Phenol-cyclohexanone-adipic acid electrocatalytic coupling system

Abstract

The application discloses a phenol-cyclohexanone-adipic acid electrocatalytic coupling system, and 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 contains cyclohexanone as a substrate; the cathode electrolyte is one or more of Keggin type, Dawson type and Anderson type polyacids, and contains phenol as a substrate. 40 ] and H6[SiW 12 O 40 ] are selected as the anode electrolyte and the cathode electrolyte, and a first electro-synthesis scheme for preparing adipic acid from phenol under acidic conditions is developed; compared with existing technologies, the electro-synthesis scheme has higher yield and selectivity in adipic acid generation and fast reaction rate.

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 in the production of various polymer materials, such as polyamides (e.g., nylon 66) and polyesters (engineering plastics), with an annual output of millions of tons. Therefore, achieving green chemical production of adipic acid is of great significance. Currently, the most mature industrial adipic acid production process uses benzene as a raw material. In recent years, the use of biomass phenol as a raw material has attracted widespread attention. However, the first step of the reaction, phenol hydrogenation, is still carried out under a high-temperature and high-pressure hydrogen atmosphere, which is harsh and has 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 generated adipate needs 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, the need for subsequent treatment of the prepared product adipate, and low product selectivity in the process of preparing adipic acid by electrochemical reaction.

[0005] To achieve the above objectives, the present invention provides a phenol-cyclohexanone-adipic acid electrocatalytic coupling system, which includes 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 therein is cyclohexanone; and the cathode electrolyte is one or more of Keggin-type, Dawson-type, and Anderson-type polyacids, and the substrate contained therein is phenol.

[0006] Electrochemical synthesis is an environmentally friendly and efficient method for producing adipic acid. It typically involves two half-reactions: a cathode reduction reaction and an anodic oxidation reaction. However, in practical applications, the anodic oxidation reaction typically uses an alkaline electrolyte to produce the adipate salt, which requires further acidification or hydrolysis, requiring additional energy and reagents, significantly limiting the practical application of electrochemical synthesis of adipic acid. To address this issue, the present invention specifically proposes finding a suitable redox electrolyte under acidic conditions, enabling both half-reactions to proceed under acidic conditions while maintaining 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 cathode electrolyte, the first electrosynthesis scheme for adipic acid from phenol under acidic conditions was developed. 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 the 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 SiW 12 O 40 ] 4- (2>n>0), store e - / H + ; Subsequently, the stored e - / H + [H n SiW 12 O 40 ] 4- Under a Pd / C ratio of 10%, phenol is selectively hydrogenated to cyclohexanone with a conversion rate of up to 100% and a selectivity exceeding 99%. In the electrocatalytic reaction process of the present invention, not only can adipic acid be selectively generated in the anodic reaction, but cyclohexanone can also be selectively generated in the cathodic reaction. The generated cyclohexanone can be used as a raw material for the anodic reaction to further prepare adipic acid, thereby achieving 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- The transfer process means that the cyclohexanone produced by the cathode can fully meet the consumption of the cyclohexanone of 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 range of use of electrocatalytic reaction, an electrolysis device driven by photovoltaic or wind energy can also be built, which provides an ideal solution for on-demand production in practical application and solves the problem of space-time demand of products.

[0009] Preferably, the anode electrolyte is one or more of 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 ], and the concentration of the anode electrolyte is 0.1-0.5 mol / L.

[0010] The cathode electrolyte is one or more of 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 0.1-0.5 mol / L.

[0011] Preferably, the anolyte is H6[PV3Mo9O 40 ] and the catholyte is H6[SiW 12 O 40 ].

[0012] Preferably, the concentration of cyclohexanone is 0.1-3 mol / L and the concentration of phenol is 0.1-3 mol / L.

[0013] 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.

[0014] Preferably, the cathode side of the proton exchange membrane is loaded with one or more of noble metal catalyst, non-noble metal catalyst, and non-metal catalyst.

[0015] 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 catalyst.

[0016] Preferably, the reaction conditions of the electrocatalytic coupling system are as follows: the voltage is 1.0-1.4 V, the temperature is 75-85℃, and the time is 1.5-2 h.

[0017] Therefore, the phenol-cyclohexanone-adipic acid electrocatalytic coupling system with the above structure has the following beneficial effects:

[0018] (1) The present application solves the problems of long reaction path, easy generation of a large amount of nitrogen oxides, and the like in traditional thermal catalysis, and avoids the problems of low conversion rate of cyclohexanone in alkaline electrolyte, additional energy required for separation of adipate, and the like. The present application has higher yield and selectivity of adipic acid and faster reaction rate, and the yield of adipic acid can reach 98%.

[0019] (2) The electrochemical preparation of adipic acid in the present application is carried out under acidic conditions. Compared with the electrocatalytic oxidation of cyclohexanone under other alkaline conditions, adipic acid can be precipitated from the solution by crystallization, and the adipic acid product can be directly separated without subsequent steps, which is simple and convenient.

[0020] (3) The present application first uses phenol as a raw material to carry out reduction and oxidation reactions at the cathode and anode respectively and simultaneously, realizes the continuous production of phenol to cyclohexanone and cyclohexanone to adipic acid, significantly improves the electron utilization rate, and provides a feasible route for the green production of adipic acid.

[0021] (4) The present application uses polyoxometalate as the electrolyte for oxidation and reduction, and the electrode design is simple and suitable for industrial large-scale use.

[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a structural diagram of the device of Example 1;

[0024] Figure 2 Schematic diagram of the reaction in the electrolytic cell during the electrocatalytic process;

[0025] Figure 3 Graph showing the percentage changes in cyclohexanone and adipic acid concentration over time in Example 1;

[0026] Figure 4 H6[PV3Mo9O 40 ]Infrared spectra before and after electrolysis reaction;

[0027] Figure 5 H6[PV3Mo9O 40 ] Before and after electrolysis 51 VNMR spectra;

[0028] Figure 6 H6[PV3Mo9O 40 ] Capillary electrophoresis images before and after electrolysis reaction;

[0029] Figure 7 H4[SiW 12 O 40 ]Infrared spectra before and after electrolysis cycle;

[0030] Figure 8 H4[SiW 12 O 40 ]XRD patterns before and after electrolysis cycle;

[0031] Figure 9 H4[SiW 12 O 40 ] Capillary electrophoresis images before and after electrolysis cycle;

[0032] Figure 10 is the adipic acid yield of different types of anolytes;

[0033] Figure 11 is the cyclohexanone yield of different catalysts;

[0034] Figure 12 is the phenol conversion rate and cyclohexanone yield under different types of cathode electrolytes;

[0035] Figure 13 is the yield of cyclohexanone at different cathode electrolyte concentrations;

[0036] Figure 14LSV curves under different cathode electrolytes;

[0037] Figure 15 is the yield and selectivity of cyclohexanone at different voltages;

[0038] Figure 16 This is the thermogravimetric curve of adipic acid prepared in Example 1. DETAILED DESCRIPTION

[0039] 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 specific operation process, but the present invention is not limited to this embodiment.

[0040] Example 1

[0041] A phenol-cyclohexanone-adipic acid 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 10 wt%.

[0042] 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 under the following conditions: voltage of 1.0 V, temperature of 80° C., and time of 1.5 h.

[0043] 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 time and space demand problem of the product. The schematic diagram of the electrolytic cell in this embodiment is shown in FIG. Figure 2As 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 the 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 SiW 12 O 40 ] 4- (2>n>0), store e - / H + ; Subsequently, the stored e - / H + [H n SiW 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%.

[0044] Test Example 1

[0045] (1) Stability of adipic acid production by anolyte

[0046] The above electrocatalytic reaction was cycled 8 times, and the substrate concentration was replenished 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 test results are as follows: Figure 3 As shown. Figure 3 As can be seen, 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 present invention has good selectivity for adipic acid and high conversion rate for cyclohexanone.

[0047] from Figure 16 It can also be seen that the purity of the prepared adipic acid is 99%, which is relatively high.

[0048] (2) Structural stability of anode electrolyte

[0049] 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 .

[0050] Capillary electrophoresis experimental conditions: fused silica capillaries (50 μm inner diameter, 365 μm outer diameter, Yongnian, Hebei, China) were used, with a total capillary length of 50 cm and an effective length of 40 cm. The detection wavelength was set at 254 nm. The capillary electrophoresis separation buffer was 0.1 M malonic acid (pH 2.5), the separation voltage was set at -18 kV, and the sample was hydrodynamically injected into the capillary (10 cm, 20 s).

[0051] from Figure 4-Figure 6 It can be seen that the polyacid H6[PV3Mo9O 40 ]’s infrared spectrum, 51 The VNMR and capillary electrophoresis patterns are consistent, proving that H6[PV3Mo9O 40 ]Stability of polyacid structure.

[0052] (3) Stability of cathode electrolyte

[0053] For H6[SiW in Example 1 12 O 40 ]The stability of cathode electrolyte in 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 Figure 9 The experimental conditions of capillary electrophoresis were the same as those in (2).

[0054] from Figure 7 It can be seen that H4[SiW 12 O 40 ] Fourier transform infrared spectrum, 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-covalent oxygen atom) and M-Oc-M (c: corner-covalent oxygen atom). The peak positions did not move before and after the reaction, indicating that H4[SiW 12O 40 ]It has good structural stability before and after the reaction.

[0055] from Figure 8 and Figure 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.

[0056] Example 2

[0057] 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 ].

[0058] 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.

[0059] The yield of adipic acid was tested, and the test results are shown in Figure 10 ,from Figure 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 ] was the electrolyte, the yield of adipic acid was 0.479 mmol h -1 cm -2 . With H5[PV2Mo 10 O 40 ] was 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] was the electrolyte, the yield of adipic acid was 0.719 mmol h -1 cm -2 VOSO4 was used as the electrolyte, and the adipic acid yield was 0.1626 mmol h -1 cm -2 . H6[PV3W9O 40 ] as the electrolyte, the yield of adipic acid was 0.3652 mmol h -1 cm -2 When the anode electrolyte is H6[PV3Mo9O 40 ], the yield of adipic acid is the highest.

[0060] Example 3

[0061] The difference between this embodiment and embodiment 1 is that the types of catalysts loaded on the cathode side of the proton exchange membrane are different. In this embodiment, the catalyst is Pt / C, Rh / C or Pt / Al2O3. Pt / C, Rh / C or Pt / Al2O3 are all purchased from Aladdin, and the loading amounts of Pt and Rh are both 10 wt%.

[0062] The conversion rate of phenol and the yield of cyclohexanone were tested, and the test results are shown in Figure 11 ,from Figure 11 As can be seen in the data, when Pd / C, Pt / C, Rh / C, and Pt / Al2O3 are used as catalysts, the phenol conversion rate is close to 100%. However, the cyclohexanone yield is 99% when using Pd / C as the catalyst, 0.3% when using Pt / C as the catalyst, 1.2% when using Rh / C as the catalyst, and 2.6% when using Pt / Al2O3 as the catalyst. Only when using Pd / C as the catalyst can the phenol conversion rate and cyclohexanone yield be maintained at a high level.

[0063] Example 4

[0064] 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 ].

[0065] The conversion rate of phenol and the yield of cyclohexanone were tested, and the test results are shown in Figure 12 ,from Figure 12 It can be seen that H6[SiW 12 O 40] is the cathode electrolyte, the phenol conversion rate is close to 100%, and the cyclohexanone yield is 99%. 12 O 40 ] is the cathode electrolyte, the phenol conversion rate is 80% and the cyclohexanone yield is 70%. 12 O 40 ],H6[PV3Mo9O 40 ],H6[PV3W9O 40 ] is 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.

[0066] Example 5

[0067] The difference between this embodiment and embodiment 1 is the concentration of the cathode electrolyte. In this embodiment, the concentration of the cathode electrolyte is 0.1, 0.2, 0.3, 0.4, and 0.5 mol / L.

[0068] The yield of cyclohexanone was tested, and the test results are shown in Figure 13 ,from Figure 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%.

[0069] Example 6

[0070] The difference between this embodiment and embodiment 1 is that the cathode electrolyte is replaced with 1 mol / L H2SO4.

[0071] The LSV curve test was carried out on the above system, and the test results are as follows Figure 14 As shown, from Figure 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 obtained when 1 M sulfuric acid is used as the anode electrolyte, which is very close to the industrial current density. The electrocatalytic coupling system of the present invention can be applied to the industrial production of adipic acid.

[0072] Example 7

[0073] 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.

[0074] The yield and selectivity of cyclohexanone were tested, and the test results were as follows: Figure 15 As shown, from Figure 15 As can be seen in the figure, when the anode reacts at 80°C at various voltages, the conversion of cyclohexanone to adipic acid at the anode is 100% with a selectivity exceeding 98%. At voltages ranging from 1.0 to 1.4 V (vs. Ag / AgCl), the conversion and selectivity of phenol to cyclohexanone at the cathode also exceed 99%. However, when the voltage exceeds 1.4 V (vs. Ag / AgCl), significant hydrogen evolution side reactions begin to occur at the cathode, causing the phenol conversion and the Faradaic efficiency of cyclohexanone to gradually decrease with increasing voltage. At voltages of 1.6 V, 1.8 V, and 2.0 V (vs. Ag / AgCl), phenol conversions reach 92%, 83%, and 77%, respectively, and the selectivity of cyclohexanone product remains above 99% in all cases. Even at 2.0 V (vs. Ag / AgCl), the cyclohexanone production at the cathode is approximately 1.16 equivalents, which still meets the cyclohexanone consumption at the anode.

[0075] 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 cathode electrolyte, and developed the first electrosynthetic scheme for the preparation of adipic acid from phenol under acidic conditions. Compared with existing technologies, the yield and selectivity of adipic acid production are higher and the reaction rate is faster.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. 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 solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A phenol-cyclohexanone-adipic acid electrocatalytic coupling system, characterized in that: The electrocatalytic coupling system includes 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. 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 anolyte 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 ] one or more of the above, the concentration of the cathode electrolyte is 0.1~0.5mol / L; The cathode side of the proton exchange membrane is loaded with a Pd / C catalyst.

2. The 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.

3. 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 iridium oxide-loaded TiO2, and the cathode electrode is graphite paper.

4. 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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