Electrolytic devices and electrolytic systems

Abstract

To provide an electrolytic device that can reduce the amount of electrolytic energy consumed. [Solution] The electrolytic device 10 is characterized by comprising: an anode electrode 22 containing an anode catalyst that generates protons by electrolytic oxidation of H2; a first chamber 24 in which the anode electrode 22 is located and a gas containing H2 is supplied; a second chamber 26 in which an electrolyte containing alkali metal ions is supplied; a cathode electrode 28 containing a cathode catalyst that generates H2 and hydroxide ions by electrolytic reduction of H2O; a third chamber 30 in which the cathode electrode 28 is located and an aqueous medium is supplied; a first cation exchange membrane 32 located between the first chamber 24 and the second chamber 26; and a second cation exchange membrane 34 located between the second chamber 26 and the third chamber 30.

Description

[Technical Field]

[0001] The present invention relates to an electrolytic device and an electrolytic system equipped with the electrolytic device. [Background technology]

[0002] As a technology that can contribute to carbon neutralization, carbonate ion species (carbonate ion (CO3 2- ) and bicarbonate ions (HCO3) - There is interest in electrolytic devices that utilize technologies such as electrolysis (which refers to at least one of the above) or electrolysis technology to obtain CO2 reduction valuable products from carbon dioxide, or electrodialysis technology that recovers carbon dioxide using an alkaline aqueous solution containing carbonate ion species and separates and concentrates carbon dioxide from the recovered solution containing carbon dioxide.

[0003] For example, Patent Documents 1-6 and Non-Patent Document 1 disclose an electrodialysis apparatus that separates and concentrates carbon dioxide by applying voltage to the anode and cathode electrodes. Also, Patent Documents 7-12 and Non-Patent Documents 2-3 disclose a technique for separating and recovering an aqueous lithium hydroxide solution from the acid treatment solution of the positive electrode active material used in lithium-ion batteries, although not for the purpose of separating and concentrating carbon dioxide, by utilizing electrodialysis technology. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent Publication No. 5848964 [Patent Document 2] Japanese Patent Publication No. 2012-096975 [Patent Document 3] Patent Publication No. 5750220 [Patent Document 4] Japanese Patent Publication No. 2008-100211 [Patent Document 5] International Publication No. 2022 / 235708 [Patent Document 6] Patent Gazette No. 5952104 [License 7] Special Announcement No. 2012-234732 [License 8] Patent Gazette No. 7143466 [License 9] Patent Gazette No. 6864739 [License 10] Special Announcement No. 2014-173144 [License 11] Patent Gazette No. 7101995 [License 12] International Publication No. 2024 / 014540 [Non-licensed literature]

[0005] [Non-licensed Document 1] A. Iizuka et al., “Carbon dioxide recovery from carbonate solutions using bipolar membrane electrodialysis”, Separation and Purification Technology, 101, 49(2012) [Non-licensed Document 2] KH Chan, M. Malik, and G. Azimi, “Separation of lithium, nickel, manganese, and cobalt from waste lithium-ion batteries using electrodialysis”, Resour. Conserv. Recycl., 178, 106076(2022) [Non-licensed Document 3] J. -MA Juve, FMS Christensen, Y. Wang, and Z. Wei, “Electrodialysis for metal removal and recovery: A review”, Chem. Eng. J., 435, 134857(2022) [Overview of the project] [Problems that the invention aims to solve]

[0006] However, conventional electrodialysis technology has the problem that the voltage that must be applied between the two electrodes to drive the reaction is high, resulting in high electrolytic energy consumption.

[0007] Therefore, the present invention aims to provide an electrolytic device that can reduce the amount of electrolytic energy consumed. [Means for solving the problem]

[0008] The electrolytic device according to this embodiment comprises an anode electrode including an anode catalyst that generates protons by electrolytic oxidation of H2, a first chamber in which the anode electrode is located and a gas containing H2 is supplied, a second chamber in which an electrolyte containing alkali metal ions is supplied, a cathode electrode including a cathode catalyst that generates H2 and hydroxide ions by electrolytic reduction of H2O, a third chamber in which the cathode electrode is located and an aqueous medium is supplied, a first cation exchange membrane located between the first and second chambers, and a second cation exchange membrane located between the second and third chambers, wherein when a voltage is applied to the anode electrode and the cathode electrode, the protons generated at the anode electrode are supplied to the second chamber through the first cation exchange membrane, the alkali metal ions in the second chamber are supplied to the third chamber through the second cation exchange membrane, and in the third chamber, an aqueous alkali hydroxide solution is generated by the reaction of the alkali metal ions with the hydroxide ions generated at the cathode electrode.

[0009] Furthermore, in the electrolytic device, it is preferable that the anode electrode is in contact with the first cation exchange membrane.

[0010] Furthermore, in the electrolytic device, it is preferable that the cathode electrode is in contact with the second cation exchange membrane.

[0011] Furthermore, in the electrolytic device, it is preferable that the electrolyte containing the alkali metal ions contains carbonate ion species, and that when a voltage is applied to the anode electrode and the cathode electrode, the protons react with the carbonate ion species in the second chamber.

[0012] Furthermore, in the electrolytic device, the alkali metal ion is Li + , Rb + , Cs + It is preferable to include at least one of the following.

[0013] Furthermore, in the electrolytic device, it is preferable that the anode catalyst includes a first catalyst that promotes the hydrogen oxidation reaction in an acidic environment.

[0014] Furthermore, in the electrolytic device, it is preferable that the anode catalyst includes a second catalyst that promotes the oxygen evolution reaction in an acidic environment.

[0015] Furthermore, in the electrolytic device, it is preferable that the first catalyst contains at least one element selected from the group consisting of Pt, Pd, Rh, Re, Au, and Ni.

[0016] Furthermore, in the electrolytic device, it is preferable that the second catalyst includes at least one selected from the group consisting of Ir oxide, Ru oxide, a mixture containing Ir oxide and Ru oxide, and a composite oxide containing Ir and Ru.

[0017] Furthermore, in the electrolytic device, it is preferable that both the first cation exchange membrane and the second cation exchange membrane are perfluorosulfonic acid polymer membranes.

[0018] Furthermore, in the electrolytic device, it is preferable that the cathode catalyst includes a catalyst that promotes the H2 generation reaction.

[0019] Furthermore, in the electrolytic device, it is preferable that the cathode catalyst contains at least one element selected from the group consisting of Pt, Pd, Rh, Re, Ni, Co, and Mo.

[0020] Furthermore, in the electrolytic device, it is preferable that the height of the second chamber be 5 mm or less.

[0021] Furthermore, in the electrolytic device, it is more preferable that the height of the second chamber be 2 mm or less.

[0022] Furthermore, in the electrolytic device, it is preferable that the average linear velocity of the aqueous medium flowing through the third chamber is 15 cm / min or more.

[0023] Furthermore, the electrolytic device according to this embodiment is characterized by comprising the electrolytic device, a gas-liquid separation device for separating the discharge liquid containing H2 discharged from the third chamber into gas-liquid, and an H2 supply mechanism for supplying the H2 separated by the gas-liquid separation device to the first chamber. [Effects of the Invention]

[0024] According to the present invention, it is possible to provide an electrolytic device that can reduce the amount of electrolytic energy consumed. [Brief explanation of the drawing]

[0025] [Figure 1] This is a schematic diagram showing an example of an electrolytic system according to this embodiment. [Figure 2] This figure shows the measurement results of the applied voltage of the electrolytic device during the electrodialysis test in Examples 1-3 and Comparative Examples 1-3. [Modes for carrying out the invention]

[0026] Embodiments of the present invention will be described below. This embodiment is just one example of how the present invention can be implemented, and the present invention is not limited to this embodiment.

[0027] Figure 1 is a schematic diagram showing an example of an electrolytic system according to this embodiment. The electrolytic system 1 shown in Figure 1 comprises an electrolytic device 10, a gas-liquid separation device 12, and an H2 supply mechanism 14.

[0028] The electrolytic device 10 shown in Figure 1 includes an anode electrode 22, a first chamber 24, a second chamber 26, a cathode electrode 28, a third chamber 30, a first cation exchange membrane 32, a second cation exchange membrane 34, and frame members 36a and 36b. The first chamber 24 is provided between the frame member 36a and the first cation exchange membrane 32, and the anode electrode 22 is positioned there. The anode electrode 22 is adjacent to the first cation exchange membrane 32. In the first chamber 24, a flow channel 23 through which a gas containing H2 flows is provided between the anode electrode 22 and the frame member 36a. The third chamber 30 is provided between the frame member 36b and the second cation exchange membrane 34, and the cathode electrode 28 is positioned there. The cathode electrode 28 is adjacent to the second cation exchange membrane 34. In the third chamber 30, a flow channel 29 through which an aqueous medium flows is provided between the cathode electrode 28 and the frame member 36b. The second chamber 26 is located between the first cation exchange membrane 32 and the second cation exchange membrane 34. That is, the first cation exchange membrane 32 is located between the first chamber 24 and the second chamber 26, and the second cation exchange membrane 34 is located between the second chamber 26 and the third chamber 30. The second chamber 26 is a channel through which an electrolyte containing alkali metal ions and carbonate ion species flows. Here, carbonate ion species refers to carbonate ions (CO3). 2- ) and bicarbonate ions (HCO3) - This refers to at least one of the following. In the electrolytic device 10 shown in Figure 1, the anode electrode 22, cathode electrode 28, cation exchange membrane, etc. are structurally supported by frame materials 36a, 36b. The frame materials 36a, 36b can be made of metal, plastic, glass, etc.

[0029] The anode electrode 22 is an electrode that includes an anode catalyst and generates protons by the electrolytic oxidation of H2. Preferably, the anode catalyst includes a first catalyst that promotes the hydrogen oxidation reaction in an acidic environment and a second catalyst that promotes the oxygen evolution reaction in an acidic environment. The cathode electrode 28 includes a cathode catalyst and generates H2 and hydroxide ions (OH) by the reductive electrolysis of H2O. - This is an electrode that generates H2. The cathode catalyst preferably contains a catalyst that promotes the H2 evolution reaction.

[0030] The gas-liquid separation device 12 includes, for example, a gas-liquid separator 16 and a discharge line 18. One end of the discharge line 18 is connected to the flow path 29 of the third chamber 30, and the other end is connected to the gas-liquid separator 16. The gas-liquid separator 16 is, for example, a conventionally known device capable of separating gas and liquid.

[0031] The H2 supply mechanism 14 shown in Figure 1 is a supply line for supplying gas containing H2 to the first chamber 24. For example, one end of the supply line is connected to the gas-liquid separator 16, and the other end is connected to the flow path 23 of the first chamber 24. The H2 supply mechanism 14 may also be equipped with a pump to adjust the amount of gas containing H2 supplied, or it may be equipped with a gas cylinder filled with H2 and a blower to supply air in order to stably supply gas containing H2. In the following, the H2 supply mechanism 14 will be described as the supply line 14.

[0032] In Figure 1, reference numeral 70 denotes a power source that applies a voltage between the anode electrode 22 and the cathode electrode 28. The power source 70 is not particularly limited and may include a chemical battery (including primary batteries, secondary batteries, etc.), a constant voltage source, a solar cell, etc.

[0033] Next, we will describe an example of the operation of the electrolysis system 1 shown in Figure 1.

[0034] A gas containing H2 is supplied from the supply line 14 to the flow path 23 of the first chamber 24. The gas containing H2 is, for example, a mixed gas of air and hydrogen gas. Further, the gas containing H2 may be humidified by a humidifier before being supplied to the flow path 23 of the first chamber 24 and supplied to the flow path 23 of the first chamber 24 as a humidified gas containing moisture. Also, an electrolytic solution containing alkali metal ions and carbonate ion species is supplied from the supply line to the second chamber 26. Further, an aqueous medium is supplied from the supply line to the flow path 29 of the third chamber 30.

[0035] When a voltage is applied between the cathode electrode 28 and the anode electrode 22 by the power source 70, on the first chamber 24 side, when the gas containing H2 passing through the flow path 23 contacts the anode electrode 22, for example, H2 in the gas is oxidized, and protons (H + ) are generated. Also, water in the gas is oxidized, and oxygen (O2) and protons (H + ) are generated. The protons generated at the anode electrode 22 pass through the first cation exchange membrane 32 and are supplied to the second chamber 26. Then, carbonate ions or bicarbonate ions in the electrolytic solution supplied to the second chamber 26 react with the protons that have moved to the second chamber 26 side through the first cation exchange membrane 32, and carbon dioxide (neutral CO2 molecules) is generated, or bicarbonate ions are generated from carbonate ions. The alkali metal ions in the electrolytic solution passing through the second chamber 26 pass through the second cation exchange membrane 34 and are supplied to the third chamber 30. Then, on the third chamber 30 side, when the aqueous medium passing through the flow path 29 contacts the cathode electrode 28, for example, H2O is reduced, and H2 and hydroxide ions (OH - ) are generated, and further, the hydroxide ions react with the alkali metal ions that have moved to the third chamber 30 side through the second cation exchange membrane 34, and an aqueous alkali solution is generated.

[0036] The carbon dioxide generated in the second chamber 26 is discharged from the second chamber 26 together with, for example, the electrolytic solution supplied to the second chamber 26, and is separated into a gas containing carbon dioxide and a liquid by, for example, a gas-liquid separator (not shown), and each is recovered.

[0037] The H2 and alkali hydroxide aqueous solution generated in the third chamber 30 are discharged from the third chamber 30 as wastewater and supplied to the gas-liquid separator 16 via the discharge line 18. In the gas-liquid separator 16, the wastewater is separated into a gas containing H2 and an alkali hydroxide aqueous solution. The alkali hydroxide aqueous solution is recovered, and the gas containing H2 is supplied from the supply line 14 to the flow path 23 of the first chamber 24.

[0038] As shown in Figure 1, the electrolytic device 10 has a three-chamber configuration: a first chamber 24 where the anode electrode 22 is placed, a third chamber 30 where the cathode electrode 28 is placed, and a second chamber 26 placed between the first chamber 24 and the third chamber 30 via a cation exchange membrane. Through electrodialysis, an alkali hydroxide aqueous solution is produced, and even carbon dioxide is produced. Therefore, the applied voltage to the electrolytic device 10 can be reduced compared to conventional multi-stage electrodialysis with five or more chambers, and consequently, energy consumption can be reduced.

[0039] The following describes in detail the first cation exchange membrane 32, the second cation exchange membrane 34, the anode electrode 22, the cathode electrode 28, the electrolyte containing alkali metal ions, the gas containing H2, etc.

[0040] The first cation exchange membrane 32 and the second cation exchange membrane 34 can be conventionally known membranes, but perfluorosulfonic acid polymer membranes such as Nafion or Flemion are preferred in terms of hydrogen ion conductivity, alkali metal ion conductivity, and water permeability, for example.

[0041] It is preferable that the anode electrode 22 is in contact with the first cation exchange membrane 32, and more preferably that the anode electrode 22 and the first cation exchange membrane 32 are joined together. This reduces the resistance when protons generated at the anode electrode 22 move to the second chamber 26. As a result, the H2 utilization rate is improved, and the applied voltage to the electrolytic device 10 is further reduced.

[0042] The anode catalyst is not particularly limited as long as it is a catalyst that promotes the electrolytic oxidation of H2, but as mentioned above, it is preferable that it includes a first catalyst that promotes the hydrogen oxidation reaction in an acidic environment and a second catalyst that promotes the oxygen evolution reaction in an acidic environment. The presence of such catalysts promotes the H2O oxidation reaction. + In addition to generation (which requires an anode potential of 1.23V or higher), H2 is also produced by the oxidation reaction. + The generation process (the anode potential can be 0 or higher) is further promoted, allowing for a reduction in the applied voltage to the electrolytic device 10, and consequently, a reduction in energy consumption. Incidentally, the potential determination reaction of the anode electrode 22 is xH2O + (1-x)H2 → x / 2O2 + 2H + +2e - (0≦x<1), and the lowest potential is +1.23V. Here, x is H + This represents the contribution rate of H2O as a raw material (reactant) in the production process. When H2 is oxidized by the supply of a gas containing H2, x < 1, so the potential of the anode electrode 22 decreases, and the applied voltage decreases. Furthermore, if the contribution rate of the H2 oxidation reaction is increased by a catalyst that promotes hydrogen oxidation and oxygen evolution reactions in an acidic environment, the utilization of H2O and O2 evolution will decrease, so x will become smaller, and the applied voltage will be reduced even further.

[0043] The first catalyst that promotes the hydrogen oxidation reaction in an acidic environment is a catalyst that satisfies the following condition (1). (1) A 1M KOH aqueous solution is supplied to the second chamber at 10 mL / min, and He gas containing 3.5% H2 is supplied to the first chamber at 20 mL / min, resulting in a current density of 10 mA / cm² between the anode and cathode electrodes. 2 A catalyst that achieves an H2 utilization rate of 90% or more at the anode electrode when a constant current is applied. The anode electrode is a catalyst sheet made by coating a catalyst ink, which is a mixture of the catalyst, Nafion solution, pure water, and ethanol, into a sheet, and the catalyst content is 0.11 mg / cm² per geometric area of ​​the anode electrode. 2 Furthermore, the catalyst sheet is thermocompressed and bonded to the cation exchange film. The cathode electrode is made of Pt deposited at a density of 250 nm on carbon paper, and generates H2 with 100% current efficiency.

[0044] The second catalyst that promotes the oxygen evolution reaction in an acidic environment is a catalyst that satisfies the following condition (I). (I) A 1M KOH aqueous solution is supplied to the second chamber at 10 mL / min, and He gas containing 3.5% H2 is supplied to the first chamber at 20 mL / min, resulting in a current density of 10 mA / cm² between the anode and cathode electrodes. 2 A catalyst that, when a constant current is applied, exhibits a current efficiency of 90% or more for the oxygen evolution reaction at the anode electrode. The anode electrode is a catalyst sheet prepared by coating a sheet with a catalyst ink, which is a mixture of the catalyst, Nafion solution, pure water, and ethanol. The catalyst content is 2 mg / cm² per geometric area of ​​the anode electrode. 2 Furthermore, the catalyst sheet is thermocompressed and bonded to the cation exchange film. The cathode electrode is made of Pt deposited at a density of 250 nm on carbon paper, and generates H2 with 100% current efficiency.

[0045] The first catalyst is not particularly limited as long as it satisfies the aforementioned conditions, but for example, H2 oxidation reaction + To further promote the formation of the product, the catalyst is preferably one that contains at least one element selected from the group consisting of Pt, Pd, Rh, Re, Au, and Ni. Specifically, it may be the metals Pt, Pd, Rh, Re, Au, or Ni, or an alloy or compound containing such metal. The compound containing such metal may be an oxide, hydroxide, or complex. The first catalyst may be a single type or two or more types may be used in combination.

[0046] The second catalyst is not particularly limited as long as it satisfies the aforementioned conditions, but for example, H2O oxidation reaction + In terms of further promoting generation, it is preferable to include at least one selected from the group consisting of Ir oxide, Ru oxide, a mixture containing Ir oxide and Ru oxide, and a composite oxide containing Ir and Ru.

[0047] The anode catalyst content is, for example, 0.35 mg / cm² per geometric area of ​​the anode electrode 22, which can further reduce the energy consumption of the electrolytic device 10. 2 It is preferable that the above is true. If the anode catalyst content is too high, it may lead to an increase in the cost of the electrolytic device 10, so the upper limit of the anode catalyst content is 1.5 mg / cm² per geometric area of ​​the anode electrode 22. 2 The following is preferable:

[0048] The anode electrode 22 may contain a polymer. The polymer functions, for example, as a binder to increase the bonding strength between the anode electrode 22 and the first cation exchange membrane 32. Examples of polymers include cation exchange resins and anion exchange resins, but cation exchange resins are preferred in terms of bonding strength and proton conductivity, and perfluorosulfonic acid ions such as Nafion® (manufactured by DuPont) and Flemion (manufactured by Asahi Glass Co., Ltd.) are particularly preferred.

[0049] The polymer content is, for example, 0.06 mg / cm² per unit area of ​​the anode electrode 22, in order to increase the bonding strength between the anode electrode 22 and the first cation exchange membrane 32. 2 It is preferable that the polymer content is as described above. Furthermore, if the polymer content becomes too high, the conductivity of the anode electrode 22 may decrease, which may lead to a decrease in catalytic activity. Therefore, the upper limit of the polymer content is 0.20 mg / cm² per unit area of ​​the anode electrode 22. 2 The following is preferable:

[0050] The anode electrode 22 may contain a conductive material. Examples of conductive materials include carbon materials such as carbon black, activated carbon, fullerene, carbon nanotubes, graphene, Ketjenblack, and diamond; transparent conductive oxides such as indium tin oxide, fluorine-doped tin oxide, aluminum-doped zinc oxide, and antimony-doped tin oxide; metals such as copper, aluminum, titanium, silver, and tungsten; or alloys containing at least one of these metals.

[0051] An example of a method for fabricating the anode electrode 22 is described below. By applying a catalyst ink containing an anode catalyst, polymer, etc., onto a PTFE substrate, a porous sheet-like anode electrode 22 can be fabricated. Furthermore, by placing the fabricated anode electrode 22 on the first cation exchange membrane 32 and heat-pressing them together, the anode electrode 22 and the first cation exchange membrane 32 can be joined.

[0052] A diffusion layer may be installed in the first chamber 24 to enhance the diffusivity of the gas containing H2. The diffusion layer may be made of, for example, a porous metal body or metal mesh made of titanium, titanium alloy, or stainless steel, or a porous conductive substrate such as carbon paper.

[0053] The H2-containing gas supplied to the first chamber 24 is, for example, a mixture of air or an inert gas (e.g., nitrogen gas, noble gas, etc.) and hydrogen gas, and is preferably a humidified gas. The hydrogen gas concentration in the gas may be, for example, 1% or more and 20% or less. Furthermore, the degree of humidification of the humidified gas is preferably such that the moisture content is higher than that of air at 25°C and 50% humidity. Specifically, the moisture content in the humidified gas is 11.5 g / m³. 3 It is preferable that the above conditions are met.

[0054] Preferably, the cathode electrode 28 is in contact with the second cation exchange membrane 34, and preferably, the cathode electrode 28 and the second cation exchange membrane 34 are joined together. This makes it possible to minimize the influence of the ion conduction resistance of the aqueous medium flowing through the third chamber 30, and further reduces the applied voltage to the electrolytic device 10.

[0055] The cathode catalyst is not particularly limited as long as it is a catalyst that promotes the electrolytic reduction of H2O, but as mentioned above, it is preferable that it includes a catalyst that promotes the H2 generation reaction. A catalyst that promotes the H2 generation reaction is a catalyst that satisfies the following conditions: When constant current electrolysis is performed while supplying an alkaline aqueous solution with pH > 7 to the third chamber 30, if the applied voltage can be reduced when electrolysis is performed with a catalyst supported on the cathode electrode 28 than when electrolysis is performed with only a porous conductive substrate made of carbon (such as carbon paper), then the catalyst supported on the substrate is a catalyst that promotes the H2 generation reaction.

[0056] The catalyst that promotes the H2 evolution reaction is preferably a catalyst containing at least one element selected from the group consisting of Pt, Pd, Rh, Re, Ni, Co, and Mo. Specifically, it may be a metal such as Pt, Pd, Rh, Re, Ni, Co, or Mo, or an alloy or compound containing such a metal. The compound containing such a metal may be an oxide, hydroxide, or complex. The cathode catalyst may be a single type or two or more types may be used in combination.

[0057] The cathode catalyst content is, for example, 0.35 mg / cm² per geometric area of ​​the cathode electrode 28, which can further reduce the energy consumption of the electrolytic device 10. 2 It is preferable that the above is true. If the cathode catalyst content is too high, it may lead to an increase in the cost of the electrolytic device 10. Therefore, the upper limit of the cathode catalyst content is 1.5 mg / cm² per geometric area of ​​the cathode electrode 28. 2 The following is preferable:

[0058] An example of a method for fabricating a cathode electrode 28 is described below. A porous cathode electrode 28 can be fabricated by supporting a cathode catalyst on a porous conductive substrate such as carbon paper using a vapor deposition method such as sputtering. Furthermore, the fabricated cathode electrode 28 and the second cation exchange film 34 can be joined by placing the fabricated cathode electrode 28 on the second cation exchange film 34 and heat-pressing them together.

[0059] The electrolyte containing alkali metal ions supplied to the second chamber 26 is, for example, a rare metal ion such as Li + , Rb + , Cs + It is preferable that the solution contains at least one of the following. For example, the acid treatment solution for the positive electrode active material of a lithium-ion secondary battery is Li + Although it is an acidic aqueous solution containing [a specific substance], by supplying such an acid treatment solution of the positive electrode active material to the second chamber 26, an aqueous lithium hydroxide solution can be generated and recovered in the third chamber 30.

[0060] The electrolyte containing alkali metal ions may contain at least one of the carbonate ion species, either carbonate ions or bicarbonate ions. Examples of electrolytes containing alkali metal ions and carbonate ion species include solutions containing alkali metal bicarbonates or alkali metal carbonates such as lithium bicarbonate (LiHCO3), sodium bicarbonate (NaHCO3), potassium bicarbonate (KHCO3), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), cesium bicarbonate (CsHCO3), and rubidium bicarbonate (RhHCO3). As described above, according to this embodiment, by supplying the electrolyte containing alkali metal ions and carbonate ion species to the second chamber 26, CO2 can be separated and recovered in the second chamber 26, and an alkali hydroxide aqueous solution can be generated and recovered in the third chamber 30.

[0061] Furthermore, the electrolyte containing alkali metal ions may also contain alcohols such as methanol, ethanol, and acetone. Additionally, the electrolyte containing alkali metal ions may contain, for example, cations such as imidazolium ions and pyridinium ions, and BF4 - PF6 - It may also contain an ionic liquid or an aqueous solution thereof, which consists of a salt with anions such as the above and is in a liquid state over a wide temperature range.

[0062] The aqueous medium supplied to the third chamber 30 may be, for example, water, pure water, or an aqueous solution containing an electrolyte. Examples of electrolytes include sodium bicarbonate, potassium bicarbonate, potassium carbonate, potassium sulfate, potassium tetraborate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, and potassium hydroxide.

[0063] The height of the second chamber 26, that is, the distance between the first cation exchange membrane 32 and the second cation exchange membrane 34, is preferably 5 mm or less, and more preferably 2 mm or less. This further reduces the ion conduction resistance in the second chamber 26, and thus further reduces the electrolytic energy consumption. The lower limit of the height of the second chamber 26 is the amount of protons (H) supplied from the first chamber 24 to the second chamber 26. + However, the current does not remain in the second chamber 26 but flows directly into the third chamber 30, suppressing a decrease in current efficiency, so a thickness of 0.1 mm or more is sufficient.

[0064] The average linear velocity of the aqueous medium flowing through the third chamber 30 is preferably 15 cm / min or more, and more preferably 15 cm / min or more and 25 m / min or less, in terms of improving the amount of alkali hydroxide aqueous solution produced. [Examples]

[0065] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0066] <Example 1> Electrodialysis tests were conducted using the electrolytic device shown in Figure 1. A Nafion N-115 membrane was used as the first cation exchange membrane. A loading of 0.39 mg / cm³ was applied to one side of the first cation exchange membrane. 2 IrO2 and loading amount 0.11 mg / cm³ 2An anode electrode was fabricated by supporting Pt. A Nafion N-115 film was used for the second cation exchange membrane. For the cathode electrode, a 250 nm layer of Pt was deposited on one side of porous carbon paper (TGP-H-060, manufactured by Toray Industries, Inc.) by sputtering. This cathode electrode was placed on one side of the second cation exchange membrane. The geometric area of ​​the cathode electrode is 2.5 cm × 2.5 cm. The cross-sectional area of ​​the second chamber is 0.06 cm². 2 The dimensions were set to (0.3cm × 0.2cm). The cross-sectional area of ​​the flow path in the third chamber is 0.065cm². 2 I set it to (0.1cm x 0.05cm).

[0067] During the electrodialysis test, 0.136 mol / L K is added to the second chamber. + A 400 ppm (total pressure 1 bar) CO2 equilibrium solution (0.0355 mol / L K2CO3 + 0.065 mol / L KHCO3) containing the above was delivered at a rate of 1 cm. 3 The fluid was supplied at a rate of / min. In addition, an aqueous solution containing 0.0328 mol / L K2CO3 + 0.0343 mol / L KHCO3 was delivered to the third chamber via a flow path at a rate of 1 cm². 3 A supply was placed at a rate of 15.38 cm / min (average linear velocity). In addition, He gas containing 3.6% H2 was supplied to the flow path of the first chamber at a supply rate of 20 cm / min. 3 The current was supplied at / min. In the electrodialysis test, the current density between the two electrodes was 10 mA / cm². 2 A constant current was applied, and the voltage (applied voltage) of the electrolysis device during the electrodialysis test was measured.

[0068] <Comparative Example 1> On one side of the first cation exchange membrane, a loading of 1.13 mg / cm² was applied. 2 The anode electrode was fabricated by supporting IrO2, and humidified Ar gas was supplied to the flow path of the first chamber at a flow rate of 30 cm 3 The electrodialysis test was performed in the same manner as in Example 1, except that the supply was at / min, and the voltage (applied voltage) of the electrolytic device was measured.

[0069] <Example 2> The pumping rate of the CO2 equilibrium solution in the second chamber was set to 0.5 cm. 3The electrodialysis test was performed in the same manner as in Example 1, except that the setting was changed to / min, and the voltage (applied voltage) of the electrolytic device was measured.

[0070] <Comparative Example 2> In the second room, K + The pumping rate of the CO2 equilibrium solution containing [the substance] is 0.5 cm. 3 The electrodialysis test was performed in the same manner as in Comparative Example 1, except that the setting was changed to / min, and the voltage (applied voltage) of the electrolysis device was measured.

[0071] <Example 3> In the flow path of the first chamber, the airflow rate of He gas containing H2 is 30 cm. 3 The setting was changed to / min, and the current density between both electrodes was 20 mA / cm². 2 The electrodialysis test was performed in the same manner as in Example 1, except that a constant current was applied, and the voltage (applied voltage) of the electrolytic device was measured.

[0072] <Comparative Example 3> Current density between both electrodes: 20 mA / cm² 2 The electrodialysis test was performed in the same manner as in Comparative Example 1, except that a constant current was applied, and the voltage (applied voltage) of the electrolytic device was measured.

[0073] Figure 2 shows the measurement results of the applied voltage of the electrolytic devices during electrodialysis tests for Examples 1-3 and Comparative Examples 1-3. As shown in Figure 2, the applied voltage of the electrolytic device in Example 1 was lower than that of the electrolytic device in Comparative Example 1, resulting in a reduction in electrolytic energy consumption. Similar results were obtained in the comparison between Example 2 and Comparative Example 2, and between Example 3 and Comparative Example 3.

[0074] "Note": Structure of the present invention Configuration 1: An anode electrode containing an anode catalyst, which generates protons by electrolytic oxidation of H2, The anode electrode is placed in a first chamber to which a gas containing H2 is supplied, A second chamber is supplied with an electrolyte containing alkali metal ions, A cathode electrode containing a cathode catalyst, which generates H2 and hydroxide ions by electrolytic reduction of H2O, A third chamber is provided, in which the cathode electrode is located and an aqueous medium is supplied. A first cation exchange membrane is placed between the first chamber and the second chamber, The device comprises a second cation exchange membrane positioned between the second chamber and the third chamber, An electrolytic device characterized in that, when a voltage is applied to the anode electrode and the cathode electrode, the protons generated at the anode electrode are supplied to the second chamber through the first cation exchange membrane, the alkali metal ions in the second chamber are supplied to the third chamber through the second cation exchange membrane, and in the third chamber, an alkali hydroxide aqueous solution is generated by the reaction of the alkali metal ions with the hydroxide ions generated at the cathode electrode. Configuration 2: The electrolytic device according to configuration 1, characterized in that the anode electrode is in contact with the first cation exchange membrane. Configuration 3: The electrolytic device according to configuration 1 or 2, characterized in that the cathode electrode is in contact with the second cation exchange membrane. Configuration 4: The electrolyte containing alkali metal ions contains carbonate ion species, An electrolytic device according to any one of configurations 1 to 3, characterized in that a voltage is applied to the anode electrode and the cathode electrode, causing the proton to react with the carbonate ion species in the second chamber. Configuration 5: The alkali metal ion is Li + , Rb + , Cs + An electrolytic device according to any one of configurations 1 to 4, characterized by including at least one of the above. Configuration 6: The electrolytic device according to any one of configurations 1 to 5, characterized in that the anode catalyst includes a first catalyst that promotes the hydrogen oxidation reaction in an acidic environment. Composition 7: The electrolytic device according to configuration 6, characterized in that the anode catalyst includes a second catalyst that promotes the oxygen evolution reaction in an acidic environment. Composition 8: The electrolytic device according to configuration 6, characterized in that the first catalyst contains at least one element selected from the group consisting of Pt, Pd, Rh, Re, Au, and Ni. Composition 9: The electrolytic device according to configuration 7, characterized in that the second catalyst comprises at least one selected from the group consisting of Ir oxide, Ru oxide, a mixture containing Ir oxide and Ru oxide, and a composite oxide containing Ir and Ru. Configuration 10: The electrolytic device according to any one of configurations 1 to 9, characterized in that both the first cation exchange membrane and the second cation exchange membrane are perfluorosulfonic acid polymer membranes. Composition 11: The electrolytic device according to any one of configurations 1 to 10, characterized in that the cathode catalyst includes a catalyst that promotes the H2 generation reaction. Composition 12: The electrolytic device according to configuration 11, characterized in that the cathode catalyst contains at least one element selected from the group consisting of Pt, Pd, Rh, Re, Ni, Co, and Mo. Composition 13: The electrolytic device according to any one of configurations 1 to 12, characterized in that the height of the second chamber is 5 mm or less. Composition 14: The electrolytic device according to configuration 13, characterized in that the height of the second chamber is 2 mm or less. Composition 15: The electrolytic device according to any one of configurations 1 to 14, characterized in that the average linear velocity of the aqueous medium flowing through the third chamber is 15 cm / min or more. Composition 16: The electrolytic device described in any one of configurations 1 to 15, A gas-liquid separator for separating the H2-containing discharge liquid from the third chamber into gas and liquid, An electrolysis system characterized by comprising an H2 supply mechanism that supplies the H2 separated by the gas-liquid separation device to the first chamber. [Explanation of symbols]

[0075] 1 Electrolysis system, 10 Electrolytic device, 12 Gas-liquid separator, 14 H2 supply mechanism (supply line), 16 Gas-liquid separator, 18 Discharge line, 22 Anode electrode, 23, 29 Flow channels, 24 First chamber, 26 Second chamber, 28 Cathode electrode, 30 Third chamber, 32 First cation exchange membrane, 34 Second cation exchange membrane, 36a, 36b Frame material, 70 Power supply.

Claims

1. Includes an anode catalyst, H ２ an anode electrode that generates protons by electrolytic oxidation, The anode electrode is arranged, H ２ A first room is supplied with gas containing, A second chamber is supplied with an electrolyte containing alkali metal ions, Contains a cathode catalyst, H ２ H is produced by the electrolytic reduction of O. ２ and a cathode electrode that generates hydroxide ions, A third chamber is provided, in which the cathode electrode is located and an aqueous medium is supplied. A first cation exchange membrane is disposed between the first chamber and the second chamber, The device comprises a second cation exchange membrane disposed between the second chamber and the third chamber, An electrolytic device characterized in that, when a voltage is applied to the anode electrode and the cathode electrode, the protons generated at the anode electrode are supplied to the second chamber through the first cation exchange membrane, the alkali metal ions in the second chamber are supplied to the third chamber through the second cation exchange membrane, and in the third chamber, an alkali hydroxide aqueous solution is generated by the reaction of the alkali metal ions with the hydroxide ions generated at the cathode electrode.

2. The electrolytic device according to claim 1, characterized in that the anode electrode is in contact with the first cation exchange membrane.

3. The electrolytic device according to claim 1 or 2, characterized in that the cathode electrode is in contact with the second cation exchange membrane.

4. The electrolyte containing alkali metal ions contains carbonate ion species, The electrolytic device according to claim 1 or 2, characterized in that a voltage is applied to the anode electrode and the cathode electrode, causing the proton to react with the carbonate ion species in the second chamber.

5. The alkali metal ion is Li ＋ , Rb ＋ , Cs ＋ The electrolytic device according to claim 1 or 2, characterized by comprising at least one of the following.

6. The electrolytic device according to claim 1 or 2, characterized in that the anode catalyst includes a first catalyst that promotes a hydrogen oxidation reaction in an acidic environment.

7. The electrolytic device according to claim 6, characterized in that the anode catalyst includes a second catalyst that promotes the oxygen evolution reaction in an acidic environment.

8. The electrolytic device according to claim 6, characterized in that the first catalyst comprises at least one element selected from the group consisting of Pt, Pd, Rh, Re, Au, and Ni.

9. The electrolytic device according to claim 7, characterized in that the second catalyst comprises at least one selected from the group consisting of Ir oxide, Ru oxide, a mixture containing Ir oxide and Ru oxide, and a composite oxide containing Ir and Ru.

10. The electrolytic device according to claim 1 or 2, characterized in that both the first cation exchange membrane and the second cation exchange membrane are perfluorosulfonic acid polymer membranes.

11. The cathode catalyst is H ２ The electrolytic device according to claim 1 or 2, characterized by containing a catalyst that promotes the generation reaction.

12. The electrolytic device according to claim 11, characterized in that the cathode catalyst contains at least one element selected from the group consisting of Pt, Pd, Rh, Re, Ni, Co, and Mo.

13. The electrolytic device according to claim 1 or 2, characterized in that the height of the second chamber is 5 mm or less.

14. The electrolytic device according to claim 13, characterized in that the height of the second chamber is 2 mm or less.

15. The electrolytic device according to claim 1 or 2, characterized in that the average linear velocity of the aqueous medium flowing through the third chamber is 15 cm / min or more.

16. The electrolytic device according to claim 1 or 2, The H discharged from the third chamber ２ and a gas-liquid separator that separates the discharged liquid containing the same The H that has been separated by the gas-liquid separation device ２ H supplies to the first chamber. ２ An electrolytic system characterized by comprising a supply mechanism.

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