Control device for organic compound production system, control method for organic compound production system, and organic compound production system

Abstract

The present invention aims to improve the production rate of organic hydrides while suppressing a decrease in the Faraday efficiency of an organic hydride production system. [Solution] The organic hydride production system 1 comprises an electrolytic cell 2 having a cathode chamber 18, a cathode fluid supply device 8 capable of supplying any cathode fluid selected from a plurality of cathode fluids having different concentrations of the substance to be hydrided to the cathode chamber 18, and a control device 10 that controls the cathode fluid supply device 8 to supply to the cathode chamber 18 a cathode fluid having a specific concentration of the substance to be hydrided that is determined according to the magnitude of the current flowing through the electrolytic cell 2.

Description

[Technical Field]

[0001] The present invention relates to an organic hydride production system, a control device for the organic hydride production system, and a control method for the organic hydride production system. [Background technology]

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

[0003] Regarding organic hydride production technology, a conventional organic hydride production system is known that includes an electrolytic cell having an oxidizing electrode that generates protons from water and a reducing electrode that hydrogenates an organic compound having an unsaturated bond (substance to be hydrogenated) (see, for example, Patent Document 1). In this organic hydride production system, water is supplied to the oxidizing electrode, and the substance to be hydrogenated is supplied to the reducing electrode while a current is passed between the oxidizing electrode and the reducing electrode, whereby hydrogen is added to the substance to be hydrogenated, thereby obtaining an organic hydride. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2012 / 091128 Summary of the Invention [Problem to be solved by the invention]

[0005] As a result of extensive research into the above-mentioned organic hydride production technology, the present inventors have come to realize that with conventional technology, increasing the production rate of organic hydrides can result in a decrease in the Faraday efficiency.

[0006] The present invention has been made in view of these circumstances, and one of its objectives is to provide a technology for improving the production rate of organic hydrides while suppressing a decrease in the Faraday efficiency of an organic hydride production system. [Means for solving the problem]

[0007] One aspect of the present invention is an organic hydride production system that includes an electrolytic cell having a cathode chamber that houses a cathode electrode that hydrogenates a substance to be hydrided in a cathode solution with protons to produce an organic hydride, a cathode solution supply device that can supply to the cathode chamber any cathode solution selected from a plurality of cathode solutions having different concentrations of the substance to be hydrided, and a control device that controls the cathode solution supply device to supply to the cathode chamber a cathode solution having a specific concentration of the substance to be hydrided that is determined according to the magnitude of the current flowing through the electrolytic cell.

[0008] Another aspect of the present invention is a control device for an organic hydride production system including an electrolytic cell and a cathode solution supply device. The electrolytic cell has a cathode chamber that houses a cathode electrode that hydrogenates a substance to be hydrided in the cathode solution with protons to produce an organic hydride. The cathode solution supply device is capable of supplying to the cathode chamber any cathode solution selected from a plurality of cathode solutions having different concentrations of the substance to be hydrided. The control device controls the cathode solution supply device to supply to the cathode chamber a cathode solution having a specific concentration of the substance to be hydrided that is determined according to the magnitude of the current flowing through the electrolytic cell.

[0009] Another aspect of the present invention is a method for controlling an organic hydride production system including an electrolytic cell having a cathode chamber containing a cathode electrode for hydrogenating a substance to be hydrided in a cathode solution with protons to produce an organic hydride, the method comprising supplying, to the cathode chamber, a cathode solution having a specific concentration of the substance to be hydrided determined according to the magnitude of a current flowing through the electrolytic cell.

[0010] Any combination of the above components, and conversion of the expression of the present disclosure into a method, device, system, etc., are also valid aspects of the present disclosure. [Effects of the Invention]

[0011] According to the present invention, it is possible to improve the production rate of organic hydrides while suppressing a decrease in the Faraday efficiency of an organic hydride production system. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of an organic hydride manufacturing system according to a first embodiment. [Figure 2] FIG. 1 is a graph showing the relationship between the current density of an electrolytic cell and the toluene concentration at which hydrogen gas is generated. [Figure 3] FIG. 1 is a diagram showing the IV characteristics of an electrolytic cell. [Figure 4] FIG. 10 is a graph showing the relationship between toluene concentration and cell voltage. [Figure 5] 10 is a flowchart showing an example of selection control of a storage unit. [Figure 6] FIG. 10 is a schematic diagram of an organic hydride manufacturing system according to a second embodiment. [Figure 7] FIG. 1 is a schematic diagram of an organic hydride manufacturing system according to a first modified example. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described below based on preferred embodiments with reference to the drawings. The embodiments are illustrative and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention. Identical or equivalent components, parts, and processes shown in each drawing are designated by the same reference numerals, and redundant description will be omitted where appropriate. The scale and shape of each part shown in each drawing are set for convenience to facilitate explanation and should not be interpreted as limiting unless otherwise specified. Furthermore, when terms such as "first" and "second" are used in this specification or claims, these terms do not indicate any order or importance, but are intended to distinguish one configuration from another. Furthermore, some components that are not important for explaining the embodiments are omitted from each drawing.

[0014] (Embodiment 1) 1 is a schematic diagram of an organic hydride production system 1 according to Embodiment 1. The organic hydride production system 1 mainly comprises an electrolytic cell 2, a power supply 4, an anolyte supply device 6, a catholyte supply device 8, and a control device 10.

[0015] The electrolytic cell 2 hydrogenates the material to be hydrogenated, which is a dehydrogenated form of an organic hydride, by an electrochemical reduction reaction to produce the organic hydride. The electrolytic cell 2 has an anode electrode 12, a cathode electrode 14, an anode chamber 16, a cathode chamber 18, and a diaphragm 20.

[0016] The anode electrode 12 (anode) oxidizes water in the anolyte to generate protons. The anode electrode 12 contains an anode catalyst, such as iridium (Ir), ruthenium (Ru), or platinum (Pt), or an oxide of these metals. The anode catalyst may be dispersed and supported on or coated on an electronically conductive substrate. The substrate may be made of a material primarily composed of a metal, such as titanium (Ti) or stainless steel (SUS). Examples of the substrate form include woven or nonwoven sheets, mesh, porous sintered bodies, foamed molded bodies, and expanded metals. The anode catalyst may also be applied directly to the diaphragm 20.

[0017] The cathode electrode 14 (negative electrode) hydrogenates the substance to be hydrogenated in the cathode solution with protons to produce an organic hydride. The cathode electrode 14 of this embodiment has a catalyst layer 14a and a diffusion layer 14b. The catalyst layer 14a is disposed closer to the membrane 20 than the diffusion layer 14b. The catalyst layer 14a of this embodiment is in contact with the main surface of the membrane 20. The catalyst layer 14a contains, for example, platinum or ruthenium as a cathode catalyst that hydrogenates the substance to be hydrogenated. Preferably, the catalyst layer 14a also contains a porous catalyst carrier that supports the cathode catalyst. The catalyst carrier is made of an electron-conductive material such as porous carbon, porous metal, or porous metal oxide. For example, the catalyst layer 14a is formed by directly applying the cathode catalyst to the membrane 20.

[0018] The cathode catalyst is coated with an ionomer (cation exchange type ionomer). For example, a catalyst carrier supporting the cathode catalyst is coated with the ionomer. Examples of the ionomer include perfluorosulfonic acid polymers such as Nafion (registered trademark) and Flemion (registered trademark). It is preferable that the ionomer partially coats the cathode catalyst. This allows the three elements (substances to be hydrogenated, protons, and electrons) required for the electrochemical reaction in the catalyst layer 14a to be efficiently supplied to the reaction field.

[0019] The diffusion layer 14b uniformly diffuses the liquid material to be hydrogenated, which is supplied from the outside, into the catalyst layer 14a. The organic hydride produced in the catalyst layer 14a is discharged to the outside of the catalyst layer 14a through the diffusion layer 14b. The diffusion layer 14b in this embodiment is in contact with the main surface of the catalyst layer 14a opposite the diaphragm 20. The diffusion layer 14b is made of a conductive material such as carbon or metal. The diffusion layer 14b is a porous body such as a sintered body of fibers or particles, or a foam molded body. Specific examples of materials that can be used to form the diffusion layer 14b include woven carbon fabric (carbon cloth), nonwoven carbon fabric, and carbon paper.

[0020] The anode electrode 12 is housed in the anode chamber 16. The anode chamber 16 is defined by, for example, a diaphragm 20, an end plate 22a, and a spacer 24a. The end plate 22a is a plate made of a metal such as stainless steel or titanium, and is installed on the opposite side of the anode electrode 12 from the diaphragm 20. As an example, the end plate 22a has a groove-shaped flow path on its main surface facing the anode electrode 12. The anolyte supplied to the anode chamber 16 passes through this flow path to the anode electrode 12 and is then discharged from the anode chamber 16 through this flow path. The spacer 24a is a frame-shaped sealing material disposed between the diaphragm 20 and the end plate 22a. The space in the anode chamber 16 excluding the anode electrode 12 constitutes the flow path for the anolyte.

[0021] The end plate 22a is also provided with a first anode opening 26 and a second anode opening 28 that communicate between the inside and outside of the anode chamber 16. The first anode opening 26 is disposed lower than the second anode opening 28. In this embodiment, the first anode opening 26 is provided on the bottom surface of the anode chamber 16, and the second anode opening 28 is provided on the top surface of the anode chamber 16. The first anode opening 26 and the second anode opening 28 may or may not overlap when viewed vertically.

[0022] The cathode electrode 14 is housed in the cathode chamber 18. The cathode chamber 18 is defined by, for example, a diaphragm 20, an end plate 22b, and a spacer 24b. The end plate 22b is a plate made of a metal such as stainless steel or titanium, and is installed on the opposite side of the cathode electrode 14 from the diaphragm 20. As an example, the end plate 22b has a groove-shaped flow path on its main surface facing the cathode electrode 14. The catholyte supplied to the cathode chamber 18 passes through this flow path to the cathode electrode 14 and is discharged from the cathode chamber 18 through this flow path. The spacer 24b is a frame-shaped sealing material disposed between the diaphragm 20 and the end plate 22b. The space in the cathode chamber 18 excluding the cathode electrode 14 forms a flow path for the catholyte.

[0023] The end plate 22b is also provided with a first cathode opening 30 and a second cathode opening 32 that communicate between the inside and outside of the cathode chamber 18. The first cathode opening 30 is disposed lower than the second cathode opening 32. In this embodiment, the first cathode opening 30 is provided in the bottom surface of the cathode chamber 18, and the second cathode opening 32 is provided in the top surface of the cathode chamber 18. The first cathode opening 30 and the second cathode opening 32 may or may not overlap when viewed vertically.

[0024] The anode chamber 16 and the cathode chamber 18 are separated by a diaphragm 20. The diaphragm 20 is sandwiched between the anode electrode 12 and the cathode electrode 14. In this embodiment, the diaphragm 20 is made of a proton-conductive solid polymer electrolyte membrane, and allows protons to move from the anode chamber 16 to the cathode chamber 18. The solid polymer electrolyte membrane is not particularly limited as long as it is made of a proton-conductive material, and examples thereof include fluorine-based ion exchange membranes having sulfonic acid groups.

[0025] An anolyte is supplied to the anode chamber 16 by an anolyte supply device 6. The anolyte contains water to be supplied to the anode electrode 12. Examples of the anolyte include an aqueous sulfuric acid solution, an aqueous nitric acid solution, an aqueous hydrochloric acid solution, pure water, and ion-exchanged water.

[0026] A cathode fluid is supplied to the cathode chamber 18 by the cathode fluid supply device 8. The cathode fluid contains an organic hydride raw material (material to be hydrogenated) to be supplied to the cathode electrode 14. As an example, the cathode fluid does not contain any organic hydride before the organic hydride production system 1 starts operating, and after the start of operation, the cathode fluid is mixed with organic hydride produced by electrolysis, thereby becoming a mixed liquid of the material to be hydrogenated and the organic hydride. The material to be hydrogenated and the organic hydride are preferably liquids at 20°C and 1 atmosphere.

[0027] The material to be hydrogenated and the organic hydride used in this embodiment are not particularly limited as long as they are organic compounds that can add / desorb hydrogen by reversibly causing a hydrogenation reaction / dehydrogenation reaction. A wide range of materials to be hydrogenated and organic hydrides can be used, such as acetone-isopropanol systems, benzoquinone-hydroquinone systems, and aromatic hydrocarbon systems. Among these, aromatic hydrocarbon systems are preferred from the viewpoint of transportability during energy transportation.

[0028] The aromatic hydrocarbon compound used as the substance to be hydrogenated is a compound containing at least one aromatic ring. Examples of aromatic hydrocarbon compounds include benzene, alkylbenzene, naphthalene, alkylnaphthalene, anthracene, diphenylethane, etc. Alkylbenzenes include compounds in which 1 to 4 hydrogen atoms of the aromatic ring are substituted with a linear or branched alkyl group having 1 to 6 carbon atoms. Examples of such compounds include toluene, xylene, mesitylene, ethylbenzene, diethylbenzene, etc. Alkylnaphthalenes include compounds in which 1 to 4 hydrogen atoms of the aromatic ring are substituted with a linear or branched alkyl group having 1 to 6 carbon atoms. Examples of such compounds include methylnaphthalene, etc. These may be used alone or in combination.

[0029] The substance to be hydrogenated is preferably at least one of toluene and benzene. Nitrogen-containing heterocyclic aromatic compounds such as pyridine, pyrimidine, pyrazine, quinoline, isoquinoline, N-alkylpyrrole, N-alkylindole, and N-alkyldibenzopyrrole can also be used as the substance to be hydrogenated. Organic hydrides are the hydrogenated versions of the above-mentioned substances to be hydrogenated, and examples thereof include cyclohexane, methylcyclohexane, dimethylcyclohexane, and piperidine.

[0030] Although only one electrolytic cell 2 is shown in FIG. 1, the organic hydride production system 1 may have multiple electrolytic cells 2. In this case, the electrolytic cells 2 are aligned, for example, so that the anode chambers 16 and cathode chambers 18 are aligned in the same direction, and are stacked with a current-carrying plate sandwiched between adjacent electrolytic cells 2. This electrically connects the electrolytic cells 2 in series. The current-carrying plate is made of a conductive material such as metal. The electrolytic cells 2 may be connected in parallel, or a combination of series and parallel connections may be used.

[0031] The reaction that occurs in the electrolytic cell 2 when toluene (TL) is used as an example of the substance to be hydrogenated is as follows: When toluene is used as the substance to be hydrogenated, the resulting organic hydride is methylcyclohexane (MCH). <Electrode reaction at the anode electrode> 3H2O → 3 / 2O2 + 6H + +6e - <Electrode reaction at the cathode electrode> TL+6H + +6e - →MCH

[0032] That is, the electrode reaction at the anode electrode 12 and the electrode reaction at the cathode electrode 14 proceed in parallel. Protons produced by the electrolysis of water at the anode electrode 12 are supplied to the cathode electrode 14 via the diaphragm 20. Electrons produced by the electrolysis of water are supplied to the cathode electrode 14 via the end plate 22a, the external circuit, and the end plate 22b. The protons and electrons supplied to the cathode electrode 14 are used to hydrogenate toluene at the cathode electrode 14. As a result, methylcyclohexane is produced.

[0033] Therefore, according to the organic hydride producing system 1 of this embodiment, the electrolysis of water and the hydrogenation reaction of the material to be hydrogenated can be carried out in one step. This makes it possible to improve the efficiency of organic hydride production compared to conventional techniques that produce organic hydrides through a two-stage process consisting of a process of producing hydrogen by water electrolysis or the like and a process of chemically hydrogenating the material to be hydrogenated in a reactor of a plant or the like. Furthermore, since there is no need for a reactor for chemical hydrogenation or a high-pressure vessel for storing hydrogen produced by water electrolysis or the like, it is possible to significantly reduce equipment costs.

[0034] At the cathode electrode 14, in addition to the main reaction of hydrogenation of the material to be hydrogenated, the side reaction of hydrogen gas generation described below may occur. As the amount of material to be hydrogenated supplied to the catalyst layer 14a becomes insufficient, this side reaction becomes more likely to occur. <Possible side reactions at the cathode electrode> 2H + +2e - →H2

[0035] The power supply 4 is a DC power supply that supplies power to the electrolytic cell 2. When power is supplied from the power supply 4 to the electrolytic cell 2, a predetermined electrolysis voltage is applied between the anode electrode 12 and the cathode electrode 14 of the electrolytic cell 2, causing an electrolysis current to flow. The power supply 4 receives power from a power supply device 34 and supplies power to the electrolytic cell 2. The power supply device 34 can be configured as a power generation device that generates power using renewable energy, such as a wind power generation device or a solar power generation device. The power supply device 34 is not limited to a power generation device that uses renewable energy, and may be a system power supply, or a power storage device that stores power from a renewable energy power generation device or a system power supply. Alternatively, it may be a combination of two or more of these.

[0036] The anode fluid supply device 6 supplies the anode fluid to the anode chamber 16. The anode fluid supply device 6 has an anode fluid tank 36, a first anode pipe 38, a second anode pipe 40, and an anode pump 42. The anode pump 42 may be a known pump such as a gear pump or a cylinder pump. Note that the anode fluid supply device 6 may circulate the anode fluid using a fluid delivery device other than a pump.

[0037] The anolyte tank 36 stores the anolyte to be supplied to the anode chamber 16. The anolyte tank 36 is connected to the anode chamber 16 by a first anode pipe 38. One end of the first anode pipe 38 is connected to the anolyte tank 36, and the other end is connected to the first anode opening 26. An anode pump 42 is provided midway along the first anode pipe 38. The anolyte tank 36 is also connected to the anode chamber 16 by a second anode pipe 40. One end of the second anode pipe 40 is connected to the second anode opening 28, and the other end is connected to the anolyte tank 36.

[0038] The anode pump 42 drives the anode fluid in the anode fluid tank 36, causing it to flow through the first anode piping 38 and into the anode chamber 16 from the first anode opening 26. The anode fluid is supplied to the anode chamber 16 and used for an electrode reaction at the anode electrode 12. The anode fluid in the anode chamber 16 is returned to the anode fluid tank 36 via the second anode piping 40. Oxygen gas is generated by an electrode reaction at the anode electrode 12. As a result, oxygen gas is mixed into the anode fluid discharged from the anode chamber 16. The anode fluid tank 36 also functions as a gas-liquid separator, separating the oxygen gas in the anode fluid from the anode fluid and discharging it outside the system. A gas-liquid separation tank may be provided along the second anode piping 40.

[0039] The cathode fluid supplying device 8 supplies the cathode chamber 18 with a cathode fluid selected from a plurality of cathode fluids with different concentrations of the hydride to be added. The cathode fluid supplying device 8 of this embodiment includes a plurality of reservoirs 44, a first cathode pipe 46, a second cathode pipe 48, a cathode pump 50, and first on-off valves 52 to 10 on-off valves 70. The cathode pump 50 may be a known pump such as a gear pump or a cylinder pump. The cathode fluid supplying device 8 may also use a liquid delivery device other than a pump to circulate the cathode fluid. The first on-off valves 52 to 10 on-off valves 70 may be known valves such as solenoid valves or air-driven valves. The number of cathode fluids selected is not limited to one. When multiple cathode fluids are selected, they may be mixed in a line by a line blending method and supplied to the cathode chamber 18.

[0040] The multiple storage sections 44 individually store multiple cathode solutions with different concentrations of the substance to be hydrided (by concentration). The cathode solution supply device 8 of this embodiment has multiple storage sections 44, including an ultra-high concentration storage section 44a, a high concentration storage section 44b, a medium concentration storage section 44c, a low concentration storage section 44d, and an ultra-low concentration storage section 44e. The concentration of the substance to be hydrided in the cathode solution stored in each storage section 44 is highest in the ultra-high concentration storage section 44a, second highest in the high concentration storage section 44b, third highest in the medium concentration storage section 44c, fourth highest in the low concentration storage section 44d, and lowest in the ultra-low concentration storage section 44e. The concentration of the substance to be hydrided in each cathode solution is calculated from the ratio of the substance to be hydrided in the cathode solution to the organic hydride, which is the hydrogenated form of the substance to be hydrided. In the present embodiment, the number of the plurality of storage sections 44 is five, but this is not limiting. The number of the plurality of storage sections 44 may be two or more, or three or more. The upper limit of the number of the plurality of storage sections 44 is not particularly limited, but may be, for example, six or less, five or less, or four or less.

[0041] For example, in a preparation stage before the start of operation of the organic hydride production system 1, cathode fluid whose concentrations of the substances to be hydrided have been adjusted in advance is stored in the ultra-high concentration reservoir 44a to the ultra-low concentration reservoir 44e. As an example, the ultra-high concentration reservoir 44a stores a cathode fluid whose concentration of the substances to be hydrided is 100 mol %. The ultra-low concentration reservoir 44e stores a cathode fluid whose concentration of the substances to be hydrided is 5 mol %. The high concentration reservoir 44b, the medium concentration reservoir 44c, and the low concentration reservoir 44d store cathode fluids whose concentrations of the substances to be hydrided are 75 mol %, 50 mol %, and 25 mol %, respectively. A concentration of 5 mol % of the substances to be hydrided is an example of a target concentration that should ultimately be reached when the cathode fluid is electrolyzed in the electrolytic cell 2, but this value can be changed to any value from the perspective of the energy efficiency of the present system. The concentration of the substance to be hydrided in the catholyte stored in the ultra-low concentration reservoir 44e may be 0 mol %. The concentration of the substance to be hydrided in each catholyte can be set appropriately based on experiments or simulations.

[0042] In the present embodiment, each storage section 44 is configured by a tank that is independent of the other. However, this is not limiting, and for example, the inside of one tank may be partitioned into a plurality of spaces that are independent of the other, and each space may configure a storage section 44.

[0043] The plurality of storage sections 44 are connected to the cathode chamber 18 by a first cathode pipe 46. One end of the first cathode pipe 46 branches into a plurality of sections connected to the respective storage sections 44, and the other end is connected to the first cathode opening 30. In this embodiment, one end of the first cathode pipe 46 branches into five sections, namely, a first branch pipe 46a to a fifth branch pipe 46e. The first branch pipe 46a to the fifth branch pipe 46e are arranged in this order, with the first branch pipe 46a being disposed closest to the first cathode opening 30. The first branch pipe 46a is connected to the ultra-high concentration storage section 44a, the second branch pipe 46b to the high concentration storage section 44b, the third branch pipe 46c to the medium concentration storage section 44c, the fourth branch pipe 46d to the low concentration storage section 44d, and the fifth branch pipe 46e to the ultra-low concentration storage section 44e. The arrangement order of the ultra-high concentration reservoir 44a to the ultra-low concentration reservoir 44e is not particularly limited.

[0044] A cathode pump 50 is provided in the first cathode pipe 46 in a region closer to the first cathode opening 30 than the first branch pipe 46a. A first on-off valve 52 is provided in the first branch pipe 46a. A second on-off valve 54 is provided in the second branch pipe 46b. A third on-off valve 56 is provided in the third branch pipe 46c. A fourth on-off valve 58 is provided in the fourth branch pipe 46d. A fifth on-off valve 60 is provided in the fifth branch pipe 46e.

[0045] The plurality of reservoirs 44 are also connected to the cathode chamber 18 by a second cathode pipe 48. One end of the second cathode pipe 48 is connected to the second cathode opening 32, and the other end is branched into a plurality of pipes connected to the respective reservoirs 44. In this embodiment, the other end of the second cathode pipe 48 is branched into five pipes, namely, a sixth branch pipe 48a to a tenth branch pipe 48e. The sixth branch pipe 48a is connected to the ultra-high concentration reservoir 44a, the seventh branch pipe 48b is connected to the high concentration reservoir 44b, the eighth branch pipe 48c is connected to the medium concentration reservoir 44c, the ninth branch pipe 48d is connected to the low concentration reservoir 44d, and the tenth branch pipe 48e is connected to the ultra-low concentration reservoir 44e.

[0046] A sixth on-off valve 62 is provided in the sixth branch pipe 48a. A seventh on-off valve 64 is provided in the seventh branch pipe 48b. An eighth on-off valve 66 is provided in the eighth branch pipe 48c. A ninth on-off valve 68 is provided in the ninth branch pipe 48d. A tenth on-off valve 70 is provided in the tenth branch pipe 48e.

[0047] The cathode pump 50 drives the cathode fluid in each reservoir 44, causing it to flow through the first cathode piping 46 and into the cathode chamber 18 from the first cathode opening 30. Which reservoir 44 the cathode fluid is supplied to the cathode chamber 18 from can be switched depending on the open / close states of the first to fifth on-off valves 52 to 60. The cathode fluid is supplied to the cathode chamber 18 and is used for an electrode reaction at the cathode electrode 14. The cathode fluid in the cathode chamber 18 is returned to each reservoir 44 via the second cathode piping 48. Which reservoir 44 the cathode fluid is returned to can be switched depending on the open / close states of the sixth to tenth on-off valves 62 to 70.

[0048] As described above, hydrogen gas may be generated at the cathode electrode 14 due to a side reaction. When a side reaction occurs, hydrogen gas is mixed into the cathode fluid discharged from the cathode chamber 18. Each reservoir 44 also functions as a gas-liquid separator, separating the hydrogen gas in the cathode fluid from the cathode fluid and discharging it to the outside of the system. A gas-liquid separation tank may be provided midway along the second cathode piping 48. When protons move from the anode chamber 16 side to the cathode chamber 18 side through the diaphragm 20, they move along with water molecules. Therefore, water is mixed into the cathode fluid discharged from the cathode chamber 18. To address this, an oil-water separation tank may be provided midway along the second cathode piping 48 to separate the water in the cathode fluid from the cathode fluid.

[0049] The organic hydride producing system 1 also has a concentration sensor 72 that detects the concentration of the substance to be hydrided in the cathode fluid stored in each storage section 44. The concentration sensor 72 can be configured with a known sensor, and its installation location can be appropriately selected depending on the detection method of the sensor, etc. For example, the concentration sensor 72 can be configured with an analytical instrument such as a gas chromatograph installed in each storage section 44 or each branch pipe (in-line measurement). Furthermore, for example, the concentration sensor 72 may detect the concentration of the substance to be hydrided in the cathode fluid in each storage section 44 based on the color of the cathode fluid to which a pigment (e.g., a transition metal compound such as FeCl3) that becomes colored by coexistence with the aromatic ring of the substance to be hydrided has been added. The concentration sensor 72 repeatedly transmits a signal indicating the detection result to the control device 10.

[0050] In the present embodiment, a portion of the piping connecting each storage section 44 and the cathode chamber 18 is shared. That is, one end of the first cathode piping 46 branches and is connected to each storage section 44. The other end of the second cathode piping 48 branches and is connected to each storage section 44. However, this configuration is not limiting, and the piping connecting each storage section 44 and the cathode chamber 18 may be independent for each storage section 44.

[0051] The control device 10 controls the supply of power from the power source 4 to the electrolytic cell 2. The potentials of the anode electrode 12 and the cathode electrode 14 are controlled by the control device 10. The control device 10 is realized as a hardware configuration by elements and circuits such as a computer CPU and memory, and as a software configuration by a computer program, etc., but in Figure 1 it is depicted as a functional block realized by the cooperation of these. It will be obvious to those skilled in the art that these functional blocks can be realized in various ways by combining hardware and software.

[0052] At least one of a signal indicating the voltage of the electrolytic cell 2, a signal indicating the potential of the anode electrode 12, and a signal indicating the potential of the cathode electrode 14 is input to the control device 10 from a detection unit 74 provided in the electrolytic cell 2. The detection unit 74 can detect the potential of each electrode and the voltage of the electrolytic cell 2 using a known method. The detection unit 74 has, for example, a known voltmeter.

[0053] When the detection unit 74 detects the potential of the anode electrode 12 or the cathode electrode 14, a reference electrode is provided on the diaphragm 20. The reference electrode is maintained at a reference electrode potential. For example, the reference electrode is a reversible hydrogen electrode (RHE). One terminal of the detection unit 74 is connected to the reference electrode, and the other terminal is connected to the electrode to be detected, thereby detecting the potential of the electrode relative to the reference electrode. When the detection unit 74 detects the voltage of the electrolytic cell 2, one terminal of the detection unit 74 is connected to the anode electrode 12, and the other terminal is connected to the cathode electrode 14, thereby detecting the potential difference between the two electrodes, i.e., the voltage. The detection unit 74 transmits a signal indicating the detection result to the control device 10.

[0054] The detection unit 74 also includes a current detection unit that detects the current flowing between the anode electrode 12 and the cathode electrode 14. The current detection unit is configured, for example, with a known ammeter. The current value detected by the current detection unit is input to the control device 10. The control device 10 may previously store information on the current-voltage characteristics (IV characteristics) of the electrolytic cell 2. If the control device 10 stores information on the IV characteristics, this information may be updateable as desired. The IV characteristics of the electrolytic cell 2 are determined by the catalyst composition of each electrode, the type of diffusion layer and substrate, the type of diaphragm 20, the flow path structure of the anolyte and catholyte in the electrolytic cell 2, the dimensions of each component, and other factors, and can be measured and determined in advance. In this case, the control device 10 receives a signal indicating the amount of power supplied from the power supply device 34 to determine the amount of power that can be supplied to the electrolytic cell 2 from the power source 4, and calculates the voltage to be applied to the electrolytic cell 2 from the IV characteristics, i.e., controls the value of the current flowing through the electrolytic cell 2.

[0055] The controller 10 also controls the anode fluid supply device 6 and the cathode fluid supply device 8. Specifically, the controller 10 controls the driving of the anode pump 42 and the cathode pump 50. The controller 10 also controls the opening and closing of the first on-off valve 52 to the tenth on-off valve 70.

[0056] In the organic hydride production system 1, one possible approach to increasing the production rate of organic hydride is to apply a high voltage to the electrolytic cell 2 to increase the current (e.g., current density) flowing through the electrolytic cell 2. However, increasing the current density of the electrolytic cell 2 leads to a shortage of the substance to be hydrided, making side reactions more likely to occur. The occurrence of side reactions leads to a decrease in the faradaic efficiency of the organic hydride production system 1, so it is desirable to avoid them as much as possible.

[0057] With the cathode and anode fluids supplied to the electrodes at given flow rates, whether or not a side reaction occurs when the current density in the electrolytic cell 2 is at a certain value depends on the concentration of the substance to be hydrided in the cathode fluid. Therefore, by adjusting the current density in the electrolytic cell 2 according to the concentration of the substance to be hydrided in the cathode fluid, it is possible to improve the production rate of organic hydride while suppressing a decrease in the faradaic efficiency. However, the timing of a request to increase or decrease the current density does not necessarily coincide with a change in the amount of power that can be supplied from the power source 4 to the electrolytic cell 2.

[0058] For example, if the power supply device 34 is a power generation device that generates power using renewable energy, the amount of power generated will vary significantly depending on weather conditions. For example, in the case of a solar power generation device, the amount of power generated will decrease on cloudy days or after sunset. This can lead to situations where the amount of power supplied from the power supply device 34 is insufficient when it is desired to increase the current density in the electrolytic cell 2. Furthermore, even if the amount of power supplied from the power supply device 34 is sufficient, it can also lead to situations where the current density in the electrolytic cell 2 cannot be increased because the concentration of the substance to be hydrided in the cathode fluid is low. This makes it difficult to achieve an efficient electrolysis reaction that corresponds to the concentration of the substance to be hydrided in the cathode fluid.

[0059] In contrast, the cathode fluid supply device 8 according to the present embodiment has multiple reservoirs 44, namely, ultra-high concentration reservoir 44a to ultra-low concentration reservoir 44e, as described above. The cathode fluid supply device 8 can supply any one of multiple cathode fluids having different concentrations of the substance to be hydrided to the cathode chamber 18. In other words, the concentration of the substance to be hydrided in the cathode fluid to be supplied to the cathode chamber 18 can be switched. The control device 10 controls the cathode fluid supply device 8 so as to supply the cathode chamber 18 with a cathode fluid having a specific concentration of the substance to be hydrided.

[0060] The specific concentration of the substance to be hydrided is determined according to the magnitude of the current flowing through the electrolytic cell 2. That is, a lower limit of the concentration of the substance to be hydrided is determined based on the magnitude of the current flowing through the electrolytic cell 2, and the specific concentration of the substance to be hydrided is determined based on this lower limit. In a first example, the specific concentration of the substance to be hydrided is determined based on the lower limit and the concentration of the substance to be hydrided in each cathode fluid stored in each reservoir 44 at the time the specific concentration of the substance to be hydrided is set. In a second example, the specific concentration of the substance to be hydrided is determined by calculation based on the lower limit and a predetermined margin. In this embodiment, the first example will be described. The second example will be described in the second embodiment, which will be described later. Instead of adjusting the current density of the electrolytic cell 2 according to the concentration of the substance to be hydrided in the cathode fluid supplied to the cathode chamber 18, by selecting the concentration of the substance to be hydrided in the cathode fluid supplied to the cathode chamber 18 according to the current density of the electrolytic cell 2, the production rate of organic hydride can be increased while suppressing a decrease in the faradaic efficiency.

[0061] In the first example described above, the specific concentration of the substance to be hydrided is set by the control device 10. The control device 10 first determines the lower limit of the concentration of the substance to be hydrided in the catholyte to be supplied to the cathode chamber 18 based on the magnitude of the current flowing through the electrolytic cell 2, for example, the magnitude of the current density. The current density of the electrolytic cell 2 can be determined based on a signal received from the detection unit 74. Furthermore, the control device 10 can calculate the voltage value to be applied to the electrolytic cell 2 by storing information on the IV characteristics in advance as described above and receiving signals indicating the amount of power supply from the power source 4 or the power supply device 34. When the power supply device 34 is a combination of at least two of a renewable energy power generation device, a grid power source, and a power storage device, the amount of power supply is the total amount of power supplied from the combination.

[0062] The lower limit of the concentration of the substance to be hydrided is, for example, the concentration of the substance to be hydrided at which hydrogen gas is generated (or begins to be generated). The relationship between the current density of the electrolytic cell 2 and the concentration of the substance to be hydrided at which hydrogen gas is generated is determined depending on the catalyst composition of each electrode, the type of diffusion layer and substrate, the type of diaphragm 20, the flow path structure of the anolyte and catholyte in the electrolytic cell 2, the dimensions of each part, and the like, and can be determined by measuring in advance. In the measurement, the start of hydrogen gas generation can be confirmed, for example, visually or by automatic detection using an optical analysis device that utilizes the difference in refractive index between liquid and gas.

[0063] Furthermore, the control device 10 of this embodiment determines the lower limit of the concentration of the substance to be hydrided based on the amount of decrease in the concentration of the substance to be hydrided in the cathode chamber 18, in addition to the magnitude of the current density in the electrolytic cell 2. For example, the control device 10 sets the lower limit of the concentration of the substance to be hydrided, which is determined based on the magnitude of the current density in the electrolytic cell 2, as a provisional lower limit, and determines the true lower limit by adding the amount of decrease in the concentration of the substance to be hydrided in the cathode chamber 18 to the provisional lower limit.

[0064] The catholyte that flows into the cathode chamber 18 is subjected to an electrolytic reaction at the cathode electrode 14. As a result, the concentration of the substance to be hydrided in the catholyte gradually decreases within the cathode chamber 18. By determining the lower limit of the substance to be hydrided concentration taking into account the amount of decrease in the concentration of the substance to be hydrided within the cathode chamber 18, the possibility of a side reaction occurring due to a shortage of substance to be hydrided can be further reduced. This decrease in the concentration of the substance to be hydrided is theoretically greatest when comparing the inlet (first cathode opening 30) and outlet (second cathode opening 32) of the cathode chamber 18. For this reason, it is preferable to use the difference in the concentration of the substance to be hydrided between the inlet and outlet of the cathode chamber 18 as the amount of decrease in the concentration of the substance to be hydrided in the cathode chamber 18.

[0065] The flow rate of the cathode fluid is determined according to the cathode pump 50. The volume of the cathode chamber 18 is also predetermined. The conversion rate of the substance to be hydrided to organic hydride when the cathode fluid is flowed at a predetermined flow rate can be calculated based on the amount of power supplied to the electrolytic cell 2. Therefore, the control device 10 can calculate the amount of decrease in the concentration of the substance to be hydrided in the cathode chamber 18 based on the amount of power supplied to the electrolytic cell 2 when selecting the reservoir 44. The lower limit may be set based only on the magnitude of the current density in the electrolytic cell 2, without taking into account the amount of decrease in the concentration of the substance to be hydrided in the cathode chamber 18. In this case, the process of setting the lower limit can be simplified.

[0066] The control device 10 then selects a storage unit 44 that stores a cathode solution having a specific concentration of the substance to be hydrided from among the storage units 44 that store a cathode solution having a concentration of the substance to be hydrided that is equal to or higher than a set lower limit. The control device 10 can determine the concentration of the substance to be hydrided in each storage unit 44 by receiving a signal from the concentration sensor 72. Note that, in a state in which no side reactions are occurring, the control device 10 can calculate the amount of organic hydride produced from the cathode solution stored in each storage unit 44 based on the amount of cathode solution filled in each storage unit 44, the amount of cathode solution supplied from each storage unit 44 to the cathode chamber 18, and the total amount of power supplied to the electrolytic cell 2 while the cathode solution was being supplied, and can then use the result to calculate the concentration of the substance to be hydrided in the cathode solution stored in each storage unit 44. In this case, the concentration sensor 72 can be omitted. The amount of cathode fluid supplied from each reservoir 44 to the cathode chamber 18 can be calculated from the state of each open / close valve and the driving time of the cathode pump 50.

[0067] If a side reaction occurs, it becomes difficult to accurately calculate the decrease in the concentration of the substance to be hydrided in the cathode chamber 18. In consideration of such a case, it is preferable to provide a concentration sensor in the second cathode pipe 48 near the outlet of the cathode chamber 18. This allows the concentration sensors 72 provided in each reservoir 44 to be consolidated into the concentration sensor located near the outlet of the cathode chamber 18.

[0068] The control device 10 selects the storage unit 44 storing the cathode solution having a concentration of the substance to be hydrided that is equal to or greater than the lower limit as the storage unit 44 storing the cathode solution having the specific concentration of the substance to be hydrided. As an example, the control device 10 of the present embodiment selects the storage unit 44 storing the cathode solution having a concentration of the substance to be hydrided that is equal to or greater than the lower limit and closest to the lower limit as the storage unit 44 storing the cathode solution having the specific concentration of the substance to be hydrided. This makes it easier to maintain the concentration of the substance to be hydrided in the ultra-high concentration storage unit 44a or the high concentration storage unit 44b at a high concentration. Therefore, even if the lower limit fluctuates, the state in which the cathode solution having a concentration of the substance to be hydrided that is equal to or greater than the lower limit can be maintained for a longer period of time.

[0069] In this embodiment, the control device 10 controls the catholyte supply device 8 to supply the catholyte from a reservoir 44 that stores a catholyte having a specific concentration of the substance to be hydrided to the cathode chamber 18. That is, the control device 10 controls each on-off valve to form a flow path connecting the selected reservoir 44 and the cathode chamber 18, and drives the cathode pump 50. If a reservoir 44 that meets the selection criteria for the reservoir 44 is found, the control device 10 controls the catholyte supply device 8 to supply the catholyte from that reservoir 44. If there is no reservoir 44 that stores a catholyte whose concentration of the substance to be hydrided is equal to or higher than the lower limit, the control device 10 controls the catholyte supply device 8 to supply the catholyte from, for example, the reservoir 44 that stores the catholyte with the highest concentration of the substance to be hydrided. In this case, the control device 10 controls the power source 4 to achieve a current density that does not cause hydrogen gas generation at the concentration of the substance to be hydrided in the supplied catholyte.

[0070] In the first example, a margin may be added to the lower limit value, as in the second example described below. That is, the control device 10 may add a predetermined margin to a lower limit value based solely on the magnitude of the current flowing through the electrolytic cell 2, or to a lower limit value determined based on the magnitude of the current and the amount of concentration decrease in the cathode chamber 18, and determine the specific concentration of the substance to be hydrided based on the resulting concentration of the substance to be hydrided. The predetermined margin can be set as appropriate based on experiments or simulations.

[0071] For example, when the specific concentration of the substance to be hydrided is 100 mol%, the control device 10 opens the first on-off valve 52 and closes the second on-off valve 54 to the fifth on-off valve 60, and drives the cathode pump 50. As a result, the cathode fluid stored in the ultra-high concentration reservoir 44a and having a concentration of the substance to be hydrided of 100 mol% is supplied to the cathode chamber 18. The control device 10 also opens the sixth on-off valve 62 and closes the seventh on-off valve 64 to the tenth on-off valve 70, and returns the cathode fluid discharged from the cathode chamber 18 to the ultra-high concentration reservoir 44a, which is the supply source. As a result, it is possible to prevent the amount of cathode fluid in each reservoir 44 from being uneven.

[0072] It is possible to appropriately determine to which reservoir 44 the cathode fluid discharged from the cathode chamber 18 is returned. For example, to avoid a decrease in the concentration of the substance to be hydrided in the cathode fluid stored in the ultra-high concentration reservoir 44a, the cathode fluid can be supplied from the ultra-high concentration reservoir 44a to the cathode chamber 18 and returned to a reservoir 44 other than the ultra-high concentration reservoir 44a. In this case, if the concentration of the substance to be hydrided in the cathode fluid in the reservoir 44 to which the cathode fluid is returned is lower than the concentration of the substance to be hydrided in the cathode fluid at the cathode chamber outlet, this operation can increase the concentration of the substance to be hydrided in the cathode fluid in that reservoir 44. However, if the reservoir 44 that supplies the cathode fluid to the cathode electrode 14 and the reservoir 44 that returns the cathode fluid from the cathode chamber 18 are different, the amount of cathode fluid stored in each reservoir 44 will be uneven. For this reason, it is preferable that each reservoir 44 is provided with a known volume detector or mass detector, such as a liquid level gauge, to grasp the amount of catholyte.

[0073] The control device 10 repeats, at a predetermined timing, setting the lower limit value of the concentration of the substance to be hydrogenated and selecting the storage unit 44. For example, the control device 10 repeats setting the lower limit value of the concentration of the substance to be hydrogenated and selecting the storage unit 44 at a predetermined time period. The execution timing of setting the lower limit value and selecting the storage unit can be set appropriately based on experiments or simulations.

[0074] In this embodiment, the ultra-high concentration reservoir 44a to the ultra-low concentration reservoir 44e are prepared in advance. Therefore, at the time of starting operation of the organic hydride production system 1, a state is established in which any catholyte selected from a plurality of catholytes having different concentrations of the substance to be hydrided can be supplied to the cathode chamber 18. However, this configuration is not limited thereto. For example, the priority of use of each reservoir 44 may be set in advance, and catholyte having the same concentration of the substance to be hydrided may be stored in all reservoirs 44 before starting operation of the organic hydride production system 1. In this case, as operation time passes, the concentration of the substance to be hydrided in the catholyte begins to vary among the reservoirs 44. As a result, a state is established in which any catholyte selected from a plurality of catholytes having different concentrations of the substance to be hydrided can be supplied to the cathode chamber 18.

[0075] The inventors have verified the effects obtained by the above-described control based on the following tests. The tests described below are merely examples and do not limit the present invention in any way.

[0076] (Test 1: Evaluation of the relationship between current density and the concentration of hydride species that generates hydrogen) First, an anode electrode made of iridium oxide (IrO2) (geometric area 100 cm2) was 2 ), an anode chamber (volume 40 mL), and a cathode electrode (geometric area 100 cm) consisting of platinum-ruthenium-supported carbon (Pt Ru / C). 2 An electrolytic cell was prepared which was equipped with a cathode chamber (volume 10 mL), a separator made of Nafion (registered trademark) N117 (manufactured by DuPont), and a reference electrode (standard hydrogen electrode) inserted in the cathode chamber.

[0077] Using this electrolytic cell, 0.2 A / cm 2 Constant-current electrolysis (preliminary run) was carried out for 10 minutes at a current density of 0.01%. The entire electrolytic cell was maintained at 60°C during electrolysis. A 1M aqueous sulfuric acid solution was passed through the anode chamber at a flow rate of 20 mL / min. The cathode chamber was passed through the reservoir at a flow rate of 20 mL / min. The cathode solution was 0.5 mol of 100 mol% toluene.

[0078] After the preliminary run, the current density was set to 0.7 A / cm 2 The current density was increased to 0.05 A / cm and constant current electrolysis was started. The conditions were the same as those for the preliminary run except for the current density. After the start of electrolysis, when bubbles (hydrogen gas generated by a side reaction) were confirmed at the outlet of the electrolytic cell, the current density was increased to 0.05 A / cm. 2 Just lower it to 0.65A / cm 2 In addition, while adjusting the current density, 0.2 mL of the cathode solution was sampled from the reservoir, and the concentrations of toluene and methylcyclohexane were measured by gas chromatography. The toluene concentration at which bubbles were visually confirmed was determined to be the concentration at which hydrogen gas was generated at that current density, in other words, the concentration at which the Faraday efficiency decreased.

[0079] Current density 0.65A / cm 2 Continue constant current electrolysis at 0.05 A / cm. When bubbles are observed at the outlet of the electrolytic cell, reduce the current density to 0.05 A / cm. 2 In addition, 0.2 mL of the catholyte was sampled from the reservoir, and the concentrations of toluene and methylcyclohexane were measured. This measurement was performed at a current density of 0.2 A / cm 2 This was repeated until bubbles were observed. The measurement results are shown in Figure 2. Figure 2 is a diagram showing the relationship between the current density of the electrolytic cell and the toluene concentration at which hydrogen gas is generated. From Figure 2, it was confirmed that the relationship between the current density of the electrolytic cell and the concentration of the substance to be hydrided at which hydrogen gas is generated can be determined in advance by Test 1. In Figure 2, the maximum current density was 0.7 A / cm 2 However, this is due to the limitations of the evaluation equipment, and the upper limit of the current density is set to 0.7 A / cm 2 It is not intended to be limited to.

[0080] (Test 2: Evaluation of IV characteristics) A preliminary run was carried out using the same electrolytic cell and reaction conditions as in Test 1, except that 2.056 mol of 100 mol% toluene was used as the catholyte. After the preliminary run, a current density of 0.05 A / cm 2 Constant current electrolysis was carried out at 0.05 A / cm for 3 minutes, and the cell voltage was measured. The conditions were the same as those for the preliminary run, except for the current density. After that, the current density was increased to 0.05 A / cm. 2By increasing the current density to 0.1A / cm 2 Constant current electrolysis was carried out at a current density of 0.7 A / cm for 3 minutes, and the cell voltage was measured. 2 This was repeated until the IV characteristics of the electrolytic cell were evaluated using the above measurement procedures. The evaluation results are shown in Figure 3. Figure 3 is a diagram showing the IV characteristics of the electrolytic cell. From Figure 3, it was confirmed that the IV characteristics of the electrolytic cell can be determined in advance by Test 2.

[0081] (Test 3: Evaluation of the effect of hydride concentration on cell voltage) Using the electrolytic cell after Test 2, a current density of 0.7 A / cm 2 Constant-current electrolysis was carried out at 1000 kJ / min for 243 minutes. Other than the current density, the conditions were the same as those for the preliminary run. 0.2 mL of catholyte was sampled from the reservoir approximately every 827 seconds from the start of electrolysis, and the concentrations of toluene and methylcyclohexane were measured by gas chromatography. Electrolysis was terminated 243 minutes after the start of electrolysis. After electrolysis was terminated, the catholyte in the reservoir was also sampled and the concentrations of toluene and methylcyclohexane were measured. The measurement results are shown in Figure 4. Figure 4 shows the relationship between toluene concentration and cell voltage.

[0082] From the results of Test 1, the current density was 0.7 A / cm 2 It is known that when constant-current electrolysis is performed at a toluene concentration of 27 mol% or less, hydrogen is generated and the faradaic efficiency decreases. Figure 4 confirms that when electrolysis proceeds at a toluene concentration above 27 mol%, i.e., when the faradaic efficiency is approximately 100%, there is almost no increase in the cell voltage of the electrolytic cell. The increase in cell voltage as the toluene concentration decreases from 100 mol% to 30 mol% is only 10 mV. On the other hand, when electrolysis proceeds at a toluene concentration of 27 mol% or less, i.e., when the faradaic efficiency decreases, it is confirmed that the increase in cell voltage increases as the toluene concentration decreases.

[0083] Because the increase in cell voltage was only 10 mV in the range of the target substance concentration where hydrogen generation was not observed, it was confirmed that the effect of the target substance concentration on the IV characteristics was negligible in the control according to this embodiment. Taking into account the 10 mV increase, the cell voltage in the IV characteristics shown in Figure 2 can be adjusted to a value 10 mV higher overall, more preferably 20 mV higher, and used to determine the current density of the electrolytic cell, thereby further reducing the possibility of a decrease in the Faraday efficiency. Furthermore, Figure 4 confirms that when electrolysis proceeds within the range of the target substance concentration where hydrogen generation is not observed, the target substance concentration decreases by approximately 5 mol% approximately every 827 seconds.

[0084] (Test 4: Confirmation of the effect of selective control of storage section according to the embodiment) Example 1 A preliminary run was carried out using the same electrolytic cell and reaction conditions as in Test 1, except that a mixed solution of 0.25 mol of toluene and 0.25 mol of methylcyclohexane (toluene concentration 50 mol%, methylcyclohexane concentration 50 mol%) was used as the cathode solution. After the preliminary run, a current density of 0.7 A / cm was applied. 2 Constant-current electrolysis was carried out for 10 minutes. After electrolysis, 0.2 mL of the cathode solution was sampled from the reservoir, and the concentrations of toluene and methylcyclohexane were measured by gas chromatography. The toluene concentration decreased to 35.5 mol%, and the conversion rate was 14.5 mol%.

[0085] The average cell voltage during constant current electrolysis was 2.341 V. It was also confirmed that electrolysis proceeded with a faradaic efficiency of 100%. Furthermore, based on the flow rate of toluene at 20 mL / min and the volume of the cathode chamber, it was confirmed that the toluene concentration at the outlet of the cathode chamber was 3.9 mol% lower than that at the inlet. Furthermore, when the electrode area was 100 cm, 2 Therefore, the current value is 70 A. Therefore, electrolysis was carried out with a power of 163.87 W (= 70 A × 2.341 V). In other words, if the power supply device can supply a power of 163.87 W continuously for 10 minutes, the current density will be 0.7 A / cm. 2By selecting a reservoir that stores a cathode solution with a toluene concentration of 50 mol %, it is possible to improve the production rate of organic hydride while suppressing a decrease in the faradaic efficiency.

[0086] (Comparative Example 1) A preliminary run and a current of 0.7 A / cm were carried out in the same manner as in Example 1, except that a mixed solution of 0.15 mol of toluene and 0.35 mol of methylcyclohexane (toluene concentration: 30 mol%, methylcyclohexane concentration: 70 mol%) was used as the cathode fluid. 2 Constant-current electrolysis was carried out at 2.361 V for 10 minutes. After the electrolysis was completed, the toluene concentration had decreased to 19.2 mol%, and the conversion rate was 10.8 mol%. The average cell voltage during constant-current electrolysis was 2.361 V. It was also confirmed that electrolysis proceeded with a faradaic efficiency of 74%. Since the current value was 70 A, electrolysis was carried out with a power of 165.27 W (= 70 A × 2.361 V). In other words, if the power supply device can continuously supply a power of 165.27 W for 10 minutes, electrolysis can be carried out at a current density of 0.7 A / cm. 2 In this case, if a reservoir for storing a catholyte with a toluene concentration of 30 mol % is selected, the faradaic efficiency will decrease.

[0087] Example 2 After the preliminary run, the constant current electrolysis was 0.4A / cm 2 The test was carried out in the same manner as in Comparative Example 1, except that it was carried out at 21.7 mol %. After the electrolysis was completed, the toluene concentration had decreased to 21.7 mol %, and the conversion rate was 8.3 mol %. The average cell voltage during constant current electrolysis was 2.077 V. It was also confirmed that electrolysis proceeded with a faradaic efficiency of 100%. Since the current value was 40 A, electrolysis was carried out with a power of 83.08 W (= 40 A × 2.077 V). In other words, if the power supply device can continuously supply a power of 83.08 W for 10 minutes, electrolysis can be carried out at a current density of 0.4 A / cm 2. 2 By selecting a reservoir that stores a cathode solution with a toluene concentration of 30 mol %, it is possible to improve the production rate of organic hydride while suppressing a decrease in the faradaic efficiency.

[0088] Comparison of Example 1, Comparative Example 1, and Example 2 confirmed that by selecting the concentration of the substance to be hydrided in the cathode solution supplied to the cathode chamber according to the amount of power supplied from the power supply device to the electrolytic cell, it is possible to suppress the decrease in the faradaic efficiency and improve the production rate of organic hydride. Furthermore, in Example 1, the difference in the concentration of the substance to be hydrided between the inlet and outlet of the cathode chamber was 3.9 mol%. From this, it can be seen that the electrolytic cell of Example 1 was used at a current density of 0.7 A / cm 2 When electrolysis is performed using the above method, it is preferable to set the lower limit of the concentration of the substance to be hydrided to a value that is at least 3.9 mol % higher than the concentration of the substance to be hydrided determined by the magnitude of the current flowing through the electrolytic cell 2.

[0089] The selection control of the storage unit will be described below. Fig. 5 is a flowchart showing an example of the selection control of the storage unit. This control flow is repeatedly executed by the control device 10 at a predetermined timing.

[0090] First, the control device 10 acquires the current value (current density) of the electrolytic cell 2 based on signals received from the detection unit 74, the power source 4, the power supply device 34, etc. (S101). Next, the control device 10 calculates the amount of decrease in the concentration of the substance to be hydrided in the cathode chamber 18 from the acquired current value. Then, based on the current value and the amount of decrease, the control device 10 sets a lower limit for the concentration of the substance to be hydrided in the catholyte to be supplied to the electrolytic cell 2 (S102).

[0091] Based on the signal received from the concentration sensor 72, the control device 10 determines whether there is a storage unit 44 storing cathode fluid having a concentration of the substance to be hydrided equal to or greater than a set lower limit (S103). If there is a corresponding storage unit 44 (Y in S103), the control device 10 selects this storage unit 44 as the storage unit 44 storing the cathode fluid having the specific concentration of the substance to be hydrided (S104). If there are multiple corresponding storage units 44, the control device 10 selects the storage unit 44 storing the cathode fluid having a concentration of the substance to be hydrided equal to or greater than the lower limit and closest to the lower limit. The control device 10 then controls the on-off valves and the cathode pump 50 to supply cathode fluid from the selected storage unit 44 to the cathode chamber 18 (S105), and ends this routine.

[0092] If there is no corresponding storage unit 44 (N in S103), the controller 10 selects a storage unit 44 that stores the cathode solution having the highest concentration of the substance to be hydrided (S106). The controller 10 also adjusts the amount of power supplied from the power source 4 to the electrolytic cell 2 according to the concentration of the substance to be hydrided in the selected storage unit 44 (S107). The controller 10 then controls the on-off valves and the cathode pump 50 to supply the cathode solution from the selected storage unit 44 to the cathode chamber 18 (S105), and ends this routine.

[0093] As described above, the organic hydride producing system 1 according to this embodiment includes an electrolytic cell 2, a cathode solution supply device 8, and a control device 10. The electrolytic cell 2 has an anode electrode 12, a cathode electrode 14, an anode chamber 16, a cathode chamber 18, and a diaphragm 20. The anode electrode 12 oxidizes water in the anolyte to produce protons. The cathode electrode 14 hydrogenates the substance to be hydrided in the catholyte with the protons to produce organic hydride. The anode chamber 16 accommodates the anode electrode 12. The cathode chamber 18 accommodates the cathode electrode 14. The diaphragm 20 separates the anode chamber 16 from the cathode chamber 18 and allows protons to move from the anode chamber 16 side to the cathode chamber 18 side. The catholyte supply device 8 can supply the cathode chamber 18 with any catholyte selected from a plurality of catholytes having different concentrations of the substance to be hydrided. The control device 10 controls the catholyte supply device 8 so as to supply the catholyte having a specific concentration of the substance to be hydrided, which is determined according to the magnitude of the current flowing through the electrolytic cell 2, to the cathode chamber 18.

[0094] In this way, by switching the concentration of the substance to be hydrided in the cathode fluid supplied to the cathode chamber 18 depending on the magnitude of the current flowing through the electrolytic cell 2, it is possible to improve the production rate of organic hydride while suppressing a decrease in the faradaic efficiency of the organic hydride production system 1.

[0095] Furthermore, the cathode fluid supply device 8 of this embodiment has multiple storage units 44 that individually store multiple cathode fluids. The control device 10 determines a lower limit for the concentration of the substance to be hydrided in the cathode fluid to be supplied to the cathode chamber 18, based on the magnitude of the current flowing through the electrolytic cell 2. Then, from the storage units 44 that store cathode fluids with concentrations of the substance to be hydrided that are equal to or higher than the lower limit, the control device 10 selects a storage unit 44 that stores cathode fluid with a specific concentration of the substance to be hydrided. Next, the control device 10 controls the cathode fluid supply device 8 to supply the cathode fluid from the selected storage unit 44 to the cathode chamber 18.

[0096] In this way, by storing a plurality of cathode solutions with different concentrations of the substance to be hydrided separately and selecting a cathode solution suitable for the magnitude of the current flowing through the electrolytic cell 2, it is possible to quickly switch the concentration of the substance to be hydrided in the cathode solution in response to fluctuations in the amount of power supplied from the power supply device 34. This makes it possible to further improve the production rate of organic hydrides.

[0097] Furthermore, the control device 10 of this embodiment determines the lower limit based on the amount of decrease in the concentration of the substance to be hydrided in the cathode chamber 18, in addition to the magnitude of the current flowing through the electrolytic cell 2. This makes it possible to further reduce the possibility of a decrease in the faradaic efficiency of the organic hydride producing system 1.

[0098] Furthermore, the control device 10 of this embodiment selects the storage unit 44 storing the cathode solution having a concentration of the substance to be hydrided that is equal to or greater than the lower limit and closest to the lower limit as the storage unit 44 storing the cathode solution having the specific concentration of the substance to be hydrided. This makes it possible to maintain the state in which the cathode solution having a concentration of the substance to be hydrided that is equal to or greater than the lower limit for a longer period of time. This makes it easier to both suppress the decrease in the Faraday efficiency and increase the production rate of organic hydrides.

[0099] (Embodiment 2) The second embodiment has a configuration that is generally common to the first embodiment, except for the structure of the cathode fluid supply device 8. The following description of the second embodiment will focus on the configuration that is different from the first embodiment, and the common configuration will be explained briefly or omitted.

[0100] 6 is a schematic diagram of an organic hydride production system 1 according to a second embodiment. The organic hydride production system 1 mainly comprises an electrolytic cell 2, a power supply 4, an anolyte supply device 6, a catholyte supply device 8, and a control device 10. The electrolytic cell 2 has an anode electrode 12, a cathode electrode 14, an anode chamber 16, a cathode chamber 18, and a diaphragm 20. The power supply 4 supplies power to the electrolytic cell 2. The anolyte supply device 6 supplies anolyte to the anode chamber 16. The anolyte supply device 6 has an anolyte tank 36, a first anode pipe 38, a second anode pipe 40, and an anode pump 42.

[0101] The cathode fluid supply device 8 supplies cathode fluid to the cathode chamber 18. The cathode fluid supply device 8 can supply any cathode fluid selected from a plurality of cathode fluids having different concentrations of the substance to be hydrided to the cathode chamber 18. The cathode fluid supply device 8 of this embodiment has a first reservoir 44f, a second reservoir 44g, a third reservoir 44h, a first cathode pipe 46, a second cathode pipe 48, a third cathode pipe 76, a cathode pump 50, and eleventh on-off valves 78 to 18th on-off valves 94. The eleventh on-off valves 78 to 18th on-off valves 94 can be configured with known valves such as solenoid valves or air-driven valves.

[0102] The first storage section 44f stores a first catholyte having a first concentration of the substance to be hydrogenated. The second storage section 44g stores a second catholyte having a second concentration of the substance to be hydrogenated that is lower than the first concentration of the substance to be hydrogenated. The third storage section 44h can receive the first catholyte supplied from the first storage section 44f and the second catholyte supplied from the second storage section 44g. Therefore, the third storage section 44h can store a mixed catholyte obtained by mixing the first catholyte and the second catholyte. As an example, the first concentration of the substance to be hydrogenated is 100 mol%, and the second concentration of the substance to be hydrogenated is 5 mol%. The first concentration of the substance to be hydrogenated and the second concentration of the substance to be hydrogenated can be set appropriately based on experiments and simulations.

[0103] In this embodiment, the first to third storage sections 44f to 44h are configured as tanks independent of one another. However, this is not limiting. For example, a single tank may be partitioned into a plurality of independent spaces, and each space may constitute the first to third storage sections 44f to 44h. Furthermore, the number of storage sections that store the catholyte that is the raw material for the mixed catholyte is not limited to two, the first storage section 44f and the second storage section 44g, but may be three or more. For example, the catholyte supply device 8 may have a storage section that stores a third catholyte having a third concentration of the hydride, and the mixed catholyte may be prepared by combining the first to third catholytes.

[0104] The first to third storage sections 44f to 44h are connected to the cathode chamber 18 by the first cathode pipe 46. One end of the first cathode pipe 46 branches into multiple parts and is connected to the first to third storage sections 44f to 44h, and the other end is connected to the first cathode opening 30. In this embodiment, one end of the first cathode pipe 46 branches into three parts, an eleventh branch pipe 46f to a thirteenth branch pipe 46h. The eleventh branch pipe 46f is disposed closest to the first cathode opening 30. The eleventh branch pipe 46f is connected to the first storage section 44f, the twelfth branch pipe 46g to the second storage section 44g, and the thirteenth branch pipe 46h to the third storage section 44h.

[0105] A cathode pump 50 is provided in a region of the first cathode pipe 46 that is closer to the first cathode opening 30 than the eleventh branch pipe 46f. A seventeenth on-off valve 92 is provided in a region of the first cathode pipe 46 that is closer to the first cathode opening 30 than the cathode pump 50. An eleventh on-off valve 78 is provided in the eleventh branch pipe 46f. A twelfth on-off valve 80 is provided in the twelfth branch pipe 46g. A thirteenth on-off valve 82 is provided in the thirteenth branch pipe 46h.

[0106] The first to third storage sections 44f to 44h are also connected to the cathode chamber 18 by the second cathode pipe 48. One end of the second cathode pipe 48 is connected to the second cathode opening 32, and the other end branches into multiple parts that are connected to the first to third storage sections 44f to 44h. In this embodiment, the other end of the second cathode pipe 48 branches into three parts: a fourteenth branch pipe 48f to a sixteenth branch pipe 48h. The fourteenth branch pipe 48f is connected to the first storage section 44f, the fifteenth branch pipe 48g is connected to the second storage section 44g, and the sixteenth branch pipe 48h is connected to the third storage section 44h. A fourteenth on-off valve 84 is provided in the fourteenth branch pipe 48f. A fifteenth on-off valve 86 is provided in the fifteenth branch pipe 48g. A sixteenth on-off valve 88 is provided midway along the sixteenth branch pipe 48h.

[0107] The first cathode fluid in the first reservoir 44f, the second cathode fluid in the second reservoir 44g, and the mixed cathode fluid in the third reservoir 44h flow into the cathode chamber 18 from the first cathode opening 30 via the first cathode piping 46 by driving the cathode pump 50. Which reservoir 44 the cathode fluid is supplied to the cathode chamber 18 from can be switched depending on the open / close states of the eleventh to thirteenth on-off valves 78 to 82. The cathode fluid is supplied to the cathode chamber 18 and is used for the electrode reaction at the cathode electrode 14. The cathode fluid in the cathode chamber 18 is returned to the first to third reservoirs 44f to 44h via the second cathode piping 48. Which reservoir 44 the cathode fluid is returned to can be switched depending on the open / close states of the fourteenth to sixteenth on-off valves 84 to 88.

[0108] The third reservoir 44h is connected to the cathode pump 50 by the third cathode pipe 76. An eighteenth on-off valve 94 is provided midway along the third cathode pipe 76. When the cathode pump 50 is driven while the eleventh on-off valve 78 and the eighteenth on-off valve 94 are open and the twelfth on-off valve 80, the thirteenth on-off valve 82, and the seventeenth on-off valve 92 are closed, the first cathode fluid in the first reservoir 44f moves to the third reservoir 44h via the first cathode pipe 46, the cathode pump 50, and the third cathode pipe 76. Furthermore, when the cathode pump 50 is driven while the twelfth on-off valve 80 and the eighteenth on-off valve 94 are in an open state and the eleventh on-off valve 78, the thirteenth on-off valve 82, and the seventeenth on-off valve 92 are in a closed state, the second cathode fluid in the second reservoir 44g moves to the third reservoir 44h via the first cathode pipe 46, the cathode pump 50, and the third cathode pipe 76.

[0109] The organic hydride producing system 1 also has a concentration sensor 72 that detects the concentrations of the substance to be hydrided in the first cathode fluid, the second cathode fluid, and the mixed cathode fluid. The concentration sensor 72 repeatedly transmits a signal indicating the detection result to the control device 10. The control device 10 can also calculate the concentrations of the substance to be hydrided in the cathode fluid stored in the first to third reservoirs 44f to 44h based on the amount of cathode fluid filled in the first to third reservoirs 44f to 44h, the amount of cathode fluid supplied from the first to third reservoirs 44f to 44h to the cathode chamber 18, and the total amount of power supplied to the electrolytic cell 2 while the cathode fluid is being supplied.

[0110] In the present embodiment, some of the piping connecting the first to third storage sections 44f to 44h to the cathode chamber 18 is shared. However, this configuration is not limiting, and the piping connecting the first to third storage sections 44f to 44h to the cathode chamber 18 may be independent for each storage section 44.

[0111] The control device 10 controls the supply of power from the power source 4 to the electrolytic cell 2. The control device 10 also controls the anolyte supply device 6 and the catholyte supply device 8. Specifically, the control device 10 controls the driving of the anode pump 42 and the cathode pump 50. The control device 10 also controls the opening and closing of the eleventh on-off valve 78 to the eighteenth on-off valve 94.

[0112] The cathode fluid supply device 8 according to this embodiment has first to third reservoirs 44f to 44h, and is capable of supplying any cathode fluid selected from a plurality of cathode fluids having different concentrations of the substance to be hydrided to the cathode chamber 18. The control device 10 controls the cathode fluid supply device 8 so as to supply the cathode chamber 18 with a cathode fluid having a specific concentration of the substance to be hydrided. By selecting the concentration of the substance to be hydrided in the cathode fluid to be supplied to the cathode chamber 18 in accordance with the current density of the electrolytic cell 2, it is possible to increase the production rate of organic hydride while suppressing a decrease in the faradaic efficiency.

[0113] The control device 10 of this embodiment controls the catholyte supply device 8 to supply the first catholyte and the second catholyte to the third reservoir 44h to produce a catholyte having a specific concentration of the substance to be hydrided. The control device 10 calculates the mixing ratio of the first catholyte and the second catholyte so that the mixed catholyte has the specific concentration of the substance to be hydrided. The control device 10 then controls the on-off valves and the cathode pump 50 so that the calculated amount of first catholyte is supplied from the first reservoir 44f to the third reservoir 44h. The control device 10 also controls the on-off valves and the cathode pump 50 so that the calculated amount of second catholyte is supplied from the second reservoir 44g to the third reservoir 44h.

[0114] As a result, a mixed cathode fluid having a specific concentration of the analyte to be hydrided is prepared in the third reservoir 44h. The controller 10 then controls the cathode fluid supply device 8 to supply the mixed cathode fluid from the third reservoir 44h to the cathode chamber 18. The controller 10 also controls the various on-off valves to return the mixed cathode fluid discharged from the cathode chamber 18 to the third reservoir 44h.

[0115] The specific concentration of the substance to be hydrided in this embodiment is determined based on the second example described above. That is, the specific concentration of the substance to be hydrided is set by the control device 10. The control device 10 in this embodiment determines the specific concentration of the substance to be hydrided based on the magnitude of the current flowing through the electrolytic cell 2 and the amount of decrease in the concentration of the substance to be hydrided in the cathode chamber 18. The control device 10 first determines a provisional lower limit value for the concentration of the substance to be hydrided in the catholyte to be supplied to the cathode chamber 18 based on the magnitude of the current flowing through the electrolytic cell 2, for example, the magnitude of the current density. The control device 10 then determines the true lower limit value by adding the amount of decrease in the concentration of the substance to be hydrided in the cathode chamber 18 to the provisional lower limit value. The control device 10 determines the specific concentration of the substance to be hydrided by adding a predetermined margin to the true lower limit value. The predetermined margin can be set as appropriate based on experiments or simulations. The lower limit value may be set based only on the magnitude of the current density in the electrolytic cell 2, without considering the amount of decrease in the concentration of the substance to be hydrided in the cathode chamber 18. The margin may also be zero.

[0116] Basically, the control device 10 controls the cathode fluid supply device 8 to supply the mixed cathode fluid from the third reservoir 44h to the cathode chamber 18. However, when a predetermined condition is satisfied, the cathode fluid supply device 8 may be controlled to supply the cathode fluid directly from the first reservoir 44f or the second reservoir 44g to the cathode chamber 18.

[0117] For example, if the concentration obtained by adding a margin to the true lower limit is equal to or greater than the first concentration of the substance to be hydrided, the first concentration of the substance to be hydrided may be set as the specific concentration of the substance to be hydrided. In this case, the control device 10 controls the catholyte supply device 8 to supply the first catholyte from the first storage unit 44f to the cathode chamber 18. Similarly, if the concentration obtained by adding a margin to the true lower limit is equal to or less than the second concentration of the substance to be hydrided, the second concentration of the substance to be hydrided may be set as the specific concentration of the substance to be hydrided. In this case, the control device 10 controls the catholyte supply device 8 to supply the second catholyte from the second storage unit 44g to the cathode chamber 18. Furthermore, for example, if the power supply device 34 is configured as a solar power generation device and there is little time left until sunset, the control device 10 may control the catholyte supply device 8 to supply the first catholyte from the first storage unit 44f to the cathode chamber 18 in accordance with the remaining amount of the first catholyte in the first storage unit 44f.

[0118] When the concentration of the target substance to be hydrided in the second reservoir 44g is substantially the same as the target concentration to be ultimately achieved by electrolysis, the supply of catholyte to the third reservoir 44h may be from the first reservoir 44f only. Therefore, for example, when the power supply device 34 is configured as a solar power generation device and there is little time left until sunset, the catholyte may be supplied from the first reservoir 44f to the cathode chamber 18, and the catholyte discharged from the cathode chamber 18 may be returned to the third reservoir 44h. This allows the catholyte to be transferred from the first reservoir 44f to the third reservoir 44h while the electrolysis reaction continues. Preferably, the supply tank is switched from the first reservoir 44f to the third reservoir 44h when the amount of catholyte and the concentration of the target substance to be hydrided in the third reservoir 44h satisfy predetermined requirements. Such control makes it possible to effectively utilize the time during which the material to be hydrogenated is transferred from the first storage section 44f to the third storage section 44h.

[0119] As described above, the control of supplying the cathode fluid in the first storage section 44f to the cathode chamber 18 and returning the cathode fluid in the cathode chamber 18 to the third storage section 44h can be appropriately performed by the control device 10 depending on the amount of power supply expected at that time and the concentration and amount of the substance to be hydrogenated in the cathode fluid stored in each of the first storage section 44f and the third storage section 44h.

[0120] Furthermore, even if the concentration of the substance to be hydrided in the cathode fluid in the second reservoir 44g is higher than the target concentration to be achieved by electrolysis, for example, if the power supply device 34 is configured with a solar power generation device and there is little time left until sunset, there is no need to supply the cathode fluid from the second reservoir 44g to the third reservoir 44h. In other words, when only a short period of power supply is expected, if the concentration of the substance to be hydrided in the cathode fluid in the third reservoir 44h is equal to or higher than the lower limit, electrolysis can be performed by supplying the cathode fluid from the third reservoir 44h to the electrolytic cell 2. Furthermore, if the concentration of the substance to be hydrided in the cathode fluid in the third reservoir 44h is less than the lower limit, electrolysis can be performed by supplying the cathode fluid from the first reservoir 44f to the electrolytic cell 2.

[0121] The control device 10 repeats setting the specific concentration of substances to be hydrided and preparing the mixed catholyte at a predetermined timing. For example, the control device 10 repeats setting the specific concentration of substances to be hydrided and preparing the mixed catholyte at a predetermined time period. The execution timing of setting the specific concentration of substances to be hydrided and preparing the mixed catholyte can be set appropriately based on experiments or simulations.

[0122] As described above, the organic hydride production system 1 according to this embodiment, like the organic hydride production system 1 according to embodiment 1, can improve the production rate of organic hydride while suppressing a decrease in Faraday efficiency.

[0123] Furthermore, cathode fluid supply device 8 of this embodiment has at least a first reservoir 44f that stores a first cathode fluid having a first concentration of the substance to be hydrogenated, a second reservoir 44g that stores a second cathode fluid having a second concentration of the substance to be hydrogenated that is lower than the first concentration of the substance to be hydrogenated, and a third reservoir to which the first cathode fluid is supplied from the first reservoir and to which the second cathode fluid is supplied from the second reservoir. Control device 10 controls cathode fluid supply device 8 to supply at least the first cathode fluid, and if necessary, the second cathode fluid, to third reservoir 44h to generate a cathode fluid having a specific concentration of the substance to be hydrogenated, and to supply the cathode fluid from third reservoir 44h to cathode chamber 18.

[0124] With this configuration, it is possible to supply a catholyte having a specific concentration of the substance to be hydrided to the cathode chamber 18 while maintaining the concentrations of the substance to be hydrided in the first catholyte and the second catholyte. This makes it possible to avoid the situation described in the first embodiment where electrolysis has to be performed at a lower current density while supplying a catholyte having a concentration below the specific concentration of the substance to be hydrided to the cathode chamber 18. This makes it possible to further improve the production rate of organic hydride. Furthermore, since the number of reservoirs 44 can be reduced compared to the organic hydride producing system 1 according to the first embodiment, it is possible to reduce the equipment costs and installation space.

[0125] On the other hand, in the organic hydride production system 1 according to the present embodiment, it takes time to prepare the mixed cathode solution. Therefore, the organic hydride production system 1 according to the first embodiment can respond more quickly to fluctuations in the amount of power supplied from the power supply device 34 than the organic hydride production system 1 according to the present embodiment.

[0126] The organic hydride production system 1 according to the second embodiment may be exemplified by the following first modification. FIG. 7 is a schematic diagram of the organic hydride production system 1 according to the first modification. The cathode liquid supply device 8 according to this modification has, instead of the third cathode pipe 76, a fourth cathode pipe 96 connecting the first reservoir 44f and the third reservoir 44h, and a fifth cathode pipe 98 connecting the second reservoir 44g and the third reservoir 44h. A first mixing pump 100 is provided in the fourth cathode pipe 96. A second mixing pump 102 is provided in the fifth cathode pipe 98. The first mixing pump 100 and the second mixing pump 102 are controlled by the control device 10.

[0127] By driving the first mixing pump 100, the first cathode fluid in the first reservoir 44f can be moved to the third reservoir 44h via the fourth cathode piping 96. Furthermore, by driving the second mixing pump 102, the second cathode fluid in the second reservoir 44g can be moved to the third reservoir 44h via the fifth cathode piping 98. In this way, a mixed cathode fluid having a specific concentration of the substance to be hydrided is prepared in the third reservoir 44h.

[0128] According to this modification, the first and second cathode solutions can be directly supplied to the third reservoir 44h without being diverted to the cathode pump 50 side. This reduces the time required to prepare the mixed cathode solution. Therefore, compared to the organic hydride manufacturing system 1 according to the second embodiment, this modification can improve the ability to follow fluctuations in the amount of power supplied from the power supply device 34.

[0129] The embodiments of the present invention have been described in detail above. The above-described embodiments merely illustrate specific examples of implementing the present invention. The content of the embodiments does not limit the technical scope of the present invention, and many design modifications, such as changing, adding, or deleting components, are possible within the scope of the inventive concept defined in the claims. A new embodiment with design modifications will combine the effects of the combined embodiments and modifications. In the above-described embodiments, content that allows such design modifications is emphasized by using notations such as "in this embodiment" or "in this embodiment," but design modifications are also permitted even in content without such notation. Any combination of the above-described components is also valid as an aspect of the present invention.

[0130] The embodiments may be specified by the following items. [Item 1] an electrolytic cell (2) having a cathode chamber (18) containing a cathode electrode (14) for hydrogenating a substance to be hydrogenated in a cathode solution with protons to produce an organic hydride; a cathode solution supply device (8) capable of supplying any cathode solution selected from a plurality of cathode solutions having different concentrations of the substance to be hydrided to a cathode chamber (18); a control device (10) that controls the cathode solution supply device (8) to supply, to the cathode chamber (18), a cathode solution having a specific concentration of the substance to be hydrided, which concentration is determined according to the magnitude of the current flowing through the electrolytic cell (2); Organic hydride production system (1). [Item 2] the cathode fluid supply device (8) has a plurality of reservoirs (44) for respectively storing a plurality of cathode fluids; The control device (10) determines a lower limit value of the concentration of the substance to be hydrogenated in the cathode fluid to be supplied to the cathode chamber (18) based on the magnitude of the current, selects a reservoir (44) for storing the cathode fluid having the specific concentration of the substance to be hydrogenated from among reservoirs (44) for storing the cathode fluid having the concentration of the substance to be hydrogenated equal to or higher than the lower limit value, and controls the cathode fluid supply device (8) to supply the cathode fluid from the selected reservoir (44) to the cathode chamber (18). Item 1 Organic hydride production system (1). [Item 3] The control device (10) determines the lower limit based on the magnitude of the current as well as the amount of decrease in the concentration of the substance to be hydrided in the cathode chamber (18). Item 2 Organic hydride production system (1). [Item 4] the control device (10) selects a storage section (44) for storing a cathode solution having a concentration of the substance to be hydrogenated that is equal to or greater than the lower limit value and closest to the lower limit value as a storage section (44) for storing a cathode solution having a specific concentration of the substance to be hydrogenated; Item 2 or 3 of the organic hydride production system (1). [Item 5] The catholyte supply device (8) a first reservoir (44f) configured to store a first catholyte having a first concentration of the substance to be hydrided; a second reservoir (44g) for storing a second catholyte having a second concentration of the substance to be hydrided that is lower than the first concentration of the substance to be hydrided; a third reservoir (44h) capable of receiving a supply of the first cathode fluid from the first reservoir (44f) and a supply of the second cathode fluid from the second reservoir (44g); the control device (10) controls the cathode fluid supply device (8) to supply the first cathode fluid and the second cathode fluid to the third reservoir (44h) to generate a cathode fluid having a specific concentration of the substance to be hydrided, and to supply the cathode fluid from the third reservoir (44h) to the cathode chamber (18); Item 1 Organic hydride production system (1). [Item 6] The control device (10) determines the specific concentration of the substance to be hydrided based on the magnitude of the current as well as the amount of decrease in the concentration of the substance to be hydrided in the cathode chamber (18). Item 5 Organic hydride production system (1).

[0131] [Item 7] A control device (10) for an organic hydride production system (1) including an electrolytic cell (2) and a cathode liquid supply device (8), The electrolytic cell (2) has a cathode chamber (18) containing a cathode electrode (14) that hydrogenates a substance to be hydrogenated in a cathode solution with protons to produce an organic hydride; the cathode solution supply device (8) is capable of supplying any cathode solution selected from a plurality of cathode solutions having different concentrations of the substance to be hydrided to the cathode chamber (18); the control device (10) controls the cathode solution supply device (8) to supply, to the cathode chamber (18), a cathode solution having a specific concentration of the substance to be hydrided, which is determined according to the magnitude of the current flowing through the electrolytic cell (2); A control device (10) for an organic hydride production system (1).

[0132] [Item 8] A method for controlling an organic hydride production system (1) including an electrolytic cell (2) having a cathode chamber (18) containing a cathode electrode (14) that hydrogenates a substance to be hydrided in a cathode solution with protons to produce an organic hydride, the method comprising: supplying a cathode solution having a specific concentration of the substance to be hydrided, the concentration being determined according to the magnitude of the current flowing through the electrolytic cell (2), to the cathode chamber (18); A method for controlling an organic hydride production system (1). [Industrial Applicability]

[0133] The present invention can be used in an organic hydride production system, a control device for an organic hydride production system, and a control method for an organic hydride production system. [Explanation of symbols]

[0134] 1 organic hydride production system, 2 electrolytic cell, 8 catholyte supply device, 10 control device, 14 cathode electrode, 18 cathode chamber, 44 reservoir, 44f first reservoir, 44g second reservoir, 44h third reservoir.

Claims

1. A control device for an organic hydride production system including an electrolytic cell and a catholyte supply device, the electrolytic cell has a cathode chamber accommodating a cathode electrode that hydrogenates a substance to be hydrogenated in a cathode solution with protons to produce an organic hydride; the cathode solution supply device is capable of supplying any cathode solution selected from the plurality of cathode solutions having different concentrations of the substance to be hydrided to the cathode chamber; the control device controls the cathode fluid supply device to supply the cathode fluid having a specific concentration of the substance to be hydrided, the concentration being determined according to the magnitude of the current flowing through the electrolytic cell, to the cathode chamber. Control device for organic hydride production system.

2. 1. A control method for an organic hydride production system including an electrolytic cell having a cathode chamber accommodating a cathode electrode that hydrogenates a substance to be hydrided in a cathode solution with protons to produce an organic hydride, the method comprising: supplying the cathode solution having a specific concentration of the substance to be hydrided, the concentration being determined according to the magnitude of the current flowing through the electrolytic cell, to the cathode chamber; A method for controlling an organic hydride production system.

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