A method for preparing 2,5-furandicarboxylic acid from fructose.

Abstract

This invention relates to the field of chemical synthesis technology and discloses a method for preparing 2,5-furandicarboxylic acid from fructose, comprising the following steps: preparing reaction system A containing fructose, an organic bromide, a solid acid catalyst, and water; performing a dehydration reaction to separate the solid acid catalyst and obtain a fructose dehydration reaction solution; preparing reaction system B containing the fructose dehydration reaction solution, a co-oxidant, an oxidation catalyst, and acetic acid; performing an oxidation reaction under an oxidizing gas atmosphere; separating the product to obtain 2,5-furandicarboxylic acid. This invention utilizes a co-oxidant, which can reduce the requirement for fructose concentration in the one-pot preparation of 2,5-furandicarboxylic acid while ensuring the yield and purity of FDCA, thereby improving production efficiency. Furthermore, it reduces or even eliminates the use of hydrobromic acid in the oxidation reaction, thus reducing corrosion to equipment.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and in particular to a method for preparing 2,5-furandicarboxylic acid using fructose as a raw material. Background Technology

[0002] With the depletion of fossil resources and the increasing prominence of environmental problems such as the greenhouse effect and white pollution, bio-based synthetic polymer materials have attracted widespread attention. Currently commercialized bio-based materials include polylactic acid, polyhydroxy fatty acids, and polyglycolic acid. These polymers lack a rigid aromatic ring structure, resulting in poor mechanical and heat resistance. In contrast, polyethylene 2,5-furandicarboxylic acid (PEF), obtained by polymerizing bio-based 2,5-furandicarboxylic acid with ethylene glycol, exhibits superior performance. The key monomer for synthesizing PEF is 2,5-furandicarboxylic acid (FDCA).

[0003] In the biomass-based FDCA production route, the dehydration of fructose to 5-hydroxymethylfurfural (HMF) followed by further oxidation to FDCA is considered the most promising route for industrialization. The commercially successful Co / Mn / Br catalytic oxidation of p-xylene shows great potential for HMF oxidation to FDCA, but it requires high purity HMF. Low HMF purity significantly impacts the yield and purity of the FDCA product. Therefore, after obtaining HMF from fructose, it needs to be separated and purified to obtain high-purity HMF before further oxidation to FDCA to achieve high product yield and purity. This process results in low production efficiency. Furthermore, HMF has poor stability, and side reactions may occur during separation and purification. The separation process also requires a large amount of extractant, generating significant waste liquid and high energy consumption.

[0004] Patent CN115028608A describes a one-pot method for the direct preparation of 2,5-furandicarboxylic acid from fructose. After the HMF is obtained through dehydration, it is not separated and purified, but directly oxidized by Co / Mn / Br catalysis to generate FDCA. Although the "one-pot method" improves production efficiency, it requires a high amount of hydrogen bromide and a low concentration of substrate (fructose) solution to achieve a high FDCA yield. Hydrogen bromide is prone to corroding equipment, and a low fructose solution concentration is not conducive to improving production efficiency. Summary of the Invention

[0005] To address the aforementioned technical problems—namely, the need for a low fructose concentration and the excessive use of hydrogen bromide in the one-pot preparation of 2,5-furandicarboxylic acid from fructose—this invention provides a method for preparing 2,5-furandicarboxylic acid using fructose as a raw material. This method, while ensuring the product yield and purity of the one-pot preparation of 2,5-furandicarboxylic acid, reduces the requirement for fructose concentration and minimizes or even eliminates the use of hydrogen bromide in the oxidation reaction.

[0006] The specific technical solution of this invention is as follows:

[0007] A method for preparing 2,5-furandicarboxylic acid from fructose includes the following steps:

[0008] (1) Prepare reaction system A containing fructose, organic bromide, solid acid catalyst and water, carry out dehydration reaction, separate solid acid catalyst, and obtain fructose dehydration reaction solution;

[0009] (2) Prepare reaction system B containing fructose dehydration reaction solution, co-oxidant, oxidation catalyst and acetic acid, carry out oxidation reaction under oxidizing gas atmosphere, separate the product, and obtain 2,5-furandicarboxylic acid.

[0010] This invention adds a co-oxidant during the oxidation reaction, which is oxidized together with HMF by the oxidizing gas. This reduces the impact of HMF purity on the yield and purity of the product FDCA. Thus, in the one-pot preparation of FDCA from fructose (without separating and purifying HMF after the dehydration reaction), the requirement for substrate (fructose) concentration is reduced. This allows for increased fructose concentration in the dehydration reaction system (i.e., reaction system A) while ensuring FDCA yield and purity, thereby improving production efficiency.

[0011] In addition, the co-oxidant can promote the oxidation of HMF to FDCA. While ensuring the yield and purity of FDCA, a lower oxidation reaction temperature can be used, thereby reducing the side reactions of HMF at high temperatures. At the same time, it can also reduce or even avoid the use of hydrogen bromide in the oxidation reaction, thereby reducing the corrosion of equipment.

[0012] Preferably, in step (1), the mass percentage of fructose in the fructose, organic bromide, and water is 30-80%, more preferably 30-50%. As the fructose concentration increases, a side reaction producing humin is more likely to occur during the dehydration reaction, reducing the purity of the dehydration product HMF and consequently decreasing the yield and purity of the subsequent oxidation product FDCA. This invention, by using a co-oxidant during the oxidation reaction, can reduce the impact of HMF purity on the yield and purity of FDCA. Therefore, when the fructose concentration increases, the decrease in FDCA yield and purity is smaller, thus achieving a relatively high FDCA yield and purity even at higher fructose concentrations.

[0013] Preferably, in step (1), the organic bromide is one or more of choline bromide, quaternary ammonium salt containing bromine, and imidazole ionic liquid containing bromine, and the mass ratio of the organic bromide to fructose is (0.2-2):1.

[0014] Further, in step (1), the organic bromide is one or more of the following: choline bromide, tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide, 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium bromide, 1-octyl-3-methylimidazolium bromide, and 1-butyl-2,3-dimethylimidazolium bromide.

[0015] Preferably, in step (1), the solid acid catalyst is a sulfonic acid resin and / or an acidic molecular sieve, and the mass ratio of the solid acid catalyst to fructose is (0.015-0.05):1.

[0016] Further, in step (1), the solid acid catalyst is one or more of Amberlyst-15, Hβ and HZSM-5.

[0017] Preferably, in step (1), the temperature of the dehydration reaction is 80-140°C and the time is 10 min-5 h. More preferably, the temperature is 90-130°C and the time is 30 min-4 h.

[0018] Preferably, in step (2), the co-oxidant is one or more of acetaldehyde, triacetaldehyde and methyl ethyl ketone, and more preferably triacetaldehyde.

[0019] Using acetaldehyde, triacetaldehyde, or methyl ethyl ketone as co-oxidants can effectively reduce the impact of HMF purity on the yield and purity of FDCA, promote the oxidation of HMF to FDCA, and the product of these three co-oxidants after the oxidation reaction is acetic acid, which is the same as the solvent in the oxidation reaction. No separation is required after the reaction, and acetic acid can be separated from 2,5-furandicarboxylic acid through simple operations (such as crystallization).

[0020] Preferably, in step (2), the oxidation catalyst contains cobalt, manganese and an auxiliary catalytic element in a molar ratio of 1:(0.015~0.15):(0~0.12); the auxiliary catalytic element is at least one of iron, zirconium, zinc, copper and nickel.

[0021] Preferably, in step (2), the oxidation catalyst is a metal salt soluble in the acetic acid.

[0022] Preferably, in step (2), the amount of oxidation catalyst added in reaction system B, calculated as metal element, is 1000-6000 ppm, and more preferably 1500-5000 ppm.

[0023] Preferably, the mass ratio of the co-oxidant to fructose is (0.2-1.5):1, and more preferably (0.4-1.1):1.

[0024] In the process of preparing HMF from fructose through dehydration, a side reaction can easily occur, producing humin, resulting in low purity of HMF in the fructose dehydration reaction solution. Increasing the amount of co-oxidant can help reduce the impact of HMF purity on the yield and purity of FDCA to a greater extent. However, if the amount of co-oxidant added is too large, it can cause excessive oxidation reaction and generate byproducts. This invention, by introducing a co-oxidant and controlling the mass ratio of the co-oxidant to fructose within the aforementioned range, can further improve the yield and purity of FDCA prepared from fructose in a one-pot process.

[0025] Preferably, in step (2), the oxidation reaction is carried out at a temperature of 120-200°C for 10 min-1 h, and more preferably at a temperature of 130-180°C.

[0026] Preferably, in step (2), the oxidizing gas is air, or a mixture of air and CO2; the pressure of the oxidizing gas atmosphere is 0.4 to 5 MPa.

[0027] Further, the oxidizing gas is a mixture of air and CO2 in a volume ratio of 1:(0.125-4), and more preferably a volume ratio of 1:(0.15-2).

[0028] Furthermore, the pressure of the oxidizing gas atmosphere is 0.5–4 MPa.

[0029] Preferably, step (2) includes the following steps: mixing fructose dehydration reaction solution, co-oxidant and a portion of acetic acid to prepare a reaction raw material solution; adding another portion of acetic acid and oxidation catalyst into the reaction vessel, heating to the oxidation reaction temperature, adding the reaction raw material solution into the reaction vessel under an oxidizing gas atmosphere, carrying out the oxidation reaction, separating the product, and obtaining 2,5-furandicarboxylic acid.

[0030] Preferably, in step (2), during the preparation of the reaction raw material solution, the mass ratio between the fructose dehydration reaction solution and the portion of acetic acid is 1:(3-10), and more preferably 1:(4-8).

[0031] Preferably, in step (2), the method for separating the product is crystallization.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] (1) The present invention utilizes a co-oxidizing agent, which can reduce the requirement for fructose concentration in the one-pot preparation of 2,5-furandicarboxylic acid while ensuring the yield and purity of FDCA, thereby improving production efficiency and reducing or even avoiding the use of hydrobromic acid in the oxidation reaction, thereby reducing the corrosion of equipment.

[0034] (2) In this invention, by using acetaldehyde, triacetaldehyde or methyl ethyl ketone as co-oxidant, the influence of HMF purity on the yield and purity of the product FDCA can be effectively reduced, and HMF can be oxidized to FDCA. At the same time, the product after the co-oxidant participates in the oxidation reaction can be separated from FDCA by a simple operation. Detailed Implementation

[0035] The present invention will be further described below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of the inventive concept are included in the present invention, and the scope of protection of the present invention is defined by the appended claims and any equivalents thereof.

[0036] General Implementation Examples

[0037] A method for preparing 2,5-furandicarboxylic acid from fructose includes the following steps:

[0038] (1) Prepare reaction system A containing fructose, organic bromide, solid acid catalyst and water, carry out dehydration reaction, separate solid acid catalyst, and obtain fructose dehydration reaction solution;

[0039] (2) Prepare reaction system B containing fructose dehydration reaction solution, co-oxidant, oxidation catalyst and acetic acid, carry out oxidation reaction under oxidizing gas atmosphere, separate the product, and obtain 2,5-furandicarboxylic acid.

[0040] In one specific implementation, in step (1), the mass percentage of fructose in fructose, organic bromide and water is 30-80%.

[0041] In one specific implementation, in step (1), the organic bromide is one or more of choline bromide, quaternary ammonium salt containing bromine, and imidazole ionic liquid containing bromine, and the mass ratio between the organic bromide and fructose is (0.2-2):1.

[0042] In one specific embodiment, in step (1), the solid acid catalyst is a sulfonic acid resin and / or an acidic molecular sieve, and the mass ratio between the solid acid catalyst and fructose is (0.015~0.05):1.

[0043] In one specific implementation, in step (1), the temperature of the dehydration reaction is 80-140°C and the time is 10 min-5 h.

[0044] In one specific implementation, in step (2), the co-oxidant is one or more of acetaldehyde, triacetaldehyde, and methyl ethyl ketone.

[0045] In one specific embodiment, in step (2), the oxidation catalyst contains cobalt, manganese and an auxiliary catalytic element in a molar ratio of 1:(0.015~0.15):(0~0.12); the auxiliary catalytic element is at least one of iron, zirconium, zinc, copper and nickel.

[0046] In one specific implementation, in step (2), the amount of oxidation catalyst added to the reaction system B, calculated as metal element, is 1000-6000 ppm.

[0047] In one specific embodiment, the mass ratio of the co-oxidant to fructose is (0.2-1.5):1.

[0048] In one specific implementation, in step (2), the temperature of the oxidation reaction is 120-200°C and the time is 10 min-1 h.

[0049] In one specific implementation, in step (2), the oxidizing gas is air, or a mixture of air and CO2 with a volume ratio of 1:(0.125-4); the pressure of the oxidizing gas atmosphere is 0.4-5 MPa.

[0050] As a specific implementation method, step (2) includes the following steps: mixing fructose dehydration reaction solution, co-oxidant and a portion of acetic acid to prepare a reaction raw material solution; adding another portion of acetic acid and oxidation catalyst into a reaction vessel, heating to the oxidation reaction temperature, and then adding the reaction raw material solution into the reaction vessel under an oxidizing gas atmosphere to carry out the oxidation reaction, separating the product to obtain 2,5-furandicarboxylic acid; during the preparation of the reaction raw material solution, the mass ratio between the fructose dehydration reaction solution and the portion of acetic acid is 1:(3~10).

[0051] In one specific implementation, the method for separating the product in step (2) is crystallization.

[0052] Examples 1-8: Effects of organic bromides and solid acid catalysts on the reaction

[0053] The preparation of 2,5-furandicarboxylic acid using fructose as a raw material follows these steps:

[0054] (1) Dehydration reaction:

[0055] A certain amount of fructose, 500g of organic bromide, 100g of water and a certain amount of solid acid catalyst were added to a 2L reactor. Stirring was started, and the temperature was raised to the dehydration reaction temperature. The reaction was carried out for a certain period of time, and then the solid acid catalyst was separated by filtration to obtain the fructose dehydration reaction solution.

[0056] (2) Oxidation reaction:

[0057] A certain amount of co-oxidant was added to the fructose dehydration reaction solution, and then mixed with a certain amount of acetic acid to obtain the reaction feed solution. 6000g of acetic acid and a certain amount of oxidation catalyst were added to a 20L reactor. After heating to the reaction temperature, 6000g of the reaction feed solution was introduced under an oxidizing gas atmosphere (feeding rate 60g / min, time 100min) to carry out the oxidation reaction. 5-Hydroxymethylfurfural was converted to 2,5-furandicarboxylic acid, and the co-oxidant was converted to acetic acid. After the reaction, 2,5-furandicarboxylic acid was separated by crystallization, detected by high-performance liquid chromatography, and the fructose conversion rate, purity, and yield of 2,5-furandicarboxylic acid were calculated.

[0058] The dehydrated reaction solution and the final 2,5-furandicarboxylic acid were sampled and detected by high-performance liquid chromatography (HPLC). The conversion rate of the raw materials and the yield of the product were calculated. The specific methods are as follows (the detection and calculation methods in the following examples and comparative examples are the same):

[0059] (1) The formulas for calculating raw material conversion rate and product yield are as follows:

[0060] Fructose conversion rate = (molar amount of fructose converted / molar amount of fructose added) × 100%;

[0061] HMF yield = (molar amount of HMF generated / molar amount of fructose added) × 100%;

[0062] FDCA yield = (molar amount of FDCA generated / molar amount of HMF entering the oxidation reactor) × HMF yield.

[0063] (2) In calculating the conversion rate and yield, the molar amounts of "converted fructose," "generated HMF," and "generated FDCA" were determined using high-performance liquid chromatography (HPLC). The purity of FDCA was also determined using HPLC. The detection methods for each component are as follows:

[0064] Fructose: The instrument was an Agilent 1260, the column was a Hi-Plex H, the column temperature was 65℃, the detector was differential, the mobile phase was 5mM sulfuric acid aqueous solution, and the flow rate was 0.4mL / min;

[0065] HMF: The instrument was an Agilent 1260, the column was an Eclipse XDB-C18, the column temperature was 40℃, the detector was UV, the mobile phase was a mixture of methanol and water with a volume ratio of 9:1, the flow rate was 1mL / min, and the detection wavelength was 283nm.

[0066] FDCA: The instrument was an Agilent 1260, the column was an Eclipse XDB-C18, the column temperature was 35℃, the detector was UV, the mobile phase was a mixture of trifluoroacetic acid aqueous solution (mass fraction of 0.1%) and methanol with a volume ratio of 2:3, the flow rate was 1 mL / min, and the detection wavelength was 260 nm.

[0067] The specific parameter settings, raw material selections, and test results for Examples 1 to 8 are shown in Tables 1 and 2.

[0068] Table 1. Parameter settings, raw material selection, and test results for Examples 1-4

[0069]

[0070]

[0071] 1 Fructose mass fraction: refers to the mass percentage of fructose, organic bromide and water in step (1), i.e. fructose mass fraction = fructose mass / (fructose mass + organic bromide mass + water mass) × 100%; the "fructose mass fraction" in the following tables has the same meaning.

[0072] 2 Added amount: refers to the mass of fructose added in step (1); the same meaning applies to "added amount" in the tables below.

[0073] 3 Dehydration reaction solution: Acetic acid (m:m): Here, "acetic acid" refers to the acetic acid added when preparing the "reaction raw material solution"; the "dehydration reaction solution: acetic acid (m:m)" in the following tables all have the same meaning.

[0074] 4 Oxidation reaction temperature and time: The oxidation reaction time here is started from the time when the reaction raw material liquid is added; the "oxidation reaction temperature and time" in the tables below all have the same meaning.

[0075] Table 2 shows the parameter settings, raw material selection, and test results for Examples 5-8.

[0076]

[0077]

[0078] Examples 9-14: Effect of fructose mass fraction on the reaction

[0079] The preparation of 2,5-furandicarboxylic acid using fructose as a raw material follows these steps:

[0080] (1) Dehydration reaction:

[0081] A certain amount of fructose, 500g of organic bromide, 100g of water, and a certain amount of solid acid catalyst were added to a 2L reactor. Stirring was started, and the mixture was heated to the dehydration reaction temperature and reacted for a certain period. The solid acid catalyst was then separated by filtration, yielding a fructose dehydration reaction solution. Samples were taken, analyzed by high-performance liquid chromatography (HPLC), and the yield of 5-hydroxymethylfurfural was calculated.

[0082] (2) Oxidation reaction:

[0083] A certain amount of co-oxidant was added to the fructose dehydration reaction solution, and then mixed with a certain amount of acetic acid to obtain the reaction feed solution. 6000g of acetic acid and a certain amount of oxidation catalyst were added to a 20L reactor. After heating to the reaction temperature, 6000g of the reaction feed solution was introduced under an oxidizing gas atmosphere (feeding rate 60g / min, time 100min) to carry out the oxidation reaction. 5-Hydroxymethylfurfural was converted to 2,5-furandicarboxylic acid, and the co-oxidant was converted to acetic acid. After the reaction, 2,5-furandicarboxylic acid was separated by crystallization, detected by high-performance liquid chromatography, and the fructose conversion rate, purity, and yield of 2,5-furandicarboxylic acid were calculated.

[0084] The specific parameter settings, raw material selections, and test results for Examples 9-14 are shown in Tables 3 and 4.

[0085] Table 3. Parameter settings, raw material selection, and test results for Examples 9-11

[0086]

[0087]

[0088] Table 4 shows the parameter settings, raw material selection, and test results for Examples 12-14.

[0089]

[0090] Examples 15-22: Effect of the ratio of dehydration reaction solution to acetic acid on the reaction

[0091] The preparation of 2,5-furandicarboxylic acid using fructose as a raw material follows these steps:

[0092] (1) Dehydration reaction:

[0093] A certain amount of fructose, 500g of organic bromide, 100g of water, and a certain amount of solid acid catalyst were added to a 2L reactor. Stirring was started, and the mixture was heated to the dehydration reaction temperature and reacted for a certain period. The solid acid catalyst was then separated by filtration, yielding a fructose dehydration reaction solution. Samples were taken, analyzed by high-performance liquid chromatography (HPLC), and the yield of 5-hydroxymethylfurfural was calculated.

[0094] (2) Oxidation reaction:

[0095] A certain amount of co-oxidant was added to the fructose dehydration reaction solution, and then mixed with a certain amount of acetic acid to obtain the reaction feed solution. 6000g of acetic acid and a certain amount of oxidation catalyst were added to a 20L reactor. After heating to the reaction temperature, 6000g of the reaction feed solution was introduced under an oxidizing gas atmosphere (feeding rate 60g / min, time 100min) to carry out the oxidation reaction. 5-Hydroxymethylfurfural was converted to 2,5-furandicarboxylic acid, and the co-oxidant was converted to acetic acid. After the reaction, 2,5-furandicarboxylic acid was separated by crystallization, detected by high-performance liquid chromatography, and the fructose conversion rate, purity, and yield of 2,5-furandicarboxylic acid were calculated.

[0096] The specific parameter settings, raw material selections, and test results for Examples 15-22 are shown in Tables 5 and 6.

[0097] Table 5. Parameter settings, raw material selection, and test results for Examples 15-18

[0098]

[0099] Table 6 shows the parameter settings, raw material selection, and test results for Examples 19-22.

[0100]

[0101]

[0102] Examples 23-25: Effect of Co-oxidant Type on the Reaction

[0103] The preparation of 2,5-furandicarboxylic acid using fructose as a raw material follows these steps:

[0104] (1) Dehydration reaction:

[0105] A certain amount of fructose, 500g of organic bromide, 100g of water, and a certain amount of solid acid catalyst were added to a 2L reactor. Stirring was started, and the mixture was heated to the dehydration reaction temperature and reacted for a certain period. The solid acid catalyst was then separated by filtration, yielding a fructose dehydration reaction solution. Samples were taken, analyzed by high-performance liquid chromatography (HPLC), and the yield of 5-hydroxymethylfurfural was calculated.

[0106] (2) Oxidation reaction:

[0107] A certain amount of co-oxidant was added to the fructose dehydration reaction solution, and then mixed with a certain amount of acetic acid to obtain the reaction feed solution. 6000g of acetic acid and a certain amount of oxidation catalyst were added to a 20L reactor. After heating to the reaction temperature, 6000g of the reaction feed solution was introduced under an oxidizing gas atmosphere (feeding rate 60g / min, time 100min) to carry out the oxidation reaction. 5-Hydroxymethylfurfural was converted to 2,5-furandicarboxylic acid, and the co-oxidant was converted to acetic acid. After the reaction, 2,5-furandicarboxylic acid was separated by crystallization, detected by high-performance liquid chromatography, and the fructose conversion rate, purity, and yield of 2,5-furandicarboxylic acid were calculated.

[0108] The specific parameter settings, raw material selections, and test results for Examples 23-25 ​​are shown in Table 7.

[0109] Table 7. Parameter settings, raw material selection, and test results for Examples 23-25

[0110]

[0111]

[0112] Analyzing the experimental results of Examples 23-25, it can be seen that:

[0113] Compared to acetaldehyde and methyl ethyl ketone, using paraldehyde as a co-oxidant achieves higher FDCA yields and purity. This is because the co-oxidant is first oxidized in acetic acid solvent to form peroxides, which then change the valence state of the metal elements in the catalyst through oxidation, promoting HMF oxidation. While acetaldehyde and methyl ethyl ketone have similar structures, their peroxide formation mechanism differs from that of paraldehyde. The higher activity of paraldehyde may be due to the higher oxidative activity of the peroxides formed from paraldehyde compared to acetaldehyde and methyl ethyl ketone.

[0114] Examples 26-35: Effect of Co-oxidant Dosage on the Reaction

[0115] The preparation of 2,5-furandicarboxylic acid using fructose as a raw material follows these steps:

[0116] (1) Dehydration reaction:

[0117] A certain amount of fructose, 500g of organic bromide, 100g of water, and a certain amount of solid acid catalyst were added to a 2L reactor. Stirring was started, and the mixture was heated to the dehydration reaction temperature and reacted for a certain period. The solid acid catalyst was then separated by filtration, yielding a fructose dehydration reaction solution. Samples were taken, analyzed by high-performance liquid chromatography (HPLC), and the yield of 5-hydroxymethylfurfural was calculated.

[0118] (2) Oxidation reaction:

[0119] A certain amount of co-oxidant was added to the fructose dehydration reaction solution, and then mixed with a certain amount of acetic acid to obtain the reaction feed solution. 6000g of acetic acid and a certain amount of oxidation catalyst were added to a 20L reactor. After heating to the reaction temperature, 6000g of the reaction feed solution was introduced under an oxidizing gas atmosphere (feeding rate 60g / min, time 100min) to carry out the oxidation reaction. 5-Hydroxymethylfurfural was converted to 2,5-furandicarboxylic acid, and the co-oxidant was converted to acetic acid. After the reaction, 2,5-furandicarboxylic acid was separated by crystallization, detected by high-performance liquid chromatography, and the fructose conversion rate, purity, and yield of 2,5-furandicarboxylic acid were calculated.

[0120] The specific parameter settings, raw material selections, and test results for Examples 26–35 are shown in Tables 8 and 9.

[0121] Table 8. Parameter settings, raw material selection, and test results for Examples 26-30

[0122]

[0123]

[0124] Table 9. Parameter settings, raw material selection, and test results for Examples 31-35

[0125]

[0126]

[0127] Analyzing the experimental results of Examples 26-35, it can be seen that:

[0128] Under conditions of full reaction (HMF conversion rate of 99.9% or higher), the yield and purity of FDCA first increase and then decrease with the increase of the amount of co-oxidant. This is because the co-oxidant can promote the HMF→FDCA reaction and reduce the influence of HMF purity on the yield and purity of the product FDCA. However, when the amount of co-oxidant is too large, it will cause excessive oxidation reaction and generate by-products.

[0129] Comparative Examples 1–8: Effect of not using a co-oxidizing agent on the reaction

[0130] The preparation of 2,5-furandicarboxylic acid using fructose as a raw material follows these steps:

[0131] (1) Dehydration reaction:

[0132] A certain amount of fructose, 500g of organic bromide, 100g of water, and a certain amount of solid acid catalyst were added to a 2L reactor. Stirring was started, and the mixture was heated to the dehydration reaction temperature and reacted for a certain period. The solid acid catalyst was then separated by filtration, yielding a fructose dehydration reaction solution. Samples were taken, analyzed by high-performance liquid chromatography (HPLC), and the yield of 5-hydroxymethylfurfural was calculated.

[0133] (2) Oxidation reaction:

[0134] The fructose dehydration reaction solution was mixed with a certain amount of acetic acid to obtain a reaction feed solution. 6000g of acetic acid and a certain amount of oxidation catalyst were added to a 20L reactor. After heating to the reaction temperature, 6000g of the reaction feed solution was introduced under an oxidizing gas atmosphere (feeding rate 60g / min, time 100min) to carry out the oxidation reaction. After the reaction was completed, 2,5-furandicarboxylic acid was separated by crystallization, detected by high-performance liquid chromatography, and the fructose conversion rate, purity, and yield of 2,5-furandicarboxylic acid were calculated.

[0135] Furthermore, to ensure that the oxidation reactions in Examples 23-25 ​​and Comparative Examples 1-2 were carried out sufficiently, the HMF conversion rate was measured to be greater than 99.9%. The HMF conversion rate was calculated as follows: HMF conversion rate = molar amount of converted HMF / molar amount of HMF in the added fructose dehydration reaction solution × 100%; wherein, the HMF detection method was the same as described in Example 1.

[0136] For Comparative Examples 1 to 8, the specific parameter settings, raw material selection, and test results are shown in Tables 10 and 11.

[0137] Table 10 shows the parameter settings, raw material selection, and test results for Comparative Examples 1–4.

[0138]

[0139]

[0140] Table 11 Parameter settings, raw material selection, and test results for comparative examples 5–8

[0141]

[0142] Analyzing the experimental results of Examples 23-25 ​​and Comparative Examples 1-8, it can be seen that:

[0143] (1) According to Examples 23-25 ​​and Comparative Examples 1-8, by introducing co-oxidants acetaldehyde, triacetaldehyde or methyl ethyl ketone into the reaction system for preparing FDCA by HMF oxidation, the yield and purity of FDCA can be improved while reducing the use of hydrobromic acid and lowering the reaction temperature.

[0144] (2) According to Examples 9-14 and Comparative Examples 3-8, while ensuring the fructose conversion rate, the yield of HMF decreased (i.e., the purity of HMF decreased) and the yield and purity of FDCA decreased as the fructose concentration increased; however, by adding a co-oxidizing agent, the influence of fructose concentration on the yield and purity of FDCA can be reduced.

[0145] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Unless otherwise specified, the raw materials and equipment used in this invention are commonly used in the art; and unless otherwise specified, the methods used in this invention are conventional methods in the art.

[0146] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing 2,5-furandicarboxylic acid from fructose, characterized in that, Includes the following steps: (1) Prepare reaction system A containing fructose, organic bromide, solid acid catalyst and water, carry out dehydration reaction, separate solid acid catalyst, and obtain fructose dehydration reaction solution; the organic bromide is one or more of choline bromide, quaternary ammonium salt containing bromine and imidazole ionic liquid containing bromine; (2) Prepare reaction system B containing fructose dehydration reaction solution, co-oxidant, oxidation catalyst and acetic acid, carry out oxidation reaction under oxidizing gas atmosphere, separate the product to obtain 2,5-furandicarboxylic acid; the co-oxidant is triacetaldehyde; the oxidation catalyst contains cobalt, manganese and auxiliary catalytic elements in a molar ratio of 1:(0.015~0.15):(0~0.12), and the auxiliary catalytic element is at least one of iron, zirconium, zinc, copper and nickel.

2. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that, In step (1), the mass percentage of fructose in fructose, organic bromide and water is 30-80%.

3. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that, In step (1), the mass ratio between the organic bromide and fructose is (0.2~2):

1.

4. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that, In step (1), the solid acid catalyst is a sulfonic acid resin and / or an acidic molecular sieve, and the mass ratio between the solid acid catalyst and fructose is (0.015~0.05):

1.

5. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that, In step (1), the temperature of the dehydration reaction is 80~140℃ and the time is 10 min~5 h.

6. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that, The mass ratio of the co-oxidant to fructose is (0.2~1.5):

1.

7. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that, In step (2), the temperature of the oxidation reaction is 120~200℃.

8. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that, In step (2), the oxidation reaction takes 10 min to 1 h.

9. The method for preparing 2,5-furandicarboxylic acid according to claim 1, characterized in that, The specific process of step (2) includes the following steps: mixing fructose dehydration reaction solution, co-oxidant and a portion of acetic acid to prepare reaction raw material solution; adding another portion of acetic acid and oxidation catalyst into the reaction vessel, heating to the oxidation reaction temperature, adding the reaction raw material solution into the reaction vessel under an oxidizing gas atmosphere to carry out the oxidation reaction, separating the product to obtain 2,5-furandicarboxylic acid.

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