Methods for producing lactones

Abstract

To provide a method for producing lactones which, when producing lactones by hydrogenating one or more selected from a group consisting of dicarboxylic acids, dicarboxylic acid anhydrides, and dicarboxylic acid esters in the presence of a catalyst, enables obtaining a target material under milder conditions, in higher selectivity, and in higher yield than conventional methods by using a catalyst which has excellent activity stability, does not show decrease in conversion even when used for a long time, and can provide the target material in high selectivity and in high yield over a long time.SOLUTION: There is provided, a method for producing lactones, comprising using a ruthenium-based catalyst comprising the following (1) to (3): (1) ruthenium; (2) two or more kinds of organic phosphines; and (3) a conjugated base of an acid having a pKa of less than 2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing lactones by hydrogenating one or more raw material compounds selected from the group consisting of dicarboxylic acids, dicarboxylic acid anhydrides, and dicarboxylic acid esters. [Background technology]

[0002] Methods for producing lactones by hydrogenating one or more substances selected from the group consisting of dicarboxylic acids, dicarboxylic acid anhydrides, and dicarboxylic acid esters have been studied for a long time, and various catalysts have been proposed to date. For example, numerous methods have been proposed for producing lactones by hydrogenation reaction methods such as fixed bed or liquid-phase suspension using nickel-based catalysts (e.g., Patent Document 1), cobalt-based catalysts (e.g., Patent Document 2), copper-chromium-based catalysts (e.g., Patent Document 3), and copper-zinc-based catalysts (e.g., Patent Document 4). On the other hand, methods for producing lactones using homogeneous ruthenium catalysts to carry out the above hydrogenation reactions are also known, for example, Patent Document 5 describes [RuX n (PR1R2R3) x L y It is described that a hydrogenation reaction is carried out under conditions of 40 to 400 psi using a catalyst of type ]. Furthermore, Patent Document 6 describes a hydrogenation reaction using a similar catalyst in the presence of an organic amine. Moreover, Patent Document 7 describes [Ru m X n (SnCl2)(MR3) n L y It is described that the hydrogenation reaction is carried out using a catalyst of type [ ].

[0003] However, conventional methods using nickel-based catalysts, cobalt-based catalysts, copper-chromium-based catalysts, and copper-zinc-based catalysts, as described above, all have the problem of inevitably requiring the use of harsh conditions of several tens of atmospheres or more. Furthermore, while the conventional method using the homogeneous ruthenium catalyst described above has the advantage of allowing the hydrogenation reaction to proceed under relatively mild conditions, it suffers from a somewhat low level of catalytic activity, an extremely short catalyst lifespan, and the fatal problem of corrosion of the reactor due to the use of halogens.

[0004] To solve these problems, the applicant has proposed a method for producing lactones using a ruthenium-based catalyst containing ruthenium, an organophosphine, and a conjugate base of an acid with a pKa less than 2 (Patent Document 8). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Special Publication No. 43-6947 [Patent Document 2] Japanese Patent Application Publication No. 51-95057 [Patent Document 3] Special Publication No. 38-20119 [Patent Document 4] Special Publication No. 42-14463 [Patent Document 5] U.S. Patent No. 3957827 [Patent Document 6] U.S. Patent No. 4485246 [Patent Document 7] U.S. Patent No. 4485245 [Patent Document 8] Special Publication No. 7-78054 [Overview of the project] [Problems that the invention aims to solve]

[0006] When producing lactones by hydrogenating dicarboxylic acids, dicarboxylic acid anhydrides, and / or dicarboxylic acid esters, using a ruthenium-based catalyst described in Patent Document 8 and carrying out the reaction in a homogeneous liquid-phase reaction allows for obtaining the target product with high selectivity under milder conditions compared to conventional methods. Furthermore, because this catalyst has excellent activity stability, no decrease in conversion rate is observed even after prolonged use, allowing for the acquisition of the target product with high selectivity over extended periods. However, this method results in a low reaction yield of the target product, and there is room for improvement in the reaction yield of the target product.

[0007] Although Patent Document 8 provides examples of organic phosphines, such as alkyl phosphines, it does not mention the use of two or more of these organic phosphines in combination, and in the examples in Patent Document 8, only trioctylphosphine or triphenylphosphine are used individually.

[0008] The present invention aims to improve upon the problem of reaction yield of ruthenium-based catalysts described in Patent Document 8, and to provide a method for producing lactones that allows for the production of lactones under milder conditions compared to conventional methods, by using a catalyst that exhibits excellent activity stability, does not show a decrease in conversion rate even after prolonged use, and can produce the target product with high selectivity and high yield over a long period of time. [Means for solving the problem]

[0009] As a result of diligent research to solve the above problems, the present inventors have found that by using a mixture of two or more organic phosphines in the ruthenium-based catalyst described in Patent Document 8, the reaction yield can be significantly improved. In other words, the gist of this invention is as follows:

[0010] [1] In a method for producing lactones by hydrogenating one or more selected from the group consisting of dicarboxylic acids, dicarboxylic anhydrides and dicarboxylic esters in the presence of a catalyst, a ruthenium-based catalyst containing the following (1) to (3) is used as the catalyst, and the method for producing lactones is characterized by this. (1) Ruthenium (2) Two or more kinds of organic phosphines (3) The conjugate base of an acid having a pKa smaller than 2

[0011] [2] The method for producing lactones according to [1], wherein at least one of the two or more kinds of organic phosphines is an alkyl phosphine.

[0012] [3] The method for producing lactones according to [1] or [2], wherein at least one of the two or more kinds of organic phosphines is an aryl phosphine.

[0013] [4] The method for producing lactones according to any one of [1] to [3], wherein at least one of the two or more kinds of organic phosphines is an organic phosphine having any one of an oxygen atom, a nitrogen atom and a sulfur atom.

Advantages of the Invention

[0014] According to the present invention, in producing lactones by hydrogenating one or more selected from the group consisting of dicarboxylic acids, dicarboxylic anhydrides and dicarboxylic esters in the presence of a catalyst, a catalyst having excellent activity stability and showing no decrease in conversion rate even after long-term use is used, and the target product can be obtained at a high selectivity and high yield over a long period of time. By using this catalyst, the target product can be obtained at a high selectivity and high yield under mild conditions as compared with the conventional method.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, the present invention will be described in detail. However, the present invention is not limited to the following description and can be arbitrarily modified and implemented without departing from the gist of the present invention. In this specification, when expressing numerical values or physical property values before and after using "~", the values before and after shall be used as including those values.

[0016] The method for producing lactones of the present invention is a method for producing lactones by hydrogenating one or more selected from the group consisting of dicarboxylic acids, dicarboxylic anhydrides, and dicarboxylic esters (hereinafter sometimes referred to as "raw material compounds") in the presence of a catalyst. The method is characterized by using a ruthenium-based catalyst containing the following (1) to (3). (1) Ruthenium (2) Two or more kinds of organic phosphines (3) The conjugate base of an acid having a pKa smaller than 2

[0017] <Raw material compound> The dicarboxylic acids, dicarboxylic anhydrides, and dicarboxylic esters used as raw material compounds in the present invention are saturated or unsaturated dicarboxylic acids having 3 to 7 carbon atoms or derivatives thereof. As the ester, an alkyl ester is preferred. Particularly, as the carboxylic acid skeleton, a derivative having 4 carbon atoms is preferred. <000,0106>Specific examples of the raw material compounds include fumaric acid, succinic acid, maleic anhydride, succinic anhydride, dimethyl maleate, diethyl fumarate, di-n-butyl succinate, monomethyl succinate, monomethyl maleate, and the like. These raw material compounds may be used alone or in combination of two or more, but usually only one kind is used.

[0018] <Ruthenium-based catalyst> The ruthenium-based catalyst used in the present invention contains the following (1) to (3). (1) Ruthenium (2) Two or more kinds of organic phosphines (3) The conjugate base of an acid having a pKa smaller than 2

[0019] (ruthenium) In terms of supply form, both metallic ruthenium and ruthenium compounds can be used as ruthenium. Ruthenium compounds used include ruthenium oxides, hydroxides, inorganic salts, organic salts, and complex compounds. Specifically, examples include ruthenium dioxide, ruthenium tetroxide, ruthenium dihydrate, ruthenium chloride, ruthenium bromide, ruthenium iodide, ruthenium nitrate, ruthenium acetate, tris(acetylacetone)ruthenium, sodium hexachlororuthenate, dipotassium tetracarbonylruthenate, pentacarbonylruthenium, cyclopentadienyldicarbonylruthenium, dibromotricarbonylruthenium, chlorotris(triphenylphosphine)hydridotrithenium, bis(tri-n-butylphosphine)tricarbonylruthenium, dodecacarbonyltriruthenium, tetrahydridodecacarbonyltetraruthenium, dicesium octadecacarbonylhexalthenate, and tetraphenylphosphonium undecacarbonylhydridotriruthenate. These metallic ruthenium and ruthenium compounds may be used individually or as a mixture of two or more.

[0020] From the viewpoint of reaction yield, the amount of metallic ruthenium and ruthenium compounds used is preferably such that the concentration of ruthenium in 1 L of reaction solution is typically 0.0001 to 100 moles, more preferably 0.001 to 10 moles.

[0021] (Organophosphine) Organophosphines are thought to contribute to controlling the electronic state of ruthenium or stabilizing its active state. Examples of such organic phosphines include alkylphosphines, cycloalkylphosphines, arylphosphines, alkylarylphosphines, and polyfunctional phosphines.

[0022] The alkyl group of the alkylphosphine preferably has 1 to 12 carbon atoms, and trialkylphosphine is particularly preferred. The three alkyl groups of the trialkylphosphine do not all need to be the same; they may all be the same or different, or two may be the same and one different. Furthermore, substituents such as phenyl groups may be substituted on the alkyl group. It may also have an alkyl group and a cycloalkyl group.

[0023] Specific examples of alkylphosphines include tridecanylphosphine, trinonylphosphine, trioctylphosphine, triheptylphosphine, trihexylphosphine, tripentylphosphine, tributylphosphine, tripropylphosphine, triethylphosphine, trimethylphosphine, dimethyloctylphosphine, dioctylmethylphosphine, dimethylheptylphosphine, diheptylmethylphosphine, dimethylhexylphosphine, dihexylmethylphosphine, dimethylcyclohexylphosphine, dicyclohexylmethylphosphine, dimethylpentylphosphine, dipentylmethylphosphine, dimethylbutylphosphine, dibutylmethylphosphine, and tripenzylphosphine.

[0024] Of these, trioctylphosphine, tri-n-butylphosphine, and dimethyl-n-octylphosphine are preferred as alkylphosphines from the viewpoint of reaction yield, with trioctylphosphine being more preferred. These alkylphosphines may be used individually or as a mixture of two or more. Examples of cycloalkylphosphines include triarylphosphines such as tricyclohexylphosphine. These cycloalkylphosphines may be used individually or as a mixture of two or more.

[0025] Examples of arylphosphines include triarylphosphines such as triphenylphosphine. These arylphosphines may be used individually or in combination of two or more.

[0026] Examples of alkylarylphosphines include dimethylphenylphosphine. These alkylarylphosphines may be used individually or as a mixture of two or more. Examples of polyfunctional phosphines include 1,2-bis(diphenylphosphino)ethane, 1,1,2,2-dimethylphosphinoethane, 1,1,2,2-dimethylphosphinopropane, 1,1,2,2-dimethylphosphinobutane, 1,1,2,2-dioctylphosphinoethane, 1,1,2,2-dioctylphosphinopropane, 1,1,2,2-dioctylphosphinobutane, 1,1,2,2-dihexylphosphinoethane, 1,1,2,2-dihexylphosphinopropane, and 1,1,2,2 Examples include -dihexylphosphinbutane, 1,1,2,2-dibutylphosphinoethane, 1,1,2,2-dibutylphosphinopropane, 1,1,2,2-dibutylphosphinbutane, 1,1-diphosfinan, 1,4-dimethyl-1,4-diphosphane, 1,3-dimethylphosphorinan, 1,4-dimethylphosphorinan, 8-methyl-8-phosphinovicyclooctane, 4-methyl-4-phosphatetracyclooctane, 1-methylphosphoran, 1-methylphosphonan, etc. These polyfunctional phosphines may be used individually or as a mixture of two or more.

[0027] Furthermore, it is also preferable that these organic phosphines have substituents such as hydroxyl groups, carboxylic acid groups, amino groups, and thiol groups, thereby having one or more heteroatoms such as oxygen atoms, nitrogen atoms, and sulfur atoms. Examples of such organic phosphines include alkyl phosphines having heteroatoms such as tris(2-carboxyethyl)phosphine, 3-hydroxyphenyldiphenylphosphine, and aryl phosphines having heteroatoms such as 2-(diphenylphosphino)benzoic acid. These heteroatom-containing organic phosphines may be used individually or in combination of two or more types.

[0028] The ruthenium-based catalyst used in the present invention may contain two or more of these organophosphines, and there are no particular restrictions on the combination of the two or more organophosphines. However, it is preferable that at least one of the organophosphines is an alkylphosphine, and at least one is an arylphosphine. Furthermore, it is preferable that at least one is a heteroatom-containing phosphine. The heteroatom-containing phosphine may also be an alkylphosphine and / or an arylphosphine.

[0029] Preferred combinations of organophosphines include the following: Combinations of trialkylphosphines such as trioctylphosphine and tri-n-butylphosphine with heteroatom-containing arylphosphines such as 3-hydroxyphenyldiphenylphosphine and 2-(diphenylphosphino)benzoic acid. Combinations of alkylphosphines having heteroatoms, such as tris(2-carboxyethyl)phosphine, and arylphosphines, such as triphenylphosphine.

[0030] The amount of these organic phosphines used is typically in the range of 0.1 to 1000 moles, preferably 1 to 100 moles, of two or more organic phosphines in total, per mole of ruthenium.

[0031] Furthermore, in order to more effectively obtain the effects of the present invention by using two or more types of organic phosphines, for example, when using two types of organic phosphines, such as organic phosphine A and organic phosphine B, it is preferable that the phosphine equivalent ratio of organic phosphine A to organic phosphine B be in the range of organic phosphine A:organic phosphine B = 1:0.5 to 2, and particularly 1:0.7 to 1.3. Even when using three or more types of organic phosphines, it is preferable that the ratio of the sum of two or more of them to the remaining one type falls within the above range.

[0032] These organic phosphines can be supplied to the reaction system either on their own or in the form of complexes with ruthenium.

[0033] (Conjugate bases of acids with a pKa less than 2) Conjugate bases of acids with a pKa less than 2 act as additional accelerators to ruthenium in the ruthenium-based catalyst used in the present invention. By using conjugate bases of acids with a pKa less than 2, the hydrogenation reaction can proceed under relatively mild conditions, taking advantage of the benefits of ruthenium, the main component. In particular, improvements in hydrogenation catalyst activity, activity stability, and selectivity of the target product can be achieved.

[0034] The conjugate base of an acid with a pKa less than 2 can be any conjugate base that generates such a conjugate base during catalyst preparation or in the reaction system, and the supply form can be a Brønsted acid with a pKa less than 2 or various salts of such an acid.

[0035] Specifically, examples include Brønsted acids such as inorganic acids like nitric acid, perchloric acid, borofluoric acid, hexafluorophosphate, and fluorosulfonic acid, and organic acids such as trichloroacetic acid, dichloroacetic acid, trifluoroacetic acid, methanesulfonic acid, dodecylsulfonic acid, octadecylsulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and sulfonated styrene-divinylbenzene copolymer, or alkali metal salts, alkaline earth metal salts, ammonium salts, and silver salts of these acids. Furthermore, these acids can be added in the form of acid derivatives, which are thought to produce conjugate bases in the reaction system. For example, similar effects can be expected when added to the reaction system in the form of acid halides, acid anhydrides, esters, acid amides, etc.

[0036] In the present invention, the amount of conjugate base used for an acid with a pKa less than 2 is typically in the range of 0.01 to 1000 moles, preferably 0.1 to 100 moles, per mole of ruthenium.

[0037] (neutral ligand) The ruthenium-based catalyst used in this invention may further contain a neutral ligand. Such neutral ligands include hydrogen; olefins such as ethylene, propylene, butene, cyclopentene, cyclohexene, butadiene, cyclopentadiene, cyclooctadiene, and norvonadiene; oxygen-containing compounds such as carbon monoxide, diethyl ether, anisole, dioxane, tetrahydrofuran, acetone, acetophenone, benzophenone, cyclohexanone, propionic acid, caproic acid, butyric acid, benzoic acid, ethyl acetate, allyl acetate, benzyl benzoate, benzyl stearate, and valerolactone; nitrous oxide, acetonitrile, propionitrile, benzonitrile, cyclohexyl isonitrile, butylamine, aniline, toluidine, triethylamine, pyrrole, pyridine, N-methylformamide, acetamide, and 1,1,3,3-tetranitrile. Examples include nitrogen-containing compounds such as tramethylurea, N-methylpyrrolidone, caprolactam, and nitromethane; sulfur-containing compounds such as carbon disulfide, n-butyl mercaptan, thiophenol, dimethyl sulfide, dimethyl disulfide, thiophene, dimethyl sulfoxide, and diphenyl sulfoxide; and phosphorus-containing compounds other than organic phosphines, such as tributylphosphine oxide, ethyl diphenylphosphine oxide, triphenylphosphine oxide, diethylphenyl phosphine, diphenylethyl phosphine, diphenylmethylphosphonate, O,O-dimethylmethylphosphonothiolate triethyl phosphine, triphenyl phosphine, triethyl phosphine, triphenyl phosphine, and hexamethylphosphoric triamide. These may be used individually or in combination of two or more.

[0038] As described above, neutral ligands exist, and in the method for producing lactones according to the present invention, the raw material compound, reaction product, reaction solvent, etc., may also act simultaneously as neutral ligands.

[0039] (Method for producing ruthenium-based catalysts) The ruthenium-based catalyst used in the present invention may be synthesized and isolated in advance and then used (for example, J. Organometal. Chem. 77 C-31 ('74)), or the precursors thereof may be separately added to the reaction system to prepare the ruthenium-based catalyst in the reaction system and then used.

[0040] As a method for synthesizing the ruthenium-based catalyst used in the present invention, for example, M is added to a halogen-containing ruthenium compound such as cyclooctadiene dichlororuthenium or dichlorotris triphenylphosphine ruthenium. + Y - (M represents an alkali metal, an alkaline earth metal, a metal of Group 11 of the periodic table, or an onium cation, and Y represents a conjugate base of an acid having a pKa smaller than 2) can be synthesized by treatment with a salt such as (for example, Inorg. Chem. 17 1965 ('78), see the following formula [1]).

[0041]

Chemical formula

[0042] (In the formula, X represents a halogen such as chlorine or bromine, L represents an organic phosphine or a neutral ligand. M and Y have the same meanings as defined above.)

[0043] <Method for producing lactones> In the method for producing lactones of the present invention, the hydrogenation reaction of the raw material compound can be carried out in the absence of a solvent, that is, using the raw material compound itself as a solvent, or a solvent other than the raw material compound can also be used.

[0044] Examples of such solvents include ethers such as diethyl ether, anisole, tetrahydrofuran, ethylene glycol dimethyl ether, and dioxane; ketones such as acetone, methyl ethyl ketone, and acetophenylone; alcohols such as methanol, ethanol, n-butanol, benzyl alcohol, phenol, ethylene glycol, and diethylene glycol; carboxylic acids such as formic acid, acetic acid, propionic acid, and toluic acid; esters such as methyl acetate, n-butyl acetate, and benzyl benzoate; aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and tetralin; aliphatic hydrocarbons such as n-hexane, n-octane, and cyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, and chlorobenzene; and nitromethane and nitrobenzene. Examples of compounds include: carboxylic acid amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; hexamethylphosphate triamide; other amides such as N,N,N',N'-tetraethylsulfamide; ureas such as N,N'-dimethylimidazolidone and N,N,N,N-tetramethylurea; sulfones such as dimethyl sulfone and tetramethylene sulfone; sulfoxides such as dimethyl sulfoxide and diphenyl sulfoxide; lactones such as γ-butyrolactone and ε-caprolactone; polyethers such as tetraglyceride (tetraethylene glycol dimethyl ether) and 18-crown-6; nitriles such as acetonitrile and benzonitrile; carbonate esters such as dimethyl carbonate and ethylene carbonate, etc. These solvents may be used individually or as a mixture of two or more.

[0045] To carry out the hydrogenation reaction according to the method of the present invention, the raw material compound, catalyst component, and optionally a solvent are charged into a reaction vessel, and hydrogen is introduced to it. The hydrogen may be diluted with a reaction-inert gas such as nitrogen or carbon dioxide.

[0046] The reaction temperature is typically 50-250°C, preferably 100-200°C. The hydrogen partial pressure in the reaction system is typically 0.1-100 kg / cm³. 2 Preferably 1 to 10 kg / cm³2 Therefore, it is possible to carry out the process under lower or higher pressures, but this is not industrially advantageous.

[0047] The reaction can be carried out in either batch or continuous mode. In the batch mode, the reaction time is typically 1 to 20 hours.

[0048] The target lactones can be recovered from the reaction product by conventional separation and purification methods such as distillation and extraction. Furthermore, the distillation residue can be recycled back into the reaction system as a catalytic component. [Examples]

[0049] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples unless it exceeds its gist. The various manufacturing conditions and evaluation result values ​​in the following examples have meaning as preferred upper or lower limits in embodiments of the present invention, and the preferred range may be defined by a combination of the aforementioned upper or lower limits and the values ​​of the following examples or the values ​​of the examples themselves.

[0050] In the following examples and comparative examples, trioctylphosphine (hereinafter abbreviated as "P(Oct)3") and 3-hydroxyphenyldiphenylphosphine (hereinafter abbreviated as "L3") were used as organophosphines, and γ-butyrolactone (hereinafter abbreviated as "GBL") was produced by hydrogenation of succinic anhydride (hereinafter abbreviated as "SAH") according to the following reaction formula.

[0051] [ka]

[0052] [ka]

[0053] [Example 1] 5.0 mg of ruthenium acetylacetonate (Ru: 0.0125 mmol), 25.5 mg of P(Oct)3 (0.06875 mmol), 15.7 mg of L3 (0.05625 mmol), 9.5 mg of p-toluenesulfonic acid monohydrate (0.05 mmol), and 6.0 mL of tetraglyme (TEGM) were charged into a 30 mL glass test tube and heat-treated under an argon atmosphere. This catalyst solution was transferred to a stainless steel reactor, and 0.60 g of succinic anhydride (SAH) (6.0 mmol) was added as a starting compound. The reaction was carried out by heating at 170 °C for 3 hours at a hydrogen gauge pressure of 0.80 MPa.

[0054] The GBL yield was determined by gas chromatography analysis of the resulting reaction product. The yield of succinic acid (SA), a by-product, was determined by high-performance liquid chromatography analysis of the reaction product. These results are shown in Table 1. In this Example 1, the amounts of P(Oct)3 and L3 used were 5.5 moles and 4.5 moles respectively (totaling 10 moles) per mole of Ru.

[0055] [Examples 2-4] The hydrogenation reaction was carried out in the same manner as in Example 1, except that the amounts of P(Oct)3 and L3 used were changed so that they corresponded to the molar amounts shown in Table 1 per mole of Ru. The GBL yield and SA yield were determined in the same manner, and the results are shown in Table 1.

[0056] [Comparative Example 1] In Example 1, the hydrogenation reaction was carried out in the same manner as in Example 1, except that only P(Oct)3 was added as the organic phosphine in the amount shown in Table 1 per mole of Ru. The GBL yield and SA yield were determined in the same manner, and the results are shown in Table 1.

[0057] [Comparative Example 2] In Example 1, the hydrogenation reaction was carried out in the same manner as in Example 1, except that only L3 was added as the organic phosphine in the amount shown in Table 1 per mole of Ru. The GBL yield and SA yield were determined in the same manner, and the results are shown in Table 1.

[0058] [Table 1]

[0059] From Table 1, the following can be seen. In Comparative Examples 1 and 2, where only one type of organic phosphine was used as the ruthenium-based catalyst, the GBL yields were 50% (Comparative Example 1) and 36% (Comparative Example 2), which are not satisfactory yields. In contrast, in Examples 1-4, which used two types of organic phosphines in the ruthenium-based catalyst, the GBL yield was improved, and by optimizing the ratio of the two types of organic phosphines used, an extremely high yield of up to 67% was achieved.

Claims

1. A method for producing lactones by hydrogenating one or more substances selected from the group consisting of dicarboxylic acids, dicarboxylic acid anhydrides, and dicarboxylic acid esters in the presence of a catalyst, wherein the catalyst used is a ruthenium-based catalyst containing the following (1) to (3): A method for producing lactones, wherein one of the two types of organic phosphines described in (2) below is a trialkylphosphine having three alkyl groups with 1 to 12 carbon atoms, and the other is a triarylphosphine. (1) Ruthenium (2) Two types of organophosphines (3) Conjugate base of an acid with a pKa less than 2

2. The method for producing lactones according to claim 1, wherein one of the two types of organic phosphines is an organic phosphine having a substituent containing an oxygen atom, a nitrogen atom, or a sulfur atom.

3. The method for producing lactones according to claim 1 or 2, wherein when the two types of organic phosphines are organic phosphine A and organic phosphine B, the phosphine equivalent ratio of organic phosphine A to organic phosphine B is organic phosphine A:organic phosphine B = 1:0.5 to 2.

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