Purification method and application of 2, 5-furandicarboxylic acid

Abstract

The invention discloses a purification method and application of 2, 5-furandicarboxylic acid, belongs to the technical field of chemical material preparation, and aims to effectively remove trace impurities in 2, 5-furandicarboxylic acid, and the color and transparency of the 2, 5-furandicarboxylic acid purified by the method and a polyethylene furandicarboxylate sample prepared by the method are improved. The method comprises the steps of alkali dissolution, decoloration, acidification, impurity removal, water washing and crystallization, oxygen-enriched gas is introduced in the three steps of alkali dissolution, water washing and crystallization for treatment, and the obtained purified 2, 5-furandicarboxylic acid is used for synthesis preparation of polyester, so that the prepared purified 2, 5-furandicarboxylic acid is low in impurity content and high in yield. The polyester chip prepared by polymerization has a more excellent color value.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical material preparation, and particularly relates to a purification method and application of 2,5-furandicarboxylic acid. Background Art

[0002] The material properties of polyethylene furandicarboxylate (PEF) have been studied by a large number of research institutions. Compared with the petroleum-based analogue polyethylene terephthalate (PET), PEF has a higher glass transition temperature (about 87 °C) and better physical and chemical properties. What attracts the most attention is its amazing water vapor barrier performance. The oxygen barrier of PEF is 10 times that of PET, the carbon dioxide barrier of PEF is 6 to 10 times that of PET, and the water resistance of PEF is 2 times that of PET. Although its performance is excellent, at present, the PEF prepared by esterification and melt polycondensation of FDCA (2,5-furandicarboxylic acid) and ethylene glycol will all change color, producing PEF products ranging from amber, brown to black.

[0003] It has been found through research that the color change of PEF products is mainly related to the residual amounts of organic impurities and inorganic impurities in the monomers. Among them, organic impurities such as 5-hydroxymethylfurfural (5-HMF) produce oxidation intermediates through insufficient oxidation: 5-formyl-2-furancarboxylic acid (FFCA), 2,5-diformylfuran (DFF), 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), etc., and inorganic impurities such as catalysts and raw material monomers used in the preparation of FDCA: impurities such as iron, copper, and tin. The existence of the above impurities will cause color reaction and uncontrollable side reactions during the polymerization process, resulting in the coloring of the final polyester product. Therefore, the purification treatment of FDCA is crucial for the quality of downstream products.

[0004] There are currently studies on the purification of 2,5-furandicarboxylic acid. For example, Patent CN115028610B discloses a purification method of 2,5-furandicarboxylic acid, which includes mixing crude FDCA, a metal ion remover, and a recrystallization solvent, heating and fully dissolving FDCA under the protection of an inert gas, then cooling and crystallizing, filtering, washing, and drying to obtain preliminarily refined FDCA; then, under the protection of an inert gas, the preliminarily refined FDCA is dissolved in a solvent, and a hydrogenation reaction is carried out under the action of a hydrogenation catalyst and hydrogen, and then cooling and crystallizing, filtering, washing, and drying to obtain pure 2,5-furandicarboxylic acid. This process conducts metal ion remover treatment and enhanced washing before the hydrogenation reaction to avoid hydrogenation catalyst poisoning, but the loss of the catalyst during the hydrogenation process will lead to the introduction of new impurities. Patent CN118184613A discloses a purification method of 2,5-furandicarboxylic acid, which includes adding unpurified 2,5-furandicarboxylic acid to mixed solvent I, heating and stirring, then filtering out the solid matter, adding it to mixed solvent II, stirring at room temperature, filtering, washing with water, and drying to obtain purified 2,5-furandicarboxylic acid. This process washes 2,5-furandicarboxylic acid with a mixed solvent, which can only wash away organic impurities. Inorganic impurities are insoluble in the mixed solvent, so the finally purified 2,5-furandicarboxylic acid still contains inorganic impurities, resulting in uncontrollable side reactions during the polymerization process and causing the polyester to be colored.

[0005] In summary, to improve the polymerization performance of 2,5-furandicarboxylic acid and solve the problem of polyester product coloring, it is urgent to find an efficient purification method for 2,5-furandicarboxylic acid to remove trace impurities in 2,5-furandicarboxylic acid. Summary of the Invention

[0006] The present invention provides a purification method and application of 2,5-furandicarboxylic acid, which can effectively remove trace impurities in 2,5-furandicarboxylic acid and solve the problem of polyester coloring during the polymerization of 2,5-furandicarboxylic acid in the prior art.

[0007] To achieve the above objectives, the present invention adopts the following technical solutions: A purification method of 2,5-furandicarboxylic acid, comprising the following steps: Alkaline dissolution: Dissolve unpurified 2,5-furandicarboxylic acid in an alkaline solution to prepare a 2,5-furandicarboxylic acid alkaline solution; Decolorization: Add activated carbon to the 2,5-furandicarboxylic acid alkaline solution, heat to 25-40 °C and stir. After stirring evenly, filter to obtain the decolorized 2,5-furandicarboxylic acid alkaline solution; Acid precipitation: An acidic aqueous solution is added to the decolorized alkaline solution of 2,5-furandicarboxylic acid for acidification. The pH value is controlled to be ≤2, and the acidification temperature is controlled within 50°C. The solid of 2,5-furandicarboxylic acid gradually precipitates to obtain the acidified 2,5-furandicarboxylic acid mixture. The acidified 2,5-furandicarboxylic acid mixture is suction filtered to obtain the crude 2,5-furandicarboxylic acid; Impurity removal: Add 2 - 5 times the mass fraction of pure water to the crude 2,5-furandicarboxylic acid, and add a metal chelating agent of 0.05 - 1% of the mass fraction of 2,5-furandicarboxylic acid. Heat up to 25 - 100°C, stir for 20 - 180 min, then cool down to 60°C and filter to obtain 2,5-furandicarboxylic acid; Water washing: Add 2 - 5 times the mass fraction of pure water to the 2,5-furandicarboxylic acid after impurity removal. Heat up to 25 - 100°C, stir for 20 - 180 min, then cool down to 60°C and filter to obtain 2,5-furandicarboxylic acid; Crystallization: Add 2 - 5 times the mass fraction of pure water to the 2,5-furandicarboxylic acid obtained after water washing. Heat up to 80 - 100°C, stir for 20 - 180 min, then cool down at a rate of 20°C / h to 0 - 20°C and filter. The wet solid obtained is dried to obtain the purified 2,5-furandicarboxylic acid.

[0008] In the above steps, the three steps of alkali dissolution, water washing, and crystallization need to be treated by introducing oxygen. The oxygen is an oxygen-rich gas with an oxygen concentration greater than 21% or pure oxygen.

[0009] The alkaline solution is one or more of sodium hydroxide aqueous solution and potassium hydroxide aqueous solution. The concentration of the alkaline aqueous solution is 1 - 10 mol / L, and the addition amount is 1 - 5 times the mass fraction of 2,5-furandicarboxylic acid.

[0010] The particle size of the activated carbon is 10 - 200 mesh, and the addition amount is 7% - 15% of the mass fraction of 2,5-furandicarboxylic acid.

[0011] The acidic aqueous solution is an inorganic acid aqueous solution, and the inorganic acid is one or more of hydrochloric acid, sulfuric acid, and nitric acid.

[0012] The metal chelating agent is one or more of disodium ethylenediaminetetraacetate and tetrasodium ethylenediaminetetraacetate.

[0013] The method for synthesizing polyethylene furandicarboxylate using the purified 2,5-furandicarboxylic acid obtained by the above purification method includes the following steps: Slurrying: Add the purified 2,5-furandicarboxylic acid, ethylene glycol, and germanium oxide into the polymerization kettle. Control the temperature in the kettle at 100 - 150°C and slurry for 20 - 40 min to obtain a mixed slurry; Esterification: Continuously raise the temperature of the reaction kettle to 195 - 210 °C for esterification reaction to obtain an esterification product; Polycondensation: Add a stabilizer to the esterification product. After stirring for 10 - 30 min, raise the temperature of the reaction kettle to 240 - 250 °C. After pre-polycondensation and polycondensation, polyethylene furandicarboxylate is obtained.

[0014] Among them, the molar ratio of 2,5-furandicarboxylic acid, ethylene glycol, and germanium oxide is 1:(1.2 - 1.8):(0.0005 - 0.001).

[0015] The stabilizer is one or more of triphenyl phosphate, triethyl phosphate, and trimethyl phosphate, and the addition amount is 0.03 - 0.05% of the mass fraction of 2,5-furandicarboxylic acid.

[0016] Beneficial effects: The present invention provides a purification method and application of 2,5-furandicarboxylic acid. Compared with the prior art, it has the following advantages: 1. In the present invention, trace chromogenic impurities in 2,5-furandicarboxylic acid are removed by decolorization with activated carbon. At the same time, by introducing oxygen-rich gas in the three steps of alkali dissolution, water washing, and crystallization, organic impurities and inorganic impurities in 2,5-furandicarboxylic acid undergo oxidation reactions. The oxidized inorganic impurities undergo chelation reactions with metal chelating agents during the impurity removal process to form water-soluble metal impurities, and the oxidized organic impurities form water-soluble impurities. Further, through the water washing and crystallization processes, water-soluble organic impurities and water-soluble metal inorganic impurities are removed; 3. The 2,5-furandicarboxylic acid purified by the method of the present invention has high purity and low impurity content, and the color and transparency of the polyester prepared by polymerization are significantly improved; 4. In the purification method of the present invention, no organic solvent is required, the whole process is safe, environmentally friendly, and the process is simple and easy to operate. Specific embodiments

[0017] The present invention will be described in detail below with specific examples: Example 1

[0018] A purification method of 2,5-furandicarboxylic acid, the specific steps are as follows: Alkali dissolution: Dissolve 500 g of unpurified 2,5-furandicarboxylic acid in 500 g of sodium hydroxide aqueous solution (concentration 10 mol / L) to prepare a 2,5-furandicarboxylic acid alkaline solution, and continuously introduce an oxygen / nitrogen mixed gas (oxygen concentration 21%) throughout the process; Decolorization: Add 35 g of activated carbon with a particle size of 10 mesh to the 2,5-furandicarboxylic acid alkaline solution, raise the temperature to 25 °C and stir. After stirring evenly, filter to obtain a decolorized 2,5-furandicarboxylic acid alkaline solution; Acid precipitation: Hydrochloric acid aqueous solution is added to the decolorized alkaline solution of 2,5-furandicarboxylic acid for acidification treatment. The pH value is controlled to be equal to 2, and the acidification temperature is controlled within 50 °C. The solid of 2,5-furandicarboxylic acid will gradually precipitate, and the acidified 2,5-furandicarboxylic acid mixture is obtained. The acidified 2,5-furandicarboxylic acid mixture is filtered by suction to obtain the crude 2,5-furandicarboxylic acid; Impurity removal: The crude 2,5-furandicarboxylic acid is added to 1000 g of pure water, and 0.25 g of disodium ethylenediaminetetraacetate is added. The temperature is raised to 25 °C, and after stirring for 20 min, the temperature is lowered to 60 °C, and then filtered to obtain 2,5-furandicarboxylic acid; Washing: 1000 g of pure water is added to the 2,5-furandicarboxylic acid obtained by impurity removal, the temperature is raised to 25 °C, and stirred for 20 min. The whole process is continuously passed through a mixed gas of oxygen / nitrogen (oxygen concentration 21%). The temperature is lowered to 60 °C, and then filtered to obtain 2,5-furandicarboxylic acid; Crystallization: 1000 g of pure water is added to the 2,5-furandicarboxylic acid obtained by washing, the temperature is raised to 80 °C, and stirred for 20 min. The whole process is continuously passed through a mixed gas of oxygen / nitrogen (oxygen concentration 21%). After cooling to 0 °C at a cooling rate of 20 °C / h, it is filtered, and the obtained wet solid is dried in an oven at 70 °C to obtain the purified 2,5-furandicarboxylic acid.

[0019] The method for preparing polyethylene furandicarboxylate using the purified 2,5-furandicarboxylic acid of this example is as follows: Slurrying: Weigh 1000 g of purified 2,5-furandicarboxylic acid, 635 g of ethylene glycol, and 0.3 g of germanium oxide and add them to the polymerization kettle. Control the temperature in the kettle at 150 °C and slurry for 20 min to obtain a mixed slurry; Esterification: Continue to raise the temperature of the reaction kettle to 210 °C for esterification reaction to obtain an esterification product; Polycondensation: Add 0.3 g of triphenyl phosphate to the esterification product, stir for 10 min, then raise the temperature of the reaction kettle to 240 °C, and obtain polyethylene furandicarboxylate after pre-polycondensation and polycondensation. Example 2

[0020] A purification method for 2,5-furandicarboxylic acid is as follows: Alkali dissolution: 500 g of unpurified 2,5-furandicarboxylic acid is dissolved in 2500 g of sodium hydroxide aqueous solution (concentration 1 mol / L) to prepare an alkaline solution of 2,5-furandicarboxylic acid. The whole process is continuously passed through pure oxygen; Decolorization: Add 75 g of activated carbon with a particle size of 200 mesh to the alkaline solution of 2,5-furandicarboxylic acid, raise the temperature to 40 °C and stir. After stirring evenly, filter to obtain the decolorized alkaline solution of 2,5-furandicarboxylic acid; Acid precipitation: Sulfuric acid aqueous solution is added to the decolorized alkaline solution of 2,5-furandicarboxylic acid for acidification treatment. The pH value is controlled to be equal to 2, and the acidification temperature is controlled within 50 °C. The solid of 2,5-furandicarboxylic acid will gradually precipitate, and the acidified 2,5-furandicarboxylic acid mixture is obtained. The acidified 2,5-furandicarboxylic acid mixture is filtered by suction to obtain crude 2,5-furandicarboxylic acid; Impurity removal: The crude 2,5-furandicarboxylic acid is added to 2500 g of pure water, and 5 g of sodium ethylenediaminetetraacetate is added. The temperature is raised to 100 °C, and after stirring for 180 min, the temperature is lowered to 60 °C, and then filtered to obtain 2,5-furandicarboxylic acid; Washing: 2500 g of pure water is added to the 2,5-furandicarboxylic acid obtained by impurity removal. The temperature is raised to 100 °C, and stirred for 180 min. Pure oxygen is continuously introduced throughout the process. The temperature is lowered to 60 °C, and then filtered to obtain 2,5-furandicarboxylic acid; Crystallization: 2500 g of pure water is added to the 2,5-furandicarboxylic acid obtained by washing. The temperature is raised to 100 °C, and stirred for 180 min. Pure oxygen is continuously introduced throughout the process. After cooling at a rate of 20 °C / h to 20 °C, it is filtered. The obtained wet solid is dried in an oven at 70 °C to obtain purified 2,5-furandicarboxylic acid.

[0021] The method for preparing polyethylene furandicarboxylate using the purified 2,5-furandicarboxylic acid of this example is as follows: Slurrying: Weigh 1000 g of purified 2,5-furandicarboxylic acid, 477 g of ethylene glycol, and 0.9 g of germanium oxide and add them into the polymerization kettle. Control the temperature in the kettle at 150 °C and slurry for 40 min to obtain a mixed slurry; Esterification: Continue to raise the temperature of the reaction kettle to 195 °C for esterification reaction to obtain an esterification product.

[0022] Polycondensation: Add 0.5 g of triethyl phosphate to the esterification product, stir for 10 min, then raise the temperature of the reaction kettle to 250 °C. After pre-polycondensation and polycondensation, polyethylene furandicarboxylate is obtained. Example 3

[0023] This example provides a purification method for 2,5-furandicarboxylic acid, and the specific steps are as follows: Alkaline dissolution: Dissolve 500 g of unpurified 2,5-furandicarboxylic acid in 2000 g of sodium hydroxide aqueous solution (concentration 5 mol / L) to prepare an alkaline solution of 2,5-furandicarboxylic acid. Pure oxygen / nitrogen mixer (oxygen concentration 50%) is continuously introduced throughout the process; Decolorization: 60 g of activated carbon with a particle size of 100 mesh was added to the alkaline solution of 2,5-furandicarboxylic acid, and the temperature was raised to 40 °C for stirring. After stirring evenly, filtration was carried out to obtain the decolorized alkaline solution of 2,5-furandicarboxylic acid; Acid precipitation: A nitric acid aqueous solution was added to the decolorized alkaline solution of 2,5-furandicarboxylic acid for acidification treatment. The pH value was controlled to be equal to 2, and the acidification temperature was controlled within 50 °C. The solid of 2,5-furandicarboxylic acid would gradually precipitate, and the acidified mixed solution of 2,5-furandicarboxylic acid was obtained. The acidified mixed solution of 2,5-furandicarboxylic acid was suction-filtered to obtain the crude product of 2,5-furandicarboxylic acid; Impurity removal: The crude product of 2,5-furandicarboxylic acid was added to 2000 g of pure water, and 1 g of tetrasodium ethylenediaminetetraacetate was added. The temperature was raised to 80 °C, and after stirring for 100 min, the temperature was lowered to 60 °C, and filtration was carried out to obtain 2,5-furandicarboxylic acid.

[0024] Washing: The 2,5-furandicarboxylic acid obtained by impurity removal was added to 2000 g of pure water, the temperature was raised to 80 °C, and stirring was carried out for 100 min. Pure oxygen was continuously introduced throughout the process. The temperature was lowered to 60 °C, and filtration was carried out to obtain 2,5-furandicarboxylic acid.

[0025] Crystallization: The 2,5-furandicarboxylic acid obtained by washing was added to 2000 g of pure water, the temperature was raised to 90 °C, and stirring was carried out for 100 min. Pure oxygen was continuously introduced throughout the process. After cooling at a rate of 20 °C / h to 10 °C, filtration was carried out, and the obtained wet solid was dried in an oven at 70 °C to obtain the purified 2,5-furandicarboxylic acid.

[0026] This example provides a preparation scheme for polyethylene furandicarboxylate, and the specific steps are as follows: Slurrying: 1000 g of purified 2,5-furandicarboxylic acid, 715 g of ethylene glycol, and 0.6 g of germanium oxide were weighed and added to the polymerization kettle. The temperature in the kettle was controlled at 150 °C, and slurrying was carried out for 40 min to obtain a mixed slurry; Esterification: The temperature of the reaction kettle was continuously raised to 200 °C for esterification reaction to obtain an esterification product.

[0027] Polycondensation: 0.5 g of trimethyl phosphate was added to the esterification product, and after stirring for 10 min, the temperature of the reaction kettle was raised to 250 °C. After pre-polycondensation and polycondensation, polyethylene furandicarboxylate was obtained. Comparative Example 1

[0028] This comparative example used unpurified 2,5-furandicarboxylic acid as a polymerization monomer.

[0029] This comparative example also provides a preparation scheme for polyethylene furandicarboxylate, and the specific steps are as follows: Pulping: Weigh 1000 g of unpurified 2,5-furandicarboxylic acid, 635 g of ethylene glycol, and 0.5 g of germanium oxide and add them to the polymerization kettle. Control the temperature in the kettle at 150 °C and pulp for 40 min to obtain a mixed slurry; Esterification: Continue to raise the temperature of the reaction kettle to 200 °C for esterification reaction to obtain an esterification product;

[0030] Polycondensation: Add 0.3 g of trimethyl phosphate to the esterification product, stir for 10 min, then raise the temperature of the reaction kettle to 240 °C. After prepolycondensation and polycondensation, polyethylene furandicarboxylate is obtained. Comparative Example 2

[0031] The difference between the preparation of purified 2,5-furandicarboxylic acid in this comparative example and Example 1 is that oxygen-rich gas is not introduced in the three steps of alkali dissolution, water washing, and crystallization, and other processes are exactly the same as those in Example 1.

[0032] This comparative example also provides a preparation scheme for polyethylene furandicarboxylate. The specific steps are as follows: Pulping: Weigh 1000 g of purified 2,5-furandicarboxylic acid, 700 g of ethylene glycol, and 0.3 g of germanium oxide and add them to the polymerization kettle. Control the temperature in the kettle at 150 °C and pulp for 30 min to obtain a mixed slurry; Esterification: Continue to raise the temperature of the reaction kettle to 210 °C for esterification reaction to obtain an esterification product;

[0033] Polycondensation: Add 0.3 g of trimethyl phosphate to the esterification product, stir for 30 min, then raise the temperature of the reaction kettle to 240 °C. After prepolycondensation and polycondensation, polyethylene furandicarboxylate is obtained. Comparative Example 3

[0034] The difference between the preparation of purified 2,5-furandicarboxylic acid in this comparative example and Example 1 is that the impurity removal process is not carried out, and other steps are exactly the same as those in Example 1.

[0035] This comparative example also provides a preparation scheme for polyethylene furandicarboxylate. The specific steps are as follows: Pulping: Weigh 1000 g of purified 2,5-furandicarboxylic acid, 700 g of ethylene glycol, and 0.3 g of germanium oxide and add them to the polymerization kettle. Control the temperature in the kettle at 150 °C and pulp for 30 min to obtain a mixed slurry; Esterification: Continue to raise the temperature of the reaction kettle to 210 °C for esterification reaction to obtain an esterification product;

[0036] Polycondensation: Add 0.3 g of trimethyl phosphate to the esterification product, stir for 30 min, then raise the temperature of the reaction kettle to 240 °C. After prepolycondensation and polycondensation, polyethylene furandicarboxylate is obtained.

[0037] In the examples and comparative examples of the present invention, the purity of the finally obtained 2,5-furandicarboxylic acid was tested by HLPC, and the impurity content was tested by ICP and ash content. The intrinsic viscosity of the polyethylene furandicarboxylate chips prepared by polymerizing 2,5-furandicarboxylic acid was measured by a capillary viscometer. The L value and b value of the chromaticity were measured according to the dry pulverization method in Test Methods for Fiber Grade Polyester (PET) Chips of GB / T 14190-2017.

[0038] The test results of the 2,5-furandicarboxylic acid and polyethylene furandicarboxylate chips prepared in the above examples and comparative examples are shown in Table 1 below: Table 1 Test Results of 2,5-Furandicarboxylic Acid and Polyethylene Furandicarboxylate Chips

[0039] It can be seen from the above experimental results that the 2,5-furandicarboxylic acid purified by the process of the present invention has higher purity, lower impurity content and lower ash content, and the prepared polyethylene furandicarboxylate has higher viscosity and more excellent hue compared with the polymer materials prepared by other purification processes.

[0040] The above are only the preferred embodiments of the present invention, which will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements made all fall within the protection scope of the present invention.

Claims

1. A method for purifying 2,5-furandicarboxylic acid, characterized in that: The following steps are involved: Alkaline dissolution: unpurified 2,5-furandicarboxylic acid is dissolved in an alkaline solution, and oxygen is continuously introduced during the whole process to obtain an alkaline solution of 2,5-furandicarboxylic acid; Decolorization: Add activated carbon to the alkaline solution of 2,5-furandicarboxylic acid for decolorization; Acid precipitation: add an acidic aqueous solution to the decolorized 2,5-furandicarboxylic acid alkaline solution, control the pH value to ≤ 2, and the temperature to be controlled within 50°C, perform acidification treatment, obtain an acidified 2,5-furandicarboxylic acid mixed solution, and obtain crude 2,5-furandicarboxylic acid after filtration; Impurity removal: Use metal chelating agent to remove impurities from crude 2,5-furandicarboxylic acid; Water washing: adding pure water to the 2,5-furandicarboxylic acid after impurity removal, heating and stirring, continuously introducing oxygen during the whole process, cooling and filtering to obtain 2,5-furandicarboxylic acid; Crystallization: Add pure water to the washed 2,5-furandicarboxylic acid, heat up and stir, continuously introduce oxygen during the whole process, cool down at a rate of 20°C / h, cool down and filter, and obtain purified 2,5-furandicarboxylic acid after drying.

2. The method for purifying 2,5-furandicarboxylic acid according to claim 1, characterized in that: The oxygen is nutrient-rich gas with an oxygen concentration greater than 21% or pure oxygen.

3. The method for purifying 2,5-furandicarboxylic acid according to claim 1 or 2, characterized in that: The concentration of the alkaline solution is 1-10 mol / L, and the amount added is 1-5 times the mass fraction of 2,5-furandicarboxylic acid.

4. The method for purifying 2,5-furandicarboxylic acid according to claim 1, characterized in that: The specific steps of decolorization are: adding activated carbon to the alkaline solution of 2,5-furandicarboxylic acid, wherein the amount of activated carbon added is 7%-15% of the mass fraction of 2,5-furandicarboxylic acid, heating to 25-40°C and stirring, stirring evenly, filtering to obtain the decolorized alkaline solution of 2,5-furandicarboxylic acid.

5. The method for purifying 2,5-furandicarboxylic acid according to claim 1 or 4, characterized in that: The activated carbon particle size is 10-200 meshes.

6. The method for purifying 2,5-furandicarboxylic acid according to claim 1, characterized in that: The specific process of impurity removal is: add 2-5 times the mass fraction of pure water to the crude 2,5-furandicarboxylic acid, and add 0.05-1% of the mass fraction of metal chelating agent of 2,5-furandicarboxylic acid, heat to 25-100°C, stir for 20-180 minutes, cool to 60°C, filter, and obtain 2,5-furandicarboxylic acid.

7. The method for purifying 2,5-furandicarboxylic acid according to claim 1 or 2, characterized in that: During the washing process, the temperature is raised to 25-100°C; the stirring time is 20-180 minutes; the temperature is lowered to 60°C for filtration.

8. The method for purifying 2,5-furandicarboxylic acid according to claim 1 or 2, characterized in that: During the crystallization process, the temperature is raised to 80-100°C; the stirring time is 20-180 minutes; the temperature is lowered to 0-20°C for filtration, and the cooling rate is 20°C / h.

9. Use of the purified 2,5-furandicarboxylic acid obtained by the method according to any one of claims 1 to 8, characterized in that: The method for purifying 2,5-furandicarboxylic acid for synthesizing polyethylene furandicarboxylate comprises the following steps: Beating: adding purified 2,5-furandicarboxylic acid, ethylene glycol and germanium oxide into a polymerization reactor in a molar ratio of 1: (1.2-1.8): (0.0005-0.001), controlling the temperature in the reactor at 100-150° C., beating for 20-40 minutes to obtain a mixed slurry; Esterification: Continue to raise the temperature of the reactor to 195-210°C to carry out esterification reaction to obtain esterification products; Polycondensation: Add a stabilizer to the esterification product, stir for 10-30 minutes, raise the temperature of the reactor to 240-250°C, and obtain polyethylene furandicarboxylate after pre-polycondensation and polycondensation.

10. The use of purified 2,5-furandicarboxylic acid according to claim 9, characterized in that: The amount of the stabilizer added is 0.03-0.05% by mass of 2,5-furandicarboxylic acid.

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