Method for producing fluorine-containing compound and electrolytic solution

Abstract

To provide a method for producing a fluorine-containing compound, hardly causing an anode effect when producing the fluorine-containing compound such as fluorine gas by electrolyzing an electrolytic solution.SOLUTION: The method for producing a fluorine-containing compound includes an electrolysis step of electrolyzing an electrolytic solution using an anode and a cathode to produce a fluorine-containing compound. The electrolytic solution contains hydrogen fluoride, a metal fluoride, and a complex ion represented by the chemical formula [MXn] m -. In the chemical formula [MXn] m -, M represents an ion of a d-block element having 4 or more and 8 or less electrons in the outermost d-orbital, X represents a halogen atom, m representing the valence of the complex ion is an integer of 1 or more and 5 or less, and n representing the number of X's is an integer of 2 or more and 10 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a fluorine-containing compound and an electrolyte solution. [Background technology]

[0002] Fluorine gas can be synthesized by electrolyzing an electrolyte solution containing hydrogen fluoride and potassium fluoride. A carbonaceous electrode can be used as the anode when electrolyzing the electrolyte solution. However, there is a risk of a phenomenon (hereinafter sometimes referred to as the "anode effect") occurring during electrolysis, in which the flow of current decreases and the electrolysis voltage increases. This anode effect occurs because an insulating film is formed on the surface of the carbonaceous electrode.

[0003] Once the anode effect occurs, it becomes difficult to continue electrolysis. Also, once the anode effect occurs, the electrode becomes difficult to pass current due to the insulating coating, making it difficult to reuse the electrode for electrolysis. Therefore, once the anode effect occurs, electrolysis cannot be carried out stably. Patent Document 1 discloses a technique for producing fluorine gas by electrolyzing a molten salt obtained by adding a metal chloride hydrate to a mixture of hydrogen fluoride and potassium fluoride. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 60-5674 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the technique disclosed in Patent Document 1, it is possible to suppress the occurrence of the anode effect by adding a hydrate of a metal chloride, but there has been a demand for a technique that can further suppress the occurrence of the anode effect. An object of the present disclosure is to provide a method for producing a fluorine-containing compound such as fluorine gas, which is less susceptible to the anode effect when producing the fluorine-containing compound by electrolyzing an electrolyte solution, and an electrolyte solution. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the present disclosure is as follows [1] to

[21] . [1] An electrolysis step is provided in which an electrolyte is electrolyzed using an anode and a cathode to produce a fluorine-containing compound; The electrolyte contains hydrogen fluoride, a metal fluoride, and a compound represented by the chemical formula [MXn] m- and a complex ion represented by The chemical formula [MXn] m- wherein M is an ion of a d-block element having 4 or more and 8 or less electrons in the outermost d orbital, X is a halogen atom, m indicating the valence of the complex ion is an integer of 1 or more and 5 or less, and n indicating the number of Xs is an integer of 2 or more and 10 or less.

[0007] [2] An electrolytic solution production step is provided before the electrolysis step, in which the hydrogen fluoride, the metal fluoride, and a metal complex compound represented by the chemical formula AmMXn are mixed to produce the electrolytic solution; [1] The method for producing a fluorine-containing compound according to [1], wherein in the chemical formula AmMXn, A is an alkali metal cation or an ammonium ion, MXn is an anion, M is an ion of a d-block element having 4 to 8 electrons in the outermost d orbital, X is a halogen atom, m indicating the number of A is an integer of 1 to 5, and n indicating the number of X is an integer of 2 to 10.

[0008] [3] The method for producing a fluorine-containing compound according to [1] or [2], wherein M is at least one metal ion selected from the group consisting of platinum, palladium, gold, iridium, rhodium, ruthenium, and silver. [4] The method for producing a fluorine-containing compound according to [2], wherein A is at least one cation selected from the group consisting of potassium, cesium, and rubidium.

[0009] [5] The method for producing a fluorine-containing compound according to any one of [1] to [4], wherein X is at least one of a fluorine atom and a chlorine atom. [6] The method for producing a fluorine-containing compound according to any one of [1] to [5], wherein M is an ion of a d-block element having 5 or more and 7 or less electrons in the outermost d orbital.

[0010] [7] The method for producing a fluorine-containing compound according to any one of [1] to [6], wherein the metal fluoride is at least one of potassium fluoride, ammonium fluoride, and cesium fluoride. [8] The method for producing a fluorine-containing compound according to any one of [1] to [7], wherein the content of ions of the d-block element in the electrolytic solution is 1 ppm by mass or more and 10% by mass or less.

[0011] [9] The method for producing a fluorine-containing compound according to any one of [1] to [8], wherein the water content in the electrolytic solution is 1 ppm by mass or more and 100 ppm by mass or less.

[10] The method for producing a fluorine-containing compound according to any one of [1] to [9], wherein the fluorine-containing compound is at least one of fluorine gas, nitrogen trifluoride, fluorocarbon, chlorofluorocarbon, and hydrofluorocarbon.

[11] The method for producing a fluorine-containing compound according to any one of [1] to

[10] , wherein the anode is a carbonaceous electrode.

[0012]

[12] An electrolyte that generates a fluorine-containing compound by electrolysis, Hydrogen fluoride and metal fluorides with the chemical formula [MXn] m- and a complex ion represented by The chemical formula [MXn] m- wherein M is an ion of a d-block element having 4 or more and 8 or less electrons in the outermost d orbital, X is a halogen atom, m indicating the valence of the complex ion is an integer of 1 or more and 5 or less, and n indicating the number of Xs is an integer of 2 or more and 10 or less.

[0013]

[13] The electrolyte solution according to

[12] , further containing an ion represented by chemical formula A, wherein A is an alkali metal cation or an ammonium ion.

[14] The electrolyte solution according to

[12] or

[13] , wherein M is at least one metal ion selected from the group consisting of platinum, palladium, gold, iridium, rhodium, ruthenium, and silver.

[15] The electrolyte solution according to

[13] , wherein A is at least one cation selected from the group consisting of potassium, cesium, and rubidium.

[0014]

[16] The electrolyte solution according to any one of

[12] to

[15] , wherein X is at least one of a fluorine atom and a chlorine atom.

[17] The electrolyte solution according to any one of

[12] to

[16] , wherein M is an ion of a d-block element having 5 to 7 electrons in the outermost d orbital.

[18] The electrolytic solution according to any one of

[12] to

[17] , wherein the metal fluoride is at least one of potassium fluoride, ammonium fluoride, and cesium fluoride.

[0015]

[19] The electrolyte solution according to any one of

[12] to

[18] , wherein the content of ions of the d-block element is 1 ppm by mass or more and 10% by mass or less.

[20] The electrolyte solution according to any one of

[12] to

[19] , wherein the water content is 1 ppm by mass or more and 100 ppm by mass or less.

[21] The electrolyte solution according to any one of

[12] to

[20] , wherein the fluorine-containing compound is at least one of fluorine gas, nitrogen trifluoride, fluorocarbon, chlorofluorocarbon, and hydrofluorocarbon. [Effects of the Invention]

[0016] According to the present disclosure, the anode effect is unlikely to occur when an electrolytic solution is electrolyzed to produce a fluorine-containing compound such as fluorine gas. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment of the present disclosure will be described below. Note that this embodiment shows an example of the present disclosure, and the present disclosure is not limited to this embodiment. Furthermore, various modifications or improvements can be made to this embodiment, and such modifications or improvements can also be included in the present disclosure.

[0018] The method for producing a fluorine-containing compound according to this embodiment includes an electrolysis step in which an electrolyte solution is electrolyzed using an anode and a cathode to produce a fluorine-containing compound. The electrolyte solution contains hydrogen fluoride (HF), a metal fluoride, and a compound represented by the chemical formula [MXn]. m- and a complex ion represented by the chemical formula [MXn] m- In the formula, M is an ion of a d-block element having 4 to 8 electrons in the outermost d orbital, X is a halogen atom, m, which indicates the valence of the complex ion, is an integer of 1 to 5, and n, which indicates the number of Xs, is an integer of 2 to 10.

[0019] According to the method for producing a fluorine-containing compound according to this embodiment, a compound represented by the chemical formula [MXn] m- Since the electrolytic solution contains the complex ion represented by the formula (I), the anode effect is unlikely to occur when the electrolytic solution is electrolyzed to produce a fluorine-containing compound such as fluorine gas (F2). Therefore, the electrolysis can be stably carried out, and the fluorine-containing compound can be stably produced.

[0020] The electrolyte solution according to this embodiment is an electrolyte solution that generates a fluorine-containing compound by electrolysis, and includes hydrogen fluoride, a metal fluoride, and a fluorine-containing compound represented by the chemical formula [MXn] m- and a complex ion represented by the chemical formula [MXn] m- In the formula, M is an ion of a d-block element having 4 to 8 electrons in the outermost d orbital, X is a halogen atom, m, which indicates the valence of the complex ion, is an integer of 1 to 5, and n, which indicates the number of Xs, is an integer of 2 to 10.

[0021] The electrolyte solution according to this embodiment has the chemical formula [MXn] m-Since the electrolyte solution according to this embodiment contains the complex ion represented by the formula (I), the anode effect is unlikely to occur when the electrolyte solution according to this embodiment is electrolyzed to produce a fluorine-containing compound such as fluorine gas. Therefore, by using the electrolyte solution according to this embodiment, electrolysis can be carried out stably, and therefore a fluorine-containing compound can be produced stably.

[0022] Conventionally, electrolysis of an electrolyte solution has had to be carried out at a low current density that makes it difficult for the anode effect to occur. For example, conventionally, the current density was 0.1 to 0.2 A / cm 2 However, when electrolysis is carried out at a low current density, there is a problem that the amount of fluorine-containing compounds produced by electrolysis is low.

[0023] In contrast, in the case of the method for producing a fluorine-containing compound according to this embodiment, or in the case of producing a fluorine-containing compound by electrolyzing the electrolyte solution according to this embodiment, the current is 0.3 A / cm 2 High current densities (e.g., 2 A / cm 2 ), electrolysis of the electrolyte can be carried out while preventing the occurrence of the anode effect. Therefore, electrolysis can be carried out stably for a long period of time. 2 Since electrolysis can be carried out at such a high current density, the amount of fluorine-containing compound produced per unit time can be increased.

[0024] Furthermore, in the method for producing a fluorine-containing compound according to this embodiment, or in the case of producing a fluorine-containing compound by electrolyzing the electrolyte solution according to this embodiment, even if an electrode in which the anode effect has occurred once can be used, a current can be passed through the electrode again, and therefore, even if an electrode in which the anode effect has occurred once can be used again for electrolysis of the electrolyte solution.

[0025] The method for producing a fluorine-containing compound according to this embodiment and the electrolyte solution according to this embodiment will be described in further detail below. [Electrolyte] The electrolyte solution to be electrolyzed in the method for producing a fluorine-containing compound according to this embodiment and the electrolyte solution according to this embodiment (hereinafter, both may be simply referred to as "electrolyte solution") contain hydrogen fluoride, a metal fluoride, and a compound represented by the chemical formula [MXn] m- It contains a complex ion represented by the chemical formula [MXn] m- The above is as stated above.

[0026] The electrolytic solution containing the complex ion can be produced by mixing hydrogen fluoride, a metal fluoride, and a metal complex compound represented by the chemical formula AmMXn. That is, the method for producing a fluorine-containing compound according to this embodiment may include, prior to the electrolysis step, an electrolytic solution production step of mixing hydrogen fluoride, a metal fluoride, and a metal complex compound represented by the chemical formula AmMXn to produce an electrolytic solution, wherein A in the chemical formula AmMXn is an alkali metal cation or an ammonium ion, MXn is an anion, M is an ion of a d-block element having 4 to 8 electrons in its outermost d orbital, X is a halogen atom, m representing the number of A is an integer of 1 to 5, and n representing the number of X is an integer of 2 to 10.

[0027] That is, the method for producing a fluorine-containing compound according to this embodiment includes: an electrolyte solution production step of mixing hydrogen fluoride, a metal fluoride, and a metal complex compound represented by the chemical formula AmMXn to produce an electrolyte solution; and an electrolysis step of electrolyzing the electrolyte solution using an anode and a cathode to produce a fluorine-containing compound, wherein A in the chemical formula AmMXn is an alkali metal cation or an ammonium ion, MXn is an anion, M is an ion of a d-block element having 4 or more and 8 or less electrons in the outermost d orbital, X is a halogen atom, m indicating the number of A's is an integer of 1 or more and 5 or less, and n indicating the number of X's is an integer of 2 or more and 10 or less.

[0028] Thus, the electrolyte may further contain an ion represented by the chemical formula A, where A is an alkali metal cation or an ammonium ion (NH + ) The ion A contained in the electrolyte and the ion A in the metal complex compound represented by the chemical formula AmMXn may be an alkali metal cation, an alkaline earth metal cation, or an ammonium ion, but is preferably an alkali metal cation, and more preferably at least one cation selected from potassium (K), cesium (Cs), and rubidium (Rb).

[0029] M in the complex ion contained in the electrolytic solution and M in the metal complex compound represented by the chemical formula AmMXn are ions of d-block elements having 4 to 8 electrons in the outermost d orbital, preferably ions of d-block elements having 5 to 7 electrons in the outermost d orbital, and more preferably ions of at least one metal selected from the group 5, 7, 8, 9, 10, and 11 elements of the periodic table.

[0030] M is more preferably at least one metal ion selected from platinum (Pt), palladium (Pd), gold (Au), iridium (Ir), ruthenium (Ru), silver (Ag), nickel (Ni), rhodium (Rh), osmium (Os), cobalt (Co), copper (Cu), manganese (Mn), tantalum (Ta), and niobium (Nb), and particularly preferably at least one metal ion selected from platinum, palladium, gold, iridium, rhodium, ruthenium, and silver.

[0031] The outermost electron configuration of these metals is preferably a tetravalent state in the d6 orbital (six electrons arranged in the d orbital) for platinum, palladium, and nickel, a tetravalent state in the d5 orbital (five electrons arranged in the d orbital) for iridium and rhodium, a trivalent state in the d7 orbital (seven electrons arranged in the d orbital) for gold and silver, and a tetravalent state in the d4 orbital (four electrons arranged in the d orbital) for ruthenium.

[0032] X in the complex ion contained in the electrolyte and X in the metal complex compound represented by the chemical formula AmMXn are ligands. X is preferably at least one of a fluorine atom (F), a chlorine atom (Cl), an iodine atom (I), and a bromine atom (Br), more preferably at least one of a fluorine atom and a chlorine atom, and even more preferably a fluorine atom.

[0033] m is the valence of the ion in the complex ion contained in the electrolyte solution, and is also a number indicating the number of As in the metal complex compound represented by the chemical formula AmMXn. m is an integer of 1 or more and 5 or less, but may be an integer of 1 or more and 3 or less. n in the complex ion contained in the electrolytic solution and n in the metal complex compound represented by the chemical formula AmMXn are numbers indicating the number of X. n is an integer of 2 or more and 10 or less, but may be an integer of 2 or more and 7 or less.

[0034] In the method for producing a fluorine-containing compound according to this embodiment, an electrolyte solution can be produced by mixing hydrogen fluoride, a metal fluoride, and a metal complex compound represented by the chemical formula AmMXn. However, instead of the metal complex compound represented by the chemical formula AmMXn, a fluoride, chloride, oxide, or elemental metal of a d-block element having 4 or more and 8 or less electrons in the outermost d orbital (e.g., platinum, palladium, gold, iridium, rhodium, ruthenium, and silver) may be used.

[0035] When preparing an electrolyte solution by mixing hydrogen fluoride, a metal fluoride, and a metal complex compound represented by the chemical formula AmMXn, it is preferable that the metal complex compound has high solubility. It is also more preferable to use a fluorine compound as the metal complex compound, which is less likely to generate impurities.

[0036] Examples of metal complex compounds in which M is platinum and A is a potassium cation include fluoride complexes such as K2PtF4, K2PtF5, K2PtF6, KPtF3, KPtF4, and KPtF5, and chloride complexes such as K2PtCl4, K2PtCl5, K2PtCl6, KPtCl3, KPtCl4, and KPtCl5.

[0037] Examples of metal complex compounds in which M is platinum and A is a cesium cation or a rubidium cation include metal complex compounds in which the potassium cation in the above-mentioned fluoride complexes or chloride complexes is replaced with a cesium cation or a rubidium cation, such as Cs2PtF6. When nitrogen trifluoride (NF3) is produced as the fluorine-containing compound, a metal complex compound in which M is platinum and A is an ammonium ion may be used, such as (NH4)2PtF6 or (NH4)2PtF5.

[0038] K2PtF6 is a preferred metal complex compound because it is easily soluble. By mixing a chloride complex such as K2PtCl6 or K2PtCl5 with hydrogen fluoride and a metal fluoride, and then electrolyzing it using a carbonaceous electrode or a diamond electrode to generate fluorine gas, the chloride complex can be converted into a fluoride complex, yielding K2PtF6. Alternatively, the chloride complex can be converted to a fluoride complex to obtain K2PtF6 by placing solid powder of K2PtCl6 in a platinum dish, placing the platinum dish in a horizontal cylindrical reactor, heating it to 250-400°C by external heating, and passing fluorine gas through it.

[0039] In the case of a fluoride complex in which M is platinum, K2PtF6, in which the valence of platinum is tetravalent, is preferred. By adding K2PtF6, the effect of suppressing the anode effect is quickly achieved. In the case of K2PtF4, K2PtF5, etc., in which the number of electrons in the d orbital of platinum is 7 or 8 (the valence of platinum is 2 or 3), it is preferable to pre-electrolyze the electrolyte in order to fully exhibit the effect of suppressing the anode effect. Pre-electrolysis refers to the process in which a current of 0.05 to 0.5 A / cm is applied prior to electrolysis to produce a fluorine-containing compound.2 This is an operation in which electrolysis is carried out for a certain period of time at a current density of 1000 kJ / s.

[0040] Examples of metal complex compounds in which M is palladium and A is a potassium cation include fluoride complexes such as K2PdF4, K2PdF5, K2PdF6, KPdF3, KPdF4, and KPdF5. When nitrogen trifluoride is produced as the fluorine-containing compound, a metal complex compound in which M is palladium and A is an ammonium ion may be used, such as (NH4)2PdF6 and (NH4)2PdF5.

[0041] K2PdF6 is a preferred metal complex compound because it is easily soluble. By mixing a chloride complex such as K2PdCl6 or K2PdCl5 with hydrogen fluoride and a metal fluoride, and then electrolyzing it using a carbonaceous or diamond electrode to generate fluorine gas, the chloride complex can be converted into a fluoride complex, yielding K2PdF6. Alternatively, the chloride complex can be converted to a fluoride complex to obtain K2PdF6 by placing solid powder of K2PdCl6 in a platinum dish, placing the platinum dish in a horizontal cylindrical reactor, heating it to 250-400°C by external heating, and passing fluorine gas through it.

[0042] In the case of a fluoride complex in which M is palladium, K2PdF6 is preferred. By adding K2PdF6, the effect of suppressing the anode effect is quickly achieved. For K2PdF4, K2PdF5, etc., in which the number of electrons in the d orbital of palladium is 7 or 8 (the valence of palladium is divalent or trivalent), it is preferable to pre-electrolyze the electrolyte in order to fully demonstrate the effect of suppressing the anode effect.

[0043] Examples of metal complex compounds where M is gold and A is a potassium cation include fluoride complexes such as KAuF4, K2AuF5, and KAuF3. When nitrogen trifluoride is produced as the fluorine-containing compound, a metal complex compound in which M is gold and A is an ammonium ion may be used, such as (NH4)AuF4 or (NH4)AuF3.

[0044] KAuF4 is a preferred metal complex compound because it is easily soluble. By mixing a chloride complex such as KAuCl4 with hydrogen fluoride and a metal fluoride, and then electrolyzing the mixture using a carbonaceous or diamond electrode to generate fluorine gas, the chloride complex can be converted to a fluoride complex, yielding KAuF4. Alternatively, the chloride complex can be converted to a fluoride complex to obtain KAuF4 by placing solid powder of KAuCl4 in a platinum dish, placing the platinum dish in a horizontal cylindrical reactor, heating it to 250-400°C by external heating, and passing fluorine gas through it.

[0045] In the case of a fluoride complex in which M is gold, KAuF4 is preferred. By adding KAuF4, the effect of suppressing the anode effect is quickly achieved. For KAuF3 and other compounds in which the number of electrons in the gold d orbital is 9 (gold has a valence of 2), it is preferable to pre-electrolyze the electrolyte in order to fully exert the effect of suppressing the anode effect.

[0046] Examples of metal complex compounds where M is iridium and A is potassium cation include fluoride complexes such as K2IrF6, KirF3, KirF6, and K3IrF6, as well as K2IrCl6, KirCl4, K2IrCl4, KirCl5, K3IrCl6, K4IrCl6, KirCl6, and K4Ir2Cl. 10 and chloride complexes such as K3Ir2Cl9. When nitrogen trifluoride is produced as the fluorine-containing compound, a metal complex compound in which M is iridium and A is an ammonium ion may be used, such as (NH4)2IrF6 and (NH4)IrF6.

[0047] K2IrF6 is a preferred metal complex compound because it is easily soluble. By mixing a chloride complex such as K2IrCl6 with hydrogen fluoride and a metal fluoride, and then electrolyzing it using a carbonaceous electrode or diamond electrode to generate fluorine gas, the chloride complex can be converted into a fluoride complex, yielding K2IrF6. Alternatively, the chloride complex can be converted to a fluoride complex to obtain K2IrF6 by placing solid powder of K2IrCl6 in a platinum dish, placing the platinum dish in a horizontal cylindrical reactor, heating it to 250-400°C by external heating, and passing fluorine gas through it.

[0048] In the case of a fluoride complex in which M is iridium, K2IrF6 is preferred. By adding K2IrF6, the effect of suppressing the anode effect is quickly achieved. For K2IrCl4, K2IrF5, etc., in which the number of electrons in the d orbital of iridium is 5 or 6 (the valence of iridium is divalent or trivalent), it is preferable to pre-electrolyze the electrolyte in order to fully achieve the effect of suppressing the anode effect.

[0049] Examples of metal complex compounds in which M is ruthenium and A is a potassium cation include fluoride complexes such as K2RuF6, KRuF6, and K3RuF6, and chloride complexes such as K2RuCl6, K2RuCl5, K3RuCl6, and K4RuCl6. When nitrogen trifluoride is produced as the fluorine-containing compound, a metal complex compound in which M is ruthenium and A is an ammonium ion may be used, such as (NH4)2RuF6 and (NH4)RuF6. In the case of K3RuF6 and the like, in which the number of electrons in the d orbital of ruthenium is 5 (ruthenium has a valence of 3), it is preferable to pre-electrolyze the electrolyte in order to fully exert the effect of suppressing the anode effect.

[0050] Examples of metal complex compounds where M is silver and A is a potassium cation include fluoride complexes such as KAgF4, KAgF3, KAgF2, K2AgF4, K3AgF4, K2AgF6, and K5AgF6, and chloride complexes such as KAgCl3, KAgCl4, K3AgCl4, KAg2Cl3, and KAg4Cl5.

[0051] When nitrogen trifluoride is produced as the fluorine-containing compound, a metal complex compound in which M is silver and A is an ammonium ion may be used, for example (NH4)AgF2. In the case of a fluoride complex in which M is silver, KAgF4 is preferred. For KAgF3, KAgF2, etc., in which the number of electrons in the d orbital of silver is 9 or 10 (the valence of silver is divalent or monovalent), it is preferable to pre-electrolyze the electrolyte in order to fully exert the effect of suppressing the anode effect.

[0052] Examples of metal complex compounds where M is rhodium and A is potassium cation include fluoride complexes such as KRhF3, K2RhF6, K3RhF6, and KRhF6, as well as K2RhCl3, KRhCl4, K2RhCl5, K3RhCl6, K2RhCl6, and K4Rh2Cl. 10 and chloride complexes such as K3Rh2Cl9.

[0053] When nitrogen trifluoride is produced as the fluorine-containing compound, a metal complex compound in which M is rhodium and A is an ammonium ion may be used, for example (NH4)3RhF6. In the case of a fluoride complex in which M is rhodium, K2RhF6 is preferred. In the case of KRhF3, K3RhF6, etc., in which the number of electrons in the d orbital of rhodium is 5 or 6 (the valence of rhodium is divalent or trivalent), it is preferable to pre-electrolyze the electrolyte in order to fully exert the effect of suppressing the anode effect.

[0054] Examples of metal complex compounds in which M is nickel and A is a potassium cation include fluoride complexes such as KNiF3, K2NiF4, KNiF4, K3NiF5, K2NiF6, K3NiF6, K4NiF6, and K3NiF7, and chloride complexes such as KNiCl3, K2NiCl4, and K2NiCl6. When producing nitrogen trifluoride as the fluorine-containing compound, a metal complex compound in which M is nickel and A is an ammonium ion may be used. Examples include (NH4)NiCl3, (NH4)2NiCl4, (NH4)2NiF4, and (NH4)NiF4.

[0055] In the case of a fluoride complex in which M is nickel, K2NiF6 is preferred. By adding K2NiF6, the effect of suppressing the anode effect is quickly achieved. For KNiF3, K2NiF4, K3NiF5, K4NiF6, etc., in which the number of electrons in the nickel d orbital is 7 or 8 (the nickel valence is divalent or trivalent), it is preferable to pre-electrolyze the electrolyte in order to fully achieve the effect of suppressing the anode effect.

[0056] The content of d-block element ions dissolved in the electrolyte is not particularly limited, and even if the d-block element ions are dissolved in the electrolyte in a supersaturated state, there is no effect on the suppression of the anode effect, and the presence of undissolved solids in the electrolyte is not a problem. If the content of d-block element ions is low, the suppression effect of the anode effect will be weaker, but the anode effect can be suppressed more effectively than if the content of d-block element ions were zero.

[0057] The content of d-block element ions in the electrolyte may be 1 ppm by mass or more and 10% by mass or less, 10 ppm by mass or more and 5% by mass or less, or 20 ppm by mass or more and 3% by mass or less. The lower limit of the content of d-block element ions in the electrolyte may be 1 ppm by mass or more, 10 ppm by mass or more, or 20 ppm by mass or more, and the upper limit may be 10% by mass or less, 5% by mass or less, or 3% by mass or less.

[0058] The type of metal fluoride is not particularly limited, but may be at least one of potassium fluoride (KF), ammonium fluoride (NHF), and cesium fluoride (CsF). One type of metal fluoride may be used alone, or two or more types may be used in combination.

[0059] When potassium fluoride or cesium fluoride is used as the metal fluoride, fluorine gas is produced by electrolysis of the electrolyte, and when ammonium fluoride is used, nitrogen trifluoride is produced by electrolysis of the electrolyte. When the electrolyte contains hydrogen fluoride, a metal fluoride, and a complex ion (hereinafter sometimes referred to as a "KF-HF-based electrolyte"), the concentration of hydrogen fluoride in the electrolyte may be in the range of 38% by mass to 43% by mass. If the concentration of hydrogen fluoride in the electrolyte is within this range, the melting point of the electrolyte is low at approximately 70°C, so the heating energy required to melt the electrolyte is low, making it economical. The lower the concentration of hydrogen fluoride in the electrolyte, the higher the melting point of the electrolyte.

[0060] To lower the melting point of the electrolyte, it is effective to use cesium fluoride as the metal fluoride (hereinafter, this may be referred to as a "CsF-HF-based electrolyte"). Alternatively, it is effective to use both potassium fluoride and cesium fluoride as the metal fluorides. If the mass ratio of hydrogen fluoride to cesium fluoride in the electrolyte is hydrogen fluoride:cesium fluoride = 2.6:1 (such an electrolyte may be referred to as "CsF 2.6HF". The same applies to KF-HF-based electrolytes, etc.), it will be in liquid form at room temperature and will be easy to handle. However, CsF-HF-based electrolytes are more expensive than KF-HF-based electrolytes, and therefore are not suitable for the industrial production of fluorine gas, which requires large amounts of electrolyte, but are advantageous for generating fluorine gas in small electrolytic cells.

[0061] When nitrogen trifluoride gas is produced by electrolysis of an electrolyte, an electrolyte containing ammonium fluoride is used. That is, an NHF-HF-based electrolyte, a KF-NHF-HF-based electrolyte, an NHF-CsF-HF-based electrolyte, a KF-NHF-CsF-HF-based electrolyte, or the like can be used. If these electrolytes contain the above complex ions, they can suppress the anode effect.

[0062] According to the method for producing a fluorine-containing compound of this embodiment, in addition to fluorine gas and nitrogen trifluoride, fluorocarbons, chlorofluorocarbons, and hydrofluorocarbons can be produced. That is, the fluorine-containing compound is at least one of fluorine gas, nitrogen trifluoride, fluorocarbons, chlorofluorocarbons, and hydrofluorocarbons.

[0063] The electrolyte used in producing fluorocarbons, chlorofluorocarbons, and hydrofluorocarbons is the same as the electrolyte used in producing fluorine gas. When producing fluorocarbons, chlorofluorocarbons, and hydrofluorocarbons, electrolysis can be carried out while the raw material organic substances such as hydrocarbons and halogenated hydrocarbons are supplied to the electrolyte in the gas phase or dispersed in the liquid phase, thereby causing the fluorination reaction of the organic substances to proceed at the anode. The product may also be discharged from the electrolytic cell in the gas phase or deposited in the electrolytic cell in the liquid phase.

[0064] Specific examples of fluorocarbons include tetrafluoromethane (CF), hexafluoroethane (C2F6), octafluoropropane (C3F8), and decafluorobutane (C4F 10 ) etc. Specific examples of chlorofluorocarbons include trichlorofluoromethane (CCl3F), chlorotrifluoromethane (CClF3), 1,2-dichloro-1,1,2,2-tetrafluoroethane (C2Cl2F4), and the like. Specific examples of hydrofluorocarbons include trifluoromethane (CHF3), difluoromethane (CH2F2), and 1,1,1-trifluoroethane (CH3CF3).

[0065] [Water concentration of electrolyte] Solid KF·HF, KF, and CsF typically contain several hundred ppm of water by mass, while hydrogen fluoride contains 100–200 ppm by mass. Water also adheres to the interior of the equipment used to prepare the electrolyte and the electrolytic cell where the electrolyte is electrolyzed. Furthermore, if metal oxides such as rust are present inside the equipment used to prepare the electrolyte or the electrolytic cell where the electrolyte is electrolyzed, hydrogen fluoride reacts with the metal oxide to produce water. Furthermore, the electrolyte may come into contact with the atmosphere during the electrolyte handling process, and the electrolyte may absorb water from the atmosphere. For these reasons, electrolytes produced by mixing hydrogen fluoride, metal fluorides, and metal complex compounds contain water, and the water concentration is usually greater than 100 ppm by mass and less than 1% by mass.

[0066] If the electrolytic solution contains water, the effect of suppressing the anode effect due to complex ions may be reduced. Therefore, in the method for producing a fluorine-containing compound according to this embodiment and the electrolytic solution according to this embodiment, it is preferable that the water content in the electrolytic solution is low. For example, it is preferable that the water content in the electrolytic solution is 1 mass ppm or more and 100 mass ppm or less.

[0067] A method for reducing the water content in the electrolytic solution includes the above-mentioned method of performing pre-electrolysis. That is, a method of performing electrolysis on an electrolytic solution in which the water content has been reduced by performing pre-electrolysis. The timing of performing pre-electrolysis is not particularly limited, and pre-electrolysis may be performed on an electrolytic solution produced by mixing hydrogen fluoride, a metal fluoride, and a metal complex compound, or on a mixture of hydrogen fluoride and a metal fluoride before mixing with the metal complex compound.

[0068] A low-water content electrolyte can be obtained by subjecting a mixture of hydrogen fluoride and a metal fluoride to pre-electrolysis, and then mixing the resulting mixture of hydrogen fluoride and a metal fluoride with a metal complex compound. The low-water content electrolyte thus produced is effective in suppressing the anode effect caused by complex ions.

[0069] Here, we will show an example of a method for measuring the water content in an electrolyte using KF·2HF as an example. The water content in an electrolyte can be measured, for example, using a moisture analyzer having the following configuration. The moisture analyzer includes a nickel cylindrical heating element, a gas supply pipe that supplies an inert gas such as nitrogen gas into the cylindrical heating element, a heater such as an electric heater that heats the cylindrical heating element, a thermometer such as a thermocouple that measures the temperature inside the cylindrical heating element, and an analyzer such as an FT-IR analyzer that analyzes the gas discharged from the cylindrical heating element. This moisture analyzer is installed inside a glove box that is maintained at low humidity.

[0070] The mass of the measured electrolyte sample is placed in a platinum boat-shaped tray, which is then placed inside the cylindrical heating section. An inert gas is supplied into the cylindrical heating section through a gas supply pipe. The cylindrical heating section is pressurized by the inert gas to maintain its airtightness. The cylindrical heating section is then heated by a heater while a constant flow of inert gas is supplied to the cylindrical heating section through the gas supply pipe. The cylindrical heating section is heated in stages from room temperature to 350°C.

[0071] The gas evaporated from the sample by heating is discharged from the cylindrical heating section together with the inert gas and sent to the FT-IR analyzer. Continuous analysis is then performed by the FT-IR analyzer, and the absorption wave number is 1400 cm. -1 From 1899cm -1 The water content is quantified from the peak intensity in the range, and the total amount of evaporated water is calculated from the integrated value of the period from when the water peak was detected until it disappeared. The water content in the electrolyte can be calculated from the total amount of evaporated water and the mass of the sample.

[0072] [Electrolytic cell] There are no particular limitations on the type of electrolytic cell used in the method for producing a fluorine-containing compound according to this embodiment, and any electrolytic cell can be used as long as it is capable of electrolyzing an electrolytic solution to generate a fluorine-containing compound such as fluorine gas. Because the electrolytic solution is corrosive, the inner surface of the electrolytic cell and other parts that come into contact with the electrolytic solution are preferably made of a fluororesin (e.g., Teflon (registered trademark)) or a metal such as iron (Fe), nickel, or Monel (trademark).

[0073] If the components constituting the electrolytic cell and immersed in the electrolytic solution contain iron, which is a source of iron ions, or copper, which is a source of copper ions, they will dissolve in the electrolytic solution unless they are cathodic protected. Therefore, it is preferable not to use materials containing iron or copper for the components constituting the electrolytic cell and immersed in the electrolytic solution. If cathodic protection is provided, there is no particular problem. Usually, the inside of the electrolytic cell is partitioned by a partition member such as a partition wall into an anode chamber in which an anode is placed and a cathode chamber in which a cathode is placed, so that the fluorine-containing compound generated at the anode and the hydrogen gas (H) generated at the cathode do not mix with each other.

[0074] The material of the anode is not particularly limited, but the anode may be a carbonaceous electrode. That is, as the anode, for example, a carbonaceous electrode formed of a carbon material such as diamond, diamond-like carbon, amorphous carbon, graphite, or glassy carbon can be used. When electrolysis is performed at a high current density, amorphous carbon is preferred. Amorphous carbon is preferred when the current density is 0.9 A / cm. 2 Even if the temperature is low, the anode effect is unlikely to occur during electrolysis. As the cathode, for example, a metal electrode made of a metal such as iron, nickel, copper, or a copper-nickel alloy (for example, Monel (trademark)) can be used.

[0075] [Method for confirming the suppression effect of the anode effect] The anode effect is a phenomenon in which the anode current becomes difficult to flow. The current before the anode current stops flowing is called the critical current density. Critical current density can be measured by increasing the current linearly with time and measuring the current when the voltage suddenly rises, or by increasing the current by a certain step current, holding that current for a certain period of time, and then stepping up the current again. Since the critical current density value changes depending on the rate at which the current is increased, it is necessary to use the same measurement method for all critical current densities to compare them.

[0076] For example, the critical current density can be measured by the following method: First, the applied current density is set to 0.025 A / cm 2 This current was maintained for 15 minutes, and after 15 minutes, the current density was reduced to 0.025 A / cm 2 Step up to 0.05A / cm 2 This current is maintained for 15 minutes. This operation is repeated until the anode effect occurs and the current density at which the voltage rises sharply is taken as the critical current density.

[0077] When the anode effect occurs, the voltage rises to 20 V. When the voltage reaches 20 V, the measurement is terminated. The anode electrode is left immersed in the electrolyte, and after the measurement, the anode is left immersed in the electrolyte for 30 minutes, and then the current density is set to 0.025 A / cm. 2 In the case of the conventional electrolyte other than the electrolyte according to the present embodiment, the current starts to flow at the initially applied current of 0.025 A / cm 2 In contrast, in the case of the electrolyte according to the present embodiment, even the electrode where the anode effect occurred cannot pass a current of 0.025 A / cm 2 upon re-energization, and the voltage rises to 20 V. 2 When the current density is increased again and the critical current density is measured, it can reach 0.5 A / cm depending on the type of metal complex compound. 2 Even at this temperature, the anode effect may not occur.

[0078] In addition, the electrolyte solution according to this embodiment has a current of 0.025 A / cm every 15 minutes. 2 Critical current density measurement method up to 2A / cm 2However, there are some cases where a sudden voltage rise does not occur. In this case, the step-up current is set to 0.1A / cm 2 Increasing the voltage can cause a sudden increase in voltage (anode effect).

[0079] With conventional electrolytes, once a carbonaceous electrode experiences the anode effect, in which voltage suddenly rises, it is unable to pass current again, even if the current density is reduced. This is thought to be due to the formation of an insulating fluoride coating on the surface of the carbonaceous electrode. When a fluoride coating is formed on a carbonaceous electrode, the surface becomes water-repellent, making it difficult for the electrode surface to be wetted by the electrolyte, and therefore current does not flow.

[0080] The electrolyte solution according to this embodiment has a critical current density (approximately 0.1 to 0.3 A / cm) higher than that of conventional electrolyte solutions. 2 ) with a current density more than 10 times higher than that of 2 Furthermore, in the electrolyte solution according to this embodiment, even in an electrode in which the anode effect has been generated under conditions that make it easy for the anode effect to occur even at a low current density (conditions that increase the rate of current), if the application of current is stopped once and then applied again at a low current density, current can be passed through the electrode.

[0081] To date, no electrolytes have been reported that exhibit this behavior. For example, when fluorine gas is generated by electrolysis of a molten salt electrolyte KF 2HF containing 0.5 mass% K2PtF6, the current is 0.025 A / cm 2 Even when measuring the critical current density by the step current of 15 minutes, the 2 However, no anode effect occurs. In this case, the current efficiency for fluorine gas generation is 90-95%. This is because a side reaction occurs in which K2PtF6 undergoes an oxidation-reduction reaction at the anode and cathode, and this does not reduce the current efficiency of the main reaction (fluorine gas generation reaction).

[0082] After electrolysis, the carbonaceous electrode was removed from the electrolyte, washed with water, and dried. SEM-EDS analysis was then used to check whether platinum was present on the surface of the carbonaceous electrode. This confirmed that platinum was present, albeit in a small amount, on the surface of the carbonaceous electrode. Therefore, the added K2PtF6 complex ion [PtF6] 2- It is thought that this acts on the surface of the carbonaceous electrode.

[0083] Although the mechanism of the above-mentioned effect of the electrolyte solution according to this embodiment cannot be clearly explained, it is thought that the formation of a fluoride film on the surface of the carbonaceous electrode is suppressed. 2- It is thought that the fluoride platinate ions of these metals act as catalysts, making it easier for fluoride ions to be discharged.Alkali metal fluoride complexes of platinum (IV), palladium (IV), gold (III), etc., which have the effect of suppressing the anode effect, have the oxidizing power to split water, so it is expected that they have the ability to oxidize fluoride ions.

[0084] When a fluorine-containing compound is produced by electrolyzing the electrolyte solution according to this embodiment, not only can the electrolysis be carried out at a high current density, but also at a low current density of 0.01 to 0.3 A / cm 2 Therefore, the anode can be used for electrolysis of electrolytes for a long period of time (for example, one year or more) without replacement. [Example]

[0085] The present disclosure will be described more specifically below with reference to examples and comparative examples. Example 1 <Dehydration process> An electrolytic cell was prepared, equipped with an anode chamber in which an anode was installed and a cathode chamber in which a cathode was installed. The anode chamber and cathode chamber were separated by a partition wall to prevent the anode gas and cathode gas from mixing. The anode was a carbon electrode with a conductive diamond coating on its surface, and was shaped like a square with each side measuring 1 cm. The cathode was a nickel plate, and was shaped like a rectangle measuring 2 cm in length and 5 cm in width. All parts of this electrolytic cell that came into contact with the electrolyte and the gas were made of Teflon (registered trademark).

[0086] 800 g of KF·2HF was placed in the electrolytic cell and heated to 80-90°C. 2 Pre-electrolysis was performed at a current density of 1000 kJ / min to dehydrate the KF·2HF. Nitrogen gas was supplied to the anode chamber from the outside at a flow rate of 200 mL / min, and the fluorine gas generated from the anode was sent from the electrolytic cell to the potassium iodide aqueous solution trap. The extracted fluorine gas was absorbed and removed by the potassium iodide aqueous solution. The oxygen gas concentration in the gas discharged from the potassium iodide aqueous solution trap was then measured by gas chromatography. Two hours after the start of pre-electrolysis, oxygen gas was no longer detected, and it was determined that the dehydration of the KF·2HF was complete.

[0087] Since the hydrogen fluoride in KF·2HF is consumed during pre-electrolysis, hydrogen fluoride is intermittently supplied to KF·2HF during pre-electrolysis to maintain the hydrogen fluoride concentration in KF·2HF within the range of 40 to 43 mass%. KF·2HF prepared in this manner is called post-dehydration KF·2HF.

[0088] <Electrolyte manufacturing process> After dehydration, the electrolyte was prepared by mixing potassium hexachloroplatinate (IV) (K2PtCl6) crystal powder manufactured by Kanto Chemical Co., Ltd. The amount of potassium hexachloroplatinate (IV) added was 0.5 mass% of the total amount of the mixture of KF·2HF and potassium hexachloroplatinate (IV) after dehydration. After dehydration, part of the potassium hexachloroplatinate (IV) crystalline powder dissolved in KF·2HF, and the remainder dispersed or precipitated in KF·2HF. The addition of potassium hexachloroplatinate (IV) caused the KF·2HF to assume a pale yellow color after dehydration.

[0089] A portion of the produced electrolyte was sampled and the platinum concentration in the electrolyte was measured by ICP atomic emission spectrometry, which confirmed that approximately 400 mass ppm of platinum was dissolved in the electrolyte as a metal component. In addition, a portion of the produced electrolyte solution was sampled to measure the water content. As a result, the water content in the electrolyte solution was 58 mass ppm. The water content in the electrolyte solution was measured using the above-mentioned FT-IR analyzer.

[0090] <Electrolysis process> After applying a current of 1457 mA·hr, the electrolyte was electrolyzed at constant current at 80-90°C using a carbon electrode FE-8 (1 cm square) manufactured by Toyo Tanso Co., Ltd. as the anode, to produce fluorine gas. 2 The current density was then increased to 0.025 A / cm every 15 minutes. 2 The voltage was measured by increasing the current stepwise to 0.025A / cm every 15 minutes. 2 The operation to increase the current is set to "0.025A / cm 2 The voltage measurement result was 0.025A / cm 2 Step operation with a current density of 2A / cm 2 The current efficiency of fluorine gas generation was 91%.

[0091] 2A / cm 2 The current density was increased to 0.1 A / cm. Then, the current was stopped. 2 The current density was increased to 0.1 A / cm every 15 minutes. 2 The voltage was measured by increasing the current stepwise at 0.1 A / cm every 15 minutes. 2 The operation to increase the current is called "0.1A / cm2 Step operation.

[0092] Current density is 0.5A / cm 2 After a while, the voltage reached 20 V or more, and the anode effect occurred. The current was stopped and the current was passed through the same electrode again. The initial current density was set to 0.025 A / cm. 2 When the current started to flow, it was possible to pass a current of 0.025 A / cm at a cell voltage of 5 V. 2 When step operation was performed, the current density was 0.5 A / cm 2 As will be explained later, when a conventional electrolyte that does not contain a metal complex compound is used, an electrode that has experienced the anodic effect once cannot pass a current again. The ability to pass a current again after the anodic effect has occurred is due to the effect of the metal complex compound.

[0093] Example 2 Constant current electrolysis of the electrolyte was carried out in the same manner as in Example 1, except that an ABR grade carbon electrode (1 cm square shape) manufactured by SGL was used as the anode, and the critical current density was measured. 2 Step operation with a current density of 2A / cm 2 The current efficiency of fluorine gas generation was 92%.

[0094] As in Example 1, 2 A / cm 2 The current density was increased to 0.1 A / cm. Then, the current was stopped. 2 The current density was started at 0.1 A / cm 2 Step operation with a current density of 0.5 A / cm 2 After a while, the voltage reached 20V or more, and the anode effect occurred.

[0095] The current was stopped once and then tried to pass it again to the same electrode. The initial current density was 0.025 A / cm 2 When the current started to flow, it was possible to pass a current of 0.025 A / cm at a cell voltage of 5 V. 2When step operation was performed, the current density was 0.5 A / cm 2 As will be explained later, when a conventional electrolyte that does not contain a metal complex compound is used, an electrode that has experienced the anodic effect once cannot pass a current again. The ability to pass a current again after the anodic effect has occurred is due to the effect of the metal complex compound.

[0096] Example 3 <Dehydration process> 800 g of NHF·2HF was placed in an electrolytic cell similar to that used in Example 1 and heated to 100°C. The anode and cathode used were also the same as those used in Example 1. NHF·2HF was prepared by blowing hydrogen fluoride into NHF·HF manufactured by Morita Chemical Industry Co., Ltd.

[0097] and 0.3A / cm 2 Pre-electrolysis was performed at a current density of 1000 kJ / min to dehydrate NHF·2HF. Nitrogen gas was supplied to the anode chamber from the outside at a flow rate of 200 mL / min, and nitrogen trifluoride gas generated from the anode was sent from the electrolytic cell to a potassium iodide aqueous solution trap. The extracted nitrogen trifluoride gas was absorbed and removed by the potassium iodide aqueous solution. The oxygen gas concentration in the gas discharged from the potassium iodide aqueous solution trap was then measured by gas chromatography. Two hours after the start of pre-electrolysis, oxygen gas was no longer detected, indicating that the dehydration of NHF·2HF was complete. The NHF·2HF prepared in this manner is referred to as dehydrated NHF·2HF.

[0098] <Electrolyte manufacturing process> After dehydration, the electrolyte was prepared by mixing potassium hexachloroplatinate(IV) crystalline powder manufactured by Kanto Chemical Co., Ltd. The amount of potassium hexachloroplatinate(IV) added was 0.5 mass% of the total amount of the mixture of NHF·2HF and potassium hexachloroplatinate(IV) after dehydration.

[0099] After dehydration, part of the potassium hexachloroplatinate(IV) crystalline powder dissolved in NHF·2HF, and the remainder dispersed or precipitated in NHF·2HF. The addition of potassium hexachloroplatinate(IV) caused the NHF·2HF to assume a pale yellow color after dehydration. The hydrogen fluoride concentration in the electrolyte was 51.7 mass %.

[0100] A portion of the produced electrolyte was sampled and the platinum concentration in the electrolyte was measured by ICP atomic emission spectrometry, which confirmed that 370 mass ppm of platinum was dissolved in the electrolyte as a metal component. In addition, a portion of the produced electrolyte solution was sampled to measure the water content. As a result, the water content in the electrolyte solution was found to be 81 mass ppm. The water content in the electrolyte solution was measured using the above-mentioned FT-IR analyzer.

[0101] <Electrolysis process> Constant-current electrolysis of the electrolyte was carried out in the same manner as in Example 1, except that an ABR grade carbon electrode (1 cm square shape) manufactured by SGL was used as the anode, and that the electrolyte was prepared by mixing potassium hexachloroplatinate (IV) crystal powder with NHF·2HF after dehydration. The critical current density was measured and found to be 0.025 A / cm. 2 Step operation with a current density of 2A / cm 2 The current efficiency of nitrogen trifluoride gas generation was 58%.

[0102] Example 4 <Dehydration process> 1000 g of CsF·2.3HF was placed in an electrolytic cell similar to that used in Example 1 and heated to 30°C. The anode and cathode used were also the same as those used in Example 1. CsF·2.3HF was prepared by blowing hydrogen fluoride into cesium fluoride (Sigma-Aldrich).

[0103] and 0.3A / cm 2Pre-electrolysis was performed at a current density of 1000 kJ / min to dehydrate CsF·2.3HF. Nitrogen gas was supplied to the anode chamber from the outside at a flow rate of 200 mL / min, and fluorine gas generated from the anode was sent from the electrolytic cell to a potassium iodide aqueous solution trap. The extracted fluorine gas was then absorbed and removed by the potassium iodide aqueous solution. The oxygen gas concentration in the gas discharged from the potassium iodide aqueous solution trap was then measured by gas chromatography. Two hours after the start of pre-electrolysis, oxygen gas was no longer detected, indicating that dehydration of CsF·2.3HF was complete. The CsF·2.3HF prepared in this manner is referred to as dehydrated CsF·2.3HF.

[0104] <Electrolyte manufacturing process> An electrolyte was prepared by mixing crystalline powder of cesium hexachloroplatinate(IV) (Cs2PtCl6) with dehydrated CsF·2.3HF. The amount of cesium hexachloroplatinate(IV) added was 0.2 mass% of the total mixture of CsF·2.3HF and cesium hexachloroplatinate(IV) after dehydration. This cesium hexachloroplatinate(IV) was prepared by adding two equivalents of cesium chloride (CsCl) to an 8 mass% hexachloroplatinic acid solution (H2PtCl6 solution) and evaporating it to dryness.

[0105] The hydrogen fluoride concentration in the electrolytic solution was 25.0 mass %. A portion of the produced electrolyte was sampled and the platinum concentration in the electrolyte was measured by ICP atomic emission spectrometry, which confirmed that 290 mass ppm of platinum was dissolved in the electrolyte as a metal component. In addition, a portion of the produced electrolyte solution was sampled to measure the water content. As a result, the water content in the electrolyte solution was 60 mass ppm. The water content in the electrolyte solution was measured using the above-mentioned FT-IR analyzer.

[0106] <Electrolysis process> Constant-current electrolysis of the electrolyte was carried out in the same manner as in Example 1, except that an ABR grade carbon electrode (1 cm square shape) manufactured by SGL was used as the anode, and an electrolyte was prepared by mixing CsF·2.3HF with cesium hexachloroplatinate (IV) crystal powder after dehydration, and the critical current density was measured. The result was 0.025 A / cm 2 Step operation with a current density of 2A / cm 2 The current efficiency of fluorine gas generation was 92%.

[0107] Example 5 <Dehydration process> In the same manner as in Example 1, KF·2HF was produced after dehydration. <Electrolyte manufacturing process> The electrolyte was prepared by mixing potassium hexachloropalladate(IV) crystal powder (K2PdCl6) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. with dehydrated KF·2HF. The amount of potassium hexachloropalladate(IV) added was 0.5 mass% of the total amount of the mixture of dehydrated KF·2HF and potassium hexachloropalladate(IV).

[0108] After dehydration, part of the potassium hexachloropalladate(IV) crystalline powder dissolved in KF·2HF, and the remainder dispersed or precipitated in KF·2HF. The color of the KF·2HF changed from red to brown due to the addition of potassium hexachloropalladate(IV). A portion of the produced electrolyte solution was sampled and the palladium concentration in the electrolyte solution was measured by ICP atomic emission spectrometry, which confirmed that 380 mass ppm of palladium was dissolved in the electrolyte solution as a metal component. In addition, a portion of the produced electrolyte solution was sampled to measure the water content. As a result, the water content in the electrolyte solution was 69 mass ppm. The water content in the electrolyte solution was measured using the above-mentioned FT-IR analyzer.

[0109] <Electrolysis process> A carbon electrode (1 cm square) with a conductive diamond coating on its surface was used as the anode, and the electrolyte obtained above was subjected to constant current electrolysis at 0.6 A / cm. 2 The current density was 0.025 A / cm and continued until the current flow reached 10,000 mA·hr. After that, an ABR grade carbon electrode (1 cm square) manufactured by SGL was used as the anode. 2 When step operation was performed, the current density was 1.4 A / cm 2 The anode effect occurs some time after the critical current density reaches 1.4 A / cm 2 The current efficiency of fluorine gas generation at this time was 89%.

[0110] Current density 1.4A / cm 2 When the anode effect occurred, the current was stopped and the current was passed through the same electrode again. The initial current density was 0.025 A / cm 2 When the current started to flow, it was possible to pass a current of 0.025 A / cm at a cell voltage of 5.5 V. 2 When step operation was performed, the current density was 0.5 A / cm 2 No anode effect occurred even when the temperature reached 1000°C.

[0111] Example 6 <Dehydration process> In the same manner as in Example 1, KF·2HF was produced after dehydration. <Electrolyte manufacturing process> An electrolyte was produced by mixing separately prepared potassium hexafluoroplatinate(IV) (K2PtF6) crystalline powder with dehydrated KF·2HF. The amount of potassium hexafluoroplatinate(IV) added was 0.5 mass% of the total amount of the mixture of dehydrated KF·2HF and potassium hexafluoroplatinate(IV). Part of the potassium hexafluoroplatinate(IV) crystalline powder dissolved in dehydrated KF·2HF, while the remainder dispersed or precipitated in dehydrated KF·2HF. The preparation method for potassium hexafluoroplatinate(IV) will be described in detail later.

[0112] A portion of the produced electrolyte was sampled and the platinum concentration in the electrolyte was measured by ICP atomic emission spectrometry, which confirmed that 430 mass ppm of platinum was dissolved in the electrolyte as a metal component. In addition, a portion of the produced electrolyte solution was sampled to measure the water content. As a result, the water content in the electrolyte solution was 49 mass ppm. The water content in the electrolyte solution was measured using the above-mentioned FT-IR analyzer.

[0113] Here, we will explain the method for preparing potassium hexafluoroplatinate(IV). 10 g of potassium hexachloroplatinate(IV) powder was placed on a platinum dish, and this platinum dish was placed inside a horizontal nickel tube with an inner diameter of 1 inch. This nickel tube could be heated externally using an electric heater. Fluorine gas at a flow rate of 50 mL / min and nitrogen gas at a flow rate of 500 mL / min were supplied into the nickel tube, and the internal temperature of the nickel tube was raised to 350°C. Potassium hexachloroplatinate(IV) and hydrogen fluoride were reacted under the flow of a mixed gas of fluorine gas and nitrogen gas.

[0114] After the reaction was carried out for 2 hours, the supply of fluorine gas was stopped and the nickel tube was cooled to room temperature. The platinum dish was then removed from the nickel tube and its mass was measured, revealing that 7.98 g of powder had been obtained. 99.7 mol% of potassium hexachloroplatinate (IV) had been converted to potassium hexafluoroplatinate (IV).

[0115] <Electrolysis process> Constant-current electrolysis of the electrolyte was carried out in the same manner as in Example 1, except that an ABR grade carbon electrode (1 cm square shape) manufactured by SGL was used as the anode, and that the electrolyte was prepared by mixing potassium hexafluoroplatinate (IV) crystal powder with KF·2HF after dehydration. The critical current density was measured and found to be 0.025 A / cm. 2 Step operation with a current density of 2A / cm 2 The current efficiency of fluorine gas generation was 95%.

[0116] As in Example 1, 2 A / cm 2 The current density was increased to 0.1 A / cm. Then, the current was stopped. 2 The current density was started at 0.1 A / cm 2 Step operation with a current density of 0.5 A / cm 2 After a while, the voltage reached 20V or more, and the anode effect occurred.

[0117] The current was stopped once and then tried to pass it again to the same electrode. The initial current density was 0.025 A / cm 2 When current started to flow, it was possible to pass a current of 0.025 A / cm at a cell voltage of 5.6 V. 2 When step operation was performed, the current density was 0.5 A / cm 2 No anode effect occurred even when the temperature reached .

[0118] Example 7 <Dehydration process> In the same manner as in Example 1, KF·2HF was produced after dehydration. <Electrolyte manufacturing process> An electrolyte was prepared by mixing potassium tetrachloroaurate(III) (KAuCl4) crystal powder manufactured by Sigma-Aldrich with dehydrated KF·2HF. The amount of potassium tetrachloroaurate(III) added was 0.2 mass% of the total mixture of dehydrated KF·2HF and potassium tetrachloroaurate(III). Some of the potassium tetrachloroaurate(III) crystal powder dissolved in the KF·2HF after dehydration, while the remainder dispersed or precipitated in the KF·2HF after dehydration. Due to the addition of potassium tetrachloroaurate(III), the KF·2HF turned a pale yellow color after dehydration.

[0119] A portion of the produced electrolyte was sampled and the gold concentration in the electrolyte was measured by ICP atomic emission spectrometry, which confirmed that 340 mass ppm of gold was dissolved in the electrolyte as a metal component. In addition, a portion of the produced electrolyte solution was sampled to measure the water content. As a result, the water content in the electrolyte solution was 67 mass ppm. The water content in the electrolyte solution was measured using the above-mentioned FT-IR analyzer.

[0120] <Electrolysis process> A carbon electrode (1 cm square) with a conductive diamond coating on its surface was used as the anode, and the electrolyte obtained above was subjected to constant current electrolysis at 0.6 A / cm. 2 The current density was 0.025 A / cm and continued until the current flow reached 10,000 mA·hr. After that, an ABR grade carbon electrode (1 cm square) manufactured by SGL was used as the anode. 2 When step operation was performed, the current density was 1.6 A / cm 2 The anode effect occurs some time after the critical current density reaches 1.6 A / cm 2 The current efficiency of fluorine gas generation at this time was 89%.

[0121] Current density 1.6A / cm 2 When the anode effect occurred, the current was stopped and the current was passed through the same electrode again. The initial current density was 0.025 A / cm 2 The current begins to flow as 0.025A / cm 2 When step operation was performed, the current density was 0.2 A / cm 2 No anode effect occurred even when the temperature reached .

[0122] The current was stopped once and then tried to pass it again to the same electrode. The initial current density was 0.025 A / cm 2 When the current started to flow, it was possible to pass a current of 0.025 A / cm at a cell voltage of 5.5 V. 2 When step operation was performed, the current density was 0.5 A / cm 2 No anode effect occurred even when the temperature reached .

[0123] Example 8 <Dehydration process> In the same manner as in Example 1, KF·2HF was produced after dehydration. <Electrolyte manufacturing process> An electrolyte was prepared by mixing potassium hexachloroiridate(IV) (K2IrCl6) crystal powder (Sigma-Aldrich) with dehydrated KF·2HF. The amount of potassium hexachloroiridate(IV) added was 0.2 mass% of the total mixture of dehydrated KF·2HF and potassium hexachloroiridate(IV). Some of the potassium hexachloroiridate(IV) crystal powder dissolved in the KF·2HF after dehydration, while the remainder dispersed or precipitated in the KF·2HF after dehydration. Due to the addition of potassium hexachloroiridate(IV), the KF·2HF turned gray to black after dehydration.

[0124] A portion of the produced electrolyte was sampled and the iridium concentration in the electrolyte was measured by ICP atomic emission spectrometry, which confirmed that 390 mass ppm of iridium was dissolved in the electrolyte as a metal component. In addition, a portion of the produced electrolyte solution was sampled to measure the water content. As a result, the water content in the electrolyte solution was 75 mass ppm. The water content in the electrolyte solution was measured using the above-mentioned FT-IR analyzer.

[0125] <Electrolysis process> A carbon electrode (1 cm square) with a conductive diamond coating on its surface was used as the anode, and the electrolyte obtained above was subjected to constant current electrolysis at 0.6 A / cm. 2 The current density was 0.025 A / cm and continued until the current flow reached 10,000 mA·hr. After that, an ABR grade carbon electrode (1 cm square) manufactured by SGL was used as the anode. 2 When the step operation was performed, the current density was 2 A / cm 2 The current efficiency for fluorine gas evolution was 83%.

[0126] As in Example 1, 2 A / cm 2The current density was increased to 0.1 A / cm. Then, the current was stopped. 2 The current density was started at 0.1 A / cm 2 Step operation with a current density of 0.5 A / cm 2 After a while, the voltage reached 20V or more, and the anode effect occurred.

[0127] The current was stopped once and then tried to pass it again to the same electrode. The initial current density was 0.025 A / cm 2 When the current started to flow, it was possible to pass a current of 0.025 A / cm at a cell voltage of 5 V. 2 When step operation was performed, the current density was 0.5 A / cm 2 No anode effect occurred even when the temperature reached .

[0128] Example 9 <Dehydration process> In the same manner as in Example 1, KF·2HF was produced after dehydration. <Electrolyte manufacturing process> The electrolyte was prepared by mixing potassium hexachlororuthenate(IV) (K2RuCl6) crystal powder manufactured by Thermo Scientific with dehydrated KF·2HF. The amount of potassium hexachlororuthenate(IV) added was 0.2 mass% of the total amount of the mixture of dehydrated KF·2HF and potassium hexachlororuthenate(IV). After dehydration, part of the potassium hexachlororuthenate(IV) crystalline powder dissolved in KF·2HF, while the remainder dispersed or precipitated in KF·2HF. The addition of potassium hexachlororuthenate(IV) caused the KF·2HF to turn brown or black after dehydration.

[0129] A portion of the produced electrolyte was sampled and the ruthenium concentration in the electrolyte was measured by ICP atomic emission spectrometry, which confirmed that 390 mass ppm of ruthenium was dissolved in the electrolyte as a metal component. In addition, a portion of the produced electrolyte solution was sampled to measure the water content. As a result, the water content in the electrolyte solution was 52 mass ppm. The water content in the electrolyte solution was measured using the above-mentioned FT-IR analyzer.

[0130] <Electrolysis process> A carbon electrode (1 cm square) with a conductive diamond coating on its surface was used as the anode, and the electrolyte obtained above was subjected to constant current electrolysis at 0.6 A / cm. 2 The current density was 0.025 A / cm and continued until the current flow reached 10,000 mA·hr. After that, an ABR grade carbon electrode (1 cm square) manufactured by SGL was used as the anode. 2 When step operation was performed, the current density was 1.4 A / cm 2 The anode effect occurs some time after the critical current density reaches 1.4 A / cm 2 The current efficiency of fluorine gas generation at this time was 97%.

[0131] Current density 1.4A / cm 2 When the anode effect occurred, the current was stopped and the current was passed through the same electrode again. The initial current density was 0.025 A / cm 2 The current begins to flow as 0.025A / cm 2 When step operation was performed, the current density was 0.2 A / cm 2 No anode effect occurred even when the temperature reached .

[0132] The current was stopped once and then tried to pass it again to the same electrode. The initial current density was 0.025 A / cm 2 When current started to flow, it was possible to pass a current of 0.025 A / cm at a cell voltage of 6.2 V. 2 When step operation was performed, the current density was 0.5 A / cm 2 No anode effect occurred even when the temperature reached .

[0133] Comparative Example 1 Constant-current electrolysis of the electrolyte was carried out in the same manner as in Example 1, except that dehydrated KF·2HF, which did not contain potassium hexachloroplatinate(IV), was used as the electrolyte, and the critical current density was measured.

[0134] The result is 0.025A / cm 2 Step operation with a current density of 0.250 A / cm 2 The anode effect occurs when the critical current density reaches 0.250 A / cm 2 The current efficiency for fluorine gas generation was 95%. When the anode effect occurred, the current was stopped and an attempt was made to pass current through the same electrode again. The initial current density was 0.025 A / cm. 2 When a current was applied again, no current flowed and the voltage reached 20V.

[0135] Comparative Example 2 Constant-current electrolysis of the electrolyte was carried out in the same manner as in Example 2, except that dehydrated KF·2HF, which did not contain potassium hexachloroplatinate(IV), was used as the electrolyte, and the critical current density was measured.

[0136] The result is 0.025A / cm 2 Step operation with a current density of 0.250 A / cm 2 The anode effect occurs when the critical current density reaches 0.250 A / cm 2 The current efficiency for fluorine gas generation was 90%. When the anode effect occurred, the current was stopped and an attempt was made to pass current through the same electrode again. The initial current density was 0.025 A / cm 2 When a current was applied again, no current flowed and the voltage reached 20V.

[0137] Comparative Example 3 Constant-current electrolysis of the electrolyte was carried out in the same manner as in Example 3, except that dehydrated NHF·2HF, which did not contain potassium hexachloroplatinate(IV), was used as the electrolyte, and the critical current density was measured.

[0138] The result is 0.025A / cm 2Step operation with a current density of 0.2 A / cm 2 The anode effect occurs some time after the critical current density reaches 0.2 A / cm 2 When the anode effect occurred, the current was stopped and the same electrode was re-energized. The initial current density was 0.025 A / cm 2 When a current was applied again, no current flowed and the voltage reached 20V.

[0139] Comparative Example 4 Constant-current electrolysis of the electrolyte was carried out in the same manner as in Example 2, except that dehydrated KF·2HF containing lithium fluoride (LiF) was used as the electrolyte instead of potassium hexachloroplatinate(IV), and the critical current density was measured.

[0140] The result is 0.025A / cm 2 Step operation with a current density of 0.275A / cm 2 The anode effect occurs when the critical current density reaches 0.275 A / cm 2 The current efficiency for fluorine gas generation was 86%. When the anode effect occurred, the current was stopped and an attempt was made to pass current through the same electrode again. The initial current density was 0.025 A / cm 2 When a current was applied again, no current flowed and the voltage reached 20V.

[0141] Comparative Example 5 Constant-current electrolysis of the electrolyte was carried out in the same manner as in Example 1, except that dehydrated KF·2HF containing nickel(II) chloride hexahydrate (NiCl2·6H2O) was used as the electrolyte instead of potassium hexachloroplatinate(IV), and the critical current density was measured. The amount of nickel(II) chloride hexahydrate added was such that the concentration of nickel(II) chloride in the total mixture of dehydrated KF·2HF and nickel(II) chloride was 0.2 mass%.

[0142] A carbon electrode grade ABR (1 cm square) manufactured by SGL was used as the anode, and the current was 0.025 A / cm 2When step operation was performed, the current density was 0.250 A / cm 2 The anode effect occurs when the critical current density reaches 0.250 A / cm 2 When the anode effect occurred, the current was stopped and the same electrode was re-energized. The initial current density was 0.025 A / cm 2 When a current was applied again, no current flowed and the voltage reached 20V.

Claims

1. an electrolysis step in which an electrolyte solution is electrolyzed using an anode and a cathode to produce a fluorine-containing compound; The electrolyte solution contains hydrogen fluoride, a metal fluoride, and a compound represented by the chemical formula [MXn] m- and a complex ion represented by The chemical formula [MXn] m- wherein M is an ion of a d-block element having 4 or more and 8 or less electrons in the outermost d orbital, X is a halogen atom, m indicating the valence of the complex ion is an integer of 1 or more and 5 or less, and n indicating the number of Xs is an integer of 2 or more and 10 or less.

2. an electrolytic solution production step of mixing the hydrogen fluoride, the metal fluoride, and a metal complex compound represented by a chemical formula AMXn to produce the electrolytic solution is provided before the electrolysis step; 2. The method for producing a fluorine-containing compound according to claim 1, wherein A in the chemical formula AmMX is an alkali metal cation or an ammonium ion, MX is an anion, M is an ion of a d block element having 4 or more and 8 or less electrons in the outermost d orbital, X is a halogen atom, m indicating the number of As is an integer of 1 or more and 5 or less, and n indicating the number of Xs is an integer of 2 or more and 10 or less.

3. 3. The method for producing a fluorine-containing compound according to claim 1, wherein M is an ion of at least one metal selected from the group consisting of platinum, palladium, gold, iridium, rhodium, ruthenium, and silver.

4. 3. The method for producing a fluorine-containing compound according to claim 2, wherein A is at least one cation selected from the group consisting of potassium, cesium, and rubidium.

5. 3. The method for producing a fluorine-containing compound according to claim 1, wherein X is at least one of a fluorine atom and a chlorine atom.

6. 3. The method for producing a fluorine-containing compound according to claim 1, wherein M is an ion of a d-block element having 5 to 7 electrons in the outermost d orbital.

7. 3. The method for producing a fluorine-containing compound according to claim 1, wherein the metal fluoride is at least one of potassium fluoride, ammonium fluoride, and cesium fluoride.

8. 3. The method for producing a fluorine-containing compound according to claim 1, wherein the content of ions of the d-block elements in the electrolyte solution is from 1 ppm by mass to 10% by mass.

9. 3. The method for producing a fluorine-containing compound according to claim 1, wherein the water content in the electrolytic solution is 1 ppm by mass or more and 100 ppm by mass or less.

10. 3. The method for producing a fluorine-containing compound according to claim 1, wherein the fluorine-containing compound is at least one of fluorine gas, nitrogen trifluoride, fluorocarbon, chlorofluorocarbon, and hydrofluorocarbon.

11. 3. The method for producing a fluorine-containing compound according to claim 1, wherein the anode is a carbonaceous electrode.

12. An electrolyte solution that generates a fluorine-containing compound by electrolysis, Hydrogen fluoride, metal fluoride, and the chemical formula [MXn] m- and a complex ion represented by The chemical formula [MXn] m- wherein M is an ion of a d-block element having 4 or more and 8 or less electrons in the outermost d orbital, X is a halogen atom, m indicating the valence of the complex ion is an integer of 1 or more and 5 or less, and n indicating the number of Xs is an integer of 2 or more and 10 or less.

13. 13. The electrolyte solution according to claim 12, further comprising an ion represented by chemical formula A, wherein A is an alkali metal cation or an ammonium ion.

14. 14. The electrolyte solution according to claim 12, wherein M is an ion of at least one metal selected from the group consisting of platinum, palladium, gold, iridium, rhodium, ruthenium, and silver.

15. 14. The electrolyte of claim 13, wherein A is at least one cation selected from the group consisting of potassium, cesium, and rubidium.

16. 14. The electrolyte solution according to claim 12, wherein X is at least one of a fluorine atom and a chlorine atom.

17. 14. The electrolyte solution according to claim 12, wherein M is an ion of a d-block element having 5 to 7 electrons in the outermost d orbital.

18. 14. The electrolytic solution according to claim 12 or 13, wherein the metal fluoride is at least one of potassium fluoride, ammonium fluoride, and cesium fluoride.

19. 14. The electrolyte solution according to claim 12, wherein the content of ions of the d-block elements is 1 ppm by mass or more and 10% by mass or less.

20. The electrolytic solution according to claim 12 or 13, wherein the water content is 1 ppm by mass or more and 100 ppm by mass or less.

21. 14. The electrolytic solution according to claim 12 or 13, wherein the fluorine-containing compound is at least one of fluorine gas, nitrogen trifluoride, fluorocarbon, chlorofluorocarbon, and hydrofluorocarbon.