Catalyst and method for producing the same, catalyst reaction tube, and catalyst precursor

Abstract

A novel catalyst is provided. This catalyst achieves one or more of the following: (i) reaction at a lower temperature than conventional technology, (ii) reaction at a lower pressure than conventional technology, (iii) improved reaction efficiency, and (iv) improved durability. [Solution] A catalyst according to one aspect of the present invention is a fibrous catalyst containing a metal oxygenate. The metal oxygenate is layered and is one or more selected from the group consisting of titanates, molybdates, vanadates, tungstates, manganeses, nickelates, ironates, zirconates, germanates, and composite salts thereof. Catalytically active species are inserted between the layers of the layered metal oxygenate.

Description

Technical Field

[0001] The present invention relates to a catalyst, a method for producing the same, a catalytic reaction tube, and a catalyst precursor.

Background Art

[0002] There is a technology that reacts carbon dioxide discharged from industrial facilities and the like with hydrogen to produce methane, formic acid, and the like. This technology is expected as a carbon-neutral technology aimed at reducing carbon dioxide.

[0003] For example, as one of the methanation catalysts for carbon dioxide, ruthenium-based catalysts are known. For example, Non-Patent Document 1 discloses CC y the methanation of carbon dioxide by a catalyst. According to this, it is said that the conversion rate of carbon dioxide reached a maximum of 52% under the conditions of temperature: 180 ° C, pressure: 2 MPa, and catalyst amount: 250 mg (see FIG. 6 of the present application). A

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The conventional technologies as described above still require high temperature and / or high pressure for the reaction. In addition, there is still room for improvement in reaction efficiency and catalyst durability.

[0006] One aspect of the present invention aims to provide a catalyst that satisfies one or more of the following. · It can make the reaction proceed at a lower temperature than the prior art. · It can make the reaction proceed at a lower pressure than the prior art. · Its reaction efficiency is improved compared to the prior art. · Its durability is improved compared to the prior art.

Means for Solving the Problem

[0007] The present invention includes the following aspects. <1> A fibrous catalyst containing a metal oxygen acid salt containing a catalytic active species, wherein the metal oxygen acid salt is layered, the metal oxygen acid salt is one or more selected from the group consisting of titanates, molybdates, vanadates, tungstates, manganates, nickelates, ferrites, zirconates, germanates, and composite salts thereof, the catalytic active species is inserted into the interlayer of the layered metal oxygen acid salt, catalyst. <2> The composition of the metal oxygen acid salt is A x B (w-x) M y O z represented by, The catalyst according to <1>: wherein, A is the catalytic active species, B is a cation other than the catalytic active species; M is one or more selected from the group consisting of titanium, molybdenum, vanadium, tungsten, manganese, nickel, iron, zirconium, and germanium, x is 0.01 to w; y is 3 to 6; z is 7 to 13; w is a value that makes the total charge zero. <3> <1> or <2> Contains the catalyst described above, Catalytic reaction tube. <4> A method for producing a catalyst containing a layered metal oxyacid, comprising the following step S3: Step S3: A step of replacing at least a portion of the cations contained between the layers of the above metal oxyacid with catalytically active species; Here, The above catalyst is fibrous, The above-mentioned metal oxygen salts are one or more selected from the group consisting of titanates, molybdates, vanadates, tungstates, manganeses, nickelates, ironates, zirconates, germanates, and composite salts thereof. <5> The process further includes the following step S2 prior to the above step S3: <4> Manufacturing method described: Step S2: A step in which a metal oxide is hydrothermally treated under basic conditions to form a fibrous metal oxyacid. <6> The pH in step S3 above is 2.5 or higher. <4> or <5> The manufacturing method described above. <7> The temperature in step S3 described above is 80-220°C. <4> ~ <6> A method for producing a catalyst as described in any one of the following. <8> A fibrous catalyst precursor containing a metal oxygenate, The above metal oxygen salts are layered, The above-mentioned metal oxygen salt is one or more selected from the group consisting of titanates, molybdates, vanadates, tungstates, manganeses, nickelates, ironates, zirconates, germanates, and complex salts thereof. Catalyst precursor. [Effects of the Invention]

[0008] According to one aspect of the present invention, a catalyst is provided that satisfies one or more of the following conditions. • The reaction can proceed at lower temperatures than with conventional technology. • The reaction can proceed at lower pressure than with conventional technology. • Reaction efficiency is improved compared to conventional technology. • Durability has been improved compared to conventional technology. [Brief explanation of the drawing]

[0009] [Figure 1] This is a flowchart illustrating an example of a method for producing a catalyst according to one aspect of the present invention. [Figure 2] This is a schematic diagram illustrating an example of ion exchange in a method for producing a catalyst according to one aspect of the present invention. [Figure 3] This figure shows an example of the manufacturing process for catalytic reaction tubes. [Figure 4] This is an SEM image of the surface of the catalytic reaction tube. [Figure 5] This graph shows the relationship between the temperature of the methanation reaction and the activity of the catalyst. [Figure 6] This is a graph showing the durability of the catalyst disclosed in Non-Patent Document 1. [Figure 7] The left panel shows an SEM image of fibrous sodium titanate produced during the manufacturing process of catalytic reaction tubes. The right panel shows a histogram of the fiber diameter distribution. [Figure 8] The left panel is a TEM image representing the surface of the catalytic reaction tube. The right panel is a histogram showing the particle size distribution inserted between the titanate anion layers. [Modes for carrying out the invention]

[0010] The following describes in detail some examples of embodiments of the present invention, but the present invention is not limited to the embodiments described below, and various modifications may be made within the scope of the claims. Embodiments that combine the technical means described in different embodiments are also included in the technical scope of the present invention.

[0011] Unless otherwise specified in this specification, the numerical range "A to B" means "greater than or equal to A and less than or equal to B". In this specification, the composition of metal oxygen salts is A x M yO z (A x Ti y O z etc.) may be abbreviated, but this description does not prevent the presence of cations other than the catalytic active species, and A x B (w-x) M y O z (A x B (w-x) Ti y O z etc.) should be read as.

[0012] [1. Catalyst] The catalyst according to one embodiment of the present invention contains a metal oxygen acid salt containing a catalytic active species. "Metal oxygen acid salt" is a salt of a polyatomic anion containing metal atoms and oxygen atoms and a cation. In one embodiment, the catalytic active species and the metal oxygen acid anion are bonded by an ionic interaction.

[0013] The metal oxygen acid salt is one or more selected from the group consisting of titanates, molybdates, vanadates, tungstates, manganates, nickelates, ferrites, zirconates, germanates, and composite salts thereof. Therefore, the metal oxygen acid anion is an anion containing one or more atoms selected from the group consisting of titanium atoms, molybdenum atoms, vanadium atoms, tungsten atoms, manganese atoms, nickel atoms, iron atoms, zirconium atoms, germanium atoms, and oxygen atoms (or consisting of these). In one embodiment, the composition of the metal oxygen acid anion is represented by [M n O 2n+1 2- (n is a positive integer). More specific examples include MO3 2- , M2O5 2- , M3O7​​​​​​​​​​Examples include the following. In these formulas, M is one or more atoms selected from the group consisting of titanium, molybdenum, vanadium, tungsten, manganese, nickel, iron, zirconium, and germanium atoms.

[0014] Metal oxygen anions may contain metal atoms other than the main metal atom (for example, titanium atoms in the case of titanates). The content of such metal atoms may be 10 atomic% or less, 5 atomic% or less, 3 atomic% or less, or 1 atomic% or less, with the total number of metal atoms contained in the metal oxygen anion being 100 atomic%.

[0015] Metal oxyacid salts may contain anions other than metal oxyacid anions. An example of such anion is F - Cl - , Br - , I - , OH - NO3 - SO4 2- These include, for example, one type of anion or two or more types. In one embodiment, the metal oxyacid salt does not contain any anions other than the metal oxyacid anion.

[0016] In one embodiment, the metal oxygenate contains a titanate. The titanate contains titanate ions and catalytically active species. A titanate ion is an anion containing (or consisting of) titanium atoms and oxygen atoms. In one embodiment, the titanate ion is [Ti n O 2n+1 ] 2- It can be expressed as (where n is a positive integer). A more specific example is TiO3. 2- Ti2O5 2- Ti3O7 2- Ti4O9 2- Ti5O 11 2- Ti6O 13 2- These are some examples.

[0017] The catalytically active species contained in metal oxygen salts are not particularly limited. The catalytically active species may consist of only one element or may contain multiple elements (for example, it may have a core-shell structure). In one embodiment, the catalytically active species is a cation that is positively charged as a whole. Examples of catalytically active species include ruthenium ions and palladium-silver catalysts (catalysts having a palladium core and a silver shell).

[0018] Metal oxygen salts may contain cations other than catalytically active species. Examples of such cations include H + na + , K + NH4 + Mg 2+ Ni 2+ Co 2+ , Al 3+ These include, for example, a single type of cation or two or more types. In one embodiment, the metal oxyacid salt does not contain cations other than catalytically active species.

[0019] Metal oxyacid salts are layered. Typically, they have a structure in which catalytically active species are inserted between layers formed by metal oxyacid anions. In particular, when the catalytically active species are cations as a whole, the interaction between the anion and cation leads to a tendency towards high stability.

[0020] The layered structure of the metal oxygenate may be localized. That is, a uniform layered structure does not need to be maintained throughout the entire catalyst particle. For example, different layered structures may be in contact with each other via discontinuous surfaces. Alternatively, the catalyst may contain portions that do not have a layered structure. In one embodiment, the portion with a layered structure accounts for 50% or more, 70% or more, or 90% or more of the total volume of the catalyst.

[0021] The composition of metal oxygen salts is A x B (w-x) M y O z It may also be represented by:

[0022] In the formula, A is a catalytically active species. Examples of catalytically active species are as illustrated above.

[0023] In the formula, B is a cation other than the catalytically active species. Examples of such cations are as illustrated above.

[0024] In the formula, M is one or more elements selected from the group consisting of titanium, molybdenum, vanadium, tungsten, manganese, nickel, iron, zirconium, and germanium. However, M may also contain small amounts of other metal atoms. The content of such metal atoms can be 10 atomic% or less, 5 atomic% or less, 3 atomic% or less, or 1 atomic% or less, with the total number of M being 100 atomic%.

[0025] In the formula, x is 0.01 or greater. x may also be 0.05 or greater, 0.1 or greater, or 0.5 or greater. Theoretically, the upper limit of x is w. x / w represents the degree to which catalytically active species are inserted, and generally, a larger value is preferable.

[0026] In the equation, y is between 3 and 6, and z is between 7 and 13. In one embodiment, z = 2y + 1. In one embodiment, (y,z) = (3,7), (4,9), (5,11), or (6,13).

[0027] In the formula, w is the value that makes the total charge zero. A is a divalent cation, and M y O z Assuming that B is a divalent anion, if B is a monovalent cation, w=2; if B is a divalent cation, w=1; and if B is a trivalent cation, w=2 / 3. Even when B consists of multiple types of cations with different valencies, w can be determined based on the valency and abundance of each cation.

[0028] As mentioned above, the catalyst contains metal oxyacids, which are layered microscopically. On the other hand, the macroscopic shape of the catalyst is fibrous.

[0029] The aspect ratio (fiber length / fiber diameter) of the fibrous catalyst can be 3 or greater, 5 or greater, 10 or greater, 50 or greater, 70 or greater, or 100 or greater. The lower limit of the fiber length of the fibrous catalyst can be 1 μm or greater, 5 μm or greater, 10 μm or greater, or 20 μm or greater. The upper limit of the fiber length of the fibrous catalyst can be 10 mm or less, 1 mm or less, 500 μm or less, 100 μm or less, or 10 μm or less. The lower limit of the fiber diameter of the fibrous catalyst can be 0.5 nm or greater, 1 nm or greater, 5 nm or greater, or 10 nm or greater. The upper limit of the fiber diameter of the fibrous catalyst can be 1 mm or less, 0.5 mm or less, 100 μm or less, 50 μm or less, or 10 μm or less. The fiber length and fiber diameter of the catalyst are determined by analysis of SEM images.

[0030] One aspect of the present invention is a catalytic reaction tube containing the above-described catalyst. The catalytic reaction tube has a tubular structure and is used in a catalytic reaction. In one embodiment, the above-described catalyst is distributed on at least a portion of the surface of the catalytic reaction tube.

[0031] The lower limit of the catalytic reaction tube diameter may be 5 mm or more, 10 mm or more, or 15 mm or more. The upper limit of the diameter may be 50 mm or less, 45 mm or less, or 30 mm or less. The lower limit of the catalytic reaction tube length may be 10 mm or more, 20 mm or more, or 30 mm or more. The upper limit of the length may be 200 mm or less, 150 mm or less, or 100 mm or less.

[0032] The structure of the catalytic reaction tube is not particularly limited. For example, the catalytic reaction tube may have one through-hole or multiple through-holes. A larger number of through-holes increases the surface area of ​​the catalytic reaction tube, which can lead to improved reaction efficiency.

[0033] [2. Catalyst Precursor] One aspect of the present invention is a catalyst precursor containing a metal oxygenate. This catalyst precursor is fibrous. The explanation of the metal oxygenate and the fibrous nature is as described in Section [1], so a further explanation is omitted.

[0034] Catalyst precursors differ from catalysts in that they do not contain catalytically active species. The metal oxyacid salts contained in catalyst precursors have a structure in which cations are inserted between layers formed by metal oxyacid anions. By exchanging at least some of these cations with catalytically active species, the catalyst precursor becomes a catalyst.

[0035] [3. Method for producing catalysts] One aspect of the present invention is a method for producing a catalyst. This method includes a step (step S3) of exchanging at least a portion of the cations contained between the layers of a metal oxygenate with catalytically active species. The catalyst obtained by this method is fibrous. The explanation of metal oxygenate and fibrous form is as described in Section [1], so a further explanation is omitted.

[0036] Figure 1 is a flow chart illustrating an example of a catalyst manufacturing method. The manufacturing method will be described in detail below based on this flow chart.

[0037] [3.1.Process S1] In step S1, the substrate is fired in air to oxidize at least a portion of it. This step is optional and not essential to the manufacturing method.

[0038] The substrate ultimately becomes part of the metal oxygen anion contained in the catalyst. Therefore, the substrate contains one or more materials selected from the group consisting of titanium, molybdenum, vanadium, tungsten, manganese, nickel, iron, zirconium, and germanium.

[0039] The shape of the substrate is not particularly limited. Typically, a fibrous catalyst is formed on the surface of the substrate. In this respect, the substrate does not have to be in powder form. In one embodiment, the substrate is tubular. A catalyst reaction tube can be manufactured from such a substrate. Of course, a non-tubular substrate may be used and later assembled into a tubular shape.

[0040] In process S1, the lower limit of the firing temperature may be 500°C or higher, 550°C or higher, 600°C or higher, or 650°C or higher. The upper limit of the firing temperature may be 1000°C or lower, 950°C or lower, 800°C or lower, or 850°C or lower. In process S1, the lower limit of the firing time may be 1 hour or higher, 2 hours or higher, or 3 hours or higher. The upper limit of the firing time may be 12 hours or lower, 11 hours or lower, or 10 hours or lower.

[0041] [3.2.Process S2] In step S2, the oxidized substrate is subjected to hydrothermal treatment under basic conditions to convert at least a portion of it into fibrous metal oxyacid salts. This step is optional and not essential to the manufacturing method.

[0042] Specifically, in step S2, the substrate is heated while in contact with a basic aqueous solution. The metal oxyacid obtained through step S2 is microscopically layered, with cations distributed between the layers of metal oxyacid anions. This metal oxyacid can serve as a catalyst precursor.

[0043] In step S2, the lower limit of the base concentration in the aqueous solution may be 1 mol / L or more, 3 mol / L or more, or 5 mol / L or more. The upper limit of the base concentration may be 20 mol / L or less, 17 mol / L or less, or 15 mol / L or less. The lower limit of the hydrothermal treatment temperature may be 50°C or more, 100°C or more, or 150°C or more. The upper limit of the hydrothermal treatment temperature may be 500°C or less, 400°C or less, or 300°C or less. The lower limit of the hydrothermal treatment time may be 1 hour or more, 3 hours or more, or 5 hours or more. The upper limit of the hydrothermal treatment time may be 24 hours or less, 18 hours or less, or 12 hours or less.

[0044] [3.3.Process S3] In step S3, at least some of the cations contained between the layers of the layered metal oxygenate anions are replaced with catalytically active species. This results in a catalyst in which catalytically active species are inserted between the layers of the layered metal oxygenate salts. Figure 2 illustrates an example where the metal oxygenate anion is a titanate anion and the catalytically active species is a ruthenium ion.

[0045] Layered metal oxyacid salts are substances that contain (or consist of) metal oxyacid anions and catalytically active species cations. Metal oxyacid anions have been explained in Section [1], so a further explanation is omitted.

[0046] The exchange between cations and catalytically active species contained in layered metal oxygen salts can be carried out, for example, as follows: 1. Layered metal oxygen salts and catalytically active species are arranged together in a solvent. Water is an example of a solvent. 2. Mix the reaction system by stirring or other means as needed. 3. Heat-treat the reaction system. The heat-treating time may be 10 to 48 hours.

[0047] The lower limit of the solvent pH in Step 1 can be 2.5 or higher, 2.7 or higher, or 3.0 or higher. If the pH is within the above range, the exchange tends to proceed successfully. The upper limit of the solvent pH in Step 1 can be 10.0 or lower, or 9.5 or lower. If the pH is within the above range, it is easier to prevent the metal oxyacid from dissolving into the solvent. Here, the pH mentioned above is the pH before the metal oxyacid and catalytically active species (or their precursors) are added. In particular, since many metal oxyacids are weak bases, the pH of the solvent may rise when they are added.

[0048] The lower limit of the heat treatment temperature in step 3 may be 80°C or higher, 100°C or higher, 120°C or higher, or 140°C or higher. The upper limit of the heat treatment temperature in step 3 may be 220°C or lower, 200°C or lower, 180°C or lower, or 160°C or lower.

[0049] [4. Use of Catalysts] One aspect of the present invention involves the use of the catalyst or catalytic reaction tube described above. The reaction in which the catalyst or catalytic reaction tube is used is not particularly limited.

[0050] In one embodiment, methane is produced by contacting a catalyst with carbon dioxide and hydrogen. Typically, one molecule of methane and two molecules of water are obtained from one molecule of carbon dioxide and four molecules of hydrogen. In this case, the catalytically active species may be a ruthenium ion.

[0051] In other embodiments, formic acid is produced by contacting the catalyst with carbon dioxide and hydrogen. Typically, one molecule of formic acid is obtained from one molecule of carbon dioxide and one molecule of hydrogen. In this case, the catalytically active species may be a palladium-silver catalyst. A method for methane or oxidizing carbon dioxide using the catalyst or catalytic reaction tube according to the embodiment includes a step of contacting the catalyst or catalytic reaction tube with carbon dioxide and hydrogen.

[0052] By using the catalyst or catalytic reaction tube described above, the reaction can proceed even under low temperature and low pressure conditions. In one embodiment, the lower limit of the reaction temperature may be 80°C or higher, 90°C or higher, 100°C or higher, 110°C or higher, 120°C or higher, 130°C or higher, 140°C or higher, 150°C or higher, or 160°C or higher. In one embodiment, the upper limit of the reaction temperature may be 200°C or lower. In one embodiment, the lower limit of the reaction pressure may be 0.1 MPa or higher or 0.2 MPa or higher. In one embodiment, the upper limit of the reaction pressure may be 1 MPa or lower.

[0053] The reaction efficiency can be increased by using the catalyst or catalytic reaction tube described above. In one embodiment, the reaction efficiency may be 10% or more, 20% or more, 30% or more, 40% or more, or 50% or more. In one embodiment, the above reaction efficiencies are achieved under the low temperature and low pressure conditions described above. The reaction conditions for measuring the reaction efficiency of the catalyst may be those described in Example 1.

[0054] By using the catalyst described above, the durability of the catalyst can be improved. In one embodiment, the reaction efficiency when the reaction is carried out continuously for 200 hours may be 50% or more. The reaction conditions for evaluating the durability of the catalyst may be those described in Example 1. [Examples]

[0055] [Manufacturing Example 1] A catalyst containing layered ruthenium titanate was prepared. The procedure is as follows. The catalyst obtained in this way is in powder form and does not correspond to the catalyst according to one embodiment of the present invention. 1. 0.11552 g of ruthenium chloride hydrate (RuCl3·nH2O), 0.10504 g of sodium bicarbonate, and 25 mL of water were mixed with stirring for 30 minutes. The pH of the mixture was 3.05. 2. Add 0.1 g of sodium titanate (Na2Ti3O7) and mix for 30 minutes while stirring. 3. The resulting mixture was subjected to hydrothermal treatment at 160°C for 24 hours with stirring. This replaced some of the sodium ions in the sodium titanate with ruthenium ions. 4. The solids were filtered out and the mixture was washed with water. 5. The solid components were dried at 100°C for 3 hours. In this way, a catalyst containing layered ruthenium titanate was obtained.

[0056] [Manufacturing Example 2] A catalyst was obtained in the same manner as in Production Example 1, except that the amount of ruthenium chloride hydrate was changed to 1.7331 g, the amount of sodium bicarbonate was changed to 1.5751 g, the amount of water was changed to 350 mL, and the amount of sodium titanate added was changed to 1.5 g. The catalyst obtained in this manner is in powder form and does not correspond to the catalyst according to one embodiment of the present invention.

[0057] [Manufacturing Example 3] The catalytic reaction tube was prepared using the following procedure. An overview of the process is shown in Figure 3. 1. A tubular member with a diameter of 23 mm and a length of 70 mm was fabricated using a metal 3D printer. The material composition of the tubular member, with the total weight being 100% by weight, was titanium: 89.5% by weight, aluminum: 6.35% by weight, and vanadium: 4.15% by weight. 2. The fabricated tubular members were fired in air at 750°C for 6 hours. In this way, oxidized tubular members were obtained. 3. The oxidized tubular member was subjected to hydrothermal treatment at 210°C for 8 hours. A 10 mol / L sodium hydroxide aqueous solution was used as the basic aqueous solution. In this way, fibrous sodium titanate (Na2Ti3O7) was formed on the surface of the tubular member. 4. The tubular member was subjected to hydrothermal treatment at 120°C for 24 hours with 1.1554 g of ruthenium chloride hydrate (RuCl3·nH2O) and 1.5751 g of sodium bicarbonate dissolved in 350 mL of distilled water. This replaced some of the sodium ions contained in the sodium titanate with ruthenium ions. 5. After ion exchange, the tubular member was dried at 100°C for 3 hours. In this way, a catalytic reaction tube with fibrous catalyst distributed on its surface was obtained (Figure 4 shows an SEM image of the surface). The catalyst contained in this catalytic reaction tube corresponds to the catalyst according to one embodiment of the present invention.

[0058] [Example 1] The catalytic activity of a catalyst and catalytic reaction tube according to one embodiment of the present invention was investigated. Specifically, catalysts and catalytic reaction tubes were prepared according to Production Examples 1 to 3, and the conversion rate of carbon dioxide by the obtained catalysts or catalytic reaction tubes was measured. The measurement conditions for the conversion rate were as follows. • Reaction pressure: 0.1 MPa Reaction temperature: 100°C, 120°C, 140°C, 160°C, or 180°C ·Catalyst weight: 50mg • Composition of raw material gas: H2:CO2:N2 = 71.25:23.75:5 (H2:CO2 = 3:1, CO2 concentration = 23.75% by volume) • Flow rate of raw gas: 20 mL / min ·Space velocity (GHSV): 24,000 / h

[0059] The results are shown in Figure 5. As can be seen from the figure, the catalytic reaction tube containing the fibrous catalyst showed a higher conversion rate in the low-temperature range (particularly in the 100-160°C range) than the powdered catalyst and the catalysts of the conventional technology.

[0060] For reference, the catalytic activity of the powdered catalyst under low-temperature conditions was not affected even when the scale of preparation was increased (generally, catalytic activity can change when the preparation is scaled up, but this phenomenon did not occur with the catalyst according to one embodiment of the present invention). The microscopic structure of the powdered catalyst and the fibrous catalyst (surface of the catalytic reaction tube) are the same. Therefore, it is expected that the catalytic activity of the catalyst according to one embodiment of the present invention will not be affected under low-temperature conditions even when the scale of preparation is increased.

[0061] [Manufacturing Example 4] A catalytic reaction tube was prepared using a procedure similar to that of Manufacturing Example 3. Because this catalytic reaction tube contains a different type of catalytic active species, its catalytic activity differs from that of the catalytic reaction tube prepared in Manufacturing Example 3. The specific procedure is as follows. 1. A tubular member with a diameter of 23 mm and a length of 70 mm was fabricated using a metal 3D printer. The material composition of the tubular member, with the total weight being 100% by weight, was titanium: 89.5% by weight, aluminum: 6.35% by weight, and vanadium: 4.15% by weight. 2. The fabricated tubular members were fired in air at 750°C for 8 hours. In this way, oxidized tubular members were obtained. 3. The oxidized tubular member was subjected to hydrothermal treatment at 210°C for 8 hours. A 10 mol / L sodium hydroxide aqueous solution was used as the basic aqueous solution. In this way, fibrous sodium titanate (Na2Ti3O7) was formed on the surface of the tubular member. 4. 200 mL of palladium precursor solution (palladium ion concentration: 5 mM) was circulated through a tubular member over 3 hours. The flow rate was 20 mL / min. In this way, some of the cations contained in the fibrous titanate were exchanged for palladium ions. 5. 200 mL of silver precursor solution (silver ion concentration: 15 mM) was circulated through a tubular member over 3 hours. The flow rate was 20 mL / min. In this way, some of the cations contained in the fibrous titanate were further exchanged for silver ions. At this time, it is thought that core-shell particles, with palladium as the core and silver as the shell, were formed between the titanate anion layers. 6. 200 mL of sodium borohydride aqueous solution (4 mM) was circulated through a tubular member over 5 minutes. The flow rate was 20 mL / min. 7. After ion exchange, the tubular member was dried at 100°C for 3 hours. In this way, a catalytic reaction tube with fibrous catalyst distributed on its surface was obtained. The catalyst contained in this catalytic reaction tube corresponds to the catalyst according to one embodiment of the present invention.

[0062] The left panel of Figure 7 shows an SEM image of the surface of the tubular member in step 3. The right panel of the same figure shows a histogram representing the distribution of fiber diameters (fiber diameters were measured from the SEM image). The median fiber diameter in the histogram was 0.47 μm. Furthermore, EDX analysis revealed that the elemental distribution on the surface of the tubular member was 13.6 atomic% Na, 28.1 atomic% Ti, and 58.3 atomic% O. From this, it was confirmed that the fibrous portion produced in step 3 was sodium titanate.

[0063] The left panel of Figure 8 shows a TEM image of the surface of the tubular member in step 7. The right panel of the same figure shows a histogram representing the particle size distribution of core-shell particles inserted between the titanate anion layers (particle size was measured from the TEM image). The median particle size in the histogram was 7.78 nm. These particles are thought to be palladium or silver atoms.

[0064] [Example 2] Using the catalytic reaction tube prepared in Production Example 4, sodium bicarbonate was reduced to produce sodium formate (NaHCO3 + H2 → HCOONa + H2O). The reaction conditions were as follows. Reaction temperature: 80℃ • Reaction time: 2 hours • H2 gas flow rate: 10 mL / min • Concentration of NaHCO3 aqueous solution: 1M • Flow rate of NaHCO3 aqueous solution: 0.50 mL / min

[0065] In this way, sodium formate was produced using the catalyst according to one embodiment of the present invention. Since sodium formate can be easily converted to formic acid under acidic conditions, this production method can also be applied to the production of formic acid. After the reaction time, the amount of sodium formate produced was 0.46 mmol. Turnover rate per mole of palladium (mol) HCOONa / mol Pd ) was 46. [Industrial applicability]

[0066] This invention can be used in the production of methane or formic acid, etc.

Claims

1. A fibrous catalyst containing a metal oxygenate containing catalytically active species, The above metal oxygen salts are layered, The above-mentioned metal oxygen salt is one or more selected from the group consisting of titanates, molybdates, vanadates, tungstates, manganeses, nickelates, ironates, zirconates, germanates, and complex salts thereof. The catalytically active species is inserted between the layers of the above-mentioned layered metal oxygenate. catalyst.

2. The composition of the above metal oxygen salt is A ｘ B （ｗ－ｘ） M ｙ O ｚ Represented by, The catalyst according to claim 1: During the ceremony, A is the catalytically active species described above, B is a cation other than the catalytically active species mentioned above; M is one or more elements selected from the group consisting of titanium, molybdenum, vanadium, tungsten, manganese, nickel, iron, zirconium, and germanium. x is 0.01 to w; y is between 3 and 6; z is between 7 and 13; w is the value that makes the total charge zero.

3. A catalyst comprising the catalyst described in claim 1 or 2, Catalytic reaction tube.

4. A method for producing a catalyst containing a layered metal oxyacid, comprising the following step S3: Step S3: A step of replacing at least a portion of the cations contained between the layers of the above metal oxygenate with catalytically active species; Here, The above catalyst is fibrous, The above-mentioned metal oxygen salt is one or more selected from the group consisting of titanates, molybdates, vanadates, tungstates, manganeses, nickelates, ironates, zirconates, germanates, and composite salts thereof.

5. The manufacturing method according to claim 4, further comprising the following step S2 prior to step S3: Step S2: A step in which a metal oxide is hydrothermally treated under basic conditions to form a fibrous metal oxyacid.

6. The pH in step S3 above is 2.5 or higher. The manufacturing method according to claim 4.

7. The temperature in step S3 described above is 80 to 220°C. A method for producing a catalyst according to claim 4.

8. A fibrous catalyst precursor containing a metal oxygenate, The above metal oxygen salts are layered, The above-mentioned metal oxygen salt is one or more selected from the group consisting of titanates, molybdates, vanadates, tungstates, manganeses, nickelates, ironates, zirconates, germanates, and complex salts thereof. Catalyst precursor.

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