A method for continuously and efficiently synthesizing N-methyl-p-nitroaniline

Abstract

The present application discloses a method for continuously and efficiently synthesizing N-methyl-p-nitroaniline, comprising the following steps: S1, using an organic solvent to prepare 1-fluoro-4-nitrobenzene solution, stirring and dissolving, filtering and removing impurities, transferring to container A for insulation; S2, using an organic solvent to prepare methylamine solution, adding a preferred catalyst, controlling the temperature at 25 DEG C-50 DEG C, transferring the prepared solution to container B for insulation; S3, using an organic solvent to exhaust, ensuring that there is no bubble in micro mixer and continuous flow reactor, utilizing a transfer pump to introduce material from container A and container B into continuous flow reactor in a certain ratio through a micro mixer, regulating the temperature and pressure in the reactor for reaction to obtain a reaction solution; S4, after the reaction solution flows out, it is collected in container C, the collected reaction solution is filtered, washed with an organic solvent, and dried to obtain a crude product N-methyl-p-nitroaniline. The present application effectively solves the problems of high safety risk of intermittent kettle process, complicated steps, and long reaction time.

Description

Technical Field

[0001] The present invention relates to the technical field of energetic materials, in particular to a method for continuously and efficiently synthesizing N-methyl-p-nitroaniline. Background Art

[0002] N-Methyl-4-nitroaniline (N-Methyl-4-nitroaniline) is an important organic chemical raw material and dye intermediate, widely used in the pharmaceutical, fragrance, electrolysis, and electroplating industries. It is also a widely used neutralizer in solid propellants, where it can increase the service life of solid propellants, reduce the combustion signal characteristics of the propellant tail, and, as a combustion enhancer component, improve the propellant's combustion efficiency, providing more thrust and higher power output. In mixed explosives, it can be used to adjust the explosion velocity of the mixed explosives and change the explosion characteristics of the mixed explosives to adapt them to different application requirements. N-Methyl-4-nitroaniline has polarization properties and can be used as a benchmark for testing nonlinear optical materials.

[0003] The existing N-methyl-p-nitroaniline (N-M-p-nitroaniline) production method uses p-nitrochlorobenzene as the raw material and requires a reaction time of more than 3 hours at 160°C and 2 MPa. This synthesis is primarily a traditional kettle process, which results in high online dosage, high safety risks, and long reaction times. Therefore, with safety in production becoming increasingly important, there is an urgent need to optimize the process to reduce the safety risks associated with the existing p-nitrochlorobenzene method for producing N-M-p-nitroaniline, addressing the high process risks and long reaction times associated with the existing N-M-p-nitroaniline production process. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a method for continuously and efficiently synthesizing N-methyl-p-nitroaniline.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions: A method for continuously and efficiently synthesizing N-methyl-p-nitroaniline comprises the following steps:

[0006] S1. Prepare a 1-fluoro-4-nitrobenzene solution using an organic solvent at a dissolution temperature of 25°C-90°C, stir and dissolve for 20 minutes, filter to remove impurities, and transfer the 1-fluoro-4-nitrobenzene solution to a corrosion-resistant container A for insulation;

[0007] S2. Prepare a methylamine solution using an organic solvent, add the catalyst to the methylamine solution, control the temperature at 25°C-50°C, and transfer the prepared solution to a corrosion-resistant container B for insulation;

[0008] S3, using an organic solvent to exhaust to ensure that there are no bubbles in the micro mixer and the continuous flow reactor, using a delivery pump to introduce the materials from the corrosion-resistant container A and the corrosion-resistant container B into the continuous flow reactor in a certain proportion through the micro mixer, and adjusting the temperature and pressure in the reactor to react to obtain a reaction solution;

[0009] S4. After the reaction liquid flows out, it is collected in a corrosion-resistant container C. The collected reaction liquid is filtered, washed with an organic solvent, and dried to obtain a crude product N-methyl-p-nitroaniline.

[0010] Furthermore, in step S3, the reaction temperature is 25°C-65°C, the pressure is 0-1 MPa, and the reaction residence time is 1 min-20 min.

[0011] Furthermore, in step S1, the organic solvent is one or more of methanol, N,N-dimethylformamide, ethylene glycol, acetone or ethyl acetate.

[0012] Furthermore, in step S2, the organic solvent is one or more of methanol, ethylene glycol, acetone or ethyl acetate.

[0013] Furthermore, in step S2, the mass concentration of the methylamine solution is 10%-35%.

[0014] Furthermore, in step S2, the amount of the catalyst used is 0.2%-2% of the mass of 1-fluoro-4-nitrobenzene, wherein the catalyst is one or more of copper, cupric chloride, copper sulfate, cuprous chloride, cuprous oxide, cuprous iodide, potassium iodide or lithium bromide.

[0015] Furthermore, in step S3, the mass ratio of 1-fluoro-4-nitrobenzene solution to methylamine solution is 1:1-1:10, the molar ratio of 1-fluoro-4-nitrobenzene to methylamine is 1:1-1:20, and the micromixer is a T-type micromixer, a Y-type micromixer or an ultrasonic micromixer.

[0016] Furthermore, in step S3, the liquid holdup of the continuous flow reactor is 1 mL-500 mL, and the flow rate is 0.1 mL / min-250 mL / min.

[0017] In summary, the present invention has the following beneficial effects:

[0018] 1. In this application, the present invention provides a method for continuously and efficiently synthesizing N-methyl-p-nitroaniline. In the method of the present invention, a solution is prepared with 1-fluoro-4-nitrobenzene and methylamine as raw materials, and the solution is introduced into a continuous flow reactor through a micromixer under the action of a preferred catalyst for reaction to obtain high-purity N-methyl-p-nitroaniline. The synthesis method is simple and safe, reduces the reaction temperature and pressure, shortens the reaction time, and can effectively solve the problems of high safety risks, complicated steps, and long reaction time of the existing intermittent reactor process, thereby achieving efficient and continuous preparation, improving the inherent safety of the process, and having good application prospects.

[0019] 2. In the present application, in the process of preparing 1-fluoro-4-nitrobenzene solution, the key steps include selecting a suitable organic solvent, controlling the dissolution temperature and the stirring and dissolving time. First, the organic solvent is one or more of methanol, N,N-dimethylformamide, ethylene glycol, acetone or ethyl acetate, and the above organic solvents can dissolve in each other to ensure that the solute can be fully dissolved. The dissolution temperature is between 25°C and 90°C. This temperature range is neither too high to cause decomposition of the solvent or solute, nor too low to cause low dissolution efficiency. Finally, the stirring and dissolving time is set to 20 minutes. This is to ensure that the solute can be evenly dispersed in the solvent, avoid local over-concentration or over-diluted conditions, and also help to accelerate the dissolution process. After the dissolution is completed, the insoluble matter or impurities can be removed by filtering to further purify the solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention provides a process flow diagram of a method for continuously and efficiently synthesizing N-methyl-p-nitroaniline. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application; it is obvious that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0022] Example 1

[0023] The present invention discloses a method for continuously and efficiently synthesizing N-methyl-p-nitroaniline, comprising the following steps:

[0024] S1. Prepare 200 mL of a 20% by mass 1-fluoro-4-nitrobenzene methanol solution, stir and dissolve at 25°C for 20 minutes, filter to remove impurities, and transfer the 1-fluoro-4-nitrobenzene methanol solution to a corrosion-resistant container A for insulation.

[0025] S2. Prepare 1000 mL of a 30% by mass methylamine methanol solution, add the catalyst cuprous chloride, where the cuprous chloride accounts for 1% by mass of 1-fluoro-4-nitrobenzene, stir and dissolve at 25°C, and transfer the solution to a corrosion-resistant container B for insulation.

[0026] S3. The synthesis system was vented using the solution in the corrosion-resistant container B via a metering pump; the temperature in the continuous flow reactor was set to 25° C. and the pressure was 0.5 MPa. A methanol solution of 1-fluoro-4-nitrobenzene and a methanol solution of methylamine were mixed via a T-type mixer at flow rates of 5 mL / min and 15 mL / min, respectively, and then pumped into the continuous flow reactor for a reaction residence time of 5 min.

[0027] S4. The yellow suspension was collected in a corrosion-resistant container C, filtered, washed with methanol, and dried to obtain the finished product of N-methyl-p-nitroaniline with a yield of 92.3%. Samples were taken and characterized by nuclear magnetic resonance spectroscopy, infrared spectroscopy, and elemental analysis: Nuclear magnetic resonance spectrum: 13 C NMR (DMSO-d6, 125MHz), δ: 154.282, 136.019, 126.220, 109.920, 30.012; 1 HNMR (DMSO-d6, 125 MHz), δ: 2.7896, 6.5954, 6.6146, 7.3057, 8.0002, 8.0188; infrared spectrum: IR (KBr) ν: 3358, 1691, 1538, 1455, 1307, 1106, 827; elemental analysis: the molecular formula of N-methyl-p-nitroaniline is C7H8N2O2, theoretical value: C 55.26, H 5.263, N 18.42; found value: C 55.36, H 5.301, N 18.55.

[0028] Example 2

[0029] S1. Prepare a 20% by mass solution of 1-fluoro-4-nitrobenzene in 200 mL of N,N-dimethylformamide, stir and dissolve at 40°C for 20 minutes, filter to remove impurities, and transfer the 1-fluoro-4-nitrobenzene methanol solution to corrosion-resistant container A for insulation.

[0030] S2. Prepare 1000 mL of a 35% by mass methylamine methanol solution, add the catalyst cuprous chloride, where the cuprous chloride accounts for 0.2% of the mass of 1-fluoro-4-nitrobenzene, stir and dissolve at 40°C, and transfer the solution to a corrosion-resistant container B for insulation.

[0031] S3. Exhaust the synthesis system using the solution in the corrosion-resistant container B via a metering pump; set the temperature in the continuous flow reactor to 40° C. and the pressure to 1 MPa; mix the methanol solution of 1-fluoro-4-nitrobenzene and the methanol solution of methylamine via an ultrasonic micromixer at flow rates of 10 mL / min and 15 mL / min, respectively, and pump the mixture into the continuous flow reactor for a reaction residence time of 5 min;

[0032] S4. The yellow suspension was collected in a corrosion-resistant container C, filtered, washed with methanol, and dried to obtain the finished product of N-methyl-p-nitroaniline with a yield of 91.4%.

[0033] Example 3

[0034] S1. Prepare 200 mL of a 30% by mass 1-fluoro-4-nitrobenzene methanol solution, stir and dissolve at 90°C for 20 minutes, filter to remove impurities, and transfer the 1-fluoro-4-nitrobenzene methanol solution to a corrosion-resistant container A for insulation.

[0035] S2. Prepare 1000 mL of a 10% by mass methylamine solution in methanol, add the catalyst cuprous oxide (0.5% by mass of 1-fluoro-4-nitrobenzene), stir and dissolve at 50°C, and transfer the solution to a corrosion-resistant container B for insulation.

[0036] S3. The synthesis system was vented using the solution in the corrosion-resistant container B via a metering pump; the temperature in the continuous flow reactor was set to 50° C. and the pressure was set to 0.1 MPa. A methanol solution of 1-fluoro-4-nitrobenzene and a methanol solution of methylamine were mixed via an ultrasonic micromixer at flow rates of 10 mL / min and 15 mL / min, respectively, and then pumped into the continuous flow reactor for a reaction residence time of 5 min.

[0037] S4. The yellow suspension was collected in a corrosion-resistant container C, filtered, washed with methanol, and dried to obtain the finished product of N-methyl-p-nitroaniline with a yield of 94.2%.

[0038] Example 4

[0039] S1. Prepare 200 mL of a 30% by mass 1-fluoro-4-nitrobenzene methanol solution, stir and dissolve at 50°C for 20 minutes, filter to remove impurities, and transfer the 1-fluoro-4-nitrobenzene methanol solution to a corrosion-resistant container A for insulation.

[0040] S2. Prepare 1000 mL of a 30% by mass methylamine methanol solution, add the catalyst cuprous oxide, where the cuprous oxide accounts for 2% of the mass of 1-fluoro-4-nitrobenzene, stir and dissolve at 50°C, and transfer the solution to a corrosion-resistant container B for insulation.

[0041] S3. Exhaust the synthesis system using the solution in the corrosion-resistant container B via a metering pump; set the temperature in the continuous flow reactor to 50° C. and the pressure to atmospheric pressure; mix the methanol solution of 1-fluoro-4-nitrobenzene and the methanol solution of methylamine via an ultrasonic micromixer at flow rates of 5 mL / min and 20 mL / min, respectively, and pump the mixture into the continuous flow reactor for a reaction residence time of 10 min;

[0042] S4. The yellow suspension was collected in a corrosion-resistant container C, filtered, washed with methanol, and dried to obtain the finished product of N-methyl-p-nitroaniline with a yield of 90.2%.

[0043] Example 5

[0044] S1. Prepare 200 mL of a 30% by mass 1-fluoro-4-nitrobenzene methanol solution, stir and dissolve at 65°C for 20 minutes, filter to remove impurities, and transfer the 1-fluoro-4-nitrobenzene methanol solution to a corrosion-resistant container A for insulation.

[0045] S2. Prepare 1500 mL of a 20% by mass methylamine methanol solution, add potassium iodide as a catalyst, the potassium iodide accounting for 0.9% of the mass of 1-fluoro-4-nitrobenzene, stir and dissolve at 30°C, and transfer the solution to a corrosion-resistant container B for insulation;

[0046] S3. The synthesis system was vented using the solution in the corrosion-resistant container B via a metering pump; the temperature in the continuous flow reactor was set to 60° C. and the pressure was 1 MPa. A methanol solution of 1-fluoro-4-nitrobenzene and a methanol solution of methylamine were mixed via a Y-type micromixer at flow rates of 5 mL / min and 10 mL / min, respectively, and then pumped into the continuous flow reactor for a reaction residence time of 15 min.

[0047] S4. The yellow suspension was collected in a corrosion-resistant container C, filtered, washed with methanol, and dried to obtain the finished product of N-methyl-p-nitroaniline with a yield of 93.8%.

[0048] In summary, the present invention provides a method for continuously and efficiently synthesizing N-methyl-p-nitroaniline. In the method of the present invention, a solution is prepared using 1-fluoro-4-nitrobenzene and methylamine as raw materials, and the solution is introduced into a continuous flow reactor through a micromixer under the action of a preferred catalyst for reaction to produce high-purity N-methyl-p-nitroaniline. The synthesis method is simple and highly safe, reduces the reaction temperature and pressure, and shortens the reaction time. The method can effectively solve the problems of high safety risks, complicated steps, and long reaction time in the existing intermittent reactor process, achieves efficient and continuous preparation, improves the inherent safety of the process, and has good application prospects.

[0049] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for continuously and efficiently synthesizing N-methyl-p-nitroaniline, characterized in that: The steps include: S1. Prepare a 1-fluoro-4-nitrobenzene solution using an organic solvent at a dissolution temperature of 25°C-90°C, stir and dissolve for 20 minutes, filter to remove impurities, and transfer the 1-fluoro-4-nitrobenzene solution to a corrosion-resistant container A for insulation; S2. Prepare a methylamine solution using an organic solvent, add the catalyst to the methylamine solution, control the temperature at 25°C-50°C, and transfer the prepared solution to a corrosion-resistant container B for insulation; S3, using an organic solvent to exhaust to ensure that there are no bubbles in the micro mixer and the continuous flow reactor, using a delivery pump to introduce the materials from the corrosion-resistant container A and the corrosion-resistant container B into the continuous flow reactor in a certain proportion through the micro mixer, and adjusting the temperature and pressure in the reactor to react to obtain a reaction solution; S4, after the reaction liquid flows out, it is collected in a corrosion-resistant container C, and the collected reaction liquid is filtered, washed with an organic solvent, and dried to obtain a crude product N-methyl-p-nitroaniline; In step S3, the reaction temperature is 25°C-65°C, the pressure is 0-1 MPa, and the reaction residence time is 1 min-20 min; In step S2, the mass concentration of the methylamine solution is 10%-35%; In step S2, the amount of the catalyst used is 0.2% to 2% of the mass of 1-fluoro-4-nitrobenzene, wherein the catalyst is one or more of copper, cupric chloride, copper sulfate, cuprous chloride, cuprous oxide, cuprous iodide, potassium iodide or lithium bromide; In step S3, the mass ratio of 1-fluoro-4-nitrobenzene solution to methylamine solution is 1:1-1:10, the molar ratio of 1-fluoro-4-nitrobenzene to methylamine is 1:1-1:20, and the micromixer is a T-type micromixer, a Y-type micromixer, or an ultrasonic micromixer; In step S3, the liquid holding capacity of the continuous flow reactor is 1 mL-500 mL, and the flow rate is 0.1 mL / min-250 mL / min.

2. A method for continuously and efficiently synthesizing N-methyl-p-nitroaniline according to claim 1, characterized in that: In step S1, the organic solvent is one or more of methanol, N,N-dimethylformamide, ethylene glycol, acetone or ethyl acetate.

3. A method for continuously and efficiently synthesizing N-methyl-p-nitroaniline according to claim 1, characterized in that: In step S2, the organic solvent is one or more of methanol, ethylene glycol, acetone or ethyl acetate.

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