A method for preparing spherical 3-nitro-1,2,4-triazol-5-one crystals

Abstract

The application provides a method for preparing spherical 3-nitro-1,2,4-triazol-5-one crystals, and relates to the technical field of energetic crystal materials. The method comprises the following steps: dissolving 3-nitro-1,2,4-triazol-5-one in a solvent to obtain an explosive solution; and introducing a non-solvent and the explosive solution into a micro-reactor for mixing, initial crystallization and crystallization to obtain the spherical 3-nitro-1,2,4-triazol-5-one crystals; wherein the solvent comprises one or more of N-methylpyrrolidone, acetone and gamma-butyrolactone, and the non-solvent comprises 1,2-dichloroethane and / or chloroform; the micro-reactor comprises a valve-type mixer and a labyrinth reactor connected in sequence, the mixing and initial crystallization are performed in the valve-type mixer, and the crystallization is performed in the labyrinth reactor. The NTO crystals prepared based on the micro-reaction technology have high sphericity, small particle size and narrow particle size distribution (particle size distribution is 6-16 mu m).

Description

Technical Field

[0001] This invention relates to the field of energetic crystal materials technology, and in particular to a method for preparing spherical 3-nitro-1,2,4-triazol-5-one crystals. Background Technology

[0002] 3-nitro-1,2,4-triazol-5-one (C2H2N4O3, NTO), as a representative of the new generation of high-energy insensitive energetic materials, has become one of the research hotspots for explosives researchers both domestically and internationally in recent years, since its development as an energetic material by the Los Alamos laboratory in 1983. NTO explosive has a density as high as 1.93 g / cm³. 3 While NTO boasts a theoretical detonation energy close to that of RDX and a sensitivity close to TATB, exhibiting thermal stability and insensitivity to external stimuli, its safety performance surpasses that of B explosives, and its energy is comparable to B explosives, all at a lower cost. However, typical NTO crystals are serrated, rod-like in shape, resulting in poor formability and low charge density in mixed explosives, limiting their applications. Furthermore, NTO crystals are prone to agglomeration, with typical products having particle sizes ranging from tens to hundreds of micrometers, increasing their sensitivity to accidental impacts and diminishing their superior performance.

[0003] Reports indicate that after ultrafine processing, NTO crystals change from rod-shaped to cubic, significantly reducing their mechanical sensitivity and increasing their detonation velocity. Furthermore, regularly shaped NTO crystals, such as spherical crystals, are easier to fill and have smaller interparticle gaps, resulting in increased charge density and energy released per unit volume, which can improve the performance of mixed explosives to some extent. Therefore, how to prepare NTO particles with smaller particle size and regular morphology has become a focus of attention for many researchers. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a method for preparing spherical 3-nitro-1,2,4-triazol-5-one crystals. The spherical 3-nitro-1,2,4-triazol-5-one crystals prepared by the present invention have small particle size, narrow particle size distribution (particle size distribution of 6-16 μm), and high crystal sphericity.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing spherical 3-nitro-1,2,4-triazol-5-one crystals, comprising the following steps:

[0007] 3-Nitro-1,2,4-triazol-5-one was dissolved in a solvent to obtain an explosive solution;

[0008] The non-solvent and the explosive solution were respectively passed into a microreactor for mixing, initial crystallization and crystallization to obtain the spherical 3-nitro-1,2,4-triazol-5-one crystals.

[0009] The solvent includes one or more of N-methylpyrrolidone, acetone and γ-butyrolactone, and the non-solvent includes 1,2-dichloroethane and / or chloroform.

[0010] Starting from the feed end of the non-solvent and explosive solution, the microreactor includes a valve mixer and a tortuous reactor connected in sequence, wherein mixing and initial crystallization take place in the valve mixer and crystallization takes place in the tortuous reactor.

[0011] Preferably, the concentration of the explosive solution is 0.03–0.5 g / mL.

[0012] Preferably, the flow rate of the explosive solution into the microreactor is 0.8–2.2 mL / min, the flow rate of the non-solvent into the microreactor is 5–15 mL / min, and the flow rate ratio of the non-solvent to the explosive solution is 5–19.

[0013] Preferably, the temperature of the explosive solution is 69–72°C, and the temperature of the non-solvent is 19–23°C.

[0014] Preferably, the mixing and initial crystallization temperature is 19–23°C.

[0015] Preferably, the residence times of the explosive solution and the non-solvent in the valve mixer are 0.41–1.125 min and 0.06–0.18 min, respectively.

[0016] Preferably, the crystallization temperature is 19–23°C.

[0017] Preferably, the residence time of the mixture obtained from mixing and initial crystallization in the curved reactor is 0.66 to 1.95 min.

[0018] Preferably, the crystallization process further includes solid-liquid separation, washing, and drying of the obtained explosive suspension to obtain spherical 3-nitro-1,2,4-triazol-5-one crystals.

[0019] Preferably, the spherical 3-nitro-1,2,4-triazol-5-one crystals have a particle size distribution of 6–16 μm.

[0020] This invention provides a method for preparing spherical 3-nitro-1,2,4-triazol-5-one (NTO) crystals, comprising the following steps: dissolving 3-nitro-1,2,4-triazol-5-one in a solvent to obtain an explosive solution; passing a non-solvent and the explosive solution into a microreactor for mixing, initial crystallization, and crystallization, respectively, to obtain the spherical 3-nitro-1,2,4-triazol-5-one crystals; the solvent includes one or more of N-methylpyrrolidone, acetone, and γ-butyrolactone, and the non-solvent includes 1,2-dichloroethane and / or chloroform; the microreactor comprises a valve mixer and a tortuous reactor connected in sequence, wherein the mixing and initial crystallization are carried out in the valve mixer, and the crystallization is carried out in the tortuous reactor. Compared with the prior art, this invention has the following beneficial effects:

[0021] This invention employs a solvent-nonsolvent method to prepare spherical 3-nitro-1,2,4-triazol-5-one crystals by recrystallization with specific solvents and nonsolvents;

[0022] Furthermore, this invention employs a micro-reaction method, which consists of a valve mixer and a tortuous reactor to form a micro-reaction crystallization system. The NTO explosive solution and non-solvent are mixed efficiently and intensely in the valve mixer, and under the effect of high heat and mass transfer in the tortuous reactor, the crystallization environment in the micro-region is highly uniform, which is conducive to obtaining crystals with smaller particle size and narrower distribution. At the same time, the small micro-nano particles have a tendency to spontaneously assemble into spherical particles due to their high specific surface energy.

[0023] Furthermore, the present invention achieves the purpose of controlling the morphology and particle size distribution of NTO crystals by controlling the concentration of the explosive solution, the flow rate of the explosive solution and non-solvent, and the crystallization temperature.

[0024] The NTO crystals prepared using the micro-reaction technology of this invention have high sphericity, small particle size, and a narrow particle size distribution range of 6–16 μm. Furthermore, the method of this invention is simple to operate, efficient, and conducive to the stable and effective batch preparation of spherical NTO crystals. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall apparatus for preparing spherical 3-nitro-1,2,4-triazol-5-one crystals in an embodiment of the present invention. Figure 1 In the middle, 1-solution gas collecting bottle, 2-non-solvent gas collecting bottle, 3-1-high pressure plunger pump, 3-2-high pressure plunger pump, 4-insulation device, 5-coaxial heat exchanger, 6-valve mixer, 7-curved reactor, 8-crystallized product gas collecting bottle;

[0026] Figure 2 SEM image of the NTO crystal prepared in Example 1;

[0027] Figure 3 SEM image of the NTO crystal prepared in Example 2;

[0028] Figure 4 SEM image of the NTO crystal prepared in Example 3;

[0029] Figure 5 SEM image of the NTO crystal prepared in Example 4;

[0030] Figure 6 SEM image of the NTO crystal prepared for Comparative Example 1;

[0031] Figure 7 SEM image of the NTO crystal prepared for Comparative Example 2. Detailed Implementation

[0032] This invention provides a method for preparing spherical 3-nitro-1,2,4-triazol-5-one crystals, comprising the following steps:

[0033] 3-Nitro-1,2,4-triazol-5-one was dissolved in a solvent to obtain an explosive solution;

[0034] The non-solvent and the explosive solution were respectively passed into a microreactor for mixing, initial crystallization and crystallization to obtain the spherical 3-nitro-1,2,4-triazol-5-one crystals.

[0035] The solvent includes one or more of N-methylpyrrolidone, acetone and γ-butyrolactone, and the non-solvent includes 1,2-dichloroethane and / or chloroform.

[0036] Starting from the feed end of the non-solvent and explosive solution, the microreactor includes a valve mixer and a tortuous reactor connected in sequence, wherein mixing and initial crystallization take place in the valve mixer and crystallization takes place in the tortuous reactor.

[0037] This invention involves dissolving 3-nitro-1,2,4-triazol-5-one (NTO) in a solvent to obtain an explosive solution. In this invention, the solvent comprises one or more of N-methylpyrrolidone, acetone, and γ-butyrolactone, preferably N-methylpyrrolidone or γ-butyrolactone; the concentration of the explosive solution is preferably 0.03–0.5 g / mL, more preferably 0.4–0.5 g / mL.

[0038] This invention involves passing a non-solvent and the explosive solution into a microreactor for sequential mixing, initial crystallization, and crystallization to obtain the spherical 3-nitro-1,2,4-triazol-5-one crystals. In this invention, the non-solvent includes 1,2-dichloroethane and / or chloroform, preferably 1,2-dichloroethane. This invention employs a solvent-non-solvent method; the addition of a non-solvent reduces the solubility of the solute (i.e., NTO) in the crystallization system, thereby causing the solute to precipitate and form crystals.

[0039] In this invention, starting from the feed end of the non-solvent and explosive solutions, the microreactor includes a valve-type mixer and a tortuous reactor connected in sequence. In this embodiment, the valve-type mixer is provided by Efliner Chemical Technology (Shanghai) Co., Ltd., model number 0111-2-0011-F, and allows a fluid volume of 0.9 mL to pass through. The valve-type mixer includes two parallel channels: a solution inlet module and a non-solvent inlet module. A blockage or other malfunction in one channel will not affect the normal operation of the other channel. In this invention, the tortuous reactor is provided by Efliner Chemical Technology (Shanghai) Co., Ltd., model number 0211-2-0321-F, and allows a fluid volume of 11.3 mL to pass through.

[0040] In this invention, the temperature of the explosive solution is preferably 69–72°C, and the temperature of the non-solvent is preferably 19–23°C. To ensure the accuracy of the crystallization temperature, before the non-solvent and explosive solution are introduced into the microreactor, the non-solvent is preferably heated to 19–23°C using a coaxial heat exchanger, and the explosive solution is kept at 69–72°C using a heat preservation device.

[0041] In this invention, the flow rate of the explosive solution introduced into the microreactor is preferably 0.8–2.2 mL / min, more preferably 1.0 mL / min; the flow rate of the non-solvent introduced into the microreactor is preferably 5–15 mL / min, more preferably 5–10 mL / min; the flow ratio of the non-solvent to the explosive solution is preferably 5–19, more preferably 5–15. In this invention, the non-solvent and explosive solution are preferably stored separately in gas collecting bottles and introduced into the microreactor under the action of a high-pressure plunger pump or a syringe pump.

[0042] In this invention, the mixing and initial crystallization are carried out in a valve-type mixer, that is, the non-solvent and the explosive solution are first introduced into the valve-type mixer in the microreactor by a high-pressure plunger pump or injection pump. In this invention, the mixing and initial crystallization temperature is preferably 19–23°C. In the valve-type mixer, the flow rate of the non-solvent is much greater than the flow rate of the explosive solution, so when the non-solvent and the explosive solution are mixed, the effect of a very small amount of explosive solution on the mixing temperature is negligible, and the mixing, initial crystallization, and subsequent crystallization temperatures can be equivalent to the temperature of the non-solvent.

[0043] In this invention, the residence times of the explosive solution and the non-solvent in the valve mixer are preferably 0.41–1.125 min and 0.06–0.18 min, respectively. In the valve mixer, the explosive solution flows through a narrow channel through 3×5 fine holes (3 groups of small holes on the same plane, 5 small holes in each group) and is then cut into radially arranged fine streams by a 36×210 μm disc (36 teeth on the disc, with a tooth width of 210 μm) and enters the mixing zone of the valve mixer. It undergoes initial mixing with the non-solvent, which forms a circulating flow, and crystallization begins at the end of the valve mixer, i.e., the initial crystallization.

[0044] In this invention, the crystallization is carried out in a tortuous reactor, that is, the mixture obtained from mixing and initial crystallization enters the tortuous reactor. In this invention, the crystallization temperature is preferably 19–23°C, more preferably 20°C. In this invention, the residence time of the mixture obtained from mixing and initial crystallization in the tortuous reactor is preferably 0.66–1.95 min. In this invention, the mixture obtained from mixing and initial crystallization is further mixed after entering the tortuous reactor to increase the crystallization time.

[0045] In this invention, the valve mixer and the tortuous reactor constitute a micro-reaction crystallization system. The efficient and intense mixing of the NTO explosive solution and non-solvent in the valve mixer, coupled with the high heat and mass transfer in the tortuous reactor, results in a highly uniform crystallization environment within the micro-region. This is beneficial for obtaining crystals with smaller particle sizes and narrower distributions. Furthermore, the smaller micro- and nano-particles, due to their higher specific surface energy, tend to spontaneously assemble into spherical particles. Moreover, this invention controls the morphology and particle size distribution of NTO crystals by controlling the types of solvents and non-solvents, the concentration of the explosive solution, the flow rates of the explosive solution and non-solvents, and the crystallization temperature. Specifically, the types of solvents and non-solvents and the crystallization temperature have a significant impact on the morphology of the NTO crystals; the concentration of the explosive solution affects the uniformity of the crystal morphology and the particle size distribution range; and the flow rate ratio of the non-solvent to the explosive solution has a significant impact on the particle size of the NTO crystals.

[0046] Figure 1This is a schematic diagram of the overall system used in this embodiment of the invention for preparing spherical 3-nitro-1,2,4-triazol-5-one crystals. Figure 1 In this system, 1-solution gas collecting bottle, 2-non-solvent gas collecting bottle, 3-1-high-pressure plunger pump, 3-2-high-pressure plunger pump, 4-insulation device, 5-coaxial heat exchanger, 6-valve mixer, 7-torsional reactor, and 8-crystallized product gas collecting bottle. Among these, 1-solution gas collecting bottle, 2-non-solvent gas collecting bottle, 3-1-high-pressure plunger pump, and 3-2-high-pressure plunger pump constitute a fluid drive system; 4-insulation device, 5-coaxial heat exchanger, 6-valve mixer, and 7-torsional reactor constitute a microreactor system, and within this microreactor system, 6-valve mixer and 7-torsional reactor constitute a microreactor.

[0047] In the embodiments of the present invention, the following methods are utilized: Figure 1 The specific steps for preparing spherical 3-nitro-1,2,4-triazol-5-one crystals in the system shown are as follows:

[0048] The solvent and non-solvent are placed in gas collecting bottle 1 and gas collecting bottle 2 respectively. Under the action of high-pressure plunger pump 3-1 and high-pressure plunger pump 3-2, the microchannel of the microreactor is rinsed multiple times with the solvent and non-solvent until it is colorless.

[0049] Then, the explosive solution and the non-solvent are placed in gas collecting bottle 1 and gas collecting bottle 2 respectively. The flow rate of the explosive solution is set to 0.8-2.2 mL / min and the flow rate of the non-solvent is set to 5-15 mL / min. The explosive solution at the specified flow rate is kept warm by the heat preservation device 4. The non-solvent at the specified flow rate is heat exchanged by the coaxial heat exchanger 5.

[0050] The heat-insulated explosive solution and the heat-exchanged non-solvent solution are respectively fed into valve mixer 6 for mixing and initial crystallization, and then into curved reactor 7 for crystallization at a temperature of 19-23℃ to obtain explosive suspension.

[0051] The explosive suspension is collected as a crystallized product by the crystallization product gas collecting bottle 8.

[0052] The micro-reaction technology-based recrystallized explosive particle preparation system used in this invention is simple to operate and has the effectiveness and efficiency of product preparation and process screening. It is very suitable for screening and optimizing experimental parameters in the process of NTO crystal morphology and particle size control. It has excellent mass and heat transfer characteristics, high controllability, good operability and high safety that are unmatched by traditional batch reaction systems.

[0053] In this invention, the crystallization process preferably further includes solid-liquid separation, washing, and drying of the obtained explosive suspension to obtain spherical 3-nitro-1,2,4-triazol-5-one crystals; the washing is preferably water washing, and the drying is preferably freeze drying.

[0054] In this invention, the preferred particle size distribution of the spherical 3-nitro-1,2,4-triazol-5-one crystals is 6–16 μm. The NTO crystals prepared by this invention have high sphericity, small particle size, and a narrow particle size distribution range.

[0055] To further illustrate the present invention, the method for preparing spherical 3-nitro-1,2,4-triazol-5-one crystals provided by the present invention will be described in detail below with reference to examples, but these should not be construed as limiting the scope of protection of the present invention.

[0056] In the examples, N-methylpyrrolidone (analytical grade) was obtained from Tianjin Dingshengxin Chemical Co., Ltd., γ-butyrolactone (analytical grade) from Shanghai Maclean Biochemical Technology Co., Ltd., and 1,2-dichloroethane (analytical grade) from Sinopharm Chemical Reagent Co., Ltd. All these analytical grade reagents can be used without further purification; the valve mixer was provided by Evans Chemical Technology (Shanghai) Co., Ltd., model number 0111-2-0011-F; the tortuous reactor was provided by Evans Chemical Technology (Shanghai) Co., Ltd., model number 0211-2-0321-F; the morphology of the products in the examples was obtained by scanning electron microscopy using a TescanMira3LMH from Tescan GmbH, Czech Republic.

[0057] Example 1

[0058] Preparation of spherical NTO crystals based on microreaction technology (device such as...) Figure 1 As shown in the image, the parameter settings are as follows:

[0059] The solvent was N-methylpyrrolidone, the non-solvent was 1,2-dichloroethane, the NTO solution concentration was 0.5 g / mL, the NTO solution flow rate was 1.0 mL / min, the non-solvent flow rate was 5.0 mL / min, and the crystallization temperature was 20 °C.

[0060] The specific preparation steps are as follows:

[0061] (1) First, weigh 2.5g NTO and dissolve it in 5mL of N-methylpyrrolidone (NMP) to obtain the explosive solution. Place it in a gas collecting bottle and keep it at 70°C using a heat preservation device. The non-solvent is heated to 20°C by a coaxial heat exchanger.

[0062] (2) Under the action of a high-pressure plunger pump, NMP and 1,2-dichloroethane were used to flush the microchannel multiple times until it became colorless;

[0063] (3) Set the flow rate of the explosive solution to 1.0 mL / min and the flow rate of the non-solvent to 5.0 mL / min;

[0064] (4) Under the action of the high-pressure plunger pump, the explosive solution is introduced into the valve mixer. After passing through the narrow channel of the valve mixer and through 3×5 fine holes, it is cut into radially arranged fine streams by the 36×210μm disc and enters the mixing zone of the valve mixer. After initial mixing and initial crystallization with the non-solvent forming a circulating state, it enters the tortuous reactor for crystallization at a crystallization temperature of 20℃.

[0065] (5) Pour the explosive suspension collected from the curved reactor into the sand core funnel, then turn on the circulating water vacuum pump to filter and wash, and then put it into the freeze dryer to dry, so as to obtain a fine explosive powder product.

[0066] The refined product, i.e., spherical NTO crystals, was collected and characterized under a scanning electron microscope (SEM). The SEM images are shown below. Figure 2 As shown.

[0067] Example 2

[0068] Preparation of spherical NTO crystals based on microreaction technology (device such as...) Figure 1 As shown in the image, the parameter settings are as follows:

[0069] The solvent was γ-butyrolactone, the non-solvent was 1,2-dichloroethane, the NTO solution concentration was 0.03 g / mL, the NTO solution flow rate was 1.0 mL / min, the non-solvent flow rate was 5.0 mL / min, and the crystallization temperature was 20℃.

[0070] The specific preparation steps are as follows:

[0071] (1) First, 0.3g of NTO was dissolved in 10mL of γ-butyrolactone to obtain the explosive solution. The solution was placed in a gas collecting bottle and kept at 70°C by a heat preservation device. The non-solvent was heated to 20°C by a coaxial heat exchanger.

[0072] (2) Under the action of a high-pressure plunger pump, γ-butyrolactone and 1,2-dichloroethane were used to flush the microchannel multiple times until it became colorless;

[0073] (3) Set the flow rate of the explosive solution to 1.0 mL / min and the flow rate of the non-solvent to 5.0 mL / min;

[0074] (4) Under the action of the high-pressure plunger pump, the explosive solution is introduced into the valve mixer. After passing through the narrow channel of the valve mixer and through 3×5 fine holes, it is cut into radially arranged fine streams by the 36×210μm disc and enters the mixing zone of the valve mixer. After initial mixing and initial crystallization with the non-solvent forming a circulating state, it enters the tortuous reactor for crystallization at a crystallization temperature of 20℃.

[0075] (5) Pour the explosive suspension collected from the curved reactor into the sand core funnel, then turn on the circulating water vacuum pump to filter and wash, and then put it into the freeze dryer to dry, so as to obtain a fine explosive powder product.

[0076] The refined product, i.e., spherical NTO crystals, was collected and characterized under a scanning electron microscope (SEM). The SEM images are shown below. Figure 3 As shown.

[0077] Example 3

[0078] Preparation of spherical NTO crystals based on microreaction technology (device such as...) Figure 1 As shown in the image, the parameter settings are as follows:

[0079] The solvent was N-methylpyrrolidone, the non-solvent was 1,2-dichloroethane, the NTO solution concentration was 0.4 g / mL, the NTO solution flow rate was 1.0 mL / min, the non-solvent flow rate was 5.0 mL / min, and the crystallization temperature was 20 °C.

[0080] The specific preparation steps are as follows:

[0081] (1) First, weigh 2.0g NTO and dissolve it in 5mL of N-methylpyrrolidone (NMP) to obtain the explosive solution. Place it in a gas collecting bottle and keep it at 70°C using a heat preservation device. The non-solvent is heated to 20°C by a coaxial heat exchanger.

[0082] (2) Under the action of a high-pressure plunger pump, NMP and 1,2-dichloroethane were used to flush the microchannel multiple times until it became colorless;

[0083] (3) Set the flow rate of the explosive solution to 1.0 mL / min and the flow rate of the non-solvent to 5 mL / min;

[0084] (4) Under the action of the high-pressure plunger pump, the explosive solution is introduced into the valve mixer. After passing through the narrow channel of the valve mixer and through 3×5 fine holes, it is cut into radially arranged fine streams by the 36×210μm disc and enters the mixing zone of the valve mixer. After initial mixing and initial crystallization with the non-solvent forming a circulating state, it enters the tortuous reactor for crystallization at a crystallization temperature of 20℃.

[0085] (5) Pour the explosive suspension collected from the curved reactor into the sand core funnel, then turn on the circulating water vacuum pump to filter and wash, and then put it into the freeze dryer to dry, so as to obtain a fine explosive powder product.

[0086] The refined product, i.e., spherical NTO crystals, was collected and characterized under a scanning electron microscope (SEM). The SEM images are shown below. Figure 4 As shown.

[0087] Example 4

[0088] Preparation of spherical NTO crystals based on microreaction technology (device such as...) Figure 1 As shown in the image, the parameter settings are as follows:

[0089] The solvent was N-methylpyrrolidone, the non-solvent was 1,2-dichloroethane, the NTO solution concentration was 0.5 g / mL, the NTO solution flow rate was 1.0 mL / min, the non-solvent flow rate was 15.0 mL / min, and the crystallization temperature was 20 °C.

[0090] The specific preparation steps are as follows:

[0091] (1) First, weigh 2.5g NTO and dissolve it in 5mL of N-methylpyrrolidone (NMP) to obtain an explosive solution. Place it in a gas collecting bottle and keep it at 70°C using a heat preservation device. The non-solvent is heated to 20°C by a coaxial heat exchanger.

[0092] (2) Under the action of a high-pressure plunger pump, NMP and 1,2-dichloroethane were used to flush the microchannel multiple times until it became colorless;

[0093] (3) Set the flow rate of the explosive solution to 1.0 mL / min and the flow rate of the non-solvent to 15.0 mL / min;

[0094] (4) Under the action of the high-pressure plunger pump, the explosive solution is introduced into the valve mixer. After passing through the narrow channel of the valve mixer and through 3×5 fine holes, it is cut into radially arranged fine streams by the 36×210μm disc and enters the mixing zone of the valve mixer. After initial mixing and initial crystallization with the non-solvent forming a circulating state, it enters the tortuous reactor for crystallization at a crystallization temperature of 20℃.

[0095] (5) Pour the explosive suspension collected from the curved reactor into the sand core funnel, then turn on the circulating water vacuum pump to filter and wash, and then put it into the freeze dryer to dry, so as to obtain a fine explosive powder product.

[0096] The refined product, i.e., spherical NTO crystals, was collected and characterized under a scanning electron microscope (SEM). The SEM images are shown below. Figure 5 As shown.

[0097] Depend on Figures 2-5 As can be seen, Example 1 yielded spherical NTO with a dense surface and an average particle size of 9.93 μm; Example 2 yielded spherical NTO particles with a particle size distribution of 5–16 μm, a rough surface, and a small number of irregularly distributed needle-like crystals attached to the edges; Example 3 yielded spherical NTO with a dense surface, a large number of small blocky crystals attached, and a particle size distribution of 6–12 μm; Example 4 yielded spherical NTO crystals with a particle size distribution of 5–16 μm, a rough crystal surface, and scattered irregularly distributed small particles.

[0098] Comparative Example 1

[0099] NTO preparation based on microreaction technology (device such as...) Figure 1 As shown in the image, the parameter settings are as follows:

[0100] The solvent was N-methylpyrrolidone, the non-solvent was dichloromethane, the NTO solution concentration was 0.5 g / mL, the NTO solution flow rate was 1.0 mL / min, the non-solvent flow rate was 15.0 mL / min, and the crystallization temperature was 20℃.

[0101] The specific preparation steps are as follows:

[0102] (1) First, 2.5g of NTO was weighed and dissolved in 5mL of N-methylpyrrolidone to obtain an explosive solution. The solution was placed in a gas collecting bottle and kept at 70°C by a heat preservation device. The non-solvent was heated to 20°C by a coaxial heat exchanger.

[0103] (2) Under the action of a high-pressure plunger pump, NMP and dichloromethane were used to flush the microchannel multiple times until it became colorless;

[0104] (3) Set the flow rate of the explosive solution to 1.0 mL / min and the flow rate of the non-solvent to 15 mL / min;

[0105] (4) Under the action of the high-pressure plunger pump, the explosive solution is introduced into the valve mixer. After passing through the narrow channel of the valve mixer and through 3×5 fine holes, it is cut into radially arranged fine streams by the 36×210μm disc and enters the mixing zone of the valve mixer. After initial mixing and initial crystallization with the non-solvent forming a circulating state, it enters the tortuous reactor for crystallization at a crystallization temperature of 20℃.

[0106] (5) Pour the explosive suspension collected from the curved reactor into the sand core funnel, then turn on the circulating water vacuum pump to filter and wash, and then put it into the freeze dryer to dry, so as to obtain a fine explosive powder product.

[0107] The refined products were collected and characterized under a scanning electron microscope (SEM). SEM observations showed that... Figure 6 As shown.

[0108] Depend on Figure 6 It can be seen that the particle size distribution of the obtained product is 0.6 to 3.0 μm, and the morphology is an irregular slender strip with a small number of rod-shaped crystals attached to the surface.

[0109] Comparative Example 2

[0110] NTO preparation based on microreaction technology (device such as...) Figure 1 As shown in the image, the parameter settings are as follows:

[0111] The solvent was N-methylpyrrolidone, the non-solvent was 1,2-dichloroethane, the NTO solution concentration was 0.5 g / mL, the NTO solution flow rate was 1.0 mL / min, the non-solvent flow rate was 15.0 mL / min, and the crystallization temperature was 55℃.

[0112] The specific preparation steps are as follows:

[0113] (1) First, weigh 2.5g NTO and dissolve it in 5mL of N-methylpyrrolidone to obtain an explosive solution. Place it in a gas collecting bottle and keep it at 70°C using a heat preservation device. The non-solvent is heated to 55°C by a coaxial heat exchanger.

[0114] (2) Under the action of a high-pressure plunger pump, NMP and 1,2-dichloroethane were used to flush the microchannel multiple times until it became colorless;

[0115] (3) Set the flow rate of the explosive solution to 1.0 mL / min and the flow rate of the non-solvent to 15 mL / min;

[0116] (4) Under the action of the high-pressure plunger pump, the explosive solution is cut into radially arranged fine streams by a 36×210μm disc after passing through a narrow channel through 3×5 fine holes. It enters the mixing zone of the valve mixer, where it undergoes initial mixing and initial crystallization with the non-solvent that forms a circulating state. Then, it enters the curved reactor for crystallization at a crystallization temperature of 55℃.

[0117] (5) Pour the explosive suspension collected from the curved reactor into the sand core funnel, then turn on the circulating water vacuum pump to filter and wash, and then put it into the freeze dryer to dry, so as to obtain a fine explosive powder product.

[0118] The refined products were collected and characterized under a scanning electron microscope (SEM). The SEM images are shown below. Figure 7 As shown.

[0119] Depend on Figure 7 It can be seen that the obtained products are blocky and bundle-like crystals with rough surfaces, and the particle size distribution is 8 to 22 μm. The product morphology and particle size are diverse.

[0120] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing spherical 3-nitro-1,2,4-triazol-5-one crystals, characterized in that, Includes the following steps: 3-Nitro-1,2,4-triazol-5-one was dissolved in a solvent to obtain an explosive solution; the concentration of the explosive solution was 0.4~0.5 g / mL. The non-solvent and the explosive solution are separately introduced into a microreactor for mixing, initial crystallization, and crystallization to obtain the spherical 3-nitro-1,2,4-triazol-5-one crystals; the flow rate ratio of the non-solvent to the explosive solution is 5~19; the temperature of the explosive solution is 69~72℃, and the temperature of the non-solvent is 19~23℃; the mixing and initial crystallization temperatures are 19~23℃; the crystallization temperature is 19~23℃. The solvent is one or more of N-methylpyrrolidone and γ-butyrolactone, and the non-solvent is 1,2-dichloroethane; Starting from the feed end of the non-solvent and explosive solution, the microreactor includes a valve mixer and a tortuous reactor connected in sequence, wherein mixing and initial crystallization take place in the valve mixer and crystallization takes place in the tortuous reactor.

2. The method according to claim 1, characterized in that, The flow rate of the explosive solution into the microreactor is 0.8~2.2 mL / min, and the flow rate of the non-solvent into the microreactor is 5~15 mL / min.

3. The method according to claim 1, characterized in that, The residence times of the explosive solution and the non-solvent in the valve mixer are 0.41~1.125 min and 0.06~0.18 min, respectively.

4. The method according to claim 1, characterized in that, The residence time of the mixture obtained after mixing and initial crystallization in the curved reactor is 0.66~1.95 min.

5. The method according to claim 1, characterized in that, The crystallization process further includes solid-liquid separation, washing, and drying of the resulting explosive suspension to obtain spherical 3-nitro-1,2,4-triazol-5-one crystals.

6. The method according to claim 1 or 5, characterized in that, The spherical 3-nitro-1,2,4-triazol-5-one crystals have a particle size distribution of 6~16 μm.

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