Method for preparing adiponitrile and hexanetrinitrile through acrylonitrile electrolytic reduction

Abstract

The invention discloses a method for preparing adiponitrile and hexanetrinitrile through acrylonitrile electrolytic reduction, and belongs to the technical field of electrochemistry. The invention relates to a method for preparing adiponitrile and hexane trinitrile through acrylonitrile electrolytic reduction, which comprises the following steps: mixing acrylonitrile and electrolyte, and then carrying out electrolytic reduction to obtain adiponitrile and hexane trinitrile; the electrolyte comprises the following components: a supporting electrolyte, an electrode protective agent, a complexing agent, quaternary ammonium salt and an easily oxidized substance. The method provided by the invention can co-produce adiponitrile and hexanetricarbonitrile, and solves the problems that only the target is focused on the output of adiponitrile and the hexanetricarbonitrile with high added value is treated as waste in electrochemical synthesis in the prior art; and moreover, by adding an easily oxidized substance, the anodic oxidation potential is reduced, the generation of oxygen is inhibited, the generation of an oxygen evolution reaction is inhibited, the stability and safety of the reaction are improved, meanwhile, the cell voltage is reduced, the current efficiency in the electrolysis process is improved, and the electrolysis power consumption is reduced, so that the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the field of electrochemical technology, in particular to a method for preparing adiponitrile and hexanetrinitrile by electrolytic reduction of acrylonitrile. Background Art

[0002] Adiponitrile (AND), English name: Adiponitrile, CAS number: 111-69-3, molecular formula: C6H8N2, molecular weight: 108.14, boiling point: 295℃, adiponitrile is an important organic chemical intermediate, mainly used in the production of PA66, 1,6-hexamethylene diisocyanate (HDI) and PA610 and other materials. With the development of technology, the application field of adiponitrile has gradually expanded, and it has been used as a synthetic high-grade environmentally friendly coating, polymer additives, electroplating additives, extractants, etc.

[0003] 1,3,6-Hexanetricarbonitrile (HTCN), English name: 1,3,6-Hexanetricarbonitrile, CAS number: 1772-25-4, molecular formula: C9H 11 N3, molecular weight: 161.20, boiling point: 441℃, 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 the highly toxic CN - Therefore, hexanetrinitrile is increasingly valued as an important intermediate for industrial organic synthesis and electrolyte additives for lithium-ion batteries.

[0004] At present, acrylonitrile electrolysis is generally used to prepare adiponitrile, and hexane trinitrile with extremely high added value can be produced while preparing adiponitrile. The method for preparing adiponitrile by electrolysis of acrylonitrile has the advantages of wide raw material sources, low cost, simple process, mild reaction conditions and safe and controllable reaction process, but in the process of electrolysis of acrylonitrile without diaphragm, oxygen will be produced at the anode and a small amount of hydrogen will be produced at the cathode. The explosion range of oxygen and hydrogen is 4.0-95%. In a closed or semi-closed electrolysis environment, explosive mixed gas is easily formed. Once encountering the excitation conditions such as fire source, high temperature or electric spark, it is possible to cause a violent explosion reaction, causing inestimable damage to production facilities, personnel safety and environment. In addition, the explosion range of acrylonitrile gas is between 3.05-17.5%. In the electrolysis process, a certain amount of acrylonitrile volatile gas will be produced in the reaction system. The acrylonitrile volatile gas is mixed with the by-product oxygen, which may reach the dangerous concentration of acrylonitrile volatile gas, increasing the possibility of accidents. How to improve the safety of electrolysis reaction has become a technical problem that those skilled in the art need to solve urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing adiponitrile and hexanetrinitrile 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 hexanetrinitrile, and solves the problem that the prior art only focuses on the output of adiponitrile in electrochemical synthesis, and treats hexanetrinitrile with high added value as waste; and the present invention reduces the anodic oxidation potential by adding easily oxidizable substances such as methanol, inhibits the generation of oxygen, inhibits the occurrence of oxygen evolution reaction, improves the stability and safety of the reaction, and at the same time reduces the cell voltage, improves the current efficiency in the electrolysis process, reduces the electrolysis power consumption, and thus reduces the production cost.

[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 hexanetrinitrile by electrolytic reduction of acrylonitrile, comprising the following steps:

[0008] acrylonitrile and an electrolyte are mixed and then electrolytically reduced to obtain adiponitrile and hexanetrinitrile (1,3,6-hexanetrinitrile);

[0009] The components of the electrolyte include: supporting electrolyte, electrode protective agent, complexing agent, quaternary ammonium salt and easily oxidizable substances.

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

[0011] The concentration of the electrode protective agent in the electrolyte is 1 to 4 wt.%; the electrode protective agent includes borax;

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

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

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

[0015] The quaternary ammonium salt includes tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide or tetrabutylammonium hydroxide.

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

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

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

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

[0020] The borax in the invention is used to alleviate the corrosion of the electrolyte to the electrode; the complexing agent is used to avoid the deposition of metal ions; the quaternary ammonium salt is used to enhance the conductivity of the electrolyte and improve the solubility of acrylonitrile; and the easily oxidizable substance is used for anodic oxidation to replace the oxygen evolution reaction.

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

[0022] Furthermore, 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 using titanium-based iridium oxide as the electrode material is a DSA electrode.

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

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

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

[0028] Furthermore, the pH value of the electrolyte is 7.5-8.

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

[0030] (1) The method of the present invention can co-produce adiponitrile and hexanetrinitrile, thereby solving the problem that the prior art only focuses on the output of adiponitrile in electrochemical synthesis and treats hexanetrinitrile with high added value as waste.

[0031] (2) Under the premise of low linear speed and high content of acrylonitrile, the present invention can greatly improve the yield and total current efficiency of electrolyzing acrylonitrile to produce adiponitrile and 1,3,6-hexanetrinitrile by adjusting the spacing between the pole plates. The anode is replaced by methanol oxidation to replace the oxygen evolution reaction, which inhibits the generation of oxygen, eliminates the problem of oxygen, hydrogen and acrylonitrile forming highly explosive gas, and improves the stability and safety of the diaphragm-free electrolysis process. At the same time, the anode potential, the cell voltage of 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) The present invention introduces easily oxidizable substances such as methanol, formaldehyde, formic acid, ethanol, acetaldehyde, acetic acid, oxalic acid, glyoxal, ethylene glycol, and glycerol during the electrolysis process, thereby inhibiting the oxygen evolution reaction at the anode. Instead of transferring 4 mol of electrons to produce 1 mol of oxygen, 6 mol of electrons are transferred to produce 1 mol of carbon dioxide, thereby greatly reducing the generation of oxygen, avoiding the problem of explosive mixed gas formation by volatile gases such as oxygen, hydrogen, and acrylonitrile, and improving the safety of the electrolysis reaction process in the diaphragmless electrolytic cell, making the reaction process of acrylonitrile electrolysis to produce adiponitrile safer.

[0033] (4) The present invention improves the current efficiency of the electrolysis process and reduces the energy consumption of the electrolysis reaction by regulating the amount of current passed during the electrolysis reaction (electrolytic reduction reaction), thereby reducing production costs. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

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

[0036] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may 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 associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0037] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in this document are 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, wherein the size of the cathode and the anode in the electrolytic cell are both 60 mm×266 mm×26 mm, the anode and the cathode are arranged in parallel, the electrolyte is pumped and circulated, a condensation recovery device is connected above the storage tank, the condensation temperature is 5° C., so as to reflux the volatilized acrylonitrile gas, and the condensation device is connected to a gas chromatograph through a gas line pipe to detect the oxygen content in the gas generated by the reaction. During the reaction, the cell voltage and the instantaneous oxygen content are measured once for each increase of 0.1 F / mol in the amount of electricity passed. After the reaction is completed, acrylonitrile, adiponitrile and hexane trinitrile are quantitatively analyzed by gas chromatography, 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 hexanetrinitrile by electrolytic reduction of acrylonitrile:

[0042] Weigh 200g of potassium dihydrogen phosphate, 40g of borax and 10g of EDTA sodium salt, and then weigh 30g of tetrabutylammonium hydroxide, add to 1520mL of deionized water, stir to dissolve and adjust the solution pH to 8, pour the solution into a circulating single-chamber electrolytic cell, use a lead plate as the cathode, a 304 stainless steel plate as the anode, a distance of 3mm between the anode and cathode plates, a pump flow rate of 52.5L / h, and a linear velocity of the electrolyte in the electrolytic cell of 0.081m / s. Turn on the pump stirring and constant temperature water bath device, set the reaction temperature to 35°C, and set the electrolysis current density to 1750A / m 2 . After the temperature of the reaction liquid reaches the set temperature, add 200g of acrylonitrile and 16g of methanol (0.33mol / L), turn on the power supply, and perform electrolytic reduction reaction. Record the starting cell voltage, record the voltage once every 0.1F / mol increase in the amount of power supplied, and measure the instantaneous oxygen content (data are shown in Table 1). When the amount of power supplied reaches 0.7F / mol, the electrolytic reaction is terminated. The results show that the yield of adiponitrile is 54.99%, the yield of hexanetrinitrile is 19.66%, and the total current efficiency of adiponitrile and hexanetrinitrile is 97.75%.

[0043] Table 1 Changes in oxygen content during electrolysis

[0044]

[0045] Example 2

[0046] A method for preparing adiponitrile and hexanetrinitrile by electrolytic reduction of acrylonitrile:

[0047] Weigh 200g of potassium dihydrogen phosphate, 40g of borax and 10g of EDTA sodium salt, and then weigh 30g of tetrabutylammonium hydroxide, add to 1520mL of deionized water, stir to dissolve and adjust the solution pH to 8, pour the solution into a circulating single-chamber electrolytic cell, use a lead plate as the cathode, a 304 stainless steel plate as the anode, a distance of 3mm between the anode and cathode plates, a pump flow rate of 52.5L / h, and a linear velocity of the electrolyte in the electrolytic cell of 0.081m / s. Turn on the pump stirring and constant temperature water bath device, set the reaction temperature to 35°C, and set the electrolysis current density to 1750A / m 2 . After the temperature of the reaction liquid reaches the set temperature, add 200g of acrylonitrile and 32g (0.66mol / L) of methanol, turn on the power supply, and perform electrolytic reduction reaction. Record the starting cell voltage, record the voltage once for every 0.1F / mol increase in the amount of power supplied, and measure the instantaneous oxygen content (data are shown in Table 2). When the amount of power supplied reaches 0.7F / mol, end the electrolytic reaction. The results show that the yield of adiponitrile is 54.89%, the yield of hexanetrinitrile is 20.94%, and the total current efficiency of adiponitrile and hexanetrinitrile is 98.82%.

[0048] Table 2 Changes in oxygen content during electrolysis

[0049]

[0050] Example 3

[0051] A method for preparing adiponitrile and hexanetrinitrile by electrolytic reduction of acrylonitrile:

[0052] Weigh 200g of potassium dihydrogen phosphate, 40g of borax and 10g of EDTA sodium salt, and then weigh 30g of tetrabutylammonium hydroxide, add to 1520mL of deionized water, stir to dissolve and adjust the solution pH to 8, pour the solution into a circulating single-chamber electrolytic cell, use a lead plate as the cathode, a 304 stainless steel plate as the anode, a distance of 3mm between the anode and cathode plates, a pump flow rate of 52.5L / h, and a linear velocity of the electrolyte in the electrolytic cell of 0.081m / s. Turn on the pump stirring and constant temperature water bath device, set the reaction temperature to 35°C, and set the electrolysis current density to 1750A / m 2. After the temperature of the reaction liquid reaches the set temperature, add 200g of acrylonitrile and 46g of ethanol (0.66mol / L), turn on the power supply, and perform electrolytic reduction reaction. Record the starting cell voltage, record the voltage once for every 0.1F / mol increase in the amount of power supplied, and measure the instantaneous oxygen content (data are shown in Table 3). When the amount of power supplied reaches 0.7F / mol, end the electrolytic reaction. The results show that the yield of adiponitrile is 54.10%, the yield of hexanetrinitrile is 21.22%, and the total current efficiency of adiponitrile and hexanetrinitrile is 97.96%.

[0053] Table 3 Changes in oxygen content during electrolysis

[0054]

[0055] Example 4

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

[0057] Weigh 200g of potassium dihydrogen phosphate, 40g of borax and 10g of EDTA sodium salt, and then weigh 30g of tetrabutylammonium hydroxide, add to 1520mL of deionized water, stir to dissolve and adjust the solution pH to 8, pour the solution into a circulating single-chamber electrolytic cell, use a lead plate as the cathode, a 304 stainless steel plate as the anode, a distance of 3mm between the anode and cathode plates, a pump flow rate of 52.5L / h, and a linear velocity of the electrolyte in the electrolytic cell of 0.081m / s. Turn on the pump stirring and constant temperature water bath device, set the reaction temperature to 35°C, and set the electrolysis current density to 1750A / m 2 . After the temperature of the reaction liquid reaches the set temperature, add 200g of acrylonitrile and 31g of ethylene glycol (0.33mol / L), turn on the power supply, and perform electrolytic reduction reaction. Record the starting cell voltage, record the voltage once for every 0.1F / mol increase in the amount of power supplied, and measure the instantaneous oxygen content (data are shown in Table 4). When the amount of power supplied reaches 0.7F / mol, end the electrolytic reaction. The results show that the yield of adiponitrile is 54.88%, the yield of hexanetrinitrile is 19.66%, and the total current efficiency of adiponitrile and hexanetrinitrile is 97.03%.

[0058] Table 4 Changes in oxygen content during electrolysis

[0059]

[0060] Example 5

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

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

[0063] Table 5 Changes in oxygen content during electrolysis

[0064]

[0065] Example 6

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

[0067] Weigh 200g of potassium dihydrogen phosphate, 40g of borax and 10g of EDTA sodium salt, and then weigh 30g of tetrabutylammonium hydroxide, add to 1520mL of deionized water, stir to dissolve and adjust the solution pH to 8, pour the solution into a circulating single-chamber electrolytic cell, use a lead plate as the cathode, a 304 stainless steel plate as the anode, a distance of 3mm between the anode and cathode plates, a pump flow rate of 52.5L / h, and a linear velocity of the electrolyte in the electrolytic cell of 0.081m / s. Turn on the pump stirring and constant temperature water bath device, set the reaction temperature to 35°C, and set the electrolysis current density to 1750A / m 2 . After the temperature of the reaction liquid reaches the set temperature, add 200g of acrylonitrile and 46g of glycerol (0.33mol / L), turn on the power supply, and perform electrolytic reduction reaction. Record the starting cell voltage, record the voltage and measure the instantaneous oxygen content for every 0.1F / mol increase in the amount of power supplied (data are shown in Table 6). When the amount of power supplied reaches 0.7F / mol, end the electrolytic reaction. The results show that the yield of adiponitrile is 55.03%, the yield of hexanetrinitrile is 19.81%, and the total current efficiency of adiponitrile and hexanetrinitrile is 97.94%.

[0068] Table 6 Changes in oxygen content during electrolysis

[0069]

[0070] Comparative Example 1

[0071] Weigh 200g potassium hydrogen phosphate, 40g borax and 10g EDTA sodium salt, and then weigh 30g tetrabutylammonium hydroxide, add to 1520mL deionized water, stir to dissolve and adjust the solution pH to 8, pour the solution into a circulating single-chamber electrolytic cell, use a lead plate as the cathode, a stainless steel plate as the anode, a distance of 3mm between the anode and cathode plates, a pump flow rate of 52.5L / h, and a linear velocity of the electrolyte in the electrolytic cell of 0.081m / s. Turn on the pump stirring and constant temperature water bath device, set the reaction temperature to 35°C, and set the electrolysis current density to 1750A / m 2 . After the temperature of the reaction liquid reaches the set temperature, add 200g of acrylonitrile, turn on the power supply, and perform electrolytic reduction reaction. Record the initial cell voltage, record the voltage once for every 0.1F / mol increase in the amount of power supplied, and measure the instantaneous oxygen content (data are shown in Table 7). When the amount of power supplied reaches 0.7F / mol, end the electrolytic reaction. The results show that the yield of adiponitrile is 55.21%, the yield of hexanetrinitrile is 20.52%, and the total current efficiency of adiponitrile and hexanetrinitrile 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 speed and a certain amount of current, the overall current efficiency of the electrolysis reaction is high, the overall yield of adiponitrile and 1,3,6-hexanetrinitrile is high and the added value is high, and with the addition of easily oxidizable substances such as methanol, the cell voltage decreases as a whole during the reaction, inhibiting the oxygen evolution reaction, and the yield and current efficiency do not change significantly, indicating that the addition of easily oxidizable substances such as methanol reduces the cell voltage, inhibits the anode oxygen evolution reaction, reduces the electrolysis power consumption, eliminates the explosion hazard, improves the safety of diaphragmless electrolysis, and has good application value.

[0075] Comparative Example 2

[0076] Same as Example 2, except that the amount of electricity passed is 0.9 F / mol.

[0077] The yield of adiponitrile was 58.71%, the yield of hexanetrinitrile was 21.21%, and the total current efficiency of adiponitrile and hexanetrinitrile was 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 hexanetrinitrile was 7.23%, and the total current efficiency of adiponitrile and hexanetrinitrile was 51.74%.

[0083] Table 9 Changes in oxygen content during electrolysis

[0084]

[0085] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing adiponitrile and hexanetrinitrile by electrolytic reduction of acrylonitrile, characterized in that: The following steps are involved: acrylonitrile and an electrolyte are mixed and then electrolytically reduced to obtain adiponitrile and hexanetrinitrile; The components of the electrolyte include: supporting electrolyte, electrode protective agent, complexing agent, quaternary ammonium salt and easily oxidizable substances.

2. The method according to claim 1, characterized in that The concentration of the supporting electrolyte in the electrolyte is 7.5-12.5wt.%; the supporting electrolyte includes phosphate; The concentration of the electrode protective agent in the electrolyte is 1 to 4 wt.%; the electrode protective agent includes borax; The concentration of the complexing agent in the electrolyte is 0.5-1.5wt.%; 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, characterized in that 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 to 15 wt.%; The easily oxidizable substance includes methanol, formaldehyde, formic acid, ethanol, acetaldehyde, acetic acid, oxalic acid, glyoxal, ethylene glycol or glycerol.

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 20-50°C, and the current density is 500-5000A / m 2 , the amount of electricity passed is 0.5~0.9F / mol.

7. The method according to claim 1, characterized in that During the electrolytic reduction, the distance between the cathode and the anode is 0.1 to 5 mm; The material of the cathode includes any one of cadmium, lead and cadmium-lead alloy; the material of the anode includes any one of carbon steel, stainless steel, nickel and titanium-based iridium oxide.

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

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