Process for recovering NMF and MDG from stripping waste liquid

Abstract

The invention relates to the technical field of stripping waste liquid recovery, in particular to a process for recovering NMF and MDG from stripping waste liquid. The recovery process comprises the following steps: stripping waste liquid passes through a filter, filtrate enters an extractive distillation tower, a eutectic solvent is used as an extraction agent for separation, light components of MDG and water are obtained at the top of the tower, and heavy components of NMF and the extraction agent are obtained at the bottom of the tower; the light components flow into a flash tank for flash evaporation, crude MDG is extracted from the tank bottom and then enters a demetalization tower for reduced pressure distillation, and electronic-grade MDG is obtained; the heavy components enter a vacuum rectification tower for vacuum rectification, crude NMF is extracted from the tower top, the extraction agent is recovered from the tower kettle, the crude NMF enters a demetallization tower for vacuum distillation, and electronic-grade NMF is obtained; according to the recovery process, NMF and MDG are effectively separated, the content of metal ions is reduced, and the purity requirement of high-purity electronic-grade chemicals is met.

Description

Technical Field

[0001] The present invention relates to the technical field of stripping waste liquid recovery, and specifically relates to a process for recovering NMF and MDG from stripping waste liquid. Background Art

[0002] In the manufacture of flat panel display devices such as liquid crystal displays and organic light-emitting diode displays, photoresist stripping liquid is used to remove photoresist to ensure the accuracy of the pixel structure and electrode pattern of the display device. While a large amount of photoresist stripping liquid is used, a large amount of stripping waste liquid is also generated. The stripping waste liquid contains a large number of components with reusable value, so it is necessary to recycle and treat the waste liquid. For a photoresist stripping liquid mainly composed of N-methylformamide (NMF) and methyl diglycol (MDG), after use, the photoresist stripping liquid becomes stripping waste liquid due to the introduction of other impurities. After separation and purification of the stripping waste liquid, a mixture mainly composed of NMF and MDG is obtained, and the mixture needs to be further separated and purified to obtain high-purity NMF and MDG.

[0003] Currently, CN112851541A discloses a method and device for recovering NMF and MDG from photoresist stripping liquid waste liquid, which includes the following steps: (1) The photoresist stripping liquid waste liquid is filtered and then dehydrated; (2) The dehydrated photoresist stripping liquid waste liquid is subjected to vacuum distillation to obtain NMF, MDG and high-boiling substances; (3) NMF and MDG are electrolyzed to obtain recovery liquids of NMF and MDG; (4) The high-boiling substances are incinerated; The recovered mixture obtained by this recovery method is a mixture of NMF and MDG, and NMF and MDG are not well separated. Another example is that CN109096142A discloses an industrial separation method for N-methylformamide and methyl diglycol, including the following steps: 1) Pressure reduction and degassing: Perform vacuum degassing treatment on NMF and MDG to prevent foaming and splashing caused by a sudden drop in pressure after the material enters the molecular distillation column; 2) Molecular distillation: The degassed material enters the molecular distillation column, and the separation and purification of NMF and MDG are realized by using the different molecular mean free paths of the two components. Although the purity of the finished NMF and MDG reaches more than 99%, the removal rate of metal ions is relatively low, which cannot meet the purity requirements of high-purity electronic grade chemicals, and the energy consumption is relatively high.

[0004] Based on the above statements, the present invention proposes a process for recovering NMF and MDG from stripping waste liquid. Summary of the Invention

[0005] In view of the fact that in the existing recovery process of photoresist stripping waste liquid, it is difficult to effectively separate NMF and MDG, and the removal rate of metal ions is difficult to reach the electronic grade, the present invention provides a process for recovering NMF and MDG from stripping waste liquid.

[0006] The technical solution of the present invention is as follows: A process for recovering NMF and MDG from stripping waste liquid, comprising the following steps: S1. The stripping waste liquid enters a filter to remove solid impurities, and the filtrate enters an extractive distillation column. Using a deep eutectic solvent as an extractant, extractive distillation separation is carried out. Light components of diethylene glycol methyl ether and water are taken out from the top of the column, and heavy components of N-methylformamide and the extractant are taken out from the bottom of the column; S2. The light components of diethylene glycol methyl ether and water flow into a flash tank for flashing, and crude diethylene glycol methyl ether is taken out from the bottom of the flash tank; the crude diethylene glycol methyl ether enters a demetallization column and is subjected to vacuum distillation to obtain electronic-grade diethylene glycol methyl ether; S3. The heavy components of N-methylformamide and the extractant enter a vacuum distillation column for vacuum distillation. Electronic-grade N-methylformamide is taken out from the top of the column, and the extractant is recovered from the bottom of the column.

[0007] Preferably, the process conditions of the extractive distillation column in step (1) are: the pressure is 70 kPa, the reflux ratio is 0.5 - 3.0, the number of trays is 30 - 50, the mixture feed tray is 8 - 25, the extractant feed position is 2 - 6, the top temperature of the column is 145 °C, the bottom temperature of the column is 180 - 200 °C, and the extractive distillation time is 50 - 60 min.

[0008] Preferably, the mass ratio of the extractant to the stripping waste liquid in step (1) is (1.5 - 2):1.

[0009] Preferably, the deep eutectic solvent in step (1) is N-butylpyridinium bromide and diethylene glycol with a molar ratio of 1:(2 - 4).

[0010] Preferably, the flashing pressure of the flash tank in step (2) is 8 kPa, and the flashing temperature is 100 °C.

[0011] Preferably, 1,3-cyclohexanediamine and phosphorus pentoxide are added in advance in the demetallization column in step (2).

[0012] Preferably, the mass ratio of the crude diethylene glycol methyl ether, 1,3-cyclohexanediamine, and phosphorus pentoxide is 100:(1 - 3):(5 - 10).

[0013] Preferably, the process conditions of the vacuum distillation in step (2) are: the pressure is 5 kPa, the top temperature of the column is 80 - 100 °C, and the bottom temperature of the column is 100 - 120 °C.

[0014] Preferably, the process conditions of the vacuum distillation in step (3) are: the bottom temperature of the column is 140 - 150 °C, the top temperature of the column is 85 - 95 °C, the pressure is 1 - 1.5 kPa, the cooling water temperature is 11 - 13 °C, and the distillation time is 10 - 15 h.

[0015] Preferably, the stripping waste liquid comprises 45-60 wt% of N-methylformamide, 35-50 wt% of diethylene glycol methyl ether, 100-3000 ppm of resist, and the balance is water. Beneficial effects

[0016] (1) In the extractive distillation process of the present invention, a deep eutectic solvent is added, and N-butylpyridinium bromide and diethylene glycol are used as the deep eutectic solvent. N-butylpyridinium bromide is a hydrogen bond acceptor, and diethylene glycol is a hydrogen bond donor; the carbonyl group and secondary amino group in the NMP molecule are strong hydrogen bond acceptors and donors, and can form stronger hydrogen bonds with the hydroxyl group, bromide ion and pyridine nitrogen atom of the deep eutectic solvent. Moreover, the NMF molecule is smaller and more rigid, and is more likely to enter the interstitial space of the hydrogen bond network of the deep eutectic solvent. Therefore, NMF is more easily selectively extracted than MDG, and thus NMF and MDG can be effectively separated; in the subsequent process, the heavy components of N-methylformamide and the extractant are subjected to vacuum distillation, and the deep eutectic solvent can also be used as a demetalizing agent, significantly reducing the metal ion content of N-methylformamide.

[0017] (2) In the demetalization process of the crude MDG of the present invention, 1,3-cyclohexanediamine and phosphorus pentoxide are added. On the one hand, phosphorus pentoxide reacts with water to generate phosphoric acid to remove trace water in the MDG. The phosphate group provided by phosphoric acid and 1,3-cyclohexanediamine act synergistically to form an amine-phosphate complex, enhancing the trapping efficiency of metal ions and greatly reducing the metal ion content, which can meet the purity requirements of high-purity electronic grade chemicals; on the other hand, in the vacuum distillation process, phosphorus pentoxide may cause the phenomenon of excessive dehydration and damage to the MDG structure. 1,3-cyclohexanediamine can act as a protective agent to obtain a more pure electronic grade MDG.

[0018] (3) The recovery process of the present invention has simple process steps and is easy to operate. The extractant used has the characteristics of pollution-free, easy recovery and recyclable use, realizes the separation of NMF and MDG with close boiling points, effectively reduces the production cost; and through the demetalization step, the obtained NMF and MDG have a purity of 99.99%, and the content of metal ions reaches the electronic level, having broad application prospects. Description of the drawings

[0019] Figure 1 It is a schematic flow chart of an industrial device for the process of recovering NMF and MDG from stripping waste liquid proposed by the present invention. Specific embodiments

[0020] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further elaborated through embodiments, but the present invention is not limited thereto.

[0021] Example 1 provides a process for recovering NMF and MDG from stripping waste liquid.

[0022] The stripping waste liquid is from the liquid crystal display manufacturing industry and includes 55 wt% N-methylformamide, 40 wt% diethylene glycol methyl ether, 1000 ppm of resist, and the balance is water. A process for recovering NMF and MDG from stripping waste liquid includes the following steps: S1. The stripping waste liquid enters a filter to remove solid impurities, and the filtrate enters an extractive distillation column. Extractive distillation separation is carried out using a deep eutectic solvent as the extractant. The process conditions of the extractive distillation column are: the pressure is 70 kPa, the reflux ratio is 2.0, the number of trays is 40, the mixture feed tray is the 15th, the extractant feed position is the 3rd, and the top temperature of the extractive distillation column is 145 °C, the bottom temperature is 200 °C, the extractive distillation time is 60 min. The light components of diethylene glycol methyl ether and water are taken out from the top of the column, and the heavy components of N-methylformamide and the extractant are taken out from the bottom of the column. Among them, the mass ratio of the extractant to the stripping waste liquid is 2:1; the deep eutectic solvent is N-butylpyridinium bromide and diethylene glycol with a molar ratio of 1:3. S2. The light components of diethylene glycol methyl ether and water flow into a flash tank for flashing. The flashing pressure is 8 kPa, the flashing temperature is 100 °C, and the crude diethylene glycol methyl ether is taken out from the bottom of the flash tank. The crude diethylene glycol methyl ether enters a demetallization column. 1,3-cyclohexanediamine and phosphorus pentoxide are added in advance in the column, and vacuum distillation is carried out at a pressure of 5 kPa, the top temperature is 80 °C, the bottom temperature is 100 °C, and the middle distillate is collected to obtain electronic-grade diethylene glycol methyl ether. Among them, the mass ratio of the crude diethylene glycol methyl ether, 1,3-cyclohexanediamine, and phosphorus pentoxide is 50:1:5. S3. The heavy components of N-methylformamide and the extractant enter a vacuum distillation column for vacuum distillation. The process conditions of the vacuum distillation are: the bottom temperature is 140 °C, the top temperature is 85 °C, the pressure is 1 kPa, the cooling water temperature is 13 °C, the distillation time is 15 h, and the electronic-grade N-methylformamide is taken out from the top of the column, and the extractant is recovered from the bottom of the column.

[0023] The calculation methods for the recovery rates of electronic-grade MDG and electronic-grade NMF are as follows: Recovery rate (MDG) = (mass of electronic-grade MDG / mass of MDG in the stripping waste liquid) × 100%; Recovery rate (NMF) = (mass of electronic-grade NMF / mass of NMF in the stripping waste liquid) × 100%; The moisture content of crude MDG, electronic-grade MDG, and electronic-grade NMF is detected by a Karl Fischer moisture meter, and the residual metal ions in crude MDG, electronic-grade MDG, electronic-grade NMF, and the three are detected by a high-resolution inductively coupled plasma mass spectrometer (HR-TCP-MS); The specific results are shown in Table 1-1 and Table 1-2.

[0024] Table 1-1

[0025] Table 1-2

[0026] Example 2 provides a process for recovering NMF and MDG from stripping waste liquid.

[0027] The stripping waste liquid comes from the liquid crystal display manufacturing industry and includes 55 wt% N-methylformamide, 40 wt% diethylene glycol methyl ether, 1000 ppm of resist, and the balance is water; A process for recovering NMF and MDG from stripping waste liquid includes the following steps: S1. The stripping waste liquid enters a filter to remove solid impurities, and the filtrate enters an extractive distillation column. Extractive distillation separation is carried out using a deep eutectic solvent as the extractant. The process conditions of the extractive distillation column are: the pressure is 70 kPa, the reflux ratio is 3.0, the number of trays is 30, the mixture feed tray is the 8th, the extractant feed position is the 2nd, and the top temperature of the extractive distillation column is 145 °C, the bottom temperature is 180 °C, and the extractive distillation time is 50 min. The light components of diethylene glycol methyl ether and water are taken out from the top of the column, and the heavy components of N-methylformamide and the extractant are taken out from the bottom of the column; Among them, the mass ratio of the extractant to the stripping waste liquid is 1.5:1; the deep eutectic solvent is N-butylpyridinium bromide and diethylene glycol with a molar ratio of 1:2; S2. The light components of diethylene glycol methyl ether and water flow into a flash tank for flash evaporation. The flash evaporation pressure is 8 kPa, and the flash evaporation temperature is 100 °C. Crude diethylene glycol methyl ether is taken out from the bottom of the flash tank; The crude diethylene glycol methyl ether enters a demetalization column, and 1,3-cyclohexanediamine and phosphorus pentoxide are added in advance in the column. Vacuum distillation is carried out at a pressure of 5 kPa, the top temperature is 90 °C, and the bottom temperature is 110 °C. The middle distillate is collected to obtain electronic-grade diethylene glycol methyl ether; Among them, the mass ratio of crude diethylene glycol methyl ether, 1,3-cyclohexanediamine, and phosphorus pentoxide is 100:1:8; The heavy components of S3, N-methylformamide and the extractant enter the vacuum distillation column for vacuum distillation. The process conditions for vacuum distillation are as follows: the temperature at the bottom of the column is 145 °C, the temperature at the top of the column is 90 °C, the pressure is 1.25 kPa, the temperature of the cooling water is 11 °C, the distillation time is 10 h, and electronic-grade N-methylformamide is taken out from the top of the column, and the extractant is recovered from the bottom of the column.

[0028] The calculation methods for the recovery rates of electronic-grade MDG and electronic-grade NMF are as follows: Recovery rate (MDG) = (mass of electronic-grade MDG / mass of MDG in the stripping waste liquid) × 100%; Recovery rate (NMF) = (mass of electronic-grade NMF / mass of NMF in the stripping waste liquid) × 100%; The moisture content of crude MDG, electronic-grade MDG, and electronic-grade NMF is detected by a Karl Fischer moisture meter, and the residual metal ions in crude MDG, electronic-grade MDG, electronic-grade NMF, and the three are detected by a high-resolution inductively coupled plasma mass spectrometer (HR-TCP-MS); The specific results are shown in Table 2-1 and Table 2-2.

[0029] Table 2-1

[0030] Table 2-2

[0031] Example 3 provides a process for recovering NMF and MDG from the stripping waste liquid.

[0032] The stripping waste liquid comes from the liquid crystal display manufacturing industry and includes 55 wt% of N-methylformamide, 40 wt% of diethylene glycol methyl ether, 1000 ppm of resist, and the balance is water; A process for recovering NMF and MDG from the stripping waste liquid includes the following steps: S1. The stripping waste liquid enters a filter to remove solid impurities, and the filtrate enters an extractive distillation column for extractive distillation separation with a deep eutectic solvent as the extractant. The process conditions for the extractive distillation column are as follows: the pressure is 70 kPa, the reflux ratio is 3.0, the number of trays is 50, the mixture feed tray is the 25th, the extractant feed position is the 6th, and the temperature at the top of the extractive distillation column is 145 °C, the temperature at the bottom of the column is 200 °C, the extractive distillation time is 60 min, and the light components of diethylene glycol methyl ether and water are taken out from the top of the column, and the heavy components of N-methylformamide and the extractant are taken out from the bottom of the column; Among them, the mass ratio of the extractant to the stripping waste liquid is 1.8:1; the deep eutectic solvent is N-butylpyridinium bromide and diethylene glycol with a molar ratio of 1:4; The light components of diethylene glycol methyl ether and water flow into a flash tank for flashing. The flashing pressure is 8 kPa and the flashing temperature is 100 °C. The crude diethylene glycol methyl ether is drawn from the bottom of the flash tank. The crude diethylene glycol methyl ether enters a demetallization tower, where 1,3-cyclohexanediamine and phosphorus pentoxide are added in advance. It is subjected to vacuum distillation at a pressure of 5 kPa, with a top temperature of 100 °C and a bottom temperature of 120 °C. The middle distillate is collected to obtain electronic-grade diethylene glycol methyl ether; Among them, the mass ratio of the crude diethylene glycol methyl ether, 1,3-cyclohexanediamine, and phosphorus pentoxide is 100:3:10; S3. The heavy components of N-methylformamide and the extractant enter a vacuum distillation column for vacuum distillation. The process conditions for vacuum distillation are: the bottom temperature of the column is 150 °C, the top temperature is 95 °C, the pressure is 1.5 kPa, the cooling water temperature is 13 °C, and the distillation time is 13 h. Electronic-grade N-methylformamide is drawn from the top of the column, and the extractant is recovered from the bottom of the column.

[0033] The calculation methods for the recovery rates of electronic-grade MDG and electronic-grade NMF are as follows: Recovery rate (MDG) = (mass of electronic-grade MDG / mass of MDG in the stripping waste liquid) × 100%; Recovery rate (NMF) = (mass of electronic-grade NMF / mass of NMF in the stripping waste liquid) × 100%. The moisture content of the crude MDG, electronic-grade MDG, and electronic-grade NMF is detected by a Karl Fischer moisture meter, and the residual metal ions in the crude MDG, electronic-grade MDG, electronic-grade NMF, and all three are detected using a high-resolution inductively coupled plasma mass spectrometer (HR-TCP-MS). The specific results are shown in Tables 3-1 and 3-2.

[0034] Table 3-1

[0035] Table 3-2

[0036] Comparative Example 1 provides a process for recovering NMF and MDG from stripping waste liquid.

[0037] The stripping waste liquid is from the liquid crystal display manufacturing industry and includes 55 wt% N-methylformamide, 40 wt% diethylene glycol methyl ether, 1000 ppm of resist, and the balance is water; A process for recovering NMF and MDG from stripping waste liquid includes the following steps: S1. The stripping waste liquid enters the filter to remove solid impurities. The filtrate enters the extractive distillation column, and extractive distillation separation is carried out using diethylene glycol as the extractant. The process conditions of the extractive distillation column are as follows: the pressure is 70 kPa, the reflux ratio is 2.0, the number of trays is 40, the mixture feed tray is the 15th, the extractant feed position is the 3rd, and the top temperature of the extractive distillation column is 145 °C, the bottom temperature is 200 °C. The extractive distillation time is 60 min. The light components of diethylene glycol methyl ether and water are taken out from the top of the column, and the heavy components of N-methylformamide and the extractant are taken out from the bottom of the column. Among them, the mass ratio of the extractant to the stripping waste liquid is 2:1. S2. The light components of diethylene glycol methyl ether and water flow into the flash tank for flashing. The flashing pressure is 8 kPa, and the flashing temperature is 100 °C. The crude diethylene glycol methyl ether is taken out from the bottom of the flash tank. The crude diethylene glycol methyl ether enters the de-metallization column. 1,3-cyclohexanediamine and phosphorus pentoxide are added in advance in the column, and vacuum distillation is carried out at a pressure of 5 kPa, the top temperature is 80 °C, and the bottom temperature is 100 °C. The middle distillate is collected to obtain electronic-grade diethylene glycol methyl ether. Among them, the mass ratio of the crude diethylene glycol methyl ether, 1,3-cyclohexanediamine, and phosphorus pentoxide is 50:1:5. S3. The heavy components of N-methylformamide and the extractant enter the vacuum distillation column for vacuum distillation. The process conditions of the vacuum distillation are as follows: the bottom temperature is 140 °C, the top temperature is 85 °C, the pressure is 1 kPa, the cooling water temperature is 13 °C, and the distillation time is 15 h. Electronic-grade N-methylformamide is taken out from the top of the column, and the extractant is recovered from the bottom of the column.

[0038] The calculation methods for the recovery rates of electronic-grade MDG and electronic-grade NMF are as follows: Recovery rate (MDG) = (mass of electronic-grade MDG / mass of MDG in the stripping waste liquid) × 100%; Recovery rate (NMF) = (mass of electronic-grade NMF / mass of NMF in the stripping waste liquid) × 100%. The moisture content of the crude MDG, electronic-grade MDG, and electronic-grade NMF is detected by a Karl Fischer moisture meter, and the residual metal ions in the crude MDG, electronic-grade MDG, electronic-grade NMF, and the three are detected by a high-resolution inductively coupled plasma mass spectrometer (HR-TCP-MS). The specific results are shown in Table 4-1 and Table 4-2.

[0039] Table 4-1

[0040] Table 4-2

[0041] The difference between Comparative Example 1 and Example 1 lies in that in step (1), diethylene glycol is used as the extractant. Combining Table 4-1 and Table 4-2, it can be seen that the deep eutectic solvent obtained by mixing N-butylpyridinium bromide and diethylene glycol used in the present invention is more conducive to the separation of NMF and MDG, greatly improving the recovery rates of the two, and the extractant can also adsorb certain metal ions, significantly reducing the metal ion content in NMF.

[0042] Comparative Example 2 provides a process for recovering NMF and MDG from stripping waste liquid.

[0043] The stripping waste liquid is derived from the liquid crystal display manufacturing industry and includes 55 wt% N-methylformamide, 40 wt% diethylene glycol methyl ether, 1000 ppm of resist, and the balance is water; A process for recovering NMF and MDG from stripping waste liquid includes the following steps: S1. The stripping waste liquid enters a filter to remove solid impurities, and the filtrate enters an extractive distillation column for extractive distillation separation using a deep eutectic solvent as the extractant. The process conditions of the extractive distillation column are: the pressure is 70 kPa, the reflux ratio is 2.0, the number of trays is 40, the mixture feed tray is the 15th, the extractant feed position is the 3rd, and the top temperature of the extractive distillation column is 145 °C, the bottom temperature is 200 °C, the extractive distillation time is 60 min. The light components of diethylene glycol methyl ether and water are taken out from the top of the column, and the heavy components of N-methylformamide and the extractant are taken out from the bottom of the column; Among them, the mass ratio of the extractant to the stripping waste liquid is 2:1; the deep eutectic solvent is N-butylpyridinium bromide and diethylene glycol with a molar ratio of 1:3; S2. The light components of diethylene glycol methyl ether and water flow into a flash tank for flashing. The flashing pressure is 8 kPa, the flashing temperature is 100 °C, and the crude diethylene glycol methyl ether is taken out from the bottom of the flash tank; the crude diethylene glycol methyl ether enters a demetallization column. Bentonite is added in advance in the column, and vacuum distillation is carried out. The pressure is 5 kPa, the top temperature is 80 °C, the bottom temperature is 100 °C, and the middle distillate is collected to obtain electronic-grade diethylene glycol methyl ether; Among them, the mass ratio of the crude diethylene glycol methyl ether to bentonite is 10:1; S3. The heavy components of N-methylformamide and the extractant enter a vacuum distillation column for vacuum distillation. The process conditions of the vacuum distillation are: the bottom temperature is 140 °C, the top temperature is 85 °C, the pressure is 1 kPa, the cooling water temperature is 13 °C, the distillation time is 15 h, and electronic-grade N-methylformamide is taken out from the top of the column, and the extractant is recovered from the bottom of the column.

[0044] The calculation methods for the recovery rates of electronic-grade MDG and electronic-grade NMF are as follows: Recovery rate (MDG) = (mass of electronic-grade MDG / mass of MDG in the stripping waste liquid) × 100%; Recovery rate (NMF) = (mass of electronic-grade NMF / mass of NMF in the stripping waste liquid) × 100%; The moisture content of crude MDG, electronic-grade MDG, and electronic-grade NMF was detected using a Karl Fischer moisture analyzer, and the residual metal ions in crude MDG, electronic-grade MDG, electronic-grade NMF, and all three were detected using a high-resolution inductively coupled plasma mass spectrometer (HR-TCP-MS); The specific results are shown in Tables 5-1 and 5-2.

[0045] Table 5-1

[0046] Table 5-2

[0047] The difference between Comparative Example 2 and Example 1 is that bentonite was added in advance inside the demetalization tower in step (2). Combining Tables 5-1 and 5-2, it can be seen that adding 1,3-cyclohexanediamine and phosphorus pentoxide in advance inside the demetalization tower of the present invention greatly improves the removal rates of moisture and metal ions, obtaining high-purity electronic-grade MDG.

[0048] It should be noted that the above disclosed embodiments only illustrate the technical solutions of the present invention and are not used to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, any person skilled in the art should understand that modifications, various changes, and equivalent substitutions made without departing from the technical solutions of the present invention should all fall within the protection scope of the present invention.

Claims

1. A process for recovering NMF and MDG from stripping waste liquid, characterized in that, It includes the following steps: S1. The stripping waste liquid enters a filter to remove solid impurities. The filtrate enters an extractive distillation column, and extractive distillation separation is carried out using a deep eutectic solvent as the extractant. The light components of diethylene glycol methyl ether and water are taken out from the top of the column, and the heavy components of N-methylformamide and the extractant are taken out from the bottom of the column; S2. The light components of diethylene glycol methyl ether and water flow into a flash tank for flashing, and the crude diethylene glycol methyl ether is taken out from the bottom of the flash tank; The crude diethylene glycol methyl ether enters a demetallization column and is subjected to vacuum distillation to obtain electronic-grade diethylene glycol methyl ether; S3. The heavy components of N-methylformamide and the extractant enter a vacuum distillation column for vacuum distillation. Electronic-grade N-methylformamide is taken out from the top of the column, and the extractant is recovered from the bottom of the column.

2. The process for recovering NMF and MDG from stripping waste liquid according to claim 1, characterized in that, The process conditions of the extractive distillation column in step (1) are: the pressure is 70 kPa, the reflux ratio is 0.5 - 3.0, the number of trays is 30 - 50, the mixture feed tray is 8 - 25, the extractant feed position is 2 - 6, the top temperature of the column is 145 °C, the bottom temperature of the column is 180 - 200 °C, and the extractive distillation time is 50 - 60 min.

3. The process for recovering NMF and MDG from stripping waste liquid according to claim 1, characterized in that, The mass ratio of the extractant to the stripping waste liquid in step (1) is (1.5 - 2):

1.

4. The process for recovering NMF and MDG from stripping waste liquid according to claim 1, characterized in that, The deep eutectic solvent in step (1) is N-butylpyridinium bromide and diethylene glycol with a molar ratio of 1:(2 - 4).

5. The process for recovering NMF and MDG from stripping waste liquid according to claim 1, characterized in that, The flashing pressure of the flash tank in step (2) is 8 kPa, and the flashing temperature is 100 °C.

6. The process for recovering NMF and MDG from stripping waste liquid according to claim 1, characterized in that, 1,3-cyclohexanediamine and phosphorus pentoxide are added in advance in the demetallization column in step (2).

7. The process for recovering NMF and MDG from stripping waste liquid according to claim 6, characterized in that, The mass ratio of the crude diethylene glycol methyl ether, 1,3-cyclohexanediamine, and phosphorus pentoxide is 100:(1 - 3):(5 - 10).

8. The process for recovering NMF and MDG from stripping waste liquid according to claim 1, characterized in that, The process conditions of the vacuum distillation in step (2) are: the pressure is 5 kPa, the top temperature of the column is 80 - 100 °C, and the bottom temperature of the column is 100 - 120 °C.

9. The process for recovering NMF and MDG from stripping waste liquid according to claim 1, characterized in that, The process conditions of the vacuum distillation in step (3) are: the bottom temperature of the column is 140 - 150 °C, the top temperature of the column is 85 - 95 °C, the pressure is 1 - 1.5 kPa, the cooling water temperature is 11 - 13 °C, and the distillation time is 10 - 15 h.

10. The process for recovering NMF and MDG from stripping waste liquid according to claim 1, characterized in that, The stripping waste liquid includes 45 - 60 wt% of N-methylformamide, 35 - 50 wt% of diethylene glycol methyl ether, 100 - 3000 ppm of resist, and the balance is water.

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