Catalyst structure and method for manufacturing the catalyst structure

Abstract

To provide a catalyst structure with a large specific surface area and high catalytic activity, and a method for easily producing such a catalyst structure. [Solution] A catalyst structure used in a reforming reaction to modify a raw material, comprising a particulate catalyst structure comprising: a core particle containing a first metal element and forming particulate matter; a coating containing a second metal element and covering the surface of the core particle; and a plurality of oxide particles containing an oxide of the first metal element and adhering to the surface of the coating, wherein both the coating and the oxide particles are exposed.

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, and is in a particulate form.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] On the other hand, Patent Document 1 discloses that a zeolite catalyst is manufactured through a process of molding and firing a mixture of powdery zeolite and a compound. Therefore, the contact state between the zeolite as the carrier and the compound as the active substance cannot be controlled, and the catalyst activity cannot be sufficiently enhanced.

[0006] Therefore, the realization of a catalyst structure having a large specific surface area and high catalyst activity 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 in the form of particulate matter, used in a reforming reaction to modify raw materials. A core particle containing a first metallic element and forming particulate matter, A coating containing a second metal element and covering the surface of the core particles, A plurality of oxide particles adhering to the surface of the coating, comprising an oxide of the first metal element, Equipped with, Both the coating and the oxide particles are exposed.

[0008] The method for manufacturing a catalyst structure according to an application example of the present invention is: A method for producing a catalyst structure according to an example of the present invention, Preparation steps for preparing the core particles, A film formation step in which the coating is formed on the surface of the core particles by atomic layer deposition, and oxides of the first metal element contained in the core particles are deposited on the surface of the coating to form oxide particles, It holds. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing a catalyst structure according to an embodiment. [Figure 2] This graph shows an example of the changes in ion detection values ​​corresponding to the amount of methanol produced when a reforming reaction is carried out to produce methanol from carbon dioxide and hydrogen using two types of catalyst structures with different average coating thicknesses. [Figure 3] This is a process diagram illustrating the method for manufacturing the catalyst structure shown in Figure 1. [Figure 4] Figure 3 is a cross-sectional view illustrating the manufacturing method of the catalyst structure shown. [Figure 5] Figure 3 is a cross-sectional view illustrating the manufacturing method of the catalyst structure shown. [Figure 6] Figure 3 is a cross-sectional view illustrating the manufacturing method of the catalyst structure shown. [Figure 7]It is a diagram showing a scanning transmission electron microscope image of a catalyst structure according to an embodiment and an elemental mapping analysis result by energy dispersive X-ray spectroscopy (EDS).

Mode for Carrying Out the Invention

[0010] Hereinafter, the catalyst structure of the present invention and the method for manufacturing the catalyst structure 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, hydrogen, water, etc., but are not limited thereto. When these raw materials come into contact with the catalyst structure 1, the raw materials are reformed and products are obtained. Examples of the products include, in addition to 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). The catalyst particle 2 includes a core particle 3, a coating 4, and a plurality of oxide particles 5.

[0015] The core particles 3 contain a first metal element and are in a particulate form. The coating 4 contains a second metal element and covers the surface of the core particles 3. The oxide particles 5 contain an oxide of the first metal element and adhere to the surface of the coating 4. In the catalyst particles 2, both the coating 4 and the oxide particles 5 are exposed.

[0016] One of the first metal element and the second metal element is an element constituting a catalyst component, and the other is an element constituting a carrier component. These elements exist in the state of a simple substance, a mixture formed by mixing with other elements, or a compound (such as an oxide) formed by combining with other elements. Therefore, when the core particles 3 and the coating 4 come into contact, the coating 4 containing the second metal element can be thinly distributed along the surface of the core particles 3. The thus thinly distributed coating 4 is considered to form catalytic active sites C at the interface with the oxide particles 5 described later. Since these catalytic active sites C are formed for each catalyst particle 2, a large number of catalytic active sites C are distributed at a predetermined interval in the entire catalyst structure 1. In addition, in the catalyst structure 1 according to the present embodiment, when the coating 4 and the plurality of oxide particles 5 come into contact, a large number of catalytic active sites C are considered to be formed while being separated from each other at these interfaces. Then, a plurality of catalytic active sites C are formed in one catalyst particle 2. As a result, in the catalyst structure 1, the contact efficiency between the raw material and the catalytic active sites C is high, and the efficiency of the reforming reaction of the raw material can be increased.

[0017] In addition, gaps are naturally formed between the catalyst particles 2. Therefore, the exchange efficiency of the raw material is increased. Furthermore, the catalyst structure 1 composed of an aggregate of the 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 increased.

[0018] Furthermore, catalyst structure 1 has high fluidity, taking advantage of the shape of catalyst particles 2. Therefore, it is easy to fill into containers and handle. Consequently, a reforming apparatus with a high density of catalytic active sites C can be constructed inexpensively. Using such a reforming apparatus, large quantities of raw materials can be efficiently reformed even in a small space, enabling the inexpensive, efficient, and large-scale production of products such as methanol. Moreover, when carbon dioxide is used as a raw material, it can contribute to achieving carbon neutrality or carbon-negative emissions.

[0019] In the following explanation, we will describe an example in which the coating 4 contains a support component and the oxide particles 5 contain a catalyst component.

[0020] 1.2. Core Particles The core particles 3 contain a first metal element. The core particles 3 function as a substrate supporting the coating 4. Furthermore, the core particles 3 also function as a source for supplying the first metal element when the oxide particles 5, described later, are formed. In other words, by including the first metal element in the core particles 3, the structure of the catalyst particles 2, to which multiple minute oxide particles 5 are attached, can be realized. Moreover, the core particles 3 themselves may also function as a catalytic component.

[0021] Examples of the first metal element include Cu, Pt, In, Zn, Ru, Sn, Au, and Re. Of these, the first metal element is preferably Cu, Pt, or In, and more preferably Cu. These elements exist as elements, mixtures, or compounds, and upon contact with the second metal element, they exhibit particularly high catalytic activity at catalytic active site C. By adjusting various conditions (temperature, pressure, feed rate of raw materials, reaction time, etc.) and then contacting this catalytic active site C with, for example, carbon dioxide and hydrogen, the probability of hydrogenation of carbon dioxide increases, thereby improving the efficiency of various reforming reactions, such as the production of methanol. Examples of these conditions include a temperature of 300°C or higher, a pressure of 1 MPa to 10 MPa, a feed rate of 100 mL / min or higher for the gas containing the raw materials, and a reaction time of 5 hours to 8 hours.

[0022] The core particles 3 may contain elements other than the first metallic element, as needed. Examples of other elements include nonmetallic elements such as oxygen, as well as at least one element selected from the first metallic element. If the other element is oxygen, an oxide compound of the first metallic element is an example. That is, the core particles 3 may contain copper oxide, platinum oxide, indium oxide, etc. Furthermore, if the other element is the first metallic element, the core particles 3 may contain alloys or intermetallic compounds of two or more first metallic elements.

[0023] As shown in Figure 1, the core particles 3 are particulate. Specific shapes of the core particles 3 include, for example, spherical shapes such as perfect spheres, ellipsoids, and ovals, as well as polyhedra, cylinders, prisms, cones, pyramids, rods, needles, etc., but other unspecified shapes are also acceptable. Furthermore, these shapes may be mixed together.

[0024] The average aspect ratio of the core particles 3 is not particularly limited, but is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and even more preferably 1.0 to 2.0. By having the average aspect ratio of the core particles 3 within the above range, a catalyst structure 1 with excellent fluidity and packing properties can be obtained. By using such a catalyst structure 1, a reforming apparatus can be constructed in which catalytic active sites C are densely contained.

[0025] The average aspect ratio of core particles 3 is calculated as follows: First, projection images of core particles 3 are captured using an electron microscope or 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 images are loaded into image processing software. Then, the image processing detects 50 or more particle images and calculates the aspect ratio. The average value of the calculated aspect ratios is then defined as the "average aspect ratio". Note that the aspect ratio is calculated by dividing the major axis by the minor axis, where the longest length of the particle image is the major axis and the longest length in the direction perpendicular to the direction of extension of the major axis is the minor axis.

[0026] The average particle diameter of the core particles 3 is not particularly limited, but is preferably 5 μm to 100 μm, more preferably 10 μm to 80 μm, and even more preferably 20 μm to 60 μm. If the average particle diameter of the core particles 3 is within the above range, a catalyst structure 1 can be obtained that has a sufficiently large specific surface area and excellent fluidity and packing properties. This makes it possible to realize a reforming device in which catalytic active sites C are densely contained.

[0027] Furthermore, if the average particle diameter of the core particles 3 falls below the lower limit, the manufacturing difficulty of the core particles 3 may increase, aggregation may occur more easily, and secondary particles may form in the catalyst structure 1, potentially reducing fluidity and packing efficiency. On the other hand, if the average particle diameter of the core particles 3 exceeds the upper limit, the specific surface area of ​​the catalyst structure 1 may decrease.

[0028] The average particle size of core particles 3 is the average particle size (equivalent circle diameter) measured from 10 or more randomly selected particle images after identifying the particle images of core particles 3 based on differences in contrast, etc., in a magnified observation image of the surface of the catalyst structure 1.

[0029] 1.3.Coating The coating 4 covers the surface of the core particles 3. Preferably, the coating 4 covers the entire surface of the core particles 3, but there may be uncovered portions.

[0030] The coating 4 contains a secondary metal element and functions as a support component on which a catalyst component is supported, for example. Examples of secondary metal elements include Zr, Hf, Ta, Zn, Mo, Ti, Ga, Al, Sn, Al, and Ru. Of these, the secondary metal element is preferably Zr, Hf, Ta, Zn, Mo, Ti, Al, or Ru, and more preferably Zr. These elements, upon contact with the primary metal element, exhibit particularly high catalytic activity at the catalytic active site C. When various conditions (temperature, pressure, raw material supply rate, reaction time, etc.) are set and, for example, carbon dioxide and hydrogen are brought into contact with this catalytic active site C, the probability of hydrogenation of carbon dioxide increases, and the efficiency of various reforming reactions, such as the production of methanol, can be increased. Examples of various conditions include a temperature of 300°C or higher, a pressure of 1 MPa to 10 MPa, a gas supply rate of 100 mL / min or higher containing the raw materials, and a reaction time of 5 hours to 8 hours.

[0031] The coating 4 may contain elements other than the second metallic element, if necessary. Other elements include, for example, nonmetallic elements such as oxygen, as well as at least one selected from the first metallic elements mentioned above. If the other element is oxygen, examples of compounds of the second metallic element include oxides. That is, the coating 4 may contain zirconium oxide, hafnium oxide, tantalum oxide, zinc oxide, molybdenum oxide, titanium oxide, aluminum oxide, ruthenium oxide, etc. By including an oxide of the second metallic element in the coating 4, a catalyst structure 1 with particularly high catalytic activity can be realized. Furthermore, if the other element is the second metallic element, the coating 4 may also contain alloys or intermetallic compounds of two or more second metallic elements.

[0032] Furthermore, the following combinations are examples of preferred combinations of the first metal element contained in the core particles 3 and the oxide particles 5 described later, and the second metal element contained in the coating 4. • If the first metallic element is Cu, the second metallic element is Zr, Hf, Ta, or Zn • If the first metallic element is Pt, the second metallic element is Mo or Ti • If the first metallic element is In, the second metallic element is Zr This combination allows for a particularly high catalytic activity of catalytic active site C.

[0033] The average thickness of the coating 4 is not particularly limited, but is preferably 0.1 nm to 5 nm, more preferably 0.3 nm to 3 nm, and even more preferably 0.5 nm to 2 nm. If the average thickness of the coating 4 is within the above range, the catalytic activity of the catalytic active site C can be particularly increased, and the efficiency of the reforming reaction can be particularly increased. One reason for this effect is that when electrons and holes are transferred between the coating 4 and the oxide particles 5, the transfer efficiency is increased. Another reason is that if the average thickness of the coating 4 is within the above range, the core particles 3 and the oxide particles 5 are in extremely close proximity through the coating 4 containing the second metal element, which further increases the efficiency of electron and hole transfer.

[0034] Furthermore, if the average thickness of the coating 4 falls below the lower limit, the thickness of the coating 4 may be insufficient, potentially reducing the efficiency of the modification reaction or preventing the coating 4 from achieving sufficient coverage. On the other hand, if the average thickness of the coating 4 exceeds the upper limit, the thickness of the coating 4 may be excessive, potentially reducing the efficiency of the modification reaction.

[0035] The average thickness of the coating 4 is the average of the measurements obtained by acquiring magnified cross-sectional images of five or more catalyst particles 2 using a scanning transmission electron microscope (STEM), etc., and measuring the thickness of each coating 4 at five or more locations.

[0036] Figure 2 is a graph showing an example of the change in ion detection values ​​corresponding to the amount of methanol produced when a reforming reaction is carried out to produce methanol from carbon dioxide and hydrogen using two types of catalyst structures with different average thicknesses of the coating 4. In Figure 2, the horizontal axis represents the reaction time [seconds] of the reforming reaction, and the vertical axis represents the ion detection value [A] with a mass-to-charge ratio m / z = 31.

[0037] Figure 2 compares the changes in ion detection levels for a catalyst structure with an average coating thickness of 1 nm and a catalyst structure with an average coating thickness of 10 nm. The ion detection value represents the amount of ions contained in the gas when a mixed gas containing carbon dioxide and hydrogen is brought into contact with the catalyst structure and then passed through a mass spectrometer. Figure 2 shows the changes in ion detection values ​​for methanol-derived ions with a mass-to-charge ratio of m / z = 31.

[0038] As shown in Figure 2, when the average thickness of the coating 4 is within the range, the ion detection value is higher compared to when the average thickness of the coating 4 is outside the range. Therefore, as shown in Figure 2, optimizing the average thickness of the coating 4 to within the range can improve the efficiency of the raw material modification reaction.

[0039] 1.4. Oxide particles Multiple oxide particles 5 contain an oxide of the first metal element and are attached to the surface of the coating 4. The oxide particles 5 are attached to only a portion of the surface of the coating 4, while the rest is exposed. In other words, in the catalyst particles 2, both the coating 4 and the oxide particles 5 are exposed.

[0040] The oxide particles 5 function as catalytic components. Therefore, in the catalyst particles 2, catalytic active sites C are formed at the interface between the coating 4 and the oxide particles 5. With both the coating 4 and the oxide particles 5 exposed, the contact efficiency between the raw materials such as carbon dioxide and hydrogen and the catalytic active sites C is increased. This makes it possible to realize a catalyst structure 1 with high efficiency in the raw material reforming reaction. Furthermore, with multiple oxide particles 5 attached to a single catalyst particle 2, the catalytic active sites C, which are divided into multiple parts, are distributed on the surface of the coating 4. This further increases the efficiency of the raw material reforming reaction by the catalyst structure 1.

[0041] Furthermore, the presence of both the coating 4 and the oxide particles 5 can be evaluated by, for example, elemental analysis of the surface using X-ray photoelectron spectroscopy (XPS) or ion scattering spectroscopy (ISS).

[0042] The oxide particles 5 preferably contain copper oxide. The oxide particles 5 containing copper oxide form catalytic active sites C that exhibit particularly high catalytic activity.

[0043] The average particle diameter of the oxide particles 5 is not particularly limited, but is preferably 0.5 nm to 100 nm, more preferably 1 nm to 50 nm, and even more preferably 5 nm to 30 nm. If the average particle diameter of the oxide particles 5 is within the above range, the size necessary for catalytic activity can be ensured in the oxide particles 5, and the number density of catalytic active sites C formed at the interface between the oxide particles 5 and the coating 4 can be increased. This particularly enhances the efficiency of the raw material modification reaction by the catalyst structure 1.

[0044] Furthermore, if the average particle size of the oxide particles 5 falls below the lower limit, the difficulty of forming the oxide particles 5 may increase. On the other hand, if the average particle size of the oxide particles 5 exceeds the upper limit, the number density of catalytic active sites C decreases, which may reduce the efficiency of the reforming reaction.

[0045] The average particle size of the oxide particles 5 is calculated by obtaining magnified cross-sectional images of five or more catalyst particles 2 using a scanning transmission electron microscope (STEM), measuring the equivalent circular diameter of each of the five or more oxide particles 5, and averaging the obtained measurements.

[0046] Furthermore, when elemental analysis of the catalyst structure 1 surface is performed by ion scattering spectroscopy (ISS), the abundance ratio of the second metal element to the first metal element is preferably 10 / 90 or more and 90 / 10 or less in terms of atomic ratio, more preferably 20 / 80 or more and 80 / 20 or less, and even more preferably 30 / 70 or more and 70 / 30 or less. Ion scattering spectroscopy allows for elemental analysis of the outermost surface of the catalyst structure 1. If the abundance ratio of the second metal element to the first metal element measured by this method is within the above range, the balance between the first and second metal elements exposed on the outermost surface of the catalyst structure 1 can be particularly optimized. In other words, the balance between the exposed area of ​​the coating 4 and the oxide particles 5 can be optimized. This significantly increases the efficiency of the reforming reaction.

[0047] Furthermore, if the abundance ratio falls below the lower limit or exceeds the upper limit, the balance between the first and second metal elements may become unbalanced, potentially reducing the efficiency of the reforming reaction.

[0048] 2. Method for manufacturing catalyst structures Next, a method for manufacturing the catalyst structure according to the embodiment (a method for manufacturing the catalyst structure 1 shown in Figure 1) will be described.

[0049] Figure 3 is a process diagram illustrating the method for manufacturing the catalyst structure 1 shown in Figure 1. Figures 4 to 6 are cross-sectional views illustrating the manufacturing method for the catalyst structure 1 shown in Figure 3. In the following explanation, the upper part of Figures 4 to 6 will be referred to as "upper" and the lower part as "lower".

[0050] The method for manufacturing the catalyst structure 1 shown in Figure 3 is the same as the method for manufacturing the catalyst structure 1 shown in Figure 1, and comprises a preparation step S102 and a film formation step S104. In the preparation step S102, core particles 3 are prepared. In the film formation step S104, a coating 4 is formed on the surface of the core particles 3 by atomic layer deposition, and oxide particles 5 are formed by depositing oxides of the first metal element contained in the core particles 3 onto the surface of the coating 4. This makes it possible to easily manufacture a catalyst structure 1 with a large specific surface area and high catalytic activity.

[0051] 2.1. Preparation process In preparation step S102, core particles 3 are prepared. As mentioned above, core particles 3 are particles containing a first metal element, such as Cu particles. The core particles 3 are provided to the next step in a state where they are contained in a tray 9, as shown in Figure 4. The constituent material of the tray 9 is not particularly limited, but a metallic material such as stainless steel is preferably used.

[0052] Furthermore, preparation step S102 may include surface treatment of the core particles 3. Examples of surface treatments include ozone treatment, in which the core particles 3 are brought into contact with ozone; plasma treatment, in which plasma is brought into contact with the core particles 3; corona treatment, in which corona discharge is performed on the core particles 3; and ultraviolet treatment, in which ultraviolet light is irradiated on the core particles 3. By performing such surface treatment, the core particles 3 are purified, and the adhesion and chemical bonding between the core particles 3 and the coating 4 are improved.

[0053] Of the surface treatments described above, ozone treatment is preferably used. Ozone treatment allows for efficient removal of organic matter and other contaminants from the surface while minimizing damage to the core particles 3, thereby achieving cleaning. The duration of ozone treatment is not particularly limited, but is preferably 1 minute or more and 60 minutes or less, and more preferably 5 minutes or more and 20 minutes or less.

[0054] 2.2. Film formation process In the film formation process S104, a coating 4 is formed on the surface of the core particles 3, as shown in Figure 5. Additionally, oxides of the first metal element contained in the core particles 3 are deposited on the surface of the coating 4. This results in the formation of oxide particles 5, as shown in Figure 6. The formation of the coating 4 and the oxide particles 5 are thought to occur alternately or almost simultaneously. Specifically, first, during the formation of the coating 4, the first metal element contained in the core particles 3 becomes suspended. Next, reactants of the coating raw material gas containing the second metal element are deposited on the surface of the core particles 3, forming the coating 4. Furthermore, after the coating 4 is formed, oxides of the first metal element are thought to be deposited on the surface of the coating 4. As a result, oxide particles 5 adhere to the surface of the coating 4, yielding catalyst particles 2.

[0055] Methods for forming the coating 4 include, for example, vacuum deposition, sputtering, CVD, and atomic layer deposition (ALD). Of these, atomic layer deposition is preferred. By forming the coating 4 using atomic layer deposition, a coating 4 with a thin film thickness and high coverage can be efficiently formed. Specifically, in atomic layer deposition, the amount of film deposited can be controlled at the atomic layer level, so the film thickness of the coating 4 can be precisely controlled, making it possible to achieve both thinness and high coverage of the coating 4.

[0056] Furthermore, in atomic layer deposition, the coating material gas and oxidizer can reach and form a film even in areas shaded from the supply source, making it easier to increase the coverage of the coating 4. In addition, atomic layer deposition makes it possible to manufacture catalyst structures 1 with less variation in the coverage of the coating 4 for each catalyst particle 2.

[0057] The raw material gas and oxidizing agent used in atomic layer deposition are appropriately selected according to the constituent materials of the coating 4. For example, the raw material gas is a gas containing precursors of the constituent materials. For example, if the second metal element contained in the coating 4 is Zr, zirconium oxide (ZrO2) can be used as the constituent material of the coating 4. In this case, the precursor may be an inorganic metal compound such as a halide containing the second metal element, but preferably an organometallic compound containing the second metal element is used. By using an organometallic compound, the vapor pressure of the raw material gas can be easily increased, so the film thickness of the coating 4 can be controlled more precisely. Examples of organometallic compounds include Zr(O2). t Examples include Bu)4 (zirconium tert-butoxide, ZTB), Zr(NEt2)4 (tetrakis(diethylamide) zirconium, TDEAZ), Zr(NMeEt)4 (tetrakis(ethylmethylamide) zirconium, TEMAZ), and Zr(NMe2)4 (tetrakis(dimethylamide) zirconium, TDMAZ).

[0058] The following describes an example of the procedure for forming the coating 4 by atomic layer deposition. First, a tray 9 containing core particles 3 is placed in a chamber that allows for vacuum and atmosphere control. Next, a coating material gas containing a precursor is introduced into the chamber, and the precursor is adsorbed onto the surface of the core particles 3. Then, after the excess coating material gas is discharged, an oxidizer is introduced into the chamber. Examples of oxidizers include ozone, plasma oxygen, and water vapor. The introduced oxidizer reacts with the precursor adsorbed on the core particles 3, and the coating 4 is formed. In this way, in atomic layer deposition, by supplying, for example, an organometallic compound containing a second metal element as a precursor for the coating 4 to core particles 3 placed under reduced pressure, the formation of the coating 4 and the formation of oxide particles 5 adhering to its surface can be carried out sequentially. This allows for the efficient production of catalyst particles 2.

[0059] The temperature of the core particles 3 when forming the coating 4 is set appropriately depending on the type of precursor and oxidizing agent, but is preferably between 100°C and 350°C, and more preferably between 120°C and 200°C. This allows the precursor to react with high precision while suppressing thermal degradation of the core particles 3. As a result, a coating 4 can be formed with a sufficiently high content of the target constituent material, enabling a highly efficient modification reaction.

[0060] Furthermore, especially when the temperature of the core particles 3 is between 120°C and 200°C, it is thought that the surface of the core particles 3 can be moderately vaporized, allowing an appropriate amount of copper atoms to suspend. The suspended copper atoms combine with the oxidizing agent and are oxidized to form an oxide of the first metal element. This oxide of the first metal element is thought to either aggregate into particulate matter and deposit on the surface of the coating 4, or to deposit on the surface of the coating 4 and then aggregate. This yields a necessary and sufficient amount of oxide particles 5.

[0061] The pressure inside the chamber when forming the coating 4 is preferably 100 Pa or less, more preferably 0.001 Pa to 10 Pa, and even more preferably 0.001 Pa to 1 Pa. This allows for optimization of the concentrations of the precursor and oxidant, thereby increasing the reaction efficiency of the precursor. Furthermore, if the pressure inside the chamber is within the above range, copper atoms can be easily removed from the surface of the core particles 3. This allows for the efficient formation of oxide particles 5 of the desired quantity and size. As a result, a coating 4 can be formed with a sufficiently high content of the desired constituent materials, enabling a highly efficient modification reaction. This yields catalyst particles 2.

[0062] The amount of oxide particles 5 formed can be adjusted according to the amount of suspended copper atoms. For example, the amount of oxide particles 5 formed can be increased by raising the temperature of the core particles 3 when forming the coating 4, lowering the pressure inside the chamber, or extending the formation time of the coating 4. Conversely, the amount of oxide particles 5 formed can be decreased by performing the opposite operations.

[0063] Figure 7 shows a scanning transmission electron microscope image of the catalyst structure according to the embodiment, and the results of elemental mapping analysis by energy-dispersive X-ray spectroscopy (EDS). The first metal element contained in the catalyst structure shown in Figure 7 is Cu, and the second metal element is Zr.

[0064] In the scanning transmission electron microscope (STEM) image shown in Figure 7, the core particles 3 and a portion of the coating 4, as well as the oxide particles 5 attached to the surface of the coating 4, are shown in light colors. This image indicates that both the coating 4 and the oxide particles 5 are exposed. Furthermore, the line analysis results of the Zr content are superimposed as a graph on this image.

[0065] In the Cu-K line mapping image shown in Figure 7, a light color is spread across the regions corresponding to core particle 3 and oxide particle 5. This image indicates that core particle 3 and oxide particle 5 contain Cu.

[0066] In the Zr-K line mapping image shown in Figure 7, a light color is spread across the region corresponding to coating 4. This image indicates that coating 4 contains Zr. Furthermore, the thickness of coating 4 can also be measured from the Zr-K line mapping image. This image shows that the thickness of coating 4 is approximately 1.1 nm. Additionally, as can be seen from the graph superimposed on the scanning transmission electron microscope (STEM) image, Zr is unevenly distributed in coating 4.

[0067] In the OK line mapping image shown in Figure 7, a light color is spread across the regions corresponding to coating 4 and oxide particles 5. This image indicates that coating 4 contains Zr oxide and oxide particles 5 contain Cu oxide.

[0068] Furthermore, after the film formation process S104, the catalyst particles 2 may be subjected to a reduction treatment as needed. By performing the reduction treatment, the oxide is reduced in at least one of the film 4 and the oxide particles 5. Specifically, when the second metal element contained in the film 4 is in an oxide state, it can be changed to a metal by reduction. In addition, the oxide of the first metal element contained in the oxide particles 5 can also be changed to a metal by reduction. This may enhance the catalytic activity at the catalytic active site C.

[0069] Examples of reducing agents used in the reduction treatment include hydrogen, carbon monoxide, and methane. Alternatively, the catalyst particles 2 may be heated under reduced pressure to reduce the oxide by thermal dissociation. Of these, a reduction treatment using hydrogen is preferred, considering the stability, efficiency, and safety of the reduction reaction. This results in a catalyst structure 1 with improved reforming efficiency.

[0070] In the case of a reduction treatment using a reducing agent, the catalyst particles 2 are heated while the reducing agent is introduced into the heating furnace.

[0071] The temperature inside the heating furnace during the reduction treatment is not particularly limited, but is preferably 100°C to 700°C, and more preferably 200°C to 500°C. The heating time is also not particularly limited, but is preferably 0.5 hours to 10 hours, and more preferably 1 hour to 5 hours. This allows for efficient enhancement of catalytic activity at catalytic active site C.

[0072] The amount of reducing agent introduced into the heating furnace during the reduction treatment is not particularly limited, but is preferably 10 mL / min to 1000 mL / min, and more preferably 50 mL / min to 500 mL / min. By adjusting to such an optimal value, it becomes easier to efficiently enhance the catalytic activity at catalytic active site C.

[0073] 3. Effects of the Embodiment As described above, the catalyst structure 1 according to the embodiment is used in a reforming reaction to modify a raw material, and is a particulate catalyst structure comprising core particles 3, a coating 4, and a plurality of oxide particles 5. The core particles 3 contain a first metal element and are particulate. The coating 4 contains a second metal element and covers the surface of the core particles 3. The oxide particles 5 contain an oxide of the first metal element and adhere to the surface of the coating 4. In the catalyst structure 1, both the coating 4 and the oxide particles 5 are exposed.

[0074] This configuration allows for the creation of a catalyst structure 1 with a large specific surface area and high catalytic activity. Furthermore, multiple catalytic active sites C are formed on each catalyst particle 2 contained within the catalyst structure 1. As a result, the catalyst structure 1 exhibits high contact efficiency between the raw material and the catalytic active sites C, thereby increasing the efficiency of the raw material modification reaction. Additionally, the catalyst structure 1 possesses high fluidity, taking advantage of the shape of the catalyst particles 2. Therefore, it is easy to fill into containers and handle.

[0075] In the catalyst structure 1 according to the above embodiment, the average particle diameter of the core particles 3 is preferably 5 μm or more and 100 μm or less.

[0076] This configuration yields a catalyst structure 1 with a sufficiently large specific surface area and excellent fluidity and packing properties. This makes it possible to realize a reforming apparatus in which catalytic active sites C are densely contained.

[0077] In the catalyst structure 1 according to the above embodiment, the average thickness of the coating 4 is preferably 0.1 nm or more and 5 nm or less.

[0078] With this configuration, the catalytic activity of catalyst structure 1 can be particularly enhanced, resulting in a particularly high efficiency of the reforming reaction.

[0079] In the catalyst structure 1 according to the above embodiment, the average particle diameter of the oxide particles 5 is preferably 0.5 nm or more and 100 nm or less.

[0080] With this configuration, the oxide particles 5 can be made to have the size necessary for catalytic activity, and the number density of catalytic active sites C formed at the interface between the oxide particles 5 and the coating 4 can be increased. As a result, the efficiency of the raw material modification reaction by the catalyst structure 1 can be particularly increased.

[0081] In the catalyst structure 1 according to the above embodiment, the coating 4 preferably contains an oxide of a second metal element. This configuration makes it possible to realize catalyst structure 1 with particularly high catalytic activity.

[0082] In the catalyst structure 1 according to the above embodiment, the first metal element is preferably Cu, Pt, or In, and the second metal element is preferably Zr, Hf, Ta, Zn, Mo, Ti, Al, or Ru. This configuration makes it possible to realize catalyst structure 1 with particularly high catalytic activity.

[0083] 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 comprises a preparation step S102 and a film formation step S104.

[0084] In preparation step S102, core particles 3 are prepared. In film formation step S104, a coating 4 is formed on the surface of the core particles 3 by atomic layer deposition, and oxide particles 5 are formed by depositing oxides of the first metal element contained in the core particles 3 onto the surface of the coating 4.

[0085] With this configuration, a catalyst structure 1 with a large specific surface area and high catalytic activity can be easily manufactured.

[0086] In the method for manufacturing the catalyst structure according to the above embodiment, the preparation step S102 may include an ozone treatment in which the core particles 3 are brought into contact with ozone.

[0087] With this configuration, damage to the core particles 3 can be minimized while efficiently removing organic matter and other substances from the surface, thereby enabling cleaning.

[0088] In the method for manufacturing the catalyst structure according to the above embodiment, when forming the coating 4 in the film formation step S104, it is preferable that the temperature of the core particles 3 is 120°C or higher and 200°C or lower.

[0089] This configuration allows for moderate vaporization of the core particle 3 surface, enabling the suspension of an appropriate amount of copper atoms. The suspended copper atoms combine with the oxidizing agent and are oxidized to form an oxide of the first metal element. These oxides of the first metal element are thought to aggregate into particulate matter and deposit on the surface of the coating 4, or to deposit on the surface of the coating 4 and then aggregate. This results in obtaining a necessary and sufficient amount of oxide particles 5.

[0090] In the method for producing the catalyst structure according to the above embodiment, the atomic layer deposition method may include the operation of supplying an organometallic compound containing a second metal element as a precursor for the coating 4 to core particles 3 placed under reduced pressure.

[0091] With this configuration, the formation of the coating 4 and the formation of oxide particles 5 adhering to its surface can be carried out sequentially. This allows for the efficient production of the catalyst structure 1.

[0092] Although the catalyst structure and method for manufacturing the catalyst structure of the present invention have been described above based on preferred embodiments, 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 any component having a similar function, or in which any component is added to the above embodiment.

[0093] Furthermore, the method for manufacturing the catalyst structure of the present invention may be modified from the above embodiment by adding any desired steps. [Explanation of Symbols]

[0094] 1...Catalyst structure, 2...Catalyst particles, 3...Core particles, 4...Coating, 5...Oxide particles, 9...Tray, C...Catalyst active site, S102...Preparation process, S104...Film formation process

Claims

1. A catalyst structure in the form of particulate matter, used in a reforming reaction to modify raw materials. A core particle containing a first metallic element and forming particulate matter, A coating containing a second metal element and covering the surface of the core particles, A plurality of oxide particles adhering to the surface of the coating, comprising an oxide of the first metal element, Equipped with, A catalyst structure characterized in that both the coating and the oxide particles are exposed.

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

3. The catalyst structure according to claim 2, wherein the average thickness of the coating is 0.1 nm or more and 5 nm or less.

4. The catalyst structure according to claim 2 or 3, wherein the average particle diameter of the oxide particles is 0.5 nm or more and 100 nm or less.

5. The catalyst structure according to claim 1 or 2, wherein the coating comprises an oxide of the second metal element.

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

7. A method for producing the catalyst structure described in claim 1, Preparation steps for preparing the core particles, A film formation step in which the coating is formed on the surface of the core particles by atomic layer deposition, and oxides of the first metal element contained in the core particles are deposited on the surface of the coating to form oxide particles, A method for producing a catalyst structure, characterized by having the following features.

8. The method for producing a catalyst structure according to claim 7, wherein the preparation step includes an ozone treatment in which the core particles are brought into contact with ozone.

9. A method for producing a catalyst structure according to claim 7 or 8, wherein when the coating is formed in the aforementioned film formation step, the temperature of the core particles is 120°C or higher and 200°C or lower.

10. The method for producing a catalyst structure according to claim 7 or 8, wherein the atomic layer deposition method includes supplying an organometallic compound containing the second metal element as a precursor for the coating to the core particles placed under reduced pressure.

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