Preparation method of high-purity N-methyl pyrrolidone
By combining low-temperature fractionation, pervaporation, and amino-modified composite adsorbent materials, the problem of removing impurities from high-purity N-methylpyrrolidone was solved, achieving a high-efficiency and low-energy purification effect.
Patent Information
- Application Number
- CN202511651421.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-12
- Publication Date
- 2026-01-23
AI Technical Summary
Existing technologies are insufficient to effectively remove impurities such as water, methylamine, and metal ions from high-purity N-methylpyrrolidone. In particular, γ-butyrolactone and N-methylpyrrolidone have similar boiling points and are difficult to separate. Furthermore, traditional distillation processes are energy-intensive and inefficient.
A method combining low-temperature fractionation with pervaporation and amino-modified composite adsorbents was adopted. First, low-boiling-point impurities were removed by low-temperature fractionation. Then, water and methylamine were removed by pervaporation using NaA molecular sieve membrane. Finally, γ-butyrolactone and metal ions were adsorbed by amino-modified composite adsorbents.
The preparation of high-purity N-methylpyrrolidone was achieved, with a product purity of 99.95 wt.%, a water content of less than 100 ppm, and a γ-butyrolactone content of less than 0.03 wt.%, which reduced energy consumption and improved separation efficiency.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of organic matter purification, in particular to a preparation method of high-purity N-methyl pyrrolidone. BACKGROUND
[0002] N-methyl pyrrolidone, molecular formula C5H9NO, is a kind of organic solvent with high boiling point, strong polarity, high stability, low toxicity, biodegradability and recyclability. N-methyl pyrrolidone is widely used in traditional petrochemical industry, plastic industry, pharmaceuticals, pesticides, coatings and other fields.
[0003] There are three main methods for synthesizing N-methyl pyrrolidone in industry, which are reaction of gamma-butyrolactone and monoamine to synthesize N-methyl pyrrolidone, reaction of gamma-butyrolactone and mixed amine to synthesize N-methyl pyrrolidone, and dehydrogenation-amination reaction of 1,4-butanediol to synthesize N-methyl pyrrolidone. Among them, the reaction of gamma-butyrolactone and monoamine to synthesize N-methyl pyrrolidone is the most common, and the boiling points of gamma-butyrolactone and N-methyl pyrrolidone are similar, which is difficult to remove. In addition, with the development of high-end manufacturing industries such as semiconductors and lithium ion batteries, the demand for high-purity N-methyl pyrrolidone is gradually increasing, and the content of water, metal ions and organic amines in the product has strict index requirements, so it is necessary to provide a preparation method of high-purity N-methyl pyrrolidone. SUMMARY
[0004] The purpose of the present application is to provide a preparation method of high-purity N-methyl pyrrolidone to solve the problems in the background art.
[0005] In order to solve the above technical problems, the present application provides the following technical scheme: a preparation method of high-purity N-methyl pyrrolidone, comprising the following steps: Step 1: mixing gamma-butyrolactone, methylamine and water, and reacting under a reaction pressure of 8-10 MPa and a reaction temperature of 285-315℃ for 3-5h to obtain N-methyl pyrrolidone crude product; after the N-methyl pyrrolidone crude product is cooled, the crude product is fractionated at 20-50℃ and 70-100℃ respectively to remove the light components with low boiling point, and obtain N-methyl pyrrolidone with light components removed; Step 2: directly conveying the N-methyl pyrrolidone with light components removed into a membrane separation unit, and removing the residual water and methylamine in the N-methyl pyrrolidone with light components removed by using a pervaporation process; Step 3: conveying the N-methyl pyrrolidone treated by the membrane separation unit into an adsorption tower to obtain high-purity N-methyl pyrrolidone.
[0006] Further, in step 1, the gamma-butyrolactone, methylamine and water are mixed in a molar ratio of (0.8-0.85):1:(2-2.5).
[0007] Further, in step 2, the permeation side pressure in the membrane separation process is 0.1-2 kPa.
[0008] Further, in step 2, the membrane material used in the pervaporation is a NaA molecular sieve membrane.
[0009] Further, in step 3, the adsorption material used in the adsorption tower is an amino-modified composite adsorption material, and the preparation method thereof comprises the following steps: S1: Take chitosan and disperse it in an aqueous acetic acid solution, stir to dissolve, then add sodium dodecyl benzene sulfonate, heat the system to 60-70°C under nitrogen protection, add acrylic acid, N,N-methylene bisacrylamide, sodium allyl sulfonate and sodium-based montmorillonite, mix and stir and react at 70-80°C for 3-4 h; after the reaction is completed, rinse with distilled water and neutralize with NaOH solution to pH=7; after filtration, add anhydrous ethanol for washing and dehydration, vacuum dry, grind, and sieve through a 140-200 mesh sieve to obtain the composite adsorption material; S2: Disperse the composite adsorption material into isopropanol, add an epichlorohydrin solution, stir and react at 50-55°C for 24 h, filter and move to an ethanol aqueous solution, add triethylenetetramine, stir and react at 60-70°C for 24 h, centrifuge, wash and dry to obtain the amino-modified composite adsorption material.
[0010] Further, in S1, the concentration of the aqueous acetic acid solution is 1-2 wt.%.
[0011] Further, in S1, the amounts of the components are as follows in terms of weight parts: 5-7 parts of chitosan, 1-1.6 parts of sodium dodecyl benzene sulfonate, 36-42 parts of acrylic acid, 2-5 parts of N,N-methylene bisacrylamide, 13-17 parts of sodium allyl sulfonate and 10-13 parts of sodium-based montmorillonite.
[0012] Further, in S1, the concentration of the NaOH solution is 1-1.2 mol / L.
[0013] Further, in S2, the solvent of the epichlorohydrin solution is a mixed solution of acetone and water in a volume ratio of 1:1.
[0014] Further, in S2, the molar ratio of epichlorohydrin to triethylenetetramine is 1:1, and the mass ratio of triethylenetetramine to the composite adsorption material is (3-5):100.
[0015] Compared with the prior art, the present application has the advantages that: the present application mainly provides a preparation method of high-purity N-methyl pyrrolidone, taking N-methyl pyrrolidone crude product obtained by the commonly used γ-butyrolactone and monoamine synthesis method in industry as a starting point, first removing low-boiling-point light component organic impurities by low-temperature fractionation technology, and then combining with pervaporation for purification. As a new technology with low energy consumption and high separation efficiency, pervaporation can effectively make up for the high-boiling-point water and methylamine impurities that are difficult to remove in the fractionation process. The kinetic diameter of water molecules is 0.28 nm, and the kinetic diameter of methylamine molecules is 0.4 nm, both of which are smaller than the pore size of NaA molecular sieve membrane (0.42 nm), so the present application uses NaA molecular sieve membrane as the pervaporation membrane material, thereby further reducing the water content and methylamine content in N-methyl pyrrolidone and improving the quality of N-methyl pyrrolidone.
[0016] When the fractionation and pervaporation processes are coupled, the present application sets the temperature of fractionation to be not more than 100 DEG C, which can remove most of the low-boiling-point organic impurities on the one hand, and on the other hand, the liquid after fractionation can directly enter the membrane separation unit for pervaporation without preheating or cooling again, thereby effectively shortening the processing time, reducing the energy consumption and improving the purification efficiency. After pervaporation treatment, the N-methyl pyrrolidone crude product contains a small amount of raw material γ-butyrolactone which has not been completely reacted and metal impurities.
[0017] Since the boiling points of γ-butyrolactone and N-methyl pyrrolidone are similar, it is difficult to effectively remove them by distillation process, and metal ions are still entrained into N-methyl pyrrolidone product in the distillation process, therefore the present application prepares a composite adsorption material capable of adsorbing γ-butyrolactone and metal ions, and further purifies by an adsorption tower. The present application takes chitosan, acrylic acid, N,N-methylene bisacrylamide, sodium allylsulfonate and sodium-based montmorillonite as raw materials, loads chitosan and polyacrylate on sodium-based montmorillonite to obtain a composite adsorption material; reacts chitosan on the surface of the composite adsorption material with epichlorohydrin and then grafts triethylenetetramine to obtain an amino-modified composite adsorption material, which realizes adsorption of γ-butyrolactone by amine-ester exchange reaction of amino groups. In addition, acrylic acid, N,N-methylene bisacrylamide and sodium allylsulfonate are polymerized, and crosslinked with chitosan to form a polymer which has good adsorption effect on metal ions. Therefore, in the adsorption tower of the present application, the amino-modified composite adsorption material can realize adsorption of γ-butyrolactone and various metal ions, and the process is simple and the obtained N-methyl pyrrolidone product has high purity. DETAILED DESCRIPTION
[0018] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.
[0019] Materials and sources used in the present application: chitosan from Shanghai Reagent Company, Ltd., with a relative molecular mass of 130000 and a degree of deacetylation of 90%; sodium-based montmorillonite from Beijing Yiwite Special Material Technology Development Co., Ltd., with a model number of PGW; NaA molecular sieve membrane from Jiangsu Jiutian High-tech Co., Ltd.
[0020] Embodiment 1: A preparation method of high-purity N-methyl pyrrolidone, comprising the following steps: Step 1: γ-butyrolactone, methylamine and water are mixed in a molar ratio of 0.8:1:2, and reacted at a reaction pressure of 8 MPa and a reaction temperature of 285 DEG C for 3 h to obtain N-methyl pyrrolidone crude product; after the N-methyl pyrrolidone crude product is cooled, the crude product is fractionated at 20 DEG C and 70 DEG C respectively to remove low-boiling light components, thereby obtaining light-removed N-methyl pyrrolidone; Step 2: The light-removed N-methyl pyrrolidone is directly transported into a membrane separation unit, and an osmotic gasification process is used to remove residual water and methylamine in the light-removed N-methyl pyrrolidone; the permeation side pressure of the membrane separation unit is 0.1 kPa; the membrane material used in the osmotic gasification process is a NaA molecular sieve membrane; Step 3: The N-methyl pyrrolidone treated by the membrane separation unit is transported into an adsorption tower to obtain high-purity N-methyl pyrrolidone; wherein the preparation method of the amino-modified composite adsorption material in the adsorption tower comprises the following steps: S1: 5 kg of chitosan is dispersed in an acetic acid aqueous solution with a mass concentration of 1 wt.%, and after stirring and dissolving, 1 kg of sodium dodecyl benzene sulfonate is added; under nitrogen protection, the system is heated to 60 DEG C; with ammonium persulfate as an initiator, 36 kg of acrylic acid, 2 kg of N,N-methylene bisacrylamide, 13 g of sodium allyl sulfonate and 10 kg of sodium-based montmorillonite are added; mixing and stirring is performed and reaction is carried out at 70 DEG C for 3 h; after the reaction is completed, the system is washed with distilled water and neutralized to pH=7 with a 1 mol / L NaOH solution; after filtration, anhydrous ethanol is added for washing and dehydration; vacuum drying is performed and grinding is carried out after drying; and the composite adsorption material is obtained after being sieved through a 140-mesh screen; S2: dispersing the composite adsorbent material into isopropyl alcohol, adding an epichlorohydrin solution, stirring and reacting at 50 DEG C for 24 h, filtering and moving to an ethanol aqueous solution, adding triethylenetetramine, stirring and reacting at 60 DEG C for 24 h, centrifugal separation, washing, drying to obtain an amino-modified composite adsorbent material; the epichlorohydrin solution is a mixed solution of acetone and water in a volume ratio of 1:1; the ethanol aqueous solution has a mass concentration of 40%; the molar ratio of epichlorohydrin to triethylenetetramine is 1:1, and the mass ratio of triethylenetetramine to the composite adsorbent material is 3:100.
[0021] Embodiment 2: a preparation method of high-purity N-methylpyrrolidone, comprising the following steps: Step 1: mixing gamma-butyrolactone, methylamine and water in a molar ratio of 0.82:1:2.2, reacting at a reaction pressure of 9 MPa and a reaction temperature of 300 DEG C for 4.5 h to obtain N-methylpyrrolidone crude product; after the N-methylpyrrolidone crude product is cooled, the crude product is fractionated at 35 DEG C and 85 DEG C respectively to remove light components with low boiling points, thereby obtaining N-methylpyrrolidone with light components removed; Step 2: directly conveying the N-methylpyrrolidone with light components removed into a membrane separation unit, and removing water and methylamine remaining in the N-methylpyrrolidone with light components removed by using a pervaporation process; the permeation side pressure of the membrane separation unit is 1 kPa; the membrane material used in the pervaporation is a NaA molecular sieve membrane; Step 3: conveying the N-methylpyrrolidone treated by the membrane separation unit into an adsorption tower to obtain high-purity N-methylpyrrolidone; wherein, the preparation method of the amino-modified composite adsorbent material in the adsorption tower comprises the following steps: S1: dispersing 6 kg of chitosan in an acetic acid aqueous solution with a mass concentration of 1.5 wt.%, stirring and dissolving, then adding 1.4 kg of sodium dodecyl benzene sulfonate, heating the system to 65 DEG C under nitrogen protection, adding 38 kg of acrylic acid, 4 kg of N,N-methylene bisacrylamide, 15 g of sodium allylsulfonate and 12 kg of sodium-based montmorillonite, mixing and stirring and reacting at 75 DEG C for 3.5 h; after the reaction is completed, washing with distilled water and neutralizing to pH=7 with a 1.05 mol / L NaOH solution; after filtration, washing with anhydrous ethanol, drying under vacuum, grinding, and passing through a 180-mesh sieve to obtain a composite adsorbent material; S2: dispersing the composite adsorbent material into isopropyl alcohol, adding an epichlorohydrin solution, stirring and reacting at 52 DEG C for 24 h, filtering and moving to an ethanol aqueous solution, adding triethylenetetramine, stirring and reacting at 65 DEG C for 24 h, centrifugal separation, washing, drying to obtain an amino-modified composite adsorbent material; the epichlorohydrin solution is a mixed solution of acetone and water in a volume ratio of 1:1; the ethanol aqueous solution has a mass concentration of 45%; the molar ratio of epichlorohydrin to triethylenetetramine is 1:1, and the mass ratio of triethylenetetramine to the composite adsorbent material is 4.5:100.
[0022] Embodiment 3: a preparation method of high-purity N-methylpyrrolidone, comprising the following steps: Step 1: mixing gamma-butyrolactone, methylamine and water in a molar ratio of 0.85:1:2.5, reacting at a reaction pressure of 10 MPa and a reaction temperature of 315 DEG C for 5 h to obtain N-methylpyrrolidone crude product; after the N-methylpyrrolidone crude product is cooled, the crude product is fractionated at 50 DEG C and 100 DEG C respectively to remove light components with low boiling points, thereby obtaining N-methylpyrrolidone with light components removed; Step 2: directly conveying the N-methylpyrrolidone with light components removed into a membrane separation unit, and removing water and methylamine remaining in the N-methylpyrrolidone with light components removed by using a pervaporation process; the permeation side pressure of the membrane separation unit is 2 kPa; the membrane material used in the pervaporation is a NaA molecular sieve membrane; Step 3: conveying the N-methylpyrrolidone treated by the membrane separation unit into an adsorption tower to obtain high-purity N-methylpyrrolidone; wherein, the preparation method of the amino-modified composite adsorbent material in the adsorption tower comprises the following steps: S1: dispersing 7 kg of chitosan in a 2 wt.% acetic acid aqueous solution, stirring and dissolving, then adding 1.6 kg of sodium dodecyl benzene sulfonate, heating the system to 70 DEG C under nitrogen protection, adding 42 kg of acrylic acid, 5 kg of N,N-methylene bisacrylamide, 17 g of sodium allylsulfonate and 13 kg of sodium-based montmorillonite, mixing and stirring and reacting at 80 DEG C for 4 h; after the reaction is completed, washing with distilled water and neutralizing to pH=7 with a 1.2 mol / L NaOH solution; after filtration, washing with anhydrous ethanol, drying under vacuum, grinding, and sieving through a 200-mesh screen to obtain a composite adsorbent material; S2: dispersing the composite adsorbent material into isopropyl alcohol, adding an epichlorohydrin solution, stirring and reacting at 55 DEG C for 24 h, filtering and moving to an ethanol aqueous solution, adding triethylenetetramine, stirring and reacting at 70 DEG C for 24 h, centrifugal separation, washing, drying to obtain an amino-modified composite adsorbent material; the epichlorohydrin solution is a mixed solution of acetone and water in a volume ratio of 1:1; the ethanol aqueous solution has a mass concentration of 50%; the molar ratio of epichlorohydrin to triethylenetetramine is 1:1, and the mass ratio of triethylenetetramine to the composite adsorbent material is 5:100.
[0023] Comparative Example 1: not using an adsorption tower for treatment, and the same parameters as in Example 1.
[0024] Step 1: mixing gamma-butyrolactone, methylamine and water in a molar ratio of 0.8:1:2, reacting at a reaction pressure of 8 MPa and a reaction temperature of 285 DEG C for 3 h to obtain a crude N-methylpyrrolidone product; after the crude N-methylpyrrolidone product is cooled, the crude product is fractionated at 20 DEG C and 70 DEG C respectively to remove light components with low boiling points, thereby obtaining a light-removed N-methylpyrrolidone product. Step 2: directly feeding the light-removed N-methylpyrrolidone into a membrane separation unit, removing residual water and methylamine in the light-removed N-methylpyrrolidone by using a pervaporation process, and obtaining a finished product by using a NaA molecular sieve membrane as the membrane material of the pervaporation.
[0025] Comparative Example 2: not using amino to modify the composite adsorbent material, and the same parameters as in Example 2.
[0026] Step 1: mixing gamma-butyrolactone, methylamine and water in a molar ratio of 0.82:1:2.2, reacting at a reaction pressure of 9 MPa and a reaction temperature of 300 DEG C for 4.5 h to obtain a crude N-methylpyrrolidone product; after the crude N-methylpyrrolidone product is cooled, the crude product is fractionated at 35 DEG C and 85 DEG C respectively to remove light components with low boiling points, thereby obtaining a light-removed N-methylpyrrolidone product. Step 2: directly feeding the light-removed N-methylpyrrolidone into a membrane separation unit, removing residual water and methylamine in the light-removed N-methylpyrrolidone by using a pervaporation process; the membrane separation unit has a permeation side pressure of 1 kPa; and a NaA molecular sieve membrane is used as the membrane material of the pervaporation. Step 3: feeding the N-methylpyrrolidone treated by the membrane separation unit into an adsorption tower to obtain high-purity N-methylpyrrolidone; wherein the preparation method of the composite adsorbent material in the adsorption tower comprises the following steps: Take 6 kg of chitosan dispersed in 1.5 wt.% acetic acid aqueous solution, after stirring and dissolving, add 1.4 kg of sodium dodecyl benzene sulfonate, under nitrogen protection, the system is heated to 65℃, with ammonium persulfate as initiator, add 38 kg of acrylic acid, 4 kg of N, N-methylene bisacrylamide, 15 g of sodium allyl sulfonate and 12 kg of sodium based montmorillonite, mix and stir and react at 75℃ for 3.5 h; after the reaction is completed, rinse with distilled water and neutralize with 1.05 mol / L NaOH solution to pH=7; after filtration, add anhydrous ethanol for washing, dehydration, vacuum drying, grinding, and passing through a 180 mesh sieve to obtain a composite adsorption material.
[0027] Comparative example 3: only use chitosan and sodium based montmorillonite to prepare a composite adsorption material, the rest of the parameters are the same as example 3.
[0028] Step 1: mix γ-butyrolactone, methylamine and water in a molar ratio of 0.85:1:2.5, react at a reaction pressure of 10 MPa and a reaction temperature of 315℃ for 5 h to obtain crude N-methyl pyrrolidone; after the crude N-methyl pyrrolidone is cooled, fractionate the crude product at 50℃ and 100℃ respectively to remove the light components with low boiling point to obtain N-methyl pyrrolidone with light components removed; Step 2: directly transport the N-methyl pyrrolidone with light components removed into a membrane separation unit to remove the residual water and methylamine in the N-methyl pyrrolidone with light components removed by using a pervaporation process; the permeation side pressure of the membrane separation unit is 2 kPa; the membrane material used for pervaporation is NaA molecular sieve membrane; Step 3: transport the N-methyl pyrrolidone treated by the membrane separation unit into an adsorption tower to obtain high purity N-methyl pyrrolidone; wherein the preparation method of the amino modified composite adsorption material in the adsorption tower comprises the following steps: S1: take 7 kg of chitosan dispersed in 2 wt.% acetic acid aqueous solution, after stirring and dissolving, add 1.6 kg of sodium dodecyl benzene sulfonate and 13 kg of sodium based montmorillonite, mix and stir and react at 80℃ for 4 h; after the reaction is completed, rinse with distilled water and neutralize with 1.2 mol / L NaOH solution to pH=7; after filtration, add anhydrous ethanol for washing, dehydration, vacuum drying, grinding, and passing through a 200 mesh sieve to obtain a composite adsorption material; S2: disperse the composite adsorption material into isopropyl alcohol, add an epichlorohydrin solution, stir and react at 55℃ for 24 h, filter and move to an ethanol aqueous solution, add triethylenetetramine, stir and react at 70℃ for 24 h, centrifugal separation, washing, drying to obtain an amino modified composite adsorption material; the epichlorohydrin solution is a mixed solution of acetone and water in a volume ratio of 1:1; the mass concentration of the ethanol aqueous solution is 50%; the molar ratio of epichlorohydrin to triethylenetetramine is 1:1, and the mass ratio of triethylenetetramine to the composite adsorption material is 5:100.
[0029] Experiment: The purity of N-methylpyrrolidone and the content of gamma-butyrolactone were tested by gas chromatography, and the water content in the product was determined by Karl Fischer water meter, and the experimental results are shown in Table 1.
[0030] Table 1. According to the ICP-MS 7900, the content of various metal ion impurities in the product was tested, and the results are shown in Table 2. Table 2 Conclusion: The data of examples 1-3 show that the purity of N-methylpyrrolidone can be improved to more than 99.95wt.% by using the process technical scheme provided by the application, while the water content is below 100ppm, and the content of gamma-butyrolactone is below 0.03wt.%. The data of example 1 and comparative example 1 show that the adsorption tower can effectively reduce the content of gamma-butyrolactone and metal ions in the product; the data of example 2 and comparative example 2 show that the amino-modified composite adsorption material has good adsorption effect on gamma-butyrolactone; the data of example 3 and comparative example 3 show that the composite adsorption material prepared by blending and polymerizing acrylic acid, N,N-methylene bisacrylamide, sodium allylsulfonate and chitosan has good adsorption effect on metal ions (especially zinc ions).
[0031] Finally, it should be pointed out that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it still can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.
Claims
1. A method for preparing anhydrous N-methylpyrrolidone, characterized in that: Includes the following steps: Step 1: Mix γ-butyrolactone, methylamine, and water, and react at a reaction pressure of 8-10 MPa and a reaction temperature of 285-315℃ for 3-5 h to obtain crude N-methylpyrrolidone; after cooling the crude N-methylpyrrolidone, fractionate the crude product at 20-50℃ and 70-100℃ respectively to remove the low-boiling light components to obtain de-light N-methylpyrrolidone; Step 2: The N-methylpyrrolidone after light removal is directly fed into the membrane separation unit, and the residual water and methylamine in the N-methylpyrrolidone after light removal are removed by pervaporation process; Step 3: The N-methylpyrrolidone processed by the membrane separation unit is fed into the adsorption tower to obtain high-purity N-methylpyrrolidone.
2. The method for preparing anhydrous N-methylpyrrolidone according to claim 1, characterized in that: In step 1, γ-butyrolactone, methylamine, and water are mixed in a molar ratio of (0.8~0.85):1:(2~2.5).
3. The method for preparing anhydrous N-methylpyrrolidone according to claim 1, characterized in that: In step 2, the permeate side pressure during membrane separation is 0.1~2 kPa, and the membrane material used for pervaporation is NaA molecular sieve membrane.
4. The method for preparing anhydrous N-methylpyrrolidone according to claim 1, characterized in that: In step 3, the adsorbent used in the adsorption tower is an amino-modified composite adsorbent, and its preparation method includes the following steps: S1: Chitosan was dispersed in an aqueous acetic acid solution and stirred until dissolved. Sodium dodecylbenzenesulfonate was added, and the system was heated to 60-70°C under nitrogen protection. Ammonium persulfate was used as an initiator, and acrylic acid, N,N-methylenebisacrylamide, sodium allyl sulfonate, and sodium montmorillonite were added. The mixture was stirred and reacted at 70-80°C for 3-4 hours. After the reaction was completed, the mixture was washed with distilled water and neutralized with NaOH solution to pH=7. After filtration, anhydrous ethanol was added for washing and dehydration. After vacuum drying, the mixture was ground and passed through a 140-200 mesh sieve to obtain the composite adsorbent material. S2: The composite adsorbent material is dispersed in isopropanol, epichlorohydrin solution is added, and the mixture is stirred at 50~55℃ for 24h. The mixture is then filtered and transferred to an ethanol aqueous solution. Triethylenetetramine is added, and the mixture is stirred at 60~70℃ for 24h. After centrifugation, washing, and drying, the amino-modified composite adsorbent material is obtained.
5. The method for preparing anhydrous N-methylpyrrolidone according to claim 4, characterized in that: In S1, the concentration of the aqueous acetic acid solution is 1~2 wt.%.
6. The method for preparing anhydrous N-methylpyrrolidone according to claim 4, characterized in that: In S1, the amounts of each component, by weight, are: 5-7 parts chitosan, 1-1.6 parts sodium dodecylbenzenesulfonate, 36-42 parts acrylic acid, 2-5 parts N,N-methylenebisacrylamide, 13-17 parts sodium allyl sulfonate, and 10-13 parts sodium montmorillonite.
7. The method for preparing anhydrous N-methylpyrrolidone according to claim 4, characterized in that: In S1, the concentration of NaOH solution is 1~1.2 mol / L.
8. The method for preparing anhydrous N-methylpyrrolidone according to claim 4, characterized in that: In S2, the solvent for the epichlorohydrin solution is a mixture of acetone and water in a volume ratio of 1:
1.
9. The method for preparing anhydrous N-methylpyrrolidone according to claim 4, characterized in that: In S2, the molar ratio of epichlorohydrin to triethylenetetramine is 1:1, and the mass ratio of triethylenetetramine to the composite adsorbent is (3~5):
100.
10. High-purity N-methylpyrrolidone prepared by the preparation method according to any one of claims 1 to 9.