Method for synthesizing 2, 5-furandicarboxylic acid and co-producing furan from furoate

Abstract

The invention discloses a method for synthesizing 2, 5-furandicarboxylic acid and co-producing furan from furoate, which comprises the following steps: synthesizing 2, 5-furandicarboxylic acid and furan by using a high-pressure reaction kettle, furoate, carbon dioxide and auxiliaries in a solvent and catalyst system through a one-pot method. A gas-liquid-solid three-phase mixture in the reaction kettle is separated, the gas phase is a mixture of furan and carbon dioxide, the mixture is discharged to a subsequent condensing device through an exhaust valve, and furan is obtained through condensation and separation; the liquid phase and the solid phase are separated through filtration, the liquid phase is a solvent and can be repeatedly used after being dewatered through a molecular sieve, the solid phase is 2, 5-furandicarboxylic acid salt and a catalyst, water is added for dissolution, then filtration is performed, the solid is dried to obtain the catalyst, and 2, 5-furandicarboxylic acid can be obtained by acidification of an aqueous solution. The method is simple and controllable in technological process, high in product purity and simple and convenient in post-treatment, and the obtained product is used for synthesis of various drugs, furyl polymers, THF and medical intermediates and has a good application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field 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 uses. It can be used to produce succinic acid, as a macrocyclic ligand and anticorrosive agent, etc. It is recognized by the U.S. Department of Energy as one of the 12 most valuable chemical products from biomass. As the only diacid with an aromatic structure, the unique rigid structure of 2,5-furandicarboxylic acid allows it to replace the traditional petroleum-based aromatic diacid terephthalic acid, and can be widely used in the production of monomers for various bio-based polymers, such as polyesters, polyamides and polyurethanes. The preparation route of 2,5-furandicarboxylic acid mainly includes dehydration cyclization of hexacarboxylic acid, oxidation of 5-hydroxymethylfurfural and carboxylation of furoic acid. Hexacarboxylic acid can be dehydrated and cyclized to obtain 2,5-furandicarboxylic acid, but the raw materials are difficult to obtain and there are many side reactions. 5-Hydroxymethylfurfural and furoic acid can be converted from biomass, which is more in line with the concept of "carbon neutrality" and has greater development prospects. The oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid is the most studied route at present. Its main disadvantages are: the process of preparing 5-hydroxymethylfurfural from cellulose has many side reactions and is difficult to separate. In addition, 5-hydroxymethylfurfural is relatively unstable and easily oxidized and hydrolyzed, resulting in a high price of 5-hydroxymethylfurfural. Although a large number of studies have focused on the oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid, there is still a lack of cheap, efficient and stable catalysts. The conversion of hemicellulose to furfural is an industrial process with a history of several decades, and the current scale is about 40 kilotons per year. And there is no selectivity problem in the process of furfural oxidation to 2-furandicarboxylic acid. Therefore, it is imperative to open up the reaction path of furoic acid to 2,5-furandicarboxylic acid. On the other hand, the conversion of hemicellulose to 2,5-furandicarboxylic acid does not compete with human food, which once again confirms the necessity and importance of opening up the reaction path of furoic acid to 2,5-furandicarboxylic acid.

[0003] The pathways for converting furan dicarboxylic acid to 2,5-furan dicarboxylic acid include: CO carbonylation, Henkel reaction, and CH bond carboxylation. Among them, 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 furan dicarboxylic acid are thermally disproportionated, one molecule produces furan, and the other molecule produces furan dicarboxylic acid. In addition to 2,5-furan dicarboxylic acid, 2,4-furan dicarboxylic 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 CH bond carboxylation reaction, in which carbon dioxide is used as a carboxyl source. This path does not produce 2,4-furandicarboxylic acid isomers and utilizes carbon dioxide in a high-value manner, and the entire conversion process has high atomic economy. The CH bond reactions currently reported in the literature all use a solvent-free system, and the reaction occurs at the interface between the molten salt and the gas. Both have the problems of high reaction energy consumption and slow reaction rate. CN116283850A dopes the raw materials and catalysts to obtain a core-shell structure, which ensures a continuous high contact area between carbon dioxide and the dissolved reactants, and the water can be removed in time, but there is still a problem of high reaction temperature. Therefore, a solvent is added to the relevant patent as a medium to promote mass transfer in the reaction, thereby reducing the reaction temperature. The introduction of solvents in CN113461645A makes the yield of 2,5-furandicarboxylic acid as high as 99%, avoiding the formation of impurities, but the reaction temperature is still high, indicating that the reaction energy barrier is still high and the system lacks corresponding activation. The introduction of solvents and catalysts in CN115991686A enables the system to be efficiently converted at 150°C to 200°C, but the catalyst is a super-alkaline catalyst, and there are problems of alkaline center aggregation and poor stability during the recovery process. CN118146180A uses activated carbon loaded with Ru and Cs (X% RuY% Cs / C) as a catalyst, combined with a rotary furnace device with a carbon dioxide generator as a reaction device, to achieve the goals of mild reaction conditions, low energy consumption and high yield, but the catalyst uses precious metals. If you want to open up the preparation path of furan acid to 2,5-furandicarboxylic acid, it is essential to develop an efficient, stable and economical catalytic system.

[0004] As a decomposition product of furoic acid, furan can be used to prepare pyrrole, thiophene, tetrahydrofuran, etc. Tetrahydrofuran is an important derivative of furan and has many important uses. Furan is etherified and reduced to obtain 2,5-dimethoxydihydrofuran, which is hydrolyzed to generate 2-hydroxy-1,4-butanedial, which can be used to synthesize scopolamine; when furan is etherified, reduced, and then catalytically hydrogenated to obtain 2,5-dimethoxytetrahydrofuran, it is hydrolyzed to generate butanedial, which is the raw material for synthesizing another alkaloid atropine.

[0005] There is no prior art process for synthesizing 2,5-furandicarboxylic acid and co-producing furan from furoate, and 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, which does not require the use of expensive and complex catalysts and has the characteristics of being environmentally friendly, streamlined and efficient. The method can not only efficiently synthesize 2,5-furandicarboxylic acid, but also co-produce furan, with high raw material utilization and adjustable product yield.

[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, then heating to the reaction temperature, and reacting in one pot to obtain a gas-liquid-solid three-phase mixture; 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 a solvent, which can be reused after dehydration through a molecular sieve. The solid phase is 2,5-furandicarboxylic acid salt and a catalyst, which is dissolved in water and then filtered. The catalyst is obtained after the solid is dried, 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, 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 two of them 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: The invention provides a method for producing 2,5-furandicarboxylic acid and furan from furoate, wherein carbon dioxide is activated by a catalyst to promote the adsorption of furoate and generate 2,5-furandicarboxylic acid, and byproduct H2O is generated during the conversion process. Furoate combines with the proton H of water to generate furoic acid, and furoic acid can be decarboxylated to generate furan under the action of the catalyst. The addition of the auxiliary carbonate can polarize the CH bond at the 5th position of furoate on the one hand, and on the other hand, the carbonate can absorb the H2O generated in the reaction, thereby regulating the yield of furan.

[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, the catalyst and the 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 has good stability.

[0020] (3) The product of the present invention is easy to recover, has high product 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 The present invention is a flowchart of the process of 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 NaOH and 26.5 g Na2CO3, add them into 500 mL 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 evenly to obtain a mixed solution:

[0029] The precipitant was titrated into the salt solution by single drop method to pH = 10, and then aged in an oil bath at 60°C for 24 hours to obtain a 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 with an oxygen flow rate of 40 mL / min and an argon flow rate of 40 mL / min to obtain the catalyst Cu2Al1O x -400.

[0031] The same method was used to prepare Cu2Al1O x -500, the calcination temperature is 500°C;

[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 NaOH and 26.5 g Na2CO3, add them into 500 mL 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 by single drop method to pH = 10, and then aged in an oil bath at 60°C for 24 hours to obtain a 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 with an oxygen flow rate of 40 mL / min and an 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] The same method was used to prepare Zn2Al1O 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 NaOH and 26.5 g Na2CO3, add them into 500 mL 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 by single drop method to pH = 10, and then aged in an oil bath at 60°C for 24 hours to obtain a 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 with an oxygen flow rate of 40 mL / min and an argon flow rate of 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 an oven at 120°C for 24 h.

[0056] Example 6: In an autoclave reactor, without additives, Cu2Al1O x -400 catalyzes cesium furoate to synthesize 2,5-FDCA and produce furan

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

[0058] When the reaction is finished and the temperature drops to 60°C, the exhaust pipeline is opened and connected to the condenser. The cooling medium is ice water. The outlet temperature of the condenser is 20°C. The outlet of the condenser 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, and the liquid phase could be used after removing water through molecular sieves. The solid phase was dissolved and filtered by adding deionized water. The filtrate was fixed to 250 mL, and the product 2,5-furandicarboxylic acid and furoic acid were quantitatively analyzed using an ultraviolet detector (wavelength of 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 cesium furoate to synthesize 2,5-furandicarboxylic acid and produce furan

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

[0063] When the reaction is finished and the temperature drops to 60°C, the exhaust pipeline is opened and connected to the condenser. The cooling medium is ice water. The outlet temperature of the condenser is 20°C. The outlet of the condenser 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, and the liquid phase could be used after removing water through molecular sieves. The solid phase was dissolved and filtered by adding deionized water. The filtrate was fixed to 250 mL, and the product 2,5-furandicarboxylic acid and furoic acid were quantitatively analyzed using an ultraviolet detector (wavelength of 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 2h to obtain 20mL 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.

[0066] Same method, change the amount of auxiliary agent cesium carbonate:

[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 an autoclave reactor with the aid of potassium carbonate x -400 catalyzes potassium furoate to synthesize 2,5-furandicarboxylic acid and produce furan

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

[0071] When the reaction is finished and the temperature drops to 60°C, the exhaust pipeline is opened and connected to the condenser. The cooling medium is ice water. The outlet temperature of the condenser is 20°C. The outlet of the condenser 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, and the liquid phase could be used after removing water through molecular sieves. The solid phase was dissolved and filtered by adding deionized water. The filtrate was fixed to 250 mL, and the product 2,5-FDCA and furoic acid were quantitatively analyzed using an ultraviolet detector (wavelength of 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 2,5-furandicarboxylic acid precipitate.

[0074] Example 9: In an autoclave reactor, cesium carbonate as an auxiliary agent was used to catalyze the synthesis of 2,5-furandicarboxylic acid and the co-production of furan using potassium furoate. Except for the catalyst, the other conditions were the same as those of 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 Cycle stability test of cesium furoate synthesis of 2,5-FDCA and furan production by -400 catalysis

[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 40mL 1,4-dioxane were added to a 100mL reactor, and carbon dioxide was introduced to replace the gas three times, followed by 2MPa carbon dioxide. The reaction temperature was set to 190°C and the reaction was carried out for 2.5h.

[0081] When the reaction is finished and the temperature drops to 60°C, the exhaust pipeline is opened and connected to the condenser. The cooling medium is ice water. The outlet temperature of the condenser is 20°C. The outlet of the condenser 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 further after removing water through a molecular sieve. The solid phase was dissolved and filtered by adding deionized water. 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 a 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, and then 2 MPa of carbon dioxide was introduced. The reaction temperature was set to 190 ° C and the reaction was carried out for 2.5 h.

[0085] When the reaction is finished and the temperature drops to 60°C, the exhaust pipeline is opened and connected to the condenser. The cooling medium is ice water. The outlet temperature of the condenser is 20°C. The outlet of the condenser 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 are separated by filtration, the liquid phase can be used after removing water through a molecular sieve, the solid phase is dissolved by adding deionized water and filtered, the filtrate is fixed to 250 mL, and the product 2,5-furandicarboxylic acid and furoic acid are quantitatively analyzed using an ultraviolet detector (wavelength of 254 nm), no furan is detected, and the yield of 2,5-furandicarboxylic acid is 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 2,5-furandicarboxylic acid precipitate.

[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. Argon was introduced to replace the gas three times, and then 2 MPa of argon was introduced. The reaction temperature was set to 190 °C and the reaction was carried out for 2.5 h.

[0090] When the reaction is finished and the temperature drops to 60°C, the exhaust pipeline is opened and connected to the condenser. The cooling medium is ice water. The outlet temperature of the condenser is 20°C. The outlet of the condenser 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 could be used after being dehydrated by molecular sieves. The solid phase was dissolved by adding deionized water and filtered. 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 and furan were 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] It can be seen from comparative example 1 and implementation 6 that furoic acid salt formation is beneficial to promoting the conversion of the reaction and the formation of 2,5-furandicarboxylic acid;

[0094] It can be seen from the comparative example 2 and the example 7 that the catalyst has a significant promoting effect on the reaction;

[0095] It can be seen from comparative example 3 and example 7 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 mechanism is speculated as follows: the catalyst activates carbon dioxide, promotes the adsorption and conversion of furoate to 2,5-furandicarboxylic acid, and the byproduct H2O is produced during the conversion process. Furoate combines with the proton H of water to form furoic acid, and furoic acid can be decarboxylated to form furan under the action of the catalyst. The addition of the auxiliary carbonate can polarize the CH bond at the 5th position of furoate and promote the insertion of carbon dioxide. On the other hand, carbonate can also absorb the H2O produced in the reaction, thereby regulating the yield of furan.

[0098] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope of the present invention, which should be covered by the protection scope 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, putting the dried furoate, catalyst, additive and solvent into a high-pressure reactor, charging carbon dioxide, then heating to a reaction temperature, and performing a one-pot reaction 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, the reaction temperature is 140-220°C, and the reaction pressure is 0.1-2MPa. 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, and furan is condensed and separated; The liquid phase and the solid phase are separated by filtration. The liquid phase is the solvent and can be reused after dehydration through a molecular sieve. The solid phase is 2,5-furandicarboxylic acid salt and a catalyst. After adding water to dissolve, the catalyst is obtained after the solid is dried. 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, characterized in that: 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, 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.

3. The method for synthesizing 2,5-furandicarboxylic acid and co-producing furan from furoate according to claim 1, characterized in that: The furoate salt is cesium furoate, potassium furoate, sodium furoate or magnesium furoate.

4. The method for synthesizing 2,5-furandicarboxylic acid and co-producing furan from furoate according to claim 1, characterized in that: The auxiliary agent is one of cesium carbonate, sodium carbonate and potassium carbonate or a mixture of two of them in any proportion.

5. The method for synthesizing 2,5-furandicarboxylic acid and co-producing furan from furoate according to claim 1, characterized in that: The solvent is 1,4-dioxane, toluene or cyclohexane.

6. The method for synthesizing 2,5-furandicarboxylic acid and co-producing furan from furoate according to claim 1, characterized in that: The acidifying agent is oxalic acid, which is acidified to pH=2 at room temperature.

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