Catalyst and method for producing lactone compounds

Abstract

Provided is a catalyst that does not require raw materials to be processed in advance, and that can be synthesized in one pod.　A catalyst according to the present disclosure produces lactone compounds from hydroxycarboxylic acids, and is characterized by containing a titanium compound and a polyhydric alcohol and / or a polyhydric amine. Furthermore, the catalyst preferably contains 0.05 mol or more of the polyhydric alcohol and / or the polyhydric amine with respect to 1 mol of the hydroxycarboxylic acids. Furthermore, a cyclic ketone may be used as a starting material of the hydroxycarboxylic acids.

Description

Catalyst, Method for Producing Lactone Compound

[0001] The present disclosure relates to a catalyst and a method for producing a lactone compound. The present application claims priority from Japanese Patent Application No. 2025-053736 filed on March 27, 2025, the content of which is incorporated herein by reference.

[0002] Lactone compounds including ε-caprolactone are widely used as raw materials for polymers of polyester polyols for polyurethane synthesis and other molding materials.

[0003] As a method for producing such a lactone compound, dehydrated 6-hydroxycaproic acid is esterified and purified with an alcohol and sulfuric acid to obtain a hydroxycaproic acid ester, and then the hydroxycaproic acid ester is added with Ti(OiPr) ４ and 1,6-hexanediol, followed by reaction and purification (reactive distillation) to obtain the lactone compound in a high yield, which is known (Patent Document 1).

[0004] Japanese National Publication No. 2000-506134

[0005] However, in the invention described in Patent Document 1, it is necessary to suppress the generation of water as a by-product, which requires a prior dehydration treatment and an esterification step of the substrate. In addition, since the above steps are required, operation in two pots is essential, and it is also necessary to provide two purification steps, which leads to the problem that the operation becomes complicated.

[0006] Accordingly, an object of the present disclosure is to provide a catalyst that does not require prior raw material treatment and enables synthesis in one pot.

[0007] As a result of intensive studies conducted by the inventors of the present disclosure to solve the above problems, they have found that a catalyst containing a titanium compound and a polyhydric alcohol and / or a polyhydric amine in a specific ratio does not require prior raw material treatment and can be synthesized in one pot. The present disclosure relates to what has been completed based on these findings.

[0008] In other words, the present disclosure provides a catalyst used for producing lactone compounds from hydroxycarboxylic acids, comprising a titanium compound and a polyhydric alcohol and / or a polyhydric amine, wherein the polyhydric alcohol and / or the polyhydric amine is present in a quantity of 0.05 moles or more per mole of the hydroxycarboxylic acid.

[0009] The above-mentioned hydroxycarboxylic acids may also be derived from cyclic ketones.

[0010] Furthermore, this disclosure provides a method for producing lactone compounds from the above-mentioned hydroxycarboxylic acids, wherein the hydroxycarboxylic acids are reacted with a polyhydric alcohol and / or polyhydric amine and a titanium compound in the presence of 0.05 moles or more of the polyhydric alcohol and / or polyhydric amine per mole of the hydroxycarboxylic acids.

[0011] In the above method for producing the lactone compound, the hydroxycarboxylic acids may be derived from cyclic ketones as starting materials.

[0012] In the above method for producing the lactone compound, it is preferable that the water content is 0.1 parts by mass or more per 100 parts by mass of the hydroxycarboxylic acid during the reaction.

[0013] Furthermore, it is preferable that the above-mentioned hydroxycarboxylic acids include a hydroxycarboxylic acid.

[0014] The above hydroxycarboxylic acids preferably include polymers of hydroxycarboxylic acids.

[0015] In the method for producing the above lactone compound, it is preferable to carry out the reaction in the presence of a polyhydric alcohol.

[0016] The polyhydric alcohol is preferably a glycol.

[0017] Furthermore, it is preferable that the above-mentioned polyhydric alcohol and / or the above-mentioned polyhydric amine and the above-mentioned titanium compound are reusable.

[0018] The catalyst of this disclosure does not require prior treatment of raw materials and can be synthesized in a single pod. Furthermore, because it is hydrolysis resistant, it can be suitably used even in the presence of water. In addition, when polyhydric alcohols and / or polyhydric amines and titanium compounds are reused, it can be made cost-effective.

[0019] [Catalyst] The catalyst of this disclosure is a catalyst used for producing lactone compounds from hydroxycarboxylic acids, and comprises a titanium compound and a polyhydric alcohol and / or a polyhydric amine, wherein the catalyst contains 0.05 moles or more of the polyhydric alcohol and / or the polyhydric amine per mole of the hydroxycarboxylic acids. By including 0.05 moles or more of the polyhydric alcohol and / or the polyhydric amine per mole of hydroxycarboxylic acids, deactivation of the titanium compound by hydrolysis can be suppressed, and catalytic activity can be exhibited even with hydroxycarboxylic acids that have not undergone prior treatment steps such as prior esterification and dehydration, thus enabling the production of lactone compounds in a single pod. In this specification, the catalyst may be referred to as "the catalyst of this disclosure".

[0020] The catalyst of this disclosure can be used to produce lactone compounds, and after separation and purification, hydroxycarboxylic acids can be added again to produce lactone compounds. In other words, the catalyst of this disclosure can be reused, and the cost of producing lactone compounds can be reduced. In particular, since the titanium compound has hydrolysis resistance due to the coordination of the polyhydric alcohol and / or the polyhydric amine, it is less likely to be deactivated and can be used repeatedly. Specifically, it is preferable that it can be used repeatedly two or more times, and more preferably three or more times.

[0021] The yield of the lactone compound produced by the catalyst of this disclosure is preferably 25% or more, more preferably 30% or more, and even more preferably 35% or more. There is no particular upper limit, but it may be 100%. The above range for the yield of the lactone compound after the reaction facilitates the production of the lactone compound in high yield after the purification step. In this disclosure, the lactone compound includes a cyclized product of the elemental hydroxycarboxylic acid used as a raw material and a cyclized product of the dimer of the above hydroxycarboxylic acid.

[0022] (Titanium Compound) The catalyst of this disclosure comprises a titanium compound. The titanium compound has the function of cyclizing the hydroxycarboxylic acid. It is presumed that by using the titanium compound, a complex can be formed with the polyhydric alcohol and / or polyhydric amine described below, thereby maintaining catalytic activity while exhibiting hydrolysis resistance. Only one titanium compound may be used, or two or more may be used.

[0023] Examples of the above-mentioned titanium compounds include titanium oxides, titanium hydroxides, titanium organic compounds, and titanium halides. Among these, titanium organic compounds are preferred, and alkoxytitanium is preferred among the titanium organic compounds. Examples of the above-mentioned alkoxytitanium include tetraethyl orthotitanate, tetraisopropyl orthotitanate, tetrabutyl orthotitanate, and ethylhexyl orthotitanate.

[0024] The properties of the above-mentioned titanium compound include dissolved state and solid state. Specifically, the solid state may be a titanium compound dispersed as bulk or supported on a carrier. The properties of the above-mentioned titanium compound are preferably in a dissolved state in order to efficiently form complexes coordinating with the polyhydric alcohol and / or polyhydric amine described below.

[0025] Furthermore, it is preferable that the above titanium compound forms a complex with the polyhydric alcohol and / or polyhydric amine described below. Specifically, when using the above titanium compound, it is preferable that 1 to 4 molecules of the polyhydric alcohol and / or polyhydric amine described below coordinate to the 6 positions, more preferably 2 to 4 molecules coordinate to the 6 positions, and even more preferably 2 molecules coordinate to the 6 positions. By forming the above complex, the above titanium compound can easily exhibit hydrolysis resistance.

[0026] Furthermore, the content of the titanium compound is preferably 0.001 moles or more, more preferably 0.002 moles or more, and even more preferably 0.003 moles or more, per mole of the hydroxycarboxylic acid. By having a titanium compound content of 0.001 moles or more, the catalytic activity can be fully exhibited. There is no particular upper limit, but for example, it is preferably 1 mole or less, more preferably 0.5 moles or less, and even more preferably 0.1 moles or less.

[0027] Furthermore, the content of the titanium compound is preferably 0.002 moles or more, more preferably 0.004 moles or more, and even more preferably 0.006 moles or more, per mole of the polyhydric alcohol and / or polyhydric amine described below. There is no particular upper limit, but for example, it is preferably 1 mole or less, more preferably 0.5 moles or less, and even more preferably 0.1 moles or less.

[0028] (Polyhydric alcohols and / or polyhydric amines) The catalyst of this disclosure contains polyhydric alcohols and / or polyhydric amines. It is presumed that by including the above polyhydric alcohols and / or polyhydric amines, a complex is formed while the polyhydric alcohols and / or polyhydric amines coordinate to the titanium compound, thereby suppressing the coordination of water molecules to the titanium compound and stabilizing the structure of the titanium compound. Furthermore, it is presumed that by covering the titanium compound with the bulky structure of the polyhydric alcohols and / or polyhydric amines, contact between the hydrated titanium compounds is suppressed, and hydrolysis resistance can be exhibited. Only one type of polyhydric alcohol and / or polyhydric amine may be used, or two or more types may be used.

[0029] The polyhydric alcohol is preferably a compound having a higher boiling point than the lactone compound. Specifically, examples include glycols such as 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, butylethylpropanediol, neopentyl glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol, as well as trimethylolpropane and glycerin. Among these, the polyhydric alcohol is preferably a glycol, and among the glycols, ethylene glycols such as ethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol are preferred, with triethylene glycol and tetraethylene glycol being particularly preferred.

[0030] Examples of the polyhydric amines mentioned above include aliphatic polyamines such as ethylenediamine, diethylenetriamine, and triethylenetetraamine.

[0031] Furthermore, the above-mentioned polyhydric alcohols and / or polyhydric amines also include compounds having one or more hydroxyl groups and one or more amino groups. Examples of compounds having one or more hydroxyl groups and one or more amino groups include aliphatic amino alcohols such as methanolamine, ethanolamine, propanolamine, butanolamine, diisopropanolamine, and 1-amino-2,3-propanediol.

[0032] Furthermore, the content of the polyhydric alcohol and / or polyhydric amine is 0.05 moles or more per mole of the hydroxycarboxylic acid, preferably 0.1 moles or more, more preferably 0.2 moles or more, and even more preferably 0.5 moles or more. A content of 0.05 moles or more of the polyhydric alcohol and / or polyhydric amine facilitates the production of lactone compounds. While there is no particular upper limit, it is preferably 5 moles or less. Also, when lactic acid is used as the hydroxycarboxylic acid, the upper limit is preferably 0.25 moles or less, and may be 0.15 moles or less.

[0033] [Method for Producing Lactone Compounds] Another embodiment of the present disclosure is a method for producing lactone compounds. The above method for producing lactone compounds is a method for producing lactone compounds from hydroxycarboxylic acids, and involves reacting the hydroxycarboxylic acids with a polyhydric alcohol and / or polyhydric amine and a titanium compound in the presence of a polyhydric alcohol and / or polyhydric amine at a rate of 0.05 moles or more per mole of hydroxycarboxylic acids. The presence of 0.05 moles or more of the polyhydric alcohol and / or polyhydric amine per mole of hydroxycarboxylic acids suppresses the deactivation of the titanium compound by hydrolysis, and allows for one-pot synthesis by omitting prior treatment steps such as prior esterification and dehydration. Furthermore, even if the raw materials produced by fermentation contain water, the polyhydric alcohol and / or polyhydric amine and the titanium compound can be repeatedly used. In this specification, the above method for producing lactone compounds may be referred to as "the method for producing lactone compounds of the present disclosure."

[0034] (Hydroxycarboxylic acids) The above-mentioned hydroxycarboxylic acids are used as substrates in the method for producing the lactone compound of this disclosure. The above-mentioned hydroxycarboxylic acids may be added directly as substrates, or hydroxycarboxylic acids produced as by-products when producing a lactone compound using a cyclic ketone as a starting material may be used as substrates. Specifically, when synthesizing a lactone compound using a cyclic ketone as a starting material, hydroxycarboxylic acids produced by the hydrolysis of the lactone compound may be used as substrates. Note that only one type of substrate may be used, or two or more types may be used.

[0035] <Cylindrical Ketones> Examples of cyclic ketones include compounds that bond with carbon atoms constituting a carbonyl group (-C(=O)-) to form an alicyclic ring. Furthermore, it is sufficient for one or more carbonyl groups to be present in the cyclic ketone, and preferably one carbonyl group is present in the cyclic ketone. The alicyclic rings include monocyclic hydrocarbon rings and polycyclic hydrocarbon rings (including spirohydrocarbon rings, ring-aggregated hydrocarbon rings, bridged-ring hydrocarbon rings, fused-ring hydrocarbon rings, and bridged-fused-ring hydrocarbon rings).

[0036] Examples of the monocyclic hydrocarbon rings mentioned above include cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, etc. ３－１２ Cycloalkane rings; such as cyclopentene and cyclohexene. ３－１２ Examples include cycloalkenes.

[0037] Examples of the above spirohydrocarbon rings include spiro[4,4]nonane, spiro[4,5]decane, spirobicyclohexane, etc. ５－１６ Examples include spirohydrocarbon rings.

[0038] Examples of the above-mentioned ring-assembled hydrocarbon rings include C such as bicyclohexane. ５－１２ Examples include ring-assembled hydrocarbon rings containing multiple cycloalkane rings.

[0039] Examples of the bridged cyclic hydrocarbon ring include bicyclic hydrocarbon rings such as pinane, bornane, norpinane, norbornane, norbornene, bicycloheptane, bicycloheptene, bicyclooctane (bicyclo[2.2.2]octane, bicyclo[3.2.1]octane, etc.); tricyclic hydrocarbon rings such as homobredane, adamantane, tricyclo[5.2.1.0 ２，６ decane, tricyclo[4.3.1.12,5]undecane; and tetracyclic hydrocarbon rings such as tetracyclo[4.4.0.1 ２，５ .1 ７，１０ dodecane, perhydro-1,4-methano-5,8-methanonaphthalene, and the like.

[0040] Examples of the fused cyclic hydrocarbon ring include fused rings formed by fusing a plurality of 5- to 8-membered cycloalkane rings, such as perhydronaphthalene (decalin), perhydroanthracene, perhydrophenanthrene, perhydroacenaphthene, perhydrofluorene, perhydroindene, and perhydrophenalene.

[0041] Examples of the bridged fused cyclic hydrocarbon ring include dimers of dienes (for example, dimers of cycloalkadienes such as cyclopentadiene, cyclohexadiene, and cycloheptadiene), and hydrogenated products thereof.

[0042] The alicyclic ring may have various substituents [for example, a halogen atom, an oxo group, a hydroxyl group, a substituted oxy group (for example, an alkoxy group, an aryloxy group, an aralkyloxy group, an acyloxy group, etc.), a substituted or unsubstituted carbamoyl group, a cyano group, a nitro group, a substituted or unsubstituted amino group, a sulfo group, a heterocyclic group, etc.]. Further, the alicyclic ring may have an aromatic or non-aromatic heterocyclic ring fused thereto.

[0043] Specific examples of the above cyclic ketone compounds include monocyclic ketone compounds such as cyclopropanone, cyclopentanone, methylcyclopentanone, n-pentylcyclopentanone, cyclohexanone, methylcyclohexanone, t-butylcyclohexanone; and bicyclic compounds such as bicyclo[2.1.0]pentan-5-one, bicyclo[3.1.0]hexan-6-one, bicyclo[4.1.0]heptan-7-one, and adamantanone.

[0044] When using the above cyclic ketone, it is preferable to add hydrogen peroxide together. Pure hydrogen peroxide may be used as the hydrogen peroxide, but from the viewpoint of handleability, it is usually used in a form diluted with an appropriate solvent (e.g., water) (e.g., 5 to 70 wt% aqueous hydrogen peroxide). The amount of hydrogen peroxide used is preferably 0.1 to 10 mol, more preferably 0.15 to 5 mol, particularly preferably 0.2 to 3 mol, per 1 mol of the cyclic ketone compound.

[0045] The above hydroxycarboxylic acids refer to hydroxycarboxylic acids and compounds that can generate hydroxycarboxylic acids during the reaction, and examples thereof include hydroxycarboxylic acids, modified hydroxycarboxylic acids, and multimers thereof (multimers of hydroxycarboxylic acids (polycaprolactone, etc.), multimers of the above modified products).

[0046] The number average molecular weight in terms of standard polystyrene of the multimer of the above hydroxycarboxylic acid is, for example, preferably 200 to 200000, more preferably 500 to 100000, still more preferably 1000 to 5000. The number average molecular weight can be measured, for example, by gel permeation chromatography (GPC).

[0047] Examples of the above-mentioned hydroxycarboxylic acid include compounds having one or more hydroxyl groups and one or more carboxyl groups, and from the viewpoint of efficiently producing lactone compounds, compounds having one hydroxyl group and one carboxyl group are preferred. Furthermore, the number of carbon atoms is preferably 2 to 10, and more preferably 3 to 8. Specific examples of the above-mentioned hydroxycarboxylic acid include glycolic acid, lactic acid, 3-hydroxypropanoic acid, γ-hydroxybutyric acid, 5-hydroxyvaleric acid, 6-hydroxyhexanoic acid, and 7-hydroxyheptanoic acid. Among these, lactic acid and 6-hydroxyhexanoic acid are particularly preferred.

[0048] Furthermore, the hydroxycarboxylic acid may be a chemically synthesized hydroxycarboxylic acid or a hydroxycarboxylic acid produced by fermentation. In the method for producing the lactone compound of this disclosure, even hydroxycarboxylic acids produced by fermentation that usually contain a large amount of water can be suitably used.

[0049] The content of the above-mentioned hydroxycarboxylic acid may be 0% by mass of the total amount of hydroxycarboxylic acids (100% by mass), but it is preferably 20% by mass or more, more preferably 80% by mass or more, and even more preferably 100% by mass. In other words, the entire amount of hydroxycarboxylic acids may be hydroxycarboxylic acid.

[0050] Furthermore, one type of hydroxycarboxylic acid may be used, or two or more types may be used.

[0051] The above-mentioned hydroxycarboxylic acid polymer may be an oligomer consisting of a single hydroxycarboxylic acid, or an oligomer containing different hydroxycarboxylic acids. Furthermore, the above-mentioned polymer is preferably an oligomer with a degree of polymerization of 100 or less, more preferably 50 or less, and even more preferably 10 or less. Having a degree of polymerization of 100 or less facilitates cyclization reactions to lactone compounds.

[0052] The content of the hydroxycarboxylic acid polymer may be 100% by mass of the total amount of hydroxycarboxylic acids (100% by mass) (i.e., the entire amount of hydroxycarboxylic acids may be the polymer), preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less. Furthermore, there is no particular lower limit, but the polymer content may be 0% by mass or 10% by mass or more.

[0053] Examples of modified hydroxycarboxylic acids include methyl esters, ethyl esters, and acetate esters of the above-mentioned hydroxycarboxylic acids. Furthermore, examples of polymers of the above-mentioned modified products include methyl esters, ethyl esters, and acetate esters of the polymers of the hydroxycarboxylic acids.

[0054] Preferably, the above-mentioned hydroxycarboxylic acids do not substantially contain modified forms of the above-mentioned hydroxycarboxylic acids or their polymers. In the method for producing lactone compounds of this disclosure, since the decrease in activity due to the by-product water is suppressed as described above, catalytic activity can be maintained even if the prior modification step is omitted. In this specification, "substantially contained" means not actively incorporating unless it is unavoidable.

[0055] Furthermore, the method for producing the lactone compound according to this disclosure preferably involves reacting the titanium compound, the polyhydric alcohol and / or the polyhydric amine, etc., in a reaction solution to which the above-mentioned hydroxycarboxylic acids are added. The above-mentioned raw material solution may or may not contain water. When the above-mentioned raw material solution contains water, the amount of water contained is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and even more preferably 0.3 parts by mass or more, based on the total amount of hydroxycarboxylic acids (100 parts by mass). In the method for producing the lactone compound according to this disclosure, even if the water content is 0.1 parts by mass or more, the hydrolysis of the titanium compound by water molecules contained in the raw materials and water synthesized as a byproduct during the synthesis of the lactone compound can be suppressed, and catalytic activity can be maintained. Furthermore, the upper limit is preferably 200 parts by mass or less.

[0056] Furthermore, the above-mentioned raw material liquid may contain components that are by-products of the hydroxycarboxylic acid produced by fermentation. Examples of such by-products include sugars, amino acids, and dicarboxylic acids.

[0057] Furthermore, the method for producing the lactone compound of this disclosure may include other components besides the hydroxycarboxylic acids, titanium compounds, polyhydric alcohols, polyhydric amines, and by-products of fermentation production. Examples of these other components include solvents other than the polyhydric alcohols and / or polyhydric amines, catalysts other than those of this disclosure, organic acids such as carboxylic acids, and boiling chips. It is also preferable that these other components are substantially absent. Specifically, the content (amount added) of these other components is preferably 5% by mass or less, more preferably 1% by mass or less, and may even be 0% by mass, based on 100% by mass of the total amount of the reaction solution containing the hydroxycarboxylic acids.

[0058] The content of the above hydroxycarboxylic acids is preferably 15 to 80% by mass, more preferably 20 to 75% by mass, and even more preferably 25 to 70% by mass, based on 100% by mass of the total amount of the reaction solution.

[0059] The content of the above-mentioned polyhydric alcohol and / or polyhydric amine is preferably 30 to 70% by mass, and more preferably 35 to 65% by mass, based on 100% by mass of the total amount of the reaction solution.

[0060] Furthermore, the content of each component (hydroxycarboxylic acids, water, titanium compounds, polyhydric alcohols, polyhydric amines, etc.) in the reaction solution is preferably within the above range at at least one point during the reaction, and may be the amount at the start of the reaction. Also, when hydroxycarboxylic acids are continuously supplied to the reactor and lactone compounds are continuously produced, the above content may remain within the above range at all times.

[0061] In the method for producing lactone compounds according to this disclosure, it is preferable that the cyclization reaction of the hydroxycarboxylic acids used as raw materials proceeds in the liquid phase (reaction solution).

[0062] The reactor used for producing the lactone compound described above is not particularly limited, but it uses at least one bottom and a separation device that allows for partial circulation of the liquid product. As the separation device, for example, a distillation column equipped with a reaction vessel, or a mixing vessel equipped with a falling thin-film distiller can be used.

[0063] Furthermore, it is preferable that the lactone compound is synthesized in a single pod in the method for producing the lactone compound of this disclosure. Since the method for producing the lactone compound of this disclosure uses a hydrolysis-resistant compound as a catalyst, it is not necessary to remove water, which is normally produced as a byproduct, in advance, and the compound can be produced in a single pod at low cost.

[0064] In the method for producing the lactone compound according to this disclosure, the titanium compound and a polyhydric alcohol and / or polyhydric amine may be added to the reaction vessel first, followed by the addition of hydroxycarboxylic acids, or each material may be added simultaneously. Before adding the hydroxycarboxylic acids, it is preferable to mix the titanium compound with the polyhydric alcohol and / or polyhydric amine and stir in order to form a hydrolysis-resistant complex. The stirring time is preferably 10 minutes to 3 hours, and more preferably 20 minutes to 2 hours. The temperature during mixing is preferably room temperature.

[0065] After adding the above-mentioned hydroxycarboxylic acids, it is preferable to carry out the reaction under heating to promote the cyclization reaction. The reaction temperature is preferably 80 to 300°C, more preferably 100 to 250°C. The reaction pressure may be carried out at atmospheric pressure, but it is preferable to reduce the pressure to 700 Torr or less, more preferably 350 Torr or less, even more preferably 60 Torr or less, and particularly preferably 10 Torr or less. There is no particular lower limit, but it may be 0.1 Torr or more. Furthermore, the reaction time is preferably 30 minutes to 30 hours, for example.

[0066] Furthermore, various components such as the hydroxycarboxylic acids, titanium compounds, polyhydric alcohols and / or polyhydric amines, and water may be added during the reaction.

[0067] Furthermore, water may be added to the reaction solution before or during the reaction, and its content may be 0.1 parts by mass or more relative to the total amount of hydroxycarboxylic acids (100 parts by mass). Preferably, the upper limit is 200 parts by mass or less. If water is already present in the reaction solution, it is preferable that the total amount, including any additionally added water, satisfies the above range.

[0068] Furthermore, the conversion rate of the hydroxycarboxylic acids in the method for producing the lactone compound according to this disclosure is preferably 95% or higher, more preferably 97% or higher, and even more preferably 99% or higher. A conversion rate of 95% or higher for the hydroxycarboxylic acids makes it easy to produce the lactone compound in high yield.

[0069] The yield of the lactone compound after the cyclization reaction is preferably 25% or more, more preferably 30% or more, and even more preferably 35% or more. There is no particular upper limit, but it may be 100%. Having the yield of the lactone compound after the reaction within the above range facilitates the production of the lactone compound in high yield after the purification step.

[0070] Furthermore, the synthesized lactone compound is preferably separated and purified by known or conventional methods such as concentration, distillation, extraction, column chromatography, or a combination thereof. In particular, in the method for producing the lactone compound of this disclosure, it is preferable that the produced lactone compound is separated and purified by distillation.

[0071] The purity of the lactone compound after separation and purification is preferably 90% or higher, more preferably 95% or higher, even more preferably 99% or higher, and particularly preferably 99.8% or higher. The yield of the lactone compound after separation and purification is preferably 50% or higher, more preferably 60% or higher, and even more preferably 70% or higher. The above purity values ​​were calculated from the peak area of ​​gas chromatography.

[0072] Furthermore, in the method for producing the lactone compound of this disclosure, hydroxycarboxylic acids can be added again to the titanium compound and the polyhydric alcohol and / or polyhydric amine after the production, separation, and purification of the lactone compound, and the lactone compound can be produced in the manner described above. In other words, the titanium compound and the polyhydric alcohol and / or polyhydric amine can be reused, thereby reducing production costs. In particular, since the titanium compound has hydrolysis resistance due to the coordination of the polyhydric alcohol and / or polyhydric amine, it is less likely to be deactivated and can be used repeatedly. Specifically, it is preferable that it can be used repeatedly two or more times, and more preferably three or more times.

[0073] Each embodiment disclosed herein can be combined with any other features disclosed herein. Furthermore, each configuration and combination thereof in each embodiment is an example, and additions, omissions, and other modifications are permitted as appropriate, without departing from the spirit of this disclosure. This disclosure is not limited by the embodiments, but is limited only by the claims.

[0074] An embodiment of this disclosure will be described in more detail below based on examples.

[0075] Comparative Example 1: 11.8 g of tetraethylene glycol and 0.1 g of water were placed in a three-necked flask and stirred at room temperature for 1 hour. Then, 8.0 g of 6-hydroxyhexanoic acid was added as the substrate, the pressure was reduced to 40 Torr, and the temperature was raised to 200°C. After 3 hours, the reaction solution was prepared and analyzed by gas chromatography (product name "GC-2025", manufactured by Shimadzu Corporation, column "DB-5", inner diameter 0.53 mm, film thickness 1.5 μm, length 30 m, column temperature 135°C). The conversion rate was calculated from the decrease in peak area of ​​6-hydroxyhexanoic acid before and after the reaction, and the yield was calculated from the peak areas of the generated ε-caprolactone and caprolactone dimer relative to the peak area of ​​6-hydroxyhexanoic acid before the reaction.

[0076] Example 1: The reaction solution was prepared in the same manner as in Comparative Example 1, except that 0.0692 g of tetraisopropyl orthotitanate was added along with tetraethylene glycol and water. The solution was analyzed by gas chromatography, and the conversion rate and yield were calculated.

[0077] Example 2: The reaction solution was prepared in the same manner as in Comparative Example 1, except that 0.0798 g of tetrabutyl orthotitanate was added along with tetraethylene glycol and water. The solution was analyzed by gas chromatography, and the conversion rate and yield were calculated.

[0078] Example 3: The reaction solution was prepared in the same manner as in Comparative Example 1, except that 0.1408 g of tetrakis(2-ethylhexyl) orthotitanate was added along with tetraethylene glycol and water. The solution was analyzed by gas chromatography, and the conversion rate and yield were calculated.

[0079] Comparative Example 2: The reaction solution was prepared in the same manner as in Comparative Example 1, except that 0.1059 g of stannous octylate was added along with tetraethylene glycol and water. The solution was analyzed by gas chromatography, and the conversion rate and yield were calculated.

[0080] Comparative Example 3: 2.95 g of tetraethylene glycol and 0.1 g of water were charged into a three-necked flask and stirred at room temperature for 1 hour. Then, 5.4 g of lactic acid was added as the substrate, and after reducing the pressure to 310 Torr, the temperature was raised to 200°C while a portion of the reaction solution was distilled into a distillation flask to obtain the distillate. After 3 hours, the reaction solution and distillate were mixed to prepare a mixture, which was analyzed by gas chromatography (product name "GC-2025", manufactured by Shimadzu Corporation, column "DB-5", inner diameter 0.53 mm, film thickness 1.5 μm, length 30 m, column temperature 135°C). The conversion rate was calculated from the decrease in peak area of ​​lactic acid before and after the reaction, and the yield was calculated from the peak area of ​​the generated lactide relative to the peak area of ​​lactic acid before the reaction.

[0081] Example 4 A mixture was prepared by mixing the reaction solution and distillate in the same manner as in Comparative Example 3, except that 0.0694 g of tetraisopropyl orthotitanate was added along with tetraethylene glycol and water. The mixture was analyzed by gas chromatography under the same conditions as in Comparative Example 3, and the conversion rate and yield were calculated.

[0082] Comparative Example 4: 3.83 g of ethylene glycol and 0.13 g of water were charged into a three-necked flask and stirred at room temperature for 1 hour. Then, 8.0 g of 6-hydroxyhexanoic acid was added as the substrate, the pressure was reduced to 40 Torr, and the temperature was raised to 140°C. The reaction mixture in the three-necked flask was then distilled into a distillation flask. After confirming that the distillation had stopped, 3.83 g of ethylene glycol was added to the three-necked flask and the liquid was distilled into the distillation flask. After confirming that the distillation had stopped, another 3.83 g of ethylene glycol was added to the three-necked flask and the liquid was distilled into the distillation flask. After confirming that the distillation had stopped, the reaction mixture and the distillate were mixed to prepare a mixture, which was analyzed by gas chromatography under the same conditions as in Comparative Example 1, and the conversion rate and yield were calculated.

[0083] Comparative Example 5: A mixture was prepared by mixing the reaction solution and distillate in the same manner as in Comparative Example 4, except that 0.0694 g of tetraisopropyl orthotitanate was added to a three-necked flask along with 3.83 g of ethylene glycol and 0.13 g of water. The mixture was analyzed by gas chromatography under the same conditions as in Comparative Example 1, and the conversion rate and yield were calculated.

[0084] Comparative Example 6: 6.4 g of diethylene glycol and 0.1 g of water were placed in a three-necked flask and stirred at room temperature for 1 hour. Then, 8.0 g of 6-hydroxyhexanoic acid was added as the substrate, the pressure was reduced to 15 Torr, and the temperature was raised to 160°C. The reaction mixture in the three-necked flask was then distilled into a distillation flask. After confirming that the distillation had stopped, 6.4 g of diethylene glycol was added to the three-necked flask and the liquid was distilled into the distillation flask. After confirming that the distillation had stopped, another 6.4 g of diethylene glycol was added to the three-necked flask and the liquid was distilled into the distillation flask. After confirming that the distillation had stopped, the reaction mixture and the distillate were mixed to prepare a mixture, which was analyzed by gas chromatography under the same conditions as in Comparative Example 1, and the conversion rate and yield were calculated.

[0085] Comparative Example 7: A mixture was prepared by mixing the reaction solution and distillate in the same manner as in Comparative Example 6, except that 0.0692 g of tetraisopropyl orthotitanate was added to a three-necked flask along with 6.4 g of diethylene glycol and 0.1 g of water. The mixture was analyzed by gas chromatography under the same conditions as in Comparative Example 1, and the conversion rate and yield were calculated.

[0086] Comparative Example 8: 9.1 g of triethylene glycol and 0.1 g of water were charged into a three-necked flask and stirred at room temperature for 1 hour. Then, 8.0 g of 6-hydroxyhexanoic acid was added as the substrate, the pressure was reduced to 10 Torr, and the temperature was raised to 190°C. The reaction mixture in the three-necked flask was then distilled into a distillation flask. After confirming that the distillation had stopped, 9.1 g of triethylene glycol was added to the three-necked flask and the liquid was distilled into the distillation flask. After confirming that the distillation had stopped, another 9.1 g of triethylene glycol was added to the three-necked flask and the liquid was distilled into the distillation flask. After confirming that the distillation had stopped, the reaction mixture and the distillate were mixed to prepare a mixture, which was analyzed by gas chromatography under the same conditions as in Comparative Example 1, and the conversion rate and yield were calculated.

[0087] Example 5 A mixture was prepared by mixing the reaction solution and distillate in the same manner as in Comparative Example 8, except that 0.0692 g of tetraisopropyl orthotitanate was added to a three-necked flask along with 9.1 g of triethylene glycol and 0.1 g of water. The mixture was analyzed by gas chromatography under the same conditions as in Comparative Example 1, and the conversion rate and yield were calculated.

[0088] Comparative Example 9: 11.8 g of tetraethylene glycol and 0.1 g of water were placed in a three-necked flask and stirred at room temperature for 1 hour. Then, 8.0 g of 6-hydroxyhexanoic acid was added as the substrate, the pressure was reduced to 10 Torr, and the temperature was raised to 195°C. The reaction mixture in the three-necked flask was then distilled into a distillation flask. After confirming that the distillation had stopped, 11.8 g of tetraethylene glycol was added to the three-necked flask and the liquid was distilled into the distillation flask. After confirming that the distillation had stopped, another 11.8 g of tetraethylene glycol was added to the three-necked flask and the liquid was distilled into the distillation flask. After confirming that the distillation had stopped, the reaction mixture and the distillate were mixed to prepare a mixture, which was analyzed by gas chromatography under the same conditions as in Comparative Example 1, and the conversion rate and yield were calculated.

[0089] Example 6 A mixture was prepared in the same manner as in Comparative Example 9, except that 11.8 g of tetraethylene glycol and 0.1 g of water were used in a three-necked flask instead of 3.83 g of ethylene glycol and 0.13 g of water, and an additional 0.0692 g of tetraisopropyl orthotitanate was added. The reaction solution and distillate were mixed, and the mixture was analyzed by gas chromatography under the same conditions as in Comparative Example 1 to calculate the conversion rate and yield.

[0090] The results for Examples 1-6 and Comparative Examples 1-9 are shown in Table 1.

[0091] As shown in the results of Examples 1-3 and Comparative Examples 1 and 2, it was confirmed that cyclized products can be obtained in high yield even in the presence of water by using tetraethylene glycol and a titanium compound in combination as polyhydric alcohols. Furthermore, from the results of Example 4 and Comparative Example 3, it was confirmed that cyclized products can also be obtained in high yield even in the presence of water when lactic acid is used as the substrate. In addition, from the results of Examples 5-6 and Comparative Examples 4-9, it was confirmed that when triethylene glycol and tetraethylene glycol are used as polyhydric alcohols, these glycols can also be used to obtain cyclized products in high yield even in the presence of water.

[0092] Example 7 In the reaction flask at the bottom of the 20-stage Oldershaw still, 200 g of 6-hydroxyhexanoic acid, 293 g of tetraethylene glycol, 200 g of water, 1.703 g of tetraisopropyl orthotitanate, and 50 boiling chips were charged as substrates. Then, the pressure was reduced to 10 Torr and the temperature was raised to 247°C, and the mixture was refluxed under full reflux for 2 hours, with the water being discharged into an external trap. Subsequently, the mixture was distilled from the top of the column over 26 hours at a reflux ratio that resulted in a distillation rate of 0.1 ml / min, yielding 172 g of ε-caprolactone with a conversion rate of 99.6% and a yield of 95.9%. The yield of the distilled ε-caprolactone (purity 99.8% or higher) was 73.3%.

[0093] Example 8 In the same manner as in Example 7, 170 g of ε-caprolactone was obtained with a conversion rate of 99.6% and a yield of 94.8%, except that 200 g of 6-hydroxyhexanoic acid (purity 25%, other polycaprolactone oligomer) was used as the substrate instead of 200 g of 6-hydroxyhexanoic acid. The yield of distilled ε-caprolactone (purity 99.8% or higher) was 69.7%.

[0094] Example 9 In the same method as in Example 7, 164 g of ε-caprolactone was obtained with a conversion rate of 99.6% and a yield of 95.2%, except that 178 g of polycaprolactone (number-average molecular weight 2000), a polymer of hydroxycarboxylic acid, was used instead of 200 g of 6-hydroxyhexanoic acid as the substrate. The yield of ε-caprolactone (purity 99.8% or higher) obtained by distillation was 68.2%.

[0095] Example 10 In the reaction flask at the bottom of the 20-stage Oldershaw still, 200 g of 6-hydroxyhexanoic acid, 293 g of tetraethylene glycol, 1.703 g of tetraisopropyl orthotitanate, and 50 boiling chips were charged as substrates. Then, the pressure was reduced to 10 Torr and the temperature was raised to 247°C, and the mixture was refluxed under full reflux for 2 hours, with the by-product water being discharged into an external trap. Subsequently, the mixture was distilled from the top of the column over 26 hours at a reflux ratio that resulted in a distillation rate of 0.1 ml / min, yielding 168 g of ε-caprolactone with a conversion rate of 98.4% and a yield of 93.1%. The yield of the distilled ε-caprolactone (purity 99.8% or higher) was 75.8%. 200 g of 6-hydroxyhexanoic acid was added to the remaining liquid in the casing, the pressure was reduced to 10 Torr, and the temperature was raised to 247°C. The mixture was refluxed under full reflux for 2 hours, and the by-product water was discharged into an external trap. Subsequently, the mixture was discharged from the top of the column over 26 hours at a reflux ratio that resulted in an outflow rate of 0.1 ml / min, yielding 164 g of ε-caprolactone with a conversion rate of 92.4% and a yield of 91.9%. The yield of distilled ε-caprolactone (purity 99.8% or higher) was 71.6%.

[0096] In Example 11, ε-caprolactone was produced in the same manner as in Example 7, except that 8.93 g of succinic acid was added. As a result, 160 g of ε-caprolactone was obtained with a conversion rate of 99.4% and a yield of 92.7%. The yield of distilled ε-caprolactone (purity of 99.8% or higher) was 80.2%.

[0097] As shown in Example 7, it was confirmed that the method for producing lactone compounds according to the present disclosure can produce lactone compounds in high yield in a single pod without pretreatment of the lactone compounds. Furthermore, as shown in Example 8, it was confirmed that lactone compounds can be produced even when a polymer of hydroxycarboxylic acid is used as a raw material. Furthermore, as shown in Example 9, it was confirmed that lactone compounds can be produced even when a polycaprolactone oligomer with a number average molecular weight of 2000 is used as a raw material. Moreover, as shown in Example 10, it was confirmed that the method for producing lactone compounds according to the present disclosure can maintain yield and purity even when hydroxycarboxylic acid is repeatedly added, and that polyhydric alcohols and titanium compounds can be reused. In addition, as shown in Example 11, it was confirmed that high yield can be maintained even in the presence of carboxylic acid.

[0098] Variations of this disclosure are described below. [Note 1] A catalyst used to produce a lactone compound from hydroxycarboxylic acids, comprising a titanium compound and a polyhydric alcohol and / or a polyhydric amine, wherein the polyhydric alcohol and / or the polyhydric amine is present in an amount of 0.05 moles or more per mole of the hydroxycarboxylic acid. [Note 2] The catalyst according to Note 1, wherein the hydroxycarboxylic acid is a cyclic ketone as the starting material. [Note 3] A method for producing a lactone compound from hydroxycarboxylic acids, comprising reacting the hydroxycarboxylic acid with a polyhydric alcohol and / or a polyhydric amine and a titanium compound, under the condition that the amount of the polyhydric alcohol and / or polyhydric amine is 0.05 moles or more per mole of the hydroxycarboxylic acid. [Note 4] The method for producing a lactone compound according to Note 3, wherein the hydroxycarboxylic acid is a cyclic ketone as the starting material. [Note 5] The method for producing a lactone compound according to Note 3 or 4, wherein the water content per 100 parts by mass of the hydroxycarboxylic acid during the reaction is 0.1 parts by mass or more. [Note 6] The method for producing a lactone compound according to any one of Notes 3 to 5, wherein the hydroxycarboxylic acids include hydroxycarboxylic acids. [Note 7] The method for producing a lactone compound according to any one of Notes 3 to 6, wherein the hydroxycarboxylic acids include polymers of hydroxycarboxylic acids. [Note 8] The method for producing a lactone compound according to any one of Notes 3 to 7, wherein the reaction is carried out in the presence of the polyhydric alcohol. [Note 9] The method for producing a lactone compound according to Note 8, wherein the polyhydric alcohol is glycols. [Note 10] The method for producing a lactone compound according to any one of Notes 3 to 9, wherein the polyhydric alcohol and / or the polyhydric amine and the titanium compound are reusable.

Claims

1. A catalyst used for producing lactone compounds from hydroxycarboxylic acids, comprising a titanium compound and a polyhydric alcohol and / or a polyhydric amine, wherein the polyhydric alcohol and / or the polyhydric amine is present in an amount of 0.05 moles or more per mole of the hydroxycarboxylic acid.

2. The catalyst according to claim 1, wherein the hydroxycarboxylic acids are derived from a cyclic ketone.

3. A method for producing lactone compounds from hydroxycarboxylic acids, comprising reacting the hydroxycarboxylic acids with a polyhydric alcohol and / or polyhydric amine and a titanium compound in the presence of a polyhydric alcohol and / or polyhydric amine at a rate of 0.05 moles or more of the polyhydric alcohol and / or polyhydric amine per mole of the hydroxycarboxylic acid.

4. The method for producing a lactone compound according to claim 3, wherein the hydroxycarboxylic acids are derived from a cyclic ketone as a starting material.

5. The method for producing a lactone compound according to claim 3 or 4, wherein the water content is 0.1 parts by mass or more per 100 parts by mass of the hydroxycarboxylic acid during the reaction.

6. The method for producing a lactone compound according to claim 3 or 4, wherein the hydroxycarboxylic acids include a hydroxycarboxylic acid.

7. The method for producing a lactone compound according to claim 3 or 4, wherein the hydroxycarboxylic acids include a polymer of hydroxycarboxylic acids.

8. A method for producing a lactone compound according to claim 3 or 4, wherein the reaction is carried out in the presence of the polyhydric alcohol.

9. The method for producing a lactone compound according to claim 8, wherein the polyhydric alcohol is a glycol.

10. A method for producing a lactone compound according to claim 3 or 4, wherein the polyhydric alcohol and / or the polyhydric amine and the titanium compound are reusable.

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