Method for purifying crude 3, 3 '-diaminobenzidine and application of crude 3, 3'-diaminobenzidine
The crude 3,3′-diaminobenzidine was purified by using a specific solvent via a solution-crystallization method, which solved the problems of high energy consumption and high cost in the existing technology. This method enables the preparation of high-purity and high-yield 3,3′-diaminobenzidine and has environmental advantages.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-11-11
- Publication Date
- 2026-05-12
AI Technical Summary
Existing purification technologies for 3,3′-diaminobenzidine suffer from problems such as large wastewater volume, high operating temperature, high energy consumption, the need for multiple crystallizations, low yield and purity, and high cost.
The crude 3,3′-diaminobenzidine was purified by a solution-crystallization method using nitrogen- or sulfur-containing organic compounds as good solvents and water or monohydric alcohols as solvents. High-purity, high-yield products were obtained through one-step crystallization.
It achieves the production of high-purity, high-yield 3,3′-diaminobenzidine products under mild conditions, with low solvent consumption, large single-batch processing capacity, and only one-step crystallization, meeting green and environmental protection requirements.
Smart Images
Figure CN122010749A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of chemical engineering separation technology, specifically relating to a method and application for purifying crude 3,3′-diaminobenzidine. Background Technology
[0002] 3,3′-Diaminobenzidine, also known as 3,3',4,4'-tetraaminobenzidine, 3,3',4,4'-benzyltetramine, and DAB, has the molecular formula C2. 12 H 14 N4, with a molecular weight of 214.27, is an analogue of benzidine and is a peanut-colored or brown solid at room temperature. Its structural formula is shown below:
[0003]
[0004] 3,3′-Diaminobenzidine, as an important monomer for synthetic polymers, can be used to prepare high-performance polymer resins and fibers. Simultaneously, due to its mutagenic properties, 3,3′-diaminobenzidine can be used for chemical staining of nucleic acids and proteins. As an analytical reagent, it is commonly used for spectrophotometric determination of selenium content. The purity of 3,3′-diaminobenzidine directly affects the accuracy of analytical detection and the value and performance of subsequent synthetic products. Therefore, increasing the production scale of 3,3′-diaminobenzidine and achieving purification of 3,3′-diaminobenzidine through the development and optimization of crystallization processes have significant practical implications and broad development prospects. CN117756640A describes a two-step heating method for synthesizing 3,3′-diaminobenzidine. First, crude 3,3′-diaminobenzidine is obtained by hot melting in hot water at 95-100℃ followed by cooling. Then, 40-50 times the mass of water, activated carbon (in a 1:1 mass ratio), and ammonium sulfate hydrochloride (an antioxidant) are added to the crude product. The mixture is then dissolved at 97-103℃, filtered, and cooled to obtain relatively pure 3,3′-diaminobenzidine. Repeated purification steps yield high-purity 3,3′-diaminobenzidine. This method involves high operating temperatures, requires nitrogen protection throughout, necessitates the addition of antioxidants, consumes a large amount of solvent, and requires multiple purification steps to obtain high-purity 3,3′-diaminobenzidine, resulting in a low overall yield. US3943175 describes a method for purifying crude 3,3′-diaminobenzidine by adding acid to form a salt, neutralizing with alkali, dissolving in boiling water, and cooling. This method requires large amounts of acid and alkali, resulting in high solvent consumption, high operating temperatures, and the purity of the 3,3′-diaminobenzidine product remains low. US3481984 describes a method involving adding a flocculant and passing an aqueous solution of 3,3′-diaminobenzidine at 120-125°C through an activated carbon column for crystallization to obtain the 3,3′-diaminobenzidine product. This method is costly and inefficient. EP0522577B1 also requires a large amount of water as a solvent and the dissolution temperature must be above 100°C during the purification of crude 3,3′-diaminobenzidine.
[0005] In summary, the purification of 3,3′-diaminobenzidine faces challenges such as large wastewater volume, high operating temperature, high energy consumption, the need for multiple crystallizations, low yield and purity, and high cost. Summary of the Invention
[0006] The purpose of this invention is to overcome the aforementioned problems in the prior art and provide a method and application for purifying crude 3,3′-diaminobenzidine. This method employs a solution-crystallization method, using a specific good solvent and a specific precipitant to purify crude 3,3′-diaminobenzidine. It has the advantages of mild conditions, no need for nitrogen protection, low solvent consumption, and large batch throughput. High-purity and high-yield 3,3′-diaminobenzidine products can be obtained through a single-step crystallization process.
[0007] To achieve the above objectives, the first aspect of the present invention provides a method for purifying crude 3,3′-diaminobenzidine, the method comprising the following steps:
[0008] (1) The crude product of 3,3′-diaminobenzidine is first mixed with a good solvent to obtain a solution containing 3,3′-diaminobenzidine; wherein the good solvent includes organic compounds containing nitrogen and / or organic compounds containing sulfur.
[0009] (2) A solution containing 3,3′-diaminobenzidine is mixed with a solvent in a second mixing process; wherein the solvent comprises water and / or a monohydric alcohol;
[0010] (3) The product obtained from the second mixture is aged, and then the aged product is subjected to a second solid-liquid separation. The solid obtained from the second solid-liquid separation is then washed and dried.
[0011] A second aspect of the present invention provides the application of the above-described method in improving the uniformity of the particle size distribution of 3,3′-diaminobenzidine crystals and / or in the preparation of 3,3′-diaminobenzidine crystals with a blocky morphology.
[0012] Through the above technical solution, the present invention achieves the following beneficial effects:
[0013] (1) The method of the present invention has the advantages of mild conditions, no need for nitrogen protection, low solvent consumption, and large batch processing capacity. High-purity and high-yield 3,3′-diaminobenzidine products can be obtained by crystallization in one step.
[0014] (2) The crude 3,3′-diaminobenzidine contains a large number of impurities (mainly soluble benzidine triamine or benzidine diamine and other benzidine compounds), which originate from the upstream process. This invention utilizes the difference in solubility of 3,3′-diaminobenzidine in different solvents and employs a solution-crystallization method to obtain a high-purity 3,3′-diaminobenzidine product. This achieves effective separation of the 3,3′-diaminobenzidine product and impurities, resulting in a product with high purity.
[0015] (3) The process of this invention is simple and energy-efficient, while ensuring high purity and high yield of the product. It meets the requirements of green environmental protection and has high industrial application value.
[0016] (4) In a preferred embodiment, the method of the present invention can obtain crystals with uniform particle size and blocky morphology; the average particle size of the crystals is 80-100 μm. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the dissolution and crystallization of high-purity 3,3′-diaminobenzidine according to the present invention;
[0018] Figure 2 , Figure 3 The images shown are microscope photographs and particle size distribution diagrams of the 3,3′-diaminobenzidine crystalline product obtained in Example 1.
[0019] Figure 4 , Figure 5 The images shown are microscope photographs and particle size distribution diagrams of the 3,3′-diaminobenzidine crystalline product obtained in Example 2.
[0020] Figure 6 , Figure 7 The images shown are microscope photographs and particle size distribution diagrams of the 3,3′-diaminobenzidine crystalline product obtained in Example 3.
[0021] Figure 8 , Figure 9 The images shown are microscope photographs and particle size distribution diagrams of the 3,3′-diaminobenzidine crystalline product obtained in Example 4.
[0022] Figure 10 , Figure 11 The images shown are microscope photographs and particle size distribution diagrams of the 3,3′-diaminobenzidine crystalline product obtained in Example 5.
[0023] Figure 12 , Figure 13 The images shown are microscope photographs and particle size distribution diagrams of the 3,3′-diaminobenzidine crystalline product obtained in Example 6.
[0024] Figure 14 , Figure 15 The images shown are microscope photographs and particle size distribution diagrams of the 3,3′-diaminobenzidine crystalline product obtained in Example 7.
[0025] Figure 16 , Figure 17 The images shown are microscope photographs and particle size distribution diagrams of the 3,3′-diaminobenzidine crystalline product obtained in Example 8.
[0026] Figure 18 , Figure 19 The images shown are microscope photographs and particle size distribution diagrams of the 3,3′-diaminobenzidine crystalline product obtained in Example 9.
[0027] Figure 20 , Figure 21 The images shown are microscope photographs and particle size distribution diagrams of the 3,3′-diaminobenzidine crystalline product obtained in Example 10.
[0028] Figure 22 , Figure 23 Microscopic photographs and particle size distribution diagrams of the 3,3′-diaminobenzidine crystalline product obtained in Comparative Example 1 are shown. Detailed Implementation
[0029] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0030] The first aspect of this invention provides a method for purifying crude 3,3′-diaminobenzidine, the method comprising the following steps:
[0031] (1) The crude product of 3,3′-diaminobenzidine is first mixed with a good solvent to obtain a solution containing 3,3′-diaminobenzidine; wherein the good solvent includes organic compounds containing nitrogen and / or organic compounds containing sulfur.
[0032] (2) A solution containing 3,3′-diaminobenzidine is mixed with a solvent in a second mixing process; wherein the solvent comprises water and / or a monohydric alcohol;
[0033] (3) The product obtained from the second mixture is aged, and then the aged product is subjected to a second solid-liquid separation. The solid obtained from the second solid-liquid separation is then washed and dried.
[0034] In this invention, the purity of the crude 3,3′-diaminobenzidine is not particularly limited and can be selected within a wide range. Typically, the purity of the crude 3,3′-diaminobenzidine is 95-97%.
[0035] According to the present invention, the good solvent can be an organic compound containing 2-10 carbon atoms, such as an organic compound containing phenyl, an organic compound containing methyl, an organic compound containing ethyl, an organic compound containing cycloalkyl, or an organic compound containing a nitrogen heterocycle; in order to further improve the purity and yield of the 3,3′-diaminobenzidine product, preferably, the good solvent includes at least one of nitrobenzene, pyridine, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and sulfolane.
[0036] According to the present invention, taking into account the purity and yield of the 3,3′-diaminobenzidine product and reducing the amount of good solvent and precipitant, preferably, the amount of the good solvent is 10-35 mL relative to 10 g of crude 3,3′-diaminobenzidine.
[0037] According to the present invention, preferably, the temperature of the first mixture is 5-30°C.
[0038] According to the present invention, preferably, step (2) further includes: contacting the solution containing 3,3′-diaminobenzidine with activated carbon before the second mixing with the solvent, then performing a first solid-liquid separation on the product obtained from the contact, and then performing a second mixing with the solvent on the solution obtained from the first solid-liquid separation.
[0039] According to the present invention, preferably, the amount of activated carbon used is 0-10g (for example, 0.1g, 0.5g, 1g, 2g, 3g, 4g, 5g, 6g, 7g, 8g, 9g, 10g, and any two of the above) relative to 100g of crude 3,3′-diaminobenzidine, and more preferably 3-10g.
[0040] According to the present invention, preferably, the contact conditions include: a temperature of 5-30°C and a time of 0.5-1h.
[0041] According to the present invention, preferably, the solvent is a C1-C5 monohydric alcohol and / or water, more preferably at least one selected from methanol, ethanol, water, isopropanol and n-propanol.
[0042] According to a preferred embodiment of the present invention, when pyridine is used as a good solvent and ethanol is used as a solvent, or when N,N-dimethylacetamide is used as a good solvent and water is used as a solvent, the purity and yield of the 3,3′-diaminobenzidine product can be further improved.
[0043] According to the present invention, preferably, the volume ratio of the solvent to the good solvent is 1-5:1 (for example, it can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, and any two of the above).
[0044] According to the present invention, preferably, the precipitant is mixed with the solution containing 3,3′-diaminobenzidine by dropwise addition; more preferably, the dropping rate of the precipitant is 100-300 μL / min relative to 10 g of crude 3,3′-diaminobenzidine.
[0045] According to the present invention, preferably, the temperature of the second mixing is 5-30°C.
[0046] According to the present invention, preferably, the aging conditions include: a temperature of 5-30°C and a time of 0.5-2 hours.
[0047] According to the present invention, preferably, the detergent used for washing is a C1-C5 monohydric alcohol and / or water, more preferably at least one selected from methanol, ethanol, water, isopropanol, and n-propanol. Typically, the detergent is the same type as the solvent used to avoid introducing more types of impurities.
[0048] In this invention, the drying conditions can be those commonly used in the art, as long as they allow the detergent to evaporate. For example, the drying conditions include: vacuum conditions, a temperature of 40-60°C, and a time of 5-8 hours.
[0049] According to a preferred embodiment of the present invention, the method employed is as follows: Figure 1 The process described above is used to purify crude 3,3′-diaminobenzidine. The purification process includes: first, dissolving crude 3,3′-diaminobenzidine in a good solvent, then adding activated carbon for adsorption, and then filtering the activated carbon to obtain a filtrate; adding a solvent to the filtrate for dissolution and crystallization to obtain a solid-liquid mixture, and then filtering, washing and drying the solid-liquid mixture to obtain the product.
[0050] A second aspect of the present invention provides the application of the above-described method in improving the uniformity of the particle size distribution of 3,3′-diaminobenzidine crystals and / or in the preparation of 3,3′-diaminobenzidine crystals with a blocky morphology.
[0051] According to a particularly preferred embodiment of the present invention, a method for purifying crude 3,3′-diaminobenzidine comprises: taking crude 3,3′-diaminobenzidine raw material and pouring it into a batch crystallizer containing pyridine (the amount of pyridine is 22-27 mL relative to 10 g of crude 3,3′-diaminobenzidine), maintaining the temperature in the crystallizer at 5-7°C, and stirring at a constant temperature until the crude product is completely dissolved; then adding activated carbon (the amount of activated carbon is 4.5-5.5 g relative to 100 g of crude 3,3′-diaminobenzidine) to the solution, and continuing to stir at a constant temperature of 5-7°C for 40-45 minutes. The solution was then rapidly vacuum filtered. The filtrate was poured into a kettle crystallizer, and a certain amount of ethanol (ethanol to pyridine volume ratio of 2.5-3.5:1) was measured. The crystallization temperature was set at 5-8℃, where the ethanol dropping rate was 280-300 μL / min relative to 10g of crude 3,3′-diaminobenzidine. After the ethanol was added, the mixture was stirred at a constant temperature of 5-8℃ for aging for 0.8-1h. The slurry was then rapidly vacuum filtered, and the solid product was thoroughly washed with ethanol. The mixture was then vacuum dried at 40-45℃ for 2.5-3h to finally obtain the 3,3′-diaminobenzidine product.
[0052] According to a particularly preferred embodiment of the present invention, a method for purifying crude 3,3′-diaminobenzidine comprises: taking crude 3,3′-diaminobenzidine raw material and pouring it into a batch crystallizer containing N,N-dimethylacetamide (the amount of N,N-dimethylacetamide is 22-27 mL relative to 10 g of crude 3,3′-diaminobenzidine), maintaining the temperature in the crystallizer at 10-12°C, and stirring at a constant temperature until the crude product is completely dissolved; then adding activated carbon (the amount of activated carbon is 9-10 g relative to 100 g of crude 3,3′-diaminobenzidine) to the solution, and continuing to stir at a constant temperature for 35 minutes. -40 min, then quickly vacuum filter; pour the filtrate into a kettle crystallizer, measure a certain amount of water (the volume ratio of water to N,N-dimethylacetamide is 1.5-2.5:1), set the crystallization temperature to 10-12℃, wherein the water dropping rate relative to 10g of crude 3,3′-diaminobenzidine is 150-160μL / min; after the water is added, continue to stir at a constant temperature and age for 1-1.2h; quickly vacuum filter the slurry, wash the solid product thoroughly with water, and vacuum dry at 45-50℃ for 2.5-3h to finally obtain the 3,3′-diaminobenzidine product.
[0053] The present invention will be described in detail below through embodiments. In the following embodiments,
[0054] Purity was tested using high performance liquid chromatography;
[0055] The formula for calculating product yield is: product weight ÷ weight of crude 3,3′-diaminobenzidine × 100%.
[0056] Example 1
[0057] Take 10.00 g of crude 3,3′-diaminobenzidine with a purity of 95.00%, pour it into a batch crystallizer containing 20 mL of nitrobenzene, and maintain the temperature in the crystallizer at 20.0℃. Stir at this temperature until the crude product is completely dissolved. Then add 1.00 g of activated carbon to the solution and continue stirring at 20.0℃ for 40 min. Then quickly vacuum filter the solution. Pour the filtrate into the batch crystallizer, add 100 mL of methanol, set the crystallization temperature to 20.0℃, and the methanol dropping rate to 200 μL / min. After the methanol is added, continue stirring at 20.0℃ and age for 1.0 h. Quickly vacuum filter the slurry, wash the solid product thoroughly with methanol, and vacuum dry at 45.0℃ for 3.0 h to finally obtain 6.50 g of 3,3′-diaminobenzidine product with a purity of 98.03%, a yield of 75.0%, and an impurity removal rate of 60.6%.
[0058] Electron micrographs of the 3,3′-diaminobenzidine product are shown below. Figure 2As shown in the figure, the obtained crystals are all blocky with uniform particle size; the particle size analysis results are as follows. Figure 3 As shown, the average particle size is around 100 μm, and there is only one narrow distribution peak, which proves that the particle size distribution is uniform.
[0059] Example 2
[0060] 10.00 g of crude 3,3′-diaminobenzidine raw material with a purity of 96.00% was poured into a batch crystallizer containing 25 mL of pyridine. The temperature inside the crystallizer was controlled at 5.0℃, and the mixture was stirred at a constant temperature until the crude product was completely dissolved. Then, 0.50 g of activated carbon was added to the solution, and the mixture was stirred at a constant temperature of 5.0℃ for 40 min. The mixture was then quickly vacuum filtered. The filtrate was poured into the batch crystallizer, and 75 mL of ethanol was added. The crystallization temperature was set at 5.0℃, and the ethanol dropping rate was 300 μL / min. After the ethanol was added, the mixture was stirred at a constant temperature of 5.0℃ for 1.0 h. The slurry was then quickly vacuum filtered, and the solid product was thoroughly washed with ethanol. The product was then vacuum dried at 45.0℃ for 3.0 h, finally yielding 8.00 g of 3,3′-diaminobenzidine product with a purity of 99.56%, a yield of 80.0%, and an impurity removal rate of 89.0%.
[0061] Electron micrographs of the 3,3′-diaminobenzidine product are shown below. Figure 4 As shown in the figure, the obtained crystals are all blocky with uniform particle size; the particle size analysis results are as follows. Figure 5 As shown, the average particle size is around 90 μm, and there is only one narrow distribution peak, which proves that the particle size distribution is uniform.
[0062] Example 3
[0063] 10.00 g of crude 3,3′-diaminobenzidine raw material with a purity of 96.00% was poured into a batch crystallizer containing 25 mL of N,N-dimethylformamide. The temperature inside the crystallizer was controlled at 17.5℃, and the mixture was stirred at a constant temperature until the crude product was completely dissolved. Then, 0.30 g of activated carbon was added to the solution, and the mixture was stirred at 17.5℃ for 40 min, followed by rapid vacuum filtration. The filtrate was poured into the batch crystallizer, and 25 mL of n-propanol was added. The crystallization temperature was set at 17.5℃, and the drop rate of n-propanol was 300 μL / min. After the n-propanol was completely added, the mixture was stirred at 17.5℃ for 1.0 h and aged. The slurry was then rapidly vacuum filtered, and the solid product was thoroughly washed with n-propanol. The product was then vacuum dried at 45.0℃ for 3.0 h, finally yielding 7.53 g of crude product. The 3,3′-diaminobenzidine product has a purity of 98.85%, a yield of 75.3%, and an impurity removal rate of 71.3%.
[0064] Electron micrographs of the 3,3′-diaminobenzidine product are shown below. Figure 6 As shown in the figure, the obtained crystals are all blocky with uniform particle size; the particle size analysis results are as follows. Figure 7 As shown, the average particle size is around 95 μm, and there is only one narrow distribution peak, which proves that the particle size distribution is uniform.
[0065] Example 4
[0066] 10.00 g of crude 3,3′-diaminobenzidine raw material with a purity of 95.00% was poured into a batch crystallizer containing 25 mL of N,N-dimethylacetamide. The temperature inside the crystallizer was controlled at 10.0℃, and the mixture was stirred at a constant temperature until the crude product was completely dissolved. Then, 1.0 g of activated carbon was added to the solution, and the mixture was stirred at a constant temperature for 40 min. The mixture was then quickly vacuum filtered. The filtrate was poured into the batch crystallizer, and 50 mL of water was added. The crystallization temperature was set at 10.0℃, and the water dropping rate was 150 μL / min. After the water was added, the mixture was stirred at a constant temperature and aged for 1.0 h. The slurry was then quickly vacuum filtered, and the solid product was thoroughly washed with water. The product was then vacuum dried at 45.0℃ for 3.0 h, finally yielding 7.88 g of 3,3′-diaminobenzidine product with a purity of 99.60%, a yield of 78.8%, and an impurity removal rate of 92.0%.
[0067] Electron micrographs of the 3,3′-diaminobenzidine product are shown below. Figure 8 As shown in the figure, the obtained crystals are all blocky with uniform particle size; the particle size analysis results are as follows. Figure 9 As shown, the average particle size is around 95 μm, and there is only one narrow distribution peak, which proves that the particle size distribution is uniform.
[0068] Example 5
[0069] 10.00 g of crude 3,3′-diaminobenzidine raw material with a purity of 95.00% was poured into a batch crystallizer containing 18 mL of dimethyl sulfoxide. The temperature inside the crystallizer was controlled at 20℃, and the mixture was stirred at a constant temperature until the crude product was completely dissolved. Then, 1.00 g of activated carbon was added to the solution, and the mixture was stirred at a constant temperature of 20℃ for 40 min. The mixture was then quickly vacuum filtered. The filtrate was poured into the batch crystallizer, and 75 mL of water was added. The crystallization temperature was set at 20.0℃, and the water dropping rate was 150 μL / min. After the water was added, the mixture was stirred at a constant temperature of 20.0℃ for 1.0 h. The slurry was then quickly vacuum filtered, and the solid product was thoroughly washed with water. The product was then vacuum dried at 45.0℃ for 3.0 h, finally yielding 7.76 g of 3,3′-diaminobenzidine product with a purity of 99.10%, a yield of 77.6%, and an impurity removal rate of 82.0%.
[0070] Electron micrographs of the 3,3′-diaminobenzidine product are shown below. Figure 10As shown in the figure, the obtained crystals are all blocky with uniform particle size; the particle size analysis results are as follows. Figure 11 As shown, the average particle size is around 100 μm, and there is only one narrow distribution peak, which proves that the particle size distribution is uniform.
[0071] Example 6
[0072] 10.00 g of crude 3,3′-diaminobenzidine raw material with a purity of 97.00% was poured into a batch crystallizer containing 30 mL of sulfolane. The temperature inside the batch crystallizer was controlled at 30.0℃, and the mixture was stirred at a constant temperature until the crude product was completely dissolved. No activated carbon was added, and then the mixture was quickly vacuum filtered. The filtrate was poured into the batch crystallizer, and 50 mL of isopropanol was added. The crystallization temperature was set at 30℃, and the isopropanol dropping rate was 150 μL / min. After the isopropanol was completely added, the mixture was stirred at a constant temperature of 30.0℃ for 1.0 h. The slurry was then quickly vacuum filtered, and the solid product was thoroughly washed with isopropanol. The product was then vacuum dried at 45.0℃ for 3.0 h, finally yielding 7.25 g of 3,3′-diaminobenzidine product with a purity of 99.38%, a yield of 72.5%, and an impurity removal rate of 79.3%.
[0073] Electron micrographs of the 3,3′-diaminobenzidine product are shown below. Figure 12 As shown in the figure, the obtained crystals are all blocky with uniform particle size; the particle size analysis results are as follows. Figure 13 As shown, the average particle size is around 95 μm, and there is only one narrow distribution peak, which proves that the particle size distribution is uniform.
[0074] Example 7
[0075] 10.00 g of crude 3,3′-diaminobenzidine raw material with a purity of 96.00% was poured into a batch crystallizer containing 25 mL of N,N-dimethylacetamide. The temperature inside the crystallizer was controlled at 10.0℃, and the mixture was stirred at a constant temperature until the crude product was completely dissolved. Then, 1.00 g of activated carbon was added to the solution, and the mixture was stirred at a constant temperature for 40 min. The solution was then rapidly filtered under vacuum. The filtrate was poured into the batch crystallizer, and 100 mL of methanol was added. The crystallization temperature was set at 10.0℃, and the methanol dropping rate was 300 μL / min. After the methanol addition was complete, the mixture was stirred at a constant temperature of 10.0℃ and aged for 1.0 h. The slurry was then rapidly filtered under vacuum, and the solid product was thoroughly washed with methanol. The product was then vacuum dried at 45.0℃ for 3.0 h, yielding 7.49 g of crude product. The 3,3′-diaminobenzidine product has a purity of 99.02%, a yield of 74.9%, and an impurity removal rate of 75.5%.
[0076] Electron micrographs of the 3,3′-diaminobenzidine product are shown below. Figure 14As shown in the figure, the obtained crystals are all blocky with uniform particle size; the particle size analysis results are as follows. Figure 15 As shown, the average particle size is around 92 μm, and there is only one narrow distribution peak, which proves that the particle size distribution is uniform.
[0077] Example 8
[0078] 10.00 g of crude 3,3′-diaminobenzidine raw material with a purity of 95.00% was poured into a batch crystallizer containing 25 mL of N,N-dimethylacetamide. The temperature inside the crystallizer was controlled at 10.0℃, and the mixture was stirred at a constant temperature until the crude product was completely dissolved. 1.00 g of activated carbon was added to the batch crystallizer, and the mixture was stirred at a constant temperature for 40 min, followed by rapid vacuum filtration. The filtrate was poured into the batch crystallizer, and 100 mL of isopropanol was added. The crystallization temperature was set at 10.0℃, and the isopropanol dropping rate was 200 μL / min. After the isopropanol was completely added, the mixture was stirred at a constant temperature of 10.0℃ and aged for 1.0 h. The slurry was then rapidly vacuum filtered, and the solid product was thoroughly washed with isopropanol. The product was then vacuum dried at 45.0℃ for 3.0 h, finally yielding 7.76 g of [product name missing]. The 3,3′-diaminobenzidine product has a purity of 99.02%, a yield of 77.6%, and an impurity removal rate of 80.4%.
[0079] Electron micrographs of the 3,3′-diaminobenzidine product are shown below. Figure 16 As shown in the figure, the obtained crystals are all blocky with uniform particle size; the particle size analysis results are as follows. Figure 17 As shown, the average particle size is around 97 μm, and there is only one narrow distribution peak, which proves that the particle size distribution is uniform.
[0080] Example 9
[0081] 10.00 g of crude 3,3′-diaminobenzidine raw material with a purity of 95.00% was poured into a batch crystallizer containing 25 mL of dimethyl sulfoxide. The temperature inside the crystallizer was controlled at 30.0 °C, and the mixture was stirred at a constant temperature until the crude product was completely dissolved. 0.1 g of activated carbon was added to the batch crystallizer, and stirring was continued at a constant temperature for 40 min, followed by rapid vacuum filtration. The filtrate was poured into the batch crystallizer, and 100 mL of n-butanol was added. The crystallization temperature was set at 30.0 °C, and the dropping rate of n-butanol was 300 μL / min. After the n-butanol addition was complete, stirring was continued at 30.0 °C, and the mixture was aged for 0.5 h. The slurry was then rapidly vacuum filtered, and the solid product was thoroughly washed with isopropanol. The product was then vacuum dried at 45.0 °C for 3.0 h, finally yielding 7.76 g of crude product. The 3,3′-diaminobenzidine product has a purity of 98.06%, a yield of 72.9%, and an impurity removal rate of 61.2%.
[0082] Electron micrographs of the 3,3′-diaminobenzidine product are shown below. Figure 18 As shown in the figure, compared to the preferred conditions, the obtained 3,3′-diaminobenzidine product, although meeting the purity requirements, has slightly inferior crystal morphology and a lower yield; the particle size analysis results are as follows. Figure 19 As shown, the average particle size is around 85 μm, and there is a small peak, indicating that there are a very small amount of fine crystals.
[0083] Example 10
[0084] Purification was carried out according to the method of Example 1, except that nitrobenzene was replaced with an equal volume of formamide. The final product purity was 97.31%, the yield was 73.8%, and the impurity removal rate was 46.2%.
[0085] Electron micrographs of the 3,3′-diaminobenzidine product are shown below. Figure 20 As shown in the figure, the obtained product consists of rod-shaped and fine particles with extremely uneven particle size distribution, and a large number of fine crystals have aggregated. This aggregation phenomenon leads to mother liquor inclusion, thereby reducing the purity of the product. The particle size analysis results are as follows: Figure 21 As shown, its particle size distribution peak is wider than that of Example 1, proving that its particle size distribution is not uniform.
[0086] Comparative Example 1
[0087] Purification was carried out according to the method of Example 1, except that methanol was replaced with an equal volume of diethyl ether. The final product purity was 96.82%, the yield was 74.2%, and the impurity removal rate was 36.4%.
[0088] Electron micrographs of the 3,3′-diaminobenzidine product are shown below. Figure 22 As shown in the figure, the obtained product is a mixture of flaky crystals and fine crystalline particles, with the flaky and fine crystals adhering to each other. This leads to inclusion in the mother liquor, severely reducing the purity of the product. The particle size analysis results are as follows: Figure 23 As shown, its particle size distribution peak is much wider than that of Example 1, proving that its particle size distribution is extremely uneven.
[0089] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A method for purifying crude 3,3′-diaminobenzidine, characterized in that, The method includes the following steps: (1) The crude product of 3,3′-diaminobenzidine is first mixed with a good solvent to obtain a solution containing 3,3′-diaminobenzidine; wherein the good solvent includes organic compounds containing nitrogen and / or organic compounds containing sulfur. (2) A solution containing 3,3′-diaminobenzidine is mixed with a solvent in a second mixing process; wherein the solvent comprises water and / or a monohydric alcohol; (3) The product obtained from the second mixture is aged, and then the aged product is subjected to a second solid-liquid separation. The solid obtained from the second solid-liquid separation is then washed and dried.
2. The method according to claim 1, wherein, The purity of the crude 3,3′-diaminobenzidine is 95-97%. And / or, the good solvent includes at least one of nitrobenzene, pyridine, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and sulfolane; And / or, relative to 10 g of crude 3,3′-diaminobenzidine, the amount of the good solvent used is 10-35 mL.
3. The method according to claim 1, wherein, The temperature of the first mixture is 5-30℃.
4. The method according to claim 1, wherein, Step (2) further includes: contacting the solution containing 3,3′-diaminobenzidine with activated carbon before the second mixing with the solvent, then performing a first solid-liquid separation on the product obtained from the contact, and then performing a second mixing with the solvent on the solution obtained from the first solid-liquid separation.
5. The method according to claim 4, wherein, The amount of activated carbon used is 0-10g relative to 100g of crude 3,3′-diaminobenzidine; And / or, the contact conditions include: a temperature of 5-30°C; The time is 0.5-1 hour.
6. The method according to claim 1, wherein, The solvent is a C1-C5 monohydric alcohol and / or water, preferably at least one of methanol, ethanol, water, isopropanol and n-propanol; And / or, the volume ratio of the solvent to the good solvent is 1-5:1; And / or, the precipitant is mixed dropwise with the solution containing 3,3′-diaminobenzidine, preferably, the dropping rate of the precipitant is 100-300 μL / min relative to 10 g of crude 3,3′-diaminobenzidine.
7. The method according to claim 1, wherein, The temperature of the second mixture is 5-30℃.
8. The method according to claim 1, wherein, The aging conditions include: a temperature of 5-30℃ and a time of 0.5-2h.
9. The method according to claim 1, wherein, The detergent used for washing is a C1-C5 monohydric alcohol and / or water, preferably at least one of methanol, ethanol, water, isopropanol and n-propanol.
10. The method according to claim 1, wherein, The drying conditions include: vacuum conditions, a temperature of 40-60℃, and a time of 3-8 hours.
11. The method according to any one of claims 1-10 is used to improve the uniformity of particle size distribution of 3,3′-diaminobenzidine crystals and / or in the preparation of 3,3′-diaminobenzidine crystals having a blocky morphology.