1,3-dimethylimidazolidinone purification apparatus and process based on coupled cooling

Abstract

This invention discloses a purification device and process for 1,3-dimethylimidazolinone based on coupled cooling, belonging to the field of chemical purification technology. It includes a main coupling unit and a membrane-assisted impurity removal unit. The main coupling unit comprises a vacuum distillation kettle and a three-stage cooling crystallization device. The vacuum distillation kettle utilizes a reduced-pressure environment to lower the boiling point of 1,3-dimethylimidazolinone (DMI), combined with the efficient mass transfer effect of θ-ring corrugated packing, to separate low-boiling substances, such as formaldehyde, from high-boiling residues, and initially enrich DMI vapor. The three-stage cooling crystallization device uses a gradient temperature field to achieve stepwise crystallization based on the melting point difference between DMI and impurities: primary crystallization preferentially separates high-purity DMI, while secondary and tertiary crystallization recover residual DMI and retain impurities, with real-time removal of crystals to prevent co-crystallization. The final product has high purity and a higher yield than traditional distillation. Vacuum distillation lowers the operating temperature, and combined with gradient crystallization, reduces repeated distillation, thus lowering overall energy consumption.

Description

Technical Field

[0001] This invention relates to the field of chemical purification technology, and in particular to a purification apparatus and process for 1,3-dimethylimidazolinone based on coupled cooling. Background Technology

[0002] 1,3-Dimethylimidazolinone (DMI), as a highly polar aprotic solvent, is widely used in high-end fields such as electronics and pharmaceuticals. However, its purification technology faces multiple challenges. Currently, industrial methods primarily rely on distillation, including azeotropic distillation and extractive distillation. But significant bottlenecks exist: because byproducts, such as 1,3-dimethyl-2-imidazolinimide, have boiling points close to DMI (both around 222-226℃), separation requires distillation columns with extremely high theoretical plate numbers, leading to a surge in energy consumption.

[0003] US Patent Application No. US4731453A discloses a method for preparing 1,3-dialkyl-2-imidazolinone. Although it can achieve a yield of over 80%, the residual amount of by-products is still 0.5%-10%.

[0004] To improve purity, Chinese patent CN104649974B discloses a method for preparing electronic-grade 1,3-dimethyl-2-imidazolinone, which develops a combined oxidation-distillation-reduction-distillation process. Impurities are removed through oxidation with potassium persulfate and reduction with sodium dithionite, achieving a purity of over 99.9%. However, the yield is only 87%-88%, and the multi-step distillation further increases energy consumption. Other auxiliary technologies, such as the MgO / SiO2 composite salt adsorption method, can remove some metal ions, but adsorbent regeneration is difficult, hindering large-scale application. The extraction-distillation method requires solvents such as n-butanol, posing a risk of secondary pollution.

[0005] The core defects of the existing technology can be summarized into three points: First, it is energy-intensive. High-temperature distillation not only consumes a lot of energy, but may also lead to partial decomposition of DMI; second, there is a contradiction between purity and yield. Repeated distillation is required to remove near-boiling impurities, which leads to a decrease in yield; third, the removal of impurities is not comprehensive. The removal effect on metal ions and tiny particles is limited, making it difficult to meet the stringent requirements of the microelectronics field. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a purification apparatus and process for 1,3-dimethylimidazolinone based on coupled cooling. The technical solution adopted is as follows:

[0007] The 1,3-dimethylimidazolinone purification device based on coupled cooling includes a main coupling unit and a membrane-assisted purification unit. The main coupling unit includes a vacuum distillation kettle and a three-stage cooling crystallization device. The outlet of the feed pump is connected to the feed inlet of the vacuum distillation kettle through a pipeline. The vacuum distillation kettle distills 1,3-dimethylimidazolinone under a set pressure. The three-stage cooling crystallization device includes a first cooling crystallizer, a second cooling crystallizer, and a third cooling crystallizer. The inlet of the first cooling crystallizer is connected to the top outlet of the vacuum distillation kettle through a pipeline and a valve. The inlet of the second cooling crystallizer is connected to the residual vapor outlet of the first cooling crystallizer through a pipeline and a valve. The inlet of the third cooling crystallizer is connected to the residual vapor outlet of the second cooling crystallizer through a pipeline and a valve. The membrane-assisted purification unit is connected to the crystallization product outlets of the first, second, and third cooling crystallizers, respectively, and removes residual solvent by nitrogen purging.

[0008] By adopting the above technical solution, the vacuum distillation vessel utilizes the vacuum environment to lower the boiling point of 1,3-dimethylimidazolinone (DMI), and combined with the efficient mass transfer effect of the θ-ring corrugated packing, separates low-boiling substances such as formaldehyde from high-boiling residues, and initially enriches DMI vapor.

[0009] The three-stage cooling crystallization device achieves stepwise crystallization by utilizing the difference in melting points between DMI and impurities (DMI melting point 7.5-8.2℃) through a gradient temperature field: the first-stage crystallization preferentially separates high-purity DMI, while the second and third-stage crystallization recovers residual DMI and retains impurities, and real-time removal of crystals avoids co-crystallization.

[0010] By monitoring key parameters in real time using infrared spectroscopy, temperature transmitters, and other methods, the controller dynamically adjusts heating, cooling, vacuum, and other systems to ensure the coordinated and stable operation of all units.

[0011] The final product has high purity, which is more than 0.5 percentage points higher than that of traditional processes; the yield is 8%-10% higher than that of traditional distillation.

[0012] Reduced pressure distillation lowers the operating temperature, and gradient crystallization reduces repeated distillation, resulting in lower overall energy consumption; residual metal ions are less than or equal to 10 ppb, and particulate impurities are completely removed, meeting the requirements for electronic-grade solvents.

[0013] The intelligent control system throughout the entire process enables precise parameter control, resulting in minimal batch stability deviations, making it suitable for large-scale continuous production.

[0014] This device overcomes the contradiction between purity, yield, and energy consumption in traditional processes, providing an integrated solution for the efficient purification of highly polar solvents.

[0015] Optionally, the vacuum distillation vessel includes a vessel body, a θ-ring corrugated packing module, a heating module, and a vacuum module. The θ-ring corrugated packing module is installed in the middle of the vessel body, and the heating module is installed at the bottom of the vessel body. Heating is achieved through heat transfer oil circulation. A feed inlet is provided in the middle of the vessel body, a distillation vapor outlet is provided at the top, and a residue outlet is provided at the bottom.

[0016] Optionally, the θ-ring corrugated packing module uses stainless steel θ-rings as packing material, with a stacking height of 2.8m-3.2m and a specific surface area of ​​up to 200m². 2 / m 3 -240m 2 / m 3 Porosity 0.90-0.94;

[0017] The heating module consists of heating coils, which are spirally distributed at the bottom of the vessel body and heated by circulating heat transfer oil, with a temperature control range of 80-180℃.

[0018] The pressure reduction module includes a vacuum regulating valve, a water ring vacuum pump, and a vacuum buffer tank. The suction port of the water ring vacuum pump is connected to the suction port of the vacuum buffer tank. The buffer suction port of the vacuum buffer tank is connected to the pressure reduction port of the vessel body through the vacuum regulating valve and pipeline, thereby controlling the vacuum degree inside the vessel body at 0.05-0.095MPa.

[0019] By adopting the above technical solution, the θ-ring corrugated packing module serves as the core separation unit. Its stainless steel θ-ring structure forms a dense gas-liquid contact interface with a specific surface area of ​​200-240 m². 2 / m 3 When the raw material is heated and vaporized, the steam comes into countercurrent contact with the descending liquid in the packing layer. The component separation is achieved by utilizing the difference in volatility between DMI and impurities. The high porosity (0.90-0.94) structure reduces airflow resistance and improves mass transfer efficiency.

[0020] The bottom spiral heating coil is heated by circulating heat transfer oil to form a uniform temperature field, providing the heat energy required for the vaporization of raw materials, while avoiding DMI decomposition caused by local overheating.

[0021] The water ring vacuum pump stabilizes the gas flow through the vacuum buffer tank, and in conjunction with the vacuum regulating valve, it precisely controls the vacuum level inside the vessel at 0.05-0.095MPa, reducing the boiling point of DMI from 2-6℃ at atmospheric pressure to -150℃, thus achieving low-temperature distillation and reducing energy consumption and the risk of thermal degradation.

[0022] A 2.8-3.2m high θ-ring packing layer can provide the separation effect equivalent to 30 theoretical plates, improving mass transfer efficiency by 40% compared to traditional bulk packing (such as Pall rings). It can effectively separate DMI and near-boiling byproducts with a boiling point difference of only 2-4℃, and the purity of single-stage distillation can reach more than 98%.

[0023] The vacuum environment reduces the distillation temperature by 70-120℃, and combined with the efficient heat transfer of heat transfer oil, the energy consumption per unit processing capacity is reduced by 50%-60% compared to atmospheric pressure distillation, while avoiding DMI decomposition caused by high temperature.

[0024] The vacuum buffer tank can buffer pressure fluctuations, and together with the uniform heating of the spiral coil, it makes the distillation process continuous and stable, and the batch purity deviation is controlled within ±0.3%.

[0025] Optionally, the first cooling crystallizer includes a crystallization cylinder, a jacket, and a centrifugal stirring and scraping device. The crystallization cylinder has a steam inlet at the top, a crystallized material outlet at the bottom, and a residual steam outlet at the lower part. The jacket is installed on the inner wall of the crystallization cylinder, and the centrifugal stirring and scraping device is installed inside the crystallization cylinder to homogenize the steam inside the crystallization cylinder and scrape off the crystallized material from the inner wall of the jacket.

[0026] Optionally, the centrifugal stirring scraper device includes a servo motor and a blade. The servo motor is installed at the bottom of the crystallization cylinder, and the blade is installed on the power shaft of the servo motor. The blade is made of polytetrafluoroethylene and has a scraper section on the outside of the blade. The gap between the outside of the scraper section and the cylinder wall is 0.3mm-0.5mm. When the blade rotates, the scraper section scrapes the crystals on the inner wall of the crystallization cylinder.

[0027] Optionally, the inlet and outlet of the jacket are connected to the inlet and outlet of the coolant circulation device, respectively, and an ethylene glycol solution at 4℃-6℃ circulates inside the jacket.

[0028] Optionally, the second and third cooling crystallizers adopt the same structure as the first cooling crystallizer.

[0029] By adopting the above technical solution, the first cooling crystallizer utilizes the 4-6℃ ethylene glycol solution in the jacket to create a low-temperature environment, causing DMI vapor from the vacuum distillation vessel to condense and preferentially crystallize within the crystallizing cylinder, taking advantage of DMI's melting point of 7.5-8.2℃. The second and third cooling crystallizers employ the same structure, using lower-temperature refrigerants (such as -5℃ calcium chloride solution and -20℃ ethanol solution) to perform gradient cooling of the residual vapor, respectively, utilizing the difference in melting points between impurities and DMI (impurities typically have melting points below -10℃) to achieve stepwise separation.

[0030] The centrifugal stirring scraper device uses a servo motor to drive the polytetrafluoroethylene blades to rotate, so that the steam is evenly distributed in the crystallization cylinder, avoiding the co-crystallization of impurities caused by local overcooling; the scraper part on the outside of the blades scrapes off the wall crystals in real time, preventing the scale layer from hindering heat transfer and ensuring stable cooling efficiency.

[0031] The PTFE blades and scraper are resistant to DMI and acidic impurities, avoiding ion contamination from metal materials; the nested structure of the jacket and crystallizer forms a closed heat transfer space, improving refrigerant circulation efficiency by more than 30%.

[0032] The first cooling crystallizer, through precise temperature control and stirring homogenization, achieves a DMI crystallization rate of 70%-75%, increasing the crystal purity from 98% to 99.5%. The second and third stage gradient cooling further captures residual DMI, increasing the total yield to over 95%. Near-boiling impurities, such as 1,3-dimethyl-2-imidazoline imine, remain in the mother liquor due to their low melting point, resulting in a final product purity of 99.99%, which is 1.5 percentage points higher than the traditional single-stage crystallization process.

[0033] The PTFE blades and scraper section are resistant to long-term immersion corrosion by DMI, solving the problem of metal ion leaching caused by corrosion in traditional stainless steel scrapers. Metal ion residue is reduced from 0.1 ppm to below 0.01 ppm. The modular design shortens the assembly and disassembly time of a single crystallizer to 2 hours. Optionally, the membrane-assisted impurity removal unit includes multiple hollow fiber membrane modules and a nitrogen circulation device. The hollow fiber membrane module includes a membrane-assisted stainless steel tube and multiple membrane bundles. One end of the membrane-assisted stainless steel tube is connected to the crystallized product distillation outlet at the bottom of the crystallization cylinder, and the other end is connected to the inlet of the finished product storage tank via a conveying device. Multiple membrane bundles are fixed at equal intervals inside the membrane-assisted stainless steel tube with epoxy resin. The inlet and outlet of the nitrogen circulation device are connected to the air inlet and outlet of the membrane-assisted stainless steel tube of the multiple hollow fiber membrane modules, respectively, to fill the hollow fiber membrane modules with nitrogen.

[0034] By employing the above technical solution, the polytetrafluoroethylene hollow fiber membrane bundle, with a molecular weight cutoff of 500 Da and a nanoscale pore structure, can precisely trap residual microparticles and colloidal impurities in the crystallized product. Combined with the purging action of a nitrogen circulation device, it can efficiently remove residual solvents and trace amounts of moisture adsorbed on the crystal surface. Testing shows that this unit can further increase the purity of DMI products from 99.5% after crystallization to over 99.99%, and reduce metal ions (Fe... 3+ Cu 2+ The total residual amount (etc.) is reduced to below 10 ppb, meeting the stringent requirements of the microelectronics field for ultra-high purity solvents.

[0035] Multiple membrane modules are designed in parallel, with membrane fiber bundles fixed at equal intervals by epoxy resin, ensuring full contact between the crystallized products and the membrane surface. The effective mass transfer area of ​​a single membrane module reaches 1.2m². 2 This represents an improvement over traditional packed membrane modules. The convection effect generated by nitrogen purging accelerates impurity diffusion, reducing solvent residue removal time from 2 hours in traditional vacuum drying to 30 minutes, and lowering unit processing energy consumption to 30 kW·h / t, which is lower than that of adsorption methods.

[0036] Optionally, it also includes an intelligent control unit, which includes a digital thermometer, a level gauge, an infrared spectrometer, three temperature transmitters, and an industrial control computer. The digital thermometer detects the internal temperature of the vessel, the level gauge monitors the liquid level inside the vessel, the infrared spectrometer is installed at the top of the vessel to monitor the DMI characteristic peak, and the three temperature transmitters monitor the temperatures inside the first, second, and third cooling crystallizers, respectively. The industrial control computer is communicatively connected to the digital thermometer, level gauge, infrared spectrometer, and three temperature transmitters, and controls the actions of the heating module, pressure reducing module, centrifugal stirring and scraping device, coolant circulation device, and nitrogen circulation device, respectively.

[0037] The purification process for 1,3-dimethylimidazolinone based on coupled cooling involves purifying 1,3-dimethylimidazolinone using a coupled cooling 1,3-dimethylimidazolinone purification device, including the following steps:

[0038] Step 1: Pre-treat industrial-grade DMI raw materials and transport the filtered raw materials to a vacuum distillation vessel via a raw material pump. When the liquid level in the vacuum distillation vessel reaches 50%-70% of its volume as monitored by the level gauge, close the feed valve.

[0039] Step 2: Activate the pressure reduction module to evacuate the vessel to a vacuum level of 0.05-0.095 MPa using a water ring vacuum pump; activate the heating module to raise the temperature at a rate of 1-2℃ / min using a spiral heating coil, while maintaining a heat transfer oil circulation flow rate of 8-12 m³ / min. 3 / h, raising the temperature inside the reactor to -150℃;

[0040] Step 3: The raw materials form a gas-liquid two-phase countercurrent contact in the θ-ring corrugated packing module. Low-boiling substances rise to the top of the vacuum distillation vessel through the packing layer, while high-boiling residues remain at the bottom of the vessel. The infrared spectrometer of the intelligent control unit monitors the DMI characteristic peak at the top of the vessel in real time. When the peak intensity is greater than or equal to 98%, the steam outlet valve at the top of the vessel is opened.

[0041] Step 4: DMI steam from the top of the vessel enters the first cooling crystallizer through a pipeline for primary crystallization. The centrifugal stirring and scraping device is started, and the PTFE blades rotate at 50-80 r / min. The scraper scrapes off the crystals on the wall in real time, and the crystals are discharged through the bottom distillation outlet every 20-30 minutes.

[0042] The residual steam from the primary crystallizer enters the second cooling crystallizer for secondary crystallization; the residual steam from the secondary crystallizer enters the third cooling crystallizer for tertiary crystallization.

[0043] Step 5: The first, second and third stage crystallization products are collected by a screw conveyor and then sent into the membrane-assisted stainless steel tube.

[0044] Step 6: Start the nitrogen circulation device. After the nitrogen is preheated to 30-50℃, it is introduced into the hollow fiber membrane module at a flow rate of 1-3L / min and purged for 25 min at a pressure of 0.1-0.2MPa.

[0045] Step 7: After purification, DMI is transported to the finished product storage tank via pipeline, and the storage tank is maintained with nitrogen protection at 0.02-0.05 MPa.

[0046] In summary, the present invention has at least one of the following beneficial technical effects:

[0047] This invention provides a 1,3-dimethylimidazolinone purification device and process based on coupled cooling. The vacuum distillation vessel utilizes a reduced-pressure environment to lower the boiling point of 1,3-dimethylimidazolinone (DMI). Combined with the efficient mass transfer effect of the θ-ring corrugated packing, low-boiling substances, such as formaldehyde, are separated from high-boiling residues, and DMI vapor is initially enriched. The three-stage cooling crystallization device uses a gradient temperature field to achieve stepwise crystallization based on the melting point difference between DMI and impurities: the first-stage crystallization preferentially separates high-purity DMI, while the second and third-stage crystallization recover residual DMI and retain impurities. Crystallized material is removed in real time to prevent co-crystallization.

[0048] By monitoring key parameters in real time using infrared spectroscopy, temperature transmitters, and other methods, the controller dynamically adjusts heating, cooling, vacuum, and other systems to ensure the coordinated and stable operation of all units.

[0049] The final product has high purity, improving by more than 0.5 percentage points compared to traditional processes; the yield is 8%-10% higher than traditional distillation. Reduced pressure distillation lowers the operating temperature, and gradient crystallization reduces repeated distillation, resulting in lower overall energy consumption; residual metal ions are less than or equal to 10 ppb, and particulate impurities are completely removed, meeting the requirements for electronic-grade solvents. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the component connection principle of the 1,3-dimethylimidazolinone purification device based on coupling cooling according to the present invention.

[0051] Figure 2 This is a schematic diagram of the vacuum distillation vessel structure of the 1,3-dimethylimidazolinone purification device based on coupled cooling according to the present invention.

[0052] Figure 3 This is a schematic diagram of the structure and principle of the first cooling crystallizer of the 1,3-dimethylimidazolinone purification device based on coupled cooling of the present invention.

[0053] Figure 4 This is a schematic diagram of the hollow fiber membrane module structure of the 1,3-dimethylimidazolinone purification device based on coupled cooling according to the present invention.

[0054] Figure 5This is a schematic diagram of the control device connection principle of the 1,3-dimethylimidazolinone purification device based on coupling cooling according to the present invention.

[0055] Explanation of reference numerals in the attached drawings: 11. Vacuum distillation vessel; 111. Vessel body; 112. θ-ring corrugated packing module; 113. Heating module; 114. Pressure reduction module; 1141. Vacuum regulating valve; 1142. Water ring vacuum pump; 1143. Vacuum buffer tank; 121. First cooling crystallizer; 1211. Crystallization cylinder; 1212. Jacket; 1213. Centrifugal stirring scraper device; 1214. Cooling liquid circulation device; 122. Second cooling crystallizer; 123. Third cooling crystallizer; 2. Membrane-assisted impurity removal unit; 21. Hollow fiber membrane module; 211. Membrane-assisted stainless steel tube; 212. Multiple membrane bundles; 22. Nitrogen circulation device; 100. Raw material pump; 101. Finished product storage tank; 31. Digital thermometer; 32. Level gauge; 33. Infrared spectrometer; 34. Temperature transmitter; 35. Industrial control computer. Detailed Implementation

[0056] The present invention will be further described in detail below with reference to the accompanying drawings.

[0057] This invention discloses a purification device and process for 1,3-dimethylimidazolinone based on coupled cooling.

[0058] Reference Figure 1 - Figure 5 Example 1, a 1,3-dimethylimidazolinone purification device based on coupled cooling, includes a main coupling unit and a membrane-assisted impurity removal unit 2. The main coupling unit includes a vacuum distillation kettle 11 and a three-stage cooling crystallization device. The outlet of the feed pump 100 is connected to the feed inlet of the vacuum distillation kettle 11 through a pipeline. The vacuum distillation kettle 11 distills 1,3-dimethylimidazolinone under a set pressure. The three-stage cooling crystallization device includes a first cooling crystallizer 121, a second cooling crystallizer 122, and a third cooling crystallizer 123; the first cooling crystallizer... The inlet of the first cooling crystallizer 121 is connected to the top outlet of the vacuum distillation vessel 11 via pipes and valves. The inlet of the second cooling crystallizer 122 is connected to the residual steam outlet of the first cooling crystallizer 121 via pipes and valves. The inlet of the third cooling crystallizer 123 is connected to the residual steam outlet of the second cooling crystallizer 122 via pipes and valves. The membrane-assisted impurity removal unit 2 is connected to the crystallization product outlets of the first cooling crystallizer 121, the second cooling crystallizer 122, and the third cooling crystallizer 123, respectively, and removes residual solvent by nitrogen purging.

[0059] The vacuum distillation vessel 11 utilizes the vacuum environment to lower the boiling point of 1,3-dimethylimidazolinone (DMI), and combined with the efficient mass transfer effect of the θ-ring corrugated packing, separates low-boiling substances such as formaldehyde from high-boiling residues, and initially enriches DMI vapor.

[0060] The three-stage cooling crystallization device achieves stepwise crystallization by utilizing the difference in melting points between DMI and impurities (DMI melting point 7.5-8.2℃) through a gradient temperature field: the first-stage crystallization preferentially separates high-purity DMI, while the second and third-stage crystallization recovers residual DMI and retains impurities, and real-time removal of crystals avoids co-crystallization.

[0061] By monitoring key parameters in real time using infrared spectroscopy, temperature transmitters, and other methods, the controller dynamically adjusts heating, cooling, vacuum, and other systems to ensure the coordinated and stable operation of all units.

[0062] The final product has high purity, which is more than 0.5 percentage points higher than that of traditional processes; the yield is 8%-10% higher than that of traditional distillation.

[0063] Reduced pressure distillation lowers the operating temperature, and gradient crystallization reduces repeated distillation, resulting in lower overall energy consumption; residual metal ions are less than or equal to 10 ppb, and particulate impurities are completely removed, meeting the requirements for electronic-grade solvents.

[0064] The intelligent control system throughout the entire process enables precise parameter control, resulting in minimal batch stability deviations, making it suitable for large-scale continuous production.

[0065] This device overcomes the contradiction between purity, yield, and energy consumption in traditional processes, providing an integrated solution for the efficient purification of highly polar solvents.

[0066] Example 2: The vacuum distillation vessel 11 includes a vessel body 111, a θ-ring corrugated packing module 112, a heating module 113, and a vacuum module 114. The θ-ring corrugated packing module 112 is installed in the middle of the vessel body 111, and the heating module 113 is installed in the bottom of the vessel body 111. It is heated by circulating heat transfer oil. The vessel body 111 has a feed inlet in the middle, a distillation vapor outlet at the top, and a residue outlet at the bottom.

[0067] In Example 3, the packing of the θ-ring corrugated packing module 112 is stainless steel θ-rings, with a stacking height of 2.8m-3.2m and a specific surface area of ​​200m². 2 / m 3 -240m 2 / m 3 Porosity 0.90-0.94;

[0068] Heating module 113 is composed of heating coils, which are spirally distributed at the bottom of the vessel body and heated by circulating heat transfer oil, with a temperature control range of 80-180℃;

[0069] The pressure reduction module 114 includes a vacuum regulating valve 1141, a water ring vacuum pump 1142, and a vacuum buffer tank 1143. The suction port of the water ring vacuum pump 1142 is connected to the suction port of the vacuum buffer tank 1143. The buffer suction port of the vacuum buffer tank 1143 is connected to the pressure reduction port of the vessel body 111 through the vacuum regulating valve 1141 and the pipeline, so as to control the vacuum degree in the vessel body 111 at 0.05-0.095MPa.

[0070] The θ-ring corrugated packing module 112 serves as the core separation unit. Its stainless steel θ-ring structure forms a dense gas-liquid contact interface with a specific surface area of ​​200-240 m². 2 / m 3 When the raw material is heated and vaporized, the steam comes into countercurrent contact with the descending liquid in the packing layer. The component separation is achieved by utilizing the difference in volatility between DMI and impurities. The high porosity (0.90-0.94) structure reduces airflow resistance and improves mass transfer efficiency.

[0071] The bottom spiral heating coil is heated by circulating heat transfer oil to form a uniform temperature field, providing the heat energy required for the vaporization of raw materials, while avoiding DMI decomposition caused by local overheating.

[0072] The water ring vacuum pump 1142 stably pumps gas through the vacuum buffer tank 1143, and works with the vacuum regulating valve 1141 to precisely control the vacuum degree inside the vessel at 0.05-0.095MPa, thereby reducing the boiling point of DMI from 222-226℃ at atmospheric pressure to 100-150℃, achieving low-temperature distillation and reducing energy consumption and the risk of thermal degradation.

[0073] A 2.8-3.2m high θ-ring packing layer can provide the separation effect equivalent to 30 theoretical plates, improving mass transfer efficiency by 40% compared to traditional bulk packing (such as Pall rings). It can effectively separate DMI and near-boiling byproducts with a boiling point difference of only 2-4℃, and the purity of single-stage distillation can reach more than 98%.

[0074] The vacuum environment reduces the distillation temperature by 70-120℃, and combined with the efficient heat transfer of heat transfer oil, the energy consumption per unit processing capacity is reduced by 50%-60% compared to atmospheric pressure distillation, while avoiding DMI decomposition caused by high temperature.

[0075] The vacuum buffer tank 1143 can buffer pressure fluctuations, and together with the uniform heating of the spiral coil, it makes the distillation process continuous and stable, and the batch purity deviation is controlled within ±0.3%.

[0076] Example 4: The first cooling crystallizer 121 includes a crystallization cylinder 1211, a jacket 1212, and a centrifugal stirring scraper device 1213. The crystallization cylinder 1211 has a steam inlet at the top, a crystallized material outlet at the bottom, and a residual steam outlet at the bottom. The jacket 1212 is installed on the inner wall of the crystallization cylinder 1211, and the centrifugal stirring scraper device 1213 is installed inside the crystallization cylinder 1211 to homogenize the steam inside the crystallization cylinder 1211 and scrape off the crystallized material from the inner wall of the jacket 1212.

[0077] Example 5: The centrifugal stirring scraper device 1213 includes a servo motor and a blade. The servo motor is installed at the bottom of the crystallization cylinder 1211, and the blade is installed on the power shaft of the servo motor. The blade is made of polytetrafluoroethylene and has a scraper part on the outside of the blade. The gap between the outside of the scraper part and the cylinder wall is 0.3mm-0.5mm. When the blade rotates, the scraper part scrapes the crystals on the inner wall of the crystallization cylinder 1211.

[0078] In Example 6, the inlet and outlet of the jacket 1212 are connected to the inlet and outlet of the coolant circulation device 1214, respectively, and an ethylene glycol solution at 4°C-6°C circulates inside the jacket 1212.

[0079] In Example 7, the second cooling crystallizer 122 and the third cooling crystallizer 123 adopt the same structure as the first cooling crystallizer 121.

[0080] The first cooling crystallizer 121 utilizes a 4-6°C ethylene glycol solution in the jacket 1212 to create a low-temperature environment, causing DMI vapor from the vacuum distillation vessel to condense and preferentially crystallize within the crystallizer cylinder 1211, taking advantage of DMI's melting point of 7.5-8.2°C. The second and third cooling crystallizers employ the same structure, using lower-temperature refrigerants (such as -5°C calcium chloride solution or -20°C ethanol solution) to provide gradient cooling to the residual vapor, achieving stepwise separation by utilizing the melting point difference between impurities and DMI (impurities typically have melting points below -10°C).

[0081] The centrifugal stirring scraper device 1213 drives the polytetrafluoroethylene blades to rotate via a servo motor, so that the steam is evenly distributed in the crystallization cylinder, avoiding the co-crystallization of impurities caused by local overcooling; the scraper part on the outside of the blades scrapes off the wall crystals in real time, preventing the scale layer from hindering heat transfer and ensuring stable cooling efficiency.

[0082] The PTFE blades and scraper are resistant to DMI and acidic impurities, avoiding ion contamination from metal materials; the nested structure of the jacket and crystallizer forms a closed heat transfer space, improving refrigerant circulation efficiency by more than 30%.

[0083] The first cooling crystallizer, through precise temperature control and stirring homogenization, achieves a DMI crystallization rate of 70%-75%, increasing the crystal purity from 98% to 99.5%. The second and third stage gradient cooling further captures residual DMI, increasing the total yield to over 95%. Near-boiling impurities, such as 1,3-dimethyl-2-imidazoline imine, remain in the mother liquor due to their low melting point, resulting in a final product purity of 99.99%, which is 1.5 percentage points higher than the traditional single-stage crystallization process.

[0084] The PTFE blades and scraper are resistant to long-term immersion corrosion by DMI, solving the problem of metal ion leaching caused by corrosion in traditional stainless steel scrapers. The residual metal ion content is reduced from 0.1ppm to below 0.01ppm. The modular design reduces the disassembly and assembly time of a single crystallizer to 2 hours.

[0085] Example 8: The membrane-assisted impurity removal unit 2 includes multiple sets of hollow fiber membrane modules 21 and a nitrogen circulation device 22. The hollow fiber membrane module 21 includes a membrane-assisted stainless steel tube 211 and multiple membrane bundles 212. One end of the membrane-assisted stainless steel tube 211 is connected to the crystallization outlet at the bottom of the crystallization cylinder 1211, and the other end is connected to the inlet of the finished product storage tank 101 through a conveying device. Multiple membrane bundles 212 are fixed inside the membrane-assisted stainless steel tube 211 at equal intervals by epoxy resin. The inlet and outlet of the nitrogen circulation device 22 are connected to the air inlet and air outlet of the membrane-assisted stainless steel tube 211 of the multiple sets of hollow fiber membrane modules 21, respectively, to fill the hollow fiber membrane module 21 with nitrogen.

[0086] The polytetrafluoroethylene hollow fiber membrane bundle 212, with a molecular weight cutoff of 500 Da, possesses a nanoscale pore structure, enabling precise trapping of residual microparticles and colloidal impurities in the crystallized product. Combined with the purging action of the nitrogen circulation device 22, it efficiently removes residual solvents and trace amounts of moisture adsorbed on the crystal surface. Testing shows that this unit can further increase the purity of DMI products from 99.5% after crystallization to over 99.99%, and remove metal ions (Fe... 3+ Cu 2+ The total residual amount (etc.) is reduced to below 10 ppb, meeting the stringent requirements of the microelectronics field for ultra-high purity solvents.

[0087] Multiple membrane modules are designed in parallel, with membrane fiber bundles fixed at equal intervals by epoxy resin, ensuring full contact between the crystallized products and the membrane surface. The effective mass transfer area of ​​a single membrane module reaches 1.2m². 2 This represents an improvement over traditional packed membrane modules. The convection effect generated by nitrogen purging accelerates impurity diffusion, reducing solvent residue removal time from 2 hours in traditional vacuum drying to 30 minutes, and lowering unit processing energy consumption to 30 kW·h / t, which is lower than that of adsorption methods.

[0088] Example 9 also includes an intelligent control unit, which includes a digital thermometer 31, a level gauge 32, an infrared spectrometer 33, three temperature transmitters 34, and an industrial control computer 35. The digital thermometer 31 detects the internal temperature of the vessel 111, the level gauge 32 monitors the liquid level inside the vessel 111, the infrared spectrometer 33 is installed at the top inside the vessel 111 and monitors the DMI characteristic peak, and the three temperature transmitters 34 monitor the temperatures inside the first cooling crystallizer 121, the second cooling crystallizer 122, and the third cooling crystallizer 123, respectively. The industrial control computer 35 is communicatively connected to the digital thermometer 31, the level gauge 32, the infrared spectrometer 33, and the three temperature transmitters 34, and controls the execution of the heating module 113, the pressure reducing module 114, the centrifugal stirring scraper device 1213, the coolant circulation device 1214, and the nitrogen circulation device 22, respectively.

[0089] Example 10, a purification process for 1,3-dimethylimidazolinone based on coupled cooling, involves purifying 1,3-dimethylimidazolinone using a coupled cooling 1,3-dimethylimidazolinone purification device, including the following steps:

[0090] Step 1: Industrial-grade DMI raw material pretreatment, and the filtered raw material is transported to vacuum distillation vessel 11 by raw material pump 100. When the liquid level in vacuum distillation vessel 11 reaches 50%-70% of the volume as monitored by liquid level gauge 32, the feed valve is closed.

[0091] Step 2: Start the pressure reduction module 114, and use the water ring vacuum pump 1142 to evacuate the vacuum level inside the vessel 111 to 0.05-0.095 MPa; turn on the heating module 113, and use the spiral heating coil to raise the temperature at a rate of 1-2℃ / min, while maintaining the heat transfer oil circulation flow rate at 8-12 m³ / min. 3 / h, raising the temperature inside the reactor to 100-150℃;

[0092] Step 3: The raw material forms a gas-liquid two-phase countercurrent contact in the θ-ring corrugated packing module 112. The low-boiling substances rise to the top of the vacuum distillation vessel 11 through the packing layer, while the high-boiling residue remains at the bottom of the vessel. The infrared spectrometer 33 of the intelligent control unit monitors the DMI characteristic peak at the top of the vessel in real time. When the peak intensity is greater than or equal to 98%, the steam outlet valve at the top of the vessel is opened.

[0093] Step 4: DMI steam from the top of the vessel enters the first cooling crystallizer 121 through a pipeline for primary crystallization. The centrifugal stirring and scraping device 1213 is started, and the polytetrafluoroethylene blades rotate at 50-80 r / min. The scraper section scrapes off the crystals on the wall in real time, and the crystals are discharged through the bottom distillation outlet every 20-30 minutes.

[0094] The residual steam from the primary crystallizer enters the second cooling crystallizer 122 for secondary crystallization; the residual steam from the secondary crystallizer enters the third cooling crystallizer 123 for tertiary crystallization.

[0095] Step 5: The first, second and third stage crystallization products are collected by a screw conveyor and then fed into the membrane-assisted stainless steel tube 211.

[0096] Step 6: Start the nitrogen circulation device 22. After the nitrogen is preheated to 30-50℃, it is introduced into the hollow fiber membrane module 21 at a flow rate of 1-3L / min and purged for 25-35min at a pressure of 0.1-0.2MPa.

[0097] Step 7: After purification, DMI is transported to finished product storage tank 101 via pipeline, and the storage tank is maintained with nitrogen protection at 0.02-0.05MPa.

[0098] The following specific embodiments illustrate the implementation principle of the present invention:

[0099] The vacuum distillation vessel 11 is made of 316L stainless steel, with a volume of 3000L, a vessel diameter of 800mm, and a height of 2500mm; the θ-ring corrugated packing module 112 uses Φ5mm stainless steel θ-rings, with a stacking height of 3m and a specific surface area of ​​220m². 2 / m 3 The porosity is 0.92; the heating module 113 is an Inconel 625 spiral coil with an area of ​​8m². 2 The heat transfer oil is model L-QD320; the pressure reducing module 114 is equipped with a 2BV5161 water ring vacuum pump with a pumping speed of 60m³ / h. 3 / h, vacuum buffer tank volume 500L.

[0100] Three-stage cooling crystallization device:

[0101] First cooling crystallizer 121: Diameter 500mm, height 1500mm, effective heat exchange area of ​​the jacket 4.5m² 2 The blades are made of polytetrafluoroethylene, with a diameter of 490 mm and a gap of 0.4 mm between the scraper and the cylinder wall.

[0102] Second / Third Cooling Crystallizers: Diameters are 400mm / 300mm respectively, heights are 1200mm / 1000mm, and the structure is the same as the first crystallizer;

[0103] Refrigerant system: First stage uses 5℃ ethylene glycol solution (60% concentration), second stage uses -5℃ calcium chloride solution (30%), and third stage uses -20℃ ethanol solution.

[0104] Membrane-assisted impurity removal unit 2: Three sets of hollow fiber membrane modules connected in parallel, each set containing 150 membrane fibers with an inner diameter of 0.6 mm, an outer diameter of 1.4 mm, and an effective membrane area of ​​1.2 m². 2 / set; nitrogen circulation device equipped with D07-19B mass flow controller.

[0105] Intelligent control unit: S7-1500 PLC, equipped with FTIR-650 infrared spectrometer, resolution 2cm. -1 PT100 platinum resistance thermometer.

[0106] Step 1: Take 5000 kg of industrial-grade DMI, purity 95.2%, containing 0.4% near-boiling impurities and 0.3% metal ions, and pass it through a 0.2 μm precision filter at a pressure of 0.25 MPa and a flow rate of 8 m³ / kg. 3 After filtration, the solution is pumped to the vacuum distillation vessel 11 via the raw material pump 100. The feed valve is closed when the liquid level reaches 1800L (60% of volume). Step 2: The vacuum module 114 is activated to stabilize the vacuum level inside the vessel at 0.08MPa; the heating module heats the solution to 120℃ at a rate of 1.5℃ / min, and the heat transfer oil circulation flow rate is 10m³ / min. 3 / h; the raw material undergoes mass transfer and separation in the θ-ring packing layer, and low-boiling-point substances are discharged from the top of the column.

[0107] Step 3: The infrared spectrometer monitors the steam at the top of the tower in real time. When the steam reaches 1620cm... -1 When the DMI characteristic peak intensity reaches 98.5%, approximately 120 minutes later, open the steam valve at the top of the tower and control the feed rate at 500 kg / h. Step 4:

[0108] Primary crystallization: Steam enters the first cooling crystallizer, jacket temperature 5℃, stirring speed 60r / min, 350kg of crystals are discharged every 30min, crystallization rate 70%;

[0109] Secondary crystallization: Residual steam enters the second crystallizer at -5℃, with a stirring speed of 80 r / min. 105 kg of crystals are discharged every 60 min, with a crystallization rate of 50%.

[0110] Three-stage crystallization: Residual vapor enters the third crystallizer at -20℃, recovering trace amounts of DMI, approximately 25 kg, and discharging 120 kg of residue.

[0111] Step 5: 480 kg of mixed crystals with a purity of 99.5% were fed into the membrane module and purged with nitrogen gas at 30°C (flow rate 2 L / min, pressure 0.15 MPa) for 30 min to remove residual solvent and metal ions.

[0112] Step 6: 470 kg of purified DMI, yield 94%, was sent to the finished product storage tank and maintained under 0.03 MPa nitrogen protection to complete a single batch of production. The total time was approximately 8 hours.

[0113] Table 1 shows the test results comparing the product with the traditional process:

[0114] Table 1

[0115]

[0116]

[0117] This embodiment utilizes a coupled process of vacuum distillation-gradient crystallization-membrane purification, which improves product purity by 0.79-0.99 percentage points and yield by 9-12 percentage points compared to traditional processes, while reducing energy consumption by 33%-42%. The control of residual metal ions and particulate impurities meets electronic-grade solvent standards, and the batch stability is significantly better than that of traditional processes. This can meet the large-scale demand for ultra-high purity DMI in fields such as microelectronics and high-end pharmaceuticals.

[0118] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A 1,3-dimethylimidazolinone purification device based on coupled cooling, characterized in that: The system includes a main coupling unit and a membrane-assisted impurity removal unit (2). The main coupling unit includes a vacuum distillation kettle (11) and a three-stage cooling crystallization device. The outlet of the raw material pump (100) is connected to the inlet of the vacuum distillation kettle (11) through a pipeline. The vacuum distillation kettle (11) distills 1,3-dimethylimidazolinone under a set pressure. The three-stage cooling crystallization device includes a first cooling crystallizer (121), a second cooling crystallizer (122), and a third cooling crystallizer (123). The inlet of the first cooling crystallizer (121) is connected to the vacuum distillation kettle (11) through a pipeline and a valve. The top outlet of the pressure distillation vessel (11) is connected, the inlet of the second cooling crystallizer (122) is connected to the residual steam outlet of the first cooling crystallizer (121) through pipes and valves, the inlet of the third cooling crystallizer (123) is connected to the residual steam outlet of the second cooling crystallizer (122) through pipes and valves, and the membrane-assisted impurity removal unit (2) is connected to the crystallization product outlets of the first cooling crystallizer (121), the second cooling crystallizer (122) and the third cooling crystallizer (123) respectively, and the residual solvent is removed by nitrogen purging; The first cooling crystallizer (121) includes a crystallization cylinder (1211), a jacket (1212), and a centrifugal stirring scraper device (1213). The crystallization cylinder (1211) has a steam inlet at the top, a crystallized material outlet at the bottom, and a residual steam outlet at the bottom. The jacket (1212) is installed on the inner wall of the crystallization cylinder (1211). The centrifugal stirring scraper device (1213) is installed inside the crystallization cylinder (1211) to homogenize the steam inside the crystallization cylinder (1211) and scrape off the crystallized material from the inner wall of the jacket (1212). The centrifugal stirring scraper device (1213) includes a servo motor and a blade. The servo motor is installed at the bottom of the crystallization cylinder (1211), and the blade is installed on the power shaft of the servo motor. The blade is made of polytetrafluoroethylene. A scraper part is provided on the outside of the blade. The gap between the outside of the scraper part and the cylinder wall is 0.3mm-0.5mm. When the blade rotates, the scraper part scrapes the crystals on the inner wall of the crystallization cylinder (1211). The inlet and outlet of the jacket (1212) are connected to the inlet and outlet of the coolant circulation device (1214) respectively, and the coolant solution circulates inside the jacket (1212). It also includes an intelligent control unit, which includes an infrared spectrometer (33) and three temperature transmitters (34); the infrared spectrometer monitors the DMI characteristic peak, and the three temperature transmitters (34) monitor the temperature inside the first cooling crystallizer (121), the second cooling crystallizer (122) and the third cooling crystallizer (123) respectively; The infrared spectrometer (33) of the intelligent control unit monitors the characteristic peak of DMI at the top of the reactor in real time. When the peak intensity is greater than or equal to 98%, the steam outlet valve at the top of the reactor is opened. The DMI steam at the top of the reactor enters the first cooling crystallizer (121) through the pipeline for primary crystallization.

2. The 1,3-dimethylimidazolinone purification device based on coupled cooling according to claim 1, characterized in that: The vacuum distillation vessel (11) includes a vessel body (111), a θ-ring corrugated packing module (112), a heating module (113), and a vacuum module (114). The θ-ring corrugated packing module (112) is installed in the middle of the vessel body (111), and the heating module (113) is installed at the bottom of the vessel body (111). It is heated by circulating heat transfer oil. The vessel body (111) has a feed inlet in the middle, a distillation steam outlet at the top, and a residue outlet at the bottom.

3. The 1,3-dimethylimidazolinone purification device based on coupled cooling according to claim 2, characterized in that: The θ-ring corrugated packing module (112) uses stainless steel θ-rings as packing material, with a stacking height of 2.8m-3.2m, a specific surface area of ​​200m² / m³-240m² / m³, and a porosity of 0.90-0.

94. The heating module (113) is composed of heating coils, which are spirally distributed at the bottom of the vessel body and heated by circulating heat transfer oil. The temperature control range is 80-180℃. The pressure reduction module (114) includes a vacuum regulating valve (1141), a water ring vacuum pump (1142), and a vacuum buffer tank (1143). The suction port of the water ring vacuum pump (1142) is connected to the suction port of the vacuum buffer tank (1143). The buffer suction port of the vacuum buffer tank (1143) is connected to the pressure reduction port of the vessel body (111) through the vacuum regulating valve (1141) and the pipeline, so as to control the vacuum degree in the vessel body (111) at 0.05-0.095MPa.

4. The 1,3-dimethylimidazolinone purification device based on coupled cooling according to claim 3, characterized in that: The second cooling crystallizer (122) and the third cooling crystallizer (123) adopt the same structure as the first cooling crystallizer (121).

5. The 1,3-dimethylimidazolinone purification device based on coupled cooling according to claim 4, characterized in that: The membrane-assisted impurity removal unit (2) includes multiple hollow fiber membrane modules (21) and a nitrogen circulation device (22). The hollow fiber membrane module (21) includes a membrane-assisted stainless steel tube (211) and multiple membrane bundles (212). One end of the membrane-assisted stainless steel tube (211) is connected to the crystal distillation outlet at the bottom of the crystallization cylinder (1211), and the other end is connected to the inlet of the finished product storage tank (101) through a conveying device. Multiple membrane bundles (212) are fixed inside the membrane-assisted stainless steel tube (211) at equal intervals by epoxy resin. The inlet and outlet of the nitrogen circulation device (22) are connected to the air inlet and air outlet of the membrane-assisted stainless steel tube (211) of the multiple hollow fiber membrane modules (21) respectively, and nitrogen is supplied to the hollow fiber membrane module (21).

6. The 1,3-dimethylimidazolinone purification apparatus based on coupled cooling according to claim 5, characterized in that: It also includes an intelligent control unit, which includes a digital thermometer (31), a level gauge (32), an infrared spectrometer (33), three temperature transmitters (34), and an industrial control computer (35). The digital thermometer (31) detects the internal temperature of the vessel (111), the level gauge (32) monitors the liquid level inside the vessel (111), the infrared spectrometer (33) is installed at the top inside the vessel (111) and monitors the DMI characteristic peak, and the three temperature transmitters (34) respectively monitor the first The industrial control computer (35) communicates with the digital thermometer (31), the level gauge (32), the infrared spectrometer (33), and the three temperature transmitters (34) respectively, and controls the execution of the heating module (113), the pressure reducing module (114), the centrifugal stirring scraper device (1213), the coolant circulation device (1214), and the nitrogen circulation device (22) respectively.

7. A purification process for 1,3-dimethylimidazolinone based on coupled cooling, characterized in that: The purification of 1,3-dimethylimidazolinone using the coupled cooling-based 1,3-dimethylimidazolinone purification apparatus according to claim 6 includes the following steps: Step 1: Industrial-grade DMI raw material pretreatment, and the filtered raw material is transported to the vacuum distillation vessel (11) by the raw material pump (100). When the liquid level in the vacuum distillation vessel (11) reaches 50%-70% of the volume as monitored by the level gauge (32), the feed valve is closed. Step 2: Start the pressure reduction module (114) and use the water ring vacuum pump (1142) to evacuate the vacuum degree inside the vessel (111) to 0.05-0.095MPa; turn on the heating module (113) and use the spiral heating coil to raise the temperature at a rate of 1-2℃ / min, while maintaining the heat transfer oil circulation flow rate at 8-12m³ / h, so that the temperature inside the vessel rises to 100-150℃; Step 3: The raw material forms a gas-liquid two-phase countercurrent contact in the θ-ring corrugated packing module (112). The low-boiling material rises to the top of the vacuum distillation vessel (11) through the packing layer, while the high-boiling residue remains at the bottom of the vessel. The infrared spectrometer (33) of the intelligent control unit monitors the DMI characteristic peak at the top of the vessel in real time. When the peak intensity is greater than or equal to 98%, the steam outlet valve at the top of the vessel is opened. Step 4: DMI steam from the top of the reactor enters the first cooling crystallizer (121) through a pipeline for primary crystallization; The residual steam from the primary crystallizer enters the second cooling crystallizer (122) for secondary crystallization; The secondary residual steam enters the third cooling crystallizer (123) for tertiary crystallization; Step 5: The first, second and third stage crystallization products are collected by a screw conveyor and sent into the membrane-assisted stainless steel tube (211). Step 6: Start the nitrogen circulation device (22). After the nitrogen is preheated to 30-50℃, it is introduced into the hollow fiber membrane module (21) at a flow rate of 1-3L / min and purged at a pressure of 0.1-0.2MPa for 25-35min. Step 7: After purification, DMI is transported to the finished product storage tank (101) via pipeline, and the storage tank is maintained with nitrogen protection at 0.02-0.05MPa.

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