Method for continuously and efficiently synthesizing N-methyl p-nitroaniline

Abstract

The invention discloses a method for continuously and efficiently synthesizing N-methyl p-nitroaniline, which comprises the following steps: S1, preparing a 1-fluoro-4-nitrobenzene solution by using an organic solvent, stirring and dissolving, filtering to remove impurities, and transferring to a container A for heat preservation; s2, preparing a methylamine solution by using an organic solvent, adding a preferred catalyst, controlling the temperature at 25-50 DEG C, and transferring the prepared solution into a container B for heat preservation; s3, exhausting by using an organic solvent, ensuring that no bubbles exist in the micro-mixer and the continuous flow reactor, introducing the material into the continuous flow reactor from the container A and the container B according to a certain proportion through the micro-mixer by using a delivery pump, and adjusting the temperature and pressure in the reactor for reaction to obtain a reaction solution; and S4, after the reaction liquid flows out, collecting the reaction liquid in a container C, filtering the collected reaction liquid, washing with an organic solvent, and drying to obtain a crude product N-methyl p-nitroaniline. The problems of high safety risk, tedious steps, long reaction time and the like of an intermittent kettle type process are effectively solved.

Description

Technical Field

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

[0002] N-methyl-p-nitroaniline is an important organic chemical raw material and dye intermediate, which is widely used in medicine, fragrance, electrolysis, electroplating and other industries; at the same time, N-methyl-p-nitroaniline is a neutralizer widely used in solid propellants, which can increase the service life of solid propellants, reduce the combustion signal characteristics of the propellant tail, and improve the combustion efficiency of propellants as a combustion enhancer component, providing more thrust and higher power output; in mixed explosives, it can be used to adjust the explosion speed of mixed explosives, change the explosion characteristics of mixed explosives, and adapt them to different application requirements; N-methyl-p-nitroaniline has polarization and can be used as a benchmark for testing nonlinear optical materials.

[0003] The existing preparation method of N-methyl-p-nitroaniline uses p-nitrochlorobenzene as the raw material, and the reaction is carried out for more than 3 hours under the process conditions of 160°C and 2MPa. The synthesis reaction is mainly based on the traditional kettle process, with large online dosage, high safety risk and long reaction time. Therefore, under the trend of increasingly important safety production, it is urgent to reduce the safety risk of the existing p-nitrochlorobenzene method for producing N-methyl-p-nitroaniline by optimizing the process, and solve the technical problems of high process risk and long reaction time in the existing N-methyl-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 purpose of the present invention is achieved by the following technical scheme: a method for continuously and efficiently synthesizing N-methyl-p-nitroaniline, comprising the following steps:

[0006] S1. Prepare a 1-fluoro-4-nitrobenzene solution using an organic solvent at a dissolving temperature of 25°C-90°C, stir and dissolve for 20 minutes, filter and 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 into 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, exhausting with an organic solvent to ensure that there are no bubbles in the micro-mixer and the continuous flow reactor, introducing the materials from the corrosion-resistant container A and the corrosion-resistant container B into the continuous flow reactor via the micro-mixer in a certain proportion by using a delivery pump, adjusting the temperature and pressure in the reactor to react and 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, cupric 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 holding capacity 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 the present application, the present invention provides a method for continuously and efficiently synthesizing N-methyl-p-nitroaniline. In the method of the present invention, 1-fluoro-4-nitrobenzene and methylamine are used as raw materials to prepare a solution, which 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 reaction conditions, 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 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 with 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 solvent or solute decomposition, 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 is a schematic diagram of a process flow of a method for continuously and efficiently synthesizing N-methyl-p-nitroaniline in an embodiment of the present invention. 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; obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application without making creative work are within the scope of protection of the present application.

[0022] Example 1

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

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

[0025] S2. Prepare 1000 mL of a methanol solution of 30% methylamine by mass, add cuprous chloride as a catalyst, the cuprous chloride accounting for 1% of the 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, exhaust the synthesis system using the solution in the corrosion-resistant container B through a metering pump; set the temperature in the continuous flow reactor to 25° C. and the pressure to 0.5 MPa, mix the methanol solution of 1-fluoro-4-nitrobenzene and the methanol solution of methylamine through a T-type mixer at a flow rate of 5 mL / min and 15 mL / min, respectively, and pump them into the continuous flow reactor for a reaction residence time of 5 min;

[0027] S4. The yellow suspension was collected in the 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 spectroscopy: 13 C NMR (DMSO-d 6 , 125MHz), δ: 154.282, 136.019, 126.220, 109.920, 30.012; 1 HNMR (DMSO-d 6 , 125MHz), 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 C 7 H 8 N 2 O 2 , theoretical value: C 55.26, H 5.263, N 18.42; measured value: C 55.36, H 5.301, N 18.55.

[0028] Example 2

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

[0030] S2. Prepare 1000 mL of a methanol solution of 35% methylamine by mass, add cuprous chloride as a catalyst, the cuprous chloride accounting 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, exhausting the synthesis system using the solution in the corrosion-resistant container B through a metering pump; setting the temperature in the continuous flow reactor to 40° C. and the pressure to 1 MPa, mixing the methanol solution of 1-fluoro-4-nitrobenzene and the methanol solution of methylamine through an ultrasonic micromixer at flow rates of 10 mL / min and 15 mL / min, respectively, and pumping them into the continuous flow reactor, and the reaction residence time is 5 min;

[0032] S4. The yellow suspension was collected in the 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 methanol solution of 1-fluoro-4-nitrobenzene with a mass fraction of 30%, stir and dissolve it at 90°C for 20 minutes, filter and remove impurities, and transfer the methanol solution of 1-fluoro-4-nitrobenzene to a corrosion-resistant container A for insulation;

[0035] S2. Prepare 1000 mL of a methanol solution of 10% methylamine by mass, add a catalyst of cuprous oxide, the cuprous oxide accounting for 0.5% 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;

[0036] S3, exhausting the synthesis system using the solution in the corrosion-resistant container B through a metering pump; setting the temperature in the continuous flow reactor to 50° C. and the pressure to 0.1 MPa, mixing the methanol solution of 1-fluoro-4-nitrobenzene and the methanol solution of methylamine through an ultrasonic micromixer at flow rates of 10 mL / min and 15 mL / min, respectively, and pumping them into the continuous flow reactor, and the reaction residence time is 5 min;

[0037] S4. The yellow suspension was collected in the 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 methanol solution of 1-fluoro-4-nitrobenzene with a mass fraction of 30%, stir and dissolve it at 50°C for 20 minutes, filter and remove impurities, and transfer the methanol solution of 1-fluoro-4-nitrobenzene to a corrosion-resistant container A for insulation;

[0040] S2. Prepare 1000 mL of a methanol solution of 30% methylamine by mass, add a catalyst of cuprous oxide, the cuprous oxide accounting 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, exhausting the synthesis system using the solution in the corrosion-resistant container B through a metering pump; setting the temperature in the continuous flow reactor to 50° C. and the pressure to normal pressure, mixing the methanol solution of 1-fluoro-4-nitrobenzene and the methanol solution of methylamine through an ultrasonic micromixer at a flow rate of 5 mL / min and 20 mL / min, respectively, and pumping them into the continuous flow reactor, and the reaction residence time is 10 min;

[0042] S4. The yellow suspension was collected in the 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 methanol solution of 1-fluoro-4-nitrobenzene with a mass fraction of 30%, stir and dissolve it at 65°C for 20 minutes, filter and remove impurities, and transfer the methanol solution of 1-fluoro-4-nitrobenzene to a corrosion-resistant container A for insulation;

[0045] S2. Prepare 1500 mL of a methanol solution of 20% methylamine by mass, 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, exhausting the synthesis system using the solution in the corrosion-resistant container B through a metering pump; setting the temperature in the continuous flow reactor to 60° C. and the pressure to 1 MPa, mixing the methanol solution of 1-fluoro-4-nitrobenzene and the methanol solution of methylamine through a Y-type micromixer at flow rates of 5 mL / min and 10 mL / min, respectively, through a metering pump, and pumping them into the continuous flow reactor for a reaction residence time of 15 min;

[0047] S4. The yellow suspension was collected in the 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, 1-fluoro-4-nitrobenzene and methylamine are used as raw materials to prepare a solution, which 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 has high safety, reduces the reaction temperature and pressure, shortens the reaction time, and can effectively solve the problems of high safety risk, complicated steps, long reaction time, etc. of the existing intermittent reactor process reaction conditions, realizes efficient and continuous preparation, improves the inherent safety of the process, and has good application prospects.

[0049] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope 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 dissolving temperature of 25°C-90°C, stir and dissolve for 20 minutes, filter and 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 into 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, exhausting with an organic solvent to ensure that there are no bubbles in the micro-mixer and the continuous flow reactor, introducing the materials from the corrosion-resistant container A and the corrosion-resistant container B into the continuous flow reactor via the micro-mixer in a certain proportion by using a delivery pump, adjusting the temperature and pressure in the reactor to react and obtain a reaction solution; 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.

2. A method for continuously and efficiently synthesizing N-methyl-p-nitroaniline according to claim 1, characterized in that: In step S3, the reaction temperature is 25°C-65°C, the pressure is 0-1MPa, and the reaction residence time is 1min-20min.

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

4. A method for continuously and efficiently synthesizing N-methyl-p-nitroaniline according to claim 2, characterized in that: In step S2, the organic solvent is one or more of methanol, ethylene glycol, acetone or ethyl acetate.

5. A method for continuously and efficiently synthesizing N-methyl-p-nitroaniline according to claim 2, characterized in that: In step S2, the mass concentration of the methylamine solution is 10%-35%.

6. A method for continuously and efficiently synthesizing N-methyl-p-nitroaniline according to claim 5, characterized in that: 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, cupric sulfate, cuprous chloride, cuprous oxide, cuprous iodide, potassium iodide or lithium bromide.

7. A method for continuously and efficiently synthesizing N-methyl-p-nitroaniline according to claim 6, characterized in that: 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.

8. A method for continuously and efficiently synthesizing N-methyl-p-nitroaniline according to claim 7, characterized in that: 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.

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