CN109912484B - Method for separating and recycling NMP from NMP brine - Google Patents
Method for separating and recycling NMP from NMP brine Download PDFInfo
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Abstract
The invention belongs to the technical field of chemical industry, and particularly relates to a method for separating and recycling NMP from NMP brine, which adopts high-boiling-point esters with stable physicochemical properties as an extracting agent to realize the separation of the NMP from the brine, combines a vacuum rectification technology to realize the good separation of the NMP from the extracting agent, directly collects high-purity NMP at the tower top, comprises the processes of neutralization pretreatment, extraction, dehydration and vacuum rectification, extracts deslagging wastewater for 3-5 times by taking the high-boiling-point esters as the extracting agent, has a solvent ratio of 1-3.5, combines extraction phases to dewater, carries out vacuum rectification on the dewatered extraction phase, and collects the NMP at the tower top. The method has the advantages of high extraction efficiency, good separation effect, high recovery rate, low resource occupancy rate, low energy consumption and little pollution, and can simultaneously obtain the NMP and the extracting agent with high purity (more than 99.9%). The method is suitable for treating the salt wastewater containing the NMP, in particular to the treatment of the aramid fiber synthetic wastewater.
Description
Technical Field
The invention belongs to the technical field of chemical industry, relates to the technical field of chemical fiber synthesis, and particularly relates to a solvent recycling technology in the chemical fiber synthesis industry.
Background
The N-methylpyrrolidone is an excellent solvent, has the advantages of strong selectivity, good chemical stability and the like, is widely applied to the aspects of high-precision electronics, circuit boards, lithium batteries and the like, is widely applied as a solvent in the industries of fibers, polyether and the like, has high NMP price, and can better recycle the NMP, thereby having great influence on the production cost of products.
For the recovery of NMP in the aqueous solution of the NMP salt, the separation of NMP and water is realized by adopting a distillation mode, the energy consumption is high, the requirement on equipment materials is high, and along with the reduction of water content, salt is separated out from NMP, so that a pipeline is blocked, the decomposition of NMP is promoted, and the yield of NMP is 60-80%. The NMP recovery rate is low, the energy consumption is high, and sticky substances are easily generated at the tower bottom.
For the recovery of NMP in NMP salt solution, the separation of NMP and water is realized by adopting the extraction mode of chloroform, dichloromethane and the like, so that NMP with higher purity can be obtained, but the extractant is easily decomposed into phosgene and the like by light, the extractant is easy to lose, the recycling recovery rate is low, and the requirements on equipment selection and a refrigeration system are strict.
Disclosure of Invention
The invention aims to provide a method for separating and recycling NMP from NMP saline solution, which solves the problems of high energy consumption, low yield, low purity, high loss rate of an extracting agent and the like in the process of recycling NMP from the NMP saline solution.
The invention aims to realize the purpose, the high boiling point esters with stable physicochemical characteristics and low volatility are used as the extracting agent to realize the separation of NMP and brine, the vacuum rectification technology is combined to realize the good separation of NMP and the extracting agent, the high-purity NMP is directly collected at the tower top, and the high-purity extracting agent is obtained at the tower bottom.
The invention relates to a method for extracting NMP from waste water containing NMP salt, which comprises the processes of neutralization pretreatment, extraction, dehydration and rectification under reduced pressure, and comprises the following specific steps:
(1) and (3) neutralization pretreatment: regulating the pH value of the wastewater containing the NMP salt to 6-7 by using a neutralizing agent, and precisely filtering to remove residues;
(2) and (3) extraction: extracting the slag-removed waste water for 3-5 times by using high-boiling-point esters as an extracting agent, wherein the solvent ratio is 1-3.5, and combining the extraction phases;
(3) and (3) dehydrating: removing water carried in the extraction phase;
(4) and (3) rectification under reduced pressure: and carrying out reduced pressure rectification on the dehydrated extract phase, and collecting NMP at the tower top.
The method for extracting NMP from waste water containing NMP salt includes the processes of neutralization pretreatment, extraction, dehydration refining and vacuum rectification, and the extracting agent in the tower bottom can be directly recycled.
The neutralizing agent is calcium carbonate.
The high boiling point esters are diethyl succinate, benzyl acetate, dimethyl phthalate or diethyl phthalate with stable physicochemical characteristics, low volatility and appropriate temperature difference.
The dehydration process in the step (3) adopts a vacuum rectification process, and the process conditions are as follows: the pressure at the top of the tower is 1-3KPa, the number of theoretical plates is 3-5, and the reflux ratio is 1-2.
The process conditions of the vacuum rectification process in the step (4) are that the pressure at the top of the tower is 1-3KPa, the number of theoretical plates is 3-8, and the reflux ratio is 1-2.
The method for separating and recycling NMP from the NMP brine has the advantages of high extraction efficiency, good separation effect, high recovery rate, low resource occupancy rate, low energy consumption and small pollution, and can simultaneously obtain high-purity NMP (more than 99.9%) and an extracting agent. Is suitable for the treatment of NMP salt-containing wastewater, in particular for the treatment of aramid fiber synthetic wastewater.
Detailed Description
The invention will now be further illustrated by reference to specific examples, which are intended to be illustrative only and not to limit the scope of the invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
Example 1
Taking 200g of wastewater with the calcium chloride content of 3% and the NMP content of 12.05%, and adding calcium carbonate to adjust the pH value to 6-7; after filtering, adding 700g of diethyl succinate serving as an extracting agent into the filtrate, carrying out extraction operation, stirring, standing for 5 minutes, and layering to separate out an extraction phase; and extracting the upper extraction raffinate phase by 700g of diethyl succinate, repeating the operation for four times, wherein 0.17% of diethyl succinate and 0.08% of NMP are remained in the extraction raffinate phase, and 0.17% of water is carried in the extraction extract phase. And combining the extract phases, and carrying out vacuum rectification dehydration on the extract phases, wherein the top pressure of a dehydration tower is 3KPa, the number of theoretical plates is 3, the reflux ratio is 2, the purity of the distilled water reaches 99.9 percent, and the content of NMP is lower than 90 ppm. After dehydration, the purification operation of NMP is carried out by vacuum rectification, the pressure at the top of the tower is 2KPa, the number of theoretical plates is 5, the reflux ratio is 1.5, the NMP with the purity of 99.9 percent and the water content of 48ppm is obtained at the top of the tower, and the yield is 99.17 percent. The recovery rate of the extracting agent at the bottom of the tower is 99.99 percent, and impurities are not detected except a small amount of NMP.
Example 2
Taking 218g of wastewater containing 5% of calcium chloride and 24% of NMP, and adding calcium carbonate to adjust the pH value to 6-7; after filtration, 300g of diethyl succinate as an extractant was added to the filtrate to perform extraction, and after stirring and standing for 2 minutes, an extract phase was separated after layering. And extracting the upper raffinate phase by 300g of diethyl succinate, repeating the operation for five times, wherein 0.13% of diethyl succinate, 0.16% of NMP and 0.21% of water in the extract raffinate phase are carried by water in the extract phase. Mixing the extract phases, and performing vacuum rectification dehydration on the extract phases, wherein the pressure at the top of the tower is 2KPa, the number of theoretical plates is 2, the reflux ratio is 1, the purity of the distilled water is 99.4, and the distilled water contains 0.5 percent of NMP. And (3) carrying out reduced pressure rectification after dehydration, wherein the pressure at the top of the dehydration tower is 3KPa, the number of theoretical plates is 5, the reflux ratio is 1, NMP with the purity of 99.9 percent and the water content of 95ppm is obtained at the top of the tower, and the yield is 97.8 percent. No impurities were detected at the column bottom extractant recovery rate of 99.98%.
Example 3
Taking 200g of wastewater containing 45.1 percent of NMP, adding calcium carbonate to adjust the pH value to 6-7; adding 200g of diethyl succinate serving as an extractant, performing extraction operation, stirring, standing for 10 minutes, layering, separating an extraction phase, performing re-extraction on the upper-layer solution, and repeating the operation for four times; 0.03 percent of diethyl succinate residue, 0.21 percent of NMP residue and 0.18 percent of entrained water in the extraction phase. And combining the extract phases, and carrying out vacuum rectification dehydration on the extract phases, wherein the top pressure of a dehydration tower is 2KPa, the number of theoretical plates is 4, and the reflux ratio is 1, so that 99.99% of water is obtained, and the content of NMP is less than 90 ppm. And (3) carrying out vacuum distillation on NMP purification operation after dehydration, wherein the pressure of the top of the vacuum distillation tower is 2KPa, the theoretical plate number is 3, the reflux ratio is 2, the NMP with the purity of 99.9 percent and the water content of 49ppm is obtained, and the yield is 99.43 percent. No impurity is detected in the extracting agent at the bottom of the tower, and the recovery rate of the extracting agent is 99.99 percent.
Example 4
Taking 210g of wastewater containing 24.9 percent of NMP, adding calcium carbonate to adjust the pH value to 6-7; after filtering, adding 200g of extractant benzyl acetate into the filtrate, carrying out extraction operation, stirring, standing for 5 minutes, separating out an extraction phase after layering, extracting the upper layer solution again by taking 200g of benzyl acetate, repeating the operation for four times, wherein 0.2% of benzyl acetate residue, 0.13% of NMP residue and 0.11% of entrained water in the extraction phase are remained in the upper layer solution. Combining extraction phases, and carrying out vacuum rectification dehydration on the extraction phases, wherein the top pressure of a dehydration tower is 2KPa, the number of theoretical plates is 3, the reflux ratio is 2, and the content of NMP in a tower top water phase is not more than 80 ppm. And (3) performing vacuum distillation on NMP for purification after dehydration, wherein the pressure of the top of the vacuum distillation tower is 2KPa, the number of theoretical plates is 8, and the reflux ratio is 1, so that the NMP with the purity of 99.9 percent and the water content of less than 40ppm is obtained, and the yield is 99.66 percent. The recovery rate of the extractant at the bottom of the column is 99.4 percent, and no impurity is detected.
Example 5
203g of waste water containing NMP19% is taken, calcium carbonate is added to adjust the pH value to 6-7; after filtering, adding 400g of extractant benzyl acetate into the filtrate, carrying out extraction operation, stirring, standing for 10 minutes, separating out an extraction phase after layering, extracting the upper layer solution again by taking 400g of benzyl acetate, repeating the operation for four times, wherein 0.23% of benzyl acetate residue, 0.11% of NMP residue and 0.14% of extraction phase entrained water are remained in the water. And combining the extraction phases, and carrying out vacuum rectification dehydration on the extraction phases, wherein the top pressure of a dehydration tower is 2KPa, the number of theoretical plates is 4, the reflux ratio is 1, and the NMP content of a tower top water phase is 80 ppm. And (3) carrying out reduced pressure distillation after dehydration, wherein the pressure of the top of the reduced pressure distillation tower is 2KPa, the number of theoretical plates is 5, the reflux ratio is 1.5, the NMP with the purity of 99.9 percent and the water content of 830ppm is obtained, and the yield is 99.51 percent. 99.98% of extractant at the bottom of the column, and no impurity was detected.
Example 6
Taking 212g of wastewater with calcium chloride content of 6% and NMP content of 18.2%, adding calcium carbonate to adjust the pH value to 6-7; after filtration, 200g of extractant benzyl acetate is added into the filtrate for extraction operation, the mixture is stirred and then is kept stand for 13 minutes, an extraction phase is separated after layering, the upper layer solution is extracted again, and after the operations are repeated twice, 0.22% of benzyl acetate residue, 3.6% of NMP residue and 0.12% of entrained water in the extraction phase are obtained. Combining extraction phases, and carrying out vacuum rectification dehydration operation on the extraction phases, wherein the top pressure of a dehydration tower is 3KPa, the number of theoretical plates is 4, the reflux ratio is 1, and the content of NMP in a tower top water phase is 78 ppm. After dehydration, NMP purification operation is carried out by decompression and rectification, the top pressure of the decompression distillation tower is 3KPa, the number of theoretical plates is 5, the reflux ratio is 1, the NMP with the purity of 99.9 percent and the water content of 90ppm is obtained, and the yield is 83.67 percent. The recovery rate of the extractant at the bottom of the column is 99.91 percent, and no impurity is detected.
Example 7
Taking 205g and 43.25g of wastewater containing 21.1 percent of NMP, and adding calcium carbonate to adjust the pH value to 6-7; after filtration, 200g of extractant dimethyl phthalate is added into the filtrate for extraction operation, the mixture is stirred and then is kept stand for 7 minutes, the extraction liquid is separated after layering, the upper layer solution is extracted again, after the operations are repeated for four times, the content of dimethyl phthalate in water is 0.47 percent, NMP residue is 0.17 percent, and the water content in the extraction phase is 1.84 percent. Combining the extract phases, and carrying out vacuum rectification dehydration operation on the extract phases, wherein the top pressure of a dehydration tower is 3KPa, the number of theoretical plates is 3, the reflux ratio is 2, and the NMP content of a tower top water phase is 68 ppm. And performing NMP vacuum distillation purification operation after dehydration, wherein the top pressure of the vacuum distillation tower is 2KPa, the number of theoretical plates is 5, and the reflux ratio is 2, so that NMP with the purity of 99.9 percent and the water content of less than 65ppm is obtained, and the yield is 99.3 percent. The recovery rate of the extractant at the bottom of the column is 99.91 percent, and no impurity is detected.
Example 8
Taking 203g of wastewater with calcium chloride content of 2% and NMP40%, and adding calcium carbonate to adjust the pH value to 6-7; after filtration, 300g of extractant dimethyl phthalate is added into the filtrate, extraction operation is carried out, the mixture is stirred and then is kept stand for 12 minutes, extraction liquid is separated after layering, the upper layer solution is extracted again, after the operations are repeated for five times, the content of dimethyl phthalate in water is 0.44%, NMP (N-methyl pyrrolidone) residue is 0.08%, and the water content in the extraction phase is 1.92%. Combining the extract phases, and carrying out vacuum rectification dehydration operation on the extract phases, wherein the top pressure of a dehydration tower is 2KPa, the number of theoretical plates is 3, the reflux ratio is 1.5, and the NMP content in water at the tower top is 55 ppm. And (3) performing NMP (N-methyl pyrrolidone) vacuum rectification purification after dehydration, wherein the top pressure of the vacuum rectification tower is 3KPa, the theoretical plate number is 4, and the reflux ratio is 2, so that the NMP yield of 99.72% with the purity of 99.9% and the water content of 73ppm is obtained. The recovery rate of the extractant at the bottom of the column is 99.96 percent, and no impurity is detected.
Example 9
Taking 211g of wastewater containing 15% of NMP, and adding calcium carbonate to adjust the pH value to 6-7; after filtering, 600g of extractant dimethyl phthalate is added into the filtrate, extraction operation is carried out, standing is carried out for 15 minutes after stirring, an extraction phase is separated after layering, the upper layer solution is extracted again, after the operation is repeated for four times, the content of dimethyl phthalate in water is 0.44%, NMP (N-methyl pyrrolidone) residue is 0.04%, and the water content in the extraction phase is 1.87%. Combining the extract phase and the extract phase, and carrying out vacuum rectification dehydration on the extract phase, wherein the top pressure of a dehydration tower is 4KPa, the number of theoretical plates is 5, the reflux ratio is 1, and the NMP content of a water phase at the top of the tower is 85 ppm. And (3) performing NMP (N-methyl pyrrolidone) vacuum rectification purification after dehydration, wherein the pressure at the top of the vacuum rectification tower is 2KPa, the theoretical plate number is 5, and the reflux ratio is 1, so that the NMP with the purity of 99.9 percent and the water content of 80ppm is obtained, and the yield is 99.41 percent. The recovery rate of the extracting agent at the bottom of the tower is 99.97 percent, and no impurity is detected.
Example 10
Taking 151.5g of wastewater with 3 percent of calcium chloride and 12 percent of NMP, and adding calcium carbonate to adjust the pH value to 6-7; after filtration, 100g of diethyl phthalate serving as an extractant was added to the filtrate to perform extraction, the mixture was allowed to stand for 15 minutes after stirring, an extract phase was separated after delamination, the upper solution was extracted again, and after repeating the above operations four times, the content of diethyl phthalate in water was 0.3%, the content of NMP remained 0.93%, and the content of water in the extract phase was 0.69%. And combining the extract phases, and carrying out vacuum rectification dehydration on the extract phases, wherein the top pressure of a dehydration tower is 4KPa, the number of theoretical plates is 3, the reflux ratio is 2, and the NMP content of a water phase at the top of the tower is 66 ppm. And (3) performing NMP (N-methyl pyrrolidone) vacuum rectification purification after dehydration, wherein the pressure at the top of the vacuum rectification tower is 3KPa, the theoretical plate number is 3, the reflux ratio is 2, the NMP with the purity of 99.9 percent and the water content of less than 69ppm is obtained, and the yield is 99.08 percent. The recovery rate of the extracting agent at the bottom of the tower is 99.90 percent, and no impurity is detected.
Example 11
Adding calcium carbonate into 162g of NMP28% wastewater to adjust the pH value to 6-7; after filtration, 200g of diethyl phthalate serving as an extractant is added into the filtrate, extraction operation is carried out, the mixture is stirred and then is kept stand for 10 minutes, an extraction phase is separated after layering, the upper layer solution is extracted again, after the operations are repeated twice, the content of dimethyl phthalate in water is 0.23%, NMP (N-methyl pyrrolidone) residues are 2.84%, and the water content in the extraction phase is 0.73%. And combining the extract phases, and carrying out vacuum rectification dehydration on the extract phases, wherein the top pressure of a dehydration tower is 3KPa, the number of theoretical plates is 3, the reflux ratio is 1.5, and the content of NMP in a tower top water phase is 88 ppm. And performing NMP reduced pressure distillation after dehydration, wherein the top pressure of the reduced pressure distillation tower is 1KPa, the number of theoretical plates is 5, the reflux ratio is 1.5, and the NMP with the purity of 99.9 percent and the water content of 80ppm is obtained, and the yield is 99.71 percent. The recovery rate of the extractant at the bottom of the column is 99.93 percent, and no impurity is detected.
Example 12
Taking 153g of wastewater containing 7% of calcium chloride and 42% of NMP, and adding calcium carbonate to adjust the pH value to 6-7; after filtration, 400g of extractant dimethyl phthalate is added into the filtrate for extraction operation, the mixture is stirred and then stands for 15 minutes, an extraction phase is separated after layering, the upper layer solution is extracted again, after the operations are repeated for four times, the content of dimethyl phthalate in water is 0.28 percent, NMP (N-methyl pyrrolidone) remains 0.03 percent, and the content of water in the extraction phase is 0.32 percent. And combining the extraction phases, and carrying out vacuum rectification dehydration on the extraction phases, wherein the top pressure of a dehydration tower is 1KPa, the number of theoretical plates is 5, the reflux ratio is 1, and the content of NMP in a water phase at the top of the tower is 56 ppm. After dehydration, NMP is subjected to vacuum distillation, the pressure at the top of the vacuum distillation tower is 1KPa, the number of theoretical plates is 4, and the reflux ratio is 1, so that NMP with the purity of 99.9 percent and the water content of 77ppm is obtained, and the yield is 99.51 percent. The recovery rate of the extracting agent at the bottom of the tower is 99.98 percent, and no impurity is detected.
Claims (5)
1. The method for separating and recycling NMP from NMP brine comprises the processes of neutralization pretreatment, extraction, dehydration and reduced pressure rectification, and is characterized in that:
(1) and (3) neutralization pretreatment: regulating the pH value of the wastewater containing the NMP salt to 6-7 by using a neutralizing agent, and precisely filtering to remove residues;
(2) and (3) extraction: extracting the slag-removed waste water 3-5 times with high-boiling-point esters as an extracting agent at a solvent ratio of 1-3.5, and mixing the extract phases;
(3) and (3) dehydrating: removing water carried in the extraction phase;
(4) and (3) rectification under reduced pressure: carrying out reduced pressure rectification on the dehydrated extract phase, and collecting NMP at the tower top;
the high boiling point ester is one of diethyl succinate, benzyl acetate, dimethyl phthalate and diethyl phthalate.
2. The method of claim 1 for separating and recycling NMP from NMP brine, characterized in that: the neutralizing agent is calcium carbonate.
3. The method for separating and recycling NMP from NMP brine according to any one of claims 1 or 2, characterized in that: and (3) adopting a vacuum rectification process in the dehydration process, wherein the tower top pressure is 1-3KPa, the theoretical plate number is 3-5, and the reflux ratio is 1-2.
4. The method for separating and recycling NMP from NMP brine according to any one of claims 1 or 2, characterized in that: the process conditions of the vacuum distillation process in the step (4) are 1-3KPa of the pressure at the top of the tower, 3-8 theoretical plates and 1-2 reflux ratio.
5. The method for extracting NMP from wastewater containing NMP salt according to any one of claims 1 or 2, wherein: the extractant in the tower bottom can be directly recycled.
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| CN110922347B (en) * | 2019-12-02 | 2022-12-06 | 山东京博聚芳新材料股份有限公司 | Method for separating N-methyl pyrrolidone from large-amount chloroform system |
Citations (4)
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| US5068358A (en) * | 1988-10-13 | 1991-11-26 | Hoechst Aktiengesellschaft | Process for extracting n-methyl-2-pyrrolidone |
| CN102993078A (en) * | 2012-12-31 | 2013-03-27 | 东华大学 | Method for purifying N-methyl pyrrolidone |
| CN106390684A (en) * | 2016-09-21 | 2017-02-15 | 苏州迈沃环保工程有限公司 | Method for recovering NMP (1-Methyl-2-pyrrolidinone) in gas by solvent with high boiling point |
| CN109134339A (en) * | 2018-09-13 | 2019-01-04 | 清华大学 | Method for recovering solvents is used in a kind of production of para-aramid fiber |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5068358A (en) * | 1988-10-13 | 1991-11-26 | Hoechst Aktiengesellschaft | Process for extracting n-methyl-2-pyrrolidone |
| CN102993078A (en) * | 2012-12-31 | 2013-03-27 | 东华大学 | Method for purifying N-methyl pyrrolidone |
| CN106390684A (en) * | 2016-09-21 | 2017-02-15 | 苏州迈沃环保工程有限公司 | Method for recovering NMP (1-Methyl-2-pyrrolidinone) in gas by solvent with high boiling point |
| CN109134339A (en) * | 2018-09-13 | 2019-01-04 | 清华大学 | Method for recovering solvents is used in a kind of production of para-aramid fiber |
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