Preparation method of 2,5-furandicarboxylic acid

Abstract

The present invention relates to a preparation method of 2,5-furandicarboxylic acid, comprising the following steps: cesium furoate and cesium dicarboxylate are uniformly mixed and placed in a reactor, a cesium salt catalyst can be selectively added, and then a solid-phase molten salt reaction is performed under nitrogen or inert gas atmosphere, stirring, and pressurization conditions to obtain an intermediate product cesium salt, and then protonation treatment and purification treatment are performed to obtain a final product 2,5-furandicarboxylic acid. The method of the present invention has a high selectivity of raw materials for FDCA of more than 96%, a simple product separation process, a high yield of the target product, and a low production cost.

Description

Technical Field

[0001] The present invention relates to the technical field of compound synthesis, and in particular to a method for preparing 2,5-furandicarboxylic acid. Background Art

[0002] The development of green and renewable biomass resources to replace traditional petroleum resources is the focus of development and research today. 2,5-Furandicarboxylic acid (hereinafter referred to as FDCA) is a new bio-based monomer derived from biomaterials such as starch and cellulose. FDCA synthesized from biomass resources has a structure similar to terephthalic acid (TPA) and can be used to synthesize bio-based high-performance polymers such as polyester and nylon or bio-based degradable copolyesters. Since there is a large amount of cellulose in nature, it is combined with the polyester industry. Polyesters and copolyesters based on furandicarboxylic acid will become key monomers for bio-based polymers. Their polymers will partially replace existing petroleum-based polyesters (such as PET and PBAT) and will provide better performance (such as mechanical properties, gas barrier properties) or new functional uses (biodegradation, elastomers, etc.). For example, polyethylene 2,5-furandicarboxylate (PEF) obtained by the polymerization of FDCA and ethylene glycol has better mechanical and thermal properties and better gas barrier properties than polyethylene terephthalate (PET).

[0003] The main methods for synthesizing FDCA are chemical and biological methods. Among them, the research on the chemical method is relatively mature, and the selectable reaction raw materials mainly include 5-hydroxymethylfurfural (HMF), furfural, hexanoic acid, diglycolic acid, etc., which are prepared by selective oxidation or dehydration cyclization. For example, Chinese Patent 202010030966.5 discloses a method for producing furandicarboxylic acid and its derivatives from furfural, which uses 5-HMF as a reactant and obtains FDCA after oxidation. The efficient conversion of HMF is currently the mainstream direction of synthesis. For example, Chinese Patent 202110936135.9 discloses a reaction system for synthesizing 2,5-furandicarboxylic acid and a production line for preparing 2,5-furandicarboxylic acid, using furanate as a reactant and obtaining FDCA after disproportionation. For example, U.S. Patent US0265896A1 discloses Fungal production of FDCA, which reacts furanate with CO2 or CN -After the reaction, it is converted into FDCA. For example, U.S. Patent No. 9938547 uses the acylation reaction of the furan ring to produce FDCA, and U.S. Patent No. 10428039 B2 uses the polysaccharide cyclization to produce FDCA. However, due to the relatively low production efficiency of bio-enzyme catalysis or engineered strain biocatalysis, most of them are in the research and development stage. The starting materials of the above raw materials can all be obtained from biomass resources, which can effectively reduce carbon emissions and greatly reduce the production cost of FDCA. The above are all carried out under solvent conditions. The present invention adopts a solid-phase molten salt method, using cesium furoate and cesium malonate as reaction raw materials, and can directly obtain 2,5-furandicarboxylate products, which are subsequently protonated and purified to obtain FDCA. Summary of the Invention

[0004] The present invention aims to provide a method for preparing 2,5-furandicarboxylic acid. The method of the present invention has high selectivity for the target product and high yield of the FDCA product.

[0005] In order to achieve the above objectives, the present invention is implemented through the following technical solutions:

[0006] The preparation method of 2,5-furandicarboxylic acid comprises the following steps: cesium furoate and cesium dicarboxylate are uniformly mixed and placed in a reactor, a cesium salt catalyst can be optionally added, and then a solid-phase molten salt reaction is carried out under nitrogen or inert gas atmosphere, stirring, and pressurization conditions to obtain an intermediate product cesium salt, and then protonation treatment and purification treatment are performed to obtain the final product 2,5-furandicarboxylic acid;

[0007] The cesium dicarboxylate salt is one or more of cesium malonate, cesium methylmalonate, cesium ethylmalonate, and cesium 1,3-acetonedicarboxylate.

[0008] Furthermore, the cesium furoate and the cesium dicarboxylate salt are mixed by dry mechanical mixing or wet mixing. The wet mixing process comprises adding the cesium dicarboxylate salt to an aqueous solution of cesium furoate, stirring uniformly, and then dehydrating. Cesium furoate can be obtained by reacting furoic acid with a cesium salt (such as cesium carbonate).

[0009] Furthermore, the cesium salt catalyst is cesium carbonate or cesium acetate; the molar ratio of the cesium furoate to the cesium dicarboxylate salt is 1:1; and the added amount of the cesium salt catalyst is 0-300% of the molar amount of the cesium furoate.

[0010] Furthermore, the inert gas is argon; the stirring speed is 50-300 rpm; and the pressurization is to control the pressure in the reactor to be 3-10 MPa.

[0011] Furthermore, the temperature of the solid-phase molten salt reaction is 200-260° C., and the reaction time is 5-72 hours. The reaction temperature is relatively low, lower than the disproportionation temperature of furoate (340-450° C.).

[0012] Furthermore, the protonation treatment is to stir the intermediate product cesium salt with a 20-25wt% sulfuric acid solution for 1-2 hours; the molar ratio of sulfuric acid in the sulfuric acid solution to the intermediate product cesium salt is (1.0-1.5):1.

[0013] Furthermore, the purification treatment is reduced pressure sublimation with a pressure of 1-50 mmHg, a temperature of 200-300° C., and a time of 0.5-6 h.

[0014] Beneficial technical effects: Compared with the existing technical route of preparing 2,5-furandicarboxylate by reacting furoate with carbonate and carbon dioxide, the present invention adopts cesium furoate and cesium malonate to carry out solid-phase molten salt reaction, the cesium malonate is decarboxylated, and the removed carboxyl group is transferred to react with the furan ring to obtain the target product. The method of the present invention has a selectivity of more than 96% for the target product, the subsequent separation process of the product is simple, the yield of the target product is high, and the cost is low. DETAILED DESCRIPTION

[0015] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, rather than all embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0016] Unless otherwise specifically stated, the numerical value set forth in these embodiments does not limit the scope of the present invention. Technology and methods known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology and methods should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments can have different values.

[0017] In the following examples, experimental methods without specific conditions are generally measured according to national standards. If there are no corresponding national standards, they are measured according to the general international standards or the standards proposed by relevant companies. Unless otherwise stated, all parts are by weight and all percentages are by weight.

[0018] Cesium furoate is obtained by adding 1.0 mol of furoic acid to a 30-50 wt% aqueous solution of cesium carbonate (cesium carbonate content is 0.55-1.0 mol). The mixture is allowed to react completely for 1.5 hours at room temperature, 1 atm pressure, and a stirring speed of 300 rpm. The mixture is then dehydrated to obtain 90-98% cesium furoate.

[0019] To obtain cesium malonate: Completely react 1.0 mol of malonic acid with 1.0 mol of cesium carbonate (or a slight excess) in aqueous solution (refer to the reaction conditions for cesium furoate), followed by dehydration, to obtain cesium malonate. The preparation process for other cesium dicarboxylates can be referenced to cesium malonate.

[0020] Example 1

[0021] The preparation method of 2,5-furandicarboxylic acid comprises the following steps:

[0022] 1.0 mol of cesium furoate and 1.2 mol of cesium malonate were mixed uniformly, and the mixture was mechanically blended, and then placed in a reactor (cesium carbonate catalyst was not added in this embodiment), and the atmosphere in the reactor was replaced with nitrogen. Under the nitrogen atmosphere, the pressure in the reactor was controlled at 10.0 MPa, and stirring was started at 300 rpm. The reactor was heated and heated. When the temperature in the reactor reached 260° C., the timing was started to carry out solid-phase molten salt reaction for 6 hours. After the reaction was completed, the heating was stopped and the temperature was cooled to room temperature to obtain To obtain the intermediate product cesium salt, 200 mL of 25 wt % sulfuric acid solution was added to the kettle to precipitate 2,5-furandicarboxylic acid (FDCA), and stirring was continued for 1 hour for protonation treatment. The material in the kettle was then subjected to HPLC analysis (absorption wavelength 254 nm), and the content of 2,5-furandicarboxylic acid was measured to be 0.15 mol. After filtration and washing, it was sublimed under reduced pressure (pressure of 5 mmHg, temperature of 220°C, time for 3.0 hours) to obtain FDCA with a purity of more than 95 wt %.

[0023] In this embodiment, the conversion rate of cesium furoate in the single-pass reaction was 15.5%, and the yield of FDCA product was 15%.

[0024] Example 2

[0025] The preparation method of 2,5-furandicarboxylic acid comprises the following steps:

[0026] 1.0 mol of cesium furoate and 1.0 mol of cesium malonate are mixed uniformly, the mixture is mechanically blended, and then placed in a reactor, 0.20 mol of cesium carbonate is added, and the atmosphere in the reactor is replaced with nitrogen. Under the nitrogen atmosphere, the pressure in the reactor is controlled at 5.0 MPa, and stirring is started at 200 rpm. The reactor is heated and heated. When the temperature in the reactor reaches 240°C, the timing is started to carry out solid-phase molten salt reaction for 10 hours. After the reaction is completed, the heating is stopped and the temperature is cooled to room temperature to obtain a medium The intermediate product cesium salt was obtained by adding 200 mL of 20 wt % sulfuric acid solution to the kettle to precipitate 2,5-furandicarboxylic acid (FDCA), and continuing to stir for 2 h for protonation treatment; the material in the kettle was then subjected to HPLC analysis (the peak position was the same as in Example 1), and the content of 2,5-furandicarboxylic acid was measured to be 0.45 mol. After filtration and washing, the product was sublimed under reduced pressure (pressure of 3 mmHg, temperature of 220° C., and time of 3.0 h) to obtain FDCA with a purity of more than 95 wt %.

[0027] In this example, the conversion rate of cesium furoate in the single-pass reaction was 45.8%, and the yield of FDCA product was 45%.

[0028] Example 3

[0029] The FDCA preparation process of this example is the same as that of Example 2, except that the amount of cesium carbonate added is 1.0 mol, and the solid-phase molten salt reaction is carried out for 72 hours. The product peak position is the same as that of Example 1.

[0030] In this example, the conversion rate of cesium furoate in the single-pass reaction was 92.3%, and the yield of FDCA product was 92.0%.

[0031] Example 3a

[0032] The FDCA preparation process of this example is the same as that of Example 2, except that 3.0 mol of cesium carbonate is added and the solid-phase molten salt reaction is carried out for 60 h. The product peak position is the same as that of Example 1.

[0033] In this embodiment, the conversion rate of cesium furoate in the single-pass reaction was 98.5%, and the yield of FDCA product was 96.5%.

[0034] Example 4

[0035] The preparation method of 2,5-furandicarboxylic acid comprises the following steps:

[0036] 1.0 mol of cesium furoate and 1.2 mol of cesium methylmalonate were mixed evenly, and the mixture was blended by wet method. Then, the mixture was placed in a reactor, 1.0 mol of cesium acetate was added, and the atmosphere in the reactor was replaced with argon. Under the argon atmosphere, the pressure in the reactor was controlled at 3.0 MPa, and stirring was started at 100 rpm. The reactor was heated and heated. When the temperature in the reactor reached 250 ° C, the timing was started to carry out solid-phase molten salt reaction for 24 hours. After the reaction was completed, the heating was stopped and the temperature was cooled to room temperature to obtain the intermediate. The product cesium salt was added to the kettle with 200 mL of a 20 wt % sulfuric acid solution to precipitate 2,5-furandicarboxylic acid (FDCA), and the mixture was stirred for 2 h for protonation. The contents of the kettle were then analyzed by HPLC (the peak position was the same as in Example 1), and the content of 2,5-furandicarboxylic acid was measured to be 0.69 mol. After filtration and washing, the mixture was sublimed under reduced pressure (pressure of 5 mmHg, temperature of 220° C., and time of 3.0 h) to obtain FDCA with a purity of more than 95 wt %.

[0037] In this example, the conversion rate of cesium furoate in the single-pass reaction was 69.6%, and the yield of FDCA product was 69%.

[0038] Comparative Example 1

[0039] The FDCA preparation process of this comparative example is the same as that of Example 2, except that the raw materials are potassium furoate, potassium malonate and potassium carbonate. In this comparative example, the single-pass reaction potassium furoate conversion rate is 30.2%, and the FDCA product yield is 18%.

[0040] The preparation process of Comparative Example 1 is the same as that of Example 2, except that the raw material cesium salt is replaced with potassium salt, which reduces the selectivity of potassium furoate for FDCA. The selectivity for FDCA in this comparative example is about 59.6%, while the selectivity for FDCA in Example 2 is about 98%. It can be seen that the use of cesium salt in a solid-phase molten salt reaction system can improve the selectivity of the raw material for the target product FDCA.

[0041] Comparative Example 2

[0042] The preparation process of this comparative example is the same as that of Example 1, except that the raw materials are potassium furoate and potassium malonate. In this comparative example, the conversion rate of potassium furoate in the single-pass reaction is less than 0.5%, and the yield of FDCA product is 0%.

[0043] Comparative Example 2 was prepared in the same manner as Example 1, except that the cesium salt was replaced with a potassium salt without adding a catalyst, so that a solid-phase molten salt reaction could not occur to obtain the target product FDCA.

[0044] As can be seen from the results of Example 1, although the yield of FDCA obtained by the solid-phase molten salt single-pass reaction of cesium furoate and cesium malonate in the present invention without the addition of the catalyst cesium carbonate or cesium acetate is relatively low (15%), the selectivity of the present invention for FDCA can basically reach over 96% when the catalyst is optionally added. On this basis, the addition of the catalyst cesium carbonate or cesium acetate can increase the yield of FDCA. Increasing the amount of catalyst used and extending the reaction time can further increase the yield of FDCA.

[0045] Compared to the traditional technical route of preparing FDCA by reacting furoate, carbonate and carbon dioxide, the carbonate in the traditional route participates in the reaction and is consumed, making it impossible to recycle and reuse. However, the present invention uses cesium malonate, which forms acetate after decarboxylation in a solid-phase molten salt reaction (the raw material is converted into a catalyst), which can be recovered and participate in the cyclic reaction. In addition, the furoate and carbonate system in the traditional route cannot form a solid-phase molten salt system. This is because the furoate and carbonate system begins to decompose at about 175°C. If the temperature is raised to above 240-280°C, the furoate raw material will be completely decomposed. However, the present invention uses cesium malonate as the raw material, which can provide the raw materials to form a molten salt system at high temperature, and then undergoes solid-phase molten salt decarboxylation to form furandicarboxylate to obtain the target product. The present invention adopts the technical route of using cesium furoate and cesium dicarboxylate to carry out the solid-phase molten salt reaction, and the target product selectivity is as high as 96% or more. The subsequent product separation process is simple, the target product yield is high, and the production cost is low.

[0046] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing 2,5-furandicarboxylic acid, characterized in that: The steps include: Cesium furoate and cesium dicarboxylate are mixed evenly and placed in a reactor, a cesium salt catalyst is added or not added, and then a solid-phase molten salt reaction is carried out under nitrogen or inert gas atmosphere, stirring, and pressurization conditions to obtain an intermediate product cesium salt, and then a protonation treatment and purification treatment are carried out to obtain a final product 2,5-furandicarboxylic acid; The cesium dicarboxylate salt is one or more of cesium malonate, cesium methylmalonate, cesium ethylmalonate, and cesium 1,3-acetone dicarboxylate; The molar ratio of the cesium furoate to the cesium dicarboxylate is 1:1; the cesium salt catalyst is cesium carbonate or cesium acetate, and the added amount of the cesium salt catalyst is 0-300% of the molar amount of the cesium furoate; The pressurization is to control the pressure in the reactor to be 3-10MPa; The temperature of the solid phase molten salt reaction is 200-260° C. and the reaction time is 5-72 hours.

2. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that: The mixing of the cesium furoate and the cesium dicarboxylate salt is dry mechanical mixing or wet mixing. The process of the wet mixing is: adding the cesium dicarboxylate salt to the aqueous solution of the cesium furoate, stirring evenly and then dehydrating.

3. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that: The inert gas is argon.

4. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that: The stirring speed is 50-300 rpm.

5. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that: The protonation treatment is to use a 20-25wt% sulfuric acid solution to stir the intermediate product cesium salt for 1-2h; the molar ratio of sulfuric acid in the sulfuric acid solution to the intermediate product cesium salt is (1.0-1.5):

1.

6. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that: The purification treatment is reduced pressure sublimation, with a pressure of 1-50 mmHg, a temperature of 200-300° C., and a time of 0.5-6 h.