Electrolytic devices

Abstract

The present invention provides an electrolytic device capable of improving the current efficiency of a desired electrodialysis reaction. [Solution] The electrolytic device according to this embodiment comprises a cathode electrode 28 containing a cathode catalyst that generates H2 and hydroxide ions by electrolytic reduction of H2O, a first chamber 30 in which the cathode electrode 28 is placed and an aqueous medium is supplied, a second chamber 26 in which an electrolyte containing alkali metal ions is supplied, and a second cation exchange membrane 34 disposed between the first chamber 30 and the second chamber 26, wherein when a voltage is applied to the cathode electrode 28, an alkali hydroxide aqueous solution is generated in the first chamber 30 by a reaction between the alkali metal ions supplied from the second chamber 26 through the second cation exchange membrane 34 and the hydroxide ions generated at the cathode electrode 28, and the average linear velocity (u1) of the aqueous medium in the first chamber 30 when the voltage is applied is greater than the average linear velocity (u2) of the electrolyte in the second chamber 26.

Description

[Technical Field]

[0001] This invention relates to the technology of electrolytic devices. [Background technology]

[0002] Technologies that can contribute to carbon neutralization include electrolysis technology to obtain CO2-reducing valuable products from carbonate ion species or carbon dioxide, and carbonate ion species (carbonate ion (CO3 2- ) and bicarbonate ions (HCO3) - There is interest in electrolytic devices that utilize electrodialysis technology, etc., to recover carbon dioxide using an alkaline aqueous solution containing at least one of the following, and separate and concentrate 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. Furthermore, Patent Documents 13-14 disclose a technique for removing sparingly soluble salts and ions that segregate during electrodialysis. [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 [License 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 [License 13] Special Announcement No. 2020-028872 [License 14] Patent Gazette No. 3416455 [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 Initiative] [Problems that the invention aims to solve]

[0006] However, conventional electrodialysis technology suffers from a problem in that the current efficiency of the electrodialysis reaction (hereinafter sometimes referred to as the desired electrodialysis reaction), in which alkali metal ions are moved from a chamber through which a liquid containing alkali metal ions flows to a chamber where the cathode electrode is located, via a cation exchange membrane, by applying current to the electrodes, is low. As a result, it has been difficult to efficiently produce, for example, alkali hydroxide aqueous solutions such as lithium hydroxide aqueous solution or carbon dioxide.

[0007] Therefore, the present invention aims to provide an electrolytic device capable of improving the current efficiency of a desired electrodialysis reaction. [Means for solving the problem]

[0008] The electrolytic device according to this embodiment comprises a cathode electrode containing a cathode catalyst that generates H2 and hydroxide ions by electrolytic reduction of H2O, a first chamber in which the cathode electrode is placed and an aqueous medium is supplied, a second chamber in which an electrolyte containing alkali metal ions is supplied, and a cation exchange membrane disposed between the first chamber and the second chamber, wherein when a voltage is applied to the cathode electrode, an alkali hydroxide aqueous solution is generated in the first chamber by a reaction between the alkali metal ions supplied from the second chamber through the cation exchange membrane and the hydroxide ions generated at the cathode electrode, and the average linear velocity (u1) of the aqueous medium in the first chamber when the voltage is applied is greater than the average linear velocity (u2) of the electrolyte in the second chamber.

[0009] In the electrolysis device, the operating current density (J) of the cathode electrode satisfies J [A / cm 2 > 0.02 A / cm 2 and it is preferable that the average linear velocity (u1) of the aqueous medium satisfies u1 [cm / min] ≥ 77 cm / min × C (where C is the solubility correction coefficient).

[0010] In the electrolysis device, it is preferable that the average flow rate (V1) of the aqueous medium in the first chamber satisfies V1 [cm 3 / min] ≥ 5 cm 3 / min × C (where C is the solubility correction coefficient).

[0011] In the electrolysis device, the operating current density (J) of the cathode electrode satisfies 0 A / cm 2 < J [A / cm 2 ≤ 0.02 A / cm 2 and it is preferable that the average linear velocity (u1) of the aqueous medium satisfies u1 [cm / min] ≥ 3850 [cm 3 / A·min] × C × J [A / cm 2 (where C is the solubility correction coefficient).

[0012] In the electrolysis device, it is preferable that the average flow rate (V1) of the aqueous medium in the first chamber is greater than the average flow rate (V2) of the electrolytic solution in the second chamber.

[0013] At the same time, in the electrolysis device, the ratio (u1 / u2) of the average linear velocity (u1) of the aqueous medium in the first chamber to the average linear velocity (u2) of the electrolytic solution in the second chamber is preferably 5 or more.

[0014] In the electrolysis device, the ratio (V1 / V2) of the average flow rate (V1) of the aqueous medium in the first chamber to the average flow rate (V2) of the electrolytic solution in the second chamber is preferably 5 or more.

Advantages of the Invention

[0015] According to the present invention, it is possible to provide an electrolytic device that can improve the current efficiency of a desired electrodialysis reaction. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram showing an example of an electrolytic system according to this embodiment. [Figure 2] This is a schematic diagram showing another example of the electrolytic device of this embodiment. [Figure 3] This is a schematic diagram showing another example of the electrolytic device of this embodiment. [Figure 4] This figure illustrates preferred conditions for the average linear velocity u1 of an aqueous medium to improve current efficiency in a desired electrodialysis reaction. [Figure 5] (a) is a figure showing the relationship between current efficiency and dialysis progress indicators in Experimental Example 2-1, (b) is a figure showing the relationship between current efficiency and dialysis progress indicators in Experimental Example 2-2, and (c) is a figure showing the relationship between current efficiency and dialysis progress indicators in Experimental Example 2-3. [Figure 6] This figure shows the relationship between the current efficiency and the average flow rate of the aqueous medium in the first chamber in Experimental Example 3. [Modes for carrying out the invention]

[0017] 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.

[0018] 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, an H2 supply mechanism 14, an aqueous medium supply device 15, and an electrolyte supply device 17.

[0019] The electrolytic device 10 shown in Figure 1 includes an anode electrode 22, a third chamber 24, a second chamber 26, a cathode electrode 28, a first chamber 30, a first cation exchange membrane 32, a second cation exchange membrane 34, and frame members 36a and 36b. The third chamber 24 is provided between the frame member 36a and the first cation exchange membrane 32, and the anode electrode 22 is located there. The anode electrode 22 is adjacent to the first cation exchange membrane 32. In the third chamber 24, a flow channel 23 through which a gas containing H2 flows is located between the anode electrode 22 and the frame member 36a. The first chamber 30 is provided between the frame member 36b and the second cation exchange membrane 34, and the cathode electrode 28 is located there. The cathode electrode 28 is adjacent to the second cation exchange membrane 34. In the first chamber 30, a flow channel 29 through which an aqueous medium flows is located 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 third chamber 24 and the second chamber 26, and the second cation exchange membrane 34 is located between the second chamber 26 and the first 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 and 36b. The frame materials 36a and 36b can be made of metal, plastic, glass, etc.

[0020] The anode electrode 22 contains an anode catalyst and is an electrode that generates protons, for example, by applying a voltage. The cathode electrode 28 contains a cathode catalyst and generates H2 and hydroxide ions (OH) by the reductive electrolysis of H2O. - This is an electrode that generates ).

[0021] The gas-liquid separation device 12 includes, for example, a gas-liquid separator 16 and discharge lines 18a and 18b. One end of discharge line 18a is connected to the flow path 29 of the first chamber 30, and the other end is connected to the gas-liquid separator 16. Discharge line 18b is connected to the liquid outlet of the gas-liquid separator 16. The gas-liquid separator 16 is, for example, a conventionally known device capable of separating gas and liquid.

[0022] The H2 supply mechanism 14 shown in Figure 1 is a supply line for supplying gas containing H2 to the third chamber 24. For example, one end of the supply line is connected to the gas outlet of the gas-liquid separator 16, and the other end is connected to the flow path 23 of the third 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.

[0023] The aqueous medium supply device 15 is a device that supplies aqueous medium to the first chamber 30, and includes, for example, aqueous medium supply lines 40a, 40b and supply pumps 42a, 42b. The aqueous medium supply line 40a is connected to the flow path 29 of the first chamber 30. One end of the aqueous medium supply line 40b is connected to the discharge line 18b, and the other end is connected to the aqueous medium supply line 40a. The supply pump 42a is installed in the aqueous medium supply line 40a, and the supply pump 42b is installed in the aqueous medium supply line 40b. In this embodiment, the aqueous medium supply line 40b and supply pump 42b are not required.

[0024] The electrolyte supply device 17 is a device that supplies electrolyte to the second chamber 26, and includes, for example, an electrolyte supply line 44 and a supply pump 42c installed on the electrolyte supply line 44. The electrolyte supply line 44 is connected to the second chamber 26.

[0025] 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.

[0026] Next, we will describe an example of the operation of the electrolysis system 1 shown in Figure 1.

[0027] A gas containing H2 is supplied from the supply line 14 to the flow path 23 of the third chamber 24. The gas containing H2 is, for example, a mixture of air and hydrogen gas. Alternatively, the gas containing H2 may be humidified by a humidifier before being supplied to the flow path 23 of the third chamber 24, and supplied to the flow path 23 of the third chamber 24 as a humidified gas containing moisture. Furthermore, by operating the supply pump 42c, an electrolyte containing alkali metal ions and carbonate ions is supplied from the electrolyte supply line 44 to the second chamber 26 at a predetermined flow rate. In addition, by operating the supply pump 42a, an aqueous medium is supplied from the aqueous medium supply line 40a to the flow path 29 of the first chamber 30 at a predetermined flow rate.

[0028] When a voltage is applied between the cathode electrode 28 and the anode electrode 22 by the power supply 70, on the third chamber 24 side, when the gas containing H2 passing through the flow path 23 comes into contact with the anode electrode 22, for example, the H2 in the gas is oxidized and protons (H) are formed. + ) is produced. Also, water in the gas is oxidized to produce oxygen (O2) and protons (H + ) and 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 and bicarbonate ions in the electrolyte 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, generating carbon dioxide (neutral CO2 molecules) or bicarbonate ions from carbonate ions. Alkali metal ions in the electrolyte passing through the second chamber 26 pass through the second cation exchange membrane 34 and are supplied to the first chamber 30. Then, on the first chamber 30 side, when the aqueous medium passing through the channel 29 comes into contact with the cathode electrode 28, for example, H2O is reduced to H2 and hydroxide ions (OH) -A hydroxide ion is generated, and further reacts with alkali metal ions that have moved to the first chamber 30 side through the second cation exchange membrane 34 to produce an alkali hydroxide aqueous solution.

[0029] The carbon dioxide generated in the second chamber 26 is discharged from the second chamber 26 together with the electrolyte supplied to the second chamber 26, and is separated into a gas and liquid containing carbon dioxide by a gas-liquid separator (not shown), for example, and recovered separately.

[0030] The H2 and alkali hydroxide aqueous solution generated in the first chamber 30 are discharged from the first chamber 30 as wastewater and supplied to the gas-liquid separator 16 through the discharge line 18a. 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 discharged to the discharge line 18b, and the gas containing H2 is supplied from the supply line 14 to the flow path 23 of the third chamber 24. A portion of the alkali hydroxide aqueous solution may be supplied as an aqueous medium at a predetermined flow rate through the aqueous medium supply line 40b to the flow path 29 of the first chamber 30 by the operation of the supply pump 42b.

[0031] In this embodiment, the average linear velocity (u1) of the aqueous medium in the first chamber 30 when a voltage is applied to the electrodes is made greater than the average linear velocity (u2) of the electrolyte in the second chamber 26. By setting u1 > u2, the current efficiency of the electrodialysis reaction (the desired electrodialysis reaction described above) that moves alkali metal ions from the second chamber 26 to the first chamber 30 via the second cation exchange membrane 34 can be improved. The reason for the above effect is not fully clear, but the following is inferred.

[0032] For example, the cation that permeates the second cation exchange membrane 34 is K + or H + In this case, the reaction at cathode electrode 28 is expressed as follows: K + In this case: 2K + +2H2O+2e - →2K + (aq) + 2OH - (aq) + H2 H + In this case: 2H + +2e - →H2

[0033] The above K + In this case, the reaction will not proceed unless H2O is present near the cathode electrode 28. On the other hand, the above H + In this case, the reaction proceeds even if H2O is not present near the cathode electrode 28. For example, in the case of a 0.05 M aqueous K2CO3 solution, the cation concentration ratio [K + ] / [H + ] is 3 x 10 10 Therefore, under the conditions where the average linear velocity of the aqueous medium in the first chamber 30 is high, the supply of H2O to the cathode electrode 28 is sufficient, and all of the above reactions proceed, but from the cation concentration ratio, the above K + It is thought that the reaction in this case proceeds preferentially. Furthermore, under conditions where the average linear velocity of the aqueous medium into the first chamber 30 is high, the KOH aqueous solution (2K) generated at the cathode electrode 28 + (aq) + 2OH - (aq)) and H2 are efficiently discharged from the first chamber 30. Therefore, H + More K + Because it is easier for the second cation exchange membrane 34 to permeate, K is released from the second chamber 26 to the first chamber 30 via the second cation exchange membrane 34. + The current efficiency of the electrodialysis reaction that moves alkali metal ions is improved. In this embodiment, H is transferred to the second chamber 26 through the first cation exchange membrane 32. + K is supplied and enters the first chamber 30 through the second cation exchange membrane 34. + When K is supplied, the pH in the second chamber 26 decreases, so for example, if carbonate ion species are supplied to the second chamber 26, the carbonate ion species in the second chamber 26 are more easily converted to CO2. On the other hand, under conditions where the average linear velocity of the aqueous medium in the first chamber 30 is low, the above K + The reaction is less likely to occur in the case of the above H + In the case of K, the reaction proceeds preferentially. + More H +In this case, H is more easily permeated through the second cation exchange membrane 34, and the current efficiency of the desired electrodialysis reaction decreases. + Even if it is supplied, K is supplied to the first chamber 30 through the second cation exchange membrane 34. + H + Because it is supplied, the pH of chamber 26 hardly changes.

[0034] Figure 2 is a schematic diagram showing another example of the electrolytic device of this embodiment. In the electrolytic device 11a shown in Figure 2, components similar to those in the electrolytic device 10 shown in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted. In the electrolytic device 11a shown in Figure 2, a fluid passage chamber and ion exchange membrane group 46 involved in electrodialysis are arranged between the second chamber 26 and the anode electrode 22.

[0035] The fluid-permeable chamber / ion-exchange membrane group 46 consists of one or more fluid-permeable chambers and one or more ion-exchange membranes, which are alternately arranged between the second chamber 26 and the anode electrode 22. The ion-exchange membranes constituting the fluid-permeable chamber / ion-exchange membrane group 46 are selected from cation-exchange membranes, anion-exchange membranes, bipolar membranes composed of cation-exchange membranes and anion-exchange membranes, etc. The second chamber 26 is provided between the ion-exchange membrane at one end of the fluid-permeable chamber / ion-exchange membrane group 46 and the second cation-exchange membrane 34. Although not shown in the diagram, the anode electrode 22 may be adjacent to a fluid-permeable chamber located at the other end of the fluid-permeable chamber / ion-exchange membrane group 46, or it may be adjacent to an ion-exchange membrane located at the other end of the fluid-permeable chamber / ion-exchange membrane group 46.

[0036] An example of the operation of the electrolytic device 11a shown in Figure 2 will be described. An alkaline aqueous solution (electrolyte) containing alkali metal ions is supplied into the second chamber 26, and an aqueous medium is supplied to the flow path 29 of the first chamber 30. An aqueous medium is also supplied to the liquid passage chamber of the liquid passage chamber / ion exchange membrane group 46 as appropriate. When a voltage is applied between the cathode electrode 28 and the anode electrode 22 by the power supply 70, alkali metal ions in the electrolyte passing through the second chamber 26 pass through the second cation exchange membrane 34 and are supplied to the first chamber 30. Then, on the first chamber 30 side, when the aqueous medium passing through the flow path 29 comes into contact with the cathode electrode 28, for example, H2O is reduced to H2 and hydroxide ions (OH) - A hydroxide ion is generated, and further reacts with alkali metal ions that have moved to the first chamber 30 side through the second cation exchange membrane 34 to produce an alkali hydroxide aqueous solution. In the liquid passage chamber / ion exchange membrane group 46, for example, anions move from the second chamber 26, or cations (e.g., protons) move to the second chamber 26, and the desired desalting or concentration is achieved.

[0037] Figure 3 is a schematic diagram showing another example of the electrolytic device of this embodiment. In the electrolytic device 11b shown in Figure 3, components similar to those in the electrolytic device 10 shown in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted. In the electrolytic device 11b shown in Figure 3, an anion exchange membrane 48 is positioned between the second chamber 26 and the third chamber 24.

[0038] An example of operation of the electrolytic device 11b shown in Figure 3 will be described. As an aqueous medium, for example, an acidic aqueous solution is supplied to the channel 23 of the third chamber 24. In addition, an acidic aqueous solution (electrolyte) containing alkali metal ions is supplied to the second chamber 26. Furthermore, an aqueous medium is supplied to the channel 29 of the first chamber 30. When a voltage is applied between the cathode electrode 28 and the anode electrode 22 by the power supply 70, water is oxidized by the anode electrode 22 on the third chamber 24 side, producing oxygen (O2) and protons (H2). +) and are generated. Anions in the acidic aqueous solution passing through the second chamber 26 move to the third chamber 24 side via the anion exchange membrane 48 and react with protons generated at the anode electrode 22 to obtain a concentrated acidic aqueous solution. The concentrated acidic aqueous solution and oxygen discharged from the third chamber 24 are separated into gas and liquid forms, for example by a gas-liquid separator, and recovered separately. Alkali metal ions in the acidic aqueous solution passing through the second chamber 26 pass through the second cation exchange membrane 34 and are supplied to the first chamber 30. Then, on the first chamber 30 side, when the aqueous medium passing through the channel 29 comes into contact with the cathode electrode 28, for example, H2O is reduced to H2 and hydroxide ions (OH) - ) is generated, and further reacts with alkali metal ions that have moved to the first chamber 30 side through the second cation exchange membrane 34 to produce an alkali hydroxide aqueous solution. The waste liquid (H2 and alkali hydroxide aqueous solution) discharged from the first chamber 30 is separated into gas containing H2 and alkali hydroxide aqueous solution by the gas-liquid separator 16, for example, as described above. A portion of the alkali hydroxide aqueous solution is supplied to the flow path 29 of the first chamber 30, and the gas containing H2 is supplied to the flow path 23 of the third chamber 24.

[0039] In the electrolytic devices (11a, 11b) shown in Figures 2 and 3, the average linear velocity (u1) of the aqueous medium in the first chamber 30 when a voltage is applied to the electrodes is made greater than the average linear velocity (u2) of the electrolyte in the second chamber 26. By setting u1 > u2, the current efficiency of the electrodialysis reaction that moves alkali metal ions from the second chamber 26 to the first chamber 30 via the second cation exchange membrane 34 can be improved, similar to the electrolytic device 10 shown in Figure 1.

[0040] The average linear velocity is the speed of the liquid passing through the cross-sectional area of ​​the flow path per unit time, and is calculated by dividing the flow rate by the cross-sectional area of ​​the flow path. The average linear velocity of the electrolyte in the second chamber 26 (u2 [cm / min]) is given by the average flow rate of the electrolyte in the second chamber 26 (V2 [cm 3 [ / min]) the flow path cross-sectional area of ​​the second chamber 26 [cm 2This value is calculated by dividing by ]. Also, the average linear velocity of the aqueous medium in the first chamber 30 (u1 [cm / min]) is the average flow rate of the aqueous medium in the first chamber 30 (V1 [cm 3 [ / min]) the flow path cross-sectional area [cm²] of the first chamber 30 2 This value was calculated by dividing by [ ].

[0041] Methods to ensure u1 > u2 include, for example, the following: For example, increasing the pump output of at least one of the supply pumps 42a and 42b to make the average flow rate of the aqueous medium supplied to the first chamber 30 higher than the average flow rate of the electrolyte supplied to the second chamber 26, thereby ensuring u1 > u2. Alternatively, for example, designing the cross-sectional area of ​​the first chamber 30 (essentially the cross-sectional area of ​​the flow path 29) to be smaller than the cross-sectional area of ​​the second chamber 26, thereby ensuring u1 > u2. Of these methods, it is preferable to ensure u1 > u2 by making the average flow rate of the aqueous medium supplied to the first chamber 30 higher than the average flow rate of the electrolyte supplied to the second chamber 26, due to the ease of changing the average linear velocity, etc.

[0042] Figure 4 illustrates preferred conditions for the average linear velocity u1 of the aqueous medium for improving current efficiency in a desired electrodialysis reaction. As preferred conditions for current efficiency in the above-mentioned desired electrodialysis reaction, it is desirable to define an average linear velocity u1 of the aqueous medium that allows for efficient discharge of alkali metal ions from the first chamber 30, regardless of the operating current density of the cathode electrode 28. Considering this point, it is preferable that the average linear velocity u1 be in the region greater than or equal to the dashed line (1) shown in Figure 4. Specifically, in order to further improve current efficiency in the above-mentioned desired electrodialysis reaction, it is preferable that the average linear velocity (u1) of the aqueous medium satisfies u1 [cm / min] ≥ 77 cm / min × C, and that the operating current density (J) of the cathode electrode 28 is J [A / cm 2 >0.02A / cm 2 It is more preferable that the average linear velocity (u1) of the aqueous medium satisfies u1 [cm / min] ≥ 77 cm / min × C. Furthermore, it is preferable that the average flow rate (V1) of the aqueous medium in the first chamber 30 is V1 [cm 3 / min]≧5cm 3 It is more preferable to satisfy / min × C.

[0043] Here, the operating current density (J) of the cathode electrode 28 is the value obtained by dividing the operating current at the cathode electrode 28 by the geometric area of ​​the cathode electrode 28. Also, C is the solubility correction coefficient, and C = C sat (KOH, 25℃) / C sat (MOH, T(°C)). Here, MOH represents the hydroxide (alkali hydroxide) of an alkali metal M (M: Li, Na, K, Rb, Cs, Fr). sat (KOH, 25℃) indicates the solubility (saturation concentration) of KOH at 25℃, C sat (MOH, T(°C)) represents the solubility (saturation concentration) of alkali hydroxide MOH produced in chamber 1, 30, at the operating temperature T°C.

[0044] Furthermore, as a preferred condition for current efficiency in the desired electrodialysis reaction described above, it is desirable to define the average linear velocity u1 of the aqueous medium, which is proportional to the operating current density of the cathode electrode 28. Specifically, u1 [cm / min] = 3850 [cm 3 / A·min]×C×J[A / cm 2 It is preferable that the average linear velocity u1 be the region above the dashed line (2) in Figure 4 as defined by ]. That is, in terms of further improving the current efficiency in the desired electrodialysis reaction described above, the average linear velocity (u1) of the aqueous medium is u1 [cm / min] ≥ 3850 [cm 3 / A·min]×C×J[A / cm 2 It is preferable that the following conditions be met, and furthermore, 0 <J[A / cm 2 ]≦0.02A / cm 2 The following conditions are met, and the average linear velocity (u1) of the aqueous medium is u1 [cm / min] ≥ 3850 [cm 3 / A·min]×C×J[A / cm 2 It is more preferable that the following conditions are met. C is the solubility correction coefficient mentioned above. Note that u1[cm / min]≧3850[cm 3 / A·min]×C×J[A / cm 2 ] is derived as follows:

[0045] The rate of supply of alkali metal ions to chamber 1, 30, v(M) +) [mol / cm 2 / s] is represented by v(M + ) = J[A / cm 2 / F[C / mol] (F: Faraday constant, 96485 C / mol). The liquid feeding of the aqueous medium to the first chamber 30 serves as an exclusion force that suppresses the retention of the alkali metal ion (M + ) that has moved to the first chamber 30 through the second cation exchange membrane 34 on the surface of the second cation exchange membrane 34. This exclusion force X[cm / mol·cm + of M -2 is defined as X = U1[cm / s] / v(M + ) [mol / cm + / s] using the average linear velocity U1[cm / s] = u1[cm / min] / 60 of the aqueous medium in the first chamber 30. Under the conditions where the effect of improving the current efficiency was confirmed in Experimental Example 3 described later, M = K (that is, C 2 (KOH, 25 °C) = 19.6 mol / L, v0(M sat ) = 2.07×10 + mol / cm -7 / s (= (0.02 A / cm 2 ) / (96485 C / mol)), U 2 = 1.28 cm / s (= (77 cm / min) / (60 s / min)), considering these, the exclusion force X of M 1,0 can be expressed as X = U1 / v(M + ) ≥ C·U + / v0(M 1,0 ) [mol / cm + / s]. C is the solubility correction coefficient and is expressed as C = C sat (KOH, 25 °C) / C sat (MOH, T(°C)), and C sat (KOH, 25 °C) is 19.6 mol / L. From these, u1[cm / min] = U1[cm / s]×60 [s / min] ≥ 60C·U 1,0 ·v(M + ) = 3850 [cm 3 / A·min] CJ[A / cm 2 is derived.

[0046] Furthermore, in order to further improve the current efficiency in the desired electrodialysis reaction described above, the ratio (u1 / u2) of the average linear velocity (u1) of the aqueous medium in the first chamber 30 to the average linear velocity (u2) of the electrolyte in the second chamber 26 is preferably 5 or more. The upper limit of u1 / u2 is not particularly limited, but it may be 50 or less.

[0047] Furthermore, in order to further improve the current efficiency in the desired electrodialysis reaction described above, the ratio (V1 / V2) of the average flow rate of the aqueous medium in the first chamber 30 to the average flow rate (V2) of the electrolyte in the second chamber 26 is preferably 5 or more. The upper limit of V1 / V2 is not particularly limited, but it may be 50 or less.

[0048] 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.

[0049] 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.

[0050] The anion exchange membrane 48 used in the electrolytic device 11b in Figure 3 can be a conventionally known membrane, such as NeoSepta, Celemion, or Sustenion.

[0051] The anode electrode 22 is an oxidizing electrode that generates protons, for example, by applying a voltage. The anode electrode 22 is preferably in contact with the first cation exchange membrane 32, as shown in Figure 1, and more preferably the anode electrode 22 and the first cation exchange membrane 32 are joined together. This keeps the resistance low when the protons generated at the anode electrode 22 move to the second chamber 26. Furthermore, the anode electrode 22 is preferably in contact with the anion exchange membrane 48, as shown in Figure 3, and more preferably the anode electrode 22 and the anion exchange membrane 48 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 24.

[0052] The anode catalyst is, for example, a catalyst that promotes proton generation, and is preferably a catalyst containing at least one element selected from the group consisting of Pt, Pd, Rh, Re, Au, Ni, Ir, and Ru. Specifically, it may be a metal of Pt, Pd, Rh, Re, Au, Ni, Ir, or Ru, an alloy or compound containing such a metal, etc. The compound containing such a metal may be an oxide, hydroxide or complex, etc. The anode catalyst may be a single type or two or more types may be used in combination.

[0053] The anode catalyst content is, for example, 0.35 mg / cm² per geometric area of ​​the anode electrode 22, which can reduce the energy consumption of the electrolytic device. 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, 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:

[0054] 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 or the anion exchange membrane 48. 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.

[0055] 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 and the anion exchange membrane 48. 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:

[0056] 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.

[0057] 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 a first cation exchange membrane 32 or anion exchange membrane 48 and heat-pressing them, the anode electrode 22 and the first cation exchange membrane 32 or anion exchange membrane 48 can be joined together.

[0058] A diffusion layer may be installed in the third chamber 24 to enhance the diffusivity of gases 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.

[0059] The H2-containing gas supplied to the third 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.

[0060] The fluid supplied to chamber 3 24 is not limited to gases containing H2, but may also be humidified gases such as air or inert gases (e.g., nitrogen gas, noble gases, etc.), or an aqueous medium. The aqueous medium may be water, pure water, or an aqueous solution containing an electrolyte or a water-soluble hydrogen-containing compound. Examples of electrolytes include sodium bicarbonate (NaHCO3), potassium bicarbonate (KHCO3), potassium carbonate (K2CO3), potassium sulfate (K2SO4), potassium tetraborate (K2B4O7), dipotassium hydrogen phosphate (K2HPO4), potassium dihydrogen phosphate (KH2PO4), potassium hydroxide (KOH), sulfuric acid (H2SO4), and hydrochloric acid (HCl). Examples of water-soluble hydrogen-containing compounds include methanol (CH3OH), ethanol (C2H5OH), and hydrazine (N2H4).

[0061] The cathode electrode 28 is preferably in contact with the second cation exchange membrane 34, and it is preferable that 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 first chamber 30.

[0062] The cathode catalyst is not particularly limited as long as it is a catalyst that promotes the electrolytic reduction of H2O, but it is preferably a catalyst that contains at least one element selected from the group consisting of Pt, Pd, Rh, Re, Ni, Co, and Mo, and specifically may be the metals Pt, Pd, Rh, Re, Ni, Co, or Mo, or alloys or compounds containing such metals. The compounds containing such metals may be oxides, hydroxides, or complexes. The cathode catalyst may be used alone or in combination of two or more types.

[0063] The cathode catalyst content is, for example, 0.35 mg / cm² per geometric area of ​​the cathode electrode 28, which can reduce the energy consumption of the electrolytic device. 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:

[0064] 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.

[0065] 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 first chamber 30.

[0066] 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 first chamber 30.

[0067] Furthermore, the electrolyte containing alkali metal ions may also contain oxygen-containing organic solvents such as methanol, ethanol, acetone, ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate. Additionally, the electrolyte containing alkali metal ions may include, 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.

[0068] The aqueous medium supplied to the first 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.

[0069] The present invention will be described in more detail below with reference to experimental examples, but the present invention is not limited to the following experimental examples.

[0070] <Experimental Example 1> An electrodialysis test was performed using the electrolytic device shown in Figure 1. A Nafion N-115 membrane was used as the first cation exchange membrane. A loading of 1.31 mg / cm³ was applied to one side of the first cation exchange membrane. 2 An anode electrode was fabricated by supporting IrO2. 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 flow channel in the second chamber is 0.06 cm². 2 The dimensions were set to (0.3cm × 0.2cm). The cross-sectional area of ​​the first chamber was set to 0.065cm². 2 I set it to that.

[0071] During the electrodialysis test, humidified Ar gas was supplied to the flow path of the third chamber at an average flow rate of 30 cm³. 3 The solution is supplied at a rate of / min, and a 0.05 mol / L K2CO3 aqueous solution (electrolyte) is added to the second chamber at an average flow rate of 1.2 cm. 3 The fluid was supplied at a rate of / min. A 0.05 mol / L K2CO3 aqueous solution (aqueous medium) was supplied to the first chamber's flow path at an average flow rate of 2.3 cm³. 3 The current was supplied at / min. In the electrodialysis test, the current density between the two electrodes was 10.4 mA / cm². 2 A constant current was applied. After more than 30 minutes had elapsed since the start of the electrodialysis test, the effluent discharged from the second chamber was collected, and the K contained in the fluid was measured. + The concentration was measured. K + The concentration is measured by K + The test was performed using a concentration meter (manufactured by Toa DKK). The K2CO3 aqueous solution supplied to the second chamber before the electrodialysis test was measured. + The concentration was also measured. K before and after the electrodialysis test. + The current efficiency η (%) was calculated from the concentration change ΔC (mol / L) using the following formula. As a result, the current efficiency η was 80% or higher. This current efficiency is due to the transfer of cations from the second chamber to the first chamber via the cation exchange membrane. + This is the current efficiency in the electrodialysis reaction that moves the material. (|ΔC|×V2 / 60 / 1000) / (I / F)×100 V2: Average flow rate of K2CO3 aqueous solution in the second chamber [cm²] 3 / min] I: Current [A] F: Faraday constant, 96485 C / mol

[0072] Next, with the supply of K2CO3 aqueous solution to the second chamber stopped, the same electrodialysis test was performed as described above, and the current efficiency was calculated to be less than 40%.

[0073] Finally, the supply of K2CO3 aqueous solution to the second chamber was resumed, and the electrodialysis test was performed in the same manner as above. The current efficiency was calculated and found to have recovered to over 80%.

[0074] As can be seen from these results, by making the average linear velocity of the aqueous medium in the first chamber (u1 ≈ 35 cm / min) greater than the average linear velocity of the electrolyte in the second chamber (u2 = 2 cm / min) during the electrodialysis test, the current efficiency of the desired electrodialysis reaction can be improved.

[0075] <Experimental Example 2-1> In the second chamber, 0.136 mol / L K + A 400 ppm (total pressure 1 bar) CO2 equilibrium solution (electrolyte containing 0.0355 mol / L K2CO3 + 0.065 mol / L KHCO3) containing the above was poured at an average flow rate (V2) of 1 cm². 3 The system is supplied at a rate of / min (average linear velocity u2 = 16.67 cm / min), and an aqueous solution (aqueous medium) containing 0.0328 mol / L K2CO3 + 0.0343 mol / L KHCO3 is introduced into the flow path of the first chamber at an average flow rate (V1) of 1 cm 3 / min (average linear velocity u1 = 15.38 cm / min) or average flow rate (V1) 15 cm 3 The supply was at a rate of / min (average linear velocity u1 = 230.77 cm / min), and the current densities between the two electrodes were 10, 15, 20, 25, and 30 mA / cm². 2 An electrodialysis test was conducted under the same conditions as in Experimental Example 1, except for the application of a constant current, and the current efficiency was calculated.

[0076] <Experimental Example 2-2> In the second chamber, 0.236 mol / L K + A 400 ppm (total pressure 1 bar) CO2 equilibrium solution (electrolyte containing 0.072 mol / L K2CO3 + 0.092 mol / L KHCO3) containing the above was poured at an average flow rate (V2) of 1 cm². 3 Except for supplying at a rate of / min (average linear velocity u2 = 16.67 cm / min), the electrodialysis test was conducted under the same conditions as in Experimental Example 2-1, and the current efficiency was calculated.

[0077] <Experimental Example 2-3> In the second chamber, 0.136 mol / L K + A solution prepared by adding 0.05 mol / L K2SO4 to a 400 ppm (total pressure 1 bar) CO2 equilibrium solution (electrolyte containing 0.0355 mol / L K2CO3 + 0.065 mol / L KHCO3) containing [the specified substance] was prepared at an average flow rate (V2) of 1 cm. 3 Except for supplying at a rate of / min (average linear velocity u2 = 16.67 cm / min), the electrodialysis test was conducted under the same conditions as in Experimental Example 2-1, and the current efficiency was calculated.

[0078] Figure 5(a) shows the relationship between current efficiency and the dialysis progress index in Experimental Example 2-1, Figure 5(b) shows the relationship between current efficiency and the dialysis progress index in Experimental Example 2-2, and Figure 5(c) shows the relationship between current efficiency and the dialysis progress index in Experimental Example 2-3. The dialysis progress index is K under ideal conditions with 100% current efficiency. + Concentration change |ΔC 100% | and the K in the liquid supplied to the second chamber + Concentration C0(K + ) ratio (P=|ΔC 100% | / C0(K + )) is defined as follows. P=0 means the fluid delivery and current conditions under which there is no dialysis reaction, and P=1 means the fluid delivery and current conditions under which the dialysis reaction is completed when the current efficiency is 100% (the fluid supplied to the second chamber (i.e., the CO2 equilibrium solution of K2CO3 + KHCO3 or the equilibrium solution with K2SO4 added) reaches H2O + CO2).

[0079] As shown in Figure 5, in all experimental examples, by increasing the average linear velocity u1 from 15.38 cm / min to 230.77 cm / min, and making the average linear velocity (u1) of the aqueous medium in the first chamber greater than the average linear velocity (u2) of the electrolyte in the second chamber during the electrodialysis test, the current efficiency of the desired electrodialysis reaction was improved.

[0080] <Experimental Example 3> In the flow path of the first chamber, an aqueous solution (aqueous medium) containing 0.0328 mol / L K2CO3 + 0.0343 mol / L KHCO3 was introduced at average flow rates of 1, 5, and 15 cm. 3 The current was supplied at a rate of / min (average linear velocity u1 = 15.38, 76.92, 230.77 cm / min), and the current density between both electrodes was 20 mA / cm². 2 An electrodialysis test was conducted under the same conditions as in Example 2-1, except that a constant current was applied, and the current efficiency was calculated. The dialysis progress index in Example 3 was 0.57.

[0081] Figure 6 shows the relationship between the average flow rate of the aqueous medium in the first chamber and the current efficiency in Experimental Example 3. As shown in Figure 6, by increasing the average flow rate of the aqueous medium in the first chamber and making the average linear velocity of the aqueous medium in the first chamber (u1) greater than the average linear velocity of the electrolyte in the second chamber (u2) during the electrodialysis test, the current efficiency of the desired electrodialysis reaction described above could be improved.

[0082] From the results of the above experimental example, in order to improve the current efficiency of the desired electrodialysis reaction, it is necessary to assume that the average linear velocity of the aqueous medium in the first chamber (u1) > the average linear velocity of the electrolyte in the second chamber (u2), and that the average flow rate of the aqueous medium in the first chamber (V1) > the average flow rate of the electrolyte in the second chamber (V2), and that the average flow rate of the aqueous medium in the first chamber (V1) ≥ 5 cm 3It is preferable that the flow rate is / min, the average linear velocity of the aqueous medium in the first chamber (u1) is ≥ 77 cm / min, the ratio of the average linear velocity of the aqueous medium in the first chamber (u1 / u2) to the average linear velocity of the electrolyte in the second chamber (u2) is ≥ 5, or the ratio of the average flow rate of the aqueous medium in the first chamber (V1 / V2) to the average flow rate of the electrolyte in the second chamber (V2) is ≥ 5.

[0083] "Note": Structure of the present invention Configuration 1: A cathode electrode containing a cathode catalyst, which generates H2 and hydroxide ions by electrolytic reduction of H2O, The cathode electrode is placed in the first chamber, and an aqueous medium is supplied to it. A second chamber is supplied with an electrolyte containing alkali metal ions, The device comprises a cation exchange membrane positioned between the first chamber and the second chamber, When a voltage is applied to the cathode electrode, an alkali hydroxide aqueous solution is produced in the first chamber by a reaction between the alkali metal ions supplied from the second chamber through the cation exchange membrane and the hydroxide ions generated at the cathode electrode. An electrolytic device characterized in that the average linear velocity (u1) of the aqueous medium in the first chamber when the voltage is applied is greater than the average linear velocity (u2) of the electrolyte in the second chamber. Configuration 2: The operating current density (J) of the cathode electrode is J [A / cm²]. 2 >0.02A / cm 2 The electrolytic device according to configuration 1, characterized in that the above conditions are met and the average linear velocity (u1) of the aqueous medium satisfies u1 [cm / min] ≥ 77 cm / min × C (where C is a solubility correction coefficient). Configuration 3: The average flow rate (V1) of the aqueous medium in the first chamber is V1 [cm 3 / min]≧5cm 3 The electrolytic device according to configuration 2, characterized in that it satisfies / min × C (where C is a solubility correction coefficient). Configuration 4: The operating current density (J) of the cathode electrode is 0 A / cm². 2 <J[A / cm 2 ]≦0.02A / cm 2 The following conditions are met, and the average linear velocity (u1) of the aqueous medium is u1 [cm / min] ≥ 3850 [cm 3 / A·min]×C×J[A / cm 2 An electrolytic device according to any one of configurations 1 to 3, characterized in that it satisfies the following condition (where C is a solubility correction coefficient). Configuration 5: The electrolytic device according to any one of configurations 1 to 4, characterized in that the average flow rate (V1) of the aqueous medium in the first chamber is greater than the average flow rate (V2) of the electrolyte in the second chamber. Configuration 6: The electrolytic device according to any one of configurations 1 to 5, characterized in that the ratio (u1 / u2) of the average linear velocity (u1) of the aqueous medium in the first chamber to the average linear velocity (u2) of the electrolyte in the second chamber is 5 or more. Composition 7: An electrolytic device according to any one of configurations 1 to 6, characterized in that the ratio (V1 / V2) of the average flow rate (V1) of the aqueous medium in the first chamber to the average flow rate (V2) of the electrolyte in the second chamber is 5 or more. [Explanation of Symbols]

[0084] 1 Electrolytic system, 10,11a,11b Electrolytic devices, 12 Gas-liquid separator, 14 H2 supply mechanism (supply line), 15 Aqueous medium supply device, 16 Gas-liquid separator, 17 Electrolyte supply device, 18a,18b Discharge line, 22 Anode electrode, 23,29 Flow channels, 24 Third chamber, 26 Second chamber, 28 Cathode electrode, 30 First chamber, 32 First cation exchange membrane, 34 Second cation exchange membrane, 36a,36b Frame material, 40a,40b Aqueous medium supply line, 42a,42b,42c Supply pump, 44 Electrolyte supply line, 46 Liquid passage chamber / ion exchange membrane group, 48 Anion exchange membrane, 70 Power supply.

Claims

1. Contains a cathode catalyst, H ２ H is produced by the electrolytic reduction of O. ２ and a cathode electrode that generates hydroxide ions, The cathode electrode is positioned in the first chamber, and an aqueous medium is supplied to it. A second chamber is supplied with an electrolyte containing alkali metal ions, The device comprises a cation exchange membrane disposed between the first chamber and the second chamber, When a voltage is applied to the cathode electrode, an alkali hydroxide aqueous solution is produced in the first chamber by a reaction between the alkali metal ions supplied from the second chamber through the cation exchange membrane and the hydroxide ions generated at the cathode electrode. The average linear velocity (u) of the aqueous medium in the first chamber when the voltage is applied. １ ) is the average linear velocity of the electrolyte in the second chamber (u ２ An electrolytic device characterized by being larger than ).

2. The operating current density (J) of the cathode electrode is J [A / cm²]. ２ ]>0.02A / cm ２ The conditions are met, and the average linear velocity (u) of the aqueous medium are satisfied. １ ) but, u １ The electrolytic device according to claim 1, characterized in that [cm / min] ≥ 77 cm / min × C (where C is a solubility correction coefficient).

3. The average flow rate (V １ ) of the aqueous medium in the first chamber is such that V １ [cm ３ / min] ≥ 5 cm ３ / min × C (where C is a solubility correction coefficient), and the electrolysis device according to claim 2 is characterized by this.

4. The operating current density (J) of the cathode electrode is 0 A / cm². ２ <J[A / cm ２ ]≦0.02A / cm ２ The conditions are met, and the average linear velocity (u) of the aqueous medium are satisfied. １ ) but, u １ [cm / min]≧3850[cm ３ / A・min]×C×J[A / cm ２ The electrolytic device according to claim 1, characterized in that it satisfies the following conditions (where C is a solubility correction coefficient).

5. The average flow rate (V) of the aqueous medium in the first chamber. １ ) is the average flow rate of the electrolyte in the second chamber (V ２ The electrolytic device according to any one of claims 1 to 4, characterized in that it is larger than ).

6. The average linear velocity (u) of the electrolyte in the second chamber ２ The average linear velocity (u) of the aqueous medium in the first chamber relative to ) １ ) ratio (u １ / u ２ The electrolytic device according to any one of claims 1 to 4, characterized in that the number is 5 or more.

7. The average flow rate of the electrolyte in the second chamber (V ２ ) the average flow rate of the aqueous medium in the first chamber (V １ ) ratio (V １ / V ２ The electrolytic device according to any one of claims 1 to 4, characterized in that the number is 5 or more.

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