Tubular synthesis method of alkyl nitramine compound

Abstract

The invention discloses a tubular synthesis method of an alkyl nitramine compound, which takes N, N '-dialkyl urea as a raw material, and comprises the following steps: continuously pumping nitric acid and sulfuric acid into a tubular reactor through a metering pump, and simultaneously continuously adding the N, N'-dialkyl urea into the tubular reactor through a solid charging machine for nitration reaction; nitration liquid flows into a hydrolysis kettle, and meanwhile, cold water is continuously pumped into the hydrolysis kettle through a metering pump, flows out through an overflow port of the hydrolysis kettle and enters a separator; the hydrolysate flows into a separator and is extracted three times with dichloromethane, an organic phase flows into a distillation kettle, the organic phase flows into a washer and is washed twice with water, then the organic phase flows into a collecting tank, and the product alkyl nitramine is obtained through vacuum concentration. The method can solve the problems of large nitration reaction online amount, difficult reaction temperature control, large safety risk and the like in the alkyl nitramine preparation process, and can be used for synthesis of alkyl nitramine.

Description

Technical Field

[0001] The invention belongs to the technical field of energetic material synthesis, and relates to a method for synthesizing an alkyl nitramine compound, in particular to a tubular synthesis method of an alkyl nitramine compound. The compound can be used as a synthetic precursor of an energetic plasticizer for explosives. Background Art

[0002] Ambient temperature has always been one of the important factors restricting the development of barreled weapons. It affects the burning speed of propellants. As the temperature increases, the burning speed of propellants increases exponentially. Although the loading conditions of artillery are the same, the ballistic performance of artillery is different in different regions, different seasons, and even during the day and night. The highest chamber pressure difference can reach 40-80MPa, which significantly reduces the efficiency and safety of weapons. The charge whose initial velocity and chamber pressure are less affected by ambient temperature is called low temperature coefficient charge or low temperature sensitive charge. In order to meet the needs of modern warfare environment, how to improve the influence of initial temperature on the ballistic performance of artillery has become one of the important research topics of gunpowder charging workers at home and abroad, and the use of plasticizers is a simple and effective technical approach to adjust the temperature coefficient of propellants.

[0003] Studies have shown that linear nitramine energetic plasticizers (DNDAs) are a new type of energetic plasticizer with a low temperature coefficient. The application of linear nitramine energetic plasticizers in propellant formulations and in barreled weapon charges can make the propellant show a good low-temperature effect in a wide temperature range, and at the same time can improve the ballistic performance of barreled weapons by 10-20%. Therefore, linear nitramine energetic plasticizers are one of the key factors in achieving a low temperature coefficient for barreled weapons. In recent years, many researchers have also successively carried out research on the synthesis of linear nitramine energetic plasticizers and their application in new propellants and propellants, proving the application potential of linear nitramine energetic plasticizers.

[0004] Alkyl nitramines, including metronitramine and acetonitramine, are key intermediates in the synthesis of linear nitramine energetic plasticizers. The synthesis method of alkyl nitramines mainly uses N,N'-dialkyl urea as raw material, first synthesizes N,N'-dialkyl-N,N'-dinitrourea, and then hydrolyzes it to obtain the target product. This method has the problems of large online amount of autoclave nitration reaction, difficult temperature control, harsh reaction conditions, low yield, etc., making it difficult to achieve safe and efficient preparation. Summary of the invention

[0005] In view of the deficiencies in the prior art, the object of the present invention is to provide a tubular synthesis method for an alkyl nitramine compound, which overcomes the deficiencies in the prior art of the alkyl nitramine synthesis process, such as large online amount of nitration reaction, difficult temperature control, harsh reaction conditions and low yield.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0007] A tubular synthesis method of an alkyl nitramine compound, wherein the alkyl nitramine compound is metronitramine and acetonitramine, and the structural formulas are as follows:

[0008] Metronitroamine: Acetonitrile:

[0009] The method uses N,N'-dialkyl urea and nitric-sulfuric acid as raw materials and uses a reaction system combining a tubular reactor and a kettle reactor for synthesis; the reaction system comprises a metering pump, a solid feeder, a tubular reactor, a hydrolysis kettle, a separator, a scrubber and a collecting tank; the metering pump for pumping the nitric-sulfuric acid and the solid feeder for adding N,N'-dialkyl urea are respectively connected to the feeding port of the tubular reactor, the outlet of the tubular reactor is connected to the inlet of the hydrolysis kettle, and a metering pump for cold water is also connected to the inlet of the hydrolysis kettle, the overflow port of the hydrolysis kettle is connected to the separator, the separator is connected to the scrubber, and the scrubber is connected to the collecting tank.

[0010] The present invention also includes the following technical features:

[0011] Specifically, the following steps are included:

[0012] s1, the nitric and sulfuric acid mixture is continuously pumped into the tubular reactor via a metering pump, and N,N'-dialkyl urea is continuously added into the tubular reactor via a solid feeder to carry out nitration reaction;

[0013] s2, the nitrification liquid flows into the hydrolysis kettle, and at the same time, cold water is continuously pumped into the hydrolysis kettle through a metering pump, and then flows out through the overflow port of the hydrolysis kettle and enters the separator;

[0014] s3, the hydrolyzate flows into a separator, is extracted three times with dichloromethane, the organic phase flows into a scrubber, is washed twice with water, and then flows into a collecting tank, and is concentrated in vacuo to obtain the product alkyl nitramine.

[0015] Specifically, the N,N'-dialkyl urea is N,N'-dimethyl urea and N,N'-diethyl urea.

[0016] Specifically, in the s1, the reaction temperature is 0-20°C, the reaction residence time is 10-30 min, the nitric acid-sulfuric acid mixture enters the tubular reactor through a metering pump at 15.3-18 g / min, N,N'-dimethylurea is continuously added to the tubular reactor through a solid feeder at 3-6 g / min, and the mass ratio of nitric acid, sulfuric acid and N,N'-dialkylurea is 1-4:1-3:1.

[0017] Specifically, in s1, the nitric acid and sulfuric acid mixed acid enters the tubular reactor through a metering pump at 15.3 g / min, N,N'-dimethylurea is continuously added to the tubular reactor through a solid feeder at 3 g / min, the mass ratio of nitric acid, sulfuric acid and N,N'-dialkylurea is 2.8:2.3:1, the nitration reaction temperature is 10°C, and the reaction residence time is 10 min.

[0018] Specifically, in s2, the reaction temperature is 30°C to 50°C, the reaction residence time is 10min to 60min, the stirring speed is 100rpm to 300rpm, and the mass ratio of the nitration solution entering the hydrolysis kettle to the cold water per unit time is 1 to 2:1.

[0019] Specifically, in s2, the mass ratio of the nitration solution to the cold water entering the hydrolysis kettle per unit time is 1.6:1, the hydrolysis reaction temperature is 40°C, the reaction residence time is 30min, and the stirring speed is 230rpm.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] The present invention is a safe, highly efficient and continuous method for synthesizing alkyl nitramines, which adopts a method combining tubular and kettle reactors to synthesize alkyl nitramines through nitration and hydrolysis reactions. The nitration reaction temperature is increased from -10 to 0°C to 0 to 20°C, the tubular reaction effectively reduces the online amount of the reaction, improves the safety of the nitration reaction, realizes the continuous synthesis of alkyl nitramines, and the yield can reach 89.6%. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the tubular synthesis process of the alkyl nitramine compound in the present invention.

[0023] Figure 2 The figure is the hydrogen nuclear magnetic resonance spectrum of the metronitamine synthesized by the present invention.

[0024] Figure 3 The carbon-NMR spectrum of the metronitamine synthesized by the present invention is shown in FIG.

[0025] Figure 4 The infrared spectrum of metronitamine synthesized by the present invention.

[0026] Figure 5 The high performance liquid chromatogram of the metronitamine synthesized by the present invention.

[0027] The meaning of each number in the figure is:

[0028] 1. Metering pump, 2. Solid feeder, 3. Tubular reactor, 4. Hydrolysis kettle, 5. Hydrolysis kettle overflow port, 6. Separator, 7. Scrubber, 8. Collection tank. DETAILED DESCRIPTION

[0029] The present invention provides a tubular synthesis method of an alkyl nitramine compound. In view of the current situation in which the nitration reaction has a large online amount, difficult temperature control, harsh reaction conditions, and low yield in the alkyl nitramine synthesis method, a continuous synthesis method with milder reaction conditions, small online amount, high safety, and high efficiency is sought. The present invention strengthens the mass transfer and heat transfer of the synthesis process by using a method combining a tubular reactor with a kettle reactor, realizes the continuity of the synthesis process, increases the nitration reaction temperature, reduces the online amount of the reaction, and improves the reaction efficiency and product yield.

[0030] The alkyl nitramine compounds are metronitramine and acetonitramine, and their structural formulas are as follows:

[0031] Metronitroamine: Acetonitrile

[0032] The method uses N,N'-dialkylurea and nitric acid and sulfuric acid as raw materials and uses a reaction system combining a tubular reactor and a tank reactor for synthesis; Figure 1 The reaction system includes a metering pump 1, a solid feeder 2, a tubular reactor 3, a hydrolysis kettle 4, a separator 6, a scrubber 7 and a collecting tank 8; the metering pump 1 for pumping nitric and sulfuric acid mixed acid and the solid feeder 2 for adding N,N'-dialkyl urea are respectively connected to the feed port of the tubular reactor 3, the outlet of the tubular reactor 3 is connected to the inlet of the hydrolysis kettle 4, and the metering pump 1 for cold water is also connected to the inlet of the hydrolysis kettle 4, the overflow port 5 of the hydrolysis kettle is connected to the separator 6, the separator 6 is connected to the scrubber 7, and the scrubber 7 is connected to the collecting tank 8.

[0033] The steps include:

[0034] (1) nitric acid and sulfuric acid are continuously pumped into a tubular reactor via a metering pump, and N,N'-dialkyl urea is continuously added into the tubular reactor via a solid feeder to carry out a nitration reaction;

[0035] The reaction temperature is 0-20°C, the reaction residence time is 10-30 minutes, the nitric acid-sulfuric acid mixed acid is fed into the tubular reactor through a metering pump at a rate of 15.3-18 g / min, N,N'-dimethylurea is continuously fed into the tubular reactor through a solid feeder at a rate of 3-6 g / min, and the mass ratio of nitric acid, sulfuric acid and N,N'-dialkylurea is 1-4:1-3:1;

[0036] (2) The nitrification liquid flows into the hydrolysis kettle, and at the same time, cold water is continuously pumped into the hydrolysis kettle through a metering pump, and then flows out through the overflow port of the hydrolysis kettle and enters the separator;

[0037] The reaction temperature is 30°C to 50°C, the reaction residence time is 10min to 60min, the stirring speed is 100rpm to 300rpm, and the mass ratio of the nitration liquid to the cold water entering the hydrolysis kettle per unit time is 1 to 2:1;

[0038] (3) The hydrolyzate flows into a separator, is extracted three times with dichloromethane, and the organic phase flows into a distillation kettle. The organic phase flows into a scrubber, is washed twice with water, and then flows into a collection tank, and is concentrated in vacuo to obtain the product alkyl nitramine.

[0039] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0040] Embodiment 1:

[0041] The present embodiment provides a tubular synthesis method of an alkyl nitramine compound, wherein nitric acid and sulfuric acid are prepared into a mixed acid at a mass ratio of 2.8:2.3, the nitric and sulfuric acid mixed acid is fed into a tubular reactor at a rate of 15.3 g / min through a metering pump, and N,N'-dimethylurea is continuously fed into the tubular reactor at a rate of 3 g / min through a solid feeder, wherein the mass ratio of nitric acid, sulfuric acid and N,N'-dimethylurea is 2.8:2.3:1, and a nitration reaction is carried out, the reaction temperature is 10°C, and the reaction residence time is 10 min; the nitrated solution flows into a hydrolysis kettle, and cold water is fed into the hydrolysis kettle through a metering pump; The pump continuously pumps into the hydrolysis kettle at a speed of 12 g / min to carry out hydrolysis reaction. The mass ratio of the nitration liquid to the cold water entering the hydrolysis kettle per unit time is 1.6:1. Then it flows out through the overflow port of the hydrolysis kettle and enters the separator. The hydrolysis reaction temperature is 40°C, the reaction residence time is 30 min, and the stirring speed is 230 rpm. The hydrolysis liquid flows into the separator and is extracted three times with dichloromethane. The organic phase flows into the scrubber, is washed twice with water, and then flows into the collection tank. It is vacuum concentrated to obtain 155.1 g of the product metronidamine with a yield of 89.6% (HPLC, see Figure 5 ).

[0042] Structure identification:

[0043] IR(KBr),υ(cm -1 ): 3367(NH), 2939(-CH3), 1601, 1306(-NO2), see Figure 4 ;

[0044] 1 H NMR (DMSO-d6), δ: 2.99 (s, 3H), 11.86 (s, 1H, -NH-), see Figure 2 ;

[0045] 13C NMR (DMSO-d6), δ: 32.67 (-CH3), see Figure 3 ;

[0046] Elemental analysis (CH4N2O2, %):

[0047] Calculated, C 15.79, H 5.263, N 36.84;

[0048] Found, C 16.16, H 5.312, N 37.28.

[0049] The above structural identification data confirm that the substance obtained by this method is indeed the target product metronidamine.

[0050] Embodiment 2:

[0051] The present embodiment provides a tubular synthesis method of an alkyl nitramine compound, wherein nitric acid and sulfuric acid are prepared into a mixed acid at a mass ratio of 3.3:1.8, the nitric and sulfuric acid mixed acid is fed into a tubular reactor at a rate of 15.3 g / min through a metering pump, and N,N'-dimethylurea is continuously fed into the tubular reactor at a rate of 3 g / min through a solid feeder to perform a nitration reaction, wherein the mass ratio of nitric acid, sulfuric acid and N,N'-dimethylurea is 3.3:1.8:1, the reaction temperature is 10°C, and the reaction residence time is 10 min; the nitrated solution flows into a hydrolysis kettle, and cold water is added to the reactor. The mixture was continuously pumped into the hydrolysis kettle at a speed of 12 g / min via a metering pump to carry out a hydrolysis reaction. The mass ratio of the nitration liquid to the cold water entering the hydrolysis kettle per unit time was 1.6:1. The mixture then flowed out through the overflow port of the hydrolysis kettle and entered the separator. The hydrolysis reaction temperature was 40°C, the reaction residence time was 30 min, and the stirring speed was 230 rpm. The hydrolysis liquid flowed into the separator and was extracted three times with dichloromethane. The organic phase flowed into the scrubber, was washed twice with water, and then flowed into the collecting tank. The product metronidamine was obtained by vacuum concentration with a yield of 72.5% of 125.5 g.

[0052] Embodiment 3:

[0053] The present embodiment provides a tubular synthesis method for an alkyl nitramine compound, wherein nitric acid and sulfuric acid are prepared into a mixed acid at a mass ratio of 2.8:2.3, the nitric and sulfuric acid mixed acid is fed into a tubular reactor at a rate of 18 g / min through a metering pump, and N,N'-dimethylurea is continuously fed into the tubular reactor at a rate of 3 g / min through a solid feeder to perform a nitration reaction, wherein the mass ratio of nitric acid, sulfuric acid and N,N'-dimethylurea is 3.3:2.7:1, the reaction temperature is 10°C, and the reaction residence time is 10 min; the nitrated solution flows into a hydrolysis kettle, and cold water is passed through the The metering pump continuously pumps the solution into the hydrolysis kettle at a speed of 12 g / min to carry out the hydrolysis reaction. The mass ratio of the nitration solution entering the hydrolysis kettle to the cold water per unit time is 1.6:1. The solution then flows out through the overflow port of the hydrolysis kettle and enters the separator. The hydrolysis reaction temperature is 40°C, the reaction residence time is 30 min, and the stirring speed is 230 rpm. The hydrolysis solution flows into the separator and is extracted three times with dichloromethane. The organic phase flows into the scrubber, is washed twice with water, and then flows into the collecting tank. The product metronidamine is obtained by vacuum concentration with a yield of 80.7%.

[0054] Embodiment 4:

[0055] The present embodiment provides a tubular synthesis method of an alkyl nitramine compound, wherein nitric acid and sulfuric acid are prepared into a mixed acid at a mass ratio of 2.8:2.3, the nitric and sulfuric acid mixed acid is fed into a tubular reactor at a rate of 15.3 g / min through a metering pump, and N,N'-dimethylurea is continuously fed into the tubular reactor at a rate of 6 g / min through a solid feeder to perform a nitration reaction, wherein the mass ratio of nitric acid, sulfuric acid and N,N'-dimethylurea is 2.8:2.3:2, the reaction temperature is 10°C, and the reaction residence time is 10 min; the nitrated solution flows into a hydrolysis kettle, and cold water is added to the reactor. The mixture was continuously pumped into the hydrolysis kettle at a speed of 12 g / min via a metering pump to carry out a hydrolysis reaction. The mass ratio of the nitrated liquid to the cold water entering the hydrolysis kettle per unit time was 1.6:1. The mixture then flowed out through the overflow port of the hydrolysis kettle and entered the separator. The hydrolysis reaction temperature was 40°C, the reaction residence time was 30 min, and the stirring speed was 230 rpm. The hydrolyzed liquid flowed into the separator and was extracted three times with dichloromethane. The organic phase flowed into the scrubber, was washed twice with water, and then flowed into the collecting tank. The product metronidamine was obtained by vacuum concentration with a yield of 77.3%.

[0056] Embodiment 5:

[0057] The present embodiment provides a tubular synthesis method of an alkyl nitramine compound, wherein nitric acid and sulfuric acid are prepared into a mixed acid at a mass ratio of 2.8:2.3, the nitric and sulfuric acid mixed acid is fed into a tubular reactor at a rate of 15.3 g / min through a metering pump, and N,N'-dimethylurea is continuously fed into the tubular reactor at a rate of 3 g / min through a solid feeder to perform a nitration reaction, wherein the mass ratio of nitric acid, sulfuric acid and N,N'-dimethylurea is 2.8:2.3:1, the reaction temperature is 0°C, and the reaction residence time is 10 min; the nitrated solution flows into a hydrolysis kettle, and cold water is passed through the The metering pump continuously pumps the solution into the hydrolysis kettle at a speed of 12 g / min to carry out the hydrolysis reaction. The mass ratio of the nitration solution entering the hydrolysis kettle to the cold water per unit time is 1.6:1. The solution then flows out through the overflow port of the hydrolysis kettle and enters the separator. The hydrolysis reaction temperature is 40°C, the reaction residence time is 30 min, and the stirring speed is 230 rpm. The hydrolysis solution flows into the separator and is extracted three times with dichloromethane. The organic phase flows into the scrubber, is washed twice with water, and then flows into the collecting tank. The product metronidamine is obtained by vacuum concentration with a yield of 79.4%.

[0058] Embodiment 6:

[0059] The present embodiment provides a tubular synthesis method for an alkyl nitramine compound, wherein nitric acid and sulfuric acid are prepared into a mixed acid at a mass ratio of 2.8:2.3, the nitric and sulfuric acid mixed acid is fed into a tubular reactor at a rate of 15.3 g / min through a metering pump, and N,N'-dimethylurea is continuously fed into the tubular reactor at a rate of 3 g / min through a solid feeder to perform a nitration reaction, wherein the mass ratio of nitric acid, sulfuric acid and N,N'-dimethylurea is 2.8:2.3:1, the reaction temperature is 10°C, and the reaction residence time is 20 min; the nitrated solution flows into a hydrolysis kettle, and cold water is added to the reactor. The mixture was continuously pumped into the hydrolysis kettle at a speed of 12 g / min via a metering pump to carry out a hydrolysis reaction. The mass ratio of the nitrated liquid to the cold water entering the hydrolysis kettle per unit time was 1.6:1. The mixture then flowed out through the overflow port of the hydrolysis kettle and entered the separator. The hydrolysis reaction temperature was 40°C, the reaction residence time was 30 min, and the stirring speed was 230 rpm. The hydrolyzed liquid flowed into the separator and was extracted three times with dichloromethane. The organic phase flowed into the scrubber, was washed twice with water, and then flowed into the collecting tank. The product metronidamine was obtained by vacuum concentration with a yield of 86.1% of 149.0 g.

[0060] Embodiment 7:

[0061] The present embodiment provides a tubular synthesis method of an alkyl nitramine compound, wherein nitric acid and sulfuric acid are prepared into a mixed acid at a mass ratio of 2.8:2.3, the nitric and sulfuric acid mixed acid is fed into a tubular reactor at a rate of 15.3 g / min through a metering pump, and N,N'-dimethylurea is continuously fed into the tubular reactor at a rate of 3 g / min through a solid feeder to carry out a nitration reaction, wherein the mass ratio of nitric acid, sulfuric acid and N,N'-dimethylurea is 2.8:2.3:1, the reaction temperature is 10°C, and the reaction residence time is 10 min; the nitrated solution flows into a hydrolysis kettle, and cold water is added to the mixture. The mixture was continuously pumped into the hydrolysis kettle at a speed of 12 g / min via a metering pump to carry out a hydrolysis reaction. The mass ratio of the nitrified liquid to the cold water entering the hydrolysis kettle per unit time was 1.6:1. The mixture then flowed out through the overflow port of the hydrolysis kettle and entered the separator. The hydrolysis reaction temperature was 50°C, the reaction residence time was 50 min, and the stirring speed was 230 rpm. The hydrolyzed liquid flowed into the separator and was extracted three times with dichloromethane. The organic phase flowed into the scrubber, was washed twice with water, and then flowed into the collecting tank. The product metronidamine was obtained by vacuum concentration with a yield of 88.2% at 152.7 g.

[0062] Embodiment 8:

[0063] The present embodiment provides a tubular synthesis method of an alkyl nitramine compound, wherein nitric acid and sulfuric acid are prepared into a mixed acid at a mass ratio of 2.8:2.3, the nitric and sulfuric acid mixed acid is fed into a tubular reactor at a rate of 15.3 g / min through a metering pump, and N,N'-diethylurea is continuously fed into the tubular reactor at a rate of 3 g / min through a solid feeder to perform a nitration reaction, wherein the mass ratio of nitric acid, sulfuric acid and N,N'-diethylurea is 2.8:2.3:1, the reaction temperature is 10°C, and the reaction residence time is 10 min; the nitrated solution flows into a hydrolysis kettle, and cold water is added to the reactor. The mixture was continuously pumped into the hydrolysis kettle at a speed of 12 g / min via a metering pump to carry out a hydrolysis reaction. The mass ratio of the nitrified liquid to the cold water entering the hydrolysis kettle per unit time was 1.6:1. The mixture then flowed out through the overflow port of the hydrolysis kettle and entered the separator. The hydrolysis reaction temperature was 40°C, the reaction residence time was 30 min, and the stirring speed was 230 rpm. The hydrolyzed liquid flowed into the separator and was extracted three times with dichloromethane. The organic phase flowed into the scrubber, was washed twice with water, and then flowed into the collecting tank. The product acetonitramine was obtained by vacuum concentration with a yield of 87.2% by weight.

Claims

1. A tubular synthesis method for an alkyl nitramine compound, characterized in that: The alkyl nitramine compounds are metronitramine and acetonitramine, and their structural formulas are as follows: Metronitroamine: Acetonitrile: The method uses N,N'-dialkyl urea and nitric-sulfuric acid as raw materials and uses a reaction system combining a tubular reactor and a kettle reactor for synthesis; the reaction system comprises a metering pump, a solid feeder, a tubular reactor, a hydrolysis kettle, a separator, a scrubber and a collecting tank; the metering pump for pumping the nitric-sulfuric acid and the solid feeder for adding N,N'-dialkyl urea are respectively connected to the feeding port of the tubular reactor, the outlet of the tubular reactor is connected to the inlet of the hydrolysis kettle, and a metering pump for cold water is also connected to the inlet of the hydrolysis kettle, the overflow port of the hydrolysis kettle is connected to the separator, the separator is connected to the scrubber, and the scrubber is connected to the collecting tank.

2. The tubular synthesis method of an alkyl nitramine compound according to claim 1, characterized in that: The following steps are involved: s1, the nitric and sulfuric acid mixture is continuously pumped into the tubular reactor via a metering pump, and N,N'-dialkyl urea is continuously added into the tubular reactor via a solid feeder to carry out nitration reaction; s2, the nitrification liquid flows into the hydrolysis kettle, and at the same time, cold water is continuously pumped into the hydrolysis kettle through a metering pump, and then flows out through the overflow port of the hydrolysis kettle and enters the separator; s3, the hydrolyzate flows into a separator, is extracted three times with dichloromethane, the organic phase flows into a scrubber, is washed twice with water, and then flows into a collecting tank, and is concentrated in vacuo to obtain the product alkyl nitramine.

3. The tubular synthesis method of an alkyl nitramine compound according to claim 1, characterized in that: The N,N'-dialkyl urea is N,N'-dimethyl urea and N,N'-diethyl urea.

4. The tubular synthesis method of an alkyl nitramine compound according to claim 2, characterized in that: In the s1, the reaction temperature is 0-20°C, the reaction residence time is 10-30 min, the nitric acid-sulfuric acid mixture enters the tubular reactor through a metering pump at a rate of 15.3-18 g / min, N,N'-dimethylurea is continuously added to the tubular reactor through a solid feeder at a rate of 3-6 g / min, and the mass ratio of nitric acid, sulfuric acid and N,N'-dialkylurea is 1-4:1-3:

1.

5. The tubular synthesis method of an alkyl nitramine compound according to claim 4, characterized in that: In the s1, nitric acid and sulfuric acid mixed acid enters the tubular reactor through a metering pump at a rate of 15.3 g / min, N,N'-dimethylurea is continuously added into the tubular reactor through a solid feeder at a rate of 3 g / min, the mass ratio of nitric acid, sulfuric acid and N,N'-dialkylurea is 2.8:2.3:1, the nitration reaction temperature is 10°C, and the reaction residence time is 10 min.

6. The tubular synthesis method of an alkyl nitramine compound according to claim 2, characterized in that: In the s2, the reaction temperature is 30°C to 50°C, the reaction residence time is 10min to 60min, the stirring speed is 100rpm to 300rpm, and the mass ratio of the nitration solution entering the hydrolysis kettle to the cold water per unit time is 1 to 2:

1.

7. The tubular synthesis method of an alkyl nitramine compound according to claim 6, characterized in that: In s2, the mass ratio of the nitration solution to the cold water entering the hydrolysis kettle per unit time is 1.6:1, the hydrolysis reaction temperature is 40°C, the reaction residence time is 30min, and the stirring speed is 230rpm.

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