diffusion electrode are connected to each other. A two-compartment process has been developed in which the electrolytic cell is partitioned into two compartments, an anode compartment and a cathode gas compartment, in close contact, substantially eliminating the catholyte compartment.

For example, in Patent Document 1, an anode chamber and a cathode chamber are partitioned by an ion exchange membrane, an anode is installed in the anode chamber, a liquid retention layer and a gas diffusion electrode are installed in the cathode chamber, and sodium chloride is placed in the anode chamber. In a two-chamber electrolytic cell in which water is electrolyzed by supplying an oxygen-containing gas to each of the cathode chambers, a liquid-retaining layer having a predetermined liquid-retaining amount per unit volume of the liquid-retaining layer is provided between the ion-exchange membrane and the gas diffusion electrode. The provided electrolytic cell is described.

Further, Patent Document 2 describes a gas diffusion electrode in which an electrode substrate carries a catalyst layer containing a hydrophilic catalyst and a hydrophobic binder, wherein the electrode substrate is carbon cloth, carbon paper, carbon foam, and carbon sintered body. and a salt electrolytic cell using the gas diffusion electrode are disclosed.

International Publication No. 2012/008060 JP 2006-219694 A

However, in the techniques such as Patent Documents 1 and 2, it is necessary to separately install a liquid retention layer and a hydrophilic layer between the ion exchange membrane and the gas diffusion electrode, and the ease of assembly of the electrolytic cell is reduced. There was room for improvement. In addition, Patent Document 2 does not describe the installation direction of the gas diffusion electrodes in the salt electrolytic cell.

One aspect of the present invention has been made in view of the above problems, and an object of the present invention is to provide an electrolytic cell for a two-chamber method of salt electrolysis with gas diffusion electrodes, which is easy to assemble, and a technique for using the same.

As a result of intensive studies by the present inventors in order to solve the above problems, conventionally, after forming a gas diffusion cathode by applying a reaction layer to a substrate made of a carbon material, a separate liquid is applied to the ion exchange membrane side. A retention layer and a hydrophilic layer were attached, but by forming a reaction layer on one side (the side opposite to the ion exchange membrane side) of a hydrophilic and conductive electrode support layer, a liquid retention layer and a hydrophilic membrane are provided. In addition, it is possible to obtain an electrolytic cell of the gas diffusion electrode salt electrolysis two-chamber method that has good performance even if it is not required, and according to such an electrolytic cell, it is not necessary to provide a liquid retention layer or a hydrophilic film, so that it is easy to assemble. The present inventors have found new findings such as the fact that the present invention has been completed. That is, one embodiment of the present invention includes the following aspects.
<1> An anode chamber and a cathode chamber are partitioned by an ion exchange membrane, an anode electrode is installed in the anode chamber, a cathode electrode is installed in the cathode chamber, saline solution is placed in the anode chamber, and oxygen is placed in the cathode chamber. In a gas diffusion electrode salt electrolysis two-chamber electrolytic cell in which contained gases are respectively supplied and electrolyzed, the cathode electrode comprises a hydrophilic and conductive electrode support layer and one surface of the electrode support layer. a conductive reaction layer containing a hydrophilic catalyst and a hydrophobic resin disposed on the side of the gas diffusion electrode; A gas diffusion electrode salt electrolysis two-chamber electrolytic cell in which a layer is arranged so as to be in contact with the ion-exchange membrane on the side opposite to the side on which the reaction layer is arranged.
<2> The electrode support layer according to <1>, wherein the liquid retention amount per unit volume of the electrode support layer is 0.10 g-H ₂ O/cm ³ to 0.80 g-H ₂ O/cm ³ . electrolytic cell.
<3> The electrode support layer includes carbon, zirconium oxide, ceramics, polytetrafluoroethylene, a copolymer of ethylene tetrafluoride and propylene hexafluoride, aramid resin, polyimide resin, vinyl chloride resin, nickel, stainless steel, The electrolytic cell according to <1> or <2>, which is made of at least one selected from the group consisting of silver and gold.
<4> The electrolytic cell according to any one of <1> to <3>, wherein a hydrophobic resin layer is arranged so as to be in contact with the surface of the gas diffusion electrode on which the reaction layer is arranged.
<5> A method for producing chlorine gas, comprising the step of electrolyzing a saline solution using the electrolytic cell according to any one of <1> to <4> above.
<6> A method for producing sodium hydroxide, comprising the step of electrolyzing a saline solution using the electrolytic cell according to any one of <1> to <4> above.

ADVANTAGE OF THE INVENTION According to one Embodiment of this invention, it is effective in the ability to provide an electrolytic cell which is easy to assemble.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically showing the structure of an electrolytic cell for a two-chamber method of gas diffusion electrode salt electrolysis according to one embodiment of the present invention.

Embodiments of the present invention are described in detail below. Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more (including A and greater than A) and B or less (including B and less than B)".

<1. Gas diffusion electrode salt electrolysis two-chamber electrolytic cell>
An electrolytic cell for the gas diffusion electrode salt electrolysis two-chamber method according to one embodiment of the present invention is divided into an anode chamber and a cathode chamber by an ion exchange membrane, an anode electrode is installed in the anode chamber, and a cathode is installed in the cathode chamber. In the electrolytic cell of the gas diffusion electrode salt electrolysis two-chamber method in which electrodes are installed and electrolysis is performed by supplying a saline solution to the anode chamber and an oxygen-containing gas to the cathode chamber, the cathode electrode is hydrophilic and A gas consisting of only two layers, a conductive electrode support layer and a conductive reaction layer disposed on one side of the surface of the electrode support layer and containing a hydrophilic catalyst and a hydrophobic resin. a diffusion electrode, wherein the electrode support layer of the gas diffusion electrode is arranged in the cathode chamber so as to be in contact with the ion-exchange membrane on a surface opposite to the surface on which the reaction layer is arranged; This is an electrolytic cell of the gas diffusion electrode salt electrolysis two-chamber method. An embodiment of the present invention will be described in detail below.

As shown in FIG. 1, an electrolytic cell 1 for gas diffusion electrode salt electrolysis two-chamber method according to one embodiment of the present invention comprises an ion-exchange membrane 2, an anode chamber 3, a cathode chamber 4, an anode electrode 5, and a gas diffusion electrode. (Cathode electrode) 7, cushion material 8, cathode chamber back plate (cathode terminal) 9, anode gasket 10, cathode gasket 11, anolyte inlet 12, anolyte and gas outlet 13, oxygen-containing gas inlet 14, water It is composed of a sodium oxide aqueous solution outlet 15 .

An electrolytic cell 1 is partitioned into an anode chamber 3 and a cathode chamber 4 by an ion exchange membrane 2 . An anode electrode 5 is arranged on the anode chamber 3 side of the ion exchange membrane 2 . On the cathode chamber 4 side of the ion exchange membrane 2, a gas diffusion electrode 7, a cushion material 8, and a cathode chamber back plate (cathode terminal) 9 are installed in this order. The gas diffusion electrode 7 is composed of an electrode support layer 6a and a reaction layer 6b. The direct current is finally discharged by the cushion material 8 . The anode gasket 10 is for fixing the anode electrode 5 and the cathode gasket 11 is for fixing the gas diffusion electrode 7 to the electrolytic cell 1 .

An anolyte (salt solution) inlet 12 is formed near the bottom of the anode chamber 3 . An anolyte (unreacted saline solution) and (chlorine) gas outlet 13 is formed on the upper wall side of the anode chamber 3 . An oxygen-containing gas inlet 14 is formed in the side wall near the top of the cathode chamber 4 , and a sodium hydroxide aqueous solution outlet 15 is formed in the side wall near the bottom of the cathode chamber 4 . The sodium hydroxide aqueous solution outlet 15 also functions as an outlet for excess oxygen gas.

An anolyte (salt solution) is supplied to the anode chamber 3 of the electrolytic cell 1 from an anolyte inlet 12, and an oxygen-containing gas (for example, oxygen gas, air, etc.) is supplied to the cathode chamber 4 from an oxygen-containing gas inlet 14. be done. The electrolytic cell 1 operates by energizing between both electrodes.

In Patent Document 1 described above, the "liquid retention layer" is arranged between the gas diffusion electrode and the ion exchange membrane 2, and in Patent Document 2, the "hydrophilic layer" is the gas diffusion electrode and the ion exchange membrane. It is a configuration arranged between On the other hand, in one embodiment of the present invention, the gas diffusion electrode 7 does not need to separately provide a liquid retention layer or a hydrophilic layer on the ion exchange membrane side, and has a liquid retention function (function as a hydrophilic layer). It is composed of only two layers, an electrode supporting layer 6a provided and a reaction layer 6b provided with a reaction function. According to this configuration, there is no need to separately form a liquid retention layer (hydrophilic layer) between the gas diffusion electrode 7 and the ion exchange membrane 2, so assembly is facilitated.

In one embodiment of the present invention, in the gas diffusion electrode 7, the electrode supporting layer 6a is in contact with the ion exchange membrane 2 on the side opposite to the side on which the reaction layer 6b is formed. In other words, in the cathode chamber 4, the gas diffusion electrode 7 has a two-layer structure of the electrode supporting layer 6a and the reaction layer 6b, and the ion exchange membrane 2, the electrode supporting layer 6a and the reaction layer 6b are arranged in this order. there is According to this configuration, compared to the case where the ion exchange membrane 2 and the reaction layer 6b are in contact with each other, after the electrolysis is started by supplying the current to the electrolytic cell 1, after a predetermined time has elapsed, There is an advantage that the resistance can be lowered. It is considered that this is because the electrode support layer 6a is liquid-retentive or hydrophilic.

The cathodic reaction at the gas diffusion electrode is a reaction that produces only hydroxide ions from water and oxygen. Since the anolyte (unreacted saline solution) passes through the ion exchange membrane 2 and is supplied to the gas diffusion electrode 7, the water that contributes to the reaction is should be present in an amount and uniform concentration sufficient to react. According to this configuration, a sufficient amount and uniform concentration of water can be present in the electrode support layer 6a, so that the amount of resistance increase caused by a one-sided flow concentrated in a portion of the current or an uneven concentration distribution of water can be reduced. In other words, when the ion-exchange membrane 2, the reaction layer 6b, and the electrode support layer 6a are arranged in this order, a sufficient amount of water can be continuously present at a uniform concentration on the interface between the ion-exchange membrane 2 and the gas diffusion electrode 7. It may become difficult and lead to an increase in resistance.

In addition, according to the gas diffusion electrode 7 of one embodiment of the present invention, the electrolytic cell 1 has a higher There is also the advantage that the resistance between the anode and the cathode can be lowered after a predetermined time has elapsed after the start of electrolysis by supplying current. It is considered that this is because water of a sufficient amount and uniform concentration to react exists on the electrolytic area interface between the ion exchange membrane 2 and the gas diffusion electrode 7 .

Further, when the liquid retaining layer is provided, it is considered that the contact resistance between the liquid retaining layer and the gas diffusion electrode and the resistance of the electrode supporting layer itself are generated more than in the present configuration, resulting in an increase in resistance.

The electrode support layer 6a is hydrophilic and conductive, and functions as a support on which the reaction layer 6b is formed. The electrode support layer 6a also functions as a hydrophilic layer (liquid retention layer). The electrode support layer 6a is not particularly limited as long as it is generally used as a support for gas diffusion electrodes, but it preferably has the ability to retain a liquid, particularly the generated aqueous sodium hydroxide solution. Also, the electrode support layer 6a preferably has chemical and physical resistance to sodium hydroxide. By chemical resistance is meant a material that is resistant to high alkalis, and by physical resistance is meant a material that has adequate strength for the loads applied to the electrolytic cell.

The electrode support layer 6a preferably has a good liquid retention function. For example, as the liquid retention function, the liquid retention amount per unit volume of the electrode supporting layer is preferably 0.10 g-H ₂ O/cm ³ to 0.80 g-H ₂ O/cm ³ , and 0.15 g- H ₂ O/cm ³ to 0.70 g-H ₂ O/cm ³ is more preferable, and 0.20 g-H ₂ O/cm ³ to 0.60 g-H ₂ O/cm ³ is further preferable. preferable. The liquid holding capacity of the electrode support layer as used herein is defined by immersing the electrode support layer in an aqueous solution having a sodium hydroxide concentration of 34.5% by weight for one day and then washing it with water to completely remove the aqueous sodium hydroxide solution. If A is the weight when completely dried, and B is the weight when the completely dried electrode support layer is taken out after being immersed in pure water for 1 hour, it is defined as BA. The liquid retention amount per unit volume is defined as a value obtained by dividing the liquid retention amount by the volume of the electrode support layer used for measuring the liquid retention amount. In the examples, the same definition was used for measurement.

The electrode support layer 6a is made of carbon, zirconium oxide, ceramics, polytetrafluoroethylene, a copolymer of ethylene tetrafluoride and propylene hexafluoride, aramid resin, polyimide resin, vinyl chloride resin, nickel, stainless steel, silver, and It is preferably made of at least one selected from the group consisting of gold. Among them, a porous carbon-based substrate is preferable. As the porous carbon-based substrate, for example, a cloth made of a carbon material, a sintered fiber, a foam, or the like can be used. Among these, either the cloth or the fiber sintered body is preferable from the viewpoint of upsizing and the ease of mass production, and commercially available fiber sintered bodies such as carbon cloth and carbon paper can be used.

Since the electrode support layer 6a is required to allow oxygen and generated sodium hydroxide to permeate therethrough, it preferably has adequate porosity in addition to sufficient electrical conductivity. A ratio of 30 to 95% is preferred. The thickness of the electrode support layer 6a is preferably in the range of 0.1 to 1 mm in consideration of mechanical strength such as tensile strength and permeation distance of oxygen and generated sodium hydroxide.

The reaction layer 6b is a conductive reaction layer arranged on one side of the surface of the electrode supporting layer 6a and containing a hydrophilic catalyst and a hydrophobic resin.

The hydrophilic catalyst used in the reaction layer 6b is composed of at least one of silver, platinum, and palladium, which are electrochemically stable in a high-temperature, high-concentration alkali. alloys can be used. From the point of view of cost, it is preferable to use silver as a single metal, or silver-palladium alloys and silver-platinum alloys in which a small amount of palladium or platinum is added to silver. These hydrophilic catalysts can be suitably used in the form of commercially available particles, but are not limited to these, and may be used after synthesis according to a known method. For example, particles synthesized by a wet method of mixing silver nitrate, silver nitrate and palladium nitrate, or silver nitrate and dinitrodiammineplatinum nitric acid aqueous solution with a reducing agent, or dry methods such as vapor deposition and sputtering can be used. The hydrophilic catalyst may have a particle size of 0.001 to 50 μm, more preferably 0.001 to 1 μm.

The hydrophobic resin used for the reaction layer 6b functions as a binder for the hydrophilic catalyst. For example, a fluororesin that is chemically stable in a high-temperature, high-concentration alkali can be used. Specifically, polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene/propylene hexafluoride copolymer (FEP), or the like powder or suspension A turbid aqueous solution may preferably be used. The hydrophobic resin imparts sufficient gas permeability to the electrode and contributes to good electrolysis performance by preventing excessive wetting of the electrode with sodium hydroxide produced. 005 to 10 μm is preferred.

Moreover, the reaction layer 6b can also contain a carbon material in addition to the hydrophilic catalyst and the hydrophobic resin. Examples of carbon materials include carbon powder, graphite, graphene, carbon nanotubes, fullerene, diamond, and the like. By containing a carbon material, there is an advantage that conductivity and hydrophilicity can be improved.

As a method for forming the reaction layer 6b on the electrode support layer 6a, a conventionally known method can be suitably used, and there is no particular limitation. For example, a reaction layer 6b can be formed on one side of the electrode support layer 6a by coating and drying a slurry or resin mixture obtained by mixing, stirring, and defoaming a hydrophilic catalyst and a hydrophobic resin on the electrode support layer 6a. The application of the slurry or resin mixture may be performed manually using a writing brush, a brush, or a scraper, or may be performed using a coating machine, a spray drying device, or the like.

Moreover, it is preferable that a hydrophobic resin layer (not shown) is further arranged so as to be in contact with the surface of the gas diffusion electrode 7 on which the reaction layer 6b is arranged. That is, in the cathode chamber 4, it is preferable that the ion exchange membrane 2, the electrode supporting layer 6, the reaction layer 6b, and the hydrophobic resin layer are provided in this order. The hydrophobic resin layer can be formed, for example, by coating the surface of the gas diffusion electrode 7 on which the reaction layer 6b is formed with a hydrophobic resin. With such a configuration, the contact resistance of the gas diffusion electrode 7 can be further reduced. As the hydrophobic resin, those mentioned above can be preferably used.

As the ion-exchange membrane 2, an ion-exchange membrane for general gas diffusion electrode salt electrolysis two-chamber method can be used, and it is not particularly limited.

As the anode electrode 5, an insoluble anode for general gas diffusion electrode salt electrolysis two-chamber method can be suitably used, and although not particularly limited, an insoluble titanium electrode called DSA can be exemplified.

The cushion material 8 is for bringing the gas diffusion electrode 7 into close contact with the ion exchange membrane 2 . It is preferable that the cushioning material 8 is accommodated in a compressed state to generate a reaction force on the cushioning material 8 and that the reaction force is used to bring the gas diffusion electrode 7 into close contact with the ion exchange membrane 2 . In the two-chamber method, with the ion-exchange membrane 2 as a boundary, the anode chamber 3 is subjected to hydraulic pressure from saline solution, and the cathode chamber 4 is subjected to gas pressure. The reaction force of the cushion material 8 is designed according to the differential pressure between the liquid pressure and the gas pressure. By making the lower part larger than the upper part, the pressure applied to the ion exchange membrane 2 and the anode electrode 5 can be equalized.

As such a cushion material 8, it is possible to use a coil material or a wavy mat material. Since the coil has elasticity in the diametrical direction and a reaction force is generated in this direction, the coil axis can be arranged parallel to the back plate of the cathode gas chamber. By adjusting, the reaction force of the cushioning material may be made larger in the lower part than in the upper part. As the wavy mat material, a demister mesh obtained by knitting metal wires into a wavy pattern can be used. should be made larger at the bottom than at the top.

Moreover, it is preferable that the saline solution supplied to the anode chamber 3 is strictly purified. Calcium, magnesium ions, etc. are preferably removed to a 10 ppb level using a chelating resin.

Moreover, the oxygen-containing gas supplied to the cathode chamber 4 is preferably humidified. Examples of humidification methods include a method of sprinkling water on the oxygen-containing gas supplied to the electrolytic cell 1 to humidify the water, and a method of blowing the oxygen-containing gas into water to humidify the water.

Between the ion-exchange membrane 2 and the cathode chamber 4, sodium hydroxide dissolves in the permeated water that permeates the ion-exchange membrane 2 from the anode chamber 3 to form an aqueous sodium hydroxide solution. The generated aqueous sodium hydroxide solution diffuses in the electrode supporting layer 6a of the gas diffusion electrode 7, falls particularly by gravity, reaches the lower end of the electrode supporting layer 6a, and flows down as droplets to the bottom of the cathode chamber 4, thereby removing excess oxygen. It is taken out of the electrolytic cell 1 from the sodium hydroxide aqueous solution outlet 15 together with the contained gas.

The electrolysis conditions of the electrolytic cell 1 are preferably a current density of 1 to 10 kA/m ² , and the temperatures of the anode chamber 3 and the cathode chamber 4 during electrolysis are not particularly limited, and are commonly used. Any temperature is acceptable. For example, in order to maximize the performance of the ion exchange membrane 2, it is preferable to set the temperature range according to the current density. The temperature range may be appropriately set according to the type of the ion exchange membrane 2. For example, when the current density is 1.0 kA/m ² or more and less than 2.0 kA/m ² , the temperature range is 68 to 82°C. Preferably, when it is 2.0 kA/m ² or more and less than 3.0 kA/m ² , it is preferably 77 to 85°C, and when it is 3.0 kA/m ² or more, it is preferably 80 to 90°C.

<2. Method for producing chlorine gas and sodium hydroxide>
In addition, one embodiment of the present invention includes a method for producing chlorine gas, which has a step of electrolyzing a saline solution (electrolyzing a saline solution to produce chlorine gas) using the electrolytic cell 1 described above. obtain. Further, in one embodiment of the present invention, there is provided a method for producing sodium hydroxide, which has a step of electrolyzing a saline solution using the electrolytic cell 1 described above (electrolyzing a saline solution to produce sodium hydroxide). can be included.

When a saline solution is supplied to the anode chamber 3 of the electrolytic cell 1 and oxygen is supplied to the cathode chamber 4, electricity is passed between the anode electrode 5 and the gas diffusion electrode 7, and the ion exchange membrane 2 Sodium hydroxide is produced on the surface of the cathode chamber 4 side, and this sodium hydroxide permeates the gas diffusion electrode 7 as an aqueous solution.

In this way, the sodium hydroxide that has passed through the gas diffusion electrode 7 is collected in the lower part of the cathode chamber 4 and taken out from the sodium hydroxide aqueous solution outlet 15 together with unreacted oxygen. On the other hand, the chlorine gas generated on the surface of the anode electrode 5 is collected in the upper part of the anode chamber 3 and taken out from the anode liquid and gas outlet 13 .

According to the method for producing chlorine gas or sodium hydroxide according to one embodiment of the present invention, chlorine gas or sodium hydroxide can be obtained easily.

EXAMPLES Hereinafter, one embodiment of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these. One embodiment of the present invention can be modified and implemented as long as it conforms to the spirit of the above and later descriptions, and all of them are included in the technical scope of the present invention. In the following examples and comparative examples, "parts" and "%" mean parts by weight or % by weight.

(Example 1)
<Preparation of gas diffusion electrode (cathode electrode)>
As the suspension forming the reaction layer, 2.4 g of silver powder (Silcoat, manufactured by Fukuda Metal Foil Industry Co., Ltd.) and 0.8 g of polytetrafluoroethylene aqueous suspension (31JR, manufactured by Mitsui Fluorochemical Co., Ltd.) and carboxyl 0.06 g of methylcellulose sodium (manufactured by Wako Pure Chemical Industries, Ltd.) was mixed at 2000 rpm for 5 minutes using a stirrer with defoaming function, and then defoamed at 2200 rpm for 5 minutes.

The obtained suspension was applied to one surface of a carbon cloth (manufactured by AvCarb Material Solutions, 1071HCB, 9 cm long×9 cm wide×0.4 mm thick) as an electrode support layer using a brush. It was applied to an area of 6 cm so as to be 250 g/m ² and dried in a hot air dryer at 120° C. for 1 hour to form a reaction layer, thereby producing a gas diffusion electrode serving as a cathode electrode. The carbon cloth used as the electrode support layer has a liquid retention amount per unit volume of 0.40-H ₂ O/cm ³ .

<Preparation of electrolytic cell>
An electrolytic cell was produced with a configuration as shown in FIG. In the electrolytic cell (0.336 dm 2 electrolytic cell manufactured by Chlorine Engineers Co., Ltd.), DSE (registered trademark) manufactured by Permelec Electrode Co., Ltd. was used as the anode electrode, and A1001 manufactured by Asahi Kasei Corporation was used as the ion exchange membrane.

The anode electrode is pressed in the direction of the ion exchange membrane in the anode chamber with the ion exchange membrane positioned in the vertical direction sandwiched therebetween, and the gas diffusion electrode is placed on the surface opposite to the surface on which the reaction layer is arranged in the cathode chamber. Then, the carbon cloth was tightly fixed using a cushion material so that the carbon cloth was in contact with the ion-exchange membrane, and an electrolytic cell was constructed.

<Salt electrolysis experiment>
In the salt electrolysis experiment, saturated saline solution at 80° C. was supplied to the anode chamber through the anolyte inlet, and PSA-enriched oxygen (93 % by volume ) was supplied to the cathode chamber through the oxygen-containing gas inlet. After confirming that saturated saline and oxygen were supplied to the anode chamber and cathode chamber, respectively, a current of 10 A (current density of 3 kA/m ² ) was supplied to both the anode electrode and the gas diffusion electrode. After the electric current was supplied, electrolysis was performed while controlling the temperature of the anolyte and the gas outlet at 80° C. and the concentration of the aqueous sodium hydroxide solution to be 35%.

The resistance between the anode electrode and the gas diffusion electrode was monitored and measured by the current interrupter method using a pulse generator and an oscilloscope.

In the electrolytic cell having this configuration, the resistance between the anode and the cathode was 0.31 V on the 4th day after starting electrolysis by supplying current. Moreover, since it was not necessary to separately provide a hydrophilic layer between the ion exchange membrane and the gas diffusion electrode, the assembly was easy.

(Example 2)
A polytetrafluoroethylene aqueous suspension (manufactured by Mitsui Fluorochemical Co., Ltd., 31JR) was further applied to the surface side of the reaction layer of the gas diffusion electrode to the extent that unevenness was not generated, except that a hydrophobic resin layer was formed. , an electrolytic cell having the same structure as in Example 1 was prepared, and electrolysis was performed under the same conditions.

In the electrolytic cell having this configuration, the resistance between the anode and the cathode was 0.30 V on the 4th day after starting electrolysis by supplying current. It is believed that the formation of the hydrophobic resin layer alleviated the contact resistance of the electrodes and further suppressed the resistance between the anode and the cathode as compared with Example 1. In addition, as in Example 1, there was no need to separately provide a hydrophilic layer between the ion exchange membrane and the gas diffusion electrode, so assembly was easy.

(Example 3)
Carbon powder (manufactured by Denki Kagaku Kogyo Co., Ltd., AB-11) 0.0024 g and carbon powder (manufactured by Denki Kagaku Kogyo Co., Ltd., AB-6) 0.0024 g were added to the suspension forming the reaction layer. , an electrolytic cell having the same structure as in Example 1 was prepared, and electrolysis was performed under the same conditions.

In the electrolytic cell having this configuration, the resistance between the anode and the cathode was 0.31 V on the 4th day after starting electrolysis by supplying current. In addition, as in Examples 1 and 2, since it was not necessary to separately provide a hydrophilic layer between the ion exchange membrane and the gas diffusion electrode, assembly was easy.

(Comparative example 1)
In the cathode chamber, an electrolytic cell having the same structure as in Example 1 except that the carbon cloth of the gas diffusion electrode was fixed in close contact with the ion exchange membrane on the surface where the reaction layer was arranged, Electrolysis was performed under similar conditions.

In the electrolytic cell having this configuration, the resistance between the anode and the cathode deteriorated to 0.70 V on the 4th day after starting electrolysis by supplying current.

(Comparative example 2)
As the gas diffusion electrode of the cathode, a carbon cloth substrate two-chamber method GDE manufactured by Permelec Electrode Co., Ltd. is used, and a hydrophilic carbon cloth manufactured by Permelec Electrode Co., Ltd. is placed between the gas diffusion electrode and the ion exchange membrane. An electrolytic cell was produced in the same manner as in Example 1, except that it was arranged, and electrolysis was performed under the same conditions.

In the electrolytic cell having this configuration, the resistance between the anode and the cathode was 0.38 V on the 4th day after starting electrolysis by supplying current.

On the other hand, in the electrolytic cell of this configuration, since the carbon cloth, which is a hydrophilic layer, was placed between the gas diffusion electrode and the ion exchange membrane, the number of members increased, and the ease of assembly was inferior to that of Example 1. .

Compared to Examples 1 to 3, in Comparative Example 2, the contact resistance between the hydrophilic layer and the gas diffusion electrode and the resistance of the hydrophilic layer itself were extra.

1 electrolytic cell 2 ion exchange membrane 3 anode chamber 4 cathode chamber 5 anode electrode 6a electrode support layer 6b reaction layer 7 gas diffusion electrode (cathode electrode)
8 Cushion material 9 Cathode chamber back plate (cathode terminal)
10 anode gasket 11 cathode gasket 12 anolyte inlet 13 anolyte and gas outlet 14 oxygen-containing gas inlet 15 sodium hydroxide aqueous solution outlet

Claims (6)

An anode chamber and a cathode chamber are partitioned by an ion exchange membrane, an anode electrode is installed in the anode chamber, a cathode electrode is installed in the cathode chamber, saline solution is placed in the anode chamber, and an oxygen-containing gas is placed in the cathode chamber. , in a gas diffusion electrode salt electrolysis two-chamber electrolytic cell, in which electrolysis is performed by supplying
The cathode electrode is
a hydrophilic and conductive electrode support layer;
a gas diffusion electrode consisting of only two layers: a conductive reaction layer disposed on one side of the surface of the electrode support layer and containing a hydrophilic catalyst and a hydrophobic resin;
In the cathode chamber, the electrode support layer of the gas diffusion electrode is arranged so as to be in contact with the ion-exchange membrane on the side opposite to the side on which the reaction layer is arranged.
Gas diffusion electrode salt electrolysis two-chamber electrolytic cell. 2. The electrolytic cell according to claim 1, wherein the electrode supporting layer has a liquid retention amount of 0.10 g-H ₂ O/cm ³ to 0.80 g-H ₂ O/cm ³ per unit volume of the electrode supporting layer. The electrode support layer includes carbon, zirconium oxide, ceramics, polytetrafluoroethylene, a copolymer of ethylene tetrafluoride and propylene hexafluoride, aramid resin, polyimide resin, vinyl chloride resin, nickel, stainless steel, silver, and 3. The electrolytic cell according to claim 1, which is made of at least one selected from the group consisting of gold. The electrolytic cell according to any one of claims 1 to 3, wherein a hydrophobic resin layer is arranged so as to be in contact with the surface of the gas diffusion electrode on which the reaction layer is arranged. A method for producing chlorine gas, comprising the step of electrolyzing a saline solution using the electrolytic cell according to any one of claims 1 to 4. A method for producing sodium hydroxide, comprising the step of electrolyzing a saline solution using the electrolytic cell according to any one of claims 1 to 4.

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