JP7073104B2 - Electrode for chlorine generation and its manufacturing method - Google Patents

Description

The present invention relates to an electrode for generating chlorine, particularly an electrode used for producing on-site sodium hypochlorite using dilute salt water such as seawater electrolysis, and a method for producing the same.

Conventionally, a method for producing hypochlorite by electrolysis of salt water has been known, and it is widely known in the art to use a coating film of a mixed metal oxide as an electrode.

For example, in Patent Document 1, platinum-platinum oxide-lutenium dioxide having a composition of 3 to 42% by weight of platinum, 3 to 34% by weight of palladium oxide, and 42 to 94% by weight of ruthenium dioxide on titanium or a titanium alloy as an anode. A ternary mixture of platinum group metals and a mixture of 20 to 40% by weight of titanium dioxide coated with the mixture is disclosed.

Further, in Patent Document 2, the electrode for producing chlorine and hypochlorite in particular is a film of a mixed oxide of a platinum group metal oxide and a valve metal oxide, and platinum of ruthenium, palladium and iridium. It consists of a group metal oxide and a titanium oxide, and the molar ratio of the platinum group metal oxide to the valve metal oxide is 90:10 to 40:60, and the molar ratio of ruthenium to iridium is 90:10 to 50:50. It is disclosed that the molar ratio of palladium oxide to ruthenium oxide and iridium oxide is 5:95 to 40:60.

Further, Patent Document 3 describes 10 to 45% by weight of palladium oxide, 15 to 45% by weight of yttrium oxide, 10 to 40% by weight of titanium dioxide, and 10 as an anode for producing hypochlorite. It has been proposed to have a coating containing up to 20% by weight platinum and an oxide of at least one metal selected from 2 to 10% by weight cobalt, lanthanum, cerium and yttrium.

Special Publication No. 59-24192 Special Table No. 2008-528804 Japanese Patent No. 3319880

Electrodes having platinum group oxides as described in Patent Documents 1 to 3 have high oxidation efficiency of chloride ions, and generate high-concentration hypochlorite ions with high chlorine generation efficiency exceeding 90%. It is possible, and it is possible to obtain a high concentration of hypochlorite at a lower power intensity than that of a conventional anode.

However, this is based on the premise that salt water (sodium chloride aqueous solution) having a high concentration of 2.5 to 32% is used as the electrolytic solution, and 1% or less that can be used for thinner salt water such as ballast water. When the salt water of No. 1 is used as an electrolytic solution, there is a problem that the chlorine generation efficiency is remarkably lowered.

Further, when such a low-concentration salt water is used as an electrolytic solution, a high voltage is required for electrolysis of the salt water, so that the load on the electrode is large and the life of the electrode is short.

In view of the above circumstances, the present invention provides an electrode for chlorine generation having high chlorine generation efficiency and excellent long-term durability even when used for electrolysis of low-concentration salt water. Is the main purpose. Further, it is also an object of the present invention to provide a method for producing the chlorine generating electrode, a method for producing hypochlorite using the chlorine generating electrode, and an electrolytic cell provided with the electrode.

The present inventors have made diligent studies to solve the above problems. As a result, it is a chlorine generating electrode including a conductive substrate and a catalyst layer provided on the conductive substrate, and the catalyst layer contains at least palladium oxide, ruthenium oxide, and titanium oxide. The chlorine generation electrode, in which palladium oxide is a particle with an average particle size of 5 μm or less, has high chlorine generation efficiency and long-term durability even when used for electrolysis of low-concentration salt water. I found it to be excellent. The present invention has been completed by further studies based on these findings.

That is, the present invention provides the inventions of the following aspects.
Item 1. A chlorine generating electrode comprising a conductive substrate and a catalyst layer provided on the conductive substrate.
The catalyst layer contains at least palladium oxide, ruthenium oxide, and titanium oxide.
The palladium oxide is an electrode for generating chlorine, which is a particle having an average particle diameter of 5 μm or less.
Item 2. Item 2. The catalyst layer has an X-ray diffraction peak intensity of 500 cps or more in the range of the diffraction peak 2θ = 33 ° to 35 ° of palladium oxide, which is measured by an X-ray diffraction method using CuKα rays. Chlorine generation electrode.
Item 3. The catalyst layer has an X-ray diffraction peak half-value width in the range of the diffraction peak 2θ = 33 ° to 35 ° of palladium oxide measured by an X-ray diffraction method using CuKα rays, which is 1.5 deg or less. The electrode for generating chlorine according to 1 or 2.
Item 4. Item 2. Chlorine generation according to any one of Items 1 to 3, wherein the proportion of the palladium metal contained in the catalyst layer is 1 mol% or more when the metal element contained in the catalyst layer is 100 mol%. Electrode for.
Item 5. Item 6. The electrode for chlorine generation according to any one of Items 1 to 4, which is used for electrolysis of salt water having a concentration of 1% or less.
Item 6. A method for manufacturing a chlorine generating electrode, comprising a conductive substrate and a catalyst layer provided on the conductive substrate.
At least, a coating step of applying a solution containing a palladium compound, a ruthenium compound, and a titanium compound onto a conductive substrate, and
A firing step of firing the conductive substrate coated with the solution, and
Equipped with
A method for producing an electrode for chlorine generation, which uses palladium oxide particles having an average particle diameter of 5 μm or less as the palladium compound.
Item 7. A method for manufacturing a chlorine generating electrode, comprising a conductive substrate and a catalyst layer provided on the conductive substrate.
At least, a coating step of applying a solution containing a palladium compound, a ruthenium compound, and a titanium compound onto a conductive substrate, and
A firing step of firing the conductive substrate coated with the solution, and
Equipped with
At least one of palladium chloride and palladium nitrate was used as the palladium compound.
A method for producing a chlorine generating electrode, which is heated at a temperature of 400 to 600 ° C. in the firing step to generate palladium oxide particles having an average particle diameter of 5 μm or less from the palladium chloride.
Item 8. The catalyst layer formed by the firing step has an X-ray diffraction peak intensity in the range of diffraction peak 2θ = 33 ° to 35 ° of palladium oxide measured by an X-ray diffraction method using CuKα rays at 500 cps or more. Item 6. The method for manufacturing a chlorine generating electrode according to Item 6 or 7.
Item 9. The catalyst layer formed by the firing step has an X-ray diffraction peak half-value width in the range of diffraction peak 2θ = 33 ° to 35 ° of palladium oxide measured by an X-ray diffraction method using CuKα rays. Item 6. The method for producing a chlorine generating electrode according to any one of Items 6 to 8, which is 5 deg or less.
Item 10. An electrolytic cell provided with the chlorine generating electrode according to any one of Items 1 to 5.
Item 11. A method for producing hypochlorite, comprising a step of electrolyzing an aqueous metal chloride solution using the chlorine generating electrode according to any one of Items 1 to 5.

According to the present invention, it is possible to provide an electrode for chlorine generation having high chlorine generation efficiency and excellent long-term durability even when used for electrolysis of low-concentration salt water. Further, according to the present invention, it is also possible to provide a method for producing the chlorine generating electrode, a method for producing hypochlorite using the chlorine generating electrode, and an electrolytic cell provided with the electrode.

It is an SEM image of the catalyst layer surface of the anode obtained in Example 1 (5,000 times). It is an SEM image of the catalyst layer surface of the anode obtained in Example 2 (5,000 times). It is an SEM image of the catalyst layer surface of the anode obtained in Example 3 (5,000 times). It is an SEM image of the catalyst layer surface of the anode obtained in Example 4 (10,000 times). It is an SEM image of the catalyst layer surface of the anode obtained in Example 5 (10,000 times). It is an SEM image of the catalyst layer surface of the anode obtained in Comparative Example 1 (5,000 times). It is an SEM image of the catalyst layer surface of the anode obtained in Comparative Example 2 (5,000 times). It is an SEM image of the catalyst layer surface of the anode obtained in Comparative Example 3 (5,000 times). 6 is a graph showing the relationship between 2θ (°) obtained by measuring X-ray diffraction and peak intensity (cps) for the catalyst layer of the anode obtained in Example 2. 6 is a graph showing the relationship between 2θ (°) obtained by measuring X-ray diffraction and peak intensity (cps) for the catalyst layer of the anode obtained in Example 3. 6 is a graph showing the relationship between 2θ (°) obtained by measuring X-ray diffraction and peak intensity (cps) for the catalyst layer of the anode obtained in Example 4. It is a graph which shows the relationship between the temperature and chlorine generation efficiency at a salt water concentration of 0.1%. It is a graph which shows the relationship between the temperature and chlorine generation efficiency at a salt water concentration of 0.15%. It is a graph which shows the relationship between the temperature and chlorine generation efficiency at a salt water concentration of 0.5%. It is a graph which shows the time-dependent change of the electrolysis time and the chlorine generation efficiency at the time of using the anode of Example 4 and Comparative Example 1.

The electrode for generating chlorine of the present invention includes a conductive substrate and a catalyst layer provided on the conductive substrate. Further, in the chlorine generating electrode of the present invention, the catalyst layer contains at least palladium oxide, ruthenium oxide, and titanium oxide, and the palladium oxide is a particle having an average particle diameter of 5 μm or less. And. By providing such a specific catalyst layer, the chlorine generating electrode of the present invention is used for electrolysis of low-concentration salt water (for example, salt water having a concentration of 1% or less) (that is, an electrolytic solution). However, even in the case of low-concentration salt water), the chlorine generation efficiency is high and the effect of excellent long-term durability can be exhibited. Hereinafter, the chlorine generating electrode of the present invention will be described in detail.

The electrode for generating chlorine of the present invention includes a conductive substrate and a catalyst layer. The material of the conductive substrate is not particularly limited, and examples thereof include those used for known chlorine generating electrodes. Specific examples of the material of the conductive substrate include valve metals such as titanium, tantalum, zirconium, and niobium, and alloys of two or more types of valve metals. The shape of the conductive substrate is not particularly limited, and examples thereof include a plate shape, a disk shape, a rod shape, a cylindrical shape, an expanded metal, and a punching metal.

The surface of the conductive substrate may be sandblasted (roughened) or the like, if necessary, for the purpose of exerting an anchoring effect on the catalyst layer. Sandblasting is a surface treatment method in which a high-pressure gas containing sandy particles is sprayed onto the surface of a material. The sandblasting treatment can be performed by a known method. For example, the surface roughness of the conductive substrate can be controlled by adjusting the type of abrasive used, the processing time, and the like. Examples of the material of the sand-like particles include alumina, glass, iron and the like. Further, after the sandblasting treatment, a degreasing treatment or the like may be performed, if necessary.

Although it depends on the particle size used for the sandblasting treatment, the surface roughness Ra (arithmetic mean roughness) of the surface of the conductive substrate subjected to the roughening treatment is, for example, in the range of about 0.5 to 10 μm. Be done. The surface roughness Ra can be set outside this range by changing the particle size used for the sandblasting treatment.

Further, the surface of the conductive substrate may be surface-treated with an acid or the like. The acid is not particularly limited, and examples thereof include sulfuric acid, nitric acid, hydrochloric acid, oxalic acid, and hydrofluoric acid.

The thickness of the conductive substrate is not particularly limited and is appropriately set according to the size of the electrolytic cell in which the chlorine generating electrode is installed, and examples thereof include about 0.5 to 10 mm.

In the chlorine generating electrode of the present invention, a catalyst layer is provided on the conductive substrate. The catalyst layer contains at least palladium oxide, ruthenium oxide, and titanium oxide. More specifically, a film formed by the catalyst layer is formed on the surface of the conductive substrate.

In the chlorine generating electrode of the present invention, the average particle size of the palladium oxide particles contained in the catalyst layer is 5 μm or less. As described above, the conventional electrode for chlorine generation has a problem that the chlorine generation efficiency is significantly lowered when, for example, low-concentration salt water is used as the electrolytic solution, and further, when low-concentration salt water is used as the electrolytic solution. Since a high voltage is required for electrolysis of salt water, there is a problem that the load on the electrode is large and the life of the electrode is short. On the other hand, in the present invention, the catalyst layer contains palladium oxide, ruthenium oxide, and titanium oxide, and the average particle size of palladium oxide is set to 5 μm or less, so that the concentration of salt water is low. Even when it is used for electrolysis of the above, it can exhibit an effect of high chlorine generation efficiency and excellent long-term durability.

The reason for this can be considered, for example, as follows. That is, when comparing the surface areas of palladium oxide dispersed in the catalyst layer at the same molar ratio, the smaller the average particle size of palladium oxide, the larger the surface area and the more active sites. Therefore, it is considered that the function as a catalyst is enhanced by the average particle size of palladium oxide contained in the catalyst layer being 5 μm or less. The chlorine generation electrode of the present invention can exhibit high chlorine generation efficiency, especially when used for electrolysis of a low concentration metal chloride aqueous solution (particularly salt water) having a concentration of about 0.1 to 1%. ..

The average particle size of palladium oxide may be 5 μm or less, but is preferably 0.01 from the viewpoint of further improving the long-term durability of the electrode while further increasing the chlorine generation efficiency of the chlorine generation electrode of the present invention. It is about 5 μm, more preferably about 0.01 to 2.5 μm, still more preferably about 0.1 to 1.8 μm.

When palladium oxide, ruthenium oxide, and titanium oxide are used as raw materials in the chlorine generating electrode of the present invention, the average particle size of these is measured under the following conditions.

(Measurement of average particle size)
Measuring equipment: Laser scattered particle distribution measuring device LA-950 manufactured by HORIBA, Ltd.
Measurement method: Start suction to increase the dispersion force of the sample. After that, compressed air is supplied in the range of 0.4 to 0.8 MPa to carry out forced dispersion. The state without the sample is measured as a blank. The strength of the feeder is adjusted, and when the transmittance reaches 70 to 90%, the measurement is started.
Measurement conditions: The transmittance is 70 to 90%, the number of repetitions is 30 times, and the particle size reference is the volume.

On the other hand, when observing the catalyst layer of the electrode for chlorine generation of the present invention and measuring the average particle size of palladium oxide, ruthenium oxide, and titanium oxide, the average particle size of these particles is the catalyst layer, respectively. The average value of the major axis of 20 particles existing in the field of view of the SEM image of.

In the present invention, the proportion of palladium oxide contained in the catalyst layer is not particularly limited, but from the viewpoint of further enhancing the long-term durability of the electrode while further increasing the chlorine generation efficiency of the chlorine generating electrode of the present invention, the catalyst is used. When the metal element contained in the layer is 100 mol%, the ratio of the palladium metal contained in the catalyst layer is preferably 1 mol% or more, more preferably 1 to 90 mol%, and 3 to 3 to 90 mol%. It is more preferably 75 mol%, and particularly preferably 5 to 75 mol%.

From the same viewpoint, the proportion of the ruthenium metal contained in the catalyst layer is preferably 1 mol% or more, more preferably 1 to 90 mol%, still more preferably 3 to 70 mol%. It is particularly preferably 3 to 50 mol%. From the same viewpoint, the proportion of the titanium metal contained in the catalyst layer is preferably 1 mol% or more, more preferably 5 to 90 mol%, still more preferably 10 to 70 mol%. It is particularly preferably 15 to 60 mol%.

In the present invention, the catalyst layer may contain other components in addition to palladium oxide, ruthenium oxide, and titanium oxide. Examples of other components include platinum group metals or platinum group metal oxides, and specific examples thereof include platinum, iridium oxide, and rhodium oxide. Further, transition metal oxides such as manganese oxide, cobalt oxide and chromium oxide, and tantalum oxide, zirconium oxide, niobium oxide and the like may be contained as valve metal oxides. As the ratio of other components, the ratio of the metal contained in the catalyst layer is preferably 60 mol% or less, more preferably 5 to 50 mol%, and further preferably 5 to 40 mol%. preferable.

Further, from the viewpoint of further increasing the chlorine generation efficiency of the chlorine generation electrode of the present invention and further enhancing the long-term durability of the electrode, in the present invention, the catalyst layer is measured by an X-ray diffraction method using CuKα rays. The X-ray diffraction peak intensity in the range of the diffraction peak 2θ = 33 ° to 35 ° of palladium oxide is preferably 500 cps or more, more preferably 500 to 4000 cps, and further preferably 1000 to 4000 cps. It is preferably 1300 to 4000 cps, and particularly preferably 1300 to 4000 cps. When the peak intensity is 500 cps or more, stable chlorine generation efficiency can be suitably maintained. Further, the higher the peak intensity, the higher the crystallinity of palladium oxide, and the more preferably the function as a catalyst can be exhibited.

From the same viewpoint, the catalyst layer has an X-ray diffraction peak half-value width in the range of diffraction peak 2θ = 33 ° to 35 ° of palladium oxide, which is measured by an X-ray diffraction method using CuKα rays. It is preferably 5 deg or less, more preferably 0.1 to 1.0 deg, further preferably 0.1 to 0.9 deg, and particularly preferably 0.1 to 0.8 deg. When the peak width is 1.5 deg or less, stable chlorine generation efficiency can be suitably maintained. Further, the narrower the peak width, the higher the crystallinity of palladium oxide, and the more preferably the function as a catalyst can be exhibited.

In the present invention, the X-ray diffraction of the catalyst layer is measured under the following conditions.
(Measurement of X-ray diffraction)
Measuring equipment: Ultima IV, manufactured by Rigaku Co., Ltd.
Measurement method: Install a measurement sample so that X-rays can be emitted from the main body of the measuring device. After performing aging by applying current and voltage, measurement is performed by irradiating X-rays.
X-ray source: CuKα ray output setting: 40kV, 40mA
Optical conditions at the time of measurement:
Divergence slit = 0.2mm
Scattering slit = 2 °
Light receiving slit = 0.15 mm
Diffraction peak position: 2θ ≒ 34 °
Measurement range: 5 ° to 90 °
Scan speed: 20 ° / min
Sample preparation: Cut the electrode to 35 mm x 50 mm x 1 mm.

The thickness of the catalyst layer is not particularly limited and is appropriately set according to the size of the electrolytic cell in which the chlorine generation electrode is installed, and examples thereof include about 0.1 to 10 μm.

In the present invention, the catalyst layer can be formed, for example, as follows. First, a coating step of applying at least a solution containing a palladium compound, a ruthenium compound, and a titanium compound onto a conductive substrate is performed. At this time, the ratio of the palladium compound, the ruthenium compound, and the titanium compound is adjusted so as to be the ratio of the palladium metal, the ruthenium metal, and the titanium metal in the above-mentioned catalyst layer. The solution may contain other components as described above.

The palladium compound is not particularly limited as long as it becomes palladium oxide in the catalyst layer after the firing step described later, and examples thereof include palladium oxide, palladium chloride, and palladium nitrate. Among these, palladium oxide and palladium chloride are preferable. The ruthenium compound is not particularly limited as long as it becomes ruthenium oxide in the catalyst layer after the firing step described later, and examples thereof include ruthenium oxide, ruthenium chloride, and ruthenium nitrate. Of these, ruthenium oxide is preferred. The titanium compound is not particularly limited as long as it becomes titanium oxide in the catalyst layer after the firing step described later, and examples thereof include butyl titanate, titanium alcoholate, and titanium trichloride. Of these, butyl titanate and titanium alcoholate are preferable. The liquid used for the solution is not particularly limited, and examples thereof include organic solvents such as n-butanol, propanol, and hexanol.

For example, in order to include palladium oxide in the catalyst layer, it is preferable to include palladium oxide in the solution, but even when palladium chloride, palladium nitrate, etc. are used, palladium chloride, palladium nitrate, etc. are used in the firing step described later. Should be converted to palladium oxide. For example, in the coating step, at least one of palladium chloride and palladium nitrate is used as the palladium compound, and in the firing step described later, the mixture is heated at a temperature of 400 to 600 ° C. and has an average particle size of 5 μm from palladium chloride, palladium nitrate and the like. The following palladium oxide particles can be produced.

Next, a firing step of firing the conductive substrate coated with the solution is performed. As a result, a catalyst layer is formed on the surface of the conductive substrate. It is preferable to dry the solution on the conductive substrate before firing.

The above-mentioned coating step and firing step may be repeated a plurality of times. By repeating the process a plurality of times, the thickness of the catalyst layer can be increased.

The heating temperature in the firing step is not particularly limited, but is preferably about 400 to 650 ° C, more preferably about 450 to 650 ° C, and even more preferably about 450 to 600 ° C. The firing time is preferably about 5 to 60 minutes, more preferably about 5 to 40 minutes, and even more preferably about 5 to 30 minutes.

By performing the above coating step and firing step, the electrode for chlorine generation of the present invention provided with the conductive substrate and the catalyst layer provided on the conductive substrate can be suitably manufactured.

Details of palladium oxide and the like that can be used in the method for producing a chlorine generating electrode of the present invention are as described above. Further, for the catalyst layer formed by the firing step, the X-ray diffraction peak intensity and peak width in the range of the diffraction peak 2θ = 33 ° to 35 ° of palladium oxide measured by the X-ray diffraction method using CuKα rays are also obtained. , As mentioned above.

The chlorine generating electrode of the present invention can be arranged in an electrolytic cell. That is, the electrolytic cell of the present invention includes the above-mentioned electrode for chlorine generation. In the electrolytic cell of the present invention, the chlorine generating electrode serves as an anode, and further includes a cathode. The material constituting the cathode is not particularly limited, and examples thereof include stainless steel and titanium.

Further, hypochlorite can be suitably produced by electrolyzing an aqueous metal chloride solution using the chlorine generating electrode of the present invention. The metal chloride aqueous solution preferably includes salt water (for example, ballast water, seawater, etc.), potassium chloride aqueous solution, and the like. Examples of the hypochlorite include sodium hypochlorite and potassium hypochlorite.

As described above, the chlorine generating electrode of the present invention can be suitably used for electrolysis of low-concentration salt water having a concentration of, for example, 1% or less. That is, in the method for producing hypochlorite using the chlorine generating electrode of the present invention, the concentration of metal chloride in the aqueous metal chloride solution is preferably 1% or less.

The temperature at the time of electrolysis is not particularly limited, but even when it is used for electrolysis of low-concentration salt water, it is preferable from the viewpoint of high chlorine generation efficiency and improvement of long-term durability. The temperature is about 2 to 35 ° C, more preferably about 5 to 30 ° C.

The current density during electrolysis is not particularly limited, but even when used for electrolysis of low-concentration salt water, it is preferable from the viewpoint of high chlorine generation efficiency and improvement of long-term durability. Is about 1 to 20 A / dm ² , more preferably about 1 to 15 A / dm ² .

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the examples. In the following examples and comparative examples, the average particle size and the X-ray diffraction measurement were performed under the following conditions.

The average particle size of palladium oxide used as a raw material for measuring the average particle size was measured under the following conditions.
Measuring equipment: Laser scattered particle distribution measuring device LA-950 manufactured by HORIBA, Ltd.
Measurement method: Start suction to increase the dispersion force of the sample. After that, compressed air is supplied in the range of 0.4 to 0.8 MPa to carry out forced dispersion. The state without the sample is measured as a blank. The strength of the feeder is adjusted, and when the transmittance reaches 70 to 90%, the measurement is started.
Measurement conditions: The transmittance is 70 to 90%, the number of repetitions is 30 times, and the particle size reference is the volume.

Regarding the average particle size of palladium oxide contained in the catalyst layer, the surface of the catalyst layer is observed by SEM, and the major axis of 20 particles observed in the visual field is measured and used as the average value. Since the particle diameters of palladium oxide, ruthenium oxide, and titanium oxide used as raw materials are significantly different, it is possible to distinguish between palladium oxide particles and other particles by the SEM image.

Measurement of X-ray diffraction The measurement of X-ray diffraction of the catalyst layer was performed under the following conditions.
Measuring equipment: Ultima IV, manufactured by Rigaku Co., Ltd.
Measurement method: Install a measurement sample so that X-rays can be emitted from the main body of the measuring device. After performing aging by applying current and voltage, measurement is performed by irradiating X-rays.
X-ray source: CuKα ray output setting: 40kV, 40mA
Optical conditions at the time of measurement:
Divergence slit = 0.2mm
Scattering slit = 2 °
Light receiving slit = 0.15 mm
Diffraction peak position: 2θ ≒ 34 °
Measurement range: 5 ° to 90 °
Scan speed: 20 ° / min
Sample preparation: Cut the electrode to 35 mm x 50 mm x 1 mm.

[Example 1]
The surface of a conductive substrate (thickness 1 mm) made of a titanium flat plate was sandblasted with # 36 alumina. Palladium oxide, ruthenium chloride, and butyl titanate having a predetermined average particle size were added to the surface of the conductive substrate roughened in this manner as raw materials for the catalyst layer in an n-butanol solution (the composition of the catalyst layer is shown in Table 1). The value (mol%) shown in (1) was applied, and the mixture was dried at 120 ° C. for 10 minutes and then fired at 500 ° C. for 10 minutes. This coating-drying-baking process was repeated to prepare an anode having a catalyst layer on the surface of the conductive substrate. The average particle size of palladium oxide used as a raw material was 0.52 μm. Further, the X-ray diffraction of the catalyst layer of the anode was measured using CuKα rays, and the X-ray diffraction peak intensity and the full width at half maximum at 2θ≈34 ° were obtained. The results are shown in Table 1. The SEM image (5,000 times) of the surface of the catalyst layer of the anode obtained in Example 1 is shown in FIG.

[Example 2]
The surface of a conductive substrate (thickness 1 mm) made of a titanium flat plate was sandblasted with # 36 alumina. Palladium oxide, ruthenium chloride, and butyl titanate having a predetermined average particle size were added to the surface of the conductive substrate roughened in this manner as raw materials for the catalyst layer in an n-butanol solution (the composition of the catalyst layer is shown in Table 1). The value (mol%) shown in (1) was applied, and the mixture was dried at 120 ° C. for 10 minutes and then fired at 450 ° C. for 10 minutes. This coating-drying-baking process was repeated to prepare an anode having a catalyst layer on the surface of the conductive substrate. The average particle size of palladium oxide used as a raw material was 0.17 μm. Further, the X-ray diffraction of the catalyst layer of the anode was measured using CuKα rays, and the X-ray diffraction peak intensity and the full width at half maximum at 2θ≈34 ° were obtained. The results are shown in Table 1. The SEM image (5,000 times) of the surface of the catalyst layer of the anode obtained in Example 2 is shown in FIG. Further, with respect to the catalyst layer of the anode obtained in Example 2, a graph of the relationship between 2θ (°) obtained by measuring X-ray diffraction and the peak intensity (cps) is shown in FIG.

[Example 3]
The surface of a conductive substrate (thickness 1 mm) made of a titanium flat plate was sandblasted with # 36 alumina. Palladium oxide, ruthenium chloride, and butyl titanate having a predetermined average particle size were added to the surface of the conductive substrate roughened in this manner as raw materials for the catalyst layer in an n-butanol solution (the composition of the catalyst layer is shown in Table 1). The value (mol%) shown in (1) was applied, and the mixture was dried at 120 ° C. for 10 minutes and then fired at 550 ° C. for 10 minutes. This coating-drying-baking process was repeated to prepare an anode having a catalyst layer on the surface of the conductive substrate. The average particle size of palladium oxide used as a raw material was 1.53 μm. Further, the X-ray diffraction of the catalyst layer of the anode was measured using CuKα rays, and the X-ray diffraction peak intensity and the full width at half maximum at 2θ≈34 ° were obtained. The results are shown in Table 1. The SEM image (5,000 times) of the surface of the catalyst layer of the anode obtained in Example 3 is shown in FIG. Further, with respect to the catalyst layer of the anode obtained in Example 3, a graph of the relationship between 2θ (°) obtained by measuring X-ray diffraction and the peak intensity (cps) is shown in FIG.

[Example 4]
An anode was prepared in the same manner as in Example 1 except that cobalt nitrate was added as a raw material for the catalyst layer so as to have the composition shown in Table 1. Further, the X-ray diffraction of the catalyst layer of the anode was measured using CuKα rays, and the X-ray diffraction peak intensity and the full width at half maximum at 2θ≈34 ° were obtained. The results are shown in Table 1. FIG. 4 shows an SEM image (10,000 times) of the surface of the catalyst layer of the anode obtained in Example 4. Further, with respect to the catalyst layer of the anode obtained in Example 4, a graph of the relationship between 2θ (°) obtained by measuring X-ray diffraction and the peak intensity (cps) is shown in FIG.

[Example 5]
The surface of a conductive substrate (thickness 1 mm) made of a titanium flat plate was sandblasted with # 36 alumina. An n-butanol solution containing a predetermined amount of palladium chloride, ruthenium chloride, and butyl titanate as catalyst raw materials on the surface of the conductive substrate roughened in this manner (the composition of the catalyst layer is shown in Table 1 (values shown in Table 1). (Mole%)) was applied and dried at 120 ° C. for 10 minutes, and then calcined at 500 ° C. for 10 minutes. This coating-drying-baking process was repeated to prepare an anode having a catalyst layer on the surface of the conductive substrate. When the surface of the catalyst layer of the obtained anode was observed by SEM, particles of palladium oxide having a size of about 0.4 to 0.5 μm were observed, and the major axis was measured for any 20 particles by the above method to obtain the average particle diameter. As a result of calculation, it was 0.15 μm. Further, the X-ray diffraction of the catalyst layer of the anode was measured using CuKα rays, and the X-ray diffraction peak intensity and the full width at half maximum at 2θ≈34 ° were obtained. The results are shown in Table 1. FIG. 5 shows an SEM image (10,000 times) of the surface of the catalyst layer of the anode obtained in Example 5.

[Comparative Example 1]
The surface of a conductive substrate (thickness 1 mm) made of a titanium flat plate was sandblasted with # 36 alumina. An n-butanol solution containing a predetermined amount of palladium chloride, ruthenium chloride, and butyl titanate as catalyst raw materials was applied to the surface of the conductive substrate roughened in this manner (the composition of the catalyst layer is shown in Table 1). After drying at 120 ° C. for 10 minutes, firing treatment was performed at 400 ° C. for 10 minutes. This coating-drying-baking process was repeated to prepare an anode having a catalyst layer on the surface of the conductive substrate. When the surface of the catalyst layer of the obtained anode was observed by SEM, no particles of palladium oxide were observed. Further, the X-ray diffraction of the catalyst layer of the anode was measured using CuKα rays, and the X-ray diffraction peak intensity and the full width at half maximum at 2θ≈34 ° were obtained. The results are shown in Table 1. FIG. 6 shows an SEM image (5,000 times) of the surface of the catalyst layer of the anode obtained in Comparative Example 1.

[Comparative Example 2]
The surface of a conductive substrate (thickness 1 mm) made of a titanium flat plate was sandblasted with # 36 alumina. An n-butanol solution containing a predetermined amount of ruthenium chloride and butyl titanate as catalyst raw materials was applied to the surface of the conductive substrate roughened in this manner (the composition of the catalyst layer is the value shown in Table 1 (mol). %), And then a drying treatment at 120 ° C. for 10 minutes and then a firing treatment at 500 ° C. for 10 minutes. This coating-drying-baking process was repeated to prepare an anode having a catalyst layer on the surface of the conductive substrate. X-ray diffraction was measured for the obtained catalyst layer of the anode, but since the catalyst layer did not contain palladium, naturally no X-ray diffraction peak was observed at 2θ≈34 °. FIG. 7 shows an SEM image (5,000 times) of the surface of the catalyst layer of the anode obtained in Comparative Example 2.

[Comparative Example 3]
An anode was prepared in the same manner as in Example 1 except that the average particle size of palladium oxide used as a raw material was 5.14 μm. Further, the X-ray diffraction of the catalyst layer of the anode was measured using CuKα rays, and the X-ray diffraction peak intensity and the full width at half maximum at 2θ≈34 ° were obtained. The results are shown in Table 1. FIG. 8 shows an SEM image (5,000 times) of the surface of the catalyst layer of the anode obtained in Comparative Example 3.

<Measurement of chlorine generation efficiency from 0.1% salt water>
Using the anodes obtained in Examples 1 to 5 and Comparative Examples 1 to 3, stainless steel as the cathode, 0.1% salt water (sodium chloride aqueous solution) at a current density of 3 A / dm ² and an electrolysis temperature of 17 ° C., respectively. ) Was electrolyzed, and the chlorine generation efficiency (after 1100 hours had elapsed) was obtained from the effective chlorine concentration. The results are shown in Table 1.

* In Table 1, the average particle size of palladium oxide in Example 5 is a value measured by observing the surface of the catalyst layer with SEM.

<Measurement of the relationship between salt water concentration and chlorine generation efficiency>
Using the anode obtained in Example 4 and stainless steel as the cathode, salt water having each salt water concentration (0.1%, 0.15% or 0.5%) was electrolyzed to generate chlorine from the effective chlorine concentration. I asked for efficiency. At this time, as shown in the graphs of FIGS. 12 to 14, the chlorine generation efficiency (after 1100 hours had elapsed) was determined when the current density was 4.2 A / dm ² at each salt water concentration. Graphs showing the relationship between temperature and chlorine generation efficiency are shown in FIGS. 12 to 14. As is clear from the graph shown in FIG. 12, when the salt water concentration was 0.1%, the chlorine generation efficiency was 50% or more even when the electrolysis temperature was 10 ° C. As is clear from the graph shown in FIG. 13, when the salt water concentration was 0.15%, the chlorine generation efficiency was 50% or more even when the electrolysis temperature was 5 ° C. As is clear from the graph shown in FIG. 14, when the salt water concentration was 0.5%, the chlorine generation efficiency was 70% or more even when the electrolysis temperature was 2 ° C.

<Changes in electrolysis time and chlorine generation efficiency over time>
Using the anodes obtained in Example 4 and Comparative Example 1 and stainless steel as the cathode, 0.1% salt water (sodium chloride aqueous solution) was electrolyzed at a current density of 3 A / dm ² and an electrolytic temperature of 2 ° C. The chlorine generation efficiency was calculated from the effective chlorine concentration. This electrolysis was continued, and the changes over time in the electrolysis time and chlorine generation efficiency were measured. The obtained graph is shown in FIG. As is clear from the graph shown in FIG. 15, when the anode of Example 4 was used, the chlorine generation efficiency did not decrease so much even if the electrolysis time exceeded 4500 hours (chlorine generation in 0 hours of electrolysis). The efficiency was 46%, and the chlorine generation efficiency was 42% after 4573 hours of electrolysis). On the other hand, when the anode of Comparative Example 1 is used, the initial chlorine generation efficiency is high (the chlorine generation efficiency is 46% in 0 hours of electrolysis), but when the electrolysis time exceeds 1000 hours, the chlorine generation efficiency is high. Was significantly reduced (chlorine generation efficiency was 39% in 1176 hours).

Claims (7)

A chlorine generating electrode comprising a conductive substrate and a catalyst layer provided on the conductive substrate.
The catalyst layer contains at least palladium oxide, ruthenium oxide, and titanium oxide.
The palladium oxide is a particle having an average particle diameter of 5 μm or less, and has an average particle diameter of 5 μm or less.
The catalyst layer has an X-ray diffraction peak half-value width in the range of palladium oxide diffraction peak 2θ = 33 ° to 35 °, which is measured by an X-ray diffraction method using CuKα rays, and is 1.5 deg or less.
An electrode for generating chlorine used for electrolysis of an aqueous metal chloride solution having a concentration of 0.1 to 1%. The chlorine generation electrode according to claim 1, wherein the proportion of the palladium metal contained in the catalyst layer is 1 mol% or more when the metal element contained in the catalyst layer is 100 mol%. The electrode for chlorine generation according to claim 1 or 2, which is used for electrolysis of salt water having a concentration of 0.1 to 1% . A method for manufacturing a chlorine generating electrode, comprising a conductive substrate and a catalyst layer provided on the conductive substrate.
At least, a coating step of applying a solution containing a palladium compound, a ruthenium compound, and a titanium compound onto a conductive substrate, and
A firing step of firing the conductive substrate coated with the solution, and
Equipped with
The method for producing a chlorine generating electrode according to any one of claims 1 to 3, wherein palladium oxide particles having an average particle diameter of 5 μm or less are used as the palladium compound. A method for manufacturing a chlorine generating electrode, comprising a conductive substrate and a catalyst layer provided on the conductive substrate.
At least, a coating step of applying a solution containing a palladium compound, a ruthenium compound, and a titanium compound onto a conductive substrate, and
A firing step of firing the conductive substrate coated with the solution, and
Equipped with
At least one of palladium chloride and palladium nitrate was used as the palladium compound.
3. The method for manufacturing an electrode for chlorine generation described in 1. An electrolytic cell provided with the chlorine generating electrode according to any one of claims 1 to 3. A method for producing hypochlorite, comprising a step of electrolyzing an aqueous metal chloride solution using the chlorine generating electrode according to any one of claims 1 to 3.

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