Synthesis system and process for 4-nitro-N-methylphthalimide

Abstract

The invention relates to a synthesis system and process for 4-nitro-N-methylphthalimide, which takes N-methylphthalimide and fuming nitric acid as reaction raw materials and concentrated sulfuric acid as a catalyst, and divides the reaction raw materials into two streams of fluid, one stream of fluid is a solution formed by N-methylphthalimide dissolved in concentrated sulfuric acid or halogenated hydrocarbon, the other stream of fluid is mixed acid of fuming nitric acid and concentrated sulfuric acid, and the two streams of fluid enter the microchannel reactor for nitration reaction after being preheated by a preheating system; and finally, staying through a delayed reaction heat removal system, and collecting a reaction product 4-nitro-N-methylphthalimide after heat exchange. Compared with a kettle type process, the continuous automatic production of the 4-nitro-N-methylphthalimide is realized with less investment, and the reaction time is shortened from 3-4 hours to less than 10 minutes while the product yield is ensured, so that the intrinsically safe production of a nitration process is realized.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemical synthesis, and in particular to a synthesis process of 4-nitro-N-methylphthalimide. Background Art

[0002] 4-Nitro-N-methylphthalimide is an important intermediate for the synthesis of new materials. There are two methods for the synthesis of 4-nitro-N-methylphthalimide: one is a method of using 4-nitrophthalic anhydride to react with monomethylamine. The disadvantage is that 4-nitrophthalic anhydride is an unconventional chemical. At the same time, the reaction has many by-products and low yield, so it is not suitable for industrial production. Another method is a method of nitrating N-methylphthalimide (NMP for short) with mixed acid. This method has mature technology, simple operation, high yield, and the waste acid can also be repeatedly applied by concentration, and has been industrialized.

[0003] However, the current nitration process of N-methylphthalimide and mixed acid reaction adopts a kettle process. The nitration kettle process has two problems: 1. The reaction time is long, which affects the production capacity. 2. The reactor is large in size and the reaction liquid storage volume is large. The nitration reaction is a dangerous process. If the dripping is improperly controlled or out of control, it will cause the instantaneous heat to be unable to be removed in time, and the pressure will rise sharply, resulting in the risk of explosion. Therefore, it is urgent to develop a process for synthesizing 4-nitro-N-methylphthalimide, taking into account both economic benefits and production safety issues. Summary of the invention

[0004] In view of the above problems, the present invention proposes a synthesis system and process for 4-nitro-N-methylphthalimide, which utilizes a microchannel reactor to achieve continuous automatic production, taking into account both economic benefits and production safety issues.

[0005] To achieve the above objectives, the following technical scheme is adopted: a synthesis system for 4-nitro-N-methylphthalimide, comprising a preheating system, a microchannel reactor and a delayed reaction heat extraction system,

[0006] The preheating system is used to preheat two reaction fluids, and includes a first preheating pipeline and a second preheating pipeline.

[0007] The microchannel reactor is used as a reaction container for two reaction fluids.

[0008] The delayed reaction heat extraction system is used to extend the reaction time and remove the heat generated by the reaction, and includes a delayed reaction device and a heat exchange device. The delayed reaction device is located in the heat exchange device.

[0009] The first preheating pipeline and the second preheating pipeline in the preheating system are connected to the microchannel reactor, and the microchannel reactor is connected to the delayed reaction device through the pipeline.

[0010] Furthermore, the first preheating pipeline and the second preheating pipeline both include a liquid inlet pipeline, a hydraulic diaphragm pump, a preheating coil and a preheating device. The liquid inlet pipeline is connected to the preheating coil through a hydraulic diaphragm pump, and the preheating coil is in the preheating device.

[0011] Furthermore, the heat exchange medium of the heat exchange equipment and the preheating equipment is heat exchange oil.

[0012] Furthermore, the delayed reaction device is a coil reactor.

[0013] Furthermore, a plurality of temperature measuring points are arranged on the outer wall of the coil of the coil reactor.

[0014] Furthermore, the diameter of the coil of the coil-tube reactor is 8 mm.

[0015] Furthermore, the heat exchange medium of the heat exchange equipment and the preheating equipment is heat exchange oil.

[0016] The present invention also provides a synthesis process for 4-nitro-N-methylphthalimide, and the process steps are as follows:

[0017] S1. Two streams of fluid enter the first preheating pipeline and the second preheating pipeline respectively, and after being pressurized and stabilized, enter the preheating coil for preheating. The fluid in the first preheating pipeline is a solution formed by N-methylphthalimide dissolved in concentrated sulfuric acid or halogenated hydrocarbons, and the fluid in the second preheating pipeline is a mixed acid of fuming nitric acid and concentrated sulfuric acid. The ratio of sulfuric acid to nitric acid in the mixed acid is 1-4:1, and the molar ratio of nitric acid to N-methylphthalimide in the two streams is 1.1-1.6;

[0018] S2. The preheated fluid in the first preheating pipeline and the fluid in the second preheating pipeline enter the microchannel reactor for mixed reaction. The channel size of the microchannel reactor is 100-1000 μm, the reaction temperature is 40-80 ° C, the pressure is 0-0.5 MPag, and the reaction time is 2-8 min;

[0019] S3. The reaction product enters the delayed reaction device and is collected after staying there for 5.2-6.2 minutes.

[0020] Preferably, the preheated mixed acid fluid in the second preheating pipeline enters the microchannel reactor in a double feeding manner.

[0021] The invention has the beneficial effects as follows: the invention uses N-methylphthalimide and fuming nitric acid as reaction raw materials, and concentrated sulfuric acid as catalyst, and divides the two fluids into two streams, one of which is a solution formed by N-methylphthalimide dissolved in concentrated sulfuric acid or halogenated hydrocarbons, and the other is a mixed acid of fuming nitric acid and concentrated sulfuric acid. The two streams are preheated by a preheating system and enter a microchannel reactor for nitration reaction, and finally stay in a delayed reaction heat extraction system, and collect the reaction product 4-nitro-N-methylphthalimide after heat exchange. Compared with the kettle process of the invention, the continuous automatic production of 4-nitro-N-methylphthalimide is realized with less investment, while ensuring the product yield, the reaction time is reduced from 3-4 hours to within 10 minutes, thereby realizing the intrinsically safe production of the nitration process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of the invented synthesis system.

[0023] As shown in the figure: 1. First preheating pipeline; 2. Second preheating pipeline; 3. Delayed reaction device; 4. Heat exchange equipment; 5. Microchannel reactor; 900. Liquid inlet pipeline; 901. Hydraulic diaphragm pump; 902. Preheating coil; 903. Preheating equipment. DETAILED DESCRIPTION

[0024] Example 1

[0025] like Figure 1 The embodiment shown provides a synthesis system for 4-nitro-N-methylphthalimide, including a preheating system, a microchannel reactor 5 and a delayed reaction heat extraction system.

[0026] The preheating system is designed as two pipelines, including a first preheating pipeline 1 and a second preheating pipeline 2. The first preheating pipeline 1 and the second preheating pipeline 2 both include a liquid inlet pipeline 900, a hydraulic diaphragm pump 901, a preheating coil 902 and a preheating device 903. The liquid inlet pipeline 900 is connected to the preheating coil 902 through the hydraulic diaphragm pump 901. The preheating coil 902 is in the preheating device 903, wherein the heat exchange medium of the preheating device 903 is heat exchange oil;

[0027] The delayed reaction heat extraction system includes a delayed reaction device 3 and a heat exchange device 4. The delayed reaction device 3 is in the heat exchange device 4. The delayed reaction device 3 adopts a coil reactor with a coil diameter of 8 mm and a plurality of temperature measuring points are arranged on the outer wall of the coil. The heat exchange medium of the preheating device 4 is heat exchange oil.

[0028] The preheating coils 902 of the first preheating pipeline 1 and the second preheating pipeline 2 are both connected to the microchannel reactor 5, and the microchannel reactor 5 is connected to the delayed reaction device 3 through a pipeline to form a synthesis system for 4-nitro-N-methylphthalimide, wherein the structural form of the channel of the microchannel reactor 5 can adopt a multi-layer horizontal diffusion structure, a plate-type heart-shaped structure, or an umbrella-shaped structure, and its channel size is 100-1000μm.

[0029] The synthesis system provided in this example is used to synthesize 4-nitro-N-methylphthalimide according to the following steps. The steps are as follows:

[0030] S1. A mixture of N-methylphthalimide + concentrated sulfuric acid (98% wt) is used as the first fluid, wherein the mass ratio of the mixture is N-methylphthalimide: concentrated sulfuric acid = 1:4, and a mixed acid of fuming nitric acid + concentrated sulfuric acid is used as the second fluid, wherein the molar ratio of sulfuric acid to nitric acid is 3.5, and the molar ratio of nitric acid to N-methylphthalimide in the two fluids is controlled to be 1.1, and the first fluid in the first preheating pipeline is controlled to feed at 7.1 ml / min by a hydraulic diaphragm pump, and the second fluid in the second preheating pipeline is controlled to feed at 4.2 ml / min by a hydraulic diaphragm pump, and the two fluids enter the φ3 preheating coil respectively, and the preheating coils in the first preheating pipeline and the second preheating pipeline are located in an oil bath, and the temperature is controlled at 50°C;

[0031] S2. The two preheated fluids enter the microchannel reactor for mixed reaction, the reaction temperature is 40°C, the pressure is 0 MPag, the reaction time is 2 min, and the channel size of the microchannel reactor is 100 μm;

[0032] S3. After the reaction, the product enters the delayed coil reactor and stays there for 6.2 minutes. The coil reactor is located in an oil bath, and then the product is collected.

[0033] The collected product was crystallized by adding water and filtered, dissolved in dichloroethane and analyzed by liquid chromatography. The product content was 90.6%, the unreacted raw material content was 0.5%, and the impurity content was 9.1%.

[0034] Example 2

[0035] In this example, the synthesis system provided in Example 1 is used to synthesize 4-nitro-N-methylphthalimide according to the following steps. The steps are as follows:

[0036] S1. Use a mixture of N-methylphthalimide + ethylene dichloride as the first fluid, wherein the mass ratio of the mixture is N-methylphthalimide: ethylene dichloride = 1:6, use a mixed acid of fuming nitric acid + concentrated sulfuric acid as the second fluid, wherein the molar ratio of sulfuric acid to nitric acid is 4, and the molar ratio of nitric acid to N-methylphthalimide in the two fluids is controlled to be 1.1, the first fluid in the first preheating pipeline is controlled to feed at 10.1 ml / min by a hydraulic diaphragm pump, and the second fluid in the second preheating pipeline is controlled to feed at 3.3 ml / min by a hydraulic diaphragm pump, and the two fluids enter the φ3 preheating coil respectively, and the preheating coils in the first preheating pipeline and the second preheating pipeline are located in an oil bath, and the temperature is controlled at 60°C;

[0037] S2. The two preheated fluids enter the microchannel reactor for mixed reaction, the reaction temperature is 40°C, the pressure is 0 MPag, the reaction time is 2 min, and the channel size of the microchannel reactor is 100 μm;

[0038] S3. After the reaction, the product enters the delayed coil reactor and stays there for 5.2 minutes. The coil reactor is located in an oil bath, and then the product is collected.

[0039] The product was collected and separated into layers, and the oil phase was taken for liquid chromatography analysis, which showed that the product content was 71.7%, the unreacted raw material content was 25.2%, and the impurity content was 2.1%.

[0040] Example 3

[0041] In this example, the synthesis system provided in Example 1 is used to synthesize 4-nitro-N-methylphthalimide according to the following steps. The steps are as follows:

[0042] S1. A mixture of N-methylphthalimide + concentrated sulfuric acid (98% wt) is used as the first fluid, wherein the mass ratio of the mixture is N-methylphthalimide: concentrated sulfuric acid = 1:2.5, and a mixed acid of fuming nitric acid + concentrated sulfuric acid is used as the second fluid, wherein the molar ratio of sulfuric acid to nitric acid is 2, and the molar ratio of nitric acid to N-methylphthalimide in the two fluids is controlled to be 1.6, the first fluid in the first preheating pipeline is controlled to feed at 8.5 ml / min by a hydraulic diaphragm pump, and the second fluid in the second preheating pipeline is controlled to feed at 4.1 ml / min by a hydraulic diaphragm pump, and the two fluids enter the φ3 preheating coil respectively, and the preheating coils in the first preheating pipeline and the second preheating pipeline are located in an oil bath, and the temperature is controlled at 78°C;

[0043] S2. The two preheated fluids enter the microchannel reactor for mixed reaction. In this example, the preheated mixed acid fluid in the second preheating pipeline enters the microchannel reactor in two feeding methods. The reaction temperature is 80°C, the pressure is 0.5MPag, the reaction time is 8min, and the channel size of the microchannel reactor is 1000μm.

[0044] S3. The reaction product enters a delayed coil reactor and stays there for 5.5 min. The coil reactor is located in an oil bath, and then the product is collected.

[0045] The product was collected, crystallized by adding water and filtered, dissolved in dichloroethane and analyzed by liquid chromatography. The content of the product was 84.2%, the content of the unreacted raw material was 8.1%, and the impurity was 7.7%.

[0046] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A synthesis system for 4-nitro-N-methylphthalimide, characterized in that: It includes a preheating system, a microchannel reactor (5) and a delayed reaction heat extraction system. The preheating system is used to preheat two reaction fluids, and comprises a first preheating pipeline (1) and a second preheating pipeline (2). The microchannel reactor (5) is a reaction vessel for two reaction fluids. The delayed reaction heat extraction system is used to extend the reaction time and remove the heat generated by the reaction, and comprises a delayed reaction device (3) and a heat exchange device (4). The delayed reaction device (3) is located in the heat exchange device (4). The first preheating pipeline (1) and the second preheating pipeline (2) in the preheating system are connected to the microchannel reactor (5), and the microchannel reactor (5) is connected to the delayed reaction device (3) through pipelines.

2. The synthesis system according to claim 1, characterized in that: The first preheating pipeline (1) and the second preheating pipeline (2) both include a liquid inlet pipeline (900), a hydraulic diaphragm pump (901), a preheating coil (902) and a preheating device (903). The liquid inlet pipeline (900) is connected to the preheating coil (902) via the hydraulic diaphragm pump (901), and the preheating coil (902) is in the preheating device.

3. The synthesis system according to claim 2, characterized in that: The heat exchange medium of the heat exchange device (4) and the preheating device (903) is heat exchange oil.

4. The synthesis system according to claim 3, characterized in that: The delayed reaction device (3) is a coil reactor.

5. The synthesis system according to claim 4, characterized in that: A plurality of temperature measuring points are arranged on the outer wall of the coil of the coil-type reactor.

6. The synthesis system according to claim 5, characterized in that: The diameter of the coil of the coil-tube reactor is 8 mm.

7. The synthesis system according to claim 6, characterized in that: The heat exchange device and the preheating device use heat exchange oil as the heat exchange medium.

8. The synthesis process of the synthesis system according to claim 1, characterized in that: The process steps are as follows: S1. Two streams of fluid enter the first preheating pipeline and the second preheating pipeline respectively, and after being pressurized and stabilized, enter the preheating coil for preheating. The fluid in the first preheating pipeline is a solution formed by N-methylphthalimide dissolved in concentrated sulfuric acid or halogenated hydrocarbons, and the fluid in the second preheating pipeline is a mixed acid of fuming nitric acid and concentrated sulfuric acid. The ratio of sulfuric acid to nitric acid in the mixed acid is 1-4:1, and the molar ratio of nitric acid to N-methylphthalimide in the two streams is 1.1-1.6; S2. The preheated fluid in the first preheating pipeline and the fluid in the second preheating pipeline enter the microchannel reactor for mixed reaction. The channel size of the microchannel reactor is 100-1000 μm, the reaction temperature is 40-80 ° C, the pressure is 0-0.5 MPag, and the reaction time is 2-8 min; S3. The reaction product enters the delayed reaction device and is collected after staying there for 5.2-6.2 minutes.

9. The synthesis process according to claim 8, characterized in that: The preheated mixed acid fluid in the second preheating pipeline enters the microchannel reactor in a two-feed manner.

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