Apparatus for producing organic hydride and method for producing organic hydride

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 apparatus and organic hydride production method

[0001] The present invention relates to an organic hydride manufacturing apparatus and an organic hydride manufacturing method.

[0002] In recent years, the use of renewable energy sources such as solar, wind, hydroelectric, and geothermal power has been expected to reduce carbon dioxide emissions during the energy generation process. One example is a system that generates hydrogen by electrolyzing water using electricity derived from renewable energy. Organic hydride systems have also attracted attention as an energy carrier for the large-scale transport and storage of hydrogen derived from renewable energy.

[0003] As a technology for producing organic hydrides, an organic hydride production apparatus is known that includes an anode electrode that generates protons from water, a cathode electrode that hydrogenates an organic compound having an unsaturated bond (a substance to be hydrogenated), and an electrolyte membrane that separates the anode electrode and the cathode electrode (see, for example, Patent Document 1). In this organic hydride production apparatus, protons are produced by oxidation of water at the anode electrode, and these protons migrate to the cathode electrode side through the electrolyte membrane, where the substance to be hydrogenated is hydrogenated by the protons, thereby producing an organic hydride.

[0004] International Publication No. 2012 / 091128

[0005] In the organic hydride production apparatus described above, protons combine with water in the anode chamber to form oxonium ions, which then migrate to the cathode electrode side through the electrolyte membrane. When the three elements of oxonium ions, the substance to be hydrogenated, and electrons are present in the reaction field at the cathode electrode, protons are consumed from the oxonium ions, resulting in the hydrogenation of the substance to be hydrogenated. This generates water. Water solvated with the protons also migrates with the ion migration. Hereinafter, the water that migrates through the electrolyte membrane with the ion migration will be referred to as "electroosmotic water" for convenience. If electroosmotic water accumulates on the cathode electrode side, it may inhibit the hydrogenation of the substance to be hydrogenated or require a complicated process for separating the water from the organic hydride. This can result in a decrease in the efficiency of organic hydride production.

[0006] The present invention has been made in view of the above circumstances, and one of its objects is to provide a technique for improving the efficiency of producing organic hydrides.

[0007] One aspect of the present invention is an organic hydride manufacturing apparatus that includes a cathode electrode that produces an organic hydride and hydroxide ions from a material to be hydrided and water, an anode electrode that oxidizes the hydroxide ions to produce oxygen, and an electrolyte membrane that is composed of an anion exchange membrane and is disposed between the cathode electrode and the anode electrode to transfer hydroxide ions from the cathode electrode side to the anode electrode side.

[0008] Another aspect of the present invention is a method for producing an organic hydride using the organic hydride production apparatus of the above aspect, which method includes generating an organic hydride and hydroxide ions from a substance to be hydrided and water at a cathode electrode, transferring the hydroxide ions to an anode electrode through an electrolyte membrane, and oxidizing the hydroxide ions at the anode electrode to produce oxygen.

[0009] Any combination of the above components, and conversion of the expression of the present disclosure into a method, device, system, etc., are also valid aspects of the present disclosure.

[0010] According to the present invention, the production efficiency of organic hydrides can be improved.

[0011] 1 is a schematic diagram of an organic hydride production system according to an embodiment of the present invention, and is a diagram showing the evaluation results of the Faraday efficiency and the evaluation results of water contamination in the cathode fluid in each example and comparative example.

[0012] The present invention will be described below with reference to the drawings, based on preferred embodiments. The embodiments are merely illustrative and do not limit the technical scope of the present invention. Not all features or combinations thereof described in the embodiments are necessarily essential to the invention. Therefore, many design modifications, such as changes, additions, or deletions of components, are possible within the scope of the invention as defined in the claims. A new embodiment incorporating design modifications will combine the effects of the combined embodiments and modifications. In the embodiments, design modifications that are possible are emphasized by using terms such as "in this embodiment" or "in this embodiment." However, design modifications are also permitted even in areas without such notation. Any combination of the components described in the embodiments is also valid 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 descriptions are omitted where appropriate. Furthermore, the scale and shape of each part shown in each drawing are set for convenience and should not be construed as limiting unless otherwise specified. Furthermore, when terms such as "first" and "second" are used in this specification or claims, these terms do not represent any order or importance, but are used to distinguish one configuration from another. Furthermore, in each drawing, some members that are not important for explaining the embodiments are omitted.

[0013] FIG. 1 is a schematic diagram of an organic hydride production system 1 according to an embodiment. The organic hydride production system 1, as an example, includes an organic hydride production apparatus 2, a cathode liquid supply apparatus 4, and an anolyte supply apparatus 6. Note that while FIG. 1 illustrates only one organic hydride production apparatus 2, the organic hydride production system 1 may include a plurality of organic hydride production apparatuses 2. In this case, the organic hydride production apparatuses 2 are stacked, oriented in the same direction so that the cathode electrodes 10 and anode electrodes 12 are aligned, and electrically connected in series. Note that the organic hydride production apparatuses 2 may be connected in parallel, or a combination of series and parallel connections may be used.

[0014] The organic hydride production apparatus 2 is an electrolysis cell that produces organic hydride by hydrogenating a material to be hydrogenated, which is a dehydrogenated form of organic hydride, through an electrochemical reduction reaction. The organic hydride production apparatus 2 includes a membrane electrode assembly 8, a pair of plate members 16 a, 16 b, and a pair of gaskets 18 a, 18 b. The membrane electrode assembly 8 includes a cathode 10 (negative electrode), an anode 12 (positive electrode), and an electrolyte membrane 14. Although the present embodiment will be described using the membrane electrode assembly 8 as an example, the organic hydride production apparatus 2 may have a so-called zero-gap electrode structure in which an electrode, formed by applying an anode catalyst to a solid support substrate, is in physical contact with the electrolyte membrane.

[0015] The cathode electrode 10 generates an organic hydride and hydroxide ions from a material to be hydrogenated and water. The cathode electrode 10 contains a cathode catalyst for hydrogenating the material to be hydrogenated with water, such as a noble metal such as platinum (Pt), ruthenium (Ru), or palladium (Pd), or a base metal such as nickel (Ni). Preferably, the cathode electrode 10 also contains a porous catalyst support that supports the cathode catalyst. The catalyst support is made of an electron-conductive material such as porous carbon, porous metal, or porous metal oxide.

[0016] The cathode catalyst is coated with an anion-exchange ionomer. For example, a catalyst support supporting the cathode catalyst is coated with the ionomer. An example of the ionomer is a polymer such as Fumion (registered trademark). It is preferable that the ionomer partially coats the cathode catalyst. This allows the three elements (substance to be hydrided, water, and electrons) necessary for the electrochemical reaction at the cathode electrode 10 to be efficiently supplied to the reaction field.

[0017] An example of the cathode electrode 10 includes a catalyst layer 10a and a diffusion layer 10b. The catalyst layer 10a is disposed closer to the electrolyte membrane 14 than the diffusion layer 10b. The catalyst layer 10a contains the above-described cathode catalyst, catalyst support, and ionomer. The diffusion layer 10b is in contact with the main surface of the catalyst layer 10a opposite the electrolyte membrane 14. The diffusion layer 10b uniformly diffuses the externally supplied hydride into the catalyst layer 10a. The organic hydride generated in the catalyst layer 10a is discharged to the outside of the cathode electrode 10 through the diffusion layer 10b. The diffusion layer 10b is made of a conductive material such as carbon or metal. The diffusion layer 10b is a porous material such as a sintered body of fibers or particles, or a foam molded body. Examples of materials that can be used for the diffusion layer 10b include woven carbon fabric (carbon cloth), nonwoven carbon fabric, and carbon paper. The diffusion layer 10b may be omitted.

[0018] The anode electrode 12 oxidizes hydroxide ions to generate oxygen. The anode electrode 12 contains an anode catalyst for oxidizing hydroxide ions, such as a metal or oxide thereof, such as iridium (Ir), ruthenium (Ru), platinum (Pt), iron (Fe), cobalt (Co), or nickel (Ni), or a carbon material or partial oxide thereof, such as graphene. The anode catalyst may be dispersed and supported on or coated on an electronically conductive substrate. The substrate is composed of a material primarily composed of a metal, such as titanium (Ti) or stainless steel (SUS). Examples of the substrate form include a woven or nonwoven sheet, a mesh, a porous sintered body, a foam, and an expanded metal.

[0019] The electrolyte membrane 14 is disposed between the cathode electrode 10 and the anode electrode 12. The electrolyte membrane 14 is composed of an anion exchange membrane and transfers hydroxide ions from the cathode electrode 10 side to the anode electrode 12 side. Examples of anion exchange membranes that can be used for the electrolyte membrane 14 include known anion exchange membranes such as Fumasep (registered trademark) (manufactured by FuMA-Tech). The electrolyte membrane 14 is preferably composed of a polymer having a main chain that is resistant to the substance to be hydrided. Examples of such polymers include polymers having aromatic rings in the main chain skeleton, such as polyarylene. Having a rigid skeleton such as polyarylene in the electrolyte membrane 14 can enhance resistance to the substance to be hydrided. This can further suppress cross-leakage of the substance to be hydrided to the anode electrode side.

[0020] The plate members 16a and 16b are made of a metal such as stainless steel or titanium. The plate member 16a is stacked 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 by a gasket 18a. The gap between the plate member 16b and the membrane electrode assembly 8 is sealed by a gasket 18b. When the organic hydride production system 1 includes only one organic hydride production apparatus 2, the pair of plate members 16a and 16b may correspond to so-called end plates. When the organic hydride production system 1 includes multiple organic hydride production apparatuses 2 and another organic hydride production apparatus 2 is arranged next to the plate member 16a or the plate member 16b, the plate member may correspond to so-called separators.

[0021] A cathode flow path 20 is connected to the cathode electrode 10. The cathode flow path 20 supplies and discharges the cathode fluid LC to and from the cathode electrode 10. Note that a groove may be provided on a main surface of the plate member 16a facing the cathode electrode 10, and this groove may constitute the cathode flow path 20.

[0022] An anode flow path 22 is connected to the anode electrode 12. The anode flow path 22 supplies and discharges the anolyte LA to and from the anode electrode 12. A groove may be provided in a main surface of the plate member 16b facing the anode electrode 12, and this groove may constitute the anode flow path 22.

[0023] A cathode liquid LC is supplied to the cathode electrode 10 by a cathode liquid supply device 4. The cathode liquid supply device 4 has a cathode liquid tank 24, a first cathode pipe 26, a second cathode pipe 28, and a cathode pump 30. The cathode liquid LC is stored in the cathode liquid tank 24. The cathode liquid LC contains an organic hydride raw material, i.e., a material to be hydrided. As an example, the cathode liquid LC does not contain any organic hydride before the organic hydride production system 1 starts operating, and becomes a mixed liquid of the material to be hydrided and the organic hydride when the organic hydride generated by electrolysis is mixed in after the operation starts. The material to be hydrided and the organic hydride are preferably liquids at 20°C and 1 atmosphere.

[0024] The material to be hydrogenated 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 reaction / dehydrogenation reaction. The material to be hydrogenated and the organic hydride used in this embodiment can be a wide variety of materials, such as acetone-isopropanol, benzoquinone-hydroquinone, and aromatic hydrocarbons. Among these, aromatic hydrocarbons are preferred from the viewpoint of transportability during energy transport. Generally, aromatic hydrocarbon-based materials and organic hydrides are hydrophobic and undergo phase separation from water at 20°C and 1 atmosphere.

[0025] The aromatic hydrocarbon compound used as the compound to be hydrogenated 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 one to four hydrogen atoms on the aromatic ring are substituted with a linear or branched alkyl group having one to six carbon atoms. Examples of such compounds include toluene, xylene, mesitylene, ethylbenzene, and diethylbenzene. Alkylnaphthalenes include compounds in which one to four hydrogen atoms on the aromatic ring are substituted with a linear or branched alkyl group having one to six carbon atoms. Examples of such compounds include methylnaphthalene. These compounds may be used alone or in combination.

[0026] The substance to be hydrogenated is preferably at least one of toluene and benzene. Nitrogen-containing heterocyclic aromatic compounds such as quinoline, isoquinoline, N-alkylpyrrole, N-alkylindole, and N-alkyldibenzopyrrole can also be used as the substance to be hydrogenated. Organic hydrides are the hydrogenated versions of the above-mentioned substances to be hydrogenated, and examples thereof include cyclohexane, methylcyclohexane, dimethylcyclohexane, and decahydroquinoline.

[0027] The cathode fluid 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 cathode fluid tank 24, and the other end of the first cathode pipe 26 is connected to the inlet of the cathode flow path 20. A cathode pump 30 is provided midway along the first cathode pipe 26. The cathode pump 30 may be a known pump such as a gear pump or a cylinder pump. Note that the cathode fluid supply device 4 may circulate the cathode fluid LC using a liquid delivery device other than a pump. The cathode fluid 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 flow path 20, and the other end of the second cathode pipe 28 is connected to the cathode fluid tank 24.

[0028] The cathode pump 30 drives the cathode fluid LC in the cathode fluid tank 24 to flow into the cathode electrode 10 via the first cathode pipe 26. The cathode fluid LC that has flowed into the cathode electrode 10 is used for an electrode reaction at the cathode electrode 10. The cathode fluid LC in the cathode electrode 10 is returned to the cathode fluid tank 24 via the second cathode pipe 28. As an example, the cathode fluid tank 24 also functions as a gas-liquid separator. Hydrogen gas may be generated at the cathode electrode 10 due to a side reaction. Therefore, the cathode fluid LC discharged from the cathode electrode 10 may contain hydrogen gas. The cathode fluid tank 24 separates the hydrogen gas in the cathode fluid LC from the cathode fluid LC and discharges it to the outside of the system.

[0029] The electrolyte membrane 14 in this embodiment is made of an anion exchange membrane. This prevents excessive water from moving from the anode electrode 12 to the cathode electrode 10, as will be described in detail later. Therefore, in theory, it is possible to prevent water from mixing into the cathode fluid LC to a negligible level. However, the cathode fluid supply device 4 may be provided with an oil-water separator for separating water from the cathode fluid LC, if necessary. Alternatively, the cathode fluid tank 24 may function as the oil-water separator.

[0030] The cathode fluid supply device 4 of the present embodiment circulates the cathode fluid LC between the cathode electrode 10 and the cathode fluid tank 24. However, the present invention is not limited to this configuration, and the cathode fluid LC may be sent from the cathode electrode 10 to the outside of the system without being returned to the cathode fluid tank 24.

[0031] An anolyte LA is supplied to the anode electrode 12 by an anolyte supply device 6. The anolyte supply device 6 has an anolyte tank 32, a first anode pipe 34, a second anode pipe 36, and an anode pump 38. The anolyte tank 32 stores the anolyte LA. The anolyte LA contains water. Examples of the anolyte LA include an alkaline solution such as an aqueous potassium hydroxide solution; ion-exchanged water; and an aqueous solution containing an inorganic electrolyte such as potassium sulfate.

[0032] The anolyte tank 32 is connected to the anode electrode 12 via a first anode pipe 34. One end of the first anode pipe 34 is connected to the anolyte tank 32, and the other end of the first anode pipe 34 is connected to an inlet of the anode flow path 22. An anode pump 38 is provided midway along the first anode pipe 34. The anode pump 38 may be 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 delivery device other than a pump. The anolyte tank 32 is also connected to the anode electrode 12 via a second anode pipe 36. One end of the second anode pipe 36 is connected to an outlet of the anode flow path 22, and the other end of the second anode pipe 36 is connected to the anolyte tank 32.

[0033] The anolyte LA in the anolyte tank 32 flows into the anode electrode 12 via the first anode pipe 34 by driving the anode pump 38. Some of the water in the anolyte LA that has flowed into the anode electrode 12 diffuses through the electrolyte membrane 14 toward the cathode electrode 10 and is used for the 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 anolyte tank 32 also functions as a gas-liquid separator. Oxygen gas is generated by the electrode reaction at the anode electrode 12. Therefore, the anolyte LA discharged from the anode electrode 12 contains oxygen gas. The anolyte tank 32 separates the oxygen gas in the anolyte LA from the anolyte LA and discharges it to the outside of the system.

[0034] The anolyte supply device 6 of the present embodiment circulates the anolyte LA between the anode electrode 12 and the anolyte tank 32. However, the present invention is not limited to this configuration, and the anolyte LA may be sent from the anode electrode 12 to the outside of the system without being returned to the anolyte tank 32.

[0035] Electric power is supplied to the organic hydride production apparatus 2 from an external power source (not shown). When electric power is supplied from the power source to the organic hydride production apparatus 2, a predetermined cell voltage is applied between the cathode electrode 10 and the anode electrode 12 of the organic hydride production apparatus 2, causing an electrolytic current to flow. The power source transmits electric power supplied from a power supply device to the organic hydride production apparatus 2. The power supply device may be a power generation device that generates electric power 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 system power supply, or a power storage device that stores electric power from the renewable energy power generation device or the system power supply. It may also be a combination of two or more of these. Furthermore, the configuration of the organic hydride production system 1 is not limited to that described above, and the configuration of each component may be modified as appropriate.

[0036] In the organic hydride production apparatus 2, when toluene (TL) is used as an example of the substance to be hydrogenated, the reaction that occurs is as follows. When toluene is used as the substance to be hydrogenated, the organic hydride obtained is methylcyclohexane (MCH). <Electrode reaction at the cathode electrode> TL + 6H ２ O+6e － →MCH+6OH － <Electrode reaction at the anode electrode> 6OH － →3 / 20 ２ +3H ２ O+6e －

[0037] 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 produce methylcyclohexane and hydroxide ions. The hydroxide ions produced 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 produce oxygen, water, and electrons. The electrons produced by the oxidation of the hydroxide ions are supplied to the cathode electrode 10 via an external circuit and are used in the electrode reaction at the cathode electrode 10.

[0038] Therefore, according to the organic hydride manufacturing apparatus 2 of this embodiment, the oxidation reaction of hydroxide ions and the hydrogenation reaction of the material to be hydrogenated can be carried out in one step. This improves the efficiency of organic hydride manufacturing compared to conventional techniques for manufacturing organic hydrides through a two-stage process consisting of a process for producing hydrogen by water electrolysis or the like and a process for chemically hydrogenating the material to be hydrogenated in a reactor of a plant or the like. Furthermore, since a reactor for chemical hydrogenation and a high-pressure vessel for storing hydrogen produced by water electrolysis or the like are not required, a significant reduction in facility costs can be achieved.

[0039] The organic hydride production apparatus 2 of this embodiment is an AEM (Anion Exchange Membrane) type, which transfers hydroxide ions from the cathode electrode 10 to the anode electrode 12. Therefore, the ion transfer direction is opposite to that of a conventional PEM (Proton Exchange Membrane) type apparatus. In this case, the transfer of water from the anode electrode 12 side to the cathode electrode 10 side is theoretically only due to diffusion caused by the water concentration gradient. Hereinafter, water that moves from one electrode side to the other electrode side due to the water concentration gradient will be referred to as "physically diffused water." In the AEM type, the water concentration at the anode is higher than that at the cathode. Therefore, 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 is only physically diffused water, and does not include electroosmotic water. This makes it possible to prevent excessive water from entering the cathode electrode 10 and to prevent the diffusion of the substance to be hydrided from being hindered by the water in the cathode electrode 10. Note that the water originally held in the electrolyte membrane 14 may also enter the cathode electrode 10 as part of the physically diffused water, but the amount of this water is also minute compared to the amount of electroosmotic water in a PEM-type device.

[0040] This makes it easier for the substance to be hydrided to reach the reaction site. Therefore, a shortage of the substance to be hydrided can be avoided, and the occurrence of side reactions can be suppressed. This makes it possible to suppress a decrease in the efficiency of the electrode reaction at the cathode electrode 10, i.e., the faradaic efficiency. In particular, it is possible to suppress a decrease in reaction efficiency when a catholyte with a low concentration of the substance to be hydrided is supplied to the cathode electrode 10. As a result, the production efficiency of organic hydrides is improved. Furthermore, since the accumulation of water at the cathode electrode 10 can be suppressed, the process of separating the organic hydride and water from each other becomes easier or can be omitted. This also improves the production efficiency of organic hydrides.

[0041] In addition, in the PEM type, water is locally lost near the interface between the anode catalyst layer and the electrolyte membrane due to an electrode reaction at the anode electrode. Meanwhile, a large amount of electroosmotic water exists near the interface between the cathode catalyst layer and the electrolyte membrane. Therefore, due to the water concentration gradient, water on the cathode electrode side can return to the anode electrode side. Therefore, the direction of water movement due to physical diffusion is opposite to that of the AEM type. Furthermore, if the anode fluid LA is, for example, a solution containing a supporting electrolyte, water can return from the cathode electrode side to the anode electrode side due to the osmotic pressure caused by the electrolyte concentration gradient. Hereinafter, water moving from one electrode side to the other electrode side due to the electrolyte concentration gradient will be referred to as "osmotic migration water" where appropriate. In the PEM type, osmotic migration water moves from the cathode electrode 10 side to the anode electrode 12 side.

[0042] Therefore, in a PEM-type system, physically diffused water and osmotically migrated water move from the cathode electrode side to the anode electrode side. Hereinafter, the water that moves from the cathode electrode side to the anode electrode side in a PEM-type system (physically diffused water + osmotically migrated water) will be referred to as "back-diffused water" where appropriate. The "back" in "back-diffused water" means that it is in the opposite direction to the direction of ion migration. Furthermore, the phenomenon that occurs in a PEM-type system, in which back-diffused water returns to the anode electrode side, is referred to as "back-diffusion of water."

[0043] When back-diffusion of water occurs, trace amounts of the substance to be hydrided dissolved in the water may also move to the anode electrode side along with the water. As a result, the substance to be hydrided may poison the anode catalyst. In contrast, in this embodiment, accumulation of water at 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 substance to be hydrided can be suppressed. Furthermore, loss of the substance to be hydrided from the cathode electrode 10 can also be suppressed. These factors improve the production efficiency of organic hydrides.

[0044] In addition, in the case of a PEM-type fuel cell, the reaction proceeds as protons move from the anolyte to the cathode electrode in the form of oxonium ions. Therefore, it is necessary to ensure a proton (oxonium ion) conduction path in the anolyte. Therefore, from the viewpoints of reaction promotion, proton activity, etc., the anolyte is preferably neutral to acidic. Furthermore, from the viewpoint of efficient proton conduction, the anode catalyst and cathode catalyst are preferably coated with a strongly acidic proton exchange ionomer. Therefore, the anode catalyst and cathode catalyst are placed in an acidic atmosphere. Therefore, 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.

[0045] On the other hand, in this embodiment, hydroxide ions migrate from the cathode electrode 10 side to the anode electrode 12 side. For this reason, the anolyte is preferably neutral to alkaline. Furthermore, from the viewpoint of efficient hydroxide ion conduction, it is preferable that the anode catalyst and the cathode catalyst are coated with an alkaline anion exchange ionomer. Therefore, the anode catalyst and the 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 usable anode catalysts in a neutral to alkaline atmosphere than in an acidic atmosphere. Therefore, this embodiment can increase the design flexibility of the organic hydride manufacturing apparatus 2 and facilitate reductions in component costs, etc.

[0046] The lower the solubility in water of the material to be hydrogenated and the organic hydride, the more effective the suppression of water migration from the anode electrode 12 side to the cathode electrode 10 side. For example, when the solubility in water at 25°C of at least one of the material to be hydrogenated and the organic hydride is preferably 3 g / 100 mL or less, more preferably 2 g / 100 mL or less, the suppression of water migration is more effective. When the solubility in water of at least one of the material to be hydrogenated and the organic hydride is 3 g / 100 mL or less, it becomes significantly difficult for the material to be hydrogenated and the organic hydride to remove water. Therefore, the suppression of water migration is more effective. An example of a material to be hydrogenated and an organic hydride for which this effect is particularly expected is benzene (0.18 g / 100 mL H ２ O) and cyclohexane (0.36 g / 100 mL H ２ 0), toluene (0.05 g / 100 mL H ２ O) and 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) and the like are exemplified.

[0047] The water used in the electrode reaction at the cathode electrode 10 is preferably supplied by physically diffused water that enters from the electrolyte membrane 14. This physically diffused water includes at least one of water derived from the anolyte LA and water originally retained in the electrolyte membrane 14. That is, the water in the anolyte LA diffuses from the anode electrode 12 side to the cathode electrode 10 side through the electrolyte membrane 14 due to the water concentration gradient. The electrolyte membrane 14 may also absorb and retain moisture from the atmosphere. Alternatively, the electrolyte membrane 14 may be subjected to a hydration treatment during assembly of the organic hydride production apparatus 2. This water may also enter the cathode electrode 10 side due to the water concentration gradient.

[0048] The amount of water entering the cathode electrode 10 from the electrolyte membrane 14 is preferably adjusted to an amount necessary and sufficient for hydrogenation of the substance to be hydrogenated at the cathode electrode 10, but not inhibiting the substance from reaching the reaction site. Insufficient water entering the cathode electrode 10 results in a lack of water as a substrate, and the ionomer in the cathode catalyst layer is not wetted, making it difficult to form ion conduction paths between ion exchange groups. This may inhibit the hydrogenation of the substance to be hydrogenated. Conversely, excessive water entering the cathode electrode 10 may inhibit the substance to be hydrogenated from reaching the reaction site. As a result, hydrogen generation due to side reactions may become dominant at the cathode electrode 10. The amount of water is determined by the physical diffusion of water through the electrolyte membrane 14 and the osmotic migration of water. 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 fluid, and other factors. The amount of water is, for example, the amount of water per unit time during non-electrolysis and per area of ​​the electrolyte membrane 14 (mg / min / m ２ ) The appropriate range of the amount of water can be defined, for example, as the number of ion-exchange groups per area of ​​the ionomer in the cathode catalyst layer (mmol / m ２ ) for the amount of water per unit time and area of ​​the electrolyte membrane 14 during non-electrolysis (mmol / min / m ２ When the water flow rate is expressed as a ratio ( / min) of the water content of the cathode catalyst layer to the water content of the cathode catalyst layer, the ratio is preferably 1.05 to 1.70 / min. By setting the water flow rate to 1.05 / min or more, it is possible to more reliably prevent the performance of the organic hydride manufacturing apparatus 2 from being impaired by a lack of water that would otherwise inhibit hydrogenation. Furthermore, by setting the water flow rate to 1.70 / min or less, it is possible to more reliably prevent the reaction from being impaired by excess water accumulating in the cathode catalyst layer.

[0049] The cathode electrode 10 uses at least one of water derived from the anolyte LA that has entered the cathode electrode 10 from the electrolyte membrane 14 and water derived from the electrolyte membrane 14 for reaction with the substance to be hydrided. This makes it easier to prevent water from hindering the diffusion of the substance to be hydrided, complicating the organic hydride recovery process, and causing back diffusion of water, compared to when water is supplied directly to the cathode electrode 10 from outside the organic hydride production apparatus 2. It is preferable that the water used at the cathode electrode 10 is only water that enters from the electrolyte membrane 14, but direct absorption of water into the cathode electrode 10 from outside may also be combined as appropriate.

[0050] The embodiments may be specified by the following items: [Item 1] An organic hydride manufacturing apparatus (2) comprising: a cathode electrode (10) that produces organic hydride and hydroxide ions from a material to be hydrided and water; an anode electrode (12) that oxidizes the hydroxide ions to produce oxygen; and an electrolyte membrane (14) that is composed of an anion exchange membrane and is disposed between the cathode electrode (10) and the anode electrode (12) and that transfers hydroxide ions from the cathode electrode (10) side to the anode electrode (12) side. [Item 2] The organic hydride manufacturing apparatus (2) according to item 1, wherein the anode electrode (12) is supplied with an anolyte (LA) containing water, the electrolyte membrane (14) contains water, and the cathode electrode (10) uses the water entering from the electrolyte membrane (14) for a reaction with the material to be hydrided. [Item 3] A method for producing an organic hydride using the organic hydride production apparatus (2) described in item 1 or 2, comprising: generating an organic hydride and hydroxide ions from a material to be hydrided and water at a cathode electrode (10); transferring the hydroxide ions to an anode electrode (12) through an electrolyte membrane (14); and oxidizing the hydroxide ions at the anode electrode (12) to produce oxygen.

[0051] Examples of the present invention will be described below, but these examples are merely illustrative examples for suitably explaining the present invention and do not limit the present invention in any way.

[0052] Example 1 A quaternary ammonium-based AEM-type electrolyte membrane having a polyarylene skeleton (Fumasep (registered trademark) FAA-3-PK-130, manufactured by FuMA-Tech) was prepared. The thickness of this electrolyte membrane was 130 μm. The water permeability of this electrolyte membrane during non-electrolysis was measured according to the following procedure.

[0053] Specifically, the electrolyte membrane was cut into a circular shape with a diameter of 40 mm. The electrolyte membrane was sandwiched between two flange glass cells of an H-type cell (VB9B, manufactured by EC Frontier Corporation) and fixed between circular Viton (registered trademark) gaskets. The exposed portion of the electrolyte membrane was set to a diameter of 28 mm. 25 mL of a 1 mol / L KOH aqueous solution was filled into one flange glass cell. The weight of the entire H-type cell was measured, and the measured weight was designated as the initial weight (A mg). The openings of both flange glass cells were sealed with parafilm and allowed to stand. After a predetermined time had elapsed, the parafilm sealing the openings was removed, and water that had diffused into the flange glass cell on the side not filled with KOH solution was wiped away. The weight of the entire H-type cell was measured again, and the measured weight was designated as the termination weight (B mg). The water permeability during non-electrolysis was then calculated based on the following formula (1): Formula (1): (A - B) [mg] / Standing time [min] / Area of ​​exposed portion of electrolyte membrane [m ２ ]

[0054] IrO ２ A catalyst (manufactured by Furuya Metal Co., Ltd.), a quaternary ammonium anion exchange ionomer (Fumion (registered trademark) FAA-3-SOLUT-10, manufactured by FuMA-Tech Co., Ltd.), pure water, and 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 The ionomer / catalyst ratio (I / Cat) was set to 0.1. The prepared anode catalyst ink was applied to one main surface of the AEM-type electrolyte membrane to form an anode catalyst layer.

[0055] A PtRu / C catalyst (TEC61E54, manufactured by Tanaka Kikinzoku Kogyo K.K.), a quaternary ammonium 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.) were mixed to prepare a cathode catalyst ink. The catalyst loading density of the cathode catalyst ink was 1 mg / cm. ２ The ionomer / carbon ratio (I / C) was set to 0.8. The prepared cathode catalyst ink was applied to the opposite main surface of an AEM electrolyte membrane having an anode catalyst layer 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 using the following formula (2). The ion exchange capacity (IEC) of the quaternary ammonium-based anion-exchange ionomer used in this example was 1.86 mmol / g. Formula (2): (water permeability during non-electrolysis [mg / min / m ２ ] / molecular weight of water [g / mol]) / (ionomer content in catalyst layer [mg / m ２ ] × ionomer ion exchange capacity [mmol / g])

[0056] The organic hydride production apparatus of Example 1 was obtained by stacking a cathode end plate, a cathode side gasket, a diffusion layer, an AEM-type electrolyte membrane with a cathode catalyst layer and an anode catalyst layer stacked thereon, an anode side gasket, and an anode end plate in this order. Titanium plates equipped with flow paths for each liquid were used for each end plate. Each gasket was made of Viton (registered trademark). The effective electrode area of ​​the organic hydride production apparatus was 25 cm ２ It was decided.

[0057] Toluene was passed through the cathode of the organic hydride production apparatus as a cathode fluid at a flow rate of 20 mL / min. A 1 mol / L KOH aqueous solution was passed through the anode as an anode fluid at a flow rate of 20 mL / min. An electrolysis reaction was then carried out at a temperature of 60°C and a predetermined cell voltage. The faradaic efficiency was calculated from the amount of electricity consumed in the electrolysis reaction and the amount of organic hydride produced. A faradaic efficiency of 80% or greater was evaluated as ◯, and an efficiency of less than 80% was evaluated as ×. After the electrolysis reaction, the aqueous layer in the cathode fluid container was separated and weighed to measure the amount of water in the cathode fluid. A water content of less than 1% of the total cathode fluid after electrolysis was evaluated as ◯, and an efficiency of 1% or greater was evaluated as ×. The results are shown in Figure 2.

[0058] (Example 2) Except for the use of ion-exchanged water for the water permeability measurement and the anode fluid, the water permeability measurement, the production of an organic hydride production apparatus, the electrolysis treatment, the calculation of the permeate rate ratio, and the various evaluations were carried out in the same manner as in Example 1. The results are shown in Figure 2.

[0059] 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 of this electrolyte membrane was measured in the same manner as in Example 2.

[0060] IrO ２ A catalyst (manufactured by Furuya Metal Co., Ltd.), a polyfluorosulfonic acid-based cation exchange ionomer (Nafion (registered trademark) DE2020CS, manufactured by The Chemours Company), ion-exchanged water, and 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 The ionomer / catalyst ratio (I / Cat) was set to 0.1. The prepared anode catalyst ink was applied to one main surface of the PEM electrolyte membrane described above to form an anode catalyst layer.

[0061] A PtRu / C catalyst (TEC61E54, manufactured by Tanaka Kikinzoku Kogyo K.K.), a polyfluorosulfonic acid-based cation exchange ionomer (Nafion (registered trademark) DE2020CS, manufactured by The Chemours Company), ion-exchanged water, and 1-propanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed to prepare a cathode catalyst ink. The catalyst loading density of the cathode catalyst ink was 1 mg / cm. ２ The ionomer / carbon ratio (I / C) was 0.5. The prepared cathode catalyst ink was applied to the opposite main surface of a PEM electrolyte membrane, on one of which an anode catalyst layer was formed, 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 in the ionomer was calculated in the same manner as in Examples 1 and 2. The ion exchange capacity of the polyfluorosulfonic acid-based cation-exchange ionomer used in this comparative example was 1.00 mmol / g.

[0062] The cathode end plate, the cathode side gasket, the diffusion layer, the PEM electrolyte membrane with the cathode catalyst layer and the anode catalyst layer stacked thereon, the anode side gasket, and the anode end plate were stacked in this order to obtain an organic hydride production apparatus of Comparative Example 1. The end plates and spacers used were the same as those used in Example 1. The effective electrode area of ​​the organic hydride production apparatus was 25 cm ２ Using the obtained organic hydride production apparatus, electrolysis and various evaluations were carried out in the same manner as in Example 2. The results are shown in FIG.

[0063] 2 shows the evaluation results of the Faraday efficiency and the evaluation results of water contamination in the cathode solution in each example and comparative example. Comparison of Examples 1 and 2 with Comparative Example 1 confirmed that when the organic hydride production apparatus was equipped with an AEM-type electrolyte membrane, the proportion of water contamination in the cathode solution after electrolysis was extremely small, less than 1%, and a Faraday efficiency of 80% or more was obtained at least at any cell voltage. Therefore, it was confirmed that the use of an AEM-type electrolyte membrane can improve the production efficiency of organic hydrides.

[0064] Furthermore, a comparison between Example 1 and Example 2 confirmed that a Faraday efficiency of 80% or higher can be achieved over a wider range of cell voltages when the anolyte does not contain a supporting electrolyte than when the anolyte contains a supporting electrolyte. Furthermore, Example 2 demonstrated higher water permeability during non-electrolysis and a higher ratio of the amount of permeated water to the amount of ionomer ion exchange groups compared to Example 1. This indicates that reducing the supporting electrolyte concentration of the anolyte can prevent physically diffused water that migrates from the anode electrode 12 side to the cathode electrode 10 side from returning to the anode electrode 12 side as osmotically transferred water due to the supporting electrolyte concentration gradient. This allows more water to be supplied to the cathode electrode 10 side. This prevents the water supply to the cathode electrode 10 from becoming the rate-limiting factor for the cathode reaction. Therefore, increasing the cell voltage can increase the current density of the electrolysis reaction, in other words, the reaction rate. In any of Examples 1 and 2 and Comparative Example 1, cross-leakage of toluene to the anode electrode side was not observed.

[0065] The present invention can be used in an organic hydride manufacturing apparatus and an organic hydride manufacturing method.

[0066] 2 organic hydride production apparatus, 10 cathode electrode, 12 anode electrode, 14 electrolyte membrane, LA anolyte, LC catholyte.

Claims

1. A cathode electrode that generates organic hydrides and hydroxide ions from a hydride and water, An anode electrode that oxidizes hydroxide ions to produce oxygen, The device comprises an electrolyte membrane composed of an anion exchange membrane, which is positioned 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 manufacturing equipment.

2. The anode electrode receives a supply of anode solution containing water, The electrolyte membrane contains water, The cathode electrode uses the water entering from the electrolyte membrane for the reaction with the hydrogenated substance. The apparatus for producing organic hydride according to claim 1.

3. The anion exchange membrane is composed of a polymer having a main chain resistant to the hydrogenated substance, The organic hydride production apparatus according to claim 1 or 2.

4. The polymer has an aromatic ring in its main chain skeleton. The organic hydride production apparatus according to claim 3.

5. The polymer is polyarylene, The organic hydride production apparatus according to claim 4.

6. The cathode electrode has a cathode catalyst, The anode electrode has an anode catalyst, The cathode catalyst and the anode catalyst are coated with an alkaline anion-exchange type ionomer. The organic hydride production apparatus according to claim 1 or 2.

7. The cathode electrode has a catalyst layer containing a cathode catalyst and an ionomer, The amount of water entering through the electrolyte membrane is expressed as the ratio ( / min) of the amount of water per unit time during non-electrolytic operation and per unit area of ​​the electrolyte membrane (mol / min / m²) to the number of ion exchange groups per unit area of ​​the ionomer in the catalyst layer (mol / m²), which is between 1.05 / min and 1.70 / min. The organic hydride production apparatus according to claim 2.

8. The anode solution is neutral to alkaline. The organic hydride production apparatus according to claim 2.

9. The organic hydride production apparatus is: The system includes a cathode liquid tank for storing the cathode liquid supplied to the cathode electrode, The cathode liquid tank functions as at least one of a gas-liquid separator and an oil-water separator. The organic hydride production apparatus according to claim 1 or 2.

10. At least one of the material and thickness of the electrolyte membrane is adjusted based on the amount of water required for the reaction with the hydride and the amount of water that inhibits the hydride from reaching the cathode electrode. The organic hydride production apparatus according to claim 2.

11. The hydrogenated substance is toluene, The aforementioned organic hydride is methylcyclohexane. The organic hydride production apparatus according to claim 1 or 2.

12. A cathode electrode that generates organic hydrides and hydroxide ions from a hydride and water, An anode electrode that oxidizes hydroxide ions to produce oxygen, The device comprises an electrolyte membrane composed of an anion exchange membrane, which is positioned between the cathode electrode and the anode electrode to move the hydroxide ions from the cathode electrode side to the anode electrode side, The anode electrode receives a supply of anode solution containing water, The electrolyte membrane contains water, The cathode electrode uses the water entering from the electrolyte membrane for the reaction with the hydrogenated substance. The amount of water entering through the electrolyte membrane is adjusted based on the amount of water required for the reaction with the hydrogenate and the amount of water that inhibits the hydrogenate from reaching the cathode electrode. Organic hydride manufacturing equipment.

13. The amount of water entering through the electrolyte membrane is adjusted by controlling at least one of the operating temperature of the organic hydride production apparatus and the supporting electrolyte concentration of the anode solution. The organic hydride production apparatus according to claim 12.

14. The cathode electrode has a catalyst layer containing a cathode catalyst and an ionomer, The amount of water entering through the electrolyte membrane is 1.05 to 1.70 / min, expressed as the ratio ( / min) of the amount of water per unit time and area of ​​the electrolyte membrane (mol / min / m²) during the non-electrolytic phase to the number of ion exchange groups per unit area of ​​the ionomer in the catalyst layer (mol / m²). The organic hydride production apparatus according to claim 12 or 13.

15. A method for producing an organic hydride using the organic hydride production apparatus described in claim 1 or 2, At the cathode electrode, an organic hydride and hydroxide ions are generated from the hydride and water. The hydroxide ions are moved 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.

16. The anode electrode receives a supply of anode solution containing water, The electrolyte membrane contains water, The cathode electrode uses the water entering from the electrolyte membrane for the reaction with the hydrogenated substance. This includes adjusting the amount of water entering through the electrolyte membrane based on the amount of water required for the reaction with the hydrogenate and the amount of water that inhibits the hydrogenate from reaching the cathode electrode. The method for producing an organic hydride according to claim 15.

17. The amount of water entering through the electrolyte membrane is adjusted by controlling at least one of the operating temperature of the organic hydride production apparatus and the supporting electrolyte concentration of the anode solution. The method for producing an organic hydride according to claim 16.

18. The cathode electrode has a catalyst layer containing a cathode catalyst and an ionomer, The amount of water entering through the electrolyte membrane is 1.05 to 1.70 / min, expressed as the ratio ( / min) of the amount of water per unit time and area of ​​the electrolyte membrane (mol / min / m²) during the non-electrolytic phase to the number of ion exchange groups per unit area of ​​the ionomer in the catalyst layer (mol / m²). The method for producing an organic hydride according to claim 16.