Method for producing hydrogen gas

Abstract

This method for producing hydrogen gas comprises a step for obtaining hydrogen gas by irradiating a mixture containing a substrate containing at least one substance selected from the group consisting of chitin, cellulose, hemicellulose, lignin, glucose, cellobiose, starch, and alcohol and a catalyst containing a base metal component with light, the mixture containing a substrate containing at least one substance selected from the group consisting of chitin, cellulose, hemicellulose, lignin, glucose, cellobiose, starch, and alcohol.

Description

Technical Field

[0001] This disclosure relates to a method for producing hydrogen. Background Technology

[0002] To achieve a carbon-neutral society, methods for obtaining hydrogen from renewable biomass resources and alcohols are being investigated. Non-Patent Literature 1 describes a method for generating hydrogen from methanol using an iridium complex under reflux. Non-Patent Literature 2 describes a method for generating hydrogen from cellulose using an iridium complex at 135°C.

[0003] Existing technical documents Non-patent literature Non-patent literature 1: K. Fujita etc., Hydrogen Production from a Methanol-WaterSolution Catalyzed by an Anionic Iridium Complex Bearinga FunctionalBipyridonate Ligand under Weakly Basic Conditions, Angew. Chem.Int. Ed., 2015, 54, pp. 9057-9060 Non-patent literature 2: G. Toyooka etc., Hydrogen production from cellulosecatalyzed by an iridium complex in ionic liquid under mild conditions, Catal.Sci. Technol., 2021, 11, pp 2273-2279 Summary of the Invention

[0004] The problem that the invention aims to solve Previously, catalysts containing precious metals such as iridium were used in reactions to produce hydrogen from biomass resources and alcohols. However, precious metals are expensive and difficult to obtain in large quantities. Furthermore, reactions using conventional catalysts containing precious metals require high temperatures, which imposes a significant environmental burden. This disclosure provides a method for producing hydrogen that can obtain hydrogen from readily available raw materials using a mild and simple process while employing a catalyst containing base metals.

[0005] Methods for solving problems One aspect of this disclosure provides a method for producing hydrogen, comprising the step of obtaining hydrogen by irradiating a mixture comprising a substrate and a catalyst, wherein the substrate comprises at least one selected from the group consisting of chitin, cellulose, hemicellulose, lignin, glucose, cellobiose, starch, and alcohols, and the catalyst comprises a base metal component.

[0006] The aforementioned method for producing hydrogen utilizes a catalyst containing a base metal component and light as an energy source to obtain hydrogen from a substrate comprising at least one selected from the group consisting of chitin, cellulose, hemicellulose, lignin, glucose, cellobiose, starch, and alcohols. By using such a method, hydrogen can be obtained through a mild and simple process.

[0007] Invention Effects This disclosure provides a method for producing hydrogen, which can generate hydrogen from readily available raw materials using a catalyst containing base metal components through a mild and simple process. Attached Figure Description

[0008] [ Figure 1 [A diagram illustrating the reaction of producing hydrogen from methanol using metal ions as a catalyst.]

[0009] [ Figure 2 [A diagram illustrating the reaction in which hydrogen is produced from a compound containing hydroxyl groups using a manganese complex as a catalyst.]

[0010] [ Figure 3 [A diagram illustrating the reaction in which hydrogen is produced from a compound containing hydroxyl groups using an iron complex as a catalyst.]

[0011] [ Figure 4 [Image showing the detection of formaldehyde in the solution after the reaction in Example 5.] Detailed Implementation

[0012] The following describes embodiments of this disclosure. However, these embodiments are merely examples for illustrating this disclosure and are not intended to limit this disclosure to the following content. The upper or lower limit of the numerical range explicitly stated in this disclosure can be replaced with any value shown in the embodiments. The numerical range exemplified by "a~b" is a range with a as the lower limit, b as the upper limit, and including both a and b. Furthermore, the upper and lower limits stated separately can be arbitrarily combined. Unless otherwise specified, the materials or components exemplified in this disclosure can be used individually or in combination with two or more. In the description, elements having the same characteristics or functions are marked with the same symbols, and repeated descriptions are omitted.

[0013] One embodiment of the hydrogen production method includes a step of obtaining hydrogen by irradiating a mixture comprising a substrate and a catalyst, wherein the substrate comprises at least one selected from the group consisting of chitin, cellulose, hemicellulose, lignin, glucose, cellobiose, starch, and alcohols, and the catalyst comprises a base metal component. By including such a step, hydrogen can be produced without using high-energy sources such as high temperatures and expensive noble metal catalysts. Therefore, hydrogen can be obtained from readily available raw materials using a mild and simple process.

[0014] Chitosan, cellulose, hemicellulose, starch, and lignin are polysaccharides or macromolecules that can be found in biomass resources. Therefore, they are as readily available as alcohols. Biomass resources include woody biomass, marine biomass, and insect biomass. Woody biomass includes plants such as those in the genera *Cephalotaxus*, *Pinus*, *Larch*, *Abies*, and *Eucalyptus*. Marine biomass includes crustaceans such as snow crab (*Chionoecetes opilio*) shells and king crab (*Paralithodescamtschaticus*) shells. Insect biomass includes insect exoskeletons.

[0015] Glucose is a monosaccharide and can be included in the aforementioned biomass resources. Cellobiose is a disaccharide and can be included in the aforementioned biomass resources. Glucose and cellobiose can be decomposition products obtained from the breakdown of the aforementioned polysaccharides or macromolecules. The aforementioned biomass resources can include monosaccharides or disaccharides other than glucose and cellobiose.

[0016] Lignin can be kraft lignin. Kraft lignin can be a substance obtained by drying the black liquor removed during pulping from wood. From the viewpoint of promoting the reaction, lignin can include kraft lignin.

[0017] Alcohols can be straight-chain, branched, or cyclic. Examples of straight-chain alcohols include methanol, ethanol, and propanol (1-propanol). Examples of branched alcohols include isopropanol (2-propanol), 2-methyl-1-propanol, and 2-methyl-2-propanol. Examples of cyclic alcohols include cyclohexanol, cyclohexane-methanol, and cyclohexane-ethanol. Additionally, alcohols can also be polyols such as ethylene glycol, propylene glycol, and butanediol.

[0018] The substrate can be a polysaccharide or polymer selected directly from the group consisting of chitin, cellulose, hemicellulose, and lignin, or a biomass resource containing such a polysaccharide or polymer. The substrate can be glucose as a monosaccharide, cellobiose as a disaccharide, or a biomass resource containing such a monosaccharide or disaccharide. One or more of the above-mentioned biomass resources, monosaccharides, disaccharides, polysaccharides, and polymers can be mixed for use. When using an alcohol as a substrate, the alcohol can be used directly or mixed with the above-mentioned biomass resources, monosaccharides, disaccharides, polysaccharides, or polymers. One or more of the above-mentioned alcohols can be used.

[0019] Catalysts contain base metal components. Base metals are metals that are not precious metals, such as iron, manganese, nickel, copper, and zinc. Base metals are more readily available and cheaper than precious metals. Catalysts containing base metal components can be catalysts in which base metals are constituent elements. Examples of catalysts containing base metal components include ionic metal compounds containing base metal ions and complex compounds containing base metal complexes. Hereinafter, catalysts containing divalent or trivalent base metal ions will be referred to as "catalyst 1", catalysts containing manganese complexes will be referred to as "catalyst 2", and catalysts containing iron complexes will be referred to as "catalyst 3".

[0020] Catalysts containing base metal components can be used as catalysts for producing hydrogen. Therefore, the first catalyst, the second catalyst, and the third catalyst described above can be used as catalysts for producing hydrogen.

[0021] <Catalyst 1 and Reaction Conditions> The base metal component of the first catalyst comprises at least one of the group consisting of divalent and trivalent metal ions. That is, the first catalyst comprises divalent or trivalent base metal ions. Such base metal ions can be obtained by dissolving a metal compound or its hydrate in an alcohol and water, etc. Examples of such metal compounds include iron compounds, copper compounds, nickel compounds, zinc compounds, and manganese compounds. Examples of iron compounds include, for example, Fe. III Cl3, Fe II Cl2, Fe III (NO3)3, Fe II (NO3)2, Fe III 2(SO4)3 and Fe II (SO4), etc. Examples of copper compounds include Cu. II Cl2, Cu II SO4, etc. Examples of nickel compounds include Ni. II Cl2, etc. Examples of zinc compounds include Zn.II Cl2, etc. Examples of manganese compounds include Mn. II Cl2 and Mn II (NO3) 2, etc.

[0022] Examples of hydrates of metallic compounds include Fe. III Cl3·6H2O, Fe II Cl2·4H2O, Fe III (NO3)3·9H2O, Fe II (NO3)2·6H2O, Fe III 2(SO4)3·nH2O, Fe II (SO4)·nH2O, Cu II Cl2·2H2O, Cu II SO4·5H2O、Ni II Cl2·6H2O, Zn II Cl2·6H2O, Mn II Cl2·4H2O, Mn II Cl2·6H2O, and Mn II (NO3)2·nH2O, etc. The above-mentioned catalysts containing metal ions are readily available because they contain base metal components. Furthermore, catalysts containing metal ions can further promote hydrogen production when alcohols are used as substrates. From the viewpoint of further improving reactivity with alcohols and increasing the amount of hydrogen produced, the metal ion preferably includes iron ions selected from the group consisting of divalent and trivalent ions. Furthermore, from the viewpoint of further increasing the amount of hydrogen produced, the catalyst is more preferably ferric chloride, which includes at least one of the group consisting of divalent and trivalent ions. The above-mentioned catalysts containing divalent or trivalent base metal ions can be used as catalysts for producing hydrogen.

[0023] In the process of obtaining hydrogen, a catalyst containing divalent or trivalent metal ions can be mixed with a substrate comprising at least one monosaccharide, disaccharide, polysaccharide, polymer, or biomass resource selected from the group consisting of chitin, cellulose, hemicellulose, glucose, cellobiose, starch, and lignin to prepare a mixture. The catalyst in the mixture can be present in a proportion of 0.001–30 μmol, 0.025–2.5 μmol, 0.25–1.25 μmol, or 0.5–1.0 μmol relative to 100 mg of substrate. Maintaining the catalyst content within the above ranges can further promote the reaction. Polar solvents such as water, acetonitrile, propionitrile, ethyl acetate, dimethylformamide, dimethyl sulfoxide, and anisole can be used.

[0024] In the hydrogen production process, a catalyst containing divalent or trivalent metal ions can be mixed with a substrate containing an alcohol to prepare a mixture. In this case, the catalyst in the mixture can be contained in a proportion of 0.01 to 2.0 μmol, 0.01 to 1.0 μmol, 0.1 to 0.5 μmol, or 0.2 to 0.4 μmol relative to 1.5 mL of the alcohol as the substrate. By maintaining the catalyst content within the above ranges, the reaction can be further promoted. When using an alcohol as the substrate, since the alcohol is a liquid, a solvent is not required in the mixing with the catalyst. When using an alcohol as the substrate, water can be used as the solvent.

[0025] To promote the reaction, the mixture may contain a base. The base facilitates the removal of hydrogen atoms from the hydroxyl groups of the substrate coordinated with the catalyst. The base can be an inorganic or organic base. Inorganic bases may include, for example, sodium hydroxide, potassium hydroxide, and lithium hydroxide. Organic bases may include, for example, triethylamine, diazabicycloundecene, 1,8-bis(dimethylamino)naphthalene, and pyridine. The concentration of the base in the mixture relative to the total amount of the mixture after adding the base may be 10 mM or more, 50 mM or more, or 90 mM or more. Maintaining the base concentration within this range further promotes the reaction. The concentration of the base relative to the total amount of the mixture after adding the base may be 1000 mM or less, 500 mM or less, 250 mM or less, or 100 mM or less. Maintaining the base concentration within this range provides excellent operability. An example of a base concentration is 10–1000 mM.

[0026] Hydrogen gas can be obtained by irradiating the resulting mixture with light. The light can be visible light or ultraviolet light. For example, sunlight can be used. From the viewpoint of further promoting the reaction, ultraviolet light is preferred. Ultraviolet light can contain wavelengths of 250–385 nm, 275–385 nm, or 275–350 nm. Furthermore, the intensity of the ultraviolet light can be 1–1000 mW, 3–100 mW, 5–25 mW, or 7–20 mW. Such ultraviolet light allows for easy irradiation, has low intensity, and is highly safe. For example, such ultraviolet light can be applied using a 300W xenon light source, "MAX-303" (trade name), manufactured by Asahi Spectrophotometer Co., Ltd.

[0027] When irradiating with visible light, the visible light can contain wavelengths of 385-780 nm, 385-740 nm, 400-700 nm, or 450-600 nm. Furthermore, the intensity of the visible light can be 0.01-500 W, 0.05-100 W, 0.1-10 W, 0.15-1 W, 200-750 mW, or 250-500 mW. Such visible light is easy to irradiate and offers high safety. For example, such visible light can be irradiated using a 300W xenon light source, "MAX-303" (trade name), manufactured by Asahi Spectrophotometer Co., Ltd. Sunlight can contain wavelengths of both ultraviolet and visible light as described above.

[0028] Light irradiation can be carried out at room temperature or while the mixture is being heated. The temperature of the mixture during light irradiation can be, for example, 15–80°C or 20–60°C. By maintaining the temperature of the mixture during light irradiation within the above range, hydrogen can be obtained from the substrate using a gentler and simpler process. Furthermore, heating the mixture can also promote the reaction.

[0029] Before irradiating the mixture with light, a pretreatment step of heating the mixture can be performed. The heating temperature in the pretreatment step can be, for example, 120~200℃, 130~180℃, or 140~170℃. The heating time can be 2~6 hours or 3~5 hours. By performing the pretreatment step, the reaction for hydrogen generation can be promoted.

[0030] Light irradiation can be carried out in a nitrogen atmosphere with a purity of 99% by volume or higher, or in an air atmosphere. Carrying the reaction in an air atmosphere further promotes the reaction and simplifies the process. To achieve a nitrogen atmosphere, techniques such as the Schlenk line and glove boxes can be used. By carrying out the reaction in a nitrogen atmosphere, even when the catalyst contains metal complexes, the reaction can proceed.

[0031] The reaction mechanism for producing hydrogen from methanol using metal ions as catalysts is speculated as follows: Figure 1 As shown. Figure 1 (1) shows the metal ion M coordinated to the oxygen atom of methanol. n＋For simplicity, the coordinated methanol that is not involved in the reaction is represented by L. Due to the addition of base to the mixture, the proton of the hydroxyl group in methanol is released from the compound in (1), giving compound (2). By applying light energy to compound (2), as shown in (3), the coordination of the metal ion with oxygen is released, giving a free radicalized methoxy group. As shown in (4), the free radicalized methoxy group reacts with the CH bond of other methanol molecules coordinated to the metal ion and abstracts hydrogen, becoming methanol again. Thus, the compound with free radicalized carbon shown in (5) is obtained.

[0032] (5) The radicalized carbon bonds with the metal ion, temporarily forming a cyclic structure as shown in (6). Then, as the reaction proceeds, as shown in (7), the hydride and formaldehyde coordinate to the metal ion. After the formaldehyde is released from the metal ion, methanol coordinates with the metal ion again. At this time, the hydride coordinated to the metal ion bonds with the proton of the hydroxyl group to generate hydrogen gas. Hydrogen gas can be produced in this way. Then, the reaction returns to the state of (2), so the catalyst can be reused and the reaction can be repeated. As for the reaction after (2), the energy applied from the outside is only light energy, so hydrogen gas can be produced in a milder and simpler process by using such a catalyst. Even if the substrate is a monosaccharide, disaccharide, polysaccharide, or polymer derived from biomass resources, the hydroxyl group in the monosaccharide, disaccharide, polysaccharide, or polymer can be used to carry out the reaction in the same steps. It should be noted that the mechanism of hydrogen gas production is not limited to the above mechanism. In addition, gases other than hydrogen gas can also be produced. Examples of gases other than hydrogen include methane and ethane.

[0033] <Second Catalyst and Reaction Conditions> The second catalyst contains a manganese complex. Hydrogen gas can be obtained by irradiating a mixture of the manganese complex (as catalyst) and the substrate with light. The reactivity with chitin is improved by making the catalyst a manganese complex. Regarding the hydrogen gas generation process, the reaction temperature can be directly applied as described in the first catalyst section. Furthermore, the pretreatment process described in the first catalyst section can be performed before irradiating the mixture with light.

[0034] Manganese complexes can be solid or liquid. Being liquid, they offer superior operability and reactivity compared to solid catalysts because no solvent is required. Manganese complexes can be, for example, at least one complex selected from the group shown in formulas (a) and (b) below. The manganese complex of formula (a) is liquid, and the manganese complex of formula (b) is solid. Such manganese complexes can be commercially available. Furthermore, catalysts containing manganese complexes of formulas (a) and (b) below can be used as catalysts for the production of hydrogen.

[0035] [Chemical Formula 1] [Chemical Formula 2] When the catalyst contains a manganese complex, the catalyst content in the mixture containing the substrate and catalyst, relative to 1.0 mmol of substrate, can be 40–600 μmol, 80–300 μmol, or 120–200 μmol. By maintaining the catalyst content within these ranges, the reactivity is improved. It should be noted that when the substrate is a polysaccharide or polymer, the substrate mass can be converted to the monomer composition for calculation. For example, the mass of 101 mg of chitosan can be converted to N-acetyl-D-glucosamine (molecular weight: 203.2 g / mol) as a chitosan monomer, calculated as 0.101 g / 203.2 g / mol ≈ 0.5 mmol.

[0036] Hydrogen gas can be obtained by irradiating a mixture containing a manganese complex as a catalyst and a substrate with light. The light can be visible light or ultraviolet light. For example, sunlight can be used. Ultraviolet light can contain wavelengths of 250–385 nm, or 275–350 nm. For example, ultraviolet light can contain wavelengths of 300–385 nm. The intensity of the ultraviolet light can be 1–1000 mW, 10–500 mW, 20–100 mW, or 25–80 mW. Such ultraviolet light allows for easy irradiation and is highly safe. For example, such ultraviolet light can be obtained using a 300W xenon light source, "MAX-303" (trade name), manufactured by Asahi Spectrophotometer Co., Ltd.

[0037] Visible light can include wavelengths of 385–780 nm, 385–740 nm, 400–700 nm, or 450–600 nm. Furthermore, the intensity of visible light can be 0.01–500 W, 0.05–100 W, 0.1–10 W, 0.15–1 W, or 250–500 mW. Such visible light is easy to irradiate and offers high safety. For example, it can be irradiated using a 300 W xenon light source, "MAX-303" (trade name), manufactured by Asahi Spectrophotometer Co., Ltd. Sunlight can contain wavelengths of both ultraviolet and visible light.

[0038] Light irradiation can be carried out in a nitrogen atmosphere with a purity of 99% by volume or higher, or in an air atmosphere. For example, a Schilek technique and a glove box can be used to achieve a nitrogen atmosphere. By conducting the reaction in a nitrogen atmosphere, it is possible to carry out the reaction even when the catalyst contains metal complexes. Conducting the reaction in an air atmosphere simplifies the process.

[0039] To promote the reaction, the mixture may contain a base. The base facilitates the removal of hydrogen atoms from the hydroxyl groups of the substrate coordinated with the catalyst. The base can be an inorganic or organic base. Inorganic bases may include, for example, sodium hydroxide, potassium hydroxide, and lithium hydroxide. Organic bases may include, for example, triethylamine, diazabicycloundecene, 1,8-bis(dimethylamino)naphthalene, and pyridine. The concentration of the base in the mixture relative to the total amount of the mixture after adding the base may be 10 mM or more, 50 mM or more, or 90 mM or more. Maintaining the base concentration within this range further promotes the reaction. The concentration of the base relative to the total amount of the mixture after adding the base may be 1000 mM or less, 500 mM or less, 250 mM or less, or 100 mM or less. Maintaining the base concentration within this range provides excellent operability. An example of a base concentration is 10–1000 mM.

[0040] Using the manganese complex of formula (a) as a catalyst, the reaction mechanism for the production of hydrogen from compounds with hydroxyl groups is speculated as follows: Figure 2 As shown. For Figure 2 When the manganese complex of (1) is irradiated with light, the CO coordinated in the manganese complex is released due to the light energy, generating (2). The hydroxyl group coordinates with the released portion to form a ring structure as shown in (3). Then, the reaction proceeds within the ring structure, as shown in (4), to obtain a manganese complex coordinated with hydride ions. The hydride ions coordinated in the manganese complex are released as hydrogen gas due to the light energy, and the manganese complex returns to (2). Hydrogen gas can be obtained in this way. Since the reaction returns to (2), the used manganese complex can be reused as a catalyst and the reaction can be repeated. Therefore, hydrogen can be produced by a milder and simpler process. It should be noted that the mechanism of hydrogen production is not limited to the above mechanism. In addition, gases other than hydrogen can also be produced. Examples of gases other than hydrogen include methane and ethane.

[0041] <Third Catalyst and Reaction Conditions> The third catalyst contains an iron complex. Hydrogen can be obtained by irradiating a mixture containing the iron complex as a catalyst and the substrate with light. Regarding the hydrogen-producing process, the reaction temperature can be directly applied as described in the first catalyst. Furthermore, a pretreatment process as described in the first catalyst can be performed before irradiating the mixture with light. The iron complex can be, for example, the iron complex shown in formula (c) below. The catalyst shown in formula (c) can be a commercially available product. Additionally, a catalyst containing the iron complex of formula (c) below can be used as a catalyst for hydrogen production.

[0042] [Chemical Formula 3] When the catalyst contains an iron complex, it can be mixed with a monosaccharide, disaccharide, polysaccharide, polymer, or biomass resource selected from the group consisting of chitin, cellulose, hemicellulose, glucose, cellobiose, starch, and lignin as the substrate to prepare a mixture. The catalyst in the mixture can be contained in a proportion of 0.025–2.5 μmol, 0.25–1.25 μmol, or 0.5–1.0 μmol relative to 100 mg of substrate. Maintaining the catalyst content within the above range can further promote the reaction. Polar solvents such as acetonitrile, propionitrile, ethyl acetate, dimethylformamide, dimethyl sulfoxide, and anisole can be used.

[0043] A mixture can be prepared by mixing a catalyst containing an iron complex with a substrate containing an alcohol. In this case, the catalyst in the mixture can be contained in a proportion of 0.001 to 0.5 μmol, 0.01 to 0.2 μmol, or 0.03 to 0.1 μmol relative to 1.5 mL of the alcohol as the substrate. By keeping the catalyst content within the above range, the reaction can be further promoted.

[0044] Hydrogen gas can be obtained by irradiating a mixture containing an iron complex as a catalyst and a substrate with light. The light can be visible light or ultraviolet light. For example, sunlight can be used. Ultraviolet light can contain wavelengths of 250–385 nm, 275–350 nm, or, for example, 300–385 nm. The intensity of the ultraviolet light can be 1–1000 mW, 10–500 mW, 20–100 mW, or 25–80 mW. Such ultraviolet light allows for easy irradiation and is highly safe. For example, such ultraviolet light can be applied using a 300W xenon light source, "MAX-303" (trade name), manufactured by Asahi Spectrophotometer Co., Ltd.

[0045] Visible light can include wavelengths of 385–780 nm, 385–740 nm, 400–700 nm, or 450–600 nm. Furthermore, the intensity of visible light can be 0.01–500 W, 0.05–100 W, 0.1–10 W, 0.15–1 W, or 250–500 mW. Such visible light is easy to irradiate and offers high safety. For example, it can be irradiated using a 300 W xenon light source, "MAX-303" (trade name), manufactured by Asahi Spectrophotometer Co., Ltd. Sunlight can contain wavelengths of both ultraviolet and visible light.

[0046] Light irradiation can be carried out in a nitrogen atmosphere with a purity of 99% by volume or higher, or in an air atmosphere. For example, a Schilek technique and a glove box can be used to achieve a nitrogen atmosphere. By conducting the reaction in a nitrogen atmosphere, it is possible to carry out the reaction even when the catalyst contains metal complexes. Conducting the reaction in an air atmosphere simplifies the process.

[0047] To promote the reaction, the mixture may contain a base. The base facilitates the removal of hydrogen atoms from the hydroxyl groups of the substrate coordinated with the catalyst. The base can be an inorganic or organic base. Inorganic bases may include, for example, sodium hydroxide, potassium hydroxide, and lithium hydroxide. Organic bases may include, for example, triethylamine, diazabicycloundecene, 1,8-bis(dimethylamino)naphthalene, and pyridine. The concentration of the base in the mixture relative to the total amount of the mixture after adding the base may be 10 mM or more, 50 mM or more, or 90 mM or more. Maintaining the base concentration within this range further promotes the reaction. The concentration of the base relative to the total amount of the mixture after adding the base may be 1000 mM or less, 500 mM or less, 250 mM or less, or 100 mM or less. Maintaining the base concentration within this range provides excellent operability. An example of a base concentration is 10–1000 mM.

[0048] Using the iron complex of formula (c) as a catalyst, the reaction mechanism for the production of hydrogen from compounds with hydroxyl groups is speculated as follows: Figure 3 As shown. For Figure 3 When the iron complex in (1) is irradiated with light, the light energy causes the iron complex to transform from a binuclear structure to a mononuclear structure (2), and the hydroxyl group partially coordinates with the vacated coordination sites to form a cyclic structure as shown in (3). Then, the reaction proceeds within the cyclic structure, as shown in (4), to obtain an iron complex coordinated with hydride ions. The hydride ions coordinated in the iron complex are released as hydrogen gas due to the light energy, and the iron complex returns to (2). In this way, hydrogen gas can be obtained. Since the reaction returns to (2), the used iron complex can be reused as a catalyst and the reaction can be repeated. Therefore, hydrogen gas can be produced with a milder and simpler process. It should be noted that the mechanism of hydrogen gas production is not limited to the above mechanism. In addition, gases other than hydrogen gas can also be produced. Examples of gases other than hydrogen gas include methane and ethane.

[0049] The above describes several embodiments of this disclosure, but this disclosure is not limited to the embodiments described above.

[0050] This disclosure includes several implementation methods.

[0051] [1] A method for producing hydrogen, comprising a step of obtaining hydrogen by irradiating a mixture comprising a substrate and a catalyst, wherein the substrate comprises at least one selected from the group consisting of chitin, cellulose, hemicellulose, lignin, glucose, cellobiose, starch, and alcohol, and the catalyst comprises a base metal component.

[0052] [2] The method for producing hydrogen as described in [1], wherein the aforementioned base metal component comprises at least one selected from the group consisting of divalent and trivalent metal ions.

[0053] [3] The method for producing hydrogen as described in [2], wherein the aforementioned metal ions include iron ions.

[0054] [4] The method for producing hydrogen as described in [3], wherein the aforementioned light includes ultraviolet light.

[0055] [5] A method for producing hydrogen as described in any one of [1] to [4], wherein the catalyst comprises ferric chloride.

[0056] [6] A method for producing hydrogen as described in any one of [1] to [5], wherein the aforementioned steps are performed under a nitrogen atmosphere or an air atmosphere.

[0057] [7] The method for producing hydrogen as described in [1], wherein the aforementioned catalyst comprises a manganese complex.

[0058] [8] The method for producing hydrogen as described in [7], wherein the aforementioned manganese complex comprises at least one selected from the group consisting of the following formulas (a) and (b).

[0059] [Chemical Formula 4] [Chemical Formula 5] [9] The method for producing hydrogen as described in [1], wherein the aforementioned catalyst comprises an iron complex.

[0060]

[10] The method for producing hydrogen as described in [9], wherein the aforementioned mixture comprises the iron complex dissolved in a polar solvent.

[0061]

[11] A method for producing hydrogen as described in any one of [7] to

[10] , wherein the aforementioned light comprises at least one selected from the group consisting of ultraviolet light and visible light.

[0062]

[12] A method for producing hydrogen as described in any one of [1] to

[11] , wherein the aforementioned mixture contains an alkali.

[0063] Example The following examples and references illustrate the content of this disclosure in more detail. It should be noted that this disclosure is not limited to the following examples.

[0064] <Hydrogen Production Using Metal Ions as Catalysts> (Example 1) Commercially available cedar wood powder was used as the substrate, trivalent ferric chloride (manufactured by Fujifilm and Koichi Chemical Co., Ltd.) as shown in Table 1 as the catalyst, acetonitrile as the solvent, and triethylamine as the base. 1.5 mL of acetonitrile, 40 mg of cedar wood powder, and 0.26 μmol of catalyst were added to a quartz container, and the catalyst was dissolved in the acetonitrile. Triethylamine was then added further to bring the total amount of triethylamine relative to the total amount added to 180 mM.

[0065] Next, a stir bar was added to the quartz container, and a glove box was used to create a nitrogen atmosphere inside the container, which was then sealed with a diaphragm. While vigorously stirring at room temperature (approximately 20°C), the reaction between the substrate and catalyst was initiated by irradiation with ultraviolet light at a wavelength of 275–385 nm and an intensity of 10 mW. The ultraviolet irradiation was performed using an ultraviolet irradiation apparatus (300W xenon light source, trade name: MAX-303, manufactured by Asahi Spectrophotometer Co., Ltd.). The irradiation time, i.e., the reaction time, was set to 15 hours. After irradiation, the gas phase was fed to gas chromatography to determine the amount of hydrogen produced. Furthermore, the catalyst conversion number (TON) and the catalyst conversion frequency per hour (TOF) were calculated. The results are shown in Table 1.

[0066] (Example 2) Methanol was prepared as the substrate, and trivalent ferric chloride, the same as in Example 1, was used as the catalyst. Methanol is a liquid, therefore no solvent was used in Example 2. 1.5 mL of methanol and 0.26 μmol of catalyst were added to a quartz container. Then, a stir bar was added to the quartz container, and a nitrogen atmosphere was created inside the container using a glove box, which was then sealed with a diaphragm. The reaction between the substrate and catalyst was initiated by vigorous stirring at room temperature (approximately 20°C) and irradiation with ultraviolet light at a wavelength of 250–385 nm and an intensity of 10 mW. The ultraviolet irradiation was performed using an ultraviolet irradiation apparatus (300 W xenon light source, trade name: MAX-303, manufactured by Asahi Spectrophotometer Co., Ltd.). The irradiation time, i.e., the reaction time, was set to 3 hours. After irradiation, the gas phase was supplied to a GC, and the amount of hydrogen produced was measured. Additionally, TON and TOF were determined. The results are shown in Table 1.

[0067] (Example 3) Sodium hydroxide was added as a base to make the total amount of sodium hydroxide 90 mM relative to the total amount of sodium hydroxide added, and the reaction was initiated. Otherwise, the reaction was carried out using the same steps as in Example 2, and the amount of hydrogen produced was measured to determine TON and TOF. The results are shown in Table 1.

[0068] (Example 4) The reaction was carried out in an air atmosphere, except that the reaction was carried out using the same steps as in Example 3. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 1.

[0069] (Example 5) The concentration of sodium hydroxide was set to 900 mM relative to the total amount of sodium hydroxide added. Otherwise, the reaction was carried out using the same steps as in Example 4, and the amount of hydrogen produced was measured to determine TON and TOF. The results are shown in Table 1.

[0070] (Example 6) Using triethylamine as a base and light with a wavelength of 275–385 nm, the reaction was carried out using the same steps as in Example 3. The amount of hydrogen produced was measured, and the TON and TOF were determined. The results are shown in Table 1.

[0071] (Example 7) Using ethanol as a substrate, the reaction was carried out using the same steps as in Example 4, and the amount of hydrogen produced was measured to determine TON and TOF. The results are shown in Table 1.

[0072] (Example 8) Using divalent ferric chloride (manufactured by Fujifilm and Koko Pure Chemical Industries Co., Ltd.) as a catalyst, as shown in Table 1, the concentration of sodium hydroxide was set to 250 mM relative to the total amount of sodium hydroxide added. Otherwise, the reaction was carried out using the same steps as in Example 4, and the amount of hydrogen produced was measured to determine TON and TOF. The results are shown in Table 1.

[0073] (Example 9) Using ferric nitrate in the trivalent form shown in Table 1 (manufactured by Fujifilm and Koko Pure Chemical Industries Co., Ltd.) as a catalyst, the amount of catalyst was set to 0.026 μmol. Otherwise, the reaction was carried out using the same steps as in Example 8, and the amount of hydrogen produced was measured to determine TON and TOF. The results are shown in Table 1.

[0074] (Example 10) Using trivalent ferric sulfate (manufactured by Fujifilm and Kohden Chemical Co., Ltd.) as a catalyst, as shown in Table 1, the amount of catalyst was set to 0.013 μmol. Otherwise, the reaction was carried out by the same procedure as in Example 8, and the amount of hydrogen produced was measured to determine TON and TOF. The results are shown in Table 1.

[0075] (Example 11) Using divalent ferric sulfate (manufactured by Fujifilm and Kohden Chemical Co., Ltd.) as a catalyst, as shown in Table 1, the amount of catalyst was set to 0.026 μmol. Otherwise, the reaction was carried out using the same steps as in Example 8, and the amount of hydrogen produced was measured to determine TON and TOF. The results are shown in Table 1.

[0076] (See Example 1 for reference) 100 mg of sulfate lignin (manufactured by Nippon Paper Co., Ltd.) was prepared as the substrate, and the iron compound shown in Table 2 (manufactured by Fujifilm and Koko Pure Chemical Industries Co., Ltd.) was prepared as the catalyst. The catalyst was dissolved in 3 g of water to prepare an aqueous catalyst solution, with the amount of catalyst being 0.04 mmol relative to 100 mg of substrate. 100 mg of substrate was added to the prepared aqueous catalyst solution as the test sample. While the test sample was vigorously stirred with a stirrer at room temperature (approximately 20°C), it was irradiated with visible light at a wavelength of 385–740 nm and an intensity of 200 mW to initiate the reaction between the substrate and the catalyst. Visible light irradiation was performed using a visible light irradiation device (300 W xenon light source, trade name: MAX-303, manufactured by Asahi Spectrophotometer Co., Ltd.). The irradiation time, i.e., the reaction time, was set to 18 hours. The reaction conditions are shown in Table 2.

[0077] After the vacuum distillation reaction, the low-boiling-point compounds separated from the sample were determined by GC-MS to perform qualitative and quantitative analysis of methanol. The peak area of ​​methanol was converted using a pre-prepared standard curve to calculate the amount of methanol produced. The amount of methanol produced is shown in Table 2.

[0078] (See Example 2 for reference) The amount of methanol produced was determined by using the iron compound (manufactured by Fujifilm and Kojun Chemical Co., Ltd.) shown in Table 2 as a catalyst, otherwise the reaction was carried out in the same manner as in Reference Example 1. The results are shown in Table 2.

[0079] (See Example 3 for reference) The amount of methanol produced was determined by using the iron compound (manufactured by Fujifilm and Kojun Chemical Co., Ltd.) shown in Table 2 as a catalyst, otherwise the reaction was carried out in the same manner as in Reference Example 1. The results are shown in Table 2.

[0080] (See Example 4 for reference) The iron compounds shown in Table 2 were used as catalysts, and the reaction was carried out at a ratio of 0.02 mmol of catalyst relative to 100 mg of substrate. Otherwise, the reaction was carried out in the same manner as in Reference Example 1, and the amount of methanol produced was determined. The results are shown in Table 2.

[0081] (See Example 5 for reference) The iron compounds shown in Table 2 were used as catalysts, and the reaction was carried out at a ratio of 0.10 mmol of catalyst relative to 100 mg of substrate. Otherwise, the reaction was carried out in the same manner as in Reference Example 1, and the amount of methanol produced was determined. The results are shown in Table 2.

[0082] (See Example 6 for reference) Using the iron compounds shown in Table 2 as catalysts, the amount of substrate used was set to 50 mg, and the catalyst was reacted at a ratio of 0.04 mmol relative to 50 mg of substrate. Otherwise, the reaction was carried out in the same manner as in Reference Example 1, and the amount of methanol produced was determined. The results are shown in Table 2.

[0083] (See Example 7 for reference) Sodium lignosulfonate (Sigma-Aldrich) was used as the substrate, and the iron compounds shown in Table 2 were used as the catalyst. Otherwise, the reaction was carried out in the same manner as in Reference Example 1, and the amount of methanol produced was determined. The results are shown in Table 2.

[0084] (See Example 8 for reference) Commercially available cedar powder was used as the substrate, the iron compounds shown in Table 2 were used as the catalyst, and the amount of substrate was set to 50 mg. Otherwise, the reaction was carried out in the same manner as in Reference Example 1, and the amount of methanol produced was determined. The results are shown in Table 2.

[0085] (See Example 9 for reference) Wood flour recovered from waste was used as the substrate, and the iron compounds shown in Table 2 were used as the catalyst. Otherwise, the reaction was carried out in the same manner as in Reference Example 1, and the amount of methanol produced was determined. The results are shown in Table 2.

[0086] (See Example 10) The amount of methanol produced was determined by using the manganese compound (manufactured by Sigma-Aldrich) shown in Table 2 as a catalyst, otherwise by the same method as in Reference Example 1. The results are shown in Table 2.

[0087] [Table 1] [Table 2] As shown in Table 1, it was confirmed that hydrogen gas can be generated from cedar wood powder, methanol, and ethanol by using a metal compound containing divalent or trivalent metal ions as a catalyst and irradiating with ultraviolet light. It was also confirmed that the reaction can proceed under either a nitrogen atmosphere or an air atmosphere, and that the amount of hydrogen gas produced can be increased by adding a base.

[0088] As shown in Reference Examples 1-10 of Table 2, it was confirmed that methanol was generated when biomass resources such as sulfate lignin reacted with metal compounds under visible light. Thus, the polymers of biomass resources such as lignin were irradiated with visible light using a catalyst containing a base metal component to generate methanol. It can be assumed that in Example 1, the hydroxyl groups contained in the polymers such as lignin in cedar powder reacted under ultraviolet light and a metal compound catalyst to generate hydrogen. Therefore, it can be assumed that if ultraviolet light is irradiated in Reference Examples 1-10, hydrogen gas is generated in the same manner as in Example 1.

[0089] <Hydrogen Production Using Manganese Complexes as Catalysts> (Example 12) 101 mg of chitosan (manufactured by Fujifilm and Koujun Pharmaceutical Co., Ltd.) was prepared as the substrate, and the manganese complex shown in formula (a) below (manufactured by Sigma-Aldrich) was prepared as the catalyst. The amount of chitosan 101 mg was converted to 0.5 mmol of N-acetyl-D-glucosamine as a monomer. 75 μmol of the manganese complex was added to a quartz container. Then, a stir bar was added to the quartz container, and a nitrogen atmosphere was created inside the quartz container using a glove box, which was then sealed with a diaphragm. The reaction between the substrate and the catalyst was initiated by vigorously stirring at room temperature (approximately 20°C) while irradiating with ultraviolet light at a wavelength of 300–385 nm and an intensity of 50 mW. The ultraviolet irradiation was performed using an ultraviolet irradiation device (300 W xenon light source, trade name: MAX-303, manufactured by Asahi Spectrophotometer Co., Ltd.). The irradiation time, i.e., the reaction time, was set to 2 hours. After irradiation, the gas phase was supplied to a GC, and the amount of hydrogen produced was measured. In addition, TON and TOF were determined. The results are shown in Table 3.

[0090] [Chemical Formula 6] (Example 13) The irradiation light was set to visible light with a wavelength of 385-740 nm and an intensity of 200 mW. The reaction was carried out using the same steps as in Example 12. The amount of hydrogen produced was measured, and TON and TOF were determined. Visible light irradiation was performed using a visible light irradiation device (300W xenon light source, trade name: MAX-303, manufactured by Asahi Spectrophotometer Co., Ltd.). The results are shown in Table 3.

[0091] (Example 14) Using 101 mg of snow crab shell as a substrate, the reaction was carried out following the same procedures as in Example 12. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 3.

[0092] (Example 15) Using 101 mg of king crab shell as a substrate, the reaction was carried out following the same procedures as in Example 12. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 3.

[0093] (Example 16) Cyclohexane-methanol was used as the substrate, with an amount of 61 μL (0.5 mol). The reaction was carried out using the same procedures as in Example 12. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 3.

[0094] (Example 17) Using 81 mg of cellulose (manufactured by Fujifilm and Koichi Pure Chemical Industries, Ltd.) as a substrate, the reaction was carried out following the same procedures as in Example 12. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 3. It should be noted that the amount of 81 mg of cellulose is equivalent to 0.5 mmol of glucose as a monomer.

[0095] (Example 18) Using 101 mg of sulfate lignin (manufactured by Nippon Paper Co., Ltd.) as a substrate, the reaction was carried out following the same procedures as in Example 12. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 3.

[0096] (Example 19) Using 101 mg of commercially available cedar wood powder as a substrate, the reaction was carried out following the same procedures as in Example 12. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 3.

[0097] (Example 20) The manganese complex shown in formula (b) below (manufactured by Sigma-Aldrich) was used as a catalyst, and the reaction was carried out using the same steps as in Example 12. The amount of hydrogen produced was determined, and TON and TOF were calculated. The results are shown in Table 3.

[0098] [Chemical Formula 7] [Table 3] As shown in Table 3, it can be seen that when manganese complex is used as a catalyst, hydrogen can be generated from polymers and alcohols derived from biomass resources by irradiation.

[0099] <Hydrogen Production Using Iron Complexes as Catalysts> (Example 21) Commercially available cedar wood powder was used as the substrate, an iron complex (manufactured by Fujifilm and Koichi Chemical Co., Ltd.) as shown in formula (c) was used as the catalyst, acetonitrile was used as the solvent, and triethylamine was used as the base. 1.5 mL of acetonitrile, 40 mg of cedar wood powder, and 0.21 μmol of catalyst were added to a quartz container, and the catalyst was dissolved in the acetonitrile. Triethylamine was then added further to bring the total amount of triethylamine to 90 mM relative to the total amount after adding triethylamine.

[0100] Next, a stir bar was added to the quartz container, and a glove box was used to create a nitrogen atmosphere inside the container, which was then sealed with a diaphragm. While vigorously stirring at room temperature (approximately 20°C), the reaction between the substrate and catalyst was initiated by irradiation with ultraviolet light at a wavelength of 300–385 nm and an intensity of 10 mW. The ultraviolet irradiation was performed using an ultraviolet irradiation apparatus (300W xenon light source, trade name: MAX-303, manufactured by Asahi Spectrophotometer Co., Ltd.). The irradiation time, i.e., the reaction time, was set to 15 hours. After irradiation, the gas phase was supplied to a GC to determine the amount of hydrogen produced. Additionally, the total oxygen ionization (TON) and time to fire (TOF) were calculated. The results are shown in Table 4.

[0101] [Chemical Formula 8] (Example 22) Using 40 mg of sulfate lignin (manufactured by Nippon Paper Corporation) as a substrate, the reaction was carried out following the same procedures as in Example 21. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 4.

[0102] (Example 23) Methanol was prepared as the substrate, and the iron complex (manufactured by Fujifilm and Kojun Chemical Co., Ltd.) used in Example 21 was prepared as the catalyst. Methanol is a liquid, therefore no solvent was used. 1.5 mL of methanol was added to a quartz container to dissolve 0.051 μmol of the catalyst. Then, a stir bar was added to the quartz container, and a nitrogen atmosphere was created inside the container using a glove box, which was then sealed with a diaphragm. The reaction between the substrate and catalyst was initiated by vigorous stirring at room temperature (approximately 20°C) and irradiation with ultraviolet light at a wavelength of 300–385 nm and an intensity of 10 mW. Ultraviolet irradiation was performed using an ultraviolet irradiation apparatus (300 W xenon light source, trade name: MAX-303, manufactured by Asahi Spectrophotometer Co., Ltd.). The irradiation time, i.e., the reaction time, was set to 3 hours. After irradiation, the gas phase was supplied to a GC, and the amount of hydrogen produced was measured. Additionally, TON and TOF were determined. The results are shown in Table 4.

[0103] (Example 24) Sodium hydroxide was added as a base to make the total sodium hydroxide concentration 90 mM relative to the total amount of sodium hydroxide added, and the reaction was initiated. Otherwise, the reaction was carried out using the same steps as in Example 23. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 4.

[0104] (Example 25) The irradiation light was set to visible light with a wavelength of 385-740 nm and an intensity of 100 mW. The reaction was carried out using the same steps as in Example 23. Visible light irradiation was performed using a visible light irradiation device (300W xenon light source, trade name: MAX-303, manufactured by Asahi Spectrophotometer Co., Ltd.). The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 4.

[0105] (Example 26) The irradiated light was set to sunlight, and the reaction was carried out using the same steps as in Example 23. Natural sunlight was used at the Experimental Biological Environment Control Center of Kyushu University. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 4.

[0106] (Example 27) Using triethylamine as a base, the reaction was carried out following the same steps as in Example 24. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 4.

[0107] (Example 28) Using ethanol as a substrate, the reaction was carried out following the same steps as in Example 27. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 4.

[0108] [Table 4] It was confirmed that, when using an iron complex as a catalyst, hydrogen gas can be generated from cedar wood powder, sulfate lignin, methanol, and ethanol by light irradiation. Furthermore, it was confirmed that the reaction can be accelerated by adding a base.

[0109] [Confirmation of formaldehyde formation] To confirm the mechanism of hydrogen generation when methanol is used as a substrate, the formaldehyde content in the post-reaction solution was detected. Formaldehyde was detected using the acetylacetone method described in Nash, T. The colorimetric estimation of formaldehyde by means of the Hantzsch reaction. Biochem. J. 1953, 55(3), 416-421. Specifically, an acetate-ammonium acetate buffer solution was prepared by mixing 0.8 mL of 2.26 M aqueous acetic acid solution and 20 mL of 2.25 M aqueous ammonium acetate solution. Additionally, 50 mL of acetylacetone solution was prepared by adding water to 0.35 mL of acetylacetone and 0.7 mL of ethanol. In the reaction using ferric chloride or an iron complex of formula (c) as a catalyst and methanol as a substrate, the post-reaction solution was diluted 10-fold with water, and 2 mL of acetate-ammonium acetate buffer solution and 2 mL of acetylacetone solution were added to 0.1 mL of the resulting solution. The solution was then heated at 60 °C for 15 minutes, cooled to room temperature, and the absorption spectrum was measured. Figure 4 This is the formaldehyde detection result from Example 5. (For example...) Figure 4 As shown, an absorption band at 410 nm was observed, thus confirming the formation of formaldehyde.

[0110] Since formaldehyde is generated after the reaction, it can be assumed that the reaction of oxidizing the hydroxyl group of the substrate to an aldehyde group is promoted by a catalyst and light, and hydrogen gas is generated along with the reaction.

[0111] (Example 29) 1-Propanol was prepared as the substrate, and trivalent ferric chloride (as in Example 1) was used as the catalyst. Since 1-propanol is a liquid, no solvent was used in Example 29. 1.5 mL of 1-propanol, 0.0026 μmol of catalyst, and sodium hydroxide as a base were added to a quartz container, bringing the total sodium hydroxide concentration to 250 mM. A stir bar was then added to the quartz container, and the container was sealed with a diaphragm under an air atmosphere. The reaction between the substrate and catalyst was initiated by vigorous stirring at room temperature (approximately 20°C) and irradiation with ultraviolet light at a wavelength of 250–385 nm and an intensity of 10 mW. The ultraviolet irradiation was performed using a 300 W xenon light source (trade name: MAX-303, manufactured by Asahi Spectrophotometer Co., Ltd.). The irradiation time, i.e., the reaction time, was set to 3 hours. After irradiation, the gas phase was supplied to a GC, and the amount of hydrogen produced was measured. The total oxygen ionization (TON) and time to fire (TOF) were also determined. The results are shown in Table 5.

[0112] (Example 30) Using 2-propanol as a substrate, the reaction was carried out using the same steps as in Example 29, and the amount of hydrogen produced was determined to calculate TON and TOF. The results are shown in Table 5.

[0113] [Table 5] <Hydrogen production using water as a solvent> (Example 31) Methanol was prepared as the substrate, divalent ferric chloride (same as in Example 8) as the catalyst, and water as the solvent. 0.54 mL of methanol, 0.96 mL of water, and 0.26 μmol of catalyst were added to a quartz container to dissolve the methanol and catalyst in water. Then, a stir bar was added to the quartz container, and the container was sealed with a diaphragm under an air atmosphere. The reaction between the substrate and catalyst was initiated by vigorous stirring at room temperature (approximately 20°C) and irradiation with ultraviolet light at a wavelength of 250–385 nm and an intensity of 10 mW. The ultraviolet irradiation was performed using an ultraviolet irradiation apparatus (300 W xenon light source, trade name: MAX-303, manufactured by Asahi Spectrophotometer Co., Ltd.). The irradiation time, i.e., the reaction time, was set to 3 hours. After irradiation, the gas phase was supplied to a GC to determine the amount of hydrogen produced. Additionally, the TON and TOF were calculated. The results are shown in Table 6.

[0114] (Example 32) Using ethanol as a substrate, the reaction was carried out following the same steps as in Example 31, and the amount of hydrogen produced was determined, along with the TON and TOF. The results are shown in Table 6. In Example 32, methane was also detected in the gas phase in addition to hydrogen. The amount of methane produced was 0.57 μmol, and the TON and TOF of the catalyst in the methane production were 2.19 and 0.73, respectively.

[0115] (Example 33) Using 1-propanol as a substrate, the reaction was carried out following the same procedures as in Example 31, and the amount of hydrogen produced was determined, along with the TON and TOF. The results are shown in Table 6. In Example 33, ethane was detected in the gas phase in addition to hydrogen. The amount of ethane produced was 0.86 μmol, and the TON and TOF of the catalyst in ethane production were 3.30 and 1.1, respectively.

[0116] (Example 34) Using 2-propanol as the substrate, with a substrate volume of 0.3 mL and a solvent (water) volume of 1.2 mL, the reaction was carried out using the same steps as in Example 31. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 6.

[0117] (Example 35) Using glucose as a substrate, glucose was dissolved in 1.5 mL of solvent (water) at a concentration of 100 mM. Otherwise, the reaction was carried out using the same procedure as in Example 31, and the amount of hydrogen produced was measured to determine TON and TOF. The results are shown in Table 6.

[0118] (Example 36) Using divalent copper chloride (manufactured by Fujifilm and Koichi Chemical Co., Ltd.) as a catalyst, as shown in Table 6, the reaction was carried out following the same steps as in Example 31. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 6.

[0119] (Example 37) Using divalent nickel chloride (manufactured by Fujifilm and Koichi Chemical Co., Ltd.) as a catalyst, as shown in Table 6, the reaction was carried out using the same steps as in Example 31, and the amount of hydrogen produced was measured to determine TON and TOF. The results are shown in Table 6.

[0120] (Example 38) Using divalent zinc chloride (manufactured by Fujifilm and Koichi Chemical Co., Ltd.) as a catalyst, as shown in Table 6, the reaction was carried out following the same steps as in Example 31, and the amount of hydrogen produced was measured to determine TON and TOF. The results are shown in Table 6.

[0121] (Example 39) Using divalent manganese chloride (manufactured by Fujifilm and Koichi Chemical Co., Ltd.) as a catalyst, as shown in Table 6, the reaction was carried out using the same steps as in Example 31, and the amount of hydrogen produced was measured to determine TON and TOF. The results are shown in Table 6.

[0122] (Example 40) Cellobiose was prepared as the substrate, trivalent ferric chloride (same as in Example 1) as the catalyst, and water as the solvent. 10 mg of cellobiose, 1.5 mL of water, and 2.6 μmol of catalyst were added to a quartz container, dissolving the catalyst in the water. Note that the cellobiose was not dissolved in the water. Then, a stir bar was added to the quartz container, and the container was sealed with a diaphragm under an air atmosphere. While vigorously stirring at room temperature (approximately 20°C), the reaction between the substrate and catalyst was initiated by irradiating with ultraviolet light at a wavelength of 250–385 nm and an intensity of 10 mW. The ultraviolet irradiation was performed using an ultraviolet irradiation device (300 W xenon light source, trade name: MAX-303, manufactured by Asahi Spectrophotometer Co., Ltd.). The irradiation time, i.e., the reaction time, was set to 3 hours. After irradiation, the gas phase was supplied to a GC, and the amount of hydrogen produced was measured. Additionally, TON and TOF were determined. The results are shown in Table 6.

[0123] (Example 41) Using starch as a substrate, the reaction was carried out using the same steps as in Example 40, and the amount of hydrogen produced was measured to determine TON and TOF. The results are shown in Table 6.

[0124] (Example 42) Using cellulose as a substrate, the reaction was carried out using the same steps as in Example 40, and the amount of hydrogen produced was measured to determine TON and TOF. The results are shown in Table 6.

[0125] (Example 43) Using chitin as a substrate, the reaction time was set to 16 hours. Otherwise, the reaction was carried out using the same steps as in Example 40, and the amount of hydrogen produced was measured to determine TON and TOF. The results are shown in Table 6.

[0126] (Example 44) Chitosan was used as the substrate, and divalent copper sulfate (manufactured by Fujifilm and Koh Genuine Chemicals Co., Ltd.) as the catalyst, as shown in Table 6. The reaction time was set to 16 hours. Otherwise, the reaction was carried out using the same steps as in Example 40. The amount of hydrogen produced was measured, and TON and TOF were determined. The results are shown in Table 6.

[0127] [Table 6] <Research on Pretreatment> (Example 44) Cellulose was prepared as the substrate, trivalent ferric chloride (same as in Example 1) as the catalyst, and water as the solvent. 10 mg of cellulose, 1.5 mL of water, and 2.6 μmol of catalyst were added to a quartz container, dissolving the catalyst in the water. Note that the cellulose was not dissolved in the water. Then, a stir bar was added to the quartz container, and the container was sealed with a diaphragm under air atmosphere and heated at 150°C for 4 hours for pretreatment. After pretreatment, the reaction between the substrate and catalyst was initiated by vigorous stirring at room temperature (approximately 20°C) and irradiation with ultraviolet light at a wavelength of 250–385 nm and an intensity of 10 mW. Ultraviolet irradiation was performed using an ultraviolet irradiation device (300 W xenon light source, trade name: MAX-303, manufactured by Asahi Spectrophotometer Co., Ltd.). The irradiation time, i.e., the reaction time, was set to 16 hours. After irradiation, the gas phase was supplied to a GC to determine the amount of hydrogen produced. Additionally, TON and TOF were determined. As a result, the amount of hydrogen produced was 0.61 μmol, TON was 0.23, and TOF was 0.014.

[0128] (Example 45) Cellulose and 2-propanol were prepared as substrates, trivalent ferric chloride (same as in Example 1) as catalyst, and water as solvent. 10 mg of cellulose, 2.1 μL of 2-propanol, 1.5 mL of water, and 2.6 μmol of catalyst were added to a quartz container, and the catalyst and 2-propanol were dissolved in water. Then, without pretreatment, the reaction was carried out using the same steps as in Example 44, and the amount of hydrogen produced was measured to determine TON and TOF. The results showed that the amount of hydrogen produced was 0.7 μmol, TON was 0.27, and TOF was 0.056.

[0129] (Example 46) Cellulose and 2-propanol were prepared as substrates, trivalent ferric chloride (same as in Example 1) as catalyst, and water as solvent. 10 mg of cellulose, 2.1 μL of 2-propanol, 1.5 mL of water, and 2.6 μmol of catalyst were added to a quartz container, and the catalyst and 2-propanol were dissolved in water. Then, the pretreatment and reaction were performed using the same steps as in Example 44, and the amount of hydrogen produced was measured to determine TON and TOF. The results showed that the amount of hydrogen produced was 1.48 μmol, TON was 0.57, and TOF was 0.036. A comparison with Example 45 confirmed that the amount of hydrogen produced increased by performing pretreatment.

[0130] Industrial availability According to this disclosure, a method for producing hydrogen can be provided, which uses a catalyst containing a base metal component to produce hydrogen from readily available raw materials through a mild and simple process.

Claims

1. A method for producing hydrogen, comprising a step of obtaining hydrogen by irradiating a mixture comprising a substrate and a catalyst, wherein the substrate comprises at least one selected from the group consisting of chitin, cellulose, hemicellulose, lignin, glucose, cellobiose, starch, and alcohols, and the catalyst comprises a base metal component.

2. The method for producing hydrogen as described in claim 1, wherein, The base metal component comprises at least one selected from the group consisting of divalent and trivalent metal ions.

3. The method for producing hydrogen as described in claim 2, wherein, The metal ions include iron ions.

4. The method for producing hydrogen as described in claim 3, wherein, The light includes ultraviolet light.

5. The method for producing hydrogen according to any one of claims 1 to 4, wherein, The catalyst contains ferric chloride.

6. The method for producing hydrogen according to any one of claims 1 to 4, wherein, The process is carried out under a nitrogen atmosphere or an air atmosphere.

7. The method for producing hydrogen as described in claim 1, wherein, The catalyst contains a manganese complex.

8. The method for producing hydrogen as described in claim 7, wherein, The manganese complex comprises at least one of the following formulas (a) and (b): [Chemical Formula 1] [Chemical Formula 2] 。 9. The method for producing hydrogen as described in claim 1, wherein, The catalyst contains an iron complex.

10. The method for producing hydrogen as described in claim 9, wherein, The mixture contains the iron complex dissolved in a polar solvent.

11. The method for producing hydrogen according to any one of claims 7 to 10, wherein, The light includes at least one selected from the group consisting of ultraviolet light and visible light.

12. The method for producing hydrogen as described in claim 1 or 2, wherein, The mixture contains an alkali.

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