Method for recovering N-tert-butyl acrylamide from AMPS production kettle residues

Abstract

The invention belongs to the technical field of recycling of chemical byproducts and purification of fine chemicals, and particularly relates to a method for efficiently recovering N-t-BAA (N-tert-butyl acrylamide) from AMPS (2-acrylamide-2-methylpropanesulfonic acid) production kettle residues. The method comprises the following steps: by taking AMPS production kettle residues as raw materials, firstly, effectively separating and removing sulfonic acid byproducts, inorganic salts and water-soluble impurities in the kettle residues through a multi-stage water-phase crystallization and suspension separation technology; an industrial-grade N-t-BAA initial product is obtained; and carrying out deep impurity removal and crystal form reforming through a recrystallization technology to obtain a high-purity N-t-BAA product (the purity is greater than or equal to 99.5%).

Description

Technical Field

[0001] This invention belongs to the field of chemical by-product resource utilization and fine chemical purification technology, specifically relating to a process for efficiently recovering and purifying N-tert-butylacrylamide (Nt-BAA) from reactor residues generated during AMPS production. Background Technology

[0002] AMPS (2-acrylamido-2-methylpropanesulfonic acid) is an important vinyl sulfonic acid monomer widely used in water treatment, oil extraction, textiles, papermaking, and polymer synthesis industries. During its synthesis, a considerable amount of N-tert-butylacrylamide (Nt-BAA) is often produced as a byproduct. Currently, most of the Nt-BAA-containing reactor residues generated in industrial production are disposed of as hazardous waste, resulting in both resource waste and environmental pressure.

[0003] Traditional methods for recovering Nt-BAA from such wastes often suffer from high energy consumption, long process flows, large solvent usage, low product purity, significant wastewater and residue production, and poor economic efficiency. For example, sublimation recovery requires high vacuum and high temperature (120-150℃) conditions, resulting in higher energy consumption than this invention. It also places stringent requirements on equipment sealing performance and temperature resistance, limiting the batch throughput and hindering large-scale production. Furthermore, N-tert-butylacrylamide is prone to thermal decomposition during sublimation, leading to a product yield of only 60-70%, which fails to meet the demands of efficient industrial recovery. Solvent recrystallization, while simple, offers limited product purity (typically ≤99%), requires fewer solvent recycling cycles, and is costly. Therefore, developing an efficient and low-cost recovery process is of significant industrial application value. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention aims to provide a method for recovering high-purity N-tert-butylacrylamide from AMPS production reactor residues, focusing on solving the problems of low product purity, large solvent consumption, excessive waste liquid, high cost, and difficulty in scaling up existing processes.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for recovering N-tert-butylacrylamide (Nt-BAA) from reactor residues in the production of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), the method comprising the following steps: (1) Add water to the residue in the 2-acrylamide-2-methylpropanesulfonic acid production reactor, let it stand, separate the layers, and discharge the lower aqueous phase; (2) Add water to the upper mixture obtained in step (1), let it stand, separate the layers twice, and remove the lower aqueous phase; (3) Collect the upper slurry after the second stratification in step (2), filter and separate it to obtain the primary product of N-tert-butylacrylamide; (4) The primary product obtained in step (3) is subjected to crystallization or precipitation treatment; (5) Filter the crystallized slurry obtained in step (4), wash the resulting filter cake, and dry it to obtain N-tert-butylacrylamide.

[0006] According to an embodiment of the present invention, in step (4), the crystallization process is gradient cooling crystallization; preferably, the primary product obtained in step (3) is dissolved in an organic solvent to form a saturated solution, and then crystallized by gradient cooling.

[0007] According to an embodiment of the present invention, in step (4), the crystallization process is carried out by using a good solvent and a bad solvent; preferably, the primary product obtained in step (3) is dissolved in a good solvent to form a saturated solution, and then a bad solvent is added to crystallize.

[0008] According to an embodiment of the present invention, the method includes the following steps: (1) Add water to the residue of the 2-acrylamide-2-methylpropanesulfonic acid production reactor, heat up, stir, cool, let stand, separate and discharge the lower aqueous phase; (2) Add water to the upper mixture obtained in step (1), stir, let stand, separate the layers twice, and remove the lower aqueous phase; (3) Collect the upper slurry after the second stratification in step (2), filter and separate it, wash the obtained solid with water, dry it, and obtain the primary product of N-tert-butylacrylamide; (4) Dissolve the primary product obtained in step (3) in an organic solvent to form a saturated solution, and then crystallize by gradient cooling; Alternatively, the primary product obtained in step (3) can be dissolved in a good solvent to form a saturated solution, and then a poor solvent can be added to induce crystallization. (5) Filter the crystallized slurry obtained in step (4), wash the resulting filter cake, and dry it to obtain N-tert-butylacrylamide.

[0009] According to an embodiment of the present invention, the mother liquor obtained by filtering the crystallized slurry obtained in step (4) is recovered in step (5); preferably, the recovered mother liquor is recycled; preferably, the recovered mother liquor is used as an organic solvent or good solvent in step (4); preferably, the number of times it is recycled is not less than 5 times (e.g., 5-8 times, such as 5, 6, 7, 8 times, etc.). Wherein, the single recovery rate is not less than 85%. Wherein, the mother liquor can be recycled 5 times, and each time the purity of the Nt-BAA refined product is ≥99.5%, the sulfonate content is less than 0.1%, and the product yield is greater than 91%.

[0010] According to an embodiment of the present invention, the recovered mother liquor is recycled at least 5 times, and then distilled to recover the solvent. Preferably, the recovered solvent can be used as the organic solvent or good solvent in step (4). According to an embodiment of the present invention, the recovered solvent can be used as the organic solvent or good solvent in step (4) for gradient cooling crystallization or precipitation; preferably, the mother liquor after filtering the obtained crystallization slurry can be further recycled; preferably, the mother liquor is used as the organic solvent or good solvent in step (4); preferably, the number of times it is recycled is not less than 5 times (e.g., 5-8 times, e.g., 5 times, 6 times, 7 times, 8 times, etc.). Among them, the mother liquor can be recycled 5 times, and the purity of the Nt-BAA refined product is ≥99.5% each time, the sulfonate content is less than 0.1%, and the product yield is greater than or equal to 91%.

[0011] According to an embodiment of the present invention, in step (1), the amount of water added is 1-2 times the residual mass of the reactor, for example 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, etc., preferably 1.4-1.6 times or 1.5 times; and / or, the temperature is raised to 30℃-50℃, for example 30℃, 35℃, 40℃, 45℃, 50℃; and / or, the stirring temperature is 30℃-50℃, for example 30℃, 35℃, 40℃, 45℃, 50℃; and / or, the temperature is cooled to room temperature (for example 25℃); and / or, the temperature is allowed to stand for 3-8 hours (for example 4 hours); and / or, the lower aqueous phase rich in sulfonic acid compounds is separated and discharged.

[0012] According to an embodiment of the present invention, in step (2), the amount of water added is 0.3-0.5 times the residual mass of the vessel in step (1), for example, 0.3 times, 0.4 times, or 0.5 times; and / or, the stirring temperature is 30℃-50℃, for example, 30℃, 35℃, 40℃, 45℃, or 50℃; and / or, the vessel is left to stand for 3-8 hours (for example, 4 hours).

[0013] According to an embodiment of the present invention, in step (3), the obtained solid is rinsed with pre-cooled water; preferably, the temperature of the pre-cooled water is 5°C-10°C (e.g., 8°C); preferably, the rinsing is performed 1-3 times (e.g., 2 times). According to an embodiment of the present invention, in step (3), the drying temperature is 60°C-70°C (e.g., 65°C); and / or, the drying time is 6-8 hours (e.g., 7 hours).

[0014] According to an embodiment of the present invention, the purity of the N-tert-butylacrylamide primary product obtained in step (3) is greater than 98%, for example 98.5%.

[0015] According to an embodiment of the present invention, in step (4), the organic solvent is selected from ethanol; and / or, a saturated solution is formed by heating, for example, heating to a reflux temperature, for example, 60°C-80°C (e.g., 70°C). According to an embodiment of the present invention, in step (4), the gradient cooling procedure is as follows: the temperature for forming the saturated solution is reduced to below 10°C (e.g., 0°C-10°C, 2°C, 5°C); preferably, the temperature for forming the saturated solution is a reflux temperature, for example, 60°C-80°C (e.g., 70°C); preferably, the cooling rate is 0.1°C / min-1°C / min, for example, 0.2°C / min, 0.4°C / min, 0.5°C / min, 0.8°C / min.

[0016] According to an embodiment of the present invention, in step (4), the good solvent is ethanol; and / or, the poor solvent is selected from water; and / or, the crystallization temperature is below 10°C (e.g., 0°C-10°C, 2°C, 5°C). According to an embodiment of the present invention, in step (4), a saturated solution is formed by heating, for example, heating to the reflux temperature, for example, 60°C-80°C (e.g., 70°C).

[0017] According to an embodiment of the present invention, in step (4), after gradient cooling crystallization or precipitation, the crystal is kept warm for 1-5 hours, for example 2 hours.

[0018] According to an embodiment of the present invention, in step (5), the obtained filter cake is washed with a pre-cooled (0°C-5°C, for example 0°C) solvent. According to an embodiment of the present invention, the solvent is a mixed solvent comprising a good solvent and a bad solvent; preferably, the good solvent is ethanol; preferably, the bad solvent is selected from n-hexane; preferably, the volume ratio of the good solvent to the bad solvent is 1-3:3-1, for example 1:1.

[0019] According to an embodiment of the present invention, in step (5), the drying temperature is 50°C-70°C (e.g., 55°C); and / or the drying time is 6-10 hours (e.g., 9 hours).

[0020] According to an embodiment of the present invention, the purity of the N-tert-butylacrylamide obtained in step (5) is greater than 99%, for example 99.83%; preferably, the content of sulfonic acid compounds (e.g., sulfonates) in the N-tert-butylacrylamide obtained in step (5) is less than 0.1%, for example 0.07%. According to an embodiment of the present invention, the yield of the method is, for example, 91.3%.

[0021] The method provided by this invention can recover high-purity N-tert-butylacrylamide, with a purity greater than 99% and a sulfonic acid compound (e.g., sulfonate) content of less than 0.1%, and a yield of over 90%.

[0022] According to an embodiment of the present invention, the method includes the following steps: (1) Cooling and crystallization of primary aqueous phase: Add 1 to 2 times (e.g. 1.5 times) the mass of the AMPS production reactor residue to water, heat the mixture to 30-50°C or 35-50°C (e.g. 45°C), stir evenly, then cool naturally to room temperature and let stand for 3-8 hours (e.g. 4 hours) to allow it to fully separate into layers, separate and discharge the lower aqueous phase rich in sulfonic acid compounds; (2) Secondary water washing and stratification: Add 0.3 to 0.5 times (e.g. 0.4 times) of the initial mass of the residue to the upper mixture obtained in step (1), stir evenly at 30-50℃ or 35-50℃ (e.g. 45℃), and then let stand for 3-8 hours (e.g. 4 hours) to carry out secondary stratification, separate and discharge the lower water phase; (3) Solid-liquid separation and primary product acquisition: Collect the upper slurry after secondary stratification in step (2), filter and separate it, wash the obtained solid twice with a small amount of pre-cooled (5-10℃) deionized water, and dry it at 60-70℃ for 6-8 hours to obtain N-tert-butylacrylamide primary product (white solid with a purity ≥98%). (4) Deep purification: Dissolve the primary product obtained in step (3) in a good organic solvent (good solvent), heat until completely dissolved to form a saturated or near-saturated solution, and then cool to below 10°C for crystallization by using a programmed temperature gradient crystallization or adding a poor solvent for crystallization. (5) Refined product acquisition and solvent recovery: The crystallized slurry obtained in step (4) is filtered, and the resulting filter cake is washed with a pre-cooled mixture of good / bad solvents (V:V=1:1) and dried at 50-70℃ under normal pressure for 5-10 hours to obtain N-tert-butylacrylamide (purity ≥99.5%, high-purity Nt-BAA product). Collect the mother liquor after filtering the crystallized slurry from step (5) and use it as an organic solvent or good solvent in step (4) for recycling; the number of recycling times shall not be less than 5 times; After the recycling process is completed, the solvent is recovered by distillation and concentration. The recovered solvent can be recycled as an organic solvent or good solvent in step (4).

[0023] According to an embodiment of the present invention, the method does not use sublimation and does not require adjusting the pH of the system with alkali.

[0024] Beneficial effects This invention provides a method for recovering high-purity N-tert-butylacrylamide from AMPS production reactor residue. This method avoids the sublimation method (which requires high vacuum and high temperature conditions, resulting in higher energy consumption than this invention, stringent requirements for equipment sealing and temperature resistance, limited batch throughput, and difficulty in large-scale production; furthermore, N-tert-butylacrylamide is prone to thermal decomposition during sublimation, leading to a product yield of only 60-70%, failing to meet the demands of efficient industrial recovery) and also avoids the use of alkali to adjust the pH of the system (adding alkali generates a large amount of salt impurities, increasing the difficulty of subsequent wastewater treatment, resulting in 40% higher wastewater discharge than this invention, and significantly increasing disposal costs). This method solves the problems of high energy consumption, long process flow, large solvent usage, low product purity, large amounts of wastewater and waste residue, and poor economic efficiency associated with existing processes.

[0025] Compared with the prior art, the present invention has the following significant advantages: Energy saving and emission reduction: Using water as the main separation medium and adopting multi-stage suspension separation technology, the generation of wastewater is greatly reduced. Compared with existing technologies, energy consumption is reduced by more than 30%, wastewater discharge is reduced by 50%, and treatment costs are reduced by 25-30%. High resource utilization: Solvent recycling times ≥ 5 times, recovery rate ≥ 90%; Nt-BAA single recovery efficiency ≥ 85%, and average yield is stable at over 90%, far exceeding existing technologies, realizing the resource utilization of reactor residue; High product purity: By combining "aqueous phase multi-stage crystallization-precipitation" with "solvent recrystallization", the product purity is as high as 99.5% or more, and the sulfonate residue is ≤0.1%, meeting the needs of high-end applications; The process is stable and reliable: the step parameters are clear, the operation is strong, it is applicable to AMPS reactor residues with different Nt-BAA contents (15-50%), and it is suitable for large-scale production. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0027] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0028] The residue from the AMPS (2-acrylamide-2-methylpropanesulfonic acid) production reactor used was obtained from a chemical plant. Analysis showed that its Nt-BAA (N-tert-butylacrylamide) content was about 40-50 wt%, its AMPS content was about 15-25 wt%, and the remainder was water, inorganic salts, and polymers.

[0029] Purity analysis method for Nt-BAA (HPLC analysis): Instrument: Agilent 1260 HPLC system; Chromatographic column: YMC J'sphere ODS-H80C18 reversed-phase column (4.6 mm × 150 mm, 4 μm); Mobile phase: 0.01 mol / L dipotassium hydrogen phosphate-acetonitrile (v:v; 50:50); Flow rate: 0.5 mL / min; Column temperature: 30℃; Detection wavelength: 225 nm; Injection volume: 20 μL.

[0030] Example 1 (1) Take 1 kg of AMPS production reactor residue (based on factory discharge liquid) and place it in a 2 L reactor equipped with stirring and temperature control. Add 1.5 kg of deionized water and heat the reaction to 45°C. Stir until homogeneous. Then cool naturally to 25°C and let stand for 4 hours. After separation, discharge the lower aqueous phase (about 1.3 kg).

[0031] (2) Add 0.4 kg of deionized water to the residue, stir evenly at 35°C, let stand for 4 hours, and separate the lower aqueous phase. Filter the upper slurry, rinse the filter cake twice with 100 mL of pre-cooled (8°C) deionized water, and dry the resulting wet cake at 65°C for 7 hours to obtain 425 g of white Nt-BAA primary product with an HPLC purity of 98.5%.

[0032] (3) Take 400 g of the above primary product, add 800 mL of anhydrous ethanol, and heat to 70 °C and reflux to dissolve. Then cool to 2 °C at 0.4 °C / min and maintain the temperature for crystal growth for 2 hours. Filter and wash with 50 mL of pre-cooled (0 °C) ethanol-n-hexane (1:1) mixture. Dry the wet product at 55 °C for 9 hours to obtain 365 g of purified Nt-BAA product. Collect the mother liquor (for subsequent recycling). The purified product was analyzed by HPLC and found to have a purity of 99.83% (retention time of 4.715 min, symmetrical peak shape, and no impurity peak interference) and a sulfonate content of 0.07%.

[0033] The overall yield of this batch was 85.12% (overall yield = product mass after recrystallization / mass of Nt-BAA in AMPS reactor residue).

[0034] Example 2: Mother liquor circulation experiment

[0035] The mother liquor collected in Example 1 was used as the solvent (instead of anhydrous ethanol) for recrystallization in step (3) of the next batch of primary product (400 g), under the same operating conditions as step (3) of Example 1. The mother liquor can be recycled 5 times, and the purity of the Nt-BAA purified product is ≥99.5% each time, with a sulfonate content of less than 0.1%.

[0036] After being recycled 5 times, the mother liquor is concentrated by distillation to recover the solvent and then recrystallized for the next round of product.

[0037] Table 1. Product purity and yield data after 5 cycles of mother liquor reuse.

[0038] Product purity 1 The primary product (400 g) was recrystallized according to step (3) of Example 1, with the mother liquor collected in Example 1 as the solvent; the purity of Nt-BAA in the refined product after recrystallization was determined.

[0039] Product yield 2 Mass of Nt-BAA in the purified product after recrystallization / Mass of Nt-BAA in the residue of the AMPS production reactor.

[0040] Example 3: Solvent Recovery and Recycling Experiment The ethanol recovered in Example 2 (solvent ethanol recovered by distillation and concentration after five cycles of mother liquor) was used in a new round of deep purification steps. Following the same steps as in Example 1, the recovered ethanol was used as the recrystallization solvent (instead of anhydrous ethanol) in step (3) to recrystallize another batch of primary product (purity 98.3%).

[0041] The mother liquor was recycled and circulated 5 times according to Example 2. The results showed that the mother liquor could be recycled 5 times, and the purity of the Nt-BAA refined product was ≥99.5% each time, and the sulfonate content was less than 0.1%.

[0042] Table 2. Product purity and yield data after 5 cycles of mother liquor reuse.

[0043] Experimental results show that the process and solvent recovery method of the present invention are stable and reliable. After being recycled 5 times, the product purity is still maintained above 99.5%, and the yield does not show a significant decrease.

[0044] Example 4: Study on Recycling Process 4.1 Referring to Example 1, the amount of deionized water added in step (1) was adjusted to 1.7 kg and 1.3 kg. All other conditions remained unchanged.

[0045] The results showed that when the amount of deionized water added was 1.7 kg, the product yield in the recycling experiment in Example 2 decreased by 2-3% per cycle, and the amount of wastewater increased, resulting in high treatment costs. When the amount of deionized water added was 1.3 kg, the accumulation rate of impurities in the mother liquor accelerated, and the product purity dropped to below 99% after three cycles in the recycling experiment in Example 2.

[0046] 4.2 Referring to Example 1, in step (1), the exothermic reaction temperature was adjusted to 25 °C and 55 °C, and the mixture was stirred until homogeneous. All other conditions remained unchanged.

[0047] The results showed that when the stirring temperature was 25℃, the residual amount of sulfonic acid impurities in the mother liquor increased, and the sulfonate content of the product after recycling was prone to exceed the standard (>0.1%). When the stirring temperature was 55℃, not only did it increase energy consumption, but it may also cause intermolecular polymerization or hydrolysis reactions, resulting in a decrease in product purity.

[0048] 4.3 Referring to Example 1, 800 mL of methanol was added in step (3), and the other conditions remained unchanged.

[0049] The results showed that when methanol was used as the solvent, solvent azeotropy was likely to occur during the mother liquor circulation process, which led to a decrease in the purity of the recovered solvent. After 5 cycles, the product yield dropped to below 85%.

[0050] Comparative Example 1 (Regular water washing) Referring to step (1) in Example 1, the residue of the lower aqueous phase was filtered and dried, and the resulting product was light yellow with an HPLC purity of only 92.8%.

[0051] Comparative Example 2 (Rapid Cooling) Referring to Example 1, the recrystallization cooling rate in step (3) was adjusted from 0.4℃ / min to 5℃ / min (rapid cooling), while other conditions remained unchanged. The results showed that the final product had small crystals and a purity of only 99.1%.

[0052] Furthermore, when the mother liquor was recycled (refer to Example 2) for the third time, the product purity had dropped to 98.8% and the yield had dropped to 85%.

[0053] Comparative Example 3 (Alkali Treatment) Referring to Example 1, in step (1), after adding 1.5 kg of water, 5% sodium hydroxide solution is added to adjust the pH to 8-9, and the other conditions remain unchanged.

[0054] The results showed that the purity of the primary product obtained in step (2) was only 95.2%, and the purity of the product after recrystallization in step (3) was only 98.5%, with a yield of 85%. This indicates that the alkali treatment introduced additional impurities, which reduced the product purity and yield, and the product purity had dropped to 98.0% when the mother liquor was recycled (Example 2) for the second time.

[0055] The above embodiments illustrate that the process of the present invention can efficiently and economically recover high-purity Nt-BAA from AMPS reactor residue, and the solvent can be recycled, making it suitable for industrial applications.

[0056] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recovering N-tert-butylacrylamide from reactor residues in the production of 2-acrylamide-2-methylpropanesulfonic acid, the method comprising the following steps: (1) Add water to the residue in the 2-acrylamide-2-methylpropanesulfonic acid production reactor, let it stand, separate the layers, and discharge the lower aqueous phase; (2) Add water to the upper mixture obtained in step (1), let it stand, separate the layers twice, and remove the lower aqueous phase; (3) Collect the upper slurry after the second stratification in step (2), filter and separate it to obtain the primary product of N-tert-butylacrylamide; (4) The primary product obtained in step (3) is subjected to crystallization or precipitation treatment; (5) Filter the crystallized slurry obtained in step (4), wash the resulting filter cake, and dry it to obtain N-tert-butylacrylamide.

2. The method according to claim 1, characterized in that, The mother liquor obtained in step (4) after filtering the crystallized slurry in step (5) is recycled; Preferably, the recovered mother liquor is recycled. Preferably, the recovered mother liquor is used as the organic solvent or good solvent in step (4); Preferably, the number of times it is recycled is no less than 5 times.

3. The method according to claim 1, characterized in that, The method includes the following steps: (1) Add water to the residue of the 2-acrylamide-2-methylpropanesulfonic acid production reactor, heat up, stir, cool, let stand, separate and discharge the lower aqueous phase; (2) Add water to the upper mixture obtained in step (1), stir, let stand, separate the layers twice, and remove the lower aqueous phase; (3) Collect the upper slurry after the second stratification in step (2), filter and separate it, wash the obtained solid with water, dry it, and obtain the primary product of N-tert-butylacrylamide; (4) Dissolve the primary product obtained in step (3) in an organic solvent to form a saturated solution, and then crystallize by gradient cooling; Alternatively, the primary product obtained in step (3) can be dissolved in a good solvent to form a saturated solution, and then a poor solvent can be added to induce crystallization. (5) Filter the crystallized slurry obtained in step (4), wash the resulting filter cake, and dry it to obtain N-tert-butylacrylamide.

4. The method according to any one of claims 1-3, characterized in that, After the mother liquor is recycled, it is distilled to recover the solvent. Preferably, the recovered solvent is used as the organic solvent or good solvent in step (4); Preferably, the recovered solvent is used as the organic solvent or good solvent in step (4) for gradient cooling crystallization or precipitation. Preferably, the recovered solvent is used as the organic solvent or good solvent in step (4) for gradient cooling crystallization or precipitation, and the mother liquor after filtration of the resulting crystallized slurry is recycled. Preferably, the mother liquor is used as the organic solvent or good solvent in step (4); Preferably, the number of times it is recycled is no less than 5 times.

5. The method according to any one of claims 1-3, characterized in that, In step (1), the amount of water added is 1-2 times the residual mass of the vessel; And / or, raise the temperature to 30℃-50℃; And / or, the stirring temperature is 30℃-50℃; And / or, cool to room temperature; And / or, let stand for 3-8 hours; And / or, separate and drain the lower aqueous phase rich in sulfonic acid compounds.

6. The method according to any one of claims 1-3, characterized in that, In step (2), the amount of water added is 0.3-0.5 times the residual mass of the vessel in step (1); And / or, the stirring temperature is 30℃-50℃; And / or, let stand for 3-8 hours.

7. The method according to any one of claims 1-3, characterized in that, In step (3), the obtained solid is rinsed with pre-cooled water; preferably, the temperature of the pre-cooled water is 5℃-10℃; preferably, the rinsing is performed 1-3 times; And / or, in step (3), the drying temperature is 60℃-70℃; and / or, the drying time is 6-8 hours.

8. The method according to any one of claims 1-3, characterized in that, In step (4), the crystallization process is gradient cooling crystallization; preferably, the primary product obtained in step (3) is dissolved in an organic solvent to form a saturated solution, and then crystallized by gradient cooling. And / or, in step (4), the crystallization process is carried out by using a good solvent and a bad solvent; preferably: the primary product obtained in step (3) is dissolved in a good solvent to form a saturated solution, and then a bad solvent is added to crystallize; And / or, in step (4), the organic solvent is selected from ethanol; And / or, in step (4), a saturated solution is formed by heating; And / or, in step (4), the gradient cooling procedure is as follows: the temperature at which the saturated solution is formed is reduced to below 10°C; preferably, the temperature at which the saturated solution is formed is the reflux temperature; preferably, the cooling rate is 0.1°C / min-1°C / min; And / or, in step (4), the good solvent is ethanol; And / or, in step (4), the undesirable solvent is selected from water; And / or, in step (4), the crystallization temperature is below 10°C; And / or, in step (4), after gradient cooling crystallization or precipitation, heat preservation is performed to grow crystals; preferably, heat preservation is performed to grow crystals for 1-5 hours.

9. The method according to any one of claims 1-3, characterized in that, In step (5), the obtained filter cake is washed with a pre-cooled solvent; preferably, the solvent is a mixed solvent including a good solvent and a bad solvent; preferably, the good solvent is ethanol; preferably, the bad solvent is selected from n-hexane; preferably, the volume ratio of the good solvent to the bad solvent is 1-3:3-1. And / or, in step (5), the drying temperature is 50℃-70℃; and / or, the drying time is 6-10 hours.

10. The method according to any one of claims 1-3, characterized in that, The method includes the following steps: (1) Cooling and crystallization of primary aqueous phase: Add 1 to 2 times the mass of the AMPS production reactor residue to water, heat the mixture to 30-50°C, stir evenly, then cool naturally to room temperature, let stand for 3-8 hours to allow it to fully separate into layers, separate and discharge the lower aqueous phase rich in sulfonic acid compounds; (2) Secondary water washing and stratification: Add 0.3 to 0.5 times the initial mass of the reactor residue to the upper mixture obtained in step (1), stir evenly at 30-50℃, and then let stand for 3-8 hours to carry out secondary stratification, separate and discharge the lower water phase; (3) Solid-liquid separation and primary product acquisition: Collect the upper slurry after secondary stratification in step (2), filter and separate it, wash the obtained solid twice with a small amount of pre-cooled deionized water, and dry it at 60-70℃ for 6-8 hours to obtain N-tert-butylacrylamide primary product. (4) Deep purification: Dissolve the primary product obtained in step (3) in a good solvent, heat until completely dissolved to form a saturated or near-saturated solution, and then cool to below 10°C for crystallization by using a programmed temperature gradient crystallization or adding a poor solvent for crystallization. (5) Refined product acquisition and solvent recovery: The crystallized slurry obtained in step (4) is filtered, the resulting filter cake is washed with a pre-cooled mixture of good / bad solvents, and dried at 50-70℃ and normal pressure for 5-10 hours to obtain N-tert-butylacrylamide; Collect the mother liquor after filtering the crystallized slurry from step (5) and use it as an organic solvent or good solvent in step (4) for recycling; the number of recycling times shall not be less than 5.

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