JP2023117830A - Bi-tetrahydrofuran dicarboxylic acid compound and method for producing the same - Google Patents

Abstract

To provide a novel bi-tetrahydrofuran dicarboxylic acid compound and a method for producing the same.SOLUTION: The present invention provides a method for producing a bi-tetrahydrofuran dicarboxylic acid compound that includes hydrogenating a bi-furan dicarboxylic acid compound having a structure represented by the formula (2), using a catalyst carrying a noble metal on an alumina carrier. Preferably the catalyst is a catalyst carrying a noble metal selected from Pd, Ru and Rh on an alumina carrier. (In the formula (2), R's independently represent a hydrogen atom or an alkyl group).SELECTED DRAWING: None

Description

The present invention relates to a novel bitetrahydrofurandicarboxylic acid compound and a method for producing the same.

In recent years, as a means of reducing consumption of fossil fuels such as petroleum and coal and contributing to the mitigation of global warming, the development of biomass polymers produced using biomass as a raw material has been desired. Bifuran compounds, in which two furan rings are bonded, have been attracting attention as raw materials for obtaining monomers for biomass polymers.

As a method for synthesizing a dicarboxylic acid by hydrogenating a furan ring, 2,5-furandicarboxylic acid (hereinafter sometimes abbreviated as "FDCA") is prepared in acetic acid using a Pd/activated carbon catalyst according to the following reaction formula. A method of obtaining 2,5-tetrahydrofurandicarboxylic acid (hereinafter sometimes abbreviated as "THFDCA") by hydrogenation with tetrahydrofurandicarboxylic acid has been reported (Patent Document 1).

As a method for synthesizing the dimer of the tetrahydrofuran compound, according to the following reaction formula, a diene diol is converted to a bissilyl ether with a silylating agent, and then synthesized by intramolecular iodoetherification with an iodinating agent such as N-iodosuccinimide. There is a reported example (Non-Patent Document 1).

WO2017/061858

Fujioka Hiromichi, et al. Heterocycles (2014), 88(2), 1323-1336

The dimeric bitettrahydrofurandicarboxylic acid compound has a higher thermal decomposition initiation temperature than the furandicarboxylic acid as shown in Patent Document 1 due to its structure, and is expected as a raw material for highly heat-resistant resins. Although its development is desired, no report has been made so far on a bitetrahydrofurandicarboxylic acid compound.

In addition, the synthesis method shown in Non-Patent Document 1 requires the reaction to be carried out at a low temperature of -78°C, making mass production difficult. In addition, the compound synthesized in Non-Patent Document 1 is not a dicarboxylic acid compound, and a manufacturing method suitable for a dicarboxylic acid compound is required.

In view of the above problems, the present inventors have an object to provide a novel bitetrahydrofurandicarboxylic acid compound and a method for producing the same.

The inventors of the present invention conducted extensive studies to solve the above problems, and succeeded in hydrogenating a bifurandicarboxylic acid compound produced from a biomass raw material to develop a novel bittrahydrofurandicarboxylic acid compound. Furthermore, they have found that the hydrogenation of this bifurandicarboxylic acid compound can be carried out with high selectivity by using a specific catalyst.
The present invention has been achieved based on such findings, and the gist thereof is as follows.

[1] A bittrahydrofurandicarboxylic acid compound having a structure represented by the following formula (1).

(In formula (1), each R independently represents a hydrogen atom or an alkyl group.)

[2] Bitetrahydrofurandicarboxylic acid according to [1], wherein a bifurandicarboxylic acid compound having a structure represented by the following formula (2) is hydrogenated using a catalyst in which a noble metal is supported on an alumina carrier. A method for producing an acid compound.

(In formula (2), R has the same definition as in formula (1).)

[3] The method for producing a bittrahydrofurandicarboxylic acid compound according to [2], wherein the catalyst is a catalyst in which a noble metal selected from Pd, Ru and Rh is supported on an alumina carrier.

The bitetrahydrofurandicarboxylic acid compound of the present invention can be produced by hydrogenation of a bifurandicarboxylic acid compound produced from a biomass raw material.
The method of using biomass raw materials as starting materials for chemical raw materials is, for example, that the production of plant raw materials can be dispersed and diversified in various places, so that the supply of raw materials is extremely stable, and that it is done in the global environment of the atmosphere, and carbon dioxide is produced. Since the material balance of carbon absorption and release is relatively balanced, it has the advantage of potentially possessing the feasibility of a recycling-oriented society, including recycling, which cannot be expected from fossil resource raw materials. Therefore, the industrial utility value of the bitetrahydrofurandicarboxylic acid compound of the present invention is extremely high.
The bitetrahydrofurandicarboxylic acid compound of the present invention is used as a raw material monomer for polyesters and polyamides. It is expected to be applied to biomass polymers such as polyesters and polyamides, which require significantly high heat resistance.
According to the method for producing a bitetrahydrofurandicarboxylic acid compound of the present invention, such a bittrahydrofurandicarboxylic acid compound of the present invention can be produced with high selectivity.

Although the present invention will be described in detail below, the descriptions of the constituent elements described below are representative examples of embodiments of the present invention, and the present invention is not limited to these contents.

[bitetrahydrofurandicarboxylic acid compound]
The bitetrahydrofurandicarboxylic acid compound of the present invention has a structure represented by the following formula (1).

(In formula (1), each R independently represents a hydrogen atom or an alkyl group.)

In the above formula (1), examples of the alkyl group for R include alkyl groups having 1 to 8 carbon atoms such as methyl group and ethyl group, and preferably 1 to 3 carbon atoms.
From the viewpoint of solubility and economy, R is preferably a methyl group, an ethyl group, or a propyl group, and particularly preferably a methyl group.
Two R's in formula (1) may be the same or different, but from the viewpoint of ease of synthesis, they are preferably the same.

[Method for Producing Bitetrahydrofurandicarboxylic Acid Compound]
In the method for producing a bitettrahydrofurandicarboxylic acid compound of the present invention, a bifurandicarboxylic acid compound having a structure represented by the following formula (2) (hereinafter sometimes referred to as "birfurandicarboxylic acid compound (2)"). is hydrogenated using a catalyst in which a noble metal is supported on an alumina carrier to produce the above bittrahydrofurandicarboxylic acid compound of the present invention.

(In formula (2), R has the same definition as in formula (1).)

As in the formula (1), the alkyl group for R in the formula (2) includes an alkyl group having 1 to 8 carbon atoms such as a methyl group and an ethyl group, preferably 1 to 3. .
From the viewpoint of solubility and economy, R is preferably a methyl group, an ethyl group, or a propyl group, and particularly preferably a methyl group.
Two R's in formula (2) may be the same or different, but from the viewpoint of ease of synthesis, they are preferably the same.

<Hydrogenation reaction of bifurandicarboxylic acid compound (2)>
In the method for producing a bittrahydrofurandicarboxylic acid compound of the present invention, a catalyst in which a noble metal is supported on an alumina carrier is used for the hydrogenation of the bifurandicarboxylic acid compound (2).
In the present invention, the use of this unique catalyst is an important requirement for the selective hydrogenation of the bifurandicarboxylic acid compound (2). The yield is low, and the hydrogenation selectivity is also low without noble metal catalysts.
Examples of noble metals include platinum metal elements such as gold (Au), silver (Ag), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt). However, Rd, Ru and Rh are preferred from the viewpoint of raw material availability and ease of catalyst preparation. Only one kind of these noble metals may be used, or two or more kinds thereof may be used.

In the alumina-supported catalyst, the supported amount of noble metal is preferably 0.1% by mass or more, more preferably 1% by mass or more, and preferably 15% by mass or less, more preferably 10% by mass. If the amount of noble metal supported is at least the above lower limit, high hydrogenation reaction activity can be obtained, and if it is at most the above upper limit, hydrocracking is suppressed, resulting in a high yield.

The hydrogenation reaction of bifurandicarboxylic acid compound (2) is preferably carried out at a temperature of 50° C. or higher, more preferably 80° C. or higher, preferably 200° C. or lower, more preferably 180° C. or lower, and the hydrogen gas pressure is , preferably 1 MPa or more, more preferably 2 MPa or more, preferably 20 MPa or less, more preferably 10.0 MPa or less, from the viewpoint of suppressing reaction efficiency and side reactions and improving yield.

As a method for operating the hydrogenation reaction, the hydrogenation catalyst is suspended in a solution of the bifurandicarboxylic acid compound (2), a so-called suspended bed method, or a fixed bed of the hydrogenation catalyst and the bifurandicarboxylic acid A so-called fixed-bed method or the like, in which a solution of compound (2) is allowed to flow, can usually be employed. Furthermore, for example, in a method using a suspended bed, a hydrogenation catalyst and a bifurandicarboxylic acid compound (2) are charged in a pressure vessel, and after replacing the space in the pressure vessel with hydrogen gas, the hydrogenation is carried out at a predetermined temperature for a predetermined time. There is a method of stirring, or a method of blowing hydrogen gas into the reaction vessel instead of substituting with hydrogen gas. Further, for example, in the method using a fixed bed, there is a method in which a solution of the bifurandicarboxylic acid compound (2) and hydrogen gas are passed in parallel through a tank (for example, a packed tower) packed with a hydrogenation catalyst. Any of these methods can be used in the present invention.

The reaction solvent is not particularly limited as long as it is inert to the hydrogenation reaction and capable of dissolving the bifurandicarboxylic acid compound (2). , ester solvents such as ethyl acetate, alcohol solvents such as methanol and ethanol, water, and the like can be used.
Among these, ether solvents such as THF and dioxane are preferable from the viewpoint of the solubility of the bifurandicarboxylic acid compound.
These solvents may be used alone or in combination of two or more.

The concentration of the bifurandicarboxylic acid compound (2) in the bifurandicarboxylic acid compound (2) solution to be subjected to the hydrogenation reaction is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 50% by mass or less. , more preferably 30% by mass or less. If the concentration of bifurandicarboxylic acid compound (2) is at least the above lower limit, it is advantageous in terms of economy, and if it is at most the above upper limit, it is advantageous in terms of solubility in solvents.

The amount of the hydrogenation catalyst used is not particularly limited, but for example, in a method using a suspended bed, the hydrogenation catalyst is preferably 2% by mass or more, more preferably 5% by mass, relative to the bifurandicarboxylic acid compound. It is the above, and preferably 30% by mass or less, more preferably 20% by mass or less, can shorten the reaction time and is preferable from the viewpoint of economy.

Although the reaction time varies depending on conditions such as the reaction temperature and hydrogen gas pressure, it is usually about 0.5 to 5 hours, and the furan ring of the bifurandicarboxylic acid compound (2) is hydrogenated to form a tetrahydrofuran ring. can be done.

After the hydrogenation reaction, the target bitetrahydrofurandicarboxylic acid compound can be separated and recovered by filtering the catalyst, and can be purified by crystallization if necessary.

According to the method for producing a bittrahydrofurandicarboxylic acid compound of the present invention, for example, methyl bifurandicarboxylate, which is a bifurandicarboxylic acid compound in which R is a methyl group in the above formula (2), is shown in Examples below. (hereinafter sometimes abbreviated as "BFDM"), in the above formula (1), methyl bitetrahydrofurandicarboxylate (hereinafter referred to as "BTHFDM"), which is a bittrahydrofurandicarboxylic acid compound in which R is a methyl group. may be abbreviated.) can be produced with high selectivity.
In this hydrogenation reaction, as shown in Examples below, methyl tetrahydro-2-(5-methoxy-5-oxopentyl)-4-furancarboxylate in which one furan ring is opened (hereinafter referred to as It is sometimes abbreviated as "THFOH".) and half hydrides in which only one furan ring is hydrogenated, but by using a hydrogenation catalyst in which a noble metal is supported on an alumina carrier, these by-products The amount of product produced can be greatly reduced compared to when other metal-supported catalysts are used.

<Hydrolysis of Bitetrahydrofurandicarboxylic Acid Alkyl Ester>
When a bifrangicarboxylic acid alkyl ester in which R in the formula (2) is an alkyl group is used as the bifrangicarboxylic acid compound (2), hydrogenation of the bifrangicarboxylic acid compound (2) yields bitetrahydrofuran. A dicarboxylic acid alkyl ester can be obtained, but bitetrahydrofurandicarboxylic acid is sometimes more suitable than bittrahydrofurandicarboxylic acid alkyl ester when used as a raw material for producing resins such as polyesters and polyamides.
In this case, the bitetrahydrofurandicarboxylic acid alkyl ester is hydrolyzed to form a salt, which is then neutralized to be used as bittrahydrofurandicarboxylic acid.
Hydrolysis of the bitetrahydrofurandicarboxylic acid alkyl ester is preferably carried out using a base in a solvent.

Preferred solvents for hydrolysis include primary alcohols such as methanol and ethanol; secondary alcohols such as 2-propanol (isopropanol), sec-butanol, cyclopentanol and cyclohexanol; -tertiary alcohols such as cyclopropanol, 1-adamantanol, tert-butanol, t-amyl alcohol; ethers such as tetrahydrofuran (THF) and 1,4-dioxane; hexane, heptane, benzene, toluene, xylene, cumene, etc. Chlorinated solvents such as methylene chloride, chloroform and trichlorethylene; Ketones such as acetone and 2-butanone; N,N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, dimethylsulfoxide, aprotic polar solvents such as hexamethylphosphoric triamide; nitriles such as acetonitrile and propionitrile; esters such as ethyl acetate and n-butyl acetate; These may be used individually by 1 type, and may use 2 or more types together.
Among these, it is preferable to use a solvent containing alcohol.

Suitable bases for hydrolysis include inorganic Bronsted bases such as sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium hydrogencarbonate, potassium hydrogencarbonate; pyridine, triethylamine, dimethylaminopyridine, diisopropylethylamine, organic Bronsted bases such as N-methylmorpholine; These may be used individually by 1 type, and may use 2 or more types together.
Among these, inorganic Bronsted bases are preferable, and sodium hydroxide, potassium hydroxide, and lithium hydroxide are more preferable from the viewpoint of availability and solubility.

The reaction conditions for converting the bittrahydrofurandicarboxylic acid alkyl ester into a salt are not particularly limited, and conventionally known hydrolysis reaction conditions can be appropriately employed, and the reaction temperature is preferably −30° C. or higher, more preferably. It is -20°C or higher, more preferably -10°C or higher, preferably 100°C or lower, more preferably 50°C or lower, and still more preferably 40°C or lower. The reaction time is preferably 10 minutes or longer, more preferably 20 minutes or longer, still more preferably 30 minutes or longer, and preferably 24 hours or shorter, more preferably 10 hours or shorter, and still more preferably 5 hours or shorter.

Acids to be added to the bittrahydrofurandicarboxylic acid alkyl ester salts include inorganic acids such as hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid and phosphoric acid, or salts thereof; formic acid, acetic acid, propionic acid, oxalic acid Acids, organic acids such as trifluoroacetic acid, methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid, or salts thereof; lithium tetrafluoroborate, boron trifluoride, boron trichloride, tribromide Lewis acids such as boron, aluminum trichloride, zinc chloride, zinc bromide, zinc iodide, tin tetrachloride, tin tetrabromide, tin dichloride, titanium tetrachloride, titanium tetrabromide, trimethyliodosilane; alumina, silica gel , oxides such as titania; minerals such as montmorillonite; These may be used individually by 1 type, and may use 2 or more types together.

The reaction conditions for producing bittrahydrofurandicarboxylic acid by adding an acid to a salt of bittrahydrofurandicarboxylic acid alkyl ester are not particularly limited, and conventionally known deprotection reaction conditions using an acid can be appropriately employed. The reaction temperature is preferably −30° C. or higher, more preferably −20° C. or higher, still more preferably −10° C. or higher, preferably 100° C. or lower, more preferably 50° C. or lower, further preferably 40° C. or lower. is. The reaction time is preferably 10 minutes or longer, more preferably 20 minutes or longer, still more preferably 30 minutes or longer, and preferably 24 hours or shorter, more preferably 10 hours or shorter, and still more preferably 8 hours or shorter.

Bitetrahydrofurandicarboxylic acid obtained by hydrolysis can be separated, recovered and purified by extracting with ethyl acetate or the like, washing with water, and distilling off the solvent.

By carrying out such hydrolysis, as shown in the examples below, for example, bittrahydrofurandicarboxylic acid (hereinafter sometimes abbreviated as "BTHFDA") can be obtained from BTHFDM.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

In the following examples and comparative examples, the raw material BFDM was synthesized by the method described in Reference (Macromolecules, 2018, 51, 1822-1829). Moreover, the analysis method of the hydrogenation reaction liquid and the analysis method of dicarboxylic acid are as follows.

(1) Analysis of Hydrogenation Reaction Liquid The hydrogenation reaction liquid was analyzed by gas chromatography (GC) analysis under the following conditions.
<Analysis conditions>
Column: Agilent DB-5, length 30 m, film thickness 0.25 μm, diameter 0.25 mm
Injection temperature: 250°C
Detection temperature: 280°C
Temperature rising program conditions: 50°C (hold for 5 minutes) → 10°C/min → 250°C (hold for 5 minutes)
Detector: FID

(2) Analysis of Dicarboxylic Acid Dicarboxylic acid was analyzed by liquid chromatography (LC) analysis under the following conditions.
Column: MCIGEL CK08EH manufactured by Mitsubishi Chemical Corporation, diameter 8 mm, length 300 mm
Eluent: 0.1% THF/ _H2O
Flow rate: 1 mL/min
Detector: RI

[Example 1]

BFDM 0.25 g (1.0 mmol), 5% Pd/Al ₂ O ₃ catalyst (N E Chemcat S-Type) 0.025 g, THF 4.75 g and a stirrer were placed in a stainless steel autoclave having a capacity of 50 mL. The lid was put on, hydrogen gas was injected at 3 MPa at room temperature, the temperature was raised to 150° C. with stirring, and the reaction was carried out for 2 hours. After the reaction, it was cooled to room temperature and purged with hydrogen gas. The obtained hydrogenation reaction liquid was analyzed by gas chromatography. Table 1 shows the results.

[Example 2]
As a catalyst, 0.025 g of a 5% Ru/alumina catalyst (manufactured by N E Chemcat) was used, and the reaction was carried out in the same manner as in Example 1 except that the reaction temperature was 100°C. Table 1 shows the results.

[Example 3]
The same method as in Example 2 was repeated except that 0.025 g of a 5% Rh/alumina catalyst (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the catalyst. Table 1 shows the results.

[Comparative Example 1]
The same procedure as in Example 1 was repeated except that 0.025 g of a 5% Pd/SiO ₂ catalyst (manufactured by N E Chemcat) was used as the catalyst. Table 1 shows the results.

[Comparative Example 2]
As a catalyst, 0.025 g of 5% Pd/activated carbon catalyst (E-Type, manufactured by N E Chemcat) was used, and the reaction temperature was changed to 100° C., but the same method as in Example 1 was carried out. Table 1 shows the results.

[Comparative Example 3]
It was carried out in the same manner as in Comparative Example 2 except that the reaction temperature was changed to 150°C. Table 1 shows the results.

[Comparative Example 4]
The same procedure as in Example 1 was repeated except that 0.1 g of Raney nickel catalyst (R-200 manufactured by Nikko Rica) was used as the catalyst. Table 1 shows the results.

Among the products in the hydrogenation reaction solution, products other than BTHFDM and THFOH are presumed to be half hydrides represented by the following formula.

From the results of the above examples and comparative examples, only catalysts in which a noble metal is supported on an alumina carrier have a specific high hydrogenation catalytic ability for the hydrogenation of bifurandicarboxylic acid compounds. It can be seen that the hydrogenation selectivity is remarkably poor when the type of catalyst is different, and the hydrogenation selectivity is very low even with a nickel catalyst.

[Example 4]
A stainless steel autoclave with a capacity of 200 mL was charged with 9.95 g (39.8 mmol) of BFDM, 1.00 g of 5% Pd/Al ₂ O ₃ catalyst (N E Chemcat S-Type), and 80 mL of THF, and hydrogen gas was added at room temperature. After press-fitting at 1 MPa, the temperature was raised. After the internal temperature of the autoclave reached 80°C, hydrogen gas was further injected to make the internal pressure 5 MPa, and the reaction was carried out at 100°C for 2 hours. After the reaction, it was cooled to room temperature and purged with hydrogen gas. After filtering the reaction solution, the filtrate was concentrated to obtain 10.8 g of BTHFDM as a pale yellow solid. (Purity 99.3%)
Identification of BTHFDM was performed by GC-MS. The data are given below.
GC-MS calculated for [C ₁₂ H ₁₈ O ₆ +1] ⁺ , [M+1] ⁺ = m/z = 259.1, found: 259

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ＢＴＨＦＤＡの同定は^１Ｈ－ＮＭＲで行った。データを以下に記す。
^１Ｈ－ＮＭＲ（４００ＭＨｚ，ＣＤ３ＯＤ）：１．６８－１．７８（ｍ，１Ｈ），１．８８－２．０３（ｍ，２Ｈ），２．０８－２．１８（ｍ，３Ｈ），２．２６－２．３７（ｍ，２Ｈ），４．０３－４．１５（ｍ，２Ｈ），４．４３－４．５１（ｍ，２Ｈ） [Example 5]

50 mL of methanol and 10 mL of water were added to 10.8 g (41.8 mmol) of BTHFDM and cooled to 4° C. in an ice bath. After slowly adding 13.4 g of a 50% by mass sodium hydroxide aqueous solution thereto, the mixture was returned to room temperature and reacted for 9 hours. About 11 mL of concentrated hydrochloric acid was added to the mixture to neutralize it to about pH 7. After concentrating the methanol, extraction was performed twice with 50 mL of ethyl acetate, and the organic layer was washed with saturated brine and dried over anhydrous magnesium sulfate. After filtering the desiccant, the white solid obtained by concentrating the filtrate was vacuum-dried to obtain 5.80 g of BTHFDA. (Yield 60.3%, LC purity 99.2%)
BTHFDA was identified by ¹ H-NMR. The data are given below.
¹ H-NMR (400 MHz, CD3OD): 1.68-1.78 (m, 1H), 1.88-2.03 (m, 2H), 2.08-2.18 (m, 3H), 2 .26-2.37 (m, 2H), 4.03-4.15 (m, 2H), 4.43-4.51 (m, 2H)

[Synthesis Example 1]

A stainless steel autoclave with a capacity of 200 mL was charged with 16.35 g (0.105 mol) of FDCA (manufactured by Tokyo Kasei), 0.97 g of 5% Pd/C catalyst (E-Type manufactured by N E Chemcat) and 150 mL of water. A gas of 1 MPa was injected to raise the temperature. Hydrogen gas was pressurized to 5 MPa at 130°C. The temperature reached 150°C in 15 minutes, and the reaction was continued for 45 minutes. After the reaction, it was cooled to room temperature and purged with hydrogen gas. After filtering the reaction solution, the filtrate was concentrated. The resulting yellow solid was dried in a vacuum dryer to obtain 15.18 g of THFDCA. (Yield 90.5%, LC purity 96.0%)
Identification of THFDCA was performed by ¹ H-NMR. The data are given below.
¹ H-NMR (400 MHz, CD3OD): 1.96 (s, 2H), 2.22 (s, 2H), 4.48 (s, 2H), 12.3 (bs, 2H)

[Measurement results of TG-DTA (thermogravimetry - differential thermal analysis)]
A 5 mg sample was placed in an Al-pan, and the temperature was raised from 30° C. to 600° C. at a rate of 10°/min under a nitrogen gas flow of 200 mL/min to measure the weight loss start temperature.
As a result, the thermal decomposition initiation temperature of BTHFDA obtained in Examples 1 to 3 was 271° C., and the thermal decomposition initiation temperature of THFDCA obtained in Synthesis Example 1 was 230° C., indicating high heat resistance of BTHFDA.

Claims (3)

A bitetrahydrofurandicarboxylic acid compound having a structure represented by the following formula (1).

(In formula (1), each R independently represents a hydrogen atom or an alkyl group.) The bitetrahydrofurandicarboxylic acid compound according to claim 1, wherein a bifurandicarboxylic acid compound having a structure represented by the following formula (2) is hydrogenated using a catalyst in which a noble metal is supported on an alumina carrier. Production method.

(In formula (2), R has the same definition as in formula (1).) 3. The method for producing a bitetrahydrofurandicarboxylic acid compound according to claim 2, wherein the catalyst is a catalyst in which a noble metal selected from Pd, Ru and Rh is carried on an alumina carrier.