A process for the synthesis of furan-2,5-dicarboxylic acid salt co-producing furan

Abstract

The application discloses a method for synthesizing 2,5-furan dicarboxylic acid and furan from furanate, which comprises the following steps: using a high-pressure reaction kettle, furanate, carbon dioxide and an additive are subjected to one-pot synthesis of 2,5-furan dicarboxylic acid and furan under a solvent and a catalyst system; a gas-liquid-solid three-phase mixture in the reaction kettle is separated; gas phase is a mixture of furan and carbon dioxide, is discharged to a subsequent condensing device through an exhaust valve, and furan is obtained through condensing and separating; liquid phase and solid phase are separated through filtering; the liquid phase is a solvent, can be reused after water removal through a molecular sieve, the solid phase is 2,5-furan dicarboxylic acid salt and a catalyst, is dissolved after adding water, is filtered, and the catalyst is obtained after drying of the solid; and 2,5-furan dicarboxylic acid is obtained after acidification of the aqueous solution. The method has the advantages of simple and controllable process, high product purity, simple post-treatment, and good application prospect of the obtained product in synthesis of various medicines, furan-based polymers, THF and medical intermediates.

Description

Technical Field

[0001] The present invention belongs to the technical fields of fine chemicals and carbon neutrality, and relates to a method for synthesizing 2,5-furandicarboxylic acid from furoate and co-producing furan. Background Art

[0002] 2,5-Furandicarboxylic acid has a wide range of applications, including the production of succinic acid, as a macrocyclic ligand, and as an anticorrosive agent. It has been recognized by the U.S. Department of Energy as one of the 12 most valuable biomass-derived chemical products. As the only aromatic diacid among these, 2,5-furandicarboxylic acid's unique rigid structure makes it a suitable alternative to the traditional petroleum-based aromatic diacid terephthalic acid. It is widely used as a monomer in the production of various bio-based polymers, such as polyesters, polyamides, and polyurethanes. The preparation of 2,5-furandicarboxylic acid primarily involves dehydration and cyclization of hexacarboxylic acid, oxidation of 5-hydroxymethylfurfural, and carboxylation of furoic acid. Dehydration and cyclization of hexacarboxylic acid can produce 2,5-furandicarboxylic acid, but the raw materials are difficult to obtain and are subject to numerous side reactions. 5-Hydroxymethylfurfural and furoic acid can be converted from biomass, which is more in line with the concept of "carbon neutrality" and offers greater development prospects. The oxidation of 5-HMF to 2,5-FU is currently the most studied route. However, its main drawbacks are: the numerous side reactions and difficulty separating 5-HMF from cellulose are associated with its production. Furthermore, 5-HMF is relatively unstable and susceptible to oxidation and hydrolysis, leading to its high price. While extensive research has focused on the oxidation of 5-HMF to 2,5-FU, a cost-effective, efficient, and stable catalyst is still lacking. The conversion of hemicellulose to furfural is a decades-old industrial process, currently operating at a scale of approximately 40 kilotons per year. Furthermore, the oxidation of furfural to 2-FU is not selective. Therefore, developing a pathway for the conversion of furoic acid to 2,5-FU is imperative. Furthermore, the conversion of hemicellulose to 2,5-FU does not compete with human food, further underscoring the necessity and importance of developing a pathway for the conversion of furoic acid to 2,5-FU.

[0003] The pathway for converting furanic acid to 2,5-furandicarboxylic acid includes: CO carbonylation, Henkel reaction, and C-H bond carboxylation. The CO carbonylation step is complex and the reaction conditions are harsh. The Henkel reaction is a thermal disproportionation reaction of aromatic carboxylic acids, that is, two molecules of furanic acid are thermally disproportionated, one molecule produces furan, and the other molecule produces furandicarboxylic acid. In addition to 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid isomers are still present during the reaction, and the reaction catalysts are CdI2, CdCl2, ZnCl2, and CuI. In the post-reaction treatment, the catalysts are all soluble in water, which is not conducive to separation, and Cd 2+It is toxic and harmful to human health. In 2016, Kanan proposed a carbonate-promoted C-H bond carboxylation reaction, in which carbon dioxide serves as the source of carboxyl groups. This pathway avoids the production of 2,4-furandicarboxylic acid isomers and effectively utilizes carbon dioxide, resulting in a highly atom-efficient conversion process. All C-H bond reactions reported in the literature currently utilize solvent-free systems, with the reaction occurring at the interface between the molten salt and the gas. Both suffer from high energy consumption and slow reaction rates. CN116283850A dopes the raw materials and catalyst to create a core-shell structure, ensuring a continuous high contact area between carbon dioxide and the dissolved reactants and allowing for the timely removal of water. However, the high reaction temperature remains a concern. Therefore, the related patent adds a solvent as a medium to promote mass transfer during the reaction, thereby lowering the reaction temperature. The introduction of a solvent in CN113461645A achieves a 99% yield of 2,5-furandicarboxylic acid and avoids the formation of impurities. However, the reaction temperature remains high, indicating a high reaction energy barrier and a lack of activation. CN115991686A introduces a solvent and catalyst, enabling efficient conversion at temperatures between 150°C and 200°C. However, the catalyst is a superalkaline catalyst, which suffers from the aggregation of alkaline centers and poor stability during the recovery process. CN118146180A uses activated carbon-supported Ru and Cs (X% RuY% Cs / C) as a catalyst, combined with a rotary furnace equipped with a carbon dioxide generator as a reaction apparatus, achieving mild reaction conditions, low energy consumption, and high yields. However, the catalyst uses a precious metal. To successfully develop a production pathway for the conversion of furoic acid to 2,5-furandicarboxylic acid, the development of an efficient, stable, and economical catalytic system is essential.

[0004] Furan, a decomposition product of furoic acid, can be used to produce pyrrole, thiophene, and tetrahydrofuran. Tetrahydrofuran is an important derivative of furan with numerous applications. Furan is etherified and reduced to produce 2,5-dimethoxydihydrofuran, which is hydrolyzed to produce 2-hydroxy-1,4-butanedialdehyde, which can be used to synthesize anisodine. When furan is etherified, reduced, and then catalytically hydrogenated to produce 2,5-dimethoxytetrahydrofuran, it is hydrolyzed to produce succinaldehyde, a raw material for the synthesis of another alkaloid, atropine.

[0005] There is no existing process for synthesizing 2,5-furandicarboxylic acid and co-producing furan from furoate. In addition, the technology for producing 2,5-furandicarboxylic acid and furan has the problems of high cost, serious environmental pollution and difficulty in large-scale production, which seriously restricts the industrial mass production of 2,5-furandicarboxylic acid and furan. Summary of the Invention

[0006] The present invention provides a process for synthesizing 2,5-furandicarboxylic acid from furoate and co-producing furan. This process eliminates the need for expensive and complex catalysts and is environmentally friendly, streamlined, and efficient. This process not only efficiently synthesizes 2,5-furandicarboxylic acid while simultaneously co-producing furan, but also achieves high raw material utilization and controllable product yields.

[0007] The technical solution of the present invention:

[0008] A method for synthesizing 2,5-furandicarboxylic acid and co-producing furan from furoate comprises the following steps:

[0009] S1. Putting the dried furoate, catalyst, auxiliary agent and solvent into a high-pressure reactor, charging carbon dioxide, and then heating to the reaction temperature to obtain a gas-liquid-solid three-phase mixture by a one-pot reaction; wherein the mass ratio of the catalyst to the furoate is 0.05-1, the molar ratio of the auxiliary agent to the furoate is 0-1, the mass ratio of the furoate to the solvent is 0.012-0.04, the reaction temperature is 140-220° C., and the reaction pressure is 0.1-2 MPa;

[0010] S2. The gas-liquid-solid three-phase mixture in the reactor is separated. The gas phase is a mixture of furan and carbon dioxide, which is discharged to the subsequent condensation device through an exhaust valve and condensed to obtain furan; the liquid phase and the solid phase are separated by filtration. The liquid phase is the solvent, which can be reused after dehydration through a molecular sieve. The solid phase is 2,5-furandicarboxylic acid salt and the catalyst, which are dissolved in water and then filtered. The solid is dried to obtain the catalyst, and the aqueous solution is acidified to obtain 2,5-furandicarboxylic acid.

[0011] The furoate is cesium furoate, potassium furoate, sodium furoate or magnesium furoate;

[0012] The catalyst is a non-precious metal mixed oxide, including a III-valent metal and a II-valent metal, wherein the III-valent metal is Al, and the II-valent metal is one or a combination of two of Cu, Co, Zn and Ni, and the molar ratio of the II-valent metal to the III-valent metal is 0.5 to 4;

[0013] The auxiliary agent is one of cesium carbonate, sodium carbonate or potassium carbonate or a mixture of the two in any proportion;

[0014] The solvent is 1,4-dioxane, toluene or cyclohexane;

[0015] The acidifying agent is oxalic acid, which is acidified to pH=2 at room temperature.

[0016] Principle of the Invention: This invention provides a method for producing 2,5-furandicarboxylic acid and furan from furoate. A catalyst activates carbon dioxide, promoting the adsorption of furoate and the formation of 2,5-furandicarboxylic acid. HO is also produced as a byproduct during the conversion process. Furoate combines with H protons from water to form furoic acid, which, in turn, decarboxylates under the action of the catalyst to produce furan. The addition of a carbonate additive polarizes the C-H bond at position 5 of furoate and absorbs the H2O produced during the reaction, thereby regulating furan production.

[0017] Beneficial effects of the present invention:

[0018] (1) The present invention regulates the yields of 2,5-furandicarboxylic acid and furan by regulating the auxiliary agent, catalyst and system reaction conditions, wherein the yield of 2,5-furandicarboxylic acid can reach up to 73%, and the yield of furan can reach up to 54%.

[0019] (2) The addition of solvent makes the system highly efficient in mass transfer. The introduction of catalyst and solvent makes the reaction conditions mild and the catalyst stable.

[0020] (3) The product of the present invention is easy to recover, has high purity, and is simple to post-process. The obtained product can be used for the synthesis of various drugs, furan-based polymers, THF and pharmaceutical intermediates, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a process flow chart for synthesizing 2,5-furandicarboxylic acid and co-producing furan from furoate.

[0022] Figure 2 Cu2Al1O in Example 1 x -400 catalyst XRD pattern.

[0023] Figure 3 Cu2Al1O in Example 10 x -400 catalyst stability test chart. DETAILED DESCRIPTION

[0024] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0025] Example 1

[0026] Cu2Al1O x The preparation of -400 catalyst adopts the co-precipitation method, which includes the following steps:

[0027] Preparation of precipitant: Weigh 40 g of NaOH and 26.5 g of Na2CO3 into 500 mL of deionized water and mix well to obtain a mixed solution;

[0028] Preparation of precursor salt solution: 48.3 g Cu(NO3)2·3H2O and 37.5 g Al(NO3)3·9H2O were added to 150 mL deionized water and mixed well to obtain a mixed solution:

[0029] The precipitant was titrated into the salt solution using a single drop method to a pH of 10, and then aged in an oil bath at 60°C for 24 hours to obtain the reaction product.

[0030] The reaction product was washed with deionized water until the pH of the filtrate was 7.0, dried at 80 °C for 16 h, and calcined at 400 °C for 4 h in an atmosphere of oxygen flow rate of 40 mL / min and argon flow rate of 40 mL / min to obtain the catalyst Cu2Al1O x -400.

[0031] Cu2Al1O was prepared by the same method x -500, the calcination temperature is 500℃;

[0032] Cu2Al1O x -600, the calcination temperature is 600℃;

[0033] Cu2Al1O x -800, and its calcination temperature is 800℃.

[0034] Example 2

[0035] Ni2Al1O x Preparation of -400 catalyst

[0036] Preparation of precipitant: Weigh 40 g of NaOH and 26.5 g of Na2CO3 into 500 mL of deionized water and mix well to obtain a mixed solution;

[0037] Preparation of precursor salt solution: 58.2 g Ni(NO3)2·6H2O and 37.5 g Al(NO3)3·9H2O were added to 150 mL deionized water and mixed well to obtain a mixed solution;

[0038] The precipitant was titrated into the salt solution using a single drop method to a pH of 10, and then aged in an oil bath at 60°C for 24 hours to obtain the reaction product.

[0039] The reaction product was washed with deionized water until the pH of the filtrate was 7.0, dried at 80 °C for 16 h, and calcined at 400 °C for 4 h in an atmosphere of oxygen flow rate of 40 mL / min and argon flow rate of 40 mL / min to obtain the catalyst Ni2Al1O x -400.

[0040] Co2Al1O was prepared by the same method x-400, the mass of Co(NO3)2·6H2O is 58.2g;

[0041] Zn2Al1O was prepared by the same method x -400, and the mass of Zn(NO3)2·6H2O is 59.5g.

[0042] Example 3: Cu1Zn1Al1O x Preparation of -400 catalyst

[0043] Preparation of precipitant: Weigh 40 g of NaOH and 26.5 g of Na2CO3 into 500 mL of deionized water and mix well to obtain a mixed solution;

[0044] Preparation of precursor salt solution: 42.2 g Cu(NO3)2·6H2O, 29.7 g Zn(NO3)2·6H2O and 37.5 g Al(NO3)3·9H2O were added to 150 mL deionized water and mixed well to obtain a mixed solution:

[0045] The precipitant was titrated into the salt solution using a single drop method to a pH of 10, and then aged in an oil bath at 60°C for 24 hours to obtain the reaction product.

[0046] The reaction product was washed with deionized water until the pH of the filtrate was 7.0, dried at 80 °C for 16 h, and calcined at 400 °C for 4 h in an atmosphere of oxygen flow rate 40 mL / min and argon flow rate 40 mL / min to obtain the catalyst Cu1Zn1Al1O x -400.

[0047] The same method was used to prepare Cu1Co1Al1O x -400, the mass of Co(NO3)2·6H2O is 29.1g, and the mass of Cu(NO3)2·6H2O is 24.2g;

[0048] Ni1Co1Al1O was prepared by the same method. x -400, the mass of Co(NO3)2·6H2O is 29.1g, and the mass of Ni(NO3)2·6H2O is 29.1g;

[0049] The same method was used to prepare Zn1Ni1Al1O x -400, the mass of Zn(NO3)2·6H2O is 29.7g, and the mass of Ni(NO3)2·6H2O is 29.1g;

[0050] The same method was used to prepare Cu1Ni1Al1O x -400, the mass of Cu(NO3)2·6H2O is 24.2g, and the mass of Ni(NO3)2·6H2O is 29.1g;

[0051] The same method was used to prepare Zn1Co1Al1O x -400, the mass of Co(NO3)2·6H2O is 29.1g, and the mass of Zn(NO3)2·6H2O is 29.7g.

[0052] Example 4: Preparation of cesium furoate

[0053] Weigh 6.52 g of cesium carbonate and dissolve it in 20 mL of deionized water. Stir for 10 min, slowly add 4.48 g of furoic acid, stir for 30 min, and dry the mixture in a 120°C oven for 24 h.

[0054] Example 5: Preparation of Potassium Furoate

[0055] Weigh 2.76 g of potassium carbonate and dissolve it in 20 mL of deionized water. Stir for 10 min. Slowly add 4.48 g of furoic acid and stir for 30 min. Dry the mixture in a 120°C oven for 24 h.

[0056] Example 6: In an autoclave reactor, without additives, Cu2Al1O x -400 catalyzes the synthesis of 2,5-FDCA and furan using cesium furoate

[0057] Weigh 0.7319g cesium furoate, 90mg Cu2Al1O x -400 catalyst and 40 mL of 1,4-dioxane were added to a 100 mL reactor, and carbon dioxide was introduced to replace the gas three times, followed by 2 MPa of carbon dioxide. The reaction temperature was set at 190 ° C and the reaction was carried out for 2.5 h.

[0058] When the reaction is completed and the temperature drops to 60°C, the exhaust pipe is opened and connected to the condenser. The cooling medium is ice water. The condenser outlet temperature is 20°C. The condenser outlet is connected to the gas-liquid separation tank. The liquid phase in the separation tank is furan and the gas phase is carbon dioxide.

[0059] The liquid and solid phases were separated by filtration. The liquid phase was freed from water by molecular sieves and could be reused. The solid phase was dissolved in deionized water and filtered. The filtrate was diluted to 250 mL and the products, 2,5-furandicarboxylic acid and furoic acid, were quantitatively analyzed using a UV detector (wavelength 254 nm). The yield of furan was 54% and the yield of 2,5-furandicarboxylic acid was 44%.

[0060] The analyzed solution was evaporated at 110° C. for 2 h to obtain 20 mL of concentrated solution, which was acidified to pH 2 by adding oxalic acid at room temperature, and filtered to obtain 2,5-furandicarboxylic acid precipitate.

[0061] Example 7: In an autoclave reactor, with the aid of cesium carbonate, Cu2Al1O x-400 catalyzes the synthesis of 2,5-furandicarboxylic acid and the co-production of furan using cesium furoate

[0062] Weigh 0.7319g cesium furoate, 90mg Cu2Al1O x -400 catalyst, 0.6514 g cesium carbonate and 40 mL 1,4-dioxane were added to a 100 mL reactor, and carbon dioxide was introduced to replace the gas three times, followed by 2 MPa carbon dioxide. The reaction temperature was set at 190 ° C and the reaction was carried out for 2.5 h;

[0063] When the reaction is completed and the temperature drops to 60°C, the exhaust pipe is opened and connected to the condenser. The cooling medium is ice water. The condenser outlet temperature is 20°C. The condenser outlet is connected to the gas-liquid separation tank. The liquid phase in the separation tank is furan and the gas phase is carbon dioxide.

[0064] The liquid and solid phases were separated by filtration. The liquid phase was freed from water by molecular sieves and could be reused. The solid phase was dissolved in deionized water and filtered. The filtrate was diluted to 250 mL and the products, 2,5-furandicarboxylic acid and furoic acid, were quantitatively analyzed using a UV detector (wavelength 254 nm). The yield of 2,5-furandicarboxylic acid was 73%, and the yield of furan was 15%.

[0065] The analyzed solution was evaporated at 110° C. for 2 h to obtain 20 mL of concentrated solution, which was acidified to pH 2 by adding oxalic acid at room temperature, and filtered to obtain a precipitate of 2,5-furandicarboxylic acid.

[0066] Use the same method, but change the amount of cesium carbonate as the additive:

[0067] When the amount of cesium carbonate was 0.4887 g, the yield of 2,5-furandicarboxylic acid was 50% and the yield of furan was 20%;

[0068] When the amount of cesium carbonate was 0.3285 g, the yield of 2,5-furandicarboxylic acid was 25%, and the yield of furan was 30%.

[0069] Example 8: Cu2Al1O in the presence of potassium carbonate as an auxiliary agent in an autoclave reactor x -400 catalyzes potassium furoate to synthesize 2,5-furandicarboxylic acid and co-produce furan

[0070] Weigh 0.4530g potassium furoate, 90mg Cu2Al1O x -400 catalyst, 0.2026 g potassium carbonate and 40 mL 1,4-dioxane were added to a 100 mL reactor, and carbon dioxide was introduced to replace the gas three times, followed by 2 MPa carbon dioxide. The reaction temperature was set at 190 ° C and the reaction was carried out for 2.5 h;

[0071] When the reaction is completed and the temperature drops to 60°C, the exhaust pipe is opened and connected to the condenser. The cooling medium is ice water. The condenser outlet temperature is 20°C. The condenser outlet is connected to the gas-liquid separation tank. The liquid phase in the separation tank is furan and the gas phase is carbon dioxide.

[0072] The liquid and solid phases were separated by filtration. The liquid phase was freed from water by molecular sieves and could be reused. The solid phase was dissolved in deionized water and filtered. The filtrate was diluted to 250 mL and the products, 2,5-FDCA and furoic acid, were quantitatively analyzed using a UV detector (wavelength 254 nm). The yield of furan was 12% and the yield of 2,5-furandicarboxylic acid was 60%.

[0073] The analyzed solution was evaporated at 110°C for 2 h to obtain 20 mL of concentrated solution, which was acidified by adding oxalic acid at room temperature and filtered to obtain a precipitate of 2,5-furandicarboxylic acid.

[0074] Example 9: In an autoclave reactor, 2,5-furandicarboxylic acid was synthesized with furan from potassium furoate in the presence of cesium carbonate as an auxiliary agent. The catalyst was used in the same manner as in Example 7. The results are shown in Table 1.

[0075] Table 1. Product yields under different catalysts

[0076] catalyst Furan yield (%) 2,5-FDCA yield (%) <![CDATA[Ni2Al1O x -400]]> 23 64 <![CDATA[Co2Al1O x -400]]> 27 60 <![CDATA[Zn2Al1O x -400]]> 30 63 <![CDATA[Zn1Co1Al1O x -400]]> 29 62 <![CDATA[Cu1Co1Al1O x -400]]> 20 70 <![CDATA[Ni1Co1Al1O x -400]]> 25 65 <![CDATA[Zn1Ni1Al1O x -400]]> 27 65 <![CDATA[Cu1Ni1Al1O x -400]]> 22 64 <![CDATA[Cu1Zn1Al1O x -400]]> 30 62

[0077] Example 10: Cu2Al1O in an autoclave reactor x Cyclic stability test of cesium furoate synthesis of 2,5-FDCA and furan production using -400 catalyst

[0078] The filtered catalyst was washed with deionized water and then dried in air at 120°C. The remaining reaction steps were the same as in Example 7. The catalyst was recycled four times. The effect was shown in FIG. Figure 3 .

[0079] Comparative Example 1: Comparative Example 6, the substrate in the reaction system does not form a salt

[0080] Weigh 0.3360g furoic acid, 90mg Cu2Al1O x -400 catalyst and 40 mL of 1,4-dioxane were added to a 100 mL reactor, and carbon dioxide was introduced to replace the gas three times, followed by 2 MPa of carbon dioxide. The reaction temperature was set at 190 ° C and the reaction was carried out for 2.5 h.

[0081] When the reaction is completed and the temperature drops to 60°C, the exhaust pipe is opened and connected to the condenser. The cooling medium is ice water. The condenser outlet temperature is 20°C. The condenser outlet is connected to the gas-liquid separation tank. The liquid phase in the separation tank is furan and the gas phase is carbon dioxide.

[0082] The liquid and solid phases were separated by filtration, and the liquid phase could be used after removing water through molecular sieves. The solid phase was dissolved in deionized water and filtered, and the filtrate was fixed to 250 mL. The products 2,5-furandicarboxylic acid and furoic acid were quantitatively analyzed using an ultraviolet detector (wavelength of 254 nm). No 2,5-furandicarboxylic acid was detected, and the furan yield was 19%.

[0083] Comparative Example 2: Comparative Example 7, the reaction system does not add catalyst

[0084] 0.7319 g of cesium furoate, 0.6514 g of cesium carbonate, and 40 mL of 1,4-dioxane were weighed and added to a 100 mL reactor. Carbon dioxide was introduced to replace the gas three times, followed by 2 MPa of carbon dioxide. The reaction temperature was set at 190 °C and the reaction was carried out for 2.5 h.

[0085] When the reaction is completed and the temperature drops to 60°C, the exhaust pipe is opened and connected to the condenser. The cooling medium is ice water. The condenser outlet temperature is 20°C. The condenser outlet is connected to the gas-liquid separation tank. The liquid phase in the separation tank is furan and the gas phase is carbon dioxide.

[0086] The liquid and solid phases were separated by filtration. The liquid phase was removed by molecular sieves and could be used again. The solid phase was dissolved in deionized water and filtered. The filtrate was diluted to 250 mL. The products 2,5-furandicarboxylic acid and furoic acid were quantitatively analyzed using an ultraviolet detector (wavelength of 254 nm). No furan was detected, and the yield of 2,5-furandicarboxylic acid was 20%.

[0087] The analyzed solution was evaporated at 110°C for 2 h to obtain 20 mL of concentrated solution, which was acidified by adding oxalic acid at room temperature and filtered to obtain a precipitate of 2,5-furandicarboxylic acid.

[0088] Comparative Example 3: Comparative Example 7, the reaction system was filled with argon

[0089] 0.7319 g of cesium furoate, 0.6514 g of cesium carbonate, and 40 mL of 1,4-dioxane were weighed and added to a 100 mL reactor. The reaction was then filled with argon to replace the gas three times, followed by 2 MPa of argon. The reaction temperature was set at 190 °C and the reaction was continued for 2.5 h.

[0090] When the reaction is completed and the temperature drops to 60°C, the exhaust pipe is opened and connected to the condenser. The cooling medium is ice water. The condenser outlet temperature is 20°C. The condenser outlet is connected to the gas-liquid separation tank. The liquid phase in the separation tank is furan and the gas phase is carbon dioxide.

[0091] The liquid and solid phases were separated by filtration, and the liquid phase was free of water after being passed through a molecular sieve before being used. The solid phase was dissolved in deionized water and filtered, and the filtrate was diluted to 250 mL. The products 2,5-furandicarboxylic acid and furoic acid were quantitatively analyzed using an ultraviolet detector (wavelength of 254 nm). No 2,5-furandicarboxylic acid or furan was detected.

[0092] Comparing Example 6 with Example 7, it can be seen that the presence of the auxiliary carbonate is beneficial to improving the yield of 2,5-furandicarboxylic acid, and as the amount of carbonate increases, the selectivity of 2,5-furandicarboxylic acid increases;

[0093] From the observation of Comparative Example 1 and Example 6, it can be seen that the salification of furoic acid is beneficial to promoting the conversion of the reaction and the formation of 2,5-furandicarboxylic acid;

[0094] From the observation of Comparative Example 2 and Example 7, it can be seen that the catalyst has a significant promoting effect on the reaction;

[0095] From the observation of Comparative Example 3 and Example 7, it can be seen that the carboxyl group is derived from carbon dioxide;

[0096] Combining Comparative Example 2, Comparative Example 3 and Example 7, it is shown that the catalyst cannot directly catalyze the decarboxylation of furoate to produce furan.

[0097] The hypothesized mechanism is as follows: The catalyst activates carbon dioxide, promoting the adsorption and conversion of furoate to 2,5-furandicarboxylic acid. This conversion is accompanied by the production of H₂O as a byproduct. Furoate combines with H₂ protons from water to form furoic acid, which, under the action of the catalyst, decarboxylates to furan. The addition of carbonate as an auxiliary agent polarizes the C₆H bond at the 5-position of furoate, promoting CO₂ insertion. Furthermore, carbonate absorbs the H₂O produced during the reaction, thereby regulating furan production.

[0098] 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 can make equivalent replacements or changes based on the technical solution and inventive concept of the present invention within the technical scope of the present invention, and they should be covered by the scope of protection of the present invention.

Claims

1. A method for synthesizing 2,5-furandicarboxylic acid and co-producing furan from furoate, characterized in that: The following steps are involved: S1, placing the dried furoate, catalyst, additive and solvent into a high-pressure reactor, filling it with carbon dioxide, and then heating it to the reaction temperature to react in a one-pot process to obtain a gas-liquid-solid three-phase mixture; The mass ratio of the catalyst to the furoate is 0.05-1, the molar ratio of the auxiliary agent to the furoate is 0-1, the mass ratio of the furoate to the solvent is 0.012-0.04, and the reaction temperature is 140-220 o C, reaction pressure is 0.1~2 MPa; The catalyst is a non-precious metal mixed oxide, including a III-valent metal and a II-valent metal, wherein the III-valent metal is Al, and the II-valent metal is one or a combination of two of Cu, Co, Zn, and Ni, and the molar ratio of the II-valent metal to the III-valent metal is 0.5-4; The auxiliary agent is one of cesium carbonate, sodium carbonate, and potassium carbonate, or a mixture of two of them in any proportion; S2, separating the gas-liquid-solid three-phase mixture in the reactor, wherein the gas phase is a mixture of furan and carbon dioxide, which is discharged through an exhaust valve to a subsequent condensation device for condensation and separation to obtain furan; The liquid phase and the solid phase are separated by filtration. The liquid phase is the solvent and can be reused after removing water through a molecular sieve. The solid phase is 2,5-furandicarboxylic acid salt and a catalyst. After adding water to dissolve, it is filtered. The solid is dried to obtain the catalyst, and the aqueous solution is acidified to obtain 2,5-furandicarboxylic acid.

2. The method for synthesizing 2,5-furandicarboxylic acid and co-producing furans from furoate according to claim 1, wherein The furoate is cesium furoate, potassium furoate, sodium furoate or magnesium furoate.

3. The method for synthesizing 2,5-furandicarboxylic acid and co-producing furans from furoate according to claim 1, wherein The solvent is 1,4-dioxane, toluene or cyclohexane.

4. The method for synthesizing 2,5-furandicarboxylic acid and co-producing furans from furoate according to claim 1, wherein The acidifying agent is oxalic acid, acidified to pH at room temperature 2.

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