Alkane dehydrogenation catalyst and method for producing hydrogen using the same

Abstract

Provided are: a catalyst that is used in a reaction for producing hydrogen from an alkane without emission of CO2; a method for producing hydrogen without emission of CO2 by using the catalyst; and a method for producing ammonia using, as a reducing agent, hydrogen produced using the catalyst. The alkane dehydrogenation catalyst according to the present disclosure contains a graphene having at least one structure selected from an atom vacancy structure, a 1-hydrogenated atom vacancy structure, a 2-hydrogenated atom vacancy structure, a 3-hydrogenated atom vacancy structure, and a nitrogen-substituted atom vacancy structure. The graphene preferably has 2-200 of the structures per 100 nm2 of the atomic film of the graphene. In addition, the hydrogen production method according to the present disclosure includes a step for extracting hydrogen from an alkane by using the alkane dehydrogenation catalyst.

Description

[Technical field]

[0001] The present disclosure relates to an alkane dehydrogenation catalyst and a method for producing hydrogen using the catalyst. This disclosure claims priority to Japanese Patent Application No. 2019-135780, filed in Japan on July 24, 2019, the contents of which are incorporated herein by reference. [Background technology]

[0002] Modern life is becoming more and more dependent on electrical energy. However, when electrical energy is obtained by burning fossil fuels, the problem is that the CO2 emitted by the burning of fossil fuels causes the greenhouse effect.

[0003] Hydrogen has therefore been drawing attention as a renewable energy source that does not emit CO2. Hydrogen can be combined with oxygen to generate electricity, or burned to produce thermal energy, without emitting CO2.

[0004] It is known that such useful hydrogen can be produced from fossil fuels by the steam reforming method (Patent Document 1). It is also known that hydrogen can be produced by the carbon monoxide shift reaction (Patent Document 2). However, this method has the problem that CO2 is emitted when hydrogen is produced. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-185059 A [Patent Document 2] JP 2006-232610 A Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, an object of the present disclosure is to provide a catalyst for use in a reaction for producing hydrogen from alkanes without emitting CO2. Another object of the present disclosure is to provide a method for producing hydrogen from alkanes without emitting CO2 using the catalyst. [Means for solving the problem]

[0007] As a result of intensive research by the present inventors to solve the above problems, they have found that by using graphene having at least one structure selected from an atom deficiency structure, a one-hydrogenated atom deficiency structure, a two-hydrogenated atom deficiency structure, a three-hydrogenated atom deficiency structure, and a nitrogen-substituted atom deficiency structure as an alkane dehydrogenation catalyst, hydrogen can be extracted from alkanes without emitting CO2. The present disclosure has been completed based on these findings.

[0008] That is, the present disclosure provides an alkane dehydrogenation catalyst comprising graphene having at least one structure selected from an atom deficiency structure, a one-hydrogenated atom deficiency structure, a two-hydrogenated atom deficiency structure, a three-hydrogenated atom deficiency structure, and a nitrogen-substituted atom deficiency structure.

[0009] The present disclosure also provides a method for producing a graphene having at least one structure selected from an atom deficiency structure, a one-hydrogenated atom deficiency structure, a two-hydrogenated atom deficiency structure, a three-hydrogenated atom deficiency structure, and a nitrogen-substituted atom deficiency structure, the method comprising the steps of: forming a 100 nm atomic film of graphene; 2 The alkane dehydrogenation catalyst has 2 to 200 carbon atoms per carbon atom.

[0010] The present disclosure also provides a method for producing an alkane dehydrogenation catalyst, comprising the step of bombarding raw graphene with high-energy particles to obtain the alkane dehydrogenation catalyst.

[0011] The present disclosure also provides a method for producing the alkane dehydrogenation catalyst, using graphene obtained by a detonation method as raw graphene.

[0012] The present disclosure also provides a method for producing hydrogen, comprising the step of extracting hydrogen from an alkane using the alkane dehydrogenation catalyst.

[0013] The present disclosure also provides a method for producing hydrogen, which involves a step of occluding hydrogen extracted from an alkane in atomic deficiency sites of graphene.

[0014] The present disclosure also provides a hydrogen production device that produces hydrogen by the above method.

[0015] The present disclosure also provides a method for producing ammonia, comprising producing hydrogen by the above-mentioned method and using the resulting hydrogen to reduce nitrogen oxides to obtain ammonia.

[0016] The present disclosure also provides an ammonia producing apparatus that produces ammonia by the above-mentioned method. Effect of the Invention

[0017] According to the alkane dehydrogenation catalyst of the present disclosure, hydrogen can be extracted from alkanes without emitting CO2 and without requiring a large amount of energy. In addition, the extracted hydrogen can be safely stored in the alkane dehydrogenation catalyst, and the stored hydrogen can be extracted as needed. In addition, a large amount of energy is not required when extracting hydrogen.

[0018] The hydrogen obtained in this way is extremely useful as a renewable energy source, and does not emit CO2 even when burned and used as thermal energy.

[0019] Therefore, the hydrogen obtained by the hydrogen production method disclosed herein is a "carbon-free" energy source that does not emit CO2 throughout the entire process from production to use. The hydrogen thus obtained can be used, for example, as an energy source for fuel cell vehicles and the like.

[0020] Furthermore, if hydrogen obtained by the above-mentioned hydrogen production method is used as a reducing agent for nitrogen oxides, ammonia can be produced efficiently. Here, ammonia is a substance with a high hydrogen density, and is liquefied under mild conditions. Furthermore, the possibility of using ammonia itself as a fuel has emerged. If ammonia could be used as a fuel, fuel would not be required when extracting energy from ammonia. For this reason, ammonia is suitable for mass transportation and storage of hydrogen energy, and is extremely useful as an energy carrier.

[0021] Therefore, if useful ammonia is produced as described above using hydrogen obtained by the hydrogen production method, it will be possible to store a large amount of hydrogen safely without emitting CO2 and to convert it into energy as needed. [Brief description of the drawings]

[0022] [Figure 1] FIG. 2 is a schematic diagram showing an atomic deficiency structure of V / graphene. [Diagram 2] FIG. 1 is a schematic diagram showing a one hydrogen atom deficiency structure of V1 / graphene. [Diagram 3] FIG. 1 is a schematic diagram showing a two-hydrogen atom deficiency structure of V11 / graphene. [Figure 4] FIG. 1 is a schematic diagram showing a three hydrogen atom deficiency structure of V111 / graphene. [Diagram 5] FIG. 1 is a schematic diagram showing a nitrogen-substituted atom deficiency structure of VNCC / graphene. [Figure 6] FIG. 1 is a schematic diagram showing hydrogen absorption and release reactions at atomic vacancies in V1 / graphene. [Figure 7] FIG. 1 is a schematic diagram showing hydrogen absorption and release reactions at atomic vacancies in VNCC / graphene. [Figure 8] FIG. 1 is a schematic diagram showing hydrogen absorption and release reactions at atomic vacancies in V111 / graphene. [Figure 9] FIG. 1 is a flow diagram showing an example of a schematic configuration of a hydrogen production device according to the present disclosure. [Figure 10]FIG. 1 is a schematic diagram of a reaction vessel 11 having a mesh-like catalyst supporting structure. [Figure 11] FIG. 1 is a flow diagram showing an example of a schematic configuration of an ammonia producing apparatus according to the present disclosure. [Figure 12] FIG. 2 is a graph showing the change in hydrogen amount before and after the reaction of the catalyst (2) obtained in Example 2 with n-butane. [Figure 13] FIG. 2 is a graph showing the change in hydrogen amount before and after reaction with an alkane for each site of the catalyst (2) obtained in Example 2. [Figure 14] FIG. 2 is a graph showing the change in hydrogen amount at the atom deficiency site of the catalyst (2) obtained in Example 2 before and after reaction with an alkane. [Figure 15] FIG. 1 shows the evaluation results of the reaction pathway and activation barrier between V1 / graphene and n-octane, obtained by an electronic state calculation method based on the density functional theory. [Figure 16] FIG. 1 shows the reaction pathway and activation barrier evaluation results of VNCC / graphene with n-octane, obtained by electronic structure calculation based on density functional theory. [Figure 17] FIG. 17 is a diagram showing that there are multiple stages between (1)-a and (1)-b-2 in FIG. 16. [Figure 18] FIG. 1 shows the evaluation results of the reaction pathway and activation barrier between V111 / graphene and n-octane, obtained by an electronic state calculation method based on the density functional theory. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] [Alkane dehydrogenation catalyst] The alkane dehydrogenation catalyst of the present disclosure includes graphene having at least one structure (preferably a structure including an atom deficiency site) selected from an atom deficiency structure, a one-hydrogenated atom deficiency structure, a two-hydrogenated atom deficiency structure, a three-hydrogenated atom deficiency structure, and a nitrogen-substituted atom deficiency structure. In one example of the alkane dehydrogenation catalyst, the atom deficiency structure, the one-hydrogenated atom deficiency structure, the two-hydrogenated atom deficiency structure, the three-hydrogenated atom deficiency structure, or the nitrogen-substituted atom deficiency structure of graphene acts as an active site.

[0024] Although a typical catalyst contains a metal as an active component, when the alkane dehydrogenation catalyst contains graphene having at least one structure selected from an atom deficiency structure, a 1-hydrogenated atom deficiency structure, a 2-hydrogenated atom deficiency structure, a 3-hydrogenated atom deficiency structure, and a nitrogen-substituted atom deficiency structure, the structure acts as an active site, and therefore there is no need to contain a metal. The alkane dehydrogenation catalyst may contain any metal, but the metal content may be, for example, 1 wt % or less, 0.1 wt % or less, or 0.01 wt % or less of the graphene content, or may be substantially free of metal.

[0025] The alkane dehydrogenation catalyst may contain graphene having at least one structure selected from an atom deficiency structure, a one-hydrogenated atom deficiency structure, a two-hydrogenated atom deficiency structure, a three-hydrogenated atom deficiency structure, and a nitrogen-substituted atom deficiency structure. However, it is preferable to select and use a structure according to the application, since a more excellent catalytic effect (or an effect of lowering the activity barrier) can be obtained.

[0026] For example, when the main purpose is to lower the activity barrier of the hydrogen absorption reaction from alkanes, it is preferable to use graphene containing at least an atomic deficiency structure as a catalyst, because graphene containing at least an atomic deficiency structure has a particularly excellent hydrogen adsorption power and is therefore particularly effective in lowering the activity barrier.

[0027] When the main purpose is to lower the activity barrier of the reaction of abstracting a hydrogen atom from an alkane, it is preferable to use graphene containing at least a nitrogen-substituted atom deficiency structure as a catalyst, because graphene containing at least a nitrogen-substituted atom deficiency structure has the effect of dividing the reaction of abstracting a hydrogen atom from an alkane into multiple steps and lowering the activity barrier of each step.

[0028] In addition, in order to repeatedly perform the hydrogen absorption-release cycle from an alkane, it is preferable to use graphene containing at least two hydrogen atom deficiency structures or three hydrogen atom deficiency structures as a catalyst. When graphene containing at least two hydrogen atom deficiency structures or three hydrogen atom deficiency structures is used as a catalyst, energy is required to remove one hydrogen atom from an alkane, but thereafter, the alkane that has been destabilized by removing one hydrogen atom spontaneously decomposes and releases hydrogen. This is because the active layer wall of the hydrogen absorption-release reaction can be lowered, and the cycle can be smoothly carried out without requiring a large amount of energy.

[0029] The alkane dehydrogenation catalyst can lower the activity barrier associated with the dehydrogenation reaction of alkanes without generating CO2, and can efficiently extract hydrogen from alkanes under mild conditions. In addition, the hydrogen extracted from alkanes can be stored on the alkane dehydrogenation catalyst, and the stored hydrogen can be released as needed.

[0030] (Graphene with atomic defects) The graphene having atomic defects in the present disclosure (sometimes referred to as "V / graphene" in the present specification) is a graphene having sp 2 Graphene is a two-dimensional atomic membrane in which carbon atoms are bonded in a honeycomb lattice pattern. A hole is formed when a carbon atom is missing from a specific location in graphene, i.e., when a carbon atom that should be present in a perfect honeycomb structure is missing (see Figure 1).

[0031] The V / graphene has an atomic deficiency structure (sometimes referred to as a "V structure" in this specification) that acts as an active site (more specifically, lowers the activity barrier during the hydrogen absorption and / or desorption reaction).

[0032] The V / graphene is a 100 nm thick graphene atomic film. 2It is preferable that the number of V structures is, for example, 2 to 200 (particularly, 50 to 150, and particularly 70 to 120) per unit area. If the number of V structures is too few or too many, the effects of the present invention according to the present disclosure tend to be difficult to obtain.

[0033] The V / graphene may have either of two types of edge structures, a zigzag type and an armchair type. Furthermore, the V / graphene may have one or more types of substituents at the edge. Examples of the substituents include hydrogen atoms, halogen atoms, C 1-20 Examples of the functional group include an alkyl group and an oxygen-containing functional group.

[0034] The graphene constituting the V / graphene is, among others, a graphene having a large area (for example, 10 nm 2 or less), such as epitaxial graphene or graphene contained in soot (or graphite) obtained by a detonation method. 2 More than 100 nm, preferably 2 Thin film graphene having a large area of ​​at least 100 nm is preferred in that it stably improves heat resistance and at the same time, the surface area including catalytic active sites per unit weight of the catalyst becomes sufficiently large, or the specific surface area becomes sufficiently large.

[0035] (Graphene with 1, 2, or 3 hydrogen atom deficiencies) The graphenes having one, two, or three hydrogen atom deficiencies in the present disclosure are sp 2 Graphene is a two-dimensional atomic membrane in which carbon atoms are bonded in a honeycomb lattice. A hole is formed when a carbon atom is missing from a specific location in the graphene, i.e., a carbon atom that should be present in a perfect honeycomb structure is missing. 2 It has a structure in which 1 to 3 hydrogen atoms are bonded to a carbon atom.

[0036] More specifically, the graphene having one hydrogen atom deficiency (sometimes referred to as “V1 / graphene” in this specification) has a structure of sp 2Graphene is a two-dimensional atomic membrane in which carbon atoms are bonded in a honeycomb lattice. A hole is formed when a carbon atom is missing from a specific location in the graphene, i.e., a carbon atom that should be present in a perfect honeycomb structure is missing. 2 It has a structure in which a hydrogen atom is bonded to one of the carbon atoms (see Figure 2).

[0037] In the present disclosure, the graphene having two hydrogen atom defects (referred to herein as "V 11 Graphene (sometimes called "graphene") is a 2 Graphene is a two-dimensional atomic membrane in which carbon atoms are bonded in a honeycomb lattice. A hole is formed when a carbon atom is missing from a specific location in the graphene, i.e., a carbon atom that should be present in a perfect honeycomb structure is missing. 2 It has a structure in which one hydrogen atom is bonded to each of any two carbon atoms (see Figure 3).

[0038] In the present disclosure, the graphene having three hydrogenated atom defects (referred to herein as "V 111 Graphene (sometimes called "graphene") is a 2 Graphene is a two-dimensional atomic membrane in which carbon atoms are bonded in a honeycomb lattice. A hole is formed when a carbon atom is missing from a specific location in the graphene, i.e., a carbon atom that should be present in a perfect honeycomb structure is missing. 2 It has a structure in which one hydrogen atom is bonded to each of three carbon atoms (see Figure 4).

[0039] In the V1 / graphene, a structure with one hydrogen atom missing (sometimes referred to as a "V1 structure" in this specification) acts as an active site. The above V 11 / Graphene has a two hydrogen atom deficiency structure (referred to herein as "V 11 The structure (sometimes referred to as the "structure") acts as an active site. The above V 111 / Graphene has a three hydrogen atom deficiency structure (referred to herein as "V 111The structure (sometimes referred to as the "structure") acts as an active site. Incidentally, "acting as an active site" means acting to lower the activity barrier during the hydrogen absorption and / or desorption reaction.

[0040] In the graphene having one, two or three hydrogen atom deficiencies, V1 structure, V 11 Structure and V 111 The structure selected is a 100 nm graphene atomic membrane. 2 It is preferable that, for example, 2 to 200 (particularly, 50 to 150, and particularly 70 to 120) are present per V1 structure. 11 Structure and V 111 If the presence of a structure selected from the structures is insufficient or excessive, the effects of the invention according to the present disclosure tend to be difficult to obtain.

[0041] The edge structure of the graphene having one, two or three hydrogen atom defects may be of two types, a zigzag type and an armchair type. Furthermore, the graphene having one, two or three hydrogen atom defects may have one or more types of substituents at the edge. Examples of the substituents include hydrogen atoms, halogen atoms, C 1-20 Examples of the functional group include an alkyl group and an oxygen-containing functional group.

[0042] The graphene constituting the graphene having one, two, or three hydrogen atom defects may be a large-area graphene (e.g., 10 nm 2 ) such as epitaxial graphene or graphene contained in soot (or graphite) obtained by a detonation method. 2 More than 100 nm, preferably 2 Thin film graphene having a large area of ​​at least 100 nm is preferred in that it stably improves heat resistance and at the same time, the surface area including catalytic active sites per unit weight of the catalyst becomes sufficiently large, or the specific surface area becomes sufficiently large.

[0043] (Graphene with nitrogen-substituted atomic defects) In the present disclosure, the graphene having nitrogen-substituted atomic defects (referred to herein as "V NGraphene (sometimes called "graphene") is a 2 Graphene is a two-dimensional atomic membrane in which carbon atoms are bonded in a honeycomb lattice. A hole is formed when a carbon atom is missing from a specific location in the material. In other words, a carbon atom that should be present in a perfect honeycomb structure is missing. The hole is then surrounded by 12 sp 2 sp on any one of the carbon atoms or near the hole 2 A structure in which any one of the carbon atoms is replaced by a nitrogen atom (referred to herein as "V N The structure is sometimes referred to as a "structure" (see FIG. 5).

[0044] V N The local arrangement of nitrogen and carbon in the structure is, for example, a ketoimine structure, an imine structure, a planar carbon nitride structure (=graphitic carbon nitride), etc. N / Graphene is one type of V selected from the above structures N may have a structure, or may have two or more types of V N It may have a structure.

[0045] The above V N The nitrogen atom content in graphene is V N The content is, for example, 100 ppm to 7 wt % of the total amount of graphene, and among these, 3 to 5 wt % is preferred since it can further lower the activity barrier associated with the dehydrogenation reaction of alkanes. N If the presence of the structure is insufficient or excessive, the effects of the invention according to the present disclosure tend to be difficult to obtain.

[0046] And the V N / Graphene has a nitrogen-substituted atom-deficient structure (referred to herein as "V NCC The carbon nanotube structure (sometimes referred to as a "structure") acts as an active site (specifically, lowers the activity barrier during the hydrogen absorption and / or desorption reaction).

[0047] The above V N / Graphene is a 100nm thick film of graphene atoms. 2For example, 2 to 200 (especially 50 to 150, especially 70 to 120) V NCC It is preferred that the compound has the structure V NCC If the presence of the structure is insufficient or excessive, the effects of the invention according to the present disclosure tend to be difficult to obtain.

[0048] The above V N There are two types of edge structures of graphene: zigzag type and armchair type, either of which may be used. N The graphene may have one or more kinds of substituents at the end. Examples of the substituents include a hydrogen atom, a halogen atom, and C 1-20 Examples of the functional group include an alkyl group and an oxygen-containing functional group.

[0049] The above V N As the graphene constituting the graphene, in particular, epitaxial graphene and thin-film graphene isolated from graphite obtained by the detonation method are used. 2 More than 100 nm, preferably 2 Thin film graphene having a large area of ​​at least 100 nm is preferred in that it stably improves heat resistance and at the same time, the surface area including catalytic active sites per unit weight of the catalyst becomes sufficiently large, or the specific surface area becomes sufficiently large.

[0050] [Method of manufacturing alkane dehydrogenation catalyst] The alkane dehydrogenation catalyst can be produced through a process of bombarding raw graphene with high-energy particles.

[0051] The above-mentioned alkane dehydrogenation catalyst is preferably produced through the following steps. Step A: Producing raw graphene Step B: Collision of high-energy particles (electrons, ions, etc.) with the graphene obtained

[0052] (Method of producing an alkane dehydrogenation catalyst containing V / graphene) The alkane dehydrogenation catalyst containing V / graphene can be produced, for example, through the following steps. Step A: Producing raw graphene Step B: Collision of the obtained graphene with high-energy particles to obtain graphene with atomic defects (=V / graphene).

[0053] Step A is a step of producing raw graphene, that is, graphene that is a raw material for an alkane dehydrogenation catalyst. The raw graphene can be produced by various methods, but it is preferable to use at least one selected from epitaxial graphene and chemically synthesized single-layer nanographene, since it can increase the specific surface area and thereby maximize the contact area between the active sites of the catalyst and the alkane in the gas phase or liquid phase.

[0054] Alternatively, graphene obtained by a CVD method in which a hydrocarbon such as methane is heated in the presence of a metal catalyst may be used.

[0055] Furthermore, thin-film graphene obtained by the detonation method (details will be described later) may contain nitrogen in some parts, and this can also be used as raw graphene for V / graphene or V1 / graphene.

[0056] Epitaxial graphene can be synthesized, for example, by pyrolyzing a SiC substrate (for example, by heating at an extremely high temperature of about 2150° C.).

[0057] Examples of the high energy particles used in step B include electrons and ions.

[0058] As a method for colliding electrons with graphene, a method of directly irradiating graphene with an electron beam or an internal electron irradiation method utilizing the Compton effect caused by gamma ray irradiation can be used.

[0059] As the ions, it is preferable to use ions obtained by ionizing an inert gas (for example, argon gas, neon gas, helium gas, xenon gas, krypton gas, nitrogen gas, etc.).

[0060] As a method for bombarding graphene with ions, for example, a vacuum chamber (with a vacuum level of, for example, 0.1×10) having a high-melting-point transition metal filament heated to about 1000 to 2500° C. and an electrically insulated grid electrode is used. -5 ~1.5×10 -5 A method in which a small amount of inert gas is introduced into a filament at 1000 rpm (1 Pa), a voltage of, for example, 0 to 500 V is applied between a filament and a grid electrode to extract thermoelectrons, which ionize the inert gas, and a high voltage (for example, 0.02 to 4.0 kV) is applied between the target graphene and the electrode to collide the ions with the surface of the target graphene at high speed (the ion collision time is, for example, 1 to 60 minutes), thereby ejecting carbon atoms that constitute the graphene (ion sputtering method).

[0061] By colliding high-energy particles with graphene, it is possible to knock carbon atoms out of the graphene structure at any position, creating atomic vacancies, while basically maintaining the graphene structure.

[0062] (V1 / Method of producing an alkane dehydrogenation catalyst containing graphene) The alkane dehydrogenation catalyst containing V1 / graphene can be produced, for example, through the following steps. Step A: Producing raw graphene Step B: Collision of the obtained graphene with high-energy particles to obtain graphene with atomic defects (=V / graphene). Step C: Hydrogenating graphene with atomic deficiencies (=V / graphene) to obtain graphene with one hydrogenated atomic deficiency (=V1 / graphene)

[0063] Steps A and B can be performed using a method similar to the method for producing an alkane dehydrogenation catalyst containing V / graphene.

[0064] The hydrogenation of V / graphene in step C can be carried out, for example, by reacting V / graphene with hydrogen gas (molecular hydrogen).

[0065] The hydrogen partial pressure during hydrogenation is, for example, 10 -7 This pressure is about 2 atm. This introduces hydrogen atoms into the atomic vacancies of graphene, resulting in V1 / graphene.

[0066] The alkane dehydrogenation catalyst comprising V1 / graphene can also be prepared via the following steps. Step A: Producing raw graphene Step D: The obtained raw graphene is bombarded with hydrogen ions to form atomic vacancies and to hydrogenate the graphene, thereby obtaining V1 / graphene.

[0067] In step A, a method similar to the method for producing an alkane dehydrogenation catalyst containing V / graphene can be adopted.

[0068] In step D, the hydrogen ions can be collided with the raw graphene by contacting molecular hydrogen with a high-melting-point transition metal filament heated to about 1000 to 2500°C, and then reacting the generated atomic hydrogen with the raw graphene.

[0069] (V 11 / Method of manufacturing an alkane dehydrogenation catalyst containing graphene) V 11 For example, the graphene-containing alkane dehydrogenation catalyst is produced by bombarding the raw graphene with hydrogen ions to form atomic vacancies and hydrogenate the graphene, resulting in the formation of V 11 Alternatively, V / graphene or V1 / graphene can be produced by hydrogenation.

[0070] (V 111 / Method of manufacturing an alkane dehydrogenation catalyst containing graphene) V 111 For example, the graphene-containing alkane dehydrogenation catalyst is produced by bombarding the raw graphene with hydrogen ions to form atomic vacancies and hydrogenate the graphene, resulting in the formation of V 111 Alternatively, V / graphene, V1 / graphene, or V11 / Graphene can also be produced by hydrogenating it.

[0071] (V N / Method of manufacturing an alkane dehydrogenation catalyst containing graphene) V N The graphene-containing alkane dehydrogenation catalyst can be produced, for example, through the following steps. Step A: Producing raw graphene Step E: The obtained raw graphene is bombarded with nitrogen ions to form atomic vacancies and to nitrogenize the graphene to obtain graphene having nitrogen-substituted atomic vacancies (=V N / graphene)

[0072] In step A, a method similar to the method for producing an alkane dehydrogenation catalyst containing V / graphene can be adopted.

[0073] As a method for bombarding the raw graphene with nitrogen ions in step E, for example, a nitrogen beam source may be used as the ion source of an ion sputtering device, and an acceleration voltage may be set to about 0.1 to 1 MeV (preferably 0.18 to 0.22 MeV), and the raw graphene may be irradiated with a nitrogen beam to form defects and perform nitrogen substitution at the same time. Note that the raw graphene may be exposed to nitrogen gas during or after the irradiation with the nitrogen beam.

[0074] Also, V N The graphene-containing alkane dehydrogenation catalyst can also be produced through the following steps. Step A': Producing nitrogen-containing raw graphene Step F: The obtained nitrogen-containing raw graphene is bombarded with high-energy particles to produce graphene having nitrogen-substituted atomic defects (=V N / graphene)

[0075] Step A' is a step of producing nitrogen-containing raw graphene. As the nitrogen-containing raw graphene, graphene obtained by a detonation method (more specifically, thin-film graphene contained in soot (or graphite) obtained by a detonation method) and CVD-synthesized graphene are preferable because they have a large specific surface area, and therefore the contact area between the active site of the catalyst and the alkane in the gas phase or liquid phase is maximized.

[0076] In the detonation method, graphene can be produced through the following steps. [1] An explosive with an electric detonator attached is placed inside a pressure-resistant container for detonation, and the container is sealed in a state where atmospheric gas and the explosive coexist. The container is made of, for example, iron, and has a volume of, for example, 0.1 to 40 m. 3 As the explosive, a mixture of trinitrotoluene (TNT) and cyclotrimethylenetrinitramine, i.e., hexogen (RDX), can be used. The mass ratio of TNT to RDX (TNT / RDX) is, for example, in the range of 40 / 60 to 60 / 40.

[0077] [2] Next, an electric detonator is detonated to detonate the explosives inside the container. During the detonation, the explosives undergo partial incomplete combustion, liberating carbon, which then produces graphite.

[0078] [3] Next, leave it at room temperature for about 24 hours to cool the container and its interior. After cooling, scrape off the graphite containing impurities (= crude graphite) adhering to the inner wall of the container with a spatula and collect it.

[0079] [4] Next, the recovered crude graphite is subjected to a purification treatment to obtain purified graphite. The purification treatment is preferably carried out by a method in which the crude graphite is washed by stirring in a washing solution [water or an acidic dispersion solution (e.g., hydrochloric acid, nitric acid, sulfuric acid), then pulled out of the washing solution and dried. The drying temperature can be appropriately selected within a range from room temperature to 1500°C. After drying, the crude graphite may be further annealed by holding it at a temperature from room temperature to 1500°C for 1 minute to 5 hours.

[0080] The purified graphite obtained by the above method is composed of a plurality of graphenes bonded together by van der Waals forces, and graphene can be isolated from the graphite. As a method for isolating graphene, a well-known and commonly used method can be adopted, such as a method of peeling off the graphene on a silicon oxide surface or cutting and peeling off the graphene by a mechanical method (e.g., milling method).

[0081] CVD-synthesized graphene can be produced by a method (CVD method) in which a hydrocarbon such as methane and ammonia are heated in the presence of a metal catalyst.

[0082] Step F can be performed in the same manner as step B, except that nitrogen-containing raw graphene is used instead of graphene.

[0083] The nitrogen content in the nitrogen-containing raw graphene is, for example, in the range of 1 ppm to 50% by weight, and in particular, in the range of 1 to 10% by weight, from the viewpoint of enhancing the catalytic effect of the resulting alkane dehydrogenation catalyst.

[0084] V N As the raw material for the graphene-containing alkane dehydrogenation catalyst, in addition to the nitrogen-containing raw material graphene, for example, a raw material graphene having a nitro group, an amide group, an oxime structure, or a nitrile structure, a raw material nanographene having any of the groups or structures, and a polycyclic aromatic compound having any of the groups or structures can be used.

[0085] [Hydrogen production methods] The method for producing hydrogen according to the present disclosure includes a step of extracting hydrogen from an alkane using the alkane dehydrogenation catalyst.

[0086] In the above step, hydrogen extracted from the alkane is absorbed in the atom vacancy sites of the alkane dehydrogenation catalyst, and the absorbed hydrogen can be released from the alkane dehydrogenation catalyst as required.

[0087] Therefore, the method for producing hydrogen preferably comprises the following steps: Step (1): A step of extracting hydrogen from alkanes using an alkane dehydrogenation catalyst and storing it (hydrogen absorption step) Step (2): Step of releasing hydrogen from alkane dehydrogenation catalyst (hydrogen releasing step)

[0088] As the alkane (=raw material alkane), for example, an alkane having 3 to 25 carbon atoms can be used. Specific examples of the alkane include linear or branched alkanes such as n-propane, n-butane, isobutane, n-pentane, n-hexane, n-heptane, n-octane, 3-methylheptane, n-nonane, and paraffin; and cycloalkanes such as cyclopropane, cyclopentane, cyclohexane, and cyclooctane. These can be used alone or in combination of two or more. The raw material alkane may also contain components other than alkanes.

[0089] The amount of the alkane dehydrogenation catalyst used is, for example, about 0.0001 to 1 part by weight, and preferably 0.01 to 0.25 parts by weight, relative to 100 parts by weight of the alkane.

[0090] For example, the alkane dehydrogenation catalyst may be V / graphene, V1 / graphene, or V 11 / Graphene, or V N When graphene is used, the following reaction takes place in the above step (1) (hydrogen storage step), allowing a large amount of hydrogen to be stored in the catalyst. Step (1)-1: A hydrogen atom site of an alkane is adsorbed to an atom vacancy site of graphene, and two hydrogen atoms are removed from the alkane, and the two removed hydrogen atoms are incorporated into the atom vacancy site. Step (1)-2: The hydrogen atoms captured at the atomic vacancy sites are diffused from the sites to other sites on the graphene and stored there.

[0091] For example, when V / graphene is used as an alkane dehydrogenation catalyst, in step (1)-1, the hydrogen atom site of the alkane is adsorbed to the atom-deficient site of the V structure of graphene, and the atom-deficient site takes in two hydrogen atoms of the alkane. As a result, the structure of the atom-deficient site changes from an atom-deficient structure (V structure) to a two-hydrogen atom-deficient structure (V 11 structure).

[0092] The resulting two hydrogen atom deficient structure (V 11 In the step (1)-2, two hydrogen atoms present at the atom-deficient site of graphene migrate from the atom-deficient site to another site of the graphene by a surface diffusion reaction (migration) and are adsorbed on the carbon atom of the migration site. As a result, the structure of the atom-deficient site returns from the two-hydrogen atom-deficient structure to the atom-deficient structure.

[0093] In addition, the resulting two hydrogen atom deficiency structure (V 11 The other part of the structure is V, which is described later as an alkane dehydrogenation catalyst. 11 / The change is similar to that seen when graphene is used.

[0094] For example, when V1 / graphene is used as an alkane dehydrogenation catalyst, in step (1)-1, the hydrogen atom site of the alkane is adsorbed to the atom-deficient site of the V1 structure of graphene, and the atom-deficient site takes in two hydrogen atoms of the alkane. As a result, the structure of the atom-deficient site changes from a one-hydrogenated atom-deficient structure (V1 structure) to a three-hydrogenated atom-deficient structure (V 111 The structure changes to (Figure 6).

[0095] The resulting three hydrogen atom deficient structure (V 111 Then, in step (1)-2, two of the three hydrogen atoms present at the atom-deficient site migrate from the atom-deficient site to another site by a surface diffusion reaction (migration) and are adsorbed onto the carbon atom at the migration site. As a result, the structure at the atom-deficient site returns from a three-hydrogenated atom-deficient structure to a one-hydrogenated atom-deficient structure.

[0096] In addition, the three hydrogen atom deficiency structure (V 111The other part of the structure is V, which is described later as an alkane dehydrogenation catalyst. 111 / The change is similar to that seen when graphene is used.

[0097] For example, V is used as an alkane dehydrogenation catalyst. 11 When graphene is used, in step (1)-1, the hydrogen atom site of the alkane is converted to the V of the graphene. 11 The alkane is adsorbed to the atom-deficient site of the structure, and the atom-deficient site takes in two hydrogen atoms of the alkane. As a result, the structure of the atom-deficient site becomes a two-hydrogen atom-deficient structure (V 11 structure), the four hydrogen atom missing structure (V 211 structure).

[0098] Then, in step (1)-2, the two hydrogen atoms present at the atom-deficient site migrate from the atom-deficient site of graphene to another site by a surface diffusion reaction (migration) and are adsorbed on the carbon atom of the migration site. As a result, the structure of the atom-deficient site returns from a four-hydrogenated atom-deficient structure to a two-hydrogenated atom-deficient structure.

[0099] For example, V is used as an alkane dehydrogenation catalyst. N When graphene is used, in step (1)-1, the hydrogen atom site of the alkane is converted to the V of the graphene. NCC The alkane is adsorbed to the atom-deficient site of the structure, and the atom-deficient site takes in two hydrogen atoms of the alkane. As a result, the structure of the atom-deficient site becomes a nitrogen-substituted atom-deficient structure (V NCC From the structure), the two hydrogen nitrogen substituted atom missing structure (V NCHCH The structure changes to (Figure 7).

[0100] Then, in step (1)-2, the two hydrogen atoms present at the atom-deficient site migrate from the atom-deficient site to another site by a surface diffusion reaction (migration) and are adsorbed on the carbon atom of the migration destination. As a result, the structure of the atom-deficient site returns from the dihydrogen nitrogen-substituted atom-deficient structure to the nitrogen-substituted atom-deficient structure.

[0101] When the structure of the graphene at the atomic vacancy site is restored in step (1)-2 as described above, the reaction (= hydrogen absorption reaction) proceeds again in the order of steps (1)-1 to (1)-2. As this hydrogen absorption reaction proceeds continuously, a large amount of hydrogen atoms can be extracted from the alkane and stored in the alkane dehydrogenation catalyst.

[0102] The amount of storable hydrogen atoms is, for example, 10 or more (for example, 10 to 30), preferably 20 or more (for example, 20 to 30) per atomic vacancy of graphene. The amount of storable hydrogen atoms is expressed by the ratio V1 / graphene (or V N / graphene) 1cm 2 For example, 1.0×10 16 1.0×10 or more (preferably 1.0×10 16 ~1.5×10 16 pcs).

[0103] In addition, in step (2), the hydrogen atoms stored in the alkane dehydrogenation catalyst in the above step (1) can be fused to form a hydrogen molecule by reversely carrying out the reaction in the order of step (1)-2 to step (1)-1, and the hydrogen molecule can be released from the alkane dehydrogenation catalyst.

[0104] For example, when V1 / graphene is used as the alkane dehydrogenation catalyst, in a three-hydrogen atom deficiency resulting from the absorption of hydrogen atoms, two of the three hydrogen atoms present in the atom deficiency are fused to form a hydrogen molecule, and the formed hydrogen molecule can be released to the outside. After the hydrogen molecule is released, a one-hydrogen atom deficiency is restored, but when a hydrogen atom moves there by migration, a three-hydrogen atom deficiency is formed again, and the above reaction proceeds. If this reaction proceeds continuously, a large amount of hydrogen molecules can be released from the alkane dehydrogenation catalyst.

[0105] As the alkane dehydrogenation catalyst, V NWhen graphene is used, in a dihydrogenated nitrogen-substituted atomic deficiency formed by absorbing a hydrogen atom, two hydrogen atoms present in the atomic deficiency are fused to form a hydrogen molecule, and the formed hydrogen molecule can be released to the outside. After the hydrogen molecule is released, the nitrogen-substituted atomic deficiency is restored, but when a hydrogen atom moves to this location by migration, a dihydrogenated nitrogen-substituted atomic deficiency is formed again, and the above reaction proceeds. If this reaction proceeds continuously, a large amount of hydrogen molecules can be released from the alkane dehydrogenation catalyst.

[0106] The above alkane dehydrogenation catalysts are V / graphene, V1 / graphene, and V 11 / Graphene, and V N Using at least one of the above, hydrogen is removed from an alkane, and the raw alkane is decomposed to generate a small alkane and an alkyne via an intermediate (a compound having a dangling bond that provides a lone electron pair). For example, n-octane represented by the following formula (P1) is used as the raw material, and two hydrogen atoms are removed from n-octane at the site surrounded by the dotted line. As a result, n-pentane represented by the following formula (P3) and propyne represented by the following formula (P4) are mainly generated via the intermediate represented by the following formula (P2). [ka]

[0107] Therefore, when V1 / graphene is used as the alkane dehydrogenation catalyst to extract hydrogen from n-octane, the following reaction proceeds in step (1) (hydrogen absorption step), and hydrogen is obtained together with n-pentane and propyne. As is clear from the reaction formula below, no CO2 is generated in this step. [ka]

[0108] When V1 / graphene is used as the alkane dehydrogenation catalyst, the activation barrier for the hydrogen absorption reaction is dramatically lowered compared to when graphene without atomic deficiencies is used. The ΔE1 is, for example, about 3.1 eV, and the ΔE2 is, for example, about 1.6 eV.

[0109] When V1 / graphene is used as the alkane dehydrogenation catalyst, the hydrogen absorption reaction can be advanced by heating to, for example, about 450 to 750°C.

[0110] When V1 / graphene is used as the alkane dehydrogenation catalyst, in step (2) (hydrogen releasing step), the hydrogen stored in the alkane dehydrogenation catalyst can be released without requiring a large amount of energy through the following reaction. [ka]

[0111] The above ΔE3 is, for example, about 4.7 eV. The above hydrogen releasing reaction can be advanced by heating at, for example, about 680 to 1200°C.

[0112] In addition, the alkane dehydrogenation catalyst may be a nitrogen-containing catalyst having a high affinity for hydrogen, such as V N When hydrogen is extracted from n-octane using graphene, the following reaction proceeds in step (1) (hydrogen absorption step), and hydrogen is obtained as a reaction product together with n-pentane and propyne. N When V1 / graphene is used, the reaction proceeds in more stages than when V1 / graphene is used. This lowers the activation barrier at each stage compared to when V1 / graphene is used. This makes it possible to proceed with the reaction under milder conditions than when V1 / graphene is used. [ka]

[0113] As the alkane dehydrogenation catalyst, VN When graphene is used, the above ΔE1-1 is, for example, about 1.7 eV, and the above ΔE1-2 is, for example, about 1.7 eV.

[0114] V N When graphene is used, the hydrogen absorption reaction can be promoted by heating at about 300 to 500° C., for example.

[0115] On the other hand, V N When graphene is used, the hydrogen release reaction has a value of ΔE3 of about 4.7 eV. Therefore, the reaction can be accelerated by heating the graphene at a temperature of about 680 to 1200° C.

[0116] [ka]

[0117] The reaction pressure in this case is, for example, about 100 to 1500 kPa. The reaction atmosphere is not particularly limited as long as it does not inhibit the reaction, and may be, for example, any of an air atmosphere, a nitrogen atmosphere, an argon atmosphere, and the like.

[0118] For example, V is used as the alkane dehydrogenation catalyst. 11 / Graphene and / or V 111 When graphene is used, the following reaction takes place in the above step (1) (hydrogen storage step), allowing a large amount of hydrogen to be stored in the catalyst.

[0119] Hereinafter, V will be used as the alkane dehydrogenation catalyst. 111 The case where graphene is used as the alkane dehydrogenation catalyst will be described in detail. 11 / When graphene is used, V 11 V from structure 111 Same as above except for the change in structure.

[0120] Step (1)-11: The hydrogen atom site of the alkane is V of graphene 111It adsorbs to the atom vacancy site of the structure, and one hydrogen atom is removed from the alkane. The removed hydrogen atom is 111 The missing atoms in graphene are incorporated into the missing atoms in the structure. As a result, the missing atoms in graphene are converted into a three-hydrogen missing atom structure (V 111 structure), the four hydrogen atom missing structure (V 211 structure). Step (1)-12: The alkane from which one hydrogen atom has been removed spontaneously decomposes to produce small alkanes and alkynes via intermediates, releasing one hydrogen atom. The released hydrogen atom is adsorbed and stored on a carbon atom at a site other than the atomic defect site of graphene. Step (1)-13: One of the four hydrogen atoms present at the atom-deficient site migrates from the atom-deficient site to another site by a surface diffusion reaction (migration) and is adsorbed on the carbon atom of the migration site. As a result, the structure of the atom-deficient site returns from a four-hydrogenated atom-deficient structure to a three-hydrogenated atom-deficient structure.

[0121] Thus, the three hydrogen atom deficiency structure (V 111 When the structure (a) is restored, the reaction (= hydrogen absorption reaction) proceeds again in the order of steps (1)-11 to (1)-12. As this hydrogen absorption reaction proceeds continuously, a large amount of hydrogen atoms can be extracted from the alkane and stored in the alkane dehydrogenation catalyst.

[0122] In addition, V is used as the alkane dehydrogenation catalyst. 111 When graphene is used to remove one hydrogen atom from an alkane, the raw alkane produces an unstable intermediate, which spontaneously decomposes to produce a small alkane and an alkene from which one hydrogen has been removed, and the alkene from which one hydrogen has been removed releases another hydrogen to produce an alkyne.

[0123] For example, n-octane represented by the following formula (P1) is used as a raw material, and as a result of removing one hydrogen atom from n-octane at the site surrounded by a dotted line, an intermediate represented by the following formula (P2') is generated. The intermediate represented by the following formula (P2') then spontaneously decomposes to mainly produce n-pentane represented by the following formula (P3) and an intermediate represented by the following formula (P4') in which one hydrogen atom is removed from propylene. The intermediate represented by the following formula (P4') then releases one hydrogen atom to generate propyne represented by the following formula (P4). [ka]

[0124] Therefore, V is used as the alkane dehydrogenation catalyst. 111 When using graphene to extract hydrogen from n-octane, the following reaction takes place in step (1) (hydrogen absorption step), and hydrogen is obtained along with n-pentane and propyne. As is clear from the reaction formula below, no CO2 is produced in this step. [ka]

[0125] As the alkane dehydrogenation catalyst, V 111 When graphene is used, the activation barrier of the hydrogen absorption reaction is dramatically lowered compared to when graphene without atomic deficiency is used as a catalyst. The above ΔE11 is, for example, about 4.0 eV, and the above ΔE12 is, for example, about 3.3 eV.

[0126] As the alkane dehydrogenation catalyst, V 111 When graphene is used, the hydrogen absorption reaction can be promoted by heating at about 570 to 950° C., for example.

[0127] As the alkane dehydrogenation catalyst, V 111When graphene is used, in step (2) (hydrogen releasing step), the hydrogen stored in the alkane dehydrogenation catalyst can be released without requiring a large amount of energy through the following reaction. [ka]

[0128] Step (2)-1: V of graphene 211 Hydrogen atoms migrate from other parts of graphene to the atom-deficient parts of the structure. Then, the structure of the atom-deficient parts becomes V 211 V from structure 221 The structure changes to a 5-hydrogen atom defect structure. Step (2)-2: Two of the five hydrogen atoms present in the atomic vacancy of graphene are fused to form a hydrogen molecule, and the formed hydrogen molecule is released to the outside.

[0129] The structure of the atomic deficiency site is V after releasing the hydrogen molecule. 111 Returning to the structure, this V 111 When a hydrogen atom migrates to the atom vacancy site of the structure, the structure of the atom vacancy site becomes V 111 V from structure 211 When this reaction continues, a large amount of hydrogen molecules can be released from the alkane dehydrogenation catalyst.

[0130] The above ΔE13 is, for example, about 1.1 eV, and the above ΔE14 is, for example, about 1.3 eV. The above hydrogen releasing reaction can be advanced by heating at, for example, about 270 to 480°C.

[0131] In addition, V after hydrogen molecule release 111 / Graphene can also release hydrogen atoms to the outside through the following reaction, but the activation barrier for the following reaction (ΔE15 below) is about 4.7 eV, and heating to about 680 to 1200°C is required. [ka]

[0132] Therefore, the above V 111 -V 211 -V 221 -V 111 The cycle of extracting, absorbing, and releasing hydrogen from alkanes is preferable because it allows hydrogen to be produced, stored, and released efficiently with a small amount of energy.

[0133] The reaction pressure of the hydrogen absorption reaction is, for example, about 1 to 1500 kPa. The reaction atmosphere is not particularly limited as long as it does not inhibit the reaction, and may be, for example, any of an air atmosphere, a nitrogen atmosphere, an argon atmosphere, and the like.

[0134] Also, V 111 / Graphene has another V 111 It also functions as a catalyst to promote the dehydrogenation reaction from graphene, which also produces hydrogen. [ka]

[0135] V 111 / Graphene also generates hydrogen through the following decomposition reaction (=dehydrogenation reaction). [ka]

[0136] As described above, by using the alkane dehydrogenation catalyst of the present disclosure, hydrogen can be extracted from alkanes by appropriately applying energy, and the extracted hydrogen can be released.

[0137] In addition, the catalytic effect of the alkane dehydrogenation catalyst may decrease as the atomic vacancies are repaired over time, but in such a case, the catalyst can be reactivated by bombarding it with ions to form atomic vacancies again, and therefore the catalyst can be used repeatedly, which is economical.

[0138] In the hydrogen production method of the present disclosure, hydrogen is obtained as a reaction product together with decomposition products of the raw alkane such as n-pentane and propyne. The reaction products are then separated by a well-known conventional method to obtain hydrogen, which is useful as a renewable energy source.

[0139] Hydrogen obtained in this manner not only does not generate CO2 when used as energy, but also does not generate CO2 during the hydrogen production process. Therefore, hydrogen obtained by the hydrogen production method disclosed herein is a "carbon-free" energy source that does not emit CO2 in any process from production to use.

[0140] In addition, hydrogen obtained using the above-mentioned alkane dehydrogenation catalyst can be used as a reducing agent for reducing nitrogen oxides, etc. Furthermore, by reducing nitrogen oxides, etc. using the above-mentioned alkane dehydrogenation catalyst, ammonia can be produced, and no CO2 is generated even during the ammonia production stage.

[0141] [Hydrogen production equipment] The hydrogen production device of the present disclosure includes a means (or device) for producing hydrogen by the above-mentioned hydrogen production method. Examples of the means or device include a reaction vessel for reacting an alkane dehydrogenation catalyst with an alkane, a heating means (or a heating device), a means (or a separation device) for separating hydrogen and decomposition products of the alkane from the product, and a releasing means for releasing the separated hydrogen.

[0142] By using the above-mentioned device, hydrogen can be efficiently produced with low energy without generating CO2 using alkanes such as n-pentane and propane as raw materials. In addition, hydrogen can be released as needed. Therefore, the above-mentioned hydrogen production device can be used as a device that supplies hydrogen to a fuel cell that uses hydrogen as fuel, and the above-mentioned fuel cell can be used as a power source for, for example, a fuel cell vehicle or the like.

[0143] An example of the hydrogen production apparatus is shown in Fig. 9. This hydrogen production apparatus includes a reaction vessel 1 in which a substrate member 30 carrying an alkane dehydrogenation catalyst 2 is fixed by a holding member 31, an alkane storage tank 3 in which raw alkane is stored, a reaction vessel heating device 4a, an alkane pressure control device 5a, a hydrogen release pressure control device 5b, an alkane / alkyne release pressure control device 5c, a lower alkane release pressure control device 5d, a gas separator 6, a gas separator heating device 4b, a gas separator cooling device 7, a hydrogen storage tank 8, an alkene / alkyne storage tank 9, and a lower alkane storage tank 10. Furthermore, this hydrogen production apparatus includes a control device 100.

[0144] The reaction vessel 1 is provided with an alkane supply port 20a, an emergency release port 20b, and a product gas release port 20c.

[0145] The alkane supply port 20a is connected to the alkane supply valve VLa via a first alkane supply piping member. The alkane supply valve VLa is connected to the alkane storage tank 3 via a second alkane supply piping member. The alkane pressure control device 5a, which operates under the control of the control device 100, controls the alkane supply valve VLa to adjust the amount of alkane supplied from the alkane storage tank 3 to the reaction vessel 1.

[0146] The emergency release port 20b is connected to the emergency release valve VLb via a first emergency release piping member. Here, the emergency release valve VLb is closed during normal operation. When the pressure inside the reaction vessel 1 measured by the pressure gauge PG exceeds a predetermined value, the valve opens. Then, the gas that has passed through the emergency release valve VLb is released to the outside via a second emergency release piping member.

[0147] The product gas release port 20c is connected to the gas separation device 6 via a product gas piping member.

[0148] The gas separation device 6 is provided with an inlet connected to a product gas outlet 20c, a hydrogen outlet 21a, an alkene / alkyne outlet 21b, and a lower alkane outlet 21c.

[0149] The hydrogen release port 21a is connected to a first hydrogen release valve VLc via a first hydrogen release piping member. The first hydrogen release valve VLc is then connected to the hydrogen storage tank 8 via a second hydrogen release piping member. The hydrogen release pressure control device 5b, which operates under the control of the control device 100, adjusts the amount of hydrogen supplied from the gas separation device 6 to the hydrogen storage tank 8 by controlling the release pressure of the produced hydrogen.

[0150] The alkene / alkyne discharge port 21b is connected to the alkene / alkyne discharge valve VLd via a first alkene / alkyne discharge piping member. The alkene / alkyne discharge valve VLd is connected to the alkane / alkyne storage tank 9 via a second alkene / alkyne discharge piping member. The alkene / alkyne pressure control device 5c, which operates under the control of the control device 100, adjusts the amount of alkane and / or alkyne supplied from the gas separation device 6 to the alkane / alkyne storage tank 9 by controlling the discharge pressure of the produced alkene and / or alkyne.

[0151] The light alkane discharge port 21c is connected to the light alkane discharge valve VLe via a first light alkane discharge piping member. The light alkane discharge valve VLe is connected to the light alkane storage tank 10 via a second light alkane discharge piping member. The light alkane pressure control device 5d, which operates under the control of the control device 100, adjusts the amount of light alkane supplied from the gas separation device 6 to the light alkane storage tank 10 by controlling the discharge pressure of the produced light alkane.

[0152] The reaction vessel 1 is sealed with the substrate member 30 housed therein. The alkane dehydrogenation catalyst 2 prepared in a powder form is fixed to the surface of the substrate member 30 or a mesh-like catalyst support structure using a support such as a low activity metal, graphite, alumina, or the like.

[0153] A mass spectrometer may be provided to confirm that the produced gas contains hydrogen. The mass spectrometer may be installed, for example, in a separate chamber that can be separated from the reaction vessel 1 by a gate valve. The produced gas may be introduced into the separate chamber via a heat-resistant membrane or tube (for example, a palladium membrane or tube).

[0154] The gas separation device 6 introduces the product gas produced in the reaction vessel 1 through the product gas outlet 20c, and separates the gas into hydrogen, a mixed gas of alkenes and / or alkynes, and lower alkanes by a gas separation membrane. Of the separated gases, hydrogen is discharged from a hydrogen outlet 21a, the mixed gas of alkenes and / or alkynes from an alkene-alkyne outlet 21b, and the lower alkanes from a lower alkane outlet 21c. The temperature inside the gas separation device 6 is controlled by the gas separation device heating device 4b and the gas separation device cooling device 7, which are controlled through the control device 100.

[0155] As the gas separation membrane, a porous or non-porous polymer membrane such as polyimide, silica membrane, zeolite membrane, carbon membrane, or the like can be used alone or in combination of two or more kinds.

[0156] The reaction vessel 1 can be replaced with a reaction vessel 11 having a mesh-like catalyst supporting structure for the purpose of increasing the contact area between the raw alkane and the catalyst.

[0157] An example of a reaction vessel 11 having a mesh-like catalyst support structure is shown in Fig. 10. The reaction vessel 11 is equipped with a temperature raising device 4c, a pressure control device 5e, and a discharge port 20d.

[0158] The reaction vessel 11 is connected to an alkane supply port 20a and a product gas discharge port 20c, similar to the reaction vessel 1. The alkane supply port 20a is further connected to an alkane supply valve VLa via a first alkane supply piping member. The product gas discharge port 20c is further connected to a gas separation device 6 via a product gas piping member.

[0159] According to the hydrogen production device, by increasing the temperature inside the reaction vessel 1 or reaction vessel 11 to about 300 to 750°C, hydrogen can be stored in the alkane dehydrogenation catalyst using the alkane as a raw material, and at the same time, alkenes and / or alkenes and lower alkanes can be produced. By increasing the temperature inside the reaction vessel 1 or reaction vessel 11 to about 650 to 1200°C, the stored hydrogen can be released from the alkane dehydrogenation catalyst. The reaction pressure at this time is, for example, about 1 to 1500 kPa. The released hydrogen is released from the production gas release port 20c, separated from the lower alkanes, alkenes, and alkynes by the gas separator 6, and stored in the hydrogen storage tank 8.

[0160] By utilizing the hydrogen production device having the above configuration, hydrogen can be produced without generating CO2, and hydrogen can be safely stored and taken out when needed.

[0161] [Ammonia production method and ammonia production apparatus] The hydrogen obtained without generating CO2 by the hydrogen production method of the present disclosure (or the hydrogen obtained without generating CO2 by using the hydrogen production device of the present disclosure) can be suitably used, for example, as a reducing agent. x If used as a reducing agent for NO, NO2, etc., ammonia can be produced without generating CO2.

[0162] The ammonia production apparatus of the present disclosure includes a means for producing ammonia by the hydrogen production method. An example of the ammonia production apparatus is shown in Fig. 11. The ammonia production apparatus includes a hydrogen production apparatus A equipped with a hydrogen discharge port 21a, a hydrogen supply valve VLg, a hydrogen buffer 12, a second hydrogen supply valve VLh, and a NO x Supply device 13 and NO x The system includes a reduction device 14, an ammonia separation device 15, a second exhaust gas purification device 16, an ammonia supply valve VLi, and an ammonia storage tank 17.

[0163] The hydrogen production device A is the above-mentioned hydrogen production device except for the hydrogen release port 21a. After the first hydrogen release piping member is removed, the hydrogen release port 21a is reconnected to the third hydrogen release piping member, and is connected to the second hydrogen release valve VLg via the third hydrogen release piping member. Furthermore, the second hydrogen release valve VLg is connected to the hydrogen buffer 12 via the fourth hydrogen release piping member.

[0164] On the other hand, NO x The supply device 13 supplies an inert gas (=NO x Gases that are inert to reactions with oxygen and hydrogen, such as nitrogen gas, helium gas, and argon gas, and NO x The mixed gas of NO x This is a device that supplies the mixed gas to the reduction device 14. For example, the mixed gas is selectively extracted from the exhaust gas of a boiler or an internal combustion engine, and the NO x Any device capable of supplying the reduction device 14 can be used.

[0165] The hydrogen buffer 12 is connected to the second hydrogen supply valve VLh via a first hydrogen supply piping member. Further, the second hydrogen supply valve VLh supplies NO x It is connected to the reduction device 14.

[0166] NO x The reduction device 14 is NO x NO which activates the reaction with hydrogen x The catalyst support base member may be provided with a reduction catalyst. x The reduction catalyst may be Cu-ZSM-5, alumina, or a platinum group catalyst such as platinum. As a result of the reduction reaction using hydrogen supplied from the hydrogen production device A as a reducing agent, a reaction gas containing ammonia is obtained.

[0167] NO x The reduction device 14 is connected to an ammonia separation device 15 via a reaction gas releasing member.

[0168] The ammonia separator 15 traps the ammonia contained in the reaction gas in water or a suitable adsorbent material and separates the nitrogen gas contained in the reaction gas. The nitrogen gas is sent to the exhaust purification device 16 via the exhaust supply piping member, and a small amount of unreacted NO is separated. x After purification treatment, the wastewater is released to the outside.

[0169] When ammonia is trapped using water, it is dissolved in water and stored in an ammonia storage tank. The ammonia can then be extracted by evaporating the water. When ammonia is trapped using an adsorbent, the ammonia is extracted by, for example, increasing the temperature of the adsorbent and stored in an ammonia storage tank.

[0170] By using the above ammonia production unit, alkanes and NO x By supplying this as a raw material, ammonia can be produced without generating CO2.

[0171] The above-mentioned configurations and combinations thereof of the present disclosure are merely examples, and addition, omission, substitution, and modification of the configurations are possible as appropriate within the scope of the present disclosure. Furthermore, the present disclosure is not limited to the embodiments, but is limited only by the claims. EXAMPLES

[0172] The present disclosure will be described more specifically below with reference to examples, but the present disclosure is not limited to these examples.

[0173] Example 1 (Production of alkane dehydrogenation catalyst) (Preparation of raw graphene) First, the explosive with the electric detonator attached was placed in a pressure-resistant container (made of iron, volume: 15 m 3) and the container was sealed. 0.50 kg of a mixture of TNT and RDX (TNT / RDX (mass ratio) = 50 / 50) was used as the explosive. Next, an electric detonator was detonated to detonate the explosive in the container. Next, the container and its inside were allowed to cool at room temperature for 24 hours. After this cooling, crude graphene (containing graphene produced by the above-mentioned detonation method and impurities) attached to the inner wall of the container was collected.

[0174] The obtained crude graphene was washed once with water and dried under reduced pressure. It was then heated and washed with 20% hydrochloric acid, centrifuged to obtain a precipitate, which was dried under reduced pressure and further annealed at 800°C for 180 minutes to obtain purified graphene. This was used as raw graphene.

[0175] The resulting purified graphene was dispersed in CS2 to obtain a dispersion liquid, which was then used to form a film on a conductive substrate by a drop-cast method to obtain a thin-film graphene.

[0176] (Sputtering process) Next, argon gas (2×10 -3 The graphene thin film was then irradiated with argon ions (0.4 μA) accelerated by an ion accelerating gun (ion accelerating voltage: 100 eV) at a current of 10 Pa for 30 minutes. 2 We obtained a V / graphene catalyst (1) with approximately one atomic deficiency structure per unit area. The amount of atomic deficiency structures introduced was estimated from the total ion current, assuming that the probability of deficiency generation by ions was 100%.

[0177] (Quantitative determination of hydrogen) The amount of hydrogen in the obtained catalyst (1) was measured by RBS / ERDA method under the following conditions. It was 9×10 15 atoms / cm 2 It was. <Measurement conditions> Incident ion: Helium ion (1.8 MeV) Recoil ion: Hydrogen ion Helium ion filter material: Aluminum Incident beam angle: 75° Recoil angle: 30°

[0178] Example 2 (Production of alkane dehydrogenation catalyst) As the raw graphene, instead of graphene obtained by the detonation method, multi-layer epitaxial graphene synthesized by heating a SiC substrate (product name "SiC single crystal wafer", manufactured by Nippon Steel & Sumitomo Metal Materials Co., Ltd.) at 2150°C was used, and the argon ion irradiation time was changed to 5 minutes. In the same manner as in Example 1, a catalyst (2) containing V / graphene was obtained. The amount of hydrogen contained in the catalyst (2) was 1.2 × 10 16 atoms / cm 2 It was.

[0179] Example 3 (Production of alkane dehydrogenation catalyst) The same purified graphene as in Example 1 was used as raw graphene, and the position for creating an atomic defect was set to a carbon atom position adjacent to a nitrogen atom in the purified graphene, and sputtering treatment was performed in the same manner as in Example 1. N Catalyst (3) containing V / graphene and V / graphene was obtained. The amount of hydrogen contained in catalyst (3) was 9 × 10 15 atoms / cm 2 The nitrogen content was 4% by weight of the total amount of the catalyst (3).

[0180] Example 4 (Production of Hydrogen) As a catalyst, 5 μg of the catalyst (2) obtained in Example 2 and 8 g of butane were charged into a reactor and reacted at room temperature for 30 minutes under normal pressure. After the reaction was completed, V1 / graphene and V 111 The catalyst containing graphene was taken out and the amount of hydrogen was measured by RBS / ERDA method. The amount of hydrogen produced was calculated by subtracting the amount of hydrogen contained in the catalyst before butane was reacted from the amount of hydrogen contained in the catalyst after butane was reacted. The results are shown in Figures 12 to 14.

[0181] 12 to 14 show that the hydrogen extracted from butane is stored in the atom vacancy sites of the catalyst.

[0182] Example 5 (production of hydrogen) The reaction path and activation barrier were calculated by the electronic state calculation method based on the density functional theory for the case where 745 g of catalyst (4) containing V1 / graphene obtained after the reaction in Example 4 was reacted with 114 g of n-octane. The results are shown in FIG. 15.

[0183] In addition, the activity barrier of the thermal decomposition reaction that decomposes n-octane into n-pentane and propyne is not less than 5 eV. Therefore, it was necessary to heat at a high temperature of about 700 to 1500°C. However, as shown in FIG. 15, by using the alkane dehydrogenation catalyst of the present disclosure, the activity barrier is lowered to 3.1 eV, and the reaction proceeds at a mild temperature of about 450 to 700°C.

[0184] Example 6 (Production of Hydrogen) The same procedure as in Example 5 was carried out except that the catalyst (3) obtained in Example 3 was used as the catalyst. The results are shown in Figures 16 and 17.

[0185] As shown in Figures 16 and 17, the thermal decomposition reaction of n-octane into n-pentane and propyne proceeds as follows: 16 It can be seen that by increasing the number of steps to obtain the above, the activation barrier at each step becomes smaller, and the reaction proceeds at a milder temperature.

[0186] Example 7 (Production of Hydrogen) As a catalyst, V obtained after the reaction of Example 4 was used. 111 The same procedure was carried out as in Example 5, except that the graphene-containing catalyst (5) was used. The results are shown in FIG.

[0187] As shown in Figure 18, the thermal decomposition reaction of n-octane into n-pentane and propyne proceeds as follows: 17 In the stage where n-pentane and propyne are obtained through this process, hydrogen adsorption onto the graphene surface further reduces the activation barriers for hydrogen diffusion and hydrogen desorption, allowing the reaction to proceed at a higher hydrogen partial pressure in the gas phase.

[0188] As a summary of the above, the configuration of the present disclosure and its variations are set forth below. [1] Graphene having at least one structure selected from an atom deficiency structure, a one-hydrogenated atom deficiency structure, a two-hydrogenated atom deficiency structure, a three-hydrogenated atom deficiency structure, and a nitrogen-substituted atom deficiency structure. [2] At least one structure selected from the group consisting of an atom deficiency structure, a one-hydrogen atom deficiency structure, a two-hydrogen atom deficiency structure, a three-hydrogen atom deficiency structure, and a nitrogen-substituted atom deficiency structure is formed on a 100 nm atomic layer of graphene. 2 The graphene according to [1], having 2 to 200 per one molecule. [3] The graphene according to [1] or [2], which is an alkane dehydrogenation catalyst. [4] Use of the graphene according to [1] or [2] as a catalyst for dehydrogenating alkane. [5] A method for producing graphene, comprising the steps of bombarding raw graphene with high-energy particles to obtain the graphene according to any one of [1] to [3]. [6] The method for producing graphene according to [5], wherein graphene obtained by a detonation method is used as raw graphene. [7] A method for producing hydrogen, comprising a step of extracting hydrogen from an alkane using the graphene described in [1] or [2]. [8] A method for producing hydrogen according to [7], which includes a step of absorbing hydrogen extracted from an alkane into atomic vacancies in graphene. [9] A hydrogen production apparatus that produces hydrogen by the method described in [7] or [8].

[10] An alkane dehydrogenation catalyst comprising graphene having at least one structure selected from an atom deficiency structure, a one-hydrogenated atom deficiency structure, a two-hydrogenated atom deficiency structure, a three-hydrogenated atom deficiency structure, and a nitrogen-substituted atom deficiency structure.

[11] The graphene has at least one structure selected from an atom deficiency structure, a one-hydrogenated atom deficiency structure, a two-hydrogenated atom deficiency structure, a three-hydrogenated atom deficiency structure, and a nitrogen-substituted atom deficiency structure, the graphene having an atomic film of 100 nm. 2 The alkane dehydrogenation catalyst according to

[10] , wherein the number of carbon atoms per one carbon atom is 2 to 200.

[12] A method for producing an alkane dehydrogenation catalyst, comprising the step of bombarding raw graphene with high-energy particles to obtain the alkane dehydrogenation catalyst according to

[10] or

[11] .

[13] The method for producing an alkane dehydrogenation catalyst according to

[12] , wherein graphene obtained by a detonation method is used as raw graphene.

[14] A method for producing hydrogen, comprising a step of extracting hydrogen from an alkane using the alkane dehydrogenation catalyst according to

[10] or

[11] .

[15] A method for producing hydrogen according to

[14] , which includes a step of absorbing hydrogen extracted from an alkane into atomic vacancies in graphene.

[16] A method for producing ammonia, comprising producing hydrogen by the method according to any one of [7], [8],

[14] , and

[15] , and using the hydrogen to reduce nitrogen oxides to obtain ammonia.

[17] An ammonia production apparatus for producing ammonia by the method described in

[16] . [Industrial Applicability]

[0189] According to the alkane dehydrogenation catalyst of the present disclosure, hydrogen can be extracted from alkanes without emitting CO2 and without requiring a large amount of energy. The obtained hydrogen is extremely useful as a renewable energy source, and does not emit CO2 even when combusted to use as thermal energy. [Explanation of symbols]

[0190] 1 Reaction vessel 2. Alkane dehydrogenation catalyst 3. Alkane Storage Tanks 4a Reaction vessel heating device 4b Gas separation device heating device 4c Heating device 5a Alkane pressure control device 5b Hydrogen release pressure control device 5c Alkane / alkyne discharge pressure control device 5d Lower alkane discharge pressure control device 5e Pressure control device 6 Gas Separation Device 7 Gas separator cooling device 8. Hydrogen storage tank 9. Alkene / Alkyne Storage Tanks 10. Low Alkane Storage Tanks 11 Reaction vessel 12 Hydrogen Buffer 13 NO x feeding device 14 NO x Reduction Device 15 Ammonia separation unit 16 Second exhaust purification device 17 Ammonia storage tank 20a Alkane supply port 20b Emergency outlet 20c Production gas outlet 20d outlet 21a Hydrogen release port 21b Alkene / alkyne outlet 21c Lower alkane outlet 30 Substrate material 31 Retaining member 100 Control device VLa Alkane Supply Valve VLb Emergency Release Valve VLd Alkene-Alkyne Release Valve VLe Light Alkane Release Valve PG Pressure Gauge A Hydrogen production equipment VLg Hydrogen supply valve VLh Second hydrogen supply valve VLi Ammonia Supply Valve

Claims

1. An alkane dehydrogenation catalyst comprising the following graphene: Graphene: Graphene having at least one structure selected from a one-hydrogenated atom-deficient structure, a two-hydrogenated atom-deficient structure, a three-hydrogenated atom-deficient structure, and a nitrogen-substituted atom-deficient structure, and having 2 to 200 of the structures per 100 nm 2 of the graphene atomic film.

2. An alkane dehydrogenation catalyst as described in claim 1, which does not contain metal or has a metal content of 1 weight % or less of the graphene content.

3. A method for producing an alkane dehydrogenation catalyst, comprising: obtaining the alkane dehydrogenation catalyst according to claim 1 or 2 through a step of colliding raw graphene with high-energy particles.

4. The method for producing an alkane dehydrogenation catalyst according to claim 3, wherein graphene obtained by a detonation method is used as raw graphene.

5. A method for producing hydrogen, comprising a step of extracting hydrogen from an alkane using the alkane dehydrogenation catalyst according to claim 1 or 2.

6. The method for producing hydrogen according to claim 5 , comprising a step of occluding hydrogen extracted from an alkane in atomic vacancies of graphene.

7. A hydrogen production device which produces hydrogen by the method according to claim 5 or 6.

8. 7. A method for producing ammonia, comprising producing hydrogen by the method according to claim 5 or 6, and using the hydrogen thus produced to reduce nitrogen oxides to obtain ammonia.

9. An apparatus for producing ammonia, which produces ammonia by the method according to claim 8.

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