Catalyst structure and method for producing catalyst structure

Abstract

To provide a catalyst structure having a large specific surface area, and comprising catalytic active sites in high density, as well as a method for producing the same.SOLUTION: Provided is a catalyst structure used for a reforming reaction to modify a raw material, the catalyst structure comprising a plurality of catalyst particles, the catalyst particles each including: a core particle containing a first metal element and having a particulate form; and a coating containing a second metal element and partially covering the surface of the core particle. It is preferable that the first metal element is Cu, Pt, or In, and that the second metal element is Zr, Hf, Ta, Zn, Mo, or Ti.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a catalyst structure and a method for manufacturing the catalyst structure.

Background Art

[0002] In a reforming reaction for reforming a raw material to obtain a reformed product, a catalyst for enhancing the reaction efficiency is used. The catalyst has a carrier and an active substance supported thereon. As a method for enhancing the reaction efficiency of the reforming reaction, there is a method of enhancing the contact efficiency between the raw material and the catalyst active sites by increasing the specific surface area of the catalyst.

[0003] For example, Patent Document 1 discloses a zeolite catalyst used for reforming a raw material. This zeolite catalyst contains a mixture of zeolite and a compound containing an alkaline earth metal and silicon.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The zeolite catalyst described in Patent Document 1 is manufactured through a process of molding and firing a mixture of powdery zeolite and a compound. Therefore, it is impossible to control the contact state between the zeolite as the carrier and the compound as the active substance, and it is difficult to arrange the catalyst active sites at a high density.

[0006] Therefore, the realization of a catalyst structure having a large specific surface area and a high density of catalyst active sites has become an issue.

Means for Solving the Problems

[0007] The catalyst structure according to an application example of the present invention is A catalyst structure used in a reforming reaction for reforming raw materials, composed of a plurality of catalyst particles, wherein the catalyst particles include a first metal element and are core particles having a particulate shape, and include a second metal element and are a film covering a part of the surface of the core particles, and are provided with the above.

[0008] A method for manufacturing a catalyst structure according to an application example of the present invention is a method for manufacturing a catalyst structure according to an application example of the present invention, including a core particle dispersion step of dispersing a plurality of the core particles containing the first metal element on a flexible film having flexibility; a core particle pressing step of pressing the core particles to embed a part of the core particles into the flexible film; a film forming step of forming the film containing the second metal element on the flexible film in which the core particles are embedded; a detachment step of detaching the core particles having the film formed thereon from the flexible film to obtain the catalyst structure, and has the above steps.

Brief Description of Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the catalyst structure and the method for manufacturing the catalyst structure of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

[0011] 1. Catalyst Structure First, the catalyst structure according to the embodiment will be described. FIG. 1 is a cross-sectional view showing a catalyst structure 1 according to the embodiment.

[0012] The catalyst structure 1 shown in FIG. 1 is used as a catalyst in a reforming reaction for reforming a raw material. Examples of the raw material include carbon oxides such as carbon monoxide and carbon dioxide, hydrocarbons such as methane and propane, etc., but are not limited thereto. When these raw materials are brought into contact with the catalyst structure 1, the raw materials are reformed to obtain products. Examples of the products include hydrogen, hydrocarbons such as methane and propane, alcohols such as methanol and ethanol, etc., but are not limited thereto.

[0013] In the following description, for the sake of convenience of explanation, the case where carbon dioxide and hydrogen are used as raw materials and the product is methanol will be described as an example.

[0014] 1.1. Catalyst Particles The catalyst structure 1 shown in FIG. 1 is composed of a plurality of catalyst particles 2 (an aggregate of catalyst particles 2).

[0015] The catalyst particle 2 includes a core particle 3 and a coating 4. The core particle 3 contains a first metal element and is in a particulate form. The coating 4 contains a second metal element and is in contact with the core particle 3.

[0016] One of the first metal element and the second metal element is a catalyst component, and the other is a carrier. By contacting each other, they form catalytic active sites C at the interface between the core particles 3 and the coating 4. Since these catalytic active sites C are formed for each catalyst particle 2, a large number of catalytic active sites C are distributed at predetermined intervals throughout the catalyst structure 1. Also, gaps are naturally formed between the catalyst particles 2. Therefore, the catalyst structure 1 has a high contact efficiency between the raw material and the catalytic active sites C, and can enhance the efficiency of the reforming reaction of the raw material.

[0017] In addition, the catalyst structure 1 composed of an aggregate of catalyst particles 2 has a large specific surface area. Therefore, more contact opportunities between the raw material and the catalytic active sites C can be ensured, and from this perspective, the efficiency of the reforming reaction of the raw material can also be enhanced.

[0018] Furthermore, the catalyst structure 1 has high fluidity by making use of the shape of the catalyst particles 2. Therefore, it is easy to fill in a container or the like, and is easy to handle. Thus, a reforming device with catalytic active sites C densely integrated can be constructed at low cost. By using such a reforming device, a large amount of raw material can be efficiently reformed even in a space-saving manner, and products such as methanol can be manufactured in large quantities at low cost and efficiently. Also, especially when carbon dioxide is used as the raw material, it can contribute to the realization of carbon neutrality or carbon negativity.

[0019] 1.2. Core particles The core particle 3 contains a first metal element and functions as a catalyst component, for example. Examples of the first metal element include Cu, Pt, In, Zn, Ru, Sn, Au, Re, etc. Among these, the first metal element is preferably Cu, Pt, or In. By contacting these elements with a second metal element, a particularly high catalytic activity is exhibited at the catalytic active site C. When carbon dioxide and hydrogen are brought into contact with this catalytic active site C under adjusted various conditions (temperature, pressure, supply rate of raw materials, reaction time, etc.), the probability of carbon dioxide being hydrogenated increases, and the efficiency of various reforming reactions such as the production of methanol can be enhanced. Examples of the various conditions include a temperature of 300 °C or higher, a pressure of 1 to 10 MPa, a supply rate of the gas containing the raw materials of 100 mL / min or higher, and a reaction time of 5 to 8 hours, etc.

[0020] The coverage rate of the first metal element on the surface of the core particle 3 (the ratio occupied by the first metal element on the outermost surface of the core particle 3) is not particularly limited, but is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more. If the coverage rate of the first metal element is within the above range, the catalytic activity of the catalytic active site C can be further enhanced, so that the efficiency of the reforming reaction of the raw materials by the catalyst structure 1 can be further improved.

[0021] The core particle 3 may contain elements other than the first metal element, if necessary. That is, the first metal element may exist alone or as a compound or mixture with other elements. Specific examples of the single substance include metallic copper, metallic platinum, etc. Examples of the compound include oxides of the first metal element, and specific examples include indium oxide, etc. Examples of the mixture include alloys containing the first metal element.

[0022] As shown in FIG. 1, the core particle 3 is in a particulate shape. Specific examples of the shape of the core particle 3 include spherical shapes such as a perfect sphere, an ellipsoid, and an oblate spheroid, as well as polyhedrons, cylinders, prisms, cones, pyramids, rod shapes, needle shapes, etc., but may also be other unspecified irregular shapes. Also, these shapes may be mixed.

[0023] The average aspect ratio of the core particles 3 is not particularly limited, but is preferably 1.0 or more and 5.0 or less, more preferably 1.0 or more and 3.0 or less, and still more preferably 1.0 or more and 2.0 or less. When the average aspect ratio of the core particles 3 is within the above range, the catalyst structure 1 excellent in fluidity and fillability can be obtained. By using such a catalyst structure 1, a reforming apparatus containing a high density of catalyst active sites C can be constructed.

[0024] The average aspect ratio of the core particles 3 is calculated as follows. First, an image of the core particles 3 is taken with an electron microscope or an optical microscope. At this time, the imaging magnification is set so that 50 to 100 core particles 3 are captured in one image. Next, the obtained image is loaded into image processing software. Then, by image processing, 50 or more particle images are detected and the aspect ratio is calculated. Then, the average value of the calculated aspect ratios is defined as the "average aspect ratio". The aspect ratio is obtained by long diameter / short diameter when the maximum length of the particle image is taken as the long diameter and the maximum length in the direction orthogonal to the extending direction of the long diameter is taken as the short diameter.

[0025] The average particle diameter of the core particles 3 is not particularly limited, but is preferably 100 nm or less, more preferably 10 nm or more and 60 nm or less, and still more preferably 15 nm or more and 40 nm or less. If the average particle diameter of the core particles 3 is within the above range, a catalyst structure 1 having a sufficiently large specific surface area and excellent fluidity and fillability can be obtained. Thereby, a reforming apparatus containing a high density of catalyst active sites C can be realized.

[0026] In addition, when the average particle diameter of the core particles 3 is less than the lower limit value, the manufacturing difficulty of the core particles 3 may increase, or aggregation may easily occur to form secondary particles of the catalyst structure 1, resulting in a decrease in fluidity and fillability. On the other hand, when the average particle diameter of the core particles 3 exceeds the upper limit value, the specific surface area of the catalyst structure 1 may decrease.

[0027] The average particle size of the core particles 3 is the average value of the particle sizes (equivalent circle diameters) measured with 10 or more randomly extracted particle images after identifying the particle images of the core particles 3 based on differences in contrast or the like in the enlarged observation image of the surface of the catalyst structure 1.

[0028] 1.3. Coating The coating 4 covers a part of the surface of the core particles 3. As a result, in the catalyst particles 2, as shown in FIG. 1, a region (interface region) where the surface of the core particles 3 and the surface of the coating 4 are adjacent to each other is formed. As a result, when the catalyst particles 2 are filled in a container or the like, this interface region is three-dimensionally distributed at a high density, and the contact efficiency with the raw material is increased. Thereby, a catalyst structure 1 with high reforming reaction efficiency can be realized. Note that FIG. 1 is a schematic diagram, and the film formation state of the coating 4 is not limited to the state of FIG. 1. For example, in the boundary region, the thickness of the coating 4 may be configured to gradually decrease.

[0029] The coating 4 contains a second metal element and functions, for example, as a carrier on which the catalyst is supported. Examples of the second metal element include Zr, Hf, Ta, Zn, Mo, Ti, Ga, Al, Sn, etc. Among these, the second metal element is preferably Zr, Hf, Ta, Zn, Mo, or Ti. By contacting these elements with the first metal element, a particularly high catalytic activity is exhibited at the catalytic active site C. After adjusting various conditions (temperature, pressure, supply rate of raw material, reaction time, etc.), when, for example, carbon dioxide and hydrogen are brought into contact with this catalytic active site C, the probability of hydrogenating carbon dioxide increases, and the efficiency of various reforming reactions such as the production of methanol can be enhanced. Examples of the various conditions include a temperature of 300°C or higher, a pressure of 1 to 10 MPa, a supply rate of the gas containing the raw material of 100 mL / min or more, and a reaction time of 5 to 8 hours.

[0030] The film 4 may contain elements other than the second metal element, if necessary. That is, the second metal element may exist alone, or may exist as a compound or mixture with other elements. Examples of the compound include oxides of the second metal element, and specific examples include zirconium oxide, hafnium oxide, tantalum oxide, zinc oxide, molybdenum oxide, titanium oxide, etc.

[0031] Moreover, the following combinations are mentioned as preferable combinations of the first metal element and the second metal element.

[0032] · When the first metal element is Cu, the second metal element is Zr, Hf, Ta or Zn · When the first metal element is Pt, the second metal element is Mo or Ti · When the first metal element is In, the second metal element is Zr According to such combinations, the catalytic activity of the catalytic active site C can be particularly enhanced.

[0033] The average thickness of the film 4 is not particularly limited, but is preferably 0.5 nm or more and 30 nm or less, more preferably 1 nm or more and 20 nm or less, and even more preferably 2 nm or more and 10 nm or less. If the average thickness of the film 4 is within the above range, the efficiency of the reforming reaction will be particularly high.

[0034] In addition, when the average thickness of the film 4 is less than the lower limit value, the thickness of the film 4 may be insufficient, resulting in a decrease in the efficiency of the reforming reaction, or the coverage rate of the film 4 may not be sufficiently increased. On the other hand, when the average thickness of the film 4 exceeds the upper limit value, the thickness of the film 4 becomes excessive, and conversely, the efficiency of the reforming reaction may decrease.

[0035] The average thickness of the film 4 is the average value of the measured values obtained by measuring the thickness of the film 4 after taking an enlarged observation image of the cross-section of the film 4 for a plurality of catalyst particles 2 using a transmission electron microscope or the like.

[0036] In addition, when performing elemental analysis of the surface of the catalyst structure 1 by ion scattering spectroscopy (ISS), the abundance ratio of the second metal element to the first metal element is preferably 20 / 80 or more and 80 / 20 or less, more preferably 30 / 70 or more and 70 / 30 or less in terms of atomic ratio. According to ion scattering spectroscopy, elemental analysis can be performed on the outermost surface of the catalyst structure 1. If the abundance ratio of the second metal element to the first metal element measured by such a method is within the above range, the balance between the first metal element and the second metal element exposed on the outermost surface of the catalyst structure 1 can be particularly optimized. That is, the balance between the exposed areas of the catalyst component and the carrier can be optimized. Thereby, the efficiency of the reforming reaction can be particularly enhanced.

[0037] In addition, when the abundance ratio is below the lower limit value or above the upper limit value, the balance between the first metal element and the second metal element deteriorates, and the efficiency of the reforming reaction may decrease.

[0038] 2. Manufacturing method of catalyst structure Next, a method for manufacturing the catalyst structure according to the embodiment (a method for manufacturing the catalyst structure 1 shown in FIG. 1) will be described.

[0039] FIG. 2 is a process diagram for explaining a method for manufacturing the catalyst structure 1 shown in FIG. 1. FIGS. 3 to 8 are cross-sectional views for explaining the method for manufacturing the catalyst structure 1 shown in FIG. 2. In the following description, the upper side in FIGS. 3 to 8 is referred to as "up" and the lower side as "down", but the actual posture (orientation with respect to the vertical direction) of each part is not limited to the posture shown in the drawings.

[0040] The method for manufacturing the catalyst structure 1 shown in FIG. 2 is a method for manufacturing the catalyst structure 1 shown in FIG. 1, and includes a flexible film preparation step S102, a core particle dispersion step S104, a core particle pressurization step S106, a film formation step S108, and a detachment step S110.

[0041] 2.1. Flexible film preparation step In the flexible film preparation step S102, first, a support substrate 5 shown in FIG. 3 is prepared. The support substrate 5 preferably has a rigidity such that it does not bend under its own weight, and more preferably has a higher rigidity than the flexible film 6 described later. This makes it easier to handle the flexible film 6 compared to the case of handling the flexible film 6 alone.

[0042] Examples of the constituent material of the support substrate 5 include metal materials, ceramic materials, glass materials, silicon materials, resin materials, and the like. Among these, from the viewpoints of rigidity, heat resistance, etc., metal materials are preferably used. The metal material is not particularly limited, and examples thereof include stainless steel, aluminum alloy, titanium alloy, and the like.

[0043] The thickness of the support substrate 5 is not particularly limited, but considering rigidity, handleability, etc., it is preferably 0.5 mm or more and 4 mm or less, and more preferably 1 mm or more and 3 mm or less.

[0044] Next, a flexible film 6 is formed on the upper surface of the support substrate 5. The flexible film 6 is a film having flexibility and has the property of embedding an object having a higher hardness than the film. The method for forming the flexible film 6 is not particularly limited, and examples thereof include a method of attaching a film, a method of applying a varnish and then solidifying or curing it, and the like. Among these, the method of attaching a film is preferably used. With this method, the flexible film 6 can be easily formed with a small number of man-hours. Also, this method is suitable in that it is easy to form a flexible film 6 having relatively excellent flexibility.

[0045] Examples of the constituent material of the flexible film 6 include polyimide, polyamide, polyamideimide, liquid crystal polymer, polyetheretherketone, polyetherimide, polyphenylene sulfide, and the like.

[0046] Among these, polyimide is preferably used. Polyimide has particularly high heat resistance and excellent chemical resistance. Therefore, even when the flexible film 6 is heated in the film formation step S108 described later, thermal decomposition or significant deformation can be prevented or suppressed.

[0047] The load deflection temperature of the constituent material of the flexible film 6 is preferably a resin material of 250°C or higher, more preferably a resin material of 280°C or higher and 400°C or lower. By using a resin material having such a load deflection temperature as the constituent material of the flexible film 6, even when the flexible film 6 is heated to a higher temperature in the film forming step S108 described later, thermal decomposition or significant deformation can be prevented or suppressed.

[0048] The load deflection temperature of the constituent material of the flexible film 6 is measured according to the method specified in JIS K 7161-1:2014, and the maximum bending stress during measurement is 1.80 MPa.

[0049] The tensile elastic modulus of the constituent material of the flexible film 6 at 25°C is preferably 0.5 GPa or more and 10 GPa or less, more preferably 2 GPa or more and 8 GPa or less, and even more preferably 3 GPa or more and 6 GPa or less. If the tensile elastic modulus is within the above range, when the core particles 3 are pressed against the flexible film 6 in the core particle pressing step S106 described later, the core particles 3 can be appropriately embedded.

[0050] If the tensile elastic modulus is below the lower limit value, the flexibility of the flexible film 6 is too high, so depending on the pressing force of the core particles 3 in the core particle pressing step S106, the embedding depth of the core particles 3 may become too deep. On the other hand, if the tensile elastic modulus exceeds the upper limit value, the flexibility of the flexible film 6 is too low, so there is a possibility that the core particles 3 cannot be sufficiently embedded.

[0051] The tensile elastic modulus of the constituent material of the flexible film 6 is measured according to the method specified in JIS K 7161-1:2014.

[0052] The thickness of the flexible film 6 is not particularly limited, but is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less. By setting the thickness of the flexible film 6 within the above range, the embedding depth of the core particles 3 in the core particle pressing step S106 can be optimized.

[0053] In addition, when the thickness of the flexible film 6 is less than the lower limit value, the embedding depth of the core particles 3 may be insufficient. On the other hand, when the thickness of the flexible film 6 exceeds the upper limit value, the flexible film 6 may be easily peeled off when heated.

[0054] Further, the thickness of the flexible film 6 is preferably within the above range and is 0.05% or more and 1.0% or less of the average particle diameter of the core particles 3, and more preferably 0.10% or more and 0.50% or less. By setting the thickness of the flexible film 6 within the above range, the thickness of the flexible film 6 can be optimized with respect to the particle diameter of the core particles 3, so that while ensuring a sufficient embedding depth of the core particles 3, the probability of the flexible film 6 peeling off can be further reduced.

[0055] 2.2. Core particle dispersion step In the core particle dispersion step S104, a plurality of core particles 3 are scattered and dispersed on the flexible film 6. The method for dispersing the core particles 3 is not particularly limited and may be any method. For example, a method of spraying the core particles 3 with a spraying device, a method of preparing a dispersion liquid in which the core particles 3 are dispersed in a dispersion medium, applying this, and then removing the dispersion medium, etc. can be mentioned. By dispersing the core particles 3, as shown in FIG. 4, the core particles 3 can be arranged on the flexible film 6.

[0056] The dispersion density of the core particles 3 is not particularly limited, but is preferably set to such an extent that the core particles 3 are separated from each other.

[0057] 2.3. Core particle pressing step In the core particle pressing step S106, an operation of pressing the core particles 3 dispersed on the flexible film 6 is performed. Thereby, a part of the core particles 3 can be embedded in the flexible film 6, and it is possible to easily divide the portion where the film 4 is formed and the portion where the film 4 is not formed in the film forming step S108 described later. Further, according to the operation of pressing the core particles 3, a plurality of core particles 3 can be simultaneously embedded in the flexible film 6, which is useful from the viewpoints of workability and efficiency.

[0058] The method of pressing the core particles 3 is not particularly limited and may be any method. In FIG. 5, the press 7 is lowered so that the core particles 3 approach the flexible film 6. Thereby, a pressing force P is applied to the core particles 3.

[0059] The core particles 3 are embedded in the flexible film 6 as shown in FIG. 6 under the pressing force P. At this time, by adjusting the pressing force P, only a part of the core particles 3 is embedded as shown in FIG. 6.

[0060] Specifically, it is preferable to adjust the pressing force P so that 20% or more and 80% or less of the surface area of the core particles 3 is embedded in the flexible film 6, and it is more preferable to adjust the pressing force P so that 30% or more and 70% or less is embedded in the flexible film 6. Thereby, in the film forming step S108 described later, the balance between the exposed area of the core particles 3 and the covering area by the film 4 can be optimized. That is, catalyst particles 2 with an optimized balance between the exposed areas of the catalyst component and the carrier can be manufactured. As a result, a catalyst structure 1 with particularly enhanced reforming reaction efficiency can be obtained.

[0061] Note that when the ratio of the above area is less than the lower limit value or exceeds the upper limit value, the balance between the exposed area of the core particles 3 and the covering area by the film 4 may deteriorate.

[0062] The configuration of the press 7 is not particularly limited as long as it has a function of applying the pressing force P to the core particles 3. The press 7 may be configured to apply the pressing force P with a roller or the like, for example.

[0063] 2.4. Film Formation Process In the film formation process S108, as shown in FIG. 7, a film 4 is formed on the flexible film 6 in which the core particles 3 are embedded. As a result, the film 4 is formed on the portion of the surface of the core particles 3 that is exposed from the flexible film 6. On the other hand, the film 4 is not formed on the portion embedded in the flexible film 6.

[0064] Examples of the method for forming the film 4 include a vacuum evaporation method, a sputtering method, a CVD method, an atomic layer deposition method (ALD), etc. Among these, the atomic layer deposition method is preferably used. By performing the process of forming the film 4 by the atomic layer deposition method, a film 4 with a thin film thickness and a high coverage rate can be efficiently formed. Specifically, in the atomic layer deposition method, since the film formation amount can be controlled at the atomic layer level, the film thickness of the film 4 can be precisely controlled. Furthermore, in the atomic layer deposition method, since the raw material gas and the oxidizing agent can also penetrate into the shaded portion from the raw material gas supply source to form a film, it is easy to increase the coverage rate of the film 4. Therefore, according to the atomic layer deposition method, a catalyst structure 1 with little variation in the coverage rate of the film 4 for each catalyst particle 2 can be manufactured.

[0065] The raw material gas and the oxidizing agent used in the atomic layer deposition method are appropriately selected according to the constituent material of the film 4. For example, the raw material gas is a gas containing a precursor of the constituent material. For example, when the second metal element contained in the film 4 is Zr, zirconium oxide (ZrO 2 ) can be used as the constituent material of the film 4. In this case, examples of the precursor include Zr(O t Bu) 4 (zirconium tert-butoxide, ZTB), Zr(NEt 2 ) 4 (tetrakis(diethylamide)zirconium, TDEAZ), Zr(NMeEt) 4 (tetrakis(ethylmethylamide)zirconium, TEMAZ), Zr(NMe 2 ) 4 (tetrakis(dimethylamide)zirconium, TDMAZ), etc.

[0066] Hereinafter, an example of the formation procedure of the film 4 by the atomic layer deposition method will be described. First, a flexible film 6 in which the core particles 3 are embedded is placed in a chamber capable of evacuation and atmosphere control. Next, a raw material gas containing a precursor is introduced into the chamber and adsorbed on the core particles 3 and the flexible film 6. Next, after discharging the excess precursor, an oxidizing agent is introduced into the chamber. Examples of the oxidizing agent include ozone, plasma oxygen, water vapor, etc. The introduced oxidizing agent reacts with the precursor adsorbed on the core particles 3 and the flexible film 6, and the film 4 is formed.

[0067] The temperature in the chamber when forming the film 4 is appropriately set according to the type of the precursor, the oxidizing agent, etc., but it is preferably 100°C or higher and 350°C or lower, and more preferably 200°C or higher and 300°C or lower. Thereby, while suppressing the deterioration of the core particles 3 and the flexible film 6 due to heat, the precursor can be reacted with high precision. As a result, a film 4 having a sufficiently high content of the target constituent material and enabling a highly efficient reforming reaction can be formed.

[0068] The pressure in the chamber when forming the film 4 is preferably 100 Pa or less, more preferably 0.001 Pa or more and 10 Pa or less, and even more preferably 0.001 Pa or more and 1 Pa or less. Thereby, since the concentration of the precursor and the oxidizing agent can be optimized, the reaction efficiency of the precursor can be increased. As a result, a film 4 having a sufficiently high content of the target constituent material and enabling a highly efficient reforming reaction can be formed. Thereby, the catalyst particles 2 are obtained.

[0069] 2.5. Desorption step In the desorption step S110, a desorption treatment is performed on the catalyst particles 2 (core particles 3 on which the film 4 is formed). The desorption treatment is a treatment for detaching the catalyst particles 2 from the flexible film 6. Thereby, a plurality of the catalyst particles 2 shown in FIG. 1 can be recovered simultaneously, and the catalyst structure 1 is obtained.

[0070] As the detachment process, for example, as shown in FIG. 8, in a state where the flexible film 6 is disposed below the support substrate 5, a process of applying mechanical energy, electrical energy, thermal energy, etc. to the flexible film 6 can be mentioned. Among these, as the detachment process of applying mechanical energy, as shown in FIG. 8, a process of applying vibration B to the flexible film 6 can be mentioned. By applying vibration B, the catalyst particles 2 can be swung and easily detached from the flexible film 6.

[0071] According to the method as described above, a large number of catalyst particles 2 including the core particles 3 and the coating 4 covering only a part of the surface thereof can be manufactured at once. Thereby, the catalyst structure 1 having a large specific surface area and a high density of catalyst active sites C can be efficiently manufactured.

[0072] Note that a reduction process may be performed on the catalyst particles 2 before or after the detachment step S110. By performing the reduction process, oxides are reduced in at least one of the core particles 3 and the coating 4. Specifically, when the constituent material of the core particles 3 is a metal such as Cu, the Cu oxide contained in the core particles 3 is reduced to the Cu metal. On the other hand, unlike the present embodiment, when the constituent material of the coating 4 is a metal such as Cu, the Cu oxide contained in the coating 4 is reduced to the Cu metal. As a result, the catalytic activity at the catalyst active site C is enhanced.

[0073] Examples of the reducing agent used for the reduction process include hydrogen, carbon monoxide, methane, etc. Further, the catalyst particles 2 may be heated under reduced pressure to reduce the oxide by thermal dissociation. Among these, considering the stability, efficiency, safety, etc. of the reduction reaction, the reduction process using hydrogen is preferably used. By performing the reduction process, the catalytic activity of the catalyst active site C is enhanced. Thereby, the catalyst structure 1 with improved reforming efficiency can be obtained.

[0074] In the case of the reduction process using a reducing agent, the catalyst particles 2 are heated while introducing the reducing agent into the heating furnace.

[0075] The temperature in the heating furnace during the reduction treatment is not particularly limited, but is preferably 100°C or higher and 700°C or lower, more preferably 200°C or higher and 500°C or lower. Also, the heating time is not particularly limited, but is preferably 0.5 hours or longer and 10 hours or shorter, more preferably 1 hour or longer and 5 hours or shorter. Thereby, the catalytic activity can be enhanced efficiently.

[0076] The introduction amount of the reducing agent into the heating furnace during the reduction treatment is not particularly limited, but is preferably 10 mL / min or more and 1000 mL / min or less, more preferably 50 mL / min or more and 500 mL / min or less. By adjusting to such an optimum value, it becomes easier to efficiently enhance the catalytic activity.

[0077] 3. Effects Exhibited by the Embodiment As described above, the catalyst structure 1 according to the embodiment is a catalyst structure used in a reforming reaction for reforming a raw material, and is composed of a plurality of catalyst particles 2. The catalyst particles 2 include a core particle 3 containing a first metal element and having a particulate shape, and a coating 4 containing a second metal element and covering a part of the surface of the core particle 3.

[0078] According to such a configuration, since it is composed of a plurality of catalyst particles 2 each having a catalytic active site C formed thereon, a catalyst structure 1 having a large specific surface area and a high density of catalytic active sites C can be obtained. Further, the catalyst structure 1 has high fluidity by taking advantage of the shape of the particulate catalyst particles 2. For this reason, it is easy to fill into a container or the like and is easy to handle.

[0079] Also, the average particle diameter of the core particles 3 is preferably 5 nm or more and 100 nm or less. According to such a configuration, a catalyst structure 1 having a sufficiently large specific surface area and excellent fluidity and fillability can be obtained. Thereby, a reforming apparatus in which catalytic active sites C are contained at a high density can be realized.

[0080] Also, the average thickness of the coating 4 is preferably 0.5 nm or more and 30 nm or less. According to such a configuration, the efficiency of the reforming reaction becomes particularly high.

[0081] Further, when the first metal element is Cu, Pt, or In, the second metal element is preferably Zr, Hf, Ta, Zn, Mo, or Ti. According to such a configuration, the catalytic activity of the catalytic active site C can be particularly enhanced.

[0082] Further, when performing elemental analysis of the surface by ion scattering spectroscopy (ISS), the abundance ratio of the second metal element to the first metal element is preferably 20 / 80 or more and 80 / 20 or less in terms of atomic ratio.

[0083] According to such a configuration, the balance between the first metal element and the second metal element exposed on the outermost surface of the catalyst structure 1 can be particularly optimized. That is, the balance between the exposed areas of the catalyst component and the carrier can be optimized. Thereby, the efficiency of the reforming reaction can be particularly enhanced.

[0084] Further, the method for manufacturing the catalyst structure according to the above embodiment is a method for manufacturing the catalyst structure 1 according to the above embodiment, and includes a core particle dispersion step S104, a core particle pressurization step S106, a film formation step S108, and a detachment step S110. In the core particle dispersion step S104, a plurality of core particles 3 containing a first metal element are dispersed on a flexible film 6 having flexibility. In the core particle pressurization step S106, the core particles 3 are pressurized to embed a part of the core particles 3 into the flexible film 6. In the film formation step S108, a film 4 containing a second metal element is formed on the flexible film 6 in which the core particles 3 are embedded. In the detachment step S110, the core particles 3 on which the film 4 is formed are detached from the flexible film 6 to obtain the catalyst structure 1.

[0085] According to such a configuration, a catalyst structure 1 having a large specific surface area and a high density of catalytic active sites C can be efficiently manufactured. Further, according to the operation of pressurizing the core particles 3, a plurality of core particles 3 can be simultaneously embedded in the flexible film 6, which is useful from the viewpoints of workability and efficiency.

[0086] In addition, the core particle pressing step S106 preferably includes an operation of pressing the core particles 3 such that 20% or more and 80% or less of the surface area of the core particles 3 is embedded in the flexible film 6. According to such a configuration, in the film formation step S108, the balance between the exposed area of the core particles 3 and the coating area by the film 4 can be optimized. That is, catalyst particles 2 with an optimized balance of the exposed areas of the catalyst component and the carrier can be manufactured. As a result, the catalyst structure 1 with particularly enhanced reforming reaction efficiency can be obtained.

[0087] In addition, the constituent material of the flexible film 6 is preferably a resin material having a load deflection temperature of 250°C or higher when the maximum bending stress is 1.8 MPa.

[0088] According to such a configuration, even when the flexible film 6 is heated to a higher temperature in the film formation step S108, thermal decomposition or significant deformation can be prevented or suppressed.

[0089] In addition, the desorption step S110 preferably includes an operation of applying vibration to the flexible film 6. According to such a configuration, since the catalyst particles 2 can be oscillated, they can be easily desorbed from the flexible film 6.

[0090] In addition, the flexible film 6 is preferably supported on a support substrate 5 having higher rigidity than the flexible film 6.

[0091] According to such a configuration, the handling of the flexible film 6 becomes easier compared to the case of handling the flexible film 6 alone.

[0092] In addition, the film formation step S108 preferably includes a process of forming the film 4 by atomic layer deposition.

[0093] According to such a configuration, a film 4 with a thin film thickness and a high coverage rate can be efficiently formed. Specifically, in the atomic layer deposition method, since the film formation amount can be controlled at the atomic layer level, the film thickness of the film 4 can be precisely controlled. Furthermore, in the atomic layer deposition method, since the raw material gas and the oxidizing agent can penetrate into the shaded portions from the raw material supply source to form a film, it is easy to increase the coverage rate of the film 4. Therefore, according to the atomic layer deposition method, a catalyst structure 1 with little variation in the coverage rate of the film 4 for each catalyst particle 2 can be manufactured.

[0094] As described above, the catalyst structure and the method for manufacturing the catalyst structure of the present invention have been described based on preferred embodiments, but the present invention is not limited thereto. For example, the catalyst structure according to the present invention may be one in which each part of the above embodiment is replaced with an arbitrary component having the same function, or an arbitrary component may be added to the above embodiment.

[0095] Also, the method for manufacturing the catalyst structure of the present invention may be one in which an arbitrary target process is added to the above embodiment.

Explanation of Reference Numerals

[0096] 1... Catalyst structure, 2... Catalyst particles, 3... Core particles, 4... Film, 5... Support substrate, 6... Flexible film, 7... Press machine, B... Vibration, C... Catalytic active site, P... Pressing force, S102... Flexible film preparation process, S104... Core particle dispersion process, S106... Core particle pressurization process, S108... Film formation process, S110... Desorption process

Claims

1. A catalyst structure used in a reforming reaction for reforming a raw material, composed of a plurality of catalyst particles, wherein the catalyst particles include a first metal element and are core particles having a particulate shape, and include a second metal element and a coating that covers a part of the surface of the core particles, and the catalyst structure is characterized by comprising the above.

2. The catalyst structure according to claim 1, wherein an average particle diameter of the core particles is 5 nm or more and 100 nm or less.

3. The catalyst structure according to claim 1 or 2, wherein an average thickness of the coating is 0.5 nm or more and 30 nm or less.

4. The first metal element is Cu, Pt, or In, and the second metal element is Zr, Hf, Ta, Zn, Mo, or Ti, and the catalyst structure according to claim 1 or 2.

5. The catalyst structure according to claim 1 or 2, wherein when elemental analysis of the surface is performed by ion scattering spectroscopy (ISS), a ratio of the second metal element to the first metal element is 20 / 80 or more and 80 / 20 or less in terms of atomic number ratio.

6. A method for manufacturing the catalyst structure according to claim 1 or 2, including a core particle dispersion step of dispersing a plurality of the core particles containing the first metal element on a flexible film having flexibility; a core particle pressurization step of pressurizing the core particles to embed a part of the core particles in the flexible film; a coating formation step of forming the coating containing the second metal element on the flexible film in which the core particles are embedded; and a detachment step of detaching the core particles having the coating formed thereon from the flexible film to obtain the catalyst structure. The method for manufacturing a catalyst structure is characterized by comprising the above.

7. The method for manufacturing a catalyst structure according to claim 6, wherein the core particle pressurization step includes an operation of pressurizing the core particles such that 20% or more and 80% or less of a surface area of the core particles is embedded in the flexible film.

8. The method for manufacturing a catalyst structure according to claim 6, wherein a constituent material of the flexible film is a resin material having a load deflection temperature of 250°C or more when a maximum bending stress is 1.80 MPa.

9. The method for manufacturing a catalyst structure according to claim 6, wherein the detachment step includes an operation of applying vibration to the flexible film.

10. The method for manufacturing a catalyst structure according to claim 6, wherein the flexible film is supported on a support substrate having higher rigidity than the flexible film.

11. The method for manufacturing a catalyst structure according to claim 6, wherein the film forming step includes a process of forming the film by atomic layer deposition method.

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