A method for electrochemically selective debromination to prepare acetoacetanilide

Abstract

The present application relates to the technical field of aniline preparation, in particular to a method for electrochemically selectively debrominating to prepare acetoacethylaniline. The method comprises the following steps: (1) using sulfuric acid aqueous solution as an anode liquid, using organic alkali aqueous solution as a cathode liquid, putting bromoacetoacethylaniline as a reaction raw material into the cathode liquid, mixing uniformly, electrolyzing to debrominate, and obtaining a suspension; (2) adjusting the pH value of the suspension to be acidic, separating to obtain a solid and an acid liquid, and the white filter cake obtained after the solid is washed with water and dried is acetoacethylaniline; (3) performing electrodialysis dissociation on the acid liquid obtained in step (2) to obtain organic alkali and recovered acid liquid respectively. The present application uses bromoacetoacethylaniline as a raw material to prepare acetoacethylaniline, is environmentally friendly and convenient to use, and has value from the perspective of green chemistry and economy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aniline preparation, and particularly relates to a method for electrochemically selectively debrominating to prepare acetoacetanilide. BACKGROUND

[0002] Acetoacetanilide is an important organic intermediate and has a wide range of application scenarios in the chemical industry, such as being used as a dye or organic pigment, being used for synthesizing pesticides or fungicides, or being used as a pharmaceutical intermediate.

[0003] In the method provided by the prior art, acetoacetanilide is mostly prepared by acylation reaction of divinyl ketone and aniline. For example, patent CN103224455A discloses a preparation method of N-acetoacetanilide. The specific steps of the method include: adding N-acetoacetanilide seed crystals and an emulsifier into stirring deionized water at 0-10 DEG C for reaction, then adding divinyl ketone and aniline dropwise at the same time under certain temperature control, and after reaction and heat preservation, cooling to 0 DEG C, filtering, and drying to obtain N-acetoacetanilide.

[0004] CN104356018A discloses a synthesis and crystallization method of N-acetoacetanilide compounds. Under an oxygen-free condition, aniline compounds and divinyl ketone are subjected to diacetylation reaction in an organic solvent. The aniline compounds are selected from aniline, 2,4-dimethylaniline, or o-methoxyaniline, o-toluidine, or o-chloroaniline. After the reaction is completed, the material is subjected to gradient cooling by passing a condensing medium into the cooling pipe of the reaction kettle, so as to obtain the crystallization of the N-acetoacetanilide compounds.

[0005] CN116102445A discloses a method for reducing impurities in N-acetoacetanilide. The method includes adding low-carbon alcohol dropwise into raw material divinyl ketone to generate alcoholysis reaction, adding divinyl ketone and aniline into ethanol solution in a proportion to generate acylation reaction and generate N-acetoacetanilide, starting heat preservation after the dropwise addition is completed, then cooling and crystallizing, and centrifuging and drying to obtain N-acetoacetanilide finished product.

[0006] It can be seen that the above-mentioned traditional methods for preparing acetoacetanilide all use divinyl ketone and aniline as raw materials to prepare acetoacetanilide. Such methods have the following disadvantages: first, the raw material divinyl ketone is prone to polymerization reaction, is difficult to store, and has a strong irritating odor. From the perspectives of environmental protection and operability, using divinyl ketone as a raw material has insurmountable disadvantages. SUMMARY

[0007] The present application aims to overcome the drawbacks of the prior art traditional process using diacetylphenylamine as raw material, and provides a method for preparing acetylacetanilide by electrochemical selective debromination, which uses bromoacetylacetanilide as raw material and prepares acetylacetanilide by electrochemical debromination.

[0008] The method breaks the shackles of conventional processes and conventional raw materials, and is based on using waste bromoacetylacetanilide as raw material to design a new process route to prepare acetylacetanilide. Bromoacetylacetanilide has two bromine sites and is prone to isomerization. If the mixture is not post-treated, it can only be disposed of as hazardous waste, increasing industrial costs. Therefore, the present application uses bromoacetylacetanilide as raw material to prepare acetylacetanilide, which is environmentally friendly and convenient to use, and has value from the perspective of green chemistry and economy.

[0009] However, during the research process, it was found that the technical difficulty of the method lies in the fact that the raw material bromoacetylacetanilide has two carbonyl groups which are easily destroyed. Therefore, in the process of preparing acetylacetanilide from bromoacetylacetanilide, how to effectively protect the two carbonyl groups of bromoacetylacetanilide becomes a key technical point.

[0010] Therefore, the present application adopts the following technical scheme:

[0011] A method for preparing acetylacetanilide by electrochemical selective debromination, comprising the following steps:

[0012] (1) Using a sulfuric acid aqueous solution as an anode liquid and an organic base aqueous solution as a cathode liquid, mixing bromoacetylacetanilide as a reaction raw material into the cathode liquid, electrolytic debromination, and obtaining a suspension.

[0013] Among them, the electrolysis voltage is 2V-10V, the electrolysis temperature is 0℃-50℃, the electrolysis time is 1-4h, and the current density is 0.5A / dm 2 .

[0014] The size of the electrolysis voltage directly affects the electron transfer rate of the electrolysis process and the generation of reaction intermediates. When the voltage is moderate, the electron transfer efficiency is high, thereby improving the reaction rate. However, too low a voltage can result in low electron transfer efficiency, thereby resulting in low reaction efficiency. Therefore, a suitable electrolysis voltage should be selected.

[0015] If the voltage of the electrolytic debromination is lower than 2V, the time required for electrolysis will exceed 48h, and the production efficiency is low. However, if it is higher than 10V, the system will be chaotic.

[0016] If the electrolysis temperature is lower than 0℃, the time required for electrolysis will exceed 24h, which is not conducive to efficient reaction. If the temperature is higher than 50℃, the electrode life will be affected.

[0017] The electrolysis time is less than 1 h, the raw material reaction is incomplete, if higher than 4 h, the reaction conversion rate is low, and many impurities are generated in the system.

[0018] (2) The pH value of the suspension is adjusted to be acidic, solid and acid liquid are separated, and the white filter cake obtained after water washing and drying of the solid is acetoacetanilide.

[0019] (3) The acid liquid obtained in step (2) is subjected to electrodialysis dissociation to obtain organic base and recovered acid liquid respectively; the organic base is returned to step (1) as the cathode liquid raw material, and the recovered acid liquid is returned to step (2) to adjust the pH value of the suspension.

[0020] The power supply voltage of the electrodialysis dissociation is 5-50 V, the membrane pair voltage is 0-4.8 V, and the current density is 200-600 A / m 2 ; the electrodialysis time is 0.5-1.5 h. The power supply voltage = membrane pair voltage x logarithm + electrode plate voltage.

[0021] If the power supply voltage is lower than 5 V, the reaction time is prolonged, and the raw material conversion is incomplete; if higher than 50 V, the service life of the electrodialysis membrane is affected.

[0022] If the electrodialysis time is less than 0.5 h, the raw material reaction is incomplete; and if more than 1.5 h, the electrodialysis reaction has been completed, and the electricity is wasted.

[0023] In the application, the bromoacetoacetanilide in step (1) of the method for preparing acetoacetanilide by electrochemical selective debromination is at least one of 2-bromo-3-oxo-N-phenylbutyramide and 4-bromo-3-oxo-N-phenylbutyramide.

[0024] In the application, the electrolysis reaction temperature in step (1) of the method for preparing acetoacetanilide by electrochemical selective debromination is 5-50 DEG C, and the optimal reaction temperature is 25 DEG C; the electrolysis time is 2 h.

[0025] In the application, the cathode for electrolysis in step (1) of the method for preparing acetoacetanilide by electrochemical selective debromination is a copper electrode; and the anode for electrolysis is a graphdiyne electrode. The cathode of the electrode system in the application is a graphdiyne electrode, which is aimed at the field of debromination.

[0026] In the application, the organic base in step (1) of the method for preparing acetoacetanilide by electrochemical selective debromination is at least one of triethylamine, trimethylamine, tripropylamine or tributylamine. The organic base in the application is defined as the common knowledge in the field, that is, an organic compound with which the system pH is greater than 7 after being mixed with water. The use of the organic base is helpful to electrolysis and is conducive to the selectivity of the electrolysis reaction; when inorganic electrolyte is used, the selectivity is poor.

[0027] In the present application, the pH value of the anolyte in step (1) is 1-3, the pH value of the catholyte is 9-11; the concentration of bromoacetoacetanilide in the catholyte is 0.05 mol / L-2 mol / L.

[0028] Preferably, the pH value of the anolyte in step (1) is 1.5-2.5, the pH value of the catholyte is 9.5-10.5; the concentration of bromoacetoacetanilide in the catholyte is 0.5 mol / L-1 mol / L.

[0029] In the present application, the pH value of the suspension in step (2) is adjusted to 1-5; the solid and the acid liquid are obtained by cooling and filtration separation. Dilute sulfuric acid is used to adjust the pH value of the suspension.

[0030] In the present application, the power voltage for the electrodialysis in step (3) is 22 V, and the membrane voltage is 2.0 V.

[0031] In the present application, the acid liquid in step (3) is first adjusted to pH 10 or more by using an organic base, and the solid precipitate is removed by suction filtration; the filtrate is subjected to ion adsorption to remove organic matter and heavy metal ions, and then the pH value of the filtrate is adjusted to neutral for electrodialysis. Sulfuric acid is used to adjust the pH value to neutral.

[0032] Compared with the prior art, the present application has the following advantages:

[0033] The present application does not use divinyl ketone as a raw material, avoiding the storage and odor problems of divinyl ketone, and also avoiding the disadvantages of polymers. The reaction process in the method of the present application is simple, does not use hydrogen, and is safer; no by-product benzoic acid is produced, the produced liquid alkali is recycled by combining electrolysis and electrodialysis, no waste water is discharged, thereby realizing the coordinated development of economic benefits and environmental benefits, and the preparation method has high yield and high purity of the obtained product, and has good application value.

[0034] The present application avoids the production of by-products by electrochemical selective debromination, compared with the method of recovering acetoacetanilide by hydrogenation debromination, no hydrogen is used, the reaction is safer, and the present application does not discharge waste water. The present application has reasonable design, simple process, and mild reaction conditions, and provides a new idea for the synthesis method of acetoacetanilide. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The HPLC spectrum of the product acetoacetanilide standard sample.

[0036] Figure 2 HPLC chromatogram of 4-bromo-3-oxo-N-phenylbutanamide as a raw material.

[0037] Figure 3 HPLC chromatogram of the reaction solution of Example 1.

[0038] Figure 4 HPLC chromatogram of the reaction solution of Example 1.

[0039] Figure 5 HPLC chromatogram of the reaction solution of Example 2.

[0040] Figure 6 HPLC chromatogram of the reaction solution of Comparative Example 1.

[0041] Figure 7 HPLC chromatogram of the reaction solution of Comparative Example 4.

[0042] Figure 8 HPLC chromatogram of the reaction solution of Comparative Example 5.

[0043] Figure 9 HPLC chromatogram of the reaction solution of Comparative Example 7. DETAILED DESCRIPTION

[0044] The present application is further illustrated below in conjunction with the accompanying drawings and examples.

[0045] In the examples and comparative examples provided by the present application, each raw material and experimental equipment is a commonly used existing commercially available raw material and experimental equipment in the art, and the specific sources are not described here.

[0046] Example 1

[0047] The method for electrochemically selectively debrominating to prepare acetoacetylaniline includes the following steps:

[0048] (1) In the H-shaped electrolytic cell, a copper electrode with a size of 3×3×0.1 cm is used as the cathode, and a graphdiyne electrode with the same apparent size is used as the anode (3×3×0.1 cm).

[0049] A 1L aqueous solution of sulfuric acid with a concentration of 0.5 mol / L is used as the anolyte, and the pH is 1; a 1L aqueous solution of triethylamine with a concentration of 1 mol / L is used as the catholyte, and the pH is 10; 1L of a 4-bromo-3-oxo-N-phenylbutanamide aqueous solution with a concentration of 0.2 mol / L is used as the reaction raw material and is added to the catholyte and mixed uniformly by a magnetic pump.

[0050] The electrolytic cell is subjected to electrolytic debromination by direct current, wherein the electrolysis voltage is 10V, the electrolysis temperature is 25℃, the electrolysis time is 2h, and the current density is 0.5A / dm 2A suspension was obtained.

[0051] The reaction formula for preparing acetoacetanilide by electrolytic debromination of 4-bromo-3-oxo-N-phenylbutyramide is as follows:

[0052] .

[0053] (2) The pH value of the suspension obtained in step (1) was adjusted to 1 using 10wt% dilute sulfuric acid. Then the suspension was cooled and filtered to separate the solid and acid solution.

[0054] The obtained solid was washed with water and dried to obtain a white filter cake, namely 35.4g of acetylacetanilide.

[0055] like Figure 2 As shown, t R =21.8 min is the peak of 4-bromo-3-oxo-N-phenylbutyramide.

[0056] like Figure 1 As shown, t R =14.3 min is the peak of acetoacetanilide.

[0057] pass Figure 3 It can be seen that t R The peak of acetoacetanilide was observed at 14.1 min. The purity of the obtained acetoacetanilide was 99.6%, and the yield was 99.5%.

[0058] (3) First, adjust the pH of the acid solution obtained in step (2) to 10 using 0.5 mol of triethylamine, and remove the solid precipitate in the waste liquid by filtration; then, pass the filtrate through an ion adsorption chelating resin to remove residual organic matter and heavy metal ions, and then add 5% sulfuric acid solution to the filtrate to adjust the pH to 2.

[0059] Assemble the electrodialysis unit, start the magnetic pump, and add 1L of neutral filtrate, 0.3L of pure water, 0.3L of pure water, and 1L of 1% triethylamine aqueous solution to the salt chamber, acid chamber, alkali chamber, and electrode chamber of the bipolar membrane electrodialysis system, respectively.

[0060] At a power supply voltage of 50V, a membrane voltage of 4.8V, and a current density of 400A / m², the membrane voltage was maintained. 2 Under these conditions, the process was completed after 0.5 hours. The alkali chamber produced 1.45 mol of triethylamine (97% recovery rate), and the acid chamber effluent contained 5.18% hydrobromic acid. The hydrobromic acid in this case was produced by the combination of removed bromide ions and hydrogen ions.

[0061] The organic base is returned to step (1) as a cathode liquid raw material, and the recovered acid is returned to step (2) to adjust the pH value of the suspension.

[0062] Example 2

[0063] The specific steps of the electrochemical selective debromination method for preparing acetoacetanilide are as follows:

[0064] (1) In an H-type electrolytic cell, a copper electrode is used as the cathode (3×3×0.1cm) and a graphdiyne electrode of the same apparent size is used as the anode (3×3×0.1cm).

[0065] 1 L of 0.5 mol / L sulfuric acid aqueous solution was used as the anolyte, pH=1; 1 L of 1 mol / L triethylamine aqueous solution was used as the catholyte, pH=10; 1 L of 0.2 mol / L bromoacetanilide aqueous solution was added to the catholyte as a reactant and mixed using a magnetic pump. This bromoacetanilide was prepared by mixing 4-bromo-3-oxo-N-phenylbutyramide and 2-bromo-3-oxo-N-phenylbutyramide in a 1:1 mass ratio.

[0066] Direct current was applied to the electrolytic cell for electrolytic debromination. The electrolysis voltage was 3V, the electrolysis temperature was 5℃, the electrolysis time was 4h, and the current density was 0.5A / dm³. 2 A suspension was obtained.

[0067] The reaction formula (1) for preparing acetoacetanilide by electrolytic debromination of 4-bromo-3-oxo-N-phenylbutyramide is as follows:

[0068] (1).

[0069] The reaction formula (2) for preparing acetoacetanilide by electrolytic debromination of 2-bromo-3-oxo-N-phenylbutyramide is as follows:

[0070] (2).

[0071] (2) The pH value of the suspension obtained in step (1) was adjusted to 1 using 10wt% dilute sulfuric acid. Then the suspension was cooled and filtered to separate the solid and acid solution.

[0072] The obtained solid was washed with water and dried to obtain a white filter cake, namely 35.5g of acetylacetanilide.

[0073] pass Figure 5 It can be seen that t R The peak of acetoacetanilide was observed at 14.2 min. The purity of the obtained acetoacetanilide was 99.0%, and the yield was 99.6%.

[0074] (3) The acid solution obtained in step (2) is adjusted to pH=10 by using 0.5 mol of triethylamine, and the solid precipitate in the waste liquid is removed by suction filtration; then the filtrate is subjected to ion adsorption by ion adsorption chelating resin, and after removing the residual organic substances and heavy metal ions, 5% sulfuric acid solution is added to the filtrate to adjust pH=2.

[0075] The electrodialyzer is assembled, the magnetic pump is started, and 1L of neutral filtrate, 0.3L of pure water, 0.3L of pure water, and 1L of 1% triethylamine aqueous solution are added to the salt chamber, acid chamber, base chamber, and electrode chamber of the bipolar membrane electrodialysis system, respectively.

[0076] Under the conditions of a power voltage of 48V, a membrane pair voltage of 4V, and a current density of 400A / m 2 , the operation is ended after 40min, and the base chamber produces 1.43mol of organic base triethylamine (recovery rate 95%); the acid chamber produces 4.91% of hydrobromic acid.

[0077] The organic base is returned to step (1) as the cathode liquid raw material, and the recovered acid solution is returned to step (2) for adjusting the pH value of the suspension.

[0078] Example 3

[0079] The method for preparing acetoacetanilide by electrochemical selective debromination, and the specific steps are as follows:

[0080] (1) In the H-shaped electrolytic cell, a copper electrode (3×3×0.1cm) is used as the cathode, and a graphite electrode (3×3×0.1cm) with the same apparent size is used as the anode.

[0081] 1L of 0.5mol / L sulfuric acid aqueous solution is used as the anode liquid, and the pH value is 1; 1L of 1mol / L triethylamine aqueous solution is used as the cathode liquid, and the pH value is 10; 1L of 0.2mol / L 2-bromo-3-oxo-N-phenylbutyramide aqueous solution is used as the reaction raw material and is mixed uniformly by using a magnetic pump.

[0082] The electrolytic debromination is carried out by applying direct current to the electrolytic cell, wherein the electrolytic voltage is 6V, the electrolytic temperature is 25℃, the electrolytic time is 2h, and the current density is 0.5A / dm 2 ; and a suspension is obtained.

[0083] The reaction formula of the raw material 2-bromo-3-oxo-N-phenylbutyramide for preparing acetoacetanilide by electrolytic debromination is as follows:

[0084] .

[0085] (2) The pH value of the suspension obtained in step (1) was adjusted to 1 using 10wt% dilute sulfuric acid. Then the suspension was cooled and filtered to separate the solid and acid solution.

[0086] The obtained solid was washed with water and dried to obtain a white filter cake of 34.7 g of acetoacetanilide. The purity of the obtained acetoacetanilide was 99.2% and the yield was 97.6%.

[0087] (3) First, adjust the pH of the acid solution obtained in step (2) to 10 using 0.5 mol of triethylamine, and remove the solid precipitate in the waste liquid by filtration; then, pass the filtrate through an ion adsorption chelating resin to remove residual organic matter and heavy metal ions, and then add 5% sulfuric acid solution to the filtrate to adjust the pH to 1.

[0088] Assemble the electrodialysis unit, start the magnetic pump, and add 1L of neutral filtrate, 0.3L of pure water, 0.3L of pure water, and 1L of 1% triethylamine aqueous solution to the salt chamber, acid chamber, alkali chamber, and electrode chamber of the bipolar membrane electrodialysis system, respectively.

[0089] At a power supply voltage of 22V, a membrane voltage of 2V, and a current density of 400A / m², 2 Under these conditions, the operation was terminated after 0.5 hours. The content of triethylamine, an organic base produced in the alkali chamber, was 1.48 mol (recovery rate 99%); the content of hydrobromic acid in the effluent from the acid chamber was 5.03%.

[0090] The organic base is returned to step (1) as a cathode liquid raw material, and the recovered acid is returned to step (2) to adjust the pH value of the suspension.

[0091] Comparative Example 1

[0092] The difference from Example 1 is that the electrolysis temperature in step (1) is 25°C, the electrolysis voltage is 1V, and the electrolysis time is 2h.

[0093] The resulting white filter cake contained 28.7g of acetylaniline.

[0094] pass Figure 6 It can be seen that t R The peak value of acetoacetanilide was observed at 14.0 min. The purity of the obtained acetoacetanilide was 65.96%, and the yield was 53.4%.

[0095] In step (3), the power supply voltage for electrodialysis is 4V, the membrane voltage is 0.2V, and the current density is 400A / m. 2 Under these conditions, the process ended after 1.5 hours. The content of triethylamine, an organic base, produced in the alkali chamber was 1.03 mol (recovery rate 68%), and the content of hydrobromic acid in the effluent from the acid chamber was 4.59%.

[0096] The others are the same as in Example 1.

[0097] The organic base is returned to step (1) as catholyte raw material and the recovered acid solution is used to adjust the pH of the suspension in step (2).

[0098] Comparative Example 2

[0099] The difference from Example 1 is that the electrolysis temperature in step (1) is 25°C and the electrolysis voltage is 14 V. The electrolysis time is 2 h.

[0100] The white filter cake obtained is acetoacetanilide 29.4 g.

[0101] The purity of the acetoacetanilide obtained is 42.4% and the yield is 35.2%.

[0102] The power supply voltage for the electrodialysis in step (3) is 22 V, the membrane pair voltage is 2 V and the current density is 400 A / m 2 After 40 min, the operation is stopped. The organic base triethylamine is produced in the base chamber with a content of 0.85 mol (recovery rate 57%) and the hydrogen bromide content of the water in the acid chamber is 5.23%.

[0103] The rest is the same as in Example 1.

[0104] Comparative Example 3

[0105] The difference from Example 1 is that the electrolysis temperature in step (1) is 60°C and the electrolysis voltage is 10 V. The electrolysis time is 2 h.

[0106] The white filter cake obtained is acetoacetanilide 32.5 g.

[0107] The purity of the acetoacetanilide obtained is 47.9% and the yield is 43.9%.

[0108] The power supply voltage for the electrodialysis in step (3) is 22 V, the membrane pair voltage is 2 V and the current density is 400 A / m 2 After 40 min, the operation is stopped. The organic base triethylamine is produced in the base chamber with a content of 0.94 mol (recovery rate 62%) and the hydrogen bromide content of the water in the acid chamber is 5.18%.

[0109] The rest is the same as in Example 1.

[0110] Comparative Example 4

[0111] The difference from Example 1 is that the electrolysis temperature in step (1) is 0°C and the electrolysis voltage is 3.0 V. The electrolysis time is 2 h.

[0112] The white filter cake obtained is acetoacetanilide 28.3 g.

[0113] The rest is the same as in Example 1. Figure 7It can be seen that t R The peak value for acetoacetanilide was observed at 14.1 min. The purity of the obtained acetoacetanilide was 46.6%, and the yield was 37.3%.

[0114] In step (3), the power supply voltage for electrodialysis is 22V, the membrane voltage is 2V, and the current density is 400A / m. 2 Under these conditions, the operation was terminated after 40 minutes. The content of triethylamine, an organic base produced in the alkali chamber, was 0.85 mol (recovery rate 57%); the content of hydrobromic acid in the effluent from the acid chamber was 3.71%.

[0115] The others are the same as in Example 1.

[0116] Comparative Example 5

[0117] The difference from Example 1 is that the electrolysis temperature in step (1) is 25°C, the electrolysis voltage is 1.0V, and the electrolysis time is 4h.

[0118] The resulting white filter cake contained 30.2g of acetylacetanilide.

[0119] pass Figure 8 It can be seen that t R The peak of acetoacetanilide was observed at 14.2 min. The purity of the obtained acetoacetanilide was 57.5%, and the yield was 49%.

[0120] In step (3), the power supply voltage for electrodialysis is 22V, the membrane voltage is 2V, and the current density is 400A / m. 2 Under these conditions, the operation ended after 40 minutes. The content of triethylamine, an organic base produced in the alkali chamber, was 0.97 mol (recovery rate 65%); the content of hydrobromic acid in the effluent from the acid chamber was 4.38%.

[0121] The others are the same as in Example 1.

[0122] Comparative Example 6

[0123] The difference from Example 1 is that the electrolysis temperature in step (1) is 25°C, the electrolysis voltage is 10V, and the electrolysis time is 2h.

[0124] The resulting white filter cake contained 33.5g of acetylacetanilide.

[0125] The purity of the obtained acetoacetanilide was 98.2%, and the yield was 92.8%.

[0126] In step (3), the power supply voltage for electrodialysis is 2V, the membrane voltage is 1.5V, and the current density is 400A / m. 2 Under these conditions, the operation ended after 2 hours. The content of triethylamine, an organic base produced in the alkali chamber, was 1.31 mol (recovery rate 89%); the content of hydrobromic acid in the effluent from the acid chamber was 3.07%.

[0127] Other embodiments are similar to Example 1.

[0128] Comparative Example 7

[0129] A method for preparing acetoacetanilide, the specific steps are as follows:

[0130] Take 51.2g 4-bromo-3-oxo-N-phenylbutyramide, 0.2g palladium-carbon, 350g methanol, 150g water, and load them into a 1L high-pressure reactor. Replace with N2 for three times, then replace with H2 for three times, and keep the pressure at 0.5MPa. Open the stirring at 400rpm, and react at 25℃. After 12h, the liquid is detected by HPLC, and the conversion rate of the raw material is 75.4%.

[0131] As shown in Figure 9 t R =14.1min is the peak of acetoacetanilide. The obtained liquid is concentrated after simple filtration and extraction, and white filter cake 38g is obtained after separation, with purity of 13.1% and yield of 14%.

[0132] Brominated acetoacetanilide is subjected to hydrogenation debromination under the action of palladium-carbon catalyst. The analysis shows that there are many by-products in the reaction system, and the selectivity and product yield of the reaction are lower than those of electrochemical debromination.

[0133] Comparative Example 8

[0134] The difference from Example 2 is that the cathode liquid in step (1) is 1L of 1mol / L sodium hydroxide (1mol); and the electrolysis time is 5h.

[0135] White filter cake 15.7g is obtained, with purity of 80.5% and yield of 44.1%.

[0136] In step (3), 1 L of neutral filtrate, 0.3L of pure water, 0.3L of pure water, and 1L of 1% sodium hydroxide aqueous solution are respectively added to the salt chamber, acid chamber, base chamber, and electrode chamber of the bipolar membrane electrodialysis system.

[0137] The electrodialysis time is 70min. Sodium hydroxide 0.88mol is produced in the base chamber (recovery rate 58.3%); and the water hydrogen bromide content in the acid chamber is 3.57%.

[0138] Other embodiments are similar to Example 2.

[0139] When inorganic electrolyte is used, the selectivity is poor. Compared with inorganic bases, organic bases are more easily combined with related ions in experiments, promote the progress of the positive reaction, and thus improve the reaction yield.

[0140] Comparative Example 9

[0141] The difference from Example 2 is that the same apparent size of graphene electrode is used as an anode (3x3x0.1cm) in the step (1). The electrolysis time is 5h.

[0142] A white filter cake 20.8g is obtained, the purity is 77%, and the yield is 58.4%.

[0143] In the step (3), 1L of neutral filtrate, 0.3L of pure water, 0.3L of pure water and 1L of 1% sodium hydroxide aqueous solution are respectively added to the salt chamber, the acid chamber, the base chamber and the pole chamber of the bipolar membrane electrodialysis system. The experiment is ended after 70min of operation, and 0.75mol of triethylamine is produced in the base chamber (the recovery rate is 0.50%); the water produced in the acid chamber contains 4.03% of hydrobromic acid.

[0144] The other is the same as Example 2.

[0145] The graphene electrode in the present example is not the best choice in the debromination process.

Claims

1. A method for preparing acetoacetanilide by electrochemical selective debromination, characterized in that, Includes the following steps: (1) Using sulfuric acid aqueous solution as anolyte and organic base aqueous solution as catholyte, bromoacetylaniline as a reaction raw material is added into the catholyte and mixed well, and then electrolyzed to debrominate to obtain a suspension; The electrolysis voltage is 2V-10V, the electrolysis temperature is 0℃-50℃, the electrolysis time is 1-4h, and the current density is 0.5A / dm³. 2 ; (2) Adjust the pH of the suspension to acidic, separate the solid and acid solution, and the white filter cake obtained after washing and drying the solid is acetylacetanilide; (3) The acid solution obtained in step (2) is subjected to electrodialysis to dissociate it, and organic base and recovered acid solution are obtained respectively; the organic base is returned to step (1) as cathodic liquid raw material, and the recovered acid solution is returned to step (2) to adjust the pH value of the suspension. The electrodialysis dissociation power supply voltage is 5-50V, the membrane pair voltage is 0-4.8V, and the current density is 200-600A / m. 2 Electrodialysis time is 0.5-1.5 hours. In step (1), the bromoacetylaniline is at least one of 2-bromo-3-oxo-N-phenylbutyramide and 4-bromo-3-oxo-N-phenylbutyramide; In step (1), the cathode used for electrolysis is a copper electrode; the anode used for electrolysis is a graphdiyne electrode.

2. The method for preparing acetoacetanilide by electrochemical selective debromination according to claim 1, characterized in that, The electrolysis temperature in step (1) is 5-50℃.

3. The method for preparing acetoacetanilide by electrochemical selective debromination according to claim 2, characterized in that, The electrolysis temperature in step (1) is 25°C and the electrolysis time is 2 hours.

4. The method for preparing acetoacetanilide by electrochemical selective debromination according to claim 1, characterized in that, In step (1), the organic base is selected from at least one of triethylamine, trimethylamine, tripropylamine or tributylamine.

5. The method for preparing acetoacetanilide by electrochemical selective debromination according to claim 1, characterized in that, In step (1), the pH value of the anolyte is 1-3, and the pH value of the catholyte is 9-11; the concentration of bromoacetanilide in the catholyte is 0.05mol / L-2mol / L.

6. The method for preparing acetoacetanilide by electrochemical selective debromination according to claim 5, characterized in that, In step (1), the pH value of the anolyte is 1.5-2.5, and the pH value of the catholyte is 9.5-10.5; the concentration of bromoacetanilide in the catholyte is 0.5mol / L-1mol / L.

7. The method for preparing acetoacetanilide by electrochemical selective debromination according to claim 1, characterized in that, In step (2), the pH value of the suspension is adjusted to 1-5; after cooling and filtration, the solid and acid are separated.

8. The method for preparing acetoacetanilide by electrochemical selective debromination according to claim 1, characterized in that, In step (3), the power supply voltage for electrodialysis dissociation is 22V, and the membrane pair voltage is 2.0V.

9. The method for preparing acetoacetanilide by electrochemical selective debromination according to claim 1, characterized in that, In step (3), the acid solution is first adjusted to pH 10 or higher using an organic base, and then filtered to remove the solid precipitate. After removing organic matter and heavy metal ions from the filtrate by ion adsorption, the pH of the filtrate is adjusted to neutral and then electrodialysis is performed.

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