Method for continuously synthesizing 1, 3-dimethyl-2-imidazolinone
Through continuous catalytic synthesis in a tubular reactor, the problems of cumbersome high-temperature and high-pressure operation and low reaction efficiency in batch kettle synthesis method are solved, and the efficient continuous synthesis of 1,3-dimethyl-2-imidazolinone is achieved , improves reaction efficiency and safety, achieving a yield of more than 90% and a raw material conversion rate of more than 98%.
Patent Information
- Application Number
- CN202411333991.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-24
- Publication Date
- 2024-12-27
AI Technical Summary
The existing industrial process of producing 1,3-dimethyl-2-imidazolinone has problems such as high temperature and high pressure conditions, complicated operation, long reaction cycle, low reaction yield and major safety hazards, especially the intermittent kettle synthesis method is difficult. Achieve continuous reactions.
Continuous catalytic synthesis is carried out using a tubular reactor, by preparing mixed reaction materials and performing heating and pressurization reaction in a heating delay tube, using N,N-dimethylformamide and 1,3-dimethyl-2-imidazole As a combined reaction solvent, linone controls reaction conditions such as temperature, pressure and flow rate to ensure the continuity and efficiency of the reaction.
The reaction cycle has been significantly shortened, the yield of 1,3-dimethyl-2-imidazolinone has been improved, the operation simplicity and safety of the process has been improved, and the reaction efficiency has been significantly improved, with a yield of more than 90%. The conversion rate reaches more than 98%.
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Figure CN119192086A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for continuously synthesizing 1,3-dimethyl-2-imidazolidinone, and belongs to the field of organic synthesis. Background Art
[0002] 1,3-Dimethyl-2-imidazolidinone (DMI) is classified as a strong polar solvent due to the strong electron-withdrawing effect of the carbonyl structure in its molecule. DMI has excellent solubility. It is not only miscible with polar solvents such as water and methanol, but also soluble in non-polar solvents such as petroleum ether and cyclohexane. It can accelerate the reaction rate and increase the product yield in some chemical reactions. In terms of toxicity, toxicological studies on DMI have shown that it does not irritate the skin and has no adverse reactions such as allergies. In addition, DMI also has excellent properties such as low melting point, high boiling point, high flash point and high stability, which makes it have higher use value and safety in the production and application process.
[0003] At present, there are several methods for industrial production of 1,3-dimethyl-2-imidazolidinone: Phosgene method: N,N'-dimethylethylenediamine is used as raw material, phosgene is introduced, and triethylamine is used as an acid-binding agent to react at 20°C to obtain DMI. The yield of the product is about 70% (Applied Chemical Industry, 2009, 38(9): 1283-1285).
[0004] Carbon dioxide-methylamine method: Ethylene glycol and methylamine are used as raw materials, and a certain amount of carbon dioxide gas is introduced. The temperature is raised to 250°C, and the pressure during the reaction reaches 12 MPa. The cyclization condensation reaction is carried out under high temperature and high pressure. The product yield is 66% (Synthetic Chemistry, 2000, 8(4):301-306).
[0005] Carbon dioxide method: N,N'-dimethylethylenediamine and carbon dioxide are used as raw materials, triphenyl antimony oxide is selected as the catalyst, and tetraphosphorus decasulfide is used as the co-catalyst. The reaction occurs at 80°C with a cyclization condensation reaction, and the product yield is about 85% (Mao Chenlu, Development of Efficient and Clean Production Process for 1,3-Dimethyl-2-Imidazolidinone, Xiamen University, 2020, 1(4): 5-10).
[0006] 2-Imidazolidinone methylation method: 2-Imidazolidinone is used as raw material, methyl iodide is used as methylation reagent, tert-butyl alcohol is used as solvent, and the reaction is stirred at 30°C for 12 hours. The product yield is about 85%. (CN:111410633A, 2020-07-14).
[0007] The process for directly synthesizing 1,3-dimethyl-2-imidazolidinone using N,N'-dimethylethylenediamine and urea as raw materials is similar to the above process, but is subject to the high temperature and high pressure reaction conditions of the process, the limitations of the acidic system on equipment application, the difficulty in controlling continuous reactions and other problems. There are currently no reports on continuous synthesis, and only a few reports on intermittent batch synthesis methods. However, the intermittent batch synthesis method has the problems of harsh reaction conditions (reaction temperature > 200°C, reaction pressure > 1.4Mpa), cumbersome operation, low production efficiency, long reaction cycle (hours), low reaction yield, and great safety hazards. Summary of the invention
[0008] In order to overcome the problems existing in the current preparation process of 1,3-dimethyl-2-imidazolidinone, the present invention provides a method for continuously catalytically synthesizing 1,3-dimethyl-2-imidazolidinone using a tubular reactor, which can not only obtain a product with a higher yield, but also greatly shorten the reaction cycle of 1,3-dimethyl-2-imidazolidinone, and the process operation is simple, the process is easy to control, and the safety is high.
[0009] The specific steps of the present invention are as follows:
[0010] (1) preparing a mixed material: using N,N-dimethylformamide and 1,3-dimethyl-2-imidazolidinone as a combined reaction solvent; adding the combined reaction solvent, N,N'-dimethylethylenediamine, urea, and acetic acid into a stirring kettle and stirring them uniformly to form a mixed reaction material E;
[0011] (2) stirring and heating the mixed reaction material to obtain a mixed reaction material F after the solution becomes clear;
[0012] (3) The mixed reaction material F is transported to the heating delay tube by a horizontal flow pump for heating and pressurizing reaction to obtain a liquid G containing the reaction product.
[0013] The reaction equation is shown below:
[0014]
[0015] According to some embodiments of the present invention, in the combined reaction solvent, the mass proportion of 1,3-dimethyl-2-imidazolidinone is 30%-50%, preferably 50%.
[0016] According to some embodiments of the present invention, the molar concentration of N,N'-dimethylethylenediamine in the mixed reaction material E in step 1) is 0.001-0.02 mol / mL, preferably 0.002-0.005 mol / mL, the molar concentration of urea is 0.001-0.02 mol / mL, preferably 0.002-0.005 mol / mL, and the amount of acetic acid added is 60%-200% of the mass of urea, preferably 100%-180%. The molar ratio of N,N'-dimethylethylenediamine to urea is in the range of 1:(1-1.5), preferably 1:1.
[0017] According to some embodiments of the present invention, in step (2), the stirring and heating temperature is 80 to 130° C., preferably 90 to 120° C. The stirring time is 0.5 to 3 h, preferably 1 to 3 h.
[0018] According to some embodiments of the present invention, the flow rate of the mixed reaction material F in the heating delay tube is 2.0 to 8.0 mL / min, preferably 2.0 to 5.0 mL / min. The reaction time of the mixed reaction material F in the microreactor is 2 min to 10 min, preferably 4 min to 9 min. The reaction temperature is 200° C. to 280° C., preferably 210° C. to 250° C. The reaction pressure is 1.4 MPa to 3 MPa, preferably 1.4 MPa to 2 MPa.
[0019] According to some embodiments of the present invention, the heating delay tube is a coil tube, and the inner diameter of the coil tube is 1.5 mm to 3 mm, preferably 2 mm.
[0020] According to some embodiments of the present invention, a cooling delay tube and a one-way valve are sequentially arranged downstream of the heating delay tube along the material flow direction, and the one-way valve is used to prevent backflow caused by unstable system pressure, and the liquid G containing the reaction product is cooled to room temperature through the cooling delay tube, and the cooled material can be collected by a solution collection bottle after being discharged through the one-way valve. Further, the inner diameter of the cooling delay tube is the same as that of the heating delay tube. The present invention uses N, N-dimethylformamide and 1, 3-dimethyl-2-imidazolidinone as a combined solvent to prepare a mixed liquid of N, N'-dimethylethylenediamine and urea to continuously synthesize 1, 3-dimethyl-2-imidazolidinone in a tubular reactor, the synthesis reaction time is less than 10min, the yield of 1, 3-dimethyl-2-imidazolidinone reaches more than 90%, and the conversion rate of the main raw material N, N'-dimethylethylenediamine reaches more than 98%. Compared with the prior art, the reaction process can be operated continuously, and the process reaction efficiency and operation safety are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 The present invention is a process flow chart for the continuous synthesis of 1,3-dimethyl-2-imidazolidinone.
[0022] Figure 2 This is the gas chromatogram of the product standard sample.
[0023] Figure 3 This is the gas chromatogram of the raw material (N,N'-dimethylethylenediamine) standard.
[0024] Figure 4 It is the gas chromatogram of the mixed solution of the reaction products. DETAILED DESCRIPTION
[0025] The present invention is further described and illustrated below in conjunction with specific embodiments. The embodiments are merely exemplary of the present disclosure and do not define the scope of limitation. The technical features of each embodiment of the present invention may be combined accordingly without conflicting with each other.
[0026] like Figure 1 The device for continuously synthesizing 1,3-dimethyl-2-imidazolidinone used in the embodiments and comparative examples of the present invention is shown, and the device mainly includes a heating stirring kettle for mixing related materials and solvents, and preheating and stirring the materials, a horizontal flow pump for conveying materials (adjustable conveying flow), a heating delay tube (in the form of a coil, with an inner diameter of 2mm) as a reaction area, a cooling delay tube for cooling the materials, a back pressure valve and a solution collection bottle. The one-way valve is used to prevent backflow caused by unstable system pressure, and the liquid G containing the reaction product is cooled to room temperature through the cooling delay tube, and the cooled material can be collected in a solution collection bottle after being discharged through the one-way valve.
[0027] Embodiment 1:
[0028] A mixture was prepared with N,N-dimethylformamide and 1,3-dimethyl-2-imidazolidinone as combined solvents (mass fraction of each was 50%), the concentration of N,N'-dimethylethylenediamine in the mixture was 0.001 mol / mL, the concentration of urea was 0.001 mol / mL, and the amount of organic acid acetic acid was 100% of the mass amount of the reactant urea. The materials were added to a stirred tank and stirred at 120°C for 1 hour. The material was transported to the heating delay tube through a horizontal flow pump at a flow rate of 2mL / min to start the reaction. At this time, the molar ratio of N,N'-dimethylethylenediamine to urea in the reaction liquid was 1:1. The reaction liquid entered the heating temperature control zone, and the temperature of the reaction coil was controlled at 250℃, the reaction pressure was 2.0MPa, the inner diameter of the delay tube was 2mm, and the reaction residence time of the material in the temperature control zone was controlled to be 9min. The reaction product was cooled by the cooling delay tube at the outlet of the system and then collected. The collected samples were analyzed by gas chromatography and combined with the external standard curve to calculate that the yield of 1,3-dimethyl-2-imidazolidinone was 92.67%, and the conversion rate of N,N'-dimethylethylenediamine was 98.35%. Among them, Figure 2This is the gas chromatogram of the product standard sample. Figure 3 This is the gas chromatogram of the raw material (N,N'-dimethylethylenediamine) standard. Figure 4 It is the gas chromatogram of the mixed solution of the reaction products.
[0029] Embodiment 2:
[0030] A mixture was prepared with N,N-dimethylformamide and 1,3-dimethyl-2-imidazolidinone as combined solvents (mass fraction of each was 50%), wherein the concentration of N,N'-dimethylethylenediamine was 0.002 mol / mL, and the concentration of urea was 0.002 mol / mL. The amount of organic acid acetic acid was 140% of the mass amount of the reactant urea. The materials were added into a stirred tank and stirred at 100°C for 2 hours. The material was transported to the heating delay tube through a horizontal flow pump at a flow rate of 2 mL / min to start the reaction. At this time, the molar ratio of N,N'-dimethylethylenediamine to urea in the reaction liquid was 1:1. The reaction liquid entered the heating temperature control zone, and the temperature of the reaction coil was controlled at 220°C, the reaction pressure was 1.7 MPa, the inner diameter of the delay tube was 2 mm, and the reaction residence time of the two streams of material in the temperature control zone was 6 min. The reaction product was cooled at the system outlet through a cooling delay tube and then collected. The collected samples were analyzed by gas chromatography and combined with the external standard curve to calculate that the yield of 1,3-dimethyl-2-imidazolidinone was 91.32%, and the conversion rate of N,N'-dimethylethylenediamine was 98.07%.
[0031] Embodiment 3:
[0032] A mixture was prepared with N,N-dimethylformamide and 1,3-dimethyl-2-imidazolidinone as combined solvents (mass fraction of each was 50%), wherein the concentration of N,N'-dimethylethylenediamine was 0.0015 mol / mL, and the concentration of urea was 0.0015 mol / mL. The amount of organic acid acetic acid was 180% of the mass amount of the reactant urea. The materials were added into a stirred tank and stirred at 90°C for 3 hours. The material was transported to the heating delay tube through a horizontal flow pump at a flow rate of 2 mL / min to start the reaction. At this time, the molar ratio of N,N'-dimethylethylenediamine to urea in the reaction liquid was 1:1. The reaction liquid entered the heating temperature control zone, and the temperature of the reaction coil was controlled at 210°C, the reaction pressure was 1.4 MPa, the inner diameter of the delay tube was 2 mm, and the reaction residence time of the two streams of material in the temperature control zone was 4 min. The reaction product was cooled at the system outlet through a cooling delay tube and then collected. The collected samples were analyzed by gas chromatography and combined with the external standard curve to calculate that the yield of 1,3-dimethyl-2-imidazolidinone was 90.45%, and the conversion rate of N,N'-dimethylethylenediamine was 98.58%.
[0033] Comparative Example 1:
[0034] The mixed material was prepared with single N,N-dimethylformamide as solvent, and the urea concentration was 0.002mol / mL. The amount of organic acid acetic acid was 140% of the mass amount of the reactant urea. The material was added to the stirring kettle and stirred at 100℃ for 2h. The material was transported to the heating delay tube through a horizontal flow pump at a flow rate of 2mL / min to start the reaction. At this time, the molar ratio of N,N'-dimethylethylenediamine to urea in the reaction liquid was 1:1. The reaction liquid entered the heating temperature control zone, and the delay tube temperature was controlled at 220℃, the reaction pressure was 1.7MPa, the inner diameter of the delay tube was 2mm, and the reaction residence time of the two streams of material in the temperature control zone was 6min. The reaction product was collected after cooling through the cooling delay tube at the outlet of the system. The collected samples were analyzed by gas chromatography and combined with the external standard curve to calculate that the yield of 1,3-dimethyl-2-imidazolidinone was 45.78%, and the conversion rate of N,N'-dimethylethylenediamine was 97.93%. Comparison of Comparative Example 1 with Example 2 shows that selecting a combined solvent (N,N-dimethylformamide and 1,3-dimethyl-2-imidazolidinone) as the solvent for the method of the present invention can significantly improve the yield of 1,3-dimethyl-2-imidazolidinone compared to a single solvent.
[0035] Comparative Example 2:
[0036] A mixed material (mass fraction of 50%) was prepared with N,N-dimethylformamide and 1,3-dimethyl-2-imidazolidinone as combined solvents, wherein the concentration of N,N'-dimethylethylenediamine was 0.001 mol / mL and the concentration of urea was 0.001 mol / mL. The amount of organic acid acetic acid was 100% of the mass amount of the reactant urea. The materials were added to a stirring tank and stirred at room temperature for 1 hour, and the mixed solution was in a slurry state without forming a clear solution. The slurry solution material is transported to the heating delay tube at a flow rate of 2mL / min through a horizontal flow pump to start the reaction. In the process of transporting the slurry solution, the problem of solid particles blocking the channel is easy to occur. The molar ratio of N,N'-dimethylethylenediamine to urea in the reaction solution is 1:1. The reaction solution enters the heating temperature control zone, and the temperature of the heating delay tube is controlled at 250°C. The reaction pressure is 2.0MPa, the inner diameter of the delay tube is 2mm, and the reaction residence time of the two streams of materials in the temperature control zone is 9min. The reaction product is collected after cooling the cooling delay tube at the outlet of the system. The collected samples are analyzed by gas chromatography and combined with the external standard curve to calculate that the yield of 1,3-dimethyl-2-imidazolidinone is 29.305%, and the conversion rate of N,N'-dimethylethylenediamine is 55.36%. Comparative Example 2 is compared with Example 1. It can be seen that simply mixing the materials evenly before feeding is not enough to smoothly implement the present invention. Example 1 strictly controls the temperature of the stirring kettle during material stirring and mixing to ensure that the mixed material is converted into a clear solution before feeding into the heating delay tube. This method ensures the smooth transportation of the raw materials, and the material feed amount is more accurate, avoiding problems such as reactor pipeline blockage and poor reaction effect, and greatly improves the raw material conversion rate and the yield of the target product.
[0037] Comparative Example 3:
[0038] A mixture was prepared with N,N-dimethylformamide and 1,3-dimethyl-2-imidazolidinone as combined solvents (mass fraction of each was 50%), wherein the concentration of N,N'-dimethylethylenediamine was 0.0015 mol / mL, and the concentration of urea was 0.0015 mol / mL. The amount of organic acid acetic acid was 40% of the mass amount of the reactant urea. The materials were added into a stirred tank and stirred at 90°C for 3 hours. The material is transported to the heating delay tube by a horizontal flow pump at a flow rate of 2mL / min to start the reaction. At this time, the molar ratio of N,N'-dimethylethylenediamine to urea in the reaction solution is 1:1, the reaction solution enters the heating temperature control zone, the delay tube temperature is controlled at 210°C, the reaction pressure is 1.4MPa, the inner diameter of the delay tube is 2mm, the reaction residence time of the two streams of material in the temperature control zone is 4min, the reaction product is collected after cooling the delay tube at the outlet of the system, and the collected samples are analyzed by gas chromatography and combined with the external standard curve to calculate that the yield of 1,3-dimethyl-2-imidazolidinone is 25.33%, and the conversion rate of N,N'-dimethylethylenediamine is 56.89%. Compared with Example 3, it can be seen that the amount of organic acid acetic acid is adjusted in Comparative Example 3, and the raw material conversion rate and the yield of the target product are greatly reduced.
[0039] Comparative Example 4:
[0040] A mixture was prepared with N,N-dimethylformamide and 1,3-dimethyl-2-imidazolidinone as combined solvents (mass fraction of each was 50%), wherein the concentration of N,N'-dimethylethylenediamine was 0.0015 mol / mL, and the concentration of urea was 0.0015 mol / mL. The amount of organic acid acetic acid was 300% of the mass amount of the reactant urea. The materials were added into a stirred tank and stirred at 90°C for 3 hours. The material was transported to the heating delay tube through a horizontal flow pump at a flow rate of 2mL / min to start the reaction. At this time, the molar ratio of N,N'-dimethylethylenediamine to urea in the reaction liquid was 1:1. The reaction liquid entered the heating temperature control zone, and the temperature of the delay tube was controlled at 210℃, the reaction pressure was 1.4MPa, and the inner diameter of the delay tube was 2mm. The reaction residence time of the two streams of materials in the temperature control zone was 4min. The reaction product was collected after being cooled by the cooling delay tube at the outlet of the system. There was black flocculent precipitation in the collected reaction liquid at the beginning of the reaction. After running for 20min, the pipeline was blocked and the experiment could not be completed smoothly. The main reason is that under high temperature and high pressure, excessive acid content will cause corrosion of stainless steel pipelines.
[0041] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. For ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.
Claims
1. A method for continuously synthesizing 1,3-dimethyl-2-imidazolidinone, characterized in that: The steps include: (1) Using N,N-dimethylformamide and 1,3-dimethyl-2-imidazolidinone as a combined reaction solvent; adding the combined reaction solvent, N,N'-dimethylethylenediamine, urea, and acetic acid into a stirring tank and stirring them uniformly to form a mixed reaction material E; (2) stirring and heating the mixed reaction material to obtain a mixed reaction material F after the solution becomes clear; (3) The mixed reaction material F is transported to a heating delay tube through a horizontal flow pump for heating and pressurizing reaction to obtain a liquid G containing a reaction product; wherein the inner diameter of the heating delay tube is 1.5 mm to 3 mm.
2. The method according to claim 1, characterized in that: In step (1), the mass proportion of 1,3-dimethyl-2-imidazolidinone in the combined reaction solvent is 30%-50%.
3. The method according to claim 1, characterized in that: In step (1), the concentration range of N, N'-dimethylethylenediamine in the mixed reaction material E is 0.001-0.02 mol / mL, the concentration range of urea in the mixed reaction material E is 0.001-0.02 mol / mL, the molar ratio of N, N'-dimethylethylenediamine to urea is 1: (1-1.5), and the amount of acetic acid used is 60%-200% of the quality of the reactant urea.
4. The method according to claim 1, characterized in that: In step (2), the stirring and heating temperature is 80 to 130° C., and the stirring time is 0.5 to 3 h.
5. The method according to claim 1, characterized in that: In step (3), the flow rate of the mixed reaction material F in the heating delay tube is 2.0 to 8.0 mL / min.
6. The method according to claim 1, characterized in that: In step (3), the temperature of the heating and pressurizing reaction is 200° C. to 280° C., the reaction pressure is 1.4 MPa to 3 MPa, and the reaction residence time is 2 min to 10 min.
7. The method according to claim 1, characterized in that: In step (3), the heating delay tube is a coil, and the material is 316L stainless steel.
8. The method according to claim 1, characterized in that: In step (3), a cooling delay tube and a one-way valve are sequentially arranged downstream of the heating delay tube along the material flow direction. The one-way valve is used to prevent backflow caused by unstable system pressure. The liquid G containing the reaction product is cooled to room temperature through the cooling delay tube.