Carbon monoxide production method and method for converting carbon dioxide into carbon monoxide

Abstract

One aspect of a method for producing CO according to the present disclosure involves: irradiating a mixture including a metal and a metal oxide with microwaves in an atmosphere of a gas containing CO2; and bringing carbon into contact with the mixture being irradiated with microwaves in the atmosphere of the gas containing CO2. The metal includes at least one metallic element selected from among Fe, Co, Ni, Mn, Cu, and Ti. The metal oxide is at least one metal oxide selected from among compounds represented by general formula (1): MaMbO3 [where Ma represents one metallic element selected from among alkaline earth metals and lanthanoids, and Mb represents the same metallic element as the metallic element contained in the metal].

Description

Method for producing carbon monoxide and method for converting carbon dioxide to carbon monoxide

[0001] This disclosure relates to a method for producing CO and a method for converting CO

[0004] to CO.

[0002] In recent years, from the perspective of environmental protection, effective utilization of natural gas and reduction of emissions of global warming gases have been demanded. CO, which is one of the global warming gases, ２ is stably present in the atmosphere after being emitted from thermal power plants, iron-making plants, cement plants, chemical plants, etc., enhancing the greenhouse effect.

[0003] As one measure to reduce the emissions of CO ２ , it is a method of reacting the emitted CO ２ with other substances to obtain reaction products. In this case, since the emitted CO ２ is consumed as a starting material, the emissions of CO ２ can be reduced. For example, a method of using the dry reforming reaction to convert plastic waste into H ２ and CO by CO ２ gas has been proposed (see Non-Patent Document 1). The proposed method is a method of irradiating plastic waste and CO ２ gas with microwaves on a metal oxide catalyst to decompose them into H ２ and CO. [[ID=​Furthermore, CO can be used as a main component of industrial gaseous fuels such as reactor gas and water gas, and can also be used as a reducing agent in metallurgy. In addition, CO can be used as a raw material in the production of industrially important compounds, including methanol, and can be used as a starting material for various organic substances, making it extremely useful.

[0007] Peng Zhang et al., Applied Catalysis B: Environment and Energy, Volume 345, 15 May 2024, 123718. Hamashima Tatsuya et al., Proceedings of the 130th Symposium on Catalysis, Presentation No. 1D01.

[0008] This disclosure relates to a method for producing CO efficiently and stably, and to CO ２ The objective is to provide a method for converting to CO.

[0009] The means to solve the aforementioned problem are as follows: That is, <1> CO ２ Irradiating a mixture containing metals and metal oxides with microwaves in an atmosphere of gas containing CO ２ A method for producing CO, comprising: bringing carbon into contact with the mixture being irradiated with microwaves under an atmosphere of gas containing; and wherein the metal is a metal containing at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti, and the metal oxide is at least one metal oxide selected from compounds represented by the following general formula (1): MaMbO ３...General formula (1) However, in the general formula (1), Ma represents one metal element selected from alkaline earth metals and lanthanides, and Mb represents the same metal element as the metal element contained in the metal. <2> The mixture containing the metal and the metal oxide is a method for producing CO according to <1>, wherein the metal is precipitated by partially hydrogen-reducing a precursor mixture containing at least one metal oxide selected from the compounds represented by the general formula (1), or at least one metal oxide selected from the compounds represented by the general formula (1) and at least one metal oxide represented by the following general formula (2). Mb ｘ O ｙ ...General formula (2) However, in general formula (2), Mb represents the same metallic element as Mb in general formula (1), x and y represent positive integers indicating the composition ratio of Mb to O, and y is y = xz / 2, where z is the oxidation state of Mb. <3> The metal is Ni, and the metal oxide is LaNiO ３ The method for producing CO described in <1> or <2> above is as follows: <4> The mixture containing the metal and the metal oxide is H ２ LaNiO at temperatures above 300°C under an atmosphere of gas containing ３ , or LaNiO ３ The CO method described in <3> above is obtained by heating a precursor mixture of and NiO and partially reducing it by hydrogen to precipitate Ni. <5> The LaNiO ３ , or the LaNiO ３ The heating of the precursor mixture of the carbon and NiO is performed by radiant heat, as described in <4> above. <6> The heating of the carbon and the mixture is performed by heating the temperature of the carbon and the mixture to 300°C or more and 1,300°C or less, as described in any one of <1> to <5> above. <7> CO ２ Irradiating a mixture containing metals and metal oxides with microwaves in an atmosphere of gas containing CO ２In an atmosphere of gas containing CO, carbon is brought into contact with the mixture being irradiated with microwaves, and the metal is a metal containing at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti, and the metal oxide is at least one metallic oxide selected from compounds represented by the following general formula (1), CO ２ This is a method for converting to CO. MaMbO ３ ...General formula (1) However, in the general formula (1), Ma represents one metal element selected from alkaline earth metals and lanthanides, and Mb represents the same metal element as the metal element contained in the metal. <8> The mixture containing the metal and the metal oxide is obtained by partially hydrogen-reducing a precursor mixture containing at least one metal oxide selected from the compounds represented by the general formula (1), or at least one metal oxide selected from the compounds represented by the general formula (1) and at least one metal oxide represented by the general formula (2) below, thereby precipitating the metal as described in <7> CO ２ This is a method for converting to CO. Mb ｘ O ｙ ...General formula (2) However, in general formula (2), Mb represents the same metallic element as Mb in general formula (1), x and y represent positive integers indicating the composition ratio of Mb to O, and y is y = xz / 2, where z is the oxidation state of Mb. <9> The metal is Ni, and the metal oxide is LaNiO ３ The CO described in <7> or <8> above is the CO ２ This is a method for converting to CO. <10> The mixture containing the metal and the metal oxide is H ２ LaNiO at temperatures above 300°C under an atmosphere of gas containing ３ , or LaNiO ３ The CO2 described in <9> above is obtained by heating a precursor mixture of NiO and partially reducing it with hydrogen to precipitate Ni. ２ This is a method for converting to CO. <11> The LaNiO ３ , or the LaNiO ３The heating of the precursor mixture of the NiO is carried out by radiant heat, as described in <10> above. ２ This is a method for converting to CO. <12> In the contact, the temperature of the carbon and the mixture is heated to 300°C or more and 1,300°C or less, as described in any one of <7> to <11> above. ２ This is a method for converting to CO.

[0010] According to embodiments of this disclosure, a method for producing CO that can efficiently and stably produce CO and CO ２ This can provide a method for converting to CO.

[0011] Figure 1 shows the diffraction patterns obtained by X-ray diffraction (XRD) of the products obtained in Preparation Example 1, Production Example 1, and Comparative Production Example 1. The horizontal axis represents 2θ (degree), and the vertical axis represents Intensity (a.u.). Figure 2A shows the temperature change of the reaction tube during the reaction from 0 to 140 minutes in Example 1, and the CO2 flowing through the reaction tube. ２ This graph shows the relationship between the change in concentration and the change in the concentration of generated CO. The vertical axis on the left represents the CO in the gas at the outlet of the reaction tube, calculated from the values ​​detected by the mass spectrometer. ２ or CO concentration (g / m³) ３ Figure 2B shows the temperature of the reaction tube (°C) on the right axis and the time (minutes) on the horizontal axis. In Comparative Example 1, the temperature of the reaction tube and the amount of CO2 flowing through the reaction tube were shown from 0 minutes to 140 minutes. ２ This graph shows the relationship between the change in concentration and the change in the concentration of generated CO. The vertical axis on the left represents the CO in the gas at the outlet of the reaction tube, calculated from the values ​​detected by the mass spectrometer. ２ or CO concentration (g / m³) ３ Figure 2C shows the temperature of the reaction tube (°C) on the right axis and the time (minutes) on the horizontal axis. In Comparative Example 2, the temperature of the reaction tube and the amount of CO2 flowing through the reaction tube were shown from 0 minutes to 140 minutes. ２ This graph shows the relationship between the change in concentration and the change in the concentration of generated CO. The vertical axis on the left represents the CO in the gas at the outlet of the reaction tube, calculated from the values ​​detected by the mass spectrometer. ２ or CO concentration (g / m³) ３Figure 2D shows the temperature of the reaction tube (°C) on the right axis and the time (minutes) on the horizontal axis. In Comparative Example 3, the temperature of the reaction tube and the amount of CO2 flowing through the reaction tube were shown from 0 minutes to 140 minutes. ２ This graph shows the relationship between the change in concentration and the change in the concentration of generated CO. The vertical axis on the left represents the CO in the gas at the outlet of the reaction tube, calculated from the values ​​detected by the mass spectrometer. ２ or CO concentration (g / m³) ３ The graph shows the temperature of the reaction tube (°C) on the right axis and the time (minutes) on the horizontal axis.

[0012] The embodiments of this disclosure will be described in detail below. However, the embodiments are not limited to the following description and may be modified as appropriate without departing from the gist of this disclosure. Furthermore, in this specification, the "~" indicating a numerical range means that the numbers described before and after it are included as the lower and upper limits, respectively, unless otherwise specified.

[0013] (Method for producing CO) The method for producing CO (hereinafter also referred to as "carbon monoxide") as disclosed herein is CO ２ Irradiating a mixture containing metals and metal oxides with microwaves in an atmosphere of gas containing CO2 (hereinafter also referred to as "carbon dioxide"), ２ The method for producing CO of the present disclosure further includes, if necessary, contacting carbon with the mixture being irradiated with microwaves in an atmosphere of gas containing, wherein the metal is a metal containing at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti, and the metal oxide is at least one metal oxide selected from compounds represented by the following general formula (1). The method for producing CO of the present disclosure may further include, if necessary, other processes other than irradiating with microwaves and contacting. MaMbO ３ ...General formula (1) However, in the above general formula (1), Ma represents one metallic element selected from alkaline earth metals and lanthanides, and Mb represents the same metallic element as the metallic element contained in the above metal.

[0014] The inventors of the present invention have diligently studied methods for efficiently and stably producing CO, and have found that when producing CO from carbon using only metal oxides (i.e., at least one metal oxide selected from the compounds represented by general formula (1)) that have been conventionally used as catalysts, stable heating may not be possible. Furthermore, they have found that when a mixture containing metal and metal oxides is used as a catalyst, and at least one metal oxide selected from the compounds represented by general formula (1) is used as the metal oxide, the CO production efficiency is significantly improved compared to when only metal oxides (i.e., at least one metal oxide selected from the compounds represented by general formula (1)) are used as a catalyst in the conventional method.

[0015] The method for producing CO according to this disclosure is shown in the following reaction formula 1, and the reaction proceeds by the Boudouard reaction. [Reaction formula 1] C + CO ２ →2CO

[0016] <Irradiating with microwaves> Irradiating with microwaves is CO ２ This involves irradiating a mixture containing metals and metal oxides with microwaves in an atmosphere of gas containing [a specific substance].

[0017] When microwaves are irradiated onto the mixture, the mixture directly absorbs the microwaves and is heated. There are no particular restrictions on the temperature of the heated mixture, and it can be appropriately selected depending on the purpose, but it is preferably 300°C to 1,300°C, and more preferably 700°C to 1,200°C. When the temperature of the heated mixture is 300°C to 1,300°C, high catalytic activity can be obtained and energy efficiency is good. The temperature of the heated mixture can be measured using known temperature measuring instruments such as resistance thermometers and thermocouples.

[0018] <<Mixture>> The mixture comprises a metal and a metal oxide, and may further contain other components as needed. The mixture is intended to act as a catalyst in the CO production method of this disclosure.

[0019] -Metal- The metal in the mixture is a metal containing at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti.

[0020] There are no particular restrictions on the state of the metal in the mixture, but it is preferable that the metal is dispersed or supported on at least one metal oxide selected from the compounds represented by general formula (1), and it is more preferable that the metal is supported on at least one metal oxide selected from the compounds represented by general formula (1).

[0021] The metal content in the mixture is not particularly limited as long as it is a mixture with the compound represented by the general formula (1), and can be appropriately selected depending on the purpose.

[0022] -Metal Oxides- The metal oxide in the mixture is at least one metal oxide selected from the compounds represented by the following general formula (1): MaMbO ３ ...General formula (1) However, in the above general formula (1), Ma represents one metallic element selected from alkaline earth metals and lanthanides, and Mb represents the same metallic element as the metallic element contained in the above metal.

[0023] Specific examples of Ma in the compound represented by the general formula (1) include alkaline earth metals such as Be, Mg, Ca, Sr, Ba, and Ra; and lanthanides such as La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0024] In the compound represented by the general formula (1), Mb represents the same metallic element as the metallic element contained in the metal. Therefore, Mb in the general formula (1) is a metal containing at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti. For example, when the metal is Ni, the compound represented by the general formula (1) is MaNiO ３ That is the case.

[0025] The compound represented by the general formula (1) above is ABO ３It is preferable that the compound has a perovskite-type structure represented by the above general formula (1). A is located at the A site of the perovskite-type structure and corresponds to Ma in the compound represented by the above general formula (1). B is located at the B site of the perovskite-type structure and corresponds to Mb in the compound represented by the above general formula (1).

[0026] A specific example of the compound represented by the general formula (1) is LaNiO ３ LaFeO ３ LaCoO ３ LaMnO ３ , BaTiO ３ SrTiO ３ These are some examples. Among these, at least one metal oxide selected from the compounds represented by the general formula (1) is LaNiO ３ It is preferable to include it.

[0027] The content of at least one metal oxide selected from the compounds represented by the general formula (1) in the mixture is not particularly limited as long as it is a mixture with a metal, and can be appropriately selected depending on the purpose.

[0028] At least one metal oxide selected from the compounds represented by the general formula (1) may be a commercially available product or may be synthesized as appropriate by known methods.

[0029] [Method for producing at least one metal oxide selected from compounds represented by general formula (1)] As a method for synthesizing at least one metal oxide selected from compounds represented by general formula (1), a method commonly used for producing compounds having a so-called perovskite-type structure can be used. For example, a method in which a basic compound is added to a solution containing a compound having Ma as a constituent element in general formula (1) and a compound having Mb as a constituent element in general formula (1) to obtain a precipitate, and then calcined in air is preferred in terms of good dispersibility.

[0030] The compound containing Ma as a constituent element in the general formula (1) is not particularly limited as long as it can yield at least one metal oxide selected from the compounds represented by the general formula (1), dissolves in the solution, and produces a precipitate of the compound containing Ma as a constituent element upon addition of a basic compound. However, from the viewpoint of solubility and other factors, it is preferable to use a salt containing Ma as a constituent element in the general formula (1). Examples of salts containing Ma as a constituent element in the general formula (1) include nitrates, carbonates, acetates, chlorides, and bromides containing Ma as a constituent element in the general formula (1). These may be used individually or in combination of two or more. Among these, nitrates containing Ma as a constituent element in the general formula (1) are preferred from the viewpoint of solubility and workability such as calcination.

[0031] The compound containing Mb as a constituent element in the general formula (1) is not particularly limited as long as it can yield at least one metal oxide selected from the compounds represented by the general formula (1), dissolves in the solution, and produces a precipitate of the compound containing Mb as a constituent element upon addition of a basic compound. However, from the viewpoint of solubility and other factors, it is preferable to use a salt containing Mb as a constituent element in the general formula (1). Examples of salts containing Mb as a constituent element in the general formula (1) include nitrates, carbonates, acetates, chlorides, or bromides containing Mb as a constituent element in the general formula (1). These may be used individually or in combination of two or more. Among these, nitrates containing Mb as a constituent element in the general formula (1) are preferred from the viewpoint of solubility and workability such as calcination.

[0032] The solvent for the solution is not particularly limited as long as it can dissolve the compound containing Ma as a constituent element in general formula (1) and the compound containing Mb as a constituent element in general formula (1), but water or alcohol is preferred in terms of ease of handling. Examples of alcohols include methanol, ethanol, and 2-propanol. These may be used individually or in combination of two or more. Furthermore, glycols such as ethylene glycol may be added to the solution for purposes such as adjusting the dispersibility of each substance used in the synthesis.

[0033] The basic compound that can be added to the solution is not particularly limited as long as it can precipitate compounds containing Ma as a constituent element in general formula (1) and compounds containing Mb as a constituent element in general formula (1). However, tetramethylammonium hydroxide (hereinafter also referred to as "TMAH") is preferably used because it dissolves easily in the solution and does not easily remain in the catalyst after calcination. There are no particular restrictions on the method of adding the basic compound to the solution, but it is preferable to add it as a solution in which the basic compound is dissolved in water or alcohol, as this offers good workability and makes it easy to obtain a uniform precipitate. Examples of alcohols that can be used to dissolve the basic compound are the same as those used for the solutions of compounds containing Ma as a constituent element in general formula (1) and compounds containing Mb as a constituent element in general formula (1). There are no particular restrictions on the concentration of the basic compound in the solution, but from the viewpoint of workability and the uniformity of the precipitate obtained, it is preferably 0.5% by mass or more and 50% by mass or less, and more preferably 1% by mass or more and 30% by mass or less, relative to the total mass of the solution of the basic compound.

[0034] Another synthesis method for synthesizing at least one metal oxide selected from the compounds represented by the general formula (1) is to physically mix a compound containing Ma as a constituent element in the general formula (1) and a compound containing Mb as a constituent element in the general formula (1), and then calcine them in air. The compound containing Ma as a constituent element in the general formula (1) and the compound containing Mb as a constituent element in the general formula (1) that can be used in the other synthesis method are not particularly limited as long as they can yield at least one metal oxide selected from the compounds represented by the general formula (1) by calcination, but from the viewpoint of stability, it is preferable that they be an oxide containing Ma as a constituent element in the general formula (1) and an oxide containing Mb as a constituent element in the general formula (1), respectively.

[0035] In the synthesis of at least one metal oxide selected from the compounds represented by the general formula (1), there are no particular restrictions on the molar ratio of the compound containing Ma in the general formula (1) as a constituent element to the compound containing Mb in the general formula (1) as a constituent element, and it can be appropriately selected according to the purpose. There are no particular restrictions on the molar ratio of Mb in the compound containing Mb in the general formula (1) to Ma in the compound containing Ma in the general formula (1) as a constituent element, and it can be selected according to the purpose, and it may be in the range of 0.8 to 3. When the molar ratio of Mb in the compound containing Mb in the general formula (1) to Ma in the compound containing Mb in the general formula (1) as a constituent element is 0.8 to 3, it is close to the ratio of Mb to Ma in at least one metal oxide selected from the compounds represented by the general formula (1), and therefore at least one metal oxide selected from the compounds represented by the general formula (1) can be suitably obtained.

[0036] Furthermore, if the molar ratio of Mb in a compound containing Mb in general formula (1) to Ma in a compound containing Ma in general formula (1) is greater than 1, a compound represented by the following general formula (2) may be formed together with at least one metal oxide selected from the compounds represented by general formula (1). If it is desired to form only at least one metal oxide selected from the compounds represented by general formula (1) and not the compound represented by the following general formula (2), the molar ratio is preferably 0.80 or more and 1.00 or less. Also, if the compound represented by the following general formula (2) is to be formed together with at least one metal oxide selected from the compounds represented by general formula (1), the molar ratio is preferably greater than 1.00 and 3.00 or less, and more preferably 1.01 or more and 3.00 or less.

[0037] Mb ｘ O ｙ ...General formula (2) However, in general formula (2), Mb represents the same metal element as Mb in general formula (1), x and y represent positive integers indicating the composition ratio of Mb to O, and y is y = xz / 2, where z is the oxidation state of Mb. For example, at least one of the metal oxides selected from the compounds represented by general formula (1) is LaNiO ３ In this case, the compound represented by the general formula (2) is NiO.

[0038] In the synthesis of at least one metal oxide selected from the compounds represented by the general formula (1), there are no particular restrictions on the calcination temperature of the mixture of a compound containing Ma as a constituent element in the general formula (1) and a compound containing Mb as a constituent element in the general formula (1), and the temperature can be appropriately selected depending on the type of at least one metal oxide selected from the compounds represented by the general formula (1). For example, if the at least one metal oxide selected from the compounds represented by the general formula (1) is LaNiO ３ In this case, from the viewpoint of uniformity, stability, and energy efficiency of the resulting metal oxide, the firing temperature of the mixture is preferably 300°C to 1,200°C, and more preferably 550°C to 950°C.

[0039] -Other Components- The other components in the mixture are not particularly limited as long as they can produce CO, and can be appropriately selected according to the purpose. For example, the mixture may further contain a compound represented by the following general formula (3) and a compound represented by the following general formula (4). These may be used individually or in combination of two or more.

[0040] --Compound represented by general formula (3)-- Ma ｐ O ｑ ...General formula (3) In general formula (3), Ma represents the same metallic element as Ma in general formula (1), p and q represent positive integers that express the composition ratio of Ma to O, and q is q = pr / 2, where r is the oxidation state of Ma.

[0041] Since Ma in the general formula (3) represents the same metallic element as Ma in the general formula (1), Ma in the general formula (3) is at least one metallic element selected from alkaline earth metals and lanthanides. For example, if the at least one metal oxide selected from the compounds represented by the general formula (1) is LaNiO ３ In that case, the compound represented by the general formula (3) is La ２ O ３ The compound represented by general formula (3) is preferably produced by hydrogen reduction of at least one metal oxide selected from the compounds represented by general formula (1).

[0042] - Compound represented by general formula (4) - MaMbO ｚ ...General formula (4) However, in general formula (4), Ma represents the same metallic element as Ma in general formula (1), Mb represents the same metallic element as Mb in general formula (1), and z represents the valence of O less than 3.

[0043] The compound represented by the general formula (4) is a compound that maintains the structure of at least one metal oxide selected from the compounds represented by the general formula (1), but has a defect in which some oxygen atoms are missing.

[0044] Since Ma in general formula (4) is the same metallic element as Ma in general formula (1), Ma in general formula (4) is one metallic element selected from alkaline earth metals and lanthanides.

[0045] Since Mb in general formula (4) is the same metallic element as Mb in general formula (1), Mb in general formula (4) is a metal containing at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti.

[0046] For example, if at least one metal oxide selected from the compounds represented by the general formula (1) is LaNiO ３ In that case, the compound represented by the general formula (4) is LaNiO ｚ (z < 3). The compound represented by general formula (4) is preferably produced by hydrogen reduction of at least one metal oxide selected from the compounds represented by general formula (1).

[0047] The content of other components in the mixture is not particularly limited, as long as it can produce CO, and can be appropriately selected depending on the purpose.

[0048] Among these, the mixture containing metals and metal oxides is preferably one in which the metal is dispersed or supported on at least one metal oxide selected from the compounds represented by the general formula (1), and LaNiO ３ It is more preferable that the material is Ni-supporting.

[0049] [Method for Producing the Mixture] There are no particular limitations on the method for producing the mixture, and it can be appropriately selected according to the purpose. For example, a method of mixing a metal containing at least one metal element selected from Fe, Co, Ni, Mn, Cu, and Ti with at least one metal oxide selected from the compounds represented by the general formula (1); a method of partially hydrogen-reducing a precursor mixture (hereinafter sometimes abbreviated as "precursor mixture") containing at least one metal oxide selected from the compounds represented by the general formula (1) or at least one metal oxide selected from the compounds represented by the general formula (1) and a compound represented by the general formula (2) below. Among these, the method of partially hydrogen-reducing at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture is preferred as the method for producing the mixture. By partially hydrogen-reducing at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture, the metal precipitates. For example, if at least one metal oxide selected from the compounds represented by the general formula (1) is LaNiO ３ If this is the case, Ni will precipitate by partially reducing it with hydrogen.

[0050] Mb ｘ O ｙ ...General formula (2) However, in general formula (2), Mb represents the same metal element as Mb in general formula (1), x and y represent positive integers indicating the composition ratio of Mb to O, and y is y = xz / 2, where z is the oxidation state of Mb. For example, at least one of the metal oxides selected from the compounds represented by general formula (1) is LaNiO ３ In this case, the compound represented by the general formula (2) is NiO.

[0051] In this disclosure, "precursor mixture" means a mixture containing at least one metal oxide selected from the compounds represented by general formula (1) and at least one metal oxide represented by the following general formula (2), in a state in which no metal has been deposited, for use in microwave irradiation, and is a term used to distinguish it from a mixture containing metal and metal oxide used in microwave irradiation.

[0052] A method for partially hydrogen-reducing at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture is H ２ A suitable method is to partially hydrogenate a mixture of at least one metal oxide selected from the compounds represented by the general formula (1), or the precursor mixture, by heating it in an atmosphere of gas containing the above.

[0053] There are no particular restrictions on the heating temperature when partially hydrogen-reducing at least one metal oxide selected from the compounds represented by the general formula (1), or the precursor mixture, and it can be appropriately selected depending on the purpose. However, when heating is performed by external heating such as an electric furnace, a temperature of 300°C or higher is preferred, 300°C to 570°C is more preferred, 330°C to 570°C is even more preferred, and 360°C to 540°C is particularly preferred. Furthermore, when partially hydrogen-reducing only at least one metal oxide selected from the compounds represented by the general formula (1), rather than the precursor mixture, a heating temperature of 430°C to 570°C is even more preferred, and 460°C to 540°C is most preferred. When the heating temperature when partially hydrogen-reducing at least one metal oxide selected from the compounds represented by the general formula (1), or the precursor mixture, is 300°C or higher, at least one metal oxide selected from the compounds represented by the general formula (1), or the precursor mixture, can be suitably partially hydrogen-reduced.

[0054] When heating for a partial hydrogen reduction of at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture, there is no particular limitation, and it can be appropriately selected according to the purpose. At least one metal oxide selected from the compounds represented by the general formula (1) is, for example, LaNiO ３ and when heating in an atmosphere of a gas containing 0.5% by volume or more and 10% by volume or less of H ２ and 90% by volume or more and 99.5% by volume or less of N ２ , the heating time is preferably 3 minutes or more and 300 minutes or less, more preferably 5 minutes or more and 120 minutes or less, and even more preferably 10 minutes or more and 90 minutes or less.

[0055] When treating in an atmosphere of a gas containing H ２ for a partial hydrogen reduction of at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture, there is no particular limitation on the method of heating to the preferred temperature, and it can be appropriately selected according to the purpose. However, for heating at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture, preferably, heating of LaNiO ３ , or LaNiO ３ and the precursor mixture of LaNiO and NiO is preferably carried out by radiant heat, because it is easy to perform heat treatment stably at a constant temperature and it is easy to control so that at least one metal oxide selected from the compounds represented by the general formula (1) is not completely reduced.

[0056] As the atmosphere conditions for a partial hydrogen reduction of at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture, it is preferably an atmosphere of a gas containing H ２ .

[0057] The gas containing H ２ is not particularly limited as long as it contains H ２ , and it may be a gas consisting only of H ２ , or may further contain other gases other than H ２ . However, the gas containing H ２ contains H ２Furthermore, it is more preferable that the atmosphere be one containing an inert gas.

[0058] Examples of inert gases include N ２ Examples of noble gases include He and Ar. From the viewpoint of manufacturing cost, N is preferred as the inert gas. ２ That is the case.

[0059] H ２ When partially hydrogen-reducing at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture under an atmosphere of gas containing H ２ There are no particular restrictions on the concentration, and it can be selected appropriately depending on the purpose, but H ２ The amount of explosive H is preferably 0.5% to 99.5% by volume relative to the total volume of the gas containing it, more preferably 0.5% to 50% by volume, even more preferably 1% to 50% by volume, and particularly preferably 1% to 20% by volume, from the viewpoint of controlling the reduction rate and appropriately carrying out partial reduction. ２ From the perspective of handling it safely, H ２ H in relation to the total volume of the gas containing ２ The concentration is preferably 0.5% by volume or more and 10% by volume or less.

[0060] H ２ A gas containing N ２ If it contains, N in an atmosphere for partially hydrogen-reducing at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture. ２ There are no particular restrictions on the concentration, and it can be selected appropriately depending on the purpose, but H ２ The amount of explosive H is preferably 0.5% to 99.5% by volume, more preferably 50% to 99.5% by volume, even more preferably 50% to 99% by volume, and particularly preferably 80% to 99% by volume. ２ From the perspective of handling it safely, H ２ N in relation to the total volume of the gas containing ２ The concentration is preferably 90% by volume or more and 99.5% by volume or less.

[0061] A specific example of a method for partially hydrogenating at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture is, for example, H ２ LaNiO at temperatures above 300°C under an atmosphere of gas containing ３ , or LaNiO ３ One method involves heating a precursor mixture of the metal and NiO and partially reducing it with hydrogen. As a result, Ni as a metal precipitates in the mixture containing the metal and the metal oxide, and LaNiO ３ A mixture is obtained in which Ni is dispersed or supported.

[0062] Also, H ２ Before partially hydrogen-reducing at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture under an atmosphere of gas containing N ２ The pretreatment may be carried out under a gaseous atmosphere. This removes unwanted gases such as oxygen that are generated by heating at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture, and prevents unwanted impurities from being included in the mixture obtained after hydrogen reduction.

[0063] There are no particular restrictions on the temperature of the pretreatment, and it can be appropriately selected depending on the purpose, but it is preferable to carry it out at a temperature above the hydrogen reduction temperature and below the decomposition temperature of at least one metal oxide selected from the compounds represented by general formula (1) or at least one metal oxide represented by general formula (2) in the precursor mixture. Specifically, the temperature of the pretreatment is preferably 300°C to 900°C, and more preferably 360°C to 600°C. Furthermore, when hydrogen reduction is performed on only at least one metal oxide selected from the compounds represented by general formula (1) and does not include the compound represented by general formula (2), it is particularly preferable that the temperature be 430°C to 900°C, and most preferably 460°C to 900°C.

[0064] There are no particular restrictions on the duration of the pretreatment, and it can be appropriately selected depending on the purpose. However, within the preferred temperature range for pretreatment, it is preferably 1 minute to 120 minutes, more preferably 1 minute to 90 minutes, even more preferably 1 minute to 60 minutes, and particularly preferably 5 minutes to 30 minutes.

[0065] When partially hydrogen-reducing at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture, N ２ The aforementioned pretreatment under a gaseous atmosphere, and H ２ The treatment in an atmosphere containing the gas may be carried out continuously or with intervals in between, but from the viewpoint of suppressing the rapid hydrogen reduction of at least one metal oxide selected from the compounds represented by general formula (1) or the precursor mixture and carrying out a uniform partial reduction of at least one metal oxide selected from the compounds represented by general formula (1) or the precursor mixture, it is preferable to perform hydrogen reduction by heating after the pretreatment to a temperature at which at least one metal oxide selected from the compounds represented by general formula (1) or the precursor mixture does not react with hydrogen. For example, if at least one metal oxide selected from the compounds represented by general formula (1) is LaNiO ３ If that is the case, or if at least one metal oxide selected from the compounds represented by the general formula (1) in the precursor mixture is LaNiO ３ Therefore, if at least one metal oxide selected from the compounds represented by the general formula (2) is NiO, it is preferable to perform hydrogen reduction by heating after the pretreatment, returning the temperature to 200°C or below.

[0066] Furthermore, from the viewpoint of thoroughly removing unwanted gases generated by the pretreatment from the atmosphere and preventing unwanted impurities from being included in the mixture obtained after hydrogen reduction, it is preferable to wait for at least one minute, more preferably three minutes, after the pretreatment before performing hydrogen reduction. Also, from the viewpoint of productivity in the production of the mixture, the waiting time after the pretreatment before performing hydrogen reduction is preferably two hours or less, and more preferably one hour or less. The lower limit and upper limit of the waiting time after the pretreatment before performing hydrogen reduction can be combined as appropriate, for example, one minute or more and two hours or less, three minutes or more and two hours or less, three minutes or more and two hours or less, three minutes or more and one hour or less.

[0067] Whether the generation of unwanted gases has been sufficiently reduced can be determined by connecting a gas analysis device to the outlet of the heating furnace, reaction vessel, etc., used for the pretreatment and analyzing the resulting values. There are no particular restrictions on the gas analysis device, and it can be appropriately selected depending on the purpose. Examples include mass spectrometers, gas chromatographs, and Fourier transform infrared spectrometers. If the gas analysis device is a mass spectrometer, it can be determined that the generation of unwanted gases generated by the pretreatment has been sufficiently reduced if either the fluctuation of the detected value stabilizes to ±5% or less, or if it is below the lower detection limit.

[0068] When partially hydrogenating at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture, H ２ In the treatment under a gas atmosphere containing and the pretreatment, there are no particular limitations on the method of heating to the preferred temperature, and a suitable method can be selected depending on the purpose. However, heating by external heating such as an electric furnace is preferable because it is easier to control the process so that at least one metal oxide selected from the compounds represented by the general formula (1) or the precursor mixture is not completely reduced by hydrogen.

[0069] <<CO ２ Gas containing CO ２ CO in gases containing ２There are no particular restrictions on the concentration; it can be appropriately selected according to the purpose, and the lower limit is CO ２ Preferably, the amount is 1 volume% or more, and more preferably 2 volume% or more, relative to the total volume of the gas containing CO. ２ CO in gases containing ２ When the concentration of CO is 1% by volume or more, carbon can be efficiently converted to CO. ２ CO in gases containing ２ There are no particular restrictions on the upper limit of the concentration, and it is 100% CO2 by volume, excluding other gases. ２ CO2 gas can also be used. ２ CO in gases containing ２ The lower and upper limits of the concentration can be combined as appropriate, for example, CO ２ Examples include 1% to 100% by volume, 2% to 100% by volume, etc., relative to the total volume of the gas containing the substance.

[0070] CO ２ CO in gases containing ２ Other components include, for example, CO ２ As a gas that does not react with, N ２ Examples include He, Ar, and CO, and from the perspective of manufacturing cost and stability, N ２ This is preferred.

[0071] Also, carbon and CO ２ As long as it does not interfere with the purpose of the reaction, CO ２ CO ２ It is also possible to include a gas that reacts with it. For example, H ２ H ２ Examples include hydrocarbons that are gaseous at 25°C and 1 atm. Examples of hydrocarbons that are gaseous at 25°C and 1 atm include methane, ethane, ethylene, acetylene, propane, propylene, methylacetylene, butane, isobutane, 1-butene, cis-2-butene, trans-2-butene, isobutene, 1,3-butadiene, and neopentane. Off-gases from petroleum refining facilities and petrochemical facilities that contain hydrocarbons that are gaseous at 25°C and 1 atm can also be used.

[0072] These CO ２ CO in gases containing ２ Other ingredients may be used individually or in combination of two or more. ２ CO in gases containing ２ There are no particular restrictions on the concentrations of other components, and they can be selected as appropriate depending on the purpose, but CO ２ The amount is preferably 99% by volume or less, and more preferably 98% by volume or less, relative to the total volume of the gas containing the substance.

[0073] <<Microwaves>> Microwaves are electromagnetic waves, preferably with a frequency of 300 MHz to 300 GHz. Because microwaves can directly transfer energy to the material being heated, which is a dielectric, the material being heated can behave like a heat source in conventional heating methods such as electric furnaces. On the other hand, heating by microwaves is internal heating, unlike heating by electric furnaces. In the CO production method of this disclosure, the material being heated by microwaves is carbon, and a mixture of metals and metal oxides.

[0074] In irradiating with microwaves, the microwave frequency is preferably 300 MHz to 300 GHz, but there are no particular restrictions as long as the mixture absorbs microwaves and generates heat, and can be appropriately selected according to the purpose, with 0.9 GHz to 6.0 GHz being more preferable, and 2.3 GHz to 6.0 GHz being even more preferable. If the microwave frequency is 300 MHz or higher, the mixture can be heated to a temperature sufficient for CO production, and if it is 300 GHz or lower, it is preferable from the viewpoint of energy efficiency. In irradiating with microwaves, the microwave frequency can be, for example, 915 MHz ± 13 MHz, 2.45 GHz ± 0.9 GHz, etc.

[0075] There are no particular restrictions on the microwave sources that can be used for microwave irradiation; they can be appropriately selected according to the output power. Examples include diamond SAW (Surface Acoustic Wave), magnetron, klystron, gyrotron, and semiconductor oscillator. These may be used individually or in combination of two or more.

[0076] The microwave irradiation of the mixture can be carried out continuously without changing the microwave output and frequency, from the viewpoint of stabilizing the reaction state, such as reaction activity and product selectivity, as well as the temperature and temperature distribution of the microwave heating catalyst. Furthermore, for example, when carrying out two reactions with different conditions consecutively in one pot, the output and frequency can be changed midway as needed.

[0077] There are no particular restrictions on the microwave output power; it can be appropriately selected depending on the target temperature to be reached by the microwave irradiation.

[0078] <Contact> Contact is CO ２ The carbon comes into contact with the mixture being irradiated with microwaves under an atmosphere of gas containing the specified substance.

[0079] The method for producing CO in this disclosure is CO ２ CO can be produced by bringing carbon into contact with the mixture while irradiating the mixture with microwaves in an atmosphere containing a gas. Therefore, the irradiation with microwaves and the contact proceed simultaneously, but the carbon may be brought into contact with the mixture beforehand and then irradiated with microwaves to bring the mixture to the desired temperature, or the carbon may be added to the mixture after the mixture has reached the desired temperature by microwave irradiation. As a method for adding carbon to the mixture after it has reached the desired temperature, one example is to supply carbon in the form of powder or pellets using a known supply device.

[0080] The method for producing CO in this disclosure is CO ２In an atmosphere containing CO2, the mixture comes into contact with carbon, causing the carbon to decompose. Therefore, the reaction can be carried out in batches or in a continuous manner, but a batch reaction is preferable. When carrying out a continuous reaction, the mixture is placed in a reaction tube and CO2 is used as a fixed bed. ２ One method involves adding carbon or organic materials that serve as raw materials for carbon to a mixture layer while a gas containing carbon is flowing through it.

[0081] When performing a batch reaction, the mixture is placed in a reaction vessel such as a reaction tube, and solid carbon is placed on top of the fixed bed, and the inside of the reaction vessel is treated with CO2. ２ A method of heating in a gas atmosphere containing CO, or placing the mixture in a sealable reaction vessel such as an autoclave, ２ One method is to encapsulate carbon as a gaseous atmosphere containing [the substance].

[0082] The reaction vessel is made of a material that is inert to microwaves but transmits microwaves. Quartz is one example of such a material.

[0083] Upon contact, the carbon and the mixture directly absorb microwaves and are heated. There are no particular restrictions on the temperature of the heated carbon and the mixture, and they can be appropriately selected depending on the purpose, but a temperature of 300°C to 1,300°C is preferred, and a temperature of 700°C to 1,200°C is more preferred. When the temperature of the heated carbon and the mixture is 300°C to 1,300°C, high catalytic activity can be obtained and energy efficiency is good. The temperature of the heated carbon and the mixture is also the reaction temperature at which carbon undergoes catalytic decomposition upon contact. The temperature of the carbon and the mixture can be measured using known temperature measuring instruments such as resistance thermometers and thermocouples.

[0084] <<Carbon>> In the method for producing CO of this disclosure, there are no particular restrictions on the carbon, and it can be appropriately selected depending on the purpose. １２ C, １３ C, and １４Any of C may be used. Furthermore, the carbon may have a crystalline structure or may be in an amorphous state without a crystalline structure. Note that in the method for producing CO of this disclosure, the carbon does not contain carbon-containing compounds (e.g., organic compounds and metal carbides). However, as a raw material for carbon, a gaseous or liquid organic substance containing carbon atoms, such as hydrocarbons, may be brought into contact with a mixture and thermally decomposed to convert it to carbon in situ.

[0085] Specific examples of carbon include diamond, graphite, lonsdaleite, fullerene, carbon black, carbon fibers (including carbon nanotubes, carbon nanofibers, etc.), graphene, charcoal, activated carbon, bamboo charcoal, carbon nanospheres, biochar, carbonated sugar, and plant ash (e.g., rice husk ash). These carbons may also be surface-treated by ozone treatment, ultraviolet irradiation, acid treatment, or alkali treatment. These carbons may be used individually or in combination of two or more types.

[0086] There are no particular restrictions on the BET specific surface area of ​​carbon, and it can be selected according to the purpose, but efficiently CO ２ Since it is easily converted to CO, 200 m is preferred. ２ / g or more, more preferably 300m ２ It is 1 / g or more. Furthermore, there is no particular limit on the upper limit of the BET specific surface area of ​​carbon; for example, 2,300 m². ２ It is less than / g. The BET specific surface area of ​​carbon is measured in accordance with ISO 9277:2010.

[0087] There are no particular restrictions on the pore volume of carbon, and it can be selected according to the purpose, but efficiently CO ２ Since it is easily converted to CO, the concentration is preferably 0.14 cc / g or more, more preferably 0.18 cc / g or more. There is no particular upper limit to the carbon pore volume, for example, 5 cc / g or less. The pore volume is measured in accordance with the constant volume method described in ISO 15901-2:2022.

[0088] In contact with the mixture, there are no particular restrictions on the amount of the mixture used relative to the amount of carbon added, and it can be appropriately selected depending on the purpose. However, in the case of a continuous reaction, the total amount of flowing carbon is preferably 0.001 g / min to 100 g / min per 1 g of the mixture, and more preferably 0.01 g / min to 10 g / min. In the case of a batch reaction, the mass ratio (carbon:mixture) is preferably 0.001:1 to 1:1,000, and more preferably 0.01:1 to 1:100.

[0089] <Other Processing> There are no particular restrictions on other processing methods, and they can be selected as appropriate depending on the purpose. For example, this could include recovering the CO produced in the CO production method.

[0090] <<Recovery>> Recovery involves irradiating with microwaves and contacting CO ２ The objective is to recover the CO produced by the conversion of [unclear]. There are no particular restrictions on the recovery method, and any known method can be appropriately selected; for example, separation by pressurized distillation is one possible method.

[0091] CO ２ Gas containing CO ２ If other gaseous components are present, these other gaseous components may be mixed with the generated CO. In such cases, the CO and the other gaseous components may be recovered together, recovered separately, or, after being recovered together, separated by known methods.

[0092] (CO ２ Method of converting to CO) CO ２ The method for converting to CO is CO ２ Irradiating a mixture containing metals and metal oxides with microwaves in an atmosphere of gas containing CO ２ The CO of this disclosure comprises the following: under an atmosphere of gas containing, carbon coming into contact with the mixture being irradiated with microwaves, wherein the metal is a metal containing at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti, and the metal oxide is at least one metal oxide selected from compounds represented by the following general formula (1).２ The method for converting to CO may further include, if necessary, other processes other than microwave irradiation and contact. MaMbO ３ ...General formula (1) However, in the above general formula (1), Ma represents one metallic element selected from alkaline earth metals and lanthanides, and Mb represents the same metallic element as the metallic element contained in the above metal.

[0093] CO of this disclosure ２ The methods for converting to CO, including microwave irradiation, contact, and other processes, can be carried out in the same manner as the CO manufacturing method of this disclosure, so a detailed explanation is omitted. ２ Other processes in the method of converting to CO can be carried out in the same manner as other processes in the method of producing CO of this disclosure.

[0094] CO ２ The method for converting to CO, when using a mixture containing a metal and a metal oxide as a catalyst, and using at least one metal oxide selected from the compounds represented by the general formula (1) as the metal oxide, is more efficient than the conventional method when using only a metal oxide catalyst (at least one metal oxide selected from the compounds represented by the general formula (1)). ２ The conversion efficiency to CO is dramatically improved.

[0095] CO of this disclosure ２ CO conversion method ２ Conversion rate to CO (hereinafter referred to as "CO") ２ The conversion rate (sometimes referred to as the "conversion rate") is preferable as high as possible, but 40% or more is preferable, and 45% or more is more preferable. ２ CO conversion method ２ The conversion rate can be calculated, for example, using a mass spectrometer by the following procedure.

[0096] CO ２ For the signal corresponding to m / z = 44, CO of known concentration ２ / N ２Using a mixed gas, a calibration curve is prepared in advance using the absolute calibration curve method. ２ The concentration of "CO ２ (in) The CO2 was determined according to the calibration curve from the signal value at m / z = 44 shown by the mass spectrometer connected to the outlet of the reaction tube. ２ The concentration of "CO ２ (out) and according to the following formula, CO ２ Calculate the conversion rate. CO ２ Conversion rate (%) = {CO ２ (in)-CO ２ (out) / CO ２ (in) × 100

[0097] The embodiments of this disclosure will be described in more detail below with reference to preparation examples, manufacturing examples, test examples, examples, and comparative examples, but the embodiments are not limited to these preparation examples, manufacturing examples, test examples, examples, and comparative examples.

[0098] (Preparation example 1: LaNiO ３ Preparation of (Ni(NO)) Nickel(II) nitrate hexahydrate (Ni(NO)) ３ ) ２ 6H ２ 5.82 g (20.0 mmol) of lanthanum (O, formula weight 290.79, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and lanthanum (III) nitrate hexahydrate (La(NO) ３ ) ３ 6H ２ 8.66 g (20.0 mmol) of nickel(II) nitrate hexahydrate (formula weight 433.01, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was placed in a 200 mL beaker, and purified water was added up to the 50 mL mark. A stirrer tip was placed in the beaker, the opening of the beaker was covered with plastic wrap, and the mixture was stirred with a magnetic stirrer. Stirring was stopped when nickel(II) nitrate hexahydrate and lanthanum(III) nitrate hexahydrate had dissolved in the water, and the aqueous solution containing nickel(II) nitrate hexahydrate and lanthanum(III) nitrate hexahydrate was transferred to a titration burette.

[0099] Separately, 125 mL of 10% by mass tetramethylammonium hydroxide (TMAH) aqueous solution was added to a 500 mL beaker, and a stirrer tip was placed inside. While stirring the TMAH aqueous solution with a magnetic stirrer, an aqueous solution containing nickel(II) nitrate hexahydrate and lanthanum(III) nitrate hexahydrate, which had been transferred to a titration burette, was added dropwise at a rate of 2 times every 3 seconds. After the addition was complete, the mixture was stirred with a magnetic stirrer for another hour, and then allowed to stand for 1 hour. The mixture after standing was filtered by suction, and purified water was added to the filtrate and filtered by suction repeatedly until the pH of the filtrate was 8-9, and the mixture was washed. After thorough washing, the filtrate was transferred to a firing dish and baked overnight in a 90°C oven to dry it. The dried filtrate was ground using a mortar and pestle for 20 minutes. After grinding, the powder of the filtrate was transferred to a crucible and baked at 850°C for 5 hours to obtain LaNiO ３ I obtained it.

[0100] (Manufacturing Example 1: Manufacturing of Catalyst A) LaNiO obtained in Preparation Example 1 ３ 10 mg of the powder was weighed out and filled into a quartz reaction tube with an outer diameter of 10 mm and an inner diameter of 8 mm. This reaction tube was then placed in an electric furnace (ceramic electric tubular furnace, manufactured by Asahi Rika Seisakusho Co., Ltd.) equipped with a thermometer. A mass spectrometer was connected to the outlet of the reaction tube. 100 vol% N3 was added to the reaction tube. ２ The electric furnace was heated to a set temperature of 500°C while the gas was flowing at a flow rate of 100 mL / min. After the electric furnace reached 500°C, it was maintained at 500°C for 10 minutes, and then the heating by the electric furnace was stopped. After confirming that the electric furnace temperature had dropped to 25°C, 100% N2 by volume was flowed into the reaction tube. ２ Gas, H ２ and N ２ mixed gas (5% by volume H ２ / 95% N by volume ２The system was switched to a different setting and flowed at a rate of 30 mL / min. After confirming that the mass spectrometer connected to the outlet of the reaction tube was stable, the electric furnace was set to a heating rate of 10 °C / min and a temperature of 500 °C, and heating was started. After the electric furnace reached 500 °C, it was held at 500 °C for 30 minutes, then the heating by the electric furnace was stopped, and the reaction tube was cooled to 25 °C. The catalyst obtained in Production Example 1 was designated as "Catalyst A". The analysis conditions using the mass spectrometer were as follows: [Analysis Conditions] ・Apparatus: BELMASS (Microtrac-Bel Co., Ltd.) ・Emission current: 1.0 mA ・SEM: 1000 V

[0101] (Comparative manufacturing example 1: Manufacturing of catalyst B) LaNiO obtained in preparation example 1 ３ 10 mg of the powder was weighed out and filled into a quartz reaction tube with an outer diameter of 10 mm and an inner diameter of 8 mm. This reaction tube was then placed in an electric furnace (ceramic electric tubular furnace, manufactured by Asahi Rika Seisakusho Co., Ltd.) equipped with a thermometer. A mass spectrometer was connected to the outlet of the reaction tube. 100 vol% N3 was added to the reaction tube. ２ The electric furnace was heated to a set temperature of 400°C while the gas was flowing at a flow rate of 100 mL / min. After the electric furnace reached 400°C, it was maintained at 400°C for 10 minutes, and then the heating by the electric furnace was stopped. After confirming that the electric furnace temperature had dropped to 25°C, 100% N2 by volume was flowed into the reaction tube. ２ Gas, H ２ and N ２ mixed gas (5% by volume H ２ / 95% N by volume ２ The system was switched to a different setting and flowed at a rate of 30 mL / min. After confirming that the mass spectrometer connected to the outlet of the reaction tube was stable, the electric furnace was set to a heating rate of 10 °C / min and a temperature of 400 °C, and heating was started. After the electric furnace reached 400 °C, it was maintained at 400 °C for 30 minutes, then the heating by the electric furnace was stopped, and the reaction tube was cooled to 25 °C. The catalyst obtained in Comparative Production Example 1 was designated as "Catalyst B". The analysis conditions using the mass spectrometer were the same as in Production Example 1.

[0102] (Test Example 1: XRD Analysis) Catalysts A and B, which are products obtained in Production Example 1 and Comparative Production Example 1, and LaNiO obtained in Preparation Example 1. ３The following analysis was performed using X-ray diffraction (XRD) with Cu-Kα rays as the X-ray source under the following analysis conditions. The analyzed X-ray diffraction spectrum (XRD spectrum) is shown in Figure 1. [Analysis conditions] ・Apparatus: Ultima IV (manufactured by Rigaku Corporation) ・Scanning range: 20° ≤ 2θ / degree ≤ 80° ・Scanning axis: 2θ / θ

[0103] The peaks were identified by comparing the obtained X-ray diffraction patterns with literature values. From the results in Figure 1, the XRD spectrum of the powder obtained in Preparation Example 1, before heating in the electric furnace in Example 1, is LaNiO ３ Only peaks attributable to are shown, indicating that the powder is LaNiO ３ This demonstrated that the catalyst A, which was obtained in Production Example 1, is LaNiO ３ Ni, and La ２ O ３ A peak attributed to LaNiO was observed. ３ It is partially reduced by hydrogen, LaNiO ３ This means that it is a mixture containing Ni. In contrast, catalyst B, which is the product obtained in comparative production example 1, has a peak attributable to the Ni atom, LaNiO ３ In addition to the peaks attributed to LaNiO ｚ Although a peak attributed to (z < 3) was observed, no peak attributed to metallic Ni was found.

[0104] (Example 1) Using the reaction tube containing catalyst A manufactured in Production Example 1, 100 mg of activated carbon (GL Sciences Co., Ltd., Catalog No. 1001-13006) was placed on catalyst A inside the reaction tube, and the reaction tube was set in the following microwave generator instead of the electric furnace used in Production Example 1. The specific surface area of ​​the activated carbon used was 456.4 m², determined from the nitrogen adsorption isotherm measured in accordance with ISO 9277:2010 using a BET specific surface area analyzer (Nova, Anton Parr). ２The pore volume was 0.297 cc / g, determined from the nitrogen adsorption isotherm measured in accordance with the constant volume method specified in ISO 15901-2:2022. [Microwave Generator] ・Device: MR-2G-100 (manufactured by Ryowa Electronics Co., Ltd.) ・Frequency: 2.45 GHz ± 0.05 GHz ・Irradiation mode: Single mode (maximum electric field intensity on the central axis) ・Cavity size: 10 mm diameter, 100 mm length ・Maximum input power: 100 W

[0105] CO from the top of the reaction tube ２ and N ２ mixed gas (10% CO2 by volume) ２ / 90% N by volume ２ The solution was passed through at a rate of 30 mL / min. After confirming that the mass spectrometer connected to the outlet of the reaction tube was stable, microwave heating was started at a heating rate of 10°C / min. When the temperature of the reaction tube reached 800°C, the heating was stopped, and after being held at 800°C for 30 minutes, the heating was stopped.

[0106] During the reaction from 0 to 140 minutes, the generated gas was analyzed using a mass spectrometer connected to the reaction tube under the following analytical conditions: CO ２ Furthermore, mass spectrometry of CO was performed, and the CO was measured using the absolute calibration curve method based on the detected values. ２ Concentration (g / m ３ ) and CO concentration (g / m³) ３ The following values ​​were calculated for each component. The analysis conditions for mass spectrometry were as described in Manufacturing Example 1. CO ２ The signal at m / z = 44 corresponds to the signal at m / z = 28, and the signal at m / z = 28 corresponds to CO. The results are shown in Figure 2A. Figure 2A shows the temperature change of the reaction tube during the reaction from 0 to 140 minutes in Example 1, and the CO flowing through the reaction tube. ２ This graph shows the relationship between the change in concentration and the change in the concentration of generated CO.

[0107] (Comparative Example 1) In Comparative Example 1, the reaction tube containing catalyst A produced in Production Example 1 was used as is, and 100 mg of activated carbon was placed on catalyst A inside the reaction tube. This was changed to using the reaction tube containing catalyst B produced in Comparative Production Example 1 as is, and 100 mg of activated carbon was placed on catalyst B inside the reaction tube. Otherwise, the reaction tube was heated in the same manner as in Example 1, while CO was being added. ２ The concentration of CO was also measured. The results are shown in Figure 2B. Figure 2B shows the temperature change of the reaction tube during the reaction from 0 to 140 minutes in Comparative Example 1, and the CO flowing through the reaction tube. ２ This graph shows the relationship between the change in concentration and the change in the concentration of generated CO.

[0108] (Comparative Example 2) In Example 1, the reaction tube containing catalyst A produced in Production Example 1 was used as is, and 100 mg of activated carbon was placed on catalyst A inside the reaction tube, compared to the LaNiO produced in Preparation Example 1. ３ The reaction tube having the LaNiO in the reaction tube is used as is. ３ Except for the change that 100 mg of activated carbon was placed on top, the reaction tube was heated while CO was being added, in the same manner as in Example 1. ２ The concentration of CO was also measured. The results are shown in Figure 2C. Figure 2C shows the temperature change of the reaction tube during the reaction from 0 to 140 minutes in Comparative Example 2, and the CO flowing through the reaction tube. ２ This graph shows the relationship between the change in concentration and the change in the concentration of generated CO.

[0109] (Comparative Example 3) The only difference from Example 1 is that instead of placing 100 mg of activated carbon on catalyst A inside the reaction tube, 100 mg of activated carbon was placed in an empty reaction tube (a reaction tube without catalyst A). The procedure was the same as in Example 1, but the reaction tube was heated while CO was being added. ２ The concentration of CO was also measured. The results are shown in Figure 2D. Figure 2D shows the temperature change of the reaction tube during the reaction from 0 to 140 minutes in Comparative Example 3, and the CO flowing through the reaction tube. ２ This graph shows the relationship between the change in concentration and the change in the concentration of generated CO.

[0110] A mixture containing metals and metal oxides (LaNiO ３In Example 1, which used catalyst A that was partially reduced, more CO was released compared to Comparative Example 1, which used catalyst B that did not contain metal (Ni), and Comparative Example 3, which was catalyst-free. ２ It consumed and generated more CO. In other words, Example 1 consumed more CO. ２ It was converted to CO. Also, a mixture containing metals and metal oxides (LaNiO ３ In Example 1, which used catalyst A) that was partially reduced, LaNiO, which does not contain metal (Ni), was used. ３ Compared to Comparative Example 2, which used [the other method], the temperature stability when held at 800°C was superior.

[0111] As described above, this disclosure has been explained based on specific embodiments and examples, but these embodiments and examples are merely presented as examples, and this disclosure is not limited to the above embodiments and examples. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, additions, modifications, etc., are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0112] This international application claims priority under Japanese Patent Application No. 2024-157059, filed on 10 September 2024, and Japanese Patent Application No. 2024-161499, filed on 18 September 2024, which are incorporated herein by reference to the entire contents of Japanese Patent Application No. 2024-157059 and Japanese Patent Application No. 2024-161499.

Claims

1. CO ２ Irradiating a mixture containing metals and metal oxides with microwaves in an atmosphere of gas containing CO ２ A method for producing CO, comprising: bringing carbon into contact with the mixture being irradiated with microwaves in an atmosphere of gas containing; wherein the metal is a metal containing at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti; and the metal oxide is at least one metal oxide selected from compounds represented by the following general formula (1): MaMbO ３ ...General formula (1) However, in the above general formula (1), Ma represents one metallic element selected from alkaline earth metals and lanthanides, and Mb represents the same metallic element as the metallic element contained in the above metal.

2. The method for producing CO according to claim 1, wherein the mixture containing the metal and the metal oxide is obtained by partially hydrogen-reducing a precursor mixture containing at least one metal oxide selected from the compounds represented by general formula (1), or at least one metal oxide selected from the compounds represented by general formula (1) and at least one metal oxide represented by the following general formula (2), thereby precipitating the metal. Mb ｘ O ｙ ...General formula (2) In general formula (2), Mb represents the same metallic element as Mb in general formula (1), x and y represent positive integers indicating the composition ratio of Mb to O, and y is given by y = xz / 2, where z is the oxidation state of Mb.

3. The metal is Ni, and the metal oxide is LaNiO ３ The method for producing CO according to claim 1 or claim 2.

4. The mixture containing the metal and the metal oxide is heated at 300 °C or higher in an atmosphere of a gas containing H ２ to partially hydrogenate and reduce a precursor mixture of LaNiO ３ or LaNiO ３ and NiO to precipitate Ni. The method for producing CO according to claim 3 5. The LaNiO ３ , or the LaNiO ３ The method for producing CO according to claim 4, wherein the heating of the precursor mixture of the NiO is carried out by radiant heat.

6. The method for producing CO according to any one of claims 1 to 5, wherein, in the contact, the temperature of the carbon and the mixture is heated to 300°C or more and 1,300°C or less.

7. CO ２ Irradiating a mixture containing metals and metal oxides with microwaves in an atmosphere of gas containing CO ２ In an atmosphere of gas containing CO, carbon is brought into contact with the mixture being irradiated with microwaves, and the metal is a metal containing at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti, and the metal oxide is at least one metallic oxide selected from compounds represented by the following general formula (1), CO ２ A method for converting to CO. MaM NitO ３ ...General formula (1) However, in the above general formula (1), Ma represents one metallic element selected from alkaline earth metals and lanthanides, and Mb represents the same metallic element as the metallic element contained in the above metal.

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