A method for treating 2-acrylamido-2-methylpropanesulfonic acid mother liquor

Abstract

This invention discloses a method for treating the mother liquor of 2-acrylamido-2-methylpropanesulfonic acid, relating to the field of chemical technology. The method includes the following steps: S1, adding water to the mother liquor produced during the production of 2-acrylamido-2-methylpropanesulfonic acid for extraction, allowing it to stand and separate into layers, with the upper layer being an organic layer and the lower layer being an aqueous solution; S2, after extraction, the upper organic layer is distilled under reduced pressure in a distillation vessel, and the distilled solvent is recycled; distillation is stopped when precipitates are observed, followed by cooling, solid-liquid separation, and drying to obtain N-tert-butylacrylamide; the lower aqueous solution is treated with an adsorbent, filtered to obtain filtrate A, and liquid alkali is added to filtrate A until the pH reaches 8-10. After cooling, seed crystals are added, and the mixture is allowed to stand. The precipitates are then separated into solid and liquid components to obtain a solution of solid sodium sulfate and sodium 2-acrylamido-2-methylpropanesulfonic acid salt. This treatment method is low-cost, simple to operate, has high resource utilization, and produces a high-purity product.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, specifically to a method for treating 2-acrylamido-2-methylpropanesulfonic acid mother liquor. Background Technology

[0002] 2-Acrylamido-2-methylpropanesulfonic acid (AMPS) is a polymeric monomer containing sulfonic acid groups. Its structure includes sulfonic acid groups, amide groups, and unsaturated double bonds, giving it excellent properties. As a high-performance modified monomer, 2-acrylamido-2-methylpropanesulfonic acid has been widely used in industrial production such as textiles, plastics, papermaking, coatings, wastewater treatment, and oil extraction. It has been used to manufacture high-performance antistatic agents, dyes, dispersants, absorbents, flocculants, foam stabilizers, specialty coatings, and oilfield chemicals, making it a promising new organic material.

[0003] 2-Acrylamido-2-methylpropanesulfonic acid is produced by reacting acrylonitrile, sulfuric acid, and isobutylene. Side reactions are unavoidable during the production process. In addition, the acrylonitrile used in the reaction is in excess, as it serves as both a solvent and a reactant. Therefore, a large amount of mother liquor is generated during the solid-liquid separation process of 2-acrylamido-2-methylpropanesulfonic acid. This mother liquor contains some dissolved 2-acrylamido-2-methylpropanesulfonic acid product, as well as some by-product components and unreacted sulfuric acid residues.

[0004] Existing methods for treating mother liquor primarily involve vacuum distillation, with the distilled solvent recycled. The concentrate produced during distillation is either incinerated as hazardous waste or undergoes simple processing to extract substances such as N-tert-butylacrylamide. For example, CN114933675A mentions a comprehensive utilization method for 2-acrylamido-2-methylpropanesulfonic acid distillation concentrate. This method treats the concentrate obtained after distilling off the solvent from the mother liquor. The concentrate is mixed with water to precipitate N-tert-butylacrylamide, which is then further processed. However, because N-tert-butylacrylamide is obtained in an aqueous system, drying is difficult, and the product has high water content and high sulfate residue, resulting in poor overall product quality, low utilization rate, and difficult production operations. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for treating 2-acrylamido-2-methylpropanesulfonic acid mother liquor. This method involves pretreatment of the mother liquor before distillation, resulting in low cost, simple operation, high resource utilization, and low sulfate residue and high purity of the extracted product.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for treating 2-acrylamido-2-methylpropanesulfonic acid mother liquor includes the following steps:

[0008] S1. Add water to the mother liquor produced during the production of 2-acrylamido-2-methylpropanesulfonic acid for extraction. Stir for 20-40 minutes and allow to stand to separate into layers. The upper layer is an organic layer and the lower layer is an aqueous solution. The extraction is performed ≥2 times. Collect the aqueous solution after each separation for later use.

[0009] S2. After extraction, the upper organic layer enters the distillation vessel for vacuum distillation, and the distilled solvent is recycled. Distillation is stopped when precipitates are found in the vessel. The mixture is then cooled, separated from the solid, and dried to obtain N-tert-butylacrylamide.

[0010] After the lower aqueous solution is collected, an adsorbent is added, and the mixture is stirred for 30-60 minutes before filtration to obtain filtrate A. Liquid alkali is added to filtrate A until the pH is 8-10, and the temperature is lowered to 0-5℃. Seed crystals are added, and the mixture is allowed to stand for 4-6 hours. The precipitate is then separated into solid and liquid components to obtain solid and filtrate B. The solid is sodium sulfate, and filtrate B is a solution of sodium 2-acrylamido-2-methylpropanesulfonate.

[0011] In step S1, the mother liquor produced during the production of 2-acrylamido-2-methylpropanesulfonic acid is the filtrate obtained by solid-liquid separation after reacting acrylonitrile, sulfuric acid, and isobutylene to form a slurry.

[0012] Preferably, in step S1, the total amount of water added is in a weight ratio of 0.2 to 0.3 to the mother liquor.

[0013] Preferably, in step S2, the temperature after stopping distillation is 10-15°C.

[0014] Preferably, in step S2, the adsorbent is activated carbon or diatomaceous earth.

[0015] Preferably, in step S2, the amount of adsorbent added is 0.3 to 0.5% of the combined mass of the collected aqueous solution.

[0016] Preferably, in step S2, the mass concentration of the liquid alkali is ≥50%.

[0017] Preferably, in step S2, the seed crystal is anhydrous sodium sulfate or sodium sulfate decahydrate.

[0018] Preferably, in step S2, the amount of seed crystals added is 0.01 to 0.05% of the mass of filtrate A.

[0019] Preferably, in step S2, the temperature is controlled at 10-30°C, and most preferably 10-20°C during the addition of liquid alkali.

[0020] Preferably, in step S1, the number of water extractions is 2 to 5.

[0021] In step S2, the obtained sodium 2-acrylamido-2-methylpropanesulfonate has a liquid phase purity of ≥96%, the N-tert-butylacrylamide has a liquid phase purity of ≥99%, and the sulfate residue is ≤0.012%.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) This invention adopts an original process route and proposes to intervene in the treatment in advance before the mother liquor is distilled. It uses water as a medium for extraction and subsequent treatment to achieve the separation and purification of various products. It realizes the comprehensive treatment of the mother liquor for the production of 2-acrylamido-2-methylpropanesulfonic acid and can extract and prepare a variety of by-products. This treatment method has low cost, simple operation and high resource utilization. The sodium salt solution of 2-acrylamido-2-methylpropanesulfonic acid and the N-tert-butylacrylamide product obtained by this method have low sulfate residue and good quality.

[0024] (2) In this treatment method, N-tert-butylacrylamide is precipitated in an anhydrous system, which is easy to dry, which helps to save drying time, reduce water content and sulfate residue in the product, facilitates operation, and is suitable for industrial production. Attached Figure Description

[0025] The following figures are intended only to illustrate and explain the present invention and do not limit the scope of the invention. Wherein:

[0026] Figure 1 This is the liquid chromatogram of the sodium 2-acrylamido-2-methylpropanesulfonate solution prepared in Example 1;

[0027] Figure 2 This is the liquid chromatogram of N-tert-butylacrylamide prepared in Example 1. Detailed Implementation

[0028] The present invention will be further illustrated below with reference to embodiments. In the following detailed description, only certain exemplary embodiments of the invention are described by way of illustration. Undoubtedly, those skilled in the art will recognize that various modifications can be made to the described embodiments without departing from the spirit and scope of the invention. Therefore, the description is illustrative in nature and not intended to limit the scope of the claims.

[0029] Example 1

[0030] Take 2000 kg of mother liquor from the production of 2-acrylamido-2-methylpropanesulfonic acid, which contains 2% N-tert-butylacrylamide, 2% AMPS, 0.2% residual sulfuric acid and other trace impurities, and the remainder is acrylonitrile.

[0031] Extraction was carried out by adding water twice, with 200 kg of water added each time and stirring for 30 min. After that, the mixture was allowed to stand and separate into layers. The upper layer was an organic layer and the lower layer was an aqueous solution. The aqueous solution after each separation was collected for later use.

[0032] The aqueous solutions collected after two separate separations were combined, and 2 kg of activated carbon was added. The mixture was stirred for 30 min, then filtered to obtain filtrate A. 50% liquid alkali was slowly added to filtrate A, with the temperature controlled at 18℃. The pH was finally adjusted to 9.4, and alkali addition was stopped. The solution was cooled to 0℃, and 0.01% (by mass) of anhydrous sodium sulfate crystals from filtrate A were added. After standing for 4 h, crystalline substances precipitated. Solid-liquid separation was performed to obtain solid sodium sulfate and filtrate B. Filtrate B was a solution of sodium 2-acrylamido-2-methylpropanesulfonate with a liquid phase purity of 96.45% and a sulfate residue of 0.011%.

[0033] Figure 1 The liquid chromatogram of sodium 2-acrylamido-2-methylpropanesulfonate was obtained using a UV detector with methanol-water as the mobile phase, reflecting the purity of the target substance in the product solution.

[0034] The upper organic layer enters a distillation kettle for vacuum distillation, and the distilled acrylonitrile is returned to the production system as a solvent. Heating is stopped when precipitates appear in the kettle, the stirring frequency is slowed down, stirring continues while the coolant is turned on to lower the temperature. When the temperature drops to 15°C, solid-liquid separation can be performed. The resulting wet solid is dried at 50°C for 1 hour to obtain high-purity N-tert-butylacrylamide, with a liquid phase purity of 99.57%. Figure 2 (The image shows the liquid chromatogram of N-tert-butylacrylamide), with a moisture content of 0.1% and a sulfate residue of 0.012%.

[0035] In this embodiment, the concentration of each of the above substances is a mass concentration, and the same applies below.

[0036] Example 2

[0037] Take 2000 kg of the mother liquor from the production of 2-acrylamido-2-methylpropanesulfonic acid (the same as the mother liquor in Example 1).

[0038] Extraction was carried out by adding water three times to the above mother liquor, with 150 kg of water added each time and stirring for 20 min. After that, the mixture was allowed to stand and separate into layers. The upper layer was an organic layer and the lower layer was an aqueous solution. The aqueous solution after each separation was collected for later use or recycled.

[0039] After combining the aqueous solutions collected from three separate layers, 2 kg of activated carbon was added, and the mixture was stirred for 30 min. The solution was then filtered to obtain filtrate A. 50% liquid alkali was slowly added to filtrate A, with the temperature controlled at 20℃. The pH was eventually adjusted to 9.2, and alkali addition was stopped. The solution was cooled to 5℃, and 0.01% (by mass) of anhydrous sodium sulfate crystals from filtrate A was added. After standing for 4 h, crystalline substances precipitated. Solid-liquid separation was performed to obtain solid sodium sulfate and filtrate B. Filtrate B was a solution of sodium 2-acrylamido-2-methylpropanesulfonate with a liquid phase purity of 96.35% and a sulfate residue of 0.012%.

[0040] The upper organic layer enters a distillation vessel for vacuum distillation, and the distilled acrylonitrile is returned to the production system as a solvent. Heating is stopped when precipitates appear during distillation, the stirring frequency is slowed down, stirring continues, and the cooling medium is turned on. When the temperature drops to 15°C, solid-liquid separation can be performed. The resulting wet solid is dried at 50°C for 1 hour to obtain high-purity N-tert-butylacrylamide, with a liquid phase purity of 99.65%, moisture content of 0.1%, and sulfate residue of 0.01%.

[0041] Example 3

[0042] Take 2000 kg of the mother liquor from the production of 2-acrylamido-2-methylpropanesulfonic acid (the same as the mother liquor in Example 1).

[0043] Extraction was carried out by adding water twice, with 200 kg of water added each time and stirring for 30 min. After that, the mixture was allowed to stand and separate into layers. The upper layer was an organic layer and the lower layer was an aqueous solution. The aqueous solution after each separation was collected for later use or recycled.

[0044] The aqueous solutions collected after two separate separations were combined, and 2 kg of diatomaceous earth was added. The mixture was stirred for 30 min, then filtered to obtain filtrate A. 50% liquid alkali was slowly added to filtrate A, with the temperature controlled at 18℃. The pH was finally adjusted to 9.4, and alkali addition was stopped. The temperature was lowered to 3℃, and 0.05% (by mass) of sodium sulfate decahydrate crystals from filtrate A were added. After standing for 6 h, crystalline substances precipitated. Solid-liquid separation was performed to obtain solid sodium sulfate and filtrate B. Filtrate B was a sodium 2-acrylamido-2-methylpropanesulfonate solution product with a liquid phase purity of 96.43% and a sulfate residue of 0.008%.

[0045] The upper organic layer enters a distillation vessel for vacuum distillation, and the distilled acrylonitrile is returned to the production system as a solvent. Heating is stopped when precipitates appear during distillation, the stirring frequency is slowed down, stirring continues, and the cooling medium is turned on. When the temperature drops to 15°C, solid-liquid separation can be performed. The resulting wet solid is dried at 50°C for 1 hour to obtain high-purity N-tert-butylacrylamide, with a liquid phase purity of 99.60%, moisture content of 0.09%, and sulfate residue of 0.009%.

[0046] As can be seen from Examples 1 to 3, this invention adopts an original process route, and for the first time proposes to intervene in the treatment before the mother liquor is distilled. Using water as a medium for extraction and subsequent treatment, various products are separated and purified. This achieves comprehensive treatment of the mother liquor from the production of 2-acrylamido-2-methylpropanesulfonic acid, and can extract and prepare a variety of by-products. This treatment method is low in cost, simple to operate, and has a high resource utilization rate. The sodium salt solution of 2-acrylamido-2-methylpropanesulfonic acid and the N-tert-butylacrylamide product obtained by this method have high purity and low sulfate residue (both sulfate residue ≤0.012%), and are of good quality.

[0047] In this treatment method, N-tert-butylacrylamide is precipitated in an anhydrous system, which not only shortens the drying time but also results in low water content and sulfate residue in the product, making it convenient to operate and suitable for industrial production.

[0048] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for treating 2-acrylamido-2-methylpropanesulfonic acid mother liquor, characterized in that, Includes the following steps: S1. Add water to the mother liquor produced during the production of 2-acrylamido-2-methylpropanesulfonic acid for extraction. Stir for 20-40 minutes and allow to stand to separate into layers. The upper layer is an organic layer and the lower layer is an aqueous solution. The extraction is performed ≥2 times. Collect the aqueous solution after each separation for later use. The mother liquor produced in the production process of 2-acrylamido-2-methylpropanesulfonic acid is the filtrate obtained by solid-liquid separation after reacting acrylonitrile, sulfuric acid and isobutylene as raw materials to form a slurry. S2. After extraction, the upper organic layer enters the distillation vessel for vacuum distillation, and the distilled solvent is recycled. Distillation is stopped when precipitates are found in the vessel. The mixture is then cooled, separated from the solid, and dried to obtain N-tert-butylacrylamide. After the lower aqueous solution is collected, an adsorbent is added, and the mixture is stirred for 30-60 minutes before filtration to obtain filtrate A. Liquid alkali is added to filtrate A to adjust the pH to 8-10, and the temperature is lowered to 0-5°C. Seed crystals, namely anhydrous sodium sulfate or sodium sulfate decahydrate, are added. The mixture is allowed to stand for 4-6 hours, and the precipitate is separated into solid and liquid components to obtain solid and filtrate B. The solid is sodium sulfate, and filtrate B is a solution of sodium 2-acrylamido-2-methylpropanesulfonate.

2. The method for treating the 2-acrylamido-2-methylpropanesulfonic acid mother liquor as described in claim 1, characterized in that: In step S1, the total amount of water added is in a ratio of 0.2 to 0.3:1 to the weight of the mother liquor.

3. The method for treating the 2-acrylamido-2-methylpropanesulfonic acid mother liquor as described in claim 1, characterized in that: In step S2, the temperature is lowered to 10-15℃ after distillation is stopped.

4. The method for treating the 2-acrylamido-2-methylpropanesulfonic acid mother liquor as described in claim 1, characterized in that: In step S2, the adsorbent is activated carbon or diatomaceous earth.

5. The method for treating the 2-acrylamido-2-methylpropanesulfonic acid mother liquor as described in claim 1, characterized in that: In step S2, the amount of adsorbent added is 0.3 to 0.5% of the combined mass of the collected aqueous solution.

6. The method for treating the 2-acrylamido-2-methylpropanesulfonic acid mother liquor as described in claim 1, characterized in that: In step S2, the mass concentration of the liquid alkali is ≥50%.

7. The method for treating the 2-acrylamido-2-methylpropanesulfonic acid mother liquor as described in claim 1, characterized in that: In step S2, the amount of seed crystals added is 0.01 to 0.05% of the mass of filtrate A.

8. The method for treating the 2-acrylamido-2-methylpropanesulfonic acid mother liquor as described in claim 1, characterized in that: In step S2, the temperature is controlled at 10–30°C during the addition of liquid alkali.

9. The method for treating 2-acrylamido-2-methylpropanesulfonic acid mother liquor according to any one of claims 1 to 8, characterized in that: In step S1, water extraction is performed 2 to 5 times.

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