Method for producing metal carbide and hydrocarbon, and carbon-containing member

Abstract

The present invention relates to a method for producing a metal carbide, the method comprising: an electrode production step comprising a step for preparing a first molten salt containing carbonate ions and at least one first metal ion selected from alkali metal ions and alkaline earth metal ions; and a step in which a voltage is applied to the first molten salt and a carbon-containing deposit is deposited on the first electrode to obtain a second electrode. And an electrolysis step including a step of applying a voltage to a second molten salt containing at least one second metal ion selected from the group consisting of alkali metal ions and alkaline earth metal ions using the second electrode to obtain a carbide composition containing a carbide of the second metal.

Description

Technical Field

[0001] This invention relates to methods for manufacturing metal carbides and hydrocarbons, as well as carbon-containing components. Background Technology

[0002] Acetylene is an important industrial substance, serving as a raw material for various organic compounds. It is typically obtained through the reaction of metal carbides (primarily calcium carbide) with water.

[0003] Calcium carbide is typically obtained by heating a mixture of quicklime (calcium oxide) and coke to a high temperature in an electric furnace (e.g., Patent Document 1). Patent Document 2 relates to the manufacture of calcium carbide, proposing a method of first forming coke into char blocks and then mixing them with quicklime. Patent Document 3 proposes a method for manufacturing lithium carbide by reacting lithium metal obtained from the molten electrolysis of lithium chloride with carbon powders such as carbon black. Non-Patent Document 1 proposes a method for manufacturing lithium carbide by reacting lithium metal obtained from the electrolysis of molten lithium hydroxide salt with a carbon source such as carbon dioxide. Non-Patent Document 2 proposes a method for manufacturing lithium carbide by reacting lithium metal with carbon.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 61-178412 Patent Document 2: Japanese Patent Application Publication No. 2018-35328 Patent Document 3: Japanese Patent Application Publication No. 2-256626 Non-patent literature Non-patent literature 1: McEnaney JM, Rohr BA, Nielander AC, Singh AR, King LA, Norskov JK, Jaramillo TF, "A cyclic electrochemical strategy to produce acetylene from CO2, CH4, or alternative carbon sources.", Sustain Energy Fuels4:2, 752-2759 (2020) Non-patent literature 2: Uwe Ruschewitz, "Binary and ternary carbides of alkaliand alkaline-earth metals", Coordination Chemistry Reviews 244, 115-136 (2003) Summary of the Invention

[0005] The problem that the invention aims to solve When manufacturing metal carbides, the raw materials typically need to be heated to above 2000°C. This results in not only low energy efficiency but also the generation of large amounts of carbon dioxide. Furthermore, in Patent Documents 1-3, carbon itself is used directly as the carbon source for the metal carbides. In Non-Patent Document 1, while the lithium carbide yield is calculated to be no more than 20% when carbon dioxide is used as the carbon source, it is stated that using carbon as the carbon source can improve the lithium carbide yield. However, no experimental data to prove this point is presented. In Non-Patent Document 2, although the use of amorphous carbon or graphite as the carbon source is described, contact with lithium metal vapor at 800°C to 900°C, or contact with lithium metal in an arc melting furnace at approximately 3500°C or higher, is required to generate crystalline lithium carbide.

[0006] The object of this invention is to provide a method for producing metal carbides that allows the reaction to proceed rapidly at relatively low temperatures (e.g., below 800°C) and is capable of efficient production. This invention also provides a method for producing hydrocarbons from the obtained metal carbides. Furthermore, this invention provides a carbon-containing component carrying a metal carbide.

[0007] Technical solutions for solving the problem The present invention includes the following embodiments.

[0008] [1] A method for manufacturing a metal carbide, comprising: An electrode fabrication process includes: preparing a first molten salt containing at least one first metal ion selected from alkali metal ions and alkaline earth metal ions and a carbonate ion; applying a voltage to the first molten salt to cause a carbon-containing precipitate to deposit on the first electrode, thereby obtaining a second electrode; and An electrolysis process comprising applying a voltage to a second molten salt containing at least one second metal ion selected from alkali metal ions and alkaline earth metal ions using the second electrode to obtain a carbide composition containing the second metal.

[0009] [2] The method for manufacturing metal carbides as described in [1], wherein the first electrode contains at least one selected from transition metals and alloys containing transition metals.

[0010] [3] A method for manufacturing a metal carbide as described in [1] or [2], wherein the first electrode contains an alloy containing iron.

[0011] [4] A method for manufacturing a metal carbide as described in any one of [1] to [3], wherein the first electrode contains SUS304.

[0012] [5] A method for manufacturing a metal carbide as described in any one of [1] to [4], wherein the second molten salt is substantially free of carbonate ions.

[0013] [6] A method for manufacturing a metal carbide as described in any one of [1] to [5], wherein, in the electrolysis step, the first molten salt used in the electrode fabrication step is used directly as the second molten salt.

[0014] [7] A method for manufacturing a metal carbide as described in any one of [1] to [6], wherein the second molten salt contains, as an anion, at least one selected from halide ions and oxide ions.

[0015] [8] A method for manufacturing a metal carbide as described in any one of [1] to [7], wherein the first metal ion is the same as the second metal ion.

[0016] [9] A method for manufacturing a metal carbide as described in any one of [1] to [8], wherein the carbide composition further comprises at least one selected from carbon, the elemental form of the second metal, halides, carbonates, oxides, hydrides and peroxides, and the elemental form of the first metal, halides, carbonates, oxides and carbides.

[0017]

[10] A method for manufacturing a metal carbide as described in any one of [1] to [9], wherein the second molten salt contains, as the second metal ion, at least one selected from sodium ions, lithium ions and potassium ions and calcium ions.

[0018]

[11] A method for producing a hydrocarbon, comprising: An electrode fabrication process includes: preparing a first molten salt containing at least one first metal ion selected from alkali metal ions and alkaline earth metal ions and carbonate ions from carbon dioxide; and applying a voltage to the first molten salt to cause carbon-containing precipitates to be deposited on the first electrode to obtain a second electrode. An electrolysis process comprising applying a voltage to a second molten salt containing at least one second metal ion selected from alkali metal ions and alkaline earth metal ions using the second electrode to obtain a carbide composition containing the second metal; and The gas generation process includes the step of hydrolyzing the carbide of the second metal to obtain a gas containing hydrocarbons.

[0019]

[12] A method for manufacturing a hydrocarbon as described in

[11] , wherein the hydrocarbon is acetylene.

[0020]

[13] A method for producing hydrocarbons as described in

[11] or

[12] , wherein the gas contains acetylene as the hydrocarbon, and also contains at least one selected from ethylene, ethane, methane, methylacetylene, propylene, butene and hydrogen.

[0021]

[14] A carbon-containing component comprising: matrix; and A metal carbide composition supported on the matrix, comprising a carbide of at least one second metal selected from alkali metals and alkaline earth metals.

[0022]

[15] A carbon-containing component comprising: Matrix; A metal carbide layer covering at least a portion of the substrate, comprising a carbide of at least one second metal selected from alkali metals and alkaline earth metals; and A carbon layer that covers at least a portion of the metal carbide layer and contains carbon but does not substantially contain the carbide of the second metal.

[0023] Invention Effects According to the present invention, a method for producing metal carbides that can be produced rapidly at relatively low temperatures, a method for producing hydrocarbons from the obtained metal carbides, and a carbon-containing component carrying metal carbides can be provided. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating a method for manufacturing the metal carbides involved in this invention.

[0025] Figure 2 This is a flowchart illustrating a method for manufacturing hydrocarbons according to the present invention.

[0026] Figure 3A This is a photograph showing the appearance of the working electrode before the electrolysis process in Example 6-1.

[0027] Figure 3B This is a photograph showing the appearance of the working electrode after the electrolysis process in Example 6-1.

[0028] Figure 3C This is a cross-sectional photograph showing the precipitate deposited on the working electrode after the electrolysis process in Example 6-1.

[0029] Figure 4A This is a photograph showing the appearance of the working electrode after the electrolysis process in Example 6-2.

[0030] Figure 4BThis is an optical microscope photograph taken using a micro Raman spectrophotometer to observe a cross-section of the precipitate deposited on the working electrode after the electrolysis process in Example 6-2.

[0031] Figure 4C This is a graph showing the results of Raman spectrophotometric analysis of the precipitates obtained in Example 6-2. Detailed Implementation

[0032] Implementation Method 1 In the method for manufacturing metal carbides according to this embodiment, firstly, a voltage is applied to a molten salt containing at least one first metal ion selected from alkali metal ions and alkaline earth metal ions and carbonate ions from carbon dioxide, and a carbon-containing first precipitate is deposited on a first electrode made of SUS304 to obtain a second electrode (electrode fabrication step). Then, using the carbon deposited on the second electrode as a carbon source, electrolysis is performed directly using the first molten salt used in the electrode fabrication step, thereby obtaining a metal carbide (electrolysis step).

[0033] Therefore, metal carbides can be efficiently obtained at relatively low temperatures below 800°C. Furthermore, CO2, considered a cause of global warming, can be effectively utilized as a carbon source. Moreover, since the first molten salt used in the electrode fabrication process can be directly used in the next electrolysis process, i.e., the electrode fabrication and electrolysis processes can be carried out in the same electrolytic cell, production efficiency is also high.

[0034] This embodiment includes the step of hydrolyzing the metal carbide obtained by the above method to obtain hydrocarbons. Using this method, high-purity hydrocarbons can be obtained efficiently.

[0035] This embodiment includes a carbon-containing component carrying a metal carbide. This carbon-containing component can be used in the manufacture of hydrocarbons.

[0036] [Methods for manufacturing metal carbides] The method for manufacturing metal carbides according to the present invention includes the steps of: preparing a first molten salt containing at least one first metal ion selected from alkali metal ions and alkaline earth metal ions and a carbonate ion; and applying a voltage to the first molten salt to cause a carbon-containing precipitate to be deposited at a first electrode to obtain a second electrode; and An electrolysis process comprising applying a voltage to a second molten salt containing at least one second metal ion selected from alkali metal ions and alkaline earth metal ions using a second electrode to obtain a carbide composition containing a second metal carbide. Figure 1 This is a flowchart illustrating the method for manufacturing the metal carbides involved in this invention.

[0037] (I) Electrode fabrication process In the electrode fabrication process, a carbon-containing precipitate is deposited on the first electrode to create the second electrode. The carbon on the second electrode is used as a carbon source for the formation of metal carbides during the electrolysis process. The carbon-containing precipitate is deposited on the surface of the electrode with a lower potential (cathode). Hereinafter, the first electrode will sometimes be referred to as the "cathode," and the other electrode will sometimes be referred to as the "anode."

[0038] The electrode fabrication process includes: preparing a first molten salt containing at least one first metal ion selected from alkali metal ions and alkaline earth metal ions and a carbonate ion; and applying a voltage to the first molten salt to cause a carbon-containing precipitate to be deposited on the first electrode to obtain a second electrode.

[0039] (i) Preparation of the first molten salt (S11) A first molten salt containing a first metal ion and carbonate ions from carbon dioxide is prepared. The first metal ion is generated by the ionization of the salt of the first metal. Carbonic acid ions are generated by adding a gas containing carbon dioxide to the electrolytic cell. In the first molten salt, it is not necessary for both the first metal salt and carbon dioxide to be completely ionized. In this embodiment, for convenience, the salt of the first metal contained in the electrolytic cell, including the case where it is completely ionized, is sometimes referred to as the first metal salt, and the molten salt prepared from the first metal salt and carbon dioxide, including the case where it is not completely ionized, is sometimes referred to as the first molten salt.

[0040] (First metal ion) The first metal ion is selected from at least one alkali metal ion and alkaline earth metal ion. Alkali metal ions and alkaline earth metal ions have excellent functions as electrolytes.

[0041] As an alkali metal, at least one can be selected from lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). An alkali metal can be at least one selected from Li, Na, K, Rb, and Cs. In particular, an alkali metal can be at least one selected from Li, Na, K, and Cs.

[0042] Alkaline earth metals can be selected from at least one of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). Alkaline earth metals can be selected from at least one of Mg, Ca, Sr, and Ba.

[0043] (Other metal ions) The first molten salt may contain other metal ions besides the first metal ion (a third metal ion). Preferably, the salt of the third metal ion can ionize at a temperature below 800°C.

[0044] As a third metal, at least one can be selected from rare earth elements, aluminum (Al), gallium (Ga), indium (In), thallium (Tl), zinc (Zn), cadmium (Cd), gold (Au), silver (Ag), and copper (Cu). As rare earth elements, scandium (Sc), yttrium (Y), lanthanides, and actinides can be listed.

[0045] (Carbonate ions from carbon dioxide) Carbonic acid ions can be generated by adding a gas containing carbon dioxide to the electrolyzer.

[0046] A gas containing carbon dioxide (hereinafter sometimes simply referred to as CO2 gas) is brought into contact with the liquid first metal salt in a gaseous state. CO2 gas can be either blown into the gas phase section of the electrolytic cell to contact the liquid surface of the first metal salt, or it can be blown directly into the first metal salt. The CO2 gas can be a mixture of CO2 and an inert gas (typically argon). Sufficient amounts of CO2 gas can be added to the first metal salt before voltage is applied, or CO2 gas can be added to the first metal salt while voltage is being applied.

[0047] The amount of CO2 gas introduced can be appropriately set according to the amount of the first metal ions. Considering the absorption efficiency of the gas in the first metal salt, the amount of CO2 gas introduced can be, for example, above the equivalent of the first metal salt.

[0048] From the viewpoint of promoting the dissolution of CO2 into the first metal salt, the smaller the bubble diameter of the blown CO2 gas, the better. The bubble diameter of the CO2 gas is preferably 10 mm or less, more preferably 1 mm or less. The bubble diameter of the CO2 gas can be 100 nm or more, or 1 μm or more. The bubble diameter of the CO2 gas can be refined, for example, by using porous materials such as quartz glass or high-purity alumina for bubbling, or by using a stirrer, applying vibration, or irradiating with ultrasound.

[0049] The CO2 gas is preferably preheated to near the temperature of the first metal salt. Preheating helps to prevent the solidification of the first metal salt caused by a decrease in temperature.

[0050] (Other anions) The first molten salt may contain anions other than carbonate ions. Other anions include, for example, halide ions, sulfate ions, phosphate ions, nitrate ions, acetate ions, carboxylate ions, and oxide ions (O). 2－ At least one of the following. Other anions may include halide ions derived from halides of the first metal. Halides of the first metal are commonly used as molten salts and are excellent as electrolytes.

[0051] (ii) Apply voltage (S12) Next, a voltage is applied to the first molten salt. This causes CO3 to be generated at the cathode. 2－ The carbon is reduced to obtain a carbon-containing precipitate (Formula 1). The carbon in this precipitate can be polycrystalline, and can be a polycrystalline material with high crystallinity (e.g., a polycrystalline material resembling carbon nanotubes). A carbide of the first metal is also precipitated on the cathode. On the anode, O... 2－ It is oxidized to produce oxygen (Equation 2).

[0052] (Equation 1) 2CO3 2－ +8e － → 2C + 6O 2－ (Equation 2) 2O 2－ → O2+4e － When the first metal is Ca, calcium carbide (CaC2) can be deposited at the cathode (Equation 3). Metallic calcium can also be generated at the cathode (Equation 4). Some or all of the metallic calcium generated in this side reaction can become calcium carbide through further reaction (Equation 5). Alternatively, metallic calcium reacts with carbon dioxide physically dissolved in the first molten salt to become calcium carbide (Equation 6). There is also a case where the molten salt becomes turbid due to the formation of carbon fines (Equation 7). The CaO generated in (Equation 6) and (Equation 7) above will immediately dissolve in the molten salt, generating calcium ions and oxide ions (Equation 8).

[0053] (Equation 3) Ca 2＋ +2CO3 2－ +10e － → CaC2+6O 2－ (Equation 4) Ca 2＋ +2e － → Ca (Equation 5) Ca + 2C → CaC2 (Equation 6) 2CO2 + 5Ca → CaC2 + 4CaO (Equation 7) 2Ca+CO2→ C+2CaO (Equation 8) CaO → Ca 2＋ +O 2－ When the first metal is Na, K, or Li, sodium carbide (Na₂C₂), potassium carbide (K₂C₂), or lithium carbide (LiC₂) can be precipitated together with carbon through the same reaction. The same applies to other first metals.

[0054] At the anode, O 2－It is oxidized to produce oxygen. The oxygen produced at the anode is released into the gas phase. By recovering this oxygen, it can be used for other purposes.

[0055] The voltage is applied at a temperature sufficient to maintain the molten state of the first molten salt. The temperature of the electrolytic cell can be, for example, 350°C or higher, or 400°C or higher. Alternatively, the temperature can be, for example, 800°C or lower, or 700°C or lower. According to the present invention, high energy efficiency is achieved because the reaction can be carried out at such relatively low temperatures.

[0056] Regarding the applied voltage, the potential of the first electrode (cathode) should be set below the carbon deposition potential (Ec) (low). The current value should be appropriately set according to the CO2 supply per unit time. For example, the current value should be set to prevent CO3 in the first molten salt from being released. 2－ The way the concentration decreases is related to the amount of CO3 consumed at the cathode per unit time. 2－ In contrast, CO2 and O2 in the first molten salt － The reaction produces CO3 2－ More value.

[0057] In this embodiment, a cathode made of SUS304 is used. This significantly improves the Faraday efficiency. Furthermore, SUS304 is preferred due to its relatively easy availability, low cost, and excellent heat resistance. SUS304 is an austenitic stainless steel, and its composition is described in JIS G 4303, etc.

[0058] The cathode material is not limited to SUS304. Examples of cathode materials include metals such as Ag, Cu, Ni, Pb, Hg, Tl, Bi, In, Sn, Cd, Au, Zn, Ga, Ge, Fe, Pt, Pd, Ru, Ti, Cr, Mo, W, V, Nb, Ta, Zr, and their alloys. Specifically, ferrite-based stainless steels such as SUS430 can be included as alloys.

[0059] From the perspective of high Faraday efficiency, the cathode may contain at least one element selected from transition metals and alloys containing transition metals. Transition metals may include Ni, Fe, Mo, and Ti. The cathode may particularly contain iron alloys (typically stainless steel) and can be formed from iron alloys. The cathode may contain SUS304 and can be formed from SUS304.

[0060] There are no particular limitations on the material of the anode. Examples of anode materials include Pt, conductive metal oxides, glassy carbon, natural graphite, isotropic graphite, thermally decomposed graphite, plastically formed carbon, and boron-doped diamond. Examples of electrodes made of conductive metal oxides include transparent conductive electrodes obtained by forming a film of a mixed oxide of indium and tin (ITO electrode) on glass; electrodes known as DSA electrodes (trademark of De Nora Permelec Electrode Co., Ltd.) formed by forming oxides of platinum group metals such as ruthenium and iridium on a substrate such as titanium; and electrodes with La... 1－x Sr x FeO 3－δ Conductive metal oxide electrodes composed of (0≤x≤0.5 (especially 0.1≤x≤0.5), 0≤δ≤0.5), etc. Among them, conductive metal oxide anodes are preferred from the perspective of not being easily consumed by oxidation reactions.

[0061] Through the electrode fabrication process, a second electrode loaded with carbon-containing precipitates can be obtained.

[0062] (II) Electrolysis process (S2) In the electrolysis process, a second electrode obtained in the electrode fabrication process and a second molten salt containing at least one second metal ion selected from alkali metal ions and alkaline earth metal ions are used for electrolysis. Thus, by using carbon supported on the second electrode as a carbon source, a carbide composition containing a carbide of the second metal can be obtained.

[0063] (Second metal ion) The second metal ion is selected from at least one of alkali metal ions and alkaline earth metal ions. The second metal ion serves as the metal source for the target metal carbide. Alkali metal and alkaline earth metal carbides are also known as acetylene compounds, which readily produce acetylene through hydrolysis and have high industrial value. Moreover, as mentioned above, alkali metal ions and alkaline earth metal ions exhibit excellent functions as electrolytes.

[0064] From an industrial perspective, the second metal ion may contain alkaline earth metal ions or Ca ions. The second metal ion may also contain alkali metal ions along with the alkaline earth metal ions. Alkali metal ions are components that possess excellent functions as electrolytes, such as facilitating the ionization of alkaline earth metal salts, promoting the formation of alkaline earth metal ions, lowering the melting point of molten salts, and enabling electrolysis at lower temperatures. The first metal ion may contain at least one alkali metal ion selected from Li, Na, K, Rb, and Cs, and at least one alkaline earth metal ion selected from Be, Mg, Ca, Sr, and Ba. In particular, it may contain at least one Li, Na, and K ion and Ca ions.

[0065] The amount of the second metal ion contained in the second molten salt is not particularly limited. Since the second metal ion is the metal source of the target metal carbide, it is preferable to contain a sufficient amount. The molar percentage of the second metal ion relative to the total number of cations in the electrolytic cell can be 1 mol% or more, 2 mol% or more, or 3 mol% or more. The molar percentage of the second metal ion relative to the total number of cations in the electrolytic cell can be 20 mol% or less, 15 mol% or less, or 10 mol% or less. In one embodiment, the molar percentage of the second metal ion relative to the total number of cations in the electrolytic cell is 1 mol% or more and 20 mol% or less.

[0066] As in this embodiment, if the first molten salt used in the electrode fabrication process is used directly as the second molten salt, a second metal ion may be added to the electrolytic cell before the electrolysis process.

[0067] (Anions) As the second metal ion's counterpart ion (anion), examples include, for instance, halide ions, sulfate ions, phosphate ions, nitrate ions, acetate ions, carboxylate ions, and oxide ions (O). 2－ At least one of the following.

[0068] The second molten salt may contain at least one of halide ions and oxide ions as anion. Specifically, the second molten salt may contain both halide ions and oxide ions. Oxides of the second metal are readily available, but on the other hand, they tend to have higher melting temperatures. Halides of the second metal are often used as molten salts. However, using halide ions can generate halogen gases with high oxidizing power (the cause of corrosion) at the anode. In the case of containing both halide ions and oxide ions, it is possible to suppress the generation of halogen gases while lowering the melting temperature of the molten salt.

[0069] As a halogen, at least one selected from fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At) can be listed. As a halogen, it can be at least one selected from F, Cl, Br, and I, especially F and / or Cl.

[0070] The second molten salt preferably contains substantially no carbonate ions (CO3). 2－ When the second molten salt contains carbonate ions, it readily reacts with electrons generated by the discharge of the second metal (Equation 7) to form carbon. This reduces the yield of the second metal carbide. By making the second molten salt substantially free of carbonate ions, this side reaction is suppressed, and the yield of the second metal carbide can be increased.

[0071] (Equation 7) 2CO3 2－ +8e－ → 2C + 6O 2－ "Substantially free of carbonate ions" means that carbonate ions are allowed to be present to a degree that does not participate in the electrolysis reaction. For example, the second molten salt may contain approximately 1.0 mol% or less of carbonate ions. The carbonate ion concentration in the second molten salt may be less than 0.5 mol%, less than 0.3 mol%, or 0 mol%.

[0072] Examples of second metal salts containing alkaline earth metal ions include CaO, CaCl2, CaF2, CaBr2, CaI2, CaH2, and Ca3P2. Examples of second metal salts containing alkali metal ions include LiF, NaF, KF, RbF, CsF, LiCl, NaCl, KCl, RbCl, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, LiI, NaI, KI, RbI, and CsI.

[0073] The second metal ion can be the same as or different from the first metal ion. The first metal ion and the second metal ion can be the same. In this embodiment, since the first molten salt used in the electrode fabrication process is directly used as the second molten salt in the electrolysis process, the second metal ion can contain the same type of metal ion as the first metal ion.

[0074] The material of the other electrode (anode) is not particularly limited. Examples of materials that can be used as the anode are the same materials used in the electrode fabrication process. In this embodiment, the anode used in the electrode fabrication process can be used directly in the electrolysis process.

[0075] When a voltage is applied to the second molten salt, the second metal ions are reduced to form a second metal on the carbon constituting the cathode (second electrode). This second metal immediately reacts with the carbon constituting the cathode (second electrode) to obtain a composition containing the second metal carbide (metal carbide composition). If an unionized second metal salt is present in the second molten salt, applying a voltage can further promote the ionization of the second metal salt.

[0076] When the second metal is Ca, calcium carbide (CaC2) is formed (Equation 8). At the cathode, metallic calcium is also formed through a side reaction (Equation 9). Some or all of the metallic calcium produced by this side reaction further reacts to yield calcium carbide.

[0077] (Equation 8) Ca 2＋ +2C +2e － → CaC2 (Equation 9) Ca 2＋ +2e － → Ca The voltage is applied at a temperature that maintains the molten salt in a molten state. The electrolytic cell temperature can be, for example, 350°C or higher, or 400°C or higher. Alternatively, the electrolytic cell temperature can be, for example, below 800°C, or below 700°C. According to the present invention, the reaction can be carried out at such relatively low temperatures, thus achieving high energy efficiency.

[0078] Regarding the applied voltage, the cathode potential is set to be lower than the potential (Emc) at which the second metal is deposited on the cathode (low). This further improves the selectivity of the second metal carbide. If the cathode potential is too high (high), the amount of the desired second metal carbide formed tends to decrease. If the cathode potential is too low (low), although the second metal carbide will form, the metal with the highest redox potential in the molten salt will primarily precipitate. In cases where multiple metals with similar redox potentials are present in the molten salt, an alloy of multiple metals may sometimes precipitate. The potential Emc can be determined by cyclic voltammetry using the metal electrode to be used, such as a SUS304 electrode, in the molten salt being used.

[0079] When performing constant current electrolysis, the set current value should be appropriately set in a way that makes the cathode potential in the electrolysis reach the potential range described above.

[0080] Metal carbide compositions are typically obtained in a state supported on a cathode (more precisely, on a substrate from the first (second) electrode used as a cathode). When a molten salt with excellent solubility for the second metal carbide is used, the second metal carbide is obtained with some or all of it dissolved in the molten salt. When the second metal carbide is pre-dissolved in the molten salt, the second metal carbide obtained by electrolysis is more easily deposited onto the cathode and is readily obtained in a state supported on a substrate from the first electrode.

[0081] The metal carbide composition contains a carbide of a second metal. The second metal carbide is the main component of the metal carbide composition. A main component refers to a component that accounts for 50% or more by mass of the total mass of the metal carbide composition. The content of the second metal carbide can be 80% or more by mass, or 90% or more by mass of the metal carbide composition. The content of the second metal carbide can be 99.9% or less by mass, or 99% or less by mass of the metal carbide composition. In one embodiment, the content of the second metal carbide is 80% or more by mass and 99.9% or less by mass of the metal carbide composition.

[0082] The metal carbide composition may also contain, as a byproduct, at least one selected from carbon, monomers of a second metal, halides, carbonates, oxides, hydrides, and peroxides. The metal carbide composition may also contain at least one selected from monomers of a first metal, halides, carbonates, oxides, and carbides.

[0083] The metal carbide composition may also contain at least one selected from the solidified electrolyte (other metal salts), halides, oxides, metals, and hydrates of the materials constituting the device.

[0084] The carbon contained in the metal carbide composition is, for example, selected from at least one of nanomaterials such as graphite, amorphous carbon, glassy carbon, carbon nanotubes, diamond, nanodiamond, and graphene. By continuously performing electrolysis as described above, a second metal carbide can be further obtained from the carbon contained in the metal carbide composition. In this case, the yield can be further improved.

[0085] The presence and quantification of second metal carbides, second metal monomers, compounds containing second metals, and other byproducts can be performed, for example, by Raman spectrophotometry and X-ray diffraction (XRD) analysis of the composition.

[0086] [Carbon-containing components] This invention includes a carbon-containing component comprising a matrix and a metal carbide composition supported on the matrix, the metal carbide composition containing a carbide of at least one second metal selected from alkali metals and alkaline earth metals. The carbon-containing component of this invention can be used in the manufacture of hydrocarbons.

[0087] The carbon-containing component can be obtained, for example, by the manufacturing method of the metal carbide described above. That is, the carbon-containing component corresponds to the second electrode used in the electrolysis of the second molten salt described above. In this case, the substrate comes from the second electrode described above.

[0088] The metal carbide composition only needs to be supported on at least a portion of the surface of the substrate. The surface of the substrate typically corresponds to the portion of the second electrode that has been in contact with the second metal ions. "Supported" means that at least a portion of the substrate surface is coated with the metal carbide composition.

[0089] When elemental analysis is performed using energy-dispersive X-ray diffraction (EDX) on a cross-section passing through the center (or center of gravity) of a carbon-containing component, a second metal and carbon are detected in that cross-section. Since the matrix (second electrode) typically does not contain a second metal, the detection of a second metal and carbon can be considered as indicating the presence of a second metal carbide.

[0090] [Methods for manufacturing hydrocarbons] This invention includes a method for producing hydrocarbons from a second metal carbide. Specifically, the method for producing hydrocarbons according to this invention includes the aforementioned electrode fabrication and electrolysis steps, and the step of hydrolyzing the second metal carbide to obtain a gas containing hydrocarbons. Figure 2 This is a flowchart illustrating the method for manufacturing hydrocarbons according to the present invention.

[0091] (1) Electrode fabrication process (S11, S12) The second electrode is fabricated in the same manner as the electrode fabrication steps (S11 and S12) in the above-described method for manufacturing metal carbides.

[0092] (2) Electrolysis process (S2) A voltage is applied to the second molten salt in the same manner as in the electrolysis step of the aforementioned method for manufacturing metal carbides. This yields a composition containing the second metal carbide.

[0093] (3) Hydrolysis of metal carbides (S3) Next, the second metal carbide is contacted with water to undergo hydrolysis. This yields the desired hydrocarbon-containing gas. According to the present invention, the Faraday efficiency e related to hydrocarbon formation can be improved. Hydrocarbons generally have low solubility in water. Therefore, the generated hydrocarbons are rapidly released into the gas phase and subsequently recovered.

[0094] The second metal carbide can also be separated from the metal carbide composition and then hydrolyzed. Separation can be carried out, for example, by crushing the metal carbide composition and utilizing the difference in specific gravity. Alternatively, the metal carbide composition can be hydrolyzed directly. For example, the electrode on which the metal carbide composition has been deposited (which can be the "carbon-containing component" of the present invention) can be brought into direct contact with water.

[0095] Examples of hydrocarbons obtained include methane, ethane, ethylene, acetylene (C₂H₂), methylacetylene, propane, propylene, butane, and butene. Acetylene is obtained as the main component when the separated first metal carbide is used, or when the amount of byproducts (especially metal monomers) in the composition is small. The main component refers to a component that accounts for more than 50% by mass of the total mass of the recovered gas. Acetylene is an industrially important hydrocarbon.

[0096] In addition to hydrocarbons, the obtained gas may also contain water vapor, hydrogen, nitrogen, and oxygen as byproducts. The amount of byproducts is preferably 10% by mass or less of the recovered gas, more preferably 1% by mass or less. The amount of byproducts can be 0.0001% by mass or more of the recovered gas. In one embodiment, the amount of byproducts is 0.0001% by mass or more and 1% by mass or less of the recovered gas.

[0097] The resulting gas contains acetylene as a hydrocarbon, and may also contain at least one of the following: ethylene, ethane, methane, methylacetylene, propylene, butene, and hydrogen.

[0098] The presence and quantification of hydrocarbons and byproducts can be performed, for example, by gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared spectroscopy (FT-IR) with a gas chamber, or ultraviolet-visible absorption spectrometry (UV-Vis).

[0099] The amount of water in contact with the composition can be appropriately set according to the mass of the composition. For example, the amount of water should be greater than or equal to the amount necessary for hydrolyzing the metal carbides and metals contained in the composition. Furthermore, it is preferable to use water that is sufficient to completely submerge the composition and takes into account the evaporation caused by the heat generated during hydrolysis.

[0100] Hydrolysis of the second metal carbide can also produce hydroxides of the second metal along with hydrocarbons. For example, during the hydrolysis of calcium carbide, calcium hydroxide is produced together with acetylene (Formula 10).

[0101] (Equation 10) CaC2+2H2O → C2H2+Ca(OH)2 Implementation Method 2 The difference between this embodiment and the first embodiment lies in the change of the electrolytic cell used in the electrode fabrication and electrolysis processes. This difference will be explained below. In this embodiment, other features of the method for manufacturing metal carbides are the same as in the first embodiment, and therefore their description is omitted here. In this embodiment, the method for manufacturing hydrocarbons and the features of the carbon-containing components are the same as in the first embodiment, and therefore their description is omitted.

[0102] In this embodiment, the second molten salt used in the electrolysis process is prepared separately from the first molten salt used in the electrode fabrication process. The first molten salt used in the electrode fabrication process may contain residual carbonate ions, which serve as a carbon source. In this embodiment, since a second molten salt substantially free of carbonate ions can be prepared, side reactions can be suppressed, and the yield and Faraday efficiency of the second metal carbide can be further improved.

[0103] Third implementation method This embodiment differs from the first embodiment in the material of the first electrode. This difference will be explained below. In this embodiment, other features of the method for manufacturing the metal carbide are the same as in the first embodiment, and therefore their description is omitted here. In this embodiment, the method for manufacturing the hydrocarbon and the features of the carbon-containing component are the same as in the first embodiment, and therefore their description is omitted.

[0104] In this embodiment, an Fe plate is used as the first electrode. In this case, a carbon-containing component can be formed, comprising a substrate, a metal carbide layer covering at least a portion of the substrate, and a carbon layer; the metal carbide layer contains a carbide of at least one second metal selected from alkali metals and alkaline earth metals; the carbon layer covers at least a portion of the metal carbide layer and contains carbon but substantially no second metal carbide. Such a carbon-containing component can suppress the decomposition of the carbides even when stored in a humid atmosphere. The presence or absence of a second metal carbide can be confirmed by, for example, Raman spectrophotometry.

[0105] "Substantially free of second metal carbides" means that the presence of second metal carbides at a level that does not contribute to hydrocarbon formation is permissible. The carbon layer may contain, for example, less than 10,000 ppm of second metal carbides. The concentration of second metal carbides in the carbon layer can be less than 1,000 ppm, less than 500 ppm, or 0 ppm.

[0106] The embodiments of the present invention have been described in detail above, but the present invention is not limited to these embodiments, and the design can be modified without departing from the spirit of the present invention.

[0107] In the above embodiments, although carbon dioxide was used as a carbonate ion source, it is not limited to this. The carbonate ion source can be a carbonate of any metal. When a carbonate of the first metal is used, first metal ions and carbonate ions can be generated by ionization. The carbonate of the first metal can be synthesized, for example, by reacting a hydroxide of the first metal with carbon dioxide.

[0108] In the above embodiments, an electrode made of SUS304 or Fe was used as the first electrode (cathode), but it is not limited to this. The first electrode may contain other metallic materials and may be formed of carbon materials. The first electrode may also contain carbon materials such as glassy carbon, natural graphite, isotropic graphite, thermally decomposed graphite, plastically formed carbon, and conductive diamond, and may be formed of carbon materials.

[0109] In the first embodiment, the carbon-containing component obtained includes a substrate and a metal carbide composition containing a second metal supported on the substrate, but is not limited thereto. The carbon-containing component obtained by the method shown in the first embodiment may include a substrate, a metal carbide layer, and a carbon layer.

[0110] In the third embodiment, the obtained carbon-containing component comprises a substrate, a metal carbide layer, and a carbon layer, but is not limited thereto. The carbon-containing component obtained by the method shown in the third embodiment may comprise a substrate and a metal carbide composition containing a second metal supported on the substrate.

[0111] Example The present invention will be described in more detail through the following embodiments, but the present invention is not limited to these embodiments.

[0112] [Example 1-1] (1) Electrode fabrication process A mixture of 3.0 mol% CaO (i.e., LiCl / KCl / CaCl2 / CaO = 52.3 mol% / 11.6 mol% / 36.1 mol%) was added to the eutectic composition of LiCl, KCl, and CaCl2 (LiCl / KCl / CaCl2 = 50.8 mol% / 11.3 mol% / 35.0 mol% / 2.9 mol%) and dried under vacuum at 200 °C and below 100 Pa for at least 24 hours. The mixed salt was then placed in quartz containers and heated to 450 °C in an electric furnace. This yielded a molten salt of LiCl-KCl-CaCl2-CaO.

[0113] Subsequently, the working electrode (1.0cm × 1.0cm, SUS304), the counter electrode (platinum coil), and the reference electrode (Ag) were installed on the lid of the aforementioned container. ＋ ( / Ag), and seal the container with this lid. Purge CO2 into the molten salt at 450°C into the container at a flow rate of 100 mL / min for more than 30 minutes. Then, using a potentiostat, apply a voltage for 30 minutes while maintaining the working electrode at a potential of 0.9 V relative to the reference electrode. Precipitation was confirmed on the working electrode. All experimental procedures were performed in a glove box maintained under a high-purity argon atmosphere.

[0114] (2) Electrolysis process Subsequently, electrolysis was performed using the same electrolytic cell and electrodes. Specifically, a potentiostat was used to maintain the working electrode at a potential of 0.3V relative to the reference electrode for 30 minutes. Precipitation was confirmed on the working electrode. All experimental procedures were performed in a glove box maintained under a high-purity argon atmosphere. The potential of the working electrode was measured against the potential of the reference electrode (Ag). ＋ After determining the potential between / Ag) and the cathode, the value is corrected using the Li-Ca alloy precipitation potential as the reference.

[0115] (3) Hydrocarbon manufacturing The precipitate was removed and placed in a sealed test tube. Pure water was added little by little to the test tube at room temperature (23°C) to hydrolyze the precipitate. The total amount of water added was 2.5 ml. After confirming the production of bubbles in the test tube, the tube was allowed to stand until no more bubbles were observed. Then, 100 μl (microliters) of gas was collected from the test tube using an airtight syringe.

[0116] GC-MS analysis of the obtained gas using a gas chromatography (GC) apparatus confirmed the formation of C2H2 as the main component. Furthermore, methane, ethane, and hydrogen were also identified as byproducts. Additionally, water, carbon dioxide, nitrogen, oxygen, and argon were present. The amounts of each component generated were also determined. C2H2 accounted for significantly more than 50% of the mass of the recovered gas.

[0117] Regarding the formation of C2H2, the Faradaic efficiency throughout the electrode fabrication and electrolysis processes is calculated to be approximately 2.2%. Since C2H2 is generated, it can be understood that the precipitate contains CaC2 as a major component. A higher Faradaic efficiency associated with hydrocarbon gas formation implies a higher Faradaic efficiency associated with metal carbide formation.

[0118] [Examples 1-2] Except that the potential of the working electrode relative to the reference electrode was maintained at 0.6V during the electrode fabrication process and at 0.1V during the electrolysis process, the electrolysis and hydrolysis were performed in the same manner as in Examples 1-1.

[0119] It was confirmed that precipitates were formed on the working electrode.

[0120] Regarding the formation of C2H2, the Faraday efficiency throughout the electrode fabrication and electrolysis processes is calculated to be approximately 9.1%. Since C2H2 is generated, it can be understood that the precipitate formed on the working electrode during the electrolysis process contains CaC2 as a major component.

[0121] [Table 1] [Example 2-1] The potential of the working electrode relative to the reference electrode was maintained at 0.3V during the electrode fabrication process and at 0.1V during the electrolysis process. Furthermore, in the electrolysis process, the electrode was not changed, but a separately prepared electrolytic cell was used. Apart from these changes, electrolysis and hydrolysis were performed in the same manner as in Examples 1-1. The electrolytic cell used in the electrolysis process was prepared in the same manner as in Examples 1-1.

[0122] It was confirmed that precipitates were formed on the working electrode.

[0123] Regarding the formation of C2H2, the Faraday efficiency throughout the electrode fabrication and electrolysis processes is calculated to be approximately 21.5%. Since C2H2 is generated, it can be understood that the precipitate formed on the working electrode during the electrolysis process contains CaC2 as a major component.

[0124] [Example 2-2] Except that the potential of the working electrode relative to the reference electrode was maintained at 0.1V during the electrode fabrication process and at 0.1V during the electrolysis process, electrolysis and hydrolysis were performed in the same manner as in Example 2-1.

[0125] It was confirmed that precipitates were formed on the working electrode.

[0126] Regarding the formation of C2H2, the Faraday efficiency throughout the electrode fabrication and electrolysis processes is calculated to be approximately 34.6%. Since C2H2 is generated, it can be understood that the precipitate formed on the working electrode during the electrolysis process contains CaC2 as a major component.

[0127] [Table 2] [Example 3-1] The potential of the working electrode relative to the reference electrode was maintained at 0.3V during the electrode fabrication and electrolysis processes. Furthermore, the electrolysis process was performed under a CO2 atmosphere. Apart from these steps, electrolysis and hydrolysis were performed in the same manner as in Examples 1-1.

[0128] It was confirmed that precipitates were formed on the working electrode.

[0129] Regarding the formation of C2H2, the Faraday efficiency throughout the electrode fabrication and electrolysis processes is calculated to be approximately 8.4%. Since C2H2 is generated, it can be understood that the precipitate formed on the working electrode during the electrolysis process contains CaC2 as a major component.

[0130] [Example 3-2] Except for maintaining the potential of the working electrode relative to the reference electrode at 0.1V during the electrode fabrication and electrolysis processes, electrolysis and hydrolysis were performed in the same manner as in Example 3-1.

[0131] It was confirmed that precipitates were formed on the working electrode.

[0132] Regarding the formation of C2H2, the Faraday efficiency throughout the electrode fabrication and electrolysis processes is calculated to be approximately 10.3%. Since C2H2 is generated, it can be understood that the precipitate formed on the working electrode during the electrolysis process contains CaC2 as a major component.

[0133] [Table 3] [Example 4-1] The potential of the working electrode relative to the reference electrode was maintained at 0.3V during the electrode fabrication process and at 0.1V during the electrolysis process. Furthermore, except that after the electrode fabrication process, the electrode was temporarily removed from the electrolytic cell and then placed back into the same cell for electrolysis after 30 minutes, the electrolysis and hydrolysis were performed in the same manner as in Example 3-1.

[0134] It was confirmed that precipitates were formed on the working electrode.

[0135] Regarding the formation of C2H2, the Faraday efficiency throughout the electrode fabrication and electrolysis processes is calculated to be approximately 4.5%. Since C2H2 is generated, it can be understood that the precipitate formed on the working electrode during the electrolysis process contains CaC2 as a major component.

[0136] [Example 4-2] Except for maintaining the potential of the working electrode relative to the reference electrode at 0.1V during the electrode fabrication and electrolysis processes, electrolysis and hydrolysis were performed in the same manner as in Example 4-1.

[0137] It was confirmed that precipitates were formed on the working electrode.

[0138] Regarding the formation of C2H2, the Faraday efficiency throughout the electrode fabrication and electrolysis processes is calculated to be approximately 2.8%. Since C2H2 is generated, it can be understood that the precipitate formed on the working electrode during the electrolysis process contains CaC2 as a major component.

[0139] [Table 4] [Examples 5-1 to 5-49] Except for changes to the composition of the molten salt, the material of the cathode, and the electrolysis conditions as shown in Tables 5 and 6, the electrode fabrication process and hydrolysis were performed in the same manner as in Example 1-1.

[0140] In Examples 5-23 to 5-49, the potential of the working electrode is the same as that of the reference electrode (Ag). ＋ After determining the potential between the ( / Ag) and the cathode, the value was corrected using the Na-K-Ca alloy precipitation potential as a reference. In Examples 5-31 to 5-49, CaC2 was pre-added to the molten salt at a rate of 7.0 mol% relative to the molten salt.

[0141] Precipitation was confirmed on the working electrode. Hydrolysis was performed on the precipitate formed on the working electrode (corresponding to the second electrode) during the electrode fabrication process. The Faradaic efficiency in the table is a value related to the C2H2 gas produced by the precipitate formed during the electrode fabrication process. The higher the Faradaic efficiency, the more CaC2 is precipitated during the electrode fabrication process. A higher Faradaic efficiency related to the generation of C2H2 gas during the electrode fabrication process means a higher Faradaic efficiency related to the generation of C2H2 gas throughout the entire process of electrode fabrication and electrolysis. Since C2H2 is generated, it can be understood that CaC2 is a major component of the precipitate formed on the working electrode through the electrolysis process.

[0142] [Table 5] [Table 6] [Example 6-1] Except for setting the cumulative charge to 2000C, electrolysis and hydrolysis were performed in the same manner as in Examples 5-45.

[0143] XRD analysis confirmed that the precipitates formed on the working electrode during the electrode fabrication process consisted of polycrystalline solids containing carbon as the main component and CaC2 as a byproduct.

[0144] Figure 3A This is a photograph showing the appearance of the working electrode before the electrolysis process in Example 6-1. Figure 3B This is a photograph showing the appearance of the working electrode after the electrolysis process in Example 6-1. Black precipitates can be observed on the surface of the working electrode, and these precipitates have expanded to more than double their original size. Figure 3C This is a cross-sectional photograph of the precipitate formed on the working electrode after the electrolysis process in Example 6-1. From... Figure 3C It can be confirmed that the precipitate has a layered structure. Furthermore, Raman spectroscopy analysis confirms that after water is sprayed onto the cross-section, gas is generated only from the inner layer, and ignition can be confirmed when a flame is brought close to the precipitate. Therefore, it is confirmed that the inner layer is a metal carbide layer with calcium carbide as the main component, and the outer layer is a carbon layer containing carbon but not actually containing calcium carbide.

[0145] [Example 6-2] Except for changing the cumulative charge to 500C, the electrolysis and hydrolysis were performed in the same manner as in Example 6-1.

[0146] Figure 4A This is a photograph showing the appearance of the working electrode after the electrolysis process in Example 6-2. Figure 4BThis is an optical microscope photograph taken when the cross-section of the precipitate deposited on the working electrode after the electrolysis process of the same Example 6-2 is observed using a micro Raman spectrophotometer. Figure 4B The image also shows a schematic cross-sectional view of the working electrode after the electrolysis process. The optical microscope photograph corresponds to the boxed portion of this schematic cross-sectional view. Figure 4B In the diagram, location A represents the black portion on the outer side of the precipitate, location B represents the gray portion on the inner side of the precipitate, and location C represents the Fe substrate of the working electrode. From... Figure 4B It can be confirmed that the precipitate has a layered structure.

[0147] Figure 4C This is a graph showing the results of Raman spectrophotometry analysis at points A to C. The results confirm that the inner layer of the precipitate (location B) is a metal carbide layer mainly composed of calcium carbide, while the outer layer of the precipitate (location A) is a carbon layer containing carbon but not actually calcium carbide.

[0148] [Example 7-1] (1) Electrode fabrication process A mixture of 3.0 mol% CaO (i.e., NaCl / KCl / CaCl2 / CaO = 32.4 mol% / 11.3 mol% / 53.4 mol% / 2.9 mol%) was dried under vacuum at 200 °C and below 100 Pa for at least 24 hours, relative to NaCl, KCl, and CaCl2 (NaCl / KCl / CaCl2 = 33.4 mol% / 11.3 mol% / 53.4 mol% / 2.9 mol%). This mixed salt was then placed in a Ni container, placed in an electric furnace, and heated to 550 °C. This yielded a molten salt of NaCl-KCl-CaCl2-CaO.

[0149] Subsequently, a working electrode (1.0 cm × 1.0 cm, Fe), a counter electrode (platinum), and a reference electrode (Ag) were installed on the lid of the aforementioned container. ＋ (Ag), seal the container with this lid. Purge CO2 into the molten salt at 550°C into the container at a flow rate of 100 mL / min for at least 60 minutes. Maintain the gas phase in the container under a CO2 atmosphere, and using a potentiostat, apply a voltage for 30 minutes while maintaining the working electrode potential at 0.3 V relative to the reference electrode. The potential of the working electrode is the reference electrode (Ag). ＋ After determining the potential between / Ag) and the cathode, the value was corrected using the Na-K-Ca alloy precipitation potential as the reference.

[0150] It was confirmed that precipitates were formed on the working electrode. All experimental procedures were carried out in a glove box maintained in a high-purity argon atmosphere.

[0151] (2) Electrolysis process Subsequently, electrolysis was performed using a separately prepared electrolytic cell with the same composition as described above and the electrodes obtained in the electrode fabrication process described above. Specifically, a voltage was applied for 30 minutes while maintaining the potential of the working electrode at 0.3V relative to the reference electrode using a potentiometer. Precipitation was confirmed on the working electrode. All experimental procedures, including the gas phase within the container, were conducted in a glove box maintained under a high-purity argon atmosphere.

[0152] (3) Hydrocarbon manufacturing The precipitate was collected into a sealed test tube. Pure water was added little by little to the test tube at room temperature (23°C) to hydrolyze the precipitate. The total amount of water added was 2.5 ml. After confirming the production of bubbles in the test tube, the tube was allowed to stand until no more bubbles were observed. Then, 100 μl (microliter) of gas was collected from the test tube using an airtight syringe. The volume of the generated gas was determined by the water substitution method.

[0153] GC-MS analysis of the obtained gas using a gas chromatography (GC) apparatus revealed the formation of C₂H₂ as the main component. The presence of C₂H₂ indicates that CaC₂ was present as the main component in the precipitate generated on the working electrode during the electrolysis process. Furthermore, methane, ethane, and hydrogen were also identified as byproducts. Additionally, water, carbon dioxide, nitrogen, oxygen, and argon were also present. The amounts of each component generated were also confirmed. C₂H₂ accounted for significantly more than 50% of the mass of the recovered gas.

[0154] Regarding the formation of C2H2, the Faraday efficiency throughout the electrode fabrication and electrolysis processes is calculated to be approximately 42.8%. Since C2H2 is generated, it can be understood that the precipitate contains CaC2 as a major component.

[0155] [Examples 7-2 to 7-6] Except for changing the electrolysis conditions to those shown in Table 7, the electrolysis and hydrolysis were performed in the same manner as in Example 7-1.

[0156] It was confirmed that precipitates were formed on the working electrode.

[0157] The Faraday efficiency for C2H2 formation throughout the electrode fabrication and electrolysis processes is shown in Table 7. Since C2H2 is generated, it can be understood that the precipitate formed on the working electrode via the electrolysis process contains CaC2 as a major component.

[0158] [Examples 8-1 to 8-6] Except for changing the electrolysis conditions as shown in Table 7, and adding 1.0 mol% of CaC2 relative to the molten salt in the molten salt during the electrolysis process, the electrolysis and hydrolysis were carried out in the same manner as in Example 7-1.

[0159] It was confirmed that precipitates were formed on the working electrode. The Faraday efficiency for C2H2 formation throughout the electrode fabrication and electrolysis processes is shown in Table 7. Since C2H2 was formed, it can be understood that the precipitates formed on the working electrode via the electrolysis process contain CaC2 as a major component.

[0160] [Examples 9-1 to 9-6] Except for changing the electrolysis conditions as shown in Table 7, and adding 7.0 mol% of CaC2 relative to the molten salt in the electrolysis process, the electrolysis and hydrolysis were carried out in the same manner as in Example 7-1.

[0161] It was confirmed that precipitates were formed on the working electrode. The Faraday efficiency for C2H2 formation throughout the electrode fabrication and electrolysis processes is shown in Table 7. Since C2H2 was formed, it can be understood that the precipitates formed on the working electrode via the electrolysis process contain CaC2 as a major component.

[0162] [Examples 10-1 to 10-3] After the electrode fabrication process, the electrodes were temporarily removed from the electrolytic cell and, after 30 minutes, were placed back into the same cell for the electrolysis process. Otherwise, electrolysis and hydrolysis were performed in the same manner as in Examples 7-1, 7-3, and 7-5. The electrolysis conditions were as shown in Table 7, and the electrolysis process was carried out in a CO2 atmosphere.

[0163] It was confirmed that precipitates were formed on the working electrode. The Faraday efficiency for C2H2 formation throughout the electrode fabrication and electrolysis processes is shown in Table 7. Although the amount of C2H2 gas generated was not measured, since the Faraday efficiency was consistently above 0.1%, it can be understood that the precipitates formed on the working electrode during the electrolysis process contain CaC2 as a major component.

[0164] [Table 7] Molten salt: LiCl-KCl-CaCl2-CaO Examples 7-1 to 9-6: Implemented after changing the electrolytic cell between the electrode fabrication process and the electrolysis process. Examples 10-1 to 10-3: After the electrode fabrication process, the electrode is temporarily removed from the electrolytic cell. After 30 minutes, it is placed back into the same electrolytic cell for the electrolysis process. Working electrode: Fe The Faraday efficiency e related to C2H2 generation is calculated as follows.

[0165] First, the volume proportion of C2H2 in the recovered gas is calculated from the total peak area and calibration curve obtained using GC-MS analysis. Then, the volume of C2H2 generated is calculated from the volume of the gas phase within the recovery container and the calculated volume proportion of C2H2 in the gas. Finally, assuming the generated C2H2 is under standard conditions (0℃, 101 kPa), the Faraday efficiency e (%) is calculated using the following formula.

[0166] [Number 1] As shown in Tables 1 and 4, the desired second metal carbide can be obtained with high Faradaic efficiency by any electrolysis method. The Faradaic efficiency is particularly high in the series of Examples 2, 3, and 4. This is believed to be due to the lower potential during the electrode fabrication process, thus allowing for the precipitation of carbon. The Faradaic efficiency of the series in Example 2 is exceptionally high. This is believed to be because the electrolysis process is carried out under an Ar atmosphere, and the electrolytic cell is changed between the electrode fabrication and electrolysis processes, resulting in a lower concentration of carbonate ions in the second molten salt.

[0167] As can be understood from Tables 5 and 6, especially when using SUS304 as the working electrode, hydrocarbons can be obtained from the precipitates with a high Faradaic efficiency. This indicates that a large amount of CaC2 is precipitated during the electrode fabrication process. A large amount of CaC2 can also be interpreted as a large amount of carbon being precipitated.

[0168] As can be understood from Table 7, by using the NaCl-KCl-CaCl2 molten salt, hydrocarbons can be obtained from the precipitate with higher Faradaic efficiency. The second molten salt is substantially free of carbonate ions (CO3-). 2－ From a Faraday efficiency perspective, it is preferable to conduct the electrolysis process in an Ar atmosphere. Adding CaC2 to the molten salt as an additive is also preferable from a Faraday efficiency perspective. This is believed to be because it inhibits the dissolution of CaC2 generated on the working electrode into the molten salt.

[0169] Industrial availability Since the manufacturing method of the present invention can react rapidly at relatively low temperatures and efficiently obtain metal carbides, it is useful in various fields.

[0170] This application claims priority based on Japanese Patent Application No. 2023-064934 filed in Japan on April 12, 2023 and Japanese Patent Application No. 2024-048291 filed in Japan on March 25, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A method for manufacturing metal carbides, characterized in that, include: The electrode fabrication process includes: preparing a first molten salt containing at least one first metal ion selected from alkali metal ions and alkaline earth metal ions and a carbonate ion; and applying a voltage to the first molten salt to cause a carbon-containing precipitate to be deposited on the first electrode to obtain a second electrode. and An electrolysis process comprising applying a voltage to a second molten salt containing at least one second metal ion selected from alkali metal ions and alkaline earth metal ions using the second electrode to obtain a carbide composition containing the second metal.

2. The method for manufacturing metal carbides as described in claim 1, characterized in that: The first electrode contains at least one selected from transition metals and alloys containing transition metals.

3. The method for manufacturing metal carbides as described in claim 1 or 2, characterized in that: The first electrode contains an alloy containing iron.

4. The method for manufacturing metal carbides according to any one of claims 1 to 3, characterized in that: The first electrode contains SUS304.

5. The method for manufacturing metal carbides according to any one of claims 1 to 4, characterized in that: The second molten salt is essentially free of carbonate ions.

6. The method for manufacturing metal carbides according to any one of claims 1 to 5, characterized in that: In the electrolysis process, the first molten salt used in the electrode fabrication process is used directly as the second molten salt.

7. The method for manufacturing metal carbides according to any one of claims 1 to 6, characterized in that: The second molten salt contains at least one anion selected from halide ions and oxide ions.

8. The method for manufacturing metal carbides according to any one of claims 1 to 7, characterized in that: The first metal ion is the same as the second metal ion.

9. The method for manufacturing metal carbides according to any one of claims 1 to 8, characterized in that: The carbide composition further comprises at least one selected from carbon, elemental form of the second metal, halide, carbonate, oxide, hydride and peroxide, and elemental form of the first metal, halide, carbonate, oxide and carbide.

10. The method for manufacturing metal carbides according to any one of claims 1 to 9, characterized in that: The second molten salt contains, as the second metal ion, at least one selected from sodium ions, lithium ions, and potassium ions, and calcium ions.

11. A method for producing hydrocarbons, characterized in that, include: An electrode fabrication process includes: preparing a first molten salt containing at least one first metal ion selected from alkali metal ions and alkaline earth metal ions and carbonate ions from carbon dioxide; and applying a voltage to the first molten salt to cause carbon-containing precipitates to be deposited on the first electrode to obtain a second electrode. An electrolysis process comprising applying a voltage to a second molten salt containing at least one second metal ion selected from alkali metal ions and alkaline earth metal ions using the second electrode to obtain a carbide composition containing the second metal. and The gas generation process includes the step of hydrolyzing the carbide of the second metal to obtain a gas containing hydrocarbons.

12. The method for producing hydrocarbons as described in claim 11, characterized in that: The hydrocarbon is acetylene.

13. The method for producing hydrocarbons as described in claim 11 or 12, characterized in that: The gas contains acetylene as a hydrocarbon, and also contains at least one selected from ethylene, ethane, methane, methylacetylene, propylene, butene, and hydrogen.

14. A carbon-containing component, characterized in that, Include: matrix; and A metal carbide composition supported on the matrix, comprising a carbide of at least one second metal selected from alkali metals and alkaline earth metals.

15. A carbon-containing component, characterized in that, Include: Matrix; A metal carbide layer covering at least a portion of the substrate, comprising a carbide of at least one second metal selected from alkali metals and alkaline earth metals; and A carbon layer that covers at least a portion of the metal carbide layer and contains carbon but does not substantially contain the carbide of the second metal.

Images