Electrochemical method for pairwise synthesizing salicylaldehyde and dimethyl sebacate

Abstract

The invention provides an electrochemical method for synthesizing salicylaldehyde and dimethyl sebacate in pairs. The method comprises the following steps: 1) mixing monomethyl adipate, salicylic acid, alkaline electrolyte, monopotassium phosphate, sodium hydrogen sulfite, decyltrimethylammonium chloride and a solvent into electrolyte, and adding the electrolyte into an electrolytic bath; and 2) heating the electrolyte in the electrolytic cell, then carrying out an electrolytic reaction, carrying out electrolytic decarboxylation coupling on the monomethyl adipate at an anode to generate dimethyl sebacate, and reacting salicylic acid with hydrogen ions in a cathode region to generate salicylaldehyde and water. The method can effectively solve the problems of decomposition of a part of dimethyl sebacate products, reduction of reaction selectivity and yield and the like caused by hydroxyl generated by cathode hydrogen evolution and formation of a strong alkaline environment in a traditional synthesis process, and meanwhile, a byproduct salicylaldehyde is produced, so that the method has a good industrial prospect.

Description

Technical Field

[0001] The invention belongs to the field of organic electrochemical synthesis, and specifically relates to an electrochemical synthesis process for synthesizing salicylaldehyde and dimethyl sebacate in pairs. Background Art

[0002] Salicylaldehyde, also known as o-hydroxybenzaldehyde, is a colorless or light brown oily liquid with an almond flavor. It is mainly used for the synthesis of spices and bean flavoring. Because salicylaldehyde contains active hydroxyl and aldehyde structures, it is widely used in the fields of medicine, analytical reagents, polymer additives and pesticides. The method for synthesizing salicylaldehyde is mainly a synthesis route using four substances such as phenol, o-cresol, salicylic acid and salicyl alcohol as raw materials. The process for preparing salicylaldehyde using salicylic acid as raw material mostly adopts electrochemical synthesis. For example, patent CN101008086A provides a method for preparing salicylaldehyde by electrolytic reduction of salicylic acid. The method uses quaternary ammonium salt as an additive, and the cathode reaction current efficiency reaches more than 35%. Under the same conditions, it is ten percentage points higher than that without additives. The electrochemical synthesis process of salicylaldehyde is simple, but the reaction yield is low and it is not yet suitable for industrial production.

[0003] Dimethyl sebacate has a large number of applications in the field of nylon and plasticizer. At present, the production of dimethyl sebacate mainly includes castor thermal cracking process and decane biological synthesis process, both of which have the characteristics of large three wastes output and poor atom economy. Using Kolbe reaction to electrosynthesize dimethyl sebacate with monomethyl adipate as raw material has the advantages of clean production process, saving manpower and being suitable for scaled-up production. For example, patent US3652430A discloses a synthesis process for synthesizing dimethyl sebacate using monomethyl adipate, which uses methanol as solvent, decarboxylation reaction of monomethyl adipate occurs at the anode to generate carbon dioxide, and hydrogen reduction occurs at the cathode. However, the synthesis method generates hydroxyl radicals while generating hydrogen in the cathode region, causing the local pH to rise. The product dimethyl sebacate is hydrolyzed in the high pH region to generate monomethyl sebacate and sebacic acid. The monomethyl sebacate and sebacic acid continue to react in the anode region to generate byproducts such as dimethyl octadecanoate, methyl nonanoate and methyl nonenoate, which seriously reduces the raw material selectivity and product yield. Therefore, how to reduce the reduction reaction of the cathode to generate hydrogen, produce high value-added chemicals, and eliminate the hydrolysis reaction of the product dimethyl sebacate caused by the high pH in the cathode region is of great practical significance. Summary of the invention

[0004] In view of the above problems existing in the prior art, the present invention provides an electrochemical method for synthesizing salicylaldehyde and dimethyl sebacate in pairs. The method has the advantages of high conversion rate and selectivity, wide source of raw materials, simple steps, high atom economy, less three wastes, low energy consumption, low cost, etc.

[0005] The electrochemical method of the present invention uses monomethyl adipate and salicylic acid as raw materials, and improves the yield of dimethyl sebacate and salicylaldehyde by adding a compound of alkaline electrolyte, potassium dihydrogen phosphate, sodium bisulfite, and decanyltrimethylammonium chloride. The method generates a reaction of electrolyzing monomethyl adipate to synthesize dimethyl sebacate at the anode, and the generated hydrogen ions react with salicylic acid at the cathode to synthesize salicylaldehyde, thereby avoiding the problem of hydrolysis of dimethyl sebacate caused by the increase of pH in the cathode region due to hydrogen evolution reaction at the cathode.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] The present invention provides an electrochemical method for synthesizing salicylaldehyde and dimethyl sebacate in pairs, comprising the following steps:

[0008] 1) monomethyl adipate, salicylic acid, alkaline electrolyte, potassium dihydrogen phosphate, sodium bisulfite, dodecyltrimethylammonium chloride and solvent are mixed to form an electrolyte, and the electrolyte is added into an electrolytic cell;

[0009] 2) The electrolyte in the electrolytic cell in step 1) is heated and then subjected to electrolytic reaction. Monomethyl adipate is electrolytically decarboxylated and coupled at the anode to generate dimethyl sebacate. Salicylic acid reacts with hydrogen ions in the cathode region to generate salicylaldehyde and water.

[0010] In a specific embodiment, the alkaline electrolyte in step 1) is selected from any one or a combination of at least two of potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium carbonate, preferably any one or a combination of two of potassium hydroxide and sodium hydroxide.

[0011] In a specific embodiment, the amount of the alkaline electrolyte in step 1) is 10-40% of the molar amount of monomethyl adipate, such as 10%, 20%, 30%, 40%, etc., preferably 20-30%.

[0012] In a specific embodiment, the amount of salicylic acid in step 1) is 30-70% of the molar amount of monomethyl adipate, such as 30%, 40%, 50%, 60%, 70%, etc., preferably 40-50%.

[0013] In a specific embodiment, in step 1), the amount of potassium dihydrogen phosphate added is 10-40% of the molar amount of the alkaline electrolyte, such as 10%, 20%, 30%, 40%, etc., preferably 20-30%.

[0014] In a specific embodiment, the amount of sodium bisulfite added in step 1) is 50-90% by mass of the salicylic acid, such as 50%, 60%, 70%, 80%, 90%, etc., preferably 70-80%.

[0015] In a specific embodiment, in step 1), the amount of dodecyltrimethylammonium chloride added is 0.1-0.7% of the molar amount of salicylaldehyde, such as 0.1%, 0.3%, 0.5%, 0.6%, 0.7%, etc., preferably 0.3-0.5%.

[0016] In a specific embodiment, the solvent in step 1) is any one of benzene, nitrile, and alcohol solvents, or a combination of at least two of them, preferably any one of benzene, acetonitrile, methanol, ethanol, and propanol, or a combination of at least two of them.

[0017] In a specific embodiment, the mass ratio of monomethyl adipate to solvent in step 1) is 0.3-1:1, such as 0.3:1, 0.5:1, 0.7:1, 0.9:1, 1:1, etc., preferably 0.5-0.7:1.

[0018] In a specific embodiment, in the electrolysis reaction in step 2), the electrolysis temperature is 20-60°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C, etc., preferably 40-50°C; the electrolysis time is 10-40h, for example, 10h, 15h, 20h, 30h, 40h, etc., preferably 20-30h.

[0019] In a specific embodiment, in step 2), the electrolytic reaction has an electrolytic cell voltage range of 2-6 V, such as 2 V, 3 V, 4 V, 5 V, 6 V, etc., preferably 3-4 V; and an electrolytic current density of 1000-3000 A / m 2 , for example 1000A / m 2 、1500A / m 2 、2000A / m 2 、2500A / m 2 、3000A / m 2 etc., preferably 1500-2000A / m 2 .

[0020] In a specific embodiment, after the electrolysis reaction in step 2) is completed, the reaction system obtained comprises a mixture of dimethyl sebacate and salicylaldehyde;

[0021] Preferably, after the electrolysis reaction is completed, post-treatment processes such as desolventizing, filtering and desalting, and distillation are also included, which are conventional operations in the art. For example, in some examples, the reaction solution obtained by the electrolysis reaction is preferably sequentially passed through a desolventizing tower, a filtering device, a salicylaldehyde light removal tower, a salicylaldehyde product tower, a dimethyl sebacate light removal tower, a dimethyl sebacate product tower, and a heavy removal tower to obtain salicylaldehyde and dimethyl sebacate products. These post-treatment processes are all known processes in the field, and their related operations and process conditions, as well as the devices used, can all be carried out by conventional selection in the art. Technicians can optimize them based on the known processes in the prior art according to actual needs, and the present invention has no particular restrictions on this.

[0022] In a specific embodiment, the electrolytic cell of the electrochemical method of the present invention is a diaphragm-free electrolytic cell;

[0023] The electrolytic cell comprises an anode and a cathode;

[0024] Preferably, the anode is selected from a platinum electrode, a platinum-titanium electrode, a graphite electrode or a DSA electrode, and the DSA electrode is preferably any one of Ti-based PbO2, IrO2, RuO2 or tin-antimony oxide electrodes;

[0025] Preferably, the cathode is a lead electrode;

[0026] Specifically, the electrolytic cell is a diaphragmless electrolytic cell.

[0027] As a preferred embodiment, the material of the electrolytic cell is polypropylene (PP), polytetrafluoroethylene (PTFE) or titanium, preferably titanium.

[0028] The electrochemical method of the present invention does not impose any restrictions on the shape and arrangement of the electrodes in the electrolytic cell. All electrode shapes and arrangements of cathodes and anodes that can achieve electrolysis are included in the method of the present invention.

[0029] The present invention finds in the research of synthesizing salicylaldehyde and dimethyl sebacate in pairs by an electrochemical method that introducing an appropriate amount of potassium dihydrogen phosphate into the system can ensure that the cathode region maintains a weakly acidic environment during the electrolysis process, and at the same time, decanyltrimethylammonium chloride plays a role of a phase transfer catalyst, which can accelerate the mass transfer of salicylic acid in the cathode region, and sodium bisulfite can be used in combination to protect the generated salicylaldehyde from being reduced to salicyl alcohol at the cathode.

[0030] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0031] The electrochemical method of the invention can synthesize salicylaldehyde and dimethyl sebacate in pairs, improve the current efficiency of the system, and has the advantages of simple steps, high total product yield, small equipment investment, low operation risk, mild reaction conditions, less three wastes, and low energy consumption, and is suitable for wide industrial applications. DETAILED DESCRIPTION

[0032] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0033] In the embodiments and comparative examples of the present invention, the sources of the main raw materials used are as follows. Unless otherwise specified, other raw materials and reagents were purchased from commercial sources:

[0034] Platinum-titanium electrode, Xi’an Taijin Co., Ltd., coating thickness 1 μm;

[0035] Monomethyl adipate, Hailong Chemical Co., Ltd., product specification>98%;

[0036] Potassium hydroxide, Beijing Bailingwei Technology Co., Ltd., product specification>85%;

[0037] Sodium hydroxide, Beijing Bailingwei Technology Co., Ltd., product specification>85%;

[0038] Potassium dihydrogen phosphate, Shanghai Aladdin Biochemical Technology Co., Ltd., product specification> 99%;

[0039] Sodium bisulfite, Shanghai Aladdin Biochemical Technology Co., Ltd., AR;

[0040] Decyltrimethylammonium chloride, Shanghai Aladdin Biochemical Technology Co., Ltd., product specification>99%;

[0041] Salicylic acid, Shanghai Aladdin Biochemical Technology Co., Ltd., product specification>99%;

[0042] Ti-based IrO2 anode, Jiangsu Yianteng Special Electrode Co., Ltd., iridium titanium mesh 50×100;

[0043] Ti-based PbO2 anode, Jiangsu Yianteng Special Electrode Co., Ltd., lead-titanium mesh 50×100;

[0044] Ti-based RuO2 anode, Jiangsu Yianteng Special Electrode Co., Ltd., ruthenium titanium mesh 50×100;

[0045] Titanium woven wire mesh (100-500 mesh), Anping County Guanwo Wire Mesh Products Co., Ltd.

[0046] Diaphragmless electrolytic cell: Jiangyin Tianyuan Electrochemical Equipment Co., Ltd., box-type diaphragmless small-scale electrolytic cell, made of titanium.

[0047] The main analytical methods used in the examples and comparative examples of the present invention are as follows:

[0048] Salicylaldehyde and dimethyl sebacate were characterized by H spectroscopy using a nuclear magnetic resonance spectrometer (Brucker ARX-400).

[0049] The conversion rate and selectivity of salicylaldehyde and dimethyl sebacate were determined by gas chromatography area correction and normalization analysis. The chromatographic analysis conditions were as follows:

[0050] Instrument model: Shimadzu GC2010; chromatographic column: DB-5 (30×0.32×0.25); column temperature: programmed temperature rise (50°C for 4 min, then increase to 100°C at a heating rate of 5°C / min, then increase to 300°C at a heating rate of 25°C / min, and maintain for 5 min); inlet temperature: 230°C; FID temperature: 300°C; N2 flow rate: 1 mL / min; H2 flow rate: 40 mL / min; septum purge (N2) flow rate: 3 mL / min; carrier gas (N2) flow rate: 1 mL / min; split injection, split ratio: 50; injection volume: 0.1 μL.

[0051] Selectivity of dimethyl sebacate = molar yield of sebacate*2 / molar consumption of adipic acid monoester*100%

[0052] Salicylaldehyde selectivity = salicylaldehyde molar yield / salicylic acid molar consumption*100%

[0053] Current efficiency = (molar yield of salicylaldehyde + molar yield of sebacic acid diester) * 2 * 96500 / (electrolysis current * electrolysis time) * 100%

[0054] Example 1

[0055] Synthesis of salicylaldehyde and dimethyl sebacate in pairs by electrolysis:

[0056] 1) Take 80g (0.5mol) monomethyl adipate, 160g benzene, 20.7g (0.15mol) salicylic acid, 2.8g (0.05mol) potassium hydroxide, 2.72g (0.02mol) potassium dihydrogen phosphate, 10.35g sodium bisulfite, 0.035g (0.00015mol) decanyltrimethylammonium chloride, mix them evenly and transfer them to a diaphragm-free plate-and-frame electrolytic cell. The electrolytic cell anode uses a platinum-titanium electrode and the cathode uses a lead electrode.

[0057] 2) The electrolytic cell was heated to 50°C and the electrolytic reaction was started. The current density of the electrolytic cell was 3000A / m 2 , electrolysis potential 6V, 50℃ electrolysis reaction after 10h reaction ended, sampling test. After the reaction was completed, the material was passed through the desolventizing tower, filtration device, and light removal tower to collect salicylaldehyde, and then passed through the dimethyl sebacate light removal tower and heavy removal tower to collect dimethyl sebacate.

[0058] The H NMR spectrum data of dimethyl sebacate are as follows:

[0059] 1H NMR (600MHz, CDCl 3): δ3.65(6H), 2.32(4H), 1.64(4H), 1.29(6H).

[0060] The salicylaldehyde H NMR spectrum data are as follows:

[0061] 1H NMR (600MHz, CDCl 3): δ5.35(1H), 6.96(1H), 7.20(1H), 7.56(1H), 7.72(1H), 10.36(1H).

[0062] In this embodiment, the conversion rate of raw material monomethyl adipate is 83.3%, the selectivity of synthesized dimethyl sebacate is 93.7%, the conversion rate of salicylic acid is 63.2%, the selectivity of synthesized salicylaldehyde is 87.1%; and the current efficiency is 117%.

[0063] Example 2

[0064] 1) Take 80g (0.5mol) monomethyl adipate, 266.7g acetonitrile, 27.6g (0.2mol) salicylic acid, 4g (0.07mol) sodium hydroxide, 2.91g (0.02mol) potassium dihydrogen phosphate, 22.08g sodium bisulfite, 0.14g (0.0006mol) decanyltrimethylammonium chloride, mix them evenly and transfer them to a diaphragm-free plate-and-frame electrolytic cell. The anode of the electrolytic cell uses a platinum electrode and the cathode uses a lead electrode.

[0065] 2) The electrolytic cell was heated to 40°C and the electrolytic reaction was started. The current density of the electrolytic cell was 1500A / m 2 , the electrolysis potential is 4V, and the electrolysis reaction is completed at 40℃ for 20h, and sampling is performed. After the reaction is completed, the material is sequentially passed through a desolventizing tower, a filtering device, and a light removal tower to collect salicylaldehyde, and then passed through a dimethyl sebacate light removal tower and a heavy removal tower to collect dimethyl sebacate.

[0066] In this embodiment, the conversion rate of raw material monomethyl adipate is 84.2%, the selectivity of synthesized dimethyl sebacate is 91.9%, the conversion rate of salicylic acid is 64.4%, the selectivity of synthesized salicylaldehyde is 86.7%; and the current efficiency is 119%.

[0067] Example 3

[0068] 1) Take 80g (0.5mol) monomethyl adipate, 80g methanol, 34.5g (0.25mol) salicylic acid, 20.7g (0.37mol) potassium carbonate, 10g (0.074mol) potassium dihydrogen phosphate, 24.15g sodium bisulfite, 0.295g (0.00125mol) decanyltrimethylammonium chloride, mix them evenly and transfer them to a diaphragm-free plate-and-frame electrolytic cell. The anode of the electrolytic cell uses a Ti-based PbO2 electrode, and the cathode uses a lead electrode.

[0069] 2) The electrolytic cell was heated to 20°C and the electrolytic reaction was started. The current density of the electrolytic cell was 2000A / m 2 , electrolysis potential 3V, 20℃ electrolysis reaction after 30h reaction ended, sample testing. After the reaction was completed, the material was passed through the desolventizing tower, filtration device, and light removal tower to collect salicylaldehyde, and then passed through the dimethyl sebacate light removal tower and heavy removal tower to collect dimethyl sebacate.

[0070] In this embodiment, the conversion rate of raw material monomethyl adipate is 81.6%, the selectivity of synthesized dimethyl sebacate is 90.9%, the conversion rate of salicylic acid is 65.1%, the selectivity of synthesized salicylaldehyde is 84.2%; and the current efficiency is 116%.

[0071] Example 4

[0072] 1) 80g (0.5mol) monomethyl adipate, 114.3g ethanol, 48.3g (0.35mol) salicylic acid, 21.2g (0.38mol) sodium carbonate, 5.1g (0.038mol) potassium dihydrogen phosphate, 43.47g sodium bisulfite, 0.578g (0.00245mol) decanyltrimethylammonium chloride were mixed evenly and transferred to a diaphragm-free plate-and-frame electrolytic cell. The anode of the electrolytic cell is a Ti-based RuO2 electrode, and the cathode is a lead electrode.

[0073] 2) The electrolytic cell was heated to 60°C and the electrolytic reaction was started. The current density of the electrolytic cell was 1000A / m 2 , electrolysis potential 2V, 60℃ electrolysis reaction after 40h reaction ended, sample testing. After the reaction was completed, the material was passed through the desolventizing tower, filtration device, and light removal tower to collect salicylaldehyde, and then passed through the dimethyl sebacate light removal tower and heavy removal tower to collect dimethyl sebacate.

[0074] In this embodiment, the conversion rate of raw material monomethyl adipate is 80.4%, the selectivity of synthesized dimethyl sebacate is 93.6%, the conversion rate of salicylic acid is 61.7%, the selectivity of synthesized salicylaldehyde is 86.3%; and the current efficiency is 118%.

[0075] Comparative Example 1

[0076] The method of Example 1 is referred to, except that potassium dihydrogen phosphate is not added to the electrolyte, and other operations and conditions remain unchanged.

[0077] In this comparative example, the conversion rate of raw material monomethyl adipate is 35.1%, the selectivity of synthesized dimethyl sebacate is 75.4%, the conversion rate of salicylic acid is 41.3%, the selectivity of synthesized salicylaldehyde is 65.2%; and the current efficiency is 61%.

[0078] Comparative Example 2

[0079] The method of Example 1 is referred to, except that potassium dihydrogen phosphate is replaced by dipotassium hydrogen phosphate in the electrolyte, and other operations and conditions remain unchanged.

[0080] In this comparative example, the conversion rate of raw material monomethyl adipate is 40.6%, the selectivity of synthesized dimethyl sebacate is 78.2%, the conversion rate of salicylic acid is 40.2%, the selectivity of synthesized salicylaldehyde is 63.9%; and the current efficiency is 63%.

[0081] Comparative Example 3

[0082] The method of Example 1 is referred to, except that sodium bisulfite is not added to the electrolyte, and other operations and conditions remain unchanged.

[0083] In this comparative example, the conversion rate of raw material monomethyl adipate is 52.3%, the selectivity of synthesized dimethyl sebacate is 45.9%, the conversion rate of salicylic acid is 69.3%, the selectivity of synthesized salicylaldehyde is 23.9%; and the current efficiency is 45%.

[0084] Comparative Example 4

[0085] The method of Example 1 is referred to, except that sodium bisulfite is replaced with sodium sulfite in the electrolyte, and other operations and conditions remain unchanged.

[0086] In this comparative example, the conversion rate of raw material monomethyl adipate is 56.9%, the selectivity of synthesized dimethyl sebacate is 49.6%, the conversion rate of salicylic acid is 64.5%, the selectivity of synthesized salicylaldehyde is 26.9%; and the current efficiency is 48%.

[0087] Comparative Example 5

[0088] The method of Example 1 is referred to, except that no decanyltrimethylammonium chloride is added to the electrolyte, and other operations and conditions remain unchanged.

[0089] In this comparative example, the conversion rate of raw material monomethyl adipate is 70.6%, the selectivity of synthesized dimethyl sebacate is 55.5%, the conversion rate of salicylic acid is 59.9%, the selectivity of synthesized salicylaldehyde is 63.3%; and the current efficiency is 72%.

[0090] Comparative Example 6

[0091] The method of Example 1 is referred to, except that the decanyltrimethylammonium chloride in the electrolyte is replaced with decanyltrimethylammonium bromide, and other operations and conditions remain unchanged.

[0092] In this comparative example, the conversion rate of raw material monomethyl adipate is 75%, the selectivity of synthesized dimethyl sebacate is 81%, the conversion rate of salicylic acid is 52.3%, the selectivity of synthesized salicylaldehyde is 74.6%; and the current efficiency is 91%.

Claims

1. An electrochemical preparation method for synthesizing salicylaldehyde and dimethyl sebacate in pairs, characterized in that the steps include: 1) monomethyl adipate, salicylic acid, alkaline electrolyte, potassium dihydrogen phosphate, sodium bisulfite, dodecyltrimethylammonium chloride and solvent are mixed to form an electrolyte, and the electrolyte is added into an electrolytic cell; 2) The electrolyte in the electrolytic cell in step 1) is heated and then subjected to electrolytic reaction. Monomethyl adipate is electrolytically decarboxylated and coupled at the anode to generate dimethyl sebacate. Salicylic acid reacts with hydrogen ions in the cathode region to generate salicylaldehyde and water.

2. The preparation method according to claim 1, characterized in that: In the step 1), the alkaline electrolyte is selected from any one of potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium carbonate, or a combination of at least two thereof, preferably any one of potassium hydroxide and sodium hydroxide, or a combination of two thereof; Preferably, the amount of the alkaline electrolyte is 10-40% of the molar amount of monomethyl adipate, preferably 20-30%.

3. The preparation method according to claim 1 or 2, characterized in that: In step 1), the amount of salicylic acid used is 30-70% of the molar amount of monomethyl adipate, preferably 40-50%.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step 1), the amount of potassium dihydrogen phosphate added is 10-40% by mole of the molar amount of the alkaline electrolyte, preferably 20-30%.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In step 1), the amount of sodium bisulfite added is 50-90% by mass, preferably 70-80% by mass of salicylic acid.

6. The preparation method according to any one of claims 1 to 5, characterized in that: In step 1), the amount of the decanyltrimethylammonium chloride added is 0.1-0.7% by mole of the molar amount of salicylaldehyde, preferably 0.3-0.5%.

7. The preparation method according to any one of claims 1 to 6, characterized in that: In step 1), the solvent is any one of benzene, nitrile, and alcohol solvents or a combination of at least two thereof, preferably any one of benzene, acetonitrile, methanol, ethanol, and propanol or a combination of at least two thereof; Preferably, the mass ratio of monomethyl adipate to solvent is 0.3-1:1, preferably 0.5-0.7:

1.

8. The method according to any one of claims 1 to 7, characterized in that: In step 2), the electrolysis reaction is carried out at a temperature of 20-60°C, preferably 40-50°C; and a time of 10-40h, preferably 20-30h.

9. The method according to any one of claims 1 to 8, characterized in that: In step 2), the electrolytic reaction, the electrolytic cell voltage interval is 2-6V, preferably 3-4V; the electrolytic current density is 1000-3000A / m 2 , preferably 1500-2000A / m 2 .

10. The method according to any one of claims 1 to 9, characterized in that: The electrolytic cell is a diaphragmless electrolytic cell; and / or The electrolytic cell comprises an anode and a cathode; Preferably, the anode is a platinum electrode, a platinum-titanium electrode or a DSA electrode, and the DSA electrode is preferably any one of Ti-based PbO2, IrO2, and RuO2; the cathode is a lead electrode. Preferably, the electrolytic cell is a diaphragm-free plate-and-frame electrolytic cell, and the material is selected from titanium and 316L PTFE-lined.