Method for synthesizing 2,5-furandicarboxylic acid by means of carbonylation of furoic acid

Abstract

The present invention belongs to the field of furyl biomass chemicals and materials. Disclosed is a method for synthesizing 2,5-furandicarboxylic acid by means of the carbonylation of furoic acid. The method comprises: adding furoic acid and an organic alkali into a two-phase solvent system, separating two phases after the reaction is finished, adding an organic acid into the aqueous phase, filtering same, collecting a precipitate, then washing the precipitate, and drying same to obtain 2,5-furandicarboxylic acid, wherein the two-phase solvent system is a mixture of a basic metal salt solution and a biomass-based polar aprotic solvent, and a CO2-supplying reagent is added or not added into the two-phase solvent system. The synthesis process and the separation and purification process are simple, the product purity is relatively high, the carbonylation reaction rate is high, the raw material cost is reduced, and the green chemical development concept is satisfied.

Description

A method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid Technical Field

[0001] The invention belongs to the field of furan-based biomass chemicals and materials, and particularly relates to a method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid. Background Art

[0002] 2,5-Furandicarboxylic acid (FDCA), a furan-based product with an aromatic structure, shares significant structural and functional similarities with petroleum-based terephthalic acid. Poly(ethylene 2,5-furandicarboxylate) (PEF), prepared with ethylene glycol, exhibits superior thermodynamic, strength, and barrier properties to polyethylene terephthalate (PET). It is generally considered a green diacid monomer to replace terephthalic acid, thereby driving demand for FDCA. According to a research report released by the Xin Shijie Industry Research Center, the global FDCA market is expected to grow at a compound annual growth rate of over 8.5% from 2022 to 2027, reaching US$820 million in 2027.

[0003] Currently, the synthesis of FDCA primarily involves three pathways: the 5-hydroxymethylfurfural (HMF) oxidation pathway, the glucarboxylic acid pathway, and the furoic acid pathway. The HMF oxidation pathway uses HMF as a substrate and oxidizes it to FDCA via thermal or photoelectrocatalytic oxidation. The catalyst for this process is typically a precious metal, and large-scale production has been achieved. However, due to the relatively high price of HMF, the production cost of 2,5-furandicarboxylic acid is much higher than that of terephthalic acid, which limits the large-scale production and application of FDCA. The glucarboxylic acid pathway involves the selective oxidation of glucose at the C1 and C6 positions to carboxyl groups, followed by the direct synthesis of 2,5-furandicarboxylic acid under appropriate dehydration conditions. The primary challenge with this pathway is the selective oxidation step, and related theories and technologies are gradually being developed.

[0004] The furoate pathway mainly includes direct carbonylation of furoate, bromination of furoate and disproportionation of furoate.

[0005] 2

[0006] Since the preparation of FDCA by direct carbonylation with furoic acid as a carbonylation reagent and cesium carbonate as a substrate, research on the preparation of FDCA with furoic acid assisted by carbonate has continued to emerge. Chinese patent CN116283849A provides a method for preparing FDCA using cesium salt as a raw material. Chinese patent CN115991686A further supports the preparation of superbasic catalysts by carbonate loading to assist the synthesis of FDCA. However, this method is a solid heterogeneous reaction with relatively harsh reaction conditions, and related research has not made significant progress. There are two typical routes to obtain FDCA by bromination of furoic acid: direct oxidation and preparation as a Grignard reagent followed by reaction with CO

[0007] 2

[0008] Direct production. Both methods require bromination of furoic acid, a major cost-limiting factor. The disproportionation of furoic acid to produce FDCA originates from Ogata et al. (J. Am. Chem. Soc., 1957, 22: 6005-6008), who mixed benzoic acid with a metal halide to produce benzene and phthalic acid. However, the furandicarboxylic acid produced by this method has multiple isomers, and the reaction conditions are relatively harsh. Technical issues

[0009] In view of the above problems existing in the prior art, the technical problem to be solved by the present invention is to provide a method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid, which is used to address the current problems of high cost and harsh reaction conditions in the preparation of 2,5-furandicarboxylic acid. Technical Solutions

[0010] In order to solve the above problems, the technical solution adopted in the present invention is as follows:

[0011] A method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid comprises the following steps: adding furoic acid and an organic base to a biphasic solvent system; separating the two phases after the reaction; adding an organic acid to the aqueous phase; collecting the precipitate by filtration; washing the precipitate; and drying to obtain 2,5-furandicarboxylic acid; wherein the biphasic solvent system is a mixture of a basic metal salt solution and a biomass-based polar aprotic solvent; and a CO2 supplying agent is added or not added to the biphasic solvent system.

[0012] Furthermore, the volume ratio of the basic metal salt solution to the biomass-based polar aprotic solvent is 1-9:1-9.

[0013] Furthermore, the basic metal salt is one or a mixture of Na2CO3, K2CO3, NaOH and KOH, and the concentration of the basic metal salt solution is 0.5~5mol / L.

[0014] Preferably, the concentration of the basic metal salt solution is 0.5-1.5 mol / L.

[0015] Furthermore, the biomass-based polar aprotic solvent is one or a mixture of tetrahydrofuran, acetonitrile and propylene carbonate.

[0016] Furthermore, the organic base is one or more of sodium methoxide, sodium formate, sodium ethoxide, sodium acetate, triphenylacetic acid and trimethylacetic acid.

[0017] Furthermore, the concentrations of furoic acid and the organic base in the reaction system are both 0.1 to 1 mol / L. Preferably, the concentration of furoic acid in the reaction system is 0.4 to 0.6 mol / L; the concentration of the organic base in the reaction system is 0.3 to 0.5 mol / L.

[0018] Furthermore, the CO2 supply reagent is one or a mixture of triphenylacetic acid, trimethylacetic acid, ethylene carbonate and propylene carbonate.

[0019] Furthermore, the organic acid is one or a mixture of formic acid, acetic acid and propionic acid.

[0020] Further, the specific steps are as follows:

[0021] 1) dissolving a basic metal salt in water to obtain a basic metal salt solution, and then mixing the basic metal salt solution with a biomass-based polar aprotic solvent to construct a biphasic solvent system;

[0022] 2) Add furoic acid and an organic base to the biphasic solvent system constructed in step 1), with or without a CO2-donating reagent, and react at 140-220°C with continuous stirring for 1-12 hours;

[0023] 3) After the reaction is completed, the aqueous phase and the organic phase of the reaction system of step 2) are separated, the organic phase is recovered by distillation under reduced pressure at 40-80° C., an organic acid is added dropwise to the aqueous phase until no precipitation is generated, and the precipitate is collected by filtration to obtain crude 2,5-furandicarboxylic acid;

[0024] 4) The crude 2,5-furandicarboxylic acid is placed in a washing liquid and continuously washed until the conductivity of the washing liquid does not change significantly, and then dried at room temperature to obtain 2,5-furandicarboxylic acid.

[0025] Furthermore, in step 4), the washing liquid is an organic acid alcohol solution, the organic acid is the same as the organic acid used in step 3), the alcohol is methanol or ethanol, and the volume ratio of the acid to the alcohol is 5-9:1-6. Preferably, the volume ratio of the acid to the alcohol is 5-8:2-5.

[0026] Preferably, the reaction temperature of step 2) is 160-200° C., and the reaction time is 3-6 h.

[0027] Preferably, the distillation temperature in step 3) is 60-70°C.

[0028] The schematic diagram of the conversion of furoic acid into 2,5-furandicarboxylic acid in a two-phase system of the present invention is as follows:

[0029]

[0030] Wherein, base 1 is a basic metal salt; base 2 is an organic base. Beneficial effects

[0031] Beneficial effects: Compared with the prior art, the advantages of the present invention are:

[0032] (1) The basic metal salt used in the present invention can simultaneously serve as a base and a phase separation salt, promoting the formation of a two-phase system and assisting in the deprotonation of furoic acid; the biomass polar aprotic solvent can simultaneously serve as a solvent and a CO2 supply reagent.

[0033] (2) The organic base that promotes the carbonylation reaction of the present invention decomposes at a specific temperature to produce CO2 and a super base, thereby increasing the carbonylation reaction rate. After FDCA is formed, the presence of basic carbonate promotes its transfer to the aqueous phase, which is beneficial to the separation of the product.

[0034] (3) The solvent of the present invention, as an inducing agent for CO2 activation, significantly reduces the reaction energy barrier of the carbonylation process, showing that the reaction temperature range (160-200°C) is significantly lower than the current direct carbonylation reaction temperature of furoic acid (240-300°C), and the total pressure of the reaction system (0-0.3 MPa) is also lower than the currently reported furoic acid carbonylation process (3-10 MPa), and no superbase compound is used in the process.

[0035] (4) The biphasic solvent system used in the present invention not only serves as a solvent but also has a catalytic effect, thereby increasing the reaction rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG1 is an H-NMR (a) diagram of FDCA prepared in the present invention;

[0037] FIG2 is a C-NMR (b) diagram of FDCA prepared in the present invention. Best Mode for Carrying Out the Invention

[0038] The present invention will be further described below with reference to specific embodiments.

[0039] The yield, purity and conversion rate of FDCA prepared in the following examples were calculated according to the following formula:

[0040] Take 0.1g of the product before and after purification and place it evenly in a culture dish after constant weight, cover it with dust-free paper and place it in a 105℃ oven for 6h to constant weight to obtain the sample dryness; the yield of FDCA after purification is Y FDCA The calculation formula is as follows:

[0041]

[0042] where n FDCA is the molar amount of the product FDCA, n 糠酸1 is the molar amount of the reaction substrate furoic acid.

[0043] FDCA purity P FDCA The calculation formula is as follows:

[0044]

[0045] where m FDCA1 is the mass calculated by liquid chromatography, m FDCA2 is the mass to be weighed.

[0046] Conversion rate of FDCA C FDCA The calculation formula is as follows:

[0047]

[0048] where n FDCA is the molar amount of the product FDCA, n 糠酸2 is the molar amount of furoic acid reacted.

[0049] The purity of FDCA prepared in the following examples was determined by chromatographic purity and tested according to the following steps:

[0050] Take 0.1g (absolute dry equivalent) of the product, place it in a beaker, add appropriate amount of hot water to dissolve it, then wait for it to cool to room temperature and dilute to 500mL. After filtering through a 0.22 µm organic syringe filter, it is used to detect the FDCA concentration; use a liquid chromatograph (Watere2695) equipped with a differential refractive index detector (2414 RI Detetor) and an HPX-87H organic acid analytical column for analysis. The conditions are: flow rate 0.6 mL / min, column temperature 55°C, detector temperature 40°C, and mobile phase 5mM H2SO4; the actual chromatographic concentration of the dissolved sample FDCA is obtained through the drawn FDCA standard curve, and further calculation is the chromatographic purity of the sample. Example 1

[0051] A 1 mol / L aqueous Na2CO3 solution was prepared and mixed with propylene carbonate in a 1:9 (v:v) ratio to form a biphasic solvent system. Propylene carbonate also provided CO2. Furoic acid and triphenylacetic acid were then weighed and added to the biphasic solvent system. The concentrations of furoic acid and sodium acetate in the total solvent were both 0.4 mol / L (the solutes were uniformly dissolved in each phase). The reaction vessel was placed at 160°C with continuous stirring for 6 hours. After the reaction, the aqueous-organic phases were separated using a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C on a rotary evaporator to recover the solvent. Formic acid was added dropwise to the aqueous phase until no more precipitation occurred. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with a formic acid-alcohol solution (methanol:formic acid, volume ratio 8:2) until the conductivity of the washing solution did not change significantly. Finally, the crude FDCA was dried at room temperature to obtain FDCA. Example 2

[0052] A 1 mol / L aqueous Na2CO3 solution was prepared and mixed with acetonitrile in a 3:7 (v:v) ratio to form a biphasic solvent system. Furoic acid and sodium acetate were then weighed and added to the biphasic solvent system, with the concentrations of both furoic acid and sodium acetate in the total solvent at 0.4 mol / L (the solutes were uniformly dissolved in each phase). Propylene carbonate (10% by volume of the total solvent) was then added to the reaction vessel, and the reaction vessel was stirred continuously at 160°C for 4 h. After the reaction, the aqueous-organic phases were separated using a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C on a rotary evaporator to recover the solvent. Formic acid was added dropwise to the aqueous phase until no further precipitation occurred. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with a formic acid-alcohol solution (ethanol:formic acid, volume ratio 7:3) until the conductivity of the washing solution did not change significantly. Finally, the solution was dried at room temperature to obtain FDCA. Example 3

[0053] A 1 mol / L aqueous Na2CO3 solution was prepared and mixed with tetrahydrofuran in a 3:7 (v:v) ratio to form a biphasic solvent system. Furoic acid and triphenylacetic acid were then weighed and added to the biphasic solvent system, with the concentrations of furoic acid and sodium acetate in the total solvent being 0.4 mol / L (the solutes were uniformly dissolved in each phase). Propylene carbonate (10% by volume of the total solvent) was then added to the reaction vessel. The reaction vessel was stirred continuously at 160°C for 6 h. After the reaction, the aqueous-organic phases were separated using a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C on a rotary evaporator to recover the solvent. Acetic acid was added dropwise to the aqueous phase until no more precipitation occurred. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with an acetic acid alcohol solution (methanol:acetic acid, volume ratio 6:4) until the conductivity of the washing solution did not change significantly. Finally, the solution was dried at room temperature to obtain FDCA. Example 4

[0054] A 1 mol / L aqueous Na2CO3 solution was prepared and mixed with acetonitrile in a 2:8 (v:v) ratio to form a biphasic solvent system. Furoic acid and triphenylacetic acid were then weighed and added to the biphasic solvent system to concentrations of 0.4 mol / L and 0.6 mol / L, respectively, in the total solvent (the solutes were uniformly dissolved in each phase). Propylene carbonate (10% by volume of the total solvent) was then added to the reaction vessel. The reaction vessel was stirred continuously at 180°C for 4 h. After completion of the reaction, the aqueous-organic phases were separated using a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C on a rotary evaporator to recover the solvent. Formic acid was added dropwise to the aqueous phase until no further precipitation occurred. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with a formic acid-alcohol solution (methanol:formic acid, volume ratio 6:4) until the conductivity of the washing solution did not change significantly. Finally, the solution was dried at room temperature to obtain FDCA. Example 5

[0055] A 1 mol / L aqueous solution of K2CO3 was prepared and mixed with tetrahydrofuran in a 3:7 (v:v) ratio to form a biphasic solvent system. Furoic acid and trimethylacetic acid were then weighed and added to the biphasic solvent system to concentrations of 0.4 mol / L and 0.8 mol / L, respectively, in the total solvent (the solutes were uniformly dissolved in each phase). Propylene carbonate (10% by volume of the total solvent) was then added to the reaction vessel. The reaction vessel was stirred continuously at 180°C for 6 h. After completion of the reaction, the aqueous-organic phases were separated using a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C on a rotary evaporator to recover the solvent. Formic acid was added dropwise to the aqueous phase until no further precipitation occurred. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with a formic acid-alcohol solution (ethanol:formic acid, volume ratio 7:3) until the conductivity of the washing solution did not change significantly. Finally, the solution was dried at room temperature to obtain FDCA. Example 6

[0056] A 1 mol / L aqueous solution of K2CO3 was prepared and mixed with tetrahydrofuran in a 2:8 (v:v) ratio to form a biphasic solvent system. Furoic acid and sodium acetate were then weighed and added to the biphasic solvent system, with the concentrations of both furoic acid and sodium acetate in the total solvent at 0.8 mol / L (the solutes were uniformly dissolved in each phase). Propylene carbonate (10% by volume of the total solvent) was then added to the reaction vessel. The reaction vessel was stirred continuously at 200°C for 6 h. After the reaction, the aqueous-organic phases were separated using a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C on a rotary evaporator to recover the solvent. Formic acid was added dropwise to the aqueous phase until no further precipitation occurred. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with a formic acid-alcohol solution (methanol:formic acid, volume ratio 8:2) until the conductivity of the washing solution did not change significantly. Finally, the solution was dried at room temperature to obtain FDCA. Example 7

[0057] A 1 mol / L aqueous NaOH solution was prepared and mixed with propylene carbonate in a 3:7 (v:v) ratio to form a biphasic solvent system. Propylene carbonate also provided CO2. Furoic acid and sodium acetate were then weighed and added to the biphasic solvent system. The concentrations of furoic acid and sodium acetate in the total solvent were both 0.6 mol / L (the solutes were uniformly dissolved in each phase). The reaction vessel was then placed at 200°C and stirred continuously for 6 hours. After the reaction, the aqueous-organic phases were separated using a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C using a rotary evaporator to recover the solvent. Acetic acid was added dropwise to the aqueous phase until no more precipitation occurred. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with an acetic acid alcohol solution (ethanol:acetic acid in a volume ratio of 8:2) until the conductivity of the washing liquid did not change significantly. Finally, the solution was dried at room temperature to obtain FDCA. Example 8

[0058] A 1 mol / L aqueous NaOH solution was prepared and mixed with acetonitrile in a 3:7 (v:v) ratio to form a biphasic solvent system. Furoic acid and triphenylacetic acid were then weighed and added to the biphasic solvent system to a concentration of 0.4 mol / L for each of the two solvents (the solutes were uniformly dissolved in each phase). Propylene carbonate (10% by volume of the total solvent) was then added to the reaction vessel. The reaction vessel was stirred continuously at 200°C for 4 h. After the reaction, the aqueous-organic phases were separated using a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C on a rotary evaporator to recover the solvent. Formic acid was added dropwise to the aqueous phase until no further precipitation occurred. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with a formic acid-alcohol solution (ethanol:formic acid, volume ratio 8:2) until the conductivity of the washing solution did not change significantly. Finally, the solution was dried at room temperature to obtain FDCA. Example 9

[0059] A 1 mol / L aqueous KOH solution was prepared and mixed with acetonitrile in a 2:8 (v:v) ratio to form a biphasic solvent system. Furoic acid and trimethylacetic acid were then weighed and added to the biphasic solvent system. The concentrations of furoic acid and trimethylacetic acid in the total solvent were 0.4 mol / L and 0.6 mol / L, respectively (the solutes were uniformly dissolved in each phase). Trimethylacetic acid also provided CO2. The reaction vessel was then placed at 180°C with continuous stirring for 6 hours. After the reaction, the aqueous-organic phases were separated using a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C on a rotary evaporator to recover the solvent. Acetic acid was added dropwise to the aqueous phase until no more precipitation occurred. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with an acetic acid alcohol solution (methanol:acetic acid, volume ratio 7:3) until the conductivity of the washing solution did not change significantly. Finally, the crude FDCA was dried at room temperature to obtain FDCA. Example 10

[0060] A 1 mol / L aqueous KOH solution was prepared and mixed with acetonitrile in a 4:6 (v:v) ratio to form a biphasic solvent system. Furoic acid and sodium ethoxide were then weighed and added to the biphasic solvent system to a concentration of 0.4 mol / L and 0.8 mol / L, respectively, in the total solvent (the solutes were uniformly dissolved in each phase). Propylene carbonate (10% by volume of the total solvent) was then added to the reaction vessel. The reaction vessel was stirred continuously at 160°C for 4 h. After completion of the reaction, the aqueous-organic phases were separated using a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C on a rotary evaporator to recover the solvent. Acetic acid was added dropwise to the aqueous phase until no further precipitation occurred. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with an acetic acid alcohol solution (methanol:acetic acid, volume ratio 7:3) until the conductivity of the washing solution did not change significantly. Finally, the solution was dried at room temperature to obtain FDCA. Example 11

[0061] A 0.5 mol / L aqueous K2CO3 solution was prepared and mixed with acetonitrile in a 3:7 (v:v) ratio to form a biphasic solvent system. Furoic acid and trimethylacetic acid were then weighed and added to the biphasic solvent system to concentrations of 0.4 mol / L and 0.8 mol / L, respectively, in the total solvent (the solutes were uniformly dissolved in each phase). Propylene carbonate (10% by volume of the total solvent) was then added to the reaction vessel. The reaction vessel was then stirred continuously at 180°C for 6 h. After completion of the reaction, the aqueous-organic phases were separated using a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C on a rotary evaporator to recover the solvent. Formic acid was added dropwise to the aqueous phase until no further precipitation occurred. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with a formic acid-alcohol solution (ethanol:formic acid, volume ratio 8:2) until the conductivity of the washing solution did not change significantly. Finally, the FDCA was dried at room temperature to obtain FDCA. Example 12

[0062] A 0.5 mol / L aqueous NaOH solution was prepared and mixed with acetonitrile in a 2:8 (v:v) ratio to form a biphasic solvent system. Furoic acid and triphenylacetic acid were then weighed and added to the biphasic solvent system, with the concentration of each in the total solvent at 0.8 mol / L (the solutes were uniformly dissolved in each phase). Propylene carbonate (10% by volume of the total solvent) was then added to the reaction vessel. The reaction vessel was then stirred continuously at 160°C for 4 h. After completion of the reaction, the aqueous-organic phases were separated using a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C on a rotary evaporator to recover the solvent. Formic acid was added dropwise to the aqueous phase until no further precipitation occurred. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with a formic acid-alcohol solution (ethanol:formic acid, volume ratio 8:2) until the conductivity of the washing solution did not change significantly. Finally, the FDCA was dried at room temperature to obtain FDCA. Example 13

[0063] A 1 mol / L aqueous NaCl solution was prepared and mixed with N,N-dimethylformamide in a 2:8 (v:v) ratio to form a biphasic solvent system. Furoic acid and sodium acetate were then weighed and added to the biphasic solvent system, with the concentrations of both furoic acid and sodium acetate in the total solvent at 0.8 mol / L (the solutes were uniformly dissolved in each phase). Propylene carbonate (10% by volume of the total solvent) was then added to the reaction vessel. The reaction vessel was then stirred continuously at 180°C for 4 h. After completion of the reaction, the aqueous-organic phases were separated using a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C on a rotary evaporator to recover the solvent. Formic acid was added dropwise to the aqueous phase until no further precipitation occurred. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with a formic acid-alcohol solution (ethanol:formic acid, volume ratio 8:2) until the conductivity of the washing solution did not change significantly. Finally, the solution was dried at room temperature to obtain FDCA.

[0064] The yields and conversion rates of the FDCA products prepared in Examples 1 to 13 of the present invention are shown in Table 1 below.

[0065] Table 1 FDCA product yield and product conversion rate prepared in Examples 1 to 13

[0066] The purity of FDCA prepared in Examples 1 to 12 of the present invention is ≥99%. The yield of FDCA in Example 13 could not be measured due to the selected solvent.

[0067] Table 1 shows the yields and conversions of the FDCA products prepared in Examples 1 to 13. As can be seen from the table, the type of solvent is crucial for the catalytic synthesis of FDCA. The ratio of the mixed solvent, temperature, reaction time, and the type and concentration of the base and basic salt also have a significant correlation with the purity of FDCA. The mixed acid-alcohol washing solution can effectively wash out salts and other impurities in the product while ensuring low dissolution of FDCA, thereby ensuring that the purified FDCA has high purity and a relatively high yield.

[0068] Figure 1 is the H-NMR (a) spectrum of FDCA prepared by the present invention. The peaks at 7.29 ppm and 13.62 ppm represent the characteristic shifts of the H atoms on FDCA, respectively, and no other obvious chemical shift peaks were found, indicating that the purified product is relatively pure.

[0069] FIG2 is a C-NMR (b) spectrum of FDCA prepared by the present invention. As can be seen from the figure, 118.2 ppm, 146.8 ppm, and 158.6 ppm represent characteristic shifts of the C atoms on FDCA, respectively, and no other obvious chemical shift peaks are found, indicating that the purified product is relatively pure.

Claims

1. A method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid, characterized in that: Furoic acid and an organic base are added to a biphasic solvent system, the two phases are separated after the reaction is completed, the organic acid is added to the aqueous phase, the precipitate is collected by filtration, and then the precipitate is washed and dried to obtain 2,5-furandicarboxylic acid; wherein the biphasic solvent system is a mixture of an alkaline metal salt solution and a biomass-based polar aprotic solvent, and a CO2 supplying agent is added or not added to the biphasic solvent system.

2. The method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid according to claim 1, characterized in that: The volume ratio of the basic metal salt solution to the biomass-based polar aprotic solvent is 1-9:1-9.

3. The method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid according to claim 1 or 2, characterized in that: The basic metal salt is one or a mixture of Na2CO3, K2CO3, NaOH and KOH, and the concentration of the basic metal salt solution is 0.5-5 mol / L.

4. The method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid according to claim 1 or 2, characterized in that: The biomass-based polar aprotic solvent is one or a mixture of tetrahydrofuran, acetonitrile and propylene carbonate.

5. The method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid according to claim 1, characterized in that: The organic base is one or more of sodium methoxide, sodium formate, sodium ethoxide, sodium acetate, triphenylacetic acid and trimethylacetic acid.

6. The method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid according to claim 1, characterized in that: The concentrations of furoic acid and organic base in the reaction system are both 0.1-1 mol / L.

7. The method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid according to claim 1, characterized in that: The CO2 supplying reagent is one of triphenylacetic acid, trimethylacetic acid, ethylene carbonate and propylene carbonate, or a mixture of several of them.

8. The method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid according to claim 1, characterized in that: The organic acid is one of formic acid, acetic acid and propionic acid or a mixture of several of them.

9. The method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid according to claim 1, characterized in that: The specific steps are as follows: 1) dissolving a basic metal salt in water to obtain a basic metal salt solution, and then mixing the basic metal salt solution with a biomass-based polar aprotic solvent to construct a two-phase solvent system; 2) adding furoic acid and an organic base into the biphasic solvent system constructed in step 1), adding or not adding a CO2 supply reagent, and continuously stirring the reaction at 140-220°C for 1-12 hours; 3) After the reaction is completed, the water-organic phase of the reaction system in step 2) is separated, the organic phase is recovered after distillation under reduced pressure at 40-80° C., an organic acid is added dropwise to the aqueous phase until no precipitation is generated, and the precipitate is collected by filtration to obtain crude 2,5-furandicarboxylic acid; 4) The crude 2,5-furandicarboxylic acid is placed in a washing liquid and continuously washed until the conductivity of the washing liquid does not change significantly, and then dried at room temperature to obtain 2,5-furandicarboxylic acid.

10. The method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid according to claim 9, characterized in that: In step 4), the washing liquid is an organic acid alcohol solution, the organic acid is the same as the organic acid used in step 3), the alcohol is methanol or ethanol, and the volume ratio of the acid to the alcohol is 5-9:1-6.

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