JP2000064074A - Electrolytic soda process and electrolytic cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic soda process which obviates the occurrence of a pressure difference between the upper part and lower part of a gas diffusion electrode mounted at an electrolytic cell of a vertical type and obviates the occurrence of liquid leakage from a cathode chamber to a gas chamber in the lower part and the leakage of gas to an electrolytic liquid side in the upper part, and a salt electrolytic cell. SOLUTION: An electrolyte flow passage 4 is disposed between an ion exchange membrane 3 and a reaction layer 6 of the gas diffusion electrode 5. An aq. caustic soda soln. 11 and gaseous oxygen 14 are supplied from the upper part of the flow passage 4 in such a manner that the differential pressure on the liquid chamber side and the gas chamber side and the pressure difference between the upper part and the lower part do not occur. The soln. and the gas are separately supplied from the upper part of the electrolytic cell and both thereof are made to flow down as downward flow. Further, if a hydrophilic and open cellular porous body 10 having high porosity is held between the ion exchange membrane 3 and the reaction layer 6, the holding of the electrolyte flow passage 4 is made additionally surer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a salt electrolysis method capable of smoothly supplying and discharging a catholyte in salt electrolysis using a gas diffusion electrode, an electrode suitable for the electrolysis method, and a salt electrolysis cell suitable for the electrolysis method.

[0002]

2. Description of the Related Art When a gas diffusion electrode is used in a conventional ion-exchange membrane type salt electrolytic cell and it is used as an oxygen cathode, a gas diffusion electrode which is usually impermeable to liquids is used. Composed of structure. In the case of a vertical-type electrolytic cell with a height of 1.2 m or more in a practical-scale salt electrolysis cell, electrolysis is performed in a state where the electrolytic solution is filled in the liquid chamber, so the liquid pressure due to the electrolytic solution causes gas diffusion. It will be under the electrode. That is, near the liquid surface of the cathode chamber, the liquid pressure applied to the upper part of the gas diffusion electrode is close to atmospheric pressure, but near the lower end of the cathode chamber, the liquid pressure applied to the lower part of the gas diffusion electrode is at atmospheric pressure due to the height of the electrolyte. The pressure (liquid head) is applied.

[0003]

When a gas diffusion electrode is installed as an oxygen cathode in this vertical electrolytic cell and an electrolytic solution is supplied, a large liquid pressure is applied to the lower portion of the gas diffusion electrode as described above, while the upper portion is treated. Causes a problem of differential pressure that almost no hydraulic pressure is generated. This differential pressure causes liquid leakage from the catholyte compartment to the gas compartment at the bottom. If the liquid pressure and the gas pressure are made equal in the lower part of the catholyte chamber to prevent this liquid leakage, the gas pressure of the gas diffusion electrode becomes higher than the liquid pressure in the upper part of the catholyte chamber. Therefore, the gas leaks to the electrolyte side at the upper part. In addition, if the liquid pressure is higher than the gas pressure and the gas diffusion electrode has high water resistance and the seal is not sufficient, a large amount of electrolyte leaks into the gas chamber, which hinders gas supply. However, there is a problem that the electrode performance and the electrode life are reduced. In particular, the use of gas diffusion electrodes having low water pressure resistance is restricted.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems and obtained the following findings. The electrolytic solution and oxygen gas are supplied separately from the upper part of the electrolytic cell so that the pressure difference between the liquid chamber side and the gas chamber side does not occur, and the liquid is made to flow down. As a result, the catholyte and the gas flow down with almost no differential pressure, so that the catholyte does not leak into the gas chamber even in a gas diffusion electrode having a gas supply layer with a small water pressure resistance. However, if both the anolyte and the catholyte are operated at atmospheric pressure, the head of the anolyte may be pushed by the ion exchange membrane, and the ion exchange membrane may come into contact with the reaction layer of the gas diffusion electrode to prevent the catholyte from flowing. In order to prevent this, an electrolytic solution is easily permeated between the ion exchange membrane and the reaction layer of the gas diffusion electrode, and is retained, and a hydrophilic porous body that does not easily generate bubbles and is deformed by water head pressure to prevent the flow path from dripping is formed. It is effective to have a structure of sandwiching. The present invention has been made on the basis of such findings and comprises the following means.

That is, the present invention has solved the above problems by the following means. (1) An anode chamber having an anode and supplied with a saline solution,
In a salt electrolytic cell having a cathode composed of a gas diffusion electrode and a cathode chamber for generating an alkaline aqueous solution partitioned by an ion exchange membrane, an electrolyte flow between the ion exchange membrane and the reaction layer of the gas diffusion electrode which is the cathode. A passage is provided, and the electrolytic solution from the upper part of the electrolytic solution flow path and oxygen gas from the upper part of the gas chamber of the gas diffusion electrode are separately supplied so that a pressure difference between the flow path and the gas chamber does not occur, A salt electrolysis method, characterized in that it is caused to flow down as a downward flow for electrolysis. (2) A hydrophilic continuous hole for securing the electrolyte flow path,
The salt electrolysis method according to (1) above, wherein a structure having a large porosity is sandwiched between the ion exchange membrane and the reaction layer of the gas diffusion electrode, and the electrolytic solution is supplied. (3) An electrolytic solution reservoir is provided above the cathode chamber of the electrolytic cell,
A gas head is generated so that the gas phase on the liquid surface of the electrolyte solution reservoir communicates with the oxygen gas supplied by the gas diffusion electrode, and only the electrolyte solution overflowing in the electrolyte solution reservoir flows down to the electrolyte solution flow passage in the lower part of the cathode chamber. (1) or (2), characterized in that the amount of the flowing-down liquid is controlled by communicating the liquid through a container and changing the height of the liquid surface of the electrolytic solution reservoir.
The salt electrolysis method described. (4) A bubbler is provided at the electrolytic solution and the gas discharge port to pressurize the oxygen gas supplied to the gas diffusion electrode, thereby pressurizing the cathode chamber communicating with the gas chamber of the gas diffusion electrode for electrolysis. The salt electrolysis method according to any one of (1) to (3) above.

(5) A gas diffusion electrode in which a conductive porous material is used as a core material, and at least a surface side of an electrolyte solution, a reaction layer, and a gas supply layer are continuously and integrally formed from the surface side. (6) Depth 0.5 to 4 on the electrolyte flow path and / or the reaction layer side
The gas diffusion electrode according to (5) above, which has a groove having a width of 0.5 mm and a width of 0.5 mm to 4 mm.

(7) In a salt electrolytic cell in which an anode chamber having an anode and to which a saline solution is supplied and a cathode chamber having a cathode made of a gas diffusion electrode and generating an alkaline aqueous solution are partitioned by an ion exchange membrane An electrolytic solution flow path is provided between the ion exchange membrane and the reaction layer of the gas diffusion electrode that is the cathode, and an electrolytic solution supply port is provided at the upper part of the electrolytic solution flow path and at the upper part of the gas chamber of the gas diffusion electrode. An oxygen gas supply port is provided, and an electrolytic solution and oxygen gas are separately supplied from them so that a pressure difference does not occur between the flow path and the gas chamber, and a downward flow is made to flow to electrolyze. A salt electrolyzer characterized by. (8) A hydrophilic continuous hole for securing the electrolyte flow path,
The salt according to (7) above, characterized in that the structure having a large porosity is sandwiched between the ion exchange membrane and the reaction layer of the gas diffusion electrode, and the electrolytic solution is supplied to the electrolytic solution flow path having the structure. Electrolyzer. (9) An electrolytic solution reservoir is provided in the upper part of the electrolytic cell, and the gas phase on the liquid surface of the electrolytic solution reservoir and the oxygen gas supplied from the gas diffusion electrode are connected and connected to each other to generate water heads in the upper part of the electrolytic solution reservoir and the lower part of the electrolytic cell. The structure is such that the electrolytic solution overflowing in the electrolytic solution reservoir flows down to the lower part of the electrolytic cell, and the amount of the flowing-down liquid is controlled by changing the height of the liquid surface of the electrolytic solution reservoir. The salt electrolyzer described in (7) or (8) above. (10) The salt electrolyzer according to (7) above, wherein a bubbler is provided at the electrolyte and oxygen gas outlet below the cathode chamber, and the cathode chamber is pressurized with oxygen gas for electrolysis.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the first embodiment of the salt electrolysis cell of the present invention, as shown in FIG. 1, the cathode part 2 of the electrolysis cell 1 is provided with an ion exchange membrane 3 and an electrolytic solution flow path through which the electrolytic solution flows down. The cathode chamber 4, the reaction layer 6 of the gas diffusion electrode 5 acting as an oxygen cathode, the gas supply layer 7, and the gas chamber 8 were configured. A hydrophilic porous body 10 having continuous pores was provided in the cathode chamber 4, which is the lower stream of the electrolytic solution. Caustic soda solution 11
Is supplied from the caustic soda inlet 12 and flows down from the upper portion of the cathode chamber 4 into the hydrophilic porous body 10. The oxygen gas 14 is supplied from the oxygen gas inlet 15 to the gas chamber 8 of the gas diffusion electrode 5 from above at substantially the same pressure as the cathode chamber 4. The amount of the electrolytic solution flowing down through the cathode chamber 4 is controlled by the opening diameter and opening ratio of the hydrophilic porous body 10 and the thickness of the flow path. The material of the hydrophilic porous body 10 may be a metal, a metal oxide, or an organic material as long as it has corrosion resistance and is hydrophilic. It is desirable that the shape is a vertical groove, a porous body, or a net-like structure, in which the electrolytic solution can easily flow down and the increase of the liquid resistance during electrolysis is small. In particular, it is important that the shape is such that bubbles do not easily accumulate. In addition, the surface of the reaction layer 6 of the gas diffusion electrode 5 is preferably hydrophilic so that bubbles do not stay. The gas diffusion electrode 5 that can be used may be liquid-permeable or impermeable.

In the present invention, it is important that the liquid pressure of the electrolytic solution in the cathode chamber 4 which is the flow path of the electrolytic solution and the gas pressure in the gas chamber 8 of the gas diffusion electrode 4 do not differ. For that purpose, it is preferable to take a means for increasing the gas pressure in the gas chamber 8 of the gas diffusion electrode 5 as one means. Then, the gas pressure pushes the electrolytic solution in the cathode chamber to restrict the flow of the electrolytic solution so that the liquid surface of the electrolytic solution is formed at the lower end of the cathode chamber 4 in FIG. In this case, it is not necessary to apply the oxygen gas pressure to a pressure corresponding to the head of the liquid column of the electrolytic solution in the cathode chamber, which is practically as small as possible in a salt electrolytic cell using an ion exchange membrane. In order to achieve this, the distance between the ion exchange membrane and the surface of the reaction layer 6 of the gas diffusion electrode 5, that is, the thickness of the cathode chamber is made as thin as possible. Due to the viscosity and other factors, the flow resistance of the electrolyte when flowing down is large, and the entire head of the liquid column does not directly touch the lower end of the cathode chamber. Gas pressure may be applied. If the entire head of the liquid column is directly applied to the lower end of the cathode chamber, applying a gas pressure commensurate with it will cause gas to leak from the gas diffusion electrode to the cathode chamber at the upper end of the cathode chamber as described above. become.

Further, in the present invention, the electrolyte solution can freely flow out at the lower end of the cathode chamber 4 which is the flow path of the electrolyte solution, so that the difference between the electrolyte solution pressure and the gas pressure is different. It can be done easily. In this case, since the liquid reservoir is not formed at the lower end of the cathode chamber 3, the water column head does not act on the electrolyte itself even when the electrolyte flowing down into the cathode chamber 4 is filled. That is, in the usual case, in order to maintain the liquid level in the upper part of the cathode chamber 4, a rising pipe communicating with the lower part of the cathode chamber 4 is provided as a discharge pipe of the catholyte, and the catholyte overflows from there. Alternatively, a discharge valve provided in the lower portion of the cathode chamber 4 is provided with a throttle valve. In each of these cases, a water column head acts on the electrolytic solution itself. In the present invention, when the free outflow end is used as described above, the flowing electrolyte solution is filled in the cathode chamber 4 which is the lower flow portion of the electrolyte solution, but the energy due to the flowing speed is in contact with the ion exchange. It is consumed by the resistance with the membrane, and the static pressure at rest does not work on the ion exchange membrane. However, in order to always fill the electrolytic solution, the thickness of the cathode chamber 4 is considerably thin and a continuous liquid film can be formed as described above. And
By communicating the electrolytic solution with the oxygen gas at the lower end of the cathode chamber 4, it is possible to easily make the pressure of the electrolytic solution in the lower part of the cathode chamber 4 equal to the pressure of the oxygen gas in the lower part of the gas chamber.

In the second aspect of the present invention, an electrolytic solution reservoir 17 is provided above the electrolytic cell 1 so that a pressure difference between the liquid chamber side and the gas chamber side does not occur, and the gas above the liquid surface of the electrolytic solution reservoir 17 is provided. The phase and the oxygen gas inlet 15 are communicated with each other through the communication pipe 18, and the upper portion of the electrolytic solution reservoir 17 and the electrolytic cell lower chamber 20 are communicated with each other through the overflow head 21 through the water head generator 22, and the overflowed electrolytic solution is It was made to flow down to the lower chamber 20 of the electrolytic cell through the overflow pipe 21 (see FIG. 2). The electrolytic solution and the oxygen gas 14 have almost the same pressure, are supplied separately from the upper part of the electrolytic cell, the electrolytic solution flows down naturally, and the oxygen gas exits from the oxygen gas outlet 16 through the discharge pipe 23 at the lower part of the gas chamber. Since the catholyte and the gas flow down naturally with almost no pressure difference, the catholyte does not leak into the gas chamber 8 even when the gas diffusion electrode 5 having the gas supply layer 7 having a small water pressure resistance is used. However, when both the anolyte and the catholyte are operated at atmospheric pressure, the ion exchange membrane 3 is pushed by the head pressure of the anolyte, the ion exchange membrane 3 comes into contact with the reaction layer 6 of the gas diffusion electrode 5, and the catholyte does not flow. In order to prevent this, the electrolytic solution easily permeates between the ion exchange membrane 3 and the reaction layer 6 of the gas diffusion electrode, is retained, is less likely to generate air bubbles, and is a hydrophilic porous material that is deformed by the water head pressure and does not break the flow path. The structure for sandwiching the body 10 is adopted. Electrolyte channel or /
And 0.5 to 4 mm in depth and 0.5 to 4 m in width on the reaction layer 6 side.
When the groove of m is formed, the flow rates of liquid and gas can be increased. Further, the amount of the flowing-down liquid can be controlled by changing the height of the liquid surface of the electrolytic solution reservoir 17.

In another embodiment of the present invention, as shown in FIG. 4, the conductive porous body 26 is used as a core material, and at least the hydrophilic porous body 10 serving as the electrolyte flow path portion from the surface side, the reaction layer 6, An electrode, in which the gas supply layer 7 is continuously and integrally formed, is attached to the gas chamber 8, and the electrolytic solution is flown from the upper part of the gas diffusion electrode into the electrolytic solution flow path 4 with the ion exchange membrane 3 and the gas diffusion electrode as a zero gap. I decided to do it. FIG. 2 shows the structure of the electrolytic cell for the purpose of ensuring conductivity and gas passage.
A bubbler 24 was provided at the outlets of the gas and the electrolytic solution so that the cathode chamber 4 was pressurized with liquid pressure. Since the cathode chamber 4 is higher than the anolyte chamber and the ion exchange membrane 3 is pressed against the anode, electrolysis can be performed without a spacer. In this case, it is desirable that the gas diffusion electrode 5 and the ion exchange membrane 3 are hydrophilic.

An electrolytic solution reservoir 17 is provided above the electrolytic cell 1 shown in FIG. 2, and a gas phase on the liquid surface of the electrolytic solution reservoir 17 and the supply oxygen gas 14 are connected and connected by a gas connecting pipe 18.
The upper part of the electrolytic solution reservoir 17 and the lower part of the electrolytic cell 1 were connected by an overflow pipe 21 so that only the overflowed electrolytic solution could flow down to the electrolytic solution flow path in the lower part of the cathode chamber. If the overflow pipe 21 is directly connected to the lower chamber 20, the chamber of the electrolyte solution reservoir 17 and the lower chamber 20 will have the same pressure, so that the pressure due to the liquid column in the cathode chamber 4 will be lower.
In the case of zero, the lower chamber 20 with the overflow pipe 21 being applied with a head pressure corresponding to the pressure.
It is preferable to connect to the lower chamber 20 via the head generator 22 so as to connect to. FIG. 3 is a side view of only the overflow pipe 21 portion shown in FIG. 2, and the head generator 22 is shown at the lower end.

Further, in the electrolytic cell of the present invention, in FIG. 1, an aqueous solution of caustic soda, which is an electrolytic solution, and oxygen gas enter through separate inlets and are introduced into respective chambers through respective flow paths.
As shown in FIG. 7, it is desirable to integrate it with the electrolytic cell without piping. The gas and the liquid may be introduced from the same inlet and introduced into each chamber. The gas diffusion electrode used is
Silver and PTF on a 25 ppi nickel porous body with a thickness of 3 mm and a size of 11 cm x 21 cm plated with 5 microns.
The reaction layer paste consisting of E was further applied, and ethanol was added to the PTFE dispersion to form a gel, which was coated, dried, surfactant removed, dried, and heat-treated. A gas diffusion electrode having a 0.4 mm thick reaction layer and a 0.6 mm thick gas supply layer is obtained. As shown in FIG. 2, this electrode is replaced with an ion exchange membrane 3, a gas diffusion electrode 5 (electrolyte flow path 4, reaction layer 6, gas supply layer 7).
, And the gas chamber 8 is configured (see FIG. 6). The caustic soda aqueous solution 11 flows down from the upper part through the electrolytic solution flow path having the hydrophilic porous body 10. The oxygen gas 14 is supplied to the gas chamber from above through the oxygen gas inlet 15 at substantially the same pressure as the liquid chamber.

The material of the porous core material forming the electrolytic solution flow path portion of the electrode may be any material that is electrically conductive, has corrosion resistance, and is hydrophilic, and may have a flute shape, a porous body, or a mesh shape so that the electrolytic solution flows down. It is desirable to have a structure that is easy to perform and has little increase in liquid resistance during electrolysis. In particular, it is important that the shape is such that bubbles do not easily accumulate. If the gas diffusion electrode 5 and the ion exchange membrane 3 used are hydrophilic, the pressure of the caustic soda aqueous solution 11 and the oxygen gas 14 to be supplied is raised to make the liquid level in the cathode chamber higher than the liquid level in the anolyte chamber, thereby making it the anode. The spacer is not necessarily required by pressing the ion exchange membrane 3. A bubbler 24, an oxygen gas outlet 16 and a caustic soda outlet 13 shown in FIG. 2 are provided, and the cathode chamber is pressurized with liquid pressure. Head generator 2
2 and bubbler 24 are preferably integrated with the electrolytic cell.

In the present invention, when the gas diffusion electrode is formed, a conductive core material is used in order to increase its strength in the production of the gas diffusion electrode itself, and a reaction layer forming material and a gas supply layer forming material are pasted into it. The gas diffusion electrode and the hydrophilic porous body can be manufactured by pressing or coating in the shape of a circle, but at the same time, since the hydrophilic porous body is also provided on the side of the cathode chamber adjacent to the gas diffusion electrode, this gas diffusion electrode and the hydrophilic porous body are combined. It is possible to produce it. That is, FIG. 4 shows the gas diffusion electrode 5 in which the reaction layer 6 and the gas supply layer 7 are provided on one surface of the conductive porous body 26 that satisfies the properties of the hydrophilic porous body 10.
Is. FIG. 5 shows a gas diffusion electrode 5 having a structure in which a reaction layer 6 and a gas supply layer 7 are provided inside one side of a conductive porous body 26, and a portion of the conductive porous body is also provided outside the gas supply layer 7. Thus, the portion of the conductive porous body outside the gas supply layer 7 becomes a part of the porous body inside the gas chamber. Figure 6
Is a gas diffusion electrode 5 having a structure in which a reaction layer 6 and a gas supply layer 7 are provided at the center of the inside of a conductive porous body 26, and portions of the porous body are provided on both sides of the reaction layer 6 and the gas supply layer 7. It becomes the porous body 10 and the lower side becomes the porous body 9 in the gas chamber.

[0017]

EXAMPLES The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples.

Example 1 5 parts (weight, hereinafter the same) of silver fine particles (manufactured by Mitsui Mining & Smelting Co., Ltd., Ag-3010, average particle size 0.11 micron) were mixed with 1 part of surfactant Triton and 9 parts of water. In addition, disperse with an ultrasonic disperser. Add to this PTFE dispersion D-1
(Daikin Kogyo Co., Ltd.) 1 part was added, and after stirring and mixing, 2 parts of ethanol were added and stirred to cause self-organization. The precipitate was filtered through a 1 micron filter paper to obtain a mud scoop. PTFE dispersion D- that will be the gas supply layer in advance
A silver-plated foamed nickel body (manufactured by Nippon Heavy Chemical Co., Ltd., thickness 3.7) in which ethanol was added to 1 to make a paste.
mm, 10 x 20 cm square) and 0.3 mm of this mud
A reaction layer and a gas supply layer are formed by applying a thick coating and pressing at a pressure of 10 kg / cm ² and then pushing it inside. A gas diffusion electrode was obtained by drying at 80 ° C. for 3 hours, removing the surfactant with an extractor using ethanol, and then drying at 100 ° C. for 2 hours. The amount of fine silver particles used at this time was 430 g / m ² .

This gas diffusion electrode was attached to a silver-plated electrode frame, and a 1.5 mm thick 50 ppi foamed nickel body was laminated on the electrode to form an electrolyte solution flow path. This gas diffusion electrode was set in an ion exchange membrane electrolytic cell, and the anolyte pressure was increased by 100 mm water column pressure to bring it into contact with the nickel foam body in the electrolyte flow path. A 32% caustic soda aqueous solution was caused to flow down from the upper portion at a rate of 50 ml per minute, and an oxygen gas of approximately the same pressure was passed through the gas chamber at 1.5 times the theoretical value, and then an electric current was supplied. As a result, 30 A / d at 90 ° C. and 32% NaOH aqueous solution supply
An electrolytic cell voltage of m ² , 2.05 V was obtained. The electrolytic solution flowing down the flow path is combined with the surplus oxygen gas and is discharged from the lower discharge port.

Example 2 A silver-supporting carbon gas diffusion electrode was prepared. This electrode was mounted on a gas chamber overlaid with a nickel mesh, and a micromesh made by Katsura Grating Co., Ltd. (0.2NiO, 8-M60, thickness 1 mm) was placed between the ion exchange membrane and the gas diffusion electrode.
Was used as the electrolytic solution flow path. A 32% aqueous solution of caustic soda was flown down at 90 ml / min, and the operation was carried out under the same conditions as in Example 1. As a result, 30 A / dm ² , 90 ° C., 32% NaOH, and 2.11 V of 1.6 times the theoretical amount of oxygen were supplied. The cell voltage was obtained.

Example 3 A gas diffusion electrode using platinum-supporting carbon was prepared. This electrode was mounted on a gas chamber overlaid with a nickel net, and nickel micromesh corrugated 0.2 Ni, O. 2-M30, thickness 1mm
Was used as the electrolytic solution flow path. A 32% caustic soda aqueous solution was flown down at 120 ml / min and operated under the same conditions as in Example 1. As a result, 30 A / dm ² , 90 ° C., 32% NaOH aqueous solution, and 2.06 V with 1.6 times the theoretical amount of oxygen supply. The cell voltage of was obtained.

Example 4 As shown in FIG. 2, the structure of the electrolytic cell is such that an electrolytic solution reservoir is provided on the upper part of the electrolytic cell, and the gas phase on the liquid surface of the electrolytic solution reservoir and the supply gas are connected by piping to form an electrolytic solution reservoir upper part. The lower part of the electrolytic cell was connected by piping to allow the overflowed electrolytic solution to flow down to the lower part of the electrolytic cell. No bubbler was provided. The gas diffusion electrode used was silver fine particles (Mitsui Mining & Smelting Co., A
g-3010, average particle size 0.11 micron), 5 parts of 5 parts of Triton surfactant and 9 parts of water are added and dispersed by an ultrasonic disperser. Add to this PTFE dispersion D-1
1 part (manufactured by Daikin Industries, Ltd.) is added and mixed with stirring, and then 2 parts of ethanol is added and self-organized by stirring.
The precipitate was filtered through a 1 micron filter paper to obtain a mud scoop.
On a silver-plated foamed nickel body (manufactured by Nippon Heavy Industries, Ltd., thickness 3.7 mm, 10 × 20 cm square), this mud is recommended.
It was applied to a thickness of 3 mm to form a reaction layer. Immediately, ethanol is added to D-1 which will be the gas supply layer to form a paste, which is applied from above, and pressed at a pressure of 10 kg / cm ² and pushed into the inside to form the gas supply layer. 80
Dry for 3 hours at ℃, remove the surfactant with an extractor using ethanol, then dry for 2 hours at 80 ℃, 10 at 230 ℃
Heat treatment was performed for minutes to obtain an electrode. The amount of fine silver particles used at this time was 430 g / m ² .

The electrodes were attached to a silver-plated electrode frame with a gas chamber. An ion exchange membrane was sandwiched and an electrolytic cell was set. The anolyte pressure was raised to 100 mm water column higher than that of the catholyte, and the anolyte pressure was brought into contact with the nickel foam body in the electrolyte flow path. A 32% caustic soda aqueous solution was caused to flow down from the upper portion at a rate of 50 ml per minute, and an oxygen gas of approximately the same pressure was passed through the gas chamber at 1.5 times the theoretical value, and then an electric current was supplied. The exhaust gas was opened to the atmosphere. As a result, 30 A / dm at 90 ° C. and 32% NaOH aqueous solution supply
^2, cell voltage of 2.05V was obtained.

Example 5 A bubbler was provided at the gas and electrolyte discharge ports of the electrolytic cell of Example 4 so that the cathode chamber was pressurized hydraulically. A gas diffusion electrode composed of silver-supported hydrophilic carbon black (AB-12), hydrophobic carbon black (No. 6) and PTFE dispersion was attached to an electrolytic cell together with a nickel corrugate serving as a gas chamber, and an ion exchange membrane method electrolytic cell was installed. Assembled The liquid depth of the bubbler was 40 cm. 200 ml of 32% caustic soda aqueous solution was supplied per minute, and the excess electrolytic solution was overflowed. As a result of operating under the same conditions as above, 30 A / dm ² , 90 ° C., 32% NaOH aqueous solution,
An electrolytic cell voltage of 1.96 V was obtained with the supply of oxygen 1.6 times the theoretical value.

[0025]

EFFECTS OF THE INVENTION According to the present invention, the generated caustic soda is discharged downward together with the liquid flow from the upper part, and oxygen gas is supplied to the gas diffusion electrode at substantially the same pressure as that of the liquid flow. There is no pressure difference between the gas side and the gas side in the height direction. For this reason, it is no longer necessary to take thorough measures against liquid leakage from the liquid side to the gas chamber of the gas diffusion electrode. This is particularly noticeable when using a gas diffusion electrode having a nickel foam body as a core material. Even if the electrolytic solution leaks into the gas chamber, it is little and does not affect the operation performance. The flow rate of the electrolyte is the opening diameter of the flow path,
Since the opening ratio and the thickness of the flow path can be adjusted, the concentration control of the generated caustic soda becomes easy. In particular, a gas diffusion electrode, which has heretofore been unusable and has large hydrophobic pores in the gas supply layer, causing liquid leakage at a small differential pressure, can be used.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing an embodiment of an electrolytic cell of the present invention.

FIG. 2 is a cross-sectional explanatory view showing an example in which an electrolytic solution reservoir of the electrolytic cell of the present invention is provided.

FIG. 3 is a side view of an overflow pipe portion in the electrolytic cell of FIG.

FIG. 4 is a cross-sectional explanatory view showing an example of a gas diffusion electrode in which a conductive porous body is used as a core material and an electrolyte solution flow channel, a reaction layer, and a gas supply layer are integrally molded.

FIG. 5 is a cross-sectional explanatory view showing an example of a gas diffusion electrode in which an electrolyte flow path, a reaction layer, and a gas supply layer are integrally molded for the purpose of ensuring conductivity and a gas passage.

FIG. 6 is a cross-sectional explanatory view showing an example in which a gas chamber and a gas diffusion electrode are joined by a conductive gas supply layer.

FIG. 7 is a cross-sectional explanatory view showing another embodiment of the type in which the electrolytic solution reservoir of the electrolytic cell of the present invention is provided.

[Explanation of symbols]

1 electrolysis tank 2 Cathode part 3 Ion exchange membrane 4 Electrolyte flow path (cathode chamber) 5 Gas diffusion electrode 6 Reaction layer 7 gas supply layer 8 gas chambers 9 Porous body 10 Hydrophilic porous body 11 caustic soda solution 12 Caustic soda entrance 13 Caustic soda exit 14 oxygen gas 15 Oxygen gas inlet 16 Oxygen gas outlet 17 Electrolyte reservoir 18 Gas communication pipe 19 Upper chamber 20 Lower chamber 21 Overflow pipe 22 Head generator 23 Discharge pipe 24 Bubbler 25 bubbles 26 Conductive porous body

   ─────────────────────────────────────────────────── ─── Continued front page    (71) Applicant 000000941             Kanegafuchi Chemical Industry Co., Ltd.             3-2-4 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture (72) Inventor Choichi Furuya             2-14 Nakamuracho, Kofu City, Yamanashi Prefecture F-term (reference) 4K011 AA03 AA10 AA68 BA03 BA04                       CA01 CA04 DA03                 4K021 AB01 BA03 BB04 BC04 CA01                       CA08 CA09 DB01 DB31 DB36

Claims (10)

[Claims] 1. A salt electrolytic cell in which an anode chamber having an anode and to which a saline solution is supplied and a cathode chamber having a cathode composed of a gas diffusion electrode and generating an alkaline aqueous solution are partitioned by an ion exchange membrane, An electrolytic solution flow path is provided between the ion exchange membrane and the reaction layer of the gas diffusion electrode that is the cathode, and the electrolytic solution is from the upper part of the electrolytic solution flow path, and the oxygen gas is from the upper part of the gas chamber of the gas diffusion electrode. A salt electrolysis method characterized in that they are separately supplied so that a pressure difference is not generated between the flow path and the gas chamber, and are made to flow as a downward flow for electrolysis. 2. A hydrophilic structure having a continuous hole and a large porosity is sandwiched between the ion exchange membrane and the reaction layer of the gas diffusion electrode in order to secure the electrolytic solution flow path, and the electrolytic solution is filled with the electrolytic solution. The salt electrolysis method according to claim 1, wherein the salt electrolysis method is supplied. 3. An electrolytic solution reservoir is provided above the cathode chamber of the electrolytic cell, the gas phase on the liquid surface of the electrolytic solution reservoir is communicated with the oxygen gas supplied to the gas diffusion electrode, and the electrolytic solution overflows in the electrolytic solution reservoir. Only the liquid is communicated via the head generator so that it flows down to the electrolyte flow path at the bottom of the cathode chamber,
The salt electrolysis method according to claim 1 or 2, wherein the amount of the falling liquid is controlled by changing the height of the liquid surface of the electrolytic solution reservoir. 4. An electrolytic solution and a gas outlet are provided with a bubbler to pressurize oxygen gas supplied to the gas diffusion electrode, thereby pressurizing a cathode chamber communicating with the gas chamber of the gas diffusion electrode for electrolysis. Any one of Claims 1-3 characterized by the above-mentioned.
The salt electrolysis method according to the item. 5. A gas diffusion electrode in which a conductive porous body is used as a core material, and an electrolyte solution flow path portion, a reaction layer, and a gas supply layer are continuously and integrally molded from at least the surface side. 6. The gas diffusion electrode according to claim 5, wherein a groove having a depth of 0.5 to 4 mm and a width of 0.5 mm to 4 mm is provided on the electrolytic solution flow path portion and / or the reaction layer side. 7. A salt electrolytic cell in which an anode chamber having an anode and supplied with a saline solution and a cathode chamber having a cathode composed of a gas diffusion electrode and generating an alkaline aqueous solution are partitioned by an ion exchange membrane. An electrolytic solution flow path is provided between the exchange membrane and the reaction layer of the gas diffusion electrode which is the cathode, and an electrolytic solution supply port is provided above the electrolytic solution flow path and oxygen gas is provided above the gas chamber of the gas diffusion electrode. And an electrolytic solution and an oxygen gas are separately supplied from them so that a pressure difference is not generated between the flow path and the gas chamber, and the electrolytic solution is caused to flow down as a downflow to electrolyze. And salt electrolysis tank. 8. An electrolysis device having a hydrophilic continuous hole and a large porosity structure sandwiched between an ion exchange membrane and a reaction layer of a gas diffusion electrode in order to secure the electrolytic solution flow path, and having the structure. The salt electrolytic cell according to claim 7, wherein an electrolytic solution is supplied to the liquid flow path. 9. An electrolytic solution reservoir is provided above the electrolytic cell,
The gas phase on the liquid surface of the electrolyte reservoir and the oxygen gas supplied to the gas diffusion electrode are connected and connected, and the upper part of the electrolyte reservoir and the lower part of the electrolytic cell are connected and connected via a head generator, and the electrolyte reservoir is used. 9. The salt electrolysis according to claim 7 or 8, wherein the overflowed electrolytic solution is made to flow down to the lower part of the electrolytic cell, and the amount of the flowing-down liquid is controlled by changing the height of the liquid surface of the reservoir. Tank. 10. The salt electrolyzer according to claim 7, wherein a bubbler is provided at the electrolyte and oxygen gas discharge port under the cathode chamber, and the cathode chamber is pressurized with oxygen gas for electrolysis.