A method for preparing carbonyl intermediates by electrocatalytic oxidation of nickel-vanadium nanosheet catalysts

Abstract

The present invention relates to a method for preparing a carbonyl intermediate by electrocatalytic oxidation of a nickel-vanadium nanosheet catalyst. The method adopts a flow-type electrolytic cell for reaction. In the anode chamber, the nickel-vanadium nanosheet catalyst is used as a working electrode, and a reactant alcohol intermediate, a mixed solvent and a nitroxide free radical are added and stirred evenly; in the cathode chamber, a nickel plate is used as a counter electrode, an alkaline solution is used as a cathode liquid, and the anode and cathode liquid storage chambers are pumped into a reactor through a circulation pump to start an electrocatalytic oxidation reaction. After the reaction is completed, the reaction liquid is cooled and then an organic solvent is added for extraction, and the organic layer is distilled under reduced pressure to obtain a carbonyl intermediate compound. The transition metal nickel-vanadium catalyst used in the present invention has low cost, avoids the consumption of rare precious metals, and solves the technical problems of high cost, high environmental pollution, low yield, long production cycle, etc. of the process route for preparing carbonyl intermediate compounds in the current process, and has the advantages of low reaction cost, high yield, short production cycle, high time-space yield, etc.

Description

Technical Field

[0001] The invention relates to a method for synthesizing an organic chemical product, and in particular to a method for preparing a carbonyl intermediate by electrocatalytic oxidation of a nickel-vanadium nanosheet catalyst. Background Art

[0002] The oxidation of alcohols to aldehydes or carbonyls is an important reaction in organic synthesis and is widely used in the pharmaceutical and chemical industries. Usually, inorganic oxidants such as potassium permanganate, chromium trioxide, potassium dichromate, and ruthenium tetroxide are used. For example, chromium (VI) reagents include Jones oxidation (CrO3 / H2SO4 / acetone), PCC (Pyrindium Chlorochromate) oxidation, and PDC (Pyrindium Dichromate) oxidation. These reagents are easy to prepare and can also be purchased directly. PCC is acidic, so acid-sensitive substituents may participate in the reaction, while PDC can be used in a neutral environment. The general operation is relatively simple. PCC / PDC oxidation generally uses dichloromethane as a solvent, and post-treatment needs to avoid Cr(VI) pollution to the environment. DMSO oxidation includes DMSO-Cl2, DMSO-DCC oxidation (Pfitzner-Moffatt Oxidation), and DMSO-(COCl)2 oxidation (Moffatt-Swern Oxidation). This type of reaction generally has mild conditions, and the reagents need to be free of water. The byproduct dimethyl sulfide generated by the reaction has a foul odor, so post-treatment requires care. DMS-NCS oxidation (Corey-Kim Oxidation) contains DMS, i.e. dimethyl sulfide, and the mechanism is similar to Moffatt-Swern Oxidation. This method is generally suitable for the oxidation of primary and secondary alcohols, but for allyl alcohol and benzyl alcohol, their halides are generally obtained. High-valent iodine reagent (Dess-Martin) oxidation generally uses commercially available or prepared Dess-Martin reagents (precursor IBX is generally also OK), using dichloromethane as solvent. This reaction is very common, simple to operate, and proceeds quickly at room temperature. It can oxidize primary alcohols to aldehydes. In TPAP / NMO (Ley-Griffith) oxidation, NMO is a co-oxidant for ruthenium, and a catalytic amount of TPAP can be used. TPAP has weak oxidizing ability, and double bonds in the substrate can also be retained. Primary alcohols are only oxidized to aldehydes, and will not be over-oxidized to carboxylic acids. The experimental steps are simple and the reaction proceeds very quickly. Because the reaction conditions are also mild, this reaction is also applicable to substrates with easily deprotected groups. However, these methods face the following problems: 1) Hexavalent chromium is highly toxic; 2) There are many side reactions, which may partially oxidize to aldehydes, or over-oxidize to break CC bonds; 3) Functional group compatibility, strong oxidation conditions make many active functional groups such as amino groups and unsaturated bonds incompatible; 4) The system is complex and post-processing is difficult and troublesome.

[0003] Therefore, finding an efficient, mild, pollution-free, and easy-to-operate method to convert alcohols into aldehydes or carbonyls has always been a challenge in organic synthesis.

[0004] So far, there are no reports on the use of non-precious metal nickel-vanadium nanosheet catalysts for the oxidation of alcohols to aldehydes or carbonyls. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of environmental pollution, high catalyst cost, complex production process and the like in the existing carbonyl product synthesis process, and provide a method for preparing carbonyl intermediates by electrocatalytic oxidation. The present invention uses alcohol intermediates as raw materials, nickel vanadium nanosheets and nitroxide free radicals as co-catalysts, and obtains the product carbonyl intermediates by electrocatalytic oxidation. The process route has the advantages of low reaction cost, high yield, short production cycle, high time-space yield and the like.

[0006] The invention discloses a method for preparing a carbonyl intermediate by electrocatalytic oxidation of a nickel-vanadium nanosheet catalyst, which specifically comprises the following steps: using a flow-type electrolytic cell for reaction, using the nickel-vanadium nanosheet catalyst as a working electrode in an anode chamber, adding a reactant alcohol intermediate R1R2COH, a mixed solvent and a nitroxide free radical, and stirring evenly, using a nickel plate as a counter electrode and an alkaline solution as a cathode liquid in a cathode chamber, respectively pumping a solution from a feed port into a flow-type reactor through a circulation pump in an anode liquid storage chamber and a cathode liquid storage chamber, turning on a constant current meter at a certain temperature and starting an electrocatalytic oxidation reaction, turning off the constant current meter after the reaction is finished, adding an organic solvent for extraction after the reaction liquid is cooled, and performing reduced pressure distillation on an organic layer to obtain a carbonyl intermediate compound;

[0007] R1 and R2 on the alcohol intermediate independently represent hydrogen or a hydrocarbon group, and R1 and R2 cannot be hydrogen at the same time; preferably, the alcohol intermediate is benzyl alcohol (1a), cinnamyl alcohol (2a), furfuryl alcohol (3a), cyclohexylmethanol (4a), n-decanol (5a), 3-methyl-2-butene-1-ol (6a), cyclohexanol (7a), 1-phenylethanol (8a), 19-hydroxymethyl-4-androstene-3,17-dione (9a) or 17β-hydroxy-19-norandrost-4-ene-3-one (10a), and its structural formula is shown below:

[0008]

[0009] Furthermore, the present invention defines that the nickel-vanadium nanosheet catalyst used is composed of a graphite felt carrier and nickel-vanadium nanosheets supported on the graphite felt carrier, and the loading amount of the nickel-vanadium catalyst on the graphite felt is 2-3 mg / cm 2 , and its preparation method comprises the following steps:

[0010] 1) According to the feed ratio, a non-precious metal nickel raw material and a vanadium raw material are respectively dissolved in water, urea is added, and ultrasonic dispersion is performed at room temperature for 10 minutes to obtain a solution A. Furthermore, the present invention also defines that the non-precious metal nickel raw material is nickel nitrate, nickel chloride, nickel acetylacetonate or nickel acetate; the vanadium raw material is vanadium chloride, ammonium metavanadate, sodium orthovanadate, sodium metavanadate or potassium metavanadate, preferably the nickel raw material is nickel nitrate, the vanadium raw material is vanadium chloride, the molar ratio of the nickel raw material to the vanadium raw material is 1:1-5:1; the molar ratio of the metal to urea is 1:3-1:10.

[0011] 2) adding the A solution and the graphite felt carrier in step 1) into a hydrothermal kettle, and performing a hydrothermal reaction at 100-160° C. for 5-24 hours. After the reaction is completed, cooling to room temperature is performed, taking out the graphite felt carrier, and then washing it with distilled water and ethanol, and then vacuum drying it at 60° C. to obtain a supported nickel-vanadium nanosheet catalyst; preferably, the hydrothermal temperature is 120-140° C., and the hydrothermal time is 10-15 hours.

[0012] Furthermore, the present invention also defines that the volumes of the anode liquid storage chamber and the cathode liquid storage chamber are both 100-500mL; the concentration of the reactant raw material alcohol intermediate is 10-500mmol / L, preferably 100-500mmol / L; the mixed solvent of the anode liquid storage chamber is divided into a main solvent and a secondary solvent, the main solvent is a sodium carbonate aqueous solution, and its concentration is 0.1-2.0mol / L; the secondary solvent is one of acetonitrile, dichloromethane, tetrahydrofuran or acetone, and the volume ratio of the main solvent to the secondary solvent in the mixed solvent is 9:1-5:5.

[0013] Furthermore, the present invention also defines the conditions of the electrocatalytic oxidation reaction: the current is 50-2000mA, the cell voltage is 2-10V, the reaction temperature is 25-60°C, and the reaction time is 1-12 hours; the organic solvent for extraction is toluene, dichloromethane, chloroform or ethyl acetate.

[0014] Furthermore, the present invention also defines the nitroxide free radical as 2,2,6,6-tetramethylpiperidine-1-oxyl free radical (TEMPO), 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxyl free radical (ACT), 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl free radical (NH2-TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl free radical (HO-TEMPO), and the concentration of the nitroxide free radical in the anode liquid storage chamber is 1-20mmol / L, preferably 5-10mmol / L.

[0015] Furthermore, the present invention also defines that the alkaline solution in the cathode liquid storage chamber is a sodium carbonate solution with a concentration of 0.1-2.0 mol / L; and the flow rate of the circulation pump is 100-200 mL / min.

[0016] Furthermore, the present invention also defines the size of the nickel-vanadium nanosheet catalyst as 1×1 cm 2 -5×5cm 2 , preferably 3×3cm 2 .

[0017] By adopting the above technology, compared with the prior art, the present invention has the following beneficial effects:

[0018] 1) The graphite felt used in the process of the present invention is a three-dimensional material. It is used as a carrier for loading metals. Based on the high electronic conductivity, large specific surface area and high structural stability of the graphite felt, after the metal is loaded on the graphite felt, the flow state of the electrolyte can be improved and the concentration polarization can be reduced during continuous flow, so that it has excellent performance in electrocatalytic oxidation to produce carbonyl intermediates;

[0019] 2) The nickel-vanadium nanosheets and nitroxide free radicals used in the present invention are co-catalysts, and the catalytic system thereof obtains a high current density, thereby reducing the reaction time and increasing the time-space yield of the carbonyl intermediate;

[0020] 3) The co-catalytic system used in the present invention has excellent catalytic activity for a series of alcohol substrates, with a carbonyl intermediate selectivity of more than 90% and a product yield of more than 85%. Compared with a tank reactor, the space-time yield of the continuous flow reactor electrolyzer is increased by 78 times;

[0021] 4) The main solvent sodium carbonate aqueous solution (weakly alkaline reaction solution) and the secondary solvent used in the present invention can be reused, and no harmful gas or harmful waste liquid is generated. Therefore, the method process has low toxicity, is green and environmentally friendly, and greatly reduces the cost of "three wastes" treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1a This is a SEM image of the nickel-vanadium nanosheet catalyst of Example 1 at 20 μm;

[0023] Figure 1b This is a SEM image of the nickel-vanadium nanosheet catalyst of Example 1 at 1 μm;

[0024] Figure 2 This is a graph showing the change in the reaction of electrocatalytic oxidation of benzyl alcohol to benzaldehyde over time in Example 1.

[0025] Figure 3 The graph is a comparison of the space-time yields of the electrocatalytic oxidation of benzyl alcohol in Example 1 and Example 7 in a flow reactor and a tank reactor. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0027] Example 1: Synthesis of Ni2V1 / GF catalyst and electrocatalytic oxidation of benzyl alcohol to produce benzaldehyde

[0028] (1) According to the feed ratio, 387 mg of nickel nitrate and 105 mg of vanadium chloride were dissolved in 80 mL of water, and 360 mg of urea was added. The mixture was dispersed by ultrasonic at room temperature for 10 minutes. This was called solution A.

[0029] (2) Solution A in step (1) and a graphite felt carrier (size about 3×3 cm) were added to the mixture. 2 ) was added to a hydrothermal reactor, and the hydrothermal reaction was carried out at 120°C for 12 hours, then cooled to room temperature, the graphite felt was taken out, and washed twice with distilled water and ethanol alternately, and then vacuum dried at 60°C to obtain a supported catalyst, which was labeled as Ni2V1 / GF. The SEM scanning electron microscope image is shown in FIG. Figure 1a and 1b. Figure 1a , Figure 1b It can be found that the Ni2V1 / GF catalyst has a nanosheet morphology.

[0030] The catalytic performance of the Ni2V1 / GF catalyst prepared in Example 1 was tested, and the specific method was as follows:

[0031] The flow-type electrolytic cell used in the present invention is a Ni2V1 / GF catalyst (about 3×3 cm 2 ) is directly placed as the working electrode on the anode in the electrolytic cell. The volume of the anode chamber and the cathode chamber of the electrolytic cell are both 250mL. Add 1.08g of substrate benzyl alcohol, 106mg of ACT, 90mL of 0.5M sodium carbonate solution and 10mL of acetonitrile as a mixed solution to the anode chamber, and stir evenly; add 100mL of 0.5M sodium carbonate to the cathode chamber, and the anode and cathode chambers pump the solution into the reactor through a circulation pump at a flow rate of 150mL / min. The reaction temperature is controlled at 30°C by a constant temperature water bath, the constant current meter is turned on, the current is set to 1500 mA, the voltage control range is 2-4V, and the electrocatalytic oxidation reaction is started. After 0.4 hours of reaction, when no raw material point is detected by TLC and GC, the constant current meter is turned off to stop the reaction. After the electrolytic solution in the anode chamber is cooled to room temperature, it is extracted with ethyl acetate and separated by evaporation of the ethyl acetate phase to obtain the benzaldehyde product; during the reaction, the whole process is tracked by GC. As the reaction time progresses, the kinetic diagram of the oxidation of benzyl alcohol is shown as follows Figure 2 As shown in the figure, it can be seen that as the reaction time increases, the raw material benzyl alcohol gradually decreases and the product benzaldehyde gradually increases. Among them, the current density is 150mA / cm 2When the reaction reaches 0.4 hours, the conversion rate of raw material benzyl alcohol is 99%, the selectivity of benzaldehyde is 98%, the crude product is 1.0g, and the yield is 92%. By calculation, its space-time yield is 8.64kg / (m 3 h).

[0032] Example 2: Synthesis of Ni1V1 / GF catalyst and electrocatalytic oxidation of cinnamyl alcohol to produce cinnamaldehyde

[0033] (1) According to the feed ratio, 290 mg of nickel nitrate and 157 mg of vanadium chloride were dissolved in 50 mL of water, and 420 mg of urea was added. The mixture was dispersed by ultrasonic at room temperature for 10 minutes. This was called solution A.

[0034] (2) Solution A in step (1) and a graphite felt carrier (size about 3×3 cm) were added to the mixture. 2 ) was added into a hydrothermal autoclave and subjected to hydrothermal reaction at 140 °C for 10 hours. The mixture was then cooled to room temperature, and the graphite felt was taken out. The graphite felt was washed alternately with distilled water and ethanol for two times, and then dried in vacuum at 60 °C to obtain a supported catalyst, which was labeled as Ni1V1 / GF.

[0035] The catalytic performance of the Ni1V1 / GF catalyst prepared in Example 2 was tested, and the specific method was as follows:

[0036] The flow-type electrolytic cell used in the present invention is a Ni1V1 / GF catalyst (about 3×3 cm 2 ) is directly placed as the working electrode in the anode of the electrolytic cell. The volume of the anode chamber and the cathode chamber of the electrolytic cell are both 200mL. Add 1.34g of substrate cinnamyl alcohol, 156mg of TEMPO, 60mL of 1M sodium carbonate solution and 40mL of acetonitrile as a mixed solution to the anode chamber, and stir evenly; add 100mL of 1M sodium carbonate to the cathode chamber. The anode and cathode chambers pump the solution into the reactor through a circulation pump at a flow rate of 120mL / min. The reaction temperature is controlled at 40°C by a constant temperature water bath, the constant current meter is turned on, the current is set to 1000mA, the voltage control range is 2-5V, and the electrocatalytic oxidation reaction is started. After 1 hour of reaction, when there is no raw material point detected by TLC and GC, the constant current meter is turned off to stop the reaction. After the electrolytic solution in the anode chamber is cooled to room temperature, it is extracted and layered with dichloromethane, and the dichloromethane phase is evaporated and separated to obtain the cinnamaldehyde product. Among them, the current density is 100mA / cm 2 When the reaction reaches 1 hour, the conversion rate of the raw material cinnamyl alcohol is 99%, the selectivity of cinnamaldehyde is 95%, the crude product is 1.20g, and the yield is 89%. By calculation, its time-space yield is 7.70kg / (m 3 h).

[0037] Example 3: Synthesis of Ni3V1 / GF catalyst and electrocatalytic oxidation of furfuryl alcohol to produce furfural

[0038] (1) According to the feed ratio, 435 mg of nickel nitrate and 78 mg of vanadium chloride were dissolved in 60 mL of water, and 360 mg of urea was added. The mixture was dispersed by ultrasonic at room temperature for 10 minutes. This was called solution A.

[0039] (2) Solution A in step (1) and a graphite felt carrier (size about 3×3 cm) were added to the mixture. 2 ) was added into a hydrothermal autoclave and subjected to hydrothermal reaction at 140 °C for 15 hours. The mixture was then cooled to room temperature, and the graphite felt was taken out. The graphite felt was washed alternately with distilled water and ethanol for two times, and then dried in vacuum at 60 °C to obtain a supported catalyst, which was labeled as Ni3V1 / GF.

[0040] The catalytic performance of the Ni3V1 / GF catalyst prepared in Example 3 was tested, and the specific method is as follows:

[0041] The flow-type electrolyzer used in the present invention is a Ni3V1 / GF catalyst (about 3×3 cm 2 ) is directly placed as the working electrode in the anode of the electrolytic cell. The volume of the anode chamber and the cathode chamber of the electrolytic cell are both 300mL. Add 0.98g of substrate furfuryl alcohol, 312mg of TEMPO, 80mL of 1.5M sodium carbonate solution and 20mL of dichloromethane as a mixed solution to the anode chamber, and stir evenly; add 100mL of 1.5M sodium carbonate to the cathode chamber. The anode and cathode chambers pump the solution into the reactor through a circulation pump at a flow rate of 200mL / min. The reaction temperature is controlled at 25°C by a constant temperature water bath, the constant current meter is turned on, the current is set to 2000mA, the voltage control range is 2-6V, and the electrocatalytic oxidation reaction is started. After 0.8 hours of reaction, when there is no raw material point detected by TLC and GC, the constant current meter is turned off to stop the reaction. After the electrolytic solution in the anode chamber is cooled to room temperature, it is extracted and layered by toluene, and the toluene phase is evaporated and separated to obtain the furfural product. Among them, the current density is 200mA / cm 2 When the reaction reaches 0.8 hours, the conversion rate of the raw material furfuryl alcohol is 99%, the selectivity of furfural is 93%, the crude product is 0.9g, and the yield is 91%. By calculation, its space-time yield is 6.83kg / (m 3 h).

[0042] Example 4: Synthesis of Ni4V1 / GF catalyst and electrocatalytic oxidation of n-decanol to produce n-decanal

[0043] (1) According to the feed ratio, 464 mg of nickel nitrate and 63 mg of vanadium chloride were dissolved in 80 mL of water, and 480 mg of urea was added. The mixture was dispersed by ultrasonic at room temperature for 10 minutes. This was called solution A.

[0044] (2) Solution A in step (1) and a graphite felt carrier (size about 3×3 cm) were added to the mixture. 2 ) was added into a hydrothermal autoclave and subjected to hydrothermal reaction at 120 °C for 15 hours. The mixture was then cooled to room temperature, and the graphite felt was taken out. The graphite felt was washed alternately with distilled water and ethanol for two times, and then dried in vacuum at 60 °C to obtain a supported catalyst, which was labeled as Ni4V1 / GF.

[0045] The catalytic performance of the Ni4V1 / GF catalyst prepared in Example 4 was tested, and the specific method was as follows:

[0046] The flow-type electrolyzer used in the present invention is a Ni4V1 / GF catalyst (about 3×3 cm 2 ) is directly placed as the working electrode in the anode of the electrolytic cell. The volume of the anode chamber and cathode chamber of the electrolytic cell is 400mL. Add 1.58g of substrate n-decanol, 213mg of ACT, 50mL of 0.5M sodium carbonate solution and 50mL of tetrahydrofuran as a mixed solution to the anode chamber, and stir evenly; add 250mL of 0.5M sodium carbonate to the cathode chamber. The anode and cathode chambers pump the solution into the reactor through a circulation pump at a flow rate of 140mL / min. The reaction temperature is controlled at 60°C by a constant temperature water bath, the constant current meter is turned on, the current is set to 1000mA, the voltage control range is 2-4V, and the electrocatalytic oxidation reaction is started. After 2 hours of reaction, when there is no raw material point detected by TLC and GC, the constant current meter is turned off to stop the reaction. After the electrolytic solution in the anode chamber is cooled to room temperature, it is extracted and separated by chloroform, and the chloroform phase is evaporated and separated to obtain the n-decanal product. Among them, the current density is 100mA / cm 2 When the reaction reached 2 hours, the conversion rate of the raw material n-decanol was 99%, the selectivity of n-decanal was 96%, the crude product was 1.45 g, and the yield was 91%. By calculation, its space-time yield was 5.92 kg / (m 3 h).

[0047] Example 5: Synthesis of Ni5V1 / GF catalyst and electrocatalytic oxidation of cyclohexanol to produce cyclohexanone

[0048] (1) According to the feed ratio, 483 mg of nickel nitrate and 52 mg of vanadium chloride were dissolved in 100 mL of water, and 360 mg of urea was added. The mixture was dispersed by ultrasonic at room temperature for 10 minutes. This was called solution A.

[0049] (2) Solution A in step (1) and a graphite felt carrier (size about 3×3 cm) were added to the mixture. 2) was added into a hydrothermal autoclave and subjected to hydrothermal reaction at 120°C for 10 hours. The mixture was then cooled to room temperature, and the graphite felt was taken out. The graphite felt was washed alternately with distilled water and ethanol for two times, and then dried in vacuum at 60°C to obtain a supported catalyst, which was labeled as Ni5V1 / GF.

[0050] The catalytic performance of the Ni5V1 / GF catalyst prepared in Example 5 was tested, and the specific method is as follows:

[0051] The flow-type electrolytic cell used in the present invention is a Ni5V1 / GF catalyst (about 3×3 cm 2 ) is directly placed as the working electrode in the anode of the electrolytic cell. The volume of the anode chamber and cathode chamber of the electrolytic cell is 250mL. Add 0.96g of substrate cyclohexanol, 156mg of TEMPO, 70mL of 0.5M sodium carbonate solution and 30mL of acetone as a mixed solution to the anode chamber, and stir evenly; add 100mL of 0.5M sodium carbonate to the cathode chamber. The anode and cathode chambers pump the solution into the reactor through a circulation pump at a flow rate of 100mL / min. The reaction temperature is controlled at 40°C by a constant temperature water bath, the constant current meter is turned on, the current is set to 1500mA, the voltage control range is 2-8V, and the electrocatalytic oxidation reaction is started. After 4 hours of reaction, when no raw material point is detected by TLC and GC, the constant current meter is turned off to stop the reaction. After the electrolytic solution in the anode chamber is cooled to room temperature, it is extracted and layered with ethyl acetate, and the ethyl acetate phase is evaporated and separated to obtain the cyclohexanone product. Among them, the current density is 150mA / cm 2 When the reaction reaches 4 hours, the conversion rate of raw material cyclohexanol is 99%, the selectivity of cyclohexanone is 100%, the crude product is 0.9g, and the yield is 93%. By calculation, its space-time yield is 3.23kg / (m 3 h).

[0052] Example 6: Synthesis of Ni2V1 / GF catalyst and electrocatalytic oxidation of 19-hydroxymethyl-4-androstene-3,17-dione to prepare 19-formyl-4-androstene-3,17-dione

[0053] The catalytic performance of the Ni2V1 / GF catalyst prepared in Example 1 was tested, and the specific method was as follows:

[0054] The flow-type electrolytic cell used in the present invention is a Ni2V1 / GF catalyst (about 3×3 cm 2) is directly placed as the working electrode in the anode of the electrolytic cell. The volume of the anode chamber and cathode chamber of the electrolytic cell is 250mL. Add 3.0g of the substrate 19-hydroxymethyl-4-androstene-3,17-dione to the anode chamber, add 216mg of ACT, add 60mL of 0.5M sodium carbonate solution and 40mL of acetonitrile as a mixed solution, and stir evenly; add 100mL of 0.5M sodium carbonate to the cathode chamber. The anode and cathode chambers pump the solution into the reactor through a circulating pump at a flow rate of 150 mL / min. When the reaction temperature is controlled at 30℃ by a constant temperature water bath, turn on the constant current meter, set the current to 1500mA, and the voltage control range is 2-6V to start the electrocatalytic oxidation reaction. After 0.5 hours of reaction, when there is no raw material point detected by TLC and GC, turn off the constant current meter to stop the reaction, cool the electrolytic solution in the anode chamber to room temperature, extract and separate by dichloromethane, and evaporate the dichloromethane phase to obtain the benzaldehyde product. The current density is 150 mA / cm 2 When the reaction reached 0.5 hours, the conversion rate of the raw material 19-hydroxymethyl-4-androstene-3,17-dione was 99%, the selectivity of 19-formyl-4-androstene-3,17-dione was 96%, the crude product was 2.7g, and the yield was 90%. By calculation, its space-time yield was 21.01kg / (m 3 h).

[0055] Comparative Example 7:

[0056] GF directly used it for electrocatalytic oxidation of benzyl alcohol to prepare benzaldehyde. The specific method is as follows:

[0057] The flow-type electrolyzer used in the present invention is a GF catalyst (about 3×3 cm 2 ) is directly placed as the working electrode in the anode of the electrolytic cell. The volume of the anode chamber and the cathode chamber of the electrolytic cell are both 250mL. Add 1.08g of substrate benzyl alcohol, 106mg of ACT, 90mL of 0.5M sodium carbonate solution and 10mL of acetonitrile as a mixed solution in the anode chamber, and stir evenly; add 100mL of 1M sodium carbonate in the cathode chamber. The anode and cathode chambers pump the solution into the reactor through a circulation pump at a flow rate of 120mL / min. When the reaction temperature is controlled to 30°C by a constant temperature water bath, turn on the constant current meter, set the current to 500mA, and the voltage control range is 2-6V to start the electrocatalytic oxidation reaction. After 1.5 hours of reaction, when there is no raw material point detected by TLC and GC, turn off the constant current meter to stop the reaction, cool the electrolytic solution in the anode chamber to room temperature, extract and separate by dichloromethane, and evaporate and separate the dichloromethane phase to obtain the benzaldehyde product. Among them, the current density is 50mA / cm 2When the reaction reached 1.5 hours, the conversion rate of raw material benzyl alcohol was 95%, the selectivity of benzaldehyde was 92%, the crude product was 0.95g, and the yield was 87%. By calculation, its space-time yield was 1.82kg / (m 3 h).

[0058] Comparative Example 8:

[0059] The Ni2V1 / GF catalyst prepared in Example 1 was reacted by conventional kettle reactor electrolysis, and the process was as follows:

[0060] The Ni2V1 / GF catalyst (about 3×3cm 2 ) was directly used as the working electrode, 1.08 g of substrate benzyl alcohol, 106 mg of ACT, 90 mL of 0.5 M sodium carbonate solution and 10 mL of acetonitrile were added to a 100 mL autoclave reactor as a mixed solution, and stirred evenly. Graphite felt was used as the anode and platinum sheet was used as the cathode. In the comparative example, the reaction solution did not flow. Turn on the constant current meter, set the current to 50 mA, the voltage control range to 2-8 V, and start the electrocatalytic oxidation reaction for 8 hours. After the reaction, turn off the constant current meter, extract the reaction solution with dichloromethane, separate the layers, and evaporate the dichloromethane phase to obtain the benzaldehyde product. Among them, the current density is 5 mA / cm 2 GC analysis showed that when the reaction reached 8 hours, the raw material conversion rate was 50%, the selectivity of benzaldehyde was 60%, the crude product was 0.32 g, and the yield was 30%. By calculation, the space-time yield was 0.11 kg / (m 3 h).

[0061] For the reaction of preparing carbonyl intermediates by electrocatalytic oxidation of alcohol intermediates, compared with the above examples, the results are shown in Table 1.

[0062] Table 1 Electrocatalytic oxidation effect table of Examples 1-7

[0063]

[0064] From the experimental results of Examples 1-7 of the present application, it can be seen that the use of a continuous flow reactor for electrocatalytic oxidation to produce carbonyl intermediates has achieved good results. The Ni2V1 / GF catalyst used in Example 1 has a current density and space-time yield of 150 mA / cm 2 , 8.64kg / (m 3 h), its current density and space-time yield are significantly better than those of comparative example 7 (current density: 50 mA / cm 2 , space-time yield: 1.82kg / (m 3h), which indicates that the metal nickel vanadium catalyst is the active site of the electrocatalytic alcohol oxidation reaction and is very important for the reaction. When the reaction in Comparative Example 8 was carried out, a kettle reactor was used for the reaction. It can be found that the current when the kettle reactor (Comparative Example 8) was used for the reaction was very low, and the current density was only 5 mA / cm 2 , resulting in a long reaction time and poor selectivity. The yield of the final product, benzaldehyde, was only 30%, and the space-time yield was only 0.11 kg / (m 3 ·h). The continuous flow reactor was used to obtain good electrocatalytic activity, especially the continuous flow reactor of Example 1 (8.64 kg / (m 3 The space-time yield of ·h) is 78 times that of the tank reactor. The reason is that when the continuous flow reactor performs the electrocatalytic oxidation reaction, the anolyte and cathode liquid are circulating. Therefore, after the reactants are converted, they can quickly detach from the electrode surface, reducing concentration polarization, strengthening the mass transfer and heat transfer of the reaction, and promoting the electrocatalytic oxidation reaction to obtain a high space-time yield. At the same time, this reaction system can also be used for the synthesis of a variety of carbonyl intermediates and has a wide range of applicability.

[0065] The above-described embodiment is only a preferred solution of the present invention and does not limit the present invention in any form. There are other variations and modifications without exceeding the technical solution described in the claims.

Claims

1. A method for preparing carbonyl intermediates by electrocatalytic oxidation of nickel-vanadium nanosheet catalysts, characterized in that The reaction is carried out in a flow-type electrolytic cell. In the anode chamber, a nickel-vanadium nanosheet catalyst is used as a working electrode, and a reactant alcohol intermediate, a mixed solvent and a nitroxide free radical are added and stirred evenly. In the cathode chamber, a nickel plate is used as a counter electrode, and an alkaline solution is used as a cathode liquid. The anode liquid storage chamber and the cathode liquid storage chamber are respectively pumped into the flow-type reactor from the feed port through a circulation pump. At a certain temperature, a constant current meter is turned on and an electrocatalytic oxidation reaction is started. After the reaction is completed, the constant current meter is turned off. After the reaction liquid is cooled, an organic solvent is added for extraction, and the organic layer is distilled under reduced pressure to obtain a carbonyl intermediate compound. The reaction equation is as follows: ， In formula (I), R1 and R2 on the alcohol intermediate independently represent hydrogen or a hydrocarbon group, and R1 and R2 cannot be hydrogen at the same time; The nickel-vanadium nanosheet catalyst is composed of a graphite felt carrier and nickel-vanadium nanosheets supported on the graphite felt carrier. The preparation method of the nickel-vanadium nanosheet catalyst comprises the following steps: 1) According to the feed ratio, a non-precious metal nickel raw material and a vanadium raw material are respectively dissolved in water, and then urea is added, and ultrasonic dispersion is performed at room temperature for 10 minutes to obtain a solution A, wherein the non-precious metal nickel raw material is nickel nitrate, nickel chloride, nickel acetylacetonate or nickel acetate; and the vanadium raw material is vanadium chloride, ammonium metavanadate, sodium orthovanadate, sodium metavanadate or potassium metavanadate; 2) Add solution A and the graphite felt carrier in step 1) into a hydrothermal autoclave, and perform a hydrothermal reaction at 100-160° C. for 5-24 hours. After the reaction is completed, cool to room temperature, take out the graphite felt carrier, wash it with distilled water and ethanol, and then vacuum dry it to obtain a supported nickel-vanadium nanosheet catalyst.

2. The method for preparing carbonyl intermediates by electrocatalytic oxidation of nickel-vanadium nanosheet catalysts according to claim 1, characterized in that The alcohol intermediates are benzyl alcohol, cinnamyl alcohol, furfuryl alcohol, cyclohexylmethanol, n-decanol, 3-methyl-2-butene-1-ol, cyclohexanol, 1-phenylethanol, 19-hydroxymethyl-4-androstene-3,17-dione or 17β-hydroxy-19-norandrost-4-ene-3-one.

3. The method for preparing carbonyl intermediates by electrocatalytic oxidation of nickel-vanadium nanosheet catalysts according to claim 1, characterized in that The loading amount of the nickel-vanadium nanosheet catalyst on the graphite felt is 2-3 mg / cm 2 .

4. The method for preparing carbonyl intermediates by electrocatalytic oxidation of nickel-vanadium nanosheet catalysts according to claim 1, characterized in that The molar ratio of the nickel raw material to the vanadium raw material in step 1) is 1:1-5:1; the molar ratio of the metal to urea is 1:3-1:10; the hydrothermal temperature in step 2) is 120-140°C, and the hydrothermal time is 10-15 hours.

5. The method for preparing carbonyl intermediates by electrocatalytic oxidation of nickel-vanadium nanosheet catalysts according to claim 4, characterized in that The nickel raw material in step 1) is nickel nitrate, and the vanadium raw material is vanadium chloride.

6. A method for preparing carbonyl intermediates by electrocatalytic oxidation of a nickel-vanadium nanosheet catalyst according to any one of claims 1 to 5, characterized in that The volumes of the anode liquid storage chamber and the cathode liquid storage chamber are both 100-500 mL; the concentration of the reactant raw material alcohol intermediate is 10-500 mmol / L; the mixed solvent of the anode liquid storage chamber is divided into a main solvent and a secondary solvent, the main solvent is a sodium carbonate aqueous solution, and its concentration is 0.1-2.0 mol / L; the secondary solvent is one of acetonitrile, dichloromethane, tetrahydrofuran or acetone, and the volume ratio of the main solvent to the secondary solvent in the mixed solvent is 9:1-5:

5.

7. The method for preparing carbonyl intermediates by electrocatalytic oxidation of nickel-vanadium nanosheet catalysts according to claim 6, characterized in that The concentration of the alcohol intermediate as the reactant raw material is 100-500 mmol / L.

8. A method for preparing carbonyl intermediates by electrocatalytic oxidation of a nickel-vanadium nanosheet catalyst according to any one of claims 1 to 5, characterized in that When the electrocatalytic oxidation reaction is carried out, the current is 50-2000 mA, the cell voltage is 2-10 V, the reaction temperature is 25-60 ° C, and the reaction time is 1-12 hours; the organic solvent used for extraction is toluene, dichloromethane, chloroform or ethyl acetate.

9. A method for preparing carbonyl intermediates by electrocatalytic oxidation of nickel-vanadium nanosheet catalysts according to any one of claims 1 to 5, characterized in that The nitroxide free radicals are 2,2,6,6-tetramethylpiperidin-1-oxyl free radical (TEMPO), 4-acetylamino-2,2,6,6-tetramethylpiperidin-1-oxyl free radical (ACT), 4-amino-2,2,6,6-tetramethylpiperidin-1-oxyl free radical (NH2-TEMPO), and 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl free radical (HO-TEMPO), and the concentration of the nitroxide free radical in the anode reservoir is 1-20 mmol / L.

10. The method for preparing carbonyl intermediates by electrocatalytic oxidation of nickel-vanadium nanosheet catalysts according to claim 9, characterized in that The concentration of nitroxide radicals in the anode reservoir is 5-10 mmol / L.

11. A method for preparing carbonyl intermediates by electrocatalytic oxidation of nickel-vanadium nanosheet catalysts according to any one of claims 1 to 5, characterized in that The alkaline solution in the cathode storage chamber is a sodium carbonate solution with a concentration of 0.1-2.0 mol / L; the flow rate of the circulation pump is 100-200 mL / min.

12. A method for preparing carbonyl intermediates by electrocatalytic oxidation of nickel-vanadium nanosheet catalysts according to any one of claims 1 to 5, characterized in that The size of the nickel-vanadium nanosheet catalyst is 1 × 1 cm 2 - 5 × 5 cm 2 .

13. The method for preparing carbonyl intermediates by electrocatalytic oxidation of nickel-vanadium nanosheet catalysts according to claim 12, characterized in that The size of the nickel-vanadium nanosheet catalyst is 3 × 3 cm 2 .

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