Method for realizing photoelectrocatalytic synthesis of hydrazine hydrate by using trace copper ions

Abstract

The invention provides a method for realizing photoelectrocatalytic synthesis of hydrazine hydrate by using trace copper ions. According to the method, under the synergistic effect of trace copper ions and imine molecules, the photoelectric property of the photo-anode is remarkably improved, so that an efficient N-N bond coupling reaction is driven, and a corresponding azo compound is generated; and performing hydrolysis reaction to obtain hydrazine hydrate. According to the invention, photo-generated holes are used as a green oxidizing agent, so that expensive hydrogen peroxide or sodium hypochlorite which is high in environmental harm in the traditional process is avoided, and the reagent cost and environmental pollution are remarkably reduced. Meanwhile, the method has the advantages of normal-temperature and normal-pressure operation, strong reaction controllability, high safety and the like, and effectively overcomes the problems of harsh reaction conditions, more side reactions, low product selectivity and the like in the prior art. The system has excellent photoelectric performance and good amplification performance, light current output as high as 409 mA is achieved in an amplification experiment, the hydrazine hydrate generation rate reaches 6069 micromoles h <-1 >, and the high current efficiency of 93% is kept.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of photoelectrocatalysis, and particularly relates to a method for photoelectrocatalytic synthesis of hydrazine hydrate by using trace copper ions. BACKGROUND

[0002] Hydrazine hydrate is a fine chemical product with wide applications, and is mainly applied in the fields of medicine, pesticide, foaming agent, water treatment agent, rocket fuel preparation, and synthesis of analytical reagent. In industry, hydrazine hydrate is generally produced by four processes, i.e. Raschig process, urea process, ketone azine process, and hydrogen peroxide process. Among them, the Raschig process and the urea process are to synthesize hydrazine hydrate by using sodium hypochlorite to oxidize ammonia / urea. However, the reactant sodium hypochlorite has strong oxidizing property, and the product hydrazine hydrate has strong reducing property, which results in low yield of the process, and a large amount of energy needs to be consumed for evaporation and concentration of the crude hydrazine, and a large amount of salt by-product and excess ammonia / urea also need to be treated. In the 1970s, Bayer Company of Germany reformed the production process, and used ketone compounds as media to produce intermediate ketone azine by using sodium hypochlorite to oxidize ammonia and acetone, and then hydrolyzed to obtain the product hydrazine. This method uses acetone to produce intermediate ketone azine, and the ketone azine cannot be oxidized again, so there is no loss of hydrazine peroxide to nitrogen, and the product yield is greatly increased. However, the use of sodium hypochlorite still produces a large amount of salt by-product, which pollutes the environment. Although the subsequently developed hydrogen peroxide process uses hydrogen peroxide to replace sodium hypochlorite as an oxidant to avoid the formation of salt by-product, the high cost of the oxidant and the relatively inert ammonia molecule still limit its wide application.

[0003] Therefore, there is an urgent need for a green, efficient and low-cost synthesis route of hydrazine hydrate. SUMMARY

[0004] The present application provides a synthesis method of benzophenone azine, which is a photoelectrocatalytic synthesis method.

[0005] The synthesis method uses copper ions as a catalyst, uses a photoanode as a working electrode, and is carried out under light irradiation to synthesize benzophenone azine from benzophenone imine as a reaction raw material.

[0006] According to an embodiment of the present application, the concentration of copper ions is trace; preferably, the concentration of copper ions is 0-100 ppm, preferably 1-50 ppm, for example 1 ppm, 3 ppm, 5 ppm, 8 ppm, 10 ppm, 15 ppm, 18 ppm, 20 ppm, 25 ppm, 30 ppm, 35 ppm, 40 ppm, 45 ppm, 50 ppm.

[0007] According to an embodiment of the present application, the copper ions are derived from cations or corresponding compounds formed by copper elements; for example, copper nitrate.

[0008] According to embodiments of the present application, the synthesis method is an electrolysis reaction. According to embodiments of the present application, the synthesis method is an N-N coupling reaction. According to embodiments of the present application, the electrolyte of the synthesis method comprises benzophenone imine; preferably, the concentration of benzophenone imine is 0.001M-1M, for example 0.005M, 0.01M, 0.03M, 0.05M, 0.06M (60mM), 0.1M, 0.15M, 0.2M, 0.3M, 0.5M, 1M. According to embodiments of the present application, the solvent of the electrolyte is a mixed system of water-carbon tetrachloride-acetonitrile; the volume ratio is for example 5:20:75.

[0009] According to embodiments of the present application, the synthesis method uses saturated silver chloride silver as a reference electrode. According to embodiments of the present application, the synthesis method uses platinum wire or platinum-coated titanium plate as a counter electrode.

[0010] According to embodiments of the present application, the photoanode is selected from one, two or more of iron oxide photoanode, bismuth vanadate (BiVO4) photoanode, silicon anode, titanium oxide photoanode, perovskite photoanode, etc.; illustratively, the photoanode is a bismuth vanadate (BiVO4) photoanode.

[0011] According to embodiments of the present application, the light is sunlight; for example, simulated sunlight, etc.

[0012] According to embodiments of the present application, the light source of the light is a 300W xenon lamp; and is optionally further equipped with an AM1.5G filter. According to embodiments of the present application, the light intensity of the light is 100mW cm -2 .

[0013] According to embodiments of the present application, the electrolysis voltage is -0.3-3.0V AgCl / Ag , preferably -0.2-2.0V AgCl / Ag , for example -0.1V AgCl / Ag , 0V AgCl / Ag , 0.3V AgCl / Ag , 0.5V AgCl / Ag , 0.6V AgCl / Ag , 0.8V AgCl / Ag , 1.0V AgCl / Ag , 1.5V AgCl / Ag , 2.0V AgCl / Ag .

[0014] According to embodiments of the present application, the electrolysis electric quantity is 0-30C, preferably 1-25C, for example 5C, 8C, 10C, 15C, 18C, 20C, 25C, 28C.

[0015] According to an embodiment of the present application, the synthesis method comprises the following steps: taking a BiVO4 photoanode as a working electrode, saturated silver chloride as a reference electrode, platinum wire as a counter electrode, and a diphenyl ketone imine solution containing trace copper ions as an electrolyte, and performing electrolysis under sunlight to synthesize the diphenyl ketone azine.

[0016] According to an embodiment of the present application, after the synthesis reaction is completed, the reaction solution is optionally further separated and purified.

[0017] According to an embodiment of the present application, the separation and purification step specifically comprises: after the reaction is completed, the reaction mixture is extracted and washed with a solvent (such as petroleum ether) to obtain the diphenyl ketone azine. For example, the separation and purification step specifically comprises: after the reaction is completed, the reaction mixture is extracted and the solvent is evaporated; the crude product is continuously washed with petroleum ether to obtain the diphenyl ketone azine.

[0018] According to an embodiment of the present application, the extraction is performed 1-5 times, for example 3 times; and / or, the extraction solvent is a mixed solvent containing dichloromethane and water; and / or, the temperature for evaporating the solvent is 40-60°C, for example 50°C.

[0019] According to an embodiment of the present application, the solvent washing is achieved by a suction filtration device; specifically, the crude product is placed in a Buchner funnel, 5 mL of petroleum ether is added each time for washing and purification, and the process is repeated until the product appears yellowish.

[0020] According to an embodiment of the present application, the preparation method of the bismuth vanadate (BiVO4) photoanode is as follows:

[0021] (i) taking a mixed solution of bismuth nitrate, potassium iodide and p-benzoquinone as an electrodeposition solution, and electrodeposition of a bismuth oxyiodide layer (BiOI) on a fluorine-doped tin oxide coated glass (FTO glass);

[0022] (ii) adding vanadyl acetylacetonate solution to the bismuth oxyiodide layer (BiOI), and obtaining a bismuth vanadate (BiVO4) layer by high-temperature annealing (the bismuth oxyiodide layer (BiOI) is converted into the bismuth vanadate (BiVO4) by the vanadyl acetylacetonate);

[0023] (iii) removing residual vanadium oxide on the bismuth vanadate (BiVO4) layer by using an alkali solution (such as sodium hydroxide aqueous solution) to obtain the bismuth vanadate (BiVO4) photoanode.

[0024] According to an embodiment of the present application, in step (i), the concentration ratio of bismuth nitrate to potassium iodide in the electrodeposition solution is 1:1-20, preferably 1:3-18, for example 1:3, 1:5, 1:8, 1:10, 1:12, 1:15, 1:18 (for example 0.04M:0.4M).

[0025] According to embodiments of the present application, in step (i), the concentration ratio of bismuth nitrate to p-benzoquinone in the electrodeposition solution is 1:0.1-10, preferably 1:0.5-8, for example 1:0.8, 1:1, 1:2, 1:2.3, 1:3, 1:5, 1:8 (e.g. 0.028M:0.065M).

[0026] According to embodiments of the present application, in step (i), the electrodeposition solution is prepared by first preparing an aqueous solution comprising bismuth nitrate and potassium iodide, then preparing an ethanol solution of p-benzoquinone, and then mixing the aqueous solution comprising bismuth nitrate and potassium iodide with the ethanol solution of p-benzoquinone.

[0027] According to embodiments of the present application, the mixing volume ratio of the aqueous solution comprising bismuth nitrate and potassium iodide to the ethanol solution of p-benzoquinone is 1-5:1, for example 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1 (e.g. 5:2, 50mL:20mL).

[0028] According to embodiments of the present application, in step (i), the electrodeposition solution is prepared by first preparing an aqueous solution of 0.04M bismuth nitrate and 0.4M potassium iodide (50mL), then preparing an ethanol solution of 0.23M p-benzoquinone (20mL), and then mixing the two solutions.

[0029] According to embodiments of the present application, in step (i), the electrodeposition is carried out using FTO glass as the working electrode, platinum wire as the counter electrode, and saturated silver / silver chloride as the reference electrode.

[0030] According to embodiments of the present application, in step (i), the electrodeposition potential is preferably -0.1V AgCl / Ag . According to embodiments of the present application, in step (i), the electrodeposition deposition charge is preferably -0.13C cm -2 . According to embodiments of the present application, in step (ii), the vanadyl acetylacetonate is a vanadyl acetylacetonate solution dissolved in dimethyl sulfoxide. According to embodiments of the present application, in step (ii), the molar concentration of the vanadyl acetylacetonate is 0.05M-0.5M, for example 0.1M, 0.2M, 0.3M, 0.4M.

[0031] According to embodiments of the present application, in step (ii), the high-temperature annealing has a temperature of 400-500°C, preferably 450°C; and / or, the high-temperature annealing has a temperature ramping rate of 0.5-5°C min -1 , for example 2°C min -1 ; and / or, the high-temperature annealing has an annealing time of 1-3h, for example 2h.

[0032] According to an embodiment of the present application, in step (iii), the concentration of the base solution (e.g. aqueous sodium hydroxide solution) is 0.5 M to 2.0 M, for example 1.0 M. According to an embodiment of the present application, in step (iii), the time of treatment of the base solution (e.g. aqueous sodium hydroxide solution) is 5 min to 60 min, for example 15 min.

[0033] According to an embodiment of the present application, the benzophenone imine is synthesized from ammonia and benzophenone. The synthesis can be carried out by methods known in the art.

[0034] The present application also provides a method for synthesizing hydrazine hydrate or hydrazine, comprising the following steps:

[0035] (1) synthesizing benzophenone diazide by the above-mentioned method for synthesis;

[0036] (2) subjecting the benzophenone diazide to a hydrolysis reaction to obtain hydrazine hydrate or hydrazine.

[0037] According to an embodiment of the present application, the method for synthesis in step (1) is as described above.

[0038] According to an embodiment of the present application, in step (2), the hydrolysis reaction is carried out under the condition of an acid. Preferably, the acid is hydrochloric acid; preferably, the concentration of the hydrochloric acid is 1 vol% to 20 vol%, for example 10 vol%. Preferably, the hydrolysis reaction is carried out in a hydrochloric acid solution; for example, the hydrochloric acid solution is 10 vol% aqueous hydrochloric acid.

[0039] According to an embodiment of the present application, in step (2), the time of the hydrolysis reaction is 10 min to 3 h, for example 30 min.

[0040] Advantages

[0041] (1) The method of the present application first uses photo-generated hole action green oxidant, avoiding high-cost hydrogen peroxide or environmentally harmful sodium hypochlorite, greatly reducing the cost of drugs and environmental pollution.

[0042] (2) Since benzophenone can be recycled, the basic raw materials of the process are only ammonia molecules and trace amounts of copper ions, both of which are common chemical raw materials and are low in price.

[0043] (3) In addition to the synthesis of hydrazine hydrate by N-N coupling on the anode side, high-purity hydrogen gas can also be generated and collected on the cathode side at the same time, realizing the conversion of solar energy to hydrogen energy and further improving the overall process added value.

[0044] (4) Since the oxidant comes from the photoanode, the reaction process can be controlled by whether light is added and whether electricity is added, and the coupling process is operated at normal temperature and pressure without high temperature and strong exothermic links, so that the device is more simplified, the operation is more convenient, and the risk of material spraying caused by reaction out of control is avoided.

[0045] The synthetic method of the application provides a new generation of green, efficient and low-cost synthetic route of hydrazine hydrate, which has good industrialization prospect. In the future, through pilot scale-up, catalyst optimization and system integration, the application in the field of green manufacturing of fine chemicals can be promoted.

[0046] The synthetic method of the application provides a novel photoelectrochemical synthesis route of hydrazine hydrate. Diphenyl ketone imine obtained by dehydration condensation of diphenyl ketone and ammonia molecules is used as an initial substrate, and under the action of trace copper ions and photo-generated holes, diphenyl ketone azine is generated by oxidative coupling of diphenyl ketone imine, and finally hydrolysis is carried out to obtain hydrazine hydrate. The by-product diphenyl ketone can be regenerated to imine molecules by condensation with ammonia molecules again, so that the raw materials can be recycled. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 Structural characterization of the BiVO4 photoanode prepared in Example 1. Figure 1 a: X-ray diffraction pattern of the BiVO4 photoanode; Figure 1 b: UV-visible absorption spectrum of the BiVO4 photoanode; Figure 1 c: Surface morphology characterization of the BiVO4 photoanode; Figure 1 d: Surface morphology characterization (cross-sectional view) of the BiVO4 photoanode; Figure 1 e: Lattice fringe spacing in the transmission electron microscopy image; Figure 1 f: Distribution of Bi, V and O elements observed by energy dispersive spectrometer.

[0048] Figure 2 Linear sweep voltammetry curve of the BiVO4 photoanode in Example 2. H2O represents 0.3M tetraethylammonium tetrafluoroborate (TEABF4, as electrolyte) water / tetrachloromethane / acetonitrile mixed solvent. BI represents that the electrolyte is a solution containing 0.2M diphenyl ketone imine; the solvent is a water / tetrachloromethane / acetonitrile mixed solvent. BI+Cu represents that the electrolyte is a solution containing 0.2M diphenyl ketone imine and 10ppm copper ions; the solvent is a water / tetrachloromethane / acetonitrile mixed solvent. The volume ratio of the water / tetrachloromethane / acetonitrile mixed solvent is 5:20:75.

[0049] Figure 3Kinetics curve (conversion curve of benzophenone imine by BiVO4 photoanode with copper ion assistance) in Example 3. BI represents benzophenone imine, BA represents benzophenone hydrazine, BP represents by-product benzophenone, and Total represents the sum of the three substances. PEC: photoelectrocatalytic reactor. BIOR: bioreactor.

[0050] Figure 4 Amplification experiment in Example 4. Figure 4 a: flow-type electrolytic cell, respectively including stainless steel current collector 1, polytetrafluoroethylene electrolytic cell 2, platinum-coated titanium plate (Pt@Ti) 3, polytetrafluoroethylene separator 4, BiVO4 photoanode 5, and photoanode fixer 6; Figure 4 b: current difference at different cell voltages; Figure 4 c: photocurrent during electrolysis experiment; Figure 4 d: nuclear magnetic resonance hydrogen spectrum of the product; Figure 4 e: nuclear magnetic resonance carbon spectrum of the product.

[0051] Figure 5 Hydrolysis experiment in Example 5. Figure 5 a: ultraviolet-visible absorption spectrum of a series of hydrazine standard solutions under the action of chromogenic agent; Figure 5 b: standard curve at 455 nm; Figure 5 c: ultraviolet-visible absorption spectrum of reaction solution after hydrolysis for different time under the action of chromogenic agent; Figure 5 d: high performance liquid chromatogram of reaction solution after hydrolysis for different time; Figure 5 e: concentration-time curve of each substance during hydrolysis of benzophenone imine; Figure 5 f: hydrolysis equation. BA represents benzophenone hydrazine, and BP represents by-product benzophenone. DETAILED DESCRIPTION

[0052] The technical solutions of the present application will be further described in detail below in combination with specific examples. It should be understood that the following examples are only illustratively described and explained, and should not be interpreted as limiting the scope of protection of the present application. Any technology realized based on the above description of the present application is covered within the scope of protection intended by the present application.

[0053] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0054] Example 1

[0055] 1.1 Weigh 3.320 g of potassium iodide and place it in 50 mL of H2O. Adjust the pH to 1.7 with dilute nitric acid. Then add 0.9701 g of bismuth nitrate pentahydrate to prepare a 0.04 M bismuth nitrate and 0.4 M potassium iodide mixed solution A.

[0056] 1.2 Weigh 0.4972 g of p-benzoquinone into 20 mL of ethanol to prepare a 0.23 M p-benzoquinone solution B; slowly pour solution B into solution A and stir well to prepare the electrodeposition solution.

[0057] 1.3 FTO glass (fluorine-doped tin oxide coated glass) was ultrasonically cleaned in acetone and methanol for 30 min each, and then dried using nitrogen gas. The cleaned FTO glass was used as the working electrode, platinum wire as the counter electrode, and saturated silver / silver chloride as the reference electrode, at -0.1 V. AgCl / Ag Electrodeposition was performed using an electrodeposition solution with a deposition charge of -0.13 C cm⁻¹. -2 After rinsing with deionized water and drying with nitrogen, a reddish-brown BiOI electrode was obtained.

[0058] 1.4 Weigh 0.5353 g of vanadium acetylacetonate and prepare a 0.2 M dimethyl sulfoxide solution of vanadium acetylacetonate using dimethyl sulfoxide as a solvent.

[0059] 1.5 Add a solution of vanadium acetylacetonate in dimethyl sulfoxide dropwise to the BiOI electrode until it covers the entire electrode (0.16 mL / cm²). -2 Then it was placed in a muffle furnace and heated at 2°C for 1 minute. -1 The temperature was increased to 450℃, annealed at 450℃ for 2 hours, and finally naturally cooled to room temperature to obtain a BiVO4 photoanode with residual vanadium oxide on the surface.

[0060] 1.6 Residual vanadium oxide on the surface of the BiVO4 photoanode was removed using a 1.0M sodium hydroxide aqueous solution. Finally, it was rinsed with deionized water and dried with nitrogen to obtain the final BiVO4 photoanode for use.

[0061] Figure 1 Structural characterization of the BiVO4 photoanode prepared in Example 1. From the X-ray diffraction pattern ( Figure 1 As can be seen from a), the obtained product has high crystallinity, consistent with the PDF standard card (PDF#14-0688). From the ultraviolet-visible absorption spectrum (…), Figure 1 (b) It can be observed that the prepared BiVO4 photoanode exhibits good visible light absorption, with an absorption band edge of approximately 510 nm and a corresponding band gap of 2.4 eV. The surface morphology is characterized by scanning electron microscopy images (…). Figure 1 c- Figure 1 As shown in f), the BiVO4 photoanode exhibits a nanorod shape, and its cross-sectional image reveals that the BiVO4 coating is approximately 2 μm thick. The lattice fringe spacing in the transmission electron microscope image conforms to the (011) and (110) plane spacing of the monoclinic BiVO4 crystal phase. The accompanying energy dispersive spectroscopy (EDS) shows a uniform distribution of Bi, V, and O elements. These results demonstrate the successful preparation of the BiVO4 photoanode.

[0062] Example 2

[0063] Photoelectrochemical experiment: This test was conducted in a standard three-electrode system. The BiVO4 photoanode prepared in Example 1 was used as the working electrode, a platinum wire as the counter electrode, and saturated silver chloride as the reference electrode. The light source was a 300W xenon lamp equipped with an AM 1.5G filter. The light intensity was measured to be 100 mW cm⁻¹ using a photometer. -2 The test method used was linear scanning voltammetry, with a scan range of -0.5 to 1.0 V. AgCl / Ag The scan rate is 50 mV / s. -1 .

[0064] Figure 2 The figure shows the linear sweep voltammetry curve of the BiVO4 photoanode prepared in Example 1. In the figure, H2O represents the test conducted in a mixed solvent of water / carbon tetrachloride / acetonitrile (0.3M tetraethylammonium tetrafluoroborate, TEABF4, as the electrolyte), with a solvent volume ratio of 5:20:75. BI represents the test conducted in an electrolyte containing 0.2M benzophenone imine, and BI+Cu represents the test conducted in an electrolyte containing 0.2M benzophenone imine and 10 ppm copper ions. As can be seen from the figure, the photocurrent of the BiVO4 photoanode gradually increases with increasing potential. The addition of benzophenone imine leads to a voltage of 0.6V. AgCl / Ag Photocurrent from 1.1 mA cm⁻¹ -2 Increased to 2.3 mA cm -2 The combined presence of copper ions and benzophenone imine further increases the photocurrent, reaching 5.9 mA cm⁻¹. -2 .

[0065] Example 3

[0066] Photoelectrolysis experiment: The test system was the same as in Example 2, except that the concentration of benzophenone imine in the electrolyte was reduced to 60 mM (copper ions 10 ppm), and the test method was changed to chronoamperometry, with the applied voltage set to 0.6 V. AgCl / Ag The electrolysis charge was controlled between 0 and 30C. After reaching the target electrolysis charge, the liquid products were analyzed by high performance liquid chromatography. It was found that the yield of benzophenone azo was highest when the electrolysis charge was 25C.

[0067] Figure 3The conversion curve of benzophenone imine to benzophenone azine with BiVO4 photoanode under copper ion assistance. From the graph, it can be seen that the concentration of benzophenone imine (denoted as BI in the graph) gradually decreased with the electrolysis charge, while the target product benzophenone azine (denoted as BA in the graph) was gradually generated. When the electrolysis charge exceeds 25C, the concentration of benzophenone imine continues to decrease, while the concentration of benzophenone azine no longer increases but decreases, and the byproduct benzophenone (denoted as BP in the graph) begins to appear. Therefore, the optimal electrolysis charge is set to 25C, at which the yield of benzophenone azine reaches 82.7±2.7%.

[0068] Example 4

[0069] Scale-up experiment: BiVO4 photoanode was scaled up from the original 2 cm 2 to 70 cm 2 , and a flow-type electrolytic cell was used for the scale-up experiment. The experiment used a two-electrode system, with a 70 cm 2 BiVO4 photoanode as the working electrode and a platinum-coated titanium plate as the counter electrode. The electrolyte solution was a mixed solution containing 0.2 M benzophenone imine and 10 ppm copper ions, with a volume ratio of 5:20:75 H2O / CCl4 / MeCN as the solvent. According to the voltammetry curve, the electrolysis potential was selected as 0.8 V, the electrolysis time was 150 min, and the flow rate was set at 100 mL min -1 . Light and voltage were applied to the reaction device to start the photoelectrolysis, and samples were taken every 10 min for liquid product analysis. After the electrolysis was completed, the reaction solution was extracted with dichloromethane and water, and the solvent was removed by rotary evaporation. Subsequently, the crude product was purified by continuous washing with petroleum ether to obtain pure benzophenone azine.

[0070] Figure 4 Device diagram and photoelectrolysis curve for scale-up experiment. Figure 4 a is

[0071] Flow-type electrolytic cell used in the experiment. From Figure 4 b, it can be seen that when the cell voltage is set to 0.8 V, the difference between the light state and dark state current (i.e., the photocurrent) is the largest, reaching 409 mA. Therefore, 0.8 V was selected as the cell voltage in the subsequent electrolysis experiment. In the entire electrolysis experiment Figure 4 c), the photocurrent remained at about 315 mA, the production rate reached 6069 μmol h -1 , and the faraday efficiency (or current efficiency) of benzophenone azine remained at 93%, demonstrating the high activity and scalability of the system. After 2.5 h of electrolysis, the target product benzophenone azine (pale yellow solid) was purified by recrystallization, and the hydrogen / carbon nuclear magnetic resonance spectrum Figure 4 d, Figure 4e) The structure was verified and finally 4.8809 g of pure product was obtained.

[0072] Example 5

[0073] Hydrolysis experiment: To prepare hydrazine hydrate from benzophenone hydrazine, the yellowish solid collected in Example 4 was dissolved in acetonitrile containing 10 vol% HC1 and stirred at room temperature. The concentration of hydrazine hydrate was determined by colorimetry using a commercial color reagent (Merck, 1.09711.0001) and other hydrolysis products were tested by HPLC.

[0074] Figure 5 a, Figure 5 b is the UV-Vis absorption spectrum of a series of hydrazine standard solutions in the presence of color reagent and the standard curve at 455 nm. Figure 5 c is the UV-Vis absorption spectrum of the reaction solution after hydrolysis for different time in the presence of color reagent. Figure 5 d is the HPLC of the reaction solution after hydrolysis for different time. Figure 5 e is the concentration-time curve of each substance during the hydrolysis of benzophenone imine. With the increase of hydrolysis time, benzophenone imine (BA) is gradually consumed, while the concentration of hydrazine and benzophenone (BP) increases accordingly. After 60 min, the concentration of benzophenone imine decreases from 9.4 mM to 0.1 mM, while the concentration of hydrazine increases from 0 to 9.3 mM, accompanied by the formation of 18.6 mM of benzophenone. These results confirm the hydrolysis equation (f) and achieve the complete conversion of benzophenone imine to hydrazine hydrate (yield > 99%). Figure 5 f).

[0075] The above describes the embodiments of the present application. However, the present application is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for synthesizing benzophenone azine, the method being a photoelectrocatalytic synthesis method; the method using copper ions as catalysts, using a photoanode as working electrode, and being carried out under light irradiation, and using benzophenone imine as raw material to synthesize benzophenone azine. The concentration of the copper ions is trace; 2. The method of synthesis of claim 1, wherein, Preferably, the concentration of the copper ions is 1-100 ppm; Preferably, the copper ions are derived from cations or corresponding compounds formed by copper elements; for example, copper nitrate. The electrolyte of the synthesis method contains benzophenone imine; 3. The method of synthesis according to claim 1 or 2, wherein, Preferably, the concentration of the benzophenone imine is 0.001 M-1 M; Preferably, the solvent of the electrolyte is a mixed system of water-carbon tetrachloride-acetonitrile. The synthesis method uses saturated silver chloride as reference electrode; 4. The method of synthesis according to any one of claims 1 to 3, wherein, Preferably, the synthesis method uses a platinum wire or a titanium plate plated with platinum as counter electrode; Preferably, the photoanode is selected from one, two or more of iron oxide photoanode, bismuth vanadate photoanode, silicon anode, titanium oxide photoanode, perovskite photoanode, etc. Preferably, the light is simulated sunlight. Preferably, the electrolytic charge is 1-30 C. Preferably, the electrolysis voltage is -0.3 to 3.0 V AgCl / Ag ; The synthesis method comprises the following steps: using a BiVO4 photoanode as working electrode, using saturated silver chloride as reference electrode, using a platinum wire as counter electrode, using a benzophenone imine solution containing trace copper ions as electrolyte, and carrying out electrolysis under sunlight irradiation to synthesize benzophenone azine.

5. The method of synthesis according to any one of claims 1-4, wherein, Preferably, after the synthesis reaction is completed, the reaction solution is optionally further separated and purified; preferably, the separation and purification step specifically comprises: after the reaction is completed, the reaction mixture is extracted and washed with solvent, thereby obtaining benzophenone azine. The preparation method of the bismuth vanadate photoanode is as follows:

6. The method of synthesis according to any one of claims 1-5, wherein, (i) using a mixed solution of bismuth nitrate, potassium iodide and p-benzoquinone as electrodeposition solution, electrodeposition of bismuth oxyiodide layer on fluorine-doped tin oxide coated glass; (ii) adding vanadyl acetylacetonate solution to the bismuth oxyiodide layer, and obtaining bismuth vanadate layer by high-temperature annealing method; (iii) removing residual vanadium oxide on the bismuth vanadate layer by alkali solution, thereby obtaining the bismuth vanadate photoanode. In step (i), the concentration ratio of bismuth nitrate to potassium iodide in the electrodeposition solution is 1:1-20, preferably 1:3-18; 7. The method of synthesis of claim 6, wherein, Preferably, in step (i), the concentration ratio of bismuth nitrate to p-benzoquinone in the electrodeposition solution is 1:0.1-10, preferably 1:0.5-8; Preferably, in step (i), the electrodeposition solution is prepared as follows: first, prepare an aqueous solution containing bismuth nitrate and potassium iodide, then prepare an ethanol solution of p-benzoquinone, and then mix the aqueous solution containing bismuth nitrate and potassium iodide with the ethanol solution of p-benzoquinone; Preferably, in step (i), FTO glass is used as working electrode, a platinum wire is used as counter electrode, and saturated silver / chloride silver is used as reference electrode for electrodeposition; Preferably, in step (ii), the vanadyl acetylacetonate is a vanadyl acetylacetonate solution dissolved in dimethyl sulfoxide. Preferably, in step (ii), the molar concentration of the vanadyl acetylacetonate is 0.05 M-0.5 M; Preferably, in step (iii), the concentration of the alkali solution is 0.5 M-2.0 M; Preferably, in step (ii), the temperature ramp rate of the high temperature anneal is 0.5-5°C min -1 ; and / or, the temperature of the high temperature anneal is 400-500°C; and / or, the anneal time of the high temperature anneal is 1-3h; ​ Preferably, in step (iii), the time of the treatment with the alkaline solution is comprised between 5 min and 60 min. Preferably, the benzophenone imine is synthesized from ammonia and benzophenone.

8. A process for the synthesis of hydrazine hydrate or hydrazine, comprising the following steps: (1) synthesis of benzophenone hydrazide according to the process of any one of claims 1-7; (2) hydrolysis of benzophenone hydrazide to obtain hydrazine hydrate or hydrazine.

9. The method of synthesis of claim 8, wherein, In step (2), the hydrolysis is carried out in the presence of an acid; preferably, the hydrolysis time is comprised between 10 min and 3 h.

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