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

Abstract

The invention discloses a method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furanic acid, and belongs to the field of furan-based biomass chemicals and materials. The method adds furanic acid and an organic base into a two-phase solvent system, separates the two phases after the reaction is completed, adds an organic acid into the aqueous phase, collects the precipitate by filtration, then washes the precipitate, and dries it 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 supply reagent is added or not added to the two-phase solvent system. The synthesis process and separation and purification process of the invention are simple, the product purity is high, the carbonylation reaction rate is high, the raw material cost is reduced, and it conforms to the concept of green chemistry development.

Description

Technical Field

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

[0002] As a furan-based product with an aromatic structure, 2,5-furandicarboxylic acid (FDCA) has great similarities with petroleum-based terephthalic acid in structure and function. Polyethylene 2,5-furandicarboxylate (PEF) prepared from ethylene glycol is superior to polyethylene terephthalate (PET) in terms of thermodynamics, strength and barrier properties. It is generally considered to be a green diacid monomer that replaces terephthalic acid, thereby driving the release of FDCA demand. According to a research report released by the Xinshijie Industry Research Center, the global FDCA market is expected to grow at an average annual compound growth rate of more than 8.5% from 2022 to 2027, and reach US$820 million in 2027.

[0003] At present, the synthesis of FDCA mainly includes three pathways: 5-hydroxymethylfurfural (HMF) oxidation pathway, glucarboxylic acid pathway and furoic acid pathway. The HMF oxidation pathway uses HMF as a substrate and oxidizes it to FDCA through thermal catalysis or photoelectrocatalysis. The catalyst in this process is usually a precious metal, and large-scale production has been achieved. However, due to the 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 is to selectively oxidize the C1 and C6 positions of glucose to carboxyl groups, and then directly synthesize 2,5-furandicarboxylic acid after appropriate dehydration conditions. The main problem of this pathway is the selective oxidation problem in the first step, and related theories and technologies are also being gradually developed.

[0004] The furoic acid pathway mainly includes direct carbonylation of furoic acid, bromination of furoic acid and disproportionation of furoic acid. Since Banerjee et al. (Nature, 2016, 7593: 215-219) reported that FDCA was prepared by direct carbonylation with CO2 as carbonylation reagent and furoic acid as substrate assisted by cesium carbonate, the research on the preparation of FDCA by carbonate-assisted furoic acid has been emerging. Chinese patent CN116283849A provides a method for preparing FDCA with cesium salt as raw material, and Chinese patent CN115991686A further prepares superbasic catalysts with carbonate loading to assist in the synthesis of FDCA, but the pathway method is a solid heterogeneous reaction, and the reaction conditions are relatively harsh, and there is no significant progress in related research at present. There are two typical pathways for furoic acid bromination to obtain FDCA: direct oxidation and direct generation with CO2 after preparation as Grignard reagent. Both methods need to brominate furoic acid, which is the main factor limiting its product cost. The source of FDCA prepared by disproportionation of furoic acid is benzene and phthalic acid produced by mixing benzoic acid with a metal halide salt by Ogata et al. (J. Am. Chem. Soc., 1957, 22: 6005-6008). However, the furan dicarboxylic acid prepared by this method has more isomers and the reaction conditions are also more stringent. Summary of the invention

[0005] 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 solve the problems of high cost and harsh reaction conditions for the current preparation of 2,5-furandicarboxylic acid.

[0006] In order to solve the above problems, the technical solution adopted in the present invention is as follows:

[0007] A method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid, comprising adding furoic acid and an organic base into a two-phase solvent system, separating the two phases after the reaction is completed, adding an organic acid into an aqueous phase, collecting a precipitate by filtration, then washing the precipitate, and drying to obtain 2,5-furandicarboxylic acid; wherein the two-phase 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 into the two-phase solvent system.

[0008] Furthermore, the volume ratio of the basic metal salt solution to the biomass-based polar aprotic solvent is 1-9:1-9.

[0009] 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 to 5 mol / L.

[0010] Preferably, the concentration of the basic metal salt solution is 0.5 to 1.5 mol / L.

[0011] Furthermore, the biomass-based polar aprotic solvent is one or a mixture of tetrahydrofuran, acetonitrile and propylene carbonate.

[0012] Furthermore, the organic base is one or more of sodium methoxide, sodium formate, sodium ethoxide, sodium acetate, triphenylacetic acid and trimethylacetic acid.

[0013] Furthermore, the concentrations of furoic acid and 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 organic base in the reaction system is 0.3 to 0.5 mol / L.

[0014] Furthermore, the CO2 supplying reagent is one or a mixture of triphenylacetic acid, trimethylacetic acid, ethylene carbonate and propylene carbonate.

[0015] Furthermore, the organic acid is one of formic acid, acetic acid and propionic acid, or a mixture of several of them.

[0016] Further, the specific steps are as follows:

[0017] 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;

[0018] 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 and reacting at 140-220° C. for 1-12 hours;

[0019] 3) After the reaction is completed, the water-organic phase of the reaction system of 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;

[0020] 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.

[0021] Further, 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 to 9: 1 to 6. Preferably, the volume ratio of the acid to the alcohol is 5 to 8: 2 to 5.

[0022] Preferably, the reaction temperature of step 2) is 160-200° C., and the reaction time is 3-6 hours.

[0023] Preferably, the distillation temperature in step 3) is 60-70°C.

[0024] 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:

[0025]

[0026] Wherein, base 1 is a basic metal salt; base 2 is an organic base.

[0027] Beneficial effect: Compared with the prior art, the advantages of the present invention are:

[0028] (1) The basic metal salt used in the present invention can be used as a base and a phase separation salt at the same time, promoting the formation of a two-phase system and assisting the deprotonation of furoic acid; the biomass polar aprotic solvent can be used as a solvent and a CO2 supply reagent at the same time.

[0029] (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 the basic carbonate promotes its transfer to the aqueous phase, which is beneficial to the separation of the product.

[0030] (3) The solvent of the present invention, as an inducing agent for CO2 activation, significantly reduces the reaction energy barrier of the carbonylation process, and exhibits a reaction temperature range (160-200°C) that is significantly lower than the current furoic acid direct carbonylation reaction temperature (240-300°C). The total pressure of the reaction system (0-0.3MPa) is also lower than the currently reported furoic acid carbonylation process (3-10MPa), and no superbase compounds are used in the process.

[0031] (4) The biphasic solvent system used in the present invention can not only serve as a solvent, but also has a catalytic effect to increase the reaction rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 H-NMR (a) diagram of FDCA prepared in the present invention;

[0033] Figure 2 C-NMR (b) chart of FDCA prepared in the present invention. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with specific embodiments.

[0035] The yield, purity and conversion rate of FDCA prepared in the following examples were calculated according to the following calculation formula:

[0036] Take 0.1g of the product before and after purification and place it evenly in a petri 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:

[0037]

[0038] where n FDCA is the molar amount of product FDCA, n 糠酸1 is the molar amount of the reaction substrate furoic acid.

[0039] FDCA Purity P FDCA The calculation formula is as follows:

[0040]

[0041] Where m FDCA1 is the mass calculated by liquid chromatography, m FDCA2 is the mass to be weighed.

[0042] Conversion rate of FDCA FDCA The calculation formula is as follows:

[0043]

[0044] where n FDCA is the molar amount of product FDCA, n 糠酸2 is the molar amount of furoic acid reacted.

[0045] The purity of FDCA prepared in the following examples was tested by chromatographic purity according to the following steps:

[0046] 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, filter it through a 0.22μm organic syringe filter and use it to detect the FDCA concentration; use a liquid chromatograph (Watere2695) equipped with a differential refractometer detector (2414RIDetetor) and an HPX-87H organic acid analysis column for analysis, and the conditions are: flow rate 0.6mL / min, column temperature 55℃, detector temperature 40℃, and mobile phase 5mM H2SO4; obtain the actual chromatographic concentration of the dissolved sample FDCA through the drawn FDCA standard curve, and further calculate it as the chromatographic purity of the sample.

[0047] Example 1

[0048] A 1 mol / L Na2CO3 aqueous solution was prepared and configured with propylene carbonate in a ratio of 1:9 (v:v) to form a biphasic solvent system, wherein propylene carbonate also provided CO2. Subsequently, furoic acid and triphenylacetic acid were weighed and added to the biphasic solvent system, wherein the concentrations of furoic acid and sodium acetate in the total solvent were both 0.4 mol / L (the solute was uniformly dissolved in each phase), and the reaction vessel was placed at 160°C for continuous stirring for 6 hours. After the reaction, the aqueous-organic phases were separated using a separatory funnel, wherein the organic phase was subjected to reduced pressure distillation at 60°C using a rotary evaporator to recover the solvent, formic acid was added dropwise to the aqueous phase until no precipitation was produced, and the precipitate was collected by filtration to obtain crude FDCA; then, the crude FDCA was washed multiple times with a formic acid alcohol solution (the volume ratio of methanol to formic acid was 8:2) until the conductivity of the washing liquid did not change significantly, and finally, FDCA was obtained after being dried at room temperature.

[0049] Example 2

[0050] A 1 mol / L Na2CO3 aqueous solution was prepared and prepared with acetonitrile in a ratio of 3:7 (v:v) to form a two-phase solvent system. Furoic acid and sodium acetate were then weighed and added to the two-phase solvent system. The concentrations of furoic acid and sodium acetate in the total solvent were both 0.4 mol / L (the solute was uniformly dissolved in each phase). Propylene carbonate accounting for 10% of the total solvent volume was then added to the reaction vessel. The reaction vessel was placed at 160°C for continuous stirring for 4 hours. After the reaction, the water-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. Formic acid was added dropwise to the aqueous phase until no precipitation was generated. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with a formic acid alcohol solution (the volume ratio of ethanol to formic acid was 7:3) until the conductivity of the washing liquid did not change significantly. Finally, the crude FDCA was obtained after being dried at room temperature.

[0051] Example 3

[0052] A 1 mol / L Na2CO3 aqueous solution is prepared and configured with tetrahydrofuran in a ratio of 3:7 (v:v) to form a two-phase solvent system. Subsequently, furoic acid and triphenylacetic acid are weighed and added to the two-phase solvent system. The concentrations of furoic acid and sodium acetate in the total solvent are both 0.4 mol / L (the solute is uniformly dissolved in each phase). Then, propylene carbonate accounting for 10% of the total solvent volume is added to the reaction container. The reaction container is placed at 160°C and stirred for continuous reaction for 6 hours. After the reaction is completed, the water-organic phase is separated using a separatory funnel, wherein the organic phase is subjected to reduced pressure distillation at 60°C using a rotary evaporator to recover the solvent, acetic acid is added dropwise to the aqueous phase until no precipitation is generated, and the precipitate is collected by filtration to obtain crude FDCA; then, the crude FDCA is washed multiple times with an acetic alcohol solution (the volume ratio of methanol to acetic acid is 6:4) until the conductivity of the washing liquid does not change significantly. Finally, the crude FDCA is dried at room temperature to obtain FDCA.

[0053] Example 4

[0054] A 1 mol / L Na2CO3 aqueous solution was prepared and configured with acetonitrile in a ratio of 2:8 (v:v) to form a two-phase solvent system. Furoic acid and triphenylacetic acid were then weighed and added to the two-phase solvent system. The concentrations of furoic acid and triphenylacetic acid in the total solvent were 0.4 mol / L and 0.6 mol / L, respectively (the solute was uniformly dissolved in each phase). Propylene carbonate accounting for 10% of the total solvent volume was then added to the reaction vessel. The reaction vessel was placed at 180°C and stirred continuously for 4 hours. After the reaction, the water-organic phase was 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. Formic acid was added dropwise to the aqueous phase until no precipitation was generated. The precipitation was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with a formic acid alcohol solution (the volume ratio of methanol to formic acid was 6:4) until the conductivity of the washing liquid did not change significantly. Finally, the crude FDCA was dried at room temperature to obtain FDCA.

[0055] Example 5

[0056] A 1 mol / L K2CO3 aqueous solution was prepared and prepared with tetrahydrofuran in a ratio of 3:7 (v:v) to form a two-phase solvent system. Subsequently, furoic acid and trimethylacetic acid were weighed and added to the two-phase solvent system. The concentrations of furoic acid and trimethylacetic acid in the total solvent were 0.4 mol / L and 0.8 mol / L, respectively (the solute was uniformly dissolved in each phase). Then, 10% of the total solvent volume of propylene carbonate was added to the reaction container. The reaction container was placed at 180°C and stirred for continuous reaction for 6 hours. After the reaction, the water-organic phase was separated with a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C using a rotary evaporator to recover the solvent. Formic acid was added dropwise to the aqueous phase until no precipitation was generated. The precipitate was collected by filtration to obtain crude FDCA. Then, the crude FDCA was washed several times with a formic acid alcohol solution (the volume ratio of ethanol to formic acid was 7:3) until the conductivity of the washing liquid did not change significantly. Finally, it was dried at room temperature to obtain FDCA.

[0057] Example 6

[0058] A 1 mol / L K2CO3 aqueous solution was prepared and prepared with tetrahydrofuran in a ratio of 2:8 (v:v) to form a two-phase solvent system. Subsequently, furoic acid and sodium acetate were weighed and added to the two-phase solvent system. The concentrations of furoic acid and sodium acetate in the total solvent were both 0.8 mol / L (the solute was uniformly dissolved in each phase). Then, 10% of the total solvent volume of propylene carbonate was added to the reaction container. The reaction container was placed at 200°C for continuous stirring and reaction for 6 hours. After the reaction, the water-organic phase was separated with a separatory funnel. The organic phase was subjected to reduced pressure distillation at 60°C using a rotary evaporator to recover the solvent. Formic acid was added dropwise to the aqueous phase until no precipitation was generated. The precipitate was collected by filtration to obtain crude FDCA. Then, the crude FDCA was washed several times with a formic acid alcohol solution (the volume ratio of methanol to formic acid was 8:2) until the conductivity of the washing liquid did not change significantly. Finally, it was dried at room temperature to obtain FDCA.

[0059] Example 7

[0060] A 1 mol / L NaOH aqueous solution was prepared and configured with propylene carbonate in a ratio of 3:7 (v:v) to form a two-phase solvent system, wherein propylene carbonate also provided CO2. Subsequently, furoic acid and sodium acetate were weighed and added to the two-phase solvent system, wherein the concentrations of furoic acid and sodium acetate in the total solvent were both 0.6 mol / L (the solute was uniformly dissolved in each phase). The reaction vessel was then placed at 200°C for continuous stirring for 6 hours. After the reaction, the aqueous-organic phases were separated using a separatory funnel, wherein 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 precipitation was produced, and the precipitate was collected by filtration to obtain crude FDCA. Subsequently, the crude FDCA was washed multiple times with an acetic alcohol solution (the volume ratio of ethanol to acetic acid was 8:2) until the conductivity of the washing liquid did not change significantly. Finally, the crude FDCA was obtained after being dried at room temperature.

[0061] Example 8

[0062] A 1 mol / L NaOH aqueous solution was prepared and configured with acetonitrile in a ratio of 3:7 (v:v) to form a two-phase solvent system. Furoic acid and triphenylacetic acid were then weighed and added to the two-phase solvent system. The concentrations of furoic acid and triphenylacetic acid in the total solvent were both 0.4 mol / L (the solute was uniformly dissolved in each phase). Propylene carbonate accounting for 10% of the total solvent volume was then added to the reaction vessel. The reaction vessel was placed at 200° C. and stirred for continuous reaction for 4 hours. After the reaction was completed, the water-organic phase was 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. Formic acid was added dropwise to the aqueous phase until no precipitation was generated. The precipitation was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with a formic acid alcohol solution (the volume ratio of ethanol to formic acid was 8:2) until the conductivity of the washing liquid did not change significantly. Finally, the crude FDCA was obtained after being dried at room temperature.

[0063] Example 9

[0064] A 1 mol / L KOH aqueous solution was prepared and prepared with acetonitrile in a ratio of 2:8 (v:v) to form a biphasic solvent system. Subsequently, furoic acid and trimethylacetic acid were 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 solute was uniformly dissolved in each phase). Trimethylacetic acid also provided CO2. The reaction vessel was then placed at 180°C for continuous stirring for 6 hours. After the reaction, the water-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 precipitation was produced. The precipitate was collected by filtration to obtain crude FDCA. The crude FDCA was then washed multiple times with an acetic alcohol solution (the volume ratio of methanol to acetic acid was 7:3) until the conductivity of the washing liquid did not change significantly. Finally, it was dried at room temperature to obtain FDCA.

[0065] Example 10

[0066] A 1 mol / L KOH aqueous solution is prepared and configured with acetonitrile in a ratio of 4:6 (v:v) to form a two-phase solvent system. Subsequently, furoic acid and sodium ethoxide are weighed and added to the two-phase solvent system. The concentrations of furoic acid and sodium ethoxide in the total solvent are 0.4 mol / L and 0.8 mol / L, respectively (the solute is uniformly dissolved in each phase). Then, propylene carbonate of 10% of the total solvent volume is added to the reaction container. The reaction container is placed at 160° C. and stirred for continuous reaction for 4 hours. After the reaction is completed, the water-organic phase is separated by a separatory funnel. The organic phase is subjected to reduced pressure distillation at 60° C. using a rotary evaporator to recover the solvent. Acetic acid is added dropwise to the aqueous phase until no precipitation is generated. The precipitate is collected by filtration to obtain crude FDCA. Then, the crude FDCA is washed multiple times with an acetic alcohol solution (the volume ratio of methanol to acetic acid is 7:3) until the conductivity of the washing liquid does not change significantly. Finally, the crude FDCA is dried at room temperature to obtain FDCA.

[0067] Embodiment 11

[0068] A K2CO3 aqueous solution with a concentration of 0.5 mol / L is prepared and configured with acetonitrile in a ratio of 3:7 (v:v) to form a two-phase solvent system. Subsequently, furoic acid and trimethylacetic acid are weighed and added to the two-phase solvent system. The concentrations of furoic acid and trimethylacetic acid in the total solvent are 0.4 mol / L and 0.8 mol / L, respectively (the solute is uniformly dissolved in each phase). Then, propylene carbonate with a volume of 10% of the total solvent is added to the reaction container. The reaction container is then placed at 180°C for continuous stirring for 6 hours. After the reaction is completed, the water-organic phase is separated using a separatory funnel, wherein the organic phase is subjected to reduced pressure distillation at 60°C using a rotary evaporator to recover the solvent, formic acid is added dropwise to the aqueous phase until no precipitation is generated, and the precipitate is collected by filtration to obtain crude FDCA; then, the crude FDCA is washed multiple times with a formic acid alcohol solution (the volume ratio of ethanol to formic acid is 8:2) until the conductivity of the washing liquid does not change significantly. Finally, it is dried at room temperature to obtain FDCA.

[0069] Example 12

[0070] A 0.5 mol / L NaOH aqueous solution is prepared and configured with acetonitrile in a ratio of 2:8 (v:v) to form a two-phase solvent system. Subsequently, furoic acid and triphenylacetic acid are weighed and added to the two-phase solvent system. The concentrations of furoic acid and triphenylacetic acid in the total solvent are both 0.8 mol / L (the solute is uniformly dissolved in each phase). Then, 10% of the total solvent volume of propylene carbonate is added to the reaction container. The reaction container is placed at 160° C. and continuously stirred for reaction for 4 hours. After the reaction is completed, the water-organic phase is separated using a separatory funnel. The organic phase is subjected to reduced pressure distillation at 60° C. using a rotary evaporator to recover the solvent. Formic acid is added dropwise to the aqueous phase until no precipitation is generated. The precipitate is collected by filtration to obtain crude FDCA. Then, the crude FDCA is washed multiple times with a formic acid alcohol solution (the volume ratio of ethanol to formic acid is 8:2) until the conductivity of the washing liquid does not change significantly. Finally, the crude FDCA is dried at room temperature to obtain FDCA.

[0071] Embodiment 13

[0072] A 1 mol / L NaCl aqueous solution is prepared and configured with N,N-dimethylformamide in a ratio of 2:8 (v:v) to form a two-phase solvent system. Subsequently, furoic acid and sodium acetate are weighed and added to the two-phase solvent system. The concentrations of furoic acid and sodium acetate in the total solvent are both 0.8 mol / L (the solute is uniformly dissolved in each phase). Then, propylene carbonate of 10% of the total solvent volume is added to the reaction container. The reaction container is then placed at 180° C. and stirred for continuous reaction for 4 hours. After the reaction is completed, the water-organic phase is separated using a separatory funnel. The organic phase is subjected to reduced pressure distillation at 60° C. using a rotary evaporator to recover the solvent. Formic acid is added dropwise to the aqueous phase until no precipitation is generated. The precipitate is collected by filtration to obtain crude FDCA. Subsequently, the crude FDCA is washed multiple times with a formic acid alcohol solution (the volume ratio of ethanol to formic acid is 8:2) until the conductivity of the washing liquid does not change significantly. Finally, the crude FDCA is dried at room temperature to obtain FDCA.

[0073] 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.

[0074] Table 1 FDCA product yield and product conversion rate prepared in Examples 1 to 13

[0075]

[0076]

[0077] The purity of FDCA prepared in Examples 1 to 12 of the present invention is ≥99%. The yield of FDCA in Example 13 cannot be measured due to the selected solvent.

[0078] Table 1 shows the yield and conversion rate of the FDCA products prepared in Examples 1 to 13. It can be seen from the table that the type of solvent is crucial to the catalytic synthesis of FDCA, and the ratio of mixed solvents, temperature, reaction time, alkali and basic salt type concentration also have a great correlation with the purity of FDCA; the mixed acid alcohol washing liquid can effectively wash out the salt and other mixtures in the product, and at the same time ensure the low dissolution of FDCA, thereby ensuring that the purified FDCA has a relatively high yield while having a high purity.

[0079] Figure 1 In the H-NMR (a) diagram of FDCA prepared in the present invention, 7.29 ppm and 13.62 ppm represent characteristic shifts of H atoms on FDCA, respectively, and no other obvious chemical shift peaks are found, indicating that the purified product is relatively pure.

[0080] Figure 2This is the C-NMR (b) diagram of FDCA prepared in the present invention. As can be seen from the figure, 118.2ppm, 146.8ppm and 158.6ppm represent the 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 two-phase solvent system, and the two phases are separated after the reaction is completed. An organic acid is added to the aqueous phase, and the precipitate is collected by filtration, and then the precipitate is washed and dried 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 the basic metal salt is a mixture of one or more of Na2CO3, K2CO3, NaOH and KOH; the biomass-based polar aprotic solvent is acetonitrile; the organic base is one or more of sodium acetate, triphenylacetic acid and trimethylacetic acid; a CO2 supply reagent is added to the two-phase solvent system; the CO2 supply reagent is a mixture of one or more of ethylene carbonate and propylene carbonate.

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 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, characterized in that: The concentrations of furoic acid and organic base in the reaction system are both 0.1-1 mol / L.

5. 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.

6. 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.

7. The method for synthesizing 2,5-furandicarboxylic acid by carbonylation of furoic acid according to claim 6, 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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