Hydrogen production method and hydrogen supply method using boron compound

Abstract

Provided are a hydrogen production method and a hydrogen supply method that comprise: obtaining an indoline compound (4) represented by formula (IV) by hydrogenating an indole compound (3) represented by formula (III) in the presence of hydrogen and at least one boron compound (1) or (2) selected from the group consisting of boron compounds (1) represented by formula (I) and boron compounds (2) represented by formula (II); and obtaining hydrogen by dehydrogenating the indoline compound (4) in the presence of said at least one boron compound (1) or (2).

Description

Method for producing hydrogen and supplying hydrogen using boron compounds

[0001] The present invention relates to a method for producing hydrogen and a method for supplying hydrogen in the presence of a boron compound, and more specifically, to a method for producing hydrogen and a method for supplying hydrogen (each of which may include storing hydrogen, transporting hydrogen, or purifying hydrogen) by the hydrogenation of indole in the presence of a boron compound to produce indoline, and by the dehydrogenation of indoline in the presence of a boron compound to produce indole and hydrogen.

[0002] Traditionally, transition metal catalysts used in hydrogenation reactions are poisoned by carbon monoxide, making it difficult to use crude hydrogen gas as a hydrogen source. In recent years, catalysts that create a state called FLP (frustrated Lewis pair), which allows for the heterolytic cleavage of molecular hydrogen using only organic materials without the use of metals, have made it possible to carry out hydrogenation reactions even in the presence of carbon monoxide.

[0003] The hydrogenation of various heterocyclic compounds in the presence of boron compounds has been reported. For example, Patent Document 1 reports the hydrogenation of 2-methylquinoline using a mixed gas containing hydrogen, carbon monoxide, carbon dioxide, and methane in the presence of several boron compounds (see Examples 2, 4, and Comparative Examples 1-8). Patent Document 2 reports the hydrogenation of 2,5-dimethylindole using a mixed gas containing hydrogen and carbon monoxide in the presence of tris(pentafluorophenyl)borane (see Example 5).

[0004] On the other hand, dehydrogenation of various N-heterocyclo compounds in the presence of boron compounds has been reported. For example, Non-Patent Document 1 reports the production of quinoline and hydrogen by dehydrogenation of 1,2,3,4-tetrahydroquinoline and other compounds in the presence of tris(pentafluorophenyl)borane (see Table 2). Non-Patent Document 2 reports the production of indole and hydrogen by dehydrogenation of indoline and other compounds in the presence of tris(pentafluorophenyl)borane (see Table 1).

[0005] Incidentally, Non-Patent Document 3 reported the hydrogenation of 2-methylquinoline using a mixed gas containing hydrogen, carbon monoxide, and carbon dioxide in the presence of several boron compounds, and the production of 2-methylquinoline and hydrogen by dehydrogenation of 2-methyl-1,2,3,4-tetrahydroquinoline in the presence of several boron compounds (see Figures 2 and 3).

[0006] Furthermore, Non-Patent Document 3 reported that hydrogen can be purified by hydrogenating 2-methylquinoline using a mixed gas containing hydrogen, carbon monoxide, and carbon dioxide in the presence of (2,6-dichlorophenyl)bis(3,5-dichloro-2,6-difluorophenyl)borane, followed immediately by dehydrogenation of 2-methyl-1,2,3,4-tetrahydroquinoline in the presence of its boron compound, thereby producing 2-methylquinoline and hydrogen (see Figure 3).

[0007] Japanese Patent Publication No. 2020-33292 Japanese Patent Publication No. 2017-206474

[0008] Masahiro Kojima and Motomu Kanai, Angew. Chem. Int. Ed. 2016, 55, 12224-12227.Alexander FG Maier et al., Angew. Chem. Int. Ed. 2016, 55, 12219-12223.Taiki Hashimoto et. al., Sci. Adv. 8, eade0189 (2022) 26 October 2022.A. Gyoemoere et. al., ACS Catal. 5, 5366-5372 (2015).Herrington, TJ et. al., Dalton Trans. 2012, 41, 9019-9022.

[0009] The hydrogen purification method described in Non-Patent Document 3 involves hydrogenating 2-methylquinoline at 100°C for 2 hours using crude hydrogen containing 5.4 equivalents each of hydrogen, carbon monoxide, and carbon dioxide in the presence of 2 mol% of (2,6-dichlorophenyl)bis(3,5-dibromo-2,6-difluorophenyl)borane, followed by dehydrogenation of the resulting 2-methyl-1,2,3,4-tetrahydroquinoline at 200°C for 3 hours.

[0010] The hydrogenation of heterocyclic compounds and the dehydrogenation of N-heterocyclo compounds in the presence of boron compounds are not yet well understood. Furthermore, methods for producing and supplying hydrogen using the hydrogenation of heterocyclic compounds and the dehydrogenation of N-cyclo compounds are of commercial and academic interest as novel methods for hydrogen production and supply.

[0011] There is a need for hydrogen production and hydrogen supply methods that include hydrogenation of heterocyclic compounds and dehydrogenation of N-cyclo compounds more efficiently, with less energy, at lower temperatures (closer to room temperature), and in a shorter time. Such hydrogen production and hydrogen supply methods may include hydrogen purification, hydrogen storage, and / or hydrogen transport.

[0012] As a result of diligent research, the inventors have discovered that by dehydrogenating an indoline compound of an N-cyclo compound in the presence of a specific boron compound, hydrogen and an indole compound of a heterocyclic compound can be produced more efficiently, with less energy, at lower temperatures (closer to room temperature), and in a shorter time.

[0013] Furthermore, we discovered that by hydrogenating an indole compound of a heterocyclic compound in the presence of a specific boron compound to produce an indoline compound of an N-cyclo compound, and then dehydrogenating the indoline compound in the presence of the specific boron compound, we can provide a hydrogen production method and hydrogen supply method (including hydrogen purification, hydrogen storage, and / or hydrogen transport) that can be carried out more efficiently, with less energy, at lower temperatures (closer to room temperature), and in a shorter time, thereby completing the present invention.

[0014] This specification includes the following embodiments: 1. A boron compound (1) represented by the following formula (I) [In equation (I), X １ and X ２ These are H, F, Cl, Br, CF, each independently. ３ NO ２ , CN, and electron-withdrawing groups (F, Cl, Br, CF ３ NO ２selected from the group consisting of aryl groups having a substituent selected from the group consisting of CN), X １ and X ２ are not both H, and X ３ and X ４ are each independently selected from the group consisting of H, F, Cl, Br, CF ３ , and an aryl group. ] and a boron compound (2) represented by the following formula (II) [In the formula (II), X ５ and X ６ are each independently CF ３ , NO ２ , CN, and an aryl group having an electron-withdrawing group selected from the group consisting of CF ３ , NO ２ and CN. ] in the presence of at least one boron compound selected from the group consisting of: an indoline compound (4) represented by the following formula (IV) [In the formula (IV), R １ and R ６ are each independently selected from the group consisting of H, alkyl, and halogen. ] dehydrogenating to obtain hydrogen. A method for producing hydrogen, comprising: 2. The method for producing hydrogen according to 1 above, comprising heating to 90°C or higher and 230°C or lower to perform dehydrogenation to obtain hydrogen.

[0015] 3. A boron compound (1) represented by the following formula (I) [In the formula (I), X １ and X ２ are each independently selected from H, F, Cl, Br, CF ３ , NO ２ , CN, and an aryl group having an electron-withdrawing group selected from the group consisting of F, Cl, Br, CF ３ , NO ２ and CN), X １ and X ２ are not both H, and X ３ and X ４ are each independently selected from the group consisting of H, F, Cl, Br, CF ３ , and an aryl group. ] and a boron compound (2) represented by the following formula (II) [In equation (II), X ５ and X ６ Each of them operates independently, CF ３ NO ２ , CN, and electron-withdrawing group (CF ３ NO ２ Selected from the group consisting of , and CN, and an aryl group having ] At least one boron compound (1) or (2) selected from the group consisting of ] and an indole compound (3) represented by the following formula (III) in the presence of hydrogen [In equation (III), R １ and R ６ Each is independently selected from the group consisting of H, alkyl, and halogen. Hydrogenating ] yields the indoline compound (4) represented by the following formula (IV). A method for producing an indoline compound, comprising obtaining the indole compound (3). 4. A method for producing an indoline compound (4) according to 3 above, comprising hydrogenating the indole compound (3) in the presence of a mixed gas containing, in addition to hydrogen, at least one selected from the group consisting of methane, nitrogen, water, carbon monoxide, and carbon dioxide. 5. A method for producing an indoline compound (4) according to 3 or 4 above, comprising heating the indole compound (3) to 50°C or higher and 200°C or lower and hydrogenating it to obtain an indoline compound (4).

[0016] 6. Boron compound represented by the following formula (I) (1) [In equation (I), X １ and X ２ These are H, F, Cl, Br, CF, each independently. ３ NO ２ , CN, and electron-withdrawing groups (F, Cl, Br, CF ３ NO ２ Selected from the group consisting of aryl groups having (selected from the group consisting of , and CN), X １ and X ２ Both are X, not H. ３ and X ４ These are H, F, Cl, Br, CF, each independently. ３ Selected from the group consisting of , and aryl groups. ] and boron compounds (2) represented by the following formula (II) [In equation (II), X ５ and X ６ Each of them operates independently, CF ３ NO ２ , CN, and electron-withdrawing group (CF ３ NO ２ Selected from the group consisting of , and CN, and an aryl group having ] At least one boron compound (1) or (2) selected from the group consisting of ] and an indole compound (3) represented by the following formula (III) in the presence of hydrogen [In equation (III), R １ and R ６ Each is independently selected from the group consisting of H, alkyl, and halogen. Hydrogenating ] yields the indoline compound (4) represented by the following formula (IV). To obtain, and a boron compound (1) represented by the following formula (I) [In equation (I), X １ and X ２ These are H, F, Cl, Br, CF, each independently. ３ NO ２ , CN, and electron-withdrawing groups (F, Cl, Br, CF ３ NO ２ Selected from the group consisting of aryl groups having (selected from the group consisting of , and CN), X １ and X ２ Both are X, not H. ３ and X ４ These are H, F, Cl, Br, CF, each independently. ３ Selected from the group consisting of , and aryl groups. ] and boron compounds (2) represented by the following formula (II) [In equation (II), X ５ and X ６ Each of them operates independently, CF ３ NO ２ , CN, and electron-withdrawing group (CF ３ NO ２ In the presence of at least one boron compound (1) or (2) selected from the group consisting of , and CN, an indoline compound (4) represented by the following formula (IV) [In formula (IV), R １ and R ６ Each of these is independently selected from the group consisting of H, alkyl, and halogen. A method for producing hydrogen or supplying hydrogen, comprising dehydrogenating [ to obtain hydrogen.]

[0017] 7. A hydrogen production method or hydrogen supply method according to 6 above, comprising hydrogenating indole (3) in the presence of a mixed gas containing, in addition to hydrogen, at least one selected from the group consisting of methane, nitrogen, water, carbon monoxide, and carbon dioxide. 8. A hydrogen production method or hydrogen supply method according to 6 or 7 above, comprising heating an indole compound (3) to 50°C or higher and hydrogenating it to 230°C or lower to obtain an indoline compound (4). 9. A hydrogen production method or hydrogen supply method according to any one of 1, 2, 6 to 8 above, comprising heating to 90°C or higher and dehydrogenating it. 10. A hydrogen production method or hydrogen supply method according to any one of 6 to 9 above, comprising hydrogenating an indole compound (3) to obtain an indoline compound (4) and dehydrogenating the indoline compound (4) to obtain hydrogen in a batch or continuous manner. 11. A hydrogen production method or hydrogen supply method according to any one of 6 to 10 above, which may include purifying hydrogen, storing hydrogen, and / or transporting hydrogen.

[0018] The hydrogen production method of the embodiment of the present invention involves dehydrogenating an indoline compound of an N-cyclo compound in the presence of a specific boron compound, thereby enabling the production of hydrogen and indole of a heterocyclic compound more efficiently, with less energy, at lower temperatures (closer to room temperature), and in a shorter time.

[0019] Furthermore, in the hydrogen production method and hydrogen supply method according to the embodiment of the present invention, an indoline compound, which is an N-cyclo compound, is produced by hydrogenation of an indole compound, which is a heterocyclic compound, in the presence of a specific boron compound, and dehydrogenation of the indoline compound is performed in the presence of a specific boron compound. Therefore, it is possible to provide a hydrogen production method and a hydrogen supply method that can be performed more efficiently, with lower energy, at a lower temperature (a temperature closer to room temperature), and in a shorter time. The hydrogen production method and hydrogen supply method according to the embodiment of the present invention can include hydrogen purification, hydrogen storage and / or hydrogen transportation.

[0020] FIG. 1 shows the chemical formulas (formulas (I), (II), (III) and (IV)) of a boron compound (1), a boron compound (2), an indole compound (3), and an indoline compound (4) used in the method for producing hydrogen according to the embodiment of the present invention, respectively.

[0021] In one aspect, the present invention provides a method for producing hydrogen, comprising dehydrogenating an indoline compound to obtain hydrogen in the presence of a specific boron compound. The method relates to the boron compound (1) represented by the following formula (I) [In formula (I), X １ and X ２ are each independently selected from the group consisting of H, F, Cl, Br, CF ３ , NO ２ , CN, and an aryl group having an electron-withdrawing group (for example, a phenyl group, a naphthyl group, a biphenylyl group having an electron-withdrawing group selected from the group consisting of F, Cl, Br, CF ３ , NO ２ , CN), X １ and X ２ are not both H, X ３ and X ４ are each independently selected from the group consisting of H, F, Cl, Br, CF ３ , and an aryl group (for example, a phenyl group, a naphthyl group, a biphenylyl group, etc.). X １ and X ２ are each independently H, F, Cl, Br, CF ３is selected from the group consisting of CN and an aryl group having an electron-withdrawing group, and it is preferable that both are not H. X １ and X ２ are each independently more preferably selected from the group consisting of F, Cl, Br, CF ３ and an aryl group having an electron-withdrawing group. X １ and X ２ , the aryl group having an electron-withdrawing group is CF ３ and is preferably selected from a phenyl group, a naphthyl group, and a biphenylyl group each having an electron-withdrawing group selected from the group consisting of CN. X １ and X ２ , the aryl group having an electron-withdrawing group is F, Cl, Br, and CF ３ is more preferably selected from a phenyl group and a naphthyl group selected from the group consisting of: X ３ and X ４ are each independently preferably selected from the group consisting of H, F, Cl, Br, and CF ３ , X ３ and X ４ are each independently more preferably selected from the group consisting of H, F, Cl, and Br, and X ３ and X ４ are each independently preferably selected from the group consisting of H, F, and Cl.] and a boron compound (2) represented by the following formula (II) [In the formula (II), X ５ and X ６ are each independently CF ３ , NO ２ , CN, and an aryl group having an electron-withdrawing group (for example, a phenyl group, a naphthyl group, a biphenylyl group each having an electron-withdrawing group selected from the group consisting of CF ３ , NO ２ and CN) is selected from the group consisting of. X ５ and X ６ are each independently CF ３ , CN, and an aryl group having an electron-withdrawing group. X ５ and X ６Each of them operates independently, CF ３ It is more preferable to select from the group consisting of aryl groups having electron-withdrawing groups. ５ and X ６ Regarding the aryl group having an electron-withdrawing group, CF ３ It is preferable to select from a phenyl group, naphthyl group, and biphenylyl group having an electron-withdrawing group selected from the group consisting of and CN. ５ and X ６ Regarding the aryl group having an electron-withdrawing group, CF ３ It is more preferable to select from a phenyl group and a naphthyl group having ] In the presence of at least one boron compound selected from the group consisting of ], an indoline compound (4) represented by the following formula (IV) [In formula (IV), R １ and R ６ Each of these is independently selected from the group consisting of H, alkyl, and halogen. １ and R ６ Each of these is preferably independently selected from the group consisting of H, C1-C12 alkyl, F, Cl, and Br, and R １ and R ６ Each of these is more preferably independently selected from the group consisting of H, C1-C10 alkyl groups, F, Cl, and Br, and R １ and R ６ It is even more preferable that each of these be independently selected from the group consisting of H, C1-C8 alkyl groups, F, and Cl. The process includes dehydrogenating to obtain hydrogen.

[0022] The reaction conditions for the dehydrogenation reaction in a hydrogen production method, which includes obtaining hydrogen by dehydrogenating an indoline compound according to embodiments of the present invention, are not particularly limited as long as the dehydrogenation reaction targeted by the present invention can be carried out. The reaction temperature for the dehydrogenation reaction is preferably 90°C to 230°C, more preferably 95°C to 210°C, even more preferably 100°C to 190°C, and even more preferably 105°C to 180°C. The reaction pressure for the dehydrogenation reaction is preferably, for example, 0.855 atm to 1.5 atm, more preferably 0.90 atm to 1.2 atm, and even more preferably atmospheric pressure (0.95 atm to 1 atm according to JIS).

[0023] The reaction time for the dehydrogenation reaction is preferably 0.1 hours to 12 hours, more preferably 0.2 hours to 8 hours, even more preferably 0.3 hours to 4 hours, and even more preferably 0.5 hours to 2 hours. With respect to the dehydrogenation reaction, the total mol% of boron compounds (1) and (2) is preferably 0.01 mol% to 10 mol%, more preferably 0.05 mol% to 6 mol%, even more preferably 0.1 mol% to 4 mol%, and even more preferably 0.5 mol% to 3 mol%.

[0024] In another aspect of the present invention, a method for producing an indoline compound is provided, which includes hydrogenating an indole compound in the presence of a specific boron compound to obtain an indoline compound. The boron compound (1) is represented by the following formula (I). [In equation (I), X １ and X ２ These are H, F, Cl, Br, CF, each independently. ３ NO ２ CN, aryl groups having electron-withdrawing groups (e.g., F, Cl, Br, CF) ３ NO ２ Selected from the group consisting of CN, a phenyl group, naphthyl group, and biphenylyl group having an electron-withdrawing group, X １ and X２ Both are X, not H. ３ and X ４ H, F, Cl, Br, CF ３ Selected from the group consisting of , and aryl groups (e.g., phenyl group, naphthyl group, and biphenylyl group). １ and X ２ These are H, F, Cl, Br, CF, each independently. ３ It is preferably selected from the group consisting of CN and an aryl group having an electron-withdrawing group, and neither of them is H. １ and X ２ These are F, Cl, Br, and CF, each independently. ３ It is more preferable to select from the group consisting of aryl groups having electron-withdrawing groups. １ and X ２ Regarding the aryl groups having electron-withdrawing groups, they are F, Cl, Br, CF ３ Preferably, the electron-withdrawing group is selected from the group consisting of , and CN, and is selected from a phenyl group, a naphthyl group, and a biphenylyl group. １ and X ２ Regarding the aryl groups having electron-withdrawing groups, they are F, Cl, Br, and CF ３ It is more preferable to select from a phenyl group and a naphthyl group selected from the group consisting of X. ３ and X ４ These are H, F, Cl, Br, and CF, each independently. ３ It is preferable to select from the group consisting of X ３ and X ４ Each of these is more preferably independently selected from the group consisting of H, F, Cl, and Br, X ３ and X ４ Each of these is preferably independently selected from the group consisting of H, F, and Cl. ] and boron compound (2) represented by the following formula (II) [In equation (II), X ５ and X ６ Each of them operates independently, CF ３ NO ２ , CN, and aryl groups having electron-withdrawing groups (e.g., CF ３Selected from the group consisting of , and CN, and from the group consisting of electron-withdrawing groups such as phenyl groups, naphthyl groups, and biphenylyl groups. ５ and X ６ Each of them operates independently, CF ３ Preferably selected from the group consisting of CN and an aryl group having an electron-withdrawing group. ５ and X ６ Each of them operates independently, CF ３ It is more preferable to select from the group consisting of aryl groups having electron-withdrawing groups. ５ and X ６ Regarding the aryl group having an electron-withdrawing group, CF ３ It is preferable to select from a phenyl group, naphthyl group, and biphenylyl group having an electron-withdrawing group selected from the group consisting of and CN. ５ and X ６ Regarding the aryl group having an electron-withdrawing group, CF ３ It is more preferable to select from a phenyl group and a naphthyl group having ] At least one boron compound (1) or (2) selected from the group consisting of ] and an indole compound (3) represented by the following formula (III) in the presence of hydrogen [In equation (III), R １ and R ６ Each of these is independently selected from the group consisting of H, alkyl, and halogen. １ and R ６ Each of these is preferably independently selected from the group consisting of H, C1-C12 alkyl, F, Cl, and Br, and R １ and R ６ Each of these is more preferably independently selected from the group consisting of H, C1-C10 alkyl groups, F, Cl, and Br, and R １ and R ６ It is even more preferable that each of these be independently selected from the group consisting of H, C1-C8 alkyl, F, and Cl. Hydrogenating this yields an indoline compound (4) represented by the following formula (IV). This includes obtaining.

[0025] The reaction conditions for the hydrogenation reaction of the method for producing an indoline compound, which includes hydrogenating an indole compound according to an embodiment of the present invention to obtain an indoline compound, are not particularly limited as long as the hydrogenation reaction of the indole compound targeted by the present invention is carried out and an indoline compound can be obtained. The reaction temperature of the hydrogenation reaction is preferably 50°C to 200°C, more preferably 60°C to 180°C, even more preferably 70°C to 150°C, and even more preferably 75°C to 120°C. The hydrogen pressure of the hydrogenation reaction is preferably 1 atm to 120 atm, more preferably 2 atm to 100 atm, and even more preferably 4 atm to 80 atm.

[0026] The reaction time for the hydrogenation reaction is preferably 0.1 hours or more and 12 hours or less, more preferably 0.2 hours or more and 6 hours or less, even more preferably 0.4 hours or more and 3 hours or less, and even more preferably 0.5 hours or more and 2 hours or less. For the hydrogenation reaction, with respect to indole compound (3), the total mol% of boron compounds (1) and (2) is preferably 0.001 mol% or more and 20 mol% or less, more preferably 0.1 mol% or more and 15 mol% or less, even more preferably 0.5 mol% or more and 13 mol% or less, and even more preferably 1.0 mol% or more and 12 mol% or less.

[0027] The hydrogen used in the hydrogenation reaction of a method for producing an indoline compound, which includes hydrogenating an indole compound according to an embodiment of the present invention to obtain an indoline compound, may be a mixed gas containing hydrogen and other gases. In addition to hydrogen, the mixed gas may contain at least one selected from the group consisting of methane, nitrogen, water (water vapor), carbon monoxide, and carbon dioxide.

[0028] In a preferred aspect of the present invention, a method for producing hydrogen and a method for supplying hydrogen are provided, which include hydrogenating an indole compound in the presence of a specific boron compound to obtain an indoline compound, and dehydrogenating an indoline compound in the presence of a specific boron compound and an indoline compound to obtain hydrogen. The boron compound is represented by the following formula (I) (1) [In equation (I), X １ and X ２ These are H, F, Cl, Br, CF, each independently. ３ NO ２ CN, and aryl groups having electron-withdrawing groups (e.g., F, Cl, Br, CF) ３ NO ２ Selected from the group consisting of CN, a phenyl group, naphthyl group, and biphenylyl group having an electron-withdrawing group, X １ and X ２ Both are X, not H. ３ and X ４ H, F, Cl, Br, CF ３ Selected from the group consisting of , and aryl groups (e.g., phenyl group, naphthyl group, and biphenylyl group). １ and X ２ These are H, F, Cl, Br, CF, each independently. ３ Selected from the group consisting of CN and an aryl group having an electron-withdrawing group, preferably neither of which is H, X １ and X ２ These are F, Cl, Br, and CF, each independently. ３ It is more preferable to select from the group consisting of aryl groups having electron-withdrawing groups. １ and X ２ Regarding the aryl groups having electron-withdrawing groups, they are F, Cl, Br, CF ３ Preferably, the electron-withdrawing group is selected from the group consisting of , and CN, and is selected from a phenyl group, a naphthyl group, and a biphenylyl group. １ and X ２ Regarding the aryl groups having electron-withdrawing groups, they are F, Cl, Br, and CF ３It is more preferable to select from a phenyl group and a naphthyl group selected from the group consisting of X. ３ and X ４ These are H, F, Cl, Br, and CF, each independently. ３ It is preferable to select from the group consisting of X ３ and X ４ Each of these is more preferably independently selected from the group consisting of H, F, Cl, and Br, X ３ and X ４ Each of these is preferably independently selected from the group consisting of H, F, and Cl. ] and boron compound (2) represented by the following formula (II) [In equation (II), X ５ and X ６ Each of them operates independently, CF ３ NO ２ , CN, and aryl groups having electron-withdrawing groups (e.g., CF ３ Selected from the group consisting of , and CN, and from the group consisting of electron-withdrawing groups such as phenyl groups, naphthyl groups, and biphenylyl groups. ５ and X ６ Each of them operates independently, CF ３ Preferably selected from the group consisting of CN and an aryl group having an electron-withdrawing group. ５ and X ６ Each of them operates independently, CF ３ It is more preferable to select from the group consisting of aryl groups having electron-withdrawing groups. ５ and X ６ Regarding the aryl group having an electron-withdrawing group, CF ３ It is preferable to select from a phenyl group, naphthyl group, and biphenylyl group having an electron-withdrawing group selected from the group consisting of and CN. ５ and X ６ Regarding the aryl group having an electron-withdrawing group, CF ３ It is more preferable to select from a phenyl group and a naphthyl group having ] At least one boron compound (1) or (2) selected from the group consisting of ] and an indole compound (3) represented by the following formula (III) in the presence of hydrogen [In equation (III), R １ and R ６ Each of these is independently selected from the group consisting of H, alkyl, and halogen. １ and R ６ Each of these is preferably independently selected from the group consisting of H, C1-C12 alkyl, F, Cl, and Br, and R １ and R ６ Each of these is more preferably independently selected from the group consisting of H, C1-C10 alkyl groups, F, Cl, and Br, and R １ and R ６ It is even more preferable that each of these be independently selected from the group consisting of H, C1-C8 alkyl, F, and Cl. Hydrogenating this yields an indoline compound (4) represented by the following formula (IV). To obtain, and a boron compound (1) represented by the following formula (I) [In equation (I), X １ and X ２ These are H, F, Cl, Br, CF, each independently. ３ NO ２ CN, and aryl groups having electron-withdrawing groups (e.g., F, Cl, Br, CF) ３ NO ２ Selected from the group consisting of CN, a phenyl group, naphthyl group, and biphenylyl group having an electron-withdrawing group, X １ and X ２ Both are X, not H. ３ and X ４ H, F, Cl, Br, CF ３ Selected from the group consisting of , and aryl groups (e.g., phenyl group, naphthyl group, and biphenylyl group). １ and X ２ These are H, F, Cl, Br, CF, each independently. ３ It is preferably selected from the group consisting of CN and an aryl group having an electron-withdrawing group, and neither of them is H. １ and X ２ These are F, Cl, Br, and CF, each independently. ３ It is more preferable to select from the group consisting of aryl groups having electron-withdrawing groups.１ and X ２ Regarding the aryl groups having electron-withdrawing groups, they are F, Cl, Br, CF ３ Preferably, the electron-withdrawing group is selected from the group consisting of , and CN, and is selected from a phenyl group, a naphthyl group, and a biphenylyl group. １ and X ２ Regarding the aryl groups having electron-withdrawing groups, they are F, Cl, Br, and CF ３ It is more preferable to select from a phenyl group and a naphthyl group selected from the group consisting of X. ３ and X ４ These are H, F, Cl, Br, and CF, each independently. ３ It is preferable to select from the group consisting of X ３ and X ４ Each of these is more preferably independently selected from the group consisting of H, F, Cl, and Br, X ３ and X ４ Each of these is preferably independently selected from the group consisting of H, F, and Cl. ] and boron compound (2) represented by the following formula (II) [In equation (II), X ５ and X ６ Each of them operates independently, CF ３ NO ２ , CN, and aryl groups having electron-withdrawing groups (e.g., CF ３ Selected from the group consisting of , and CN, and from the group consisting of electron-withdrawing groups such as phenyl groups, naphthyl groups, and biphenylyl groups. ５ and X ６ Each of them operates independently, CF ３ Preferably selected from the group consisting of CN and an aryl group having an electron-withdrawing group. ５ and X ６ Each of them operates independently, CF ３ It is more preferable to select from the group consisting of aryl groups having electron-withdrawing groups. ５ and X ６ Regarding the aryl group having an electron-withdrawing group, CF ３It is preferable to select from a phenyl group, naphthyl group, and biphenylyl group having an electron-withdrawing group selected from the group consisting of and CN. ５ and X ６ Regarding the aryl group having an electron-withdrawing group, CF ３ It is more preferable to select from a phenyl group and a naphthyl group having ] In the presence of at least one boron compound (1) or (2) selected from the group consisting of ], an indoline compound (4) represented by the following formula (IV) [In formula (IV), R １ and R ６ Each of these is independently selected from the group consisting of H, alkyl, and halogen. １ and R ６ Each of these is preferably independently selected from the group consisting of H, C1-C12 alkyl, F, Cl, and Br, and R １ and R ６ Each of these is more preferably independently selected from the group consisting of H, C1-C10 alkyl groups, F, Cl, and Br, and R １ and R ６ It is even more preferable that each of these be independently selected from the group consisting of H, C1-C8 alkyl groups, F, and Cl. This includes dehydrogenating to obtain hydrogen.

[0029] In the hydrogen production method and hydrogen supply method of the embodiment of the present invention, which includes hydrogenating an indole compound to obtain an indoline compound and dehydrogenating an indoline compound to obtain hydrogen, the reaction conditions for hydrogenating the indole compound to obtain the indoline compound are not particularly limited as long as the hydrogen production method and hydrogen supply method to be achieved can be obtained. The reaction temperature for the hydrogenation reaction is preferably 50°C to 200°C, more preferably 60°C to 180°C, even more preferably 70°C to 150°C, and even more preferably 75°C to 120°C. The hydrogen pressure for the hydrogenation reaction is preferably 1 atm to 120 atm, more preferably 2 atm to 100 atm, and even more preferably 4 atm to 80 atm. The hydrogenation reaction is preferably carried out without a solvent. If a solvent is used, the concentration may become lower and the reaction may slow down depending on the amount of solvent used. The highest concentration can be obtained and the reaction may be the fastest in the case of no solvent.

[0030] The reaction time for the hydrogenation reaction is preferably 0.1 hours or more and 12 hours or less, more preferably 0.2 hours or more and 6 hours or less, even more preferably 0.4 hours or more and 3 hours or less, and even more preferably 0.5 hours or more and 2 hours or less. For the hydrogenation reaction, with respect to indole compound (3), the total mol% of boron compounds (1) and (2) is preferably 0.001 mol% or more and 20 mol% or less, more preferably 0.1 mol% or more and 15 mol% or less, even more preferably 0.5 mol% or more and 13 mol% or less, and even more preferably 1.0 mol% or more and 12 mol% or less.

[0031] In the hydrogen production method and hydrogen supply method of the embodiment of the present invention, which includes hydrogenating an indole compound to obtain an indoline compound and dehydrogenating the indoline compound to obtain hydrogen, the reaction conditions for dehydrogenating the indoline compound to obtain hydrogen are not particularly limited as long as the hydrogen production method and hydrogen supply method to be achieved can be obtained. The reaction temperature for the dehydrogenation reaction is preferably 90°C to 230°C, more preferably 95°C to 210°C, even more preferably 100°C to 190°C, and even more preferably 105°C to 180°C. The reaction pressure for the dehydrogenation reaction is preferably, for example, 0.855 atm to 1.5 atm, more preferably 0.90 atm to 1.2 atm, and even more preferably atmospheric pressure (0.95 atm to 1 atm according to JIS). The dehydrogenation reaction is preferably carried out without a solvent. If a solvent is used, the concentration may become lower and the reaction may slow down depending on the amount of solvent used. Without a solvent, the highest concentration can be achieved and the reaction may be the fastest. Furthermore, using a solvent may result in the solvent leaching out along with the hydrogen, potentially requiring additional effort to purify the hydrogen.

[0032] The reaction time for the dehydrogenation reaction is preferably 0.1 hours to 12 hours, more preferably 0.2 hours to 8 hours, even more preferably 0.3 hours to 4 hours, and even more preferably 0.5 hours to 2 hours. With respect to the dehydrogenation reaction, the total mol% of boron compounds (1) and (2) is preferably 0.01 mol% to 10 mol%, more preferably 0.05 mol% to 6 mol%, even more preferably 0.1 mol% to 4 mol%, and even more preferably 0.5 mol% to 3 mol%.

[0033] A hydrogen production method and hydrogen supply method according to embodiments of the present invention, which includes hydrogenating an indole compound to obtain an indoline compound and dehydrogenating the indoline compound to obtain hydrogen, may include hydrogenating indole (3) in the presence of a mixed gas containing, in addition to hydrogen, at least one selected from the group consisting of methane, nitrogen, water (steam), carbon monoxide, and carbon dioxide. Furthermore, it may include hydrogenating the indole compound (3) by heating it to 50°C or higher and 200°C or lower to obtain an indoline compound (4). It may also include dehydrogenating it by heating it to 90°C or higher and 230°C or lower. Furthermore, the hydrogenation reaction to obtain an indoline compound (4) and the dehydrogenation of the indoline compound (4) to obtain hydrogen can be carried out in a batch or continuous manner. When the hydrogenation reaction and dehydrogenation reaction are carried out consecutively, it is preferable to carry them out without a solvent. If a solvent is used in the hydrogenation reaction and dehydrogenation reaction, the concentration may become lower and the reaction may slow down depending on the amount of solvent used. Without a solvent, the highest concentration can be achieved and the reaction may be the fastest. Furthermore, if a solvent is used, the solvent may leach out along with the hydrogen, potentially requiring additional effort to purify the hydrogen. When hydrogenation and dehydrogenation reactions are carried out consecutively, the reaction temperature of the dehydrogenation reaction is usually higher than that of the hydrogenation reaction. Therefore, more solvent may leach out during the dehydrogenation reaction, leading to larger changes in the reaction concentration, which can cause problems such as difficulty in controlling the reaction rate.

[0034] A hydrogen production method and hydrogen supply method according to embodiments of the present invention, which include hydrogenating an indole compound to obtain an indoline compound and dehydrogenating the indoline compound, may include purifying hydrogen, storing hydrogen, and / or transporting hydrogen.

[0035] The present invention will be described in detail below with reference to examples and comparative examples. However, these examples represent only one aspect of the present invention, and the present invention is not limited in any way by these examples. In the descriptions of the examples, unless otherwise specified, portions that do not consider the solvent are given as being based on parts by weight and weight percent.

[0036] Boron compounds (1) and (2) (2,6-dichlorophenyl)bis(2,3,5,6-tetrafluorophenyl)borane (1)a was synthesized according to the method described in Non-Patent Document 4. (2,6-dichlorophenyl)bis(3,5-dichloro-2,6-difluorophenyl)borane (1)b was synthesized according to the method described in Patent Document 1. (2,6-dichlorophenyl)bis(3-chloro-2,6-difluorophenyl)borane (1)c was synthesized according to the method described in Non-Patent Document 3. (2,6-dichlorophenyl)bis(3,5-dibromo-2,6-difluorophenyl)borane (1)d was synthesized according to the method described in Non-Patent Document 3. (2,6-dichlorophenyl)bis(3,5-bis(3,5-di(trifluoromethyl)phenyl)-2,6-difluorophenyl)borane (1)e was synthesized according to the method described in Non-Patent Document 3. Tris(3,5-ditrifluoromethylphenyl)borane(2)a was synthesized according to the method described in Non-Patent Document 5. Tris(pentafluorophenyl)borane(1)'f was purchased from Tokyo Chemical Industry Co., Ltd.

[0037]

[0038] Examples 1-6 and Comparative Example 1. Dehydrogenation of N-methylindoline (4)a and hydrogen in the presence of various boron compounds (1) or (2). In a 10 mL two-necked flask under a nitrogen atmosphere, 3.0 mmol of 1-methylindoline, boron compound (1) or (2), and tetradecane as an internal standard were added and heated at 150°C for 1 hour in an open system (1 atm). After the reaction flask cooled to room temperature, the reaction solution was diluted with acetone and the yield of indole was determined by GC measurement. Meanwhile, the generated hydrogen was collected in a graduated cylinder and the yield of hydrogen was determined. The results are shown in Table 1.

[0039]

[0040] Examples 7-8. Dehydrogenation of 1-methylindoline (4)a and hydrogen at various temperatures in the presence of boron compound (1)d. In a 10 mL two-necked flask under a nitrogen atmosphere, N-methylindoline (3.0 or 3.5 mmol), boron compound (1)d (0.03 or 0.035 mmol), and tetradecane as an internal standard were added, and the mixture was heated at 120, 150, or 200 °C for 1 hour in an open system (1 atm). After the reaction flask was cooled to room temperature, the reaction solution was diluted with acetone, and the yield of indole was determined by GC measurement. Meanwhile, the generated hydrogen was collected in a graduated cylinder, and the yield of hydrogen was determined. The results are shown in Table 2.

[0041]

[0042] Examples 9-12. Production of indole compound (3) and hydrogen by dehydrogenation of various indoline compounds (4) in the presence of boron compound (1)b. In a 10 mL two-necked flask under a nitrogen atmosphere, indoline compound (4) (3.0 mmol), boron compound (1)b (0.03 mmol), and tetradecane as an internal standard were added and heated at 150°C for 1 hour in an open system (1 atm). After the reaction flask was cooled to room temperature, the reaction solution was diluted with acetone and the yield of indole (3) was determined by GC measurement. Meanwhile, the generated hydrogen was collected in a graduated cylinder and the yield of hydrogen was determined. The results are shown in Table 3.

[0043]

[0044] Examples 13-17. Production of 1-methylindoline (4)a by hydrogenation of 1-methylindole (3)a in the presence of various boron compounds (1). Under a nitrogen atmosphere, 1-methylindole (3)a (0.3 mmol), boron compound (1) or (2) (0.03 mmol, 10 mol%), and tetradecane as an internal standard were added to a 10 mL autoclave and sealed. The autoclave was then heated to 30 atm H ２ / CO / CO ２A mixed gas (4.1 mmol each, hydrogen at 10 atm) was added under pressure, and the mixture was allowed to stand for 30 minutes until it reached 100°C from room temperature. After that, it was heated and stirred at 100°C for 15 minutes. After the autoclave was cooled and degassed, the reaction solution was diluted with acetone and GC measurement was performed. The results are shown in Table 4.

[0045]

[0046] Examples 18-19. Production of 1-methylindoline (4)a by hydrogenation of 1-methylindole (3)a at different hydrogen pressures in the presence of boron compound (1)d. Under a nitrogen atmosphere, 1-methylindole (3)a, boron compound (1)d (2 mol%), and tetradecane as an internal standard were added to a 10 mL autoclave and sealed. The autoclave was heated to 90 atm H ２ / CO / CO ２ A mixed gas (hydrogen at 30 atm) was added under pressure, and the mixture was allowed to stand for 15 minutes until it reached 80 or 100°C from room temperature. The mixture was then heated and stirred at 80 or 100°C for 15 minutes. After cooling and degassing the autoclave, the reaction solution was diluted with acetone and GC measurements were performed. The results are shown in Table 5.

[0047]

[0048] Examples 20-21. In the presence of boron compound (1)b, indole (3) was used to heat H at 90 atm. ２ / CH ４ Continuous generation of hydrogen gas with improved purity from a gas mixture (4:1) under a nitrogen atmosphere. 1-methylindole (3)a and boron compound (1)b (2 mol%) were added to a 10 mL autoclave and sealed. 90 atm H₂ ２ / CH ４A gas mixture (4:1, hydrogen at 72 atm) was added under pressure, and the mixture was left to stand for 15 minutes from room temperature until it reached 100°C. After heating and stirring at 100°C for 45 minutes, the autoclave was cooled and degassed. After further degassing under reduced pressure, the mixture was heated in an open system (1 atm) at 150°C for 30 minutes (Example 20) or 1 hour (Example 21). After the reaction flask was cooled to room temperature, the reaction solution was diluted with acetone, and the efficiency of each reaction was estimated by GC measurement. As a result, the efficiency was 98% for hydrogenation and 70% for dehydrogenation (Example 20), or 98% for hydrogenation and 73% for dehydrogenation (Example 21). Meanwhile, the generated hydrogen was collected in a graduated cylinder, and the yield and purity of hydrogen were determined. The yield was 69% and the purity was 99.93% (Example 20), or the yield was 72% and the purity was 99.93% (Example 21).

[0049] Example 22. In the presence of boron compound (1)b, indole (3) is used to heat H at 80 atm. ２ Continuous generation of hydrogen gas with improved purity from a CO / CO2 mixed gas (1:1:1) under a nitrogen atmosphere. 1-methylindole (3)a and boron compound (1)b (2 mol%) were added to a 10 mL autoclave and sealed. 80 atm H₂ ２ A CO / CO2 mixed gas (1:1:1, hydrogen at 26.7 atm) was added under pressure, and the mixture was left to stand for 15 minutes from room temperature until it reached 100°C. After heating and stirring at 100°C for 15 minutes, the autoclave was cooled and degassed. After further degassing under reduced pressure, the mixture was heated at 150°C for 15 minutes in an open system (1 atm). After the reaction flask was cooled to room temperature, the reaction solution was diluted with acetone, and the efficiency of each reaction was estimated by GC measurement. As a result, the efficiency of hydrogenation was 89% and the efficiency of dehydrogenation was 69%. Meanwhile, the generated hydrogen was collected in a graduated cylinder, and the hydrogen yield was determined. The yield was 61%.

[0050] The hydrogen production method of the embodiment of the present invention involves dehydrogenating an indoline compound of an N-cyclo compound in the presence of a specific boron compound, thereby enabling the production of hydrogen and indole of a heterocyclic compound more efficiently, with less energy, at lower temperatures (closer to room temperature), and in a shorter time.

[0051] Furthermore, the hydrogen production method and hydrogen supply method of the embodiment of the present invention perform hydrogenation of an indole compound of a heterocyclic compound to produce an indoline compound of an N-cyclo compound in the presence of a specific boron compound, and dehydrogenation of the indoline compound in the presence of a specific boron compound. Therefore, it is possible to provide a hydrogen production method and hydrogen supply method that can be performed more efficiently, with less energy, at a lower temperature (closer to room temperature), and in a shorter time. The hydrogen production method and hydrogen supply method of the embodiment of the present invention may include hydrogen purification, hydrogen storage, and / or hydrogen transport.

[0052] (Related Application) This application claims priority under Article 4 of the Paris Convention or Article 41 of the Japanese Patent Act, based on Japanese Patent Application No. 2025-031478 filed in Japan on 28 February 2025. The contents of this basic application are incorporated herein by reference.

Claims

1. A boron compound (1) represented by the following formula (I) [In the formula (I), X １ and X ２ are each independently selected from the group consisting of H, F, Cl, Br, CF ３ , NO ２ , CN, and an aryl group having an electron withdrawing group (selected from the group consisting of F, Cl, Br, CF ３ , NO ２ , and CN), X １ and X ２ are not both H, and X ３ and X ４ are each independently selected from the group consisting of H, F, Cl, Br, CF ３ , and an aryl group] and a boron compound (2) represented by the following formula (II) [In the formula (II), X ５ and X ６ are each independently selected from CF ３ , NO ２ , CN, and an aryl group having an electron withdrawing group (selected from the group consisting of CF ３ , NO ２ , and CN).] A method for producing hydrogen, comprising dehydrogenating an indoline compound (4) represented by the following formula (IV) in the presence of at least one boron compound selected from the group consisting of the above to obtain hydrogen [In the formula (IV), R １ and R ６ are each independently selected from the group consisting of H, alkyl, and halogen.] 2. A method for producing hydrogen according to claim 1, comprising heating to 90°C or higher and 230°C or lower to dehydrogenate and obtain hydrogen.

3. Boron compound (1) represented by the following formula (I) [In equation (I), X １ and X ２ These are H, F, Cl, Br, CF, each independently. ３ NO ２ , CN, and electron-withdrawing groups (F, Cl, Br, CF ３ NO ２ Selected from the group consisting of aryl groups having (selected from the group consisting of , and CN), X １ and X ２ Both are X, not H. ３ and X ４ These are H, F, Cl, Br, CF, each independently. ３ Selected from the group consisting of , and aryl groups. ] and boron compounds (2) represented by the following formula (II) [In equation (II), X ５ and X ６ Each of them operates independently, CF ３ NO ２ , CN, and electron-withdrawing group (CF ３ NO ２ Selected from the group consisting of , and CN, an indole compound (3) represented by the following formula (III) is used in the presence of hydrogen and at least one boron compound (1) or (2) selected from the group consisting of ] [In equation (III), R １ and R ６ Each is independently selected from the group consisting of H, alkyl, and halogen. Hydrogenating ] yields the indoline compound (4) represented by the following formula (IV). A method for producing an indoline compound, including obtaining the compound.

4. A method for producing an indoline compound (4) according to claim 3, comprising hydrogenating an indole compound (3) in the presence of a mixed gas containing, in addition to hydrogen, at least one selected from the group consisting of methane, nitrogen, water, carbon monoxide, and carbon dioxide.

5. A method for producing an indoline compound (4) according to claim 3, comprising heating the indole compound (3) to 50°C or higher and 200°C or lower, and hydrogenating it to obtain an indoline compound (4).

6. Boron compound represented by the following formula (I) (1) [In equation (I), X １ and X ２ These are H, F, Cl, Br, CF, each independently. ３ NO ２ , CN, electron-withdrawing group (F, Cl, Br, CF ３ NO ２ Selected from the group consisting of aryl groups having (selected from the group consisting of CN), X １ and X ２ Both are X, not H. ３ and X ４ These are H, F, Cl, Br, CF, each independently. ３ Selected from the group consisting of , and aryl groups. ] and boron compounds (2) represented by the following formula (II) [In equation (II), X ５ and X ６ Each of them operates independently, CF ３ NO ２ , CN, and electron-withdrawing group (CF ３ NO ２ Selected from the group consisting of , and CN, an indole compound (3) represented by the following formula (III) is used in the presence of hydrogen and at least one boron compound (1) or (2) selected from the group consisting of ] [In equation (III), R １ and R ６ Each is independently selected from the group consisting of H, alkyl, and halogen. Hydrogenating ] yields the indoline compound (4) represented by the following formula (IV). To obtain, and a boron compound (1) represented by the following formula (I) [In equation (I), X １ and X ２ These are H, F, Cl, Br, CF, each independently. ３ NO ２ , CN, and electron-withdrawing groups (F, Cl, Br, CF ３ NO ２ Selected from the group consisting of aryl groups having (selected from the group consisting of , and CN), X １ and X ２ are both not H, and X ３ and X ４ are each independently selected from the group consisting of H, F, Cl, Br, CF ３ , and an aryl group.] and a boron compound (2) represented by the following formula (II) [In formula (II), X ５ and X ６ are each independently CF ３ , NO ２ , CN, and an aryl group having an electron-withdrawing group (selected from the group consisting of CF ３ , NO ２ , and CN).] In the presence of at least one boron compound (1) or (2) selected from the group consisting of, an indoline compound (4) represented by the following formula (IV) [In formula (IV), R １ and R ６ are each independently selected from the group consisting of H, alkyl, and halogen.] dehydrogenating the same to obtain hydrogen, which is a hydrogen production method or a hydrogen supply method.

7. A method for producing hydrogen or supplying hydrogen according to claim 6, comprising hydrogenating indole (3) in the presence of a mixed gas containing, in addition to hydrogen, at least one selected from the group consisting of methane, nitrogen, water, carbon monoxide, and carbon dioxide.

8. A method for producing hydrogen or supplying hydrogen according to claim 6, comprising heating an indole compound (3) to 50°C or higher and 200°C or lower to hydrogenate it and obtain an indoline compound (4).

9. A method for producing hydrogen or supplying hydrogen according to claim 1, comprising heating to a temperature of 90°C or higher and 230°C or lower to dehydrogenate the hydrogen.

10. A method for producing hydrogen or supplying hydrogen according to claim 5 or 6, wherein the hydrogenation of an indole compound (3) to obtain an indoline compound (4), and the dehydrogenation of the indoline compound (4) to obtain hydrogen, are carried out in a batch or continuous manner.

11. A method for producing hydrogen or supplying hydrogen according to claim 5 or 6, which may include purifying hydrogen, storing hydrogen, and / or transporting hydrogen.

Images