Method for producing alkaline earth metal formate

Abstract

The present invention relates to a production method for an alkaline earth metal formate, said method including a first step for producing a formate of an alkaline earth metal by reacting hydrogen, carbon dioxide, and a carbonate or bicarbonate of an alkaline earth metal using a homogeneous catalyst in the presence of a solvent in a two-phase system in which the solvent is present in a state in which the solvent has been separated into an organic phase and a water phase.

Description

Technical Field

[0001] The present invention relates to a method for producing alkaline earth metal formate.

Background Art

[0002] Conventionally, alkaline earth metal formates have been used in various applications. For example, calcium formate is used as a neutralizing agent in leather production, an accelerator for cement hardening, a feed additive, etc. As methods for producing calcium formate, various methods are known, such as a method of reacting formic acid with calcium hydroxide and a method of reacting carbon monoxide with calcium hydroxide. And in Patent Document 1, a method for producing flaky calcium formate with a particle size range of 0.2 - 5 mm from fine particles or powdery calcium formate with an average particle size of 0.2 mm or less is described.

[0003] On the other hand, due to problems such as global warming, technologies for converting carbon dioxide into useful compounds have been studied. For example, in Non-Patent Documents 1 and 2, methods for producing formate in the presence of a catalyst from carbon dioxide (CO 2 ) and hydrogen (H 2 ) have been studied.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The technique described in Non-Patent Document 1 produces formate from hydrogen and carbon dioxide using a homogeneous metal complex catalyst. However, since the reaction is carried out in a single-phase system, there is a risk of a decrease in catalytic activity and decomposition of formate during the separation of formate from the catalyst and solvent and the distillation of the solvent. In addition, the technique described in Non-Patent Document 2 produces formate from hydrogen and carbon dioxide using a heterogeneous metal complex catalyst, but the reactivity is not sufficient, and there is a need for a method that can produce formate in a higher yield.

[0007] Therefore, the present invention provides a method for producing an alkaline earth metal formate that can produce an alkaline earth metal formate in a high yield and with excellent productivity.

Means for Solving the Problems

[0008] As a result of intensive studies, the present inventors have found a method for producing an alkaline earth metal formate that can produce an alkaline earth metal formate in a high yield and with excellent productivity by carrying out the reaction in a two-phase system using a homogeneous catalyst, and have completed the present invention.

[0009] The means for solving the above problems are as follows. [1] In the presence of a solvent, in a two-phase system in which the solvent exists in a state separated into an organic phase and an aqueous phase, using a homogeneous catalyst, A method for producing an alkaline earth metal formate, comprising a first step of reacting hydrogen, carbon dioxide, and a carbonate or bicarbonate of an alkaline earth metal to produce an alkaline earth metal formate. [2] Furthermore, the method for producing an alkaline earth metal formate according to [1], comprising a second step of separating a solution containing the homogeneous catalyst from the reaction solution obtained in the first step by liquid separation. [3] The method for producing an alkaline earth metal formate according to [1] or [2], wherein the alkaline earth metal is calcium. [4] The method for producing an alkaline earth metal formate according to any one of [1] to [3], wherein the homogeneous catalyst contains at least one metal selected from ruthenium, iridium, iron, nickel, and cobalt. [5] The method for producing an alkaline earth metal formate according to any one of [1] to [4], wherein the organic phase contains at least one selected from toluene, dioxane, tetrahydrofuran, ethyl acetate, methylcyclohexane, and cyclopentyl methyl ether. [6] The method for producing an alkaline earth metal formate according to any one of [1] to [5], wherein the homogeneous catalyst is a metal complex catalyst, and a ligand of the metal complex catalyst is further added. [7] The method for producing an alkaline earth metal formate according to any one of [1] to [5], wherein the homogeneous catalyst is at least one selected from a ruthenium complex represented by the following general formula (1), a tautomer or stereoisomer thereof, and a salt compound thereof.

[0010] [Chemical formula]

[0011] (In general formula (1), R 0 represents a hydrogen atom or an alkyl group, Q 1 each independently represents CH 2 , NH, or O, R 1 each independently represents an alkyl group or an aryl group (however, when Q 1 represents NH or O, at least one of R 1 represents an aryl group), A each independently represents CH, CR 5 , or N, and R 5 represents an alkyl group, an aryl group, an aralkyl group, an amino group, a hydroxy group, or an alkoxy group, X represents a halogen atom, n represents 0 to 3, L, when there are a plurality of them, each independently represents a neutral or anionic ligand.) [8] Furthermore, a method for producing an alkaline earth metal formate according to [7], wherein a ligand represented by the following general formula (4) is added.

[0012] [Chemical formula]

[0013] (In general formula (4), R 0 represents a hydrogen atom or an alkyl group, Q 2 each independently represents NH or O, R 3 each independently represents an aryl group, A each independently represents CH, CR 5 , or N, and R 5 represents an alkyl group, an aryl group, an aralkyl group, an amino group, a hydroxy group, or an alkoxy group.) [9] In the first step, further, a quaternary ammonium salt is used as a phase transfer catalyst, and the method for producing an alkaline earth metal formate according to any one of [1] to [8].

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a method for producing an alkaline earth metal formate capable of producing an alkaline earth metal formate with high yield and excellent productivity.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described in detail. The method for producing an alkaline earth metal formate according to an embodiment of the present invention is a method for producing a formate of an alkaline earth metal including a first step of reacting hydrogen, carbon dioxide, and a carbonate or bicarbonate of an alkaline earth metal using a homogeneous catalyst in a two-phase system in which the solvent is present in a state separated into an organic phase and an aqueous phase in the presence of a solvent.

[0016] In the method for producing an alkaline earth metal formate (hereinafter, may be simply referred to as formate) according to an embodiment of the present invention, the reaction of hydrogen, carbon dioxide, and a carbonate or bicarbonate of an alkaline earth metal is preferably carried out in a catalyst solution (organic phase) in which a homogeneous catalyst (hereinafter, may be simply referred to as a catalyst) is dissolved in an organic solvent.

[0017] The formate produced by the reaction dissolves in the aqueous solvent and thus elutes into the aqueous phase. Therefore, it is possible to prevent the production reaction of the alkaline earth metal formate from stopping due to equilibrium, and it is possible to produce the alkaline earth metal formate in a high yield. Further, since the alkaline earth metal formate aqueous solution can be separated from the catalyst solution by a simple method, it is difficult to deactivate the catalyst activity, and it is possible to reuse an expensive catalyst and realize high productivity.

[0018] According to the method for producing an alkaline earth metal formate according to an embodiment of the present invention, hydrogen and carbon dioxide can also be stored as an alkaline earth metal formate. Since the alkaline earth metal formate has a high hydrogen storage density, is safe, and is stable as a chemical substance, it can be easily handled and has the advantage of being able to store hydrogen and carbon dioxide for a long time. The alkaline earth metal formate has a high solubility in an aqueous solvent and can be separated as a high-concentration aqueous solution of the alkaline earth metal formate. If necessary, the alkaline earth metal formate can be recovered as a solid by a simple operation such as distillation.

[0019] The reaction in the method for producing an alkaline earth metal formate according to an embodiment of the present invention can be carried out, for example, as follows. Prepare a reaction vessel equipped with a stirrer. If necessary, a phase transfer catalyst may be further added. Add a carbonate or bicarbonate of an alkaline earth metal dissolved in a solvent and a homogeneous catalyst solution dissolved in a solvent to the reaction vessel. Then, introduce hydrogen and carbon dioxide into the reaction vessel to carry out the reaction.

[0020] Hereinafter, the homogeneous catalyst, solvent, hydrogen, carbon dioxide, carbonate or bicarbonate of an alkaline earth metal, etc. used in the reaction will be described.

[0021] (Solvent) The solvent according to an embodiment of the present invention is not particularly limited as long as the reaction solution can be a two-phase system in which an organic phase and an aqueous phase are separated, and preferably includes a solvent in which the catalyst is dissolved to become homogeneous. The organic phase is a phase having an organic solvent as a solvent, and the aqueous phase is a phase having an aqueous solvent as a solvent. Examples of the aqueous solvent include water, methanol, ethanol, ethylene glycol, glycerin, and a mixed solvent thereof, and water is preferred from the viewpoint of low environmental load. Examples of the organic solvent include toluene, benzene, xylene, propylene carbonate, dioxane, dimethyl sulfoxide, tetrahydrofuran, ethyl acetate, methylcyclohexane, cyclopentyl methyl ether, and a mixed solvent thereof. At least one selected from toluene, dioxane, tetrahydrofuran, ethyl acetate, methylcyclohexane, and cyclopentyl methyl ether is preferable, and toluene or dioxane is preferable from the viewpoint of separability from the aqueous solvent. That is, it preferably contains at least one selected from toluene, dioxane, tetrahydrofuran, ethyl acetate, methylcyclohexane, and cyclopentyl methyl ether, and the organic phase more preferably contains toluene or dioxane.

[0022] 〔Homogeneous catalyst〕 The catalyst used in the embodiment of the present invention needs to be a homogeneous catalyst, is preferably soluble in an organic solvent, and more preferably is a compound containing a metal element (metal element compound). Examples of metal element compounds include salts of metal elements with inorganic acids such as hydride salts, oxide salts, halide salts (such as chloride salts), hydroxide salts, carbonate salts, bicarbonate salts, sulfate salts, nitrate salts, phosphate salts, borate salts, halate salts, perhalate salts, halite salts, hypohalite salts, and thiocyanate salts; salts of metal elements with organic acids such as alkoxide salts, carboxylate salts (such as acetate salts, (meth)acrylate salts, etc.), and sulfonate salts (such as trifluoromethanesulfonate salts, etc.); salts of metal elements with organic bases such as amide salts, sulfonamide salts, and sulfonimide salts (such as bis(trifluoromethanesulfonyl)imide salts, etc.); complex salts such as acetylacetone salts, hexafluoroacetylacetone salts, porphyrin salts, phthalocyanine salts, and cyclopentadiene salts; complexes or salts containing one or more of nitrogen compounds such as chain amines, cyclic amines, and aromatic amines, phosphorus compounds, compounds containing phosphorus and nitrogen, sulfur compounds, carbon monoxide, carbon dioxide, and water. These compounds may be either hydrates or anhydrides and are not particularly limited. Among these, halide salts, complexes containing phosphorus compounds, complexes containing nitrogen compounds, and complexes or salts containing compounds containing phosphorus and nitrogen are preferred because they can enhance the production efficiency of alkaline earth metal formates. These may be used alone or in combination of two or more.

[0023] As the metal element compound, commercially available ones can be used, or those produced by known methods such as the method described in Japanese Patent No. 5896539 or the methods described in Chem. Rev. 2017, 117, 9804 - 9838 and Chem. Rev. 2018, 118, 372 - 433 can be used.

[0024] The catalyst according to the embodiment of the present invention is not particularly limited, but preferably has a turnover number: TON of 10,000 or more, which is determined by the following calculation method.

[0025] TON is preferably 10,000 or more, more preferably 50,000 or more, and even more preferably 100,000 or more from the viewpoint of suppressing the production cost of alkaline earth metal formate. Further, since TON is higher the better, the upper limit is not particularly limited, but for example, it can be 10,000,000 or less.

[0026] TON calculation method: TON = X / Y Formula 1 (In Formula 1, X represents the molar amount X (mol) of potassium formate generated in the following TON calculation reaction calculated by the following Formula 2, and Y represents the molar amount (mol) of the catalyst used in the following reaction.)

[0027] X = (W / M) × (Ia × Ib / R) × (A / B) Formula 2 (In Formula 2, W is the amount (g) of dimethyl sulfoxide used for potassium formate quantification, M is the molecular weight of dimethyl sulfoxide, R is the ratio of the number of protons of dimethyl sulfoxide to the number of protons of potassium formate, Ia is the proton NMR integral value of potassium formate, Ib is the proton NMR integral value of dimethyl sulfoxide, A is the mass (g) of the aqueous solution in the lower layer obtained in the following reaction, B represents the mass (g) of the aqueous solution used for potassium formate quantification.)

[0028] TON calculation reaction: (Formate production) In a glove box under an inert gas, into a glass vial equipped with a stir bar, add 10 mmol of KHCO to 1 mL of water, and then add 0.12 μmol of the catalyst and 54 μmol of methyltrioctylammonium chloride to the solvent in which the highest TON of the catalyst can be obtained among 1 mL of toluene, dioxane, tetrahydrofuran, ethyl acetate, methylcyclohexane, and cyclopentyl methyl ether. Then, place the vial in an autoclave, seal the autoclave, and take it out of the glove box. 3 The autoclave was heated to 90 °C while stirring. Once the target temperature was reached, the autoclave was pressurized to 4.5 MPa at H 2 The reaction mixture was stirred for 18 hours, then the reaction mixture was cooled in an ice bath and the pressure was carefully released. The upper layer of the solution after the reaction was removed, and an aqueous solution of the lower layer containing potassium formate and unreacted KHCO 3 was obtained with Ag.

[0029] (Quantification of potassium formate) Take Bg of the aqueous solution of the lower layer, dissolve it in 500 μL of heavy water, add Wg of dimethyl sulfoxide as an internal standard, and then 1 perform 1H NMR measurement. Let the NMR integration value of potassium formate be Ia and the NMR integration value of dimethyl sulfoxide be Ib.

[0030] For example, for Ru catalyst 1 and Ru catalyst 7 used in the examples of the present invention, the TONs determined by the above TON calculation method are 66,000 for Ru catalyst 1 and 56,000 for Ru catalyst 7.

[0031] The homogeneous catalyst used in the method for producing an alkaline earth metal formate according to the embodiment of the present invention preferably contains at least one metal selected from ruthenium, iridium, iron, nickel, and cobalt, and preferably contains ruthenium. Among them, it is preferably at least one selected from ruthenium complexes represented by the general formula (1), their tautomers or stereoisomers, and their salt compounds. The ruthenium complex represented by the general formula (1) is soluble in an organic solvent and insoluble in water. Since the alkaline earth metal formate produced by the reaction is easily soluble in water, the separation of the catalyst and the alkaline earth metal formate is facilitated by the reaction in a two-phase system, and the separation and recovery of the catalyst and the alkaline earth metal formate from the reaction system are facilitated, enabling the production of the alkaline earth metal formate in a high yield. According to the method of the present embodiment, the alkaline earth metal formate produced by the reaction can be separated from the catalyst by a simple operation, and the expensive catalyst can be reused.

[0032] [Chemical formula]

[0033] (In general formula (1), R 0 represents a hydrogen atom or an alkyl group, Q 1 each independently represents CH 2 , NH, or O, R 1 each independently represents an alkyl group or an aryl group (however, when Q 1 represents NH or O, at least one of R 1 represents an aryl group), A each independently represents CH, CR 5 , or N, and R 5 represents an alkyl group, an aryl group, an aralkyl group, an amino group, a hydroxy group, or an alkoxy group, X represents a halogen atom, n represents 0 to 3, L, when there are a plurality of them, each independently represents a neutral or anionic ligand.)

[0034] R in general formula (1) 0 represents a hydrogen atom or an alkyl group. The alkyl group represented by R 0 includes linear, branched, cyclic substituted or unsubstituted alkyl groups. R 0 The alkyl group represented by preferably has 1 to 30 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, a t-butyl group, an n-octyl group, an eicosyl group, a 2-ethylhexyl group, etc. From the viewpoint of easy availability of raw materials, it is preferably an alkyl group having 6 or less carbon atoms, and preferably a methyl group. R in general formula (1) 0 is preferably a hydrogen atom or a methyl group.

[0035] R in general formula (1) 1 each independently represents an alkyl group or an aryl group. However, Q1 When representing NH or O, R 1 at least one of which represents an aryl group. R 1 Examples of the alkyl group represented by R include linear, branched, cyclic substituted or unsubstituted alkyl groups. R 1 Examples of the alkyl group represented by R preferably include an alkyl group having 1 to 30 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, a t-butyl group, an n-octyl group, an eicosyl group, a 2-ethylhexyl group, etc. From the viewpoint of catalytic activity, an alkyl group having 12 or less carbon atoms is preferable, and a t-butyl group is preferable.

[0036] R 1 Examples of the aryl group represented by R include substituted or unsubstituted aryl groups having 6 to 30 carbon atoms, such as a phenyl group, a p-tolyl group, a naphthyl group, an m-chlorophenyl group, an o-hexadecanoylaminophenyl group, etc. Preferably, it is an aryl group having 12 or less carbon atoms, and more preferably a phenyl group.

[0037] A is each independently CH, CR 5 , or N, and R 5 represents an alkyl group, an aryl group, an aralkyl group, an amino group, a hydroxy group, or an alkoxy group. R 5 Examples of the alkyl group represented by R include linear, branched, cyclic substituted or unsubstituted alkyl groups. R 5 Examples of the alkyl group represented by R preferably include an alkyl group having 1 to 30 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, a t-butyl group, an n-octyl group, an eicosyl group, a 2-ethylhexyl group, etc. From the viewpoint of easy availability of raw materials, an alkyl group having 12 or less carbon atoms is preferable, and a methyl group is preferable.

[0038] R 5Examples of the aryl group represented by include substituted or unsubstituted aryl groups having 6 to 30 carbon atoms, such as phenyl group, p-tolyl group, naphthyl group, m-chlorophenyl group, o-hexadecanoylaminophenyl group, etc. Preferably, it is an aryl group having 12 or less carbon atoms, and more preferably a phenyl group.

[0039] R 5 Examples of the aralkyl group represented by include substituted or unsubstituted aralkyl groups having 30 or less carbon atoms, such as trityl group, benzyl group, phenethyl group, tritylmethyl group, diphenylmethyl group, naphthylmethyl group, etc. Preferably, it is an aralkyl group having 12 or less carbon atoms.

[0040] R 5 Examples of the alkoxy group represented by preferably include substituted or unsubstituted alkoxy groups having 1 to 30 carbon atoms, such as methoxy group, ethoxy group, isopropoxy group, t-butoxy group, n-octyloxy group, 2-methoxyethoxy group, etc.

[0041] X represents a halogen atom, preferably a chlorine atom.

[0042] n represents an integer of 0 to 3 and represents the number of ligands coordinated to ruthenium. From the viewpoint of the stability of the catalyst, n is preferably 2 or 3.

[0043] When there are a plurality of Ls, each independently represents a neutral or anionic ligand. Examples of the neutral ligand represented by L include ammonia, carbon monoxide, phosphines (e.g., triphenylphosphine, tris(4-methoxyphenyl)phosphine), phosphine oxides (e.g., triphenylphosphine oxide), sulfides (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., and triphenylphosphine is preferred. Examples of the anionic ligand represented by L include hydride ion (hydrogen atom), nitrate ion, cyanide ion, etc., and hydride ion (hydrogen atom) is preferred.

[0044] In the general formula (1), it is preferable that A represents CH and Q 1 represents NH. Also, it is preferable that n represents 1 to 3 and each L independently represents a hydrogen atom, carbon monoxide, or triphenylphosphine.

[0045] The ruthenium complex represented by the general formula (1) may be used alone or in combination of two or more.

[0046] The ruthenium complex represented by the above general formula (1) is preferably a ruthenium complex represented by the following general formula (3).

[0047]

Chemical formula

[0048] (In the general formula (3), R 0 represents a hydrogen atom or an alkyl group, Q 2 each independently represents NH or O, R 3 each independently represents an aryl group, A each independently represents CH, CR5 represents C, Si, or N, and R 5 represents an alkyl group, an aryl group, an aralkyl group, an amino group, a hydroxy group, or an alkoxy group, X represents a halogen atom, n represents 0 to 3, L, when there are a plurality of them, each independently represents a neutral or anionic ligand.)

[0049] R in the general formula (3) 0 , A, R 5 , X, n, and L are respectively synonymous with R 0 , A, R 5 , X, n, and L in the general formula (1), and the preferred ranges are also the same.)

[0050] R in the general formula (3) 3 The aryl group represented by is respectively synonymous with the aryl group represented by R 1 in the general formula (1), and the preferred ranges are also the same.)

[0051] The ruthenium complexes represented by the general formula (1) and the general formula (3) can also be those produced by known methods such as the methods described in E. Pidko et al., ChemCatChem 2014, 6, 1526 - 1530, etc.)

[0052] The ruthenium complexes represented by the general formula (1) and the general formula (3) may form stereoisomers depending on the coordination mode and conformation of the ligand, and these may be a mixture of stereoisomers or a pure single isomer.)

[0053] Specific examples of the ruthenium complexes represented by the general formula (1) and the general formula (3), and the ligand, can be exemplified by the compounds described below.) In the compounds exemplified below, tBu represents a tertiary butyl group and Ph represents a phenyl group.)

[0054]

Chemical formula

[0055]

Chem.

[0056] The amount of the ruthenium complex used as a catalyst is not particularly limited as long as an alkaline earth metal formate can be produced. The amount of the ruthenium complex used as a catalyst is preferably 0.1 μmol or more, more preferably 0.5 μmol or more, and even more preferably 1 μmol or more per 1 L of the solvent in order to sufficiently exhibit the catalytic function. Further, from the viewpoint of cost, it is preferably 1 mol or less, more preferably 10 mmol or less, and even more preferably 1 mmol or less. When two or more ruthenium complexes are used, the total amount used thereof may be within the above range.

[0057] In the method for producing an alkaline earth metal formate according to an embodiment of the present invention, when the homogeneous catalyst used is a metal complex catalyst, it is preferable that the ligand forming the complex is present in excess in the reaction system. Therefore, it is preferable to further add the ligand of the metal complex catalyst used to the reaction system. For example, when the above ruthenium complex is used as a homogeneous catalyst, it is preferable to further add a ligand forming the ruthenium complex to the reaction mixture together with the above ruthenium complex. For example, when the homogeneous catalyst is a ruthenium complex represented by the general formula (1), it is preferable to further add a ligand represented by the following general formula (4).

[0058]

Chem.

[0059] (In the general formula (4), R 0 represents a hydrogen atom or an alkyl group, Q 2 each independently represents NH or O, R 3 each independently represents an aryl group, A each independently represents CH, CR 5 , or N, and R 5 represents an alkyl group, an aryl group, an aralkyl group, an amino group, a hydroxy group, or an alkoxy group.)

[0060] R in the general formula (4) 0 , Q 2 , R 3 , A, and R 5 are synonymous with R 0 , Q 2 , R 3 , A, and R 5 in the general formula (3), respectively, and the preferred ranges are also the same.)

[0061] By adding a ligand that forms a complex to the reaction system, even when the ligand is oxidized and deteriorated by oxygen or impurities contained in the system, the deteriorated ligand and the added ligand are exchanged, and the catalytic function is restored, so that the stability of the catalyst can be improved.)

[0062] The addition of the ligand represented by the general formula (4) to the reaction mixture may be carried out when preparing the reaction mixture or during the reaction, but from the viewpoint of process control, it is preferably carried out when preparing the reaction mixture.)

[0063] (Phase transfer catalyst) Since the method for producing an alkaline earth metal formate according to an embodiment of the present invention requires a reaction to be carried out in a two-phase system, a phase transfer catalyst may be used to facilitate the transfer of substances between the two phases. Examples of the phase transfer catalyst include quaternary ammonium salts, quaternary phosphates, macrocyclic polyethers such as crown ethers, nitrogen-containing macrocyclic polyethers such as cryptands, nitrogen-containing chain polyethers, polyethylene glycol and its alkyl ethers, etc. Among them, a quaternary ammonium salt is preferred from the viewpoint that the transfer of substances between an aqueous solvent and an organic solvent is easy even under mild reaction conditions.)

[0064] Examples of the quaternary ammonium salts include methyltrioctylammonium chloride, benzyltrimethylammonium chloride, trimethylphenylammonium bromide, tributylammonium tribromide, tetrahexylammonium hydrogen sulfate, decyltrimethylammonium bromide, diallyldimethylammonium chloride, dodecyltrimethylammonium bromide, dimethyldioctadecylammonium bromide, tetraethylammonium tetrafluoroborate, ethyltrimethylammonium iodide, tris(2-hydroxyethyl)methylammonium hydroxide, tetramethylammonium acetate, tetramethylammonium bromide, tetraethylammonium iodide, etc., and methyltrioctylammonium chloride is preferred.

[0065] The amount of the phase transfer catalyst used is not particularly limited as long as the alkaline earth metal formate can be produced. The amount of the 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 per 1 L of the solvent for the role of efficiently assisting the transfer of the carbonate or bicarbonate. Also, from the viewpoint of cost, it is preferably 1 mol or less, more preferably 500 mmol or less, and even more preferably 100 mmol or less. When two or more phase transfer catalysts are used, the total amount used thereof may be within the above range.

[0066] (Carbon dioxide and hydrogen) As the hydrogen used in the embodiments of the present invention, either hydrogen gas cylinders or liquid hydrogen can be utilized. As the hydrogen source, for example, hydrogen generated in the steelmaking process of ironmaking, hydrogen generated in the soda manufacturing process, etc. can be used. Also, hydrogen generated from the electrolysis of water can be utilized. The carbon dioxide used in the embodiments of the present invention may be pure carbon dioxide gas or a mixed gas containing components other than carbon dioxide. The carbon dioxide gas and other gases may be introduced separately or as a mixed gas before introduction.

[0067] Examples of components other than carbon dioxide include inert gases such as nitrogen and argon, water vapor, and any other optional components contained in exhaust gases and the like. As the carbon dioxide, carbon dioxide gas cylinders, liquid carbon dioxide, supercritical carbon dioxide, dry ice, etc. can be used. The hydrogen gas and the carbon dioxide gas may be introduced into the reaction system either individually or as a mixed gas.

[0068] The usage ratio of hydrogen and carbon dioxide is preferably the same amount or in excess of hydrogen on a molar basis. When using a hydrogen cylinder as the hydrogen used in the method for producing an alkaline earth metal formate according to the embodiment of the present invention, 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 from the viewpoint of sufficiently ensuring reactivity. Further, since the equipment tends to become large, it is preferably 50 MPa or less, more preferably 20 MPa or less, and even more preferably 10 MPa or less. Also, the pressure of the carbon dioxide used in the method for producing an alkaline earth metal formate according to the embodiment 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 from the viewpoint of sufficiently ensuring reactivity. Further, since the equipment tends to become large, it is preferably 50 MPa or less, more preferably 20 MPa or less, and even more preferably 10 MPa or less.

[0069] The hydrogen gas and the carbon dioxide gas may be bubbled (injected) into the catalyst solution. Further, after introducing the gas containing hydrogen gas and carbon dioxide, the catalyst solution, the hydrogen gas, and the carbon dioxide gas may be stirred by using a stirring device, rotating the reaction vessel, or the like.

[0070] The method for introducing carbon dioxide, hydrogen, a catalyst, a solvent, etc. used in the reaction into the reaction vessel is not particularly limited, and all raw materials etc. may be introduced at once, or some or all of the raw materials etc. may be introduced stepwise, or some or all of the raw materials etc. may be introduced continuously. Also, an introduction method combining these methods may be used.

[0071] (Hydrogen carbonate and carbonate) In the method for producing an alkaline earth metal formate according to an embodiment of the present invention, a hydrogen carbonate or carbonate of an alkaline earth metal is used. Examples of the hydrogen carbonate of an alkaline earth metal include calcium hydrogen carbonate, strontium hydrogen carbonate, barium hydrogen carbonate, radium hydrogen carbonate, etc., and calcium hydrogen carbonate is preferable from the viewpoint of high solubility in water. Examples of the alkaline earth metal carbonate include calcium carbonate, strontium carbonate, barium carbonate, radium carbonate, etc. The alkaline earth metal in the carbonate or hydrogen carbonate of the alkaline earth metal is preferably calcium. The base concentration in the reaction solution is preferably 0.1 mol / L or more. The base concentration in the reaction solution is preferably 0.1 mol / L or more, more preferably 0.5 mol / L or more, and even more preferably 1 mol / L or more from the viewpoint of increasing the maximum production amount of the formate. Also, in order to suppress the amount of precipitated salt derived from the base from increasing too much and adversely affecting the stirring of the reaction, it is preferably 30 mol / L or less, more preferably 25 mol / L or less, and even more preferably 20 mol / L or less. It is preferable to use a hydrogen carbonate and carbonate of an alkaline earth metal so that the base concentration in the reaction solution falls within the above range.

[0072] (Reaction conditions) The reaction conditions in the method for producing an alkaline earth metal formate according to an embodiment of the present invention are not particularly limited, and the reaction conditions can be appropriately changed during the reaction process. The form of the reaction vessel used in the reaction is not particularly limited. The reaction temperature is not particularly limited, but in order to allow the reaction to proceed efficiently, it is preferably 30 °C or higher, more preferably 40 °C or higher, and even more preferably 50 °C or higher. From the perspective of energy efficiency, it is preferably 200 °C or lower, more preferably 150 °C or lower, and even more preferably 100 °C or lower.

[0073] The reaction time is not particularly limited, but for example, from the perspective of ensuring a sufficient amount of formate production, it is preferably 0.5 hours or longer, more preferably 1 hour or longer, and even more preferably 2 hours or longer. From the perspective of cost, it is preferably 24 hours or shorter, more preferably 20 hours or shorter, and even more preferably 18 hours or shorter.

[0074] The concentration of the formate produced in the first step (the concentration of the formate in the aqueous phase) is preferably 0.1 mol / L or higher, more preferably 0.5 mol / L or higher, and even more preferably 1 mol / L or higher in order to increase the TON and produce the formate with high yield and excellent productivity. Also, in order to simplify the production process by producing in a state where the formate is dissolved, it is preferably 30 mol / L or lower, more preferably 25 mol / L or lower, and even more preferably 20 mol / L or lower.

[0075] After completion of the reaction in the first step, the homogeneous catalyst can be separated and recovered from the reaction solution and the alkaline earth metal salt can be isolated by performing ordinary separation, post-treatment, purification operations, etc.

[0076] (Second step) The second step is a step of separating, by liquid separation, the solution containing the homogeneous catalyst from the reaction solution obtained in the first step. The method for producing an alkaline earth metal formate according to an embodiment of the present invention preferably further includes a second step. In the embodiments of the present invention, since the reaction proceeds in a two-phase system, the alkaline earth metal formate generated by the reaction elutes into the aqueous phase. Therefore, when a homogeneous catalyst that is easily soluble in an organic solvent is used, the organic phase can be separated as a solution containing the homogeneous catalyst by liquid-liquid separation of the organic phase and the aqueous phase, and the homogeneous catalyst can be recovered. There is no particular limitation on the method of liquid-liquid separation, and a usual method is used. For example, liquid-liquid separation can be performed by taking out either the organic phase or the aqueous phase under an inert gas using a drain port of the reaction vessel, a pump for attachment, or the like. The homogeneous catalyst separated and recovered in the second step can be reused in the first step. For example, the solution containing the separated homogeneous catalyst may be directly reused in the first step, or the concentration of the homogeneous catalyst may be adjusted or isolated and recovered by operations such as concentration and purification.

Examples

[0077] Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these Examples.

[0078] 〔Synthesis of catalyst〕 (Synthesis Example 1) Synthesis of Ru catalyst 1 Ru catalyst 1 was synthesized by the following operation. Under an inert atmosphere, 40 mg (0.1 mmol) of the following ligand A was added to a suspension of 95.3 mg (0.1 mmol) of [RuHCl(PPh 3 ) 3 (CO)] in 5 ml of THF (tetrahydrofuran), and 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). The obtained yellow solution was filtered, and the filtrate was evaporated to dryness under vacuum. The obtained yellow residual oil was dissolved in a very small amount of THF (1 mL), hexane (10 mL) was slowly added to precipitate a yellow solid, which was filtered and dried under vacuum to obtain Ru catalyst 1 (55 mg, 97%) as yellow crystals. In Ru catalyst 1 and ligand A shown below, tBu represents a tertiary butyl group.

[0079] [Chemical formula]

[0080] 31 P{ 1 H}(C 6 D 6 ): 90.8 (s), 1 H(C 6 D 6 ): -14.54 (t, 1H, J = 20.0 Hz), 1.11 (t, 18H, J = 8.0 Hz), 1.51 (t, 18H, J = 8.0 Hz), 2.88 (dt, 2H, J = 16.0 Hz, J = 4.0 Hz), 3.76 (dt, 2H, J = 16.0 Hz, J = 4.0 Hz), 6.45 (d, 2H, J = 8.0 Hz), 6.79 (t, 1H, J = 8.0 Hz). 13 C{ 1 H} NMR (C 6 D 6 ): 29.8 (s), 30.7 (s), 35.2 (t, J = 9.5 Hz), 37.7 (t, J = 6.0 Hz), 37.9 (t, J = 6.5 Hz), 119.5 (t, J = 4.5 Hz), 136.4 (s), 163.4 (t, J = 5.0 Hz), 209.8 (s).

[0081] (Synthesis Example 2) Synthesis of Ru Catalyst 7 Ru Catalyst 7 was synthesized by the following procedure. Under an inert atmosphere, 142.6 mg of ligand G and 284.6 mg of [RuHCl(PPh 3 ) 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. The precipitate was dried in vacuo to obtain 154.0 mg of Ru Catalyst 7. In Ru Catalyst 7 and ligand G shown below, Ph represents a phenyl group.

[0082] [Chemical formula]

[0083] 31 P{ 1 H}NMR(CDC 3 ):95.58(br,s),29.71(s). 1 H NMR(400MHz,CD 2 Cl 2 )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),7.04 - 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).

[0084] <Example 1> (Calcium formate production reaction) In a glove box under an inert gas, 5 mmol of calcium carbonate was added to 5 mL of water in a glass vial equipped with a stir bar. Then, 0.6 μmol of Ru catalyst 7 and 270 μmol of methyltrioctylammonium chloride were added to 5 mL of toluene. After that, the vial was placed in an autoclave, and the autoclave was sealed and taken out of the glove box. The autoclave 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 pressurized to 4 MPa. After the reaction mixture was stirred for 4.5 hours, the reaction mixture was cooled in an ice bath, and the pressure was carefully released. The organic phase (solution containing the homogeneous catalyst) of the post - reaction solution was separated, and an aqueous solution containing calcium formate was obtained by removing the unreacted calcium carbonate precipitated in the aqueous phase. By the above operation, the homogeneous catalyst and calcium formate could be separated.

[0085] (Quantification method of calcium formate in aqueous solution) 100 μL of the aqueous solution containing calcium formate was taken, dissolved in 500 μL of heavy water, and 300 μL of dimethyl sulfoxide was added as an internal standard. After that, 11H NMR measurement was carried out. The molar amount (mol) X of calcium formate contained in the solution (the molar amount (mol) of calcium formate generated in the reaction) was calculated by the following formula. X = (W / M)×(Ia×Ib / R)×(A / B)

[0086] W: The amount (g) of dimethyl sulfoxide used for the quantification of calcium formate, M: The molecular weight of dimethyl sulfoxide, R: The ratio of the number of protons of dimethyl sulfoxide to the number of protons of calcium formate, Ia: The proton NMR integral value of formate ion, Ib: The NMR integral value of dimethyl sulfoxide, A: The mass (g) of the sample solution, B: The mass (g) of the solution used for quantification

[0087] Here, since W = 0.33, M = 78.13, and R = 6, it becomes as follows. X = 0.0007×Ia×Ib×(A / B)

[0088] (Calculation of the turnover number (TOF) of the catalyst) The calculation of the "TOF of the catalyst" described in Table 1 was obtained by dividing the molar amount (mol) of calcium formate generated in the reaction by 0.0006 (mol), which is the molar amount of the catalyst used in the reaction, to calculate the TON of the catalyst, and then dividing the calculated TON by 4.5, which is the reaction time (hr).

[0089] <Comparative Example 1> The description of Table 2.Entry6 (reaction temperature 60 °C, reaction pressure 4 MPa (hydrogen:carbon dioxide = 1:1), reaction time 20 hours) described in the non-patent document Green Chem., 2020, 22, 4995 - 5001 was used as Comparative Example 1. The TON of the catalyst under these conditions was 1750, and the TOF of the catalyst was calculated by dividing this TON by 20, which is the reaction time (hr).

[0090] <Comparative Example 2> The description of Fig. 6 in Non-Patent Document Journal of Molecular Catalysis A: Chemical 224 (2004) 87-91 (reaction temperature 50 °C, reaction pressure 5 MPa (hydrogen: carbon dioxide = 4:1), reaction time 24 hours) was used as Comparative Example 2. Under these conditions, since the calcium formate concentration had reached approximately 220 mmol / L with respect to the Rh catalyst concentration of 1 mmol / L, the TON of the catalyst was calculated by dividing the generated calcium formate concentration by the Rh catalyst concentration, and further the TOF was calculated by dividing by 24 which is the reaction time (hr).

[0091] The above Examples and Comparative Examples are described in Table 1.

Table 1

[0092] Example 1 in which an alkaline earth metal formate was produced using the production method according to the embodiment of the present invention showed a high TOF, indicating that it is superior in the production efficiency of the alkaline earth metal formate compared to Comparative Examples 1 and 2.

Industrial Applicability

[0093] According to the present invention, it is possible to provide a method for producing an alkaline earth metal formate capable of producing the alkaline earth metal formate in a high yield and with excellent productivity.

[0094] Although the present invention has been described in detail with reference to specific embodiments, 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 present invention. This application is based on Japanese Patent Application No. 2020-148562 filed on September 3, 2020, Japanese Patent Application No. 2021-021223 filed on February 12, 2021, Japanese Patent Application No. 2021-021224 filed on February 12, 2021, Japanese Patent Application No. 2021-021225 filed on February 12, 2021, Japanese Patent Application No. 2021-079887 filed on May 10, 2021, and Japanese Patent Application No. 2021-083416 filed on May 17, 2021, the contents of which are incorporated herein by reference.

Claims

1. In the presence of a solvent, in a two-phase system in which the solvent is present in a state separated into an organic phase and an aqueous phase, using a homogeneous catalyst, including a first step of reacting hydrogen, carbon dioxide, and a carbonate or bicarbonate of an alkaline earth metal to produce a formate of an alkaline earth metal, wherein the homogeneous catalyst is at least one selected from a ruthenium complex represented by the following general formula (1), a tautomer or stereoisomer thereof, and a salt compound thereof, A method for producing an alkaline earth metal formate. 【Chemical 1】 (In general formula (1), R 0 represents a hydrogen atom or an alkyl group, Q 1 each independently represents CH 2, NH, or O, R 1 each independently represents an alkyl group or an aryl group (provided that when Q 1 represents NH or O, at least one of R 1 represents an aryl group), A each independently represents CH, CR 5, or N, and R 5 represents an alkyl group, an aryl group, an aralkyl group, an amino group, a hydroxy group, or an alkoxy group, X represents a halogen atom, n represents 0 to 3, L, when there are a plurality of them, each independently represents a neutral or anionic ligand.)

2. Further including a second step of separating, by liquid separation, a solution containing the homogeneous catalyst from the reaction solution obtained in the first step, the method for producing an alkaline earth metal formate according to Claim 1.

3. The method for producing an alkaline earth metal formate according to Claim 1 or 2, wherein the alkaline earth metal is calcium.

4. The method for producing an alkaline earth metal formate according to any one of Claims 1 to 3, wherein the organic phase contains at least one selected from toluene, dioxane, tetrahydrofuran, ethyl acetate, methylcyclohexane, and cyclopentyl methyl ether.

5. The method for producing an alkaline earth metal formate according to any one of Claims 1 to 4, further adding a ligand of the homogeneous catalyst.

6. The method for producing an alkaline earth metal formate according to any one of Claims 1 to 5, further adding a ligand represented by the following general formula (4). 【Chemical Formula 2】 (In general formula (4), R ０ represents a hydrogen atom or an alkyl group, Q ２ each independently represents NH or O, R ３ each independently represents an aryl group, A each independently represents CH, CR ５ , or N, and R ５ represents an alkyl group, an aryl group, an aralkyl group, an amino group, a hydroxy group, or an alkoxy group.)

7. The method for producing an alkaline earth metal formate according to any one of Claims 1 to 6, wherein in the first step, a quaternary ammonium salt is further used as a phase transfer catalyst.

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