Hydrogen production methods

Abstract

The present invention provides a method for producing hydrogen that allows for the generation of hydrogen storage compounds and the dehydrogenation reaction of the generated hydrogen storage compounds to be carried out under mild conditions and at a lower cost. [Solution] A method for producing hydrogen, comprising subjecting a secondary alcohol compound obtained by hydrogenating a ketone compound using baker's yeast to a dehydrogenation reaction in the presence of a metal complex catalyst to obtain hydrogen.

Description

[Technical Field]

[0001] This invention relates to a method for producing hydrogen. [Background technology]

[0002] Hydrogen gas is expected to be a next-generation energy source that does not emit carbon dioxide when used. Safe transportation of hydrogen is essential for its effective utilization. Because hydrogen is a gas at room temperature and pressure, it has a large volume and is highly flammable, making it difficult to transport in its natural state. Therefore, in addition to methods of transporting hydrogen gas by compressing or liquefying it, the storage and transport of hydrogen in hydrogen storage materials is currently being considered. Examples of hydrogen storage materials include metal-organic frameworks (MOFs) and hydrogen storage alloys. However, storing and transporting hydrogen using these materials requires low temperature or high pressure conditions, which increases costs and poses safety risks. Organic hydrides are also known as hydrogen storage compounds. Organic hydrides can safely store hydrogen through chemical bonding under normal temperature and pressure conditions. However, the organic hydrides used in previous studies are petroleum-derived compounds such as toluene and fluorenone, and the catalytic reduction methods used in previous studies require a lot of energy for hydrogen storage and necessitate the use of expensive precious metal catalysts. Furthermore, since the above-mentioned organic hydrides are generally highly volatile liquids, they are difficult to handle during transport and storage. For this reason, solid hydrogen storage materials are being considered. For example, Patent Document 1 discloses a hydrogen carrier (hydrogen storage material) in which a hydrogen storage portion is included in the main chain and / or side chains of an organic polymer, the hydrogen storage portion generates hydrogen molecules in the presence of a catalyst and becomes an oxidation-reduction active portion, and the oxidation-reduction active portion stores hydrogen through reduction and contact with a proton source to become the hydrogen storage portion. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2015 / 005280 [Overview of the project] [Problems that the invention aims to solve]

[0004] The present invention aims to provide a method for producing hydrogen that can carry out the generation of hydrogen storage compounds and the dehydrogenation reaction of the generated hydrogen storage compounds under mild conditions and at a lower cost. [Means for solving the problem]

[0005] The inventors of this invention have discovered that secondary alcohol compounds can be efficiently obtained from ketone compounds under mild conditions by applying an enzymatic reaction using baker's yeast, and that hydrogen can also be extracted from the obtained secondary alcohol compounds (dehydrogenation reaction) with high efficiency under mild conditions. This invention was completed based on these findings and further investigations.

[0006] The above-mentioned problems of the present invention were solved by the following means. [1] A method for producing hydrogen, comprising subjecting a secondary alcohol compound obtained by hydrogenating a ketone compound using baker's yeast to a dehydrogenation reaction in the presence of a metal complex catalyst to obtain hydrogen. [2] The method for producing hydrogen according to [1], wherein the dehydrogenation reaction is carried out at 150 to 230°C. [3] The method for producing hydrogen according to [1] or [2], wherein the ketone compound is at least one of a bicyclomonoketone compound and a polyvalent ketone compound. [4] A method for producing hydrogen according to any one of [1] to [3], wherein the ketone compound is at least one of a bicyclomonoketone compound and a chain-like diketone compound. [5] A method for producing hydrogen according to any one of [1] to [4], wherein the ketone compound is at least one of a bicyclomonoketone compound and a chain-like γ-diketone compound. [6] A method for producing hydrogen according to any one of [1] to [4], wherein the ketone compound is at least one of dihydrolevoglucocenone, acetylacetone, and 2,5-hexanedione. [7] A method for producing hydrogen according to any one of [1] to [6], wherein the metal complex catalyst is an iridium complex catalyst. [8] A method for producing hydrogen according to any one of [1] to [7], comprising repeating a cycle multiple times that includes the steps of hydrogenating a ketone compound obtained by the dehydrogenation reaction using baker's yeast, and subjecting the secondary alcohol compound obtained by the hydrogenation to a dehydrogenation reaction in the presence of a metal complex catalyst to obtain hydrogen.

[0007] In this invention, a numerical range represented using "~" means a range that includes the numbers written before and after "~" as the lower limit and upper limit, respectively. [Effects of the Invention]

[0008] According to the hydrogen production method of the present invention, the generation of hydrogen storage compounds and the dehydrogenation reaction of the generated hydrogen storage compounds can be carried out under mild conditions and at a lower cost. [Modes for carrying out the invention]

[0009] Preferred embodiments of the present invention are described below, but the present invention is not limited to the embodiments described below other than those specified herein.

[0010] [Hydrogen production method] The present invention provides a method for producing hydrogen, which includes obtaining a secondary alcohol compound by hydrogenating a ketone compound using baker's yeast, and then subjecting that compound to a dehydrogenation reaction in the presence of a metal complex catalyst to obtain hydrogen.

[0011] The hydrogen production method of the present invention can be an embodiment including a step of hydrogenating a ketone compound using baker's yeast to obtain a secondary alcohol compound, and a step of subjecting the obtained secondary alcohol compound to a dehydrogenation reaction in the presence of a metal complex catalyst to obtain hydrogen. Also, the hydrogen production method of the present invention preferably includes a mode in which a cycle including a step of hydrogenating the ketone compound obtained by the dehydrogenation reaction using baker's yeast, and a step of subjecting the secondary alcohol compound obtained by this hydrogenation to a dehydrogenation reaction in the presence of a metal complex catalyst to obtain hydrogen is repeated a plurality of times.

[0012] In the hydrogen production method of the present invention, the secondary alcohol compound is obtained by hydrogenating a ketone compound using an enzymatic reaction of baker's yeast, and this enzymatic hydrogenation proceeds under mild conditions. In the hydrogen production method of the present invention, a low-molecular-weight and relatively high-boiling alcohol compound can be used as the secondary alcohol compound. In this case, the secondary alcohol compound can be handled as a liquid near room temperature. Therefore, the secondary alcohol compound as a hydrogen storage compound can be transported and stored using conventional transportation means and facilities premised on gasoline and the like. Further, the secondary alcohol compound employed in the hydrogen production method of the present invention can adopt mild conditions as compared with conventional organic hydrides even in the dehydrogenation reaction using a metal complex catalyst.

[0013] The hydrogen production method of the present invention will be described in more detail.

[0014] In the hydrogen production method of the present invention, as a reaction substrate (hydrogen storage compound) for obtaining hydrogen by dehydrogenation reaction, a secondary alcohol compound obtained by hydrogenating a ketone compound using baker's yeast is used. The hydrogenation of a ketone compound using baker's yeast occurs when a reducing coenzyme contained in baker's yeast, such as nicotinamide adenine dinucleotide (NADH), donates hydrogen to the ketone compound by the action of an enzyme contained in baker's yeast, such as alcohol dehydrogenase. As a result, the ketone compound is reduced to a secondary alcohol compound, and NADH is oxidized to the oxidized coenzyme NAD + to become. More specifically, it is considered to react as shown in the following Scheme A. The carbonyl group of the ketone compound is reduced by NADH to -O - to become, and when this -O - comes into contact with water, it extracts hydrogen from water to obtain a secondary alcohol compound. In the following Scheme A, R1 and R2 of (R1)(R2)C=O (ketone compound) are substituents bonded by a carbon atom.

[0015]

Chemical formula

[0016] NAD + is regenerated to NADH by reduction through glycolysis of sugars such as glucose, and NADH can be continuously allowed to act on the ketone compound. NADH may be continuously allowed to act on the ketone compound by supplementing baker's yeast. Nicotinamide adenine dinucleotide phosphate (NADPH) is also considered to act in the same manner as NADH as a coenzyme. In conventional production methods of organic hydrides, a noble metal catalyst was essential, but in the present invention, hydrogenation of a ketone compound can be carried out without using a noble metal catalyst, at low cost, and with reduced environmental load.

[0017] The hydrogenation of a ketone compound by baker's yeast is usually carried out in water. That is, part of the hydrogen source for the hydrogenation reaction is water, and hydrogen can be extracted and stored from the inexhaustible water.

[0018] The amount of baker's yeast can be appropriately adjusted depending on the type and amount of ketone compound, reaction time, and reaction temperature. Generally, the more baker's yeast used, the faster the reaction proceeds. By increasing the amount of baker's yeast relative to the amount of ketone moiety in the ketone compound, the reaction can be carried out over a long period without the need for NADH regeneration. For example, with baker's yeast, 0.5 to 5 g can be used per 1 mmol of the ketone portion of a ketone compound, or 1 to 5 g can be used, or 1 to 2 g can be used.

[0019] The temperature for the hydrogenation reaction of ketone compounds using baker's yeast is not particularly limited as long as it is within the range suitable for the enzymatic reaction of the baker's yeast, and is therefore inevitably a mild temperature. This hydrogenation reaction can be carried out, for example, at 25-40°C, or even at 30-40°C. The reaction time for the hydrogenation reaction of ketone compounds using baker's yeast can be appropriately set depending on the type and amount of ketone compound, the reaction temperature, etc. There are no particular restrictions. For example, the reaction time for the hydrogenation reaction of ketone compounds using baker's yeast can be 12 to 48 hours, or it can be 12 to 24 hours.

[0020] After the hydrogenation reaction, baker's yeast can be separated by centrifugation or other methods. After the hydrogenation reaction, the secondary alcohol compound may be separated from water, or it may be subjected to a dehydrogenation reaction without separation. The secondary alcohol compound can be separated, for example, by evaporating the water. The secondary alcohol compound obtained as described above can be stored. Therefore, the hydrogen production method of the present invention may include a storage step for the secondary alcohol compound. Furthermore, secondary alcohol compounds can be transported. Therefore, the hydrogen production method of the present invention may include a step of transporting secondary alcohol compounds. Because the hydrogen storage compound is a secondary alcohol compound, it offers excellent handling advantages during storage and transportation, and allows for the storage and transportation of hydrogen using existing transportation methods and facilities.

[0021] The present invention provides a method for producing hydrogen by subjecting the secondary alcohol compound obtained as described above to a dehydrogenation reaction in the presence of a metal complex catalyst. Through the dehydrogenation reaction, hydrogen is released from the secondary alcohol compound. During this process, the secondary alcohol compound is oxidized to a ketone compound.

[0022] The above dehydrogenation reaction may or may not use a solvent. When a solvent is used in the above dehydrogenation reaction, the solvent may be water or an organic solvent. Examples of organic solvents include pentane, hexane, heptane, benzene, toluene, xylene, tetrahydrofuran, diisopropyl ether, dichloromethane, methylformamide, 1-butanol, and γ-valerolactone. From the viewpoint of reducing environmental impact, it is preferable to carry out the reaction without a solvent, or to use water or γ-valerolactone, which is a solvent derived from cellulose.

[0023] The amount of metal complex catalyst in the above dehydrogenation reaction can be appropriately set depending on the type and amount of secondary alcohol compound, reaction time, reaction temperature, etc. For example, the molar ratio of the metal complex catalyst to the secondary alcohol compound can be [metal complex catalyst] / [secondary alcohol compound] = 1 / 1000 to 1 / 5, 1 / 100 to 1 / 5, 1 / 70 to 1 / 5, or 1 / 20 to 1 / 5.

[0024] The temperature of the above dehydrogenation reaction is not particularly limited. The dehydrogenation reaction can be carried out, for example, at 100-250°C, or at 150-230°C. From the viewpoint of increasing the efficiency of the dehydrogenation reaction, a high temperature reaction is preferred. It should be noted that the dehydrogenation reaction of methylcyclohexane, a well-known organic hydride, usually requires a high temperature of around 300-400°C. The reaction time for the above dehydrogenation reaction is not particularly limited. The reaction time for the dehydrogenation reaction can be, for example, 1 to 24 hours, 1 to 12 hours, or 1 to 6 hours.

[0025] The pH of the reaction solution that produces the above dehydrogenation reaction is not particularly limited. The pH of this reaction solution can be, for example, 1 to 14, 5 to 14, or 10 to 14.

[0026] In the hydrogen production method of the present invention, the hydrogen gas obtained by the above dehydrogenation reaction can be recovered by conventional methods. After the dehydrogenation reaction described above, the ketone compound may or may not be separated from the solvent. If the solvent is water, it may be subjected to a hydrogenation reaction without separation to convert it into a secondary alcohol compound. The ketone compound produced by the above dehydrogenation reaction can be subjected to the hydrogenation reaction again, as described above. That is, it can be used as a ketone compound in the hydrogen production method of the present invention. Therefore, in one embodiment of the hydrogen production method of the present invention, the ketone compound produced along with hydrogen by the dehydrogenation reaction can be stored as a raw material for the hydrogenation reaction. Accordingly, the hydrogen production method of the present invention may include a step of storing the ketone compound. Furthermore, the ketone compounds produced along with hydrogen by the above dehydrogenation reaction can be transported. Therefore, the hydrogen production method of the present invention may include a step for transporting ketone compounds. When a solvent is used in the above dehydrogenation reaction, the metal complex catalyst after the reaction can be separated from the solvent by liquid-liquid separation and extraction, column chromatography, etc. The separated metal complex catalyst can be reused as is. If the metal complex catalyst has been degraded, for example, a ligand can be added to regenerate the structure of the complex, and it can be used again in the dehydrogenation reaction.

[0027] In the hydrogen production method of the present invention, when a cycle including hydrogenation and dehydrogenation is repeated multiple times, ketone compounds and / or secondary alcohol compounds, baker's yeast, and metal complex catalysts can be appropriately replenished during the cycle.

[0028] The following describes the materials used in the hydrogen production method of the present invention.

[0029] (Baker's yeast) Baker's yeast is generally not limited to any yeast used in bread making. Examples of baker's yeast include Saccharomyces cerevisiae and Saccharomyces exigus, among other Saccharomyces species. The baker's yeast can be in any form: fresh yeast, semi-dry yeast, or dry yeast. When these baker's yeasts are reacted with ketone compounds in the presence of water, a hydrogenation reaction of the ketone compounds occurs through the action of enzymes.

[0030] (Ketone compounds) The ketone compound is not particularly limited as long as it is a compound that, through the action of baker's yeast, undergoes hydrogen bonding to produce a secondary alcohol compound. Preferably, the ketone compound is at least one of a bicyclomonoketone compound and a polyvalent ketone compound.

[0031] The above bicyclomonoketone compounds are monoketone compounds having a ring structure in which two atoms constituting the ring are linked by bonds outside the ring to form a bridge (i.e., monoketone compounds having two bridgehead atoms and three bridges connecting them). The bicyclomonoketone compound preferably has 4 to 10 ring-constituting atoms, including the atoms forming the bridge, more preferably 5 to 9, and even more preferably 6 to 8. The bicyclomonoketone compound described above preferably has 3 to 10 carbon atoms, more preferably 4 to 9, and even more preferably 4 to 8. The above bicyclomonoketone compounds may contain heteroatoms (oxygen, nitrogen, and sulfur atoms) as ring constituent elements, and it is preferable that they contain an oxygen atom. Here, heteroatoms contained in the ketone group are not considered ring constituent elements. The above bicyclomonoketone compounds preferably have 6 to 8 ring constituent atoms and contain one or two oxygen atoms as ring constituent elements. The molecular weight of the above bicyclomonoketone compound is preferably 120 to 180, more preferably 120 to 160, and even more preferably 120 to 140. Bicyclomonoketone compounds are preferably free of aromatic groups. Bicyclomonoketone compounds may have substituents on the ring atoms. Examples of substituents include alkyl groups having 1 to 10 carbon atoms (preferably 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, even more preferably 1 to 4 carbon atoms, and even more preferably methyl or ethyl carbon atoms), and groups having an active hydrogen group (-OH, -NH2, or -SH) (preferably a hydroxyl group). Bicyclomonoketone compounds are preferred, having 4 to 10 ring constituent atoms and containing an oxygen atom as a ring constituent element. Specific examples of bicyclomonoketone compounds include, for example, dihydrolevoglucocenone (Silene®), camphor, 3-methylene-2-norbornanone, and 8-oxabicyclo[3,2,1]octan-3-one. Among these, dihydrolevoglucocenone is preferable from the viewpoint of reducing environmental impact because it is a cellulose-derived compound and is biodegradable.

[0032] As for the polyvalent ketone compound, compounds having 1 to 5 ketone groups are preferred, compounds having 1 to 4 are more preferred, compounds having 1 to 3 are even more preferred, and compounds having 2 (diketone compounds) are even more preferred. A polyvalent ketone compound may be both a ketone compound and a secondary alcohol compound. In this invention, such a compound is also referred to as a "ketone compound." That is, in addition to a ketone group, a polyvalent ketone compound may have a hydroxyl group (a hydroxyl group in a configuration that can be oxidized to a ketone group) bonded to the central carbon atom of three consecutive carbon atoms. In other words, in this invention, "polyvalent ketone compound" includes compounds having one ketone group and one hydroxyl group in a configuration that can become a ketone group as described above. For this reason, ketone compound K1 in Examples 8 to 11 is also a polyvalent ketone compound in this invention. The polyvalent ketone compound may be linear or cyclic, with linear diketone compounds being preferred. It is preferable that the polyvalent ketone compound does not have an aromatic ring within the molecule. The polyvalent ketone compound is preferably a ketone compound having 5 to 10 carbon atoms, more preferably a ketone compound having 4 to 8 carbon atoms, and even more preferably a ketone compound having 4 to 7 carbon atoms. The polyvalent ketone compound preferably has a molecular weight of 80 to 170, more preferably 80 to 150, even more preferably 80 to 130, even more preferably 80 to 120, and even more preferably 100 to 130. The polyvalent ketone compound may have substituents. Examples of substituents include alkyl groups having 1 to 10 carbon atoms (preferably 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, even more preferably 1 to 4 carbon atoms, and even more preferably methyl or ethyl), and groups having an active hydrogen group (-OH, -NH2, or -SH) (preferably a hydroxyl group). From the viewpoint of increasing the mass hydrogen density through hydrogenation reactions, polyvalent ketone compounds are preferred if they have a molecular weight of 80 to 120 and contain two ketone groups (diketone compounds). Diketone compounds are preferred because they have a high boiling point and low volatility, making them easy to handle. Examples of diketone compounds include α-diketone compounds, β-diketone compounds, γ-diketone compounds, and δ-diketone compounds. The diketone compound is preferably a linear diketone compound. From the viewpoint of reaction conversion rate, linear γ-diketone compounds are preferred. The diketone compound is preferably a linear diketone compound having 5 to 10 carbon atoms, more preferably a linear diketone compound having 4 to 8 carbon atoms, even more preferably a linear diketone compound having 4 to 7 carbon atoms, and even more preferably a linear γ-diketone compound having these carbon atoms. Examples of polyvalent ketone compounds include acetylacetone, 2,5-hexanedione, and 1,4-cyclohexanedione.

[0033] The ketone compound is more preferably at least one of a bicyclomonoketone compound and a linear diketone compound, even more preferably at least one of a bicyclomonoketone compound and a linear γ-diketone compound, and even more preferably at least one of dihydrolevoglucocenone, acetylacetone, and 2,5-hexanedione.

[0034] (Secondary alcohol compounds) Secondary alcohol compounds are compounds obtained by hydrogenating the above-mentioned ketone compounds. Therefore, their preferred structure is the same as that of the ketone compound, except that the carbonyl group in the ketone group of the ketone compound is converted to a hydroxyl group. For this reason, secondary alcohol compounds corresponding to bicyclomonoketone compounds are sometimes called bicyclomonoalcohol compounds, and secondary alcohol compounds corresponding to polyhydric ketone compounds are sometimes called polyol compounds. For example, the compound corresponding to a diketone is a diol compound. In this invention, however, secondary alcohol compounds are compounds that do not have a ketone group.

[0035] (Metal complex catalyst) The metal complex catalyst is not particularly limited as long as it can produce a ketone compound and hydrogen from a secondary alcohol compound by a dehydrogenation reaction in its presence. The central metal of the metal complex catalyst is preferably one of the following: iron, copper, vanadium, cobalt, osmium, rhodium, manganese, nickel, iridium, ruthenium, platinum, palladium, etc., with iridium being more preferred. The ligands for metal complex catalysts include aqua ligands, hydroxide ligands, amine ligands (e.g., aniline, toluidine, anisidine, etc.), diamine ligands (e.g., o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, etc.), pyridine ligands (hydroxypyridine), bipyridine ligands (e.g., 6,6'-dihydroxy-2,2'-bipyridine, 2,2'-bipyridine-6,6'-dionato, 4,4'-bis(dimethylamino)-2,2'-bipyridine-6,6'-dionato, etc.), and acetylacetone ligands (acetyl It is preferable that the ligand is one or a combination thereof of the following: a cetone ligand, a porphyrin ligand, a Schiff base ligand, a phosphine ligand (e.g., triphenylphosphine, trimethylphosphine, triethylphosphine, tributylphosphine, tri-tert-butylphosphine, tricyclohexylphosphine, triethoxyphosphine, etc.), a sulfoxide ligand (e.g., dimethyl sulfoxide, etc.), a benzene ligand, a cyclopentadiene ligand (e.g., cyclopentadiene, pentamethylcyclopentadiene, etc.). Each of the above ligands may further have substituents. Examples of substituents include alkyl groups having 1 to 10 carbon atoms, amino groups (e.g., amino groups, alkylamino groups having 1 to 4 carbon atoms, etc.). The metal complex catalyst may also be in the form of a salt. For example, lithium, sodium, potassium, triflat anion (CF3SO3 - ) or salt may be used. The metal complex catalyst is preferably an iridium complex catalyst containing a bipyridine ligand, more preferably an iridium complex catalyst having aqua, 6,6'-dihydroxy-2,2'-bipyridine, and pentamethylcyclopentadiene, an iridium complex catalyst having aqua, 2,2'-bipyridine-6,6'-dionato, and pentamethylcyclopentadiene, and an iridium complex catalyst having 4,4'-bis(dimethylamino)-2,2'-bipyridine-6,6'-dionato, and pentamethylcyclopentadiene.

[0036] The present invention will be described in more detail based on examples, but the present invention is not to be limited to these examples. [Examples]

[0037] [material] Baker's yeast: Nissin Super Camellia Dry Yeast (manufactured by Nissin Flour Milling Welna Co., Ltd.) Dihydrolevoglucocenone (Cyrene®): Manufactured by Sigma-Aldrich. Acetylacetone: Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. 2,5-Hexanedione: Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. 1,6-Anhydro-3,4-dideoxy-β-D-threo-hexopyranose: Prepared as follows. 1,6-anhydro-3,4-dideoxy-β-D-threo-hexopyranose was prepared by reducing dihydrolevoglucocenone with LiAlH4 (Tokyo Chemical Industries) using anhydrous diethyl ether (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a solvent, and then purifying it by column chromatography. 2,4-Pentanediol: Manufactured by Tokyo Chemical Industry Co., Ltd. 2,5-Hexanediol: Manufactured by Tokyo Chemical Industry Co., Ltd. Catalyst 1: (Aqua(2,2'-bipyridine-6,6'-dionato)(pentamethylcyclopentadienyl)iridium(III)) (manufactured by Kanto Chemical Co., Ltd.) Catalyst 2: Aqua(6,6'-dihydroxy-2,2'-bipyridine)(pentamethylcyclopentadienyl)iridium(III)bis(triflate) (manufactured by Kanto Chemical Co., Ltd.) Toluene: Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. γ-Valerolactone: Manufactured by Tokyo Chemical Industry Co., Ltd.

[0038] [Preparation of hydrogen storage compounds (secondary alcohol compounds) (hydrogenation)] The ketone compound was hydrogenated using baker's yeast (see scheme S1 below). In this process, 1 g of baker's yeast was used for every 1 mmol of the ketone moiety of the ketone compound. The experimental procedure was as follows: 1 The reaction conversion rate was calculated using the following formula after 1H NMR measurement. The results are shown in Table 1. Reaction conversion rate = 100 × [moles of secondary alcohol compound] / ([moles of ketone compound] + [moles of secondary alcohol compound])

[0039] (Example 1) 1 g of baker's yeast was suspended in 10 mL of water and stirred at 30°C for 1 hour. Then, 1 mmol of dihydrolevoglucocenone was added to the suspension as a ketone compound and stirred at 30°C for 24 hours. In this way, the ketone compound was hydrogenated to obtain a secondary alcohol compound (1,6-anhydro-3,4-dideoxy-β-D-threo-hexopyranose) as a hydrogen storage compound.

[0040] (Example 2) In the same procedure as in Example 1, except that the ketone compound was acetylacetone and the amount of baker's yeast was 2 g, the ketone compound was hydrogenated to obtain 2,4-pentanediol as a hydrogen storage compound. (Example 3) In Example 2, the ketone compound was hydrogenated in the same manner as in Example 2, except that the ketone compound was 2,5-hexanedione, to obtain 2,5-hexanediol as a hydrogen storage compound.

[0041] [ka]

[0042] In scheme S1 above, R1 and R2 in (R1)(R2)C=O (ketone compound) are substituents bonded to a carbon atom, and specifically correspond to the substituents shown in Table 1 (the same applies to schemes S2 to S4 below).

[0043] [Table 1]

[0044] In Examples 1 and 3, a 100% reaction conversion rate was achieved by stirring at 30°C for 24 hours. In Example 2, the reaction conversion rate was also high at 89%. From the above, it can be seen that both dihydrolevoglucocenone and polyvalent ketone compounds can be used as raw materials for the hydrogenation reaction using baker's yeast, and from the viewpoint of reaction rate, bicyclomonoketone compounds and 2,5-hexanedione (a chain-like γ-diketone compound) are more preferable.

[0045] [Hydrogen production (dehydrogenation reaction): Use of organic solvents] Using the above metal complex catalyst, secondary alcohol compounds were subjected to a dehydrogenation reaction in an organic solvent (see scheme S2 below). The experimental procedure was as follows: 1 The reaction conversion rate was calculated using the following formula after 1H NMR measurement. The results are shown in Table 2. Reaction conversion rate = 100 × [moles of ketone compound] / ([moles of secondary alcohol compound] + [moles of ketone compound])

[0046] (Example 4) Under air, 1,6-anhydro-3,4-dideoxy-β-D-threo-hexopyranose (1 mmol) was used as the secondary alcohol compound, and it was added to a flask along with toluene (5 mL) as the solvent and catalyst 1 (20 molar amounts of catalyst 1 per 100 molar amounts of the secondary alcohol compound). The reaction solution was then heated and stirred under reflux at 150°C for 24 hours to dehydrogenate the secondary alcohol compound, yielding dihydrolevoglucocenone and hydrogen.

[0047] (Example 5) In Example 4, the secondary alcohol compound was subjected to a dehydrogenation reaction in the same manner as in Example 4, except that γ-valerolactone was used as the solvent, the reaction temperature was set to 230°C, and the reaction time was set to 3 hours, to obtain dihydrolevoglucocenone and hydrogen.

[0048] (Example 6) In Example 4, the secondary alcohol compound was subjected to a dehydrogenation reaction in the same manner as in Example 4, except that 2,4-pentanediol was used as the secondary alcohol compound, the amount of catalyst 1 molar was set to 5 molars per 100 molars of the secondary alcohol compound, and the reaction time was set to 6 hours, to obtain acetylacetone and hydrogen.

[0049] (Example 7) In Example 6, the secondary alcohol compound was subjected to a dehydrogenation reaction in the same manner as in Example 6, except that 2,5-hexanediol was used as the secondary alcohol compound, to obtain 2,5-hexanedione and hydrogen.

[0050] [ka]

[0051] [Table 2]

[0052] Examples 4 to 7 reveal the following. It can be seen that, using 1,6-anhydro-3,4-dideoxy-β-D-threo-hexopyranose, regardless of the type of organic solvent, a ketone compound and hydrogen can be obtained by a dehydrogenation reaction in the presence of an iridium complex catalyst (Examples 4 and 5). Among them, by subjecting the reaction to a high-temperature reaction using γ-valerolactone, a cellulose-derived solvent, as the organic solvent, a reaction conversion rate of 100% was achieved (Example 5). When toluene was used as the solvent, 2,4-pentanediol and 2,5-hexanediol showed higher reaction conversion rates compared to 1,6-anhydro-3,4-dideoxy-β-D-threo-hexopyranose. However, in Example 7 as well, by subjecting the reaction to a high-temperature reaction by replacing the solvent with a high-boiling point solvent such as γ-valerolactone, it is considered that a reaction conversion rate of 100% can also be achieved for 2,5-hexanediol. That is, by subjecting 2,5-hexanediol obtained by hydrogenating 2,5-hexanedione as a chain diketone compound to a dehydrogenation reaction in the presence of a metal complex catalyst to obtain hydrogen, both the hydrogenation reaction and the dehydrogenation reaction can proceed with a reaction conversion rate of virtually 100%.

[0053] [Production of Hydrogen (Dehydrogenation): Water Used] A secondary alcohol compound was dehydrogenated in water using a metal complex catalyst (Scheme S3 below). In Scheme S3, OTf - means a triflate anion (CF3SO3 - ). The experimental procedure is as follows. The results are shown in Table 3.

[0054] (Example 8) Under air, 2,4-pentanediol (1 mmol) as a secondary alcohol compound was used and added to a flask together with water (5 mL) and Catalyst 1 (molar amount of Catalyst 1: 5 with respect to a molar amount of 100 of the secondary alcohol compound). Then, the reaction solution was heated and stirred at 150 °C for 24 hours under reflux to subject the secondary alcohol compound to a dehydrogenation reaction, obtaining the ketone compound K1, the ketone compound K2, and hydrogen shown in Table 3.

[0055] (Example 9) In Example 8, the secondary alcohol compound was subjected to a dehydrogenation reaction in the same manner as in Example 8, except that catalyst 2 was used instead of catalyst 1, to obtain ketone compound K1, ketone compound K2, and hydrogen.

[0056] (Example 10) In Example 8, the secondary alcohol compound was subjected to a dehydrogenation reaction in the same manner as in Example 8, except that 2,5-hexanediol was used as the secondary alcohol compound, to obtain ketone compound K1, ketone compound K2, and hydrogen.

[0057] (Example 11) In Example 10, the secondary alcohol compound was subjected to a dehydrogenation reaction in the same manner as in Example 10, except that catalyst 2 was used instead of catalyst 1, to obtain ketone compound K1 and ketone compound K2.

[0058] TIFF2026094553000006.tif39167

[0059] [Table 3]

[0060] Examples 8-11 show that the dehydrogenation reaction proceeds in the presence of an iridium complex catalyst even when water is used as the solvent. Furthermore, it is clear that catalyst 1 is more suitable than catalyst 2 for increasing the efficiency of producing ketone compound K2 in which all hydroxyl groups are oxidized to carbonyl groups. It is also clear that the reaction using 2,5-hexanediol (the reaction to obtain the chain-like γ-diketone compound 2,5-hexanedione) has a higher reaction conversion rate than the reaction using 2,4-pentanediol. Furthermore, in the case of 1,6-anhydro-3,4-dideoxy-β-D-threo-hexopyranose, it has been confirmed that the catalytic reaction does not proceed sufficiently in water when catalysts 1 and 2 are used.

[0061] [Hydrogen production (dehydrogenation): No solvent used] Secondary alcohol compounds were dehydrogenated under solvent-free conditions using a metal complex catalyst (see scheme S4 ​​below). The experimental procedure is as follows. The results are shown in Table 4.

[0062] (Example 12) Under air, 1,6-anhydro-3,4-dideoxy-β-D-threo-hexopyranose (10 mmol) as a secondary alcohol compound and catalyst 1 (5 molars of catalyst 1 per 100 molars of secondary alcohol compound) were added to a flask. The reaction solution was then heated and stirred at 200°C for 24 hours to dehydrogenate the secondary alcohol compound, yielding dihydrolevoglucocenone and hydrogen.

[0063] (Example 13) In Example 12, 2,5-hexanediol was used as the secondary alcohol compound (30 mmol), the amount of catalyst 1 was set to 1.5 molars per 100 molars of the secondary alcohol compound, and the mixture was heated and stirred under reflux at 220°C. Except for these differences, 2,5-hexanedione and hydrogen were obtained in the same manner as in Example 12.

[0064] [ka]

[0065] [Table 4]

[0066] Examples 12 and 13 show that both 1,6-anhydro-3,4-dideoxy-β-D-threo-hexopyranose and 2,5-hexanediol can be dehydrogenated by a dehydrogenation reaction in the presence of an iridium complex catalyst, even without the use of a solvent. Furthermore, Examples 1 to 13 show that hydrogen can be obtained by hydrogenating a ketone compound using baker's yeast and then subjecting the resulting secondary alcohol compound to a dehydrogenation reaction in the presence of a metal complex catalyst.

Claims

1. A method for producing hydrogen, comprising subjecting a secondary alcohol compound obtained by hydrogenating a ketone compound using baker's yeast to a dehydrogenation reaction in the presence of a metal complex catalyst to obtain hydrogen.

2. The method for producing hydrogen according to claim 1, wherein the dehydrogenation reaction is carried out at 150 to 230°C.

3. The method for producing hydrogen according to claim 1, wherein the ketone compound is at least one of a bicyclomonoketone compound and a polyvalent ketone compound.

4. The method for producing hydrogen according to claim 1, wherein the ketone compound is at least one of a bicyclomonoketone compound and a chain-like diketone compound.

5. The method for producing hydrogen according to claim 1, wherein the ketone compound is at least one of a bicyclomonoketone compound and a linear γ-diketone compound.

6. The method for producing hydrogen according to claim 1, wherein the ketone compound is at least one of dihydrolevoglucocenone, acetylacetone, and 2,5-hexanedione.

7. The method for producing hydrogen according to claim 1, wherein the metal complex catalyst is an iridium complex catalyst.

8. A method for producing hydrogen according to claim 1, comprising repeating a cycle multiple times that includes the steps of hydrogenating a ketone compound obtained by the dehydrogenation reaction using baker's yeast, and subjecting the secondary alcohol compound obtained by the hydrogenation to a dehydrogenation reaction in the presence of a metal complex catalyst to obtain hydrogen.

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