A method for the electrolytic reduction of acrylonitrile to adiponitrile and hexane trinitrile

Abstract

The present invention discloses a method for electrochemically reducing acrylonitrile to adiponitrile and hexane trinitrile, belonging to the technical field of electrochemistry. The method for electrochemically reducing acrylonitrile to adiponitrile and hexane trinitrile comprises the following steps: mixing acrylonitrile and an electrolyte solution and then performing electroreduction to obtain adiponitrile and hexane trinitrile; the components of the electrolyte solution include: a supporting electrolyte, an electrode protector, a complexing agent, a quaternary ammonium salt, and an easily oxidizable substance. The method of the present invention can co-produce adiponitrile and hexane trinitrile, solving the problem in the prior art that in electrochemical synthesis, only the output of adiponitrile is emphasized, and the highly valuable hexane trinitrile is treated as waste; moreover, by adding an easily oxidizable substance, the present invention reduces the anodic oxidation potential, inhibits the generation of oxygen, inhibits the occurrence of the oxygen evolution reaction, improves the stability and safety of the reaction, simultaneously reduces the cell voltage, improves the current efficiency in the electrolysis process, reduces the electrolysis power consumption, and thus reduces the production cost.

Description

Technical Field

[0001] The present invention relates to the field of electrochemistry technology, and particularly to a method for preparing adiponitrile and hexane trinitrile by electrolytic reduction of acrylonitrile. Background Art

[0002] Adiponitrile (AND), English name: Adiponitrile, CAS No.: 111-69-3, molecular formula: C6H8N2, molecular weight: 108.14, boiling point: 295 °C. Adiponitrile is an important organic chemical intermediate, mainly used in the production of materials such as PA66, 1,6-hexamethylene diisocyanate (HDI), and PA610. With the development of technology, the application fields of adiponitrile have gradually expanded, and it has currently been used as a synthetic high-grade environmental protection coating, polymer additive, electroplating additive, extractant, etc.

[0003] 1,3,6-Hexanetricarbonitrile (HTCN), English name: 1,3,6-Hexanetricarbonitrile, CAS No.: 1772-25-4, molecular formula: C9H 11 N3, molecular weight: 161.20, boiling point: 441 °C. Hexane trinitrile is an excellent electrolyte additive. As an environmentally friendly polar aprotic solvent, it has the advantages of low viscosity, high boiling point, wide electrochemical window, high chemical stability, etc. And its decomposition products in the solvent are generally carboxylates, aldehydes, and organic amines, rather than highly toxic CN - . Therefore, hexane trinitrile is increasingly being taken seriously as an important intermediate for industrial organic synthesis and electrolyte additives for lithium-ion batteries.

[0004] Currently, it is generally adopted to prepare adiponitrile by electrolyzing acrylonitrile, and hexane trinitrile with extremely high added value can be produced while preparing adiponitrile. The method for preparing adiponitrile by electrolyzing acrylonitrile has the advantages of wide raw material sources, low cost, simple process, mild reaction conditions, and safe and controllable reaction process. However, in the process of diaphragm-free electrolysis of acrylonitrile, oxygen will be generated at the anode and a small amount of hydrogen will be generated at the cathode. The explosion range of oxygen and hydrogen is 4.0 - 95%, and it is easy to form an explosive mixture gas in a closed or semi-closed electrolysis environment. Once encountering excitation conditions such as fire source, high temperature, or electric spark, it may trigger a violent explosion reaction, causing inestimable damage to production facilities, personnel safety, and the environment. In addition, the explosion range of acrylonitrile gas is between 3.05 - 17.5%. During the electrolysis process, a certain amount of acrylonitrile volatile gas will be generated in the reaction system. The acrylonitrile volatile gas is mixed with the by-produced oxygen, and it may reach the dangerous concentration of the acrylonitrile volatile gas, increasing the possibility of accidents. And how to improve the safety of the electrolysis reaction has become a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing adiponitrile and hexane trinitrile by electrolytic reduction of acrylonitrile, so as to solve the problems existing in the above-mentioned prior art. The method of the present invention can co-produce adiponitrile and hexane trinitrile, solving the problem that in the prior art, the target in electrochemical synthesis only focuses on the output of adiponitrile, and the hexane trinitrile with high added value is treated as waste; and the present invention reduces the anodic oxidation potential, inhibits the generation of oxygen, inhibits the occurrence of oxygen evolution reaction, improves the stability and safety of the reaction, while reducing the cell voltage, improving the current efficiency in the electrolysis process, reducing the electrolysis power consumption, and thus reducing the production cost by adding easily oxidizable substances such as methanol.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The technical solution of the present invention is to provide a method for preparing adiponitrile and hexane trinitrile by electrolytic reduction of acrylonitrile, comprising the following steps:

[0008] Mix acrylonitrile and an electrolyte solution and then perform electrolytic reduction to obtain adiponitrile and hexane trinitrile (1,3,6 - hexane trinitrile);

[0009] The components of the electrolyte solution include: a supporting electrolyte, an electrode protector, a complexing agent, a quaternary ammonium salt, and an easily oxidizable substance.

[0010] Further, the concentration of the supporting electrolyte in the electrolyte solution is 7.5 - 12.5 wt.%; the supporting electrolyte includes phosphates;

[0011] The concentration of the electrode protector in the electrolyte solution is 1 - 4 wt.%; the electrode protector includes borax;

[0012] The concentration of the complexing agent in the electrolyte solution is 0.5 - 1.5 wt.%; the complexing agent includes EDTA;

[0013] The concentration of the quaternary ammonium salt in the electrolyte solution is 0.5 - 2.5 wt.%.

[0014] Further, the phosphates include disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, or potassium dihydrogen phosphate;

[0015] The quaternary ammonium salts include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide.

[0016] Further, the concentration of acrylonitrile in the electrolyte solution is 7.5 - 15 wt.%;

[0017] The easily oxidizable substances include methanol, formaldehyde, formic acid, ethanol, acetaldehyde, acetic acid, oxalic acid, glyoxal, ethylene glycol, or glycerol.

[0018] Further, the concentration of the easily oxidizable substance in the electrolyte is 0.1 to 5.0 mol / L.

[0019] Still further, the concentration of the easily oxidizable substance in the electrolyte is 1 mol / L.

[0020] In the present invention, the function of borax is to relieve the corrosion of the electrode by the electrolyte; the function of the complexing agent is to avoid the deposition of metal ions; the function of the quaternary ammonium salt is to enhance the conductivity of the electrolyte and increase the solubility of acrylonitrile; the function of the easily oxidizable substance is to be used for anodic oxidation to replace the oxygen evolution reaction.

[0021] Further, the temperature of the electrolytic reduction is 20 to 50 °C, the current density is 500 to 5000 A / m 2 , and the amount of electricity passed is 0.5 to 0.9 F / mol.

[0022] Further, the distance between the cathode and the anode during the electrolytic reduction is 0.1 to 5 mm;

[0023] The material of the cathode includes any one of cadmium (Cd), lead (Pb), and cadmium-lead alloy (70% lead and 30% cadmium); the material of the anode includes any one of carbon steel, stainless steel (such as 304 stainless steel), nickel, and titanium-based iridium oxide.

[0024] The electrode prepared with titanium-based iridium oxide as the electrode material is a DSA electrode.

[0025] Still further, the distance between the cathode and the anode during the electrolytic reduction is 0.5 to 5 mm.

[0026] Further, the linear velocity of the electrolyte during the electrolytic reduction is 0.02 to 1.5 m / s.

[0027] Still further, the linear velocity of the electrolyte during the electrolytic reduction is 0.1 to 0.5 m / s.

[0028] Still further, the pH value of the electrolyte is 7.5 to 8.

[0029] The present invention discloses the following technical effects:

[0030] (1) The method of the present invention can co-produce adiponitrile and hexane trinitrile, solving the problem that the prior art only focuses on the production of adiponitrile in electrochemical synthesis and treats the highly valuable hexane trinitrile as waste.

[0031] (2) Under the premise of low wire speed and high acrylonitrile content, by adjusting the distance between the electrodes, the present invention can greatly improve the yield of adiponitrile and 1,3,6 - hexanetricarbonitrile and the total current efficiency in the electrolysis of acrylonitrile. The anodic reaction is replaced by methanol oxidation instead of oxygen evolution reaction, inhibiting the generation of oxygen, eliminating the problem of the formation of extremely explosive gases by oxygen, hydrogen, and acrylonitrile, and improving the stability and safety of the diaphragmless electrolysis process. At the same time, the anodic potential, the cell voltage during the electrolysis process, and the electrolysis power consumption are reduced, making the acrylonitrile electrolysis process safer and with lower power consumption, and having good economic benefits and application value.

[0032] (3) During the electrolysis process, the present invention introduces easily oxidizable substances such as methanol, formaldehyde, formic acid, ethanol, acetaldehyde, acetic acid, oxalic acid, glyoxal, ethylene glycol, and glycerol, inhibiting the oxygen evolution reaction at the anode. The original process of generating 1 mol of oxygen requires the transfer of 4 mol of electrons, while now generating 1 mol of carbon dioxide requires the transfer of 6 mol of electrons, greatly reducing the generation of oxygen, avoiding the problem of the formation of explosive mixed gases by oxygen, hydrogen, and acrylonitrile and other volatile gases, improving the safety of the electrolysis reaction process in the diaphragmless electrolytic cell, and making the reaction process of electrolyzing acrylonitrile to adiponitrile safer.

[0033] (4) By regulating the amount of electricity passed during the electrolysis reaction (electrolytic reduction reaction) process, the present invention improves the current efficiency of the electrolysis process, reduces the electrical energy consumption of the electrolysis reaction, and thus reduces the production cost. Detailed Embodiments

[0034] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0035] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0036] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0037] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the specification of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0038] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0039] The electrolytic reduction reaction of the present invention is carried out in an electrolytic cell. The sizes of the cathode and anode in the electrolytic cell are both 60 mm × 266 mm × 26 mm. The anode and cathode are arranged in parallel and opposite to each other. The electrolyte is pumped and circulated. A condensation recovery device is connected above the storage tank, and the condensation temperature is 5 °C to reflux the volatilized acrylonitrile gas. The condensation device is connected to a gas chromatograph through a gas pipeline to detect the oxygen content in the gas generated by the reaction. During the reaction process, the cell voltage and the instantaneous oxygen content are measured once every time the electricity passed increases by 0.1 F / mol. After the reaction is completed, quantitative analysis of acrylonitrile, adiponitrile, and hexane trinitrile is carried out using a gas chromatograph, and the yields of adiponitrile and hexane trinitrile and the total current efficiency are calculated.

[0040] Example 1

[0041] A method for preparing adiponitrile and hexane trinitrile by electrolytic reduction of acrylonitrile:

[0042] Weigh 200 g of dipotassium hydrogen phosphate, 40 g of borax, and 10 g of sodium salt of EDTA. Then weigh 30 g of tetrabutylammonium hydroxide and add them to 1520 mL of deionized water. After stirring and dissolving, adjust the pH value of the solution to 8. Pour the solution into a circulating single-chamber electrolytic cell. Use a lead plate as the cathode and a 304 stainless steel plate as the anode. The distance between the anode and cathode plates is 3 mm, the pump flow rate is 52.5 L / h, and the linear velocity of the electrolyte in the electrolytic cell is 0.081 m / s. Turn on the stirring of the pump and the constant temperature water bath device, set the reaction temperature to 35 °C, and set the electrolytic current density to 1750 A / m 2 . After the temperature of the reaction solution reaches the set temperature, add 200 g of acrylonitrile and 16 g of methanol (0.33 mol / L), turn on the power supply, and carry out the electrolytic reduction reaction. Record the initial cell voltage, and record the voltage and measure the instantaneous oxygen content once every time the electricity passed increases by 0.1 F / mol (the data is shown in Table 1). When the electricity passed reaches 0.7 F / mol, end the electrolytic reaction. The results show that the yield of adiponitrile is 54.99%, the yield of hexane trinitrile is 19.66%, and the total current efficiency of adiponitrile and hexane trinitrile is 97.75%.

[0043] Table 1 Changes in oxygen content during electrolysis

[0044]

[0045] Example 2

[0046] A method for the electrolytic reduction of acrylonitrile to adiponitrile and hexane trinitrile:

[0047] Weigh 200 g of dipotassium hydrogen phosphate, 40 g of borax and 10 g of sodium EDTA. Then weigh 30 g of tetrabutylammonium hydroxide and add them to 1520 mL of deionized water. After stirring and dissolving, adjust the pH value of the solution to 8. Pour the solution into a circulating single-chamber electrolytic cell. Use a lead plate as the cathode and a 304 stainless steel plate as the anode. The distance between the anode and cathode plates is 3 mm, the pump flow rate is 52.5 L / h, and the linear velocity of the electrolyte in the electrolytic cell is 0.081 m / s. Turn on the stirring of the pump and the constant temperature water bath device, set the reaction temperature to 35 °C, and set the electrolytic current density to 1750 A / m 2 After the temperature of the reaction solution reaches the set temperature, add 200 g of acrylonitrile and 32 g (0.66 mol / L) of methanol. Turn on the power supply to carry out the electrolytic reduction reaction. Record the initial cell voltage, and record the voltage and measure the instantaneous oxygen content every time the electricity passed increases by 0.1 F / mol (the data is shown in Table 2). When the electricity passed reaches 0.7 F / mol, end the electrolytic reaction. The results show that the yield of adiponitrile is 54.89%, the yield of hexane trinitrile is 20.94%, and the total current efficiency of adiponitrile and hexane trinitrile is 98.82%.

[0048] Table 2 Changes in oxygen content during electrolysis

[0049]

[0050] Example 3

[0051] A method for the electrolytic reduction of acrylonitrile to adiponitrile and hexane trinitrile:

[0052] Weigh 200 g of dipotassium hydrogen phosphate, 40 g of borax and 10 g of sodium EDTA. Then weigh 30 g of tetrabutylammonium hydroxide and add them to 1520 mL of deionized water. After stirring and dissolving, adjust the pH value of the solution to 8. Pour the solution into a circulating single-chamber electrolytic cell. Use a lead plate as the cathode and a 304 stainless steel plate as the anode. The distance between the anode and cathode plates is 3 mm, the pump flow rate is 52.5 L / h, and the linear velocity of the electrolyte in the electrolytic cell is 0.081 m / s. Turn on the stirring of the pump and the constant temperature water bath device, set the reaction temperature to 35 °C, and set the electrolytic current density to 1750 A / m 2After the temperature of the reaction solution reached the set temperature, 200 g of acrylonitrile and 46 g of ethanol (0.66 mol / L) were added. The power supply was turned on to carry out the electrolytic reduction reaction. The initial cell voltage was recorded, and the voltage was recorded and the instantaneous oxygen content was measured every time the electricity passed increased by 0.1 F / mol (the data is shown in Table 3). When the electricity passed reached 0.7 F / mol, the electrolytic reaction was ended. The results showed that the yield of adiponitrile was 54.10%, the yield of hexane trinitrile was 21.22%, and the total current efficiency of adiponitrile and hexane trinitrile was 97.96%.

[0053] Table 3 Changes in oxygen content during electrolysis

[0054]

[0055] Example 4

[0056] A method for preparing adiponitrile and hexane trinitrile by electrolytic reduction of acrylonitrile:

[0057] Weigh 200 g of dipotassium hydrogen phosphate, 40 g of borax and 10 g of sodium salt of EDTA. Then weigh 30 g of tetrabutylammonium hydroxide and add it to 1520 mL of deionized water. After stirring and dissolving, adjust the pH value of the solution to 8. Pour the solution into a circulating single-chamber electrolytic cell. Use a lead plate as the cathode and a 304 stainless steel plate as the anode. The distance between the anode and cathode plates is 3 mm, the pump flow rate is 52.5 L / h, and the linear velocity of the electrolyte in the electrolytic cell is 0.081 m / s. Turn on the stirring of the pump and the constant temperature water bath device, set the reaction temperature to 35 °C, and set the electrolytic current density to 1750 A / m 2 After the temperature of the reaction solution reached the set temperature, 200 g of acrylonitrile and 31 g of ethylene glycol (0.33 mol / L) were added. The power supply was turned on to carry out the electrolytic reduction reaction. The initial cell voltage was recorded, and the voltage was recorded and the instantaneous oxygen content was measured every time the electricity passed increased by 0.1 F / mol (the data is shown in Table 4). When the electricity passed reached 0.7 F / mol, the electrolytic reaction was ended. The results showed that the yield of adiponitrile was 54.88%, the yield of hexane trinitrile was 19.66%, and the total current efficiency of adiponitrile and hexane trinitrile was 97.03%.

[0058] Table 4 Changes in oxygen content during electrolysis

[0059]

[0060] Example 5

[0061] A method for preparing adiponitrile and hexane trinitrile by electrolytic reduction of acrylonitrile:

[0062] Weigh 200 g of dipotassium hydrogen phosphate, 40 g of borax, and 10 g of sodium salt of EDTA. Then weigh 30 g of tetrabutylammonium hydroxide and add them to 1520 mL of deionized water. After stirring to dissolve, adjust the pH value of the solution to 8. Pour the solution into a circulating single-chamber electrolytic cell. Use a lead plate as the cathode and a 304 stainless steel plate as the anode. The distance between the anode and cathode plates is 3 mm, the pump flow rate is 52.5 L / h, and the linear velocity of the electrolyte in the electrolytic cell is 0.081 m / s. Turn on the stirring of the pump and the constant temperature water bath device, set the reaction temperature to 35 °C, and set the electrolytic current density to 1750 A / m 2 After the temperature of the reaction solution reaches the set temperature, add 200 g of acrylonitrile and 120 g of oxalic acid (0.88 mol / L), turn on the power supply, and carry out the electrolytic reduction reaction. Record the initial cell voltage, record the voltage and measure the instantaneous oxygen content every time the electricity passed increases by 0.1 F / mol (the data is shown in Table 5). When the electricity passed reaches 0.7 F / mol, end the electrolytic reaction. The results show that the yield of adiponitrile is 54.21%, the yield of hexane trinitrile is 19.77%, and the total current efficiency of adiponitrile and hexane trinitrile is 96.81%.

[0063] Table 5 Changes in oxygen content during electrolysis

[0064]

[0065] Example 6

[0066] A method for preparing adiponitrile and hexane trinitrile by electrolytic reduction of acrylonitrile:

[0067] Weigh 200 g of dipotassium hydrogen phosphate, 40 g of borax, and 10 g of sodium salt of EDTA. Then weigh 30 g of tetrabutylammonium hydroxide and add them to 1520 mL of deionized water. After stirring to dissolve, adjust the pH value of the solution to 8. Pour the solution into a circulating single-chamber electrolytic cell. Use a lead plate as the cathode and a 304 stainless steel plate as the anode. The distance between the anode and cathode plates is 3 mm, the pump flow rate is 52.5 L / h, and the linear velocity of the electrolyte in the electrolytic cell is 0.081 m / s. Turn on the stirring of the pump and the constant temperature water bath device, set the reaction temperature to 35 °C, and set the electrolytic current density to 1750 A / m 2 After the temperature of the reaction solution reaches the set temperature, add 200 g of acrylonitrile and 46 g of glycerol (0.33 mol / L), turn on the power supply, and carry out the electrolytic reduction reaction. Record the initial cell voltage, record the voltage and measure the instantaneous oxygen content every time the electricity passed increases by 0.1 F / mol (the data is shown in Table 6). When the electricity passed reaches 0.7 F / mol, end the electrolytic reaction. The results show that the yield of adiponitrile is 55.03%, the yield of hexane trinitrile is 19.81%, and the total current efficiency of adiponitrile and hexane trinitrile is 97.94%.

[0068] Table 6 Changes in oxygen content during electrolysis

[0069]

[0070] Comparative Example 1

[0071] Weigh 200 g of dipotassium hydrogen phosphate, 40 g of borax, and 10 g of sodium EDTA. Then weigh 30 g of tetrabutylammonium hydroxide and add them to 1520 mL of deionized water. After stirring and dissolving, adjust the pH value of the solution to 8. Pour the solution into a circulating single-chamber electrolytic cell. Use a lead plate as the cathode and a stainless-steel plate as the anode. The distance between the anode and cathode plates is 3 mm. The pump flow rate is 52.5 L / h, and the linear velocity of the electrolyte in the electrolytic cell is 0.081 m / s. Turn on the stirring of the pump and the constant-temperature water bath device. Set the reaction temperature to 35 °C and set the electrolysis current density to 1750 A / m 2 After the temperature of the reaction solution reaches the set temperature, add 200 g of acrylonitrile, turn on the power supply, and carry out the electrolytic reduction reaction. Record the initial cell voltage. Record the voltage and measure the instantaneous oxygen content every time the electricity passed increases by 0.1 F / mol (the data is shown in Table 7). When the electricity passed reaches 0.7 F / mol, end the electrolysis reaction. The results show that the yield of adiponitrile is 55.21%, the yield of hexane trinitrile is 20.52%, and the total current efficiency of adiponitrile and hexane trinitrile is 98.88%.

[0072] Table 7 Changes in oxygen content during electrolysis

[0073]

[0074] It can be seen from Examples 1 to 6 that under the conditions of low linear velocity and a certain amount of electricity passed, the overall current efficiency of the electrolytic reaction is high, the overall yields of adiponitrile and 1,3,6-hexane trinitrile are high, and the added value is high. With the addition of easily oxidizable substances such as methanol during the reaction, the cell voltage during the reaction process decreases overall, inhibiting the oxygen evolution reaction, and there is no obvious change in the yield and current efficiency. This shows that the addition of easily oxidizable substances such as methanol reduces the cell voltage, inhibits the anodic oxygen evolution reaction, reduces the electrolysis power consumption, eliminates the explosion hazard, improves the safety of diaphragm-free electrolysis, and has good application value.

[0075] Comparative Example 2

[0076] Same as Example 2, the only difference is that the electricity passed is 0.9 F / mol.

[0077] The yield of adiponitrile is 58.71%, the yield of hexane trinitrile is 21.21%, and the total current efficiency of adiponitrile and hexane trinitrile is 72.06%.

[0078] Table 8 Changes in oxygen content during electrolysis

[0079]

[0080] Comparative Example 3

[0081] Same as Example 2, except that the distance between the anode and cathode plates is 6 mm.

[0082] The yield of adiponitrile was 35.61%, the yield of hexane trinitrile was 7.23%, and the total current efficiency of adiponitrile and hexane trinitrile was 51.74%.

[0083] Table 9 Changes in oxygen content during electrolysis

[0084]

[0085] The above-described embodiments are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing adiponitrile and hexane trinitrile by electrolytic reduction of acrylonitrile, characterized in that, It includes the following steps: Mix acrylonitrile and electrolyte and then carry out electrolytic reduction to obtain adiponitrile and hexane trinitrile; The components of the electrolyte include: a supporting electrolyte, an electrode protector, a complexing agent, a quaternary ammonium salt, and an easily oxidizable substance; The easily oxidizable substance includes methanol, formaldehyde, formic acid, ethanol, acetaldehyde, acetic acid, oxalic acid, glyoxal, ethylene glycol, or glycerol; The material of the anode used in the electrolytic reduction includes any one of carbon steel, stainless steel, nickel, and titanium-based iridium oxide; During the electrolytic reduction, the distance between the cathode and the anode is 0.1 - 5 mm.

2. The method according to claim 1, characterized in that, The concentration of the supporting electrolyte in the electrolyte is 7.5 - 12.5 wt.%; the supporting electrolyte includes phosphate; The concentration of the electrode protector in the electrolyte is 1 - 4 wt.%; the electrode protector includes borax; The concentration of the complexing agent in the electrolyte is 0.5 - 1.5 wt.%; the complexing agent includes EDTA; The concentration of the quaternary ammonium salt in the electrolyte is 0.5 - 2.5 wt.%.

3. The method according to claim 2, wherein The phosphate includes disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, or potassium dihydrogen phosphate; The quaternary ammonium salt includes tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide.

4. The method according to claim 1, characterized in that, The concentration of acrylonitrile in the electrolyte is 7.5 - 15 wt.%.

5. The method according to claim 1, characterized in that, The concentration of the easily oxidizable substance in the electrolyte is 0.1 - 5.0 mol / L.

6. The method according to claim 1, characterized in that The temperature of the electrolytic reduction is 20 to 50 °C, the current density is 500 to 5000 A / m 2 , and the electricity passed is 0.5 to 0.9 F / mol.

7. The method according to claim 1, characterized in that The material of the cathode includes any one of cadmium, lead, and cadmium-lead alloy.

8. The method according to claim 1, characterized in that During the electrolytic reduction, the linear velocity of the electrolyte is 0.02 - 1.5 m / s.

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