Waste cleaning agent recovery process and system
By leveraging the synergistic effect of modified distillate and anti-polymerization agent, the problem of separating DMC and water azeotropes in waste cleaning agents was solved, achieving efficient recovery of DMC and PMA. This solved the problems of low separation purity and equipment blockage, resulting in high recovery rate and purity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-06
- Publication Date
- 2026-04-14
AI Technical Summary
Existing technologies struggle to effectively separate and recover waste cleaning agents containing DMC, PMA, and high-boiling impurities. In particular, the separation difficulties caused by the formation of a minimum azeotrope between DMC and water, along with gas-liquid stratification within the tower and uneven mass transfer interfaces, result in low product purity and equipment blockage.
Modified distillation solvents and modified anti-polymerization agents were used. The compatibility of DMC and PMA was enhanced by modifying ethylene glycol. N-methylpyrrolidone was used as a solubilizer. 1-Ethyl-3-methylimidazolium acetate was used to change the phase equilibrium between DMC and water. Hydroquinone grafts and N-phenyl-β-naphthylamine were combined to inhibit the condensation polymerization of high-boiling impurities. Polyethylene glycol 400 was used to reduce the solubility of high-boiling impurities, thereby optimizing the gas-liquid mass transfer interface and separation effect.
It improved the recovery purity of DMC and PMA, reduced the risk of tray blockage, and enhanced separation accuracy and recovery rate. The recovery rate of DMC reached 97.6%-98.8%, and the recovery rate of PMA reached 95.1%-96.2%, which is significantly better than the effect of single modifier.
Smart Images
Figure CN121850866A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of waste cleaning agent recycling technology, specifically to a waste cleaning agent recycling process and system. Background Technology
[0002] Cleaning agents containing DMC (dimethyl carbonate) and PMA (propylene glycol methyl ether acetate) are core consumables in high-end manufacturing industries such as electronics manufacturing, automotive painting, and precision instrument processing. DMC, due to its environmental friendliness and strong solubility, has a boiling point of 90-91℃ and is often used for photoresist cleaning and lithium battery electrode degreasing. PMA, with its low toxicity and high solubility, has a boiling point of 145-146℃ and is widely used for paint dilution and circuit board cleaning. During use, the cleaning agent will mix with impurities such as resin debris, oil, metal particles, and polymer colloids, forming a complex waste liquid containing DMC, PMA, and high-boiling impurities (boiling point greater than 160℃).
[0003] The waste liquid contains residual water from the cleaning process or water absorbed during storage and transportation. DMC forms a minimum azeotrope with water, PMA is slightly soluble in water, and the DMC fraction cannot be purified by ordinary distillation due to azeotropy. When the local water content in the column is too high, gas-liquid stratification will occur, the mass transfer interface will be uneven, and the top temperature / boiler temperature will fluctuate drastically. Therefore, in response to the problems mentioned in the background technology, those skilled in the art have proposed a waste cleaning agent recovery process and system. Summary of the Invention
[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a waste cleaning agent recycling process and system to solve the problems mentioned in the background art.
[0005] To achieve the above objectives, the present invention provides the following technical solution: Waste cleaning agent recycling process includes the following steps: Waste cleaning agent feed containing DMC, PMA and high-boiling impurities is added to a distillation system and heated. DMC is preferentially vaporized to form a vapor mixture containing DMC. The vapor mixture undergoes gas-liquid mass transfer through the trays and continues to rise to the top of the column, while PMA and high-boiling impurities are refluxed to the bottom of the vessel. After the steam mixture is cooled, it condenses into liquid DMC and is refluxed. The extraction valve is opened at 90-140℃ to extract the DMC product. When the temperature rises to 140-160℃, heating is stopped and the extraction of DMC product is stopped. The remaining PMA and high-boiling impurities in the reactor are extracted. The trays contain modified distillate and modified anti-polymerization agents. The modified distillation agent is prepared through the following steps: S1. Mix ethylene glycol and the modifier in a mass ratio, add the modified catalyst and anhydrous toluene, heat to 105-115℃, and keep warm for 2-3 hours to obtain the reaction system. Stop keeping warm when the amount of water removed from the reaction system is 90-95%. S2. Cool the reaction system after heat preservation to 50-60℃, filter and separate to recover the modified catalyst, and then perform vacuum distillation to remove anhydrous toluene, unreacted ethylene glycol and modifier in sequence to obtain modified ethylene glycol. S3. Heat the modified ethylene glycol from step S2 to 30-40℃, and add 1-ethyl-3-methylimidazolium acetate while stirring. Stir for 20-30 minutes, then continue stirring and add N-methylpyrrolidone. Heat to 40-50℃ and stir for 1-1.5 hours to obtain the modified distillation agent.
[0006] Furthermore, the modified catalyst is prepared through the following steps: S11. Calcine the mesoporous silica at 500-550℃ for 3-4 hours. Add anhydrous toluene to the calcined mesoporous silica. Heat the mixture to 70-80℃ under nitrogen protection and stir for 20-30 minutes. Then add chlorosulfonic acid dropwise. After the addition is complete, heat the mixture to 100-110℃ and reflux for 5-6 hours to obtain the reaction solution. The mass ratio of calcined mesoporous silica to anhydrous toluene and chlorosulfonic acid is 1:(6-8):(0.5-0.55). S12. After cooling the reaction solution to room temperature, filter it and collect the solid product. Wash the solid product with anhydrous toluene 2-4 times, then wash it with deionized water until the pH of the filtrate is 6-7. Dry the washed solid product to obtain sulfonated mesoporous silica solid catalyst. S13. Add p-toluenesulfonic acid to anhydrous ethanol, stir and add the sulfonated mesoporous silica solid catalyst from S12, and ultrasonically disperse for 20-30 min to obtain a mixed system. Evaporate the mixed system to remove ethanol and obtain a dry modified catalyst. The mass ratio of toluenesulfonic acid, anhydrous ethanol, and sulfonated mesoporous silica solid catalyst is 6:(15-21):4.
[0007] Furthermore, the modified antipolymer is prepared through the following steps: S101. Add hydroquinone to anhydrous ethanol, heat to 60-70℃ under nitrogen protection, add azobisisobutyronitrile, heat to 80-85℃, keep warm for 10-15 min, then add grafting agent dropwise, and react at a constant temperature for 3-4 h after the addition is complete to obtain the reaction system. The mass ratio of hydroquinone, anhydrous ethanol, azobisisobutyronitrile, and grafting agent is 10:(60-102):(0.38-0.60):(5-7). S102. Cool the reaction system to 35-40℃, add N-phenyl-β-naphthylamine to the cooled reaction system, stir for 20-30 min, and then add polyethylene glycol 400 to obtain a mixed system. Evaporate the mixed system to remove anhydrous ethanol to obtain the modified antipolymerization agent. The mass ratio of hydroquinone, N-phenyl-β-naphthylamine, and polyethylene glycol 400 is 10:(2.5-3.5):(0.8-1.2).
[0008] Furthermore, in step S1, the modifier is dimethylaminoethyl methacrylate and dimethylaminopropyl methacrylate in a mass ratio of (6.5-7.5):3.
[0009] Furthermore, in step S101, the grafting agent is dimethylaminoethyl methacrylate containing hydroquinone monomethyl ether, and the mass ratio of hydroquinone monomethyl ether to dimethylaminoethyl methacrylate is (1.5-2.0):100.
[0010] Furthermore, a modified anti-polymerization agent accounting for 0.3-0.5% of the total mass of the modified distillate is mixed with the modified distillate to obtain a composite system. The gas-liquid ratio of the gas phase volume flow rate on the tray of the rectification section to the volume flow rate of the composite system is 0.8-1.2, and the gas-liquid ratio of the gas phase volume flow rate on the tray of the stripping section to the volume flow rate of the composite system is 1.2-1.8.
[0011] Furthermore, in step S1, the mass ratio of ethylene glycol to the modifier is 1:(0.9-1.1), and the mass ratio of the modified catalyst, anhydrous toluene, and the total mass of ethylene glycol and the modifier is 1:(8-12):200.
[0012] Furthermore, in step S3, the mass ratio of modified ethylene glycol to 1-ethyl-3-methylimidazolium acetate is (92-95):(5-8), and the total mass ratio of N-methylpyrrolidone to modified ethylene glycol and 1-ethyl-3-methylimidazolium acetate is (2-3):100.
[0013] Furthermore, in step S11, the dropping rate of chlorosulfonic acid is 0.05-0.06 mL / min, and in step S101, the dropping rate of the grafting agent is 0.1-0.15 mL / min.
[0014] The system for waste cleaning agent recycling includes: The feeding system includes a raw material conveying device, an evaporator, and a stirring device; A distillation system, comprising a distillation column and a reboiler heating device, wherein the distillation column is provided with a rectification section tray and a stripping section tray, and the reboiler heating device heats the raw material, and the vapor-liquid mass transfer is completed on the tray; A reflux system, comprising a condenser, a reflux tank, and a reflux pump; The discharge system includes a DMC finished product discharge valve, a PMA and high-boiling-point impurity discharge valve, and a finished product storage tank. A temperature control system, comprising a temperature sensor and an intelligent temperature controller.
[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention enhances the compatibility of ethylene glycol with DMC and PMA by modifying it. Combined with the solubilizing effect of N-methylpyrrolidone, it optimizes the gas-liquid contact interface on the tray, reduces the problem of uneven liquid film caused by the high viscosity of PMA, and improves the separation accuracy of light, medium and heavy components. 1-Ethyl-3-methylimidazolium acetate, as an ionic liquid, can change the phase equilibrium relationship between DMC and water, break the lowest azeotrope between the two, reduce the interference of water on the purity of DMC, and make it easier for the purity of DMC fraction to meet the reuse standard. 2. This invention utilizes hydroquinone grafts and N-phenyl-β-naphthylamine as free radical scavengers to effectively inhibit the polycondensation reaction of high-boiling impurities in waste cleaning agents, preventing the formation of sticky colloids and coking deposits. This addresses the root cause of tray and reboiler blockage. The dispersing effect of polyethylene glycol 400 reduces the solubility of high-boiling impurities in the liquid phase, minimizing their backmixing and entrainment into the PMA fraction, thus improving the purity of PMA recovery. Simultaneously, it avoids product contamination by polymerization impurities and ensures that the recovered solvent can be directly reused. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the waste cleaning agent recovery system of the present invention; Figure 2 This is a schematic diagram of the preparation process of the modified distillation agent of the present invention; Figure 3 This is a schematic diagram of the preparation process of the modified catalyst of the present invention; Figure 4 This is a schematic diagram of the preparation process of the modified antipolymer of the present invention.
[0017] In the diagram: I. Feeding system; II. Distillation system; III. Reflux system; IV. Discharge system; V. Temperature control system; 1. Raw material conveying device; 2. Evaporation kettle; 3. Stirring device; 4. Distillation column; 5. Column reboiler heating device; 6. Column tray; 7. Condenser; 8. Reflux tank; 9. Reflux pump; 10. DMC finished product discharge valve; 11. PMA and high-boiling impurity discharge valve; 12. Finished product storage tank; 13. Temperature sensor; 14. Intelligent temperature controller. Detailed Implementation
[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0019] Please see Figures 1-4 The present invention provides a technical solution: Example 1: In this embodiment, the preparation of each modified material applied to tray 6 is carried out first. Preparation of modified distillation solvents: Weigh 100g of ethylene glycol and mix it with 90g of a modifier, the modifier being a 6.5:3 ratio of dimethylaminoethyl methacrylate to dimethylaminopropyl methacrylate. Add 0.95g of modified catalyst and 7.6g of anhydrous toluene. Heat the mixture to 105℃ and hold for 2 hours. When the water content of the reaction system reaches 90%, stop the heat treatment. Cool to 50℃ and filter to recover the modified catalyst. Remove anhydrous toluene, unreacted ethylene glycol, and the modifier by vacuum distillation to obtain modified ethylene glycol. Heat the modified ethylene glycol to 30℃ and add 5g of 1-ethyl-3-methylimidazolium acetate with stirring. After stirring for 20 minutes, add 2g of N-methylpyrrolidone. Heat the mixture to 40℃ and hold for 1 hour with stirring to obtain the modified distillate.
[0020] Preparation of modified catalysts: 10g of mesoporous silica was calcined at 500℃ for 3h, and 60g of anhydrous toluene was added. Under nitrogen protection, the temperature was raised to 70℃ and stirred for 20min. 5g of chlorosulfonic acid was added dropwise at a rate of 0.05mL / min. After the addition was completed, the temperature was raised to 100℃ and refluxed for 5h. After the reaction solution was cooled to room temperature, it was filtered. The solid product was washed twice with anhydrous toluene and then washed with deionized water until the pH of the filtrate was 6. After drying, sulfonated mesoporous silica solid catalyst was obtained. 6g of p-toluenesulfonic acid was added to 15g of anhydrous ethanol, and 4g of sulfonated mesoporous silica solid catalyst was added with stirring. The mixture was ultrasonically dispersed for 20min, and the ethanol was evaporated to remove the modified catalyst.
[0021] Preparation of modified anti-polymerization agent: Take 10g of hydroquinone and add 60g of anhydrous ethanol. Under nitrogen protection, heat to 60℃, add 0.38g of azobisisobutyronitrile, heat to 80℃ and keep warm for 10min. Add 5g of grafting agent at a rate of 0.1mL / min. The grafting agent is 1.5:100 hydroquinone monomethyl ether: dimethylaminoethyl methacrylate. After the addition is complete, keep the reaction temperature constant for 3h. Cool the reaction system to 35℃, add 2.5g of N-phenyl-β-naphthylamine and stir for 20min. Then add 0.8g of polyethylene glycol 400. Evaporate the anhydrous ethanol to remove it to obtain the modified antipolymerization agent.
[0022] Based on the modified materials used in this embodiment, the following waste cleaning agent recycling process is adopted, including the following steps: Waste cleaning agent raw material containing DMC, PMA and high-boiling impurities (polypropylene glycol methyl ether acetate) is added to distillation system II. The reboiler heating device 5 is turned on. DMC is preferentially vaporized to form a vapor mixture containing DMC. The vapor mixture rises to the top of the column after gas-liquid mass transfer through the tray 6. PMA and high-boiling impurities are refluxed to the bottom of the reboiler. The steam mixture is cooled by condenser 7 and condensed into liquid DMC for reflux. When the temperature at the top of the column stabilizes at 115°C, the DMC product discharge valve 10 is opened to collect the DMC product. When the temperature rises to 150°C, heating is stopped and the collection of DMC product is stopped. The remaining PMA and high-boiling impurities in the reactor are collected. The gas-liquid ratio of the gas phase volumetric flow rate on tray 6 of the rectification section to the volumetric flow rate of the composite system is 0.8, and the gas-liquid ratio of the gas phase volumetric flow rate on tray 6 of the stripping section to the volumetric flow rate of the composite system is 1.2. The composite system is prepared by mixing a modified distillation agent and a modified anti-polymerization agent accounting for 0.3% of its total mass.
[0023] Example 2: In this embodiment, the preparation of each modified material applied to tray 6 is carried out first. Preparation of modified distillation solvents Weigh 100g of ethylene glycol and mix it with 100g of a modifier, the modifier being a 7:3 ratio of dimethylaminoethyl methacrylate to dimethylaminopropyl methacrylate. Add 1.0g of modified catalyst and 8g of anhydrous toluene, heat to 110℃ and hold for 2.5h. Stop holding when the water removal reaches 92%. Subsequent steps are the same as in Example 1. Add 6.5g of 1-ethyl-3-methylimidazolium acetate and 2.5g of N-methylpyrrolidone to the modified ethylene glycol, heat at 45℃ and stir for 1.2h to obtain the modified distillation agent.
[0024] Preparation of modified catalysts: 10g of mesoporous silica was calcined at 525℃ for 3.5h, 70g of anhydrous toluene was added, and after stirring at 75℃, 5.25g of chlorosulfonic acid was added dropwise at 0.055mL / min. The mixture was refluxed at 105℃ for 5.5h. The subsequent washing and drying steps were the same as in Example 1. The modified catalyst was prepared by mixing p-toluenesulfonic acid, anhydrous ethanol, and sulfonated mesoporous silica solid catalyst in a ratio of 6:18:4.
[0025] Preparation of modified anti-polymerization agent: 10g hydroquinone was added to 81g anhydrous ethanol, followed by 0.49g azobisisobutyronitrile. After incubation at 82℃, 6g of grafting agent (a 1.7:100 ratio of hydroquinone monomethyl ether to dimethylaminoethyl methacrylate) was added dropwise at a rate of 0.12mL / min. After the reaction, 3.0g N-phenyl-β-naphthylamine and 1.0g polyethylene glycol 400 were added. The anhydrous ethanol was evaporated to remove the residue, yielding the modified antipolymer.
[0026] Based on the modified materials used in this embodiment, the following waste cleaning agent recycling process is adopted, including the following steps: Waste cleaning agent raw material containing DMC, PMA and high-boiling impurities (polypropylene glycol methyl ether acetate) is added to distillation system II. The reboiler heating device 5 is turned on. DMC is preferentially vaporized to form a vapor mixture containing DMC. The vapor mixture rises to the top of the column after gas-liquid mass transfer through the tray 6. PMA and high-boiling impurities are refluxed to the bottom of the reboiler. The steam mixture is cooled by condenser 7 and condensed into liquid DMC for reflux. When the temperature at the top of the column stabilizes at 115°C, the DMC product discharge valve 10 is opened to collect the DMC product. When the temperature rises to 150°C, heating is stopped and the collection of DMC product is stopped. The remaining PMA and high-boiling impurities in the reactor are collected. The gas-liquid ratio of the gas volume flow rate on tray 6 of the rectification section to the volume flow rate of the composite system is 1, and the gas-liquid ratio of the gas volume flow rate on tray 6 of the stripping section to the volume flow rate of the composite system is 1.5. The composite system is prepared by mixing a modified distillation agent and a modified anti-polymerization agent accounting for 0.4% of its total mass.
[0027] Example 3: In this embodiment, the preparation of each modified material applied to tray 6 is carried out first. Preparation of modified distillation solvents: Weigh 100g of ethylene glycol and mix it with 110g of a modifier, the modifier being a 7.5:3 ratio of dimethylaminoethyl methacrylate to dimethylaminopropyl methacrylate. Add 1.05g of modified catalyst and 8.4g of anhydrous toluene, heat to 115℃ and hold for 3 hours. Stop holding when the water removal reaches 95%. Subsequent steps are the same as in Example 1. Add 8g of 1-ethyl-3-methylimidazolium acetate and 3g of N-methylpyrrolidone to the modified ethylene glycol, heat at 50℃ and stir for 1.5 hours to obtain the modified distillation agent.
[0028] Preparation of modified catalysts: 10g of mesoporous silica was calcined at 550℃ for 4h, 80g of anhydrous toluene was added, and after stirring at 80℃, 5.5g of chlorosulfonic acid was added dropwise at 0.06mL / min. The mixture was refluxed at 110℃ for 6h. The subsequent washing and drying steps were the same as in Example 1. The modified catalyst was prepared by mixing p-toluenesulfonic acid, anhydrous ethanol, and sulfonated mesoporous silica solid catalyst in a ratio of 6:21:4.
[0029] Preparation of modified anti-polymerization agent: 10g hydroquinone was added to 102g anhydrous ethanol, followed by 0.60g azobisisobutyronitrile. After incubation at 85℃, 7g of grafting agent (2.0:100 hydroquinone monomethyl ether: dimethylaminoethyl methacrylate) was added dropwise at a rate of 0.15mL / min. After the reaction, 3.5g N-phenyl-β-naphthylamine and 1.2g polyethylene glycol 400 were added. The anhydrous ethanol was evaporated to remove the residue, yielding the modified antipolymer.
[0030] Based on the modified materials used in this embodiment, the following waste cleaning agent recycling process is adopted, including the following steps: Waste cleaning agent raw material containing DMC, PMA and high-boiling impurities (polypropylene glycol methyl ether acetate) is added to distillation system II. The reboiler heating device 5 is turned on. DMC is preferentially vaporized to form a vapor mixture containing DMC. The vapor mixture rises to the top of the column after gas-liquid mass transfer through the tray 6. PMA and high-boiling impurities are refluxed to the bottom of the reboiler. The steam mixture is cooled by condenser 7 and condensed into liquid DMC for reflux. When the temperature at the top of the column stabilizes at 115°C, the DMC product discharge valve 10 is opened to collect the DMC product. When the temperature rises to 150°C, heating is stopped and the collection of DMC product is stopped. The remaining PMA and high-boiling impurities in the reactor are collected. The gas-liquid ratio of the gas phase volumetric flow rate on tray 6 of the rectification section to the volumetric flow rate of the composite system is 1.2, and the gas-liquid ratio of the gas phase volumetric flow rate on tray 6 of the stripping section to the volumetric flow rate of the composite system is 1.8. The composite system is prepared by mixing a modified distillation agent and a modified anti-polymerization agent accounting for 0.5% of its total mass.
[0031] Example 4: This embodiment provides a system for a waste cleaning agent recycling process, including the following steps: See Figure 1 As shown, it includes a feed system I, a distillation system II, a reflux system III, a discharge system IV, and a temperature control system V. The distillation system II includes a distillation column 4 and a reboiler heating device 5. The reboiler heating device 5 continuously heats the column, raising the temperature of the raw material inside the column. DMC, which has a lower boiling point, preferentially vaporizes, forming a vapor mixture containing DMC. The vapor mixture moves upward and passes through the stripping section tray 6 and the rectification section tray 6 in sequence. The modified distillate and modified anti-polymerization agent composite system filled in the tray 6 enhances the gas-liquid mass transfer effect and prevents material polymerization. During the mass transfer process, PMA and high-boiling impurities, due to their high boiling points, will reflux back to the reboiler, achieving preliminary separation. Feeding system I is connected to distillation system II. The raw material conveying device 1 delivers waste cleaning agent raw material containing DMC, PMA and high-boiling impurities to the evaporation kettle 2 according to the set flow rate. The stirring device 3 is started to uniformly stir the raw material in the evaporation kettle 2 to avoid uneven local heating and improve the subsequent preheating efficiency. The evaporation kettle 2 receives instructions from the temperature control system V to preheat the raw material in advance to prepare for the subsequent vaporization process in distillation system II. Reflux system III is connected to both distillation system II and discharge system IV. The DMC vapor mixture rising to the top of distillation column 4 enters condenser 7 and is condensed into liquid DMC by the cooling medium. The liquid DMC flows into reflux tank 8. Part of it is pumped back to the top of distillation column 4 by reflux pump 9 to maintain the gas-liquid balance in the column and ensure the stability of distillation separation. The other part of the liquid DMC is stored in reflux tank 8 as the finished product to be collected, and will be discharged after the collection conditions are met. The discharge system IV is connected to the reflux system III and the distillation system II. When the temperature control system V detects that the temperature at the top of the distillation column 4 is stable at 90-140℃, the DMC product discharge valve 10 is automatically opened to transport the liquid DMC in the reflux tank 8 to the corresponding product storage tank 12. When the temperature at the top of the column rises to 140-160℃, it is determined that the DMC has been completely collected. The system stops heating and closes the DMC product discharge valve 10. After the temperature at the bottom of the column drops to a safe range, the PMA and high-boiling impurity discharge valve 11 is opened to discharge the remaining PMA and high-boiling impurities in the bottom of the column to the dedicated product storage tank 12. The temperature control system V is connected to the feed system I and the distillation system II. Temperature sensors 13 are distributed at key locations in the top, bottom, and middle of the distillation section of the distillation column 4. They collect temperature data in real time and transmit it to the intelligent temperature controller 14. The intelligent temperature controller 14 automatically adjusts the power of the bottom heating device 5 according to the preset temperature range to accurately control the distillation temperature. When the temperature reaches the DMC or PMA collection threshold, the intelligent temperature controller 14 sends a switching command to the corresponding discharge valve to achieve automated collection.
[0032] For the complete and detailed recycling process of the system based on the above-mentioned waste cleaning agent recycling technology, please refer to [link / reference needed]. Figure 1As shown, waste cleaning agent raw material is quantitatively fed into evaporator 2 via raw material conveying device 1. Stirring device 3 is activated to ensure uniform stirring and prevent uneven heating. The raw material is preheated via temperature control system V. The preheated raw material is then fed into distillation column 4. Reboiler heating device 5 is activated. During heating, DMC with a lower boiling point preferentially vaporizes, forming a DMC-containing vapor mixture. This vapor mixture rises, passing sequentially through stripping and rectification sections on tray 6, making full contact with the complex system on tray 6 to complete gas-liquid mass transfer. PMA and high-boiling impurities, due to their high boiling point, reflux to the reboiler. The DMC vapor mixture rising to the top of the column enters condenser 7, where it condenses into liquid DMC. The liquid DMC flows into the reflux tank 8, and a portion of it returns to the top of the column via the reflux pump 9 to maintain the gas-liquid balance within the column. When the temperature control system V detects that the top temperature of the column is stable at 90°C, 100°C, 115°C, 120°C, or 140°C, the DMC product discharge valve 10 is opened to transfer the liquid DMC in the reflux tank 8 to the product storage tank 12. When the top temperature of the column rises to 140°C, 150°C, or 160°C, it is determined that the DMC has been completely extracted. The column bottom heating is stopped and the DMC product discharge valve 10 is closed. After the column bottom temperature drops to a safe range, the PMA and high-boiling impurity discharge valve 11 is opened to discharge the remaining material in the column bottom to the dedicated product storage tank 12.
[0033] Comparative Example 1 Comparative Example 1 differs from Example 1 in that the modified distillate was replaced with toluene distillate, while the remaining steps were exactly the same as in Example 1.
[0034] Comparative Example 2 Comparative Example 2 differs from Example 1 in that the modified antipolymerizing agent is replaced with p-hydroxyanisole antipolymerizing agent, while the remaining steps are exactly the same as in Example 1.
[0035] The distillate and anti-polymerization agent prepared using the processes employed in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2 were tested. The feed rate of the waste cleaning agent was uniformly set at 20 L / h for all five test groups, the reboiler heating power was consistent, the heating rate was controlled at 5 °C / min, the reflux ratio was uniformly set at 3:1, the condenser cooling temperature was set at 25 °C, the DMC collection temperature was uniformly set at 115 °C, and the stop collection temperature was uniformly set at 150 °C. The recovery rates of DMC and PMA were calculated. The formula for calculating the DMC recovery rate is as follows: The formula for calculating PMA recovery rate is: The specific test results are shown in Table 1 below: Table 1 As can be seen from the data in Table 1, Examples 1-3, which use a composite system of modified distillate and modified antipolymer, achieved DMC recovery rates of 97.6%-98.8% and PMA recovery rates of 95.1%-96.2%, significantly higher than Comparative Examples 1 and 2, which replaced single modifiers. Comparative Example 1 used toluene as distillate, and Comparative Example 2 used p-hydroxyanisole as antipolymer, with both recovery rates below 96%, showing a significant difference. This indicates that the modified distillate can enhance gas-liquid mass transfer efficiency, and the modified antipolymer can effectively inhibit material polymerization. The synergistic effect of the two significantly improves the recovery effect. Among them, Example 2 showed the best process parameter compatibility, with DMC and PMA recovery rates of 98.8% and 96.2%, respectively, which were the best among all test groups, fully demonstrating the significant optimization effect of the modified substances on the recovery process.
[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A waste cleaning agent recycling process, characterized in that, Includes the following steps: Waste cleaning agent feed containing DMC, PMA and high-boiling impurities is added to a distillation system and heated. DMC is preferentially vaporized to form a vapor mixture containing DMC. The vapor mixture undergoes gas-liquid mass transfer through the trays and continues to rise to the top of the column, while PMA and high-boiling impurities are refluxed to the bottom of the vessel. After the steam mixture is cooled, it condenses into liquid DMC and is refluxed. The extraction valve is opened at 90-140℃ to extract the DMC product. When the temperature rises to 140-160℃, heating is stopped and the extraction of DMC product is stopped. The remaining PMA and high-boiling impurities in the reactor are extracted. The trays contain modified distillate and modified anti-polymerization agents. The modified distillation agent is prepared through the following steps: S1. Mix ethylene glycol and the modifier in a mass ratio, add the modified catalyst and anhydrous toluene, heat to 105-115℃, and keep warm for 2-3 hours to obtain the reaction system. Stop keeping warm when the amount of water removed from the reaction system is 90-95%. S2. Cool the reaction system after heat preservation to 50-60℃, filter and separate to recover the modified catalyst, and then perform vacuum distillation to remove anhydrous toluene, unreacted ethylene glycol and modifier in sequence to obtain modified ethylene glycol. S3. Heat the modified ethylene glycol from step S2 to 30-40℃, and add 1-ethyl-3-methylimidazolium acetate while stirring. Stir for 20-30 minutes, then continue stirring and add N-methylpyrrolidone. Heat to 40-50℃ and stir for 1-1.5 hours to obtain the modified distillation agent.
2. The waste cleaning agent recycling process according to claim 1, characterized in that, The modified catalyst is prepared by the following steps: S11. Calcine the mesoporous silica at 500-550℃ for 3-4 hours. Add anhydrous toluene to the calcined mesoporous silica. Heat the mixture to 70-80℃ under nitrogen protection and stir for 20-30 minutes. Then add chlorosulfonic acid dropwise. After the addition is complete, heat the mixture to 100-110℃ and reflux for 5-6 hours to obtain the reaction solution. The mass ratio of calcined mesoporous silica to anhydrous toluene and chlorosulfonic acid is 1:(6-8):(0.5-0.55). S12. After cooling the reaction solution to room temperature, filter it and collect the solid product. Wash the solid product with anhydrous toluene 2-4 times, then wash it with deionized water until the pH of the filtrate is 6-7. Dry the washed solid product to obtain sulfonated mesoporous silica solid catalyst. S13. Add p-toluenesulfonic acid to anhydrous ethanol, stir and add the sulfonated mesoporous silica solid catalyst from S12, and ultrasonically disperse for 20-30 min to obtain a mixed system. Evaporate the mixed system to remove ethanol and obtain a dry modified catalyst. The mass ratio of toluenesulfonic acid, anhydrous ethanol, and sulfonated mesoporous silica solid catalyst is 6:(15-21):
4.
3. The waste cleaning agent recycling process according to claim 1, characterized in that, The modified antipolymer agent is prepared by the following steps: S101. Add hydroquinone to anhydrous ethanol, heat to 60-70℃ under nitrogen protection, add azobisisobutyronitrile, heat to 80-85℃, keep warm for 10-15 min, then add grafting agent dropwise, and react at a constant temperature for 3-4 h after the addition is complete to obtain the reaction system. The mass ratio of hydroquinone, anhydrous ethanol, azobisisobutyronitrile, and grafting agent is 10:(60-102):(0.38-0.60):(5-7). S102. Cool the reaction system to 35-40℃, add N-phenyl-β-naphthylamine to the cooled reaction system, stir for 20-30 min, and then add polyethylene glycol 400 to obtain a mixed system. Evaporate the mixed system to remove anhydrous ethanol to obtain the modified antipolymerization agent. The mass ratio of hydroquinone, N-phenyl-β-naphthylamine, and polyethylene glycol 400 is 10:(2.5-3.5):(0.8-1.2).
4. The waste cleaning agent recycling process according to claim 1, characterized in that, In step S1, the modifier is dimethylaminoethyl methacrylate and dimethylaminopropyl methacrylate in a mass ratio of (6.5-7.5):
3.
5. The waste cleaning agent recycling process according to claim 3, characterized in that, In step S101, the grafting agent is dimethylaminoethyl methacrylate containing hydroquinone monomethyl ether, and the mass ratio of hydroquinone monomethyl ether to dimethylaminoethyl methacrylate is (1.5-2.0):
100.
6. The waste cleaning agent recycling process according to claim 3, characterized in that, A composite system is obtained by mixing a modified anti-polymerization agent, accounting for 0.3-0.5% of the total mass of the modified distillate, with the modified distillate. The gas-liquid ratio of the gas phase volumetric flow rate on the tray of the rectification section to the volumetric flow rate of the composite system is 0.8-1.2, and the gas-liquid ratio of the gas phase volumetric flow rate on the tray of the stripping section to the volumetric flow rate of the composite system is 1.2-1.
8.
7. The waste cleaning agent recycling process according to claim 1, characterized in that, In step S1, the mass ratio of ethylene glycol to modifier is 1:(0.9-1.1), and the mass ratio of modified catalyst, anhydrous toluene to the total mass of ethylene glycol and modifier is 1:(8-12):
200.
8. The waste cleaning agent recycling process according to claim 1, characterized in that, In step S3, the mass ratio of modified ethylene glycol to 1-ethyl-3-methylimidazolium acetate is (92-95):(5-8), and the total mass ratio of N-methylpyrrolidone to modified ethylene glycol and 1-ethyl-3-methylimidazolium acetate is (2-3):
100.
9. The waste cleaning agent recycling process according to claim 2, characterized in that, In step S11, the dropping rate of chlorosulfonic acid is 0.05-0.06 mL / min, and in step S101, the dropping rate of the grafting agent is 0.1-0.15 mL / min.
10. A system for recycling waste cleaning agents based on any one of claims 1-9, characterized in that, The system includes: The feeding system includes a raw material conveying device, an evaporator, and a stirring device; A distillation system, comprising a distillation column and a reboiler heating device, wherein the distillation column is provided with a rectification section tray and a stripping section tray, and the reboiler heating device heats the raw material, and the vapor-liquid mass transfer is completed on the tray; A reflux system, comprising a condenser, a reflux tank, and a reflux pump; The discharge system includes a DMC finished product discharge valve, a PMA and high-boiling-point impurity discharge valve, and a finished product storage tank. A temperature control system, comprising a temperature sensor and an intelligent temperature controller.