Method for producing catalyst for microwave heating and method for screening catalyst

Abstract

One embodiment of a method for producing a catalyst for microwave heating according to the present disclosure comprises heating at least one metal oxide selected from compounds represented by the following general formula (1) between 430°C and 570°C, inclusive, under a gas atmosphere containing H2.　General formula (1): MaMbO3 In general formula (1), Ma represents one metallic element selected from alkaline earth metals and lanthanoids, and Mb represents at least one metallic element selected from Fe, Co, Ni, Mn, Cu and Ti.

Description

Method for manufacturing a catalyst for microwave heating and method for screening a catalyst

[0001] This disclosure relates to a method for manufacturing a catalyst for microwave heating and a method for screening a catalyst.

[0002] Catalysts are used in various technological fields, including thermal power plants, steel plants, cement plants, and chemical plants. Perovskite oxides are attracting attention as one type of catalyst (see, for example, Non-Patent Documents 1 and 2).

[0003] On the other hand, microwaves can selectively heat specific sites within a catalyst, specifically the active sites where chemical reactions occur. This is expected to enable reactions at lower temperatures and shorten reaction times, thus saving energy.

[0004] Therefore, there is a need for microwave heating catalysts that exhibit excellent catalytic activity and heating stability in reactions under microwave heating conditions.

[0005] 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.

[0006] This disclosure aims to provide a method for producing a microwave heating catalyst that exhibits excellent catalytic activity and heating stability in reactions under microwave heating conditions, as well as a method for screening such catalysts.

[0007] The means to solve the aforementioned problem are as follows: That is, <1> H ２ A method for producing a microwave heating catalyst, comprising heating at least one metal oxide selected from compounds represented by the following general formula (1) at 430°C to 570°C in an atmosphere of gas containing 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 at least one metal element selected from Fe, Co, Ni, Mn, Cu, and Ti. <2> The heating is performed by radiant heat, and this is the method for producing a microwave heating catalyst according to <1>. <3> The X-ray diffraction spectrum of the microwave heating catalyst has a peak attributed to at least one metal oxide selected from the compound represented by the general formula (1), and a peak attributed to the metal derived from Mb in the at least one metal oxide selected from the compound represented by the general formula (1), and this is the method for producing a microwave heating catalyst according to <1> or <2>. <4> The metal is precipitated by partial hydrogen reduction of at least one metal oxide selected from the compound represented by the general formula (1), and this is the method for producing a microwave heating catalyst according to <3>. <5> At least one metal oxide selected from the compounds represented by the general formula (1) is LaNiO ３ This is a method for producing a microwave heating catalyst as described in any one of the above items <1> to <4>. <6> H ２ A method for producing a microwave heating catalyst, comprising heating a mixture containing at least one metal oxide selected from the compounds represented by the following general formula (1) and at least one metal oxide selected from the compounds represented by the following general formula (2) at a temperature of 300°C to 570°C under an atmosphere of gas containing 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 at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti. ｘ O ｙ・・・ General formula (2) However, in the general formula (2), Mb represents the same metal element as Mb in the general formula (1), x and y represent positive integers indicating the composition ratio of Mb and O, and y is the oxidation number of Mb as z, and y = xz / 2. <7> The method for producing a catalyst for microwave heating according to <6> above, wherein the heating is performed by radiant heat. <8> The X-ray diffraction spectrum of the catalyst for microwave heating has a peak attributed to at least one metal oxide selected from the compounds represented by the general formula (1), and a metal derived from Mb in at least one metal oxide selected from the compounds represented by the general formula (1), and at least one metal derived from Mb in at least one metal oxide selected from the compounds represented by the general formula (2). The method for producing a catalyst for microwave heating according to <6> or <7> above, which has a peak attributed to any one of the metals. <9> At least one metal oxide selected from the compounds represented by the general formula (1) is LaNiO ３ and at least one metal oxide selected from the compounds represented by the general formula (2) is NiO. The method for producing a catalyst for microwave heating according to any one of <6> to <8> above. <10> Analyzing the catalyst by X-ray diffraction method, and screening a catalyst having a peak attributed to LaNiO ３ and a peak attributed to Ni in the X-ray diffraction spectrum obtained by the X-ray diffraction method as a catalyst for microwave heating, which is a method for screening a catalyst.

[0008] According to an embodiment of the present disclosure, a method for producing a catalyst for microwave heating and a method for screening a catalyst, which are excellent in catalyst activity and heating stability in a reaction under heating conditions by microwave, can be provided.

[0009] Figure 1 shows the X-ray diffraction (XRD) spectra of the products obtained in Preparation Example 1, Example 1, Comparative Example 1, and Comparative Example 2. The vertical axis represents Intensity (a.u.), and the horizontal axis represents 2θ (degree). Figure 2 shows the X-ray diffraction (XRD) spectra of the products obtained in Preparation Example 2, Example 2, Example 3, and Comparative Example 3. The vertical axis represents Intensity (a.u.), and the horizontal axis represents 2θ (degree). Figure 3A is a graph showing the evaluation results of the hydrogen generation capacity when catalyst A from Example 1 was used in Test Example 3. The left vertical axis represents temperature (°C), the right vertical axis represents the intensity of the mass spectrometry signal (a.u.), and the horizontal axis represents the analysis time (minutes). The solid line represents H by mass spectrometry. ２ The graph shows the change in signal intensity, and the dotted line shows the change in reaction tube temperature. Figure 3B is a graph showing the evaluation results of hydrogen generation capacity when catalyst B of Comparative Example 1 was used in Test Example 3. The left vertical axis shows temperature (°C), the right vertical axis shows the intensity of the mass spectrometry signal (a.u.), and the horizontal axis shows the analysis time (minutes). The solid line shows the H2O ２ The graph shows the change in signal intensity, and the dotted line shows the change in temperature in mass spectrometry. Figure 3C is a graph showing the evaluation results of hydrogen generation capacity when catalyst C of Comparative Example 2 was used in Test Example 3. The left vertical axis shows temperature (°C), the right vertical axis shows the intensity of the mass spectrometry signal (a.u.), and the horizontal axis shows the analysis time (minutes). The solid line shows the H2O ２ The graph shows the change in signal intensity, and the dotted line shows the change in reaction tube temperature. Figure 3D is a graph showing the evaluation results of hydrogen generation capacity when catalyst E of Example 3 was used in Test Example 3. The left vertical axis shows temperature (°C), the right vertical axis shows the intensity of the mass spectrometry signal (a.u.), and the horizontal axis shows the analysis time (minutes). The solid line shows the H2O ２ The signal intensity changes over time, and the dotted line indicates the temperature change of the reaction tube.

[0010] 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.

[0011] (Method for manufacturing a microwave heating catalyst) The method for manufacturing a microwave heating catalyst according to the present disclosure includes the method for manufacturing a microwave heating catalyst according to the first embodiment and the method for manufacturing a microwave heating catalyst according to the second embodiment described below.

[0012] In this disclosure, "microwave heating catalyst" refers to a catalyst used in reactions involving heating by microwaves. There are no particular limitations on the applications of the microwave heating catalyst produced by the method for producing the microwave heating catalyst of this disclosure, and examples include electrode catalysts, photocatalysts, exhaust gas purification catalysts, hydrocarbon decomposition catalysts, and hydrogenation catalysts. Therefore, the microwave heating catalyst produced by the method for producing the microwave heating catalyst of this disclosure can be used in various technical fields such as materials like electrodes, piezoelectric elements, thermoelectric elements, and dielectrics; exhaust gas treatment in thermal power plants, steel plants, cement plants, chemical plants, etc.; hydrocarbon decomposition treatment; and chemical manufacturing processes.

[0013] The microwave heating catalyst described herein exhibits excellent catalytic activity and heating stability in reactions under microwave heating conditions. The microwave heating catalyst described herein can be suitably applied not only to reaction systems typically heated by microwaves, but also to reaction systems typically heated by radiant heat from electric furnaces or the like.

[0014] In this disclosure, "microwave" preferably refers to electromagnetic waves with a frequency of 300 MHz to 300 GHz. Because microwaves can directly transfer energy to a dielectric material to be heated, the material to be 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 radiant heat.

[0015] In the reactions using microwave heating catalysts in this disclosure, the microwave heating catalyst is the substance to be heated, but other substances to be heated can be appropriately selected depending on the reaction system using the microwave heating catalyst in this disclosure. For example, the substrate of the reaction catalyzed by the microwave heating catalyst in this disclosure may be the substance to be heated.

[0016] The microwave frequency in a reaction system using a microwave heating catalyst is preferably 300 MHz to 300 GHz, but there are no particular restrictions as long as the microwave heating catalyst in this disclosure can absorb microwaves and generate heat, and can be appropriately selected according to the purpose, with 0.9 GHz to 6.0 GHz being more preferred, and 2.3 GHz to 6.0 GHz being even more preferred. When the microwave frequency is 300 MHz or higher, the substance to be heated can be heated to a sufficient temperature, and when it is 300 GHz or lower, it is preferable from the viewpoint of energy efficiency. The microwave frequency in a reaction system using a microwave heating catalyst can be, for example, 915 MHz ± 13 MHz, 2.45 GHz ± 0.9 GHz, etc.

[0017] There are no particular restrictions on the microwave source used to apply microwaves to the material to be heated, including the microwave heating catalyst. It 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.

[0018] Microwave irradiation of a material to be heated, including a microwave heating catalyst, can be performed 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 microwave output and frequency can be changed midway as needed.

[0019] There are no particular restrictions on the microwave output in a reaction system using a microwave heating catalyst; it can be appropriately selected according to the desired temperature achieved by microwave irradiation.

[0020] There are no particular restrictions on the method of using the microwave heating catalyst, and it can be appropriately selected depending on the type of reaction catalyzed by the microwave heating catalyst. For example, one method is to bring the substrate to be catalyzed by the microwave heating catalyst into contact with the microwave heating catalyst, which is being irradiated with microwaves, under appropriately selected atmospheric conditions such as air or an inert gas. However, H ２ Reactions under atmospheric conditions containing reducing substances such as H ２ When the microwave heating catalyst of this disclosure is used in reactions that generate reducing substances such as the above, it is particularly preferable because it exhibits catalytic activity at low temperatures and has excellent heating stability compared to cases where at least one metal oxide selected from the compounds represented by general formula (1) is used as a catalyst as is, or when a catalyst obtained by hydrogen reduction of at least one metal oxide selected from the compounds represented by general formula (1) at a temperature above 570°C is used.

[0021] In this case, it is preferable that the irradiation of the microwave heating catalyst with microwaves and the contact between the microwave heating catalyst and the substrate to be reacted proceed simultaneously. However, the microwave heating catalyst and the substrate to be reacted may be brought into contact beforehand, and then irradiated with microwaves to bring the microwave heating catalyst to the desired temperature. Alternatively, after the microwave heating catalyst reaches the desired temperature by microwave irradiation, the substrate to be reacted may be added, bringing the microwave heating catalyst and the substrate to be reacted into contact. As for the method of adding the substrate to be reacted, the substrate to be reacted may be supplied directly to the microwave heating catalyst, or a substance that will serve as a precursor to the substrate to be reacted may be supplied to the microwave heating catalyst and converted into the substrate to be reacted in situ.

[0022] <First Embodiment> The method for manufacturing a microwave heating catalyst according to the first embodiment of the present disclosure is H ２The method includes heating at least one metal oxide selected from the compounds represented by the following general formula (1) at a temperature of 430°C to 570°C in an atmosphere of gas containing the above. The method for producing a microwave heating catalyst according to the first embodiment of the present disclosure may further include other treatments other than heating, if necessary. 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 at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti.

[0023] <Heating> Heating is H ２ The process involves heating at least one metal oxide selected from the compounds represented by the general formula (1) at a temperature of 430°C to 570°C in an atmosphere of gas containing the above. By heating, at least one metal oxide selected from the compounds represented by the general formula (1) can be partially reduced by hydrogen.

[0024] The heating temperature for heating is 430°C to 570°C, but 460°C to 540°C is preferred. If the heating temperature is below 430°C or above 570°C, the catalytic activity and heating characteristics of the microwave heating catalyst will decrease.

[0025] There are no particular restrictions on the heating time, and it can be appropriately selected depending on the purpose. At least one metal oxide selected from the compounds represented by the general formula (1) is, for example, LaNiO ３ Therefore, H is present in an amount of 0.5% to 10% by volume. ２ And, N 90% to 99.5% by volume ２ When heating in an atmosphere containing a gas, the heating time is preferably 5 minutes or more and 120 minutes or less, and more preferably 10 minutes or more and 90 minutes or less.

[0026] In terms of heating, there are no particular restrictions on the method of heating the at least one metal oxide selected from the compounds represented by the general formula (1), and it can be appropriately selected depending on the purpose. However, heating by radiant heat is preferred because it is easy to perform the heat treatment stably at a constant temperature and it is easy to control so that the at least one metal oxide selected from the compounds represented by the general formula (1) is not completely reduced.

[0027] <<At least one metal oxide selected from compounds represented by general formula (1)>> In general formula (1), Ma represents one metal element selected from alkaline earth metals and lanthanides. Specific examples of Ma in 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. Among these, lanthanides are preferred for Ma in general formula (1), and La is more preferred.

[0028] In the general formula (1) above, Mb represents at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti.

[0029] At least one metal oxide selected from the compounds represented by the general formula (1) is ABO ３ It 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 above general formula (1). B is located at the B site of the perovskite-type structure and corresponds to Mb in the above general formula (1).

[0030] A specific example of at least one metal oxide selected from the compounds represented by the general formula (1) is LaNiO ３ LaFeO ３ LaCoO ３ LaMnO ３ , BaTiO ３ SrTiO ３ CaTiO ３ BaCoO ３ LaCuO ３These 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.

[0031] 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.

[0032] [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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[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 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. 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 is preferably as close to 1 as possible, but it may be in the range of 0.80 to 1.00. 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 0.80 to 1.00, 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.

[0039] 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.

[0040] <<H ２ Gas containing >> H ２ Gases containing H ２ As long as it includes H ２ It may be a gas consisting only of H ２ It may also contain other gases besides H. ２If the gas containing H also contains other gases, 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 H is preferably 0.5% to 99.5% by volume relative to the total volume of the gas containing it, and more preferably 1% to 50% by volume from the viewpoint of controlling the reduction rate and appropriately carrying out the partial reduction of at least one metal oxide selected from the compounds represented by the general formula (1). ２ From the perspective of handling it safely, H ２ H in a gas containing ２ In terms of concentration, H ２ It is preferable that the amount is 0.5% by volume or more and 10% by volume or less, relative to the total volume of the gas containing the substance.

[0041] H ２ H in a gas containing ２ Other gases include, for example, N ２ Examples include He, Ar, and water vapor. These may be used individually or in combination of two or more. Among these, H ２ Gases containing N ２ It is preferable to include it.

[0042] H ２ N in a gas containing ２ There are no particular restrictions on the concentration; it can be selected appropriately depending on the purpose. ２ The amount of explosive H is preferably 0.5% to 99.5% by volume, and more preferably 50% to 99% by volume, relative to the total volume of the gas containing it. ２ From the perspective of handling it safely, H ２ N in a gas containing ２ In terms of concentration, H ２ It is preferable that the amount is 90% to 99.5% by volume relative to the total volume of the gas containing the substance.

[0043] Also, H ２ In an atmosphere of gas containing N, before partially hydrogen-reducing at least one metal oxide selected from the compounds represented by the general formula (1), ２The pretreatment may be performed 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), and prevents unwanted impurities from being included in the catalyst obtained after hydrogen reduction.

[0044] N ２ Pretreatment under a gaseous atmosphere, and H ２ The treatment in an atmosphere containing the gas (i.e., hydrogen reduction by heating) may be performed continuously or with intervals in between. However, from the viewpoint of suppressing the rapid hydrogen reduction of at least one metal oxide selected from the compounds represented by general formula (1) and performing a uniform partial reduction of at least one metal oxide selected from the compounds represented by general formula (1), it is preferable to perform hydrogen reduction by heating after the pretreatment, once the temperature has been reduced to a level where the at least one metal oxide selected from the compounds represented by general formula (1) does not react with hydrogen. For example, if the at least one metal oxide selected from the compounds represented by general formula (1) is LaNiO ３ In that case, it is preferable to perform hydrogen reduction by heating after the pretreatment, returning the temperature to 200°C or below.

[0045] Furthermore, from the viewpoint of sufficiently removing unwanted gases generated by the pretreatment from the atmosphere and preventing unwanted impurities from being included in the microwave heating catalyst obtained after hydrogen reduction, it is preferable to wait for at least one minute after the pretreatment before performing hydrogen reduction, and more preferably, to wait for at least three minutes before performing hydrogen reduction. Also, from the viewpoint of productivity in the production of the microwave heating catalyst, 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 appropriately combined, 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.

[0046] 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.

[0047] <Other Processing> Other processing may or may not be performed as needed. Furthermore, there are no particular limitations on other processing as long as it does not impair the purpose of the method for manufacturing a microwave heating catalyst of this disclosure. For example, before heating (i.e., hydrogen reducing) at least one metal oxide selected from the compounds represented by general formula (1), it may be molded by a known method into a shape appropriate to the application of the microwave heating catalyst, or after heating (i.e., hydrogen reducing) at least one metal oxide selected from the compounds represented by general formula (1), other components appropriate to the application of the microwave heating catalyst may be mixed or supported. Thus, microwave heating catalysts with other components mixed or supported are also included in the range of microwave heating catalysts obtained by the method for manufacturing a microwave heating catalyst of this disclosure.

[0048] [Microwave heating catalyst] When a microwave heating catalyst produced by the method for producing a microwave heating catalyst according to the first embodiment of this disclosure (hereinafter sometimes referred to as the "microwave heating catalyst according to the first embodiment") is analyzed by X-ray diffraction (XRD), it is preferable that the X-ray diffraction spectrum has a peak attributed to at least one metal oxide selected from the compounds represented by the general formula (1) and a peak attributed to the metal derived from Mb in the at least one metal oxide selected from the compounds represented by the general formula (1).

[0049] The X-ray diffraction spectrum of the microwave heating catalyst according to the first embodiment has peaks attributed to at least one metal oxide selected from the compounds represented by the general formula (1), which means that the microwave heating catalyst according to the first embodiment contains at least one metal oxide selected from the compounds represented by the general formula (1). The at least one metal oxide selected from the compounds represented by the general formula (1) contained in the microwave heating catalyst according to the first embodiment is as described above. Among these, the microwave heating catalyst according to the first embodiment contains LaNiO ３ It is preferable to include it.

[0050] The content of at least one metal oxide selected from the compounds represented by the general formula (1) in the microwave heating catalyst according to the first embodiment is not particularly limited and can be appropriately selected depending on the purpose, but it is preferable that it be the main component in the microwave heating catalyst. In this disclosure, "main component" means the component that has the largest amount of substance relative to the total mass of the microwave heating catalyst.

[0051] Furthermore, the X-ray diffraction spectrum of the microwave heating catalyst according to the first embodiment having a peak attributed to the metal derived from Mb in at least one metal oxide selected from the compounds represented by general formula (1) means that the microwave heating catalyst according to the first embodiment contains the metal derived from Mb in at least one metal oxide selected from the compounds represented by general formula (1). The metal derived from Mb in at least one metal oxide selected from the compounds represented by general formula (1) is at least one metal selected from Fe, Co, Ni, Mn, Cu, and Ti. Preferably, the metal derived from Mb in at least one metal oxide selected from the compounds represented by general formula (1) is precipitated by partial hydrogen reduction of at least one metal oxide selected from the compounds represented by general formula (1), and it is preferable that the metal derived from Mb in the compound represented by general formula (1) 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 derived from Mb in the compound represented by general formula (1) is supported. 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 metal derived from Mb is Ni, and LaNiO ３ Ni is dispersed or supported on top.

[0052] In the microwave heating catalyst according to the first embodiment, there are no particular restrictions on the content of the metal derived from Mb in at least one metal oxide selected from the compounds represented by the general formula (1), and it can be appropriately selected depending on the purpose. In terms of heating stability, the microwave heating catalyst according to the first embodiment has a metal deposition amount of preferably 0.1 mmol to 3.5 mmol, more preferably 0.2 mmol to 3.2 mmol, per gram of at least one metal oxide selected from the compounds represented by the general formula (1) before reduction.

[0053] In the catalyst for microwave heating according to the first embodiment, the content of the metal derived from Mb in at least one metal oxide selected from the compounds represented by the general formula (1) is, for example, when the catalyst for microwave heating according to the first embodiment is LaNiO, which is obtained by hydrogen reduction through heating the following ３ If it is obtained by hydrogen reduction by heating, the H consumed in the hydrogen reduction ２ Among them, for LaNiO ３ Heating temperature, preferably, the H consumed during the period when the temperature of the reaction tube filled with LaNiO ３ is 430 °C or higher is determined ２ To be equal to the consumption amount (mmol). This is because when measuring LaNiO ３ by the temperature-rising reduction method using hydrogen (also referred to as "H ２ -TPR measurement"), as peaks indicating the consumption of H ２ Two peaks are observed, a peak at 300 °C to 350 °C ３ and a peak at 430 °C ２ to La ２ Ni ５ O ２ Ni ２ O ５ to Ni precipitation and La ２ O ３ It is considered to correspond to the reaction of reduction ２ Ni ２ O ５ to La ２ O ３ Reduction to La ２ The measurement of H consumption amount is performed by a thermal conductivity type (TCD) detector or a mass spectrometer. La ２ Ni ２ O ５ + 2H ２ → 2Ni + La ２ O ３ + H２ O

[0054] The microwave heating catalyst according to the first embodiment may further contain at least one metal oxide selected from the compounds represented by the general formula (1) and other components other than the metal derived from Mb in at least one metal oxide selected from the compounds represented by the general formula (1). There are no particular restrictions on the other components in the microwave heating catalyst according to the first embodiment, and examples include compounds represented by the following general formula (3), compounds represented by the following general formula (4), and the like. Further, other components corresponding to the use of the microwave heating catalyst according to the first embodiment may be contained.

[0055] - Compound represented by general formula (3)- Ma ｐ O ｑ ... General formula (3) However, in the general formula (3), Ma represents the same metal element as Ma in the general formula (1), p and q represent positive integers representing the composition ratio of Ma and O, q is the oxidation number of Ma as r, and q = pr / 2.

[0056] Since Ma in the general formula (3) represents the same metal element as Ma in the general formula (1), Ma in the general formula (3) is at least one metal element selected from alkaline earth metals and lanthanoids. For example, when at least one metal oxide selected from the compounds represented by the general formula (1) is LaNiO ３ , the compound represented by the general formula (3) is La ２ O ３

[0057] - Compound represented by general formula (4)- MaMbO ｚ ... General formula (4) However, in the general formula (4), Ma represents the same metal element as Ma in the general formula (1), Mb represents the same metal element as Mb in the general formula (1), and z represents the valence of O less than 3.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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)

[0062] There are no particular restrictions on the content of the other components in the microwave heating catalyst according to the first embodiment, and they can be appropriately selected depending on the purpose.

[0063] <Second Embodiment> The method for manufacturing a microwave heating catalyst according to the second embodiment of the present disclosure is H ２ The method includes heating a mixture containing at least one metal oxide selected from the compounds represented by the following general formula (1) and at least one metal oxide selected from the compounds represented by the following general formula (2) at a temperature of 300°C to 570°C in an atmosphere of gas containing the following. The method for producing a microwave heating catalyst according to the second embodiment of the present disclosure may further include other treatments other than heating, if necessary. 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 at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti. ｘ Oｙ ...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.

[0064] The method for manufacturing a microwave heating catalyst according to the second embodiment of this disclosure is the same as the method for manufacturing a microwave heating catalyst according to the first embodiment of this disclosure, except that the metal oxide used and the heating temperature are different in the heating process. Other processes can also be carried out in the same manner as the method for manufacturing a microwave heating catalyst according to the first embodiment of this disclosure.

[0065] <Heating> Heating is H ２ The method involves heating a mixture containing at least one metal oxide selected from the compounds represented by general formula (1) and at least one metal oxide selected from the compounds represented by general formula (2) at a temperature of 300°C to 570°C under an atmosphere of gas containing the above. By heating, at least one metal oxide selected from the compounds represented by general formula (1) is partially reduced by hydrogen, and at least one metal oxide selected from the compounds represented by general formula (2) is also reduced by hydrogen.

[0066] The heating temperature is 300°C to 570°C, but preferably 360°C to 540°C. If the heating temperature is less than 300°C, the reduction of at least one metal oxide selected from the compounds represented by general formula (1) and at least one metal oxide selected from the compounds represented by general formula (2) will not proceed, making it difficult to achieve both catalytic activity and heating stability for the microwave heating catalyst. If the temperature exceeds 570°C, the heating characteristics of the microwave heating catalyst will deteriorate.

[0067] There are no particular restrictions on the heating time, and it can be appropriately selected depending on the purpose. At least one metal oxide selected from the compounds represented by the general formula (1) is, for example, LaNiO ３ The mixture is composed of at least one metal oxide selected from the compounds represented by the general formula (2), for example, NiO, and the mixture is composed of 0.5% to 10% by volume of H ２ And, N 90% to 99.5% by volume ２ When heating in an atmosphere containing a gas, the heating time is preferably 5 minutes or more and 120 minutes or less, and more preferably 10 minutes or more and 90 minutes or less.

[0068] In terms of heating, there are no particular limitations on the method of heating a mixture containing at least one metal oxide selected from the compounds represented by general formula (1) and at least one metal oxide selected from the compounds represented by general formula (2), and a suitable method can be selected depending on the purpose. However, heating by radiant heat is preferable because it allows for stable heating at a constant temperature and prevents the at least one metal oxide selected from the compounds represented by general formula (1) from being completely reduced.

[0069] <<Mixture>> The mixture comprises at least one metal oxide selected from the compounds represented by general formula (1) and at least one metal oxide selected from the compounds represented by general formula (2), and may further contain other components as needed.

[0070] - At least one metal oxide selected from compounds represented by general formula (1) - The at least one metal oxide selected from compounds represented by general formula (1) is the same as the at least one metal oxide selected from compounds represented by general formula (1) in the method for producing a microwave heating catalyst according to the first embodiment of this disclosure.

[0071] - At least one metal oxide selected from compounds represented by general formula (2) - Since Mb in general formula (2) represents the same metal element as Mb in general formula (1), Mb in general formula (2) is at least one metal element selected from Fe, Co, Ni, Mn, Cu, and Ti. For example, at least one metal oxide selected from compounds represented by general formula (1) is LaNiO ３ In this case, the compound represented by the general formula (2) is NiO.

[0072] The aforementioned mixture may be a commercially available product or may be synthesized appropriately by known methods.

[0073] [Method for producing the mixture] As a method for synthesizing the mixture, for example, a method generally used for producing compounds having a so-called perovskite-type structure is used, in which 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 1.00. For example, the mixture can be synthesized in the same manner as the method for producing at least one metal oxide selected from the compounds represented by general formula (1) described in the method for producing a microwave heating catalyst according to the first embodiment, except that 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 1.00.

[0074] Specifically, a method is preferred in that it provides good dispersibility, in which a basic compound is added to a solution containing a compound having Ma as a constituent element in the general formula (1) and a compound having Mb as a constituent element in the general formula (1), a precipitate is obtained, and then the solution is calcined in air.

[0075] Furthermore, another method for synthesizing the mixture is to physically mix a compound containing Ma as a constituent element in general formula (1) with a compound containing Mb as a constituent element in general formula (1), and then calcine the mixture in air.

[0076] 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 depending on the purpose. However, 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 is preferably greater than 1.00 and less than or equal to 3.00, more preferably between 1.01 and 3.00, and even more preferably between 1.20 and 2.00. If the molar ratio of Mb in a compound containing Mb in the general formula (1) to Ma in a compound containing Ma in the general formula (1) is greater than 1.00 and less than or equal to 3.00, then a mixture of at least one metal oxide selected from the compounds represented by the general formula (1) and at least one metal oxide selected from the compounds represented by the general formula (2) can be suitably obtained.

[0077] [Microwave Heating Catalyst] When a microwave heating catalyst produced by the method for producing a microwave heating catalyst according to the second embodiment of this disclosure (hereinafter sometimes referred to as the "microwave heating catalyst according to the second embodiment") is analyzed by X-ray diffraction (XRD), it is preferable that the X-ray diffraction spectrum has a peak attributed to at least one metal oxide selected from the compounds represented by the general formula (1), and a peak attributed to at least one of the metals: the metal derived from Mb in the at least one metal oxide selected from the compounds represented by the general formula (1), and the metal derived from Mb in the at least one metal oxide selected from the compounds represented by the general formula (2).

[0078] The X-ray diffraction spectrum of the microwave heating catalyst according to the second embodiment has peaks attributed to at least one metal oxide selected from the compounds represented by the general formula (1), which means that the microwave heating catalyst according to the second embodiment contains at least one metal oxide selected from the compounds represented by the general formula (1). The at least one metal oxide selected from the compounds represented by the general formula (1) contained in the microwave heating catalyst according to the first embodiment is as described above. Among these, the microwave heating catalyst according to the second embodiment contains LaNiO ３ It is preferable to include it.

[0079] The X-ray diffraction spectrum of the microwave heating catalyst according to the second embodiment has peaks attributed to at least one of the metals: the metal derived from Mb in at least one metal oxide selected from the compounds represented by general formula (1), and the metal derived from Mb in at least one metal oxide selected from the compounds represented by general formula (2). This means that the microwave heating catalyst according to the second embodiment contains at least one of the metals derived from Mb in at least one metal oxide selected from the compounds represented by general formula (1), and the metal derived from Mb in at least one metal oxide selected from the compounds represented by general formula (2).

[0080] The metal derived from Mb in at least one metal oxide selected from the compounds represented by general formula (1) contained in the microwave heating catalyst according to the second embodiment is, as described above, at least one metal selected from Fe, Co, Ni, Mn, Cu, and Ti.

[0081] Preferably, the metal derived from Mb in at least one metal oxide selected from the compounds represented by the general formula (1) is precipitated by partial hydrogen reduction of at least one metal oxide selected from the compounds represented by the general formula (1), and the metal derived from Mb in the compound represented by the general formula (1) is dispersed or supported on at least one metal oxide selected from the compounds represented by the general formula (1). More preferably, the metal derived from Mb in the compound represented by the general formula (1) is supported on at least one metal oxide selected from the compounds represented by the general formula (1). Furthermore, the metal derived from Mb in at least one metal oxide selected from the compounds represented by general formula (2) is preferably deposited by partial hydrogen reduction of at least one metal oxide selected from the compounds represented by general formula (2), and the metal derived from Mb in the compound represented by general formula (2) is dispersed or supported on at least one metal oxide selected from the compounds represented by general formula (1), and more preferably the metal derived from Mb in the compound represented by general formula (2) is supported on at least one metal oxide selected from the compounds represented by general formula (1).

[0082] For example, if at least one metal oxide selected from the compounds represented by the general formula (1) is LaNiO ３ In this case, at least one of the metals derived from Mb in at least one metal oxide selected from the compounds represented by general formula (1), and at least one of the metals derived from Mb in at least one metal oxide selected from the compounds represented by general formula (2), is Ni, and LaNiO ３ Ni is dispersed or supported on top.

[0083] There are no particular restrictions on the content of the mixture in the microwave heating catalyst according to the second embodiment, and it can be appropriately selected depending on the purpose, but it is preferable that it be the main component of the microwave heating catalyst.

[0084] In the microwave heating catalyst according to the second embodiment, there are no particular restrictions on the mixed mass ratio of at least one metal oxide selected from the compounds represented by general formula (1), the metal derived from Mb in the at least one metal oxide selected from the compounds represented by general formula (1), and the metal derived from Mb in the at least one metal oxide selected from the compounds represented by general formula (2) in the mixture, and can be appropriately selected depending on the purpose.

[0085] The microwave heating catalyst according to the second embodiment may further contain other components other than at least one metal oxide selected from the compounds represented by general formula (1), and at least one metal derived from Mb in the at least one metal oxide selected from the compounds represented by general formula (1), and at least one metal derived from Mb in the at least one metal oxide selected from the compounds represented by general formula (2). There are no particular limitations on the other components in the microwave heating catalyst according to the second embodiment, and examples include at least one metal oxide selected from the compounds represented by general formula (3) and at least one metal oxide selected from the compounds represented by general formula (4), as described in the microwave heating catalyst according to the first embodiment. These may be used individually or in combination of two or more. Furthermore, the microwave heating catalyst according to the second embodiment may contain other components depending on its application.

[0086] There are no particular restrictions on the content of the other components in the microwave heating catalyst according to the second embodiment, and they can be appropriately selected depending on the purpose.

[0087] (Catalyst screening method) The catalyst screening method according to the embodiment of this disclosure involves analyzing the catalyst by X-ray diffraction, and in the X-ray diffraction spectrum obtained by the X-ray diffraction method, LaNiO ３The method includes screening catalysts having peaks attributed to and peaks attributed to Ni for use as microwave heating catalysts. The catalyst screening method according to the embodiments of this disclosure may further include, if necessary, other processes other than analysis and screening.

[0088] <Analysis Procedure> The analysis involves analyzing the catalyst using X-ray diffraction. The analysis will be carried out under the following conditions: [Analysis Conditions] ・Equipment: Ultima IV (manufactured by Rigaku Corporation) ・X-ray source: Cu-Kα rays ・Scanning range: 20°≦2θ / degree≦80° ・Scanning axis: 2θ / θ

[0089] <Screening> The screening involves the X-ray diffraction spectrum obtained by the aforementioned X-ray diffraction method, which contains LaNiO ３ The objective is to screen for catalysts for microwave heating that have peaks attributed to one component and peaks attributed to Ni.

[0090] In screening, the X-ray diffraction spectrum shows LaNiO ３ As long as it has a peak attributed to and a peak attributed to Ni, LaNiO ｚ The peak La is assigned to (z < 3). ２ O ３ You may also screen for data that has peaks or other characteristics attributed to a specific group.

[0091] The catalyst screening method according to the embodiments of this disclosure can screen for microwave heating catalysts that exhibit excellent catalytic activity and heating stability in reactions under microwave heating conditions.

[0092] The embodiments of this disclosure will be described in more detail below with reference to preparation examples, examples, comparative examples, and test examples, but the embodiments are not limited to these preparation examples, examples, comparative examples, and test examples.

[0093] (Preparation example 1: LaNiO ３ Preparation of (Ni(NO)) Nickel(II) nitrate hexahydrate (Ni(NO)) ３ ) ２ 6H２ 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.

[0094] 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.

[0095] (Example 1: Production of Catalyst A) LaNiO obtained in Preparation Example 1 ３ 0.25 g of the powder was weighed out and packed 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. ２The 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 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 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 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

[0096] (Comparative Example 1: Production of Catalyst B) LaNiO obtained in Preparation Example 1 ３ 0.25 g of the powder was weighed out and packed 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 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 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 Example 1 was designated as "Catalyst B". The mass spectrometer was used under the same analytical conditions as in Example 1.

[0097] (Comparative Example 2: Production of Catalyst C) LaNiO obtained in Preparation Example 1 ３ 0.25 g of the powder was weighed out and packed 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 600°C while the gas was flowing at a flow rate of 100 mL / min. After the electric furnace reached 600°C, it was maintained at 600°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 600 °C, and heating was started. After the electric furnace reached 600 °C, it was held at 600 °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 Example 2 was designated as "Catalyst C". The mass spectrometer was used under the same analytical conditions as in Example 1.

[0098] (Test Example 1: XRD Analysis) Catalysts A to C, which are products obtained in Example 1, Comparative Example 1, and Comparative Example 2, and LaNiO obtained in Preparation Example 1. ３The following analysis was performed using X-ray diffraction (XRD) under the specified conditions. The analyzed X-ray diffraction spectrum (XRD spectrum) is shown in Figure 1. [Analysis conditions] ・Apparatus: Ultima IV (manufactured by Rigaku Corporation) ・X-ray source: Cu-Kα rays ・Scanning range: 20° ≤ 2θ / degree ≤ 80° ・Scanning axis: 2θ / θ

[0099] 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 indicated that the powder obtained in Preparation Example 1 was heated in an electric furnace. ２ and N ２ mixed gas (5% by volume H ２ / 95% N by volume ２ The XRD spectrum of catalyst A of Example 1, obtained by heating at 500°C under the flow of ) is LaNiO ３ It had both a peak attributed to LaNiO and a peak attributed to Ni. In contrast, the XRD spectrum of catalyst B in Comparative Example 1 did not have a peak attributed to Ni, and catalyst C in Comparative Example 2 had a peak attributed to LaNiO. ３ It did not have a peak that could be attributed to it.

[0100] (Preparation example 2: LaNiO ３ Preparation of a mixture of NiO and other materials) In Preparation Example 1, the amount of nickel(II) nitrate hexahydrate used was changed from 5.82 g (20.0 mmol) to 8.73 g (30.0 mmol). Otherwise, the same method as in Preparation Example 1 was used to prepare powdered LaNiO ３ A mixture of NiO was obtained.

[0101] (Example 2: Production of Catalyst D) The powdered LaNiO obtained in Preparation Example 2 ３ 0.25 g of the mixture of nitrate and NiO was weighed out and packed 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% N2 ２The 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 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 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 Example 2 was designated as "Catalyst D". The mass spectrometer was used under the same analytical conditions as in Example 1.

[0102] (Example 3: Production of Catalyst E) Powdered LaNiO obtained in Preparation Example 2 ３ 0.25 g of the mixture of nitrate and NiO was weighed out and packed 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% N2 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 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 400 °C, and heating was started. After the electric furnace reached 400 °C, it was held 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 Example 3 was designated as "Catalyst E". The mass spectrometer was used under the same analytical conditions as in Example 1.

[0103] (Comparative Example 3: Production of Catalyst F) Powdered LaNiO obtained in Preparation Example 2 ３ 0.25 g of the mixture of nitrate and NiO was weighed out and packed 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% N2 ２ The electric furnace was heated to a set temperature of 600°C while the gas was flowing at a flow rate of 100 mL / min. After the electric furnace reached 600°C, it was maintained at 600°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 600 °C, and heating was started. After the electric furnace reached 600 °C, it was held at 600 °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 Example 3 was designated as "Catalyst F". The mass spectrometer was used under the same analytical conditions as in Example 1.

[0104] (Test Example 2: XRD Analysis) Catalysts D to F, which are products obtained in Examples 2, 3, and Comparative Example 3, and LaNiO obtained in Preparation Example 2. ３ The mixture of [component name] and NiO was analyzed by X-ray diffraction (XRD) under the same analytical conditions as in Test Example 1. The analyzed X-ray diffraction spectra are shown in Figure 2.

[0105] The peaks were identified by comparing the obtained X-ray diffraction patterns with literature values. From the results in Figure 2, the XRD spectrum of the powder obtained in Preparation Example 2, before heating in the electric furnace in Example 2, is LaNiO ３ It had both a peak attributed to LaNiO and a peak attributed to NiO. This indicates that the powder obtained in Preparation Example 2 was LaNiO ３ This indicates that it is a mixture of LaNiO. Furthermore, the XRD spectra of catalyst D in Example 2 and catalyst E in Example 3 show that it is a mixture of LaNiO. ３ It had both a peak attributed to and a peak attributed to Ni. In contrast, the XRD spectrum of catalyst F in Comparative Example 3 was LaNiO ３ It did not have a peak that could be attributed to it.

[0106] (Test Example 3: Evaluation of the Hydrogen Generation Ability of Catalysts) The hydrogen generation ability of catalysts A to C and E, which were products obtained in Example 1, Comparative Example 1, Comparative Example 2, and Example 3, was evaluated by microwave heating using the following procedure. As the microwave heating device, the following microwave generator was used, which was equipped with a thermometer capable of measuring the temperature of the cavity and the reaction tube installed in the cavity and controlling the microwave irradiation. [Microwave Generator] ・Device: MR-2G-100 (manufactured by Ryowa Electronics Co., Ltd.) ・Frequency: 2.45 GHz ± 0.05 GHz ・Irradiation mode: Single mode (maximum magnetic field strength on the central axis) ・Cavity size: 10 mm diameter, 100 mm length ・Maximum input power: 100 W

[0107] The reaction tubes containing catalysts A to C and E prepared in Example 1, Comparative Example 1, Comparative Example 2, and Example 3 were used as they were. 2 mg of polyethylene (catalog No. 427772, manufactured by Sigma-Aaldric) was placed on catalysts A to C and E inside the reaction tubes, and the reaction tubes were set in a microwave generator. 100 vol% N was added from the top of the reaction tube. ２ The gas was flowed at 30 mL / min. After confirming that the mass spectrometer connected to the outlet of the reaction tube was stable, the microwave generator was set to a temperature of 70°C and heating was started. After the temperature of the reaction tube reached 70°C, and after confirming that the temperature of the reaction tube was stable, the mass spectrometer connected to the outlet of the reaction tube was used to measure H ２The detection of the corresponding m / z=2 signal is started, and after 1 minute, the reaction tube is heated to 280°C at a heating rate of 10°C / min while the mass spectrometer is used to measure H ２ The time-dependent change in the signal intensity was observed. Note that for catalyst B in Comparative Example 1 and catalyst C in Comparative Example 2, the temperature could no longer be raised as set, so the tests were terminated at 21 and 22 minutes, respectively, from the start of detection. Figure 3A shows a graph of the evaluation results of hydrogen generation capacity when catalyst A of Example 1 was used in Test Example 3. Figure 3B shows a graph of the evaluation results of hydrogen generation capacity when catalyst B of Comparative Example 1 was used in Test Example 3. Figure 3C shows a graph of the evaluation results of hydrogen generation capacity when catalyst C of Comparative Example 2 was used in Test Example 3. Figure 3D shows a graph of the evaluation results of hydrogen generation capacity when catalyst E of Example 3 was used in Test Example 3. In Figures 3A to 3D, analysis time 0 minutes is when the mass spectrometer started detecting a signal with m / z = 2.

[0108] When catalyst A from Example 1 and catalyst E from Example 3 are used, H is produced at around 210°C. ２ While the onset of H was observed, when catalyst B of Comparative Example 1 and catalyst C of Comparative Example 2 were used, H was not produced even when heated to 250°C. ２ The occurrence of [unclear] could not be confirmed. Furthermore, it was suggested that in catalyst B of Comparative Example 1, the heating rate decreased below the set value from around 100°C, and in catalyst C of Comparative Example 2, as the temperature of the reaction tube approached 250°C, the heating rate decreased below the set value, making rapid heating difficult.

[0109] 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.

[0110] This international application claims priority under Japanese Patent Application No. 2024-157060, filed on 10 September 2024, and Japanese Patent Application No. 2024-162635, filed on 19 September 2024, which are incorporated herein by reference to the entire contents of Japanese Patent Application No. 2024-157060 and Japanese Patent Application No. 2024-162635.

Claims

1. H ２ A method for producing a microwave heating catalyst, comprising heating at least one metal oxide selected from compounds represented by the following general formula (1) at 430°C to 570°C in an atmosphere of gas containing 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 at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti.

2. The method for producing a microwave heating catalyst according to claim 1, wherein the heating is performed by radiant heat.

3. The method for producing a microwave heating catalyst according to claim 1 or claim 2, wherein the X-ray diffraction spectrum of the microwave heating catalyst has a peak attributed to at least one metal oxide selected from the compounds represented by general formula (1), and a peak attributed to the metal derived from Mb in the at least one metal oxide selected from the compounds represented by general formula (1).

4. The method for producing a microwave heating catalyst according to claim 3, wherein the metal is deposited by partial hydrogen reduction of at least one metal oxide selected from the compounds represented by the general formula (1).

5. At least one metal oxide selected from the compounds represented by the general formula (1) is LaNiO ３ The method for producing a microwave heating catalyst according to any one of claims 1 to 4.

6. H ２ A method for producing a microwave heating catalyst, comprising heating a mixture containing at least one metal oxide selected from the compounds represented by the following general formula (1) and at least one metal oxide selected from the compounds represented by the following general formula (2) at a temperature of 300°C to 570°C under an atmosphere of gas containing 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 at least one metallic element selected from Fe, Co, Ni, Mn, Cu, and Ti. 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.

7. The method for producing a microwave heating catalyst according to claim 6, wherein the heating is performed by radiant heat.

8. The method for producing a microwave heating catalyst according to claim 6 or claim 7, wherein the X-ray diffraction spectrum of the microwave heating catalyst has a peak attributed to at least one metal oxide selected from the compounds represented by general formula (1), and a peak attributed to at least one metal derived from Mb in the at least one metal oxide selected from the compounds represented by general formula (1), and a peak attributed to at least one metal derived from Mb in the at least one metal oxide selected from the compounds represented by general formula (2).

9. At least one metal oxide selected from the compounds represented by the general formula (1) is LaNiO ３ The method for producing a microwave heating catalyst according to any one of claims 6 to 8, wherein at least one metal oxide selected from the compounds represented by the general formula (2) is NiO.

10. Analyzing the catalyst by X-ray diffraction method, and screening, as a catalyst for microwave heating, a catalyst having a peak attributed to LaNiO ３ and a peak attributed to Ni in the X-ray diffraction spectrum obtained by the X-ray diffraction method. A method for screening a catalyst, comprising the above steps.

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