WO2024034444A1

WO2024034444A1 - Apparatus for producing organic hydride

Info

Publication number: WO2024034444A1
Application number: PCT/JP2023/027916
Authority: WO
Inventors: 篤深澤; 康太三好; 香織高野; 孝司松岡
Original assignee: Ｅｎｅｏｓ株式会社
Priority date: 2022-08-10
Filing date: 2023-07-31
Publication date: 2024-02-15

Abstract

An apparatus 2 for producing an organic hydride according to the present invention is provided with: an anode electrode 10 which generates protons by oxidizing water; a cathode electrode 12 which generates an organic hydride by hydrogenating an object to be hydrogenated with protons; an electrolyte membrane 14 which has an EW of less than 980 and is arranged between the anode electrode 10 and the cathode electrode 12 so as to transfer protons from the anode electrode 10 side to the cathode electrode 12 side; and a low moisture content layer 44 which is arranged between the electrolyte membrane 14 and the cathode electrode 12, while having a lower moisture content than the electrolyte membrane 14.

Description

Organic hydride production equipment

The present invention relates to an organic hydride manufacturing apparatus.

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

Regarding organic hydride manufacturing technology, conventionally, an anode electrode that generates protons from water, a cathode electrode that hydrogenates an organic compound (hydrogenated product) having an unsaturated bond, and an electrolyte membrane that separates the anode electrode and the cathode electrode are used. An organic hydride production apparatus having the following is known (see, for example, Patent Document 1). In this organic hydride production equipment, water is supplied to the anode electrode, a hydride is supplied to the cathode, and a current is passed between the anode and the cathode to add hydrogen to the hydride and form an organic Hydride is obtained.

International Publication No. 2012/091128

As a result of intensive studies on organic hydride production equipment, the present inventors have come to recognize the following problems. That is, the organic hydride production apparatus can increase the reaction rate by increasing the current density. This makes it possible to improve the production efficiency of organic hydride and downsize the device. However, increasing current density can increase cell voltage in organic hydride production. Therefore, if a low-resistance electrolyte membrane with high water content is used to suppress the increase in cell voltage, the Faraday efficiency may decrease.

The present invention has been made in view of these circumstances, and one of its purposes is to provide a technology that achieves both suppression of increases in cell voltage and suppression of decreases in Faraday efficiency in the production of organic hydrides.

A certain embodiment of the present invention is an organic hydride production apparatus. This organic hydride manufacturing device has an anode electrode that oxidizes water to generate protons, a cathode electrode that hydrogenates the hydride with protons to generate organic hydride, and an EW (Equivalent Weight) of less than 980. An electrolyte membrane that is placed between the electrode and the cathode electrode and moves protons from the anode side to the cathode side, and a low water content layer that has a lower water content than the electrolyte membrane that is placed between the electrolyte membrane and the cathode electrode. Be prepared.

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

According to the present invention, it is possible to simultaneously suppress an increase in cell voltage and suppress a decrease in Faraday efficiency in organic hydride production.

1 is a schematic diagram of an organic hydride production system according to an embodiment. FIG. 1 is a cross-sectional view of an organic hydride manufacturing apparatus. FIG. 3 is a diagram showing the characteristics of electrolytic cells according to each example and each comparative example, the improvement rate of Faraday efficiency, and the amount of change in voltage.

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

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

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

plate members

16a, 16b, and a pair of

gaskets

18a, 18b. The membrane electrode assembly 8 includes an anode electrode 10 (anode), a cathode electrode 12 (cathode), and an electrolyte membrane 14.

The anode electrode 10 oxidizes water to generate protons. The anode electrode 10 includes metals such as iridium (Ir), ruthenium (Ru), and platinum (Pt), or oxides of these metals, as an anode catalyst for oxidizing water. The anode catalyst may be dispersed and supported on or coated on a substrate having electron conductivity. The base material is made of a material whose main component is a metal such as titanium (Ti) or stainless steel (SUS). Examples of the form of the base material include a sheet of woven fabric or nonwoven fabric, a mesh, a porous sintered body, a foam, an expanded metal, and the like.

The cathode electrode 12 hydrogenates the hydrided substance with protons to generate an organic hydride. The cathode electrode 12 contains, for example, platinum or ruthenium as a cathode catalyst for hydrogenating a substance to be hydrogenated. Preferably, the cathode electrode 12 includes a porous catalyst carrier supporting a cathode catalyst. The catalyst carrier is made of an electronically conductive material such as porous carbon, porous metal, porous metal oxide, or the like.

Additionally, the cathode catalyst is coated with an ionomer (cation exchange type ionomer). For example, a catalyst carrier carrying a cathode catalyst is coated with an ionomer. Examples of the ionomer include perfluorosulfonic acid polymers such as Nafion (registered trademark), Flemion (registered trademark), Fumion (registered trademark), and Aciplex (registered trademark). Preferably, the ionomer partially covers the cathode catalyst. Thereby, the three elements (hydride, protons, and electrons) required for the electrochemical reaction at the cathode electrode 12 can be efficiently supplied to the reaction field.

The cathode electrode 12 of this embodiment includes a catalyst layer 12a and a diffusion layer 12b. The catalyst layer 12a is arranged closer to the electrolyte membrane 14 than the diffusion layer 12b. The catalyst layer 12a contains the above-mentioned cathode catalyst, catalyst carrier, and ionomer. The diffusion layer 12b is in contact with the main surface of the catalyst layer 12a on the side opposite to the electrolyte membrane 14. The diffusion layer 12b uniformly diffuses the hydrogenated substance supplied from the outside into the catalyst layer 12a. Further, the organic hydride generated in the catalyst layer 12a is discharged to the outside of the cathode electrode 12 via the diffusion layer 12b. The diffusion layer 12b is made of a conductive material such as carbon or metal. Further, the diffusion layer 12b is a porous body such as a sintered body of fibers or particles, or a foam molded body. Examples of the material constituting the diffusion layer 12b include carbon woven cloth (carbon cloth), carbon nonwoven cloth, carbon paper, and the like. Note that the diffusion layer 12b may be omitted in some cases.

The electrolyte membrane 14 is arranged between the anode electrode 10 and the cathode electrode 12. The electrolyte membrane 14 moves protons from the anode electrode 10 side to the cathode electrode 12 side. The electrolyte membrane 14, as an example, is composed of a solid polymer electrolyte membrane having proton conductivity.

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

plate members

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

plate members

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

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

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

The anode electrode 10 is supplied with the anolyte LA by the anolyte supply device 4. The anolyte supply device 4 includes an anolyte tank 24, a first anode pipe 26, a second anode pipe 28, and an anode pump 30. The anode solution LA is stored in the anode solution tank 24 . The anolyte LA contains water to be supplied to the anode electrode 10. Examples of the anode solution LA include sulfuric acid aqueous solution, nitric acid aqueous solution, hydrochloric acid aqueous solution, pure water, ion exchange water, and the like.

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

The anode solution LA in the anode solution tank 24 flows into the anode electrode 10 via the first anode pipe 26 by driving the anode pump 30. The anolyte LA that has flowed into the anode electrode 10 is subjected to an electrode reaction at the anode electrode 10 . The anolyte LA in the anode electrode 10 is returned to the anolyte tank 24 via the second anode pipe 28 . As an example, the anode liquid tank 24 also functions as a gas-liquid separation section. Oxygen gas is generated at the anode electrode 10 by an electrode reaction. Therefore, the anolyte LA discharged from the anode electrode 10 contains oxygen gas. The anolyte tank 24 separates the oxygen gas in the anode solution LA from the anode solution LA and discharges it to the outside of the system.

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

A catholyte LC is supplied to the cathode electrode 12 by a catholyte supply device 6 . The catholyte supply device 6 includes a catholyte tank 32 , a first cathode pipe 34 , a second cathode pipe 36 , a third cathode pipe 38 , a cathode pump 40 , and a separation section 42 . The catholyte tank 32 stores catholyte LC. The catholyte LC contains an organic hydride raw material (hydrogenated product) to be supplied to the cathode electrode 12 . As an example, the catholyte LC does not contain any organic hydride before the operation of the organic hydride production system 1 starts, and when the organic hydride generated by electrolysis is mixed in after the start of operation, the catholyte LC becomes a mixed liquid of the hydride and the organic hydride. Become. The hydride and organic hydride are preferably liquid at 20°C and 1 atmosphere.

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

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

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

The catholyte tank 32 is connected to the cathode electrode 12 by a first cathode pipe 34. One end of the first cathode pipe 34 is connected to the catholyte tank 32, and the other end of the first cathode pipe 34 is connected to the cathode channel 22. A cathode pump 40 is provided in the middle of the first cathode pipe 34 . The cathode pump 40 can be configured with a known pump such as a gear pump or a cylinder pump. Note that the catholyte supply device 6 may circulate the catholyte LC using a liquid sending device other than a pump.

The separation section 42 is connected to the cathode electrode 12 by a second cathode pipe 36. One end of the second cathode pipe 36 is connected to the cathode channel 22, and the other end of the second cathode pipe 36 is connected to the separation section 42. The separation section 42 includes a known gas-liquid separator and a known oil-water separator. Further, the separation section 42 is connected to the catholyte tank 32 by a third cathode pipe 38. One end of the third cathode pipe 38 is connected to the separation section 42 , and the other end of the third cathode pipe 38 is connected to the catholyte tank 32 .

The catholyte LC in the catholyte tank 32 flows into the cathode electrode 12 via the first cathode pipe 34 by driving the cathode pump 40 . The catholyte LC that has flowed into the cathode electrode 12 is subjected to an electrode reaction at the cathode electrode 12 . The catholyte LC in the cathode electrode 12 flows into the separation section 42 via the second cathode pipe 36 . At the cathode electrode 12, hydrogen gas may be generated due to side reactions. Therefore, the catholyte LC discharged from the cathode electrode 12 may contain hydrogen gas. The separation unit 42 separates the hydrogen gas in the catholyte LC from the catholyte LC and discharges it out of the system. Furthermore, water moves from the anode electrode 10 to the cathode electrode 12 together with protons. Therefore, the catholyte LC discharged from the cathode electrode 12 may contain water. The separation unit 42 separates water in the catholyte LC from the catholyte LC and discharges the water to the outside of the system. The catholyte LC from which hydrogen gas and water have been separated is returned to the catholyte tank 32 via the third cathode pipe 38 .

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

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

That is, the electrode reaction at the anode electrode 10 and the electrode reaction at the cathode electrode 12 proceed in parallel. Protons generated by electrolysis of water at the anode electrode 10 pass through the electrolyte membrane 14 together with water molecules and move to the cathode electrode 12 . Further, electrons generated by water electrolysis are supplied to the cathode electrode 12 via an external circuit. The protons and electrons supplied to the cathode electrode 12 are used for hydrogenation of toluene at the cathode electrode 12. This produces methylcyclohexane.

Therefore, according to the organic hydride production system 1 according to the present embodiment, the electrolysis of water and the hydrogenation reaction of the hydride can be performed in one step. For this reason, the production efficiency of organic hydride is more efficient than the conventional technology, which produces organic hydride through a two-step process of producing hydrogen through water electrolysis, etc., and chemically hydrogenating the substance to be hydrogenated in a reactor such as a plant. can be increased. Furthermore, since a reactor for chemical hydrogenation, a high-pressure container for storing hydrogen produced by water electrolysis, etc. are not required, equipment costs can be significantly reduced.

In the cathode electrode 12, in addition to the main reaction, which is a hydrogenation reaction of the hydride, the following hydrogen gas generation reaction may occur as a side reaction. As the amount of hydride supplied to the cathode electrode 12 becomes insufficient, this side reaction becomes more likely to occur.
<Side reactions that may occur at the cathode electrode>
2H ⁺ +2e ^- →H ₂

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

Next, the structure of the organic hydride manufacturing apparatus 2 will be explained in detail. FIG. 2 is a sectional view of the organic hydride manufacturing apparatus 2. As shown in FIG. The organic hydride manufacturing apparatus 2 of this embodiment includes a low water content layer 44 and a high water content layer 46 in addition to the above-described configuration.

The electrolyte membrane 14 has an EW (Equivalent Weight) of less than 980. EW is the dry mass of electrolyte per 1 mol of sulfonic acid groups in the electrolyte membrane 14. The lower the EW, the higher the water content because the electrolyte membrane 14 has more hydrophilic sulfonic acid groups. The EW of the electrolyte membrane 14 is preferably 950 or less, more preferably 900 or less, and even more preferably 870 or less. For example, the electrolyte membrane 14 is made of a polymer having an EW of less than 980. Examples of polymers that can be used for the electrolyte membrane 14 include perfluorosulfonic acid polymers. By lowering the EW of the electrolyte membrane 14 to less than 980, the water content of the electrolyte membrane 14 can be increased compared to when the EW is 980 or more. Thereby, the ion movement resistance of the electrolyte membrane 14 can be lowered. Therefore, the cell voltage in organic hydride production can be lowered.

Therefore, by increasing the water content of the electrolyte membrane 14, the resistance of the electrolyte membrane 14 is reduced, and the current density can be increased while suppressing an increase in cell voltage. On the other hand, when the water content of the electrolyte membrane 14 is increased, the affinity of the electrolyte membrane 14 for the hydrogenated substance decreases. For this reason, it becomes difficult for the hydrophobic hydride to be supplied to the reaction field. As a result, there is a shortage of the hydride in the reaction field, making side reactions more likely to occur. Therefore, the efficiency of the electrode reaction at the cathode electrode 12, that is, the faradaic efficiency may decrease.

In contrast, in this embodiment, a low water content layer 44 is disposed between the electrolyte membrane 14 and the cathode electrode 12. One main surface of the low water content layer 44 is in contact with the electrolyte membrane 14, and the other main surface of the low water content layer 44 is in contact with the catalyst layer 12a. When the low water content layer 44 has ion exchange ability, it has a lower water content (higher EW) than the electrolyte membrane 14 and therefore has higher hydrophobicity than the electrolyte membrane 14 . For example, the low water content layer 44 is made of a polymer (for example, an ionomer) having a lower water content than the polymer constituting the electrolyte membrane 14 . The water content (%) in this embodiment is defined by the following formula (1). The "polymer in a water-containing state" in formula (1) means, for example, a polymer after being immersed in pure water for one hour.
(1) Water content = (weight of water contained in polymer/weight of polymer in water-containing state) x 100

The method for forming the low water content layer 44 is not particularly limited, and any known method can be employed. For example, a method such as applying a polymer constituting the low water content layer 44 to the surface of the electrolyte membrane 14 or the surface of the cathode electrode 12, or pressing a thin film of the polymer to the surface of the electrolyte membrane 14 or the surface of the cathode electrode 12. It is possible to adopt

Examples of polymers that can be used for the low water content layer 44 include Nafion (registered trademark), Fumion (registered trademark), and the like. Note that the low water content layer 44 may or may not function as an ion exchange membrane. By lowering the water content of the low water content layer 44 than the water content of the electrolyte membrane 14, it is possible to make it easier for the hydrogenated substance to reach the reaction field. Thereby, a shortage of the hydride can be avoided and the occurrence of side reactions can be suppressed.

In other words, the combination of setting the EW of the electrolyte membrane 14 to less than 980 and installing the low water content layer 44 between the electrolyte membrane 14 and the cathode electrode 12 suppresses the increase in cell voltage in organic hydride production and It is possible to achieve both suppression of efficiency decline. Furthermore, since it becomes easier to increase the current density, it is possible to improve the production efficiency per hour of organic hydride. Furthermore, the organic hydride manufacturing apparatus 2 can be made smaller, and the cost of the components of the organic hydride manufacturing apparatus 2 can therefore be reduced. Furthermore, by suppressing the increase in cell voltage, it is possible to suppress the cost of measures against heat generation necessary for the organic hydride manufacturing apparatus 2.

Furthermore, in this embodiment, a high water content layer 46 is arranged between the electrolyte membrane 14 and the anode electrode 10. One main surface of the high water content layer 46 is in contact with the electrolyte membrane 14 , and the other main surface of the high water content layer 46 is in contact with the anode electrode 10 . The high water content layer 46 has a higher water content (lower EW) than the electrolyte membrane 14, and therefore has higher hydrophilicity than the electrolyte membrane 14. For example, the high water content layer 46 is made of a polymer having a higher water content than the polymer constituting the electrolyte membrane 14 . The method for forming the high water content layer 46 is not particularly limited, and any known method can be employed. For example, a method such as applying a polymer constituting the high water content layer 46 to the surface of the electrolyte membrane 14 or the surface of the anode electrode 10, or pressing a thin film of the polymer to the surface of the electrolyte membrane 14 or the surface of the anode electrode 10. It is possible to adopt

Examples of polymers that can be used for the high water content layer 46 include Aquivion (registered trademark), Fumion (registered trademark), etc., which have a higher water content than the electrolyte membrane 14. By interposing the high water content layer 46 between the electrolyte membrane 14 and the anode electrode 10, the access of water to the anode catalyst is improved, and an increase in cell voltage and a decrease in Faraday efficiency can be further suppressed. Note that the high water content layer 46 may be omitted. In this case, the electrolyte membrane 14 and the anode electrode 10 are in contact with each other.

(Modified example)
The following modification examples can be given to the organic hydride manufacturing apparatus 2 according to the embodiment described above. That is, the cathode electrode 12 may contain an ionomer having a lower water content than the electrolyte membrane 14. Examples of such low water content ionomers include Nafion (registered trademark) and the like. By adding a low water content ionomer to the cathode electrode 12, as in the case of installing the low water content layer 44, it is possible to make it easier for the hydride to reach the reaction field, and it is possible to suppress the occurrence of side reactions. Therefore, the same effect as the low water content layer 44 can be achieved.

Note that the addition of the low water content ionomer to the cathode electrode 12 may be performed in place of the installation of the low water content layer 44, or may be performed together with the installation of the low water content layer 44. That is, the organic hydride production apparatus 2 only needs to include at least one of the low water content layer 44 and the low water content ionomer contained in the cathode electrode 12. When the organic hydride production apparatus 2 does not include the low water content layer 44, the electrolyte membrane 14 and the cathode electrode 12 are in contact with each other.

Furthermore, a water repellent layer (hydrophobic layer) may be provided between the low water content layer 44 and the cathode catalyst layer 12a. An example of such a water-repellent layer is a layer made of a material obtained by adding a water-repellent fluororesin such as FEP (a joint combination of tetrafluoroethylene and hexafluoropropylene) to Ketjenblack. The water-repellent layer can be formed by a known method such as applying a dispersion of the material to the surface of the catalyst layer 12a. Thereby, it is possible to make it easier for the hydride to reach the reaction field, and it is possible to improve Faraday efficiency.

Embodiments may be specified by the items described below.
[First item]
an anode electrode (10) that oxidizes water to generate protons;
a cathode electrode (12) that hydrogenates a hydride with protons to generate an organic hydride;
An electrolyte membrane (14) having an EW (Equivalent Weight) of less than 980, disposed between the anode electrode (10) and the cathode electrode (12), and transferring protons from the anode electrode (10) side to the cathode electrode (12) side. )and,
A low water content layer (44) having a lower water content than the electrolyte membrane (14) disposed between the electrolyte membrane (14) and the cathode electrode (12),
Organic hydride production equipment (2).
[Second item]
A high water content layer (46) having a higher water content than the electrolyte membrane (14) is arranged between the electrolyte membrane (14) and the anode electrode (10).
The organic hydride production apparatus (2) according to the first item.

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

(Example 1)
A polyfluorosulfonic acid-based cation exchange membrane (Aquivion (registered trademark) E87-05S, manufactured by Solvay) was prepared as an electrolyte membrane. The EW of this electrolyte membrane is 870, and the membrane thickness is 50 μm.

The water content of the electrolyte membrane was measured according to the following procedure. That is, an electrolyte membrane cut into 2 cm square pieces was dried in a dryer for 24 hours. After drying, the weight of the electrolyte membrane was measured. Subsequently, the dried electrolyte membrane was immersed in pure water for 1 hour. Thereafter, the water adhering to the surface of the electrolyte membrane was wiped off, and the weight of the water-impregnated electrolyte membrane was measured. The weight of water contained in the electrolyte membrane was obtained from the difference between the weight of the electrolyte membrane after drying and the weight of the electrolyte membrane containing water. Then, the water content (%) of the electrolyte membrane was calculated based on the following equation (2).
(2) Water content = (weight of water contained in electrolyte membrane/weight of electrolyte membrane in water-containing state) x 100

A polyfluorosulfonic acid-based cation exchange ionomer (Nafion (registered trademark) D2020CS, EW: 1100, manufactured by DuPont) was applied to one surface of the electrolyte membrane to form a low water content layer. The thickness of the low water content layer was 10 μm.

The water content of the low water content layer was measured using the following procedure. That is, the weight of a 12 cm square aluminum foil was measured, and the weight per 2 cm square of aluminum foil was calculated. This aluminum foil was spray coated with an ionomer, and a 10 μm thick low water content layer was laminated thereon. Aluminum foil with a low water content layer (hereinafter referred to as laminated aluminum foil) cut into 2 cm square pieces was dried in a dryer for 24 hours. After drying, the weight of the laminated aluminum foil was measured. Subsequently, the dried laminated aluminum foil was immersed in pure water for 1 hour. Thereafter, the moisture adhering to the surface of the laminated aluminum foil was wiped off, and the weight of the laminated aluminum foil with the low water content layer soaked with water was measured. The weight of water contained in the low water content layer was obtained from the difference between the weight of the laminated aluminum foil after drying and the weight of the laminated aluminum foil soaked with water. Furthermore, the weight of the low water content layer in a water-containing state was obtained from the difference between the weight of the laminated aluminum foil impregnated with water and the weight per 2 cm square of aluminum foil. Then, the water content (%) of the low water content layer was calculated based on the following equation (3).
(3) Moisture content = (weight of water contained in low water content layer/weight of low water content layer in water content state) x 100

PtRu/C catalyst (TEC61E54, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.), polyfluorosulfonic acid-based cation exchange ionomer (Nafion (registered trademark) D2020CS, EW: 1100, manufactured by DuPont), pure water, 1-propanol (manufactured by Wako) ) to prepare a cathode catalyst ink. The catalyst loading density of the catalyst ink was 1 mg/cm ² and the ionomer/carbon ratio (I/C) was 0.5. The prepared cathode catalyst ink was applied to the surface of the low water content layer to form a cathode catalyst layer.

As an anode electrode, a DSE (Dimensional Stable Electrode) electrode (manufactured by De Nora Permelec) having a Ti substrate coated with IrO ₂ was prepared. This DSE electrode was then laminated on the other surface of the electrolyte membrane. As a result, an electrolytic cell (organic hydride production apparatus) according to Example 1 was obtained.

Toluene as a catholyte was passed through the cathode of the obtained organic hydride manufacturing apparatus at a flow rate of 20 mL/min. Further, a 1 mol/L sulfuric acid aqueous solution as an anode solution was passed through the anode side at a flow rate of 60 mL/min. Then, constant current electrolysis was performed at a temperature of 60° C. and a current density of 1 A/cm ² . In addition, the voltage during constant current electrolysis was measured. Then, the amount of change in voltage with respect to the voltage in Comparative Example 2, which will be described later, was calculated. Furthermore, Faraday efficiency (F efficiency) was calculated from the amount of electricity consumed in constant current electrolysis and the amount of organic hydride produced. Then, the improvement rate (%) of Faraday efficiency with respect to the Faraday efficiency in Comparative Example 2, which will be described later, was calculated based on the following equation (4).
(4) Improvement rate = [1-(100-F efficiency of Example)/(100-F efficiency of Comparative Example 2)]×100

(Example 2)
In the same manner as in Example 1, except that instead of applying the ionomer, a thin film of the ionomer was pressed onto the electrolyte membrane to form a low water content layer, electrolytic cell production, constant current electrolysis, and voltage change and improvement rate were carried out. The calculation was carried out.

(Example 3)
Example 1 except that Fumion (registered trademark) FSLA-1020 (EW: 960-1000, manufactured by Fumatec) was used instead of Nafion (registered trademark) D2020CS as the polyfluorosulfonic acid-based cation exchange ionomer. Similarly, an electrolytic cell was fabricated, constant current electrolysis was performed, and the amount of voltage change and improvement rate were calculated.

(Example 4)
Fabrication of an electrolytic cell, constant current electrolysis, and calculation of voltage change and improvement rate were carried out in the same manner as in Example 1 except that a high water content layer was provided between the electrolyte membrane and the anode electrode. The high water content layer was formed by applying a polyfluorosulfonic acid-based cation exchange ionomer (Fumion (registered trademark) FSLA-710, EW: 710-740, manufactured by Fumatec) to the other surface of the electrolyte membrane. The thickness of the high water content layer was 10 μm. In addition, the water content of the high water content layer was measured using the same procedure as for the low water content layer.

(Example 5)
In the same manner as in Example 1 except that a water-repellent layer was provided between the low water content layer and the cathode catalyst layer, an electrolytic cell was prepared, constant current electrolysis was performed, and the voltage change amount and improvement rate were calculated. The water-repellent layer is Nafion (made by Lion Corporation) containing FEP (120-JRB, made by Mitsui Chemours Fluoro Products Co., Ltd.) and Ketjen black (EC600JD, made by Lion Corporation) on the surface of the low water content layer facing away from the electrolyte membrane. (registered trademark) by applying a dispersion liquid. The thickness of the water-repellent layer was 10 μm, and I/C was 0.5.

(Comparative example 1)
An electrolytic cell was prepared in the same manner as in Example 1, except that Aquivion (registered trademark) E98-05S was used instead of Aquivion (registered trademark) E87-05S as the electrolyte membrane, and the low water content layer was not provided. The fabrication, constant current electrolysis, and calculation of the improvement rate were carried out. The EW of this electrolyte membrane is 980.

(Comparative example 2)
Production of an electrolytic cell, constant current electrolysis, and calculation of voltage and Faraday efficiency were carried out in the same manner as in Example 1 except that the low water content layer was not provided.

FIG. 3 is a diagram showing the characteristics of the electrolytic cells according to each example and each comparative example, the improvement rate of Faraday efficiency, and the amount of change in voltage. As shown in FIG. 3, compared to Comparative Example 2 in which the electrolyte membrane has an EW of less than 980 but does not have a low water content layer, in Example 1-5, the electrolyte membrane has an EW of less than 980 and has a low water content layer. , the Faraday efficiency was improved by more than 20%. Furthermore, the improvement rate was higher than that of Comparative Example 1 in which the EW of the electrolyte membrane was 980. Further, in Example 5 having a water-repellent layer, the Faraday efficiency was improved more than in Examples 1-4 not having a water-repellent layer. Furthermore, in Example 1-5, the increase in voltage compared to Comparative Example 2 could be suppressed to 25 mV or less. In Example 4 having a high water content layer, the voltage could be further reduced.

From the above, by using an electrolyte membrane with an EW of less than 980 and providing a low water content layer between the electrolyte membrane and the cathode electrode, it is possible to both suppress the increase in cell voltage and suppress the decrease in Faraday efficiency in organic hydride production. It was confirmed that it is possible to It was also confirmed that the cell voltage could be further reduced by providing a high water content layer between the electrolyte membrane and the anode electrode. Furthermore, it was confirmed that Faraday efficiency could be further improved by providing a water repellent layer between the low water content layer and the cathode electrode.

The present invention can be utilized in an organic hydride manufacturing device.

2. Organic hydride production equipment, 10. Anode electrode, 12. Cathode electrode, 14. Electrolyte membrane, 44. Low water content layer, 46. High water content layer.

Claims

an anode electrode that oxidizes water to generate protons;
a cathode electrode that generates an organic hydride by hydrogenating a hydride with the proton;
an electrolyte membrane having an EW (Equivalent Weight) of less than 980, disposed between the anode electrode and the cathode electrode, and transferring the protons from the anode electrode side to the cathode electrode side;
a low water content layer having a lower water content than the electrolyte membrane and disposed between the electrolyte membrane and the cathode electrode;
Organic hydride production equipment.
comprising a high water content layer having a higher water content than the electrolyte membrane and disposed between the electrolyte membrane and the anode electrode;
The organic hydride production apparatus according to claim 1.