Method for purifying diacetone acrylamide
By employing methods such as vacuum distillation, ring-opening neutralization with ammonia, and distillation with polymerization inhibitors, the separation problem in the purification of diacetone acrylamide was successfully solved, enabling the preparation of high-purity products and cost control. These methods are applicable to coatings, photosensitive resin additives, daily chemical products, and medical and health fields.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WEIFANG KEMAI CHEM CO LTD
- Filing Date
- 2023-12-22
- Publication Date
- 2026-07-28
AI Technical Summary
In the existing technology, the purification methods for diacetone acrylamide are difficult to separate, especially since N-containing cyclic organic compounds have similar polarity to it, resulting in low product purity. Furthermore, existing methods may increase production costs or pollute the environment.
The ring-opening process involves vacuum distillation followed by neutralization and ring opening in ammonia water at a pH of 2–3. Excess ammonia water is added dropwise to remove impurities, and then a polymerization inhibitor is added for distillation. The specific steps include vacuum distillation, temperature control, pH adjustment, and vacuum distillation. A mixture of nitric oxide free radical piperidinol, 2,4-di-tert-butylphenol, and biphenyl hydroquinone is used as the polymerization inhibitor.
The preparation of high-purity diacetone acrylamide has been achieved, simplifying the operation process, reducing production costs, and avoiding environmental pollution, making it suitable for industrial applications.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of purification technology for diacetone acrylamide, and more specifically to a method for purifying diacetone acrylamide. Background Technology
[0002] Diacetone acrylamide, abbreviated as DAAM, has two reactive groups in its structure: an N-substituted amide and a methyl ketone. It readily copolymerizes with other ethylene and monomers, thereby introducing ketone carbonyl groups into the polymer. Utilizing the chemical properties of the ketone carbonyl group, it can undergo cross-linking reactions and aldol condensation with ammonia and its derivatives. It is widely used in coatings, photosensitive resin additives, daily chemical products, textiles, and medical and health fields.
[0003] There are many methods for synthesizing diacetone acrylamide, the most common of which is the reaction of acetone and acrylonitrile as raw materials, with concentrated sulfuric acid as a catalyst. Currently, the main challenge in preparing high-purity diacetone acrylamide lies in the separation and purification of the post-treatment process. Because nitrogen-containing cyclic organic compounds and diacetone acrylamide have similar polarities, separation is difficult, and the purity of the product is primarily affected by the nitrogen-containing cyclic organic compounds. Currently, there are no reports on a highly effective separation method.
[0004] Existing research reports on diacetone acrylamide include:
[0005] Application No. 201710612629.5 discloses a method for preparing high-purity diacetone acrylamide. This method involves vacuum distillation of the crude product and recrystallization in a benzene-petroleum ether solvent to obtain DAAM. This method introduces a new solvent, which not only pollutes the environment but also increases production costs due to the need for recrystallization at lower temperatures. Application No. 202211300645.8 discloses a synthesis process for diacetone acrylamide. This process uses 15% sodium hydroxide for alkali washing, but the washing temperature is not specified. The process also introduces sodium ions and sodium salts, making the synthesis process complex, increasing production costs, and reducing product yield.
[0006] Existing technologies mainly focus on the preparation of diacetone acrylamide, with limited research on the purification of the prepared reaction solution. Therefore, it is essential to develop a purification method for diacetone acrylamide. Summary of the Invention
[0007] The purpose of this invention is to provide a purification method for diacetone acrylamide, which can improve the production efficiency and purity of diacetone acrylamide.
[0008] To achieve the above objectives, the present invention adopts the following technical solution:
[0009] A method for purifying diacetone acrylamide, wherein the diacetone acrylamide is extracted from a reaction mixture prepared from acetone and acrylonitrile under the catalysis of concentrated sulfuric acid, and the purification method includes the following steps:
[0010] Step 1: The reaction mixture is subjected to vacuum distillation to remove some organic impurities, including acetone and isopropylidene acetone. After impurity removal, the reaction solution is obtained.
[0011] Step 2: Lower the temperature of the reaction solution from Step 1 to 10-20°C, add the reaction solution to ammonia water to neutralize and open the ring-shaped intermediate of the reaction solution, obtaining diacetone acrylamide and an N-containing cyclic organic compound. The concentration of ammonia water is 15-30%. During the dropwise addition, adjust the pH of the reaction solution to 2-3 to remove the N-containing cyclic organic compound. The mass of ammonia water is 1.6-1.7 times the mass of concentrated sulfuric acid. Allow the mixture to stand and separate into layers to obtain a neutralized solution.
[0012] Step 3: Add ammonia to the neutralization solution to adjust the pH to 9-10. The ammonia removes the acrylamide and N-tert-butylacrylamide produced by the side reaction. Let the mixture stand to separate the layers to obtain the organic layer.
[0013] Step 4: Add a polymerization inhibitor to the organic layer, and carry out distillation under a vacuum of 5 Pa. Collect the distillate at a temperature of 110-120℃ to obtain diacetone acrylamide.
[0014] In the above-mentioned method for purifying diacetone acrylamide, in step two, the temperature of the reaction solution is controlled at 20-25°C during the dropwise addition process, and the stirring time is 20-40 min.
[0015] In the above-mentioned purification method for diacetone acrylamide, in step one, the temperature of the reaction mixture during vacuum distillation is 50-55℃, the pressure is 0.01MPa, and the time is 20-60min.
[0016] In the above-mentioned purification method for diacetone acrylamide, in step three, the ammonia water is added for 30-60 minutes, the temperature is 30-50°C, the stirring time is 30-60 minutes, the stirring speed is 250-350 r / min, and the concentration of ammonia water is 18-20%.
[0017] In the above-mentioned method for purifying diacetone acrylamide, the polymerization inhibitor is a mixture of nitroxide free radical piperidinol, 2,4-di-tert-butylphenol and biphenyl, and the total amount of polymerization inhibitor added is 0.5 to 1% of the mass of the organic layer.
[0018] In the above-mentioned method for purifying diacetone acrylamide, the mass ratio of nitric oxide free radical piperidinol, 2,4-di-tert-butylphenol, and biphenyl hydroquinone is 1:1:1 to 3.
[0019] In the above-mentioned method for purifying diacetone acrylamide, the polymerization inhibitor is a mixture of nitroxide free radical piperidinol, 2,4-di-tert-butylphenol and biphenyl, and the total amount of polymerization inhibitor added is 0.5 to 1% of the mass of the organic layer.
[0020] In the above-mentioned purification method for diacetone acrylamide, in step one, the reaction solution obtained after impurity removal is oxazine sulfate.
[0021] In the above-mentioned purification method for diacetone acrylamide, in step two, the stirring time is 20-40 min and the stirring speed is 250-350 r / min.
[0022] Compared with the prior art, the present invention brings the following beneficial technical effects:
[0023] This invention proposes a purification method for diacetone acrylamide, which differs from existing purification methods. The method of this invention involves sequential steps such as vacuum distillation, adding ammonia to the reaction solution and controlling the pH of the reaction solution at 2-3, and adding excess ammonia to remove acrylamide and N-tert-butylacrylamide generated by the side reaction, thereby obtaining high-purity diacetone acrylamide.
[0024] Specifically, this invention removes impurities, including acetone and isopropylidene acetone, by vacuum distillation. The reaction solution after impurity removal is oxazine sulfate. Neutralization and ring-opening are achieved by adding oxazine sulfate dropwise to ammonia water, yielding the product diacetone acrylamide and the impurity N-ring-containing organic compounds. To ensure high-purity diacetone acrylamide, the pH is controlled at 2-3 during the neutralization and ring-opening process in ammonia water. At this pH, hydrogen ions in the acid form a complex salt with the N-ring-containing organic compounds, which is then dissolved in water for removal. Therefore, a pH of 2-3 is crucial. This process allows for better removal of N-cyclic organic compounds. Adding excess ammonia to the resulting neutralized solution at a pH of 9-10 removes acrylamide and N-tert-butylacrylamide produced by side reactions, facilitating subsequent distillation and purification. Adding polymerization inhibitors to the organic layer, through the combined use of nitric oxide free radical piperidinol, 2,4-di-tert-butylphenol, and biphenyl, effectively prevents the formation of oligomers and polymers of diacetone acrylamide during distillation. By employing a reasonable and effective temperature and distillation under high vacuum, high-purity diacetone acrylamide was successfully obtained.
[0025] Compared with existing technologies, this invention improves the purification process to obtain high-purity diacetone acrylamide; moreover, the purification method is simple to operate, easy to control, and can be industrially promoted and used. Detailed Implementation
[0026] This invention proposes a method for purifying diacetone acrylamide. To make the advantages and technical solutions of this invention clearer and more explicit, the invention will be further described below with reference to specific embodiments.
[0027] All the raw materials required in this invention can be purchased through commercial channels.
[0028] This invention discloses a method for preparing diacetone acrylamide. The raw materials used are acetone and acrylonitrile, with concentrated sulfuric acid as a catalyst, to react and obtain a reaction mixture. However, the reaction mixture contains a large number of impurities, which reduces the quality of diacetone acrylamide. In addition, high-quality diacetone acrylamide cannot be obtained by conventional vacuum distillation in the prior art. Therefore, this invention proposes a purification method for diacetone acrylamide, which can further improve the purity of diacetone acrylamide.
[0029] Using acetone and acrylonitrile as raw materials and concentrated sulfuric acid as a catalyst, the reaction mixture is purified using the method of this invention.
[0030] Step 1: The reaction mixture is subjected to vacuum distillation to remove some organic impurities, including acetone and isopropylidene acetone. After impurity removal, the reaction solution is obtained. The temperature of the reaction mixture during vacuum distillation is 50-55℃, the pressure is 0.01MPa, and the time is 20-60min. The reaction solution after impurity removal is oxazine sulfate.
[0031] Step 2: Lower the temperature of the reaction solution from Step 1 to 10-20°C to avoid the formation of polymers and other impurities due to excessively high temperatures. Drop the reaction solution at 10-20°C into ammonia water to neutralize and open the ring-shaped intermediate of the reaction solution (oxazine sulfate). Ring-opening yields diacetone acrylamide and N-containing cyclic organic compounds. The concentration of ammonia water is 15-30%. During the dropwise addition, the temperature of the reaction solution is controlled at 20-25°C. During the dropwise addition, the reaction solution is adjusted to be acidic with a pH of 2-3. Under this pH condition, the N-containing cyclic organic compounds are removed. The mass of ammonia water is 1.6-1.7 times the mass of concentrated sulfuric acid. After standing and separating into layers, a neutralized solution is obtained.
[0032] Step 3: Add ammonia to the neutralization solution to adjust the pH to 9-10. Remove acrylamide and N-tert-butylacrylamide produced by the side reaction by adding ammonia dropwise. Allow the solution to stand and separate into layers to obtain the organic layer. The ammonia dropwise addition time is 30-60 min, the temperature is 30-50℃, and the concentration of ammonia is 18-20%.
[0033] Step 4: Add a polymerization inhibitor to the organic layer. The polymerization inhibitor is a mixture of nitroxide-free piperidinol, 2,4-di-tert-butylphenol, and biphenyl hydroquinone. Distillation is performed under a vacuum of 5 Pa, and the distillate at 110–120°C is collected to obtain diacetone acrylamide. The total amount of polymerization inhibitor added is 0.5–1% of the mass of the organic layer; preferably, the mass ratio of nitroxide-free piperidinol, 2,4-di-tert-butylphenol, and biphenyl hydroquinone is 1:1:1–3.
[0034] The main mechanism of the purification method of the present invention will be briefly explained below.
[0035] The vacuum distillation in step one removes unreacted acetone, acrylonitrile, and isopropylidene acetone produced by the side reaction. The reaction solution obtained by vacuum distillation is oxazine sulfate. In existing technologies, directly washing the reaction solution after vacuum distillation with alkali cannot remove impurities. This invention neutralizes and ring-opens the oxazine sulfate by adding the reaction solution to ammonia water. The addition of ammonia water must meet the following conditions: the pH of the reaction solution after adding ammonia water is 2-3 (the catalyst in the reaction process is concentrated sulfuric acid, and the reaction solution contains concentrated sulfuric acid). The oxazine sulfate is neutralized and ring-opened by adding ammonia water, yielding the products diacetone acrylamide and an N-ring-containing organic compound. Because the ammonia water is added dropwise... The pH of the reaction solution in water is between 2 and 3, so hydrogen ions can form complex salts with N-cyclic organic compounds and dissolve them in water for removal. Adding excess ammonia to the resulting neutralized solution and adjusting the pH to 9 to 10 can remove acrylamide and N-tert-butylacrylamide produced by the side reaction, providing convenient conditions for subsequent distillation and purification. The combined use of nitric oxide free radical piperidinol, 2,4-di-tert-butylphenol and biphenyl can effectively prevent the formation of oligomers and polymers of diacetone acrylamide during distillation. By using a reasonable and effective temperature and distillation under high vacuum, high-purity diacetone acrylamide was successfully obtained.
[0036] The structural formula of an N-cyclic organic compound is:
[0037] The chemical equation for the formation of complex salts by hydrogen ions and N-cyclic organic compounds is shown below.
[0038]
[0039] The present invention will be further described below with reference to specific embodiments.
[0040] Example 1:
[0041] Step 1: Diacetone acrylamide reaction mixture 354g was subjected to vacuum distillation at a pressure of 0.01MPa and a temperature of 50℃ for 20 minutes to obtain 321g of reaction solution;
[0042] Step 2: Cool the reaction solution to 20°C, then slowly add the reaction solution dropwise to 301g of 18% ammonia water while stirring. The temperature is controlled at 23-24°C. After completion, the pH is measured to be 2. Continue stirring at this temperature for 30 minutes at a stirring speed of 300r / min. During this period, hydrogen ions form complex salts with N-containing cyclic organic compounds. Then allow the mixture to stand and separate into layers to obtain 301g of neutralized solution.
[0043] Step 3: Then heat to 40-41℃, add 177g of 18% ammonia water to the neutralization solution and measure the pH to be 9. Stir at this temperature for 30 minutes at a stirring speed of 300r / min. With excess ammonia water, acrylamide and N-tert-butylacrylamide produced by the side reaction can be removed. Then let stand and separate into layers to obtain 248g of organic layer (crude product solution).
[0044] Step 4: Add 0.46g of nitric oxide free radical piperidinol, 0.46g of 2,4-di-tert-butylphenol and 0.92g of biphenyl to the organic layer in Step 3, and then carry out distillation under a vacuum of 5 Pa, collecting 234g of diacetone acrylamide distillate at 110-120℃.
[0045] Example 2:
[0046] Step 1: Diacetone acrylamide reaction mixture 354g was subjected to vacuum distillation at 0.01MPa and 50℃ for 20 minutes to obtain 321g of reaction solution;
[0047] Step 2: Cool the reaction solution to 20°C, then slowly add the reaction solution dropwise to 320g of 18% ammonia water while stirring. The temperature is controlled at 23-24°C. After completion, the pH is measured to be 6. Continue stirring at this temperature for 30 minutes at a stirring speed of 300r / min. During this period, hydrogen ions form complex salts with N-containing cyclic organic compounds. Then allow the mixture to stand and separate into layers to obtain 298g of neutralized solution.
[0048] Step 3: Then heat to 40-41℃, add 175g of 18% ammonia water to the neutralization solution and measure the pH to be 9. Stir at this temperature for 30 minutes at a speed of 300r / min, and then let it stand to separate into layers to obtain 243g of organic layer (crude product solution).
[0049] Step 4: Add 0.45g of nitric oxide free radical piperidinol, 0.45g of 2,4-di-tert-butylphenol and 0.90g of biphenyl to the organic layer in Step 3, and then carry out distillation under a vacuum of 5 Pa, collecting 229g of diacetone acrylamide distillate at 110-120℃.
[0050] Example 3:
[0051] Step 1: Diacetone acrylamide reaction mixture 354g was subjected to vacuum distillation at 0.01MPa and 50℃ for 20 minutes to obtain 321g of reaction solution;
[0052] Step 2: Cool the reaction solution to 20°C, then slowly add 305g of 18% ammonia water dropwise. During the addition process, the temperature is controlled at 23-24°C. After completion, the pH is measured to be 3. Continue stirring at this temperature for 30 minutes at a stirring speed of 300r / min. During this period, hydrogen ions form complex salts with N-containing cyclic organic compounds. Then, allow the mixture to stand and separate into layers to obtain 301g of neutralized solution.
[0053] Step 3: Then heat to 40-41℃, add 199g of 18% ammonia water to the neutralization solution and measure the pH to be 12. Stir at this temperature for 30 minutes at a speed of 300r / min, and then let it stand to separate into layers to obtain 241g of organic layer (crude product solution).
[0054] Step 4: Add 0.45g of nitric oxide free radical piperidinol, 0.45g of 2,4-di-tert-butylphenol and 0.90g of biphenyl to the organic layer in Step 3, and then carry out distillation under a vacuum of 5 Pa, collecting 227g of diacetone acrylamide distillate at 110-120℃.
[0055] Example 4:
[0056] Step 1: Diacetone acrylamide reaction mixture 354g was subjected to vacuum distillation at 0.01MPa and 50℃ for 20 minutes to obtain 321g of reaction solution;
[0057] Step 2: Cool the reaction solution to 20°C, then slowly add the reaction solution dropwise to 320g of 18% ammonia water. During the addition process, the temperature is controlled at 23-24°C. After completion, the pH is measured to be 6. Continue stirring at this temperature for 30 minutes at a stirring speed of 300r / min. During this period, hydrogen ions form complex salts with N-containing cyclic organic compounds. Then, allow the mixture to stand and separate into layers to obtain 295g of neutralized solution.
[0058] Step 3: Then heat to 40-41℃, add 196g of 18% ammonia water to the neutralization solution and measure the pH to be 12. Stir at this temperature for 30 minutes at a speed of 300r / min, and then let it stand to separate into layers to obtain 236g of organic layer (crude product solution).
[0059] Step 4: Add 0.44g of nitric oxide free radical piperidinol, 0.44g of 2,4-di-tert-butylphenol and 0.88g of biphenyl to the organic layer in Step 3, and then carry out distillation under a vacuum of 5 Pa, collecting 223g of diacetone acrylamide distillate at 110-120℃.
[0060] Example 5:
[0061] Step 1: Diacetone acrylamide reaction mixture 354g was subjected to vacuum distillation at a pressure of 0.01MPa and a temperature of 50℃ for 20 minutes to obtain 332g of reaction solution;
[0062] Step 2: Cool the reaction solution to 20°C, then slowly add 315g of 18% ammonia water dropwise while stirring. The temperature is controlled at 23-24°C. After completion, the pH is measured to be 5. Continue stirring at this temperature for 30 minutes at a stirring speed of 300r / min. During this period, hydrogen ions form complex salts with N-containing cyclic organic compounds. Then allow the mixture to stand and separate into layers to obtain 283g of neutralized solution.
[0063] Step 3: Then heat to 40-41℃, add 177g of 18% ammonia water to the neutralization solution and measure the pH to be 9. Stir at this temperature for 30 minutes at a stirring speed of 300r / min. With excess ammonia water, acrylamide and N-tert-butylacrylamide produced by the side reaction can be removed. Then let stand and separate into layers to obtain 248g of organic layer (crude product solution).
[0064] Step 4: Add 0.26g of nitric oxide free radical piperidinol (ZJ701), 0.26g of p-benzoquinone, and 0.4g of phenothiazine to the organic layer in Step 3, and then carry out distillation under a vacuum of 5 Pa, collecting 230g of diacetone acrylamide distillate at 110-120℃.
[0065] Comparative Example 1:
[0066] Step 1: Diacetone acrylamide reaction mixture 354g was subjected to vacuum distillation at a pressure of 0.01MPa and a temperature of 50℃ for 20 minutes to obtain 321g of reaction solution;
[0067] Step 2: Cool the reaction solution to 20°C, then slowly add the reaction solution dropwise to 301g of 18% sodium hydroxide while stirring. The temperature is controlled at 23-24°C. After completion, the pH is measured to be 2. Continue stirring at this temperature for 30 minutes at a stirring speed of 300r / min. During this period, hydrogen ions form complex salts with N-containing cyclic organic compounds. Then allow the mixture to stand and separate into layers to obtain 280g of neutralized solution.
[0068] Step 3: Then heat to 40-41℃, add 177g of 18% sodium hydroxide to the neutralization solution and measure the pH to be 9. Stir at this temperature for 30 minutes at a speed of 300r / min. With excess sodium hydroxide, acrylamide and N-tert-butylacrylamide produced by the side reaction can be removed. Then let stand and separate into layers to obtain 224g of organic layer (crude product solution).
[0069] Step 4: Add 0.42g of nitric oxide free radical piperidinol, 0.42g of 2,4-di-tert-butylphenol and 0.84g of biphenyl to the organic layer in Step 3, and then carry out distillation under a vacuum of 5 Pa, collecting 210g of diacetone acrylamide distillate at 110-120℃.
[0070] Comparative Example 2:
[0071] Step 1: Diacetone acrylamide reaction mixture 354g was subjected to vacuum distillation at 0.01MPa and 50℃ for 20 minutes to obtain 321g of reaction solution;
[0072] Step 2: Cool the reaction solution to 20°C, then slowly add the reaction solution dropwise to 373g of 18% ammonia water while stirring. The temperature is controlled at 23-24°C. After completion, the pH is measured to be 7.5. Continue stirring at this temperature for 30 minutes at a stirring speed of 300r / min. Then let it stand to separate into layers to obtain 314g of neutralized solution.
[0073] Step 3: Then heat to 40-41℃, add 177g of 18% ammonia water to the neutralization solution and measure the pH to be 9. Stir at this temperature for 30 minutes at a stirring speed of 300r / min. With excess sodium hydroxide, acrylamide and N-tert-butylacrylamide produced by the side reaction can be removed. Then let stand and separate into layers to obtain 270g of organic layer (crude product solution).
[0074] Step 4: Cool the crude product solution to 23-24℃, add 7.24g of 16% hydrochloric acid to the crude product solution, and measure the pH to be 2 after completion. Continue stirring at this temperature for acid washing for 30 minutes at a stirring speed of 300r / min. During this period, hydrogen ions form complex salts with N-containing cyclic organic compounds. Then, allow the mixture to stand and separate into layers to obtain 243g of acid-washed organic phase.
[0075] Step 5: Add 0.45g of nitric oxide free radical piperidinol, 0.45g of 2,4-di-tert-butylphenol and 0.90g of biphenyl to the acid-washed organic phase in Step 3, and then carry out distillation under a vacuum of 5 Pa, collecting 228g of diacetone acrylamide distillate at 110-120℃.
[0076] Comparative Example 3:
[0077] Step 1: Diacetone acrylamide reaction mixture 354g was subjected to vacuum distillation at a pressure of 0.01MPa and a temperature of 50℃ for 20 minutes to obtain 321g of reaction solution;
[0078] Step 2: Cool the reaction solution to 20°C, then slowly add the reaction solution dropwise to 301g of 18% ammonia water while stirring. The temperature is controlled at 23-24°C. After completion, the pH is measured to be 2. Continue stirring at this temperature for 30 minutes at a stirring speed of 300r / min. During this period, hydrogen ions form complex salts with N-containing cyclic organic compounds. Then allow the mixture to stand and separate into layers to obtain 301g of neutralized solution.
[0079] Step 3: Then heat to 40-41℃, add 177g of 18% sodium hydroxide to the neutralization solution and measure the pH to be 9. Stir at this temperature for 30 minutes at a speed of 300r / min. With excess sodium hydroxide, acrylamide and N-tert-butylacrylamide produced by the side reaction can be removed. Then let stand and separate into layers to obtain 235g of organic layer (crude solution).
[0080] Step 4: Add 0.44g of nitric oxide free radical piperidinol, 0.44g of 2,4-di-tert-butylphenol and 0.88g of biphenyl to the organic layer in Step 3, and then carry out distillation under a vacuum of 5 Pa, collecting 221g of diacetone acrylamide distillate at 110-120℃.
[0081] Comparative Example 4:
[0082] Step 1: Diacetone acrylamide reaction mixture 354g was subjected to vacuum distillation at a pressure of 0.01MPa and a temperature of 50℃ for 20 minutes to obtain 321g of reaction solution;
[0083] Step 2: Cool the reaction solution to 20°C, then slowly add the reaction solution dropwise to 301g of 18% ammonia water while stirring. The temperature is controlled at 23-24°C. After completion, the pH is measured to be 2. Continue stirring at this temperature for 30 minutes at a stirring speed of 300r / min. During this period, hydrogen ions form complex salts with N-containing cyclic organic compounds. Then allow the mixture to stand and separate into layers to obtain 301g of neutralized solution.
[0084] Step 3: Then heat to 40-41℃, add 177g of 18% ammonia water to the neutralization solution and measure the pH to be 9. Stir at this temperature for 30 minutes at a stirring speed of 300r / min. With excess ammonia water, acrylamide and N-tert-butylacrylamide produced by the side reaction can be removed. Then let stand and separate into layers to obtain 248g of organic layer (crude product solution).
[0085] Step 4: Add 0.62g of 2,4-di-tert-butylphenol and 1.24g of biphenyl to the organic layer in Step 3, and then carry out distillation under a vacuum of 5 Pa. Collect 230g of diacetone acrylamide distillate at 110-120℃.
[0086] The diacetone acrylamide prepared in Examples 1-6 above was subjected to gas chromatography testing. The instruments, methods, and results used in the testing are as follows:
[0087] Testing instrument: Gas chromatograph HF901 (equipped with a hydrogen flame ionization detector): Shandong Huifen Instrument Co., Ltd.;
[0088] Test method: Gas chromatography is used. Under selected operating conditions, the sample is vaporized and separated by a chromatographic column.
[0089] Diacetone acrylamide was detected using a flame ionization detector and quantified using the area normalization method, as shown in Tables 1 and 2. Table 3 shows the gas phase detection data of the diacetone acrylamide reaction mixture (area normalization method), and Table 4 shows the gas phase detection data of the diacetone acrylamide product (area normalization method).
[0090] Table 1. GC detection data of major components in the diacetone acrylamide (DAAM) purification process of each embodiment.
[0091]
[0092]
[0093] Table 2. Content and yield of diacetone acrylamide (DAAM) in each example.
[0094] Example 1 99.89 84.05 Example 2 99.59 82.26 Example 3 99.80 81.54 Example 4 99.56 80.10 Example 5 99.68 82.62 Comparative Example 1 99.78 75.43 Comparative Example 2 99.79 81.90 Comparative Example 3 99.80 79.38 Comparative Example 4 99.67 82.62
[0095] Table 3. Gas phase detection data of diacetone-acrylamide reaction mixture (area normalization method)
[0096]
[0097]
[0098]
[0099] Table 4. Gas chromatography data for diacetone acrylamide (area normalization method)
[0100] 6.7089 1.1961 0.0554 7.2324 0.3621 0.0168 8.9319 0.6217 0.0288 DAAM 9.5370 2155.2290 99.8990
[0101] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection claimed in this application.
Claims
1. A method for purifying diacetone acrylamide, wherein the diacetone acrylamide is extracted from a reaction mixture, the reaction mixture being prepared from acetone and acrylonitrile as raw materials under the catalysis of concentrated sulfuric acid, characterized in that: The purification method includes the following steps: Step 1: The reaction mixture is subjected to vacuum distillation to remove some organic impurities, including acetone and isopropylidene acetone. After impurity removal, the reaction solution is obtained. Step 2: Lower the temperature of the reaction solution from Step 1 to 10-20°C, add the reaction solution to the ammonia water, and start stirring. The cyclic intermediate of the reaction solution is neutralized and ring-opened to obtain diacetone acrylamide and an N-containing cyclic organic compound. The concentration of ammonia water is 15-30%. During the addition process, the pH of the reaction solution is adjusted to 2-3. Under this pH condition, the N-containing cyclic organic compound is removed. The mass of ammonia water is 1.6-1.7 times the mass of concentrated sulfuric acid. After standing and separating into layers, a neutralized solution is obtained. The structural formula of an N-cyclic organic compound is: ; Step 3: Add ammonia to the neutralization solution to adjust the pH to 9-10. The ammonia removes the acrylamide and N-tert-butylacrylamide produced by the side reaction. Let the mixture stand to separate the layers to obtain the organic layer. Step 4: Add a polymerization inhibitor to the organic layer, and carry out distillation under a vacuum of 5 Pa. Collect the distillate at a temperature of 110-120℃ to obtain diacetone acrylamide.
2. The purification method for diacetone acrylamide according to claim 1, characterized in that: In step two, the temperature is controlled at 20-25℃ during the dropwise addition of the reaction solution to the ammonia water, and the stirring time is 20-40 minutes.
3. The purification method for diacetone acrylamide according to claim 1, characterized in that: In step one, the temperature of the reaction mixture during vacuum distillation is 50–55°C, the pressure is 0.01 MPa, and the time is 20–60 min.
4. The method for purifying diacetone acrylamide according to claim 1, characterized in that: In step three, the ammonia water is added over a period of 30–60 minutes, at a temperature of 30–50°C, for a stirring time of 30–60 minutes, at a stirring speed of 250–350 r / min, and the concentration of the ammonia water is 18–20%.
5. The method for purifying diacetone acrylamide according to claim 1, characterized in that: The polymerization inhibitor is a mixture of nitroxide free radical piperidinol, 2,4-di-tert-butylphenol and biphenyl, and the total amount of polymerization inhibitor added is 0.5 to 1% of the mass of the organic layer.
6. The purification method for diacetone acrylamide according to claim 5, characterized in that: The mass ratios of nitric oxide free radical piperidinol, 2,4-di-tert-butylphenol, and biphenyl hydroquinone were 1:1:1 to 3, respectively.
7. The method for purifying diacetone acrylamide according to claim 1, characterized in that: In step one, the reaction solution obtained after impurity removal is oxazine sulfate.
8. The method for purifying diacetone acrylamide according to claim 2, characterized in that: In step two, the stirring speed is 250-350 r / min.