Method for producing formate, method for producing formic acid, catalyst for producing formate, and ruthenium complex

Abstract

The present application relates to a method for producing formate salt, which is a method for producing formate salt by reacting hydrogen, carbon dioxide, bicarbonate or carbonate salt in the presence of a solvent using a catalyst, wherein the solvent is present in a two-phase system in which an organic solvent and an aqueous solvent are separated, and the catalyst is at least one selected from the group consisting of a ruthenium complex represented by General Formula (1) in the description, a tautomer or a stereoisomer thereof, or a chloro compound thereof.

Description

Technical Field

[0001] This invention relates to a method for manufacturing formate, a method for manufacturing formic acid, a catalyst for manufacturing formate, and a ruthenium complex. Background Technology

[0002] Due to issues such as global warming and the depletion of fossil fuels, hydrogen energy is highly anticipated as the next generation of energy.

[0003] Moreover, the dehydrogenation reaction of formic acid requires low energy and can be easily operated. Therefore, it is considered an excellent compound for hydrogen storage and has attracted much attention.

[0004] To reduce transportation costs, a high-concentration formic acid solution must be obtained when using formic acid as a hydrogen storage material.

[0005] Therefore, methods for producing formic acid from carbon dioxide (CO2) and hydrogen (H2) in the presence of a catalyst have been investigated. For example, Non-Patent Literature 1 describes a method for producing formic acid by reacting carbon dioxide with hydrogen in a hydrogenation reactor in the presence of a metal complex catalyst.

[0006] In addition, techniques for efficiently removing hydrogen from the manufactured formic acid are also important. For example, in Patent Document 1, a metal complex catalyst for removing hydrogen from formic acid was studied.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Publication No. 2016-539793

[0010] Non-patent literature

[0011] Non-patent literature 1: E. Pidko et al., ChemCatChem 2014, 6, 1526-1530 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] Furthermore, in the technology described in Patent Document 1, a method for generating hydrogen from formic acid was studied, but the generation of formic acid and the ease of separation and recovery of the catalyst were not studied.

[0014] The technology described in Non-Patent Literature 1 is a technology for generating formate from hydrogen and carbon dioxide using a metal complex catalyst in an amine-based solvent. There is room for improvement in the separation and extraction of formic acid from the catalyst and solvent, and there is a need to develop a catalyst that can generate formic acid in higher yields.

[0015] Therefore, the present invention provides a method for producing formate as a precursor of formic acid in high yield and for reusing the catalyst, a method for producing formic acid, a catalyst for producing formate, and a ruthenium complex that can be used as a catalyst for efficiently converting hydrogen into formate.

[0016] Methods for solving problems

[0017] The inventors of this application conducted repeated and in-depth research, and as a result, discovered that by using a metal complex with a specific structure as a catalyst, hydrogen can be converted into formate with high efficiency. Furthermore, a method for manufacturing formate and formic acid that can efficiently recover and reuse the catalyst was discovered, thus completing this invention.

[0018] The methods used to solve the aforementioned problems are as follows.

[0019] [1]

[0020] A method for producing formate involves reacting hydrogen with carbon dioxide, bicarbonate, or carbonate in the presence of a solvent using a catalyst.

[0021] In the aforementioned reaction, the solvent is a two-phase system existing in a state where the organic solvent and the aqueous solvent are separated.

[0022] The aforementioned catalyst is at least one selected from ruthenium complexes, tautomers or stereoisomers thereof, or chlorinated compounds thereof represented by the following general formula (1).

[0023] [Chemical Formula 1]

[0024]

[0025] (In general formula (1), R0 represents a hydrogen atom or an alkyl group,

[0026] Q1 can independently represent CH2, NH, or O.

[0027] R1 independently represents either an alkyl or an aryl group (wherein, if Q1 represents NH or O, at least one of R1 represents an aryl group).

[0028] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0029] X represents a halogen atom.

[0030] n represents 0 to 3.

[0031] In the presence of multiple L ligands, each ligand can independently represent a neutral or anionic ligand.

[0032] [2]

[0033] The method for manufacturing formate as described in [1], wherein the ruthenium complex represented by the aforementioned general formula (1) is the ruthenium complex represented by the following general formula (3).

[0034] [Chemical Formula 2]

[0035]

[0036] (In general formula (3), R0 represents a hydrogen atom or an alkyl group,

[0037] Q2 can be represented independently as NH or O.

[0038] R3 represents aryl groups independently.

[0039] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0040] X represents a halogen atom.

[0041] n represents 0 to 3.

[0042] In the presence of multiple L ligands, each ligand can independently represent a neutral or anionic ligand.

[0043] [3]

[0044] The method for manufacturing formate as described in [1], wherein R1 represents phenyl.

[0045] [4]

[0046] The method for manufacturing formate as described in [2], wherein R3 represents phenyl.

[0047] [5]

[0048] The method for manufacturing formate as described in [4], wherein the aforementioned A represents CH and the aforementioned Q2 represents NH.

[0049] [6]

[0050] The method for manufacturing formate as described in any one of [1] to [5], wherein the aforementioned R0 represents a hydrogen atom or a methyl group.

[0051] [7]

[0052] The method for manufacturing formate as described in any one of [1] to [6], wherein the aforementioned X represents a chlorine atom.

[0053] [8]

[0054] The method for manufacturing formate as described in any one of [1] to [7], wherein the aforementioned n represents 1 to 3, and the aforementioned L each independently represents a hydrogen atom, carbon monoxide, or triphenylphosphine.

[0055] [9]

[0056] The method for manufacturing formate as described in any one of [1] to [8], wherein the aforementioned organic solvent comprises toluene or dioxane.

[0057]

[10]

[0058] The method for manufacturing formate as described in any one of [1] to [9], wherein an ammonium salt is further used as a phase transfer catalyst.

[0059]

[11]

[0060] A method for manufacturing formate as described in any one of [1] to

[10] , wherein a ligand represented by the following general formula (4) is further added.

[0061] [Chemical Formula 3]

[0062]

[0063] (In general formula (4), R0 represents a hydrogen atom or an alkyl group,

[0064] Q2 can be represented independently as NH or O.

[0065] R3 represents aryl groups independently.

[0066] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0067]

[12]

[0068] A method for manufacturing formic acid includes the following steps:

[0069] The process of manufacturing formate using any one of [1] to

[11] ; and

[0070] The second step involves protonating at least a portion of the aforementioned formate to generate formic acid.

[0071]

[13]

[0072] A catalyst for the manufacture of formate, which is a catalyst for the manufacture of formate by reaction of hydrogen with carbon dioxide, bicarbonate or carbonate, the catalyst for the manufacture of formate comprising a ruthenium complex represented by the following general formula (2).

[0073] [Chemical Formula 4]

[0074]

[0075] (In general formula (2), R0 represents a hydrogen atom or an alkyl group,

[0076] Q1 can independently represent CH2, NH, or O.

[0077] R2 each independently represents an alkyl or aryl group (where at least one of R2 represents an aryl group).

[0078] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0079] X represents a halogen atom.

[0080] n represents 0 to 3.

[0081] In the presence of multiple L ligands, each ligand can independently represent a neutral or anionic ligand.

[0082]

[14]

[0083] The ruthenium complex represented by the following general formula (3)

[0084] [Chemical Formula 5]

[0085]

[0086] (In general formula (3), R0 represents a hydrogen atom or an alkyl group,

[0087] Q2 can be represented independently as NH or O.

[0088] R3 represents aryl groups independently.

[0089] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0090] X represents a halogen atom.

[0091] n represents 0 to 3.

[0092] In the presence of multiple L ligands, each ligand can independently represent a neutral or anionic ligand.

[0093]

[15]

[0094] The ruthenium complex as described in

[14] , wherein the aforementioned R3 represents a phenyl group.

[0095]

[16]

[0096] Ruthenium complexes as described in

[14] or

[15] , wherein the aforementioned A represents CH and the aforementioned Q2 represents NH.

[0097]

[17]

[0098] The ruthenium complex as described in any one of

[14] to

[16] , wherein the aforementioned R0 represents a hydrogen atom or a methyl group.

[0099]

[18]

[0100] The ruthenium complex as described in any one of

[14] to

[17] , wherein the aforementioned X represents a chlorine atom.

[0101]

[19]

[0102] The ruthenium complex as described in any one of

[14] to

[18] , wherein the aforementioned n represents 1 to 3, and the aforementioned L each independently represents a hydrogen atom, carbon monoxide, or triphenylphosphine.

[0103] Invention Effects

[0104] According to the present invention, a ruthenium complex that can be used as a catalyst for converting hydrogen to formate with high efficiency, a catalyst for formate production, a method for producing formate with high yield and reusing the catalyst, and a method for producing formic acid can be provided. Attached Figure Description

[0105] [ Figure 1 ] Figure 1 A schematic diagram illustrating an example of a three-chamber electrodialysis apparatus. Detailed Implementation

[0106] The embodiments of the present invention will now be described in detail.

[0107] The first embodiment of the present invention relates to a method for manufacturing formate, which involves reacting hydrogen with carbon dioxide, bicarbonate, or carbonate in the presence of a solvent using a catalyst to produce formate.

[0108] The aforementioned reaction takes place in a two-phase system in which the aforementioned solvent exists in a state where the organic solvent and the aqueous solvent are separated.

[0109] The aforementioned catalyst is at least one selected from ruthenium complexes, tautomers or stereoisomers thereof, or chlorinated compounds thereof represented by the following general formula (1).

[0110] [Chemical Formula 6]

[0111]

[0112] In general formula (1), R0 represents a hydrogen atom or an alkyl group.

[0113] Q1 can independently represent CH2, NH, or O.

[0114] R1 independently represents either an alkyl or an aryl group (wherein, if Q1 represents NH or O, at least one of R1 represents an aryl group).

[0115] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0116] X represents a halogen atom.

[0117] n represents 0 to 3.

[0118] In the presence of multiple L ligands, each ligand can independently represent a neutral or anionic ligand.

[0119] The second embodiment of the present invention relates to a method for manufacturing formic acid, comprising the following steps: a step of manufacturing formic acid using the aforementioned method for manufacturing formic acid salts; and a second step of protonating at least a portion of the aforementioned formic acid salts by electrodialysis to generate formic acid and water.

[0120] The catalyst for formate production according to the third embodiment of the present invention is a catalyst for producing formate by reaction of hydrogen with carbon dioxide, bicarbonate or carbonate, and it comprises a ruthenium complex represented by the following general formula (2).

[0121] [Chemical Formula 7]

[0122]

[0123] (In general formula (2), R0 represents a hydrogen atom or an alkyl group,

[0124] Q1 can independently represent CH2, NH, or O.

[0125] R2 each independently represents an alkyl or aryl group (where at least one of R2 represents an aryl group).

[0126] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0127] X represents a halogen atom.

[0128] n represents 0 to 3.

[0129] In the presence of multiple L ligands, each ligand can independently represent a neutral or anionic ligand.

[0130] Furthermore, the ruthenium complex involved in the fourth embodiment of the present invention is represented by the following general formula (3).

[0131] [Chemical Formula 8]

[0132]

[0133] (In general formula (3), R0 represents a hydrogen atom or an alkyl group,

[0134] Q2 can be represented independently as NH or O.

[0135] R3 represents aryl groups independently.

[0136] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0137] X represents a halogen atom.

[0138] n represents 0 to 3.

[0139] In the presence of multiple L ligands, each ligand can independently represent a neutral or anionic ligand.

[0140] The ruthenium complexes represented by general formulas (1) to (3) may sometimes produce stereoisomers depending on the coordination mode and conformation of the ligands. They can be a mixture of these stereoisomers or a single pure isomer.

[0141] [Manufacturing methods of formate and formic acid]

[0142] The first embodiment of the present invention relates to a method for manufacturing formate, which involves reacting hydrogen with carbon dioxide, bicarbonate, or carbonate in the presence of a solvent using a catalyst to produce formate.

[0143] The aforementioned reaction takes place in a two-phase system in which the aforementioned solvent exists in a state where the organic solvent and the aqueous solvent are separated.

[0144] The catalyst mentioned above is at least one selected from ruthenium complexes, tautomers or stereoisomers thereof, or chlorinated compounds thereof (hereinafter sometimes simply referred to as "ruthenium complexes").

[0145] The second embodiment of the present invention relates to a method for manufacturing formic acid, comprising the following steps: a step of manufacturing formic acid using the formic acid manufacturing method of the first embodiment (a first step); and a second step of protonating at least a portion of the formic acid by electrodialysis to generate formic acid and water.

[0146] <First Process>

[0147] The first step is to use a catalyst in the presence of a solvent to react hydrogen with carbon dioxide, bicarbonate, or carbonate to produce formate in the reaction solution.

[0148] In a first embodiment of the present invention, the reaction of hydrogen with carbon dioxide, bicarbonate or carbonate is carried out in a two-phase system in which the solvent exists in a state where the organic solvent and the aqueous solvent are separated, preferably in a solution containing the catalyst formed by dissolving the catalyst in the organic solvent.

[0149] The method for manufacturing formate according to the first embodiment of the present invention can be carried out, for example, as described below. A reaction vessel equipped with a stirring device is prepared, and a solvent is introduced into the reaction vessel. If necessary, a phase transfer catalyst may be further added. The catalyst is added to the reaction vessel and dissolved in the solvent to prepare a catalyst solution. Then, hydrogen, carbon dioxide, bicarbonate, or carbonate is introduced into the reaction vessel to carry out the reaction.

[0150] (solvent)

[0151] As for the solvent involved in the embodiments of the present invention, any solvent that can be used to form a two-phase system in which the organic solvent and the aqueous solvent exist in a separate state is acceptable, and there are no particular limitations. Preferably, it includes a solvent that dissolves the catalyst and makes it homogeneous.

[0152] As an aqueous solvent, examples include water, methanol, ethanol, ethylene glycol, glycerol, and mixtures thereof, with water being the preferred choice from the viewpoint of low environmental impact.

[0153] Examples of organic solvents include toluene, benzene, xylene, propylene carbonate, dioxane, dimethyl sulfoxide, and mixtures thereof. From the viewpoint of separability from aqueous solvents, toluene or dioxane is preferred, and toluene is more preferred.

[0154] (catalyst)

[0155] As described above, the catalyst used in the formate production method according to the first embodiment of the present invention is a ruthenium complex represented by general formula (1). The ruthenium complex represented by general formula (1) is soluble in organic solvents but insoluble in water. The formate produced by the reaction is readily soluble in water. Therefore, through the reaction in a two-phase system, the separation of the catalyst and the formate becomes easy, and the separation and recovery of the catalyst and the formate from the reaction system becomes easy, enabling the production of formate in high yield.

[0156] According to the method of this embodiment, the formate generated by the reaction can be separated from the catalyst using a simple operation, and the expensive catalyst can be reused.

[0157] The catalyst used in the embodiments of the present invention is at least one selected from ruthenium complexes represented by the following general formula (1), their tautomers or stereoisomers, or their chlorine compounds.

[0158] [Chemical Formula 9]

[0159]

[0160] (In general formula (1), R0 represents a hydrogen atom or an alkyl group,

[0161] Q1 can independently represent CH2, NH, or O.

[0162] R1 independently represents either an alkyl or an aryl group (wherein, if Q1 represents NH or O, at least one of R1 represents an aryl group).

[0163] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0164] X represents a halogen atom.

[0165] n represents 0 to 3.

[0166] In the presence of multiple L ligands, each ligand can independently represent a neutral or anionic ligand.

[0167] In general formula (1), R0 represents a hydrogen atom or an alkyl group. Examples of alkyl groups represented by R0 include straight-chain, branched, cyclic, substituted or unsubstituted alkyl groups.

[0168] As the alkyl group represented by R0, alkyl groups with 1 to 30 carbon atoms are preferably included, such as methyl, ethyl, n-propyl, isopropyl, tert-butyl, n-octyl, eicosyl, 2-ethylhexyl, etc. From the viewpoint of ease of raw material supply, alkyl groups with 6 or fewer carbon atoms are preferred, and methyl is preferred.

[0169] In general formula (1), R0 is preferably a hydrogen atom or a methyl atom.

[0170] In general formula (1), each R1 independently represents an alkyl or aryl group. Wherein, when Q1 represents NH or O, at least one of R1 represents an aryl group.

[0171] Examples of alkyl groups represented by R1 include straight-chain, branched, and cyclic substituted or unsubstituted alkyl groups. Preferably, alkyl groups with 1 to 30 carbon atoms are alkyl groups such as methyl, ethyl, n-propyl, isopropyl, tert-butyl, n-octyl, eicosyl, and 2-ethylhexyl. From the viewpoint of catalytic activity, alkyl groups with 12 or fewer carbon atoms are preferred, and tert-butyl is particularly preferred.

[0172] Examples of aryl groups represented by R1 include substituted or unsubstituted aryl groups with 6 to 30 carbon atoms, such as phenyl, p-tolyl, naphthyl, m-chlorophenyl, o-hexadecylaminophenyl, etc., preferably aryl groups with 12 or fewer carbon atoms, and more preferably phenyl.

[0173] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0174] Examples of alkyl groups represented by R5 include straight-chain, branched, and cyclic substituted or unsubstituted alkyl groups. Preferably, alkyl groups with 1 to 30 carbon atoms are alkyl groups such as methyl, ethyl, n-propyl, isopropyl, tert-butyl, n-octyl, eicosyl, and 2-ethylhexyl. From the viewpoint of ease of raw material supply, alkyl groups with 12 or fewer carbon atoms are preferred, and methyl is particularly preferred.

[0175] Examples of aryl groups represented by R5 include substituted or unsubstituted aryl groups with 6 to 30 carbon atoms, such as phenyl, p-tolyl, naphthyl, m-chlorophenyl, o-hexadecylaminophenyl, etc., preferably aryl groups with 12 or fewer carbon atoms, and more preferably phenyl.

[0176] As R5 represents an aralkyl group, examples include substituted or unsubstituted aralkyl groups with 30 or fewer carbon atoms, such as triphenylmethyl, benzyl, phenethyl, triphenylmethylmethyl, diphenylmethyl, naphthylmethyl, etc., and preferably aralkyl groups with 12 or fewer carbon atoms.

[0177] As the alkoxy group represented by R5, preferably substituted or unsubstituted alkoxy groups having 1 to 30 carbon atoms, such as methoxy, ethoxy, isopropoxy, tert-butoxy, n-octyloxy, 2-methoxyethoxy, etc.

[0178] X represents a halogen atom, preferably a chlorine atom.

[0179] n represents an integer from 0 to 3, indicating the number of ligands located in ruthenium. From the viewpoint of catalyst stability, n is preferably 2 or 3.

[0180] In the presence of multiple L, each independently represents a neutral or anionic ligand.

[0181] Examples of neutral ligands represented by L include ammonia, carbon monoxide, phosphine derivatives (e.g., triphenylphosphine, tri(4-methoxyphenyl)phosphine), phosphine oxides (e.g., triphenylphosphine oxide), thioethers (e.g., dimethyl sulfide), sulfoxides (e.g., dimethyl sulfoxide), ethers (e.g., diethyl ether), nitriles (e.g., p-methylbenzonitrile), heterocyclic compounds (e.g., pyridine, N,N-dimethyl-4-aminopyridine, tetrahydrothiophene, tetrahydrofuran), etc., with triphenylphosphine being preferred.

[0182] Examples of anionic ligands represented by L include hydride ions (hydrogen atoms), nitrate ions, and cyanide ions, with hydride ions (hydrogen atoms) being the most preferred.

[0183] In general formula (1), preferably, A represents CH and Q1 represents NH.

[0184] In addition, preferably, n represents 1 to 3, and L independently represents a hydrogen atom, carbon monoxide, or triphenylphosphine.

[0185] The ruthenium complex represented by general formula (1) can be used alone or in combination with two or more.

[0186] The ruthenium complex represented by the above general formula (1) is preferably the ruthenium complex represented by the following general formula (3).

[0187] [Chemical Formula 10]

[0188]

[0189] (In general formula (3), R0 represents a hydrogen atom or an alkyl group,

[0190] Q2 can be represented independently as NH or O.

[0191] R3 represents aryl groups independently.

[0192] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0193] X represents a halogen atom.

[0194] n represents 0 to 3.

[0195] In the presence of multiple L ligands, each ligand can independently represent a neutral or anionic ligand.

[0196] In general formula (3), R0, A, R5, X, n and L are synonyms of R0, A, R5, X, n and L in general formula (1), and the preferred range is also the same.

[0197] In general formula (3), R3 represents an aryl group that is synonymous with R1 in general formula (1), and the preferred range is also the same.

[0198] In general formula (3), preferably, A represents CH and Q2 represents NH.

[0199] The ruthenium complexes represented by general formulas (1), (2), and (3) can also be ruthenium complexes manufactured by known methods, etc. As known methods, for example, the methods described in Non-Patent Document 1, etc., can be used.

[0200] The amount of ruthenium complex used as a catalyst is not particularly limited as long as it can produce formate. Regarding the amount of ruthenium complex used as a catalyst, to fully exhibit catalytic function, it is preferably 0.1 μmol or more, more preferably 0.5 μmol or more, and even more preferably 1 μmol or more, relative to 1 L of both the organic phase (organic solvent) and the aqueous phase (aqueous solvent). Furthermore, from a cost perspective, it is preferably 1 mol or less, more preferably 10 mmol or less, and even more preferably 1 mmol or less. It should be noted that when using two or more ruthenium complexes, their total amount used is acceptable as long as it falls within the above-mentioned range.

[0201] In the method for manufacturing formate according to embodiments of the present invention, it is preferable that the ligands forming the complex represented by general formula (1) are present in excess in the reaction mixture. Therefore, it is preferable to further add the ligands of the complex used.

[0202] That is, in the formate manufacturing method according to the embodiments of the present invention, it is preferable to further add a ligand represented by the following general formula (4).

[0203] [Chemical Formula 11]

[0204]

[0205] (In general formula (4), R0 represents a hydrogen atom or an alkyl group,

[0206] Q2 can be represented independently as NH or O.

[0207] R3 represents aryl groups independently.

[0208] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0209] In general formula (4), R0, Q2, R3, A and R5 are synonyms of R0, Q2, R3, A and R5 in general formula (3), and the preferred range is also the same.

[0210] By adding excess ligands that form complexes to the reaction system, even if the ligands are oxidized and degraded due to oxygen or impurities in the system, the degraded ligands will exchange with the added ligands, and the catalytic function will be restored, thus improving the stability of the catalyst.

[0211] The addition of the ligand represented by the above general formula (4) to the reaction mixture can be carried out during the preparation of the reaction mixture or during the reaction, but from the point of view of process management, it is preferred to carry it out during the preparation of the reaction mixture.

[0212] (Phase transfer catalyst)

[0213] The method for manufacturing formate according to the first embodiment of the present invention requires the reaction to be carried out in a two-phase system. Therefore, a phase transfer catalyst can be used to facilitate the movement of substances between the two phases. Examples of phase transfer catalysts include quaternary ammonium salts (ammonium salts), quaternary phosphates, macrocyclic polyethers such as crown ethers, nitrogen-containing macrocyclic polyethers such as cryptane ethers, nitrogen-containing chain polyethers, polyethylene glycol and its alkyl ethers, etc. Among these, quaternary ammonium salts are preferred from the viewpoint that the movement of substances between aqueous and organic solvents is easy even under mild reaction conditions.

[0214] Examples of quaternary ammonium salts include methyltrioctylammonium chloride, benzyltrimethylammonium chloride, benzyltriethylammonium chloride, tetrabutylammonium hydroxide, tetrabutylammonium fluoride, tetrabutylammonium bromide, tetrabutylammonium iodide, trimethylphenylammonium bromide, tributyltribromide, tetrahexylammonium hydrogen sulfate, decyltrimethylammonium bromide, diallyldimethylammonium chloride, dodecyltrimethylammonium bromide, dimethylbisoctadecylammonium bromide, tetraethylammonium tetrafluoroborate, ethyltrimethylammonium iodide tris(2-hydroxyethyl)methylammonium hydroxide, tetramethylammonium acetate, tetramethylammonium bromide, and tetraethylammonium iodide, with methyltrioctylammonium chloride being the most preferred.

[0215] Regarding the amount of phase transfer catalyst used, there is no particular limitation as long as it is sufficient to produce formate. For efficient assistance in the movement of carbonates or bicarbonates, the amount of phase transfer catalyst used is preferably 0.1 mmol or more, more preferably 0.5 mmol or more, and even more preferably 1 mmol or more, relative to 1 L of organic and aqueous solvent. Furthermore, from a cost perspective, it is preferably 1 mol or less, more preferably 500 mmol or less, and even more preferably 100 mmol or less. It should be noted that when using two or more phase transfer catalysts, their total amount used is acceptable as long as it falls within the above-mentioned range.

[0216] (Carbon dioxide and hydrogen)

[0217] The hydrogen used in embodiments of the present invention can be any type of hydrogen from hydrogen storage cylinders and liquid hydrogen. For example, hydrogen produced during iron smelting or soda production can be used as a hydrogen supply source. Alternatively, hydrogen produced by the electrolysis of water can also be used effectively.

[0218] The carbon dioxide used in embodiments of the present invention can be pure carbon dioxide gas or a mixture of gases containing components other than carbon dioxide. The carbon dioxide gas and other gases can be introduced separately, or the mixture can be prepared before introduction.

[0219] Other components besides carbon dioxide include any other components contained in inactive gases such as nitrogen and argon, water vapor, and exhaust gases.

[0220] Carbon dioxide can be obtained from various sources, including carbon dioxide gas cylinders, liquid carbon dioxide, supercritical carbon dioxide, and dry ice.

[0221] Hydrogen and carbon dioxide gases can be introduced into the reaction system separately or as a mixture.

[0222] The preferred ratio of hydrogen to carbon dioxide is equal in molar terms or hydrogen in excess.

[0223] When using a hydrogen storage cylinder as hydrogen in the formate manufacturing method according to embodiments of the present invention, from the viewpoint of sufficiently ensuring reactivity, the pressure is preferably 0.1 MPa or more, more preferably 0.2 MPa or more, and even more preferably 0.5 MPa or more. Furthermore, from the viewpoint of easily scaling up the equipment, a pressure of 50 MPa or less is preferred, more preferably 20 MPa or less, and even more preferably 10 MPa or less.

[0224] Furthermore, from the viewpoint of ensuring sufficient reactivity, the pressure of carbon dioxide in the formate manufacturing method according to embodiments of the present invention is preferably 0.1 MPa or more, more preferably 0.2 MPa or more, and even more preferably 0.5 MPa or more. Additionally, from the viewpoint of easily scaling up the equipment, the pressure is preferably 50 MPa or less, more preferably 20 MPa or less, and even more preferably 10 MPa or less.

[0225] Hydrogen and carbon dioxide gases can be bubbled (blown) into the catalyst solution. Alternatively, after introducing gases containing hydrogen and carbon dioxide, the catalyst solution and the hydrogen and carbon dioxide gases can be stirred using a stirring device or by rotating the reaction vessel.

[0226] There are no particular restrictions on the methods used to introduce carbon dioxide, hydrogen, catalysts, solvents, etc., into the reaction vessel. All the raw materials can be introduced at once, a portion or all of the raw materials can be introduced in stages, or a portion or all of the raw materials can be introduced continuously. Alternatively, a combination of these methods can be used.

[0227] (Bicarbonates and carbonates)

[0228] Examples of bicarbonates and carbonates used in the first embodiment of the present invention include carbonates or bicarbonates of alkali metals or alkaline earth metals.

[0229] Examples of bicarbonates include sodium bicarbonate and potassium bicarbonate, with potassium bicarbonate being preferred from the viewpoint of high solubility in water.

[0230] Examples of carbonates include sodium carbonate, potassium carbonate, sodium potassium carbonate, and sodium sesquicarbonate.

[0231] Bicarbonates and carbonates can be formed by the reaction of carbon dioxide with a base. For example, carbon dioxide can be introduced into an alkaline solution, thereby producing bicarbonates or carbonates.

[0232] There are no particular limitations on the solvent used as an alkaline solution in the formation of bicarbonate or carbonate, and examples include water, methanol, ethanol, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, benzene, toluene, and mixtures thereof, with water being preferred, and water being more preferred.

[0233] As a base used in an alkaline solution, there are no particular limitations as long as it can react with carbon dioxide to form bicarbonate or carbonate, but hydroxides are preferred. Examples include lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, cesium bicarbonate, potassium hydroxide, sodium hydroxide, diazabicycloundecene, or triethylamine, sodium hydroxide, and potassium hydroxide. Among the above, hydroxides are preferred, potassium hydroxide and sodium hydroxide are more preferred, and potassium hydroxide is even more preferred.

[0234] The content of alkali in the alkaline solution is not particularly limited as long as it can produce bicarbonate and carbonate. From the viewpoint of ensuring the amount of formate formed, the alkali content is preferably 0.1 mol or more, more preferably 0.5 mol or more, and even more preferably 1 mol or more, relative to 1 L of aqueous solvent. Furthermore, from the viewpoint of formate reaction efficiency, the alkali content is preferably 30 mol or less, more preferably 20 mol or less, and even more preferably 15 mol or less. However, if it exceeds the solubility in the aqueous phase, the solution will become turbid.

[0235] Regarding the ratio of carbon dioxide to alkali used in the reaction of carbon dioxide with alkali, from the viewpoint of generating carbonate from carbon dioxide, a molar ratio of 0.1 or more is preferred, more preferably 0.5 or more, and even more preferably 1.0 or more. Furthermore, from the viewpoint of carbon dioxide utilization efficiency, a ratio of 8.0 or less is preferred, more preferably 5.0 or less, and even more preferably 3.0 or less.

[0236] The ratio of carbon dioxide to alkali used can be expressed as the molar ratio of carbon dioxide to alkali introduced into the reaction vessel, which is the molar amount of CO2 (mol) / the molar amount of alkali (mol).

[0237] By maintaining the carbon dioxide to alkali ratio within the aforementioned range, excess carbon dioxide input into the reaction vessel can be suppressed, unreacted carbon dioxide can be minimized, and the final formic acid conversion efficiency can be easily improved. Alternatively, in the same vessel, carbon dioxide can be hydrogenated via bicarbonate or carbonate to produce formate through the reaction of carbon dioxide with alkali.

[0238] Unreacted carbon dioxide can be recovered from the reaction vessel and reused.

[0239] There are no particular restrictions on the method or order of introducing carbon dioxide and base into the reaction vessel, but it is preferable to introduce carbon dioxide after introducing base. Furthermore, the introduction of carbon dioxide and base can be carried out continuously or intermittently.

[0240] The reaction temperature for the formation of bicarbonate or carbonate by reacting carbon dioxide with a base is not particularly limited. However, in order to dissolve carbon dioxide in the aqueous phase, the temperature is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher. Furthermore, the temperature is preferably 100°C or lower, more preferably 80°C or lower, and even more preferably 40°C or lower.

[0241] The reaction time for the formation of bicarbonate or carbonate by reacting carbon dioxide with a base is not particularly limited. However, from the viewpoint of ensuring a sufficient amount of bicarbonate or carbonate is produced, a reaction time of 0.5 hours or more is preferred, more preferably 1 hour or more, and even more preferably 2 hours or more is preferred. Furthermore, from a cost perspective, a reaction time of 24 hours or less is preferred, more preferably 12 hours or less, and even more preferably 6 hours or less is preferred.

[0242] The bicarbonate and carbonate generated by the reaction of carbon dioxide with a base can be used in the reaction of hydrogen with bicarbonate or carbonate in the formate manufacturing method according to embodiments of the present invention. Furthermore, the generation of bicarbonate or carbonate in the reaction vessel based on the reaction of carbon dioxide with a base can also be considered as the introduction of bicarbonate or carbonate into the reaction vessel in the formate manufacturing method.

[0243] (Reaction conditions)

[0244] The reaction conditions in the method for manufacturing formate according to the embodiments of the present invention are not particularly limited, and the reaction conditions can be appropriately changed during the reaction process. The shape of the reaction vessel used in the reaction is not particularly limited.

[0245] Examples of reactions of hydrogen with carbon dioxide, bicarbonate, or carbonate in the formate manufacturing method according to embodiments of the present invention include the reaction of hydrogen with carbon dioxide, the reaction of hydrogen with bicarbonate, and the reaction of hydrogen with carbonate.

[0246] In the reaction of hydrogen and carbon dioxide, the carbonation of carbon dioxide and the formation of formate based on the hydrogenation of carbonate occur simultaneously.

[0247] There are no particular restrictions on the method or order of introducing hydrogen, carbon dioxide, bicarbonate, or carbonate into the reaction vessel.

[0248] For example, in the reaction of hydrogen and carbon dioxide, it is preferable to introduce hydrogen and carbon dioxide simultaneously. Hydrogen and carbon dioxide can be introduced individually or as a mixture of gases. Furthermore, the introduction of hydrogen and carbon dioxide can be carried out continuously, either individually or intermittently.

[0249] In the reactions of hydrogen with bicarbonate and with carbonate, it is preferable to introduce hydrogen after introducing the bicarbonate or carbonate into the reaction vessel. The introduction of hydrogen and the bicarbonate or carbonate can be carried out continuously or intermittently.

[0250] The reaction temperature for the reaction of hydrogen with carbon dioxide, bicarbonate, or carbonate is not particularly limited, but for efficient reaction, it is preferably 30°C or higher, more preferably 40°C or higher, and even more preferably 50°C or higher. Furthermore, from the viewpoint of energy efficiency, it is preferably 200°C or lower, more preferably 150°C or lower, and even more preferably 100°C or lower.

[0251] The reaction temperature can be adjusted by heating or cooling, with heating being the preferred method.

[0252] In addition, in the reaction of hydrogen and carbon dioxide, for example, the temperature can be increased by heating after introducing hydrogen and carbon dioxide into the reaction vessel, or carbon dioxide can be introduced into the reaction vessel, the temperature can be increased, and then hydrogen can be introduced.

[0253] In the reaction of hydrogen with bicarbonate or carbonate, for example, preferably, hydrogen is introduced and the temperature is raised after the bicarbonate or carbonate is introduced (generated) in the reaction vessel.

[0254] The reaction time in the reaction of hydrogen with carbon dioxide, bicarbonate, or carbonate is not particularly limited. For example, from the viewpoint of sufficiently ensuring the amount of formate formed, it is preferably 0.5 hours or more, more preferably 1 hour or more, and even more preferably 2 hours or more. In addition, from the viewpoint of cost, it is preferably 24 hours or less, more preferably 12 hours or less, and even more preferably 6 hours or less.

[0255] <Second Process>

[0256] The second step is to protonate at least a portion of the aforementioned formate salt to generate formic acid and water via electrodialysis.

[0257] In an embodiment of the present invention, the formate generated in the first process dissolves into the aqueous phase, and therefore, an aqueous solution of formate can be obtained by separating the aqueous phase.

[0258] Preferably, the aqueous phase from the first step is separated, and the resulting formate aqueous solution is treated in a second step using an electrodialysis device to generate formic acid. The separated aqueous phase is the aqueous phase after the first step.

[0259] In the second step, the formate aqueous solution obtained from the first step can be used directly as described above, or the formate concentration can be adjusted by concentration or dilution as needed.

[0260] One method for diluting formate aqueous solutions is to add pure water.

[0261] Methods for concentrating aqueous formate solutions include distillation to remove water from the aqueous formate solution and using a separation membrane unit equipped with a reverse osmosis membrane to concentrate the aqueous formate solution.

[0262] From the viewpoint of suppressing formate loss caused by concentration diffusion of high-concentration formate aqueous solutions during treatment using an electrodialysis apparatus, it is preferable to separate the aqueous phase in the first step, adjust the formate concentration in the aqueous phase by dilution, and then use it in the second step.

[0263] Since a high-concentration formate aqueous solution is obtained through the first process, and the formate concentration is adjusted to a suitable concentration for electrodialysis before being supplied to the second process, TON can be further improved, and formic acid can be manufactured with higher yield and better productivity.

[0264] The degree of concentration adjustment (preferably dilution) of the formate aqueous solution obtained in the first step can be appropriately selected. The formate concentration in the formate aqueous solution after concentration adjustment is preferably a concentration suitable for electrodialysis, preferably 2.5 mol / L or more, more preferably 3 mol / L or more, and even more preferably 5 mol / L or more. Furthermore, from the viewpoint of suppressing formate loss due to concentration diffusion of the high-concentration formate aqueous solution during treatment using an electrodialysis apparatus, it is preferably 20 mol / L or less, more preferably 15 mol / L or less, and even more preferably 10 mol / L or less.

[0265] Pure water can be used for dilution. Alternatively, the water generated in the second process can also be used for dilution. By reusing the water generated in the second process during dilution, it is preferable to reduce the cost of wastewater treatment and the environmental impact.

[0266] In the formic acid manufacturing method according to embodiments of the present invention, acid may be added to the formic acid aqueous solution obtained from the first step to perform decarbonation treatment before use in the second step. That is, the aqueous phase in the first step may be separated, acid may be added to perform decarbonation treatment before use in the second step.

[0267] The formate aqueous solution obtained from the first process sometimes contains unreacted carbonates and bicarbonates generated by side reactions. If the solution containing carbonates and bicarbonates is subjected to electrodialysis, there is a concern that carbon dioxide will be generated, reducing dialysis efficiency. Therefore, by adding acid to the formate aqueous solution obtained from the first process for decarbonation followed by electrodialysis, TON can be further improved, resulting in the production of formic acid with higher yield and better productivity.

[0268] Examples of acids used in decarbonation treatment include formic acid, citric acid, acetic acid, malic acid, lactic acid, succinic acid, tartaric acid, butyric acid, fumaric acid, propionic acid, hydrochloric acid, nitric acid, and sulfuric acid, with formic acid being preferred.

[0269] Regarding the amount of acid used, from the viewpoint of suppressing the amount of carbonic acid generated during electrodialysis treatment, the amount of acid used is preferably 50% or more, more preferably 80% or more, relative to the amount of carbonic acid present in the solution. Furthermore, from the viewpoint of suppressing the deterioration of the electrodialysis apparatus by pre-neutralizing the pH of the formate solution during electrodialysis treatment, the amount of acid used is preferably 150% or less, more preferably 120% or less, relative to the amount of carbonic acid present in the solution.

[0270] In embodiments of the present invention, regarding the proportion of formate protonated in the second step, from the viewpoint of improving the purity of the recovered formic acid aqueous solution, it is preferable that 10% or more is protonated relative to the initial molar amount of formate in the formate aqueous solution, more preferably 20% or more is protonated, and even more preferably 30% or more is protonated.

[0271] Examples of electrodialysis devices include two-compartment electrodialysis devices that use bipolar membranes and anion exchange membranes or cation exchange membranes, and three-compartment electrodialysis devices that use bipolar membranes and anion exchange membranes or cation exchange membranes.

[0272] Figure 1 A schematic diagram illustrating an example of a three-chamber electrodialysis apparatus. Figure 1The electrodialysis apparatus shown comprises multiple bipolar membranes, anion exchange membranes, and cation exchange membranes, which are arranged between the anode and cathode to form an alkali tank, a sample tank (salt tank), and an acid tank. A formate aqueous solution is circulated into the sample tank while an electric current is applied, thereby continuously converting the formate into formic acid. Formic acid is recovered from the acid tank, water is recovered from the sample tank, and hydroxide is recovered from the alkali tank.

[0273] A two-chamber electrodialysis device has multiple bipolar membranes and cation exchange membranes, which are alternately arranged between the anode and the cathode. A salt chamber is formed between each bipolar membrane and the cation exchange membrane arranged on its cathode side, and an alkali tank is formed between each bipolar membrane and the cation exchange membrane arranged on its anode side. While the device is energized, an aqueous formate solution is circulated into the salt chamber. As a result, hydroxide is generated in the alkali tank, and the formate circulated into the salt chamber is continuously converted into formic acid.

[0274] The second step allows for the protonation of formate salts to obtain a formic acid solution using a simple method.

[0275] Next, the catalyst for formate production according to the third embodiment of the present invention will be described.

[0276] [Catalyst for formate production]

[0277] The catalyst for formate production according to the third embodiment of the present invention is a catalyst for producing formate by reaction of hydrogen with carbon dioxide, bicarbonate or carbonate, and it comprises a ruthenium complex represented by the following general formula (2).

[0278] [Chemical Formula 12]

[0279]

[0280] (In general formula (2), R0 represents a hydrogen atom or an alkyl group,

[0281] Q1 can independently represent CH2, NH, or O.

[0282] R2 each independently represents an alkyl or aryl group (where at least one of R2 represents an aryl group).

[0283] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0284] X represents a halogen atom.

[0285] n represents 0 to 3.

[0286] In the presence of multiple L ligands, each ligand can independently represent a neutral or anionic ligand.

[0287] In general formula (2), R0, A, R5, X, n and L are synonyms of R0, A, R5, X, n and L in general formula (1), and the preferred range is also the same.

[0288] In general formula (2), R2 represents alkyl and aryl groups that are synonymous with R1 in general formula (1), and the preferred ranges are also the same.

[0289] The ruthenium complex represented by the above general formula (2) is preferably the ruthenium complex represented by the above general formula (3).

[0290] When formate is produced using the catalyst for formate production according to the third embodiment of the present invention, the reaction can be carried out in a single phase or in a two-phase system.

[0291] The solvent used in the catalyst for formate production according to the third embodiment of the present invention is not particularly limited as long as it can produce formate. Examples include water, methanol, ethanol, ethylene glycol, glycerol, toluene, benzene, xylene, propylene carbonate, dioxane, dimethyl sulfoxide, tetrahydrofuran, and mixtures thereof.

[0292] Regarding the types and amounts of hydrogen, carbon dioxide, bicarbonate, and carbonate used in the production of formate using the catalyst for formate production according to the third embodiment of the present invention, as well as the reaction conditions, the contents described in the formate production method according to the first embodiment described above may also be appropriately adopted.

[0293] Next, the ruthenium complex represented by general formula (3) according to the fourth embodiment of the present invention will be described.

[0294] [Ruthenium complex represented by general formula (3)]

[0295] The ruthenium complex represented by general formula (3) is a novel compound.

[0296] The ruthenium complex involved in the fourth embodiment of the present invention is represented by the following general formula (3).

[0297] [Chemical Formula 13]

[0298]

[0299] (In general formula (3), R0 represents a hydrogen atom or an alkyl group,

[0300] Q2 can be represented independently as NH or O.

[0301] R3 represents aryl groups independently.

[0302] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0303] X represents a halogen atom.

[0304] n represents 0 to 3.

[0305] In the presence of multiple L ligands, each ligand can independently represent a neutral or anionic ligand.

[0306] In general formula (3), R0, A, R5, X, n and L are synonyms of R0, A, R5, X, n and L in general formula (1), and the preferred range is also the same.

[0307] In general formula (3), R3 represents an aryl group that is synonymous with R1 in general formula (1), and the preferred range is also the same.

[0308] In general formula (3), preferably, A represents CH and Q2 represents NH.

[0309] The ruthenium complex represented by general formula (3) can be prepared, for example, by adding the tripentate ligand represented by general formula (4) and the ruthenium compound represented by general formula (5) to the reaction system, respectively.

[0310] [Chemical Formula 14]

[0311]

[0312] (In general formula (4), R0 represents a hydrogen atom or an alkyl group,

[0313] Q2 can be represented independently as NH or O.

[0314] R3 represents aryl groups independently.

[0315] A can independently represent CH, CR5, or N, and R5 can represent alkyl, aryl, aralkyl, amino, hydroxyl, or alkoxy.

[0316] In general formula (4), R0, Q2, R3, A and R5 are synonyms of R0, Q2, R3, A and R5 in general formula (3), and the preferred range is also the same.

[0317] [RuHX[L]n(CO)] (5)

[0318] (In general formula (5), X represents a halogen atom, n represents 0 to 3, and L, when multiple are present, independently represents a neutral or anionic ligand.)

[0319] In general formula (5), X, n and L are synonyms with X, n and L in general formula (3), and the preferred range is also the same.

[0320] In the manufacture of the ruthenium complex represented by general formula (3), a solvent is preferably used. Specific examples of solvents that can be used include aliphatic hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as benzene, toluene and xylene, halogenated hydrocarbons such as dichloromethane and chlorobenzene, ethers such as diethyl ether, tetrahydrofuran, methyl tert-butyl ether and cyclopentylmethyl ether, alcohols such as methanol, ethanol, isopropanol, n-butyl alcohol, 2-butanol and tert-butyl alcohol, polyols such as ethylene glycol, propylene glycol, 1,2-propanediol and glycerol, amides such as dimethylformamide and dimethylacetamide, nitriles such as acetonitrile, sulfoxides such as dimethyl sulfoxide, and water, with tetrahydrofuran being the most preferred.

[0321] These solvents can be used individually or in combination of two or more.

[0322] The manufacture of the ruthenium complex represented by general formula (3) is preferably carried out in an atmosphere of inert gas or air. Examples of inert gases include argon and nitrogen, with argon being preferred. These gases and air can be used individually or in the form of a mixture.

[0323] The reaction temperature can usually be appropriately selected from the range of -50℃ to 300℃, preferably -20℃ to 250℃, and more preferably 30℃ to 200℃.

[0324] The reaction time varies depending on the conditions, including the base, solvent and reaction temperature, and can usually be appropriately selected from the range of 1 minute to 72 hours, preferably 1 minute to 24 hours, and more preferably 5 minutes to 12 hours.

[0325] The ruthenium complex represented by general formula (3) produced using the above manufacturing method can be post-processed, separated, and purified as needed. Specific examples of post-processing methods include concentration, solvent displacement, washing, extraction, back-extraction, filtration, and crystallization by adding a poor solvent. These can be performed individually or in combination. Specific examples of separation and purification methods include drying of the reaction solution, column chromatography, recrystallization, and crystal washing using a poor solvent. These can be performed individually or in combination.

[0326] The ruthenium complex represented by general formula (3) is suitable for industrial applications, capable of reacting under mild reaction conditions and with high catalytic activity. For example, formate can be produced by the hydrogenation reduction of carbon dioxide and bicarbonate in the presence of a hydrogen donor.

[0327] Example

[0328] The present invention will now be described in detail with examples and comparative examples. However, the present invention is not limited to these examples.

[0329] [Catalyst Synthesis]

[0330] (Synthetic Example 1) Synthesis of Ru Catalyst 1

[0331] Ru catalyst 1 was synthesized through the following procedures.

[0332] Under an inactive atmosphere, ligand A 40 mg (0.1 mmol) was added to a suspension of [RuHCl(PPh3)3(CO)] 95.3 mg (0.1 mmol) in THF (tetrahydrofuran) (5 ml). The mixture was stirred and heated at 65 °C for 3 hours to carry out the reaction. Then it was cooled to room temperature (25 °C).

[0333] The resulting yellow solution was filtered, and the filtrate was evaporated to dryness under vacuum. The resulting yellow residual oil was dissolved in a very small amount of THF (1 mL), and hexane (10 mL) was slowly added to precipitate the yellow solid. The precipitate was filtered and dried under vacuum to obtain Ru catalyst 1 (55 mg, 97%) as yellow crystals. In the following description of Ru catalyst 1 and ligand A, tBu represents tert-butyl.

[0334] [Chemical Formula 15]

[0335]

[0336] 31 P{ 1 H}(C6D6): 90.8(s), 1 H (C6D6): -14.54 (t, 1H, J = 20.0Hz), 1.11 (t, 18H, J = 8.0Hz), 1.51 (t, 18H, J = 8.0Hz), 2.88 (dt, 2H, J = 16.0Hz, J=4.0Hz), 3.76 (dt, 2H, J=16.0Hz, J=4.0Hz), 6.45 (d, 2H, J=8.0Hz), 6.79 (t, 1H, J=8.0Hz). 13 C{ 1 H}NMR(C6D6): 29.8(s), 30.7(s), 35.2(t, J=9.5Hz), 37.7(t, J=6.0Hz), 37.9 (t, J=6.5Hz), 119.5 (t, J=4.5Hz), 136.4 (s), 163.4 (t, J=5.0Hz), 209.8 (s).

[0337] (Synthetic Example 2) Synthesis of Ru Catalyst 2

[0338] Ru catalyst 2 was synthesized through the following procedures.

[0339] Under an inactive atmosphere, ligand B 83.9 mg (0.21 mmol) was added to a benzene (5 mL) slurry containing 200.0 mg (0.21 mmol) of [RuHCl(PPh3)3(CO)]2.

[0340] When the mixture is heated at 100°C in a sealed container for 8 hours, a transparent pink solution is obtained.

[0341] The solvent was removed under vacuum to obtain a pink solid.

[0342] To remove free PPh3, the residue was washed with pentane (5 mL), and the washing solution was passed through a silica column.

[0343] The residue was dissolved in benzene (1 mL) and passed through a column. The column was further washed with benzene (5 mL), and the product was eluted with THF.

[0344] The solvent THF was removed under vacuum, and Ru catalyst 2 was obtained as a pink solid in a yield of 95.3% (113 mg).

[0345] In the Ru catalyst 2 and ligand B shown below, tBu represents tert-butyl.

[0346] [Chemical Formula 16]

[0347]

[0348] 31 P{ 1 ¹H NMR (C6D6): 226.65 (brs). 1 H NMR (C6D6): 6.71 (t, J=8.2Hz, 1H), 6.09 (d, J=8.2Hz, 2H), 1.72 (vt, J=7.6Hz), 1.20 (vt, J=7.3Hz), -14.07 (t, J=20.7Hz, 1H). 13 C{ 1 H}NMR (C6D6): 206.84 (t, J=10.2Hz), 163.20 (t, J=3.9Hz), 142.0 (s), 102.30 (s), 4 3.18 (t, J=3.0Hz), 40.70 (t, J=7.6Hz), 30.50 (vt, J=3.8Hz), 27.85 (vt, J=2.8Hz).

[0349] (Synthetic Example 3) Synthesis of Ru Catalyst 3

[0350] Ru catalyst 3 was synthesized through the following procedures.

[0351] Under an inactive atmosphere, ligand C (397 mg, 1 mmol) was added to a suspension of [RuHCl(PPh3)3(CO)] (953 mg, 1 mmol) in THF (15 ml), the mixture was stirred, and heated at 65 °C for 12 hours. Then it was cooled to room temperature.

[0352] The precipitated pale yellow solid was filtered, washed with ether (3 mL × 3 times), and dried under vacuum to obtain Ru catalyst 3 (519 mg, 92%).

[0353] In the Ru catalyst 3 and ligand C shown below, tBu represents tert-butyl.

[0354] [Chemical Formula 17]

[0355]

[0356] 31 P{ 1 ¹H NMR (CDCl₃): 135.6 (s). 1 H NMR (CDCl3): δ-26.11 (t, J=16.0Hz, 1H), 1.32 (t, J=7.28Hz, 18H), 1.41 (t, J= 7.68Hz, 18H), 6.87 (t, J=8.04Hz, 1H), 7.14 (d, J=8.04Hz, 2H), 9.51 (br, 2H). 13 C{ 1 H}NMR (125MHz, CD3OD): 28.62 (t, J=2.7Hz), 28.87 (t, J=3.4Hz), 39.34 (t, J=10.8Hz), 41.1 0 (t, J=9.1Hz), 99.75 (t, J=3.5Hz), 143.05 (s), 164.32 (t, J=7.3Hz), 207.41 (t, J=10.7Hz).

[0357] (Synthetic Example 4) Synthesis of Ru Catalyst 5

[0358] Ru catalyst 5 was synthesized through the following procedures.

[0359] Under an inert atmosphere, a mixture of 0.51 g (0.54 mmol) of [RuHCl(PPh3)3(CO)] in 25 mL of benzene and 0.30 g (0.63 mmol) of the following ligand E was refluxed overnight to obtain a clear yellow solution. The resulting solution was then cooled to room temperature.

[0360] The solvent was completely removed under vacuum, and 30 mL of diethyl ether was added to obtain a yellow solid.

[0361] The yellow solid was recrystallized using dichloromethane / diethyl ether to give a pale yellow solid.

[0362] The solid was collected onto a filter and dried under vacuum overnight to obtain Ru catalyst 5 in a yield of 0.29 g and 85%.

[0363] In the Ru catalyst 5 and ligand E shown below, Ph represents phenyl.

[0364] [Chemical Formula 18]

[0365]

[0366] 1 H NMR (300MHz, CD2Cl2): δ-13.65 (t, J=19.9Hz, 1H), 4.13 (dt, J=16.6Hz, J=4.8Hz, 2H), 4.64 (dt, J=16.6Hz, J=4.5Hz, 2H), 6.82-7.85 (m, 23H). 31 P{ 1 H}NMR (121.51MHz, CD2Cl2): δ50.4(s)

[0367] (Synthetic Example 5) Synthesis of Ru Catalyst 7

[0368] Ru catalyst 7 was synthesized through the following procedures.

[0369] Under an inactive atmosphere, 142.6 mg of ligand G and 284.6 mg of [RuHCl(PPh3)3(CO)] were mixed in 5 mL of benzene, and the suspension was refluxed overnight. The resulting yellow precipitate was collected on a filter and washed four times with 5 mL of ether.

[0370] The precipitate was dried in a vacuum to obtain 154.0 mg of Ru catalyst 7.

[0371] In the Ru catalyst 7 and ligand G shown below, Ph represents phenyl.

[0372] [Chemical Formula 19]

[0373]

[0374] 31 P{ 1 H}NMR (CDC3): 95.58 (br, s), 29.71 (s).1 H NMR (400MHz, CD2Cl2) δ9.92 (s, 2H), 8.11 (q, J=6.6Hz, 4H), 7.38-7.24 (m, 4H), 7.20 (t, J=7.5Hz, 3H), 7.16-7.04 (m, 4H), 7.0 4-6.92 (m, 14H), 6.87 (td, J=7.6, 2.1Hz, 6H), 6.51 (d, J=8.0Hz, 1H), 6.61 (d, J=8.0Hz, 2H), -7.22 (dt, J=89.2, 23.1Hz, 1H).

[0375] (Synthetic Example 6) Synthesis of Ru Catalyst 8

[0376] Ru catalyst 8 was synthesized through the following procedure.

[0377] Under an inactive atmosphere, 161.0 mg of the following ligand H and 242.4 mg of [RuHCl(PPh3)3(CO)] were mixed with 6 mL of THF and stirred overnight at 64 °C. After cooling to room temperature, the solvent was removed under vacuum, and the residue was washed twice with 3 mL of diethyl ether. The resulting pale yellow powder was further dried under vacuum to obtain 110.2 mg of Ru catalyst 8.

[0378] In the Ru catalyst 8 and ligand H shown below, Ph represents phenyl.

[0379] [Chemical Formula 20]

[0380]

[0381] 31 PNMR(162MHz,THF-d8)δ90.19(s). 1 H NMR (400MHz, THF-d8) δ9.26 (s, 2H), 7.94 (br, 4H), 7.74 (t, J=4.6Hz, 4H), 7.43-7.32 (br12H), 2.26 (d, J=2.2Hz, 3H), -13.63 (t, J=21.6Hz, 1H).

[0382] [Example 1]

[0383] Inside an argon-atmospheric glove box, 2 mL of N,N-dimethylformamide (DMF) was added to a glass vial equipped with a rare-earth metal stir bar. Then, 2.23 mmol of aziridine (DBU) (333 μL) was added. Next, 10 mg of a 6.6 mg / mL stock solution of catalyst 7 (obtained by dissolving 6.6 mg of catalyst 7 in 1 mL of DMF) was added. Finally, the autoclave was sealed and removed from the glove box.

[0384] The autoclave is connected to an H2 / CO2 (1:1 mixture) supply line. First, it is purged to remove trace amounts of oxygen and other impurities. Then, the autoclave is pressurized to approximately 5 bar (1 bar = 0.1 MPa) at room temperature and heated to the target temperature (90°C) while stirring. When the target temperature is reached, the autoclave is further pressurized to 40 bar using the H2 / CO2 mixture (1:1).

[0385] After stirring the reaction mixture for 1.5 hours, the mixture was cooled in an ice bath, and the pressure was carefully released after cooling. 300 μL of dimethyl sulfoxide (DMSO) was added as an internal standard, and 100 μL of the sample was dissolved in 0.5 mL of D₂O. 1 1H NMR analysis was used to quantify the amount of potassium formate produced.

[0386] [Example 2]

[0387] In an argon-atmospheric glove box, potassium bicarbonate (10 mmol, 1.0 g) was measured into a glass vial equipped with a rare-earth metal stir bar. Then, solid methyltrioctylammonium chloride (54 μmol, 22 mg) was added. Next, 2 mL of water and 0.12 μmol (108 μg, equivalent to 10 μL of a 12.6 mg / mL DMF solution) of catalyst 7 were added. Finally, the autoclave was sealed and removed from the glove box.

[0388] The autoclave is connected to the H2 supply line, and is first purged to remove trace amounts of oxygen and other impurities. Then, the autoclave is pressurized to approximately 5 bar at room temperature and heated to 90°C while stirring. When the target temperature is reached, the autoclave is further pressurized to 40 bar using H2.

[0389] After stirring the reaction mixture for 2.5 hours, the reaction mixture was cooled in an ice bath, and then the pressure was carefully released.

[0390] Add 100 μL of DMSO as an internal standard, take 100 μL of the aqueous layer, dissolve it in 0.5 mL of D2O, and then... 1 Quantification of potassium formate was performed using 1H NMR analysis.

[0391] [Example 3]

[0392] Inside an argon-atmospheric glove box, in a glass vial equipped with a rare-earth metal stir bar, measure out 5 mmol (0.5 g) of potassium bicarbonate. Then, add solid methyltrioctylammonium chloride (54 μmol, 22 mg). Next, add 1 mL of toluene and 10 μL of a 6.6 mg / mL stock solution of catalyst 1. Finally, add 1 mL of water, place the vial into an autoclave, seal the autoclave, and remove it from the glove box.

[0393] The autoclave is connected to the H2 supply line, and is first purged to remove trace amounts of oxygen and other impurities. Then, the autoclave is pressurized to approximately 5 bar at room temperature and heated to 90°C while stirring. When the target temperature is reached, the autoclave is further pressurized to 40 bar using H2.

[0394] After stirring the reaction mixture for 2.5 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving the lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O. 1 Quantification of potassium formate was performed using 1H NMR.

[0395] [Example 4]

[0396] In an argon-atmospheric glove box, in a glass vial equipped with a rare-earth metal stir bar, measure out 5 mmol (0.5 g) of potassium bicarbonate. Then, add solid methyltrioctylammonium chloride (54 μmol, 22 mg). Next, add 1 mL of toluene and 10 μL of a 6.6 mg / mL stock solution of catalyst 5. Finally, add 1 mL of water, place the vial into an autoclave, seal the autoclave, and remove it from the glove box.

[0397] The autoclave is connected to the H2 supply line, and is first purged to remove trace amounts of oxygen and other impurities. Then, the autoclave is pressurized to approximately 5 bar at room temperature and heated to 90°C while stirring. When the target temperature is reached, the autoclave is further pressurized to 40 bar using H2.

[0398] After stirring the reaction mixture for 2.5 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving a lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O. 1 Quantification of potassium formate was performed using 1H NMR.

[0399] [Example 5]

[0400] In an argon-atmospheric glove box, in a glass vial equipped with a rare-earth metal stir bar, measure out 5 mmol (0.5 g) of potassium bicarbonate. Then, add solid methyltrioctylammonium chloride (54 μmol, 22 mg). Next, add 1 mL of toluene and 10 μL of a 12.6 mg / mL stock solution of catalyst 7. Finally, add 1 mL of water, place the vial into an autoclave, seal the autoclave, and remove it from the glove box.

[0401] The autoclave is connected to the H2 supply line, and is first purged to remove trace amounts of oxygen and other impurities. Then, the autoclave is pressurized to approximately 5 bar at room temperature and heated to 90°C while stirring. When the target temperature is reached, the autoclave is further pressurized to 40 bar using H2.

[0402] After stirring the reaction mixture for 4.5 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving a lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O. 1 Quantification of potassium formate was performed using 1H NMR.

[0403] [Example 6]

[0404] In an argon-atmospheric glove box, in a glass vial equipped with a rare-earth metal stir bar, measure out 5 mmol (0.5 g) of potassium bicarbonate. Then, add solid methyltrioctylammonium chloride (54 μmol, 22 mg). Next, add 1 mL of toluene and 10 μL of a 6.3 mg / mL stock solution of catalyst 8. Finally, add 1 mL of water, place the vial into an autoclave, seal the autoclave, and remove it from the glove box.

[0405] The autoclave is connected to the H2 supply line, and is first purged to remove trace amounts of oxygen and other impurities. Then, the autoclave is pressurized to approximately 5 bar at room temperature and heated to 90°C while stirring. When the target temperature is reached, the autoclave is further pressurized to 40 bar using H2.

[0406] After stirring the reaction mixture for 12 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving a lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O. 1 Quantification of potassium formate was performed using 1H NMR.

[0407] [Example 7]

[0408] In an argon-atmospheric glove box, in a glass vial equipped with a rare-earth metal stir bar, measure out 5 mmol (0.5 g) of potassium bicarbonate. Then, add solid methyltrioctylammonium chloride (54 μmol, 22 mg). Next, add 1 mL of dioxane and 10 μL of a 12.6 mg / mL stock solution of catalyst 7. Finally, add 1 mL of water, place the vial into an autoclave, seal the autoclave, and remove it from the glove box.

[0409] The autoclave is connected to the H2 supply line, and is first purged to remove trace amounts of oxygen and other impurities. Then, the autoclave is pressurized to approximately 5 bar at room temperature and heated to the target temperature (typically 90°C) while stirring. Once the target temperature is reached, the autoclave is further pressurized to 40 bar using H2.

[0410] After stirring the reaction mixture for 4.5 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving a lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O. 1 Quantification of potassium formate was performed using 1H NMR.

[0411] [Example 8]

[0412] In this embodiment, catalyst 1 was exposed to air in a solid state for 20 hours before use. Potassium bicarbonate (5 mmol, 0.5 g) was measured in a glass vial equipped with a rare-earth metal stir bar inside an argon-atmosphere glove box. Then, solid methyltrioctylammonium chloride (54 μmol, 22 mg) was added. Next, 1 mL of toluene and 10 μL of a 6.3 mg / mL stock solution of catalyst 1 after air exposure were added. Finally, 1 mL of water was added, the vial was placed in an autoclave, the autoclave was sealed, and the vial was removed from the glove box.

[0413] The autoclave is connected to the H2 supply line, and is first purged to remove trace amounts of oxygen and other impurities. Then, the autoclave is pressurized to approximately 5 bar at room temperature and heated to 90°C while stirring. When the target temperature is reached, the autoclave is further pressurized to 40 bar using H2.

[0414] After stirring the reaction mixture for 2.5 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving a lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O.1 Quantification of potassium formate was performed using 1H NMR.

[0415] [Example 9]

[0416] In this embodiment, catalyst 5 was exposed to air in a solid state for 20 hours before use. In a glove box under an argon atmosphere, potassium bicarbonate (5 mmol, 0.5 g) was measured in a glass vial equipped with a rare earth metal stir bar. Then, solid methyltrioctylammonium chloride (54 μmol, 22 mg) was added. Next, 1 mL of toluene and 7.0 μL of the stock solution of 9.0 mg / mL of catalyst 5 exposed to air (a solution obtained by dissolving 9.0 mg of catalyst 5 in 1 mL of DMF) were added. Finally, 1 mL of water was added, the vial was placed in an autoclave, the autoclave was sealed, and the vial was removed from the glove box.

[0417] The autoclave is connected to the H2 supply line, and is first purged to remove trace amounts of oxygen and other impurities. Then, the autoclave is pressurized to approximately 5 bar at room temperature and heated to 90°C while stirring. When the target temperature is reached, the autoclave is further pressurized to 40 bar using H2.

[0418] After stirring the reaction mixture for 2.5 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving a lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O. 1 Quantification of potassium formate was performed using 1H NMR.

[0419] [Example 10]

[0420] In this embodiment, catalyst 7 was exposed to air in a solid state for 20 hours before use. In a glove box under an argon atmosphere, potassium bicarbonate (5 mmol, 0.5 g) was measured in a glass vial equipped with a rare earth metal stir bar. Then, solid methyltrioctylammonium chloride (54 μmol, 22 mg) was added. Next, 1 mL of toluene and 10.5 μL of the 10.6 mg / mL stock solution of catalyst 7 exposed to air were added. Finally, 1 mL of water was added, the vial was placed in an autoclave, the autoclave was sealed, and the vial was removed from the glove box.

[0421] The autoclave is connected to the H2 supply line, and is first purged to remove trace amounts of oxygen and other impurities. Then, the autoclave is pressurized to approximately 5 bar at room temperature and heated to 90°C while stirring. When the target temperature is reached, the autoclave is further pressurized to 40 bar using H2.

[0422] After stirring the reaction mixture for 4.5 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving a lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O. 1 Quantification of potassium formate was performed using 1H NMR.

[0423] [Example 11]

[0424] In this embodiment, catalyst 8 was exposed to air in a solid state for 20 hours before use. Potassium bicarbonate (5 mmol, 0.5 g) was measured in a glass vial equipped with a rare-earth metal stir bar inside an argon-atmosphere glove box. Then, solid methyltrioctylammonium chloride (54 μmol, 22 mg) was added. Next, 1 mL of toluene and 10.5 μL of a 5.8 mg / mL stock solution of catalyst 8 after air exposure were added. Finally, 1 mL of water was added, the vial was placed in an autoclave, the autoclave was sealed, and the vial was removed from the glove box.

[0425] The autoclave is connected to the H2 supply line, and is first purged to remove trace amounts of oxygen and other impurities. Then, the autoclave is pressurized to approximately 5 bar at room temperature and heated to the target temperature (typically 90°C) while stirring. Once the target temperature is reached, the autoclave is further pressurized to 40 bar using H2.

[0426] After stirring the reaction mixture for 12 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving a lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O. 1 Quantification of potassium formate was performed using 1H NMR.

[0427] [Comparative Example 1]

[0428] In this embodiment, catalyst 2 was exposed to air in a solid state for 20 hours before use. Potassium bicarbonate (5 mmol, 0.5 g) was measured in a glass vial equipped with a rare-earth metal stir bar inside an argon-atmosphere glove box. Then, solid methyltrioctylammonium chloride (54 μmol, 22 mg) was added. Next, 1 mL of toluene and 10 μL of a 6.7 mg / mL stock solution of catalyst 2 after air exposure were added. Finally, 1 mL of water was added, the vial was placed in an autoclave, the autoclave was sealed, and the vial was removed from the glove box.

[0429] The autoclave is connected to the H2 supply line, and is first purged to remove trace amounts of oxygen and other impurities. Then, the autoclave is pressurized to approximately 5 bar at room temperature and heated to the target temperature (typically 90°C) while stirring. Once the target temperature is reached, the autoclave is further pressurized to 40 bar using H2.

[0430] After stirring the reaction mixture for 2.5 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving a lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O. 1 Quantification of potassium formate was performed using 1H NMR.

[0431] [Comparative Example 2]

[0432] In this embodiment, catalyst 3 was exposed to air in a solid state for 20 hours before use. In a glove box under an argon atmosphere, potassium bicarbonate (5 mmol, 0.5 g) was measured in a glass vial equipped with a rare earth metal stir bar. Then, solid methyltrioctylammonium chloride (54 μmol, 22 mg) was added. Next, 1 mL of toluene and 10 μL of a 6.6 mg / mL stock solution of catalyst 3 after air exposure were added. Finally, 1 mL of water was added, the vial was placed in an autoclave, the autoclave was sealed, and the vial was removed from the glove box.

[0433] The autoclave is connected to the H2 supply line, and is first purged to remove trace amounts of oxygen and other impurities. Then, the autoclave is pressurized to approximately 5 bar at room temperature and heated to the target temperature (typically 90°C) while stirring. Once the target temperature is reached, the autoclave is further pressurized to 40 bar using H2.

[0434] After stirring the reaction mixture for 2.5 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving a lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O. 1 Quantification of potassium formate was performed using 1H NMR.

[0435] The above embodiments and comparative examples are described in Table 1.

[0436] The TON (Turnover Number) in the table represents the amount of formic acid or formate produced (in molar amounts) relative to the amount of catalyst used (in molar amounts).

[0437] [Table 1]

[0438]

[0439] Examples 3-11, which produced formate using the manufacturing method according to the first embodiment, exhibited high TON (Turnover Number), demonstrating excellent formate production efficiency. Examples 1 and 2, which produced formate using the ruthenium complex according to the fourth embodiment as a catalyst, also showed high TON.

[0440] [Example 12]

[0441] In this embodiment, catalyst 7 was exposed to air in a solid state for 20 hours before use. In an argon-atmospheric glove box, potassium hydroxide (50 mmol, 2.8 g) was measured and added to 4.2 ml of distilled water to prepare a 10 mol / L potassium hydroxide aqueous solution. Next, 10.5 μL of the air-exposed catalyst 7 stock solution (10.6 mg / mL) and solid methyltrioctyl ammonium chloride (54 μmol, 22 mg) were added to 5 mL of toluene. Finally, 5 mL of toluene containing catalyst 7 and methyltrioctyl ammonium chloride was added to 5 mL of the 10 mol / L potassium hydroxide aqueous solution. The vial was placed in a 300 mL autoclave, sealed, and removed from the glove box.

[0442] The autoclave was connected to the CO2 supply line, and first, it was purged to remove trace amounts of oxygen and other impurities. Then, the autoclave was pressurized to approximately 0.4 MPa at room temperature. After stirring the solution for 1 hour, the CO2 was carefully released.

[0443] Next, the autoclave was connected to the H2 supply line and purged to remove trace amounts of CO2 and other impurities. Then, the solution was stirred while being heated to 90°C, and after heating, the H2 pressure was increased to approximately 0.5 MPa.

[0444] After stirring the reaction mixture for 18 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving a lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O. 1 Quantification of potassium formate was performed using 1H NMR.

[0445] [Example 13]

[0446] In this embodiment, catalyst 7 was exposed to air in a solid state for 20 hours before use. In an argon-atmospheric glove box, potassium hydroxide (50 mmol, 2.8 g) was measured and added to 4.2 ml of distilled water to prepare a 10 mol / L potassium hydroxide aqueous solution. Next, 10.5 μL of the air-exposed catalyst 7 stock solution (10.6 mg / mL) and solid methyltrioctyl ammonium chloride (54 μmol, 22 mg) were added to 5 mL of toluene. Finally, 5 mL of toluene containing catalyst 7 and methyltrioctyl ammonium chloride was added to 5 mL of the 10 mol / L potassium hydroxide aqueous solution. The vial was placed in a 300 mL autoclave, sealed, and removed from the glove box.

[0447] The autoclave was connected to the CO2 supply line, and first, it was purged to remove trace amounts of oxygen and other impurities. Then, the autoclave was pressurized to approximately 0.1 MPa at room temperature. After stirring the solution for 1 hour, the CO2 was carefully released.

[0448] Next, the autoclave was connected to the H2 supply line and purged to remove trace amounts of CO2 and other impurities. Then, the solution was stirred while being heated to 90°C, and after heating, the H2 was pressurized to approximately 0.4 MPa.

[0449] After stirring the reaction mixture for 18 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving a lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O. 1 Quantification of potassium formate was performed using 1H NMR.

[0450] [Example 14]

[0451] In this embodiment, catalyst 7 was exposed to air in a solid state for 20 hours before use. In an argon-atmospheric glove box, potassium hydroxide (50 mmol, 2.8 g) was measured and added to 4.2 ml of distilled water to prepare a 10 mol / L potassium hydroxide aqueous solution. Next, 10.5 μL of the air-exposed catalyst 7 stock solution (10.6 mg / mL) and solid methyltrioctyl ammonium chloride (54 μmol, 22 mg) were added to 5 mL of toluene. Finally, 5 mL of toluene containing catalyst 7 and methyltrioctyl ammonium chloride was added to 5 mL of the 10 mol / L potassium hydroxide aqueous solution. The vial was placed in a 300 mL autoclave, sealed, and removed from the glove box.

[0452] The autoclave was connected to the CO2 supply line, and first purged to remove trace amounts of oxygen and other impurities. Then, the autoclave was pressurized to approximately 0.1 MPa at room temperature. Next, the autoclave was connected to the H2 supply line and pressurized to approximately 0.4 MPa. Finally, the solution was heated to 90°C.

[0453] After stirring the reaction mixture for 18 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving a lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O. 1 Quantification of potassium formate was performed using 1H NMR.

[0454] [Example 15]

[0455] In this embodiment, catalyst 7 was exposed to air in a solid state for 20 hours before use. In an argon-atmospheric glove box, potassium hydroxide (50 mmol, 2.8 g) was measured and added to 4.2 ml of distilled water to prepare a 10 mol / L potassium hydroxide aqueous solution. Next, 10.5 μL of the air-exposed catalyst 7 stock solution (10.6 mg / mL) and solid methyltrioctyl ammonium chloride (54 μmol, 22 mg) were added to 5 mL of toluene. Finally, 5 mL of toluene containing catalyst 7 and methyltrioctyl ammonium chloride was added to 5 mL of the 10 mol / L potassium hydroxide aqueous solution. The vial was placed in a 300 mL autoclave, sealed, and removed from the glove box.

[0456] The autoclave was connected to the H2 supply line, and first purged to remove trace amounts of oxygen and other impurities. Then, the autoclave was pressurized to approximately 0.1 MPa at room temperature. Next, the autoclave was connected to the CO2 supply line and pressurized to approximately 0.4 MPa. Finally, the solution was heated to 90°C.

[0457] After stirring the reaction mixture for 18 hours, the mixture was cooled in an ice bath, and then the pressure was carefully released. The upper layer containing the catalyst and trimethylammonium chloride was removed, leaving a lower layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of DMSO was added as an internal standard, and 100 μL of the aqueous layer was dissolved in 0.5 mL of D₂O. 1 Quantification of potassium formate was performed using 1H NMR.

[0458] Examples 12 to 15 described above are shown in Table 2.

[0459] The CO2 / alkali ratio (mol / mol) in Table 2 represents the ratio of the amount of CO2 (molar amount) added to a 300 mL autoclave to the amount of KOH used (molar amount). The molar amount of CO2 added is calculated using the gas law based on the volume obtained by subtracting the volume of the added alkaline aqueous solution from the autoclave's internal volume, the CO2 filling pressure, and the ambient temperature during CO2 filling.

[0460] [Table 2]

[0461] Table 2

[0462]

[0463] *1. Formate formation (mol) relative to the amount of alkali added (mol).

[0464] *2 Turnover Number (Formate formation (mol) relative to the amount of catalyst added)

[0465] *3 The ratio of the amount of CO2 (mol) added to the amount of alkali (mol) added.

[0466] Example 12, which produced formic acid using the manufacturing method according to the first embodiment, showed a high TON (Turnover Number of Formic Acid Generated (mol) relative to the amount of catalyst added), confirming that formic acid is generated through the reaction of hydrogen and carbon dioxide using potassium hydroxide as a base. Furthermore, in Example 13, even with a CO2 filling pressure of 1 MPa, a high TON (Turnover Number of Formic Acid Generated (mol) relative to the amount of catalyst added) was observed based on the CO2 / base ratio, confirming that formic acid is generated from hydrogen and carbon dioxide.

[0467] Examples 14 and 15, which produced formic acid using the manufacturing method according to the first embodiment, showed high TON (Turnover Number, formic acid produced relative to the amount of catalyst added in mol), confirming that formic acid is produced by the reaction of hydrogen and carbon dioxide using potassium hydroxide as a base. There are no particular restrictions on the timing of heating the solution, but it is preferable to heat it after introducing hydrogen and carbon dioxide into the reaction vessel.

[0468] [Example 16]

[0469] In a glove box under inert gas conditions, 5 mL of water was measured in a glass vial equipped with a stir bar, 5 mmol of calcium carbonate was added, and then 0.6 μmol of Ru catalyst 7 and 270 μmol of methyltrioctylammonium chloride were added to 5 mL of toluene. The glass vial was then placed in an autoclave, the autoclave was sealed, and the vial was removed from the glove box.

[0470] In an autoclave, the mixture was heated to 90°C with stirring. When the target temperature was reached, a gas containing 50 vol% hydrogen and 50 vol% carbon dioxide was introduced into the autoclave, and the pressure was increased to 4 MPa. After stirring the reaction mixture for 4.5 hours, the reaction mixture was cooled in an ice bath, and the pressure was carefully released. The organic phase (containing the homogeneous catalyst) of the resulting solution was separated, and unreacted calcium carbonate precipitated in the aqueous phase was removed, thus yielding an aqueous solution containing calcium formate. Then, 100 μL of the calcium formate-containing aqueous solution was dissolved in 0.5 mL of D₂O, and 100 μL of DMSO was added as an internal standard. 1 Quantification of calcium formate was performed using ¹H NMR analysis.

[0471] [Example 17]

[0472] In a glove box under inert gas conditions, 5 mL of water was measured in a glass vial equipped with a stir bar, 5 mmol of calcium carbonate was added, and then 0.6 μmol of Ru catalyst 7 and 270 μmol of methyltrioctylammonium chloride were added to 5 mL of toluene. The glass vial was then placed in an autoclave, the autoclave was sealed, and the vial was removed from the glove box.

[0473] In an autoclave, the mixture was heated to 90°C with stirring. When the target temperature was reached, a gas containing 50 vol% hydrogen and 50 vol% carbon dioxide was introduced into the autoclave, and the pressure was increased to 4 MPa. After stirring the reaction mixture for 18 hours, the mixture was cooled in an ice bath, and the pressure was carefully released. The organic phase (containing the homogeneous catalyst) of the resulting solution was separated, and unreacted calcium carbonate precipitated in the aqueous phase was removed, yielding an aqueous solution containing calcium formate. Then, 100 μL of the calcium formate-containing aqueous solution was dissolved in 0.5 mL of D₂O, and 100 μL of DMSO was added as an internal standard. 1 Quantification of calcium formate was performed using 1H NMR analysis.

[0474] Examples 16 and 17 described above are shown in Table 3.

[0475] [Table 3]

[0476] Table 3

[0477]

[0478] *1. Formate formation (mol) relative to the amount of alkali added (mol).

[0479] *2 Turnover Number (Formate formation (mol) relative to the amount of catalyst added)

[0480] Examples 16 and 17, which produced formic acid using the manufacturing method of the first embodiment, showed high TON (Turnover Number, formic acid production in mol relative to the amount of catalyst added), confirming that formic acid can be efficiently produced by using calcium carbonate as a base through the reaction of hydrogen with alkaline earth metal salts and carbon dioxide or carbonates.

[0481] [Examples 18-21]

[0482] In a glove box under inert gas conditions, measure 1 mL of water into a glass vial equipped with a stir bar, add potassium bicarbonate in the range of 2.5–14 mmol, and then add a solution obtained by mixing 0.12 μmol of Ru catalyst 1 and 54 μmol of methyltrioctylammonium chloride with 1 mL of toluene. Then place the vial into an autoclave, seal the autoclave, and remove it from the glove box.

[0483] The autoclave was heated to 90°C with stirring. When the target temperature was reached, the autoclave was pressurized to 4 MPa using hydrogen. After stirring the reaction mixture for 2.5 hours, the reaction mixture was cooled in an ice bath, and the pressure was carefully released. The upper layer of the reacted solution was removed, leaving a lower aqueous layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of the lower aqueous layer was dissolved in 500 μL of heavy water, and 300 μL of dimethyl sulfoxide was added as an internal standard. The solution was then analyzed by... 1 Quantification of potassium formate was performed using 1H NMR.

[0484] [Examples 22-24]

[0485] In a glove box under inert gas conditions, measure 1 mL of water into a glass vial equipped with a stir bar, add sodium bicarbonate in the range of 5–10 mmol, and then add a solution obtained by mixing 0.12 μmol of Ru catalyst 1 and 54 μmol of methyltrioctylammonium chloride with 1 mL of toluene. Then place the vial into an autoclave, seal the autoclave, and remove it from the glove box.

[0486] The autoclave was heated to 90°C with stirring. When the target temperature was reached, the autoclave was pressurized to 4 MPa using hydrogen. After stirring the reaction mixture for 2.5 hours, the reaction mixture was cooled in an ice bath, and the pressure was carefully released. The upper layer of the reacted solution was removed, leaving a lower aqueous layer containing sodium formate and unreacted potassium bicarbonate. 100 μL of the lower aqueous layer was dissolved in 500 μL of heavy water, and 300 μL of dimethyl sulfoxide was added as an internal standard. The solution was then analyzed by... 1 Quantification of sodium formate was performed using 1H NMR.

[0487] Examples 18 to 24 are described in Table 4.

[0488] [Table 4]

[0489]

[0490] Examples 18-24, which produced formate using the manufacturing method described in the first embodiment, exhibited high TON (Turnover Number) and excellent formate production efficiency. It can be confirmed that formic acid can be efficiently generated even when using potassium bicarbonate or sodium bicarbonate as bases and varying the concentrations of various bases.

[0491] [Examples 25-28]

[0492] In a glove box under inactive gas conditions, in a glass vial equipped with a stir bar, measure 1 mL of water, add 5 mmol of potassium bicarbonate, and then add the solution obtained by mixing Ru catalyst 1 with 0.059–0.006 μmol of toluene and 54 μmol of methyltrioctylammonium chloride. Then place the vial into an autoclave, seal the autoclave, and remove it from the glove box.

[0493] The autoclave was heated to 90°C with stirring. Upon reaching the target temperature, the autoclave was pressurized to 4 MPa using hydrogen. The reaction mixture was stirred over 18–48 hours, then cooled in an ice bath, and the pressure was carefully released. The supernatant of the reacted solution was removed, leaving a lower aqueous layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of this lower aqueous layer was dissolved in 500 μL of heavy water, and 300 μL of dimethyl sulfoxide was added as an internal standard. The solution was then analyzed by... 1 Quantification of potassium formate was performed using 1H NMR.

[0494] Examples 25 to 28 are described in Table 5.

[0495] [Table 5]

[0496] Table 5

[0497]

[0498] ※1. Amount of formic acid generated (mol) relative to the amount of alkali added (mol).

[0499] ※2 Turnover number (Formate formation amount (mol) relative to the amount of catalyst added (mol))

[0500] Examples 25-28, which produced formate using the manufacturing method described in the first embodiment, exhibited high TON (Turnover Number) and excellent formate production efficiency. It can be confirmed that formate can be produced efficiently even with variations in catalyst concentration.

[0501] [Examples 29-43]

[0502] In a glove box under inert gas conditions, measure 1 mL of water in a glass vial equipped with a stir bar, add 5 mmol of potassium bicarbonate, and then add the solution obtained by mixing 0.12 μmol of Ru catalyst 1 and 54 μmol of methyl trioctyl ammonium chloride with 1 mL of toluene. Then place the vial into an autoclave, seal the autoclave, and remove it from the glove box.

[0503] The autoclave was heated at 65–120°C with stirring. When the target temperature was reached, the autoclave was pressurized with hydrogen at 0.5–6 MPa. After stirring the reaction mixture for 16 hours, the mixture was cooled in an ice bath, and the pressure was carefully released. The supernatant of the reacted solution was removed, leaving a lower aqueous layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of the lower aqueous layer was dissolved in 500 μL of heavy water, and 300 μL of dimethyl sulfoxide was added as an internal standard. The solution was then analyzed by... 1 Quantification of potassium formate was performed using 1H NMR.

[0504] Examples 29 to 43 are described in Tables 6 and 7.

[0505] [Table 6]

[0506]

[0507] [Table 7]

[0508] Mai 7

[0509]

[0510] ※1. Amount of formic acid generated (mol) relative to the amount of alkali added (mol).

[0511] ※2 Turnover number (Formate formation amount (mol) relative to the amount of catalyst added (mol))

[0512] Examples 29-43, which produced formate using the manufacturing method described in the first embodiment, exhibited high TON (Turnover Number) and excellent formate production efficiency. It can be confirmed that formate can be efficiently generated even with variations in reaction temperature and hydrogen pressure.

[0513] [Examples 44-48]

[0514] In a glove box under inactive gas conditions, measure 1 mL of water into a glass vial equipped with a stir bar, add potassium bicarbonate in the range of 5 mmol, and then add a solution obtained by mixing 0.13 μmol of Ru catalyst 1 and 42–57 μmol of benzyltriethylammonium chloride, tetrabutylammonium hydroxide, tetrabutylammonium fluoride, tetrabutylammonium bromide or tetrabutylammonium iodide as a phase transfer catalyst in 1 mL of toluene. Then place the vial into an autoclave, seal the autoclave and remove it from the glove box.

[0515] The autoclave was heated to 90°C with stirring. When the target temperature was reached, the autoclave was pressurized to 4.5 MPa using hydrogen. After stirring the reaction mixture for 18 hours, the reaction mixture was cooled in an ice bath, and the pressure was carefully released. The supernatant of the reacted solution was removed, leaving a lower aqueous layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of the lower aqueous layer was dissolved in 500 μL of heavy water, and 300 μL of dimethyl sulfoxide was added as an internal standard. The solution was then analyzed by... 1 Quantification of potassium formate was performed using 1H NMR.

[0516] Examples 44 to 48 are described in Table 8.

[0517] [Table 8]

[0518]

[0519] Examples 44-48, which produced formate using the manufacturing method described in the first embodiment, exhibited high TON (Turnover Number) and excellent formate production efficiency. It can be confirmed that formate can be efficiently produced even when the type of phase transfer catalyst is changed.

[0520] [Example 49]

[0521] In a glove box under inert gas conditions, 1 mL of toluene was measured into a glass vial equipped with a stir bar. 0.12 μmol of ligand A and 0.12 μmol of [RuHCl(PPh3)3(CO)] were added. The toluene solution was heated to 65 °C and stirred for 3 hours. Then, 54 μmol of methyltrioctylammonium chloride, 1 mL of water, and 5 mmol of potassium bicarbonate were added to the toluene solution. The vial was placed in an autoclave, sealed, and removed from the glove box.

[0522] The autoclave was heated to 90°C with stirring. When the target temperature was reached, the autoclave was pressurized to 4 MPa using hydrogen. After stirring the reaction mixture for 18 hours, the reaction mixture was cooled in an ice bath, and the pressure was carefully released. The supernatant of the reacted solution was removed, leaving a lower aqueous layer containing potassium formate and unreacted potassium bicarbonate. 100 μL of the lower aqueous layer was dissolved in 500 μL of heavy water, and 300 μL of dimethyl sulfoxide was added as an internal standard. The solution was then analyzed by... 1 Quantification of potassium formate was performed using 1H NMR.

[0523] Example 49 is described in Table 9.

[0524] [Table 9]

[0525] Table 9

[0526]

[0527] ※1. Formate formation (mol) relative to the amount of alkali added (mol).

[0528] ※2 Turnover number (Formate formation amount (mol) relative to the amount of catalyst added (mol))

[0529] It can be confirmed that even when a series of reactions from the synthesis of Ru catalyst to the synthesis of formate are carried out in the same glass vial, a high TON (Turnover Number) is observed, indicating excellent formate production efficiency.

[0530] Industrial availability

[0531] According to the present invention, a method for producing formate as a precursor of formic acid in high yield and for reusing the catalyst can be provided, a method for producing formic acid, a catalyst for producing formate, and a ruthenium complex that can be used as a catalyst for efficiently converting hydrogen into formate.

[0532] The invention has been described in detail and with reference to specific embodiments, but it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

[0533] This application is made based on Japanese patent applications filed on September 3, 2020 (Japanese Patent Application No. 2020-148562), February 12, 2021 (Japanese Patent Application No. 2021-021223), February 12, 2021 (Japanese Patent Application No. 2021-021224), February 12, 2021 (Japanese Patent Application No. 2021-021225), May 10, 2021 (Japanese Patent Application No. 2021-079887), and May 17, 2021 (Japanese Patent Application No. 2021-083416), the contents of which are incorporated herein by reference.

Claims

1. A method for producing formate, which involves reacting hydrogen with a bicarbonate or carbonate in the presence of a solvent using a catalyst to produce formate. In the reaction, the solvent is a two-phase system existing in a state where an organic solvent and an aqueous solvent are separated. The catalyst is at least one selected from ruthenium complexes, tautomers or stereoisomers thereof, or chlorinated compounds thereof, represented by the following general formula (1). [Chemical Formula 1] In general formula (1), R0 represents an alkyl group having 1 to 30 hydrogen atoms. Q1 can be independently represented as CH2 or NH. R1 independently represents an alkyl group having 1 to 30 carbon atoms or an aryl group having 6 to 30 carbon atoms, wherein, When Q1 represents NH, at least one of R1 represents an aryl group having 6 to 30 carbon atoms; when Q1 represents CH2, R1 represents an alkyl group having 1 to 30 carbon atoms. A represents CH. X represents a halogen atom. n represents 0 to 3. In the presence of multiple L ligands, each ligand can independently represent a neutral or anionic ligand. A phase transfer catalyst was also used in the reaction.

2. The method for manufacturing formate as described in claim 1, wherein, The ruthenium complex represented by the general formula (1) is the ruthenium complex represented by the following general formula (3). [Chemical Formula 2] In general formula (3), R0 represents an alkyl group having 1 to 30 hydrogen atoms. Q2 represents NH independently. R3 independently represents aryl groups with 6 to 30 carbon atoms. A represents CH. X represents a halogen atom. n represents 0 to 3. In the presence of multiple L, each independently represents a neutral or anionic ligand.

3. The method for manufacturing formate as described in claim 1, wherein, R1 represents phenyl.

4. The method for manufacturing formate as described in claim 2, wherein, R3 represents phenyl.

5. The method for manufacturing formate as described in claim 4, wherein, A represents CH, and Q2 represents NH.

6. The method for manufacturing formate according to any one of claims 1 to 5, wherein, R0 represents a hydrogen atom or a methyl group.

7. The method for manufacturing formate according to any one of claims 1 to 5, wherein, X represents a chlorine atom.

8. The method for manufacturing formate according to any one of claims 1 to 5, wherein, The n represents 1 to 3, and each L independently represents a hydrogen atom, carbon monoxide, or triphenylphosphine.

9. The method for manufacturing formate according to any one of claims 1 to 5, wherein, The organic solvent contains toluene or dioxane.

10. The method for manufacturing formate according to any one of claims 1 to 5, wherein, Ammonium salts were further used as phase transfer catalysts.

11. The method for manufacturing formate according to any one of claims 1 to 5, wherein, Further adding the ligand represented by the following general formula (4), [Chemical Formula 3] In general formula (4), R0 represents an alkyl group having 1 to 30 hydrogen atoms. Q2 can be represented independently as NH or O. R3 independently represents aryl groups with 6 to 30 carbon atoms. A can be independently represented by CH, CR5, or N, and R5 can be represented by an alkyl group with 1 to 30 carbon atoms, an aryl group with 6 to 30 carbon atoms, an aralkyl group with less than 30 carbon atoms, an amino group, a hydroxyl group, or an alkoxy group with 1 to 30 carbon atoms.

12. A method for manufacturing formic acid, comprising the following steps: The process of manufacturing formate using the formate manufacturing method according to any one of claims 1 to 11; and The second step involves protonating at least a portion of the formate to generate formic acid.

Images