Method for producing 2,5-dihydroxyterephthalic acid

Abstract

To provide a production method that can produce high-purity 2,5-dihydroxy terephthalic acid at high yield.SOLUTION: A method for producing high-purity 2,5-dihydroxy terephthalic acid includes following steps: (A) adding an adsorbent to an aqueous solution containing an alkali metal salt of 2,5-dihydroxy terephthalic acid, bringing the adsorbent into contact with the aqueous solution, and the removing the adsorbent; and (B) subjecting the aqueous solution resulting from step (A) to acid precipitation, and separating and recovering the precipitated crystal of 2,5-dihydroxy terephthalic acid.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing 2,5-dihydroxyterephthalic acid. [Background technology]

[0002] 2,5-Dihydroxyterephthalic acid (hereinafter sometimes referred to as DHTA) is an aromatic dicarboxylic acid with two hydroxy groups. It is used, for example, as a monomer for synthetic resins such as polyester, polyamide, and aramid, as well as a raw material for fluorescent agents and pharmaceutical intermediates, and the demand for it is increasing year by year.

[0003] Conventionally, the Kolbe-Schmitt reaction has been known as a method for introducing a carboxyl group into a compound having a phenolic hydroxyl group. For example, the Kolbe-Schmitt reaction is a chemical reaction in which an alkali metal phenoxide (alkali metal salt of phenol) is brought into contact with carbon dioxide at high temperature and pressure to carboxylate the ortho position, and then salicylic acid is obtained after neutralization with an acid.

[0004] Regarding the production of DHTA, methods of production by the Kolbe-Schmitt reaction have also been proposed. For example, there is a method in which a dihydric phenol is contacted with carbon dioxide in the presence of an alkali metal carbonate, and reacted in the presence of an alkali metal formate at a temperature higher than the melting point of the formate (Patent Document 1), and there is a method in which a hydroquinone dialkali metal salt is reacted with carbon dioxide in the presence of an alkali metal salt of phenol or naphthol (Patent Document 2). It is known that the production rate can be improved mainly by adding an organometallic salt catalyst.

[0005] However, the crude DHTA produced by the Kolbe-Schmitt reaction contains impurities such as the intermediate 2,5-dihydroxybenzoic acid (hereinafter sometimes referred to as DHBA), and therefore, in applications requiring higher purity, a purification step to remove these impurities is necessary.

[0006] As a method for purifying DHTA, a method has been proposed in which crude DHTA produced by the Kolbe-Schmitt reaction is acetylated, then recrystallized and hydrolyzed to obtain DHTA again (Patent Document 3). However, the recovery rate is less than half, and this method cannot be said to be industrially advantageous. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 11-515031 [Patent Document 2] JP 2013-245214 A [Patent Document 3] Japanese Unexamined Patent Publication No. 11841 / 1984 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a process for producing high-purity 2,5-dihydroxyterephthalic acid in high yield. [Means for solving the problem]

[0009] In view of the above problems, the present inventors have conducted intensive research and have found that high-purity 2,5-dihydroxyterephthalic acid can be prepared in high yield by removing impurities such as 2,5-dihydroxybenzoic acid contained in an aqueous solution containing an alkali metal salt of 2,5-dihydroxyterephthalic acid by adsorption with an adsorbent and then subjecting the resulting solution to acid precipitation, thereby completing the present invention.

[0010] That is, the present invention includes the following preferred embodiments. [1] (A) adding an adsorbent to an aqueous solution containing an alkali metal salt of 2,5-dihydroxyterephthalic acid, contacting the adsorbent with the aqueous solution, and then removing the adsorbent; and (B) a step of subjecting the aqueous solution obtained in the step (A) to acid precipitation and separating and recovering the precipitated crystals of 2,5-dihydroxyterephthalic acid; The method for producing high-purity 2,5-dihydroxyterephthalic acid includes the steps of: [2] The method according to [1], wherein the alkali metal salt of 2,5-dihydroxyterephthalic acid is obtained by reacting an alkali metal salt of hydroquinone with carbon dioxide. [3] The method according to [1] or [2], wherein the adsorbent is one or more selected from the group consisting of activated carbon, zeolite, silica gel, diatomaceous earth, graphite carbon and molecular sieves. [4] The method according to any one of [1] to [3], wherein the adsorbent is activated carbon. [5] The method according to any one of claims 1 to 4, wherein the high-purity 2,5-dihydroxyterephthalic acid has a content of 2,5-dihydroxybenzoic acid of less than 0.30% by mass. [6] High-purity 2,5-dihydroxyterephthalic acid having a 2,5-dihydroxybenzoic acid content of less than 0.30% by mass. Effect of the Invention

[0011] According to the present invention, high-purity 2,5-dihydroxyterephthalic acid can be obtained in high yield. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In the present invention, the term "alkali metal salt" refers simply to a monoalkali metal salt and / or a dialkali metal salt.

[0013] Examples of the alkali metal salt of DHTA used in step (A) of the present invention include lithium salt of DHTA, sodium salt of DHTA, potassium salt of DHTA, rubidium salt of DHTA, and cesium salt of DHTA. From the viewpoint of availability, sodium salt of DHTA and potassium salt of DHTA are preferred.

[0014] The alkali metal salt of DHTA used in the present invention may be one obtained by the reaction of an alkali metal salt of hydroquinone with carbon dioxide, i.e., the Kolbe-Schmitt reaction.Also, the alkali metal salt of DHTA used in the present invention may be one obtained by converting crude DHTA into an alkali metal salt using an alkali metal hydroxide or an alkali metal alkoxide such as an alkali metal t-butoxide, an alkali metal methoxide, an alkali metal ethoxide, or an alkali metal i-propoxide.

[0015] In the present invention, the term "crude DHTA" refers to DHTA having a 2,5-dihydroxybenzoic acid content of 0.30% by mass or more, and the term "high purity DHTA" refers to DHTA having a 2,5-dihydroxybenzoic acid content of less than 0.30% by mass. The crude DHTA can be obtained by subjecting the alkali metal salt of DHTA obtained by reacting the alkali metal salt of hydroquinone with carbon dioxide to acid precipitation.

[0016] The reaction apparatus used in the Kolbe-Schmitt reaction may be any reaction apparatus used in a typical Kolbe-Schmitt reaction, and may be, for example, an autoclave equipped with a stirrer and capable of handling high-pressure reactions. More preferably, the reaction apparatus has a temperature control function and is equipped with an inlet tube for carbon dioxide or an inert gas, a thermometer support tube, a pressure gauge, an exhaust tube, and the like.

[0017] Examples of the alkali metal salt of hydroquinone used in the Kolbe-Schmitt reaction include lithium salt of hydroquinone, sodium salt of hydroquinone, potassium salt of hydroquinone, rubidium salt of hydroquinone, and cesium salt of hydroquinone. From the viewpoints of availability, cost, and reactivity, sodium salt of hydroquinone and potassium salt of hydroquinone are preferred, and potassium salt of hydroquinone is more preferred from the viewpoint of superior reactivity.

[0018] The alkali metal salt of hydroquinone can be obtained by converting hydroquinone into an alkali metal salt using an alkali metal hydroxide or an alkali metal alkoxide such as an alkali metal t-butoxide, an alkali metal methoxide, an alkali metal ethoxide, an alkali metal i-propoxide, etc. In particular, from the viewpoint of economy, it is preferable to convert hydroquinone into an alkali metal salt using an alkali metal hydroxide.

[0019] The reaction of the alkali metal salt of hydroquinone with carbon dioxide may be carried out in the presence of an organic alkali metal salt.

[0020] As the organic alkali metal salt, an alkali metal salt of one or more organic compounds selected from the group consisting of phenol, naphthol, formic acid, acetic acid, propionic acid, isobutyric acid, palmitic acid, and stearic acid can be preferably used, and potassium acetate can be more preferably used because of its excellent yield.

[0021] The reaction medium used in the reaction of the alkali metal salt of hydroquinone with carbon dioxide is liquid at the reaction temperature and pressure, and is inert to the reaction of the alkali metal salt of hydroquinone with carbon dioxide. Preferably, the reaction medium has a boiling point of 220° C. or higher at atmospheric pressure.

[0022] As the reaction medium, an aliphatic, alicyclic or aromatic hydrocarbon or an ether compound having a residue thereof is suitably used, and examples thereof include light oil, kerosene, gasoline, lubricating oil, white oil, alkylbenzene, alkylnaphthalene, hydrogenated triphenyl, diphenyl ether, alkyl phenyl ether, alkyl diphenyl ether, high-boiling higher alcohols such as iso-octyl alcohol, and mixtures thereof.

[0023] The amount of the reaction medium used is usually 0.5 times or more by mass, preferably 1.0 to 15.0 times by mass, and more preferably 6.0 to 12.0 times by mass, relative to the amount of the alkali metal salt of hydroquinone.

[0024] The reaction temperature between the alkali metal salt of hydroquinone and carbon dioxide is usually 150 to 320° C., preferably 200 to 300° C., and more preferably 230 to 290° C. At temperatures lower than 150° C., the reaction tends not to proceed, whereas at temperatures higher than 320° C., the reaction plateaus, resulting in energy loss and the risk of side reactions.

[0025] The pressure during the reaction of the alkali metal salt of hydroquinone with carbon dioxide is usually 0 to 10 MPa, preferably 0 to 5 MPa, and more preferably 0 to 1 MPa of carbon dioxide pressure. If the pressure during the reaction exceeds 10 MPa, an apparatus capable of withstanding high pressure is required, which is not industrially advantageous.

[0026] The reaction time can be appropriately selected from the range of several minutes to 15 hours, preferably 10 minutes to 10 hours, more preferably 20 minutes to 10 hours, and particularly preferably 1 to 5 hours.

[0027] The alkali metal salt of DHTA obtained by such a reaction, as well as the alkali metal salt of DHTA obtained by treating crude DHTA with an alkali metal alkoxide such as an alkali metal hydroxide, an alkali metal t-butoxide, an alkali metal methoxide, an alkali metal ethoxide or an alkali metal i-propoxide, can be subjected to the process of the present invention.

[0028] In the method of the present invention, first, in step (A), an adsorbent is added to an aqueous solution containing an alkali metal salt of DHTA, the adsorbent is brought into contact with the aqueous solution, and then the adsorbent is removed.

[0029] The adsorbent is used to remove substances other than the alkali metal salt of DHTA, particularly 2,5-dihydroxybenzoic acid, which may be present in an aqueous solution containing the alkali metal salt of DHTA.

[0030] The adsorbent may be one or more selected from the group consisting of activated carbon, zeolite, silica gel, diatomaceous earth, graphite carbon, and molecular sieves, with activated carbon being preferred because of its excellent impurity removal effect.

[0031] Examples of activated carbon include porous substances made from raw materials such as sawdust, wood chips, bamboo, coconut shells, coal, and rice husks, which have been subjected to gas activation treatment or chemical activation treatment.

[0032] The activated carbon may be in the form of either powder or granules, and is preferably one in which the peak position of the pore diameter is within the range of 1 to 5 nm.

[0033] Commercially available products can be suitably used for the adsorbents such as activated carbon. Examples of gas-activated carbon include Shirasagi A, Shirasagi C, Shirasagi M, Shirasagi P (manufactured by Osaka Gas Chemicals), Taiko K type, Taiko P type (manufactured by Futamura Chemicals), Ohira Baimune brand, and Ohira MA brand (manufactured by Taihei Chemical Industries). Examples of chemically activated carbon include Carborafine, Strong Shirasagi, Refined Shirasagi, and Special Shirasagi (manufactured by Osaka Gas Chemicals).

[0034] The amount of the adsorbent used is preferably 0.1 to 50.0% by mass, more preferably 1.0 to 25.0% by mass, and further preferably 3.0 to 20.0% by mass, based on DHTA.

[0035] The contact time (adsorption time) between the aqueous solution containing an alkali metal salt of DHTA and the adsorbent is preferably from 5 to 150 minutes, more preferably from 10 to 120 minutes, and even more preferably from 15 to 90 minutes.

[0036] The contact temperature (adsorption temperature) between the aqueous solution containing an alkali metal salt of DHTA and the adsorbent is preferably 50 to 110°C, more preferably 60 to 105°C, and even more preferably 70 to 100°C.

[0037] After contacting the adsorbent with an aqueous solution containing an alkali metal salt of DHTA, the adsorbent is removed by conventional means such as filtration.

[0038] In the method of the present invention, next, in step (B), the aqueous solution obtained in step (A) is subjected to acid precipitation, and the precipitated crystals of 2,5-dihydroxyterephthalic acid are separated and recovered.

[0039] The acid used for the acid precipitation is not particularly limited, but a mineral acid is preferably used. Examples of the mineral acid include binary acids such as hydrochloric acid and hydrofluoric acid, and oxo acids such as sulfuric acid, nitric acid, phosphoric acid, and perchloric acid. Organic acids such as acetic acid and propionic acid can also be used. Among these, sulfuric acid is particularly preferred.

[0040] The acids used for the acid precipitation are preferably in the form of an aqueous solution from the viewpoint of facilitating control of the reaction temperature, etc., and for example, a 70% by mass aqueous sulfuric acid solution is preferably used.

[0041] These acids are added dropwise until the pH of the aqueous solution obtained in step (A) becomes preferably 1.0 to 3.0, more preferably 1.2 to 2.5, and even more preferably 1.5 to 2.1.

[0042] The acid precipitation time differs depending on the scale of the reaction apparatus, but is preferably 10 to 150 minutes, more preferably 30 to 120 minutes.

[0043] The acid precipitation is preferably carried out in an atmosphere of an inert gas such as nitrogen or helium.

[0044] The crystals precipitated by acid precipitation are separated into solid and liquid by a conventional method such as filtration, and are then collected as the target DHTA crystals. During solid-liquid separation, it is preferable to wash the crystals by pouring in an appropriate solvent. The solvent used during solid-liquid separation is preferably water.

[0045] The DHTA crystals thus recovered can be converted again into an alkali metal salt of DHTA, and steps (A) and (B) can be repeated to achieve a further high purity.

[0046] According to the present invention, it is possible to obtain high-purity DHTA having a content of 2,5-dihydroxybenzoic acid (DHBA) as an impurity of less than 0.30% by mass. The content of 2,5-dihydroxybenzoic acid is preferably less than 0.25% by mass, and more preferably less than 0.20% by mass.

[0047] Thus, the present invention provides high purity, i.e. low 2,5-dihydroxybenzoic acid (DHTA) having a DHBA content of less than 0.30% by mass, preferably less than 0.25% by mass, and more preferably less than 0.20% by mass. EXAMPLES

[0048] The present invention will be described in detail below with reference to examples, but the scope of the present invention is not limited thereto. The target product, 2,5-dihydroxyterephthalic acid, and the impurity, 2,5-dihydroxybenzoic acid, were analyzed by the following method.

[0049] [High performance liquid chromatography (HPLC)] Instrument: Waters Alliance 2690 / 2996 Column model number: L-Column Flow rate: 1.0mL / min Solvent ratio: H2O (pH 2.3) / CH3CN = 95 / 5 (10 min) → 80 / 20 (3.5 min) → 5 / 95 (23.5 min), gradient analysis Wavelength: 229nm Column temperature: 40℃

[0050] Reference Example 1 [Preparation of an aqueous solution containing an alkali metal salt of 2,5-dihydroxyterephthalic acid (DHTA)] In a 1 L four-neck flask equipped with a stirrer and a temperature sensor, 99.1 g (0.9 mol) of hydroquinone and 117.0 g (1.8 mol) of acetic acid were charged and stirred. While cooling and stirring the mixture in a water bath under a nitrogen stream, 636.7 g (3.6 mol) of a 48% by mass aqueous potassium hydroxide solution was added dropwise over 2 hours, and the mixture was then kept at 50°C for 1 hour to prepare an aqueous solution of dipotassium hydroquinone / potassium acetate.

[0051] The prepared aqueous solution and 661.6 g of diesel were transferred to a 2 L autoclave purged with nitrogen and stirred. The mixture was then heated to 160°C while stirring under a nitrogen stream, and 294.6 g of diesel was added and the mixture was kept at 160°C for 2 hours, after which it was sealed and heated to 230°C. The nitrogen was replaced with carbon dioxide gas, and the reaction was carried out at 0.3 MPa and 230-250°C for 3 hours while stirring.

[0052] After completion of the reaction, the mixture was cooled to 100°C, 685.1 g of water and 29.6 g of 70% by mass sulfuric acid were added, and the contents were transferred to a 5 L bottomed flask equipped with a stirrer and a temperature sensor. 2259.4 g of water was added, and the mixture was maintained at 90°C for 30 minutes with stirring under a nitrogen stream, and the aqueous layer containing an alkali metal salt of DHTA was removed (DHTA production rate: 82.5%).

[0053] Example 1 In a 5L bottomless flask equipped with a stirrer and a temperature sensor, 3442.9 g of the aqueous solution containing the alkali metal salt of DHTA obtained in the step of Reference Example 1 (147.1 g as DTHA, 0.74 moles) and 7.4 g (5.0 mass% relative to DTHA) of carborafine (Osaka Gas Chemicals powdered activated carbon, pore diameter peak position 3 nm) were added as activated carbon, and the mixture was heated to 90°C under a nitrogen stream and held at the same temperature for 30 minutes while stirring. Impurities were removed by filtration at 90°C, and the filtrate was transferred to a 5L four-neck flask equipped with a stirrer and a temperature sensor.

[0054] The filtrate was heated to 90°C under a nitrogen stream, and 70% by mass sulfuric acid was added dropwise over 90 minutes while stirring at the same temperature until the pH reached 2.0, to precipitate DHTA. The resulting suspension was cooled to 70°C, and then separated into solid and liquid, and washed with 729.7 g of water. The resulting crystals were dried at 100°C for 12 hours to obtain 127.4 g of DHTA (recovery rate 86.4%).

[0055] The obtained DHTA was quantitatively analyzed by HPLC, and the results are shown in Table 1.

[0056] Example 2 DHTA was obtained in the same manner as in Example 1, except that the adsorbent was changed to Shirasagi A (Osaka Gas Chemicals powdered activated carbon, pore diameter peak position 2 nm) (recovery rate 87.2%). The obtained DHTA was quantitatively analyzed by HPLC. The results are shown in Table 1.

[0057] Comparative Example 1 DHTA was obtained in the same manner as in Example 1, except that no adsorbent was added. The obtained DHTA was quantitatively analyzed by HPLC. The results are shown in Table 1.

[0058] Example 3 [Re-adsorption treatment] 97.5g of DHTA obtained in the step of Example 1 and 1966.3g of water were charged into a 3L bottomless flask equipped with a stirrer and a temperature sensor and stirred. The suspension was heated to 90°C under a nitrogen stream, and 48% by mass of potassium hydroxide aqueous solution was added dropwise while stirring at the same temperature until the pH reached 6.0. Then, 9.8g (10.0% by mass relative to DTHA) of Carborafine (Osaka Gas Chemicals powdered activated carbon, pore diameter peak position 3 nm) was added, and the mixture was stirred at the same temperature for 30 minutes. Impurities were removed by filtration at 90°C, and the filtrate was transferred to a 3L four-neck flask equipped with a stirrer and a temperature sensor.

[0059] The filtrate was heated to 90°C under a nitrogen stream, and 70% by mass sulfuric acid was added dropwise over 90 minutes while stirring at the same temperature until the pH reached 2.0, to precipitate DHTA. The resulting suspension was cooled to 70°C, and then separated into solid and liquid, and washed with 330.5 g of water. The resulting crystals were dried at 100°C for 12 hours to obtain 96.5 g of DHTA (recovery rate 99.0%).

[0060] The obtained DHTA was quantitatively analyzed by HPLC, and the results are shown in Table 1.

[0061] [Table 1]

[0062] As shown in Table 1, it is understood that in Examples 1 and 2 of the present invention, which include a step of treating an aqueous solution containing an alkali metal salt of DHTA with an adsorbent, DHTA of higher purity can be obtained compared to Comparative Example 1, which does not use an adsorbent. It is also understood that DHTA of even higher purity can be obtained by repeating the treatment step with an adsorbent (Example 3).

Claims

1. The following steps: (A) adding an adsorbent to an aqueous solution containing an alkali metal salt of 2,5-dihydroxyterephthalic acid, contacting the adsorbent with the aqueous solution to adsorb 2,5-dihydroxybenzoic acid in the aqueous solution, and then removing the adsorbent; and (B) a step of subjecting the aqueous solution obtained in the step (A) to acid precipitation, and separating and recovering the precipitated crystals of 2,5-dihydroxyterephthalic acid; A method for producing high purity 2,5-dihydroxyterephthalic acid, comprising: The amount of the adsorbent used is 0.1 to 50.0% by mass based on the amount of 2,5-dihydroxyterephthalic acid, and the high-purity 2,5-dihydroxyterephthalic acid has a 2,5-dihydroxybenzoic acid content of less than 0.30% by mass.

2. 2. The method according to claim 1, wherein the alkali metal salt of 2,5-dihydroxyterephthalic acid is obtained by reacting an alkali metal salt of hydroquinone with carbon dioxide.

3. 3. The method according to claim 1, wherein the adsorbent is at least one selected from the group consisting of activated carbon, zeolite, silica gel, diatomaceous earth, graphite carbon and molecular sieves.

4. The method according to any one of claims 1 to 3, wherein the adsorbent is activated carbon.

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