WO2024048340A1

WO2024048340A1 - Apparatus for producing organic hydride and method for producing organic hydride

Info

Publication number: WO2024048340A1
Application number: PCT/JP2023/029965
Authority: WO
Inventors: 浩平井手; 篤深澤; 義竜三須; 香織高野; 孝司松岡
Original assignee: Ｅｎｅｏｓ株式会社
Priority date: 2022-08-29
Filing date: 2023-08-21
Publication date: 2024-03-07

Abstract

This apparatus 2 for producing an organic hydride is provided with: a cathode electrode 10 which generates an organic hydride and hydroxide ions from an object to be hydrogenated and water; an anode electrode 12 which generates oxygen by oxidizing the hydroxide ions; and an electrolyte membrane 14 which is composed of an anion exchange membrane and is arranged between the cathode electrode 10 and the anode electrode 12 so as to transfer the hydroxide ions from the cathode electrode 10 side to the anode electrode 12 side.

Description

Organic hydride production equipment and organic hydride production method

The present invention relates to an organic hydride manufacturing apparatus and an organic hydride manufacturing method.

In recent years, in order to suppress carbon dioxide emissions during the energy generation process, there are expectations for the use of renewable energy obtained from solar power, wind power, hydropower, geothermal power generation, etc. As an example, a system has been devised that generates hydrogen by electrolyzing water using electricity derived from renewable energy. In addition, organic hydride systems are attracting attention as energy carriers for large-scale transportation and storage of hydrogen derived from renewable energy.

Regarding the production technology of organic hydride, the organic hydride has an anode electrode that generates protons from water, a cathode electrode that hydrogenates an organic compound (hydride) having an unsaturated bond, and an electrolyte membrane that separates the anode electrode and the cathode electrode. A hydride manufacturing apparatus is known (see, for example, Patent Document 1). In this organic hydride manufacturing apparatus, protons are generated by oxidation of water at the anode electrode, these protons move to the cathode electrode side via the electrolyte membrane, and the hydride is hydrogenated with the protons at the cathode electrode. Organic hydride is produced.

International Publication No. 2012/091128

In the above-described organic hydride production apparatus, protons combine with water in the anode chamber to become oxonium ions and move to the cathode electrode side via the electrolyte membrane. In the reaction field of the cathode electrode, when the three elements, oxonium ion, hydride, and electrons, are present, protons are consumed from the oxonium ion, and a hydrogenation reaction of the hydride occurs. Along with this, water is generated. Furthermore, as the ions move, the water solvated with the protons also moves at the same time. Hereinafter, the water that moves through the electrolyte membrane as ions move will be collectively referred to as "electroosmotic water". If electroosmotic water accumulates on the cathode electrode side, hydrogenation of the hydride may be inhibited or the separation process of water and organic hydride may become labor-intensive. As a result, the production efficiency of organic hydride may decrease.

The present invention has been made in view of these circumstances, and one of its objectives is to provide a technology for improving the production efficiency of organic hydride.

A certain embodiment of the present invention is an organic hydride production apparatus. This organic hydride production device is composed of a cathode electrode that generates organic hydride and hydroxide ions from a hydride and water, an anode electrode that oxidizes hydroxide ions to generate oxygen, and an anion exchange membrane. An electrolyte membrane is provided between the cathode electrode and the anode electrode to move hydroxide ions from the cathode electrode side to the anode electrode side.

Another aspect of the present invention is an organic hydride manufacturing method using the organic hydride manufacturing apparatus of the above aspect. This organic hydride production method generates organic hydride and hydroxide ions from a hydride and water at the cathode electrode, moves the hydroxide ions to the anode electrode via an electrolyte membrane, and generates hydroxide ions at the anode electrode. oxidation to produce oxygen.

Arbitrary combinations of the above components and expressions of the present disclosure converted between methods, devices, systems, etc. are also effective as aspects of the present disclosure.

According to the present invention, it is possible to improve the production efficiency of organic hydride.

1 is a schematic diagram of an organic hydride production system according to an embodiment. It is a figure which shows the evaluation result of Faraday efficiency in each Example and a comparative example, and the evaluation result of water mixing into a catholyte liquid.

Hereinafter, the present invention will be explained based on preferred embodiments with reference to the drawings. The embodiments are illustrative rather than limiting the technical scope of the present invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention. . Therefore, the content of the embodiments may be subject to many design changes, such as changes, additions, and deletions of constituent elements, without departing from the spirit of the invention defined in the claims. A new embodiment with a design change has the effects of each of the combined embodiments and modifications. In the embodiments, contents that allow such design changes are emphasized by adding expressions such as "in this embodiment" or "in this embodiment," but Design changes are also allowed in the content. Any combination of the components described in the embodiments is also effective as an aspect of the present invention. Identical or equivalent components, members, and processes shown in each drawing are designated by the same reference numerals, and redundant explanations will be omitted as appropriate. Further, the scale and shape of each part shown in each figure are set for convenience to facilitate explanation, and should not be interpreted in a limited manner unless otherwise mentioned. Furthermore, when terms such as "first" and "second" are used in this specification or the claims, these terms do not indicate any order or importance, and the terms do not indicate any order or degree of importance; This is to distinguish between the two. Further, in each drawing, some members that are not important for explaining the embodiments are omitted.

FIG. 1 is a schematic diagram of an organic hydride production system 1 according to an embodiment. An example organic hydride production system 1 includes an organic hydride production device 2, a catholyte supply device 4, and an anolyte supply device 6. Although only one organic hydride manufacturing apparatus 2 is illustrated in FIG. 1, the organic hydride manufacturing system 1 may include a plurality of organic hydride manufacturing apparatuses 2. In this case, each organic hydride manufacturing apparatus 2 is stacked with the cathode electrodes 10 and anode electrodes 12 aligned in the same direction, and electrically connected in series. Note that the organic hydride manufacturing apparatuses 2 may be connected in parallel, or may be connected in series and connected in parallel.

The organic hydride production apparatus 2 is an electrolytic cell that hydrogenates a hydrogenated substance, which is a dehydrogenated product of an organic hydride, through an electrochemical reduction reaction to produce an organic hydride. The organic hydride production apparatus 2 includes a membrane electrode assembly 8, a pair of

plate members

16a, 16b, and a pair of

gaskets

18a, 18b. The membrane electrode assembly 8 includes a cathode electrode 10 (cathode), an anode electrode 12 (anode), and an electrolyte membrane 14. In this embodiment, the membrane electrode assembly 8 will be described as an example, but the organic hydride production apparatus 2 includes an electrode coated with an anode catalyst on a hard support substrate that is brought into physical contact with an electrolyte membrane. It may have a so-called zero gap electrode structure.

The cathode electrode 10 generates organic hydride and hydroxide ions from the hydride and water. The cathode electrode 10 contains a noble metal such as platinum (Pt), ruthenium (Ru), palladium (Pd), or a base metal such as nickel (Ni) as a cathode catalyst for hydrogenating a substance to be hydrided with water. Preferably, the cathode electrode 10 includes a porous catalyst carrier supporting a cathode catalyst. The catalyst carrier is made of an electronically conductive material such as porous carbon, porous metal, porous metal oxide, or the like.

Additionally, the cathode catalyst is coated with an anion exchange type ionomer. For example, a catalyst carrier carrying a cathode catalyst is coated with an ionomer. Examples of the ionomer include polymers such as Fumion (registered trademark). Preferably, the ionomer partially covers the cathode catalyst. Thereby, the three elements (hydride, water, and electrons) necessary for the electrochemical reaction in the cathode electrode 10 can be efficiently supplied to the reaction field.

The cathode electrode 10 as an example includes a catalyst layer 10a and a diffusion layer 10b. The catalyst layer 10a is arranged closer to the electrolyte membrane 14 than the diffusion layer 10b. The catalyst layer 10a contains the above-described cathode catalyst, catalyst carrier, and ionomer. Diffusion layer 10b is in contact with the main surface of catalyst layer 10a on the side opposite to electrolyte membrane 14. The diffusion layer 10b uniformly diffuses the hydrogenated substance supplied from the outside into the catalyst layer 10a. Further, the organic hydride generated in the catalyst layer 10a is discharged to the outside of the cathode electrode 10 via the diffusion layer 10b. The diffusion layer 10b is made of a conductive material such as carbon or metal. Further, the diffusion layer 10b is a porous body such as a sintered body of fibers or particles, or a foam molded body. Examples of the material constituting the diffusion layer 10b include carbon woven cloth (carbon cloth), carbon nonwoven cloth, carbon paper, and the like. Note that the diffusion layer 10b may be omitted in some cases.

The anode electrode 12 oxidizes hydroxide ions to generate oxygen. The anode electrode 12 uses metals such as iridium (Ir), ruthenium (Ru), platinum (Pt), iron (Fe), cobalt (Co), and nickel (Ni) as an anode catalyst for oxidizing hydroxide ions. Contains carbon materials such as oxides and graphene, and partial oxides thereof. The anode catalyst may be dispersed and supported on or coated on a substrate having electron conductivity. The base material is made of a material whose main component is a metal such as titanium (Ti) or stainless steel (SUS). Examples of the form of the base material include woven or nonwoven fabric sheets, meshes, porous sintered bodies, foams, expanded metals, and the like.

The electrolyte membrane 14 is arranged between the cathode electrode 10 and the anode electrode 12. The electrolyte membrane 14 is composed of an anion exchange membrane, and moves hydroxide ions from the cathode electrode 10 side to the anode electrode 12 side. Examples of anion exchange membranes that can be used as the electrolyte membrane 14 include known anion exchange membranes such as Fumasep (registered trademark) (manufactured by FuMA-Tech). Further, it is more preferable that the electrolyte membrane 14 is made of a polymer having a main chain that is resistant to hydrogenated substances. Examples of such polymers include polymers having an aromatic ring in the main chain skeleton, such as polyarylene. When the electrolyte membrane 14 has a rigid skeleton such as polyarylene, it can increase its resistance to hydrogenated substances. Thereby, cross leakage of the hydride to the anode electrode side can be further suppressed.

The plate member 16a and the plate member 16b are made of metal such as stainless steel or titanium. The plate member 16a is laminated on the membrane electrode assembly 8 from the cathode electrode 10 side. The plate member 16b is stacked on the membrane electrode assembly 8 from the anode electrode 12 side. Therefore, the membrane electrode assembly 8 is sandwiched between the pair of

plate members

16a and 16b. The gap between the plate member 16a and the membrane electrode assembly 8 is sealed with a gasket 18a. The gap between the plate member 16b and the membrane electrode assembly 8 is sealed with a gasket 18b. When the organic hydride production system 1 includes only one organic hydride production device 2, the pair of

plate members

16a and 16b may correspond to so-called end plates. When the organic hydride production system 1 includes a plurality of organic hydride production apparatuses 2 and another organic hydride production apparatus 2 is arranged next to the plate member 16a or plate member 16b, the plate member may correspond to a so-called separator.

A cathode channel 20 is connected to the cathode electrode 10. The cathode channel 20 supplies and discharges the catholyte LC to and from the cathode electrode 10 . Note that a groove may be provided on the main surface of the plate member 16a facing the cathode electrode 10 side, and this groove may constitute the cathode flow path 20.

An anode channel 22 is connected to the anode electrode 12 . The anode channel 22 supplies and discharges the anode solution LA to and from the anode electrode 12 . Note that a groove may be provided on the main surface of the plate member 16b facing the anode electrode 12 side, and this groove may constitute the anode flow path 22.

A catholyte LC is supplied to the cathode electrode 10 by a catholyte supply device 4 . The catholyte supply device 4 includes a catholyte tank 24 , a first cathode pipe 26 , a second cathode pipe 28 , and a cathode pump 30 . The catholyte tank 24 stores catholyte LC. The catholyte LC contains an organic hydride raw material, that is, a hydride. As an example, the catholyte LC does not contain any organic hydride before the operation of the organic hydride production system 1 starts, and when the organic hydride generated by electrolysis is mixed in after the start of operation, the catholyte LC becomes a mixed liquid of the hydride and the organic hydride. Become. The hydride and organic hydride are preferably liquid at 20°C and 1 atmosphere.

The hydrogenated product and the organic hydride are not particularly limited as long as they are organic compounds that can add/desorb hydrogen by reversibly causing a hydrogenation/dehydrogenation reaction. As the hydride and organic hydride used in this embodiment, acetone-isopropanol-based, benzoquinone-hydroquinone-based, aromatic hydrocarbon-based, etc. can be widely used. Among these, aromatic hydrocarbons are preferred from the viewpoint of transportability during energy transport. Generally, aromatic hydrocarbon-based hydrides and organic hydrides are hydrophobic and undergo phase separation from water at 20° C. and 1 atm.

The aromatic hydrocarbon compound used as the hydrogenated product is a compound containing at least one aromatic ring. Examples of aromatic hydrocarbon compounds include benzene, alkylbenzene, naphthalene, alkylnaphthalene, anthracene, diphenylethane, and tetralin. Alkylbenzenes include compounds in which 1 to 4 hydrogen atoms in an aromatic ring are substituted with a straight chain alkyl group or a branched alkyl group having 1 to 6 carbon atoms. Examples of such compounds include toluene, xylene, mesitylene, ethylbenzene, diethylbenzene, and the like. Alkylnaphthalenes include compounds in which 1 to 4 hydrogen atoms in an aromatic ring are substituted with a straight chain alkyl group or a branched alkyl group having 1 to 6 carbon atoms. Examples of such compounds include methylnaphthalene. These may be used alone or in combination.

The hydrogenated product is preferably at least one of toluene and benzene. Note that nitrogen-containing heterocyclic aromatic compounds such as quinoline, isoquinoline, N-alkylpyrrole, N-alkylindole, and N-alkyldibenzopyrrole can also be used as the hydrogenated product. The organic hydride is obtained by hydrogenating the above-mentioned hydride, and examples thereof include cyclohexane, methylcyclohexane, dimethylcyclohexane, decahydroquinoline, and the like.

The catholyte tank 24 is connected to the cathode electrode 10 by a first cathode pipe 26. One end of the first cathode pipe 26 is connected to the catholyte tank 24 , and the other end of the first cathode pipe 26 is connected to the inlet of the cathode channel 20 . A cathode pump 30 is provided in the middle of the first cathode pipe 26 . The cathode pump 30 can be configured with a known pump such as a gear pump or a cylinder pump. Note that the catholyte supply device 4 may circulate the catholyte LC using a liquid sending device other than a pump. The catholyte tank 24 is also connected to the cathode electrode 10 by a second cathode pipe 28 . One end of the second cathode pipe 28 is connected to the outlet of the cathode channel 20, and the other end of the second cathode pipe 28 is connected to the catholyte tank 24.

The catholyte LC in the catholyte tank 24 flows into the cathode electrode 10 via the first cathode pipe 26 by driving the cathode pump 30 . The catholyte LC that has flowed into the cathode electrode 10 is subjected to an electrode reaction at the cathode electrode 10 . The catholyte LC in the cathode electrode 10 is returned to the catholyte tank 24 via the second cathode pipe 28 . As an example, the catholyte tank 24 also functions as a gas-liquid separation section. At the cathode electrode 10, hydrogen gas may be generated due to side reactions. Therefore, the catholyte LC discharged from the cathode electrode 10 may contain hydrogen gas. The catholyte tank 24 separates the hydrogen gas in the catholyte LC from the catholyte LC and discharges it out of the system.

Note that the electrolyte membrane 14 of this embodiment is composed of an anion exchange membrane. As a result, although details will be described later, excessive amount of water is prevented from moving from the anode electrode 12 to the cathode electrode 10. Therefore, in theory, it is possible to suppress the mixing of water into the catholyte LC to a negligible extent. However, the catholyte supply device 4 may be provided with an oil-water separator for separating water from the catholyte LC, if necessary. Alternatively, catholyte tank 24 may function as an oil-water separator.

The catholyte supply device 4 of this embodiment circulates the catholyte LC between the cathode electrode 10 and the catholyte tank 24. However, the configuration is not limited to this, and a configuration may be adopted in which the catholyte LC is sent out of the system from the cathode electrode 10 without returning to the catholyte tank 24.

The anode electrode 12 is supplied with the anolyte LA by the anolyte supply device 6. The anolyte supply device 6 includes an anolyte tank 32, a first anode pipe 34, a second anode pipe 36, and an anode pump 38. The anode solution LA is stored in the anode solution tank 32 . The anolyte LA contains water. Examples of the anode solution LA include alkaline solutions such as an aqueous potassium hydroxide solution; ion-exchanged water; and aqueous solutions containing inorganic electrolytes such as potassium sulfate.

The anolyte tank 32 is connected to the anode electrode 12 by a first anode pipe 34. One end of the first anode pipe 34 is connected to the anode liquid tank 32 , and the other end of the first anode pipe 34 is connected to the inlet of the anode channel 22 . An anode pump 38 is provided in the middle of the first anode pipe 34 . The anode pump 38 can be configured with a known pump such as a gear pump or a cylinder pump. Note that the anolyte supply device 6 may circulate the anolyte LA using a liquid feeding device other than a pump. The anolyte tank 32 is also connected to the anode electrode 12 by a second anode pipe 36 . One end of the second anode pipe 36 is connected to the outlet of the anode flow path 22 , and the other end of the second anode pipe 36 is connected to the anode liquid tank 32 .

The anode solution LA in the anode solution tank 32 flows into the anode electrode 12 via the first anode pipe 34 by driving the anode pump 38. A portion of the water in the anolyte LA that has flowed into the anode electrode 12 diffuses to the cathode electrode 10 side via the electrolyte membrane 14 and is subjected to an electrode reaction at the cathode electrode 10. The anolyte LA in the anode electrode 12 is returned to the anolyte tank 32 via the second anode pipe 36. As an example, the anode liquid tank 32 also functions as a gas-liquid separation section. At the anode electrode 12, oxygen gas is generated by an electrode reaction. Therefore, the anolyte LA discharged from the anode electrode 12 contains oxygen gas. The anolyte tank 32 separates the oxygen gas in the anode solution LA from the anode solution LA and discharges it to the outside of the system.

The anolyte supply device 6 of this embodiment circulates the anolyte LA between the anode electrode 12 and the anolyte tank 32. However, the configuration is not limited to this, and a configuration may be adopted in which the anolyte LA is sent out of the system from the anode electrode 12 without returning to the anolyte tank 32.

Power is supplied to the organic hydride production apparatus 2 from an external power source (not shown). When power is supplied from the power supply to the organic hydride manufacturing apparatus 2, a predetermined cell voltage is applied between the cathode electrode 10 and the anode electrode 12 of the organic hydride manufacturing apparatus 2, and an electrolytic current flows. The power source sends power supplied from the power supply device to the organic hydride manufacturing device 2 . The power supply device can be configured with a power generation device that generates electricity using renewable energy, such as a wind power generation device or a solar power generation device. Note that the power supply device is not limited to such a renewable energy power generation device, and may be a grid power source, or a renewable energy power generation device or a power storage device that stores power from a grid power source. good. Moreover, a combination of two or more of these may be used. Further, the configuration of the organic hydride production system 1 is not limited to that described above, and the configuration of each part can be changed as appropriate.

The reaction that occurs when toluene (TL) is used as an example of the hydrogenated substance in the organic hydride production apparatus 2 is as follows. When toluene is used as the hydride, the resulting organic hydride is methylcyclohexane (MCH).
<Electrode reaction at the cathode electrode>
TL+6H ₂ O+6e ^- →MCH+6OH ^-
<Electrode reaction at the anode electrode>
6OH ^- →3/2O ₂ +3H ₂ O+6e ^-

That is, the electrode reaction at the cathode electrode 10 and the electrode reaction at the anode electrode 12 proceed in parallel. At the cathode electrode 10, toluene is hydrogenated with water to generate methylcyclohexane and hydroxide ions. Hydroxide ions generated at the cathode electrode 10 pass through the electrolyte membrane 14 and move to the anode electrode 12 . The hydroxide ions supplied to the anode electrode 12 are oxidized at the anode electrode 12 to generate oxygen, water, and electrons. Electrons generated by the oxidation of hydroxide ions are supplied to the cathode electrode 10 via an external circuit and used for an electrode reaction at the cathode electrode 10.

Therefore, according to the organic hydride production apparatus 2 according to the present embodiment, the oxidation reaction of hydroxide ions and the hydrogenation reaction of the hydride can be performed in one step. For this reason, the production efficiency of organic hydride is more efficient than the conventional technology, which produces organic hydride through a two-step process of producing hydrogen through water electrolysis, etc., and chemically hydrogenating the substance to be hydrogenated in a reactor such as a plant. can be increased. Furthermore, since a reactor for chemical hydrogenation, a high-pressure container for storing hydrogen produced by water electrolysis, etc. are not required, equipment costs can be significantly reduced.

Furthermore, the organic hydride production apparatus 2 of this embodiment is of the AEM (Anion Exchange Membrane) type, and moves hydroxide ions from the cathode electrode 10 to the anode electrode 12. Therefore, the direction of ion movement is opposite to that of conventional PEM (Proton Exchange Membrane) type devices. In this case, the movement of water from the anode electrode 12 side to the cathode electrode 10 side is theoretically limited to diffusion due to the concentration gradient of water. Hereinafter, water that moves from one electrode side to the other electrode side due to a water concentration gradient will be appropriately referred to as "physically diffused water." In the case of the AEM type, the water concentration at the anode is higher than that at the cathode. Therefore, the physically diffused water moves from the anode electrode 12 side to the cathode electrode 10 side. In the AEM type, the flow of electroosmotic water is from the cathode electrode 10 side to the anode electrode 12 side. Therefore, the water that moves from the anode electrode 12 side to the cathode electrode 10 side does not contain electroosmotic water, but only physical diffusion water. Therefore, it is possible to prevent an excessive amount of water from entering the cathode electrode 10, and it is possible to prevent the water in the cathode electrode 10 from inhibiting the diffusion of the hydride. Note that the water originally held by the electrolyte membrane 14 can also enter the cathode electrode 10 as part of physically diffused water, but the amount of this water is also very small compared to the amount of electroosmotic water in a PEM type device.

Thereby, it is possible to make it easier for the hydrogenated substance to reach the reaction field. Therefore, the shortage of the hydride can be avoided and the occurrence of side reactions can be suppressed. Therefore, it is possible to suppress a decrease in the efficiency of the electrode reaction at the cathode electrode 10, that is, the Faraday efficiency. In particular, it is possible to suppress a decrease in reaction efficiency when a catholyte having a low concentration of hydride is supplied to the cathode electrode 10. As a result, the production efficiency of organic hydride is improved. Furthermore, since accumulation of water in the cathode electrode 10 can be suppressed, the process of separating organic hydride and water from each other becomes easier or can be omitted. In this respect as well, the production efficiency of organic hydride is improved.

In addition, in the case of the PEM type, water locally disappears near the interface between the anode catalyst layer and the electrolyte membrane due to an electrode reaction at the anode electrode. On the other hand, a large amount of electroosmotic water exists near the interface between the cathode catalyst layer and the electrolyte membrane. Therefore, water on the cathode side can return to the anode side due to the water concentration gradient. Therefore, the moving direction of physically diffused water is opposite to that of the AEM type. Further, when the anolyte LA is, for example, a solution containing a supporting electrolyte, water may return from the cathode electrode side to the anode electrode side due to osmotic pressure caused by the concentration gradient of the electrolyte. Hereinafter, water that moves from one electrode side to the other electrode side due to an electrolyte concentration gradient will be appropriately referred to as "osmotic pressure transition water." In the case of the PEM type, osmotic pressure transition water moves from the cathode electrode 10 side to the anode electrode 12 side.

Therefore, in the PEM type, physical diffusion water and osmotic pressure transition water move from the cathode electrode side to the anode electrode side. Hereinafter, water that moves from the cathode side to the anode side in the PEM type (physical diffusion water + osmotic pressure transfer water) will be appropriately referred to as "back-diffusion water." "Reverse" in "reversely diffused water" means opposite to the direction of ion movement. Furthermore, the phenomenon in which back-diffused water returns to the anode electrode side, which occurs in the PEM type, is called "back-diffusion of water."

When back-diffusion of water occurs, a trace amount of hydride dissolved in water may also move to the anode electrode side together with the water. As a result, the anode catalyst may be poisoned by the hydrogenated product. On the other hand, in this embodiment, the accumulation of water on the cathode electrode 10 is suppressed, and therefore the movement of water from the cathode electrode 10 side to the anode electrode 12 side is also suppressed. Therefore, poisoning of the anode catalyst by the hydride can be suppressed. Furthermore, loss of hydride from the cathode electrode 10 can also be suppressed. These improve the production efficiency of organic hydride.

Furthermore, in the case of the PEM type, the reaction progresses as protons move in the form of oxonium ions from the anode solution to the cathode electrode side. Therefore, it is necessary to ensure a proton (oxonium ion) conduction path in the anode solution. Therefore, from the viewpoint of reaction promotion, proton activity, etc., the anode solution is preferably neutral to acidic. Further, from the viewpoint of efficient proton conduction, the anode catalyst and the cathode catalyst are preferably coated with a strongly acidic proton exchange type ionomer. Therefore, the anode catalyst and cathode catalyst are placed under an acidic atmosphere. For this reason, each catalyst is limited to those that can be used in an acidic atmosphere. In particular, the anode catalyst is limited to materials that are resistant to acidic and oxidizing atmospheres.

On the other hand, in this embodiment, hydroxide ions move from the cathode electrode 10 side to the anode electrode 12 side. For this reason, the anolyte is preferably neutral to alkaline. Further, from the viewpoint of efficient hydroxide ion conduction, the anode catalyst and the cathode catalyst are preferably coated with an alkaline anion exchange type ionomer. Therefore, the anode catalyst and cathode catalyst are placed in a neutral to alkaline atmosphere. Therefore, each catalyst may be one that can be used in a neutral to alkaline atmosphere. There are more options for anode catalysts that can be used in a neutral to alkaline atmosphere than in an acidic atmosphere. Therefore, according to the present embodiment, it is possible to increase the degree of freedom in designing the organic hydride manufacturing apparatus 2, and it is possible to easily reduce component costs and the like.

The lower the solubility of the hydride and the organic hydride in water, the more effective is the suppression of water movement from the anode electrode 12 side to the cathode electrode 10 side. For example, when the solubility of at least one of the hydride and the organic hydride in water at 25°C is preferably 3 g/100 mL or less, more preferably 2 g/100 mL or less, water movement inhibition is more effective. do. When the solubility of at least one of the hydride and the organic hydride in water is 3 g/100 mL or less, it becomes significantly difficult to remove water by the hydride and the organic hydride. Therefore, the suppression of water movement is more effective. Hydrogenates and organic hydrides that are particularly expected to have this effect include benzene (0.18g/100mL _H2O ), cyclohexane (0.36g/100mL _H2O ), and toluene (0.05g/100mL _H2O ). ), methylcyclohexane (1.6 g/100 mL H ₂ O), naphthalene (0.003 g/100 mL H ₂ O), and decahydronaphthalene (0.001 g/100 mL H ₂ O).

The water used for the electrode reaction at the cathode electrode 10 is preferably provided by physically diffused water entering from the electrolyte membrane 14. This physical diffusion water includes at least one of water derived from the anode solution LA and water originally held by the electrolyte membrane 14. That is, water in the anolyte LA diffuses from the anode electrode 12 side to the cathode electrode 10 side via the electrolyte membrane 14 due to the water concentration gradient. Further, the electrolyte membrane 14 may absorb and retain moisture in the atmosphere. Alternatively, when assembling the organic hydride production apparatus 2, the electrolyte membrane 14 may be subjected to a hydrous treatment. This water can also enter the cathode electrode 10 side due to the water concentration gradient.

The amount of water that enters the cathode electrode 10 side from the electrolyte membrane 14 is adjusted to an amount that is necessary and sufficient for hydrogenation of the hydride at the cathode electrode 10 and does not inhibit the hydride from reaching the reaction field. It is preferable. If the amount of water entering the cathode electrode 10 side is insufficient, not only will there be a shortage of water as a substrate, but the ionomer in the cathode catalyst layer will not be wetted, making it difficult to form ion conduction paths between ion exchange groups. Therefore, hydrogenation of the hydrogenated substance may be inhibited. Conversely, if the amount of water entering the cathode electrode 10 side becomes excessive, the hydride may be inhibited from reaching the reaction field. As a result, hydrogen generation due to side reactions may become dominant in the cathode electrode 10. The amount of water is determined by physical diffusion water and osmotic pressure transfer water via the electrolyte membrane 14. Therefore, the amount of water can be controlled by the material and thickness of the electrolyte membrane 14, the operating temperature of the organic hydride production apparatus 2, the supporting electrolyte concentration of the anode solution, and the like. The amount of water can be defined, for example, as the amount of water per unit time during non-electrolysis and per area of the electrolyte membrane 14 (mg/min/m ² ). In addition, the appropriate range of the amount of water is, for example, the number of ion exchange groups per area of the ionomer in the cathode catalyst layer (mmol/m ² ), the amount of water per unit time during non-electrolysis and the area of the electrolyte membrane 14 ( When expressed as a ratio (/min) of mmol/min/m ² ), it is preferably 1.05 to 1.70/min. By setting the amount of water to 1.05/min or more, it is possible to more reliably suppress hydrogenation from being inhibited due to lack of water and the performance of the organic hydride production apparatus 2 from deteriorating. Further, by setting the water amount to 1.70/min or less, it is possible to more reliably suppress the accumulation of excessive water in the cathode catalyst layer and inhibition of the reaction.

The cathode electrode 10 uses at least one of the water derived from the anolyte LA that has entered the cathode electrode 10 from the electrolyte membrane 14 and the water derived from the electrolyte membrane 14 for reaction with the hydrided substance. As a result, compared to the case where water is directly supplied to the cathode electrode 10 from the outside of the organic hydride production apparatus 2, the diffusion of the hydride is inhibited by water, the recovery process of the organic hydride becomes complicated, and the back diffusion of water occurs. etc. can be easily suppressed. It is preferable that the water used in the cathode electrode 10 is only the water that enters from the electrolyte membrane 14, but direct water absorption into the cathode electrode 10 from the outside may be combined as appropriate.

Embodiments may be specified by the items described below.
[First item]
a cathode electrode (10) that generates organic hydride and hydroxide ions from a hydride and water;
an anode electrode (12) that oxidizes hydroxide ions to generate oxygen;
An electrolyte membrane (14) composed of an anion exchange membrane, which is arranged between the cathode electrode (10) and the anode electrode (12) and moves hydroxide ions from the cathode electrode (10) side to the anode electrode (12) side. and,
Organic hydride production equipment (2).
[Second item]
The anode electrode (12) is supplied with an anolyte (LA) containing water,
The electrolyte membrane (14) contains water,
The cathode electrode (10) uses water entering from the electrolyte membrane (14) to react with the hydride.
The organic hydride production apparatus (2) according to the first item.
[Third item]
An organic hydride production method using the organic hydride production apparatus (2) according to the first item or the second item,
generating organic hydride and hydroxide ions from the hydride and water at the cathode electrode (10);
Transferring hydroxide ions to the anode electrode (12) via the electrolyte membrane (14),
A method for producing an organic hydride comprising oxidizing hydroxide ions to produce oxygen at an anode electrode (12).

Examples of the present invention will be described below, but these examples are merely illustrative to suitably explain the present invention, and are not intended to limit the present invention in any way.

(Example 1)
A quaternary ammonium AEM type electrolyte membrane (Fumasep (registered trademark) FAA-3-PK-130, manufactured by FuMA-Tech) having a polyarylene skeleton was prepared. The thickness of this electrolyte membrane was 130 μm. The permeability of water in this electrolyte membrane during non-electrolysis was measured according to the following procedure.

That is, the electrolyte membrane was cut into a circular shape with a diameter of 40 mm. An electrolyte membrane sandwiched between two flange glass cells of an H-type cell (VB9B, manufactured by EC Frontier) with a circular Viton (registered trademark) gasket was fixed. The exposed portion of the electrolyte membrane had a diameter of 28 mm. One flange glass cell was filled with 25 mL of 1 mol/L KOH aqueous solution. The weight of the entire H-type cell was measured, and the measured weight was taken as the starting weight (Amg). The openings of the flange glass cell on both sides were sealed with parafilm and left to stand. After a predetermined period of time had elapsed, the parafilm that had sealed the opening was removed, and the water that had spread into the flange glass cell on the side that was not filled with the KOH liquid was wiped off. The weight of the entire H-type cell was measured again, and the measured weight was taken as the weight after completion (Bmg). Then, the water permeability during non-electrolysis was calculated based on the following equation (1).
Formula (1): (AB) [mg]/standing time [min]/area of exposed part of electrolyte membrane [m ² ]

IrO ₂ catalyst (manufactured by Furuya Metal Co., Ltd.), quaternary ammonium-based anion exchange ionomer (Fumion (registered trademark) FAA-3-SOLUT-10, manufactured by FuMA-Tech), pure water, and 1-propanol (Fujifilm Wa (manufactured by Hikari Pure Chemical Industries, Ltd.) to prepare an anode catalyst ink. The catalyst loading density of the anode catalyst ink was 1.5 mg/cm ² , and the ionomer/catalyst ratio (I/Cat) was 0.1. The prepared anode catalyst ink was applied to one main surface of the AEM type electrolyte membrane described above to form an anode catalyst layer.

PtRu/C catalyst (TEC61E54, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.), quaternary ammonium-based anion exchange ionomer (Fumion (registered trademark) FAA-3-SOLUT-10, manufactured by FuMA-Tech), pure water, and 1-propanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to prepare a cathode catalyst ink. The catalyst loading density of the cathode catalyst ink was 1 mg/cm ² and the ionomer/carbon ratio (I/C) was 0.8. The prepared cathode catalyst ink was applied to the opposite main surface of an AEM type electrolyte membrane in which an anode catalyst layer was formed on one main surface to form a cathode catalyst layer. Based on the composition of the cathode catalyst ink, the ratio of the permeated water amount to the ion exchange group amount of the ionomer was calculated using the following formula (2). The ion exchange capacity (IEC) of the quaternary ammonium anion exchange ionomer used in this example was 1.86 mmol/g.
Formula (2): (Non-electrolyzed water permeability [mg/min/m ² ]/molecular weight of water [g/mol])/(ionomer content in catalyst layer [mg/m ² ] x ionomer ion exchange capacity [mmol/g])

A cathode end plate, a cathode gasket, a diffusion layer, an AEM electrolyte membrane in which a cathode catalyst layer and an anode catalyst layer are laminated, an anode gasket, and an anode end plate are laminated in this order to produce the organic hydride of Example 1. Obtained manufacturing equipment. A titanium plate provided with a flow path for each liquid was used as each end plate. Each gasket was made from Viton (registered trademark). The effective electrode area of the organic hydride manufacturing apparatus was 25 cm ² .

Toluene was passed through the cathode of the organic hydride production apparatus as a catholyte at a flow rate of 20 mL/min. Further, a 1 mol/L KOH aqueous solution was passed through the anode as an anode solution at a flow rate of 20 mL/min. Then, an electrolytic reaction was carried out at a temperature of 60° C. and a predetermined cell voltage. Faraday efficiency was calculated from the amount of electricity consumed in the electrolytic reaction and the amount of organic hydride produced. The case where the Faraday efficiency was 80% or more was evaluated as ○, and the case where it was less than 80% was evaluated as ×. Further, after the electrolytic reaction, the water layer in the catholyte container was separated and weighed to measure the amount of water in the catholyte. A case where the proportion of water mixed into the entire catholyte after electrolysis was less than 1% was evaluated as ○, and a case where it was 1% or more was evaluated as ×. The results are shown in Figure 2.

(Example 2)
Measurement of water permeability, fabrication of an organic hydride production apparatus, electrolytic treatment, calculation of permeated water amount ratio, and Each evaluation was conducted. The results are shown in Figure 2.

(Comparative example 1)
A polyfluorosulfonic acid-based PEM type electrolyte membrane (Nafion (registered trademark) 117, manufactured by The Chemours Company) was prepared. The thickness of this electrolyte membrane was 180 μm. The water permeability in this electrolyte membrane was measured in the same manner as in Example 2.

IrO ₂ catalyst (manufactured by Furuya Metal Co., Ltd.), polyfluorosulfonic acid cation exchange ionomer (Nafion (registered trademark) DE2020CS, manufactured by The Chemours Company), ion exchange water, 1-propanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed to prepare an anode catalyst ink. The catalyst loading density of the anode catalyst ink was 1.5 mg/cm ² , and the ionomer/catalyst ratio (I/Cat) was 0.1. The prepared anode catalyst ink was applied to one main surface of the PEM type electrolyte membrane described above to form an anode catalyst layer.

PtRu/C catalyst (TEC61E54, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.), polyfluorosulfonic acid-based cation exchange ionomer (Nafion (registered trademark) DE2020CS, manufactured by The Chemours Company), ion exchange water, 1-propanol (Fujifilm Wako Pure (manufactured by Yakusha) to prepare a cathode catalyst ink. The catalyst loading density of the cathode catalyst ink was 1 mg/cm ² and the ionomer/carbon ratio (I/C) was 0.5. The prepared cathode catalyst ink was applied to the opposite main surface of a PEM type electrolyte membrane in which an anode catalyst layer was formed on one main surface to form a cathode catalyst layer. Based on the composition of the cathode catalyst ink, the ratio of the amount of permeated water to the amount of ion exchange groups of the ionomer was calculated in the same manner as in Examples 1 and 2. The ion exchange capacity of the polyfluorosulfonic acid cation exchange ionomer used in this comparative example was 1.00 mmol/g.

The organic hydride of Comparative Example 1 was prepared by laminating the cathode end plate, cathode gasket, diffusion layer, cathode catalyst layer, and anode catalyst layer in this order. Obtained manufacturing equipment. The same end plates and spacers as in Example 1 were used. The effective electrode area of the organic hydride manufacturing apparatus was 25 cm ² . Using the obtained organic hydride manufacturing apparatus, electrolytic treatment and various evaluations were carried out in the same manner as in Example 2. The results are shown in Figure 2.

FIG. 2 is a diagram showing the evaluation results of Faraday efficiency and the evaluation results of water mixing into the catholyte in each example and comparative example. From a comparison between Examples 1 and 2 and Comparative Example 1, when the organic hydride production apparatus is equipped with an AEM type electrolyte membrane, the proportion of water mixed in the catholyte after electrolysis is extremely small, less than 1%, and at least some It was confirmed that a Faraday efficiency of 80% or more could be obtained at this cell voltage. Therefore, it was confirmed that the production efficiency of organic hydride can be improved by using an AEM type electrolyte membrane.

Furthermore, from a comparison between Example 1 and Example 2, a faradaic efficiency of 80% or more can be obtained over a wider range of cell voltages when the anolyte does not contain a supporting electrolyte than when the anolyte contains a supporting electrolyte. This was confirmed. Furthermore, it was confirmed that Example 2 had a higher water permeability in non-electrolyzed state and a higher ratio of permeated water amount to the amount of ionomer ion exchange groups than Example 1. From this, by reducing the supporting electrolyte concentration of the anolyte, the physically diffused water that moved from the anode electrode 12 side to the cathode electrode 10 side returns to the anode electrode 12 side as osmotic pressure transition water due to the concentration gradient of the supporting electrolyte. It has been shown that this can be suppressed. Thereby, more water can be supplied to the cathode electrode 10 side. Therefore, it is possible to prevent the supply of water to the cathode electrode 10 from becoming rate-determining of the cathode reaction. Therefore, by increasing the cell voltage, the current density of the electrolytic reaction, in other words, the reaction rate can be increased. Note that in both Examples 1 and 2 and Comparative Example 1, no cross leak of toluene toward the anode electrode side was observed.

The present invention can be utilized in an organic hydride manufacturing apparatus and an organic hydride manufacturing method.

2. Organic hydride production equipment, 10. Cathode electrode, 12. Anode electrode, 14. Electrolyte membrane, LA anolyte, LC catholyte.

Claims

a cathode electrode that generates organic hydride and hydroxide ions from a hydride and water;
an anode electrode that oxidizes hydroxide ions to generate oxygen;
an electrolyte membrane configured with an anion exchange membrane and disposed between the cathode electrode and the anode electrode to move the hydroxide ions from the cathode electrode side to the anode electrode side;
Organic hydride production equipment.
The anode electrode is supplied with an anolyte containing water,
The electrolyte membrane contains water,
The cathode electrode uses water entering from the electrolyte membrane to react with the hydride.
The organic hydride production apparatus according to claim 1.
An organic hydride production method using the organic hydride production apparatus according to claim 1 or 2,
generating organic hydride and hydroxide ions from the hydride and water at the cathode electrode;
moving the hydroxide ions to the anode electrode via the electrolyte membrane;
A method for producing an organic hydride, comprising oxidizing the hydroxide ions at the anode electrode to generate oxygen.