Production method of N, N-dimethylethanolamine

Abstract

The invention relates to a production method of N, N-dimethylethanolamine, and belongs to the technical field of organic compound preparation. The problems of high energy consumption, low product yield, more impurities and the like of the preparation method of N, N-dimethylethanolamine in the prior art are solved. According to the production method disclosed by the invention, the compound ionic liquid is used as a catalyst to catalyze the reaction of ethylene oxide and dimethylamine to obtain N, N-dimethylethanolamine. According to the production method, the composite ionic liquid is adopted as the catalyst, so that the production energy consumption is reduced, the EO conversion rate and the DMEA selectivity are obviously improved, the product has few impurities and high purity which is not less than 99.98%, the problems that the catalyst is not easy to recycle and separate and the like are solved, and a good effect is achieved.

Description

Technical Field

[0001] This invention belongs to the field of organic compound preparation technology, specifically relating to a method for producing N,N-dimethylethanolamine. Background Technology

[0002] N,N-Dimethylethanolamine (DMEA) is a versatile additive widely used in polyurethane foam, coatings, paints, electrophoretic paints, epoxy and acrylic resin curing, water treatment, gas treatment, and resin synthesis to improve product performance and quality.

[0003] Patent CN 101648880 B discloses a method for preparing DMEA, comprising the following steps: (1) raw material mixing; (2) synthesis reaction; (3) deamination treatment; (4) flash evaporation treatment; (5) absorption treatment; and (6) distillation treatment to separate the DMEA product. This preparation method uses the DMEA pre-distillate instead of the circulating liquid used in the original process, increasing the DMEA content in the crude product from 70%–80% to 95%–99%, reducing the moisture content from 20%–30% to 1%–5%, reducing the impurities from 1.5%–2% to 0.3%, decreasing the ethylene oxide consumption from 0.56–0.59 to 0.51–0.54, and reducing the dimethylamine consumption from 0.58–0.60 to 0.53–0.56, thereby reducing the consumption of raw materials and energy.

[0004] Patent CN 115894261 B discloses an industrial-scale preparation method for DMEA, comprising: loading a catalyst into the catalyst tubes of a reactor; injecting water into the water seal of the isolation piston at the top of the reactor until the water seal level of the isolation piston reaches a first preset level; when the pressure of the reactor reaches a first pressure, adding a dimethylamine aqueous solution to the reactor until the liquid level in the reactor reaches a second preset level, allowing the dimethylamine aqueous solution to circulate in the reactor and a liquid phase circulation device; after the reactor reaches a preset temperature, introducing ethylene oxide gas into the reactor until the isolation piston rises from its initial position to a predetermined position; reacting the dimethylamine aqueous solution and the ethylene oxide gas, and after the isolation piston falls back to its initial position, repeating the feeding process until the amount of ethylene oxide introduced reaches a preset amount, thereby obtaining DMEA. This preparation method can ensure that the amination reaction proceeds in the forward direction, reduce the occurrence of side reactions, and improve the purity of the product.

[0005] Patent CN 115957697 A discloses a reactor for DMEA production and its production method, including a tank body, a tank cover, catalyst tubes, a piston sleeve, contact rods, and contacts. The tank cover is mounted on top of the tank body, and gaseous ethylene oxide and liquid dimethylamine flow through the tank body. Several catalyst tubes containing granular catalyst are fixedly connected to the tank body. A flexible piston sleeve is fixedly connected to the bottom of the tank cover. Colored water and pressurized nitrogen are filled between the piston sleeve and the tank cover. Contact rods are mounted on top of the piston sleeve, and two contacts are fixedly connected to the top of the tank cover at intervals. The piston sleeve rises to make contact between the contact rods and contacts and to connect the contacts with an electrical signal. This production method has the advantages of effectively inhibiting the hydration reaction of ethylene oxide and improving product yield.

[0006] Patent CN 107011191 B discloses a method for producing N,N-dimethyldiethylene glycolamine (DMAEE) and co-producing DMEA, comprising the following steps: (1) using dimethylamine aqueous solution and ethylene oxide as reaction raw materials in a molar ratio of 1:1 to 2.5; the heating reaction temperature is 40 to 140°C, the reaction pressure is 0 to 1.5 MPa, the reaction time is 2 to 6 h, and nitrogen gas is introduced to maintain the pressure during the reaction; (2) after the reaction is completed, the reaction product obtained in step (1) is subjected to vacuum distillation to obtain DEMA aqueous solution as the light component and DMAEE as the heavy component.

[0007] In existing technologies, industrial-scale DMEA production mostly uses water as a catalyst. This leads to unstable process control and low production efficiency. Furthermore, the addition of water increases the difficulty of separating and purifying the final product, resulting in lower purity and necessitating additional dehydration equipment. Therefore, developing a green catalytic production process that is energy-efficient and environmentally friendly is essential. Summary of the Invention

[0008] In view of this, in order to solve the defects of existing DMEA preparation methods such as high energy consumption, low product yield and many impurities, the present invention provides a method for producing N,N-dimethylethanolamine. This method has low energy consumption, is environmentally friendly, and significantly increases the selectivity of ethylene oxide (EO) and dimethylamine (DMA).

[0009] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows.

[0010] The method for producing N,N-dimethylethanolamine of the present invention uses a composite ionic liquid as a catalyst to catalyze the reaction of ethylene oxide and dimethylamine to obtain N,N-dimethylethanolamine.

[0011] The method for preparing the composite ionic liquid is as follows: Component A and Component B are mixed in a molar ratio of 1:0.2-5 and stirred at 60-100°C for 1-5 hours to obtain the composite ionic liquid;

[0012] Component A is one or more of the following: 1-(propyltrimethoxy)-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-octyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium acetate, 1-butyl-2,3-dimethylimidazolium chloride, N-butylpyridine bromide, tributylmethylammonium chloride, tetrabutylphosphine bromide, tetrabutylammonium bromide, tetraethylammonium bromide, tetramethylammonium bromide, 1-hydroxyethyl-2,3-dimethylimidazolium chloride, and N-butyl-N-methylpyrrolidine bromide.

[0013] Component B is one or more of ethylene glycol, diethylene glycol, triethylene glycol, glycerol, dipropylene glycol, caprolactam, ethanolamine, diethanolamine, and triethanolamine.

[0014] Preferably, the mass ratio of ethylene oxide, dimethylamine, and catalyst is 1:0.5-50:0.0005-0.5; more preferably, the mass ratio of ethylene oxide, dimethylamine, and catalyst is 1:5-20:0.001-0.1.

[0015] Preferably, the reaction temperature is 80–180°C, more preferably 110–150°C, the reaction pressure is 0.1–5 MPa, and the reaction time is 0.1–3 h; more preferably, the reaction pressure is 0.5–2 MPa, and the reaction time is 0.5–1.5 h.

[0016] Preferably, after the reaction, the resulting reaction solution is distilled to recover the catalyst and then purified to obtain N,N-dimethylethanolamine.

[0017] More preferably, the production method includes the following steps: dimethylamine is fed to a first reactor, ethylene oxide is pressurized and mixed with a catalyst, and then fed to the first reactor. Ethylene oxide and dimethylamine undergo a catalytic reaction in the first reactor. The resulting liquid phase is cooled by heat exchange and recycled back to the inlet of the first reactor. The remaining portion enters a second reactor to continue the reaction. The crude product is sent to a crude product falling film reboiler. The resulting liquid phase is returned to the inlet of the first reactor as a catalyst for recycling. The gas phase is sent to a purification tower and a product tower for two purification processes to obtain N,N-dimethylethanolamine.

[0018] More preferably, the production method includes the following steps:

[0019] S1. Reaction Stage

[0020] Nitrogen gas is used to pressurize the ethylene oxide in the feed buffer tank. The pressurized ethylene oxide is combined with the bottom discharge of the first reactor, which has been cooled by the reaction circulating liquid cooler, and the catalyst, which has been pressurized by the circulating catalyst feed pump, and enters the upper part of the first reactor. Dimethylamine enters the lower part of the first reactor. The pressurized ethylene oxide and dimethylamine react under the action of the catalyst.

[0021] The gas phase from the top outlet of the first reactor goes to the ethylene oxide absorption system. The bottom discharge of the first reactor is divided into two streams. One stream is cooled by the reaction circulating liquid cooler and then merges with the pressurized ethylene oxide and the catalyst pressurized by the circulating catalyst feed pump, returning to the first reactor. The other stream enters the second reactor for further reaction. After the reaction is completed, the gas is discharged from the top of the second reactor.

[0022] S2. Circulating catalyst recovery stage

[0023] The top discharge from the second reactor is depressurized by a pressure reducing valve and enters the crude product tank for flash separation. The gas phase generated by flash separation goes to the ethylene oxide absorption system. The liquid phase generated by flash separation is pressurized by the falling film reboiler feed pump and then merges with the liquid phase pressurized by the refining tower bottom pump. It is then sent to the crude product falling film reboiler. The gas phase generated by the evaporation of the crude product falling film reboiler is sent to the refining tower. The unevaporated liquid phase flows into the circulating catalyst tank as a catalyst. After being pressurized by the circulating catalyst feed pump, it is sent to the outlet of the reaction circulating liquid cooler, where it merges with the pressurized ethylene oxide and the bottom discharge from the first reactor that has been cooled by the reaction circulating liquid cooler, and is recycled back to the first reactor.

[0024] During the reaction stage and the circulating catalyst recovery stage, if the catalyst is insufficient, the catalyst stored in the wet solvent tank is replenished by gravity flow into the circulating catalyst tank.

[0025] S3. Refining Stage

[0026] A portion of the liquid phase at the bottom of the refining tower is pressurized by the forced circulation pump of the refining tower reboiler, then sent to the falling film reboiler of the refining tower for reboiling and returned to the refining tower. Another portion is pressurized by the bottom pump of the refining tower and merged with the liquid phase pressurized by the feed pump of the falling film reboiler, then returned to the crude product falling film reboiler for flash evaporation. The vapor phase at the top of the refining tower is condensed by the top condenser of the refining tower and sent to the refining tower reflux tank. It is then pressurized by the refining tower reflux pump and returned to the refining tower. The side stream from the refining tower is pressurized by the side stream sampling pump and sent to the product tower.

[0027] The liquid phase at the bottom of the product tower is pressurized by the forced circulation pump of the product tower reboiler and then sent to the falling film reboiler of the product tower for reboiling before returning to the product tower. Alternatively, a portion of the liquid phase at the bottom of the product tower is pressurized by the forced circulation pump of the product tower reboiler and then sent to the falling film reboiler of the product tower for reboiling before returning to the product tower, while the other portion is pressurized by the industrial-grade product delivery pump and sent to the industrial-grade product tank.

[0028] The vapor phase at the top of the product tower is condensed by the product tower top condenser and sent to the product tower reflux tank. After being pressurized by the product tower reflux pump, it returns to the product tower. The side stream from the product tower is cooled by the product tower side stream cooler and sent to the electronic grade product buffer tank. After being pressurized by the electronic grade product external pump, it is sent to the electronic grade product tank.

[0029] In the most preferred embodiment, during the reaction stage, the catalyst is combined with the bottom discharge of the first reactor, which has been cooled by the reaction circulating liquid cooler, and then preheated by the start-up preheater before being combined with the pressurized ethylene oxide and entering the upper part of the first reactor.

[0030] The bottom discharge from the first reactor is pumped to the reaction circulating liquid cooler via the reaction liquid circulation pump.

[0031] Particularly preferred, in the reaction stage, the reaction temperature in the first reactor is 80–180°C, the reaction pressure is 0.1–5 MPa, and the reaction time is 0.1–3 h; most preferred, in the reaction stage, the reaction temperature in the first reactor is 110–150°C, the reaction pressure is 0.5–2 MPa, and the reaction time is 0.5–1.5 h.

[0032] Particularly preferred, in the reaction stage, the reaction temperature in the second reactor is 80–180°C, the reaction pressure is 0.1–5 MPa, and the reaction time is 0.1–3 h; most preferred, in the reaction stage, the reaction temperature in the second reactor is 110–150°C, the reaction pressure is 0.5–2 MPa, and the reaction time is 0.5–1.5 h.

[0033] Particularly preferred is that, in the circulating catalyst recovery stage, the flash separation temperature is 50–120°C and the pressure is 0.05–0.15 MPa.

[0034] In a particularly preferred embodiment, during the circulating catalyst recovery stage, the crude product falling film reboiler undergoes negative pressure evaporation operation at a temperature of 80–130°C and a pressure of 0.5–50 kPa.

[0035] Particularly preferred is that the first reactor is a jet-type reactor and the second reactor is a tower-type reactor.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) The method for producing N,N-dimethylethanolamine of the present invention uses a composite ionic liquid as a catalyst and does not use water as a solvent, which reduces production energy consumption, significantly increases EO conversion rate and DMEA selectivity, produces DMEA product with fewer impurities and high purity (≥99.98%), and solves problems such as the difficulty in catalyst recovery and separation, and has good effects.

[0038] (2) The method for producing N,N-dimethylethanolamine of the present invention uses a high-efficiency composite ionic liquid as a catalyst. After the catalyst is deactivated, it is directly recycled without generating waste liquid or waste residue that pollutes the environment.

[0039] (3) The method for producing N,N-dimethylethanolamine of the present invention can simultaneously obtain electronic grade N,N-dimethylethanolamine (purity ≥99.98%) and industrial grade N,N-dimethylethanolamine (purity ≥99.0%), and the output of both can be adjusted according to demand.

[0040] (4) In the production method of N,N-dimethylethanolamine of the present invention, the reaction stage can adopt a coupling method of jet tube reactor (first reactor) and tower reactor (second reactor) to improve reaction efficiency and selectivity of target product and reduce production energy consumption.

[0041] (5) In the method for producing N,N-dimethylethanolamine of the present invention, the distillation column (refining column and product column) can adopt heat pump distillation technology. The gas phase at the top of the column is compressed and then pressurized and heated to provide a heat source for the bottom of the column, thereby reducing the energy consumption of the equipment. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a process flow diagram of the production method of N,N-dimethylethanolamine according to the present invention;

[0044] In the diagram, 1. Feed buffer tank; 2. First reactor; 3. Reaction liquid circulation pump; 4. Reaction liquid cooler; 5. Start-up preheater; 6. Second reactor; 7. Crude product tank; 8. Falling film reboiler feed pump; 9. Crude product falling film reboiler; 10. Circulating catalyst tank; 11. Circulating catalyst feed pump; 12. Wet solvent tank; 13. Refining column; 14. Refining column reboiler forced circulation pump; 15. Refining column falling film reboiler; 16. Refining column bottom pump. 17. Refining tower top condenser; 18. Refining tower reflux tank; 19. Refining tower reflux pump; 20. Refining tower side-stream extraction pump; 21. Product tower; 22. Product tower reboiler forced circulation pump; 23. Product tower falling film reboiler; 24. Product tower top condenser; 25. Product tower reflux tank; 26. Product tower reflux pump; 27. Product tower side-stream extraction cooler; 28. Electronic grade product buffer tank; 29. ​​Electronic grade product external pump; 30. Industrial grade product external pump. Detailed Implementation

[0045] To further understand the present invention, preferred embodiments of the present invention are described below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0046] The method for producing N,N-dimethylethanolamine of the present invention uses a composite ionic liquid as a catalyst to catalyze the reaction of ethylene oxide and dimethylamine to obtain N,N-dimethylethanolamine.

[0047] The preparation method of the composite ionic liquid is as follows: Component A and component B are mixed in a molar ratio of 1:0.2 to 5 and stirred at 60 to 100°C for 1 to 5 hours to obtain the composite ionic liquid;

[0048] Component A is one or more of the following: 1-(propyltrimethoxy)-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-octyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium acetate, 1-butyl-2,3-dimethylimidazolium chloride, N-butylpyridine bromide, tributylmethylammonium chloride, tetrabutylphosphine bromide, tetrabutylammonium bromide, tetraethylammonium bromide, tetramethylammonium bromide, 1-hydroxyethyl-2,3-dimethylimidazolium chloride, and N-butyl-N-methylpyrrolidine bromide.

[0049] Component B comprises one or more of the following: ethylene glycol, diethylene glycol, triethylene glycol, glycerol, dipropylene glycol, caprolactam, ethanolamine, diethanolamine, and triethanolamine.

[0050] The method for producing N,N-dimethylethanolamine of the present invention can obtain electronic-grade N,N-dimethylethanolamine with a purity of ≥99.98%, or electronic-grade N,N-dimethylethanolamine with a purity of ≥99.98% and industrial-grade N,N-dimethylethanolamine with a purity of ≥99.0%.

[0051] like Figure 1 As shown, the method for producing N,N-dimethylethanolamine of the present invention includes the following steps:

[0052] S1. Reaction Stage

[0053] Nitrogen gas is used to pressurize the ethylene oxide in the feed buffer tank 1. The pressurized ethylene oxide is combined with the bottom discharge of the first reactor 2, which has been cooled by the reaction circulating liquid cooler 4, and the catalyst, which has been pressurized by the circulating catalyst feed pump 11, and enters the upper side stream of the first reactor 2. Dimethylamine enters the lower side stream of the first reactor 2. The pressurized ethylene oxide and dimethylamine in the first reactor 2 react under the action of the catalyst.

[0054] The gas phase from the top outlet of the first reactor 2 goes to the ethylene oxide absorption system. The ethylene oxide absorption system is used to absorb unreacted ethylene oxide. The bottom discharge of the first reactor 2 is divided into two streams. One stream is cooled by the reaction circulating liquid cooler 4 and then merges with the pressurized ethylene oxide and the catalyst pressurized by the circulating catalyst feed pump 11, returning to the first reactor 2. The other stream enters the second reactor 6 for further reaction. After the reaction is completed, the gas is discharged from the top of the second reactor 6.

[0055] S2. Circulating catalyst recovery stage

[0056] The top discharge from the second reactor 6 is depressurized by a pressure reducing valve and enters the crude product tank 7 for flash separation. The gas phase generated by flash separation goes to the ethylene oxide absorption system. The liquid phase generated by flash separation is pressurized by the falling film reboiler feed pump 8 and then merges with the liquid phase pressurized by the refining tower bottom pump 16 and is sent to the crude product falling film reboiler 9. The gas phase generated by evaporation in the crude product falling film reboiler 9 is sent to the refining tower 13. The unevaporated liquid phase flows into the circulating catalyst tank 10 as a catalyst. After being pressurized by the circulating catalyst feed pump 11, it is sent to the outlet of the reaction circulating liquid cooler 4 and merges with the pressurized ethylene oxide and the bottom discharge of the first reactor 2 cooled by the reaction circulating liquid cooler 4, and is recycled back to the first reactor 2.

[0057] During the reaction and catalyst recovery stages, when the catalyst is insufficient, the catalyst stored in the wet solvent tank 12 flows by gravity into the circulating catalyst tank 10 to replenish it.

[0058] S3. Refining Stage

[0059] A portion of the liquid phase from the bottom of refining column 13 is pressurized by the refining column reboiler forced circulation pump 14 and then sent to the refining column falling film reboiler 15 for reboiling before returning to refining column 13. Another portion is pressurized by the refining column bottom pump 16 and then merged with the liquid phase pressurized by the falling film reboiler feed pump 8, returning to the crude product falling film reboiler 9 for flash evaporation. The vapor phase from the top of refining column 13 is condensed by the refining column top condenser 17 and sent to the refining column reflux tank 18. After being pressurized by the refining column reflux pump 19, it returns to refining column 13. The side stream from refining column 13 is pressurized by the refining column side stream sampling pump 20 and sent to product column 21.

[0060] When the product being prepared is electronic-grade N,N-dimethylethanolamine, the liquid phase at the bottom of product column 21 is pressurized by the product column reboiler forced circulation pump 22 and then sent to the product column falling film reboiler 23 for reboiling before returning to product column 21. When the product being prepared is electronic-grade N,N-dimethylethanolamine or industrial-grade N,N-dimethylethanolamine, a portion of the liquid phase at the bottom of product column 21 is pressurized by the product column reboiler forced circulation pump 22 and then sent to the product column falling film reboiler 23 for reboiling before returning to product column 21, while the other portion is sent to the industrial-grade product tank by the industrial-grade product external pump 30.

[0061] The vapor phase at the top of product tower 21 is condensed by product tower top condenser 24 and sent to product tower reflux tank 25. After being pressurized by product tower reflux pump 26, it returns to product tower 21. The side stream from product tower 21 is cooled by product tower side stream cooler 27 and sent to electronic grade product buffer tank 28. After being pressurized by electronic grade product external pump 29, it is sent to electronic grade product tank.

[0062] It should be noted that the bottom discharge of the first reactor 2 in the reaction stage is divided into two streams to ensure that the temperature of the first reactor 2 does not get too high. The specific amount of each stream is adjusted according to actual needs. Usually, 30-80% of the material is cooled by the reaction circulating liquid cooler 4 and then combined with the pressurized ethylene oxide and the catalyst pressurized by the circulating catalyst feed pump 11 before returning to the first reactor 2.

[0063] It should be noted that during the reaction stage and catalyst recovery stage, there may be situations where the catalyst is insufficient, such as at the very beginning of the reaction stage and when the conversion rate of ethylene oxide and dimethylamine is less than 90%.

[0064] In some embodiments, during the reaction stage, the catalyst is combined with the bottom discharge of the first reactor 2, which has been cooled by the reaction circulating liquid cooler 4. After being preheated by the start-up preheater 5, it is then combined with pressurized ethylene oxide and enters the upper part of the first reactor 2. Preferably, the bottom discharge of the first reactor 2 is pumped to the reaction circulating liquid cooler 4 by the reaction circulating liquid pump 3. The preferred cooling temperature is 84.7°C. The preheating temperature is 95°C.

[0065] In some embodiments, during the reaction stage, the first reactor 2 is a jet-type reactor, and the second reactor 6 is a coupled tower reactor. Preferably, the reaction temperature in the first reactor 2 is 80–180°C, the reaction pressure is 0.1–5 MPa, and the reaction time is 0.1–3 h; more preferably, the reaction temperature in the first reactor is 110–150°C, the reaction pressure is 0.5–2 MPa, and the reaction time is 0.5–1.5 h; particularly preferably, the reaction temperature in the first reactor 2 is 115°C, the pressure is 0.58 MPa, and the reaction time is 1 h. Similarly, the reaction temperature in the second reactor is preferably 80–180°C, the reaction pressure is 0.1–5 MPa, and the reaction time is 0.1–3 h; more preferably, the reaction temperature in the second reactor is 110–150°C, the reaction pressure is 0.5–2 MPa, and the reaction time is 0.5–1.5 h; particularly preferably, the reaction temperature in the second reactor 6 is 116°C, the pressure is 0.58 MPa, and the reaction time is 1 h.

[0066] In some embodiments, during the catalyst recycling stage, the flash separation temperature is preferably 50–120°C and the pressure is 0.05–0.15 MPa, and more preferably the flash separation temperature is 100.5°C and the pressure is 0.1 MPa.

[0067] In some embodiments, during the circulating catalyst recovery stage, the crude product falling film reboiler 9 undergoes negative pressure evaporation, i.e., it is connected to a vacuum system under negative pressure. The crude product falling film reboiler 9 is equipped with a heat transfer oil inlet and a heat transfer oil outlet. Preferably, the crude product falling film reboiler operates under negative pressure evaporation at a temperature of 80–130°C and a pressure of 0.5–50 kPa; more preferably, the temperature is 127°C and the pressure is 1 kPa.

[0068] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0069] In the following embodiments, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, apparatus, instruments, equipment, etc., used in the following embodiments are commercially available.

[0070] Example 1

[0071] The production method of DMEA, with an expected annual output of 10,000 tons (1.25 t / h), uses a composite ionic liquid as a catalyst (component A: 1-butyl-3-methylimidazolium bromide, component B: diethylene glycol + caprolactam, wherein the molar ratio of diethylene glycol to caprolactam is 1:1, and the molar ratio of component A to component B is 1:1, and is obtained by stirring at 60-100℃ for 1-5 h), and includes the following three stages.

[0072] S1. Reaction Stage

[0073] Nitrogen gas is used to pressurize the ethylene oxide in the feed buffer tank 1. The pressurized ethylene oxide (flow rate 760.32 kg / h, temperature 5℃, pressure 1 MPa) is combined with the bottom discharge of the first reactor 2 (flow rate 21909.6 kg / h) cooled by the reaction circulating liquid cooler 4 and the catalyst (flow rate 18816.34 kg / h) pressurized by the circulating catalyst feed pump 11 (total flow rate 41486.26 kg / h) and enters the upper side stream of the first reactor 2. Dimethylamine enters the lower side stream of the first reactor 2. The pressurized ethylene oxide and dimethylamine in the first reactor 2 react under the action of the catalyst at a reaction temperature of 115℃ and a pressure of 0.58 MPa.

[0074] The gas phase (flow rate of 0 kg / h) obtained from the top outlet of the first reactor 2 goes to the ethylene oxide absorption system, which is used to absorb unreacted ethylene oxide. The bottom discharge of the first reactor 2 is divided into two streams. One stream (flow rate of 21909.6 kg / h) is cooled by the reaction circulating liquid cooler 4 and then merges with the pressurized ethylene oxide and the catalyst pressurized by the circulating catalyst feed pump 11, returning to the first reactor 2. The other stream (flow rate of 21909.6 kg / h) enters the second reactor 6 for further reaction. The reaction temperature is 116℃ and the pressure is 0.58 MPa. After the reaction is completed, the gas is discharged from the top of the second reactor 6.

[0075] S2. Recycled catalyst recovery

[0076] The top discharge from the second reactor 6, after being depressurized by a pressure reducing valve, enters the crude product tank 7 for flash separation at a temperature of 100.5℃ and a pressure of 0.1MPa. The gas phase generated by flash evaporation (flow rate of 1407.17 kg / h) goes to the ethylene oxide absorption system, while the liquid phase generated by flash evaporation (flow rate of 20502.43 kg / h) is pressurized by the falling film reboiler feed pump 8 and then merged with the liquid phase pressurized by the refining tower bottom pump 16 (flow rate of 3591.36 kg / h), which is then sent to the crude product falling film reboiler 9 for negative pressure evaporation. The process is carried out at a temperature of 127℃ and a pressure of 1kPa. The gas phase generated by the evaporation of the crude product in the falling film reboiler 9 (flow rate of 5286.67kg / h) is sent to the refining tower 13. The unevaporated liquid phase (flow rate of 18807.12kg / h) flows into the circulating catalyst tank 10 (pressure of 0.1MPa) as a catalyst. After being pressurized by the circulating catalyst feed pump 11, it is sent to the outlet of the reaction circulating liquid cooler 4. It merges with the pressurized ethylene oxide and the bottom discharge of the first reactor 2 after being cooled by the reaction circulating liquid cooler 4, and is recycled back to the first reactor 2.

[0077] During the reaction and catalyst recovery stages, when the catalyst is insufficient (reaction conversion rate is less than 90%), the catalyst stored in the wet solvent tank 12 flows by gravity into the circulating catalyst tank 10 to replenish it. The catalyst flow rate is 3600 kg / h, the temperature is 25℃, and the pressure is 0.1 MPa.

[0078] S3. Refining Stage

[0079] A portion of the liquid phase from the bottom of refining column 13 is pressurized by the forced circulation pump 14 of the refining column reboiler and then sent to the falling film reboiler 15 for reboiling before returning to refining column 13. Another portion (flow rate of 3591.36 kg / h) is pressurized by the bottom pump 16 of the refining column and then merges with the liquid phase (flow rate of 20502.43 kg / h) pressurized by the feed pump 8 of the falling film reboiler, returning to the feed inlet of the crude product falling film reboiler 9; Refining column 1... The vapor phase at the top of column 3 is condensed by the condenser 17 at the top of the refining column and sent to the reflux tank 18 of the refining column. After being pressurized by the reflux pump 19, it returns to the refining column 13. The side stream from the refining column 13 (flow rate of 1260 kg / h) is pressurized by the side stream pump 20 and sent to the product column 21. The refining column 13 is connected to the vacuum system under negative pressure, and the non-condensable gas is sent to the ethylene oxide absorption system at a flow rate of 303.55 kg / h.

[0080] The liquid phase at the bottom of product column 21 is pressurized by the forced circulation pump 22 of the product column reboiler and then sent to the falling film reboiler 23 of the product column for reboiling before returning to product column 21. The vapor phase at the top of product column 21 is condensed by the top condenser 24 of the product column and sent to the product column reflux tank 25. After being pressurized by the product column reflux pump 26, it returns to product column 21. The side stream from product column 21 (flow rate of 1255.68 kg / h) is cooled by the product column side stream cooler 27 and sent to the electronic grade product buffer tank 28. After being pressurized by the electronic grade product external pump 29, it is sent to the electronic grade product tank.

[0081] Testing showed that the steam consumption per ton of electronic-grade DMEA produced using the method in Example 1 was 1.8 tons, no wastewater was generated during the production process, and the spent catalyst could be sent to a qualified manufacturer for centralized treatment. The EO conversion rate was ≥99.5%, and the DMEA selectivity was ≥95%.

[0082] Using the existing DMEA production process (using water instead of composite ionic liquid as the catalyst, and employing the same operating parameters in the same equipment), the product is industrial-grade DMEA. The steam consumption per ton of DMEA is 3.5 tons, and 0.65 tons of alkaline wastewater are generated. The EO conversion rate is ≥97%, and the DMEA selectivity is 80%.

[0083] As can be seen, compared with existing production methods, the production method of this invention reduces steam consumption by 1.7t, generates no wastewater during the production process, and recycles and treats spent catalysts uniformly. Using a composite ionic liquid as a catalyst significantly increases EO conversion and DMEA selectivity.

[0084] Example 2

[0085] The production method of DMEA, with an expected annual output of 20,000 tons (2.5 t / h), uses a composite ionic liquid as a catalyst (component A: tetramethylammonium bromide, component B: ethylene glycol, with a molar ratio of component A to component B of 1:1, obtained by stirring at 60-100℃ for 1-5 h), and includes the following three stages.

[0086] S1. Reaction Stage

[0087] Nitrogen gas is used to pressurize the ethylene oxide in the feed buffer tank 1. The pressurized ethylene oxide (flow rate 1520.6 kg / h, temperature 5℃, pressure 1 MPa) is combined with the bottom discharge of the first reactor 2 (flow rate 43820.5 kg / h) cooled by the reaction circulating liquid cooler 4 and the catalyst (flow rate 37635.8 kg / h) pressurized by the circulating catalyst feed pump 11 (total flow rate 81456.3 kg / h) and enters the upper side stream of the first reactor 2. Dimethylamine enters the lower side stream of the first reactor 2. The pressurized ethylene oxide and dimethylamine in the first reactor 2 react under the action of the catalyst at a reaction temperature of 115℃ and a pressure of 0.58 MPa.

[0088] The bottom discharge from the first reactor 2 is divided into two streams. One stream (flow rate of 43819.2 kg / h) is cooled by the reaction circulating liquid cooler 4 and then merges with the pressurized ethylene oxide and the catalyst pressurized by the circulating catalyst feed pump 11, returning to the first reactor 2. The other stream (flow rate of 43819.2 kg / h) enters the second reactor 6 for further reaction. The reaction temperature is 116℃ and the pressure is 0.58 MPa. After the reaction is completed, the material is discharged from the top of the second reactor 6.

[0089] S2. Recycled catalyst recovery

[0090] The top discharge from the second reactor 6, after being depressurized by a pressure reducing valve, enters the crude product tank 7 for flash separation at a temperature of 100.5℃ and a pressure of 0.1MPa. The gas phase generated by flash evaporation (flow rate of 2816.6 kg / h) goes to the ethylene oxide absorption system, while the liquid phase generated by flash evaporation (flow rate of 41002.6 kg / h) is pressurized by the falling film reboiler feed pump 8 and then merged with the liquid phase pressurized by the refining tower bottom pump 16 (flow rate of 7182.7 kg / h), which is then sent to the crude product falling film reboiler 9 for negative pressure evaporation. At a temperature of 127℃ and a pressure of 1kPa, the gas phase generated by the evaporation of the crude product falling film reboiler 9 (flow rate of 10573.3kg / h) is sent to the refining tower 13, and the unevaporated liquid phase (flow rate of 37612.0kg / h) flows into the circulating catalyst tank 10 (pressure of 0.1MPa) as a catalyst. After being pressurized by the circulating catalyst feed pump 11, it is sent to the outlet of the reaction circulating liquid cooler 4, where it merges with the pressurized ethylene oxide and the bottom discharge of the first reactor 2 cooled by the reaction circulating liquid cooler 4, and is recycled back to the first reactor 2.

[0091] During the reaction and catalyst recovery stages, when the catalyst is insufficient (reaction conversion rate is less than 90%), the catalyst stored in the wet solvent tank 12 flows by gravity into the circulating catalyst tank 10 to replenish it. The catalyst flow rate is 7200 kg / h, the temperature is 25℃, and the pressure is 0.1 MPa.

[0092] S3. Refining Stage

[0093] A portion of the liquid phase from the bottom of refining column 13 is pressurized by the forced circulation pump 14 of the refining column reboiler and then sent to the falling film reboiler 15 for reboiling before returning to refining column 13. Another portion (flow rate of 7182.7 kg / h) is pressurized by the bottom pump 16 of the refining column and then merges with the liquid phase (flow rate of 41004.9 kg / h) pressurized by the feed pump 8 of the falling film reboiler, returning to the feed inlet of the crude product falling film reboiler 9. Refining column 13... The vapor phase at the top of the refining column is condensed by the refining column top condenser 17 and sent to the refining column reflux tank 18. After being pressurized by the refining column reflux pump 19, it returns to the refining column 13. The side stream from the refining column 13 (flow rate of 2520 kg / h) is pressurized by the refining column side stream pump 20 and sent to the product column 21. The refining column 13 is connected to the vacuum system under negative pressure, and the non-condensable gas is sent to the ethylene oxide absorption system at a flow rate of 607.1 kg / h.

[0094] A portion of the liquid phase at the bottom of product column 21 is pressurized by the product column reboiler forced circulation pump 22 and sent to the product column falling film reboiler 23 for reboiling before returning to product column 21. The other portion (565.8 kg / h) is sent to the industrial-grade product tank 30 via the industrial-grade product delivery pump. The vapor phase at the top of product column 21 is condensed by the product column top condenser 24 and sent to the product column reflux tank 25, then pressurized by the product column reflux pump 26 before returning to product column 21. The side stream from product column 21 (flow rate of 1945.6 kg / h) is cooled by the product column side stream cooler 27 and sent to the electronic-grade product buffer tank 28, then pressurized by the electronic-grade product delivery pump 29 before being sent to the electronic-grade product tank.

[0095] Testing showed that the steam consumption per ton of DMEA product (electronic grade + industrial grade) produced by the method in Example 2 was 1.7 tons, no wastewater was generated during the production process, and the spent catalyst could be sent to a qualified manufacturer for centralized treatment. The EO conversion rate was ≥99.5%, and the DMEA selectivity was ≥95%.

[0096] Using the existing DMEA production process (using water instead of the composite ionic liquid as the catalyst, and employing the same operating parameters in the same equipment), the product is industrial-grade DMEA. The steam consumption per ton of DMEA is 3.5 tons, and water is used as the catalyst during production, generating 0.65 tons of alkaline wastewater. The EO conversion rate is ≥97%, and the DMEA selectivity is 80%.

[0097] As can be seen, compared with existing production methods, the production method of this invention reduces steam consumption by 1.8t, generates no wastewater during the production process, and recycles and treats spent catalysts uniformly. Using a composite ionic liquid as a catalyst significantly increases EO conversion and DMEA selectivity.

[0098] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the embodiments. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for producing N,N-dimethylethanolamine, characterized in that, Using a composite ionic liquid as a catalyst, the reaction of ethylene oxide and dimethylamine was catalyzed to obtain N,N-dimethylethanolamine. The method for preparing the composite ionic liquid is as follows: Component A and Component B are mixed in a molar ratio of 1:0.2-5 and stirred at 60-100°C for 1-5 hours to obtain the composite ionic liquid; Component A is one or more of the following: 1-(propyltrimethoxy)-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-octyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium acetate, 1-butyl-2,3-dimethylimidazolium chloride, N-butylpyridine bromide, tributylmethylammonium chloride, tetrabutylphosphine bromide, tetrabutylammonium bromide, tetraethylammonium bromide, tetramethylammonium bromide, 1-hydroxyethyl-2,3-dimethylimidazolium chloride, and N-butyl-N-methylpyrrolidine bromide. Component B is one or more of ethylene glycol, diethylene glycol, triethylene glycol, glycerol, dipropylene glycol, caprolactam, ethanolamine, diethanolamine, and triethanolamine.

2. The method for producing N,N-dimethylethanolamine according to claim 1, characterized in that, The mass ratio of ethylene oxide, dimethylamine, and catalyst is 1:0.5-50:0.0005-0.

5.

3. The method for producing N,N-dimethylethanolamine according to claim 1, characterized in that, The reaction temperature is 80–180℃, the reaction pressure is 0.1–5 MPa, and the reaction time is 0.1–3 h.

4. The method for producing N,N-dimethylethanolamine according to claim 1, characterized in that, After the reaction, the resulting reaction solution is distilled to recover the catalyst, and then purified to obtain electronic-grade N,N-dimethylethanolamine with a purity of ≥99.98%, or electronic-grade N,N-dimethylethanolamine with a purity of ≥99.98% and industrial-grade N,N-dimethylethanolamine with a purity of ≥99.0%.

5. The method for producing N,N-dimethylethanolamine according to claim 4, characterized in that, Includes the following steps: Dimethylamine is sent to the first reactor (2). Ethylene oxide is pressurized and mixed with the catalyst, and then sent to the first reactor (2). Ethylene oxide and dimethylamine react with the catalyst in the first reactor (2). The resulting liquid phase is cooled by heat exchange and recycled back to the inlet of the first reactor (2). The remaining part enters the second reactor (6) to continue the reaction. The crude product is sent to the crude product falling film reboiler (9). The resulting liquid phase is returned to the inlet of the first reactor (2) as a catalyst for recycling. The gas phase is sent to the purification tower (13) and the product tower (21) for two purifications to obtain electronic grade N,N-dimethylethanolamine with a purity of ≥99.98%, or electronic grade N,N-dimethylethanolamine with a purity of ≥99.98% and industrial grade N,N-dimethylethanolamine with a purity of ≥99.0%.

6. The method for producing N,N-dimethylethanolamine according to claim 5, characterized in that, Includes the following steps: S1. Reaction Stage Nitrogen gas is used to pressurize the ethylene oxide in the feed buffer tank (1). The pressurized ethylene oxide is combined with the bottom discharge of the first reactor (2) cooled by the reaction circulating liquid cooler (4) and the catalyst pressurized by the circulating catalyst feed pump (11) and enters the upper part of the first reactor (2). Dimethylamine enters the lower part of the first reactor (2). The pressurized ethylene oxide and dimethylamine react under the action of the catalyst. The gas phase obtained from the top outlet of the first reactor (2) goes to the ethylene oxide absorption system. The bottom discharge of the first reactor (2) is divided into two streams. One stream is cooled by the reaction circulating liquid cooler (4) and then merges with the pressurized ethylene oxide and the catalyst pressurized by the circulating catalyst feed pump (11) and returns to the first reactor (2). The other stream enters the second reactor (6) for further reaction. After the reaction is completed, the gas is discharged from the top of the second reactor (6). S2. Circulating catalyst recovery stage The top discharge of the second reactor (6) is depressurized by the pressure reducing valve and enters the crude product tank (7) for flash separation. The gas phase generated by flash evaporation goes to the ethylene oxide absorption system. The liquid phase generated by flash evaporation is pressurized by the falling film reboiler feed pump (8) and merges with the liquid phase pressurized by the refining tower bottom pump (16) and sent to the crude product falling film reboiler (9). The gas phase generated by the evaporation of the crude product falling film reboiler (9) is sent to the refining tower (13). The unevaporated liquid phase flows into the circulating catalyst tank (10) as a catalyst. After being pressurized by the circulating catalyst feed pump (11), it is sent to the outlet of the reaction circulating liquid cooler (4) and merges with the pressurized ethylene oxide and the bottom discharge of the first reactor (2) cooled by the reaction circulating liquid cooler (4) and is recycled back to the first reactor (2). During the reaction stage and the circulating catalyst recovery stage, when the catalyst is insufficient, the catalyst stored in the wet solvent tank (12) is replenished by gravity flow into the circulating catalyst tank (10); S3. Refining Stage A portion of the liquid phase from the bottom of the refining tower (13) is pressurized by the refining tower reboiler forced circulation pump (14) and sent to the refining tower falling film reboiler (15) for reboiling and then returned to the refining tower (13). Another portion is pressurized by the refining tower bottom pump (16) and merged with the liquid phase pressurized by the falling film reboiler feed pump (8) and returned to the crude product falling film reboiler (9) for flash evaporation. The vapor phase from the top of the refining tower (13) is condensed by the refining tower top condenser (17) and sent to the refining tower reflux tank (18). It is then pressurized by the refining tower reflux pump (19) and returned to the refining tower (13). The side stream from the refining tower (13) is pressurized by the refining tower side stream sampling pump (20) and sent to the product tower (21). The liquid phase at the bottom of the product tower (21) is pressurized by the product tower reboiler forced circulation pump (22) and then sent to the product tower falling film reboiler (23) for reboiling before returning to the product tower (21). Alternatively, a portion of the liquid phase at the bottom of the product tower (21) is pressurized by the product tower reboiler forced circulation pump (22) and then sent to the product tower falling film reboiler (23) for reboiling before returning to the product tower (21), while the other portion is pressurized by the industrial-grade product delivery pump (30) and sent to the industrial-grade product tank. The vapor phase at the top of the product tower (21) is condensed by the product tower top condenser (24) and sent to the product tower reflux tank (25). After being pressurized by the product tower reflux pump (26), it returns to the product tower (21). The side stream from the product tower (21) is cooled by the product tower side stream cooler (27) and sent to the electronic grade product buffer tank (28). After being pressurized by the electronic grade product external pump (29), it is sent to the electronic grade product tank.

7. The method for producing N,N-dimethylethanolamine according to claim 6, characterized in that, In the reaction stage, the catalyst is combined with the bottom discharge of the first reactor (2) cooled by the reaction circulating liquid cooler (4), and then preheated by the start-up preheater (5) before being combined with the pressurized ethylene oxide and entering the upper part of the first reactor (2). The bottom discharge of the first reactor (2) is pumped to the reaction circulating liquid cooler (4) via the reaction liquid circulation pump (3).

8. The method for producing N,N-dimethylethanolamine according to claim 6, characterized in that, During the reaction stage, the reaction temperature in the first reactor (2) is 80-180℃, the reaction pressure is 0.1-5MPa, and the reaction time is 0.1-3h. During the reaction stage, the reaction temperature in the second reactor (6) is 80-180°C, the reaction pressure is 0.1-5 MPa, and the reaction time is 0.1-3 h.

9. The method for producing N,N-dimethylethanolamine according to claim 6, characterized in that, The first reactor (2) is a jet-type reactor, and the second reactor (6) is a tower-type reactor.

10. The method for producing N,N-dimethylethanolamine according to claim 6, characterized in that, During the circulating catalyst recovery stage, the flash separation temperature is 50–120°C and the pressure is 0.05–0.15 MPa. During the circulating catalyst recovery stage, the crude product falling film reboiler (9) is subjected to negative pressure evaporation operation at a temperature of 80-130℃ and a pressure of 0.5-50kPa.

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