Rectification and purification process of NMP (N-Methylpyrrolidone)

Abstract

The invention belongs to the technical field of organic matter purification, and relates to a rectification purification process of NMP (N-Methyl Pyrrolidone). The invention aims to solve the problem that water and organic impurities are difficult to efficiently remove at the same time in the conventional NMP purification process. The method comprises the following steps: carrying out normal-pressure primary distillation treatment on a raw material NMP to obtain tower top NMP; treating the tower top NMP through an adsorption rectification unit to obtain refined NMP; the refined NMP is subjected to azeotropic distillation treatment to obtain dehydrated NMP, the water content of the dehydrated NMP is detected by a water content detection unit, azeotropic distillation is performed again if the water content is higher than a threshold value, the dehydrated NMP is introduced into a reduced pressure distillation unit if the water content is lower than the threshold value, an electronic-grade NMP product is finally obtained through a membrane separation unit, and waste heat is recovered and used for preheating the raw material NMP. According to the rectification purification process provided by the invention, an industrial-grade raw material NMP can be purified to obtain an electronic-grade NMP product, and waste heat in the distillation process can be recycled.

Description

Technical Field

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

[0002] NMP, or N-methylpyrrolidone, is a common organic solvent and a polar aprotic solvent. Thanks to its special chemical structure, NMP has good solubility for a variety of organic and inorganic substances and has been widely used in various industrial fields.

[0003] In the field of electronics industry, NMP has important application value in electrode manufacturing, circuit board printing and photoresist stripping. However, NMP will be mixed with various impurities during production and transportation, including water, other organic solvents and metal ions. These impurities will cause the performance of devices and materials to deteriorate or even fail during the production of electronic devices. Therefore, the industry has put forward a series of requirements for electronic-grade NMP, including high purity, low water content and low metal content, to meet the relevant requirements of the electronics industry. NMP products required by the electronics industry are generally purified from industrial NMP. This is because the residual by-products, metal ions and other impurities in the traditional preparation process will significantly affect the quality of battery electrodes or the photolithography process, and are difficult to directly apply in the electronics industry.

[0004] With the development of the electronics industry and increasingly stringent environmental protection requirements, the current NMP purification process needs to be more integrated, efficient, and environmentally friendly to adapt to the development of industry and society.

[0005] At present, the existing NMP purification process is difficult to remove water and organic impurities simultaneously and efficiently, which is still a major problem facing the industry.

[0006] Therefore, a distillation purification process of NMP is proposed. Summary of the invention

[0007] The object of the present invention is to provide a distillation and purification process for NMP. The present invention performs atmospheric pressure initial distillation on raw material NMP to obtain tower top NMP; the tower top NMP is treated by an adsorption distillation unit to obtain refined NMP; the refined NMP is subjected to azeotropic distillation to obtain dehydrated NMP, and the water content of the dehydrated NMP is detected by a water content detection unit. If the water content is higher than a threshold, azeotropic distillation is performed again. If the water content is lower than the threshold, the dehydrated NMP is passed into a vacuum distillation unit, and an electronic grade NMP product is finally obtained through a membrane separation unit, and the waste heat is recovered for preheating the raw material NMP. The distillation and purification process proposed by the present invention can effectively purify industrial-grade raw material NMP to obtain an electronic grade NMP product with extremely low water content and extremely low organic impurity content, and can recycle the waste heat in the distillation process.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A distillation and purification process for NMP comprises the following steps:

[0010] The raw material NMP is preheated and passed into the atmospheric pressure primary distillation unit, and the top NMP is obtained after the primary distillation treatment;

[0011] The NMP at the top of the tower is passed into an adsorption distillation unit to obtain refined NMP after adsorption distillation treatment;

[0012] The refined NMP is passed into an azeotropic distillation unit, and an azeotropic agent is introduced for azeotropic distillation treatment to obtain dehydrated NMP;

[0013] Passing the dehydrated NMP into a water content detection unit to detect whether the water content of the dehydrated NMP is higher than a threshold value;

[0014] If the water content of the dehydrated NMP is higher than the threshold value, the dehydrated NMP is passed into the azeotropic distillation unit again for azeotropic distillation treatment;

[0015] If the water content of the dehydrated NMP is lower than the threshold value, the dehydrated NMP is passed into a vacuum distillation unit to obtain high-temperature NMP after vacuum distillation treatment;

[0016] The high-temperature NMP is passed into a membrane separation unit, and after separation treatment, an electronic-grade NMP product and waste heat are obtained;

[0017] The waste heat is recovered through the heat exchange network and used for preheating the raw material NMP.

[0018] Preferably, the purity of the raw material NMP is 80-99%; the atmospheric pressure primary distillation unit includes: a degassing unit and a equilibrium distillation tower; the process of the primary distillation treatment is: the raw material NMP is passed into the degassing unit, and after degassing for 20-30 minutes, it is passed into the equilibrium distillation tower, and the top product is obtained after equilibrium distillation at 1atm, which is the top NMP.

[0019] Preferably, the operating temperature of the degassing unit is 150-180°C, and the operating pressure is 0.8 MPa; the bottom temperature of the equilibrium distillation tower is 200-220°C, the top temperature is 90-100°C, and the reflux ratio is 2-2.5.

[0020] Preferably, the adsorption distillation unit comprises: a pressurizing unit and an adsorption distillation tower; the process of adsorption distillation treatment is: the top NMP is pressurized to 1.8-2.0atm by the pressurizing unit and then passed into the adsorption distillation tower, and the bottom product after adsorption distillation treatment is refined NMP; wherein the packing layer of the adsorption distillation tower is filled with an adsorbent, and the adsorbent is an ion exchange resin; the reflux ratio of the adsorption distillation tower is 2.0-2.5, the bottom temperature is 210°C, and the top temperature is 95°C.

[0021] Preferably, the azeotropic distillation unit comprises: an entrainer premixing unit and an azeotropic distillation tower; the entrainer is a mixture of cyclohexane and toluene, wherein the mass ratio of cyclohexane to toluene is 2:1; the process of azeotropic distillation treatment is: in the entrainer premixing unit, the entrainer is mixed with refined NMP at a ratio of 2wt%, and the mixture is pressurized to 2atm and passed into the azeotropic distillation tower, wherein the bottom temperature of the azeotropic distillation tower is 210°C, the top temperature is 90°C, the reflux ratio is 3.0, and the bottom product after azeotropic distillation treatment is dehydrated NMP.

[0022] Preferably, the working process of the water content detection unit is: passing the dehydrated NMP into the water content detection unit, determining the water content by online infrared spectrum detection, and when the water content of the dehydrated NMP is higher than 100 ppm, passing the dehydrated NMP into the azeotropic distillation unit again; when the water content of the dehydrated NMP is lower than 100 ppm, passing the dehydrated NMP into the vacuum distillation unit.

[0023] Preferably, the vacuum distillation unit is a vacuum distillation tower; the process of vacuum distillation treatment is: passing the dehydrated NMP into the vacuum distillation tower, wherein the operating pressure of the vacuum distillation tower is 0.3-0.5atm, the bottom temperature is 170-180°C, the top temperature is 80-90°C, the reflux ratio is 1.5, and the top product of the vacuum distillation tower is high-temperature NMP.

[0024] Preferably, the membrane separation unit comprises: a heat exchanger, a nanofiltration unit and a reverse osmosis unit; the separation process is: high-temperature NMP is passed through the heat exchanger, cooled to 25°C and waste heat and room-temperature NMP are obtained, the room-temperature NMP is passed through the nanofiltration unit, the operating pressure is 1.5MPa, the operating temperature is 25°C, wherein the molecular weight cutoff of the nanofiltration membrane in the nanofiltration unit is 120Da, and the treated room-temperature NMP is continuously passed through the reverse osmosis unit, wherein the operating pressure of the reverse osmosis unit is 4.5MPa, the operating temperature is 25°C, and the membrane flux is 25-45L·m -2 ·h -1 , and after treatment, electronic grade NMP products are obtained.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. A degassing unit is introduced in the primary distillation process to effectively remove the volatile components dissolved in the raw material NMP before the first distillation separation. A balanced distillation process is adopted in the atmospheric pressure primary distillation unit to improve the separation efficiency of high-boiling point components, which can stably and efficiently complete the initial purification and separation of NMP and reduce the process difficulty of the subsequent purification process.

[0027] 2. The pressure unit and the adsorption distillation tower are used together to carry out adsorption distillation treatment on the NMP at the top of the tower that has been preliminarily purified. While preliminarily removing the low-boiling point components in the NMP, the adsorption of most of the metal ions is completed. The pressurization operation improves the separation efficiency of the low-boiling point components and ensures that the NMP at the top of the tower can freely pass through the packing layer containing the adsorbent, ensuring the continuity of the operation. The lower metal ion content is conducive to improving the efficiency of the subsequent distillation process.

[0028] 3. The removal efficiency of water in NMP is improved through azeotropic distillation, which avoids the problem of incomplete water removal in traditional distillation. At the same time, a water content detection unit is set up to detect the product of the azeotropic distillation unit, and the NMP product with incomplete water removal is re-treated with azeotropic distillation to ensure the extremely low water content of the product.

[0029] 4. A vacuum distillation unit is set after the azeotropic distillation unit to remove high-boiling point components in NMP more thoroughly at a lower operating temperature, while not causing decomposition and oxidation of NMP due to high temperature. At the same time, the excess entrainer introduced in the azeotropic distillation unit is also removed in the vacuum distillation unit, ensuring an extremely low content of organic impurities in the product.

[0030] 5. By setting up nanofiltration unit and reverse osmosis unit at the end of the process, the metal ions and other inorganic ions in the NMP product are removed more thoroughly, ensuring the extremely low metal ion content in the product. The operating temperature of the membrane separation process is much lower than that of the distillation process. Therefore, a heat exchange unit is set before membrane separation to recover the waste heat in the high-temperature NMP for waste heat raw material NMP, realizing the recycling of energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the distillation purification process of NMP in the present invention.

[0032] Figure 2 It is a process flow chart of the distillation purification process of NMP in the present invention. DETAILED DESCRIPTION

[0033] 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.

[0034] Reference Figure 1 and Figure 2 The schematic diagram and process flow chart shown in the figure, the present invention provides a distillation purification process of NMP, and the technical scheme is as follows:

[0035] Example 1

[0036] Industrial NMP products with a purity of 99% are used as raw material NMP.

[0037] The raw material NMP was preheated to 180°C, passed into a degassing unit, and degassed at 0.8 MPa for 30 min. Then, it was passed into a equilibrium distillation tower, and the bottom temperature was set to 220°C, the top temperature to 100°C, the reflux ratio to 2.5, the operating pressure to 1 atm, and the top product after distillation was taken as the top NMP.

[0038] The NMP at the top of the tower is pressurized to 2.0 atm by a pressurizing unit and then passed into an adsorption distillation tower, the tower bottom temperature is set to 210°C, the tower top temperature is set to 95°C, the reflux ratio is set to 2.5, and the tower bottom product is taken as refined NMP after treatment. Among them, the packing layer of the adsorption distillation tower is equipped with an ion exchange resin adsorbent.

[0039] The refined NMP is passed into the azeotropic agent premixing unit, mixed with 2wt% of the azeotropic agent and pressurized to 2atm, and then passed into the azeotropic distillation tower. The bottom temperature of the azeotropic distillation tower is 210°C, the top temperature is 90°C, the reflux ratio is 3.0, and the bottom product after azeotropic distillation treatment is dehydrated NMP.

[0040] The dehydrated NMP is passed into the water content detection unit, and the dehydrated NMP with a water content greater than 100 ppm is sent back to the azeotropic distillation tower for azeotropic distillation treatment again while maintaining process continuity, and the dehydrated NMP with a water content less than 100 ppm is sent to the vacuum distillation unit.

[0041] The dehydrated NMP was introduced into a vacuum distillation tower, and the operating pressure was set to 0.5 atm, the bottom temperature was 180°C, the top temperature was 90°C, the reflux ratio was 1.5, and the top product after vacuum distillation was high-temperature NMP.

[0042] The high-temperature NMP is passed through a heat exchanger, cooled to 25°C, and the residual heat is recovered through a heat exchange network. The normal-temperature NMP is passed through a nanofiltration unit, treated under an operating pressure of 1.5 MPa and an operating temperature of 25°C, and then passed through a reverse osmosis unit. At an operating pressure of 4.5 MPa and an operating temperature of 25°C, an electronic-grade NMP product is obtained after reverse osmosis treatment; wherein the molecular weight cutoff of the nanofiltration membrane in the nanofiltration unit is 120 Da, and the membrane flux of the reverse osmosis unit is 25-45 L·m -2 ·h -1 .

[0043] The difference between Example 2-10 and Example 1 is that some operating parameters are changed, and the overall process is the same. The changes in parameters are summarized in Table 1 and Table 2.

[0044] In Examples 11-15, based on the parameter changes, the raw material NMP used was changed to low-purity industrial NMP with a purity of 80%. The overall process was the same, and the parameter changes are summarized in Tables 1 and 2.

[0045] In Examples 16-20, based on the parameter changes, the raw material NMP used was changed to industrial NMP with a purity of 95%. The overall process was the same, and the parameter changes are summarized in Tables 1 and 2.

[0046] In Examples 21-25, based on the parameter changes, the raw material NMP used was changed to low-purity industrial NMP with a purity of 85%. The overall process was the same, and the parameter changes are summarized in Tables 1 and 2.

[0047] Table 1 Parameter changes of Examples 1-25 (I)

[0048]

[0049]

[0050] Table 2 Parameter changes in Examples 1-25 (II)

[0051]

[0052]

[0053] Comparative Example 1

[0054] The difference from Example 1 is that no degassing unit is used, and the preheated raw material NMP is directly introduced into the equilibrium distillation tower. The other process steps are the same.

[0055] Comparative Example 2

[0056] The difference from Example 1 is that equilibrium distillation is performed first and then degassing treatment is performed, and the other process steps are the same.

[0057] Comparative Example 3

[0058] The difference from Example 5 is that no pressurizing unit is used, and the atmospheric pressure top NMP is directly sent to the adsorption distillation tower for adsorption distillation treatment, and the other process steps are the same.

[0059] Comparative Example 4

[0060] The difference from Example 5 is that no ion exchange resin adsorbent is installed in the packing layer of the adsorption distillation tower, and the other process steps are the same.

[0061] Comparative Example 5

[0062] The difference from Example 11 is that the water content detection unit is removed, and only one round of azeotropic distillation treatment is performed, and the other process steps are the same.

[0063] Comparative Example 6

[0064] The difference from Example 11 is that only cyclohexane is used as the azeotropic agent, and the other process steps are the same.

[0065] Comparative Example 7

[0066] The difference from Example 11 is that only toluene is used as the azeotropic agent, and the other process steps are the same.

[0067] Comparative Example 8

[0068] The difference from Example 16 is that the vacuum distillation unit is removed, and the other process steps are the same.

[0069] Comparative Example 9

[0070] The difference from Example 16 is that the operating pressure of the vacuum distillation unit is adjusted to 1 atm, the bottom temperature is adjusted to 220° C., the top temperature is adjusted to 100° C., and the other process steps are the same.

[0071] Comparative Example 10

[0072] The difference from Example 20 is that the order of the reverse osmosis unit and the nanofiltration unit is exchanged, and the other process steps are the same.

[0073] Comparative Example 11

[0074] The difference from Example 20 is that the heat exchanger is removed, the high-temperature NMP is not cooled, and it is directly passed into the nanofiltration unit. The other process steps are the same.

[0075] Comparative Example 12

[0076] The difference from Example 20 is that the nanofiltration unit is removed and the other process steps are the same.

[0077] Comparative Example 13

[0078] The difference from Example 20 is that the reverse osmosis unit is removed, and the other process steps are the same.

[0079] Embodiment 26

[0080] The physical parameters of the distillation products obtained in Examples 1-4 and Comparative Examples 1-2 at 25° C. are compared, and the relevant parameters are summarized in Table 3.

[0081] Table 3 Physical parameters of the products obtained from Examples 1-4 and Comparative Examples 1-2

[0082]

[0083]

[0084] As shown in the physical parameter comparison of Table 3, although the operating parameters of Examples 1-4 are different, the various parameters of the electronic grade NMP products obtained are basically unaffected, and all of them can achieve high purity, low water content and low metal ion content. For Comparative Example 1, the lack of a degassing unit makes it impossible to remove the volatile components in the raw material NMP in advance before the equilibrium distillation, thereby reducing the separation efficiency of the subsequent process section, and the purity of the final product is affected to a certain extent. For electronic grade NMP, a purity of 99.45% is unacceptable. For Comparative Example 2, the process of removing volatile components is actually still handed over to the equilibrium distillation after the equilibrium distillation, and the top product of the equilibrium distillation contains most of the volatile components, and cannot be effectively separated. Degassing the top product improves the purity of the product, but still does not meet the requirements of electronic grade NMP. Therefore, the combination of a degassing unit and an equilibrium distillation can efficiently remove most of the volatile components in the raw material NMP, and improve the treatment effect of the subsequent process section to improve the purity of the electronic grade NMP finally obtained.

[0085] Embodiment 27

[0086] The physical parameters of the distillation products obtained in Examples 5-10 and Comparative Examples 3-4 at 25° C. are compared, and the relevant parameters are summarized in Table 4.

[0087] Table 4 Physical parameters of the products obtained from Examples 5-10 and Comparative Examples 3-4

[0088]

[0089] As shown in the physical parameter comparison of Table 4, although the operating parameters of Examples 5-10 are different, the various parameters of the products are basically the same and meet the requirements of high purity, low water content and low metal ion content, which means that the process provided by the present invention has an excellent purification effect on 99% purity raw material NMP. For Comparative Example 3, the lack of the pressurizing unit causes the processing pressure of the adsorption distillation tower to be insufficient, the mobile phase cannot fully contact the packing layer, and the continuity of the adsorption distillation process is reduced. While the metal ions cannot be removed well, the treatment effect of the subsequent section is reduced, resulting in a significant decrease in product purity. For Comparative Example 4, the lack of the ion exchange resin adsorbent makes it impossible for the adsorption distillation unit to remove metal ions. It can be regarded as only one more stage of distillation treatment. The purity of the obtained product basically meets the requirements, but the metal ion concentration is high and cannot meet the requirements of electronic grade NMP. Therefore, the combination of the pressurizing unit and the adsorption distillation can effectively remove metal ions while ensuring that the mobile phase is fully in contact with the packing layer, so that the purity and metal ion content of the final product meet the requirements at the same time.

[0090] Embodiment 28

[0091] The physical parameters of the distillation products obtained in Examples 11-15 and Comparative Examples 5-7 at 25° C. are compared, and the relevant parameters are summarized in Table 5. The addition ratio of the entrainer is controlled by a flow meter, and different feed rates are selected according to the density of different entrainers to ensure that the amount of the entrainer is 2 wt % of the refined NMP.

[0092] Table 5 Physical parameters of the products obtained from Examples 11-15 and Comparative Examples 5-7

[0093]

[0094] As shown in the physical parameter comparison of Table 5, although the operating parameters of Examples 11-15 are different, and the purified raw material NMP is a low concentration of 80%, the obtained NMP product still has high purity, low water content and low metal ion content, which meets the requirements of electronic grade. For Comparative Example 5, only one azeotropic distillation treatment may cause the removal of water to be not thorough enough, resulting in an increase in the water content in the product. For electronic grade NMP, a water content exceeding 100ppm will have a significant negative impact in areas such as chip etching, so only one azeotropic distillation treatment is difficult to ensure the quality requirements of the product. For Comparative Examples 6-7, if the entrainer only selects pure toluene or cyclohexane, the dehydration effect will be relatively poor, and at the same time, too many rounds of azeotropic distillation treatment will be caused, and too many entrainer impurities will be introduced, causing the purity of the final product to decrease. Therefore, the setting of the water content detection unit and the addition of the entrainer jointly ensure that while efficiently removing water, multiple azeotropic distillation treatments are not performed to reduce energy waste and ensure the high purity and low water content of the product.

[0095] Embodiment 29

[0096] The physical parameters of the distillation products obtained in Examples 16-19 and Comparative Examples 8-9 at 25°C were compared, and the relevant parameters are summarized in Table 6.

[0097] Table 6 Physical parameters of the products obtained from Examples 16-19 and Comparative Examples 8-9

[0098]

[0099] As shown in the physical parameter comparison of Table 6, the operating parameters of Examples 16-19 are different, the purified raw material NMP is 95% concentration, and the obtained NMP product has high purity, low water content and low metal ion content, which meets the requirements of electronic grade. For Comparative Example 8, the lack of vacuum distillation operation leads to a significant deterioration in the removal effect of high boiling point components, which is reflected in the product parameters as a significant reduction in purity, which obviously does not meet the requirements of high-purity solvents. For Comparative Example 9, the operating conditions of vacuum distillation are replaced by atmospheric distillation, which cannot effectively remove high boiling point components, and it is difficult to prevent the decomposition of NMP at high temperature. Therefore, the vacuum distillation unit is arranged after the azeotropic distillation unit, which can significantly improve the purity of the product, and can remove the entrainer introduced by the azeotropic distillation unit to a certain extent, forming a better linkage effect. And vacuum distillation reduces the operating pressure while reducing the operating temperature, which can effectively prevent the decomposition of NMP caused by continuous high-temperature distillation, so that the NMP product obtained by the whole process has higher purity.

[0100] Embodiment 30

[0101] The physical parameters of the distillation products obtained in Examples 20-25 and Comparative Examples 10-13 at 25°C were compared, and the relevant parameters are summarized in Table 7.

[0102] Table 7 Physical parameters of the products obtained from Examples 20-25 and Comparative Examples 10-13

[0103]

[0104]

[0105] As shown in the physical parameter comparison of Table 7, although the operating parameters of Examples 20-25 are different, and the purified raw material NMP is a low concentration of 85%, the obtained NMP product still has high purity, low water content and low metal ion content, which meets the requirements of electronic grade. For Comparative Example 10, the reverse osmosis unit is in front and the nanofiltration unit is in the back, which reduces the processing efficiency of the reverse osmosis unit. The nanofiltration unit cannot remove impurities such as particulate matter in NMP before the reverse osmosis unit, which affects the effect of the reverse osmosis unit in removing ions, causing the metal ion content of the product to be substandard. For Comparative Example 11, the high-temperature NMP directly enters the membrane separation unit, resulting in the nanofiltration membrane and the reverse osmosis membrane being unable to work at a better temperature, causing heat waste and affecting the purification efficiency, causing the product purity to decrease, and also causing the metal ion content to increase, and it is impossible to obtain qualified products. For Comparative Examples 12 and 13, the lack of nanofiltration membrane makes the reverse osmosis membrane unable to achieve the best working efficiency due to the influence of particulate matter, and both the product purity and metal ion content are affected; the lack of reverse osmosis membrane has little effect on the product purity, but the metal ion content is significantly increased. Therefore, the coordination and sequence of nanofiltration membrane and reverse osmosis membrane play an important role in ensuring the purity of NMP products and the content of metal ions. The recovery of waste heat can not only reduce process energy consumption, but also ensure the appropriate processing temperature of the membrane separation process and avoid adverse effects of high temperature on the membrane.

[0106] 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 distillation and purification process for NMP, characterized in that: The distillation purification process is as follows: The raw material NMP is preheated and passed into the atmospheric pressure primary distillation unit, and the top NMP is obtained after the primary distillation treatment; Passing the NMP at the top of the tower into an adsorption distillation unit to obtain refined NMP after adsorption distillation treatment; Passing the refined NMP into an azeotropic distillation unit, and passing an azeotropic agent into the unit for azeotropic distillation to obtain dehydrated NMP; Passing the dehydrated NMP into a water content detection unit to detect whether the water content of the dehydrated NMP is higher than a threshold value; If the water content of the dehydrated NMP is higher than a threshold value, the dehydrated NMP is passed into the azeotropic distillation unit again for the azeotropic distillation treatment; If the water content of the dehydrated NMP is lower than a threshold value, the dehydrated NMP is passed into a vacuum distillation unit to obtain high-temperature NMP after vacuum distillation treatment; Passing the high-temperature NMP into a membrane separation unit to obtain an electronic grade NMP product and waste heat after separation treatment; The waste heat is recovered through a heat exchange network and used for preheating the raw material NMP.

2. A rectification and purification process for NMP according to claim 1, characterized in that: The purity of the raw material NMP is 80-99%; The atmospheric pressure primary distillation unit comprises: a degassing unit and a balanced distillation tower; the process of the primary distillation treatment is: the raw material NMP is passed into the degassing unit, and after degassing for 20-30 minutes, it is passed into the balanced distillation tower, and the top product is obtained after balanced distillation at 1atm, which is the top NMP.

3. A rectification and purification process for NMP according to claim 2, characterized in that: The operating temperature of the degassing unit is 150-180°C, and the operating pressure is 0.8MPa; the bottom temperature of the equilibrium distillation tower is 200-220°C, the top temperature is 90-100°C, and the reflux ratio is 2-2.

5.

4. A rectification and purification process for NMP according to claim 1, characterized in that: The adsorption distillation unit comprises: a pressurizing unit and an adsorption distillation tower; the process of the adsorption distillation treatment is: the NMP at the top of the tower is pressurized to 1.8-2.0atm by the pressurizing unit and then passed into the adsorption distillation tower, and the bottom product after the adsorption distillation treatment is the refined NMP; wherein the packing layer of the adsorption distillation tower is filled with an adsorbent, and the adsorbent is an ion exchange resin; the reflux ratio of the adsorption distillation tower is 2.0-2.5, the bottom temperature is 210°C, and the top temperature is 95°C.

5. A rectification and purification process for NMP according to claim 1, characterized in that: The azeotropic distillation unit comprises: an entrainer premixing unit and an azeotropic distillation tower; the entrainer is a mixture of cyclohexane and toluene, wherein the mass ratio of the cyclohexane to the toluene is 2:1; the process of the azeotropic distillation treatment is: in the entrainer premixing unit, the azeotropic agent is mixed with the refined NMP at a ratio of 2wt%, and the mixture is pressurized to 2atm and introduced into the azeotropic distillation tower, wherein the bottom temperature of the azeotropic distillation tower is 210°C, the top temperature is 90°C, the reflux ratio is 3.0, and the bottom product after the azeotropic distillation treatment is the dehydrated NMP.

6. A rectification and purification process for NMP according to claim 1, characterized in that: The working process of the water content detection unit is as follows: the dehydrated NMP is passed into the water content detection unit, and the water content is determined by online infrared spectrum detection, wherein the threshold value is 100 ppm; when the water content of the dehydrated NMP is higher than the threshold value, the dehydrated NMP is passed into the azeotropic distillation unit again; when the water content of the dehydrated NMP is lower than the threshold value, the dehydrated NMP is passed into the vacuum distillation unit.

7. A rectification and purification process for NMP according to claim 1, characterized in that: The vacuum distillation unit is a vacuum distillation tower; the process of the vacuum distillation treatment is: the dehydrated NMP is introduced into the vacuum distillation tower, wherein the operating pressure of the vacuum distillation tower is 0.3-0.5atm, the bottom temperature is 170-180°C, the top temperature is 80-90°C, the reflux ratio is 1.5, and the top product of the vacuum distillation tower is the high-temperature NMP.

8. A rectification and purification process for NMP according to claim 1, characterized in that: The membrane separation unit comprises: a heat exchanger, a nanofiltration unit and a reverse osmosis unit; the separation process is: the high-temperature NMP is passed through the heat exchanger, cooled to 25°C and the residual heat and normal-temperature NMP are obtained, the normal-temperature NMP is passed through the nanofiltration unit, the operating pressure is 1.5MPa, the operating temperature is 25°C, wherein the molecular weight cutoff of the nanofiltration membrane in the nanofiltration unit is 120Da, and the treated normal-temperature NMP is continuously passed through the reverse osmosis unit, wherein the operating pressure of the reverse osmosis unit is 4.5MPa, the operating temperature is 25°C, and the membrane flux is 25-45L·m -2 ·h -1 , and the electronic grade NMP product is obtained after treatment.

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