Organic hydride production device and organic hydride production method

Abstract

An organic hydride production device (2) is provided with: a cathode electrode (10) that generates an organic hydride and hydroxide ions from a hydride and water; an anode electrode (12) that oxidizes hydroxide ions and generates oxygen; and an electrolyte membrane (14) that is configured from an anion exchange membrane, is disposed 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.

Description

Technical Field

[0001] The present invention relates to an organic hydride manufacturing device and an organic hydride manufacturing method. Background Art

[0002] In recent years, in order to suppress the emission of carbon dioxide in the process of energy generation, the use of renewable energy obtained by solar energy, wind power, hydropower, geothermal power, etc. is expected. As an example, a system for generating hydrogen by electrolyzing water using electricity derived from renewable energy has been designed. In addition, organic hydride systems have attracted much attention as energy carriers for large-scale transportation and storage of hydrogen derived from renewable energy.

[0003] As for the production technology of organic hydrides, there is known an organic hydride production device, which includes: an anode electrode that generates protons from water; a cathode electrode that hydrogenates an organic compound having an unsaturated bond (a hydride); and an electrolyte membrane that separates the anode electrode and the cathode electrode (for example, refer to Patent Document 1). In the organic hydride production device, protons are generated by oxidation of water at the anode electrode, and the protons move to the cathode electrode side via the electrolyte membrane, and the hydride is hydrogenated at the cathode electrode by the protons, thereby producing the organic hydride.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2012 / 091128 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] In the above-mentioned organic hydride manufacturing device, protons combine with water in the anode chamber to form oxonium ions, which move to the cathode electrode side through the electrolyte membrane. In the reaction field of the cathode electrode, if the three elements of oxonium ions, hydrides and electrons are complete, protons are consumed from the oxonium ions, causing a hydrogenation reaction of the hydrides. At the same time, water is generated. In addition, as the ions move, the water solvated with the protons also moves at the same time. Hereinafter, the water that moves with the movement of ions and through the electrolyte membrane is appropriately referred to as "electro-osmotic water". If electro-osmotic water accumulates on the cathode electrode side, it may hinder the hydrogenation of the hydrides, or it may take labor and time to separate water and organic hydrides. As a result, the manufacturing efficiency of organic hydrides may be reduced.

[0009] The present invention has been made in view of the above circumstances, and one of its objects is to provide a technology for improving the production efficiency of an organic hydride.

[0010] Solutions for solving problems

[0011] A certain aspect of the present invention is an organic hydride manufacturing device. The organic hydride manufacturing device comprises: a cathode electrode that generates an organic hydride and hydroxide ions from a hydride and water; an anode electrode that oxidizes the hydroxide ions to generate oxygen; and an electrolyte membrane that is composed of an anion exchange membrane and is arranged between the cathode electrode and the anode electrode to move the hydroxide ions from the cathode electrode side to the anode electrode side.

[0012] Another aspect of the present invention is an organic hydride manufacturing method using the organic hydride manufacturing apparatus of the above aspect. The organic hydride manufacturing method includes: generating an organic hydride and hydroxide ions from a hydride and water at a cathode electrode; moving the hydroxide ions to an anode electrode via an electrolyte membrane; and oxidizing the hydroxide ions at the anode electrode to generate oxygen.

[0013] Optional combinations of the above-described constituent elements and forms in which the expressions of the present disclosure are converted into methods, apparatuses, systems, and the like are also effective as forms of the present disclosure.

[0014] Effects of the Invention

[0015] According to the present invention, it is possible to improve the production efficiency of an organic hydride. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of an organic hydride manufacturing system according to an embodiment.

[0017] Figure 2 It is a graph showing the evaluation results of the Faraday efficiency and the evaluation results of the mixing of water into the cathode liquid in each example and comparative example. DETAILED DESCRIPTION

[0018] Hereinafter, the present invention will be described with reference to the accompanying drawings based on preferred embodiments. The embodiments are not intended to limit the scope of protection of the present invention. They are illustrative and are not limited to all the features described in the embodiments, and their combinations must be essential features of the invention. Therefore, the contents of the embodiments may be subjected to various design changes such as changes, additions, deletions, etc. of the constituent elements within the scope of the idea of ​​the invention specified in the claims. The new embodiments to which the design changes are applied have the respective effects of the combined embodiments and the deformations. In the embodiments, for the contents that can be subjected to such design changes, the expressions such as "of this embodiment" and "in this embodiment" are marked to emphasize, but even if there are no such expressions, design changes are allowed. Any combination of the constituent elements described in the embodiments is also valid as a mode of the present invention. It is assumed that the same or equivalent constituent elements, components, and processes shown in each of the drawings are marked with the same figure numerals, and repeated descriptions are appropriately omitted. In addition, the scales and shapes of the various parts shown in the figures are set for convenience in order to facilitate the description, and are not interpreted in a limiting manner unless otherwise mentioned. In addition, when the terms "first" or "second" are used in this specification or claims, the terms are not used to indicate any order or importance, but to distinguish a certain structure from other structures. In addition, some components that are not important in describing the implementation are omitted in each figure.

[0019] Figure 1 Schematic diagram of an organic hydride manufacturing system 1 according to an embodiment. The organic hydride manufacturing system 1 as an example includes an organic hydride manufacturing device 2, a cathode liquid supply device 4, and an anode liquid supply device 6. Figure 1 , only one organic hydride manufacturing device 2 is shown in the figure, but the organic hydride manufacturing system 1 may also include a plurality of organic hydride manufacturing devices 2. In this case, the organic hydride manufacturing devices 2 are stacked in the same direction, for example, in such a way that the cathode electrode 10 and the anode electrode 12 are arranged in the same manner, and are electrically connected in series. In addition, the organic hydride manufacturing devices 2 may be connected in parallel, or in combination of series connection and parallel connection.

[0020] The organic hydride manufacturing device 2 is an electrolytic cell that generates organic hydrides by hydrogenating a hydride as a dehydrogenated product of an organic hydride using an electrochemical reduction reaction. The organic hydride manufacturing device 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 addition, in this embodiment, the membrane electrode assembly 8 is cited as an example for explanation, but the organic hydride manufacturing device 2 can also have a so-called zero-gap electrode structure: an electrode coated with an anode catalyst on a solid support substrate is physically in contact with the electrolyte membrane.

[0021] The cathode electrode 10 generates an organic hydride and hydroxide ions from a hydride and water. The cathode electrode 10 contains, for example, 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 the hydride with water. In addition, it is preferred that the cathode electrode 10 contains a porous catalyst carrier that supports the cathode catalyst. The catalyst carrier is composed of, for example, an electron conductive material such as porous carbon, porous metal, or porous metal oxide.

[0022] In addition, the cathode catalyst is coated with an anion exchange type ionomer. For example, a catalyst carrier in a state of carrying a cathode catalyst is coated with an ionomer. As an ionomer, polymers such as Fumion (registered trademark) can be exemplified. The ionomer preferably partially coats the cathode catalyst. Thus, the three elements (hydride, water, and electrons) required for the electrochemical reaction at the cathode electrode 10 can be efficiently supplied to the reaction field.

[0023] The cathode electrode 10 as an example has a catalyst layer 10a and a diffusion layer 10b. The catalyst layer 10a is arranged at a position closer to the electrolyte membrane 14 than the diffusion layer 10b. The catalyst layer 10a contains the above-mentioned cathode catalyst, catalyst carrier and ionomer. The diffusion layer 10b contacts the main surface of the catalyst layer 10a on the opposite side of the electrolyte membrane 14. The diffusion layer 10b makes the hydrogenated substance supplied from the outside diffuse to the catalyst layer 10a uniformly. In addition, the organic hydride generated at the catalyst layer 10a is discharged to the outside of the cathode electrode 10 via the diffusion layer 10b. The diffusion layer 10b is composed of conductive materials such as carbon and metal. In addition, the diffusion layer 10b is a porous body such as a sintered body of fibers or particles, a foamed body. As materials constituting the diffusion layer 10b, carbon woven fabric (carbon cloth), carbon nonwoven fabric, carbon paper, etc. can be exemplified. In addition, there is also a case where the diffusion layer 10b is omitted.

[0024] The anode electrode 12 oxidizes the hydroxide ions to generate oxygen. The anode electrode 12, for example, has metals such as iridium (Ir), ruthenium (Ru), platinum (Pt), iron (Fe), cobalt (Co), nickel (Ni) and their oxides, carbon materials such as graphene and their partial oxides as anode catalysts for oxidizing the hydroxide ions. The anode catalyst can also be dispersed, carried or coated on a substrate with electronic conductivity. The substrate is, for example, composed of a material with metals such as titanium (Ti) and stainless steel (SUS) as the main component. As the form of the substrate, woven fabrics, non-woven fabric sheets, meshes, porous sintered bodies, foamed molded bodies (foams), expanded metal meshes, etc. can be exemplified.

[0025] 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, which moves hydroxide ions from the cathode electrode 10 side to the anode electrode 12 side. As an anion exchange membrane that can be used for the electrolyte membrane 14, for example, known anion exchange membranes such as Fumasep (registered trademark) (manufactured by FuMA-Tech Co., Ltd.) can be cited. In addition, the electrolyte membrane 14 is more preferably composed of a polymer having a main chain resistant to the hydride. As such a polymer, a polymer having an aromatic ring in the main chain skeleton such as polyaromatic hydrocarbons can be exemplified. By having a rigid skeleton such as polyaromatic hydrocarbons in the electrolyte membrane 14, the resistance to the hydride can be improved. As a result, the cross leakage of the hydride to the anode electrode side can be further suppressed.

[0026] The plate member 16a and the plate member 16b are made of metals such as stainless steel and titanium, for example. 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 clamped by a 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. In the case where the organic hydride manufacturing system 1 has only one organic hydride manufacturing device 2, a pair of plate members 16a and 16b can be equivalent to a so-called end plate. In the case where the organic hydride manufacturing system 1 has a plurality of organic hydride manufacturing devices 2 and other organic hydride manufacturing devices 2 are arranged next to the plate member 16a or the plate member 16b, the plate member can be equivalent to a so-called partition.

[0027] A cathode flow path 20 is connected to the cathode electrode 10. The cathode flow path 20 supplies and discharges the cathode liquid LC to and from the cathode electrode 10. In addition, grooves may be provided on the main surface of the plate member 16a facing the cathode electrode 10, and the grooves may constitute the cathode flow path 20.

[0028] The anode electrode 12 is connected to an anode channel 22. The anode channel 22 supplies and discharges the anode liquid LA to and from the anode electrode 12. In addition, a groove may be provided on the main surface of the plate member 16b facing the anode electrode 12, and the groove may constitute the anode channel 22.

[0029] The cathode liquid LC is supplied to the cathode electrode 10 by the 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, that is, a hydride. As an example, the cathode liquid LC does not contain an organic hydride before the start of operation of the organic hydride manufacturing system 1, and after the start of operation, the organic hydride generated by electrolysis is mixed to form a mixed liquid of the hydride and the organic hydride. The hydride and the organic hydride are preferably liquid at 20°C and 1 atmosphere.

[0030] The hydride and the organic hydride are not particularly limited as long as they are organic compounds that can add / remove hydrogen by reversibly undergoing hydrogenation / dehydrogenation reactions. As the hydride and the organic hydride used in the present embodiment, acetone-isopropanol system, benzoquinone-hydroquinone system, aromatic hydrocarbon system, etc. can be widely used. Among them, aromatic hydrocarbon system is preferred from the viewpoint of transportability during energy transfer. In general, the hydride and the organic hydride of the aromatic hydrocarbon system are hydrophobic and separate from the water phase at 20°C and 1 atmosphere.

[0031] Aromatic hydrocarbon compounds used as hydrogenated substances are compounds containing at least one aromatic ring. Examples of aromatic hydrocarbon compounds include benzene, alkylbenzenes, naphthalene, alkylnaphthalene, anthracene, diphenylethane, tetralin, etc. Alkylbenzenes include compounds in which 1 to 4 hydrogen atoms of the aromatic ring are substituted by straight-chain alkyl or branched alkyl groups having 1 to 6 carbon atoms. Examples of such compounds include toluene, xylene, mesitylene, ethylbenzene, diethylbenzene, etc. Alkylnaphthalene includes compounds in which 1 to 4 hydrogen atoms of the aromatic ring are substituted by straight-chain alkyl or branched alkyl groups having 1 to 6 carbon atoms. Examples of such compounds include methylnaphthalene, etc. These can be used alone or in combination.

[0032] The hydride is preferably at least one of toluene and benzene. In addition, nitrogen-containing heterocyclic aromatic compounds such as quinoline, isoquinoline, N-alkylpyrrole, N-alkylindole, and N-alkyldibenzopyrrole can also be used as the hydride. The organic hydride is a substance obtained by hydrogenating the above-mentioned hydride, and examples thereof include cyclohexane, methylcyclohexane, dimethylcyclohexane, and decahydroquinoline.

[0033] The cathode liquid tank 24 is connected to the cathode electrode 10 by means of the first cathode pipe 26. One end of the first cathode pipe 26 is connected to the cathode liquid 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 in the middle of the first cathode pipe 26. The cathode pump 30 can be composed of a well-known pump such as a gear pump or a cylinder pump. In addition, the cathode liquid supply device 4 can also use a liquid supply device other than a pump to circulate the cathode liquid LC. The cathode liquid tank 24 is also connected to the cathode electrode 10 by means of the 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 liquid tank 24.

[0034] The cathode liquid LC in the cathode liquid tank 24 flows into the cathode electrode 10 via the first cathode piping 26 due to the drive of the cathode pump 30. The cathode liquid LC flowing into the cathode electrode 10 is supplied to the electrode reaction at the cathode electrode 10. The cathode liquid LC in the cathode electrode 10 returns to the cathode liquid tank 24 via the second cathode piping 28. As an example, the cathode liquid tank 24 also functions as a gas-liquid separation unit. At the cathode electrode 10, there is a situation where hydrogen is generated due to a side reaction. Therefore, there is a situation where hydrogen is mixed in the cathode liquid LC discharged from the cathode electrode 10. The cathode liquid tank 24 separates the hydrogen in the cathode liquid LC from the cathode liquid LC and discharges it to the outside of the system.

[0035] In addition, the electrolyte membrane 14 of the present embodiment is composed of an anion exchange membrane. As a result, although the details will be discussed later, it is possible to suppress the movement of excess water from the anode electrode 12 to the cathode electrode 10. Therefore, in theory, the mixing of water into the cathode liquid LC can be suppressed to a negligible level. However, an oil-water separator for separating water from the cathode liquid LC may be provided in the cathode liquid supply device 4 as needed. Alternatively, the cathode liquid tank 24 may also function as an oil-water separator.

[0036] The cathode liquid supply device 4 of this embodiment circulates the cathode liquid LC between the cathode electrode 10 and the cathode liquid tank 24. However, the present invention is not limited to this structure, and the cathode liquid LC may be sent from the cathode electrode 10 to the outside of the system without returning it to the cathode liquid tank 24.

[0037] The anolyte LA is supplied to the anode electrode 12 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 anolyte LA is stored in the anolyte tank 32. The anolyte LA contains water. Examples of the anolyte LA include alkaline solutions such as potassium hydroxide aqueous solution, ion exchange water, and aqueous solutions containing inorganic electrolytes such as potassium sulfate.

[0038] The anode liquid tank 32 is connected to the anode electrode 12 by means of the first anode piping 34. One end of the first anode piping 34 is connected to the anode liquid tank 32, and the other end of the first anode piping 34 is connected to the inlet of the anode flow path 22. An anode pump 38 is provided in the middle of the first anode piping 34. The anode pump 38 can be composed of a known pump such as a gear pump or a cylinder pump, for example. In addition, the anode liquid supply device 6 can also use a liquid supply device other than a pump to circulate the anode liquid LA. The anode liquid tank 32 is also connected to the anode electrode 12 by means of the second anode piping 36. One end of the second anode piping 36 is connected to the outlet of the anode flow path 22, and the other end of the second anode piping 36 is connected to the anode liquid tank 32.

[0039] The anode liquid LA in the anode liquid tank 32 flows into the anode electrode 12 via the first anode piping 34 due to the drive of the anode pump 38. A portion of the water in the anode liquid LA flowing into the anode electrode 12 diffuses to the cathode electrode 10 side via the electrolyte membrane 14 to supply the electrode reaction at the cathode electrode 10. The anode liquid LA in the anode electrode 12 returns to the anode liquid tank 32 via the second anode piping 36. As an example, the anode liquid tank 32 also functions as a gas-liquid separation unit. Oxygen is generated due to the electrode reaction at the anode electrode 12. Therefore, oxygen is mixed in the anode liquid LA discharged from the anode electrode 12. The anode liquid tank 32 separates the oxygen in the anode liquid LA from the anode liquid LA and discharges it to the outside of the system.

[0040] The anolyte supply device 6 of this embodiment circulates the anolyte LA between the anode electrode 12 and the anolyte tank 32. However, the present invention is not limited to this structure, and the anolyte LA may be sent from the anode electrode 12 to the outside of the system without returning the anolyte LA to the anolyte tank 32.

[0041] Electric power is supplied to the organic hydride manufacturing device 2 from an external power supply (not shown). If electric power is supplied to the organic hydride manufacturing device 2 from the power supply, a predetermined cell voltage is applied between the cathode electrode 10 and the anode electrode 12 of the organic hydride manufacturing device 2, and an electrolysis current flows. The power supply transmits electric power supplied from the power supply device to the organic hydride manufacturing device 2. The power supply device can be composed of a power generation device that generates electric power using renewable energy, such as a wind power generation device, a solar power generation device, and the like. In addition, the power supply device is not limited to such a renewable energy power generation device, and can be a system power supply, or a power storage device that stores electric power from a renewable energy power generation device or a system power supply, and the like. In addition, it can also be a combination of two or more of them. In addition, the structure of the organic hydride manufacturing system 1 is not limited to the above-mentioned structure, and the structure of each part can be appropriately changed.

[0042] In the organic hydride manufacturing apparatus 2, the reaction that occurs when toluene (TL) is used as an example of a hydride product is as follows. When toluene is used as a hydride product, the obtained organic hydride product is methylcyclohexane (MCH).

[0043] <Electrode reaction at cathode electrode>

[0044] TL+6H2O+6e - →MCH+6OH -

[0045] <Electrode reaction at the anode electrode>

[0046] 6OH - →3 / 2O2+3H2O+6e -

[0047] 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 from water to generate methylcyclohexane and hydroxide ions. The hydroxide ions generated at the cathode electrode 10 move to the anode electrode 12 through the electrolyte membrane 14. The hydroxide ions supplied to the anode electrode 12 are oxidized at the anode electrode 12 to generate oxygen, water, and electrons. The electrons generated by the oxidation of the hydroxide ions are supplied to the cathode electrode 10 via an external circuit and used for the electrode reaction at the cathode electrode 10.

[0048] Therefore, according to the organic hydride manufacturing device 2 of the present embodiment, the oxidation reaction of hydroxide ions and the hydrogenation reaction of the hydride can be performed in one step. Therefore, compared with the prior art of manufacturing organic hydrides in two stages, namely, a process of manufacturing hydrogen by water electrolysis or the like and a process of chemically hydrogenating the hydride by a reactor in a factory or the like, the manufacturing efficiency of organic hydrides can be improved. In addition, since a reactor for chemical hydrogenation and a high-pressure container for storing hydrogen produced by water electrolysis or the like are not required, a significant reduction in equipment cost can be achieved.

[0049] In addition, the organic hydride manufacturing device 2 of the present embodiment is an AEM (Anion Exchange Membrane, anion exchange membrane) type, which moves hydroxide ions from the cathode electrode 10 to the anode electrode 12. Therefore, the movement direction of the ions is opposite to the movement direction of the ions of the previous PEM (Proton Exchange Membrane, cation exchange membrane) type device. In this case, the movement of water from the anode electrode 12 side to the cathode electrode 10 side is theoretically a diffusion caused only by the concentration gradient of water. The water that moves from one electrode side to the other electrode side due to the concentration gradient of water is appropriately referred to as "physical diffusion water" below. In the case of the AEM type, the water concentration of the anode is higher than the water concentration of the cathode. Therefore, the physical diffusion water moves from the anode electrode 12 side to the cathode electrode 10 side. In the AEM type, the flow of electroosmotic water becomes the direction from the cathode electrode 10 side toward the anode electrode 12 side. Therefore, the water moving from the anode electrode 12 side to the cathode electrode 10 side does not contain electroosmotic water, and becomes only physical diffusion water. Therefore, it is possible to suppress the entry of an excessive amount of water into the cathode electrode 10, and it is possible to suppress the diffusion of hydride from being hindered by the water in the cathode electrode 10. In addition, the water originally retained by the electrolyte membrane 14 can also enter the cathode electrode 10 as a part of the physically diffused water, but the amount of this water is also minute compared to the amount of electroosmotic water in the PEM type device.

[0050] As a result, the hydride can easily reach the reaction field. Therefore, the shortage of hydride can be avoided and the occurrence of side reactions can be suppressed. Therefore, the efficiency of the electrode reaction at the cathode electrode 10, that is, the reduction in the Faraday efficiency, can be suppressed. In particular, the reduction in reaction efficiency when the cathode liquid with a low concentration of hydride is supplied to the cathode electrode 10 can be suppressed. As a result, the production efficiency of organic hydrides is improved. In addition, the accumulation of water at the cathode electrode 10 can be suppressed, so the process of separating the organic hydride and water from each other becomes easy or can be omitted. In this regard, the production efficiency of organic hydrides is also improved.

[0051] In addition, in the case of the PEM type, water disappears locally near the interface between the anode catalyst layer and the electrolyte membrane due to the electrode reaction at the anode electrode. On the other hand, there is a large amount of electroosmotic water near the interface between the cathode catalyst layer and the electrolyte membrane. Therefore, due to the concentration gradient of water, the water on the cathode electrode side may return to the anode electrode side. Therefore, the movement direction of the physical diffusion water is opposite to the movement direction of the physical diffusion water of the AEM type. In addition, in the case where the anode liquid 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 the osmotic pressure caused by the concentration gradient of the electrolyte. The water that moves from one electrode side to the other electrode side due to the concentration gradient of the electrolyte is appropriately referred to as "osmotic pressure transfer water" below. In the case of the PEM type, the osmotic pressure transfer water moves from the cathode electrode 10 side to the anode electrode 12 side.

[0052] Therefore, in the PEM type, the physical diffusion water and the osmotic pressure transfer water move from the cathode electrode side to the anode electrode side. Hereinafter, the water (physical diffusion water + osmotic pressure transfer water) moving from the cathode electrode side to the anode electrode side in the PEM type is appropriately referred to as "reverse diffusion water". The "reverse" in "reverse diffusion water" means the opposite direction to the direction of ion movement. In addition, the phenomenon that the reverse diffusion water generated in the PEM type returns to the anode electrode side is referred to as "reverse diffusion of water".

[0053] If reverse diffusion of water is caused, a trace amount of hydride dissolved in water may also move to the anode electrode side together with water. As a result, the anode catalyst may be poisoned by the hydride. In contrast, in the present embodiment, the accumulation of water to 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. Thus, the poisoning of the anode catalyst caused by the hydride can be suppressed. In addition, the loss of the hydride from the cathode electrode 10 can also be suppressed. As a result, the manufacturing efficiency of the organic hydride is improved.

[0054] In addition, in the case of the PEM type, the reaction is carried out by the movement of protons in the form of oxonium ions from the anode liquid to the cathode electrode side. Therefore, it is necessary to ensure a proton (oxonium ion) conduction path in the anode liquid. Therefore, from the viewpoints of reaction promotion, proton activity, etc., it is preferred that the anode liquid is neutral to acidic. In addition, from the viewpoint of efficient proton conduction, the anode catalyst and the cathode catalyst are preferably coated with a strongly acidic proton exchange ionomer. Therefore, the anode catalyst and the cathode catalyst are placed in an acidic atmosphere. Therefore, each catalyst is limited to a catalyst that can be used in an acidic atmosphere. In particular, the anode catalyst is limited to a material that is resistant to an acidic atmosphere and an oxidizing atmosphere.

[0055] On the other hand, in the present embodiment, hydroxide ions move from the cathode electrode 10 side to the anode electrode 12 side. Therefore, the anolyte is preferably neutral to alkaline. In addition, 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 the cathode catalyst are placed in a neutral to alkaline atmosphere. Therefore, it is preferred that each catalyst is a catalyst that can be used in a neutral to alkaline atmosphere, and the options for anode catalysts that can be used in a neutral to alkaline atmosphere are more than the options for anode catalysts that can be used in an acidic atmosphere. Therefore, according to the present embodiment, the design freedom of the organic hydride manufacturing device 2 can be improved, and it can be easy to seek component cost reduction, etc.

[0056] The lower the solubility of the hydride and the organic hydride in water, the more effectively the migration suppression of water from the anode electrode 12 side to the cathode electrode 10 side is. 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, the migration suppression of water is more effectively exerted. When the solubility of at least one of the hydride and the organic hydride in water is 3 g / 100 mL or less, the removal of water caused by the hydride and the organic hydride becomes significantly difficult. Therefore, the migration suppression of water is more effectively exerted. Examples of hydrogenated substances and organic hydrides for which this effect is particularly expected include benzene (0.18 g / 100 mL H2O) and cyclohexane (0.36 g / 100 mL H2O), toluene (0.05 g / 100 mL H2O) and methylcyclohexane (1.6 g / 100 mL H2O), naphthalene (0.003 g / 100 mL H2O) and decalin (0.001 g / 100 mL H2O), etc.

[0057] The water used for the electrode reaction at the cathode electrode 10 is preferably supplied by physically diffused water entering from the electrolyte membrane 14. The physically diffused water contains at least one of the water originating from the anolyte LA and the water originally retained by 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 via the electrolyte membrane 14 due to the concentration gradient of the water. In addition, there is a case where the electrolyte membrane 14 absorbs and retains moisture in the atmosphere. Alternatively, when assembling the organic hydride manufacturing device 2, the electrolyte membrane 14 can be subjected to water-containing treatment. The water may also enter the cathode electrode 10 side due to the concentration gradient of the water.

[0058] It is preferred that the amount of water entering from the electrolyte membrane 14 to the cathode electrode 10 side is adjusted to be sufficient for the hydrogenation of the hydride at the cathode electrode 10 and not hindering the hydride from reaching the reaction field. If the amount of water entering the cathode electrode 10 side is insufficient, the water as the matrix is ​​insufficient. In addition, the ionomer in the cathode catalyst layer will not be wetted, and it is difficult to form an ion conduction path between the ion exchange groups. Therefore, the hydrogenation of the hydride may be hindered. On the contrary, if the amount of water entering the cathode electrode 10 side is excessive, it may hinder the hydride from reaching the reaction field. As a result, the hydrogen production caused by the side reaction at the cathode electrode 10 may become dominant. The amount of water is determined by the physical diffusion water and osmotic pressure transfer water through the electrolyte membrane 14. Therefore, the amount of water can be controlled by the material of the electrolyte membrane 14, the membrane thickness, the operating temperature of the organic hydride manufacturing device 2, the supporting electrolyte concentration of the anolyte, etc. The amount of water can be, for example, the amount of water per unit time during non-electrolysis, the amount of water per unit area of ​​the electrolyte membrane 14 (mg / min / m 2 ) is defined. In addition, the appropriate range of the water amount is expressed, for example, as the amount of water per unit time and per unit area of ​​the electrolyte membrane 14 during non-electrolysis (mmol / min / m 2 ) and the ion exchange base per unit area of ​​the ionomer in the cathode catalyst layer (mmol / m 2 ) is preferably 1.05 / min to 1.70 / min. By setting the water amount to 1.05 / min or more, it is possible to more reliably suppress the performance reduction of the organic hydride manufacturing apparatus 2 due to the lack of water hindering hydrogenation. In addition, by setting the water amount to 1.70 / min or less, it is possible to more reliably suppress the accumulation of excess water in the cathode catalyst layer and hindering the reaction.

[0059] The cathode electrode 10 uses at least one of the water from the anolyte LA entering the cathode electrode 10 from the electrolyte membrane 14 and the water from the electrolyte membrane 14 for the reaction with the hydride. As a result, compared with the case where water is directly supplied to the cathode electrode 10 from the outside of the organic hydride manufacturing apparatus 2, it is easy to suppress the diffusion obstruction of the hydride caused by water, the complication of the recovery process of the organic hydride, the occurrence of water back diffusion, etc. The water used at the cathode electrode 10 is preferably only the water entering from the electrolyte membrane 14, but it can also be appropriately combined with direct water absorption from the outside to the cathode electrode 10.

[0060] The implementation mode can also be determined by the items described below.

[0061] [Item 1] An organic hydride manufacturing apparatus (2), comprising:

[0062] a cathode electrode (10) which generates an organic hydride and hydroxide ions from a hydride and water;

[0063] an anode electrode (12) that oxidizes the hydroxide ions to generate oxygen; and

[0064] The electrolyte membrane (14) is composed of an anion exchange membrane and is arranged between the cathode electrode (10) and the anode electrode (12) to allow hydroxide ions to move from the cathode electrode (10) side to the anode electrode (12) side.

[0065] [Item 2] The organic hydride manufacturing apparatus (2) according to Item 1, wherein:

[0066] The anode electrode (12) receives a supply of an anolyte (LA) containing water.

[0067] The electrolyte membrane (14) contains water,

[0068] The cathode electrode (10) uses the water introduced from the electrolyte membrane (14) for a reaction with a hydride.

[0069] [Item 3]

[0070] A method for producing an organic hydride, which is a method for producing an organic hydride using the organic hydride production apparatus (2) according to item 1 or 2, comprising:

[0071] generating an organic hydride and hydroxide ions from a hydride and water at a cathode electrode (10);

[0072] allowing hydroxide ions to move toward the anode electrode (12) via the electrolyte membrane (14); and

[0073] The hydroxide ions are oxidized at the anode electrode (12) to generate oxygen.

[0074] Example

[0075] Hereinafter, examples of the present invention will be described. However, these examples are merely illustrative for appropriately describing the present invention and do not limit the present invention at all.

[0076] (Example 1)

[0077] A four-stage ammonium AEM electrolyte membrane having a polyaromatic skeleton (Fumasep (registered trademark) FAA-3-PK-130, manufactured by FuMA-Tech) was prepared. The thickness of the electrolyte membrane was 130 μm. The water permeability in the electrolyte membrane during non-electrolysis was measured in the following procedure.

[0078] That is, the electrolyte membrane is cut into a φ40 mm circle. The electrolyte membrane sandwiched by a circular Viton (registered trademark) gasket is fixed between two flange glass cells of an H-type cell (VB9B, manufactured by EC FRONTIER). The exposed portion of the electrolyte membrane is set to φ28 mm. 25 mL of a 1 mol / L KOH aqueous solution is filled into the flange glass cell on one side. The weight of the entire H-type cell is measured, and the measured weight is set as the starting weight (Amg). The openings of the flange glass cells on both sides are sealed with a sealing film (Parafilm) and left to stand. After a predetermined time, the sealing film that seals the opening is removed, and the water that has diffused into the flange glass cell on the side that is not filled with KOH solution is wiped off. The weight of the entire H-type cell is measured again, and the measured weight is set as the end weight (Bmg). In addition, the permeability of water during non-electrolysis is calculated based on the following formula (1).

[0079] Formula (1): (AB) [mg] / standing time [min] / area of ​​the exposed part of the electrolyte membrane [m 2 ]

[0080] The anode catalyst ink was prepared by mixing IrO2 catalyst (manufactured by FURUYA METAL), 4-grade 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.). The catalyst loading density of the anode catalyst ink was set to 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 above-mentioned AEM type electrolyte membrane to form an anode catalyst layer.

[0081] A cathode catalyst ink was prepared by mixing a PtRu / C catalyst (TEC61E54, manufactured by Tanaka Kikinzoku Kogyo 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.). The catalyst loading density of the cathode catalyst ink was set to 1 mg / cm 2 , the ionomer / carbon ratio (I / C) is set to 0.8. The cathode catalyst layer is formed by applying the prepared cathode catalyst ink to the main surface on the opposite side of the AEM type electrolyte membrane having an anode catalyst layer formed on one main surface. 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 is calculated using the following formula (2). In addition, the ion exchange capacity (IEC) of the quaternary ammonium anion exchange type ionomer used in this embodiment is 1.86 mmol / g.

[0082] 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 ]×ion exchange capacity of ionomer [mmol / g])

[0083] The cathode end plate, the cathode side gasket, the diffusion layer, the AEM type electrolyte membrane laminated with the cathode catalyst layer and the anode catalyst layer, the anode side gasket, and the anode end plate are sequentially laminated to obtain the organic hydride manufacturing device of Example 1. Each end plate uses a titanium plate with a flow path for each liquid. Each gasket is made of Viton (registered trademark). The electrode effective area of ​​the organic hydride manufacturing device is set to 25cm 2 .

[0084] Toluene was used as the cathode liquid and flowed to the cathode of the organic hydride manufacturing device at a flow rate of 20 mL / min. In addition, a 1 mol / L KOH aqueous solution was used as the anode liquid and flowed to the anode at a flow rate of 20 mL / min. And, the electrolysis reaction was carried out at a temperature of 60°C and a predetermined cell voltage. The Faraday efficiency was calculated based on the amount of electricity consumed in the electrolysis reaction and the amount of organic hydride produced. And, the case where the Faraday efficiency was 80% or more was evaluated as 0, and the case where it was less than 80% was evaluated as ×. In addition, after the electrolysis reaction, the water layer in the cathode liquid container was separated and weighed to determine the amount of water in the cathode liquid. And, the case where the mixing ratio of the electrolyzed water to the entire cathode liquid was less than 1% was evaluated as ○, and the case where it was more than 1% was evaluated as ×. The results are shown in Figure 2 middle.

[0085] (Example 2)

[0086] The water permeability measurement, the preparation of the organic hydride manufacturing apparatus, the electrolysis treatment, the calculation of the permeable water ratio, and the evaluations were carried out in the same manner as in Example 1, except that the water permeability measurement was performed and ion exchange water was used as the anolyte. Figure 2 middle.

[0087] (Comparative Example 1)

[0088] A polyfluoroalkanesulfonic acid-based PEM electrolyte membrane (Nafion (registered trademark) 117, manufactured by The Chemours Company) was prepared. The thickness of the electrolyte membrane was 180 μm. In the same manner as in Example 2, the water permeability in the electrolyte membrane was measured.

[0089] The anode catalyst ink was prepared by mixing IrO2 catalyst (manufactured by FURUYA METAL), polyfluoroalkanesulfonic acid-based cation exchange ionomer (Nafion (registered trademark) DE2020CS, manufactured by The Chemours Company), ion exchange water, and 1-propanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). The catalyst loading density of the anode catalyst ink was set to 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 above-mentioned PEM type electrolyte membrane to form an anode catalyst layer.

[0090] A cathode catalyst ink was prepared by mixing a PtRu / C catalyst (TEC61E54, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.), a polyfluoroalkanesulfonic acid-based cation exchange ionomer (Nafion (registered trademark) DE2020CS, manufactured by The Chemours Company), ion exchange water, and 1-propanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). The catalyst loading density of the cathode catalyst ink was set to 1 mg / cm 2 , the ionomer / carbon ratio (I / C) is set to 0.5. The cathode catalyst layer is formed by applying the prepared cathode catalyst ink to the main surface of the PEM type electrolyte membrane on the opposite side of the main surface on which the anode catalyst layer is formed. 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 is calculated in the same manner as in Examples 1 and 2. In addition, the ion exchange capacity of the polyfluoroalkanesulfonic acid-based cation exchange type ionomer used in this comparative example is 1.00 mmol / g.

[0091] The cathode end plate, cathode side gasket, diffusion layer, PEM type electrolyte membrane with cathode catalyst layer and anode catalyst layer, anode side gasket, and anode end plate were stacked in order to obtain the organic hydride manufacturing device of Comparative Example 1. Each end plate and each spacer used the same end plate and spacer as in Example 1. The electrode effective area of ​​the organic hydride manufacturing device was set to 25 cm 2 The obtained organic hydride manufacturing apparatus was used to carry out electrolysis treatment and various evaluations in the same manner as in Example 2. The results are shown in Figure 2 middle.

[0092] Figure 2This is a diagram showing the evaluation results of the Faraday efficiency in each embodiment and comparative example and the evaluation results of the mixing of water into the cathode liquid. From the comparison between Embodiments 1 and 2 and Comparative Example 1, it was confirmed that: when the organic hydride manufacturing device is equipped with an AEM type electrolyte membrane, the mixing ratio of water in the cathode liquid after electrolysis is less than 1%, which is extremely small, and a Faraday efficiency of 80% or more is obtained at at least any cell voltage. Therefore, it was confirmed that: by using an AEM type electrolyte membrane, the manufacturing efficiency of organic hydrides can be improved.

[0093] In addition, from the comparison between Example 1 and Example 2, it is confirmed that when the anolyte does not contain a supporting electrolyte, a Faraday efficiency of more than 80% is obtained at a wider range of cell voltages than when the anolyte contains a supporting electrolyte. In addition, it is confirmed that the water permeability, the amount of permeated water, and the ratio of the amount of ionomer ion exchange groups in non-electrolysis in Example 2 are higher than those in Example 1. Thus, it is shown that the physical diffusion water that has moved from the anode electrode 12 side to the cathode electrode 10 side can be suppressed by reducing the supporting electrolyte concentration of the anolyte, and becomes osmotic pressure transfer water due to the concentration gradient of the supporting electrolyte and returns to the anode electrode 12 side. Thus, more water can be supplied to the cathode electrode 10 side. Therefore, it is possible to avoid the supply of water to the cathode electrode 10 becoming a limitation of the cathode reaction. Therefore, the cell voltage can be increased to increase the current density of the electrolytic reaction, in other words, the reaction rate. In addition, in any of Examples 1, 2 and Comparative Example 1, no cross leakage of toluene to the anode electrode side was observed.

[0094] Industrial Applicability

[0095] The present invention can be utilized in an organic hydride manufacturing apparatus and an organic hydride manufacturing method.

[0096] Description of Reference Numerals

[0097] 2. Organic hydride manufacturing device; 10. Cathode electrode; 12. Anode electrode; 14. Electrolyte membrane; LA, anolyte; LC, cathode liquid.

Claims

1. An organic hydride production device, wherein: The organic hydride manufacturing device comprises: a cathode electrode that generates an organic hydride and hydroxide ions from a hydride and water; an anode electrode that oxidizes the hydroxide ions to generate oxygen; and The electrolyte membrane is composed of an anion exchange membrane, is disposed between the cathode electrode and the anode electrode, and allows the hydroxide ions to move from the cathode electrode side to the anode electrode side.

2. The organic hydride manufacturing device according to claim 1, wherein: The anode electrode receives a supply of an anolyte containing water, The electrolyte membrane contains water, The cathode electrode uses the water introduced from the electrolyte membrane for a reaction with the hydride.

3. A method for producing an organic hydride, which is a method for producing an organic hydride using the organic hydride production apparatus according to claim 1 or 2, wherein: The method for producing an organic hydride comprises: generating an organic hydride and hydroxide ions from the hydride and water at the cathode electrode; causing the hydroxide ions to move toward the anode electrode via the electrolyte membrane; and The hydroxide ions are oxidized at the anode electrode to generate oxygen.

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