A method for green preparation of furfuryl acid by coupling electrochemical oxidation with membrane separation

Abstract

The application discloses a kind of electrochemical oxidation-membrane separation coupling green preparation furfuryl acid method.The method uses industrial grade furfural as raw material, selects transition metal composite electrode as anode, multiple electrode as cathode, and carries out electrochemical oxidation reaction in alkaline electrolyte system;Reaction solution is removed inorganic impurities by anion exchange membrane separation, and then refined by acidification crystallization and vacuum sublimation, to obtain high-purity furfuryl acid.The application constructs "electrochemical oxidation-membrane separation-sublimation refining" coupling system, without additional chemical oxidant, by low-cost composite electrode optimization catalytic performance, combined with membrane separation and vacuum sublimation synergistic purification, solve the problems of low product purity, large wastewater discharge, high energy consumption in traditional process, meet the requirements of green chemical industry, and can be widely used in medicine, pesticide, high-end perfume and other fields.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical intermediate synthesis technology, specifically relating to a green method for preparing furoic acid by coupling electrochemical oxidation and membrane separation. Background Technology

[0002] Furoic acid is an important heterocyclic aromatic carboxylic acid, widely used in the synthesis of pharmaceutical intermediates, pesticide technicals, and high-end fragrances, with continuously growing market demand. The mainstream process for preparing furoic acid is the furfural oxidation method, which is divided into chemical oxidation and electrochemical oxidation. Chemical oxidation commonly uses oxidants such as hydrogen peroxide and potassium permanganate, but suffers from problems such as large oxidant consumption, significant wastewater discharge, and high treatment costs. While electrochemical oxidation does not require an external oxidant, it uses precious metal electrodes, leading to excessively high costs. Furthermore, the reaction solution contains many impurities, requiring multiple recrystallization purifications, resulting in low yields and large amounts of organic wastewater discharge, contradicting the principles of green production. In addition, existing processes also suffer from poor reaction selectivity and high energy consumption.

[0003] Therefore, there is an urgent need to develop a low-cost, high-purity, and wastewater-free green preparation method. Based on this, this application was developed. Summary of the Invention

[0004] To address the technical shortcomings of existing processes, such as high pollutant emissions, low product purity, high electrode costs, and high energy consumption, this invention provides a green method for the preparation of furoic acid by coupling electrochemical oxidation and membrane separation. This method achieves clean and efficient production of furoic acid by constructing an integrated system of "low-cost catalytic oxidation - precise membrane separation - green sublimation purification".

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A green method for preparing furoic acid using electrochemical oxidation-membrane separation coupling includes the following steps: 1) Electrochemical oxidation reaction: Using furfural as raw material, prepare an alkaline electrolyte aqueous solution with an initial furfural concentration of 40~60g / L at 0.05~0.15mol / L as the reaction solution; add the reaction solution to a double-chamber diaphragm electrolytic cell, using a transition metal composite electrode as the anode and a pure metal or Cu-based composite electrode as the cathode, with an electrode spacing of 2~5cm, apply a voltage of 20~30V and maintain a current of 2~4A, and stir the reaction at 20~30℃ for 2.5~3.5h; 2) Membrane separation and purification: The reaction solution obtained in step 1) is passed into an anion exchange membrane separation device, using a combined anion exchange membrane dialysis-ultrafiltration process: first, ultrafiltration is performed at 0.1~0.3MPa and 25~35℃ to retain colloidal byproducts and electrode detachment particles in the reaction solution; then, the ultrafiltration permeate is passed into an anion exchange membrane dialysis device for anion exchange membrane dialysis, using deionized water as the receiving liquid, with a liquid-liquid ratio of 1:1~2, and dialysis for 4~6 hours to remove inorganic anion impurities, and the permeate containing furoate is collected; the ultrafiltration membrane used for ultrafiltration has a molecular weight cutoff of 10000~50000 Da (equivalent particle size cutoff: 5~20 nm); 3) Acidification crystallization: Add acid solution to the permeate obtained in step 2), adjust the pH to 1.5~2.5, crystallize at a constant temperature with stirring, filter to obtain crude furoic acid, and then refine it by vacuum sublimation.

[0006] In the method of this invention, the following two points should be noted regarding electrode preparation: 1) Composite anode: Using 100~200 mesh nickel foam as substrate, the substrate is pretreated by acid washing with 1 mol / L hydrochloric acid for 10 min, ultrasonic cleaning with deionized water 3 times (5 min each time), and vacuum drying at 60℃ for 2 h; Ni-Co, Ni-Fe, and Ni-Mn composite electrodes are prepared by electrodeposition-calcination process, and each electrode has the characteristics of excellent selectivity, high activity, and strong stability. 2) Cathode: Pure metal electrodes are directly selected from finished products with a purity of ≥99.9%; Cu-Zn and Cu-Sn composite electrodes are prepared by substrate pretreatment, electrodeposition and calcination, respectively, and have the advantages of low hydrogen evolution overpotential and strong corrosion resistance.

[0007] Specifically, in step 1), the transition metal composite electrode at the anode is selected from one of Ni-Co, Ni-Fe, and Ni-Mn composite electrodes. Further, the preparation method of the Ni-Co, Ni-Fe, or Ni-Mn composite electrode is as follows: Ni-Co composite electrode: Based on nickel foam, after acid washing, ultrasonic cleaning, and drying pretreatment, it is electrodeposited at 2-3V for 30-60 min in a 0.1-0.2 mol / L Co(NO3)2 solution, and then calcined at 400-500℃ for 2-3 h with a Co loading of 5-8 wt%. Ni-Fe composite electrode: Based on nickel foam, after pretreatment (as above), it is electrodeposited at 1.8-2.8V for 40-70 min in a 0.1-0.2 mol / L FeSO4 solution, followed by calcination at 380-480℃ for 2-3 h, with an Fe loading of 4-7 wt%. Ni-Mn composite electrode: Based on nickel foam, after pretreatment (as above), it is electrodeposited at 2.2-3.2V for 35-65min in a 0.1-0.2mol / L Mn(NO3)2 solution, and then calcined at 420-520℃ for 2-3h with a Mn loading of 5-9wt%.

[0008] Furthermore, the alkaline electrolyte mentioned in step 1) is a single alkaline electrolyte or a composite alkaline electrolyte; the single alkaline electrolyte is selected from one of KOH, NaOH and LiOH; the composite alkaline electrolyte is a KOH-NaOH or KOH-LiOH mixed system with a mixing molar ratio of 1~3:1; the total concentration of the electrolyte is 0.05~0.15mol / L.

[0009] Specifically, the cathode mentioned in step 1) is selected from pure metal electrodes such as Cu, Ag, or Ni (purity ≥ 99.9%), or from Cu-Zn or Cu-Sn Cu-based composite electrodes. Further, the preparation method of the Cu-based composite electrode is as follows: Cu-Zn composite electrode: Using pure Cu sheet as substrate, after pretreatment (as above), electrodeposit at 1.5-2.5V for 20-40 min in 0.1-0.2 mol / L ZnSO4 solution, followed by calcination at 300-400℃ for 1-2 h, with a Zn loading of 3-6 wt%. Cu-Sn composite electrode: Using pure Cu sheet as substrate, after pretreatment (as above), electrodeposit at 1.8-2.8V for 25-45 min in 0.1-0.2 mol / L SnCl2 solution, followed by calcination at 350-450℃ for 1-2 h, with a Sn loading of 4-7 wt%. The ratio of the electrode surface area of ​​all cathodes to the volume of the reaction liquid is 1:5 to 1:8 cm² / mL.

[0010] As one specific implementation method, the optimal process parameters for step 1) are: initial furfural concentration of 50 g / L, electrolyte of 0.1 mol / L KOH or 0.1 mol / L KOH-NaOH mixture (molar ratio 2:1), voltage of 25 V, current of 3 A, reaction temperature of 25 °C, and reaction time of 3 h.

[0011] Furthermore, the electrolytic cell described in step 1) uses a quaternary ammonium anion exchange membrane as the diaphragm, with an ion exchange capacity of 1.2~1.8 mmol / g and a membrane thickness of 100~200 μm.

[0012] Specifically, the anion exchange membrane mentioned in step 2) is a quaternary ammonium anion exchange membrane with a pore size of 0.01~0.05μm.

[0013] Specifically, in step 3), the pH is adjusted by adding an acid solution, preferably to a pH of 2. The acid solution is hydrochloric acid, sulfuric acid, or nitric acid, etc. The hydrochloric acid solution with a mass fraction of 36-38% is preferred. The crystallization temperature is room temperature (25±5℃) and the time is 1-3 hours.

[0014] Specifically, in step 4), the vacuum sublimation purification process involves placing crude furoic acid in a sublimation apparatus and sublimating it at 130-140°C and 5-10 kPa for 2-3 hours. The product is then collected to obtain high-purity furoic acid. The optimal conditions for vacuum sublimation are: temperature 135°C, vacuum degree 7 kPa, and sublimation time 2 hours.

[0015] As one specific embodiment, the above-mentioned electrochemical oxidation-membrane separation coupled green preparation method for furoic acid includes the following steps: 1. Electrochemical oxidation reaction: 1) Ingredients: Industrial grade furfural (purity ≥98%) is added to an alkaline electrolyte aqueous solution and stirred to dissolve, resulting in a 50g / L furfural reaction solution; 2) Tank loading: A double-chamber diaphragm electrolytic cell is adopted, with a quaternary ammonium anion exchange membrane as the diaphragm. The volume ratio of the anode chamber to the cathode chamber is 1:1. The edges of the diaphragm are sealed with fluororubber. It is equipped with a constant temperature device and a hydrogen collection port. 3) Reaction: Apply 25V voltage and maintain 3A current, stir the reaction at 25℃ for 3h; ·OH is generated at the anode to oxidize furfural to produce furoate, and hydrogen is generated at the cathode for recovery. The membrane blocks the migration of substances between the anode and cathode, improving the reaction selectivity and energy utilization. 2. Membrane separation and purification: Anion exchange membrane dialysis-ultrafiltration combined process is adopted: first, ultrafiltration is carried out at 0.1~0.3MPa and 25~35℃ to retain colloidal by-products and electrode detachment particles in the reaction solution; then, the ultrafiltration permeate is passed into an anion exchange membrane dialysis device, with deionized water as the receiving liquid, liquid-liquid ratio of 1:1, dialysis for 4~6 hours to remove inorganic anion impurities, and the permeate containing furoate is collected; 3. Acidification and crystallization: 37% hydrochloric acid was added dropwise to the permeate at room temperature and with stirring at 250 r / min until the pH reached 2. After crystallization for 1.5 h, the crude furoic acid was obtained by filtration. 4. Vacuum sublimation purification: Crude furoic acid is sublimated at 135℃ and 7kPa for 2 hours, and high-purity furoic acid product is obtained by condensation and collection.

[0016] The innovations of this invention are mainly reflected in the following aspects: 1) It pioneered a variety of low-cost transition metal composite anodes to replace precious metal electrodes, reducing costs by more than 90%, and adapting to different process requirements, with by-products ≤1%; 2) Expanding diversified cathode systems, Cu-based composite electrodes reduce energy consumption by 5-8%, improve stability, and are suitable for different production scenarios; 3) Optimize the design of the dual-chamber membrane electrolyzer and adopt homologous anion exchange membranes to achieve synergistic electrolysis-separation, reduce costs, and improve ease of operation; 4) Construct an "electrochemical oxidation-membrane separation" coupled system to remove impurities at the source and solve the problem of difficult purification in traditional processes; 5) Vacuum sublimation replaces recrystallization, avoiding the use of organic solvents, eliminating wastewater discharge, and increasing product purity to over 99.9%; 6) The entire process is a closed-loop clean production process with recyclable hydrogen, offering significant environmental advantages.

[0017] Compared with the prior art, the advantages and beneficial effects of the method of the present invention are as follows: 1. Excellent product quality: The furoic acid product prepared by the method of this invention has extremely low impurity content, purity ≥99.9%, yield ≥85%, and energy consumption ≤120kWh per ton of product, meeting the needs of high-end fields; 2. Green and environmentally friendly: During the live broadcast process of this invention, no chemical oxidants are added, and no heavy metal waste residue or organic wastewater is discharged, making it green and environmentally friendly; 3. Easy to industrialize: The method of this invention has mild operating conditions and mature equipment. It can be modified based on existing equipment and is suitable for large-scale continuous production. Detailed Implementation

[0018] The technical solution of the present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited thereto.

[0019] In the following examples, all raw materials used are commercially available products that can be directly purchased or prepared using conventional techniques in the art. For example, the quaternary ammonium anion exchange membrane used is the Fumasep FAAM-15 model quaternary ammonium anion exchange membrane manufactured by Fuma-tech GmbH, Germany, with an ion exchange capacity of 1.5 mmol / g, a membrane thickness of 150 μm, and a membrane pore size of 0.03 μm.

[0020] The dual-chamber diaphragm electrolyzer used in the embodiments has a 1:1 volume ratio between the anode chamber and the cathode chamber, and the diaphragm edge is sealed with fluororubber. It is equipped with a constant temperature device and a hydrogen collection port. Its structure can adopt conventional technology in the field or directly purchase ordinary commercial products. Since it is not the innovation of this application, it will not be described in detail here.

[0021] In the following embodiments, the pretreatment of the electrode substrate is as follows: acid washing with 1 mol / L hydrochloric acid for 10 min, ultrasonic cleaning with deionized water 3 times (5 min each time), and vacuum drying at 60°C for 2 h. Example 1

[0022] Optimal process conditions.

[0023] 1. Preparation of Ni-Co composite anode: Using 150-mesh nickel foam as substrate, after pretreatment, it was electrodeposited at 2.5V for 45 min in 0.15 mol / L Co(NO3)2 solution, and then calcined at 450℃ for 2.5 h with a Co loading of 6.5 wt%.

[0024] 2. Electrochemical oxidation: 25g of industrial-grade furfural (purity ≥98%) was added to 500mL of 0.1mol / L KOH aqueous solution as the reaction solution. The reaction solution was added to a double-chamber diaphragm electrolytic cell (316L stainless steel, quaternary ammonium anion exchange membrane as the diaphragm: ion exchange capacity 1.5mmol / g, membrane thickness 150μm). The anode was equipped with the Ni-Co composite electrode prepared above, and the cathode was equipped with a 99.9% pure Cu metal electrode with an electrode spacing of 3cm. The reaction was carried out at 25V, 3A, and 25℃ with stirring for 3h, and hydrogen was recovered.

[0025] 3. Membrane separation: The reaction solution obtained in step 2 was subjected to ultrafiltration at 0.2 MPa and 30 °C (the ultrafiltration membrane used for ultrafiltration had a molecular weight cutoff of 30,000 Da). The ultrafiltration permeate was then subjected to anion exchange membrane dialysis (flow rate 15 mL / min, the anion exchange membrane was a quaternary ammonium type anion exchange membrane with a pore size of 0.03 μm), with deionized water as the receiving liquid, a liquid-liquid ratio of 1:1, and dialysis was performed at 30 °C for 5 h. 480 mL of permeate containing furoate was collected.

[0026] 4. Acidification and crystallization: Add 37% hydrochloric acid dropwise at 25℃ and 250 r / min until pH=2, crystallize for 1.5h, filter, and obtain 26.8g of crude furoic acid.

[0027] 5. Vacuum sublimation: The crude furoic acid was placed in a sublimation apparatus and sublimated for 2 hours under a vacuum of 7 kPa and a temperature of 135℃. 29.1 g of the finished furoic acid product was collected, with a purity of 99.92% and a yield of 88%. The energy consumption per ton was 115 kWh. Example 2

[0028] Parameter optimization verification.

[0029] 1. Electrochemical oxidation: Add 20g of furfural to 500mL of 0.05mol / L KOH solution, with an electrode spacing of 2cm, voltage of 20V, current of 2A, and reaction temperature of 20℃ for 3.5h. Other steps are the same as in Example 1.

[0030] 2. Membrane separation: Ultrafiltration was performed at 0.1 MPa and 25°C. The flow rate of the ultrafiltration permeate was 10 mL / min, and 470 mL of permeate was collected. Other procedures were the same as in Example 1.

[0031] 3. Acidification and crystallization: Add sulfuric acid dropwise at 25℃ and 200r / min until pH=1.5, crystallize for 2 hours, filter, and obtain 20.2g of crude furoic acid.

[0032] 4. Vacuum sublimation: The crude furoic acid was placed in a sublimation apparatus and sublimed for 3 hours under a vacuum of 5 kPa and a temperature of 130℃ to obtain 21.8 g of finished furoic acid product with a purity of 99.90% and a yield of 86%. The energy consumption per ton was 108 kWh. Example 3

[0033] Verification of high-concentration raw materials.

[0034] 1. Electrochemical oxidation: Add 30g of furfural to 500mL of 0.15mol / L KOH solution, with an electrode spacing of 5cm, voltage of 30V, current of 4A, and reaction temperature of 30℃ for 2.5h. Other steps are the same as in Example 1.

[0035] 2. Membrane separation: Ultrafiltration was performed at 0.3 MPa and 35°C. The flow rate of the ultrafiltration permeate was 20 mL / min, and 485 mL of permeate was collected. Other steps were the same as in Example 1.

[0036] 3. Acidification and crystallization: Nitric acid was added dropwise at 25℃ and 300r / min until the pH reached 2.5. Crystallization was carried out for 1 hour to obtain 32.1g of crude furoic acid.

[0037] 4. Vacuum sublimation: The crude furoic acid is placed in a sublimation apparatus and sublimated at a vacuum of 10 kPa and a temperature of 140℃ for 2.5 h to obtain 34.5 g of finished furoic acid product with a purity of 99.91% and a yield of 87%. The energy consumption per ton is 118 kWh. Example 4

[0038] Verification of Ni-Fe composite anode.

[0039] 1. Preparation of Ni-Fe composite electrode: Using 150-mesh nickel foam as substrate, after pretreatment, electrodeposit at 2.2V for 50 min in 0.15 mol / L FeSO4 solution, calcined at 430℃ for 2.5 h, with Fe loading of 5.5 wt%.

[0040] 2. Electrochemical oxidation and subsequent processes were the same as in Example 1, yielding 29.3g of product with a purity of 99.91%, a yield of 88.6%, and an energy consumption of 112kWh per ton. Example 5

[0041] Verification of Ni-Mn composite anodes.

[0042] 1. Preparation of Ni-Mn composite electrode: After pretreatment with 150-mesh nickel foam, electrodeposition was performed at 2.8V for 55 min in 0.15 mol / L Mn(NO3)2 solution, followed by calcination at 480℃ for 2.5 h, with a Mn loading of 7 wt%.

[0043] 2. Electrochemical oxidation and subsequent processes are the same as in Example 1, yielding 28.9g of finished furoic acid with a purity of 99.93%, a yield of 87.5%, and an energy consumption of 116kWh per ton. Example 6

[0044] NaOH electrolyte verification.

[0045] 1. The anode used was the Ni-Co composite electrode of Example 1. Electrochemical oxidation was performed using 500 mL of 0.1 mol / L NaOH solution as the electrolyte aqueous solution. Other parameters were the same as in Example 1.

[0046] 2. The subsequent process is the same as in Example 1, yielding 28.8g of finished furoic acid with a purity of 99.90%, a yield of 87.2%, and an energy consumption of 113kWh per ton. Example 7

[0047] Verification of KOH-NaOH composite electrolyte.

[0048] 1. The anode used was the Ni-Fe composite electrode of Example 4. Electrochemical oxidation was performed using 500 mL of 0.1 mol / L KOH-NaOH mixed solution (molar ratio 2:1) as the electrolyte aqueous solution. Other parameters were the same as in Example 1.

[0049] 2. The subsequent process is the same as in Example 1, yielding 29.4g of finished furoic acid with a purity of 99.92%, a yield of 88.9%, and an energy consumption of 110kWh per ton. Example 8

[0050] Verification of Cu-Zn composite cathode.

[0051] 1. Electrode Assembly: The anode used was the Ni-Co composite electrode from Example 1, and the cathode used was the Cu-Zn composite electrode. The Cu-Zn composite electrode was prepared as follows: using a pure Cu sheet as a substrate, after pretreatment, electrodeposition was performed at 2V for 30 min in a 0.15 mol / L ZnSO4 solution, followed by calcination at 350℃ for 1.5 h, with a Zn loading of 4.5 wt%. 2. Electrochemical oxidation was performed using the 0.1 mol / L NaOH system of Example 6, with other parameters the same as in Example 1.

[0052] 3. The subsequent process is the same as in Example 1, yielding 28.9g of finished furoic acid with a purity of 99.91%, a yield of 87.5%, and an energy consumption of 106kWh per ton. Example 9

[0053] Ag cathode verification.

[0054] 1. Electrode combination: The anode is the Ni-Fe composite electrode of Example 4, and the cathode is the Ag electrode with a purity of 99.99%. Other parameters are the same as in Example 1.

[0055] 2. Electrochemical oxidation was performed using the KOH-NaOH composite electrolyte system of Example 7, with other parameters the same as in Example 1.

[0056] 3. The subsequent process is the same as in Example 1, yielding 29.5g of finished furoic acid with a purity of 99.93%, a yield of 89.2%, and an energy consumption of 109kWh per ton.

[0057] Comparative Example

[0058] Traditional electrochemical oxidation process.

[0059] 1. The anode is a Pt-Ir alloy electrode, and the cathode is a Cu electrode with a purity of 99.9%. Other electrochemical conditions are the same as in Example 1.

[0060] 2. After the reaction, the product was directly acidified and crystallized to obtain 28.5g of crude product.

[0061] 3. The product furoic acid was recrystallized three times to obtain 21.7g of finished product, with a purity of 98.4% and a yield of 74%. The energy consumption per ton was 180kWh, and 1.2L of ethanol wastewater was generated.

[0062] This invention constructs a coupled system of "electrochemical oxidation-membrane separation-sublimation purification", which does not require the addition of external chemical oxidants. It optimizes catalytic performance through low-cost composite electrodes and combines membrane separation and vacuum sublimation for synergistic purification, solving the problems of low product purity, large wastewater discharge and high energy consumption of traditional processes. It meets the requirements of green chemical industry and can be widely used in pharmaceuticals, pesticides, high-end fragrances and other fields.

[0063] In summary, the process of this invention is simple and gentle, and the core equipment consists of mature industrial equipment. The optimized design of the dual-chamber diaphragm electrolyzer is compatible with the multi-electrode-electrolyte combination, and can be upgraded from existing production lines without large-scale new investment. Raw materials are widely available and inexpensive. The multi-electrode and electrolyte system improves process adaptability, enabling long-term continuous production. The product yield is high and the purity is excellent, meeting the needs of multiple fields. Furthermore, there is no wastewater discharge, low energy consumption, and significant environmental and economic benefits. It is suitable for large-scale industrial production, has strong industrial applicability, and a broad market prospect.

Claims

1. A green method for preparing furoic acid by coupling electrochemical oxidation and membrane separation, characterized in that, Includes the following steps: 1) Electrochemical oxidation reaction: Using furfural as raw material, prepare an alkaline electrolyte aqueous solution with an initial furfural concentration of 40~60g / L of 0.05~0.15mol / L as the reaction solution; add the reaction solution to a double-chamber diaphragm electrolytic cell, using a transition metal composite electrode as the anode and a pure metal or Cu-based composite electrode as the cathode, apply a voltage of 20~30V, maintain a current of 2~4A, and stir the reaction at 20~30℃ for 2.5~3.5h; 2) Membrane separation and purification: The reaction solution obtained in step 1) is first subjected to ultrafiltration at 0.1~0.3MPa and 25~35℃, and then the ultrafiltration permeate is subjected to anion exchange membrane dialysis with deionized water as the receiving liquid, liquid-liquid ratio 1:1~2, dialysis for 4~6h, and the permeate containing furoate is collected. 3) Acidification crystallization: Adjust the pH of the permeate obtained in step 2) to 1.5~2.5, crystallize at a constant temperature with stirring, filter, and obtain crude furoic acid. Purify by vacuum sublimation to obtain the final product.

2. The method according to claim 1, characterized in that, In step 1), the transition metal composite electrode at the anode is selected from one of Ni-Co, Ni-Fe, and Ni-Mn composite electrodes.

3. The method according to claim 2, characterized in that, The preparation methods for Ni-Co, Ni-Fe, or Ni-Mn composite electrodes are as follows: Ni-Co composite electrode: Based on nickel foam, after pretreatment, it is electrodeposited at 2-3V for 30-60 min in a 0.1-0.2 mol / L Co(NO3)2 solution, followed by calcination at 400-500℃ for 2-3 h, with a Co loading of 5-8 wt%. Ni-Fe composite electrode: Based on nickel foam, after pretreatment, electrodeposit at 1.8-2.8V for 40-70 min in 0.1-0.2 mol / L FeSO4 solution, followed by calcination at 380-480℃ for 2-3 h, with an Fe loading of 4-7 wt%. Ni-Mn composite electrode: Based on nickel foam, after pretreatment, it is electrodeposited at 2.2-3.2V for 35-65min in a 0.1-0.2mol / L Mn(NO3)2 solution, and then calcined at 420-520℃ for 2-3h with a Mn loading of 5-9wt%.

4. The method according to claim 1, characterized in that, The alkaline electrolyte mentioned in step 1) is a single alkaline electrolyte or a composite alkaline electrolyte; the single alkaline electrolyte is selected from one of KOH, NaOH and LiOH; the composite alkaline electrolyte is a KOH-NaOH or KOH-LiOH mixed system with a mixing molar ratio of 1~3:1; the total concentration of the electrolyte is 0.05~0.15mol / L.

5. The method according to claim 1, characterized in that, The cathode mentioned in step 1) is selected from Cu, Ag, or Ni pure metal electrodes, or Cu-based composite electrodes selected from Cu-Zn or Cu-Sn.

6. The method according to claim 5, characterized in that, The preparation method of Cu-based composite electrode is as follows: Cu-Zn composite electrode: using pure Cu sheet as substrate, after pretreatment, electrodepositing is performed at 1.5-2.5V for 20-40 min in a 0.1-0.2 mol / L ZnSO4 solution, followed by calcination at 300-400℃ for 1-2 h, with a Zn loading of 3-6 wt%. Cu-Sn composite electrode: using pure Cu sheet as substrate, after pretreatment, electrodepositing at 1.8-2.8V for 25-45min in 0.1-0.2mol / L SnCl2 solution, followed by calcination at 350-450℃ for 1-2h, with a Sn loading of 4-7wt%.

7. The method according to claim 1, characterized in that, The electrolytic cell described in step 1) uses a quaternary ammonium anion exchange membrane as the diaphragm, with an ion exchange capacity of 1.2~1.8 mmol / g and a membrane thickness of 100~200 μm.

8. The method according to claim 1, characterized in that, The anion exchange membrane mentioned in step 2) is a quaternary ammonium anion exchange membrane with a pore size of 0.01~0.05μm.

9. The method according to claim 1, characterized in that, In step 3), the pH is adjusted by adding an acid solution, which is hydrochloric acid, sulfuric acid, or nitric acid, and the crystallization temperature is room temperature.

10. The method according to claim 1, characterized in that, In step 4), the crude furoic acid is sublimated at 130-140℃ and 5-10kPa for 2-3 hours, and the product is collected to obtain high-purity furoic acid.