A method for regulating product selectivity of electrochemical amine oxidation reaction based on magnetohydrodynamic effect

Abstract

This invention discloses a method for controlling the selectivity of products in electrochemical amine oxidation reactions based on magnetohydrodynamic effects, relating to the field of electrochemistry. The method includes the following steps: (1) mixing the reaction substrate, base, electrolyte, and solvent uniformly to obtain an electrolyte; the reaction substrate is an amine; (2) using a two-electrode system, wherein the anode is a Graphene / Ni electrode and the cathode is a platinum electrode, adding the electrolyte to a reaction cell at room temperature, applying a magnetic field to the system, and placing the system in an Ar atmosphere for constant current electrolysis. This invention introduces a magnetic field into the electrochemical amine oxidation reaction, and the resulting magnetohydrodynamic effect significantly affects the Faraday efficiency of the substrate and the selectivity of the target product. It eliminates the need for electrode modification and the introduction of additional catalysts, providing a new approach to improving the efficiency of electrochemical organic reactions.

Description

Technical Field

[0001] This invention relates to the field of electrochemistry, and specifically to a method for controlling the selectivity of products in electrochemical amine oxidation reactions based on magnetohydrodynamic effects. Background Technology

[0002] Nitrogen compounds, as a basic framework in chemistry, medicine and agrochemicals, are widely found in biologically active natural products and drug molecules. Nitrogen free radicals are an important intermediate among them, and how to efficiently generate nitrogen free radicals remains a challenge.

[0003] Traditional methods for generating nitrogen free radicals are as follows: The first type relies on high-temperature initiation, such as high-energy ultraviolet light irradiation or free radical initiators, to induce the breaking of the NX bond and generate the corresponding nitrogen free radical intermediate. Among these, photolysis or pyrolysis of NX to generate nitrogen free radicals usually requires harsh conditions such as high-energy ultraviolet light irradiation or high reaction temperatures, and the substrate range is limited and selectivity is difficult to control. The second type uses transition metal catalysts, such as cobalt, copper, and iron, to induce the generation of nitrogen free radicals. This method mostly uses azide compounds as nitrogen sources, which faces limitations in nitrogen free radical sources, and azide compounds are highly toxic and explosive. The advent of electrochemistry provides an efficient and green pathway for the generation of nitrogen free radicals. Electrochemical nitrogen free radical reactions refer to the anodic oxidation of nitrogen precursors into nitrogen free radicals through continuous proton / electron or electron / proton transfers or step-by-step proton-coupled electron transfers to synthesize nitrogen-containing compounds.

[0004] Previous studies have often used doping and other techniques to introduce other components, defects, or phases to promote synergistic material composition and improve electrochemical performance. However, simply designing and modifying the catalyst itself to improve overall electrochemical performance is no longer sufficient for current research. Researchers have turned their attention to external fields, with the combination of magnetic fields and electrocatalysis showing great promise.

[0005] Magnetohydrodynamics refers to the Lorentz force (F) that moves charged particles in the presence of a magnetic field. The Lorentz force can cause convection of active substances around the diffusion layer in the liquid solution through momentum transfer between active ions and solvent molecules. This convection produces two effects: increasing the penetration rate of ions through the diffusion layer and reducing the thickness of the diffusion layer in electrochemical reactions.

[0006] Research on magnetohydrodynamic (MHD) effects enhancing electrochemical reactions currently focuses primarily on reactions such as HER, OER, and ORR. Li et al. reported an improvement in HER efficiency of Ni-W alloys under a magnetic field, attributing it to convection induced by MHD forces and the rapid detachment of H2 bubbles. Li et al. also discussed how magnetic fields optimize OER performance by enhancing the energy states of electrons in transition metal oxides and inducing the MHD effect near the electrode. However, early research on the application of magnetic fields in electrochemical reactions has mainly focused on aqueous phases, with very little research on organic phases. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, the present invention aims to provide a method for controlling the selectivity of products in electrochemical amine oxidation reactions based on magnetohydrodynamic effects. This method introduces a magnetic field as a fundamental control mechanism into organic electrochemical reactions, revealing that magnetohydrodynamic effects significantly influence the selectivity of the target product. This approach eliminates the need for additional energy or catalysts, providing a new avenue for improving the efficiency of electrochemical organic reactions.

[0008] The objective of this invention is achieved through the following technical solutions.

[0009] A method for controlling the selectivity of products in an electrochemical amine oxidation reaction based on magnetohydrodynamic effects includes the following steps:

[0010] (1) Electrolyte preparation: The reaction substrate, base, electrolyte and solvent are mixed evenly to obtain the electrolyte; the reaction substrate is an amine;

[0011] (2) Electrochemical amine oxidation experiment: A two-electrode system was used, in which the anode was a Graphene / Ni electrode and the cathode was a platinum electrode. Under room temperature conditions, the electrolyte was added to the reaction cell, a magnetic field was applied to the system, and the system was placed in an Ar atmosphere for constant current electrolysis.

[0012] Preferably, a neodymium iron boron magnet is used as the magnetic field source to apply a magnetic field to the system, and the strength of the magnetic field is 1700-4700 Gs.

[0013] Preferably, the amine is a secondary amine compound with the general structural formula -R2NH; the amine is one of 4-trifluoromethyl-N-methylaniline, N-methyl-4-cyanoaniline, 4-fluoro-N-methylaniline, 4-methylaminobenzoic acid, N-methyl-p-methylaniline and di(4-tert-butylphenyl)amine.

[0014] Preferably, the concentration of amine in the electrolyte is 0.005-0.05M, more preferably 0.05M.

[0015] Preferably, the base is pyridine, and the concentration of the base in the electrolyte is 0.05-0.25M, more preferably 0.05M.

[0016] Preferably, the electrolyte is [EMIm]BF4 or tetrabutylammonium fluoroborate, and the concentration of the electrolyte in the electrolyte solution is 0.1-0.3M, more preferably 0.3M.

[0017] Preferably, the solvent is acetonitrile or a mixed solution of acetonitrile, methanol, and tetrahydrofuran; when the solvent is a mixed solution of acetonitrile, methanol, and tetrahydrofuran, the concentrations of methanol and tetrahydrofuran in the electrolyte are 0.05-0.5M, more preferably 0.5M.

[0018] Preferably, the electrolysis current is 15-100mA, more preferably 15mA.

[0019] Preferably, the current density of the electrolysis is 150-300 A / m. 2 .

[0020] Preferably, a 15mA constant current electrolysis is performed using a DC power supply from a Bio-Logic electrochemical workstation, with an electrode immersion area of ​​10×10mm.

[0021] Preferably, the electrolysis time is 2-5 minutes, more preferably 2 minutes.

[0022] Preferably, the pretreatment of the electrode sheets includes the following steps: cutting the Graphene / Ni sheet and platinum sheet into square sheets; cleaning the Graphene / Ni sheet with dichloromethane, ethyl acetate, and ultrapure water; cleaning the Pt sheet in concentrated nitric acid, acetone, acetonitrile, and ultrapure water solvents respectively, and ultrasonically removing surface impurities; purging and drying with nitrogen gas between each ultrasonic cycle; polishing the surface with sandpaper from low to high grit after the operation is completed, wiping with non-woven cloth, and finally cleaning the surface with ethanol and ultrapure water, and wiping with non-woven cloth for later use.

[0023] Preferably, a 3D printer is used, preferably PP material, to model and print the electrode head that needs to hold the electrode sheet. After the electrode sheet is installed, the distance between the sheet is 1mm.

[0024] Preferably, after the reaction, 50 μL of the reaction solution is diluted to 1 mL with acetonitrile, filtered, and then subjected to high performance liquid chromatography for detection. The peak area change at 254 nm is preferred to be observed for quantitative analysis of the product.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] 1. Current research rarely introduces magnetic fields into organic phase reactions. In order to further expand the application scope of magnetic fields in electrochemical reactions, this invention introduces magnetic fields into electrochemical amine oxidation reactions, providing a new approach to improve the efficiency of electrochemical organic reactions without the need to modify the electrode plates or introduce additional catalysts.

[0027] 2. The magnetohydrodynamic effect generated by the introduction of an external magnetic field in this invention significantly affects the Faraday efficiency of the substrate and the selectivity of the target product. The influence of magnetic field strength, different electrolytes, and different substrate concentrations on the magnetic field effect was systematically studied, as the magnitude of the Lorentz force depends on these factors. Specifically, the external magnetic field can effectively promote charge transfer and mass transport. Under the action of the external magnetic field, the selectivity of self-coupled products is improved. That is, this invention can effectively utilize an external magnetic field to promote efficient energy utilization and selectivity of the target product, providing a new approach for electrochemical organic reactions. Attached Figure Description

[0028] Figure 1 This is a diagram of the electrolytic cell-magnetic field experimental setup in this invention.

[0029] Figure 2 The image shows the nuclear magnetic resonance spectrum used for qualitative analysis of the pure self-coupling product in this invention.

[0030] Figure 3 This is a graph showing the product selectivity and magnetic field effect changes of the self-coupling reaction with 4-trifluoromethyl-N-methylaniline as substrate in Example 1 of the present invention under different magnetic field strengths; where 1 represents 0 Gs, 2 represents 1700 Gs, and 3 represents 4700 Gs.

[0031] Figure 4 This is a schematic diagram illustrating the effect of different electrolyte conditions on the product selectivity of the self-coupling reaction in Example 2 of this invention, using 4-trifluoromethyl-N-methylaniline as a substrate.

[0032] Figure 5 This is a cyclic voltammetry test diagram under different magnetic field conditions conducted in Example 3 of this invention using 4-trifluoromethyl-N-methylaniline as the substrate.

[0033] Figure 6 The images show electron paramagnetic resonance (EPR) tests conducted under different magnetic field conditions in Example 4 of this invention, using 4-trifluoromethyl-N-methylaniline as the substrate.

[0034] Figure 7 This is the magnetic effect of different currents in a 0.25 mL / min flow cell in Comparative Example 1 of this invention, using 4-trifluoromethyl-N-methylaniline as a substrate. Detailed Implementation

[0035] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0036] Example 1

[0037] This embodiment describes the product selectivity and magnetic field effect changes of the self-coupling reaction with different magnetic field strengths using 4-trifluoromethyl-N-methylaniline as the substrate.

[0038] Electrode pretreatment process: Before the experiment, the Graphene / Ni sheet and platinum sheet were first cut into 10×15mm square pieces. The Graphene / Ni sheet was cleaned with dichloromethane, ethyl acetate, and ultrapure water; the Pt sheet was cleaned in concentrated nitric acid, acetone, acetonitrile, and ultrapure water solvents respectively to remove surface impurities. After each ultrasonic cleaning, the surface was purged with nitrogen and dried. After the operation, the surface was polished with sandpaper from low to high grit, and finally cleaned with ethanol and ultrapure water, and wiped with a non-woven cloth to ensure surface cleanliness.

[0039] Electrolyte preparation: Prepare 0.05M 4-trifluoromethyl-N-methylaniline as the substrate, 0.05M pyridine as the base, 0.3M [EMIm]BF4 as the supporting electrolyte, 0.5M methanol and 0.5M tetrahydrofuran as components of the electrolyte, and anhydrous acetonitrile as the solvent. Add these components to the reaction vessel and mix thoroughly to prepare the desired electrolyte.

[0040] Electrochemical amine oxidation experiments were conducted using a two-electrode system, with a Graphene / Ni electrode as the anode and a Pt electrode as the cathode. At room temperature, 1 mL of pre-prepared electrolyte was added to the reaction cell in a cuvette. Magnetic fields of 1700 Gs and 4700 Gs were applied using neodymium iron boron magnets, and the entire system was placed in a glove box filled with argon gas. During electrolysis, a constant current of 15 mA was set using the DC power supply of a Bio-Logic electrochemical workstation, and the cell voltage changes were recorded. Electrolysis was stopped after 2 minutes.

[0041] After electrolysis, the reaction solution was filtered through a 0.25 μm hydrophobic polytetrafluoroethylene (PTFE) membrane. 50 μL of the reaction solution was diluted to 1 mL with acetonitrile. Quantitative analysis of the reaction solution was performed using a Shimadzu high-performance liquid chromatograph (HPLC) at 254 nm, and the product selectivity was calculated. The purified target product was synthesized and qualitatively analyzed using NMR. The results are as follows: Figure 2 As shown.

[0042] Figure 3The graph shows the product selectivity and magnetic field effect of the self-coupling reaction with 4-trifluoromethyl-N-methylaniline as substrate under different magnetic field strengths. It can be seen that the magnetohydrodynamic effect promotes the formation of self-coupling products and increases with the increase of magnetic field. The zero field selectivity of the self-coupling products is 37.7%, which reaches 59.2% after applying a 4700GS electric field. The magnetohydrodynamic effect is about 57.2%.

[0043] Example 2

[0044] This example illustrates the effect of different electrolyte conditions on the product selectivity of the self-coupling reaction using 4-trifluoromethyl-N-methylaniline as a substrate.

[0045] Electrode pretreatment process: Before the experiment, the Graphene / Ni sheet and platinum sheet were first cut into 10×15mm square pieces. The Graphene / Ni sheet was cleaned with dichloromethane, ethyl acetate, and ultrapure water; the Pt sheet was cleaned in concentrated nitric acid, acetone, acetonitrile, and ultrapure water solvents respectively to remove surface impurities. After each ultrasonic cleaning, the surface was purged with nitrogen and dried. After the operation, the surface was polished with sandpaper from low to high grit, and finally cleaned with ethanol and ultrapure water, and wiped with a non-woven cloth to ensure surface cleanliness.

[0046] Electrolyte preparation: Prepare two solutions using 0.05M 4-trifluoromethyl-N-methylaniline as the substrate, 0.05M pyridine as the base, 0.5M methanol and 0.5M tetrahydrofuran as the electrolyte components, anhydrous acetonitrile as the solvent, and 0.3M [EMIm]BF4 or 0.3M tetrabutylfluoroborate as the supporting electrolyte.

[0047] Experimental Procedure: A two-electrode system was used for the electrochemical reaction, with a Graphene / Ni electrode as the anode and a Pt electrode as the cathode. At room temperature, 1 mL of each of the two electrolytes was added to a cuvette reaction cell. Magnetic fields of 2900 Gs and 4500 Gs were applied, and the entire system was placed in a glove box filled with argon gas. A constant current of 15 mA was set using the DC power supply of the Bio-Logic electrochemical workstation, and electrolysis was stopped after 2 minutes.

[0048] After electrolysis, the reaction solution was filtered through a 0.25 μm hydrophobic polytetrafluoroethylene filter membrane. 50 μL of the reaction solution was diluted to 1 mL with acetonitrile. The reaction solution was quantitatively analyzed and the product selectivity was calculated by using the absorbance change at 254 nm in a Shimadzu high-performance liquid chromatograph.

[0049] Figure 4This diagram illustrates the effect of different electrolyte conditions on the product selectivity of the self-coupling reaction using 4-trifluoromethyl-N-methylaniline as a substrate. It shows that for both 0.3 M [EMIm]BF4 and tetrabutylammonium fluoroborate electrolytes, the magnetohydrodynamic effect is more significant when tetrabutylammonium fluoroborate is used as the electrolyte. This is because [EMIm]BF4 has a higher viscosity, resulting in reduced fluidity of the reaction solution and consequently a slower response to the magnetic field due to its inertia and viscosity. Therefore, in electrolytes with higher viscosity, the magnetohydrodynamic effect is smaller, the fluid velocity distribution is more uniform, and the disturbance effect of the magnetic field on the fluid is suppressed, thus reducing the magnetohydrodynamic effect compared to tetrabutyl salts.

[0050] Example 3

[0051] This embodiment uses 4-trifluoromethyl-N-methylaniline as a substrate for cyclic voltammetry tests under different magnetic field conditions.

[0052] The electrode pretreatment process and electrolyte preparation are exactly the same as in Example 1.

[0053] Experimental Procedure: A three-electrode system was used for the electrochemical reaction, where the working electrode was a Pt electrode, the counter electrode was a Pt electrode, and the reference electrode was an Fc electrode. + / Fc solution. At room temperature, 6 mL of the prepared electrolyte was added to the reaction chamber in a glass bottle. A neodymium iron boron magnet was used as the magnetic field source to apply a 1700 Gs magnetic field to the system, and the entire system was placed in a glove box filled with argon gas. Cyclic voltammetry was performed using a DC power supply from a Bio-Logic electrochemical workstation. The test parameters were: scanning at a scan rate of 500 mV / s in the range of 0V to 2V, for 3 scans, with the second scan being the final result.

[0054] After electrolysis, the reaction solution was filtered through a 0.25 μm hydrophobic polytetrafluoroethylene filter membrane. 50 μL of the reaction solution was diluted to 1 mL with acetonitrile. The reaction solution was quantitatively analyzed and the product selectivity was calculated by using the absorbance change at 254 nm in a Shimadzu high-performance liquid chromatograph.

[0055] Figure 5 The cyclic voltammetry results using 4-trifluoromethyl-N-methylaniline as a substrate under different magnetic field conditions show that the limiting current densities of both the cathode and anodic regions increase in the presence of a magnetic field. This is a typical result of the MHD effect, which is attributed to the reduction in diffusion layer thickness caused by the magnetohydrodynamic effect after the introduction of the magnetic field. At the same time, the charge transfer and mass transport rates are accelerated, resulting in an increase in diffusion current.

[0056] Example 4

[0057] This embodiment uses 4-trifluoromethyl-N-methylaniline as a substrate for electron paramagnetic resonance (EPR) tests under different magnetic field conditions.

[0058] The electrode pretreatment process is exactly the same as in Example 1.

[0059] Electrolyte preparation: Prepare 0.05M 4-trifluoromethyl-N-methylaniline as substrate, 0.05M DMPO as free radical scavenger, 0.05M pyridine as base, 0.3M [EMIm]BF4 as supporting electrolyte, 0.5M methanol and 0.5M tetrahydrofuran as electrolyte components, and anhydrous acetonitrile as solvent.

[0060] Experimental Procedure: A two-electrode system was used for the electrochemical reaction, with both the anode and cathode being Pt electrodes. At room temperature, 6 mL of the prepared electrolyte was added to the reaction vessel in a glass bottle. A neodymium iron boron magnet was used as the magnetic field source to apply a magnetic field of 3500 Gs to the system. A constant current of 15 mA was set on the DC power supply of the Bio-Logic electrochemical workstation. Electrolysis was stopped after 2 minutes, and the reaction solution was collected using a capillary tube, sealed, and placed in an EPR NMR tube for measurement. The scanning range was 332-342 nm.

[0061] Figure 6 The images show electron paramagnetic resonance (EPR) measurements under different magnetic field conditions using 4-trifluoromethyl-N-methylaniline as the substrate. The results indicate that DMPO captured free radicals, confirming the reaction as a free radical reaction. Spin count calculations of the free radical concentration show that the EPR detected a reduction of approximately 40.5% in the free radical products captured by DMPO after magnetic field application. This is because the substrate amine loses electrons at the anode and is oxidized to nitrogen free radicals. Some of these nitrogen free radicals undergo self-coupling to form hydrazine compounds, while others enter the bulk solution and are captured by DMPO to form captured products. The magnetohydrodynamic effect after field application reduces the thickness of the diffusion layer on the electrode surface, effectively promoting mass transfer and increasing the collision probability of nitrogen free radicals on the electrode surface, thus favoring the occurrence of self-coupling reactions. Consequently, the concentration signal of the DMPO captured products detected by the EPR decreases, consistent with the magnetohydrodynamic effect discussed above.

[0062] Example 5

[0063] This embodiment investigates the effect of an external magnetic field on the selectivity of self-coupled products at different substrate concentrations using 4-trifluoromethyl-N-methylaniline as the substrate.

[0064] The electrode pretreatment process is exactly the same as in Example 1.

[0065] Electrolyte preparation: Reaction solutions with 4-trifluoromethyl-N-methylaniline concentrations of 0.005M, 0.05M, and 0.5M were prepared respectively. The other components and concentrations of the electrolyte were exactly the same as in Example 1.

[0066] Experimental Procedure: A three-electrode system was used to conduct the electrochemical reaction, where the working electrode and counter electrode were both Pt electrodes, and the reference electrode was Fc. + / Fc solution. At room temperature, add 6 mL of the prepared electrolyte to the reaction vessel in a glass bottle. Apply a magnetic field of 3700 Gs to the system using a neodymium iron boron magnet as the magnetic field source. Set a constant voltage to the potential of the first oxidation peak and its half-peak potential using an electrochemical workstation, and stop when the input charge is 0.2 F.

[0067] The effect of an external magnetic field on the selectivity of self-coupled products at different substrate concentrations is shown in Table 1.

[0068] At the same concentration, the first set of data represents constant-voltage electrolysis data at the half-peak potential, and the second set represents electrolysis data at the oxidation peak. Lower substrate concentrations exhibited more stable magnetohydrodynamic effects and higher selectivity for self-coupled products, while higher concentrations showed negative magnetohydrodynamic effects, indicating that the selectivity for self-coupled products decreased under an applied magnetic field at high concentrations. This is presumably because at excessively high concentrations, there is an excess of substrate on the electrode surface, and the magnetohydrodynamic effect of carrying the substrate from the bulk solution to the electrode surface is weakened, thus limiting the influence of the magnetic field. Therefore, it is recommended to conduct the reaction at low to medium concentrations, such as 0.005-0.05 M.

[0069] Table 1

[0070]

[0071] Comparative Example 1

[0072] This comparative example uses 4-trifluoromethyl-N-methylaniline as the substrate. The experimental setup employs an electrochemical flow cell, with a platinum electrode as the working electrode, to compare the selectivity of autocoupling products under different magnetic field conditions.

[0073] (1) Electrode pretreatment: Before the experiment, the platinum sheet was cut into 6×6mm square pieces and ultrasonically removed from the surface impurities in acetone, anhydrous ethanol and ultrapure water solvent for 15 minutes respectively. Nitrogen gas was used to blow dry the electrodes during each ultrasonic interval.

[0074] (2) Electrolyte preparation: 0.05M 4-trifluoromethyl-N-methylaniline was prepared as the substrate, 0.3M [EMIm]BF4 as the supporting electrolyte, 0.05M pyridine as the base, and 0.5M methanol and 0.5M tetrahydrofuran as the electrolyte components, with anhydrous acetonitrile as the solvent. The electrolyte was added to a syringe and pumped into a flow cell using a syringe pump.

[0075] (3) Electrolysis experiment: A three-electrode system was used in the experiment, in which the working electrode and the counter electrode were both platinum electrodes, and the reference electrode was a silver wire. The reaction cell was assembled, and the flow rate of the syringe pump into the reaction cell was set to 0.25 mL / min. The entire system was well sealed. An electromagnet was used to apply a magnetic field of 6500 Gs to the system, and constant current electrolysis at 15 mA, 25 mA, and 35 mA was performed using an electrochemical workstation.

[0076] (4) After electrolysis, the reaction solution was filtered using a 0.25 μm hydrophobic polytetrafluoroethylene filter membrane. 50 μL of the reaction solution was diluted to 1 mL with acetonitrile. The reaction solution was quantitatively analyzed and the product selectivity was calculated by using the absorbance change at 254 nm in a Shimadzu high performance liquid chromatograph.

[0077] Figure 7 This is a schematic diagram of the magnetic effect in a flow cell reaction using 4-trifluoromethyl-N-methylaniline as the substrate. It can be seen that even with laminar flow, the magnetohydrodynamic effect still exists in the flow cell reaction, which is equivalent to stirring. This proves that the magnetohydrodynamic effect still exists under an applied magnetic field even when the system is stirred.

[0078] The assumption that magnetohydrodynamic effects are equivalent to stirring effects is excluded.

[0079] Comparative Example 2

[0080] In this comparative example, the reaction tank was exposed to air, and all other conditions were exactly the same as in Example 1.

[0081] Table 2 shows a comparison of the results of the constant current electrolysis reaction in air and the reaction under an argon atmosphere after the start of electrolysis.

[0082] Table 2

[0083] Conversion rate / magnetic field strength 4500Gs 2100Gs 0Gs Air 0.110 0.104 0.069 Glove box - argon 0.204 0.192 0.173

[0084] As can be seen from Table 2, the conversion rate of the reaction is higher under an argon atmosphere, indicating that the Faraday efficiency is higher and the energy input utilization rate is higher in an argon atmosphere. Therefore, the reaction is chosen to be carried out in an argon atmosphere.

[0085] In summary, this invention significantly improves the efficiency of organic phase reactions by introducing an external magnetic field, resulting in a magnetohydrodynamic effect. This practical method avoids complex approaches such as structural modification and the introduction of catalysts, providing a new approach for electrochemical organic reactions.

[0086] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. Various process solutions that are not substantially different from the concept of the present invention are all within the scope of protection of the present invention.

Claims

1. A method for controlling the selectivity of products in an electrochemical amine oxidation reaction based on magnetohydrodynamic effects, characterized in that, Includes the following steps: (1) The reaction substrate, base, electrolyte, and solvent are mixed evenly to obtain an electrolyte; the reaction substrate is an amine; (2) A two-electrode system is adopted, wherein the anode is a Graphene / Ni electrode and the cathode is a platinum electrode. Under room temperature conditions, the electrolyte is added to the reaction cell, a magnetic field is applied to the system, and the system is placed in an Ar atmosphere for constant current electrolysis.

2. The method for controlling the selectivity of electrochemical amine oxidation reaction products based on magnetohydrodynamic effect according to claim 1, characterized in that, A magnetic field of 1700-4700 Gs is applied to the system using neodymium iron boron magnets as the magnetic field source.

3. The method for controlling the selectivity of electrochemical amine oxidation reaction products based on magnetohydrodynamic effect according to claim 1, characterized in that, The amine is a secondary amine compound with the general structural formula -R2NH; the amine is one of 4-trifluoromethyl-N-methylaniline, N-methyl-4-cyanoaniline, 4-fluoro-N-methylaniline, 4-methylaminobenzoic acid, N-methyl-p-methylaniline and di(4-tert-butylphenyl)amine.

4. The method for controlling the selectivity of electrochemical amine oxidation reaction products based on magnetohydrodynamic effect according to claim 1, characterized in that, The concentration of amine in the electrolyte is 0.005-0.05M.

5. The method for controlling the selectivity of electrochemical amine oxidation reaction products based on magnetohydrodynamic effect according to claim 1, characterized in that, The base is pyridine, and the concentration of the base in the electrolyte is 0.05-0.25M.

6. The method for controlling the selectivity of electrochemical amine oxidation reaction products based on magnetohydrodynamic effect according to claim 1, characterized in that, The electrolyte is [EMIm]BF4 or tetrabutylammonium fluoroborate, and the concentration of the electrolyte in the electrolyte solution is 0.1-0.3M.

7. The method for controlling the selectivity of electrochemical amine oxidation reaction products based on magnetohydrodynamic effect according to claim 1, characterized in that, The solvent is acetonitrile or a mixed solution of acetonitrile, methanol, and tetrahydrofuran; when the solvent is a mixed solution of acetonitrile, methanol, and tetrahydrofuran, the concentrations of methanol and tetrahydrofuran in the electrolyte are 0.05-0.5M, respectively.

8. The method for controlling the selectivity of electrochemical amine oxidation reaction products based on magnetohydrodynamic effect according to claim 1, characterized in that, The electrolysis current is 15-100mA.

9. The method for controlling the selectivity of electrochemical amine oxidation reaction products based on magnetohydrodynamic effect according to claim 1, characterized in that, The electrolysis time is 2-5 minutes.

10. The method for controlling the selectivity of electrochemical amine oxidation reaction products based on magnetohydrodynamic effect according to claim 1, characterized in that, The pretreatment of the electrode sheets used includes the following steps: cutting the Graphene / Ni sheet and platinum sheet into square sheets; cleaning the Graphene / Ni sheet with dichloromethane, ethyl acetate and ultrapure water; cleaning the Pt sheet in concentrated nitric acid, acetone, acetonitrile and ultrapure water solvents respectively and ultrasonically removing surface impurities; purging and drying with nitrogen gas between each ultrasonic cycle; polishing the surface with sandpaper from low to high grit after the operation is completed; wiping with non-woven cloth; finally cleaning the surface with ethanol and ultrapure water, and wiping with non-woven cloth for later use.

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