CN-121990965-A - Residual extraction method of rectifying still

Abstract

The invention discloses a rectifying still residue extraction method, and belongs to the technical fields of environmental protection and hazardous waste harmless resource utilization. The invention solves the technical problem that the recovery rate of the residual NMP in the residual rectifying still is not high. According to the invention, the NMP rectifying still residue is soaked in lignosulfonate, and then is treated by adding an organic solvent, and then is rectified, so that NMP is obtained. According to the invention, NMP is extracted by utilizing the boiling point difference between the organic solvent and the residue of the NMP rectifying kettle and temperature-controlled rectification, and the water required by dissolving the solid residue is reduced by compounding lignin sulfonate serving as a water reducing agent with water, so that the fluidity of the residue after the organic solvent is added is improved. In addition, the organic solvent is matched with water and NMP in the residue of the rectifying still to reduce the azeotropic phenomenon. According to the invention, a large amount of NMP is recovered from the residue of the NMP rectifying kettle which cannot be recycled through pretreatment and rectification by using chemical reagents such as diethylene glycol and the like, so that the NMP utilization efficiency is greatly improved.

Inventors

• ZHANG YU
• Hao Liuyan
• CAI LIHUA
• TIAN YUE

Assignees

• 田月

Dates

Publication Date

20260508

Application Date

20260119

Claims (10)

1. 1. The residual extraction method of the N-methyl pyrrolidone rectifying still is characterized by comprising the following steps of: (1) Soaking the residue of the N-methyl pyrrolidone rectifying still in water, adding lignosulfonate, continuously soaking, stirring after soaking, and then adding an organic solvent, mixing and stirring to obtain a mixture; (2) And rectifying the mixture, heating to recover the organic solvent after no N-methyl pyrrolidone is finally produced, adding water and stirring after no fraction is produced, and discharging the mixture out of a rectifying device to obtain the N-methyl pyrrolidone.
2. 2. The extraction method according to claim 1, wherein (1) the amount of water is 3-5wt% of the residue of the N-methylpyrrolidone rectifying still, and the amount of lignin sulfonate is 1wt% of water.
3. 3. The extraction method according to claim 1, wherein the soaking time after adding lignin sulfonate in (1) is 1h.
4. 4. The extraction method according to claim 1, wherein the organic solvent is added to (1) and mixed for 40 minutes.
5. 5. The extraction method according to claim 1, wherein the organic solvent in (1) is diethylene glycol, sulfolane, dimethyl sulfoxide, white oil, dioctyl phthalate, hydrogenated terphenyl, triacrylate, 1, 3-dimethyl-3, 4,5, 6-tetrahydro-2-pyrimidinone.
6. 6. The extraction method according to claim 5, wherein when the organic solvent is diethylene glycol, the mass ratio of N-methylpyrrolidone to the organic solvent in the rectifying still residue is 8:1, when the organic solvent is sulfolane, the mass ratio of N-methylpyrrolidone to the organic solvent in the rectifying still residue is 5:1, when the organic solvent is dimethyl sulfoxide, the mass ratio of N-methylpyrrolidone to the organic solvent in the rectifying still residue is 4:1, when the organic solvent is white oil, the mass ratio of N-methylpyrrolidone to the organic solvent in the rectifying still residue is 2.5:1, when the organic solvent is dioctyl phthalate, the mass ratio of N-methylpyrrolidone to the organic solvent in the rectifying still 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 the organic solvent in the rectifying still residue is 6:1, when the organic solvent is trimethyl acrylate, the mass ratio of N-methylpyrrolidone to the organic solvent in the rectifying still residue is 7:1, and when the organic solvent is trioxazole is 7:1.
7. 7. The extraction process of claim 1, wherein the rectification in (2) is performed by a batch rectification process or a continuous rectification process.
8. 8. The extraction method according to claim 1, wherein the rectification step (2) is carried out under vacuum conditions by heating and rectifying at 110 ℃ until no fraction is produced, heating to 130 ℃ until no fraction is produced, rectifying at 140-150 ℃, storing the NMP fraction produced at 140-150 ℃ separately without mixing with the previous fraction, heating to 160-250 ℃ after no NMP is produced at 140-150 ℃, and recovering the organic solvent.
9. 9. The extraction method according to claim 1, wherein the amount of water added and stirred in (2) is 3% of the residual mass of the residual rectifying still, and the stirring time is 30min.
10. 10. An N-methylpyrrolidone obtained by the extraction process according to any one of claims 1 to 9, characterized in that the purity is not less than 99%.

Description

Residual extraction method of rectifying still Technical Field The invention belongs to the technical fields of environmental protection and harmless resource utilization of hazardous wastes, and particularly relates to a residual extraction method of a rectifying still. Background N-methylpyrrolidone (NMP) is used as a high boiling point organic solvent and has wide application in the fields of pharmaceutical chemical industry, paint, resin synthesis, power battery manufacturing and the like, wherein the power battery manufacturing is the industry with the largest NMP consumption at present, the annual consumption is about 200 ten thousand tons, and the demand is continuously increased along with the growth of the power battery industry. At present, NMP is applied to a coating link of a positive electrode material in a power battery, PVDF and the positive electrode material are fully mixed and uniformly dispersed as a positive electrode material dispersing agent, then the mixture is uniformly coated on an aluminum foil, heating and drying are carried out after the coating is finished, and evaporated NMP is condensed and recovered. However, because NMP is very easy to adsorb moisture, the purity of NMP obtained by evaporation and condensation is low (the purity is 90-95%), and the strict requirement of battery production on the purity of a solvent is not met, so that the recovered NMP needs to be sent to a special rectification enterprise for rectification and purification, and the purity is more than 99.9%. The residue of the rectifying still refers to solid/semisolid waste generated by ‌ due to separation and purification of substances during the operation of chemical rectification. ‌ the waste is mainly heavy components in the waste and inorganic salt generated during pretreatment, and ‌ part of the waste is remained at the bottom of the kettle after rectification, and ‌ forms rectification kettle residues. During the rectification and purification process of the recovered NMP, a large amount of rectification kettle residues are generated. 1.5-2 tons of rectifying still residue is produced per 100 tons of rectified NMP. Because NMP can make its concentration reduce, PH <6 in power battery manufacturing use, so waste NMP can add liquid alkali in the rectification in-process and adjust to lead to there is a large amount of inorganic salt in the waste liquid, along with the rectification goes on, inorganic salt constantly concentrates, reduces heat exchange efficiency after the concentration reaches certain degree, can't continue to carry out total rectification with NMP and put forward, so need discharge it when certain concentration. 50-60% NMP can remain in the discharged rectifying still residue, and the NMP can not be completely extracted and recovered, so that resource waste is caused. At present, the rectifying still belongs to dangerous waste, and during discharging, the rectifying still is in a high-temperature state (139-145 ℃) in a rectifying device, has high solubility and belongs to a viscous liquid state, but is in a solid or semisolid state after being discharged and cooled (lower than 130 ℃), so that the still residue after being discharged cannot be continuously utilized according to the prior art, and is directly sent to a dangerous waste disposal plant for incineration disposal, NMP waste is caused, and NMP treatment cost of enterprises is increased. Therefore, a technology capable of extracting the residual NMP in the rectifying still residue is needed to be found, and NMP resource waste is reduced. Meanwhile, the technical problem that the recovery rate of NMP rectification is low because NMP has high boiling point and is a universal solvent, and NMP can be mixed with any solvent for heating and azeotropy is solved. Disclosure of Invention The invention provides a rectifying still residue extraction method for overcoming the problems in the prior art. The technical scheme of the invention is as follows: the invention aims to provide an extraction method of N-methyl pyrrolidone rectifying still residue, which comprises the following steps: (1) Soaking the residue of the N-methyl pyrrolidone rectifying still in water, adding lignosulfonate, continuously soaking, stirring after soaking, and then adding an organic solvent, mixing and stirring to obtain a mixture; (2) And (3) rectifying the mixture, heating to recover the organic solvent after no NMP is finally produced, adding water and stirring after no fraction is produced, and discharging the mixture out of a rectifying device to obtain NMP. Further limited, the water content in the step (1) is 3-5wt% of the residue of the N-methyl pyrrolidone rectifying still, the lignosulfonate content is 1wt% of the water, and the soaking time after the lignosulfonate is added is 1h. Further limited, the organic solvent is added in (1) and mixed and stirred for 40min. Further defined, the organic solvent in (1) is diethylene glycol, sulfolane, dimethy