Rectifying kettle residue extraction method

Abstract

The invention discloses a rectifying still residue extraction method, and belongs to the field of environmental protection and the technical field of hazardous waste harmless resource utilization. The technical problem that the recovery rate of residual NMP in the current rectifying still residues is not high is solved. The method comprises the following steps: soaking the residual lignosulfonate in an NMP rectifying still, adding an organic solvent for treatment, and then rectifying to obtain NMP. According to the method, the NMP is extracted by utilizing the boiling point difference between the organic solvent and the NMP rectifying still residue and temperature-controlled rectification, and the lignosulfonate is used as a water reducing agent to be compounded with water, so that the moisture required when the solid still residue is dissolved is reduced, and the flowability of the still residue after the organic solvent is added is improved. In addition, the organic solvent is matched with water and NMP (N-Methyl Pyrrolidone) in rectifying still residues, so that the azeotropic phenomenon is reduced. According to the method, the NMP rectifying still residues which cannot be recycled are pretreated with chemical reagents such as diethylene glycol and then rectified, so that a large amount of NMP is recovered, and the utilization efficiency of NMP is greatly improved.

Description

Technical Field

[0001] This invention belongs to the fields of environmental protection and the technology of harmless resource utilization of hazardous waste, and specifically relates to a method for extracting residues from a distillation vessel. Background Technology

[0002] N-Methylpyrrolidone (NMP), a high-boiling-point organic solvent, has wide applications in pharmaceuticals, chemicals, coatings, resin synthesis, and power battery manufacturing. Power battery manufacturing is currently the largest consumer of NMP, consuming approximately 2 million tons annually, and demand continues to increase with the growth of the power battery industry. Currently, NMP is used in the cathode material coating process of power batteries. It acts as a dispersant to thoroughly mix and disperse PVDF and cathode materials, then uniformly coats them onto aluminum foil. After coating, the material is heated and dried, and the evaporated NMP is condensed and recovered. However, because NMP readily absorbs moisture, the purity of the evaporated NMP is relatively low (90-95%), which cannot meet the stringent requirements of battery production for solvent purity exceeding 99.9%. Therefore, the recovered NMP needs to be sent to specialized distillation companies for further purification to achieve a purity of over 99.9%.

[0003] Distillation kettle residue refers to solid / semi-solid waste generated during the separation and purification of substances in chemical distillation operations. This waste mainly consists of heavy components in the waste material and inorganic salts generated during pretreatment. After distillation, this portion remains at the bottom of the kettle, forming distillation kettle residue. A large amount of distillation kettle residue is generated during the distillation and purification of recovered NMP. For every 100 tons of NMP distilled, 1.5-2 tons of distillation kettle residue are generated. Because NMP concentration decreases and pH < 6 during the manufacturing of power batteries, liquid alkali is added to adjust the concentration of waste NMP during distillation. This results in a large amount of inorganic salts in the waste liquid. As distillation proceeds, the inorganic salts continuously concentrate. Once the concentration reaches a certain level, the heat exchange efficiency decreases, making it impossible to completely distill out all the NMP. Therefore, it needs to be discharged at a certain concentration. The discharged distillation kettle residue retains 50-60% of NMP that has not been completely extracted and recovered, resulting in resource waste. Currently, distillation kettle residue is classified as hazardous waste. When discharged, it is in a high-temperature state (139-145°C) in the distillation unit, with high solubility and a viscous liquid state. However, after being discharged and cooled (below 130°C), it becomes a solid or semi-solid state. As a result, the kettle residue cannot be reused according to existing technology after discharge, so it is directly sent to a hazardous waste disposal plant for incineration, resulting in NMP waste and increasing the NMP treatment cost for enterprises.

[0004] Therefore, it is necessary to find a technology to extract residual NMP from distillation vessel residues to reduce NMP resource waste. At the same time, it is also necessary to address the technical challenge of low NMP distillation recovery rates due to NMP's high boiling point, its status as a universal solvent, and its ability to mix with any solvent and undergo azeotropic heating. Summary of the Invention

[0005] To overcome the aforementioned problems in the prior art, the present invention provides a method for extracting residues from a distillation vessel.

[0006] The technical solution of the present invention is as follows: One objective of this invention is to provide a method for extracting N-methylpyrrolidone distillation vessel residues, the method comprising: (1) Soak the residue of N-methylpyrrolidone distillation vessel in water, then add lignin sulfonate and continue soaking. After soaking, stir, then add organic solvent and mix to obtain a mixture; (2) The mixture is distilled until no NMP is produced. The organic solvent is recovered by heating. After no more distillate is produced, water is added and stirred. The mixture is then discharged from the distillation apparatus to obtain NMP.

[0007] Further specified, (1) the amount of water used is 3-5 wt% of the residue of N-methylpyrrolidone distillation vessel, the amount of lignin sulfonate used is 1 wt% of water, and the soaking time after adding lignin sulfonate is 1 h.

[0008] Further, the mixing time for adding organic solvent in (1) is 40 min.

[0009] Further specifying, (1) the organic solvent is diethylene glycol, sulfolane, dimethyl sulfoxide, white oil, dioctyl phthalate, hydrogenated terphenyl, triacrylate, DMPU (1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone).

[0010] Further specified, when the organic solvent is diethylene glycol, the mass ratio of N-methylpyrrolidone to organic solvent in the distillation vessel residue is 8:1; when the organic solvent is sulfolane, the mass ratio is 5:1; when the organic solvent is dimethyl sulfoxide, the mass ratio is 4:1; and when the organic solvent is white oil, the mass ratio is 2.5:1. When the organic solvent is dioctyl phthalate, the mass ratio of N-methylpyrrolidone to organic solvent in the distillation vessel residue is 6:1; when the organic solvent is DMPU, the mass ratio of N-methylpyrrolidone to organic solvent in the distillation vessel residue is 6:1; when the organic solvent is triacrylate, the mass ratio of N-methylpyrrolidone to organic solvent in the distillation vessel residue is 7:1; when the organic solvent is hydrogenated terphenyl, the mass ratio of N-methylpyrrolidone to organic solvent in the distillation vessel residue is 7:1.

[0011] Further specify that (2) distillation adopts either batch distillation or continuous distillation process.

[0012] Further specifying, the distillation process in (2) is as follows: under vacuum conditions, the distillation is carried out at 110°C until no fraction is produced, then the temperature is raised to 130°C until no fraction is produced, and finally the distillation is carried out at 140-150°C. The NMP fraction produced at 140-150°C is stored separately and not mixed with the previous fraction. After no NMP is produced at 140-150°C, the temperature is raised to 160-250°C to recover the organic solvent. The temperature of the distillation process from the beginning to the stage where no NMP is produced is controlled to be ≤150°C.

[0013] Further, the pressure of the distillation process in (2) is ≤-96KPa.

[0014] Further specified, (2) the amount of water used is 3wt% of the remaining mass of the distillation vessel.

[0015] Further specify that the stirring time for adding water in (2) is 20 min.

[0016] A second objective of this invention is to provide an N-methylpyrrolidone obtained by the above method, with a purity ≥99%.

[0017] The beneficial effects of this invention are as follows: (1) This invention extracts NMP from the distillation vessel residue by utilizing the boiling point difference between diethylene glycol and other chemical organic solvents and the NMP residue, as well as temperature-controlled distillation. By using lignin sulfonate as a water-reducing agent in synergistic compounding with water, the water required for dissolving the solid residue is reduced, improving the fluidity of the residue after adding organic solvents and lowering the NMP extraction cost. Furthermore, lignin sulfonate does not produce abnormal light components that interfere with NMP at 150-160℃, preventing contamination of the NMP produced by distillation; simultaneously, since water has a high specific heat capacity, excessive water addition leads to increased energy consumption, and the addition of lignin sulfonate can reduce energy consumption costs. The organic solvent, especially diethylene glycol, can effectively reduce azeotropic phenomena by combining with water and NMP in the distillation vessel residue.

[0018] (2) Currently, all NMP distillation vessel residue is incinerated. The extraction technology of this invention can maximize the NMP recovery rate, reduce the generation of vessel residue, and reduce secondary hazardous waste. At the same time, this invention recovers a large amount of NMP from the non-recyclable NMP distillation vessel residue by pretreatment with chemical reagents such as diethylene glycol and then distillation, which greatly improves the NMP utilization efficiency. Attached Figure Description

[0019] Figure 1 The results of gas chromatography analysis of NNMP distillation vessel residue in Example 1 are shown. Figure 2 The results of gas chromatography analysis of NMP extracted from the residue after diethylene glycol treatment and distillation in Example 1 are as follows: Figure 3 Photograph of the NMP distillation vessel residue from Example 1; Figure 4 This is a photograph of NMP extracted from the NMP distillation vessel residue of Example 1 after diethylene glycol extraction. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0023] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0024] Example 1 In this embodiment, 7.7t of NMP distillation vessel residue was taken, and its state was as follows. Figure 3 As shown, the gas chromatography detection results are as follows: Figure 1 As shown, the NMP content in the distillation vessel residue was 4.41t; (1) Add water at a concentration of 4.41% of the NMP residue to the distillation vessel residue and soak for 2 hours. Then add calcium lignosulfonate at a concentration of 1 wt% of water and continue soaking for 1 hour. After soaking, stir at a speed of 600 r / min for 30 minutes. Then add diethylene glycol and stir for 40 minutes to obtain a mixture. The mass ratio of NMP to diethylene glycol in the distillation vessel residue is 8:1. (2) The distillation process is carried out by batch distillation. The distillation process is as follows: under absolute vacuum and pressure ≤ -96KPa, the distillation is carried out at 110°C until no distillate is produced. Then the temperature is raised to 130°C until no distillate is produced. Finally, the distillation is carried out at 140-150°C. The NMP fraction produced at 140-150°C is stored separately and is not mixed with the previous fraction. After no NMP is produced in the 140-150°C temperature range, the temperature of the residue in the pot is raised to 160-165°C. Diethylene glycol is extracted and recovered by distillation. After no distillate is produced, 3wt% of the remaining residue of water is added and stirred for 20 minutes before the distillation device is removed to obtain NMP. The temperature of the distillation process from the beginning to the stage where no NMP is produced is controlled at ≤150°C.

[0025] Table 1. Distillation and Extraction Parameters of Example 1

[0026] In this embodiment, NMP was extracted from the residue after diethylene glycol treatment and distillation, as shown in... Figure 4 As shown, its gas chromatography detection results are as follows: Figure 2 As shown, the NMP extracted from the residue after diethylene glycol treatment and distillation has a purity of over 99%.

[0027] Example 2 The difference between this embodiment and Example 1 is that: (1) the organic solvent is sulfolane, and the mass ratio of NMP to sulfolane in the distillation kettle residue is 5:1; the mass of NMP in the distillation kettle residue, the mass of NMP in the distillation kettle residue, the mass of NMP obtained after distillation, the amount of calcium lignosulfonate added and the amount of water added in (1) are detailed in Table 2, and the remaining process steps and parameter settings are the same as in Example 1.

[0028] Example 3 The difference between this embodiment and embodiment 1 is that: (1) the organic solvent is dioctyl phthalate, and the mass ratio of NMP to dioctyl phthalate in the distillation kettle residue is 6:1; the mass of NMP in the distillation kettle residue, the mass of NMP in the distillation kettle residue, the mass of NMP obtained after distillation, the amount of calcium lignosulfonate added and the amount of water added in (1) are detailed in Table 2, and the other process steps and parameter settings are the same as in embodiment 1.

[0029] Example 4 The difference between this embodiment and embodiment 1 is that: (1) the organic solvent is DMPU, and the mass ratio of NMP to DMPU in the distillation kettle residue is 6:1; the mass of NMP in the distillation kettle residue, the mass of NMP in the distillation kettle residue, the mass of NMP obtained after distillation, the amount of calcium lignosulfonate added and the amount of water added in (1) are detailed in Table 2, and the remaining process steps and parameter settings are the same as in embodiment 1.

[0030] Example 5 The difference between this embodiment and Example 1 is that: (1) the organic solvent is triacrylate, and the mass ratio of NMP to triacrylate in the distillation kettle residue is 7:1; the mass of NMP in the distillation kettle residue, the mass of NMP in the distillation kettle residue, the mass of NMP obtained after distillation, the amount of calcium lignosulfonate added and the amount of water added in (1) are detailed in Table 2, and the remaining process steps and parameter settings are the same as in Example 1.

[0031] Example 6 The difference between this embodiment and embodiment 1 is that: (1) the organic solvent is hydrogenated terphenyl, and the mass ratio of NMP to hydrogenated terphenyl in the distillation kettle residue is 7:1; the mass of NMP in the distillation kettle residue, the mass of NMP in the distillation kettle residue, the mass of NMP obtained after distillation, the amount of calcium lignosulfonate added and the amount of water added in (1) are detailed in Table 2, and the remaining process steps and parameter settings are the same as in embodiment 1.

[0032] Table 2. Distillation and Extraction Parameters for Examples 2-6

[0033] Note: Because NMP readily absorbs moisture, the extracted NMP will contain water. In Examples 2-6, the initial NMP residue in the distillation vessel was small, and the experimental volume was small (laboratory-scale test), so the amount of water absorbed was relatively small. However, regardless of Examples 1 or 2-6, the actual amount of water absorbed by NMP is very small, and will not result in a large amount of water in the obtained NMP. The water content is negligible and therefore will not affect the recovery rate and purity of NMP in the extraction technology of this invention.

[0034] As can be seen from the data in Tables 1 and 2, the extraction technology of this invention can efficiently recover NMP from distillation vessel residue, with a purity of over 99%. Specifically, the recovery rates are 98.48% using diethylene glycol, 100% using sulfolane, 98.57% using dioctyl phthalate, 71.1% using DMPU, 98.45% using triacrylate, and 95.89% using hydrogenated terphenyl. From a raw material cost perspective, diethylene glycol offers the best economic benefits.

[0035] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for extracting N-methylpyrrolidone residue from a distillation vessel, characterized in that, The method includes: (1) Soak the residue of N-methylpyrrolidone distillation vessel in water, then add lignin sulfonate and continue soaking. After soaking, stir, then add organic solvent and mix to obtain a mixture; (2) The mixture is distilled until no N-methylpyrrolidone is produced. The organic solvent is recovered by heating. After no more fractions are produced, water is added and stirred. The mixture is then discharged from the distillation apparatus to obtain N-methylpyrrolidone.

2. The extraction method according to claim 1, characterized in that, (1) The amount of water used is 3-5 wt% of the residue in the N-methylpyrrolidone distillation vessel, and the amount of lignin sulfonate used is 1 wt% of water.

3. The extraction method according to claim 1, characterized in that, (1) After adding lignin sulfonate, the soaking time is 1 hour.

4. The extraction method according to claim 1, characterized in that, (1) The time for mixing and stirring the organic solvent added is 40 min.

5. The extraction method according to claim 1, characterized in that, (1) The organic solvents are diethylene glycol, sulfolane, dimethyl sulfoxide, white oil, dioctyl phthalate, hydrogenated terphenyl, triacrylate, and 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone.

6. The extraction method according to claim 5, characterized in that, When the organic solvent is diethylene glycol, the mass ratio of N-methylpyrrolidone to organic solvent in the distillation vessel residue is 8:1; when the organic solvent is sulfolane, the mass ratio is 5:1; when the organic solvent is dimethyl sulfoxide, the mass ratio is 4:1; when the organic solvent is white oil, the mass ratio is 2.5:1; when the organic solvent is dioctyl phthalate... When the solvent is ester, the mass ratio of N-methylpyrrolidone to organic solvent in the distillation vessel residue is 6:1; when the organic solvent is 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone, the mass ratio of N-methylpyrrolidone to organic solvent in the distillation vessel residue is 6:1; when the organic solvent is triacrylate, the mass ratio of N-methylpyrrolidone to organic solvent in the distillation vessel residue is 7:1; when the organic solvent is hydrogenated terphenyl, the mass ratio of N-methylpyrrolidone to organic solvent in the distillation vessel residue is 7:

1.

7. The extraction method according to claim 1, characterized in that, (2) The distillation process adopts either batch distillation or continuous distillation.

8. The extraction method according to claim 1, characterized in that, (2) The distillation process is as follows: Under vacuum conditions, the distillation is carried out at 110°C until no fraction is produced. Then the temperature is raised to 130°C and heated until no fraction is produced. Finally, the distillation is carried out at 140-150°C. The NMP fraction produced at 140-150°C is stored separately and not mixed with the previous fraction. After no NMP is produced at 140-150°C, the temperature is raised to 160-250°C and the organic solvent is recovered.

9. The extraction method according to claim 1, characterized in that, (2) The amount of water used in the stirring process is 3% of the remaining mass of the distillation vessel, and the stirring time is 30 min.

10. An N-methylpyrrolidone obtained by the extraction method according to any one of claims 1-9, characterized in that, Purity ≥ 99%.

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