Method for preparing 2, 5-furandicarboxylic acid through electro-chemical cascade catalysis

Abstract

The invention discloses a method for preparing 2, 5-furandicarboxylic acid by electro-chemical cascade catalysis, which comprises the following steps: electrolyzing a sodium chloride aqueous solution by using sodium chloride as a medium and water as an oxygen source in an ionic membrane electrolysis mode to generate sodium hypochlorite, then chemically oxidizing the sodium hypochlorite and HMF under the action of a catalyst to generate FDCA (2, 5-furandicarboxylic acid), and finally, carrying out electro-chemical cascade catalysis on the FDCA to obtain the 2, 5-furandicarboxylic acid. The acid filtrate generated in the process is treated by an electrodialysis ion exchange membrane, and is evaporated and concentrated to obtain a sodium chloride solution for recycling. According to the method, electrocatalysis and chemical catalysis technologies are coupled, efficient preparation of the FDCA is realized by taking water as an oxygen source, wastewater discharge and production cost in the production process of the FDCA are greatly reduced due to cyclic utilization of the salt-containing water and use of the HMF crude product raw material, and the technology has a good industrial application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of 2,5-furandicarboxylic acid, and specifically relates to a method for preparing 2,5-furandicarboxylic acid by electro-chemical cascade catalysis. Background Art

[0002] 2,5-Furandicarboxylic acid (FDCA) is considered to be an ideal substitute for petroleum-based terephthalic acid (PTA) and can be used to synthesize polyester materials with better barrier properties and heat resistance, such as ethylene furandicarboxylate (PEF). In addition, FDCA can also replace terephthalic acid or isophthalic acid in the preparation of bio-based new materials such as aramid, plasticizers, surfactants, adhesives, etc., and has broad commercial application prospects.

[0003] The preparation of FDCA is mainly divided into chemical catalysis, electrocatalysis and enzyme catalysis. The enzyme catalysis has the advantage of mild reaction conditions, but the reaction system has poor selectivity, low yield and more product impurities. The product purification is difficult and cannot meet the needs of downstream polyester material synthesis. In recent years, the electrocatalytic synthesis of FDCA from 5-hydroxymethylfurfural has attracted widespread attention. For example, Yan et al. (ACS Catal. 2020, 10, 5179-5189) designed an ultrathin hydrotalcite nanosheet with excellent OER performance, achieving a HMF conversion rate of over 95% and a FDCA selectivity of nearly 85%; Sun et al. (Angewandte Chemie, 2023, 62(37), e202309478) synthesized a Ni-Cu precatalyst by one-step electrodeposition, and obtained the target Ni-Cu / NF bimetallic catalyst by a two-step aging-activation method, realizing the electro-oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid at an industrial-grade current density; Qi et al. (CN118186410A) reported a method for the electrocatalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid, and achieved a 95.7% FDCA Faraday efficiency at an industrial-grade current density by adding copper salts and ligands to the anode reaction chamber. In summary, it can be seen that the electrocatalytic HMF preparation of FDCA has the characteristics of high selectivity and high yield, but it still faces the problems of complex catalyst preparation, high cost, and insufficient stability. Chemical catalytic oxidation of HMF to prepare FDCA is currently the most promising way for industrialization. For example, the air oxidation method uses a Co / Mn / Br catalytic system, but this method uses acetic acid as a solvent and requires high temperature and high pressure, which has high corrosion resistance requirements for equipment, and HMF has poor stability under acidic conditions, and the FDCA yield is low. In recent years, although many precious metal or non-precious metal oxide catalysts have shown excellent performance in the HMF oxidation preparation of FDCA, many current routes are still a certain distance away from true industrialization in terms of economic efficiency. Sodium hypochlorite is an efficient and mild HMF oxidation reagent that can achieve efficient and highly selective oxidation of HMF to prepare FDCA under relatively mild conditions, but the concentration of industrial-grade sodium hypochlorite solution is low, generally 10wt%, so a large amount of sodium hypochlorite solution needs to be consumed during the oxidation reaction, thereby generating a large amount of high-concentration salt-containing wastewater, making the process costly. Therefore, if the treatment problem of this high-concentration salt-containing wastewater can be solved, the production cost of FDCA can be significantly reduced, greatly promoting the industrialization of the process.

[0004] The main component of wastewater in the above sodium hypochlorite process is sodium chloride, which has no effect on the process of oxidizing HMF to generate FDCA. The oxidant sodium hypochlorite used in the oxidation process is actually prepared by electrolyzing sodium chloride solution in the chlor-alkali industry. Therefore, the wastewater rich in sodium chloride can be electrolyzed, and the obtained sodium hypochlorite can be recycled as an oxidant, which can greatly reduce the amount of wastewater discharged in the oxidation process and reduce the cost of wastewater treatment, which is of great significance to the industrialization of the current chemical oxidation method for preparing FDCA. Summary of the invention

[0005] In view of the above problems, the object of the present invention is to provide a method for preparing 2,5-furandicarboxylic acid by electro-chemical cascade catalysis.

[0006] The specific technical solutions are as follows:

[0007] A method for preparing 2,5-furandicarboxylic acid by electro-chemical cascade catalysis comprises the following steps:

[0008] 1) preparing a sodium chloride aqueous solution and adding sodium hydroxide;

[0009] 2) using ion membrane electrolysis to electrolyze the solution in step 1) to generate sodium hypochlorite, while recycling the byproduct hydrogen, mixing the generated sodium hypochlorite with 5-hydroxymethylfurfural (HMF) containing a catalyst, and performing a chemical oxidation reaction to obtain FDCA sodium salt, followed by filtering to separate the catalyst for reuse;

[0010] 3) adding a strong acid to the FDCA sodium salt solution obtained by filtration in step 2) to acidify the obtained FDCA, and separating the FDCA by precipitating, filtering and separating to obtain a high-purity FDCA product and an acidic filtrate;

[0011] 4) Adding an appropriate amount of alkali to the acidic filtrate of step 3) to neutralize and obtain a solution containing sodium chloride at pH=7, and treating it with an electrodialysis ion exchange membrane to obtain a pure sodium chloride solution, which is then evaporated and concentrated and returned to step 1) for recycling.

[0012] Furthermore, the mass concentration of the sodium chloride aqueous solution prepared in step 1) is 10-26.5%, and the amount of sodium hydroxide added is 1-30% of the mass of sodium chloride, preferably 10-20%; the water in step 1) is deionized water or distilled water.

[0013] Further, the membrane material selected for the ion membrane electrolysis in step 2) is a cation exchange membrane, the effective chlorine solubility of sodium hypochlorite is 5-15%, preferably 8-12%, and the catalyst is at least one of cobalt monoxide, cobalt tetraoxide, nickel oxide, nickel trioxide, copper oxide, manganese dioxide, cerium oxide, and ferric oxide; the 5-hydroxymethylfurfural (HMF) in step 2) can be HMF crystals, HMF crude products or HMF solutions, the purity of HMF crystals is 95%-100%; the purity of HMF crude products is 40% to 95%; the HMF concentration in the HMF solution is 1%-40%.

[0014] Furthermore, in step 2), the molar ratio of 5-hydroxymethylfurfural to sodium hypochlorite is 1:3-9, preferably 1:4-6; the amount of catalyst is 5-50% of the mass of 5-hydroxymethylfurfural, preferably 10-30%, the chemical oxidation reaction temperature is 30-80°C, the reaction time is 1-60min, preferably the reaction temperature is 40-70°C, the reaction time is 5-10min, and the chemical oxidation reaction process can be intermittent operation or continuous.

[0015] Furthermore, the strong acid in step 3) is hydrochloric acid, the mass concentration of the hydrochloric acid is 10-36%, and the mass ratio of the amount of hydrochloric acid to 5-hydroxymethylfurfural is 0.6-1.8:1, preferably 0.8-1.2:1; the purity of the obtained FDCA product is greater than 99%, and the pH of the acidic filtrate is less than 1.

[0016] Furthermore, the base described in step 4) is at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate.

[0017] The beneficial effects of the present invention are:

[0018] 1) The electrocatalytic and chemical catalytic technologies were coupled to achieve efficient preparation of FDCA using water as the oxygen source;

[0019] 2) The salt water in the system can be recycled, which greatly reduces wastewater discharge and wastewater treatment costs, while also reducing raw material and production costs, which is conducive to the large-scale production of FDCA;

[0020] 3) Using crude HMF as raw material, efficient, simple and highly selective oxidation of HMF to prepare FDCA was achieved, further reducing the production cost of FDCA. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a technical process flow chart of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the examples and the accompanying drawings. The detailed description of the following examples is only used to exemplarily illustrate the technical solution of the present invention and is not intended to limit the scope of protection of the present invention, that is, the present invention is not limited to the specific implementation methods described in the examples, and covers any modification, replacement and improvement of raw materials and means without departing from the spirit of the present invention.

[0023] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The raw materials, equipment, etc. used in the following embodiments and experimental examples are all commercially available products.

[0024] Main ingredients:

[0025] Jerusalem artichoke syrup (Chongqing Jiaowang, fructose content 66.7%);

[0026] 5-Hydroxymethylfurfural crystals (Innochem, product number A16451, purity 97%);

[0027] Phosphoric acid (Innochem, product number G00018, purity 85%);

[0028] Vanadium chloride (Acros, product number 197000250, purity 97%);

[0029] Tetrahydrofuran (Innochem, product number A06439, purity 99.9%);

[0030] Ethyl acetate (Innochem, product number A39719, purity 99.8%);

[0031] 2,5-Furandicarboxylic acid (Innochem, product number A06911, purity 99%);

[0032] Cobalt monoxide (Acros, product number 379200100, purity 99%);

[0033] Cobalt tetraoxide (Innochem, product number A47971, purity 99.5%);

[0034] Nickel oxide (Innochem, product number A21677, purity 99.9%);

[0035] Nickel trioxide (Innochem, product number A03188, purity 99%);

[0036] Manganese dioxide (Acros, product number 222581000, purity 99%);

[0037] Cerium oxide (Alfa, product number 011328, purity 99.9%);

[0038] Ferrous oxide (Innochem, product number A46948, purity 99%);

[0039] Sodium chloride (Innochem, product number A63214, purity 99.8%);

[0040] Sodium hydroxide (Innochem, product number A36865, purity 99%);

[0041] Sodium bicarbonate (Innochem, product number A55543, purity 99%);

[0042] Sodium carbonate (Innochem, product number A19943, purity 99.8%);

[0043] Sodium hypochlorite solution (Innochem, product number A93524, purity: active chlorine>10%);

[0044] Copper nitrate (Macklin, product number C860751-500g, purity AR grade).

[0045] Preparation method of CuO catalyst: 0.4g of sodium hydroxide is dissolved in 40mL of water to prepare a sodium hydroxide aqueous solution, and then the above solution is slowly added dropwise into 10mL of 0.5mol / L copper nitrate solution to form a blue precipitate of copper hydroxide, and then the precipitate solution is placed in an ultrasonic reactor for ultrasonication for 1h to obtain a black CuO precipitate, and the CuO catalyst powder is obtained after filtration, washing, and drying (60°C overnight).

[0046] Example 1

[0047] The preparation of crude HMF is described in the example of reference patent CN117209459A, and the specific steps are as follows: 600g Jerusalem artichoke syrup (water content 30wt%), 20g phosphoric acid (85wt% phosphoric acid content), 4g vanadium chloride, 2000g tetrahydrofuran, 140°C, reaction 60min, HMF yield 70%, tetrahydrofuran is evaporated, and then 2000g ethyl acetate is added, and extraction is carried out at room temperature. After phase separation and rotary evaporation at -0.1MPa, ethyl acetate is removed to obtain a crude HMF product, and the purity of HMF in the crude product is 58%. Take 60g of crude HMF and add it to 288g of water and stir. After fully analyzing the black rot, filter to obtain 330g of crude HMF solution, the HMF mass concentration is about 10%, and 10g of homemade copper oxide catalyst is added for standby use.

[0048] The reaction steps of using the above HMF crude solution as raw material and preparing FDCA by electro-chemical cascade catalysis are as follows: under room temperature, 260g of sodium chloride and 740g of water are added to the ion membrane electrolyzer (cation exchange membrane) to prepare a saturated sodium chloride solution with a mass fraction of about 26%, and 39g of sodium hydroxide particles are added, and the electrolysis temperature and electrolysis time are controlled so that the effective chlorine concentration of sodium hypochlorite is 10%. The electrolyte is slowly added to the above HMF crude solution containing the catalyst for reaction, and the reaction temperature is controlled to be 40°C and the reaction time is 30min. After the reaction is completed, it is filtered and the catalyst is recycled. The oxidation reaction liquid is slowly dripped into 200g of 30% industrial hydrochloric acid for acidification under stirring, and FDCA is precipitated in the form of a precipitate. The acidified liquid is filtered to obtain the FDCA product, which is washed with pure water pulp 3 times and then dried at 70°C for quantitative analysis. The acidic filtrate is adjusted to pH 7 with sodium hydroxide and then electrodialyzed to obtain a pure solution with a sodium chloride content of 16%, and then the solution is heated to evaporate the water and concentrated to 26% for reuse.

[0049] The mass yield of FDCA was determined by weighing method, and the mass yield of FDCA was calculated as follows:

[0050] FDCA mass yield [wt%] = m(FDCA) / m(HMF)×100%.

[0051] Wherein, m(FDCA) is the mass of FDCA obtained after the reaction; m(HMF) is the dry mass of HMF in the crude HMF solution;

[0052] The calculation showed that the mass yield of FDCA was 112%, and the purity of the FDCA by liquid chromatography analysis was >99.9%.

[0053] Embodiment 2-5

[0054] In other embodiments of the present invention, in order to verify the recycling performance of high brine and the influence of alkali dosage, the reaction conditions of Example 1 were adjusted: except that the 26% sodium chloride solution was evaporated and concentrated for recycling, the other reaction conditions were the same as Example 1. The reaction results are shown in Table 1 below.

[0055] Table 1 Effect of high brine reuse on FDCA mass yield

[0056]

[0057] It can be seen from the data in Table 1 that the electrolysis effect and reaction effect of the high brine after purification by electrodialysis and evaporation concentration are equivalent to those of freshly prepared sodium chloride solution.

[0058] Example 6

[0059] Slowly add 10% commercial sodium hypochlorite to the above-mentioned crude HMF solution containing the catalyst for reaction, control the reaction temperature to 40°C, and the reaction time to 30 minutes. After the reaction is completed, filter and recycle the catalyst. Slowly drop 200g of 30% industrial hydrochloric acid into the oxidation reaction solution under stirring to acidify, and FDCA precipitates out in the form of precipitation. Filter the acidified solution to obtain the FDCA product, wash it with pure water pulp three times, and then dry it at 70°C for quantitative analysis.

[0060] The mass yield of FDCA was determined by weighing method, and the mass yield of FDCA was calculated as follows:

[0061] FDCA mass yield [wt%] = m(FDCA) / m(HMF)×100%.

[0062] Wherein, m(FDCA) is the mass of FDCA obtained after the reaction; m(HMF) is the dry mass of HMF in the crude HMF solution;

[0063] The calculation showed that the mass yield of FDCA was 105%, and the purity of the FDCA by liquid chromatography analysis was >99.9%.

[0064] Using a commercial 10% sodium hypochlorite solution (actual effective chlorine 10.3%), the chemical oxidation reaction conditions were the same, and the FDCA yield was slightly lower than that in Example 1. This may be related to the stability of sodium hypochlorite. Fresh electrolyzed sodium hypochlorite has stronger effective chlorine and active oxygen activities, which is more conducive to the oxidation process of crude HMF.

[0065] Example 7

[0066] Under room temperature, 260g of sodium chloride and 740g of water are added to the ion membrane electrolyzer to prepare a saturated sodium chloride solution with a mass fraction of about 26%, and 39g of sodium hydroxide particles are added. The electrolysis temperature and electrolysis time are controlled to make the effective chlorine concentration of sodium hypochlorite 10%. The electrolyte is slowly added to the solution prepared by the above-mentioned 10% HMF crystal containing catalyst to react, and the reaction temperature is controlled to be 40°C and the reaction time is 30min. After the reaction is completed, it is filtered and the catalyst is recycled. The oxidation reaction liquid is slowly dripped into 200g of 30% industrial hydrochloric acid for acidification under stirring, and FDCA is precipitated in the form of precipitation. The acidified liquid is filtered to obtain the FDCA product, which is washed with pure water pulping 3 times and then dried at 70°C for quantitative analysis. The acidic filtrate is electrodialyzed after adjusting the pH to 7 with sodium hydroxide to obtain a pure solution with a sodium chloride content of 16%, and then the solution is heated to evaporate the water and concentrated to 26% for reuse.

[0067] The mass yield of FDCA was determined by weighing method, and the mass yield of FDCA was calculated as follows:

[0068] FDCA mass yield [wt%] = m(FDCA) / m(HMF)×100%.

[0069] Wherein, m(FDCA) is the mass of FDCA obtained after the reaction; m(HMF) is the dry mass of HMF in the crude HMF solution;

[0070] The calculation showed that the mass yield of FDCA was 120%, and the purity of the FDCA by liquid chromatography analysis was >99.9%.

[0071] Using HMF crystals as raw materials, the mass yield of FDCA reached 120%, which indicates that the higher the purity of HMF, the more conducive it is to the oxidation process. The presence of impurities may consume part of the oxygen source, resulting in insufficient oxidation.

[0072] Embodiment 8-11

[0073] In other embodiments of the present invention, in order to verify the influence of sodium chloride concentration and alkali dosage, the reaction conditions of Example 1 were adjusted: except for the different sodium chloride concentration and alkali dosage, the other reaction conditions were the same as those of Example 1. The reaction results are shown in Table 2 below.

[0074] Table 2 Effect of sodium chloride concentration and alkali dosage on FDCA mass yield

[0075]

[0076] The reduction of sodium chloride concentration is not conducive to the preparation of high-concentration sodium hypochlorite. Compared with Example 1, it can be seen from Table 2 that the mass yield and purity of FDCA show a downward trend with the reduction of the initial concentration of sodium chloride. And the higher the amount of alkali, the more conducive to the preparation of FDCA, mainly because the stronger the alkalinity, the more stable the sodium hypochlorite. Therefore, appropriate control of the amount of alkali is beneficial to the electrolysis process and the control of the yield and quality of FDCA in the subsequent chemical oxidation stage.

[0077] Examples 12-16

[0078] In other embodiments of the present invention, in order to verify the influence of the concentration of sodium hypochlorite after electrolysis and the type of catalyst, the reaction conditions of Example 1 were adjusted: except for the different concentrations of sodium hypochlorite after electrolysis and the catalyst, the other reaction conditions were the same as those of Example 1. The reaction results are shown in Table 3 below.

[0079] Table 3 Effect of electrolytic sodium hypochlorite concentration and catalyst on FDCA mass yield

[0080]

[0081]

[0082] aTo ensure that the molar ratio of sodium hypochlorite to substrate is consistent with that in Example 1, the amount of crude HMF solution and catalyst increases or decreases with the effective chlorine of sodium hypochlorite. As shown in Table 3, the electrolysis process is beneficial to the oxidation of crude HMF with the increase of the effective chlorine concentration of sodium hypochlorite. When sodium hypochlorite with 12% effective chlorine is used, the FDCA mass yield reaches 115% and the purity is >99.9% (Example 12); when sodium hypochlorite with 6% effective chlorine is used, the FDCA mass yield drops to 97% and the FDCA purity drops to 98.5% (Example 14), which indicates that the oxidation capacity is insufficient when the effective chlorine is reduced, which is not conducive to the deep oxidation of HMF to prepare FDCA. When commercial cobalt tetraoxide and nickel trioxide are used, the catalytic effect is equivalent to that of the homemade copper oxide catalyst (Examples 15 and 16), indicating that the method of preparing FDCA by electro-chemical cascade catalysis of HMF oxidation in the present invention has relatively low requirements for the chemical catalytic process and has a strong prospect for industrial application.

[0083] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the above disclosed technical content to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing 2,5-furandicarboxylic acid by electro-chemical cascade catalysis, characterized in that: The steps include: 1) preparing a sodium chloride aqueous solution and adding sodium hydroxide; 2) using ion membrane electrolysis to electrolyze the solution in step 1) to generate sodium hypochlorite, while recycling the byproduct hydrogen, mixing the generated sodium hypochlorite with 5-hydroxymethylfurfural containing a catalyst, and performing a chemical oxidation reaction to obtain FDCA sodium salt, followed by filtering to separate the catalyst for reuse; 3) adding a strong acid to the FDCA sodium salt solution obtained by filtration in step 2) to acidify the obtained FDCA, and separating the FDCA by precipitating, filtering and separating to obtain a high-purity FDCA product and an acidic filtrate; 4) Adding an appropriate amount of alkali to the acidic filtrate of step 3) to neutralize and obtain a solution containing sodium chloride at pH=7, and treating it with an electrodialysis ion exchange membrane to obtain a pure sodium chloride solution, which is then evaporated and concentrated and returned to step 1) for recycling.

2. The method for preparing 2,5-furandicarboxylic acid by electro-chemical cascade catalysis according to claim 1, characterized in that: The mass concentration of the sodium chloride aqueous solution prepared in step 1) is 10-26.5%, and the amount of sodium hydroxide added is 1-30% of the mass of the sodium chloride.

3. The method for preparing 2,5-furandicarboxylic acid by electro-chemical cascade catalysis according to claim 1, characterized in that: The membrane material selected for the ion membrane electrolysis in step 2) is a cation exchange membrane, the effective chlorine solubility of sodium hypochlorite is 5-15%, the catalyst is at least one of cobalt monoxide, cobalt tetraoxide, nickel oxide, nickel trioxide, copper oxide, manganese dioxide, cerium oxide, and ferric oxide, and the 5-hydroxymethylfurfural is 5-hydroxymethylfurfural crystals, 5-hydroxymethylfurfural crude products, or 5-hydroxymethylfurfural solution.

4. The method for preparing 2,5-furandicarboxylic acid by electro-chemical cascade catalysis according to claim 3, characterized in that: In step 2), the molar ratio of 5-hydroxymethylfurfural to sodium hypochlorite is 1:3-9, the amount of catalyst is 5-50% of the mass of 5-hydroxymethylfurfural, the chemical oxidation reaction temperature is 30-80° C., the reaction time is 1-60 min, and the chemical oxidation reaction process is intermittent operation or continuous operation.

5. The method for preparing 2,5-furandicarboxylic acid by electro-chemical cascade catalysis according to claim 1, characterized in that: The strong acid in step 3) is hydrochloric acid, the mass concentration of the hydrochloric acid is 10-36%, and the mass ratio of the hydrochloric acid to 5-hydroxymethylfurfural is 0.6-1.8:1; The purity of the obtained FDCA product is >99%, and the pH of the acidic filtrate is <1.

6. The method for preparing 2,5-furandicarboxylic acid by electro-chemical cascade catalysis according to claim 1, characterized in that: The alkali described in step 4) is at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate.

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