A process for the preparation of 3,7-dinitro-1,3,5,7-tetraazabicyclononane

Abstract

The application provides a preparation method of 3,7-dinitro-1,3,5,7-tetraazabicyclononane, comprising the following steps: 1) feeding a first material comprising urea and concentrated sulfuric acid and a second material comprising fuming nitric acid and concentrated sulfuric acid into a microchannel reactor to perform a first-stage nitration reaction, to obtain a first-stage nitration reaction liquid; 2) feeding the first-stage nitration reaction liquid into a first tubular reactor to perform a second-stage nitration reaction, to obtain a second-stage nitration reaction liquid; 3) feeding the second-stage nitration reaction liquid and water into a second tubular reactor to perform a hydrolysis reaction, to obtain a hydrolysis liquid; 4) feeding the hydrolysis liquid and a third material comprising polyoxymethylene and ammonia water into a third tubular reactor to perform a condensation cyclization reaction, to obtain 3,7-dinitro-1,3,5,7-tetraazabicyclononane. The preparation method has the advantages of high safety, less waste pollution and simple operation.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis and relates to a method for preparing 3,7-dinitro-1,3,5,7-tetraazabicyclononane. Background Technology

[0002] HMX (with the structural formula shown in Formula I) is a single-element explosive with high energy level and good overall performance, and it has been widely used in the military and aerospace fields.

[0003]

[0004] Currently, the main industrial production method for HMX is the acetic anhydride synthesis process using hexamethylenetetramine as a raw material. This process first converts hexamethylenetetramine into the intermediate 3,7-dinitro-1,3,5,7-tetraazabicyclononane (DPT, structural formula shown in Formula II), and then nitrates it to obtain HMX. This process is mature and stable, but it involves a large amount of acetic anhydride, numerous byproducts, low yield, and pollution from waste. To address these issues, researchers have developed a series of new synthetic methods for octogen in recent years, including methods using hexamethylenetetramine as a raw material, such as the DADN method and the TAT method, as well as methods using small molecules as raw materials, such as the urea method. Among them, the DADN method first converts hexamethylenetetramine into DADN (1,5-diacetyl-3,7-dinitro-1,3,5,7-tetraazacyclooctane), and then nitrates DADN to synthesize HMX under the action of a nitrifying agent; the TAT method first converts hexamethylenetetramine into DAPT (diacetylpentamethylenetetramine), and then reacts it with acetyl chloride, sodium acetate, and acetic anhydride to generate TAT (1,3,5,7-tetraacetyl-1,3,6,7-tetraazacyclooctane), and then nitrates TAT ​​to synthesize HMX; the urea method utilizes the nitroamine generated during the hydrolysis of urea to condense with excess formaldehyde and ammonia to prepare DPT (3,7-dinitro-1,3,5,7-tetraazabicyclononane), and then nitrates it to obtain HMX.

[0005]

[0006] Compared with other synthesis methods, the urea method has the advantages of low cost and high selectivity. Among them, DPT is an important intermediate in the synthesis of HMX by the urea method. At present, DPT is mainly synthesized by traditional batch reactor. However, DPT releases a lot of heat during the preparation process. The batch reactor has low mixing efficiency, slow heat and mass transfer rate, and a large amount of reaction liquid in the reactor, which can easily lead to the risk of thermal runaway and explosion.

[0007] Therefore, improving the safety of DPT preparation and reducing reaction risks are technical problems that urgently need to be solved in this field. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a method for preparing 3,7-dinitro-1,3,5,7-tetraazabicyclononane. This method uses a microchannel reactor connected in series with a tubular reactor as the reaction device, and efficiently prepares DPT through a continuous process. This preparation method has the advantages of high safety, simple operation, and low pollution from waste.

[0009] This invention provides a method for preparing 3,7-dinitro-1,3,5,7-tetraazabicyclononane, comprising the following steps:

[0010] 1) The first material, including urea and concentrated sulfuric acid, and the second material, including fuming nitric acid and concentrated sulfuric acid, are fed into a microchannel reactor to carry out the first stage nitration reaction, and the first stage nitration reaction solution is obtained.

[0011] 2) The first-stage nitration reaction solution is passed into the first tubular reactor to carry out the second-stage nitration reaction, and the second-stage nitration reaction solution is obtained.

[0012] 3) The second-stage nitration reaction solution and water are fed into the second tubular reactor to carry out the hydrolysis reaction, and the hydrolysate is obtained;

[0013] 4) The hydrolysate and a third material including paraformaldehyde and ammonia are fed into a third tubular reactor to carry out a condensation cyclization reaction to obtain 3,7-dinitro-1,3,5,7-tetraazabicyclononane.

[0014] In one optional embodiment, the molar ratio of urea to nitric acid in the fuming nitric acid is 1:(2-10).

[0015] In one optional embodiment, in step 1), the temperature of the first stage nitration reaction is -20 to 20°C, and the time is 1 to 20 minutes.

[0016] In one optional embodiment, in step 1), the rate at which the first material and the second material are introduced into the microchannel reactor is 1 to 50 mL / min.

[0017] In one optional embodiment, in step 2), the temperature of the second-stage nitration reaction is -20 to 20°C, and the time is 10 to 60 minutes.

[0018] In one optional embodiment, in step 3), the hydrolysis reaction is carried out at a temperature of 40–100°C for a time of 1–30 min.

[0019] In one alternative embodiment, in step 3), the rate at which the water is introduced into the second tubular reactor is 1 to 50 mL / min.

[0020] In one optional embodiment, in step 4), the temperature of the condensation cyclization reaction is 20–80°C, and the time is 1–30 min.

[0021] In one optional implementation, in step 4), the mass ratio of paraformaldehyde to ammonia in the third material is 1:(1-10).

[0022] In one alternative embodiment, in step 4), the rate at which the third material is introduced into the third tubular reactor is 1 to 50 mL / min.

[0023] The implementation of this invention has at least the following beneficial effects:

[0024] 1) This invention uses a microchannel reactor connected in series with a tubular reactor for the preparation of DPT. Based on the characteristics of the urea nitration reaction, it is divided into two stages, which are carried out in the microchannel reactor and the tubular reactor respectively. The first stage of nitration reaction, which has a large amount of exothermic heat, is carried out in the microchannel reactor. Taking advantage of the good mass and heat transfer effect and small liquid holding capacity of the microchannel reactor, thermal runaway and explosion phenomena during nitration are effectively avoided, thus improving the safety of the preparation process. The second stage of nitration reaction, which has a large amount of solid product precipitation, is carried out in the tubular reactor. This not only avoids the blockage of the microchannel reactor by the solid product, but also allows the preparation process to be carried out continuously, thereby making the preparation process more efficient.

[0025] 2) Compared with the traditional batch reactor method for preparing DPT, the present invention uses a microchannel reactor to connect multiple tubular reactors in series, so that the reaction processes such as nitration, hydrolysis, condensation and cyclization required in the preparation of DPT can be realized in a continuous process. This can achieve better mass and heat transfer effect to reduce the occurrence of side reactions, improve product yield, and reduce the complexity of operation.

[0026] 3) In the condensation cyclization process, this invention uses paraformaldehyde instead of the traditional formaldehyde aqueous solution, which reduces the amount of wastewater generated and makes the preparation process more environmentally friendly. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a process flow diagram for preparing 3,7-dinitro-1,3,5,7-tetraazabicyclononane according to an embodiment of the present invention.

[0029] Explanation of reference numerals in the attached figures:

[0030] 100 - First precooling device; 101 - Second precooling device; 200 - Microchannel reactor; 300 - First tubular reactor; 400 - Second tubular reactor; 500 - Third tubular reactor; 600 - Filtration device. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0032] This invention provides a method for preparing 3,7-dinitro-1,3,5,7-tetraazabicyclononane, comprising the following steps:

[0033] 1) The first material, including urea and concentrated sulfuric acid, and the second material, including fuming nitric acid and concentrated sulfuric acid, are fed into a microchannel reactor to carry out the first stage nitration reaction, and the second stage nitration reaction solution is obtained.

[0034] 2) The first-stage nitration reaction solution is passed into the first tubular reactor to carry out the second-stage nitration reaction, and the second-stage nitration reaction solution is obtained.

[0035] 3) The second-stage nitration reaction solution and water are fed into the second tubular reactor to carry out the hydrolysis reaction, and the hydrolysate is obtained;

[0036] 4) The hydrolysate and a third material, including paraformaldehyde and ammonia, are fed into a third tubular reactor to carry out a condensation cyclization reaction to obtain 3,7-dinitro-1,3,5,7-tetraazabicyclononane.

[0037] The nitration of urea can be represented by the following reaction equation:

[0038]

[0039] As can be seen from the above reaction formula, the nitration reaction of urea can be divided into two stages. The first stage is the mononitration reaction of urea. In this stage, a large amount of heat will be released during the initial mixing of the first and second materials and the mononitration reaction. The second stage is the dinitrification reaction of urea. The heat released in this process is small and relatively controllable.

[0040] In view of the above-mentioned reaction characteristics, the preparation method of the present invention uses a microchannel reactor and a tubular reactor connected in series in steps 1) and 2) to carry out the nitration reaction of urea. The first-stage nitration reaction is carried out in the microchannel reactor. The microchannel reactor has good mass and heat transfer effects and a small liquid holding volume, which can minimize the occurrence of thermal runaway and explosion during the first-stage nitration process, and greatly reduce the reaction risk. The main product in the second-stage nitration reaction is N,N-dinitrourea, which is difficult to dissolve in mixed acid solution. Therefore, the second-stage nitration reaction solution exists in the form of a suspension. If the second-stage nitration reaction continues to be carried out in the microchannel reactor, the solid will block the reactor, making it difficult to carry out the preparation process continuously. Therefore, a tubular reactor is connected in series after the microchannel reactor, so that the second-stage nitration reaction is carried out in the tubular reactor, which can avoid solid blockage of the reactor and ensure the continuous progress of the reaction.

[0041] In step 3), the hydrolysis reaction of the second-stage nitration solution mainly involves the hydrolysis of N,N-dinitrourea into nitramide and carbon dioxide under acidic conditions, which can be represented by the following reaction formula:

[0042]

[0043] In step 4), the condensation cyclization reaction between the hydrolysate and the third material is mainly the process of nitramide, formaldehyde, and ammonia reacting to generate 3,7-dinitro-1,3,5,7-tetraazabicyclononane, which can be represented by the following reaction formula:

[0044]

[0045] In this invention, paraformaldehyde is used instead of the formaldehyde aqueous solution used in the traditional process, which can reduce the amount of wastewater generated during the preparation process.

[0046] The hydrolysis reaction in step 3) and the condensation cyclization reaction in step 4) are carried out in a second tubular reactor and a third tubular reactor connected in series. The second tubular reactor is connected in series with the first tubular reactor, which allows the entire preparation process to be carried out in a continuous flow process, thereby solving the problems of long reaction time and complicated operation in the traditional batch preparation process.

[0047] In summary, this invention uses a microchannel reactor connected in series with a tubular reactor as the reaction device, enabling the preparation of DPT to be carried out in a continuous flow process, which greatly reduces the danger in the nitration process. In addition, since the above-mentioned reaction device can transfer mass and heat better than the traditional batch reactor, it can avoid the occurrence of side reactions, improve the conversion rate and product yield of the reaction, and at the same time improve the reaction efficiency, reduce the complexity of operation, and reduce the generation of waste.

[0048] The first, second, and third tubular reactors of this invention can be three independent tubular reactors connected in series, or a single tubular reactor can be divided into three sections, in which the second-stage nitration reaction, hydrolysis reaction, and condensation cyclization reaction are carried out respectively.

[0049] Furthermore, in step 1), to ensure the nitration reaction proceeds fully, the molar ratio of urea to nitric acid in fuming nitric acid can be controlled to 1:(2-10), for example, it can be a range of 1:2, 1:4:1:6:1:8:1:10, or any combination thereof. When the amount of nitric acid compared to urea is too high, side reactions such as over-nitration and oxidation are likely to occur, leading to a decrease in product yield; when the amount of nitric acid is too low, it is difficult to fully nitrate the urea, which will also lead to a decrease in product yield. Controlling the molar ratio of urea to nitric acid in fuming nitric acid within the above range is beneficial for obtaining DPT product with a higher yield.

[0050] The present invention does not specifically limit the content of urea in the first material and the content of fuming nitric acid in the second material, as long as the molar ratio of urea to nitric acid after mixing the first material and the second material meets the above range.

[0051] In this invention, the concentrated sulfuric acid in the first and second materials is an aqueous solution of sulfuric acid with a mass concentration of not less than 95%, or it can be fuming sulfuric acid, which acts as a solvent, dehydrating agent, and provides an acidic environment. The amount used is not specifically limited in this invention. In the first material, urea is solid, and to ensure that the first material can be continuously fed into the microchannel reactor in a liquid state, the amount of concentrated sulfuric acid must be sufficient to completely dissolve the urea. In the second material, the presence of concentrated sulfuric acid can adjust the reaction concentration of fuming nitric acid. In one specific embodiment, the mass ratio of urea to concentrated sulfuric acid in the first material is 1:(1-10), and the mass ratio of fuming nitric acid to concentrated sulfuric acid in the second material is 1:(1-10).

[0052] To prevent the formation of large amounts of insoluble N,N-dinitrourea in the microchannel reactor from clogging the reactor, the reaction of the first and second materials in the microchannel reactor should be controlled to be rapid and the residence time of the materials should be short.

[0053] The residence time of the materials is also the reaction time of the first and second materials in the microchannel reactor, which can be controlled by the liquid holding volume of the microchannel reactor and the feed rates of the first and second materials. For example, when the liquid holding volume of the microchannel reactor is 100 mL and the feed rates of the first and second materials are both 10 mL / min, then the reaction time of the first and second materials in the microchannel reactor is 5 min.

[0054] In one specific embodiment, in step 1), the rate at which the first material and the second material are introduced into the microchannel reactor is 1 to 50 mL / min. For example, it can be a range of 1 mL / min, 10 mL / min, 15 mL / min, 20 mL / min, 25 mL / min, 30 mL / min, 40 mL / min, 50 mL / min, or any combination thereof.

[0055] In one specific embodiment, in step 1), the temperature of the first-stage nitration reaction is -20 to 20°C, and the time is 1 to 20 minutes. For example, the temperature of the first-stage nitration reaction can be a range of -20°C, -10°C, 0°C, 10°C, 20°C, or any two of these; the time of the first-stage nitration reaction can be a range of 1 minute, 5 minutes, 10 minutes, 12 minutes, 14 minutes, 16 minutes, 20 minutes, or any two of these.

[0056] Controlling the temperature and time of the first-stage nitration reaction within the aforementioned range allows the reaction to proceed smoothly at a lower temperature, while the shorter reaction time (residence time) prevents solid blockage of the reactor and improves reaction efficiency. Preferably, the temperature of the first-stage nitration reaction is between -20°C and 0°C, as this range is more conducive to obtaining DPT products in higher yields.

[0057] Within the above flow rate range and reaction time, the first and second materials flow turbulently in the microchannel reactor, resulting in strong mixing. This ensures that the first and second materials come into full contact and react, and the strong fluidity also prevents solids from clogging the reactor.

[0058] Furthermore, in order to enable the first material and the second material to react in the microchannel reactor at a preset temperature, a pre-cooling step is included before the first material and the second material enter the microchannel reactor. The present invention does not impose a particular limitation on the pre-cooling temperature of the first material and the second material, as long as it is close to the temperature of the first stage nitration reaction.

[0059] The temperature of the second-stage nitration reaction is basically the same as or slightly higher than that of the first-stage nitration reaction, and the reaction time should be sufficient to ensure complete nitration of urea. In one specific embodiment, in step 2), the temperature of the second-stage nitration reaction is -20 to 20°C, and the time is 10 to 60 minutes. For example, the temperature of the second-stage nitration reaction can be a range of -20°C, -10°C, 0°C, 10°C, 20°C, or any combination thereof; the time of the first-stage nitration reaction can be a range of 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, or any combination thereof. Preferably, a second-stage nitration reaction temperature of -20 to 0°C is more conducive to improving product yield.

[0060] In step 3), the temperature of the hydrolysis reaction can be 40 to 100°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 70°C, 80°C, 90°C, 100°C or any combination thereof; the time of the hydrolysis reaction is 1 to 30 min, for example, 1 min, 10 min, 20 min, 25 min, 30 min or any combination thereof.

[0061] To ensure complete hydrolysis of N,N-dinitrourea in the second-stage nitration reaction solution, the amount of water used in the hydrolysis reaction should be at least twice the amount of N,N-dinitrourea. The ratio of the two amounts can be controlled based on the feed flow rates of N,N-dinitrourea and water. The feed flow rate of N,N-dinitrourea can be calculated by multiplying the concentration of N,N-dinitrourea in the second-stage nitration reaction solution by its feed flow rate.

[0062] In one specific embodiment, the rate at which water is introduced into the second tubular reactor is 1 to 50 mL / min, for example, a range of 1 mL / min, 10 mL / min, 15 mL / min, 20 mL / min, 30 mL / min, 40 mL / min, 50 mL / min, or any combination thereof.

[0063] In step 4), the temperature of the condensation cyclization reaction can be 20 to 80°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C or any combination thereof. Preferably, the temperature of the condensation cyclization reaction is 20 to 40°C. The time of the condensation cyclization reaction can be 1 to 30 min, for example, 1 min, 5 min, 10 min, 20 min, 30 min or any combination thereof.

[0064] In the third material, ammonia water serves two purposes: firstly, as a solvent to dissolve paraformaldehyde, and secondly, as a Schiff base reaction with paraformaldehyde to obtain an imine, which facilitates a condensation cyclization reaction with nitramide. In one specific embodiment, the mass ratio of paraformaldehyde to ammonia water in the third material is 1:(1-10), for example, it can be 1:1, 1:3, 1:5, 1:7, 1:10, or any combination thereof.

[0065] In one specific embodiment, the rate at which the third material is introduced into the third tubular reactor is 1 to 50 mL / min, for example, it can be a range of 1 mL / min, 10 mL / min, 20 mL / min, 30 mL / min, 40 mL / min, 50 mL / min, or any combination thereof.

[0066] In this invention, unless otherwise specified, the rate at which the first-stage nitration reaction solution is fed into the first tubular reactor is equal to the rate at which the second-stage nitration reaction solution is fed into the second tubular reactor; both are the sum of the rates at which the first and second materials are fed into the microchannel reactor. The rate at which the hydrolysate is fed into the third tubular reactor is the sum of the rates at which the first and second materials are fed into the microchannel reactor and the rate at which water is fed into the second tubular reactor.

[0067] After the condensation cyclization reaction is completed, a filtration device can be connected in series after the third tubular reactor. The obtained condensation cyclization reaction liquid can be filtered through the filtration device and washed with water to remove inorganic salts and other impurities, thereby obtaining high-purity 3,7-dinitro-1,3,5,7-tetraazabicyclononane.

[0068] The preparation method of 3,7-dinitro-1,3,5,7-tetraazabicyclononane provided by the present invention will be described in detail below with reference to specific embodiments. Unless otherwise specified, the raw materials used in the following embodiments can be obtained by commercial purchase or conventional methods, and the experimental methods without specific conditions are all conventional methods and conditions well known in the art.

[0069] Example 1

[0070] This embodiment provides a method for preparing 3,7-dinitro-1,3,5,7-tetraazabicyclononane. Figure 1 Here is a process flow diagram for the preparation of 3,7-dinitro-1,3,5,7-tetraazabicyclononane according to one embodiment, with reference to... Figure 1 The preparation method of this embodiment includes the following steps:

[0071] 1) Dissolve 1000g of urea in 3614g of concentrated sulfuric acid to prepare a urea-sulfuric acid solution with a volume of 3100mL, which is denoted as the first material; mix 400g of concentrated sulfuric acid and 3400g of fuming nitric acid (nitric acid mass concentration of 95%) to obtain a mixed acid solution with a volume of 2200mL, which is denoted as the second material; dissolve 2500g of paraformaldehyde in 15000g of ammonia water to prepare a paraformaldehyde-ammonia water solution with a volume of 17000mL, which is denoted as the third material.

[0072] 2) Set the flow rate of the feed pump for the first material to 10 mL / min, the flow rate of the feed pump for the second material to 10 mL / min, the flow rate of the feed pump for water to 35 mL / min, and the flow rate of the feed pump for the third material to 44 mL / min; set the temperature of the first precooling device 100 to 10℃, the temperature of the second precooling device 101 to 20℃, the temperature of the microchannel reactor 200 to 0℃, the temperature of the first tubular reactor 300 to 5℃, the temperature of the second tubular reactor 400 to 60℃, and the temperature of the third tubular reactor 500 to 30℃. After all temperatures reach the set temperatures, turn on the feed pumps for the first and second materials. After observing the appearance of white solids in the second tubular reactor 400, turn on the feed pump for water. After feeding water for 5-6 minutes, turn on the feed pump for the third material. After feeding the third material for 5-6 minutes, collect the reaction liquid. After the first material is completely fed, stop collecting the reaction liquid.

[0073] The microchannel reactor 200 has a liquid holding volume of 100 mL, the first tubular reactor 300 has a liquid holding volume of 600 mL, the second tubular reactor 400 has a liquid holding volume of 300 mL, and the third tubular reactor 500 has a liquid holding volume of 200 mL.

[0074] 3) Turn on the filter device 600, filter the collected reaction solution, wash with water and dry to obtain DPT product. The molar yield of DPT is 57.1% based on urea, and the HPLC purity is 99.28%.

[0075] Example 2

[0076] This embodiment provides a method for preparing 3,7-dinitro-1,3,5,7-tetraazabicyclononane. The specific steps are basically the same as in Example 1, except that the feed pump flow rate for the first material is 5 mL / min, and the feed pump flow rate for the second material is 15 mL / min. Based on urea, the molar yield of DPT prepared in this embodiment is 31.7%, and the HPLC purity is 99.12%.

[0077] Example 3

[0078] This embodiment provides a method for preparing 3,7-dinitro-1,3,5,7-tetraazabicyclononane. The specific steps are basically the same as in Example 1, except that the feed pump flow rate for the first material is 15 mL / min, and the feed pump flow rate for the second material is 5 mL / min. Based on urea, the molar yield of DPT prepared in this embodiment is 17.1%, and the HPLC purity is 99.25%.

[0079] Example 4

[0080] This embodiment provides a method for preparing 3,7-dinitro-1,3,5,7-tetraazabicyclononane. The specific steps are basically the same as in Example 1, except that the temperature of the microchannel reactor 200 is set to -20°C. Based on urea, the molar yield of DPT prepared in this embodiment is 51.3%, and the HPLC purity is 99.32%.

[0081] Example 5

[0082] This embodiment provides a method for preparing 3,7-dinitro-1,3,5,7-tetraazabicyclononane. The specific steps are basically the same as in Example 1, except that the temperature of the microchannel reactor 200 is set to 20°C. Based on urea, the molar yield of DPT prepared in this embodiment is 31.4%, and the HPLC purity is 99.08%.

[0083] Example 6

[0084] This embodiment provides a method for preparing 3,7-dinitro-1,3,5,7-tetraazabicyclononane. The specific steps are basically the same as in Example 1, except that the temperature of the third tubular reactor 500 is set to 80°C. Based on urea, the molar yield of DPT prepared in this embodiment is 28.3%, and the HPLC purity is 99.07%.

[0085] Example 7

[0086] This embodiment provides a method for preparing 3,7-dinitro-1,3,5,7-tetraazabicyclononane. The specific steps are basically the same as in Example 1, except that the temperature of the first tubular reactor 300 is set to 20°C. Based on urea, the molar yield of DPT prepared in this embodiment is 49.2%, and the HPLC purity is 99.52%.

[0087] Based on the conditions of the above embodiments, the molar ratio of urea to nitric acid, as well as the reaction temperature and reaction time of each reaction stage, were calculated. The specific values ​​are listed in Table 1.

[0088] Table 1

[0089]

[0090] The following conclusions can be drawn from Table 1.

[0091] 1) Comparing Examples 1 to 3, it can be seen that when the molar ratio of urea to nitric acid is less than 1:10 and greater than 1:2, the reaction yield is low.

[0092] 2) By comparing Examples 1, 4, 5 and 7, it can be seen that the first stage nitration reaction and the second stage nitration reaction are beneficial to the increase of DPT product yield at low temperature. When the reaction temperature reaches 20°C, the yield decreases.

[0093] 3) By comparing Examples 1 and 6, it can be seen that when the heating temperature of the condensation cyclization reaction is higher, the yield of the reaction is significantly reduced.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing 3,7-dinitro-1,3,5,7-tetraazabicyclononane, characterized in that, Includes the following steps: 1) The first material, including urea and concentrated sulfuric acid, and the second material, including fuming nitric acid and concentrated sulfuric acid, are fed into a microchannel reactor to carry out the first stage nitration reaction to obtain the first stage nitration reaction solution. The temperature of the first stage nitration reaction is -20~20℃ and the time is 1~20min. 2) The first stage nitration reaction solution is passed into the first tubular reactor to carry out the second stage nitration reaction to obtain the second stage nitration reaction solution. The temperature of the second stage nitration reaction is -20~20℃ and the time is 10~60min. 3) The second-stage nitration reaction solution and water are fed into the second tubular reactor to carry out the hydrolysis reaction to obtain the hydrolysate. The hydrolysis reaction is carried out at a temperature of 40~100℃ for a time of 1~30min. 4) The hydrolysate and a third material including paraformaldehyde and ammonia are fed into a third tubular reactor to carry out a condensation cyclization reaction to obtain 3,7-dinitro-1,3,5,7-tetraazabicyclononane. The temperature of the condensation cyclization reaction is 20~80℃ and the time is 1~30min.

2. The preparation method according to claim 1, characterized in that, In step 1), the molar ratio of urea to nitric acid in the fuming nitric acid is 1:(2~10).

3. The preparation method according to claim 1 or 2, characterized in that, In step 1), the rate at which the first material and the second material are introduced into the microchannel reactor is 1~50 mL / min.

4. The preparation method according to claim 1, characterized in that, In step 3), the rate at which water is introduced into the second tubular reactor is 1~50 mL / min.

5. The preparation method according to claim 1, characterized in that, In step 4), the mass ratio of paraformaldehyde to ammonia in the third material is 1:(1~10).

6. The preparation method according to claim 1 or 5, characterized in that, In step 4), the rate at which the third material is introduced into the third tubular reactor is 1~50 mL / min.

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