Separation and purification process of NMP

Abstract

The invention belongs to the technical field of organic matter purification, and relates to a separation and purification process of NMP (N-Methyl Pyrrolidone). The invention aims to solve the problem that an existing NMP recovery process cannot effectively treat NMP waste liquid generated by different industrial types. The method comprises the following steps: introducing an NMP recovery liquid into a primary filtration unit to obtain pretreated NMP; the conductivity of the pretreated NMP is measured, a chemical neutralization unit, an adsorption unit or a reduced pressure distillation unit is adopted for treatment according to the difference of the conductivity, obtained different products are correspondingly treated and then jointly treated through an extractive distillation unit, and product-grade NMP is obtained. According to the separation and purification process provided by the invention, various impurities in various types of NMP recovery liquid from the electronic industry can be effectively removed, and the electronic-grade NMP solvent can be efficiently recycled.

Description

Technical Field

[0001] The invention belongs to the technical field of organic matter purification and relates to a separation and purification process of NMP. Background Art

[0002] N-Methylpyrrolidone (NMP) is a commonly used polar aprotic solvent with wide application value in the chemical industry, electronics industry, etc. In recent years, with the rapid development of the electronics industry, especially the rapid expansion of production capacity in the lithium battery and semiconductor industries, the demand for high-purity NMP has become increasingly strong. Similarly, these industries have also put forward more performance requirements for high-purity NMP, such as extremely low water content, extremely low metal ion content, and extremely low organic impurity content. As an important part of the NMP production process, the purification process of NMP has also made many technical advances in recent years.

[0003] In the field of electronics industry, NMP has a wide range of applications, such as electronic component cleaning, photoresist coating, semiconductor etching, thin film deposition and battery manufacturing. The components of waste NMP generated by different process types are quite different, and it is difficult to efficiently process them through a single process. Therefore, the recycling process of waste NMP in the electronics industry needs to be designed for different impurity types, and at the same time optimize the recycling process and improve the recycling efficiency.

[0004] At present, the inability of existing NMP recovery processes to effectively treat NMP waste liquid generated by different industrial types remains an important problem facing the industry.

[0005] Therefore, a separation and purification process of NMP is proposed. Summary of the invention

[0006] The object of the present invention is to provide a separation and purification process for NMP. The present invention obtains pretreated NMP by passing NMP recovery liquid into a primary filtration unit; measures the conductivity of the pretreated NMP, and respectively uses a chemical neutralization unit, an adsorption unit or a vacuum distillation unit to treat it according to different conductivity, and after the obtained different products are treated accordingly, they are treated together by an extraction distillation unit to obtain product-grade NMP.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A separation and purification process for NMP comprises the following steps:

[0009] The NMP recovery liquid is passed into the primary filtration unit to obtain pretreated NMP after the primary filtration treatment;

[0010] The pretreated NMP was passed into the split flow unit to measure its conductivity;

[0011] If the conductivity is higher than 1S / cm, the pre-treated NMP is passed into a chemical neutralization unit to obtain pre-precipitated NMP after neutralization treatment;

[0012] If the conductivity is higher than 0.01 S / cm and lower than 1 S / cm, the pretreated NMP is passed into the adsorption unit to obtain the first pre-separated NMP after adsorption treatment;

[0013] If the conductivity is lower than 0.01 S / cm, the pre-treated NMP is passed into a vacuum distillation unit to obtain a second pre-separated NMP after vacuum distillation treatment;

[0014] Passing the pre-precipitated NMP into a precipitation unit to obtain a first pre-distilled NMP after precipitation treatment;

[0015] Passing the first pre-separated NMP and the second pre-separated NMP into a membrane separation unit to obtain a second pre-distilled NMP after separation treatment;

[0016] The first pre-separated NMP and the second pre-distilled NMP are introduced into an extractive distillation unit, and product-grade NMP is obtained after extractive distillation treatment.

[0017] Preferably, the primary filtration unit comprises: a centrifugal separation unit and a microfiltration unit; the primary filtration treatment process is: the NMP recovery liquid is passed into the centrifugal separation unit, centrifuged at 2000-3000 rpm for 20 minutes at 25°C, and then centrifuged at 5000 rpm for 5 minutes to obtain a centrifugal clear liquid; the centrifugal clear liquid is passed into the microfiltration unit, and centrifuged at 550-700 L / (m 2 h) is subjected to microfiltration treatment to obtain pretreated NMP; wherein the pore size of the filter membrane of the microfiltration unit is 0.22 μm.

[0018] Preferably, the chemical neutralization unit comprises: a pH adjustment unit and an ion precipitation unit; the neutralization treatment process is: the pretreated NMP from the diversion unit is passed into the pH adjustment unit, the pH value of the pretreated NMP is adjusted to 7-8 using sodium bicarbonate powder, and then passed into the ion precipitation unit, calcium sulfide powder is added and stirred at 500-700 rpm for 20 minutes, and then filtered to obtain the pre-precipitated NMP.

[0019] Preferably, the adsorption unit comprises: an activated carbon layer and an ion exchange resin filler layer; the adsorption treatment process is: passing the pretreated NMP into the activated carbon layer, wherein the operating pressure is 1.5 MPa and the operating temperature is 25°C, and then passing it into the ion exchange resin filler layer, wherein the ion exchange resin is a weakly acidic cation exchange resin, and the first pre-separated NMP is obtained after treatment.

[0020] Preferably, the vacuum distillation unit comprises: a dryer and a vacuum distillation tower; the process of vacuum distillation treatment is: the pretreated NMP is passed into the dryer, and after drying at 80°C, it is passed into the vacuum distillation tower, and the second pre-separated NMP is obtained after vacuum distillation; wherein the dryer is a pressure spray dryer, and the atomization pressure is 10MPa; wherein the operating pressure of the vacuum distillation tower is 0.3-0.6atm, the bottom temperature is 180°C, the top temperature is 90°C, and the reflux ratio is 2.0.

[0021] Preferably, the precipitation unit comprises: a flocculation-sedimentation unit and a sand filter tank; the precipitation treatment process is: passing the pre-precipitated NMP into the flocculation-sedimentation unit, adding a flocculant at a concentration of 0.5 g / L, controlling the pH value to be between 6 and 8 at 25°C, and treating at a stirring speed of 200 rpm for 40-80 min, passing the treated supernatant into a sand filter tank, and filtering at a filtration rate of 10 m / h to obtain a first pre-distilled NMP; wherein the flocculant is a mixture of polyaluminum ferric chloride and polyacrylamide, and the mass ratio of polyaluminum ferric chloride to polyacrylamide is 1:2.

[0022] Preferably, the membrane separation unit comprises: a nanofiltration unit and an electrodialysis unit; the separation process is: the first pre-separation NMP and the second pre-separation NMP are cooled to 25°C and then passed into the nanofiltration unit, subjected to nanofiltration treatment at an operating pressure of 0.5 MPa, and then continued to be passed into the electrodialysis unit, and electrodialysis treatment is performed at an operating voltage of 220 V, a current of 2 A and an operating pressure of 0.5 MPa to obtain a second pre-distillation NMP.

[0023] Preferably, the extractive distillation unit comprises an extractive distillation tower and a secondary distillation tower; the process of the extractive distillation treatment is: the first pre-distillation NMP and the second pre-distillation NMP are introduced into the extractive distillation tower, and the extractant is introduced according to the feed mass ratio of 1:1, and the extractive distillation is carried out under the operating conditions of the tower bottom temperature of 180°C, the tower top temperature of 100°C, the reflux ratio of 3.0, and the operating pressure of 0.1MPa, and the top product is introduced into the secondary distillation tower, and the secondary distillation is carried out under the operating conditions of the tower bottom temperature of 170°C, the tower top temperature of 80°C, the operating pressure of 80kPa, and the reflux ratio of 2.5, and the tower bottom product is taken as the product-grade NMP; wherein the extractant is dimethyl carbonate.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. A primary filtration unit is set before the NMP recovery liquid is diverted for treatment, and large particles and solid impurities are removed from the recovery liquid from different processes in advance, effectively reducing the burden of subsequent sections. At the same time, a diversion unit is set up to divert and treat the NMP recovery liquid from different sections by detecting the conductivity, which significantly improves the treatment efficiency and reduces the treatment cost while ensuring process continuity.

[0026] 2. The NMP recovery liquid from the semiconductor etching and other industrial fields is separated and purified by using a method combining chemical neutralization and precipitation treatment. Because of its conductivity greater than 1S / cm, a large amount of electrolyte ions are first removed in a non-aqueous phase, and preliminary separation and purification is performed by pH adjustment and ion coprecipitation without introducing impure water. Most of the electrolyte ions are removed after flocculation and filtration, ensuring the working efficiency of the subsequent extraction and distillation process and improving the product purity of the process line.

[0027] 3. The NMP recovery liquid with a conductivity between 0.01-1S / cm is treated by an adsorption unit and a membrane separation unit. While removing the electrolyte ions with a high content in advance, no additional distillation treatment is added. The low-boiling point organic impurities with a high content will be removed in the subsequent extraction distillation process, which simplifies the process steps and ensures that the purity of the product-grade NMP is not affected.

[0028] 4. Through vacuum distillation, the NMP recovery liquid generated in the industrial field of electronic component cleaning is separated and purified, and non-polar organic matter such as flux substances and organic dirt that exist in large quantities is removed. The main impurities in the NMP waste liquid with a conductivity of less than 0.01S / cm are high-boiling point organic matter and water. Therefore, the vacuum distillation process can efficiently purify NMP, and the purified NMP can improve the overall efficiency of the subsequent membrane separation process.

[0029] 5. After removing most of the metal ions through chemical neutralization and electrodialysis, NMP from different processes is uniformly separated and purified through extractive distillation, which effectively separates organic impurities with different boiling points in NMP. Different types of NMP from different treatment processes are uniformly treated, which simplifies the process and improves the treatment efficiency. In addition, since the electrolyte ions are basically removed in the previous process, adsorption and membrane separation operations are not required in the extractive distillation process, which reduces the operating conditions and is conducive to the establishment of a large-scale production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the separation and purification process of NMP in the present invention. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be clearly and completely described below through some embodiments and experimental examples. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Reference Figure 1 The present invention provides a separation and purification process of NMP, and the technical scheme is as follows:

[0033] Example 1

[0034] Take the NMP waste liquid from the semiconductor etching section as the NMP recovery liquid.

[0035] Basic parameters of NMP recovery liquid: NMP purity: 70%; strong acid electrolyte content: 5.4%; metal ion content: 1437 mg / L; organic impurity content: 8.4%; water content: 4.1%; corrosive by-product content: 2.2%; the remainder is other impurities.

[0036] Among them, strong acid electrolytes mainly include HF and H2SO4; metal ions mainly include Al 3+ and Cu 2+ ; Corrosive by-products mainly include CuF2 and AlF3.

[0037] The NMP recovery liquid was passed into a centrifugal separation unit, centrifuged at 2000 rpm for 20 min at 25°C, and then centrifuged at 5000 rpm for 5 min to obtain a centrifugal clear liquid; the centrifugal clear liquid was passed into a microfiltration unit, and centrifuged at 550 L / (m 2 h) is subjected to microfiltration treatment to obtain pretreated NMP; wherein the pore size of the filter membrane of the microfiltration unit is 0.22 μm.

[0038] The pretreated NMP was passed into the split flow unit and its conductivity was measured to be 9.86*10 2 S / m is significantly higher than the first threshold value, so the pretreated NMP is passed into a pH adjustment unit, and the pH value of the pretreated NMP is adjusted to 7 using sodium bicarbonate powder, and then passed into an ion precipitation unit, and calcium sulfide powder accounting for 2 wt% of the mass of the pretreated NMP is added and stirred at 500 rpm for 20 min, and then filtered to obtain the pre-precipitated NMP.

[0039] The pre-precipitated NMP is passed into a flocculation-sedimentation unit, a flocculant is added at a concentration of 0.5 g / L, the pH value is controlled between 6 at 25°C, and the treatment is carried out at a stirring speed of 200 rpm for 40 minutes. The treated supernatant is passed into a sand filter tank and filtered at a filtration rate of 10 m / h to obtain the first pre-distilled NMP; wherein the flocculant is a mixture of polyaluminum ferric chloride and polyacrylamide, and the mass ratio of polyaluminum ferric chloride to polyacrylamide is 1:2.

[0040] The first pre-distillation NMP is introduced into an extractive distillation tower, and an extractant is introduced according to a feed mass ratio of 1:1. The extractive distillation is carried out under the operating conditions of a bottom temperature of 180°C, a top temperature of 100°C, a reflux ratio of 3.0, and an operating pressure of 0.1MPa. The top product is introduced into a secondary distillation tower, and secondary distillation is carried out under the operating conditions of a bottom temperature of 170°C, a top temperature of 80°C, an operating pressure of 80kPa, and a reflux ratio of 2.5. The bottom product is product-grade NMP; wherein the extractant is dimethyl carbonate.

[0041] The process parameters of Examples 2-10 are different from those of Example 1, but the process steps and the source of NMP recovery liquid are the same. The specific parameters are summarized in Table 1.

[0042] Table 1 Variation of process parameters of Examples 1-10

[0043]

[0044] Embodiment 11

[0045] Take the waste NMP from the lithium battery manufacturing process as NMP recovery liquid.

[0046] The basic parameters of NMP recovery liquid are: NMP purity: 95%; organic impurity content: 3.1%; water content: 0.7%; lithium salt content: 0.02%; the remainder is other impurities.

[0047] The NMP recovery liquid was passed into a centrifugal separation unit, centrifuged at 2000 rpm for 20 min at 25°C, and then centrifuged at 5000 rpm for 5 min to obtain a centrifugal clear liquid; the centrifugal clear liquid was passed into a microfiltration unit, and centrifuged at 550 L / (m 2 h) is subjected to microfiltration treatment to obtain pretreated NMP; wherein the pore size of the filter membrane of the microfiltration unit is 0.22 μm.

[0048] The pretreated NMP was passed into the diversion unit, and its conductivity was measured to be 0.86S / m, which is between the first threshold and the second threshold. Therefore, the pretreated NMP was passed into the activated carbon layer, wherein the operating pressure was 1.5MPa and the operating temperature was 25°C, and then passed into the ion exchange resin filler layer, wherein the ion exchange resin was a weakly acidic cation exchange resin, and the first pre-separated NMP was obtained after treatment.

[0049] The first pre-separated NMP was cooled to 25°C and then passed into a nanofiltration unit for nanofiltration treatment at an operating pressure of 0.5 MPa, and then continued to be passed into an electrodialysis unit for electrodialysis treatment at an operating voltage of 220 V, a current of 2 A and an operating pressure of 0.5 MPa to obtain a second pre-distilled NMP.

[0050] The second pre-distillation NMP is introduced into an extractive distillation tower, and an extractant is introduced according to a feed mass ratio of 1:1. The extractive distillation is carried out under the operating conditions of a bottom temperature of 180°C, a top temperature of 100°C, a reflux ratio of 3.0, and an operating pressure of 0.1MPa. The top product is introduced into a secondary distillation tower, and secondary distillation is carried out under the operating conditions of a bottom temperature of 170°C, a top temperature of 80°C, an operating pressure of 80kPa, and a reflux ratio of 2.5. The bottom product is product-grade NMP; wherein the extractant is dimethyl carbonate.

[0051] The process parameters of Examples 12-15 and Example 11 are changed only in the treatment of the primary filtration unit, and the other process steps and the NMP recovery liquid used are the same. The specific parameters are summarized in Table 2.

[0052] Table 2 Variation of process parameters of Examples 11-15

[0053]

[0054]

[0055] Example 16

[0056] Take the waste NMP from the electronic component cleaning section as NMP recovery liquid.

[0057] The basic parameters of NMP recovery liquid are: NMP purity: 85.2%; organic impurity content: 9.4%; surfactant content: 2.3%; water content: 1.4%; the remainder is other impurities.

[0058] The NMP recovery liquid was passed into a centrifugal separation unit, centrifuged at 2000 rpm for 20 min at 25°C, and then centrifuged at 5000 rpm for 5 min to obtain a centrifugal clear liquid; the centrifugal clear liquid was passed into a microfiltration unit, and centrifuged at 550 L / (m 2 h) is subjected to microfiltration treatment to obtain pretreated NMP; wherein the pore size of the filter membrane of the microfiltration unit is 0.22 μm.

[0059] The pretreated NMP was passed into the split flow unit and its conductivity was measured to be 7.42*10 -2 S / m, which is lower than the second threshold. Therefore, the pretreated NMP is passed into a dryer, dried at 80°C, and then passed into a vacuum distillation tower, where the second pre-separated NMP is obtained after vacuum distillation; wherein the dryer is a pressure spray dryer, and the atomization pressure is 10 MPa; wherein the operating pressure of the vacuum distillation tower is 0.3 atm, the tower bottom temperature is 180°C, the tower top temperature is 90°C, and the reflux ratio is 2.0.

[0060] The second pre-separated NMP was cooled to 25°C and then passed into a nanofiltration unit for nanofiltration treatment at an operating pressure of 0.5 MPa, and then continued to be passed into an electrodialysis unit for electrodialysis treatment at an operating voltage of 220 V, a current of 2 A and an operating pressure of 0.5 MPa to obtain a second pre-distilled NMP.

[0061] The second pre-distillation NMP is passed into an extractive distillation tower, and an extractant is passed into the tower according to a feed mass ratio of 1:1. The extractive distillation is carried out under the operating conditions of a bottom temperature of 180°C, a top temperature of 100°C, a reflux ratio of 3.0, and an operating pressure of 0.1MPa. The top product is passed into a secondary distillation tower, and secondary distillation is carried out under the operating conditions of a bottom temperature of 170°C, a top temperature of 80°C, an operating pressure of 80kPa, and a reflux ratio of 2.5. The bottom product is product-grade NMP; wherein the extractant is dimethyl carbonate.

[0062] The process parameters of Examples 17-25 are different from those of Example 16, but the process steps and the source of NMP recovery liquid are the same. The specific parameters are summarized in Table 3.

[0063] Table 3 Variation of process parameters of Examples 16-25

[0064]

[0065] Comparative Example 1

[0066] The difference from Example 1 is that no centrifugal separation treatment is performed in the primary filtration unit, and other process parameters are the same.

[0067] Comparative Example 2

[0068] Different from Example 1, no microfiltration treatment is performed in the primary filtration unit, and other process parameters are the same.

[0069] Comparative Example 3

[0070] The difference from Example 1 is that no split flow treatment is performed, and the pretreated NMP is directly introduced into the adsorption unit for treatment, and other process parameters are the same.

[0071] Comparative Example 4

[0072] The difference from Example 1 is that no splitting treatment is performed, and the pretreated NMP is directly introduced into the vacuum distillation unit for treatment, and other process parameters are the same.

[0073] Comparative Example 5

[0074] The difference from Example 6 is that no neutralization treatment is performed, and other process parameters are the same.

[0075] Comparative Example 6

[0076] The difference from Example 6 is that no precipitation treatment is performed, and other process parameters are the same.

[0077] Comparative Example 7

[0078] The difference from Example 6 is that the order of the neutralization treatment and the precipitation treatment is exchanged, and the other process parameters are the same.

[0079] Comparative Example 8

[0080] The difference from Example 6 is that sodium bicarbonate powder and calcium sulfide powder are not used in the neutralization process, but are replaced by 1 wt % sodium bicarbonate aqueous solution and 2 wt % calcium sulfide suspension, and the other process parameters are the same.

[0081] Comparative Example 9

[0082] The difference from Example 11 is that no adsorption unit treatment is performed, and other process parameters are the same.

[0083] Comparative Example 10

[0084] The difference from Example 11 is that the activated carbon layer in the adsorption unit is removed, and the other process parameters are the same.

[0085] Comparative Example 11

[0086] The difference from Example 11 is that the weakly acidic cation exchange resin in the adsorption unit is removed, and the other process parameters are the same.

[0087] Comparative Example 12

[0088] The difference from Example 11 is the order of the activated carbon layer and the weakly acidic cation exchange resin in the exchange adsorption unit, and the other process parameters are the same.

[0089] Comparative Example 13

[0090] The difference from Example 16 is that the pressure of the vacuum distillation tower is changed to 1 atm, and the other process parameters are the same.

[0091] Comparative Example 14

[0092] The difference from Example 16 is that no drying treatment is performed before the reduced pressure distillation, and the other process parameters are the same.

[0093] Comparative Example 15

[0094] The difference from Example 21 is that the order of the nanofiltration unit and the electrodialysis unit is exchanged, and the other process parameters are the same.

[0095] Comparative Example 16

[0096] The difference from Example 21 is that the secondary distillation tower is removed, and the other process parameters are the same.

[0097] Comparative Example 17

[0098] The difference from Example 21 is that no extractant is introduced during the extractive distillation process, and other process parameters are the same.

[0099] Embodiment 26

[0100] The physical parameters of the separated products obtained in Examples 1-5 and Comparative Examples 1-4 at 25° C. are compared, and the relevant parameters are summarized in Table 4.

[0101] Table 4 Parameters of the isolated products obtained in Examples 1-5 and Comparative Examples 1-4

[0102]

[0103] As shown in the physical parameters of Table 4, the separated products purified by Examples 1-5 have a higher purity, which means that the separation and purification process proposed by the present invention has a better separation and purification efficiency when changing some operating parameters without changing the overall design of the process. The quality of the obtained product meets the electronic grade requirements and can be reused in the field of the electronics industry. For Comparative Example 1, the purity of the product is reduced, and the water content and chroma are increased, which means that the lack of the centrifugal separation section does not remove solid impurities in advance, which affects the separation and purification effect of NMP in the subsequent section. For Comparative Example 2, the lack of microfiltration treatment also reduces the purity of the product, and the chroma and water content are increased, which means that the comprehensive treatment efficiency of the microfiltration unit and the subsequent unit is closely related, and the two separation processes for solids in the primary filtration unit ensure the high efficiency of the subsequent treatment.

[0104] For Comparative Example 3, the high conductivity NMP recovery liquid contains a large amount of waste acid and metal ions, which is not suitable for adsorption process treatment. The purity of the final product is seriously reduced, the water content, metal ion content and chromaticity are greatly increased, and the separation effect is very poor. Comparative Example 4 also has similar results. On the whole, the diversion unit can effectively classify the NMP recovery liquid according to its conductivity, and match the corresponding treatment section by the different component characteristics corresponding to different conductivities, so as to comprehensively improve the effect of NMP separation and purification.

[0105] Embodiment 27

[0106] The physical parameters of the separated products obtained in Examples 6-10 and Comparative Examples 5-8 at 25°C were compared, and the relevant parameters are summarized in Table 5.

[0107] Table 5 Parameters of the isolated products obtained in Examples 6-10 and Comparative Examples 5-8

[0108]

[0109] As shown in the parameters in Table 5, Examples 6-10 actually differ from Examples 1-5 in only some operating parameters. When the operating process steps remain unchanged, the obtained separated products all have stable product quality and meet the electronic grade requirements. For Comparative Example 5, the lack of neutralization treatment makes it difficult for the process to effectively separate and treat a large amount of inorganic acids and metal ions, resulting in a decrease in the purity of the product, a significant increase in the metal ion content, and a certain degree of increase in water content and chromaticity, and the product cannot meet the electronic grade standard. Comparative Example 6 lacks precipitation treatment, and each separation step in the subsequent process can also effectively remove solid impurities, but the effect of solid impurities on the efficiency of the subsequent process is obvious, resulting in its separation products failing to meet the electronic grade requirements in various indicators. Comparative Example 7 simply exchanges the steps of precipitation treatment and neutralization treatment, and the various indicators of the product have decreased to a certain extent, but not obviously, and the content of metal ions cannot be extremely low, so it does not meet the electronic grade standard. Comparative Example 8 replaces the powder reagent used in the neutralization process with an aqueous solution, resulting in a significant increase in the water content of the product, a decrease in purity, and also unable to meet the requirements of electronic grade reagents. In summary, the combination of the chemical neutralization unit and the precipitation unit can effectively separate and purify the high-conductivity NMP waste liquid, remove impurities such as inorganic acids and metal ions with high content, and the sequential treatment of each section significantly improves the processing efficiency of the entire separation and purification process.

[0110] Embodiment 28

[0111] The physical parameters of the separated products obtained in Examples 11-15 and Comparative Examples 9-12 at 25°C were compared, and the relevant parameters are summarized in Table 6.

[0112] Table 6 Parameters of the isolated products obtained in Examples 11-15 and Comparative Examples 9-12

[0113]

[0114] As shown in the parameter data of Table 6, Examples 11-15 replaced the raw material source of NMP, but after being directed to the adsorption unit through the shunt unit for targeted treatment, the product parameters that meet the requirements of electronic-grade NMP are still reflected, and the partial changes in the process parameters hardly affect the quality of the product. Comparative Example 9 Due to the direct lack of treatment by the adsorption unit, a certain amount of impurities such as metal ions contained in the waste NMP from the lithium battery manufacturing section cannot be effectively removed. Comparative Example 10 and Comparative Example 11 also reflect this point. Both the weakly acidic cation exchange resin and the activated carbon layer play an important role in removing metal ions, and the presence of the activated carbon layer can effectively reduce the product chromaticity. In Comparative Example 12, the sequence of the weakly acidic cation exchange resin and the activated carbon layer is exchanged, and the overall quality of the product appears to be slightly reduced. This is because the activated carbon layer has a certain filtering function, and it can improve the adsorption efficiency of the weakly acidic cation exchange resin to metal ions as a front-end process.

[0115] Embodiment 29

[0116] The physical parameters of the separated products obtained in Examples 16-20 and Comparative Examples 13-14 at 25°C were compared, and the relevant parameters are summarized in Table 7.

[0117] Table 7 Parameters of the isolated products obtained in Examples 16-20 and Comparative Examples 13-14

[0118]

[0119] As shown in the parameter data of Table 7, for Examples 16-20, although the source of NMP is replaced with waste liquid from the electronic component cleaning section, most of the impurities are high-boiling organic matter, but the entire separation and purification process can still effectively purify it and obtain a product with stable quality, and the partial change of the process parameters does not affect the various indicators of the product. For Comparative Example 13, the vacuum distillation is changed to atmospheric distillation, and the removal effect of organic impurities is deteriorated, and some high-boiling organic impurities are difficult to complete preliminary separation with NMP, which improves the separation difficulty of subsequent processes, so the purity of the product is significantly reduced. For Comparative Example 14, no pre-drying is performed, while the water content of the product is increased, and the separation effect of other processes is also affected, and the purity of the final product is also reduced to a certain extent. In summary, the low conductivity NMP recovery liquid with high organic impurities is dried and the combined treatment of vacuum distillation can preliminarily remove a large amount of organic impurities in the recovery liquid, improve the efficiency of subsequent membrane separation and extractive distillation, and remove most of the heavy organic matter before membrane separation treatment, which is conducive to the rapid progress of the membrane separation process.

[0120] Embodiment 30

[0121] The physical parameters of the separated products obtained in Examples 21-25 and Comparative Examples 15-17 at 25°C were compared, and the relevant parameters are summarized in Table 8.

[0122] Table 8 Parameters of the isolated products obtained in Examples 21-25 and Comparative Examples 15-17

[0123]

[0124] As shown in the parameter data of Table 8, the NMP recovery liquid treated by Examples 21-25 still comes from the electronic component cleaning section and has a high organic impurity content. Therefore, similar to Examples 16-20, the quality indicators of the products are not affected by the changes in some process parameters, and all have stable electronic grade quality. While Comparative Example 15 exchanges the order of the nanofiltration unit and the electrodialysis unit, which has little effect on parameters such as the purity and water content of the product, but the electrodialysis unit cannot effectively remove the metal ions thoroughly in the front, resulting in a slightly higher metal ion content of the product. Due to the lack of the secondary distillation tower in Comparative Example 16, the resulting product contains a large amount of incompletely removed extractant, which obviously does not meet the purity requirements of the product. Comparative Example 17 is equivalent to changing the extractive distillation process to a simple atmospheric distillation process, which cannot effectively remove the high boiling point components and water in NMP, resulting in a decrease in product purity and a slight increase in water content. In summary, the combination of the membrane separation unit and the extractive distillation unit can effectively remove low-content organic impurities, water and metal ions in NMP after treatment in other sections. Extractive distillation is more effective in removing organic components and water than simple atmospheric distillation, but it will introduce impurities into the extractant, so secondary distillation is required to remove impurities to ensure that the purity of the product meets electronic grade requirements.

[0125] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A separation and purification process for NMP, characterized in that: The purification process is as follows: The NMP recovery liquid is passed into the primary filtration unit to obtain pretreated NMP after the primary filtration treatment; Passing the pretreated NMP into a split flow unit to measure its conductivity; If the conductivity is higher than the first threshold, the pre-treated NMP is passed into a chemical neutralization unit to obtain pre-precipitated NMP after neutralization treatment; If the conductivity is higher than the second threshold value and lower than the first threshold value, the pre-treated NMP is passed into the adsorption unit to obtain the first pre-separated NMP after adsorption treatment; If the conductivity is lower than the second threshold value, the pre-treated NMP is passed into a vacuum distillation unit to obtain a second pre-separated NMP after vacuum distillation treatment; Passing the pre-precipitated NMP into a precipitation unit to obtain a first pre-distilled NMP after precipitation treatment; Passing the first pre-separated NMP and the second pre-separated NMP into a membrane separation unit to obtain a second pre-distilled NMP after separation; The first pre-separated NMP and the second pre-distilled NMP are introduced into an extractive distillation unit to obtain product-grade NMP after extractive distillation treatment.

2. A separation and purification process for NMP according to claim 1, characterized in that: The primary filtration unit comprises: a centrifugal separation unit and a microfiltration unit; the primary filtration treatment process is: the NMP recovery liquid is passed into the centrifugal separation unit, centrifuged at 2000-3000 rpm for 20 minutes at 25°C, and then centrifuged at 5000 rpm for 5 minutes to obtain a centrifugal clear liquid; the centrifugal clear liquid is passed into the microfiltration unit, and centrifuged at 550-700 L / (m 2 h) to obtain the pretreated NMP; wherein the pore size of the filter membrane of the microfiltration unit is 0.22 microns.

3. A separation and purification process for NMP according to claim 1, characterized in that: The first threshold is 1 S / cm; the second threshold is 0.01 S / cm.

4. A separation and purification process for NMP according to claim 1, characterized in that: The chemical neutralization unit comprises: a pH adjustment unit and an ion precipitation unit; the neutralization treatment process is: the pretreated NMP from the diversion unit is passed into the pH adjustment unit, the pH value of the pretreated NMP is adjusted to 7-8 using sodium bicarbonate powder, and then passed into the ion precipitation unit, calcium sulfide powder is added and stirred at 500-700 rpm for 20 minutes, and then the pre-precipitated NMP is obtained after filtering.

5. A separation and purification process for NMP according to claim 1, characterized in that: The adsorption unit comprises: an activated carbon layer and an ion exchange resin filler layer; the adsorption treatment process is: passing the pretreated NMP into the activated carbon layer, wherein the operating pressure is 1.5MPa and the operating temperature is 25°C, and then passing it into the ion exchange resin filler layer, wherein the ion exchange resin is a weakly acidic cation exchange resin, and the first pre-separated NMP is obtained after treatment.

6. A separation and purification process for NMP according to claim 1, characterized in that: The vacuum distillation unit comprises: a dryer and a vacuum distillation tower; the process of the vacuum distillation treatment is: the pretreated NMP is passed into the dryer, and after drying at 80° C., it is passed into the vacuum distillation tower, and the second pre-separated NMP is obtained after vacuum distillation; wherein the dryer is a pressure spray dryer, and the atomization pressure is 10 MPa; wherein the operating pressure of the vacuum distillation tower is 0.3-0.6 atm, the tower bottom temperature is 180° C., the tower top temperature is 90° C., and the reflux ratio is 2.

0.

7. A separation and purification process for NMP according to claim 1, characterized in that: The precipitation unit comprises: a flocculation-sedimentation unit and a sand filter tank; the precipitation treatment process is: the pre-precipitated NMP is passed into the flocculation-sedimentation unit, a flocculant is added at a concentration of 0.5 g / L, the pH value is controlled to be between 6 and 8 at 25°C, and the treatment is carried out at a stirring speed of 200 rpm for 40-80 minutes, the treated supernatant is passed into the sand filter tank, and filtered at a filtration rate of 10 m / h to obtain the first pre-distilled NMP; wherein the flocculant is a mixture of polyaluminum ferric chloride and polyacrylamide, and the mass ratio of the polyaluminum ferric chloride to the polyacrylamide is 1:

2.

8. A separation and purification process for NMP according to claim 1, characterized in that: The membrane separation unit comprises: a nanofiltration unit and an electrodialysis unit; the separation process is: the first pre-separation NMP and the second pre-separation NMP are cooled to 25°C and then introduced into the nanofiltration unit, and nanofiltration treatment is performed at an operating pressure of 0.5 MPa, and then the electrodialysis unit is continued to be introduced, and electrodialysis treatment is performed at an operating voltage of 220 V, a current of 2 A and an operating pressure of 0.5 MPa to obtain the second pre-distillation NMP.

9. A separation and purification process for NMP according to claim 1, characterized in that: The extractive distillation unit comprises an extractive distillation tower and a secondary distillation tower; the process of the extractive distillation treatment is: the first pre-distillation NMP and the second pre-distillation NMP are introduced into the extractive distillation tower, the extractant is introduced according to the feed mass ratio of 1:1, the extractive distillation is carried out under the operating conditions of the tower bottom temperature of 180°C, the tower top temperature of 100°C, the reflux ratio of 3.0, and the operating pressure of 0.1MPa, the tower top product is introduced into the secondary distillation tower, the secondary distillation is carried out under the operating conditions of the tower bottom temperature of 170°C, the tower top temperature of 80°C, the operating pressure of 80kPa, and the reflux ratio of 2.5, and the tower bottom product is taken as the product-grade NMP; wherein the extractant is dimethyl carbonate.

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