Method for preparing 2,5-furandicarboxylic acid

Abstract

The present application belongs to the technical field of biomass chemicals, and provides a method for preparing 2,5-furandicarboxylic acid. The method comprises the following steps: mixing poly(ethylene 2,5-furandicarboxylate) with water, placing same in a high-pressure reaction kettle; after the reaction is completed, cooling same to room temperature, and performing solid-liquid phase separation to obtain 2,5-furandicarboxylic acid as a solid-phase product and ethylene glycol as a liquid-phase product; then, subjecting the resulting 2,5-furandicarboxylic acid to water washing and drying for later use, and measuring the yield and purity thereof. The method features mild reaction conditions, simple and readily available reactants and catalysts, high reactant conversion efficiency, easy product separation and high product purity, and a green and pollution-free reaction process and product.

Description

A method for preparing 2,5-furandicarboxylic acid Technical Field

[0001] This invention belongs to the field of biomass chemical technology, specifically relating to a method for preparing 2,5-furandicarboxylic acid. Background Technology

[0002] 2,5-Furfurandicarboxylic acid (FDCA) is an important biomass resource. It is not only biodegradable but also chemically stable, showing broad application prospects in bio-based polymers, food and pharmaceutical packaging, and other chemical intermediates. FDCA is a key monomer in biomass polymers, particularly used in the polymerization of FDCA with ethylene glycol to produce polyethylene 2,5-furandicarboxylate (PEF). PEF's thermal properties are similar to those of petroleum-based PET (polyethylene terephthalate), but its mechanical properties are better, and its gas barrier properties are significantly superior (13-19 times and 6-11 times greater for CO2 and O2, respectively). These properties give PEF a significant advantage over PET, making it a potential substitute. Therefore, the rise of PEF has led to a surge in FDCA research and continuous market growth.

[0003] Currently, FDCA can be prepared via methods such as 2,5-furandicarboxaldehyde oxidation, furfural / carbon dioxide catalysis, and 5-hydroxymethylfurfural (HMF) oxidation. Among these, the synthesis method using HMF as a raw material is the most common, mainly including stoichiometric oxidation, electrocatalysis, and chemical catalysis. Although research on FDCA preparation methods is quite mature, problems such as harsh reaction conditions, low preparation efficiency, difficulties in product separation and purification, and reduced catalyst activity upon reuse remain unresolved.

[0004] Therefore, this invention proposes a method for preparing FDCA that is not only green, economical, and efficient, but also has great potential for industrial application. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for preparing FDCA. This method has advantages such as mild reaction conditions, being green and pollution-free, simple product purification, and high product yield and purity. The optimal yield of FDCA prepared by this method reaches over 97%, and the purity reaches over 99%.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing 2,5-furandicarboxylic acid includes the following steps:

[0008] S1. Poly(2,5-furandicarboxylic acid) ethylene glycol ester is mixed with water and placed in a high-pressure reactor for reaction. After the reaction is completed, the mixture is cooled to room temperature and the solid and liquid phases are separated to obtain the solid product as 2,5-furandicarboxylic acid and the liquid product as ethylene glycol aqueous solution.

[0009] S2. The obtained 2,5-furandicarboxylic acid was washed with water and dried for later use. The yield and purity were measured.

[0010] The reaction route is as follows:

[0011] Furthermore, the compound represented by formula (1) is polyethylene 2,5-furandicarboxylate (PEF); in formula (1), n ​​is any integer ≥2.

[0012] Furthermore, in step S1, the mass ratio of polyethylene 2,5-furandicarboxylate to water is 1:1-20.

[0013] Furthermore, in step S1, the mass ratio of polyethylene 2,5-furandicarboxylate to water is 1:3-7.

[0014] Furthermore, a catalyst may be added to the high-pressure reactor in step S1; the catalyst is at least one of Brønsted acid and Lewis acid.

[0015] Furthermore, the amount of Brønsted acid used is 0-100 wt% of the PEF mass, and the amount of Lewis acid used is 0-10 wt% of the PEF mass.

[0016] Furthermore, the Brønsted acid includes, but is not limited to, at least one of sulfuric acid, acetic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, trichloroacetic acid, and methanesulfonic acid.

[0017] Furthermore, the Lewis acid is formed by any combination of metal cations and anions.

[0018] Furthermore, the metal cation includes, but is not limited to, Mg. 2+ Al 3+ Zn 2+ ,Sc 3+ Zr 4+ Hf 4+ Ta 5+ The anions include, but are not limited to, Cl-. - , Br - SO4 2- ,OTf - AcO - .

[0019] Furthermore, in step S1, the gas atmosphere in the high-pressure reactor is at least one of air, nitrogen, argon, and carbon dioxide.

[0020] Furthermore, the reaction temperature in step S1 is 100-220℃.

[0021] Furthermore, the reaction temperature in step S1 is 160-220℃.

[0022] Furthermore, the reaction time in step S1 is 2-24 hours.

[0023] Furthermore, the reaction time in step S1 is 4-6 hours.

[0024] Furthermore, the yield of 2,5-furandicarboxylic acid (FDCA) is calculated using the following formula:

[0025] The beneficial effects of this invention are:

[0026] (1) The present invention provides a preparation method for 2,5-furandicarboxylic acid, which uses only water and polyethylene 2,5-furandicarboxylic acid as reactants. The reaction conditions are mild, the conversion rate is high, and the purity of the product 2,5-furandicarboxylic acid is high.

[0027] (2) The preparation method provided by the present invention is simpler to separate the product than the 2,5-furandicarboxylic acid oxidation method and the furfural / carbon dioxide catalytic method. The solid-liquid phase separation can be completed by only one filtration. The solid phase is high-purity 2,5-furandicarboxylic acid and the liquid phase is an aqueous solution of ethylene glycol. At the same time, the liquid phase only needs one distillation to separate ethylene glycol as a by-product.

[0028] (3) Compared with the conventional catalyst system HMF oxidation method for preparing FDCA, the present invention does not use organic solvents, the reaction conditions are mild, and the preparation cost is greatly reduced. No side reactions occur during the entire reaction process, and the yield and purity of the product FDCA are high. It can be directly applied to the polymerization of PEF without additional processing of the product. The preparation method provided by the present invention can achieve full utilization of the product and no waste. It is an environmentally friendly production process with great potential for industrial application. Attached Figure Description

[0029] The invention will now be further described with reference to the accompanying drawings.

[0030] Figure 1 is a gas chromatogram of the ethylene glycol aqueous solution obtained in Example 27 of this invention;

[0031] Figure 2 is a high-performance liquid chromatogram of FDCA obtained in Example 27 of this invention. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The purity of FDCA in this invention is measured as follows: the acid value of the FDCA product is determined according to the standard GB / T 30921.5-2016 Test Methods for Industrial Purified Terephthalic Acid (PTA) Part 5: Determination of Acid Value. The purity of FDCA is determined according to the following formula:

[0034] Example 1

[0035] This embodiment provides a method for preparing 2,5-furandicarboxylic acid, including the following steps:

[0036] S1. Mix 60g of polyethylene 2,5-furandicarboxylate with 300g of water (i.e., a mass ratio of 1:5), place the mixture in a high-pressure reactor, introduce air, heat the reactor to 180°C, maintain the temperature for 4 hours, and obtain the reaction mixture after purging with a protective gas. After the reaction is completed, cool the mixture to room temperature and perform solid-liquid phase separation to obtain the solid product, which is 2,5-furandicarboxylic acid.

[0037] S2. The obtained 2,5-furandicarboxylic acid was washed with water and dried to obtain pure FDCA.

[0038] The yield of FDCA was calculated to be 90.38%, and the purity was 91.72%.

[0039] Examples 2-7

[0040] The only difference from Example 1 is the reaction temperature. The reaction process parameters and results are shown in Table 1.

[0041] Table 1

[0042] The data in Table 1 show that the yield and purity of FDCA increase significantly with increasing reaction temperature. The highest yield and purity are achieved at a reaction temperature of 180℃, but both decrease when the temperature exceeds 200℃. This is because FDCA readily decomposes above 200℃, producing carbon dioxide and water.

[0043] Examples 8-10

[0044] The only difference from Example 1 is the gas atmosphere inside the high-pressure reactor. The reaction process parameters and results are shown in Table 2.

[0045] Table 2

[0046] The data in Table 2 show that the yield and purity of FDCA are improved under the protective atmosphere of nitrogen, argon or carbon dioxide. Among them, the protective effect of CO2 is the most significant, which can effectively inhibit the decomposition of FDCA.

[0047] Examples 11-19

[0048] The only difference from Example 10 is the ratio of PEF to water. The reaction process parameters and results are shown in Table 3.

[0049] Table 3

[0050] The data in Table 3 show that when the mass ratio of PEF to water is less than 1:3, the yield and purity of FDCA do not change significantly. From the perspective of reactor efficiency, the optimal mass ratio is 1:3-7.

[0051] Examples 20-26

[0052] The only difference from Example 1 is the reaction time. The reaction process parameters and results are shown in Table 4.

[0053] Table 4

[0054] The data in Table 4 show that the yield and purity of FDCA are highest when the reaction time is 4-6 hours. As the reaction time increases, the yield and purity of FDCA decrease significantly.

[0055] Example 27

[0056] The only difference from Example 10 is that a catalyst was added to the reactor:

[0057] This embodiment provides a method for preparing 2,5-furandicarboxylic acid, including the following steps:

[0058] S1. Mix 60g of polyethylene 2,5-furandicarboxylate with 300g of water (i.e., a mass ratio of 1:5), place the mixture in a high-pressure reactor containing 0.15g of sulfuric acid, introduce carbon dioxide, heat the reactor to 180°C, maintain the temperature for 4 hours, and obtain the reaction mixture after purging with a protective gas. After the reaction is completed, cool the mixture to room temperature and perform solid-liquid phase separation to obtain the solid product, which is 2,5-furandicarboxylic acid.

[0059] S2. The obtained 2,5-furandicarboxylic acid was washed with water and dried to obtain pure FDCA.

[0060] The yield of FDCA was calculated to be 97.53%, and the purity was 99.42%.

[0061] Examples 28-33

[0062] The only difference from Example 27 is the type and amount of catalyst used in the reactor. The reaction process parameters and results are shown in Table 5.

[0063] Table 5

[0064] Table 5 shows that the addition of catalyst has a certain impact on the yield and purity of FDCA. In Example 27, when sulfuric acid was used as the catalyst, the yield (97.53%) and purity (99.42%) of FDCA were the highest. The reaction conditions were: the mass ratio of PEF to water was 1:5, the catalyst was sulfuric acid, the amount of sulfuric acid added was 0.15 g (wt% 0.05%), carbon dioxide atmosphere, and the reaction was carried out at 180°C for 4 h.

[0065] Furthermore, the liquid product ethylene glycol aqueous solution and the solid product FDCA obtained in Example 27 were analyzed by chromatography (DB-FFAP column):

[0066] (1) Gas chromatography analysis of ethylene glycol aqueous solution was performed, and the test results are shown in Figure 1:

[0067] As shown in Figure 1, the retention time of ethylene glycol (EG) was 7.651 min, and the retention time of diethylene glycol (diethylene glycol) was 12.034 min. No impurities were found in the liquid phase after the reaction. The diethylene glycol originated from impurity fragments in the reactant PEF, indirectly confirming that the reaction depolymerized the ester bonds in PEF without any other side reactions occurring.

[0068] (2) The FDCA obtained in Example 27 was analyzed by liquid chromatography. The test results are shown in Figure 2. The purity of FDCA was found to be 99.42%. The specific liquid chromatography data are shown in Table 6.

[0069] Table 6

[0070] In summary, as can be seen from Examples 1-34, Table 1-6 and Figure 1-2, the present invention provides a method for preparing FDCA. The advantages of the present invention are: mild reaction conditions, high FDCA yield and purity, simple product separation, environmentally friendly and pollution-free, and great potential for industrial application.

[0071] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. It should be understood that, in the various embodiments of this application, the sequence number of each process does not imply a sequential order of execution; some or all steps may be performed in parallel or sequentially; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0072] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application are available on the market or can be prepared by existing methods.

[0073] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions, and all technical features and optional technical features of this application can be combined to form new technical solutions.

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing 2,5-furandicarboxylic acid, characterized in that, Includes the following steps: Poly(2,5-furandicarboxylic acid) ethylene glycol ester was mixed with water and placed in a high-pressure reactor for reaction. After the reaction was completed, the mixture was cooled to room temperature and the solid and liquid phases were separated to obtain 2,5-furandicarboxylic acid as the solid phase product and ethylene glycol aqueous solution as the liquid phase product.

2. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that, The mass ratio of polyethylene 2,5-furandicarboxylate to water is 1:1-20.

3. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that, A catalyst may also be added to the high-pressure reactor; the catalyst is at least one of Brønsted acid and Lewis acid.

4. The method for preparing 2,5-furandicarboxylic acid according to claim 3, characterized in that, The amount of Brønsted acid used is 0-100 wt% of the PEF mass, and the amount of Lewis acid used is 0-10 wt% of the PEF mass.

5. The method for preparing 2,5-furandicarboxylic acid according to claim 3, characterized in that, The Brønsted acid includes, but is not limited to, at least one of sulfuric acid, acetic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, trichloroacetic acid, and methanesulfonic acid.

6. The method for preparing 2,5-furandicarboxylic acid according to claim 3, characterized in that, The Lewis acid is formed by any combination of metal cations and anions.

7. The method for preparing 2,5-furandicarboxylic acid according to claim 6, characterized in that, The metal cations include, but are not limited to, Mg. 2+ Al 3+ Zn 2+ ,Sc 3+ Zr 4+ Hf 4+ Ta 5+ The anions include, but are not limited to, Cl-. - , Br - SO4 2- ,OTf - AcO - .

8. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that, The gas atmosphere in the high-pressure reactor is at least one of air, nitrogen, argon, and carbon dioxide.

9. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that, The reaction temperature is 100-220℃.

10. A method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that, The reaction time is 2-24 hours.

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