1, 3-dimethylimidazolinone purification device and process based on coupling cooling

Abstract

The invention discloses a 1, 3-dimethylimidazolinone purification device and process based on coupling cooling, and relates to the technical field of chemical purification, the 1, 3-dimethylimidazolinone purification device comprises a main body coupling unit and a membrane-assisted impurity removal unit, and the main body coupling unit comprises a vacuum rectifying still and a three-stage cooling crystallization device. According to the reduced-pressure rectifying still, the boiling point of 1, 3-dimethylimidazolinone (DMI) is reduced by utilizing a reduced-pressure environment, low-boiling-point substances such as formaldehyde and high-boiling-point residues are separated by combining the efficient mass transfer effect of the theta-ring corrugated packing, and DMI steam is preliminarily enriched. And the third-stage cooling crystallization device realizes fractional crystallization through a gradient temperature field by utilizing the melting point difference of DMI and impurities: high-purity DMI is separated preferentially in first-stage crystallization, residual DMI is recovered and impurities are intercepted in second-stage and third-stage crystallization, and crystals are removed in real time to avoid co-crystallization. The final product has high purity, and the yield is higher than that of traditional rectification. The operation temperature is reduced by vacuum rectification, repeated rectification is reduced by combining gradient crystallization, and the total energy consumption is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical purification, and in particular to a 1,3-dimethylimidazolidinone purification device and process based on coupled cooling. Background Art

[0002] 1,3-Dimethylimidazolidinone (DMI), a highly polar aprotic solvent widely used in high-end fields such as electronics and pharmaceuticals, faces multiple challenges in its purification. Currently, distillation, including azeotropic and extractive distillation, is the core method used in industry. However, this method faces significant bottlenecks: byproducts such as 1,3-dimethyl-2-imidazolidinone (DMI) have similar boiling points to DMI (both approximately 222-226°C), requiring distillation columns with extremely high theoretical plate numbers to separate them, resulting in significant energy consumption.

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

[0004] To improve purity, Chinese patent CN104649974B discloses a method for preparing electronic-grade 1,3-dimethyl-2-imidazolidinone. This method employs a combined oxidation-distillation-reduction-distillation process, using potassium persulfate oxidation and sodium dithionite reduction to remove impurities. While purity can reach over 99.9%, the yield is only 87%-88%, and the multi-step distillation process further increases energy consumption. Other auxiliary techniques, such as MgO / SiO2 composite salt adsorption, can remove some metal ions, but adsorbent regeneration is difficult, hindering scalable application. Extraction-distillation requires the use of solvents such as n-butanol, posing a risk of secondary contamination.

[0005] The core defects of existing technologies can be summarized into three points: First, it is energy-intensive. High-temperature distillation not only consumes a lot of energy, but may also cause partial decomposition of DMI; second, there is a contradiction between purity and yield. Repeated distillation is required to remove near-boiling impurities, resulting in a decrease in yield; third, impurity removal is incomplete, and 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] In order to solve the above technical problems, the present invention provides a 1,3-dimethylimidazolidinone purification device and process based on coupled cooling. The following technical solutions are adopted:

[0007] A 1,3-dimethylimidazolidinone purification device based on coupled cooling includes a main coupling unit and a membrane-assisted impurity removal unit. The main coupling unit includes a vacuum distillation kettle and a three-stage cooling crystallization device. The outlet of a raw material pump is connected to the feed port of the vacuum distillation kettle through a pipeline. The vacuum distillation kettle distills 1,3-dimethylimidazolidinone 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 steam outlet of the first cooling crystallizer through a pipeline and a valve, and the inlet of the third cooling crystallizer is connected to the residual steam outlet of the second cooling crystallizer through a pipeline and a valve. The membrane-assisted impurity removal unit is connected to the crystallized product outlets of the first cooling crystallizer, the second cooling crystallizer, and the third cooling crystallizer, respectively, and residual solvent is removed by nitrogen purging.

[0008] By adopting the above technical solution, the vacuum distillation kettle uses the reduced pressure environment to lower the boiling point of 1,3-dimethylimidazolidinone (DMI), combined with the efficient mass transfer effect of the θ-ring corrugated packing to separate low-boiling substances such as formaldehyde from high-boiling residues, and preliminarily enrich the DMI vapor.

[0009] The three-stage cooling crystallization device uses a gradient temperature field and utilizes the melting point difference between DMI and impurities (DMI melting point 7.5-8.2°C) to achieve step-by-step crystallization: the first-stage crystallization prioritizes the separation of high-purity DMI, while the second and third-stage crystallizations recover residual DMI and intercept impurities, removing crystals in real time to avoid co-crystallization.

[0010] By real-time monitoring of key parameters through infrared spectroscopy and temperature transmitters, the controller dynamically adjusts the heating, cooling, vacuum and other systems to ensure the coordinated and stable operation of each unit.

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

[0012] Vacuum distillation reduces the operating temperature, and combined with gradient crystallization, it reduces repeated distillation and reduces total energy consumption; the metal ion residue is less than or equal to 10ppb, and particulate impurities are completely removed, meeting the requirements of electronic-grade solvents.

[0013] Intelligent regulation of the entire process enables precise control of parameters, with minimal deviation in batch stability, making it suitable for large-scale continuous production.

[0014] This device breaks through the contradiction between purity, yield and energy consumption in traditional processes and provides an integrated solution for the efficient purification of high-polarity solvents.

[0015] Optionally, the vacuum distillation kettle includes a kettle 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 kettle body, the heating module is installed at the bottom of the kettle body, and is heated by circulating heat transfer oil. A feed port is set in the middle of the kettle body, a distillation steam outlet is set at the top, and a residue outlet is set at the bottom.

[0016] Optional, theta ring corrugated packing module is filled with stainless steel theta rings, with a stacking height of 2.8m-3.2m and a specific surface area of ​​200m 2 / m 3 -240m 2 / m 3 , porosity 0.90-0.94;

[0017] The heating module is composed of heating coils, which are spirally distributed at the bottom of the kettle body and heated by circulating thermal oil. The temperature control range is 80-180℃.

[0018] The pressure reducing module includes a vacuum regulating valve, a water ring vacuum pump and a vacuum buffer tank. The exhaust port of the water ring vacuum pump is connected to the exhaust port of the vacuum buffer tank. The buffer exhaust port of the vacuum buffer tank is connected to the pressure reducing port of the kettle body through the vacuum regulating valve and the pipeline, so that the vacuum degree in the kettle body is controlled at 0.05-0.095MPa.

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

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

[0021] The water ring vacuum pump stably extracts gas through the vacuum buffer tank and cooperates with the vacuum regulating valve to accurately control the vacuum degree in the kettle at 0.05-0.095MPa, lowering the boiling point of DMI from 2-6℃ at normal pressure to -150℃, achieving low-temperature distillation and reducing energy consumption and thermal degradation risks.

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

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

[0024] The vacuum buffer tank can buffer pressure fluctuations, and combined with the uniform heating of the spiral coil, the distillation process is 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 scraper device, the crystallization cylinder is provided with a steam inlet at the top, a crystallization distillation 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 scraper device is installed inside the crystallization cylinder for homogenizing the steam inside the crystallization cylinder and scraping off the crystallized material on the inner wall of the jacket.

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

[0027] Optionally, the inlet and outlet of the jacket are respectively connected to the inlet and outlet of the coolant circulation device, and a 4° C.-6° C. ethylene glycol solution circulates in the jacket.

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

[0029] By adopting the above technical solution, the first cooling crystallizer uses a 4-6°C ethylene glycol solution in the jacket to create a low-temperature environment, allowing the DMI vapor from the vacuum distillation kettle to condense and preferentially crystallize in the crystallization cylinder, taking advantage of the DMI melting point of 7.5-8.2°C. The second and third cooling crystallizers use the same structure, respectively using lower temperature refrigerants (such as -5°C calcium chloride solution and -20°C ethanol solution) to gradient cool the residual vapor, utilizing the difference in melting points between impurities and DMI (the melting point of impurities is usually below -10°C) to achieve step-by-step separation.

[0030] The centrifugal stirring scraper device drives the polytetrafluoroethylene blade to rotate through 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 blade scrapes off the wall crystals in real time to prevent the scaling layer from hindering heat transfer and ensure stable cooling efficiency.

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

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

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

[0034] By adopting the above technical solution, the polytetrafluoroethylene hollow fiber membrane bundle with a molecular weight cut-off of 500Da and a nano-scale pore structure can accurately intercept the tiny particles and colloidal impurities remaining in the crystallized product. Combined with the purge effect of the nitrogen circulation device, it can efficiently remove the residual solvent and trace moisture adsorbed on the crystal surface. According to the test, this unit can further improve the purity of the DMI product from 99.5% after crystallization to more than 99.99%, and the metal ions (Fe 3+ 、Cu 2+ The total residual amount of solvents (such as ethanol, ethanol, etc.) is reduced to below 10ppb, meeting the stringent requirements of the microelectronics field for ultra-high purity solvents.

[0035] Multiple membrane modules are designed in parallel, and the membrane bundles are fixed at equal intervals by epoxy resin, so that the crystallized product is in full contact with the membrane surface. The effective mass transfer area of ​​a single membrane module is 1.2m 2 , an improvement over traditional packed membrane modules. The convection effect created by nitrogen purge accelerates impurity diffusion, shortening the solvent residue removal time from 2 hours in traditional vacuum drying to 30 minutes, and reducing unit processing energy consumption to 30kW·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 liquid level meter, an infrared spectrometer, three temperature transmitters and an industrial control computer. The digital thermometer detects the internal temperature of the kettle body, the liquid level meter monitors the liquid level in the kettle body, the infrared spectrometer is installed on the top of the kettle body to monitor the DMI characteristic peak, and the three temperature transmitters respectively monitor the temperatures in the first cooling crystallizer, the second cooling crystallizer and the third cooling crystallizer. The industrial control computer is respectively communicated with the digital thermometer, the liquid level meter, the infrared spectrometer and the three temperature transmitters, and respectively controls the execution actions of the heating module, the pressure reducing module, the centrifugal stirring scraper device, the coolant circulation device and the nitrogen circulation device.

[0037] The 1,3-dimethylimidazolidinone purification process based on coupled cooling is to purify 1,3-dimethylimidazolidinone using a 1,3-dimethylimidazolidinone purification device based on coupled cooling, comprising the following steps:

[0038] Step 1: pre-treat the industrial-grade DMI raw material and deliver the filtered raw material to the vacuum distillation kettle through the raw material pump. When the liquid level in the vacuum distillation kettle reaches 50%-70% of the volume as monitored by the liquid level gauge, close the feed valve;

[0039] Step 2: Start the decompression module and use the water ring vacuum pump to pump the vacuum degree in the kettle to 0.05-0.095MPa; turn on the heating module and increase the temperature at a rate of 1-2℃ / min through the spiral heating coil, and maintain the heat transfer oil circulation flow rate at 8-12m 3 / h, raising the temperature in the kettle to -150℃;

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

[0041] Step 4: DMI steam from the top of the kettle enters the first cooling crystallizer through a pipeline for primary crystallization. The centrifugal stirring scraper device is started, and the polytetrafluoroethylene blade rotates at 50-80 rpm. The scraper part scrapes off the wall crystals in real time, and the crystals are discharged through the bottom distillation outlet every 20-30 minutes.

[0042] The residual steam from the first crystallizer enters the second cooling crystallizer for secondary crystallization; the residual steam from the second 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 fed into a membrane-assisted stainless steel pipe;

[0044] Step 6: Start the nitrogen circulation device, preheat the nitrogen to 30-50°C, and then pass it into the hollow fiber membrane module at a flow rate of 1-3 L / min, and purge it at a pressure of 0.1-0.2 MPa for 25 minutes;

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

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

[0047] The present invention provides a coupled cooling-based 1,3-dimethylimidazolidinone purification device and process. A vacuum distillation reactor utilizes a reduced pressure environment to lower the boiling point of 1,3-dimethylimidazolidinone (DMI). Combined with the efficient mass transfer of θ-ring corrugated packing, this system separates low-boiling substances, such as formaldehyde, from high-boiling residues, initially enriching DMI vapor. A three-stage cooling crystallization device utilizes a gradient temperature field, exploiting the melting point difference between DMI and impurities to achieve fractional crystallization. The primary crystallization prioritizes the separation of high-purity DMI, while the secondary and tertiary crystallization stages recover residual DMI and trap impurities, removing crystals in real time to prevent co-crystallization.

[0048] By real-time monitoring of key parameters through infrared spectroscopy and temperature transmitters, the controller dynamically adjusts the heating, cooling, vacuum and other systems to ensure the coordinated and stable operation of each unit.

[0049] The final product is highly pure, exceeding the traditional process by more than 0.5 percentage points, and the yield is 8%-10% higher than traditional distillation. Vacuum distillation reduces operating temperatures, and combined with gradient crystallization, it reduces repeated distillation cycles and reduces 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic diagram of the connection principle of components of the 1,3-dimethylimidazolidinone purification device based on coupled cooling of the present invention;

[0051] Figure 2 This is a schematic diagram of the structural principle of the vacuum distillation kettle of the 1,3-dimethylimidazolidinone purification device based on coupled cooling of the present invention;

[0052] Figure 3 This is a schematic diagram of the structural principle of the first cooling crystallizer of the 1,3-dimethylimidazolidinone purification device based on coupled cooling of the present invention;

[0053] Figure 4 This is a schematic diagram of the structural principle of the hollow fiber membrane module of the 1,3-dimethylimidazolidinone purification device based on coupled cooling of the present invention;

[0054] Figure 5It is a schematic diagram of the connection principle of the control components of the 1,3-dimethylimidazolidinone purification device based on coupled cooling of the present invention.

[0055] Explanation of the accompanying symbols: 11. Vacuum distillation kettle; 111. Kettle body; 112. θ-ring corrugated packing module; 113. Heating module; 114. Decompression 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 assembly; 211. Membrane-assisted stainless steel pipe; 212. Multiple membrane bundles; 22. Nitrogen circulation device; 100. Raw material pump; 101. Finished product storage tank; 31. Digital thermometer; 32. Liquid level meter; 33. Infrared spectrometer; 34. Temperature transmitter; 35. Industrial control computer. DETAILED DESCRIPTION

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

[0057] The embodiments of the present invention disclose a 1,3-dimethylimidazolidinone purification device and process based on coupled cooling.

[0058] Reference Figure 1 - Figure 5 , Example 1, a 1,3-dimethylimidazolidinone purification device based on coupled cooling, comprising a main coupling unit and a membrane-assisted impurity removal unit 2, the main coupling unit comprising a vacuum distillation kettle 11 and a three-stage cooling crystallization device, the outlet of the raw material pump 100 is connected to the feed port of the vacuum distillation kettle 11 through a pipeline, the vacuum distillation kettle 11 distills 1,3-dimethylimidazolidinone at a set pressure, the three-stage cooling crystallization device comprises a first cooling crystallizer 121, a second cooling crystallizer 122 and a third cooling crystallizer 123; the first cooling crystallizer The inlet of the device 121 is connected to the top outlet of the vacuum distillation kettle 11 through a pipeline and a valve, the inlet of the second cooling crystallizer 122 is connected to the residual steam outlet of the first cooling crystallizer 121 through a pipeline and a valve, the inlet of the third cooling crystallizer 123 is connected to the residual steam outlet of the second cooling crystallizer 122 through a pipeline and a valve, and the membrane-assisted impurity removal unit 2 is respectively connected to the crystallized product outlets of the first cooling crystallizer 121, the second cooling crystallizer 122 and the third cooling crystallizer 123, and the residual solvent is removed by nitrogen purging.

[0059] The vacuum distillation kettle 11 utilizes a reduced pressure environment to lower the boiling point of 1,3-dimethylimidazolidinone (DMI), and combines the efficient mass transfer effect of the θ-ring corrugated packing to separate low-boiling substances such as formaldehyde and high-boiling residues, thereby preliminarily enriching DMI vapor.

[0060] The three-stage cooling crystallization device uses a gradient temperature field and utilizes the melting point difference between DMI and impurities (DMI melting point 7.5-8.2°C) to achieve step-by-step crystallization: the first-stage crystallization prioritizes the separation of high-purity DMI, while the second and third-stage crystallizations recover residual DMI and intercept impurities, removing crystals in real time to avoid co-crystallization.

[0061] By real-time monitoring of key parameters through infrared spectroscopy and temperature transmitters, the controller dynamically adjusts the heating, cooling, vacuum and other systems to ensure the coordinated and stable operation of each unit.

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

[0063] Vacuum distillation reduces the operating temperature, and combined with gradient crystallization, it reduces repeated distillation and reduces total energy consumption; the metal ion residue is less than or equal to 10ppb, and particulate impurities are completely removed, meeting the requirements of electronic-grade solvents.

[0064] Intelligent regulation of the entire process enables precise control of parameters, with minimal deviation in batch stability, making it suitable for large-scale continuous production.

[0065] This device breaks through the contradiction between purity, yield and energy consumption in traditional processes and provides an integrated solution for the efficient purification of high-polarity solvents.

[0066] In Example 2, the vacuum distillation kettle 11 includes a kettle 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 kettle body 111, and the heating module 113 is installed at the bottom of the kettle body 111. It is heated by circulating heat transfer oil. A feed port is set in the middle of the kettle body 111, a distillation steam outlet is set at the top, and a residue outlet is set at the bottom.

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

[0068] The heating module 113 is composed of a heating coil, which is spirally distributed at the bottom of the kettle body and is heated by circulating heat transfer oil with a temperature control range of 80-180°C.

[0069] The decompression module 114 includes a vacuum regulating valve 1141, a water ring vacuum pump 1142 and a vacuum buffer tank 1143. The exhaust port of the water ring vacuum pump 1142 is connected to the exhaust port of the vacuum buffer tank 1143. The buffer exhaust port of the vacuum buffer tank 1143 is connected to the decompression port of the kettle body 111 through the vacuum regulating valve 1141 and the pipeline, so that the vacuum degree in the kettle body 111 is controlled at 0.05-0.095MPa.

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

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

[0072] The water ring vacuum pump 1142 steadily extracts air through the vacuum buffer tank 1143, and cooperates with the vacuum regulating valve 1141 to accurately control the vacuum degree in the kettle at 0.05-0.095MPa, lowering the boiling point of DMI from 222-226℃ at normal pressure to 100-150℃, achieving low-temperature distillation and reducing energy consumption and thermal degradation risks.

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

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

[0075] The vacuum buffer tank 1143 can buffer pressure fluctuations and, combined with the uniform heating of the spiral coil, make 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 is provided with a steam inlet at the top, a crystallization distillation outlet at the bottom, and a residual steam outlet at the lower part, 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, and is used to homogenize the steam inside the crystallization cylinder 1211 and scrape off the crystallized material on the inner wall of the jacket 1212.

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

[0078] In Example 6, the inlet and outlet of the jacket 1212 are respectively connected to the inlet and outlet of the coolant circulation device 1214 , and a 4° C.-6° C. ethylene glycol solution circulates in 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, allowing the DMI vapor from the vacuum distillation reactor to condense and preferentially crystallize within the crystallization cylinder 1211, taking advantage of the DMI melting point of 7.5-8.2°C. The second and third cooling crystallizers employ the same structure, using a lower-temperature refrigerant (e.g., -5°C calcium chloride solution, -20°C ethanol solution) to gradient cool the residual vapor, respectively. This utilizes the difference in melting points between impurities and DMI (the melting point of impurities is typically below -10°C) to achieve step-by-step separation.

[0081] The centrifugal stirring scraper device 1213 drives the polytetrafluoroethylene blade to rotate through 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 blade scrapes off the wall crystals in real time to prevent the scaling layer from hindering heat transfer and ensure stable cooling efficiency.

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

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

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

[0085] Example 8, the membrane-assisted impurity removal unit 2 includes multiple groups of hollow fiber membrane components 21 and a nitrogen circulation device 22, the hollow fiber membrane components 21 include 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 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, and multiple membrane bundles 212 are fixed at equal intervals inside the membrane-assisted stainless steel tube 211 by epoxy resin, and the inlet and outlet of the nitrogen circulation device 22 are respectively connected to the air inlet and air outlet of the membrane-assisted stainless steel tube 211 of the multiple groups of hollow fiber membrane components 21, so that nitrogen is filled into the hollow fiber membrane component 21.

[0086] The polytetrafluoroethylene hollow fiber membrane bundle 212 has a molecular weight cut-off of 500Da and a nano-scale pore structure, which can accurately intercept the tiny particles and colloidal impurities remaining in the crystallized product. Combined with the purge effect of the nitrogen circulation device 22, it can effectively remove the residual solvent and trace moisture adsorbed on the crystal surface. According to testing, this unit can further improve the purity of the DMI product from 99.5% after crystallization to more than 99.99%, and the metal ion (Fe 3+ 、Cu 2+ The total residual amount of solvents (such as ethanol, ethanol, etc.) is reduced to below 10ppb, meeting the stringent requirements of the microelectronics field for ultra-high purity solvents.

[0087] Multiple membrane modules are designed in parallel, and the membrane bundles are fixed at equal intervals by epoxy resin, so that the crystallized product is in full contact with the membrane surface. The effective mass transfer area of ​​a single membrane module is 1.2m 2 , an improvement over traditional packed membrane modules. The convection effect created by nitrogen purge accelerates impurity diffusion, shortening the solvent residue removal time from 2 hours in traditional vacuum drying to 30 minutes, and reducing unit processing energy consumption to 30kW·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 liquid level meter 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 kettle body 111, the liquid level meter 32 monitors the liquid level in the kettle body 111, the infrared spectrometer 33 is installed on the top of the kettle body 111 to monitor the DMI characteristic peak, and the three temperature transmitters 34 respectively monitor the temperatures in the first cooling crystallizer 121, the second cooling crystallizer 122 and the third cooling crystallizer 123. The industrial control computer 35 is respectively communicated with the digital thermometer 31, the liquid level meter 32, the infrared spectrometer 33 and the three temperature transmitters 34, and respectively controls the execution actions 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.

[0089] Example 10, a 1,3-dimethylimidazolidinone purification process based on coupled cooling, wherein 1,3-dimethylimidazolidinone is purified using a 1,3-dimethylimidazolidinone purification apparatus based on coupled cooling, comprising the following steps:

[0090] Step 1: pre-treat the industrial-grade DMI raw material and deliver the filtered raw material to the vacuum distillation reactor 11 through the raw material pump 100. When the liquid level in the vacuum distillation reactor 11 reaches 50%-70% of the volume as monitored by the liquid level gauge 32, close the feed valve;

[0091] Step 2: Start the decompression module 114 and pump the vacuum degree in the kettle body 111 to 0.05-0.095 MPa through the water ring vacuum pump 1142; start the heating module 113 and increase the temperature at a rate of 1-2°C / min through the spiral heating coil, and maintain the heat transfer oil circulation flow rate at 8-12m 3 / h, raising the temperature in the kettle to 100-150℃;

[0092] Step 3: The raw materials form 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 reactor 11 through the packing layer, and the high-boiling residue remains at the bottom of the reactor. The infrared spectrometer 33 of the intelligent control unit monitors the DMI characteristic peak at the reactor top in real time. When the peak intensity is greater than or equal to 98%, the steam outlet valve at the reactor top is opened.

[0093] Step 4: DMI steam from the top of the kettle enters the first cooling crystallizer 121 through a pipeline for primary crystallization. The centrifugal stirring scraper device 1213 is started, and the polytetrafluoroethylene blade rotates at 50-80 rpm. The scraper part scrapes off the wall crystals 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 secondary residual steam 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 a membrane-assisted stainless steel pipe 211;

[0096] Step 6: Start the nitrogen circulation device 22, preheat the nitrogen to 30-50°C, and then pass it into the hollow fiber membrane module 21 at a flow rate of 1-3 L / min, and purge it at a pressure of 0.1-0.2 MPa for 25-35 minutes;

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

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

[0099] Vacuum distillation kettle 11: 316L stainless steel, volume 3000L, kettle diameter 800mm, height 2500mm; θ ring corrugated packing module 112 uses Φ5mm stainless steel θ ring, stacking height 3m, specific surface area 220m 2 / m 3 , porosity 0.92; heating module 113 is Inconel625 spiral coil, area 8m 2 , thermal oil model L-QD320; pressure reducing module 114 with 2BV5161 water ring vacuum pump, pumping speed 60m 3 / h, vacuum buffer tank capacity 500L.

[0100] Three-stage cooling crystallization device:

[0101] The first cooling crystallizer 121: diameter 500mm, height 1500mm, jacket effective heat exchange area 4.5m 2 , polytetrafluoroethylene blade, diameter 490mm, the gap between the scraper and the cylinder wall is 0.4mm;

[0102] The second / third cooling crystallizer: diameters are 400mm / 300mm, heights are 1200mm / 1000mm, and the structure is the same as the first crystallizer;

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

[0104] Membrane-assisted impurity removal unit 2: 3 groups of hollow fiber membrane modules connected in parallel, each group contains 150 membrane fibers, inner diameter 0.6mm, outer diameter 1.4mm, effective membrane area 1.2m 2 / set; nitrogen circulation device is equipped with D07-19B mass flow controller.

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

[0106] Step 1: Take 5000kg of industrial grade DMI with a purity of 95.2%, containing 0.4% near-boiling impurities and 0.3% metal ions, and filter it through a 0.2μm precision filter at a pressure of 0.25MPa and a flow rate of 8m 3 / h after filtration, and then transported to the vacuum distillation kettle 11 through the raw material pump 100. When the liquid level reaches 1800L (60% volume), the feed valve is closed. Step 2: Start the decompression module 114 and stabilize the vacuum degree in the kettle at 0.08MPa; the heating module is heated to 120℃ at a rate of 1.5℃ / min, and the heat transfer oil circulation flow rate is 10m 3 / h; the raw materials are separated by mass transfer in the θ-ring packing layer, and the low-boiling substances are discharged from the top of the tower.

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

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

[0109] Secondary crystallization: residual steam enters the second crystallizer, -5℃, stirring speed 80r / min, 105kg of crystals are discharged every 60min, and the crystallization rate is 50%;

[0110] Tertiary crystallization: The residual steam enters the third crystallizer at -20℃, recovers about 25kg of trace DMI, and discharges 120kg 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 30°C nitrogen (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 with a yield of 94% was sent to the finished product storage tank, maintained at 0.03 MPa nitrogen protection, and completed a single batch production in a total of about 8 hours.

[0113] The comparison test results between the product and the traditional process are shown in Table 1:

[0114] Table 1

[0115]

[0116]

[0117] This embodiment uses a vacuum distillation-gradient crystallization-membrane purification coupling process to improve product purity by 0.79-0.99 percentage points compared with the traditional process, increase yield by 9-12 percentage points, and reduce energy consumption by 33%-42%; the control of metal ion residues and particulate impurities meets the standards of electronic-grade solvents, and the batch stability is significantly better than that of traditional processes, which can meet the large-scale demand for ultra-high-purity DMI in fields such as microelectronics and high-end medicine.

[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, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A 1,3-dimethylimidazolidinone purification device based on coupled cooling, characterized in that: The invention comprises a main body coupling unit and a membrane-assisted impurity removal unit (2), wherein the main body coupling unit comprises a vacuum distillation kettle (11) and a three-stage cooling crystallization device, wherein the outlet of the raw material pump (100) is connected to the feed port of the vacuum distillation kettle (11) through a pipeline, the vacuum distillation kettle (11) distills 1,3-dimethylimidazolidinone under a set pressure, and the three-stage cooling crystallization device comprises 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 kettle (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 a pipeline and a valve, the inlet of the third cooling crystallizer (123) is connected to the residual steam outlet of the second cooling crystallizer (122) through a pipeline and a valve, the membrane-assisted impurity removal unit (2) is respectively connected to the crystallized product outlets of the first cooling crystallizer (121), the second cooling crystallizer (122) and the third cooling crystallizer (123), and the residual solvent is removed by nitrogen purging.

2. The 1,3-dimethylimidazolidinone purification device based on coupled cooling according to claim 1, characterized in that: The vacuum distillation kettle (11) comprises a kettle 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 kettle body (111), and the heating module (113) is installed in the bottom of the kettle body (111) and is heated by circulating heat-conducting oil. A feed inlet is provided in the middle of the kettle body (111), a distillation steam outlet is provided at the top, and a residue outlet is provided at the bottom.

3. The 1,3-dimethylimidazolidinone purification device based on coupled cooling according to claim 2, characterized in that: The packing of the θ ring corrugated packing module (112) is stainless steel θ ring, with a stacking height of 2.8m-3.2m and a specific surface area of ​​200m 2 / m 3 -240m 2 / m 3 , porosity 0.90-0.94; The heating module (113) is composed of a heating coil, which is spirally distributed at the bottom of the kettle body and is heated by circulating heat-conducting oil with a temperature control range of 80-180°C; The decompression module (114) comprises a vacuum regulating valve (1141), a water ring vacuum pump (1142) and a vacuum buffer tank (1143). The air extraction port of the water ring vacuum pump (1142) is connected to the air extraction port of the vacuum buffer tank (1143). The buffer air extraction port of the vacuum buffer tank (1143) is connected to the decompression port of the kettle body (111) through the vacuum regulating valve (1141) and a pipeline, so that the vacuum degree in the kettle body (111) is controlled at 0.05-0.095 MPa.

4. The 1,3-dimethylimidazolidinone purification device based on coupled cooling according to claim 3, characterized in that: The first cooling crystallizer (121) includes a crystallization cylinder (1211), a jacket (1212) and a centrifugal stirring scraper device (1213). The crystallization cylinder (1211) is provided with a steam inlet at the top, a crystal distillation outlet at the bottom, and a residual steam outlet at the lower part. 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) and is used to homogenize the steam inside the crystallization cylinder (1211) and scrape off the crystallized material on the inner wall of the jacket (1212).

5. The 1,3-dimethylimidazolidinone purification device based on coupled cooling according to claim 4, characterized in that: The centrifugal stirring scraper device (1213) includes a servo motor and a paddle. The servo motor is installed at the bottom of the crystallization cylinder (1211). The paddle is installed on the power shaft of the servo motor. The paddle is made of polytetrafluoroethylene. A scraper portion is provided on the outside of the paddle. The gap between the outside of the scraper portion and the cylinder wall is 0.3mm-0.5mm. When the paddle rotates, the scraper portion scrapes off the crystals on the inner wall of the crystallization cylinder (1211).

6. The 1,3-dimethylimidazolidinone purification device based on coupled cooling according to claim 5, characterized in that: The inlet and outlet of the jacket (1212) are respectively connected to the inlet and outlet of the cooling liquid circulation device (1214), and the cooling solution circulates in the jacket (1212).

7. The 1,3-dimethylimidazolidinone purification device based on coupled cooling according to claim 6, characterized in that: The second cooling crystallizer (122) and the third cooling crystallizer (123) adopt the same structure as the first cooling crystallizer (121).

8. The 1,3-dimethylimidazolidinone purification device based on coupled cooling according to claim 7, characterized in that: The membrane-assisted impurity removal unit (2) includes multiple groups of hollow fiber membrane assemblies (21) and a nitrogen circulation device (22). The hollow fiber membrane assembly (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 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. The multiple membrane bundles (212) are fixed at equal intervals inside the membrane-assisted stainless steel tube (211) by epoxy resin. The inlet and outlet of the nitrogen circulation device (22) are respectively connected to the air inlet and air outlet of the membrane-assisted stainless steel tube (211) of the multiple groups of hollow fiber membrane assemblies (21), and nitrogen is filled into the hollow fiber membrane assembly (21).

9. The 1,3-dimethylimidazolidinone purification device based on coupled cooling according to claim 8, characterized in that: The device also includes an intelligent control unit, which includes a digital thermometer (31), a liquid level meter (32), an infrared spectrum detector (33), three temperature transmitters (34) and an industrial control computer (35). The digital thermometer (31) detects the internal temperature of the kettle body (111), the liquid level meter (32) monitors the liquid level in the kettle body (111), the infrared spectrum detector (33) is installed on the top of the kettle body (111) to monitor the DMI characteristic peak, and the three temperature transmitters (34) respectively monitor the first The temperatures in the cooling crystallizer (121), the second cooling crystallizer (122) and the third cooling crystallizer (123) are respectively communicated with the digital thermometer (31), the liquid level meter (32), the infrared spectrum detector (33) and the three temperature transmitters (34), and respectively control the execution actions of the heating module (113), the pressure reducing module (114), the centrifugal stirring scraper device (1213), the cooling liquid circulation device (1214) and the nitrogen circulation device (22).

10. A 1,3-dimethylimidazolidinone purification process based on coupled cooling, characterized in that: Purifying 1,3-dimethylimidazolidinone using the coupled cooling-based 1,3-dimethylimidazolidinone purification device according to claim 9 comprises the following steps: Step 1: pre-treating industrial-grade DMI raw materials and delivering the filtered raw materials to a vacuum distillation reactor (11) via a raw material pump (100). When the liquid level in the vacuum distillation reactor (11) reaches 50%-70% of the volume as monitored by a liquid level meter (32), the feed valve is closed; Step 2: Start the decompression module (114) and pump the vacuum degree in the kettle body (111) to 0.05-0.095 MPa through the water ring vacuum pump (1142); start the heating module (113) and heat the kettle at a rate of 1-2 ° C / min through the spiral heating coil, and keep the heat transfer oil circulation flow rate at 8-12m 3 / h, raising the temperature in the kettle to 100-150℃; Step 3: The raw materials form a gas-liquid two-phase countercurrent contact in the θ-ring corrugated packing module (112), and the low-boiling substances rise to the top of the vacuum distillation reactor (11) through the packing layer, and the high-boiling residues remain at the bottom of the reactor; the infrared spectrometer (33) of the intelligent control unit monitors the DMI characteristic peak at the reactor top in real time, and when the peak intensity is greater than or equal to 98%, the steam outlet valve at the reactor top is opened; Step 4: DMI steam from the top of the kettle 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 then sent into a membrane-assisted stainless steel pipe (211); Step 6: Start the nitrogen circulation device (22), preheat the nitrogen to 30-50°C, and then pass it into the hollow fiber membrane module (21) at a flow rate of 1-3 L / min, and purge it at a pressure of 0.1-0.2 MPa for 25-35 minutes; Step 7: The purified DMI is transported to a finished product storage tank (101) via a pipeline, and the storage tank is maintained at 0.02-0.05 MPa nitrogen protection.

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