Phenol-cyclohexanone-adipic acid electro-catalysis coupling system

Abstract

The invention discloses a phenol-cyclohexanone-adipic acid electro-catalysis coupling system. The electro-catalysis coupling system comprises an anode electrode, an anode electrolyte, a proton exchange membrane, a cathode electrolyte and a cathode electrode, wherein the anode electrolyte is one or more of Keggin type polyacid, Dawson type polyacid and Anderson type polyacid and contains cyclohexanone as a substrate, and the cathode electrolyte is one or more of Keggin type polyacid, Dawson type polyacid and Anderson type polyacid and contains phenol as a substrate. According to the method, H6 [PV3Mo9O40] and H6 [SiW12O40] are selected as the anode electrolyte and the cathode electrolyte, a first electric synthesis scheme for preparing adipic acid from phenol under the acidic condition is developed, and compared with the prior art, the yield and the selectivity are higher and the reaction rate is high in the aspect of adipic acid generation.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of organic compounds, in particular to a phenol-cyclohexanone-adipic acid electrocatalytic coupling system. Background Art

[0002] Adipic acid is an important chemical used to produce various polymer materials, such as polyamide (such as nylon 66) and polyester (engineering plastics), with an annual output of millions of tons. Therefore, it is of great significance to achieve green chemical production of adipic acid. The current industrially mature adipic acid production process uses benzene as raw material. In recent years, the use of biomass phenol as raw material has attracted widespread attention. However, the first step of the reaction, phenol hydrogenation, is still carried out under high temperature and high pressure hydrogen atmosphere, with harsh conditions and low hydrogenation selectivity. In the second step, the oxidation of KA oil inevitably produces a large amount of N2O, causing serious environmental pollution. Therefore, there is an urgent need to develop a sustainable, environmentally friendly and efficient adipic acid production process.

[0003] Electrochemical synthesis is considered a promising method because it usually involves coupling two half reactions: cathode reduction and anodic oxidation. Therefore, it is expected that in one electrochemical system, the hydrogenation of phenol and the oxidation of KA oil can be coupled at the cathode and anode, respectively, and this method has opened up a new green electrochemical synthesis route for the synthesis of adipic acid from phenol. However, this research is still in its early stages, and most reported systems require complex electrode designs and usually operate at relatively low current densities. In addition, the anodic oxidation reaction usually occurs in an alkaline electrolyte, and the produced adipate salts need to be further acidified or hydrolyzed, which greatly limits their practical application. Therefore, finding a suitable redox electrolyte or catalyst and its coupling system under acidic conditions has become a key challenge in the development of a green electrosynthesis process for phenol to adipic acid. Summary of the invention

[0004] The purpose of the present invention is to provide a phenol-cyclohexanone-adipic acid electrocatalytic coupling system to solve the problems of complex electrode design in the process of preparing adipic acid by electrochemical reaction, the need for subsequent treatment of the prepared product as adipic acid salt, and low product selectivity.

[0005] To achieve the above-mentioned purpose, the present invention provides a phenol-cyclohexanone-adipic acid electrocatalytic coupling system, which comprises an anode electrode, an anode electrolyte, a proton exchange membrane, a cathode electrolyte and a cathode electrode; wherein the anode electrolyte is one or more of Keggin-type, Dawson-type and Anderson-type polyacids, and the substrate contained is cyclohexanone; and the cathode electrolyte is one or more of Keggin-type, Dawson-type and Anderson-type polyacids, and the substrate contained is phenol.

[0006] Electrochemical synthesis is an environmentally friendly and efficient method for producing adipic acid, which generally involves two half reactions, a cathode reduction reaction and an anode oxidation reaction. However, in practical applications, an anode oxidation reaction generally uses an alkaline electrolyte to prepare adipic acid salt, which requires further acidification or hydrolysis, and requires additional energy and reagents, which greatly limits the practical application of electrochemical synthesis of adipic acid. In view of the above problems, the present invention specifically proposes to find a suitable redox electrolyte under acidic conditions, so that the two half reactions can not only be carried out under acidic conditions, but also maintain a high adipic acid yield.

[0007] The present invention selects polyacid as electrolyte, specifically H6[PV3Mo9O 40 ] is the anode electrolyte, H6[SiW 12 O 40 ] as the cathode electrolyte, and developed the first electrosynthetic scheme for the preparation of adipic acid from phenol under acidic conditions. In this reaction system, 0.3 M H6[PV3Mo9O 40 ] is the anolyte for oxidizing cyclohexanone to produce adipic acid, with a conversion rate of nearly 100% and a selectivity of 98%. The generated adipic acid is directly precipitated and separated after cooling. n PV3Mo9O 40 ] 6- (3>n>1) is further electro-oxidized to an oxidized state at the graphite paper anode, thereby achieving continuous production of adipic acid from cyclohexanone at the anode. The cathode uses 0.45 MH4[SiW 12 O 40 ] as the electrolyte, which is first reduced to [H n S W 12 O 40 ] 4- (2>n>0), store e - / H + ; Then, the stored e - / H + [H n S W 12 O 40 ] 4- Under the condition of Pd / C being 10%, phenol is selectively hydrogenated to cyclohexanone, with a conversion rate of up to 100% and a selectivity of over 99%. In the electrocatalytic reaction process of the present invention, not only can adipic acid be selectively generated by the anode reaction, but cyclohexanone can also be selectively generated by the cathode reaction, and the generated cyclohexanone can be used as a raw material for the anode reaction to further prepare adipic acid, thereby realizing self-supply of cyclohexanone raw materials.

[0008] In the present invention, the oxidation of cyclohexanone to adipic acid is a 6e - transfer process, while the reduction of phenol to cyclohexanone is a 4e- This means that the cyclohexanone produced at the cathode can fully meet the consumption of cyclohexanone at the anode. Therefore, the green electrochemical synthesis route starting from phenol can fully realize the preparation of adipic acid. In addition, in order to increase the scope of application of electrocatalytic reactions, electrolysis devices driven by photovoltaic or wind energy can also be built, which provides an ideal solution for on-demand production in practical applications and solves the problem of time and space demand for products.

[0009] Preferably, the anode electrolyte is H3[PMo 12 O 40 ]、H4[PVMo 11 O 40 ]、H5[PV2Mo 10 O 40 ]、H6[PV3Mo9O 40 ]、H7[PV4Mo8O 40 ]、H8[PV5Mo7O 40 ]、H9[PV6Mo6O 40 ]、H6[P2W 18 O 62 ]、P2Mo5VW 12 、P2Mo6W 12 、H6[P2W 12 Mo6O 62 ] one or more, the concentration of the anode electrolyte is 0.1~0.5mol / L; The cathode electrolyte is H3[PMo 12 O 40 ]、H4[PVMo 11 O 40 ]、H5[PV2Mo 10 O 40 ]、H6[PV3Mo9O 40 ]、H7[PV4Mo8O 40 ]、H8[PV5Mo7O 40 ]、H9[PV6Mo6O 40 ]、H6[P2W 18 O 62 ]、P2Mo5VW 12 、P2Mo6W 12 、H6[P2W 12 Mo6O 62 ]、H6[PW 12 O 40 ]、H6[SiW 12 O 40 ] and the concentration of the cathode electrolyte is 0.1~0.5mol / L.

[0010] Preferably, the anode electrolyte is H6[PV3Mo9O 40 ], the cathode electrolyte is H6[SiW 12 O 40 ].

[0011] Preferably, the concentration of cyclohexanone is 0.1-3 mol / L, and the concentration of phenol is 0.1-3 mol / L.

[0012] Preferably, the anode electrode is one of graphite paper, titanium sheet, carbon sheet, tantalum sheet, and iridium oxide-loaded TiO2, and the cathode electrode is graphite paper.

[0013] Preferably, the cathode side of the proton exchange membrane is loaded with one or more of a noble metal catalyst, a non-noble metal catalyst and a non-metal catalyst.

[0014] Preferably, the cathode side of the proton exchange membrane is loaded with one or more of Pd / C, Pt / C, Ru / C, Cu / C, CoP, and NiP catalysts.

[0015] Preferably, the reaction conditions of the electrocatalytic coupling system are: voltage of 1.0-1.4 V, temperature of 75-85° C., and time of 1.5-2 h.

[0016] Therefore, the present invention adopts a phenol-cyclohexanone-adipic acid electrocatalytic coupling system of the above structure, which has the following beneficial effects: (1) The present invention solves the problems of a long reaction path and the easy generation of a large amount of nitrogen oxide pollution in traditional thermal catalysis, and also avoids the problems of low conversion rate of cyclohexanone in alkaline electrolyte and the additional energy required for separation of the generated adipic acid salt. The present invention has higher adipic acid yield and selectivity, faster reaction rate, and the adipic acid yield can reach 98%.

[0017] (2) The electrochemical preparation of adipic acid in the present invention is carried out under acidic conditions. Compared with other electrocatalytic oxidations of cyclohexanone under alkaline conditions, adipic acid can be precipitated from the solution by crystallization, and the adipic acid product is directly separated without the need for subsequent steps, which is simple and convenient.

[0018] (3) The present invention uses phenol as a raw material for the first time, and simultaneously carries out reduction and oxidation reactions at the cathode and anode, respectively, thereby realizing the continuous production of cyclohexanone from phenol and adipic acid from cyclohexanone, significantly improving the electron utilization rate and providing a practical route for the green production of adipic acid.

[0019] (4) The present invention utilizes polyoxometalate as the redox electrolyte, and the electrode design is simple, which is suitable for large-scale industrial use.

[0020] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a structural diagram of the device of Example 1; Figure 2 Schematic diagram of the reaction of the electrolyzer during the electrocatalytic process; Figure 3 is a graph showing the change in percentage of cyclohexanone and adipic acid over time in Example 1; Figure 4 H6[PV3Mo9O 40 ]Infrared spectra before and after electrolysis reaction; Figure 5 H6[PV3Mo9O 40 ] Before and after electrolysis 51 VNMR images; Figure 6 H6[PV3Mo9O 40 ] Capillary electrophoresis before and after electrolysis reaction; Figure 7 H4[SiW 12 O 40 ]Infrared spectra before and after electrolysis cycle; Figure 8 H4[SiW 12 O 40 ]XRD patterns before and after electrolysis cycle; Fig. 9 H4[SiW 12 O 40 ] Capillary electrophoresis images before and after electrolysis cycle; Fig.10 is the adipic acid yield of different types of anolyte; Fig.11 is the cyclohexanone yield of different catalysts; Fig.12 is the phenol conversion rate and cyclohexanone yield under different types of cathode electrolytes; Fig.13 is the yield of cyclohexanone under different concentrations of cathode electrolyte; Fig.14 LSV curves under different cathode electrolytes; Fig.15 is the yield and selectivity of cyclohexanone at different voltages; Fig.16 This is the thermogravimetric curve of adipic acid prepared in Example 1. DETAILED DESCRIPTION

[0022] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and a specific operation process, but the present invention is not limited to this embodiment.

[0023] Example 1

[0024] A phenol-cyclohexanone-adipic acid electrocatalytic coupling system, the electrocatalytic coupling system comprising an anode electrode, an anode electrolyte, a proton exchange membrane, a cathode electrolyte and a cathode electrode; wherein the anode electrolyte is H6[PV3Mo9O 40 ],H6[PV3Mo9O 40 ] concentration is 0.3M, the substrate contained is cyclohexanone, the concentration of cyclohexanone is 0.1M, the anode electrode is graphite paper, and the cathode electrolyte is H6[SiW 12 O 40 ],H6[SiW 12 O 40 ] has a concentration of 0.45 M, the substrate contained is phenol, the concentration of phenol is 0.1 M, the cathode electrode is graphite paper, the proton exchange membrane is a naphthol membrane, and the cathode side is loaded with Pd / C, which is purchased from Aladdin, and the Pt loading amount is 10wt%.

[0025] In this embodiment, the electrocatalytic process is carried out using a flow-type electrolytic cell. The structure of the flow-type electrolytic cell is as follows: Figure 1 After the flow-type electrolytic cell was assembled, an electrocatalytic reaction was carried out, and the conditions of the electrocatalytic reaction were: voltage of 1.0 V, temperature of 80° C., and time of 1.5 h.

[0026] In the present invention, cyclohexanone is oxidized to adipic acid, which is a 6e - transfer process, while the reduction of phenol to cyclohexanone is a 4e - The transfer process means that the cyclohexanone produced at the cathode can fully meet the consumption of cyclohexanone at the anode. Therefore, the green electrochemical synthesis route starting from phenol can fully realize the preparation of adipic acid. In addition, in order to allow the electrochemical reaction to occur, an electrolysis device driven by photovoltaic or wind energy can also be built, which provides an ideal solution for on-demand production in practical applications and solves the problem of time and space requirements for products. The schematic diagram of the electrolytic cell in this embodiment is shown in FIG. Figure 2 As shown in the reaction system, 0.3 M H6[PV3Mo9O 40 ] is the anolyte for oxidizing cyclohexanone to produce adipic acid, with a conversion rate of nearly 100% and a selectivity of 98%. The generated adipic acid is directly precipitated and separated after cooling. n PV3Mo9O 40 ] 6- (3>n>1) is further electro-oxidized to an oxidized state at the graphite paper anode, thereby achieving continuous production of adipic acid from cyclohexanone at the anode. The cathode uses 0.45 MH4[SiW 12 O 40 ] as the electrolyte, which is first reduced to [Hn S W 12 O 40 ] 4- (2>n>0), store e - / H + ; Then, the stored e - / H + [H n S W 12 O 40 ] 4- Under the condition of Pd / C of 10%, phenol was selectively hydrogenated to cyclohexanone with a conversion rate of up to 100% and a selectivity of over 99%.

[0027] Test Example 1 (1) Stability of adipic acid production by anode electrolyte The above electrocatalytic reaction was cycled 8 times, and the substrate concentration was supplemented to the value specified in Example 1 after each cycle, and the electrocatalytic reaction was continued. After 8 cycles, the cyclohexanone concentration and the adipic acid concentration in the anode reaction were detected. The detection results are as follows: Figure 3 As shown. Figure 3 It can be seen that the conversion rate of cyclohexanone and the yield of adipic acid remain stable after 8 cycles. As the electrochemical reaction proceeds, the concentration of cyclohexanone gradually decreases, while the concentration of adipic acid gradually increases, indicating that most of the cyclohexanone is converted into adipic acid. The adipic acid in the present invention has good selectivity, while cyclohexanone has the advantage of high conversion rate.

[0028] from Fig.16 It can also be seen that the purity of the prepared adipic acid is 99%, which is relatively high.

[0029] (2) Structural stability of anode electrolyte In Example 1, graphite paper is used as the anode electrode, so there is no need to consider the stability of the anode electrode. 40 ]The stability of the electrolyte in the long-term reaction was tested. Specifically, the H6[PV3Mo9O 40 ] infrared spectrum, 51 VNMR and capillary electrophoresis diagrams, the test results are shown in Figure 4 , Figure 5 and Figure 6 .

[0030] Experimental conditions of capillary electrophoresis: fused silica capillaries (50 μm inner diameter, 365 μm outer diameter, Yongnian, Hebei, China) were used, with a total length of 50 cm and an effective length of 40 cm. The detection wavelength was set at 254 nm. The buffer for capillary electrophoresis separation was 0.1 M malonic acid (pH = 2.5), the separation voltage was set at -18 kV, and the sample was injected into the capillary by hydrodynamic means (10 cm, 20 s).

[0031] from Figure 4-Figure 6 It can be seen that the polyacid H6[PV3Mo9O 40 ] infrared spectrum, 51 The VNMR and capillary electrophoresis patterns are consistent, proving that H6[PV3Mo9O 40 ]Stability of polyacid structure.

[0032] (3) Stability of cathode electrolyte For H6[SiW in Example 1 12 O 40 ] The stability of the cathode electrolyte in the long-term reaction was tested, specifically the H6[SiW 12 O 40 ] infrared spectrum, XRD diagram and capillary electrophoresis diagram, the test results are shown in Figure 7 , Figure 8 and Fig. 9 The experimental conditions of capillary electrophoresis are the same as (2).

[0033] from Figure 7 It can be seen that H4[SiW 12 O 40 ], 1015 cm -1 、976cm -1 、906 cm -1 and 746 cm -1 They are the characteristic vibration peaks of Si-Oa (a: tetrahedral oxygen atom), M=Od (d: terminal oxygen atom), M-Ob-M (b: corner-shared oxygen atom) and M-Oc-M (c: corner-shared oxygen atom). The peak positions did not move before and after the reaction, indicating that H4[SiW 12 O 40 ]It has good structural stability before and after the reaction.

[0034] from Figure 8 and Fig. 9 It can be seen that H4[SiW 12 O 40 ] did not change significantly, which also proved the structural stability of the cathode electrolyte.

[0035] Example 2 The difference between this embodiment and embodiment 1 is that the type of anolyte is different. The anolyte in this embodiment is H3[PMo 12 O 40 ]、H4[PVMo 11 O 40 ]、H5[PV2Mo 10 O 40 ]、H7[PV4Mo8O 40 ]、VOSO4、H6[PV3W9O 40 ] or (NH4)3[PV3Mo9O 40 ].

[0036] Reaction conditions: voltage: 1.0 V (vs. Ag / AgCl), cyclohexanone concentration: 0.1 M, concentration of various polyacids (POM): 0.3 M, temperature: 80 °C, reaction time: 1.5 h.

[0037] The yield of adipic acid was tested, and the test results are shown in Fig.10 ,from Fig.10 It can be seen that when H3[PMo 12 O 40 ] as the electrolyte, the yield of adipic acid was 0.0247 mmol h -1 cm -2 . With H4[PV1Mo 11 O 40 ] as the electrolyte, the yield of adipic acid was 0.479 mmol h -1 cm -2 . H5[PV2Mo 10 O 40 ] as the electrolyte, the yield of adipic acid was 0.719 mmolh -1 cm -2 . H6[PV3Mo9O 40 The highest adipic acid yield was 1.14 mmol h -1 cm -2 . With H7[PV4Mo8O 40 When ] was the electrolyte, the yield of adipic acid was 0.719 mmol h -1 cm -2 VOSO4 is the electrolyte, and its adipic acid yield is 0.1626mmol h -1 cm -2 . H6[PV3W9O 40 ] as the electrolyte, the yield of adipic acid was 0.3652 mmol h -1 cm -2When the anode electrolyte is H6[PV3Mo9O 40 ], the yield of adipic acid is the highest.

[0038] Example 3 The difference between this embodiment and embodiment 1 is that the type of catalyst loaded on the cathode side of the proton exchange membrane is different. In this embodiment, the catalyst is Pt / C, Rh / C or Pt / Al2O3, and Pt / C, Rh / C or Pt / Al2O3 are all purchased from Aladdin, and the loading amounts of Pt and Rh are both 10wt%.

[0039] The conversion rate of phenol and the yield of cyclohexanone were tested. The test results are shown in Fig.11 ,from Fig.11 It can be seen that when Pd / C, Pt / C, Rh / C and Pt / Al2O3 are used as catalysts, the conversion rate of phenol is close to 100%, but the cyclohexanone yield of Pd / C is 99%, while the cyclohexanone yield of Pt / C is 0.3%, the cyclohexanone yield of Rh / C is 1.2%, and the cyclohexanone yield of Pt / Al2O3 is 2.6%. Only when Pd / C is used as a catalyst, the conversion rate of phenol and the yield of cyclohexanone can be maintained at a high level.

[0040] Example 4 The difference between this embodiment and embodiment 1 is that the type of cathode electrolyte is different. The cathode electrolyte in this embodiment is H6[PW 12 O 40 ]、H3[PMo 12 O 40 ]、H6[PV3Mo9O 40 ] or H6[PV3W9O 40 ].

[0041] The conversion rate of phenol and the yield of cyclohexanone were tested. The test results are shown in Fig.12 ,from Fig.12 It can be seen that H6[SiW 12 O 40 ] as the cathode electrolyte, the phenol conversion rate is close to 100%, and the cyclohexanone yield is 99%. 12 O 40 ] as the cathode electrolyte, the phenol conversion rate was 80% and the cyclohexanone yield was 70%. 12 O 40 ],H6[PV3Mo9O 40 ],H6[PV3W9O 40 ] as the cathode electrolyte, phenol is almost not converted. This shows that only when the cathode electrolyte is a specific type, that is, H6[SiW 12 O 40] can ensure the electrochemical catalytic conversion of phenol into cyclohexanone.

[0042] Example 5 The difference between this embodiment and embodiment 1 is: the concentration of the cathode electrolyte. The concentration of the cathode electrolyte in this embodiment is 0.1, 0.2, 0.3, 0.4, and 0.5 mol / L.

[0043] The yield of cyclohexanone was tested, and the test results are shown in Fig.13 ,from Fig.13 It can be seen that when the polyacid concentration is 0.1, 0.2, 0.3, 0.4, and 0.5 mol / L, the yields of cyclohexanone are 10%, 25.6%, 67%, 96%, and 99%, respectively. With the increase of the polyacid concentration, the yield of cyclohexanone gradually increases. At 0.4~0.5 mol / L, the yield of cyclohexanone can be maintained above 95%.

[0044] Example 6 The difference between this embodiment and embodiment 1 is that the cathode electrolyte is replaced with 1 mol / L H2SO4.

[0045] The LSV curve test was carried out on the above system, and the test results are as follows: Fig.14 As shown, from Fig.14 It can be seen that the anode is in 0.5 M cyclohexanone and 0.3 M H6[PV3Mo9O 40 ]-0.45 M H3[SiW 12 O 40 ]LSV curve in electrolyte, only 1.2V voltage is required to reach 100 mA cm -2 The current density is 1.6 V lower than that of 1 M sulfuric acid as the anode electrolyte, which is very close to the result of industrial current density. The electrocatalytic coupling system of the present invention can be applied to the industrial production of adipic acid.

[0046] Example 7 The difference between this embodiment and embodiment 1 is that the voltage of the electrocatalytic reaction is different. The voltage in this embodiment is 1.2, 1.4, 1.6, 1.8, and 2.0V.

[0047] The yield and selectivity of cyclohexanone were tested, and the test results are as follows: Fig.15 As shown, from Fig.15It can be seen that when the anode reacts at 80 °C at different voltages, the conversion rate of cyclohexanone to adipic acid at the anode is 100%, and the selectivity exceeds 98%. At a voltage of 1.0~1.4V (relative to Ag / AgCl), the conversion rate and selectivity of phenol to cyclohexanone at the cathode also exceed 99%. However, when the voltage exceeds 1.4 V (relative to Ag / AgCl), obvious hydrogen evolution side reactions begin to occur at the cathode, resulting in a gradual decrease in the phenol conversion rate and the Faradaic efficiency of cyclohexanone with increasing voltage. At voltages of 1.6 V, 1.8 V, and 2.0 V (relative to Ag / AgCl), the conversion rates of phenol are 92%, 83%, and 77%, respectively, and the selectivity of cyclohexanone products is still over 99% in all cases. Even at 2.0 V (relative to Ag / AgCl), the cyclohexanone production at the cathode is about 1.16 equivalents, which can still meet the cyclohexanone consumption at the anode.

[0048] Therefore, the present invention adopts a phenol-cyclohexanone-adipic acid electrocatalytic coupling system of the above structure, and selects H6[PV3Mo9O 40 ] and H6[SiW 12 O 40 ] as the anolyte and catholyte, the first electrosynthetic scheme for the preparation of adipic acid from phenol under acidic conditions was developed, which showed higher yield and selectivity and faster reaction rate in the production of adipic acid compared with existing technologies.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A phenol-cyclohexanone-adipic acid electrocatalytic coupling system, characterized in that: The electrocatalytic coupling system comprises an anode electrode, an anode electrolyte, a proton exchange membrane, a cathode electrolyte and a cathode electrode; wherein the anode electrolyte is one or more of Keggin-type, Dawson-type and Anderson-type polyacids, and the substrate contained is cyclohexanone; and the cathode electrolyte is one or more of Keggin-type, Dawson-type and Anderson-type polyacids, and the substrate contained is phenol.

2. A phenol-cyclohexanone-adipic acid electrocatalytic coupling system according to claim 1, characterized in that: The anode electrolyte is H3[PMo 12 O 40 ]、H4[PVMo 11 O 40 ]、H5[PV2Mo 10 O 40 ]、H6[PV3Mo9O 40 ]、H7[PV4Mo8O 40 ]、H8[PV5Mo7O 40 ]、H9[PV6Mo6O 40 ]、H6[P2W 18 O 62 ]、P2Mo5VW 12 、P2Mo6W 12 、H6[P2W 12 Mo6O 62 ] one or more, the concentration of the anode electrolyte is 0.1~0.5mol / L; The cathode electrolyte is H3[PMo 12 O 40 ]、H4[PVMo 11 O 40 ]、H5[PV2Mo 10 O 40 ]、H6[PV3Mo9O 40 ]、H7[PV4Mo8O 40 ]、H8[PV5Mo7O 40 ]、H9[PV6Mo6O 40 ]、H6[P2W 18 O 62 ]、P2Mo5VW 12 、P2Mo6W 12 、H6[P2W 12 Mo6O 62 ]、H6[PW 12 O 40 ]、H6[SiW 12 O 40 ] and the concentration of the cathode electrolyte is 0.1~0.5mol / L.

3. A phenol-cyclohexanone-adipic acid electrocatalytic coupling system according to claim 1, characterized in that: The concentration of cyclohexanone is 0.1~3mol / L, and the concentration of phenol is 0.1~3mol / L.

4. The phenol-cyclohexanone-adipic acid electrocatalytic coupling system according to claim 1, characterized in that: The anode electrode is one of graphite paper, titanium sheet, carbon sheet, tantalum sheet, and TiO2 loaded with iridium oxide, and the cathode electrode is graphite paper.

5. The phenol-cyclohexanone-adipic acid electrocatalytic coupling system according to claim 1, characterized in that: The cathode side of the proton exchange membrane is loaded with one or more of a noble metal catalyst, a non-noble metal catalyst and a non-metal catalyst.

6. A phenol-cyclohexanone-adipic acid electrocatalytic coupling system according to claim 5, characterized in that: The cathode side of the proton exchange membrane is loaded with one or more catalysts selected from Pd / C, Pt / C, Ru / C, Cu / C, CoP, and NiP.

7. The phenol-cyclohexanone-adipic acid electrocatalytic coupling system according to claim 1, characterized in that: The reaction conditions of the electrocatalytic coupling system are: voltage of 1.0~1.4V, temperature of 75~85℃, and time of 1.5~3h.

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