Composite structure, method for producing a composite structure, and method for producing a compound

Abstract

To provide a novel composite structure that can enhance catalytic activity, a method for producing a composite structure and a method for producing a compound.SOLUTION: A composite structure includes: Ru particles that are metals and / or oxides of Ru with a particle size of 20 nm or less; and M particles that are metals and / or oxides of M, a different element from Ru. The composite structure has a nonwoven fabric structure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Disclosed herein are composite structures, methods for making composite structures, and methods for making compounds. [Background technology]

[0002] Previously, a composite structure has been proposed that includes a freestanding structure in which fibrous bodies composed of a first metal element, which is at least one of a noble metal, a typical metal, and a transition metal, are three-dimensionally connected, and a functional site formed on the freestanding structure and composed of a second metal element different from the first metal element (see, for example, Patent Document 1). This composite structure can provide a novel composite having a freestanding structure containing a metal element. Furthermore, a methanation catalyst has been reported in which a MOF encapsulating Ru is immobilized on the surface of silica nanofibers (see, for example, Non-Patent Document 1). A nickel (Ni)-supported catalyst has also been reported as a methanation catalyst (see, for example, Non-Patent Document 2). Furthermore, Ru-supported catalysts, in which nanosized Ru is supported, have been investigated by using a support with a large surface area, adjusting the support composition, and optimizing the Ru support method (see, for example, Non-Patent Documents 3 to 6). Furthermore, Ru nanoparticles have been investigated as a support-free catalyst (see, for example, Non-Patent Document 7). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-143442 [Non-patent literature]

[0004] [Non-Patent Document 1] Appl.Catal.B,2023,320,121972. [Non-patent document 2] Nat.Catal,2019,2,188-197 [Non-patent document 3] Energy Environ.Sci.,2009,2,315-321. [Non-patent document 4] ACSCatal.,2013,3,2449-2455. [Non-Patent Document 5] Energy,2018,43,7179-7189. [Non-patent document 6] J. Catal.,2016,333,227-237. [Non-Patent Document 7] Chem.Eng.,2019,7,11963-11969. Summary of the Invention [Problem to be solved by the invention]

[0005] One catalytic reaction is methanation, which hydrogenates a target substance such as carbon dioxide to produce methane. Patent Document 1 describes a metal nanostructured nonwoven fabric made of Ru nanoparticles, but hydrogenation techniques such as methanation have not been investigated. Furthermore, the catalyst described in Non-Patent Document 1 exhibits low catalytic performance, with a yield of 2.6 mmol / h / g-cat at 200°C. Furthermore, the catalyst described in Non-Patent Document 2 requires high temperatures of 300°C or higher (or, in some cases, high pressures of approximately 3 MPa). Furthermore, the Ru-supported catalysts described in Non-Patent Documents 3 to 6 exhibit higher catalytic performance than Ni-supported catalysts at temperatures between 150 and 300°C, but their methane production rates per unit mass are extremely low, at approximately 1.88 (mmol / h / g-cat) at 150°C, 34.5 (mmol / h / g-cat) at 200°C, and 62.7 (mmol / h / g-cat) at 300°C. In conventional Ru-supported catalysts, various efforts have been made to nanosize Ru (increase the effective area), but because a support is commonly used, the performance per unit mass of the catalyst tends to be lower due to the use of the support. Furthermore, the catalyst in Non-Patent Document 7 exhibits an activity of 32.2 (mmol / h / g-cat) at 150°C, but has the problem of using a special medium (ionic liquid) and requiring high pressure such as 125 bar.

[0006] The present disclosure has been made in consideration of such problems, and a main object of the present disclosure is to provide a novel composite structure, a method for producing a composite structure, and a method for producing a compound that can further enhance catalytic activity. [Means for solving the problem]

[0007] As a result of intensive research to achieve the above-mentioned object, the present inventors have found that when a free-standing structure containing Ru and a metal element other than Ru is formed, a novel composite structure having high hydrogenation activity, for example, methanation, can be obtained, and have thus completed the composite structure, the method for producing a composite structure, and the method for producing a compound of the present disclosure.

[0008] That is, the composite structure of the present disclosure is Ru particles that are Ru metal and / or oxide and have a particle size of 20 nm or less; The nonwoven fabric has a nonwoven structure and contains M particles, which are metals and / or oxides of element M different from Ru.

[0009] The method for manufacturing a composite structure of the present disclosure includes: A method for producing a composite structure containing Ru and an element M different from Ru, a forming step of forming a composite structure having a nonwoven fabric structure containing at least Ru particles having a particle size of 20 nm or less on the surface of a substrate having a nonwoven fabric structure by performing a vapor deposition process using a target of Ru raw material; a treatment step of immersing the composite structure in a solution containing the element M and then performing a heat treatment; It includes:

[0010] The method for preparing the compounds of the present disclosure comprises: a hydrogenation step of hydrogenating a target compound using a composite structure having a nonwoven fabric structure, the composite structure including Ru particles, which are Ru metal and / or oxide particles, each having a particle size of 20 nm or less, and M particles, which are a metal and / or oxide of M, an element different from Ru; and It includes:

[0011] Alternatively, the method for preparing the compounds of the present disclosure comprises: a hydrogenation step of hydrogenating a target compound using a composite structure having a nonwoven fabric structure and including at least Ru particles having a particle size of 20 nm or less to obtain a hydrogenated compound; It includes: [Effects of the Invention]

[0012] The present disclosure provides a novel composite structure, a method for manufacturing a composite structure, and a method for manufacturing a compound, which can further enhance catalytic activity. The reason for this effect is believed to be as follows. For example, this composite structure has a nonwoven structure in which Ru particles with a diameter of 20 nm or less form nanofibers with a width of, for example, 100 to 500 nm, and these nanofibers are overlapped. This composite structure forms a connected structure without a binder or support that coats the Ru particles and the spaces between the particles. Therefore, unlike typical supported catalysts, the active sites are not embedded in the support, and there is little overlap between Ru particles. This increases the effective area of ​​the active sites, thereby enhancing catalytic activity per unit mass. Furthermore, when the M particles function as basic sites, for example, they have the property of capturing CO2. It is believed that capturing CO2 near the Ru particles facilitates the reaction. It is also believed that metal-support interactions between the Ru and M particles enhance catalytic activity through electronic effects. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is an explanatory diagram showing an example of the outline of the configuration of a structure 20. [Figure 2] FIG. 10 is an explanatory diagram showing an example of the outline of the configuration of a structure 20B. [Figure 3] Appearance and FE-SEM image of Experimental Example 1 transferred onto a polyimide film. [Figure 4] Appearance, FE-SEM image, and HA-BSE image of Experimental Example 2 in which ZrO2 was supported. [Figure 5] FE-SEM image of Experimental Example 3, which is a Ni nonwoven fabric. [Figure 6] FE-SEM images of Ru fine powders of Experimental Examples 4 and 5. [Figure 7] FIG. 1 is an explanatory diagram showing an outline of a catalyst evaluation device. [Figure 8] FIG. 1 is a graph showing the relationship between reaction temperature and methane production rate in Experimental Examples 1 to 5. DETAILED DESCRIPTION OF THE INVENTION

[0014] [Composite structure] The composite structure of the present disclosure includes Ru particles, which are metal and / or oxides of Ru, and M particles, which are metal and / or oxides of an element M different from Ru. This composite structure has a fibrous nonwoven structure composed of Ru particles and M particles. The composite structure may have Ru particles and M particles formed on the surface of a nonwoven substrate. This composite structure is easy to handle and is preferred. Alternatively, the composite structure may have a semi-tubular structure in which Ru particles and M particles are formed on the surface of a nonwoven substrate, and then the nonwoven substrate is removed. This composite structure has a larger contact area of ​​the Ru particles, which is preferred in terms of catalytic properties. Furthermore, this composite structure may have a free-standing structure in which aggregates of nanoparticles containing Ru are connected three-dimensionally. Here, a "free-standing structure" refers to a structure that is strong enough to be handled. Furthermore, a "nonwoven structure" refers to a structure similar to the nonwoven substrate. Furthermore, a "nanoparticle" refers to a particle with a diameter of 1 nm to 20 nm. The nanoparticles may be crystalline or amorphous.

[0015] In the composite structure, the Ru particles have a particle size of 20 nm or less, preferably 10 nm or less, more preferably 8 nm or less, and may be 5 nm or less. The smaller the particle size of the Ru particles, the higher the catalytic activity at low temperatures, which is preferable. Note that this particle size refers to the maximum value of the major axis of the granular Ru present on the surface when the composite structure is observed under an electron microscope. The Ru particles may be primary particles formed by aggregation of Ru, or secondary particles formed by further aggregation of primary particles, but primary particles are more preferable.

[0016] In the composite structure, the element M is preferably a base metal, such as a Group 4 element such as Ti, Zr, or Hf, Fe, Co, Ni, Cu, or Zn, or Al, Si, or Ce. Of these, the element M is preferably one or more of Ti, Zr, Hf, and Ce. The M particles are a metal or oxide of the element M, and more preferably an oxide. The M particles are preferably, for example, zirconium oxide, titanium oxide, or cerium oxide, and more preferably zirconium oxide. The M particles have a particle size of 50 nm or less, preferably 20 nm or less, and may be 10 nm or less.

[0017] The composite structure preferably has a molar ratio M / Ru, which is the number of moles of element M relative to the number of moles of Ru, in the range of 0.01 to 0.5. This range is preferable because it allows the hydrogenation reaction of the target substance to proceed at low temperatures, such as 250°C or lower. From the perspective of reducing precious metals, a larger molar ratio M / Ru is preferable, with a value of 0.02 or higher, more preferably 0.03 or higher, and may be 0.05 or higher. Furthermore, from the perspective of improving catalytic activity, a smaller molar ratio M / Ru is preferable, with a value of 0.4 or lower, more preferably 0.3 or lower, and may be 0.2 or lower. The molar ratio M / Ru is determined by emission spectroscopy.

[0018] The composite structure may have a nonwoven fabric structure in which nanofibers, each having a width perpendicular to the longitudinal direction of the included fibrous bodies, are connected. The fibrous bodies included in the nonwoven fabric structure are formed by containing Ru and element M. The average diameter of the fibrous bodies is, for example, preferably 100 nm or more, more preferably 150 nm or more, and may be, for example, 200 nm or more. The average diameter of the fibrous bodies is, for example, preferably 500 nm or less, more preferably 400 nm or less, and may be, for example, 200 nm or less. In this case, the diameter of the substrate (see diameter d in FIG. 1), i.e., the average diameter of the substrate fibers, is, for example, preferably 50 nm or more, more preferably 100 nm or more, and may be, for example, 200 nm or more. Furthermore, when the substrate is removed, the average diameter of the substrate space formed by the substrate is, for example, preferably 250 nm or less, more preferably 200 nm or less, and may be, for example, 100 nm or less. The average diameter of the substrate fiber is the main factor determining the average diameter of the fibrous body on which Ru or oxide M is formed; a thinner diameter increases the surface area of ​​the nonwoven fabric structure. When the cross section of the fibrous body is partially missing, such as a crescent shape, the diameter of the fibrous body refers to the diameter of a pseudo-circle that includes the missing portion (see diameter D in Figure 2). This average diameter is determined by observing a predetermined field of view (e.g., five fields of view) with an SEM, determining the diameter of each fiber, and averaging these values.

[0019] FIG. 1 is an explanatory diagram showing an example of the schematic configuration of a composite structure 20. This composite structure 20 has a free-standing structure in which fibrous bodies 21 are connected three-dimensionally. This fibrous body 21 contains a fibrous base material 22 that forms a nonwoven fabric structure therein. The fibrous body 21 is composed of an aggregate of Ru particles 24 that contain Ru. Further, when the fibrous body 21 is enlarged, M particles 25 containing base metal element M and having a diameter of 1 nm or more and 50 nm or less are present on the surface. A composite structure 20 having such a structure is flexible, easy to handle, and has a large surface area, which can further enhance the catalytic activity of the Ru particles.

[0020] FIG. 2 is an explanatory diagram showing an example of the schematic configuration of another composite structure 20B. Similar to the composite structure 20, this composite structure 20B has a free-standing structure in which fibrous bodies 21 are three-dimensionally connected. The fibrous body 21 has a substrate space 22B formed therein after the fibers of the substrate 22 have been removed. The fibrous body 21 is composed of an aggregate of Ru particles 24 containing Ru. Further, when the fibrous body 21 is enlarged, M particles 25 containing a base metal element M and having a diameter of 1 nm or more and 50 nm or less are present on the surface. The composite structure 20B has a similar structure to the composite structure 20, except that the substrate space 22B is formed in the center of the fibrous body 21. The composite structure 20B having such a structure is flexible, easy to handle, and has a large surface area, which can further enhance the catalytic activity of the Ru particles 24.

[0021] [Catalyst System] The composite structure of the present disclosure may be used, for example, as a catalyst for hydrogenating a target compound. This composite structure may be used in a catalyst system including a storage section that stores the target compound and hydrogen gas, and a fixing section that fixes the composite structure disposed in the storage section and hydrogenates the target compound. The target compound may be, for example, a compound that can be hydrogenated to produce a useful compound, such as CO. Alternatively, the target compound may be one that can be converted into a desired compound by a hydrogenation reaction, such as converting a cyclic aliphatic compound (e.g., cyclohexane) from a cyclic aromatic compound (e.g., benzene), converting an aliphatic compound (e.g., ethane) from an olefin (e.g., ethylene), converting an olefin (e.g., ethylene) from an acetylene compound (e.g., acetylene), converting an alcohol (e.g., benzyl alcohol or 1-phenylethanol) from an aldehyde (e.g., benzaldehyde) or a ketone (e.g., acetophenone), converting an amine (e.g., benzylamine) from a nitrile (e.g., benzonitrile), converting an alcohol (e.g., benzyl alcohol) from a carboxylic acid (e.g., benzoic acid), or converting an amine compound (e.g., N,N-dimethylhydrazine) from a nitro or nitroso compound (e.g., N,N-dimethylnitrosamine). The gas used in the hydrogenation may be hydrogen. The compounding ratio and concentration of the target compound and hydrogen gas can be appropriately set within a desired range. The hydrogenation reaction temperature of the catalyst system may be, for example, in the range of 150°C to 300°C, or in the range of 200°C to 250°C. The heat-resistant temperature range of the composite structure, for example, 250°C or less, may be used as the hydrogenation reaction temperature. The composite structure of the present disclosure is suitable for low-temperature CO2 hydrogenation reactions. In this catalyst system, the hydrogenation reaction rate per unit mass of the catalyst (mmol / h / g-cat) is preferably higher, for example, preferably 5 or more, preferably 10 or more, more preferably 20 or more, and may even be 50 or more. This reaction rate may also be 10,000 or less.

[0022] [Method of manufacturing the compound] The present disclosure may also be directed to a method for producing a compound, for example, by hydrogenating a target compound to obtain a hydrogenated compound. This method includes a hydrogenation step in which a target compound is hydrogenated using a composite structure having a nonwoven structure, including Ru particles, which are metal and / or oxide of Ru and have a particle size of 20 nm or less, and M particles, which are metal and / or oxide of M, an element other than Ru. This compound production method uses the above-described composite structure as a catalyst. In this compound production method, preferably, methane is obtained by a methanation reaction in which CO2, the target compound, is hydrogenated using the above-described composite structure. The gas used for hydrogenation may be hydrogen. The compounding ratio and concentration of the target compound and hydrogen gas can be set within a desired range. Furthermore, the hydrogenation reaction temperature in this production method may be, for example, in the range of 150°C to 300°C, or in the range of 200°C to 250°C. The composite structure of the present disclosure is suitable for low-temperature CO2 hydrogenation reactions. In this catalyst system, the hydrogenation reaction rate per unit mass of the catalyst (mmol / h / g-cat) is preferably higher, for example, preferably 5 or more, more preferably 10 or more, more preferably 20 or more, and may be 50 or more. In addition, this reaction rate may be 10,000 or less.

[0023] Alternatively, the method for producing a compound may include a hydrogenation step of hydrogenating a target compound using a composite structure having a nonwoven fabric structure and including at least Ru particles having a particle size of 20 nm or less, to obtain a hydrogenated compound. Even if the composite structure does not include M particles, higher hydrogenation activity can be obtained.

[0024] [Manufacturing method for composite structures] The manufacturing method of the composite structure of the present disclosure is a method for manufacturing the composite structure described above. This manufacturing method may include a forming step, a processing step, and, if necessary, a removing step. In addition, in this manufacturing method, the processing step may be omitted as the case may be, and a composite structure made of Ru particles that does not contain the element M may be manufactured.

[0025] [Formation process] In the formation process, a composite structure having a nonwoven fabric structure containing at least Ru particles is formed. In this formation process, a deposition process is performed using a Ru raw material target to form Ru particles on the surface of a substrate having a nonwoven fabric structure. The Ru particles have a particle size of 20 nm or less and include Ru metal and / or oxide particles. In this process, the Ru formation method is not particularly limited, but physical vapor deposition may be used. Examples of physical vapor deposition methods include sputtering and pulsed laser deposition (PLD). Physical vapor deposition of Ru on the substrate surface may be performed from both sides of the substrate, but is preferably performed from one side. For example, when a polymer nanowire nonwoven fabric is used as the substrate, physical vapor deposition from only one side of the nanowire nonwoven fabric results in a nonwoven fabric structure composed of semi-tubular nanowires. Semi-tubular nanowires have a larger specific surface area than tubular or rod-shaped nanowires. Therefore, when used as an oxidation catalyst in a catalytic system, for example, the catalytic activity of Ru can be further enhanced. Furthermore, semi-tubular nanowires are preferable because they facilitate the removal of the substrate. The atmosphere during the deposition process may be one in which an oxidizing gas is present or an inert gas, but an inert gas is preferred. Examples of the inert gas include nitrogen gas and rare gas, and among these, Ar gas is preferred.

[0026] The substrate used in this process is preferably a polymer. When a polymer is used as the substrate, nanoparticle nucleation and particle growth proceed relatively easily on the substrate surface during the formation of the composite structure. Furthermore, a polymer substrate is preferred because it is easily removable. Examples of polymers include solvent-soluble resins. The composition of the polymer used for the substrate is not particularly limited, but examples include polyethylene (PE), polypropylene (PP), and polyvinylpyrrolidone (PVP). Furthermore, to facilitate substrate removal, a solvent-soluble polymer is preferred. Examples of solvent-soluble polymers include polyethersulfone (PES), polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), polyethylene (PE), polypropylene (PP), polyester, polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyethylene oxide (PEO), polyacrylate, and polypropylene oxide. The structure of the substrate is not particularly limited, and an optimal structure can be selected depending on the purpose. The composite structure of the present disclosure has a structure in which the surface shape of the substrate is transferred. Therefore, using a polymer with a nano-sized structure as the substrate allows the production of a free-standing membrane with a nano-sized structure. Examples of the substrate include nanowire nonwoven fabrics produced by electrospinning. The polymer nonwoven fabric used as the substrate can be produced by electrospinning. The fiber diameter of this substrate nonwoven fabric can be within the range of the diameter of the substrate space described above. The fiber diameter of the substrate nonwoven fabric can be adjusted, for example, by the polymer concentration of the solution used in electrospinning, the electric field, the solution supply rate, etc. The average diameter of the fibrous body used as the substrate is preferably 50 nm or more, more preferably 100 nm or more, and may be 200 nm or more. The average diameter of the fibrous body is preferably 500 nm or less, more preferably 300 nm or less, and may be 100 nm or less. An average diameter in the range of 50 nm to 300 nm is preferred because it further promotes the catalytic reaction.

[0027] [Processing process] In the treatment step, the composite structure is immersed in a solution containing element M, followed by heat treatment. In this step, element M can be impregnated into a composite structure made of Ru. The concentration of element M in the solution containing element M can be appropriately set depending on the desired properties. Examples of element M include Group 4 elements such as Ti, Zr, and Hf, Fe, Co, Ni, Cu, and Zn, and Al, Si, and Ce. Among these, element M is preferably one or more of Ti, Zr, Hf, and Ce. The solvent for the solution may be water or an organic solvent, but water is preferred. The heat treatment may be performed, for example, in an oxidizing atmosphere or an inert atmosphere, but is preferably performed in an oxidizing atmosphere. When performed in an oxidizing atmosphere, M particles, an oxide of element M, are obtained. The heat treatment temperature is preferably in the range of 150°C to 600°C, and more preferably in the range of 250°C to 450°C. Within this range, the M particles are oxidized while maintaining the nonwoven structure. The heat treatment time may be set appropriately depending on the properties of the composite structure, and may be, for example, in the range of 5 minutes to 1 hour, more preferably 10 minutes to 30 minutes.

[0028] [Removal process] The removal step is, for example, a process for removing all or part of the substrate after the formation step and before the treatment step. In this case, a removable substrate is used in the formation step. In this step, the substrate may be removed entirely or partially. To reduce the amount of substrate / nanoparticle interface, it is preferable to remove the entire substrate. The method for removing the substrate is not particularly limited, and an optimal method can be selected depending on the type of substrate. For example, when a solvent-soluble polymer is used as the substrate, it is preferable to remove the substrate using a solvent. Examples of solvents that can dissolve various polymers include dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), NaBH4 solution (solvent: a 1:1 mixture of water and ethanol), chloroform, acetone, alcohols such as methanol and ethanol, water, 2-methyltetrahydrofuran, dioxane, dimethyl sulfoxide, sulfolane, and nitromethane.

[0029] As described above in detail, the present disclosure provides a novel composite structure, a method for manufacturing a composite structure, and a method for manufacturing a compound, which can further enhance catalytic activity. The reason for this effect is presumed to be as follows. For example, this composite structure has a nonwoven structure in which Ru particles with a diameter of 20 nm or less form nanofibers with a width of, for example, 100 to 500 nm, and these nanofibers overlap. This composite structure forms a connected structure without a binder or support that covers the Ru particles and the spaces between them. Therefore, unlike typical supported catalysts, the active sites are not embedded in the support, and there is little overlap between Ru particles. This increases the effective area of ​​the active sites, thereby enhancing catalytic activity per unit mass. Furthermore, when M particles function as basic sites, such as oxides of Group 4 elements, they have the property of capturing CO2. It is presumed that capturing CO2 near the Ru particles facilitates the reaction. It is also presumed that metal-support interactions between the Ru and M particles enhance catalytic activity through electronic effects.

[0030] It goes without saying that the present disclosure is not limited to the above-described embodiments, and can be embodied in various forms as long as they fall within the technical scope of the present disclosure.

[0031] The present disclosure may be any of the following [1] to

[10] . [1] Ru particles, which are Ru metal and / or oxide particles having a particle size of 20 nm or less; and M particles, which are metals and / or oxides of element M different from Ru. [2] The composite structure described in [1], wherein the Ru particles and M particles have a nonwoven structure formed on the surface of a nonwoven fabric substrate, or a semi-tubular nonwoven fabric structure from which the nonwoven fabric substrate has been removed. [3] The composite structure according to [1] or [2], wherein the molar ratio M / Ru is in the range of 0.01 to 0.5. [4] The composite structure according to any one of [1] to [3], wherein the element M is one or more Group 4 elements. [5] The composite structure according to any one of [1] to [4], which is used as a catalyst for hydrogenating the target compound. [6] A method for producing a composite structure containing Ru and an element M other than Ru, a forming step of forming a composite structure having a nonwoven fabric structure containing at least Ru particles having a particle size of 20 nm or less on the surface of a substrate having a nonwoven fabric structure by performing a vapor deposition process using a target of Ru raw material; a treatment step of immersing the composite structure in a solution containing the element M and then performing a heat treatment; A method for manufacturing a composite structure comprising: [7] In the forming step, a removable substrate is used, The method for producing a composite structure according to [6], further comprising a removing step of removing the substrate after the forming step and before the treating step. [8] a hydrogenation step of hydrogenating a target compound using a composite structure having a nonwoven structure containing Ru particles, which are metal and / or oxide of Ru and have a particle size of 20 nm or less, and M particles, which are metal and / or oxide of M, an element different from Ru; A method for producing a compound comprising: [9] a hydrogenation step of hydrogenating a target compound using a composite structure having a nonwoven fabric structure and containing at least Ru particles having a particle size of 20 nm or less to obtain a hydrogenated compound; A method for producing a compound comprising:

[10] The method for producing a compound according to [8] or [9], wherein the hydrogenation step involves hydrogenating the target compound at a temperature of 250°C or less. [Example]

[0032] Specific examples of fabricating self-supporting composite structures will be described below as experimental examples. Experimental Examples 1 and 2 correspond to examples of the present disclosure, and Experimental Examples 3 to 5 correspond to comparative examples.

[0033] <Reagents> The polyvinylpyrrolidone (PVP) used for electrospinning was manufactured by Sigma-Aldrich and had an average molecular weight of 1,300,000. Methanol was manufactured by Fujifilm Wako Pure Chemical Industries. The polyimide film was manufactured by AS ONE. The target metals used for sputter deposition, Ru (diameter 63 mm x thickness 1 mm) and Ni (diameter 25 mm x thickness 1 mm), were manufactured by Toshima Manufacturing Co., Ltd. RuO2 fine powder (product number: 238058) was manufactured by Sigma-Aldrich, and Ru fine powder (product number: 384111) was manufactured by Nilaco.

[0034] <Structural analysis> Scanning electron microscope (SEM) observations and energy dispersive X-ray spectroscopy (EDX) were performed using an ultra-high-resolution field emission scanning electron microscope (S-5500, Hitachi) at an accelerating voltage of 10 kV. Secondary electron (SE) images and high-angle (HA) backscattered electron (BSE) images were also observed at a low accelerating voltage of 1.5 kV to obtain compositional information on the sample surface. X-ray photoelectron spectroscopy (XPS) measurements were performed using an XPS measurement system (ULVAC-PHI Quantera SXM) with an AlKα X-ray source. Inductively coupled plasma optical emission spectroscopy (ICP-OES) measurements were performed using an inductively coupled plasma optical emission spectroscopy (ICP-OES, Hitachi High-Tech Science PS3520UVDDII II).

[0035] <Experimental Example 1: Synthesis of Ru nonwoven fabric> PVP fiber nonwoven fabric was produced on a Cu substrate (diameter 50 mm) by electrospinning. A methanol solution containing 8% PVP by mass was used for electrospinning. The applied voltage was 1 kV / cm, the liquid delivery rate was 1 mL / h, and the total liquid delivery volume was 0.4 mL. The distance from the syringe needle to the Cu substrate was 15 cm. A commercially available small DC magnetron sputtering device (MC1000, manufactured by Hitachi) was used for sputter deposition of Ru. The sputtering target (Ru, diameter 63 mm x thickness 1 mm), the distance between the PVP nanofiber nonwoven fabric and the target was 30 mm, the current value was 40 mA, the sputtering gas was pure argon gas, and the vacuum level during sputtering was set to 7 Pa, resulting in a deposition amount of 180 μg / cm. 2 The film thickness was adjusted using a quartz crystal oscillator so that the thickness was 1 cm square. After sputter deposition, a die cutter was used to punch out 1 cm squares at locations concentric with the quartz crystal oscillator. The resulting Ru / PVP nonwoven fabric was dropped into water in a container to remove the PVP. The Ru / PVP nonwoven fabric was washed in water to obtain a PVP-free Ru nonwoven fabric. After washing the Ru nonwoven fabric with ethanol, it was transferred back into the water in the container. The Ru nonwoven fabric that floated to the water surface was scooped up with a Ti mesh (wire diameter 0.10 mm × 3 cm × 5 cm), and the side not touching the mesh was transferred to a polyimide film (Kapton: registered trademark, 2 cm square × 0.50 mm thick) so that it was attached. The fabric was then dried in a 70°C incubator for 5 minutes and then heat-treated in air at 300°C for 10 minutes to obtain the Ru nonwoven fabric of Experimental Example 1. Figure 3 shows the appearance (Fig. 3A) and FE-SEM images (Figs. 3B-D) of Experimental Example 1 transferred to a polyimide film. Electron microscope images (FE-SEM images) confirmed that the obtained Ru nonwoven fabric of Experimental Example 1 had a fibrous structure in which Ru particles with a diameter of 20 nm or less were connected.

[0036] <Experimental Example 2: Synthesis of Zr / Ru nonwoven fabric> A 2.5 mL portion of 150 mM ZrO(NO) solution was weighed into a container, and the Ru nonwoven fabric transferred to the polyimide film obtained in Experimental Example 1 was immersed in the solution and allowed to stand at 25°C for 20 hours. The sample was then removed and immersed in 3 mL of water in a container and allowed to stand at 25°C for 1 minute. The sample was removed, excess water was removed using an air blower, and the fabric was dried in a 70°C incubator for 5 minutes. It was then heat-treated in air at 300°C for 10 minutes to obtain the Zr / Ru nonwoven fabric of Experimental Example 2. Figure 4 shows the appearance (Fig. 4A), FE-SEM images (Figs. 4B-D), and HA-BSE images (Figs. 4E-F) of the ZrO-loaded Zr / Ru nonwoven fabric of Experimental Example 2. FE-SEM images confirmed that the fibrous structure of interconnected Ru particles was maintained in the obtained Zr / Ru nonwoven fabric of Experimental Example 2. Observation of the HA-BSE image confirmed the presence of ZrO2 particles, as shown in Figure 4F. Bright particles, distinct from the overall contrast of the sample, were observed scattered on the surface. Generally, the larger the atomic number, the greater the amount of secondary electrons emitted, resulting in a brighter image. Therefore, it was assumed that the particles in the bright field were Ru and the particles in the dark field were Zr. Furthermore, elemental analysis of Experimental Example 2 revealed that the molar ratio of Zr / Ru between each element was 0.13–0.15 using EDX and XPS, which have high sensitivity for detecting surface composition, and the molar ratio of Zr / Ru was 0.098 using ICP.

[0037] <Experimental Example 3: Synthesis of Ni nonwoven fabric> PVP fiber nonwoven fabric was produced on a Ti substrate (50 mm square) by electrospinning. Electrospinning was performed using a methanol solution containing 8% by mass of PVP. The applied voltage was 1 kV / cm, the liquid delivery rate was 1 mL / h, and the total liquid delivery volume was 0.4 mL. The distance from the syringe needle to the Ti substrate was 15 cm. Ni sputter deposition was performed at a base pressure of 1 × 10 -6 A magnetron RF sputtering system in a vacuum chamber of 10 Torr was used. The obtained PVP nonwoven fabric was set in the vacuum chamber of the sputtering system and 2 × 10 -2 After evacuating the chamber to a vacuum of 10.0 Pa or less, Ar (flow rate: 30 sccm) was introduced. The pressure inside the chamber was adjusted to 10.0 Pa, and Ni was evaporated (2424 seconds) at an output power of 75 W, resulting in a deposition amount of 200 μg / cm 2The film thickness was adjusted using a quartz crystal oscillator so that the thickness was 1 cm square. After sputter deposition, a die cutter was used to punch out a 1 cm square at a location concentric with the quartz crystal oscillator. Subsequent operations were performed in the same manner as in Example 1, and the film was transferred to a polyimide film (Kapton: registered trademark, 2 cm square x 0.50 mm thick). The film was then dried in a thermostatic oven at 70°C for 5 minutes and then heat-treated in air at 300°C for 10 minutes to obtain the Ni nonwoven fabric of Experimental Example 3. Figure 5 shows FE-SEM images (Figures 5A-C) of the Ni nonwoven fabric of Experimental Example 3. The FE-SEM images confirmed that the obtained Ni nonwoven fabric of Experimental Example 3 had a structure in which Ni particles with a diameter of 20 nm or less were connected.

[0038] <Experimental Example 4: Ru Fine Powder A> Commercially available RuO2 fine powder (Sigma-Aldrich, product number 238058) was reduced under a hydrogen atmosphere (100 kPa) at 300°C for 2 hours to obtain Ru fine powder. Measurements were performed using an X-ray diffraction analyzer (XRD: Rigaku RINT-TTR), and the results confirmed that the nonwoven fabric structure was Ru.

[0039] <Experimental Example 5: Ru Fine Powder B> Commercially available Ru fine powder (Nilaco, product number: 384111) was used as is. Figure 6 shows FE-SEM images of Ru fine powder A (Figure 6A) from Experimental Example 4 and Ru fine powder B (Figure 6B) from Experimental Example 5. As shown in Figure 6A, the FE-SEM image confirmed that the size of the Ru particles in Experimental Example 4 was 30 to 40 nm. Furthermore, as shown in Figure 6B, the FE-SEM image confirmed that the size of the Ru particles in Experimental Example 5 was 1 μm or more.

[0040] (Catalyst evaluation) The experiment was carried out using a differential reactor equipped with an in-line quadrupole mass spectrometer (QMS: Pfeiffer Vacuum PRISMAPRO). Figure 7 is an explanatory diagram showing an outline of the catalyst evaluation device, with Figure 7A being a general photograph, Figure 7B being a sample holder, and Figure 7C being a photograph of the sample. A nonwoven fabric catalyst transferred to a polyimide film or Ru fine powder prepared in a container made of a Ti plate was placed on the ceramic heater inside the differential reactor. After reducing the pressure inside the reactor to 180 Pa, H2 (4 sccm), CO2 (1 sccm), and Ar (70 sccm) were introduced so that the pressure inside the reactor became 106 kPa. The pressure flowing into the QMS was adjusted to 5.0 × 10 -4 The temperature was adjusted to 0.2 Pa, and the current derived from methane (m / z = 15) was monitored. The reaction was carried out from near room temperature to 300°C, with a temperature increase rate of 5°C / min. At a given flow rate, the amount of methane produced per unit time (methane production rate) was calculated by comparing the current derived from the methane generated in the reaction with the current determined from a mixed gas with a known methane concentration. The methane production rate was divided by the amount of metal (amount of catalyst) used to determine the methane production rate per unit weight of catalyst (mmol / h / g-cat).

[0041] (Reaction results and discussion) Figure 8 shows the relationship between reaction temperature and methane production rate. Table 1 summarizes the structure and methane production rate for each experimental example. For the Ru nonwoven fabric of Experimental Example 1, methane production was confirmed around 100°C, and the methane production rate increased as the reaction temperature increased. The activity was 2.3 mmol / h / g-cat at 100°C, 62.8 mmol / h / g-cat at 160°C, 1158 mmol / h / g-cat at 250°C, and 2038 mmol / h / g-cat at 300°C. On the other hand, the Ni nonwoven fabric of Experimental Example 3 exhibited an activity of 0.53 mmol / h / g-cat at 100°C, 2.4 mmol / h / g-cat at 160°C, 26.0 mmol / h / g-cat at 250°C, and 91.6 mmol / h / g-cat at 300°C. These results demonstrate that the Ru nonwoven fabric exhibits higher catalytic activity than the Ni nonwoven fabric. Furthermore, Ru fine powder A of Experimental Example 4, which had a small particle size, exhibited activities of 0.55 at 100°C, 41.7 at 160°C, 230.7 at 250°C, and 231.8 mmol / h / g-cat at 300°C, and its performance was lower than that of the Ru nonwoven fabric. On the other hand, Ru fine powder B of Experimental Example 5, which had a large particle size, exhibited activities of 0.017 at 100°C, 0.27 at 160°C, 5.1 at 250°C, and 8.8 mmol / h / g-cat at 300°C, and its performance was even lower than that of Ru fine powder A of Experimental Example 4. Thus, it was found that the methane production rate differs depending on the Ru particle size, and that the particle size of the Ru nonwoven fabric obtained in this disclosure is important.

[0042] On the other hand, with the ZrO2 / Ru nonwoven fabric in Experimental Example 2, methane production was confirmed around 100°C, and the methane production rate increased as the reaction temperature increased. The activity was 5.9 at 100°C, 145.1 at 160°C, 1783 at 250°C, and 2589 mmol / h / g-cat at 300°C. This indicates that the ZrO2 / Ru nonwoven fabric exhibits a higher methane production rate than the Ru nonwoven fabric, and that the support of ZrO2 improves catalytic performance. It is also believed that similar effects can be obtained with metal species other than Zr, such as Group 4 elements such as Ti and Hf.

[0043] Experimental Example 1, and particularly Experimental Example 2, demonstrated that hydrogenation activity could be further enhanced. The reason for this effect is believed to be as follows. For example, this composite structure has a nonwoven structure in which Ru particles with a diameter of 20 nm or less form nanofibers with a width of 100 to 500 nm and these nanofibers are overlapped. This composite structure forms a connected structure without a binder or support that covers the Ru particles and the spaces between them. Therefore, unlike typical supported catalysts, the active sites are not embedded in the support, and there is little overlap between Ru particles. This leads to a large effective area of ​​the active sites, which is believed to enhance catalytic activity per unit mass. Furthermore, zirconium oxide particles act as basic sites and have the property of capturing CO2. It is believed that the capture of CO2 near the Ru particles facilitates the reaction. It is also believed that metal-support interactions occur between the Ru particles and zirconium oxide particles, improving hydrogenation activity through electronic effects. It is also believed that a molar ratio of Zr / Ru ranging from 0.01 to 0.5 is preferable.

[0044] [Table 1]

[0045] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above embodiments, and various modifications are possible within the scope of the gist of the present disclosure. [Industrial Applicability]

[0046] The structures and methods for making the structures of the present disclosure can be used in the field of catalysis. [Explanation of symbols]

[0047] 20,20B Structure, 21 Fiber body, 22 Substrate, 22B Substrate space, 24 Ru particles, 25 M particles.

Claims

1. Ru particles which are Ru metal and / or oxide and have a particle size of 20 nm or less; M particles, which are metals and / or oxides of an element M other than Ru, and have a nonwoven structure; The molar ratio M / Ru is in the range of 0.01 or more and 0.5 or less, The element M is one or more Group 4 elements, A nonwoven fabric structure made of the Ru; M particles containing element M supported on the nonwoven fabric structure.

2. The composite structure according to claim 1 , wherein the Ru particles and M particles have a nonwoven structure formed on the surface of a nonwoven substrate, or a semi-tubular nonwoven structure from which the nonwoven substrate has been removed.

3. The composite structure according to claim 1 or 2, wherein the M particles are Zr metal or oxide.

4. 3. The composite structure according to claim 1, which is used as a catalyst for hydrogenating a target compound.

5. 3. The method for producing a composite structure according to claim 1 or 2, which contains Ru and an element M different from Ru, a forming step of forming a composite structure having a nonwoven fabric structure containing at least Ru particles having a particle size of 20 nm or less on the surface of a substrate having a nonwoven fabric structure by performing a vapor deposition process using a target of Ru raw material; a treatment step of immersing the composite structure in a solution containing the element M and then performing a heat treatment; A method for manufacturing a composite structure comprising:

6. In the forming step, a removable substrate is used, The method for producing a composite structure according to claim 5 , further comprising a removing step of removing the substrate after the forming step and before the treating step.

7. A hydrogenation step in which a target compound is hydrogenated using the composite structure according to claim 1 or 2 to obtain a hydrogenated compound; A method for producing a compound comprising:

8. The method for producing a compound according to claim 7 , wherein the target compound is hydrogenated in the hydrogenation step at a temperature range of 250° C. or less.

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