JP2008240058A - Electrolytic cell and method of manufacturing fluorine-containing gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new electrolytic cell capable of effectively preventing double-polarization phenomenon. <P>SOLUTION: The electrolytic cell 10 at least part of which is immersed in an electrolyte and which is provided with a partition body 7 for preventing gases respectively generated from an anode 3 and a cathode 5 from being mixed with each other, uses a partition body 7 formed from a metal and forming an insulating passive film 9 of a metal fluoride. The electrolytic cell 10 can prevent the double-polarization phenomenon and provide a high current efficiency by using the insulating passive film 9, which is superior in mechanical strength and hardly causes peeling or deterioration. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrolytic cell and a method for producing a fluorine-containing gas using the electrolytic cell.

Fluorine-containing gases such as fluorine gas (F ₂ gas) and nitrogen trifluoride gas (NF ₃ gas) are generally produced by a molten salt electrolysis method.

Such a fluorine-containing gas production method is carried out using a conventional electrolytic cell 60 as shown in FIG. The electrolytic cell 60 is located between the container 61 that holds the electrolytic solution, the insulating plate 62 that is disposed on the bottom surface of the container 61, the anode 63 and the cathode 65 that are immersed in the electrolytic solution, and partitions the space. The separator 61 is provided with an inner wall surface of the container 61 as a cathode 65, and the separator 67 is disposed between the cathode 65 and the plate-like anode 63 so as to surround the anode 63. For example, when producing F ₂ gas, a KF-HF molten salts in a container 61 as the electrolytic solution, it causes the application to electrolytic reaction voltage between the anode 63 and cathode 65 from an external power source (not shown) it, namely by carrying out the electrolysis operation, F ₂ gas at the anode 63, (shown in the figure, schematically, respectively black circles and white circles) H ₂ gas is generated at the cathode 65. The generated F ₂ gas and H ₂ gas are collected in separate spaces partitioned by the partition plate 67 so as not to mix with each other, and are taken out from the respective openings provided in the lid of the container 61. When producing nitrogen trifluoride gas (NF ₃ gas), NH ₄ F—HF or KF—NH ₄ F—HF molten salt is used as the electrolyte, and NF ₃ gas is used at the anode 63. H ₂ gas is generated at the cathode 65.

  Since such a molten salt contains HF and is extremely corrosive, it is desirable that not only the container 61 for holding the molten salt but also the partition plate 67 in contact with the molten salt exhibit high corrosion resistance. Conventionally, a highly corrosion-resistant metal such as Monel (an alloy of copper and nickel) is usually used as the material of the partition plate 67.

However, when the partition plate 67 made of a metal such as Monel is used, the surface 67a facing the anode 63 of the partition plate 67 functions as a cathode due to the bipolarization phenomenon, and H ₂ gas is generated on the surface 67a. appear. Further, the H ₂ gas generated on the surface 67a can immediately react with F ₂ gas existing in the vicinity to form HF.

H ₂ gas itself is flammable, and it is not preferable from the viewpoint of safety that H ₂ gas is mixed into F ₂ gas. Furthermore, since a large reaction heat is generated during the formation of HF, HF exists at a high temperature, and there is a problem that corrosion of the anode 63, the partition plate 67 (particularly near the liquid surface of the surface 67a) and the container 61 is caused. is there.

In order to prevent such a double-polarization phenomenon, at least one surface of the partition plate is covered with a fluorine-based resin (see Patent Document 1), or the partition plate is configured with the fluorine-based resin itself (patent) Reference 2) has been proposed. Further, in order to improve the separation between F ₂ gas and H ₂ gas, a diaphragm made of fluororesin is used for the gas phase part, and a diaphragm having a coarse mesh made of fluororesin is used for the electrolyte immersion part. It has also been proposed to immerse deeper than the lower end (see Patent Document 3).

JP-A-63-130789 JP 63-130790 A JP 2006-283158 A Japanese Patent Laid-Open No. 1-503631 Tamasaka Akimasa, “Electrochemical fluorination of molten fluorides containing HF with nickel and carbon anodes”, Current Topics in Electrochemistry, 2004, Vol. 10, p. 1-36

However, in the method (Patent Document 1) using a partition plate coated at least on one side with a fluororesin, the partition plate is obtained by lining a fluororesin film on a base material, and is formed by such a resin lining. The film has a problem that it has poor mechanical strength and is easily peeled off. In addition, it is said that fluororesin is stable and basically does not react with HF in molten salt or F ₂ to be produced, but from the long-term viewpoint, deterioration due to heat and reaction cannot be ignored. There is. More specifically, the fluororesin gradually decreases in molecular weight due to reaction with F ₂ and becomes mechanically brittle, or F ₂ and HF permeate the fluororesin and reach the surface of the base metal. Corrosion may occur and the gap gradually expands, and the bipolar phenomenon may occur again.

  In the method using a diaphragm and / or a diaphragm made entirely of a fluororesin (Patent Documents 2 and 3), the fluororesin has a lower mechanical strength than that of a metal, so that a sufficient strength can be obtained. The thickness of the plate / diaphragm needs to be increased, and there is a problem in that high current efficiency cannot be obtained because the insulating fluororesin exists in the entire thickness of the diaphragm and / or the diaphragm. . Furthermore, since a large amount of fluorine-based resin is used, there is a problem of high cost. In addition, as described above, there is a problem of deterioration of the fluorine-based resin.

  The present invention provides a novel electrolytic cell capable of at least reducing, and preferably eliminating, the above-mentioned conventional problems while effectively preventing a bipolar phenomenon, and a fluorine-containing gas production method using the same There is to do.

  By the way, a method of forming a passivation layer (protective layer) on the copper surface using a copper member for the anode is known, and this is a method for copper parts such as an anode connection portion provided in an electrolytic cell for fluorine production. It can be used for protection (see Patent Document 4).

  In addition, regarding the electrolysis operation using the HF-containing molten salt, various metal members are used for the anode, and whether or not a film is formed, and when a film is formed, research has been conducted on the properties. It has been reported that an insulating passive film is formed when silver, copper, cobalt, iron, or zinc is used (see Non-Patent Document 1, especially Table 2).

  The inventors of the present invention have intensively studied a novel diaphragm / membrane material capable of preventing the bipolar phenomenon, and as a result, have completed the present invention.

  According to a first aspect of the present invention, there is provided an electrolytic cell including a separator that is at least partially immersed in an electrolyte solution and prevents mixing of gases generated from an anode and a cathode, respectively, An electrolytic cell is provided that is made of a metal that forms an insulating passivation film of metal.

For example, silver, copper, cobalt, iron, zinc, or the like can be used as a metal (also referred to as “base metal” throughout the present invention) that forms an insulating passive film of a metal fluoride, but copper is preferable. . Copper is commercially available and relatively inexpensive, and is a component of Monel that has been conventionally used as a diaphragm material, and is therefore easily applied to existing manufacturing processes. Although iron is also inexpensive, Fe ²⁺ and Fe ³⁺ are present in the electrolytic solution, and these are not preferable because current efficiency is lowered by repeating the redox reaction at the cathode and the anode.

  If the electrolytic cell of the present invention is used in a method for producing a fluorine-containing gas by an electrolysis operation, an insulating passive film of metal fluoride is formed from the metal of the separator simultaneously with the electrolysis operation, and the insulating passive film Covers at least the surface of the separator immersed portion facing the cathode (hereinafter, this method is also simply referred to as “film formation method” in this specification).

  Even if the separator is only immersed in the electrolyte for producing the fluorine-containing gas, a metal fluoride film can be formed on the entire immersion part, but it takes a long time to obtain an “insulating passive” film. Cost. On the other hand, the film forming method of the present invention is bipolarized at the initial stage of the fluorine-containing gas production process in which the base metal of the separator is exposed to the electrolyte simultaneously with the electrolysis operation. By actively utilizing the phenomenon, the surface of the separator immersed portion facing the cathode functions as if it were an anode, and an insulating passive film covering at least this surface can be formed in a short time.

  In the present invention, “insulating” means electrically insulating and means that an electrochemical reaction cannot substantially occur. The electrical insulating property depends on the thickness of the film. As long as it can prevent the double polarization phenomenon. Further, “passive” means that it is stable to the electrolytic solution and does not substantially react with the components of the electrolytic solution.

  Such a film forming method of the present invention can form an insulating passive film very easily without requiring any special operation in the initial stage of the fluorine-containing gas production process. Once the insulating passive film is formed so as to cover at least the surface of the separator immersed portion facing the cathode, the bipolarization phenomenon can be prevented thereafter.

  In order to prevent the bipolarization phenomenon, it is sufficient that at least one surface of the immersion part of the separator is covered with an insulating passive film, but in order to impart corrosion resistance to the separator, It is preferable that the whole immersion part is covered with an insulating passive film. According to the film forming method as described above, the film formation is remarkable at the surface facing the cathode of the immersion part of the separator, but the film formation eventually proceeds over the entire immersion part of the separator, preferably The entire immersion part of the separator is covered with an insulating passive film of metal fluoride.

  The insulating passivation film of metal fluoride formed electrochemically as described above has the advantage of being dense and excellent in mechanical strength and difficult to peel off. In addition, the insulating passive film is extremely stable, does not react with components such as HF that can be contained in the electrolytic solution and the fluorine-containing gas that is generated, and deterioration of the film does not become a problem. Further, the insulating passive film formed electrochemically is generally thin, and there is an advantage that high current efficiency can be obtained.

  In addition, a complicated structure may be required for the separator, but according to the film forming method as described above, an easily workable material (preferably copper) can be used for the base metal, and the structure It is very easy to form an insulating passive film on the complicated base material.

  The electrolytic cell according to the first aspect of the present invention can be used in combination with the film forming method of the present invention, and can exhibit the same effects as this.

  According to a second aspect of the present invention, there is provided an electrolytic cell comprising a separator that is at least partially immersed in an electrolyte and prevents mixing of gases generated from an anode and a cathode, respectively, the separator being a base metal (Which can be the same as the above-mentioned base metal), and the insulating passive film of metal fluoride formed from the base metal faces the anode and the surface facing the cathode of the immersion part of the separator An electrolytic cell is provided in which at least one of the surfaces is covered.

  Such an electrolytic cell according to the second aspect of the present invention may be obtained by combining the electrolytic cell according to the first aspect of the present invention with the above-described film forming method. Alternatively, it may be a method different from the above-described film forming method, for example, using a separator prepared in advance by performing a passivation treatment using a base metal as an anode. It suffices that at least one of the surface facing the cathode and the surface facing the anode, preferably the entire immersion part of the separator is covered with an insulating passive film. In any case, like the above, the electrolytic cell of the present invention can prevent the bipolar phenomenon, has excellent mechanical strength of the film, hardly peels off or deteriorates, and has high current efficiency. There is an advantage that can be obtained.

Any electrolytic cell of the present invention can be suitably used in a method for producing a fluorine-containing gas by electrolysis. The fluorine-containing gas may be, for example, fluorine gas (F ₂ gas) and nitrogen trifluoride gas (NF ₃ gas), and is preferably fluorine gas (F ₂ gas).

The electrolytic solution for producing such a fluorine-containing gas is usually a molten salt containing HF. Examples of the molten salt containing HF include any ratio of KF-HF, NaF-HF, CsF-HF, NH ₄ F-HF, and a mixture thereof. Further, for example LiF, it may contain additives such as CaF _2. F ⁻ ions dissociated from HF, more specifically, HF ₂ ⁻ ions react with metal ions (eg, Cu ²⁺ ) eluted from the base metal (eg, Cu) to form an insulating passive film of metal fluoride. Can be formed.

  According to the present invention, there is provided an electrolytic cell capable of preventing the phenomenon of bipolarization, having excellent mechanical strength of the coating film, hardly causing peeling and deterioration, and obtaining high current efficiency. A fluorine-containing gas production method was provided.

An electrolytic cell and a fluorine gas (F ₂ gas) manufacturing method (including a film forming method) using the electrolytic cell in one embodiment of the present invention will be described below with reference to FIG.

  The electrolytic cell 10 of this embodiment is located between the container 1 that holds the electrolytic solution, the insulating plate 2 that is disposed on the bottom surface of the container 1, the anode 3 and the cathode 5 that are immersed in the electrolytic solution, and between these. In the container 1, a plate-like anode 3 and a cathode 5 are arranged in parallel with the separator 7 interposed therebetween. The lid of the container 1 is provided with an opening communicating with each space for housing the anode 3 and the cathode 5. The anode 3 and the cathode 5 are supported by a support member (not shown) and connected to an external power source (not shown). Note that the insulating plate 2 is not necessarily required depending on the material of the container 1.

At least a part of the separator 7 is immersed in the electrolytic solution. The structure of the separator 7 may be, for example, a plate shape above the gas phase portion and the immersion portion (near the liquid surface), and may be a screen shape provided with a plurality of holes (not shown) below the immersion portion. However, it can have any shape as long as the mixing of the F ₂ gas generated from the anode 3 and the H ₂ gas generated from the cathode 5 can be effectively prevented, and is generally referred to as a diaphragm, a diaphragm, a partition, etc. It can be like that. The immersion depth of the separator 7 can be appropriately selected depending on its structure.

  The separator 7 is made of a base metal that forms an insulating passive film of metal fluoride. In the present embodiment, copper (Cu) is used as the base metal. Copper is commercially available and relatively easy to obtain, and is softer than high hardness Monel, so it is easy to process and suitable for complex structures.

  Next, a fluorine gas manufacturing method (including a film forming method) using the electrolytic cell 10 will be described.

First, KF-HF molten salt as an electrolytic solution is put in the container 1 and subjected to electrolysis. That is, brought about by causing the application to electrolytic reaction voltage between the anode 3 and the cathode 5 from an external power source (not shown), an F ₂ gas at the anode 3, H ₂ gas at the cathode 5 .

Immediately after the separator 7 is immersed in the electrolytic solution, the base metal (Cu) of the separator 7 is exposed to the electrolytic solution, and metal ions (Cu ²⁺ ) can be eluted therefrom. When the electrolysis operation is performed, a bipolar phenomenon occurs in the base metal of the separator 7, and the surface of the separator 7 facing the cathode 5 functions as if it were an anode, and the electrolyte fluorine The component, particularly HF ₂ ^- ions generated from HF, and the eluted metal ions react with each other, and the insulating passive film 9 covering at least this surface is formed in a short time. The formation of the insulative passive film 9 first occurs remarkably on the surface facing the cathode 5 of the immersion part of the separator 7, but eventually the film is formed over the entire immersion part of the separator 7. As shown in the figure, the entire immersion part of the separator 7 is covered with an insulating passive film 9 made of metal fluoride. Without limiting the present invention, the electrochemical reaction to form the metal fluoride is shown below.

As described above, at the initial stage of the F ₂ gas production process, simultaneously with the electrolysis operation for producing the F ₂ gas, the insulating passive film 9 made of copper fluoride is formed from the copper of the separator 7, and is isolated. The immersion part of the body 7 is covered. The thickness of the insulating passive film 9 may be nonuniform depending on the covering portion of the separator 7.

  Such a coating 9 covering the immersion part of the separator 7 can be easily formed regardless of the structure of the separator 7, and this coating forming method can be carried out extremely easily than the resin lining.

  In addition, the electrochemically formed insulating metal fluoride passivation film 9 is superior in mechanical strength to resin lining and has the advantage of being difficult to peel off.

Thereafter, the electrolytic operation is continued to produce F ₂ gas. The obtained F ₂ gas and by-product H ₂ gas are collected in separate spaces partitioned by the separator 7 so as not to mix with each other, and each opening provided in the lid of the container 1 Respectively.

Although it is simple and preferable that the electrolytic operation conditions are the same at the time of film formation and F ₂ gas production, the present invention is not limited to this, and may be different. Moreover, since the separator 7 consists of copper and copper is one component of the monel generally used conventionally, it can set easily based on known electrolysis operation conditions.

As shown in the figure, when the entire immersion part of the separator 7 is covered with the insulating passive film 9, the copper which is the base metal of the separator 7 is protected by the insulating passive film and exhibits high corrosion resistance. Therefore, even if it contacts with the corrosive molten salt containing HF, corrosion can be reduced effectively. In addition, the insulating passive film 9 is extremely stable, does not react with components such as HF contained in the electrolytic solution or the generated F ₂ gas, and the deterioration of the film 9 can be ignored even in the long run. . Furthermore, even if the film 9 is peeled off for some accidental reason, the insulating passive film 9 is quickly regenerated, so that there is an advantage that self-repair is possible.

In addition, when the immersion part of the separator 7 is covered with the insulating passive film 9, the bipolarization phenomenon is prevented by the insulating property, so that the H ₂ gas is generated on the surface of the separator 7 facing the anode 3. Therefore, the H ₂ gas does not react with the F ₂ gas generated at the anode 3 to generate heat and generate HF. As a result, the safety of the F ₂ gas production process is improved.

  The separator 7 according to the present embodiment has an advantage that it has a long life compared to a monel that has been conventionally used as a material for a diaphragm. Monel causes a bipolar phenomenon, and is corroded by HF present at high temperature (especially in the vicinity of the liquid surface of the surface facing the anode 3), whereas in the separator 7 in the present embodiment, the insulating passivation is used. This is because the coating 9 can prevent the phenomenon of bipolarization, so that the presence of HF at high temperatures can be avoided and corrosion can be effectively reduced. In addition, the corrosion of the anode 3 (particularly, its support part and support member) and the container 1 can be effectively reduced.

Furthermore, according to the present embodiment, as described above, H ₂ gas is not generated on the surface of the separator 7 facing the anode 3, and therefore, the F ₂ gas generated by the H ₂ gas is generated at the anode 3. Since no HF is formed by reaction with HF, no current is consumed in such HF formation, and higher current efficiency can be obtained.

  In addition, since the insulating passive film 9 formed electrochemically as described above is generally thin, the current is much higher than when the entire separator 7 is made of an insulating material such as a fluororesin. Efficiency can be obtained. There is also an advantage that the cost is lower than in such a case.

  As mentioned above, although one embodiment of the present invention was described, the present invention is not limited to this, and various modifications are possible.

For example, in the embodiment above, while forming an insulating passivation film 9 at the initial F ₂ gas production process, to the separator 7 that preformed insulating passivation film 9 F ₂ gas production process It can also be used. In this case, if the insulating passive film 9 covers at least one of the surface facing the anode and the surface facing the cathode of the immersion part of the separator 7, the bipolarization phenomenon can be prevented. However, in order to prevent the electrolytic solution from corroding and the base metal of the separator 7 from being corroded by the electrolytic solution as in the above embodiment, the entire immersion portion of the separator 7 is covered with an insulating passive film. It is necessary to be. A part wider than the immersion part of the separator 7, for example, the entire surface of the separator 7 may be covered with an insulating passive film. For example, prior to the F ₂ gas manufacturing process, the separator 7 is used as an anode. It can be prepared in advance by forming an insulating passive film 9 on the surface thereof.

  Further, for example, the electrolytic cell 20 shown in FIG. 2 can be used instead of the electrolytic cell 10 of FIG. The electrolytic cell 20 in FIG. 2 is located between the container 11 that holds the electrolytic solution, the insulating plate 12 that is disposed on the bottom surface of the container 11, the anode 13 and the cathode 15 that are immersed in the electrolytic solution, and the like. And a separator 15 that partitions the space, and the inner wall surface of the container 11 is a cathode 15, and the separator 17 is disposed between the cathode 15 and the plate-like anode 13 so as to surround the anode 13. ing. Even if such an electrolytic cell 20 is used, the insulating passive film 19 covering the entire immersion part of the separator 17 can be formed in the same manner as in the first embodiment.

Further, for example, in the above embodiment it is assumed that the production of F ₂ gas as a fluorine-containing gas, it is also possible to produce NF ₃ gas. In this case, NH ₄ F—HF or KF—NH ₄ F—HF molten salt may be used as the electrolyte, and NF ₃ gas is generated at the anode 3 and H ₂ gas is generated at the cathode 5.

(Example)
Except for the point that an insulating plate was not used using a container made of fluororesin (more specifically, polytetrafluoroethylene resin) in the electrolytic cell, and that NF ₃ gas was produced instead of F ₂ gas, FIG. The method of Embodiment 1 was implemented using the electrolytic cell as shown in FIG.

KF · HF and hydrofluoric acid (HF) were mixed in advance to prepare KF · 2HF, and then mixed with NH ₄ F · 2HF to obtain a KF · NH ₄ F · 4HF molten salt as an electrolyte. .
The container 1 used had a rectangular parallelepiped inner wall with a capacity of 684 ml. The separator 7 was a copper plate having a length of 30 mm, a width of 40 mm, and a thickness of 0.30 mm (mass including support portion: 3.6198 g). Each of the anode 3 and the cathode 5 was a carbon plate having a length of 40 mm, a width of 10 mm, and a thickness of 10 mm. The anode 3 and the cathode 5 were arranged in parallel at an interval of 500 mm, and the separator 7 was also arranged in parallel in the center thereof.
In the container 1, the separator 7 was immersed up to 12 mm from the lower end, and the anode 3 and the cathode 5 were immersed up to 7 mm from the lower end in the electrolytic solution.
Electrolysis operation was performed in such a state. The electrolysis temperature (temperature of the electrolytic solution) was set to 100 ° C., and the electrolysis current was set to 80 mA. During the electrolysis operation, the voltage was about 8.0-8.8V. The electrolysis operation time was 168 hours.

  After the electrolytic operation, the separator (copper plate) was taken out and visually observed. As a result, almost no trace of corrosion was observed on this separator.

  The removed separator was washed with anhydrous hydrofluoric acid to remove the electrolytic solution, and mass measurement was performed. As a result, it was 3.6436 g, which was increased by 0.0238 g compared to before electrolysis. And when this was attached | subjected to XPS analysis, presence of a Cu-F bond has been confirmed. Therefore, this mass change is understood to be due to the copper existing on the surface of the separator forming copper fluoride.

  Thereafter, the separator was ultrasonically washed with warm water for 10 minutes, and mass measurement was performed again. As a result, it was 3.4255 g, which was 0.2181 g less than that after washing with anhydrous hydrofluoric acid. It is considered that the copper fluoride on the surface of the separator was removed by the ultrasonic cleaning, and it is understood that this decrease corresponds to the copper fluoride coating.

  From the above, formation of a metal fluoride film was confirmed, and it is considered that corrosion of the separator was prevented by this film.

(Comparative example)
The same operation as in the above example was performed except that a monel plate (mass 5.8196 g including a support portion) having a thickness of 0.50 mm was used as the separator instead of the copper plate having a thickness of 0.30 mm.

  After the electrolysis operation, the separator (Monel plate) was taken out and observed with the naked eye. As a result, remarkable corrosion marks were observed on the separator, particularly near the liquid surface.

  The removed separator was washed with anhydrous hydrofluoric acid in the same manner as in the Example to remove the electrolytic solution, and then mass measurement was performed. As a result, it was 5.8309 g, an increase of 0.0113 g compared to before the electrolysis operation. It was. Then, when this was subjected to XPS analysis, the presence of Cu-F bond and Ni-F bond could be confirmed. Therefore, it is understood that this mass change is due to the formation of metal fluoride such as copper fluoride and nickel fluoride by copper and nickel existing on the surface of the separator.

  Thereafter, the separator was ultrasonically washed with warm water for 10 minutes in the same manner as in the Example, and mass measurement was performed again. As a result, it was 5.5141 g, which was reduced by 0.3168 g from that after washing with anhydrous hydrofluoric acid. It is considered that the metal fluoride on the surface of the separator was removed by ultrasonic cleaning, and it is understood that this decrease corresponds to the metal fluoride film.

  From the above, it was confirmed that a metal fluoride film was formed, but this film could not prevent the corrosion of the separator.

The results of these examples and comparative examples are summarized in Table 1.

Referring to Table 1, the mass change (2)-(1) is caused by the decrease due to elution of metal ions from the separator, the increase due to fluoride ion incorporation for fluoride formation, and the residue on the surface. This is considered to correspond to the sum of the increase due to the molten salt obtained. About mass change (2)-(1), a big difference is not recognized by an Example and a comparative example, Therefore It is thought that there is no big difference in the amount of the coating films formed.
The mass change (3)-(2) is a decrease due to the removal of the coating formed on the surface of the separator, and the magnitude is considered to correspond to the coating amount. About mass change (3)-(2), the Example is smaller than a comparative example, Therefore It is thought that the film formed in the Example was thinner than the film formed in the comparative example.
Moreover, mass change (3)-(1) is a mass change before and behind electrolytic operation of the metal which comprises the separator, The magnitude | size can be defined as a corrosion amount. Regarding the mass change (3)-(1), the example is considerably smaller than the comparative example, and therefore, it is considered that the corrosion of the base metal is effectively reduced in the example than in the comparative example.
From the above, although the formation of a metal fluoride film was observed in both the example and the comparative example, it can be said that in the example, corrosion could be effectively prevented with a thinner film than in the comparative example.

  Note that the amount of coating and the amount of corrosion formed on the surface of the separator can depend on the surface area and specific gravity of the separator. In the examples and comparative examples, the vertical and horizontal dimensions of the separator are the same, and the difference in thickness is small compared to these dimensions, so the surface area is substantially the same. The specific gravity calculated from these dimensions and the mass before the electrolysis operation is also substantially the same. Therefore, for the above-described Examples and Comparative Examples, it is possible to directly compare only the mass change as described above without considering the surface area and specific gravity difference of the separator.

  The corrosion prevention effect was different between the Example and the Comparative Example because the passive film formed from Monel was conductive and could not prevent the bipolar phenomenon, whereas it was formed from copper. The passive film is insulative, which is thought to be due to the fact that the bipolarization phenomenon was prevented and corrosion was effectively reduced.

It is a figure explaining the electrolytic cell in one embodiment of this invention, and the fluorine gas manufacturing method using the same, FIG. 1 (a) is sectional drawing, FIG.1 (b) is a top view. It is a figure explaining the modification of the electrolytic cell of FIG. 1, FIG. 2 (a) is sectional drawing, FIG.2 (b) is a top view. It is a figure explaining the conventional electrolytic cell and the fluorine gas manufacturing method using the same, Fig.3 (a) is sectional drawing, FIG.3 (b) is a top view.

Explanation of symbols

1, 11, 61 Container 2, 12, 62 Insulating plate 3, 13, 63 Anode 5, 15, 65 Cathode 7, 17 Separator (base metal)
67 Separation board (Monel)
9, 19 Insulating passive film (metal fluoride)
10, 20, 60 Electrolyzer

Claims (7)

  An electrolytic cell comprising a separator that is at least partially immersed in an electrolyte and prevents mixing of gases generated from an anode and a cathode, respectively, wherein the separator forms an insulating passive film of metal fluoride. An electrolytic cell comprising:   The electrolytic cell according to claim 1 is used in a method for producing a fluorine-containing gas by an electrolysis operation, and at the same time as the electrolysis operation, an insulating passive film of metal fluoride is formed from the metal of the isolator, thereby A method in which the dynamic coating covers at least the surface of the separator immersed portion facing the cathode.   An electrolytic cell comprising a separator that is at least partially immersed in an electrolyte and prevents mixing of gases generated from the anode and the cathode, respectively, the separator made of a base metal and formed from the base metal An electrolytic cell characterized in that at least one of the surface facing the cathode and the surface facing the anode of the immersion part of the separator is covered with an insulating passive film of metal fluoride.   The electrolytic cell according to claim 1 or 3, wherein the metal is copper.   A method for producing a fluorine-containing gas by electrolysis using the electrolytic cell according to any one of claims 1, 3 and 4, or the electrolytic cell obtained by carrying out the method of claim 2.   The method according to claim 2 or 5, wherein the fluorine-containing gas is a fluorine gas.   The method according to claim 2, wherein the electrolytic solution contains HF.

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