METHOD FOR PRODUCING METAL CARBIDE AND HYDROCARBON, AND METAL-CONTAINING MEMBER

Abstract

To provide a manufacturing method that enables efficient production of metal carbide by allowing the reaction to proceed quickly at relatively low temperatures without requiring the use of combustible raw materials, a method for producing carbohydrates from the obtained metal carbide, and a metal inclusion component supported by the metal carbide.SOLUTION: A manufacturing method for a metal carbide, comprises preparing a molten salt containing a carbonate ion, preparing an electrode containing a first metal, and applying a voltage to the molten salt using the electrode to obtain a metal carbide composition containing a carbide of the first metal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing metal carbides and hydrocarbons, and to a metal-containing component. [Background technology]

[0002] Aluminum carbide is an industrially important substance due to its high hardness and melting point. It is used, for example, as a filler for metal materials and resin materials to improve the shear strength of abrasives and composite materials. Known methods for producing aluminum carbide include heating metallic aluminum or aluminum oxide and carbon to high temperatures (e.g., 1100 to 1800°C) in an arc furnace. Other proposed methods for producing aluminum carbide include contacting ammonia gas with aluminum oxide heated to high temperatures (e.g., 1000°C or higher) and carbon (see Patent Document 1), heating organometallic aluminum such as Al(CH3)3 or Al(C2H5)3 at 950 to 1100°C (see Non-Patent Document 1), and contacting metallic aluminum with a lower hydrocarbon at 500 to 900°C (see Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 1-183411 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-58810 [Non-patent literature]

[0004] [Non-Patent Document 1] Kiyoshi Itaya and Akira Kishioka, "Properties of Aluminum Carbide and Related Compounds," Inorganic Materials, 1997, Vol. 4, No. 271, pp. 633-641 Summary of the Invention [Problem to be solved by the invention]

[0005] The methods of Patent Document 1 and Non-Patent Document 1 are energy inefficient because they involve heating raw materials at high temperatures. In addition, when carbon is used as a raw material, carbon-derived impurities (phosphorus, sulfur, etc.) are introduced into the resulting metal carbide, resulting in low purity. Furthermore, using carbon derived from fossil fuels as a raw material runs counter to decarbonization. The method of Patent Document 2 is undesirable because it involves handling flammable ammonia gas, hydrocarbon gas, and organometallic compounds at high temperatures.

[0006] The present disclosure aims to provide a production method that does not require the use of flammable raw materials, allows the reaction to proceed quickly at a relatively low temperature of 800°C or less, and allows metal carbide to be obtained efficiently. The present disclosure also provides a method for producing hydrocarbons from the obtained metal carbide. In addition, the present disclosure provides a metal-containing member that supports metal carbide. [Means for solving the problem]

[0007] The present disclosure includes the following aspects. [1] preparing a molten salt containing carbonate ions; providing an electrode comprising a first metal; applying a voltage to the molten salt using the electrodes to obtain a metal carbide composition containing carbide of the first metal.

[0008] [2] The method for producing metal carbide according to [1] above, wherein the first metal includes at least one selected from the group consisting of aluminum, beryllium, manganese, scandium, yttrium, lanthanum, and cerium.

[0009] [3] The method for producing metal carbide according to [1] or [2] above, wherein the molten salt contains, as metal ions, at least one selected from the group consisting of sodium ions, lithium ions, potassium ions, rubidium, and cesium ions.

[0010] [4] The method for producing metal carbide according to any one of the above [1] to [3], wherein the molten salt contains, as metal ions, at least one selected from the group consisting of sodium ions, lithium ions, and potassium ions, and at least one selected from the group consisting of calcium ions, magnesium ions, strontium ions, and barium ions.

[0011] [5] The method for producing metal carbide according to any one of the above [1] to [4], wherein the molten salt contains a carbide of a first metal.

[0012] [6] The method for producing metal carbide according to any one of the above [1] to [5], wherein the carbide composition further contains at least one selected from the group consisting of carbon, an elemental substance, a halide, a carbonate, an oxide, a hydride, and a peroxide of the first metal, and an elemental substance, a halide, a carbonate, an oxide, and a carbide of the second metal constituting the molten salt.

[0013] [7] Preparing a molten salt containing carbonate ions; providing an electrode comprising a first metal; applying a voltage to the molten salt using the electrodes to obtain a metal carbide composition containing a carbide of the first metal; and hydrolyzing the carbide of the first metal to obtain a gas containing hydrocarbons.

[0014] [8] The method for producing hydrocarbons according to [7] above, wherein the gas contains methane.

[0015] [9] The method for producing hydrocarbons according to [7] or [8] above, wherein the gas contains methane and at least one selected from the group consisting of ethylene, ethane, acetylene, methylacetylene, propylene, butene, and hydrogen.

[0016]

[10] A substrate including a first metal; a metal carbide composition supported on the substrate, the metal carbide composition including a carbide of the first metal. [Effects of the Invention]

[0017] According to the present disclosure, it is possible to provide a production method that does not require the use of flammable raw materials, allows the reaction to proceed quickly at a relatively low temperature, and enables metal carbide to be obtained efficiently, a method for producing hydrocarbons from the obtained metal carbide, and a metal-containing member that supports metal carbide. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a flowchart illustrating a method for manufacturing metal carbide according to the present disclosure. [Figure 2] 1 is a flowchart illustrating a hydrocarbon production method according to the present disclosure. [Figure 3] 1 is a graph showing the change in current over time when current is applied to produce metal carbide in Example 1. [Figure 4] 1 is a photograph showing the appearance of a working electrode before current is applied. [Figure 5] 1 is a photograph showing the appearance of a working electrode after current is passed through it in Example 1. [Figure 6] 2 is a graph showing the results of XRD analysis of the precipitates obtained in Examples 1 to 3. [Figure 7] 1 is a graph showing the results of GC analysis of the gases generated in Examples 1 to 3. [Figure 8] 1 is a graph showing the change in current over time when current is applied to produce metal carbide in Example 2. [Figure 9] 10 is a photograph showing the appearance of the working electrode after current is passed through it in Example 2. [Figure 10] 10 is a graph showing the change in current over time when current is applied to produce metal carbide in Example 3. [Figure 11] 10 is a photograph showing the appearance of the working electrode after current is passed through it in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0019] The method for producing metal carbide according to the present disclosure includes preparing a molten salt containing carbonate ions, preparing electrodes containing a first metal, and applying a voltage to the molten salt using the electrodes to obtain a metal carbide composition containing carbide of the first metal. This allows metal carbide to be efficiently obtained at a relatively low temperature of 800°C or less (e.g., 600°C). Figure 1 is a flowchart showing the method for producing metal carbide according to the present disclosure.

[0020] A method for producing hydrocarbons according to the present disclosure includes preparing a molten salt containing carbonate ions, preparing electrodes containing a first metal, applying a voltage to the molten salt using the electrodes to obtain a metal carbide composition containing carbide of the first metal, and hydrolyzing the carbide of the first metal to obtain a gas containing hydrocarbons. This method improves the Faraday efficiency and allows for efficient production of high-purity hydrocarbons. Figure 2 is a flowchart showing the method for producing hydrocarbons according to the present disclosure.

[0021] The present disclosure provides a metal-containing component that can be used in the production of hydrocarbons, comprising a substrate containing a first metal and a metal carbide composition supported on the substrate and including a carbide of the first metal.

[0022] [Metal carbide manufacturing method] In this embodiment, carbonate ions derived from carbon dioxide are used. CO2, which is said to be a cause of global warming, can be effectively used as a carbon source to obtain a carbide composition containing carbide of the first metal.

[0023] (i) Preparation of molten salt (S11) A molten salt containing carbonate ions derived from carbon dioxide is prepared. The carbonate ions are generated by absorbing a gas containing carbon dioxide into an electrolytic bath. The molten salt also contains second metal ions. The second metal ions are generated by ionizing a salt of the second metal. In the molten salt, it is not necessary for the second metal salt and carbon dioxide to be entirely ionized. In this embodiment, for convenience, the salt of the second metal contained in the electrolytic bath will be referred to as the second metal salt, even if it is completely ionized, and the molten salt prepared from the second metal salt and carbon dioxide will be referred to as the molten salt, even if they are not completely ionized.

[0024] (carbonate ions derived from carbon dioxide) Carbonate ions are generated by absorbing a gas containing carbon dioxide into an electrolytic bath. A gas containing carbon dioxide (hereinafter sometimes referred to as CO2 gas) is brought into contact in a gaseous state with a second metal salt in a liquid state. The CO2 gas may be blown into the gas phase of the electrolytic bath to contact the liquid surface of the second metal salt, or the CO2 gas may be blown into the second metal salt. The CO2 gas may be a mixed gas of CO2 and an inert gas (typically argon). A sufficient amount of CO2 gas may be added to the second metal salt before applying a voltage, or may be added to the second metal salt while applying a voltage.

[0025] The amount of CO2 to be blown in may be appropriately set depending on the amount of the second metal ion, and is, for example, equal to or greater than the equivalent amount of the second metal salt, taking into consideration the efficiency of absorption of CO2 into the second metal salt.

[0026] In order to promote dissolution of CO into the second metal salt, it is desirable that the bubble diameter of the CO gas to be blown in be small. The bubble diameter of the CO gas may be 10 mm or less, or may be 1 mm or less. The bubble diameter of the CO gas may be 100 nm or more, or may be 1 μm or more. The CO gas bubbles can be made finer by, for example, bubbling through a porous material made of quartz glass or high-purity alumina, stirring with a stirrer, applying vibration, or irradiating with ultrasound.

[0027] It is preferable to preheat the CO2 gas to a temperature close to that of the second metal salt, as this prevents the second metal salt from being solidified due to a drop in temperature.

[0028] (other anions) The molten salt may contain anions other than carbonate ions. Examples of other anions include halide ions, sulfate ions, phosphate ions, nitrate ions, acetate ions, carboxylate ions, and oxide ions (O 2- ) is at least one selected from the group consisting of:

[0029] Other anions may include halide ions. Halides of second metals are commonly used as molten salts and are excellent electrolytes.

[0030] Other anions may include oxide ions, which facilitate ionization of CO2.

[0031] (second metal ion) The second metal ion is, for example, at least one selected from the group consisting of alkali metal ions and alkaline earth metal ions. Alkali metal ions and alkaline earth metal ions have excellent electrolyte functions.

[0032] The alkali metal may be at least one selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). The alkali metal may be at least one selected from the group consisting of Li, Na, K, Rb, and Cs. The alkali metal may particularly be at least one selected from the group consisting of Li, Na, K, and Cs.

[0033] The alkaline earth metal may be at least one selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). The alkaline earth metal may be at least one selected from the group consisting of Mg, Ca, Sr, and Ba.

[0034] In terms of industrial value, the second metal ion may include an alkaline earth metal ion. The second metal ion may include an alkali metal ion together with the alkaline earth metal ion. The alkali metal ion has excellent electrolyte properties. For example, the alkali metal ion facilitates ionization of the alkaline earth metal salt, promoting the generation of the alkaline earth metal ion and lowering the melting point of the molten salt, enabling electrolysis at a lower temperature.

[0035] The second metal ions may include at least one alkali metal ion selected from the group consisting of Li, Na, K, Rb, and Cs ions, and at least one alkaline earth metal ion selected from the group consisting of Be, Mg, Ca, Sr, and Ba ions. The second metal ions may include at least one Li, Na, and K ions, and Ca ions.

[0036] The second metal ions may further include ions of metals other than alkali metal ions and alkaline earth metal ions. The second metal ions may include the same metal ions as the first metal ions. Examples of the other metals include at least one selected from the group consisting of aluminum (Al), gallium (Ga), indium (In), thallium (Tl), zinc (Zn), cadmium (Cd), gold (Au), silver (Ag), and copper (Cu). Examples of rare earth elements include scandium (Sc), yttrium (Y), lanthanoid elements, and actinoid elements. Salts of the other metals preferably ionize at temperatures of 800°C or less.

[0037] The amount of the second metal ion contained in the molten salt is not particularly limited. Specific examples of the second metal salt contained in the molten salt include alkali metal halides such as LiF, NaF, KF, RbF, CsF, LiCl, NaCl, KCl, RbCl, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, LiI, NaI, KI, RbI, and CsI; alkaline earth metal halides such as MgF2, CaF2, SrF2, BaF2, MgCl2, CaCl2, SrCl2, BaCl2, MgBr2, CaBr2, SrBr2, BaBr2, MgI2, CaI2, SrI2, and BaI2; Examples of suitable metal salts include rare earth element halides such as ScCl3, YCl3, LaCl3, CeCl3, PrCl3, NdCl3, PmCl3, SmCl3, EuCl3, GdCl3, TbCl3, DyCl3, HoCl3, ErCl3, TmCl3, YbCl3, and LuCl3; earth metal halides such as AlCl3, GaCl3, InCl3, and TlCl3; metal oxides such as Li2O and CaO; metal carbonates such as Li2CO3, Na2CO3, and K2CO3; and metal nitrates such as LiNO3, NaNO3, and KNO3. These may be used alone or in combination of two or more. In particular, two or more metal salts may be combined because they tend to lower the melting temperature.

[0038] (additives) The molten salt may further contain an additive.

[0039] The additive contained in the molten salt may be, for example, a metal carbide containing a first metal. The inclusion of a metal carbide in the molten salt can improve the Faraday efficiency. Examples of the metal in the metal carbide include aluminum, beryllium, manganese, scandium, yttrium, lanthanum, and cerium. The metal carbide is preferably Al4C3, Be2C, Mn3C, ScC, YC, Y2C3, YC2, LaC2, or CeC2, and is particularly preferably Al4C3.

[0040] (ii) Preparation of an electrode containing a first metal (S12) An electrode containing a first metal (hereinafter, sometimes referred to as a "metal electrode") is prepared. The metal electrode functions as a cathode during electrolysis. The first metal contained in the metal electrode serves as a metal source for the target metal carbide.

[0041] The first metal may be present at least on the surface of the metal electrode, which is the portion of the metal electrode that can come into contact with the molten salt.

[0042] (first metal) The first metal is, for example, at least one selected from the group consisting of aluminum (Al), beryllium (Be), manganese (Mn), scandium (Sc), yttrium (Y), lanthanum (La), and cerium (Ce).

[0043] The metal electrode may be a compact of a first metal or an alloy thereof. The metal electrode may be a compact of another metal or alloy, or a carbon material coated with the first metal. Examples of other metals include Ag, Cu, Ni, Pb, Hg, Tl, Bi, In, Sn, Cd, Au, Zn, Pd, Ga, Ge, Fe, Pt, Pd, Ru, Cr, Mo, W, V, Nb, Ta, and Zr. Examples of the carbon material include glassy carbon (GC), natural graphite, isotropic graphite, highly oriented pyrolytic graphite (HOPG), plastic-formed carbon, and conductive diamond.

[0044] (iii) Application of voltage (S13) Next, a voltage is applied to the molten salt, which causes CO3 2- is reduced to produce carbon (Equation 1). The produced carbon reacts with the first metal contained in the metal electrode to produce carbide of the first metal. The carbide of the first metal is deposited on the cathode. When the first metal is Al, aluminum carbide is obtained (Equation 2). (Formula 1) CO3 2- +4e - → C+3O 2- (Formula 2) 3C+4Al → Al4C3

[0045] On the anode, O 2- is oxidized to generate oxygen (Equation 3). The oxygen generated on the anode is released into the gas phase. This oxygen gas can be collected and used for other purposes. (Formula 3) 2O 2- → O2+4e -

[0046] If the molten salt contains calcium ions, metallic calcium may also be produced on the cathode (Equation 4). Some or all of the metallic calcium produced in this side reaction may further react to form calcium carbide (Equation 5). Alternatively, metallic calcium may react with carbon dioxide physically dissolved in the molten salt to form calcium carbide (Equation 6). Calcium carbide may precipitate on the cathode. Fine carbon powder may be produced, causing the molten salt to become cloudy (Equation 7). The CaO produced in Equations 6 and 7 immediately dissolves in the molten salt, producing calcium ions and oxide ions (Equation 8). (Formula 4) Ca 2+ +2e - → Ca (Formula 5) Ca+2C → CaC2 (Formula 6) 2CO2+5Ca → CaC2+4CaO (Formula 7) 2Ca+CO2→ C+2CaO (Formula 8) CaO → Ca 2+ +O 2-

[0047] When the first metal is beryllium, manganese, scandium, yttrium, lanthanum, or cerium, a similar reaction occurs to deposit the carbide of the metal on the cathode.

[0048] The voltage is applied at a temperature at which the molten salt can be maintained in a molten state, i.e., a temperature approximately 10°C or higher than the melting point of the molten salt. The temperature of the electrolytic bath may be 510°C or higher, or 550°C or higher, for example, in the case of NaCl-KCl eutectic salt (melting point: 503.8°C). The temperature of the electrolytic bath may be 800°C or lower, or 700°C or lower. According to the present disclosure, the reaction proceeds at such a relatively low temperature, resulting in high energy efficiency.

[0049] The applied voltage is set so that the cathode potential is lower (more noble) than the potential (Ec) at which carbonate ions discharge on the metal electrode. This can further improve the selectivity of the first metal carbide. If the cathode potential is excessively high (more noble), the desired first metal carbide is difficult to generate. If the cathode potential is excessively low (more noble), the first metal carbide is generated, but metals contained in the molten salt whose redox potential is higher (more noble) than the set cathode potential will also precipitate. If the molten salt contains multiple metals with similar redox potentials, an alloy of the multiple metals may precipitate depending on the set cathode potential. The potential Ec can be determined by performing cyclic voltammetry measurements using the metal electrode in the molten salt to be used. The cathode potential is determined by measuring the cathode potential of a reference electrode (Ag + The potential between the electrode (Ag / Ag) and the cathode was measured and calibrated using the metal deposition potential as the standard. In the case of NaCl-KCl eutectic salt, the metal deposition potential is the deposition potential of the Na-Ca alloy.

[0050] When constant current electrolysis is performed, the set current value may be appropriately set so that the cathode potential during electrolysis falls within the above-described potential range.

[0051] (Metal Carbide Composition) The metal carbide composition includes a carbide of a first metal. The first metal carbide is a major component of the metal carbide composition. A major component is a component that accounts for 50% by mass or more of the total mass of the metal carbide composition. The content of the first metal carbide may be 80% by mass or more, or 90% by mass or more, of the mass of the metal carbide composition. The content of the first metal carbide may be 99.9% by mass or less, or 99% by mass or less, of the mass of the metal carbide composition. In one embodiment, the content of the first metal carbide is 80% by mass or more and 99.9% by mass or less of the mass of the metal carbide composition.

[0052] The metal carbide composition is usually obtained in a state supported on a cathode (strictly speaking, a substrate derived from the metal electrode used as the cathode). When a molten salt in which the first metal carbide has a high solubility is used, the first metal carbide is obtained in a state in which it is partially or entirely dissolved in the molten salt. If the first metal carbide is dissolved in the molten salt in advance, the first metal carbide obtained by electrolysis is prevented from dissolving in the molten salt, and is more likely to be obtained in a state in which it is supported on a substrate derived from the metal electrode.

[0053] The metal carbide composition may include at least one selected from the group consisting of carbon, an elemental form, a halide, a carbonate, an oxide, a hydride, and a peroxide of a first metal, and may further include at least one selected from the group consisting of an elemental form, a halide, a carbonate, an oxide, and a carbide of a second metal.

[0054] The metal carbide composition may also contain at least one selected from the group consisting of a solidified electrolyte, a halide, an oxide, a metal of a material constituting the device, and a hydrate thereof.

[0055] The carbon contained in the metal carbide composition is at least one selected from the group consisting of nanocarbon materials such as graphite, amorphous carbon, glassy carbon, carbon nanotubes, diamond, nanodiamond, and graphene.

[0056] The presence and quantity of the first metal carbide, the first metal itself, compounds containing the first metal, and other impurities can be confirmed by, for example, Raman spectroscopic analysis and X-ray diffraction (XRD) analysis of the composition.

[0057] [Metal-containing parts] The metal-containing member according to the present embodiment includes a substrate containing a first metal and a metal carbide composition containing carbide of the first metal supported on the substrate. Such a metal-containing member can be used for producing hydrocarbons.

[0058] The metal-containing member can be obtained by, for example, the above-described method for producing a metal carbide. That is, the metal-containing member can correspond to a metal electrode obtained by electrolyzing the above-described molten salt using the metal electrode. In this case, the substrate is derived from the above-described metal electrode.

[0059] The metal carbide composition may 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 metal electrode that was in contact with carbonate ions. Supported includes a state in which at least a portion of the surface of the substrate is covered with the metal carbide composition.

[0060] When an elemental analysis is performed by energy dispersive X-ray analysis (EDX) on a cross section passing through the center (or center of gravity) of a metal-containing component, the first metal and carbon are detected in the cross section. If a mixture of the first metal and carbon is detected, it can be safely assumed that the first metal carbide is present.

[0061] [Hydrocarbon manufacturing method] The method for producing hydrocarbons according to this embodiment includes preparing a molten salt containing carbonate ions derived from carbon dioxide, preparing an electrode (metal electrode) containing a first metal, applying a voltage to the molten salt using the metal electrode to obtain a metal carbide composition containing carbide of the first metal, and hydrolyzing the carbide of the first metal to obtain a gas containing hydrocarbons. This method contributes to decarbonization because it synthesizes hydrocarbons using CO2 as a raw material.

[0062] (1) Preparation of molten salt (S21) The molten salt is prepared in the same manner as in the preparation of the molten salt (S11) in the above-mentioned method for producing metal carbide.

[0063] (2) Preparation of an electrode containing a first metal (S22) A metal electrode is prepared in the same manner as in the preparation of the electrode containing the first metal (S12) in the above-described method for producing metal carbide.

[0064] (3) Applying voltage (S23) A voltage is applied to the molten salt in the same manner as in the voltage application (S13) in the above-described method for producing a metal carbide, thereby obtaining a composition containing the first metal carbide.

[0065] (4) Hydrolysis of metal carbides (S24) Next, the first metal carbide is brought into contact with water to hydrolyze it. This produces a gas containing the target hydrocarbon. Hydrocarbons generally have low solubility in water, so the produced hydrocarbons are quickly released into the gas phase and collected.

[0066] The first metal carbide may be isolated from the metal carbide composition and then hydrolyzed. Isolation is performed, for example, by pulverizing the metal carbide composition and utilizing the difference in specific gravity. Alternatively, the metal carbide composition may be hydrolyzed as is. For example, an electrode (which may be a "metal-containing member" according to the present disclosure) on which the metal carbide composition has been deposited is brought into contact with water as is. In this case, the second metal carbide that may be contained in the metal carbide composition may also be hydrolyzed to produce hydrocarbons.

[0067] Examples of hydrocarbons that can be obtained include methane (CH4), ethane, ethylene, acetylene (C2H2), methylacetylene, propane, propylene, butane, and butene. When an isolated first metal carbide is used or when the amount of impurities (particularly elemental metals) contained in the composition is small, methane is obtained as the main component. A main component is a component that accounts for 50% by mass or more of the total mass of the gas recovered. Methane is the main component of natural gas and is used as city gas.

[0068] The resulting gas may contain impurities such as water vapor, hydrogen, nitrogen, and oxygen in addition to hydrocarbons. The amount of impurities is preferably 10% by mass or less, more preferably 1% by mass or less, of the recovered gas. The amount of impurities may be 0.0001% by mass or more, or even 0.001% by mass or more, of the recovered gas. In one embodiment, the amount of impurities is 0.0001% by mass or more and 1% by mass or less of the recovered gas.

[0069] The resulting gas contains methane and may further contain at least one selected from the group consisting of ethylene, ethane, acetylene, methylacetylene, propylene, butene, and hydrogen.

[0070] The presence of hydrocarbons and impurities can be confirmed and their quantity determined by, for example, gas chromatography analysis (GC analysis), mass spectrometry (MS analysis), gas chromatography mass spectrometry (GC-MS analysis), Fourier transform infrared absorption spectrometry (FT-IR analysis) equipped with a gas cell, and ultraviolet-visible absorption spectrometry (UV-Vis analysis).

[0071] The amount of water to be brought into contact with the composition is appropriately determined depending on the mass of the composition. The amount of water is, for example, at least the amount necessary for hydrolysis of the metal carbide and metal contained in the composition. In addition, it is desirable to use an amount of water that allows the entire composition to be immersed and that takes into account evaporation due to heat generated during hydrolysis.

[0072] Hydrolysis of the first metal carbide produces hydrocarbons as well as hydroxides of the first metal. For example, the hydrolysis of aluminum carbide produces aluminum hydroxide along with methane (Equation 9). (Formula 9) Al4C3+12H2O → 3CH4+4Al(OH)3

[0073] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to these, and design changes are possible within the scope of the gist of the present disclosure.

[0074] In the above embodiment, carbon dioxide is used as the carbonate ion source, but this is not limiting. The carbonate ion source may be any metal carbonate. When a second metal carbonate is used, ionization generates the second metal ion and the carbonate ion. The second metal carbonate can be synthesized, for example, by reacting the second metal hydroxide with carbon dioxide.

[0075] In the above embodiment, the carbon-containing member obtained includes, but is not limited to, a substrate and a metal carbide composition containing a carbide of a first metal supported on the substrate. The carbon-containing member obtained by the method shown in this embodiment may include a substrate, a metal carbide layer, and a carbon layer. The carbide of the first metal may react with water or moisture in the atmosphere to hydrolyze while generating hydrocarbons (e.g., Equation 9). By providing a carbon layer on the outside of the metal carbide layer, the hydrolysis is suppressed. [Example]

[0076] The present invention will be explained in more detail with reference to the following examples, but the present invention is not limited to these examples.

[0077] [Example 1] (Metal Carbide Manufacturing) A eutectic composition of NaCl and CaCl (NaCl / CaCl = 47.9 mol% / 52.1 mol%) was mixed with 8.0 mol% CaO and dried in vacuum at 200°C and 100 Pa or less for 24 hours or more. Each of these mixed salts was placed in an alumina container, set in an electric furnace, and heated to 600°C. In this way, a NaCl-CaCl-CaO molten salt was obtained.

[0078] Next, a working electrode (1 cm x 1.5 cm Al), a counter electrode (a platinum plate of 1 cm x 1.5 cm or more), and a reference electrode (Ag + A lid (Ag / Ag) was attached and the vessel was sealed. CO2 was bubbled into the molten salt in the vessel at 600°C at a flow rate of 100 mL / min for more than 60 minutes. Next, a voltage was applied for 30 minutes using a potentio-galvanostat while maintaining the potential of the working electrode relative to the reference electrode at 0.08 V. The deposition of a precipitate on the working electrode was confirmed. All experimental procedures were performed in a glove box maintained in a high-purity argon atmosphere.

[0079] The potential change of the working electrode relative to the reference electrode is shown in Figure 3. The appearance of the working electrode before current is passed is shown in Figure 4. The appearance of the working electrode after current is passed is shown in Figure 5. Black deposits can be seen on the surface of the working electrode.

[0080] XRD analysis of the obtained precipitates confirmed that the precipitates contained Al4C3 and at least NaCl, CaCl2, and carbon as impurities. The results of XRD analysis of the obtained precipitates are shown in Figure 6. The mass ratio of impurities in the precipitates was sufficiently less than 50 mass%. Figure 6 collectively shows the analysis results of the working electrode before voltage application (before electrolysis) and the analysis results of the precipitates obtained in Examples 1 to 3.

[0081] (Hydrocarbon production) The precipitate was placed in a sealed test tube. Pure water was added to the test tube in small amounts at room temperature (23°C) to hydrolyze the precipitate. The total amount of water added was 2.5 ml. After confirming that foaming had occurred in the test tube, the test tube was left to stand until foaming ceased. Next, 100 μl (microliters) of gas was collected from the test tube using a gas-tight syringe.

[0082] The gas obtained was analyzed using a gas chromatograph (GC) and confirmed that CH4 was the main component. It was also confirmed that acetylene and hydrogen were by-produced. The gas also contained water, carbon dioxide, nitrogen, oxygen, and argon. The amount of each component produced was also confirmed. The mass percentage of CH4 in the recovered gas was well above 90 mass%. Figure 7 shows the results of the GC analysis.

[0083] The faradaic efficiency for CH4 gas production was calculated to be approximately 1.2%. The higher the faradaic efficiency for CH4 gas production, the higher the faradaic efficiency for aluminum carbide production. The faradaic efficiency for C2H2 gas production was calculated to be approximately 0.032%. The higher the faradaic efficiency for C2H2 gas production, the higher the faradaic efficiency for calcium carbide production.

[0084] [Example 2] A deposit and hydrocarbons were obtained in the same manner as in Example 1, except that a voltage was applied for 30 minutes while maintaining the potential of the working electrode relative to the reference electrode at 0.12 V.

[0085] The potential change of the working electrode relative to the reference electrode is shown in Figure 8. The appearance of the working electrode after current was applied is shown in Figure 9. Black deposits can be seen on the surface of the working electrode. XRD analysis of the obtained deposit confirmed that the deposit contained Al4C3 and, as impurities, at least NaCl, CaCl2, and carbon. The results of XRD analysis of the obtained deposit are shown in Figure 6. The mass proportion of impurities in the deposit was well below 50 mass%.

[0086] The gas obtained was analyzed using a gas chromatograph (GC) and confirmed that CH4 was the main component. It was also confirmed that acetylene and hydrogen were by-produced. Other components included water, carbon dioxide, nitrogen, oxygen, and argon. The amount of each component produced was also confirmed. The faradaic efficiency for CH4 gas production was calculated to be approximately 8.4%. The faradaic efficiency for C2H2 gas production was calculated to be approximately 1.2%. The mass proportion of CH4 in the recovered gas was well above 90%. The results of the GC analysis are shown in Figure 7.

[0087] [Example 3] A deposit and hydrocarbons were obtained in the same manner as in Example 1, except that a voltage was applied for 30 minutes while maintaining the potential of the working electrode relative to the reference electrode at 0.17 V.

[0088] The potential change of the working electrode relative to the reference electrode is shown in Figure 10. The appearance of the working electrode after current application is shown in Figure 11. Black deposits can be seen on the surface of the working electrode. XRD analysis of the obtained deposit confirmed that the deposit contained Al4C3 and, as impurities, at least NaCl, CaCl2, and carbon. The results of XRD analysis of the obtained deposit are shown in Figure 6. The mass proportion of impurities in the deposit was well below 50 mass%.

[0089] The gas obtained was analyzed using a gas chromatograph (GC) and confirmed that CH4 was the main component. It was also confirmed that acetylene, ethane, and hydrogen were by-produced. Other components included water, carbon dioxide, nitrogen, oxygen, and argon. The amount of each component produced was also confirmed. The faradaic efficiency for CH4 gas production was calculated to be approximately 14%. The faradaic efficiency for C2H2 gas production was calculated to be approximately 0.19%. The mass proportion of CH4 in the recovered gas was well above 50% by mass. The results of the GC analysis are shown in Figure 7.

[0090] [Examples 4 to 7] Precipitates and hydrocarbons were obtained in the same manner as in Example 1, except that after the NaCl-CaCl-CaO molten salt was completely melted, 6 mol% of AlC was further mixed in, and a voltage was applied for 5 minutes while maintaining the potential of the working electrode relative to the reference electrode at 0.45 V, 0.35 V, 0.25 V, and 0.15 V, respectively.

[0091] [Examples 8 to 11] Precipitates and hydrocarbons were obtained in the same manner as in Examples 4 to 7, except that voltage was applied for 10 minutes while maintaining the potential of the working electrode relative to the reference electrode at 0.45 V, 0.35 V, 0.25 V, and 0.15 V, respectively.

[0092] [Examples 12 to 15] Precipitates and hydrocarbons were obtained in the same manner as in Examples 4 to 7, except that voltage was applied for 15 minutes while maintaining the potential of the working electrode relative to the reference electrode at 0.45 V, 0.35 V, 0.25 V, and 0.15 V, respectively.

[0093] [Examples 16 to 19] Precipitates and hydrocarbons were obtained in the same manner as in Examples 4 to 7, except that the amount of Al4C3 added was 1 mol %.

[0094] The amounts of CH4 and C2H2 produced in Examples 1 to 19 are summarized in Table 1. [Table 1]

[0095] From the above results, it was confirmed that the Faraday efficiency can be improved by adding Al4C3 to the molten salt.

[0096] The faradaic efficiency e for CH4 production was calculated as follows: First, the volume fraction of CH4 contained in the collected gas was calculated from the total peak area obtained from GC analysis and the calibration curve. Next, the volume of CH4 generated was calculated from the volume of the gas phase in the collection vessel and the calculated volume fraction of CH4 in the gas. Finally, the Faraday efficiency e (%) was calculated using the following formula, assuming that the generated CH4 was under standard conditions (0°C, 101 kPa).

number

[0097] The production method of the present disclosure is useful in various fields because it does not require the use of flammable raw materials, the reaction proceeds quickly at relatively low temperatures, and metal carbide can be efficiently obtained.

Claims

1. preparing a molten salt containing carbonate ions; providing an electrode comprising a first metal; applying a voltage to the molten salt using the electrodes to obtain a metal carbide composition containing a carbide of the first metal; and hydrolyzing the carbide of the first metal to obtain a gas containing hydrocarbons.

2. The method for producing hydrocarbons according to claim 1 , wherein the gas comprises methane.

3. 3. The method for producing hydrocarbons according to claim 1, wherein the gas contains methane and at least one selected from the group consisting of ethylene, ethane, acetylene, methylacetylene, propylene, butene, and hydrogen.

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