A process for the production of tetraacetyl hexaazaisowurtzitane

Abstract

The application provides a method for producing tetraacetyl hexaazaisowurtzitane, which uses hexabenzyl hexaazaisowurtzitane crude product as raw material, removes impurities through recrystallization purification, and then prepares tetraacetyl hexaazaisowurtzitane through two-step hydrogenation. Compared with the prior art, the method has the advantages of less catalyst usage, low production cost, high product purity, and is very suitable for industrial production. According to the production method, the purity of tetraacetyl hexaazaisowurtzitane in the obtained product is greater than 99.5%.

Description

Technical Field

[0001] This invention relates to a method for producing tetraacetylhexaazaisowulzane, belonging to the field of fine chemical technology. Background Technology

[0002] Tetraacetyl-2,6,8,12-tetraacetyl-2,4,6,8,10,12-hexaazaisowurtzitane (TAIW), CAS No.: 181940-38-5, is a white powdery solid. Its molecular structure is as follows:

[0003]

[0004] Tetraacetylhexaazaisowrtzane is a key raw material for manufacturing the novel high-density energetic material hexanitrohexaazaisowrtzane. Hexanitrohexaazaisowrtzane (HNIW), commonly known as CL-20, has superior maximum detonation velocity, detonation pressure, and density compared to octogen. Its energy output per unit weight is 10-15% higher than octogen, making it the highest-energy and most powerful non-nuclear elemental explosive currently known for practical applications, with widespread demand in the manufacture of advanced weaponry. There are many synthetic routes for CL-20, but the currently verified safe and feasible method is to prepare it using tetraacetylhexaazaisowrtzane as a raw material through a simple one-step nitration. Therefore, the price and yield of tetraacetylhexaazaisowrtzane determine the future application scenarios of CL-20, making the development of a large-scale, low-cost method for its production essential.

[0005] There are many methods for synthesizing hexanitrohexaazaisowurtzite (HNIW), which can be obtained by nitrifying the following five raw materials: tetraacetyldiformylhexaazaisowurtzite (TADFIW), tetraacetyldiethylhexaazaisowurtzite (TADEIW), hexaacetylhexaazaisowurtzite (HAIW), tetraacetylhexaazaisowurtzite (TAIW), and tetraacetyldibenzylhexaazaisowurtzite (TADBIW). The first four raw materials require two hydrogenation processes from hexabenzylhexaazaisowurtzite (HBIW), while TADBIW can be obtained by only one hydrogenation process from HBIW. While using TADBIW as a raw material eliminates the need for the second step of hydrogenolysis, the nitration process is actually a nitroso-nitroso process. Specifically, the two benzyl groups on the six-membered ring of TADBIW are removed through nitrosolysis. The reaction process involves first nitrosolysis of TADBIW to tetraacetyl dinitrosohexaazaisowroughtane (TADNSIW), followed by nitrosolysis of TADNSIW to HNIW. However, the nitrating reagents used in the nitroso-nitroso-nitroso reaction using TADBIW as a raw material are expensive, and the process is more dangerous than the conventional nitric acid / sulfuric acid nitration process. Furthermore, the HNIW product prepared by this method often contains difficult-to-separate incompletely nitrated intermediates, resulting in a product purity of only 95%–98%. These difficult-to-separate impurities not only reduce the performance of HNIW but also significantly increase the risk of uncontrollable explosions during subsequent crystallization, separation, drying, and transportation.

[0006] The high cost of HNIW preparation is primarily due to the large amount of Pd catalyst required for the two-step hydrogenolysis process. Furthermore, the complex solvent system in the hydrogenolysis process makes Pd particles prone to detachment from the support and agglomeration, leading to catalyst deactivation and poor cycle performance. Therefore, exploring efficient, stable, and highly atom-utilization-efficient industrial catalysts is a crucial way to reduce the cost of HNIW.

[0007] To address the issue of excessively high catalyst costs, numerous studies and patents have reported on the impact of the support properties of supported Pd catalysts on their catalytic performance. Nielsen et al. used a 20% Pd(OH)₂ / C catalyst supported on activated carbon to hydrogenate HBIW to prepare TADBIW, achieving a TADBIW yield of 63% with Pd accounting for 5% of the HBIW mass. US Patent US5739325 used a 10% Pd / C catalyst to hydrogenate HBIW to prepare TADBIW, achieving a yield of 82-85% with Pd accounting for 0.5% of the HBIW mass. Qiu Wenge et al. selected three different activated carbons as supports to prepare catalysts, with the Pd(OH)₂ / CC-30 catalyst exhibiting the highest activity, achieving a TADBIW yield of 93% with Pd accounting for 0.3% of the HBIW mass. Lou et al. prepared PdM (M = Ni, Cu, Co, Fe) bimetallic catalysts using XC-72, activated carbon, SiO2, TiO2, and Al2O3 as catalyst supports. Among them, PdFeTi exhibited the best catalytic performance and could be used simultaneously for the hydrodebenzylation reaction of HBIW and TADBIW, with yields of 76% and 88%, respectively. Liu et al. used a Pd catalyst (Pd / ST-2.5) supported on mesoporous TiO2 to catalyze the hydrodebenzylation reaction of HBIW, achieving a TADBIW yield of 82%, with Pd dosage being 0.10% of the substrate HBIW mass. In summary, although the reported catalysts each have certain advantages, in actual industrial production, besides considering the amount of catalyst used at the time of feeding, the most significant factors affecting production costs are the catalyst recovery rate and recovery cost. Although specially supported catalysts can reduce the amount of catalyst used in a single use, the catalyst loss in the system is also relatively large, making the reduction in production costs insignificant.

[0008] With the increasing demand for HNIW from the defense industry, and considering that the one-step nitration process using TAIW as a raw material is currently the only proven method for large-scale industrial production, there is an urgent need for a method that is simple in process, has readily available raw materials, high product yield, good quality, and can be used for large-scale TAIW production. Selecting a suitable catalyst and a reasonable reaction system is key to solving this problem. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a method for producing tetraacetylhexaazaisowulzane.

[0010] This invention is achieved through the following technical solution:

[0011] <First Aspect>

[0012] This invention provides a method for purifying and refining hexabenzylhexaazaisowoodsane, comprising the following steps:

[0013] Hexabenzylhexaazaisowrutzane is purified using a mixed solvent, which includes a combination of solvents that readily dissolve hexabenzylhexaazaisowrutzane and solvents that are slightly soluble or insoluble in hexabenzylhexaazaisowrutzane.

[0014] The specific method for purifying and refining hexabenzylhexaazaisowrutzane is as follows: Hexabenzylhexaazaisowrutzane with a content of 95-98%, mixed solvent, and activated carbon are added to a reaction vessel, heated to 35-75℃ and kept at that temperature for 15 min-2 h, filtered to remove activated carbon and insoluble matter, and the filtrate is stirred and cooled to -5℃-5℃ and kept at that temperature for 30 min-2 h; a solid is precipitated, filtered, and the solid is washed with solvent and dried to obtain a powdered solid, which is the refined hexabenzylhexaazaisowrutzane.

[0015] The solvents that readily dissolve hexabenzylhexaazaisowulzane include one or more of diethyl ether, methyl tert-butyl ether, ethyl butyl ether, tetrahydrofuran, 1,4-dioxane, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, and ethylene glycol dimethyl ether.

[0016] The solvent for the slightly soluble or insoluble hexabenzylhexaazaisowulzane includes one or more of methanol, ethanol, isopropanol, acetonitrile, propionitrile, toluene, xylene, ethyl acetate, dichloromethane, and 1,2-dichloroethane.

[0017] <Second aspect>

[0018] This invention also provides hexabenzylhexaazaisowulzane prepared by the preparation method described above.

[0019] <Third aspect>

[0020] This invention provides a method for producing tetraacetylhexaazaisowulzane, comprising the following steps:

[0021] S1, hexabenzylhexaazaisowulzane, was purified and refined using a mixed solvent;

[0022] S2. The hexabenzylhexaazaisowulzane purified in step S1 is subjected to a first hydrogenation reaction under the catalysis of catalyst A to obtain tetraacetyldibenzylhexaazaisowulzane.

[0023] S3. Tetraacetyldibenzylhexaazaisowulzane is prepared by a second hydrogenation reaction under the catalysis of catalyst B.

[0024] Step S1 is as follows: Hexabenzylhexaazaisowulzane with a content of 95-98%, mixed solvent, and activated carbon are added to a reaction vessel, heated to 35-75℃ and kept at that temperature for 15 min-2 h, filtered to remove activated carbon and insoluble matter, and the filtrate is stirred and cooled to -5℃-5℃ and kept at that temperature for 30 min-2 h; the solid precipitates, is filtered, and the solid is washed with solvent and dried to obtain a powdered solid, which is the refined hexabenzylhexaazaisowulzane.

[0025] The mixed solvent comprises a combination of solvents that readily dissolve hexabenzylhexaazaisowrutzane and solvents that are slightly soluble or insoluble in hexabenzylhexaazaisowrutzane.

[0026] The solvents that readily dissolve hexabenzylhexaazaisourtzite include one or more of diethyl ether, methyl tert-butyl ether, ethyl butyl ether, tetrahydrofuran, 1,4-dioxane, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, and ethylene glycol dimethyl ether. Tetrahydrofuran is preferred.

[0027] The solvent for which hexabenzylhexaazaisowrutzane is slightly soluble or insoluble includes one or more of methanol, ethanol, isopropanol, acetonitrile, propionitrile, toluene, xylene, ethyl acetate, dichloromethane, and 1,2-dichloroethane. Acetonitrile is preferred.

[0028] As a preferred option, the activated carbon used for purification and refining can be coal-based activated carbon, wood-based activated carbon, or synthetic material activated carbon, preferably neutral coconut shell activated carbon prepared by potassium hydroxide activation treatment.

[0029] As a preferred option, the weight ratio of easily soluble solvent: slightly soluble or sparingly soluble solvent: activated carbon: crude hexabenzylhexaazaisowulzane is 0.5~2:0.5~5:0.01~0.05:1.0, preferably 0.7~1.2:2.5~3.5:0.01~0.02:1.0.

[0030] As a preferred option, in step S1, the heating temperature is controlled at 35-68℃, preferably 45-60℃; the cooling temperature is controlled at -5-5℃, preferably 0-5℃.

[0031] Step S2 specifically includes the following steps:

[0032] S2.1. Mix and stir the purified hexabenzylhexaazaisowulzane, solvent A, and catalyst activator A evenly to obtain a slurry.

[0033] S2.2. Solvent B, catalytic activator B, acetic anhydride, and catalyst A are mixed evenly in reactor A. Hydrogen gas is introduced, and the hydrogen pressure is controlled at 0.25–1.5 MPa. The temperature is lowered to -10–30°C. Then, the slurry material from step S2.1 is slowly pressed into a pressure reactor for 2–8 hours. After pressing, the reaction is continued at -10–30°C and 0.25–1.5 MPa for 2–8 hours. Then, the temperature is raised to 30–60°C, and the reaction is continued at 0.25–1.5 MPa for 2–8 hours. The temperature is lowered to 15–30°C, filtered, and washed to obtain tetraacetyl dibenzylhexaazaisowulzane.

[0034] In step S2.2, catalyst A is an activated carbon-supported palladium or palladium hydroxide catalyst; the loading weight ratio of palladium or palladium hydroxide in the catalyst is 3% to 7%; the amount of catalyst A, calculated based on the weight ratio of pure palladium to purified hexabenzylhexaazaisowartane in the catalyst, is 0.01% to 0.20%. Preferably, the loading weight ratio of palladium or palladium hydroxide in the catalyst is 3% to 5%.

[0035] The weight ratio of solvent A + solvent B, acetic anhydride, catalytic activator A + catalytic activator B, and purified hexabenzylhexaazaisowrutzane is 1–5:(0.6–2):(0.01–0.1):1.0. Preferably, it is 2–4:(0.8–1.5):(0.02–0.05):1.0.

[0036] The catalyst activator A and catalyst activator B are compounds that can decompose to release bromide ions under catalytic hydrogenation conditions; they can be liquid bromine, hydrogen bromide, bromobenzene, benzyl bromide, acetyl bromide, tribromoacetic acid, or NBS. Benzyl bromide is preferred as the catalyst activator.

[0037] Both solvent A and solvent B are DMF.

[0038] The pressure reactor A can be pressurized first, then stirred; then pressurized again, then stirred again. The pressure reactor A can be a multi-layered, self-priming stirred reactor. The reactor material includes metal alloys resistant to bromide ion corrosion under acidic conditions (Hastelloy, titanium alloy); or, the reactor lining is made of polymer (PTEE, FEP, PFA, ECTFE) or acid-resistant inorganic non-metallic materials (glass enamel, ceramic, silicon carbide); preferably, the reactor is a high-pressure reactor lined with silicon carbide-modified polytetrafluoroethylene.

[0039] Step S3 specifically involves adding solvent C, water, palladium or palladium hydroxide catalyst B, and tetraacetyl dibenzylhexaazaisowrutzane to reactor B in a certain proportion, introducing hydrogen gas, controlling the reaction pressure at 0.25–1.5 MPa, and reacting at 25–80°C for 12–48 hours; filtering, collecting the filtrate, concentrating under reduced pressure, and drying to obtain the tetraacetyl hexaazaisowrutzane.

[0040] Catalyst B is an activated carbon-supported palladium or palladium hydroxide catalyst; wherein, the loading weight ratio of palladium or palladium hydroxide in the catalyst is 5% to 10%; the amount of catalyst B is calculated as 0.02% to 0.20% based on the weight ratio of pure palladium to TADBIW (tetraacetyl dibenzyl hexaazaisowulzane) in the catalyst.

[0041] In step S3, the weight ratio of solvent C, water, and TADBIW is 1-5:(0.6-2):1.0; solvent C includes acetic acid.

[0042] The reactor B can be made of 316L stainless steel, 904 stainless steel, or T2 type titanium.

[0043] In another embodiment of the present invention, the method for producing tetraacetylhexaazaisowulzane includes the following steps:

[0044] (1) Hexabenzylhexaazaisowulzane was purified and refined using a mixed solvent;

[0045] (2) First hydrogenation reaction: The purified hexabenzylhexaazaisowulzane from step (1), solvent A, and catalyst activator A are mixed and stirred evenly to obtain a slurry. Solvent B, catalyst activator B, acetic anhydride, and catalyst A are mixed evenly in reactor A, hydrogen is introduced, and the hydrogen pressure is controlled at 0.25-1.5 MPa. The temperature is lowered to -10-30℃. Then the slurry is slowly pressed into the reactor for 2-8 hours. After pressing, the reaction is continued at -10-30℃ and 0.25-1.5 MPa for 2-8 hours. Then the temperature is raised to 30-60℃ and the reaction is continued at 0.25-1.5 MPa for 2-8 hours. The temperature is lowered to 15-30℃, filtered, and washed to obtain tetraacetyldibenzylhexaazaisowulzane.

[0046] (3) Secondary hydrogenation reaction: Solvent C, water, catalyst B, and tetraacetyl dibenzyl hexaazaisowrutzane are added to reactor B in a certain proportion, hydrogen gas is introduced, the reaction pressure is controlled at 0.25-1.5 MPa, the temperature is controlled at 25-80℃ and the reaction is carried out for 12-48 h; the mixture is filtered, the filtrate is collected, concentrated under reduced pressure, and dried to obtain the tetraacetyl hexaazaisowrutzane.

[0047] The method for producing tetraacetylhexaazaisowulzane further includes step (4) and the purification process of the product from step (3), as follows:

[0048] Add anhydrous acetic acid to the product of step (3), heat to 60-110°C, stir for 30 min-2 h, add anhydrous ethanol while stirring, continue reflux and stirring for 30 min-2 h, stir, cool to 25-38°C, filter, wash the solid with anhydrous ethanol and dry.

[0049] As another embodiment of the present invention, a method for producing tetraacetylhexaazaisowulzane includes the following steps:

[0050] 1. First, the crude hexabenzylhexaazaisowrutzane is purified. The crude hexabenzylhexaazaisowrutzane with a content of 95-98% is recrystallized using a mixed solvent. The mixed solvent is a mixture of two or more solvents in a certain proportion. The mixed solvent, hexabenzylhexaazaisowrutzane, and activated carbon are added to a reaction vessel in a certain ratio. The mixture is heated to 35-75℃ and kept at this temperature for 15 min to 2 h to completely dissolve the hexabenzylhexaazaisowrutzane. After the heating is completed, the mixture is filtered while hot to remove the activated carbon and insoluble matter. The filtrate is stirred and cooled to -5℃-5℃ and kept at this temperature for 30 min to 2 h to precipitate the solid. The solid is then filtered, washed with solvent, and dried to obtain a snow-white powder. HPLC analysis shows that the main content is >99.80% and the total content of dioxinamide impurities is <0.001%. This solid can then be used as the raw material for the next hydrogenation step.

[0051] 2. After mixing a portion of DMF, catalytic activator, acetic anhydride, and catalyst in a pressure reactor made of special material, hydrogen gas is introduced, and the reaction pressure is controlled at 0.25-1.5 MPa. After cooling to -10-30℃, a slurry mixture of hexabenzylhexaazaisowulzane, DMF, and catalytic activator is injected at a certain rate using a metering diaphragm pump. The injection time is controlled at 2-8 hours. After all the material has been injected, the reaction is continued at -10-30℃ and 0.25-1.5 MPa for 2-8 hours. Then, the temperature is raised to 30-60℃, and the reaction is continued at 0.25-1.5 MPa for 2-8 hours until the reaction is complete. HPLC analysis shows that the total content of raw materials and intermediates is <0.5%. The temperature is then lowered to 15-30℃, filtered, and the product is washed sequentially with DMF and then with deionized water. It is used directly as raw material for the next hydrogenation reaction without drying.

[0052] 3. Acetic acid, water, catalyst, and tetraacetyldibenzylhexaazaisowulzane prepared in step 2 are added to a hydrogenation pressure reactor in a certain proportion. Hydrogen gas is introduced, and the reaction pressure is controlled at 0.25-1.5 MPa. The temperature is 25-80℃, and the reaction is carried out for 12-48 hours until the reaction is completed. The total content of raw materials and intermediates is <0.5% by HPLC analysis. The catalyst is then recovered by hot filtration. The catalyst is washed with water, the filtrates are combined, concentrated to dryness, and a certain amount of anhydrous acetic acid is added again. The temperature is raised to 60-110℃, and the mixture is stirred for 30 minutes to 2 hours. A certain amount of anhydrous ethanol is added while stirring, and the mixture is refluxed and stirred for another 30 minutes to 2 hours. After stirring, the temperature is lowered to 25-38℃, filtered, and the solid is washed with anhydrous ethanol and dried to obtain a white powdery tetraacetylhexaazaisowulzane product with a content >99.5%.

[0053] The tetraacetylhexaazaisowrutzane prepared by the method described above is also within the scope of protection of this invention.

[0054] Under the material concentration ratio, reaction temperature, and pressure conditions proposed in this invention, a method is adopted in which the raw materials are slowly pressed into a reactor made of a special material for catalytic hydrogenation after recrystallization and purification. This method basically solves the problems encountered by existing processes. Because this reaction method does not easily generate N-acetylbenzylamine, which can be toxic to palladium-carbon catalysts, or heavy metal ions generated by bromide ions corroding equipment during the hydrogenation process, the catalytic debenzylation reaction can be completed under conditions of using and having a small amount of catalyst. Moreover, the catalyst can maintain good activity after the reaction, and can be reused a certain number of times while ensuring that the reaction yield does not decrease.

[0055] In this invention, the choice of material for the reactor in the first hydrogenation reaction is crucial to its success. The product generated in the first hydrogenation step is an insoluble solid, and its precipitation is highly detrimental to the catalyst surface. Therefore, it is necessary to add in-situ generated bromide ions to maintain catalyst activity. Furthermore, the reaction produces acetic acid, and under acidic conditions, bromide ions are highly corrosive to ordinary metal alloys. As the equipment corrodes, heavy metal ions dissolve in the reaction system and deposit on the surface of the hydrogen-reducing catalyst, leading to reduced catalyst activity. This results in a significant decrease in reaction yield after reducing the catalyst dosage (the weight ratio of palladium to HBIW in the catalyst is <0.2%), which is why existing technologies cannot reduce the catalyst dosage. Since the catalyst is a major cost component of the production process, the material of the first-step reactor plays a key role in reducing catalyst dosage and stabilizing product yield.

[0056] In the second step of the hydrogenation reaction, since the bromide ions of the TADBIW intermediate have been removed by washing with solvent and deionized water, the acetic acid / water system of the reaction has almost no corrosion on the 316L material reactor under the reaction conditions. The reactor material has no significant effect on the reaction, so this step does not require the use of a reactor with an expensive lining material.

[0057] This invention reveals that both excessively fast and slow loading times affect the reaction yield. Our research shows that HBIW decomposes under acidic heating conditions, and the decomposition products react with acetic anhydride to generate products toxic to the catalyst. Therefore, slowly loading HBIW into the reaction system after lowering the temperature to a safe level effectively avoids this. The hydrogenation of HBIW to prepare TADBIW involves multiple steps. First, at 15–23°C, 1–2 benzyl groups are removed, and 1–2 acetyl groups are attached to the cage-like structure, reducing the electronegativity of the cage structure and significantly improving the stability of the intermediate under acidic conditions. At this point, the intermediate is soluble in the reaction system. Then, the temperature is increased to further remove benzyl groups, yielding TADBIW, which is insoluble in the reaction system. Slowly loading HBIW into the reaction system effectively controls its concentration, inhibits decomposition, increases the reaction yield, and reduces the amount of catalyst required.

[0058] This study also conducted extensive HBIW purification experiments, finding that only THF-based ethers have good solubility for it. However, using only this one solvent results in a very low recrystallization yield. The mixed catalyst proposed in this invention effectively balances recrystallization product content and yield. We also experimentally demonstrated the use of acetone as a recrystallization solvent, but found that more than 16 times the weight of the solvent and prolonged reflux were required to dissolve the crude HBIW. This not only reduced the recrystallization product yield but also resulted in a maximum product content of only 99.3%. Our experiments revealed that when the HBIW content is less than 99.5%, the amount of palladium catalyst must exceed 0.3% (the catalyst amount is calculated based on the weight ratio of pure palladium to HBIW in the catalyst); otherwise, the TBIW yield will be very low or even nonexistent. This invention, through purification steps, achieves an HBIW content greater than 99.9%, thus reducing the amount of catalyst required.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] 1. The crude HBIW was purified by recrystallization using a mixed solvent and activated carbon adsorption. High-purity HBIW was obtained with less solvent and higher separation yield. Impurities that were toxic to palladium-carbon catalysts were completely removed, which enabled the reduction of catalyst dosage and the increase of catalyst reuse during catalytic hydrogenation.

[0061] 2. In the process of preparing TADBIW (tetraacetyldibenzylhexaazaisowulzane) by catalytic hydrogenation of HBIW, the raw materials and catalytic activator are slowly injected into the reaction system. This ensures that HBIW does not come into contact with acetic anhydride under non-reducing conditions, thus avoiding its decomposition under acidic conditions and the formation of N-acetylbenzylamines that can cause toxicity to palladium catalysts. The catalytic activator and raw materials are injected slowly together to ensure that the catalyst can maintain high activity for a long time in the first reaction stage, reduce ring-opening byproducts, and improve the reaction yield.

[0062] 3. A special self-priming multi-layer propulsion stirred reactor made of inorganic non-metallic silicon carbide material with excellent corrosion resistance to bromide ions under acidic conditions can not only avoid the safety risks caused by corrosion of pressure equipment in reactors made of metal alloy materials, but also prevent the poisoning of palladium catalyst by heavy metal ions generated by equipment corrosion in the reduction system, which greatly improves the safety of production and reduces the cost ratio of catalyst in production. Attached Figure Description

[0063] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0064] Figure 1 This is the TAIW liquid chromatogram from Example 8 of the present invention;

[0065] Figure 2 This is the TAIW hydrogen NMR spectrum in Example 8 of the present invention. Detailed Implementation

[0066] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0067] This invention provides a method for producing tetraacetylhexaazaisowulzane, the reaction formula of which is as follows:

[0068]

[0069] Preparation Example 1

[0070] Purification and refining of hexabenzylhexaazaisowurtzite

[0071] A 1000L enamel-lined reactor (with a standard anchor-type stirrer at 45 rpm) was cleaned and dried. Under nitrogen protection, 150.0 kg of THF (tetrahydrofuran), 450.0 kg of acetonitrile, and then 150.0 kg of crude HBIW (hexabenzylhexaazaisowulzane) with a purity of approximately 98% and 2.0 kg of activated carbon were added. The mixture was stirred and heated to 55°C, and maintained for 30 minutes to ensure complete dissolution of the crude product. The mixture was then filtered while hot into a 1000L crystallization reactor. The mixture was stirred and cooled to 0–5°C, and maintained at this temperature for 2 hours to ensure complete product precipitation. The mixture was then filtered at a low temperature, and the solid was washed with cold acetonitrile and dried under vacuum to obtain 142.0 kg of white solid. HPLC analysis showed that the HBIW content was 99.90%, and no oxadibenzylamine impurities were detected. The solid could be used for subsequent hydrogenation reactions.

[0072] Comparative Preparation Example 1

[0073] A 1000L enamel-lined reactor (with a standard anchor-type stirrer at 45 rpm) was cleaned and dried. Under nitrogen protection, 800 kg of acetone was added through a high-level tank. Then, 50.0 kg of crude HBIW (hexabenzylhexaazaisowulzane) with a purity of approximately 98% and 0.7 kg of activated carbon were added through the manhole. The mixture was stirred and heated to 55°C. After 30 minutes, the crude product was not completely dissolved. The temperature was then increased to 57°C and refluxed for another 30 minutes until the crude product was almost completely dissolved. The mixture was then filtered while hot into a 1000L crystallization reactor. The temperature was lowered to 0–5°C and maintained for 2 hours to allow complete product precipitation. The mixture was then filtered at a low temperature. The solid was washed with cold acetone and vacuum dried to obtain 41.0 kg of a slightly yellow solid. HPLC analysis showed that the HBIW content was 99.2% and the content of dioxinamide impurities was 0.08%.

[0074] The results showed that because HBIW has low solubility in acetone, 16 times its weight of solvent is required under prolonged heating and reflux conditions to completely dissolve the crude product. This not only increases the processing cost of recrystallization, but also causes the crude product to decompose due to excessive heating time. Using acetone as a recrystallization solvent not only results in low separation yield and efficiency, but also fails to completely remove impurities sensitive to hydrogenation.

[0075] Example 1

[0076] The first hydrogenation reaction was used to prepare TADBIW (tetraacetyldibenzylhexaazaisowrutzane).

[0077] 1. In a 10L glass reaction flask equipped with a mechanical stirrer, 2.80Kg of HBIW purified by recrystallization as in Preparation Example 1, 3.60Kg of DMF, and 60.0g of benzyl bromide were added sequentially and stirred until homogeneous. Most of the HBIW was insoluble, and a white slurry was obtained.

[0078] 2. A 20-liter silicon carbide-modified polytetrafluoroethylene-lined hydrogenation reactor (double-layer self-priming reactor) is used. The reactor is introduced with 5.60 kg of DMF solvent, 2.30 kg of acetic anhydride, 20.0 g of benzyl bromide, and 40.0 g of 3.5% (palladium loading ratio in the catalyst) palladium / C catalyst (net weight, pre-treated with DMF for anhydrous treatment). After purging with nitrogen and hydrogen, the reactor is pressurized to 0.5 MPa with hydrogen, chilled water is added, and stirring is started at 800 rpm. The temperature is then lowered to 15°C.

[0079] 3. The raw materials prepared in the glass reaction flask are pumped into the hydrogenation pressure reactor using a precision high-pressure piston pump at a rate of 1.40–1.60 kg / hour. During the pumping process, the hydrogen pressure is controlled at 0.4–0.6 MPa and the temperature at 14–17°C. After 4–5 hours of pumping, the temperature is slowly raised to 17–21°C, and the reaction continues at 0.4–0.6 MPa for 6 hours. Then, the temperature is slowly raised to 50–53°C, and the reaction continues at 0.4–0.6 MPa for 8 hours until the reaction consumes almost no hydrogen. At this point, the reaction solution is sampled and analyzed by HPLC. The remaining HBIW in the raw material is almost undetectable, and the remaining intermediate is <0.5%. The temperature is lowered to 15–20°C, nitrogen is used for purging, and the mixture is separated by filtration. The solid product is washed three times with DMF to remove impurities, washed twice with deionized water to remove DMF, dried under vacuum to constant weight, yielding 1.80 kg of grayish-white tetraacetyl dibenzyl hexaazaisowulzane product. Product samples were analyzed by HPLC, and the content was 98.6%. After deducting the weight of water and palladium-on-carbon catalyst, the separation yield of this hydrogenation step was 85.3%.

[0080] Example 2

[0081] Example 2 differs from Example 1 only in the pressing time of HBIW. Example 2 verifies the effect of different pressing times of HBIW on the reaction results during the hydrogenation of HBIW to prepare TWDBIW.

[0082] Table 1

[0083]

[0084] * The yield of TADBIW is the molar yield of the comparative raw material HBIW after vacuum drying of the separated product, deducting the catalyst and then converting the content.

[0085] Example 3

[0086] The difference between Example 3 and Example 1 is that different loadings of palladium-on-carbon catalysts were used. The total weight of palladium in the catalyst was the same as in Example 1, which was 1.40 g, and the weight ratio of palladium to raw material HBIW was 0.05%. Example 3 verified the effect of different loading weight ratios of palladium in the catalyst on the reaction results when the weight ratio of palladium to raw material HBIW in the catalyst was 0.05%.

[0087] Table 2

[0088]

[0089] * The yield of TADBIW is the molar yield of the comparative raw material HBIW after vacuum drying of the separated product, deducting the catalyst and then converting the content.

[0090] Example 4

[0091] Except for the material of the reactor lining, the operation in Example 4 was the same as in Example 1. Example 4 verified the effect of the reactor material contact parts being made of 316L stainless steel, 904 stainless steel, and T2 type titanium on the reaction yield.

[0092] Table 3

[0093]

[0094] * The yield of TADBIW is the molar yield of the comparative raw material HBIW after vacuum drying of the separated product, deducting the catalyst and then converting the content.

[0095] Compared with Example 1, under the same catalyst conditions, the material of the reaction equipment has a greater impact on the reaction yield and product content.

[0096] Comparative Example 1

[0097] The difference between Comparative Example 1 and Example 1 is that the raw material used in Comparative Example 1 is the HBIW raw material prepared by recrystallization of acetone in Comparative Preparation Example 1.

[0098] After the HBIW feedstock was fed in, the temperature was slowly raised to 17–21°C and the reaction was continued at 0.4–0.6 MPa for 6 hours. Then, the temperature was slowly raised to 50–53°C and the reaction was continued at 0.4–0.6 MPa. After 2 hours, the hydrogen consumption of the reaction was very slow. At this time, the reaction solution was sampled and analyzed by HPLC. A large amount of HBIW feedstock and intermediates remained. The reaction was continued at this temperature for 10 hours with almost no hydrogen consumption. HPLC analysis of the sample showed that HBIW decomposed and the TADIW content was less than 15%. The temperature was lowered to 15–20°C, nitrogen was used for purging, and the product was separated by filtration. The solid product was washed three times with DMF to remove impurities and twice with deionized water to remove DMF. It was then dried under vacuum to obtain 0.54 kg of dark gray-black viscous solid. HPLC analysis of the sample showed that the TADIW content was 47.3%. The separation yield of TADIW by this method in the hydrogenation reaction was 11.5%.

[0099] Comparative Example 2

[0100] The difference between Comparative Example 2 and Example 1 lies in the feeding method of HBIW, which adopts direct feeding, as detailed below:

[0101] A 20-liter silicon carbide-modified polytetrafluoroethylene-lined hydrogenation reactor was used. 9.20 kg of DMF, 2.30 kg of acetic anhydride, and 80.0 g of benzyl bromide were introduced into the reactor. After purging with nitrogen, the reactor was stirred and cooled to 10–15°C. Then, 2.80 kg of recrystallized and purified HBIW and 40.0 g of 3.5% (by weight of palladium in the catalyst) palladium / C catalyst (net weight, pre-treated with DMF for anhydrous removal) were added. After purging with nitrogen and hydrogen, the pressure was increased to 0.5 MPa. Chilled water was continuously circulated through the reactor, and stirring was started at 800 rpm. The temperature was lowered to 15°C and maintained between 14–17°C and 0.4–0.6 MPa. The reaction proceeds for 4–5 hours, then the temperature is slowly increased to 17–21°C, and the reaction continues at 0.4–0.6 MPa for 6 hours. The temperature is then slowly increased to 50–53°C, and the reaction continues at 0.4–0.6 MPa for 8 hours until the reaction consumes virtually no hydrogen. The temperature is then lowered to 15–20°C, nitrogen is used for purging, and the mixture is separated by filtration. The solid product is washed three times with DMF to remove impurities, washed twice with deionized water to remove DMF, dried under vacuum, and yields 1.31 kg of grayish-white tetraacetyldibenzylhexaazaisowulzane. HPLC analysis of the product showed a purity of 90.1%. After deducting the weight of the palladium-on-carbon catalyst, the separation yield of the TADBIW hydrogenation reaction using this method is 55.4%.

[0102] Example 5

[0103] The second hydrogenation reaction was used to prepare TAIW (tetraacetylhexaazaisowrutzane).

[0104] A 20-liter C316L hydrogen reactor (double-layer self-priming reactor, 800 rpm) was cleaned with deionized water. Then, 1.80 kg of deionized water, 9.00 kg of acetic acid, 26.0 g of 7.0% (palladium loading ratio) palladium / C catalyst (net weight), and 1.80 kg of the catalyst prepared in Example 1 were added sequentially. In the TDABIW reaction, after purging the reactor with nitrogen and hydrogen, the hydrogen pressure was increased to 0.5 MPa, and the temperature was slowly raised to 50–55 °C with stirring. The reaction was continued at this temperature and 0.4–0.6 MPa for 16 hours until hydrogen consumption was minimal. The reaction solution was sampled and analyzed by HPLC. The total content of the raw materials and intermediates was 0.2%. Nitrogen purging was performed, and the catalyst was separated by hot filtration. The catalyst was washed twice with deionized water, and the filtrates were combined and transferred to a 20-liter glass reaction flask. The filtrate was concentrated to dryness under reduced pressure, and 1.20 kg of acetic acid was added. The mixture was stirred and heated to 100–105 °C for 30 minutes. 4.80 kg of anhydrous ethanol was added, and the mixture was refluxed and stirred for another 2 hours. The mixture was then cooled to 25–30 °C and filtered. The solid was washed twice with anhydrous ethanol and dried under vacuum to obtain 990 g of white powdered tetraacetylhexaazaisowulzane with a purity of 99.6%. The separation yield of this hydrogenation step was 87.4%.

[0105] Example 6

[0106] The difference between Example 6 and Example 5 is that different loadings of palladium-on-carbon catalysts were used. The total weight of palladium in the catalyst was the same as in Example 5, 1.82 g, and the weight ratio of palladium to the raw material TADBIW was 0.10%. Example 6 verified the effect of different loading weight ratios of palladium in the catalyst on the reaction results when the weight of palladium in the catalyst was the same.

[0107] Table 4

[0108]

[0109] a. The hydrogenation reaction time refers to the time required for the reaction to proceed from a temperature of 50-55°C to a hydrogen pressure of 0.4-0.6 MPa until the system consumes virtually no hydrogen.

[0110] b. The yield of TAIW is the molar yield of the comparative intermediate TADBIW after vacuum drying of the separated product and content conversion.

[0111] The results showed that during the hydrogenation of TADBIW to prepare TAIW, the high activation energies of the two benzyl groups at positions 4 and 10 resulted in a slow reaction rate of the low-loaded palladium-carbon catalyst, which significantly prolonged the reaction time and left a large amount of raw materials and intermediates, leading to low product separation yield and purity.

[0112] Example 7

[0113] Example 7 demonstrated the multiple recycling of the catalyst, verifying the impact of reusing the 7% palladium / C hydrogenation catalyst in the TADBIW-to-TAIW preparation process on product yield and quality. The hydrogenation operation in this example was the same as in Example 5, except that the catalyst was a recycled catalyst obtained by filtering and washing with deionized water from the previous reaction solution. Furthermore, no new addition of 7% (by weight of palladium in the catalyst) palladium / C catalyst was required. This is because each hydrogenation reaction introduces 3.5% (by weight of palladium in the catalyst) palladium / C catalyst, which is carried over from the first TADBIW preparation process. Therefore, the amount of recycled catalyst increases with the number of recycling cycles.

[0114] Recovery method: The catalyst, after being washed with deionized water, is added to a 2L hydrogenation reactor, followed by 1.2Kg of deionized water. After nitrogen purging, hydrogen purging is performed. The hydrogen pressure is increased to 1.0Mpa, and stirring is started (300 rpm). The temperature is raised to 100℃ and stirred for 5 hours. The temperature is then cooled to 35℃ and filtered under nitrogen pressure. The catalyst is washed multiple times with deionized water, the water is pressed dry, and samples are taken to measure the water content and palladium content.

[0115] Cycle 1:

[0116] The catalyst from Example 5 was recovered (net weight 66.0 g) and used entirely in step S3 of this preparation.

[0117] Cycle 2:

[0118] The catalyst from cycle one was recovered (net weight 106.0g) and used entirely in step S3 of this preparation.

[0119] Cycle 3:

[0120] The catalyst from cycle two was recovered (net weight 146.0 g) and used entirely in step S3 of this preparation.

[0121] Cycle 4:

[0122] The catalyst from cycle three was recovered (net weight 186 g) and used entirely in step S3 of this preparation.

[0123] Table 5

[0124] Cycle number Reaction yield (%) <![CDATA[Total reaction time (hours) * > one 85.3 14 two 83.7 18 three 78.6 24 Four 64.7 36

[0125] *The total reaction time is from the start of the reaction until the reaction consumes almost no hydrogen. After the first two catalyst application times, the total content of raw materials and intermediates in the liquid should be less than 0.5%. If the number of catalyst application times is increased further, the raw materials will not be able to react completely.

[0126] Example 8: Scale-up Test

[0127] 1. Preparation of TADBIW (tetraacetyldibenzylhexaazaisowrutzane) by the first hydrogenation reaction

[0128] 1.1 In a 1000L mixing vessel, 140.0Kg of HBIW that has been recrystallized and purified in Preparation Example 1, 180.0Kg of DMF (N,N-dimethylformamide), and 3.0Kg of benzyl bromide were added in sequence and stirred until homogeneous. Most of the HBIW was insoluble, and a white slurry was obtained.

[0129] 1.2. Introduce the following solvents into the reactor (a 1000-liter silicon carbide-modified polytetrafluoroethylene-lined hydrogenation reactor (self-priming four-layer propeller stirring, 300 rpm), with self-priming multi-layer propeller stirring and the reactor equipped with circulating hot water for heating and cooling brine): 280.0 kg of DMF, 115.0 kg of acetic anhydride, 1.0 kg of benzyl bromide, and 2.0 kg of 3.5% (weight ratio of palladium in the catalyst) palladium / C catalyst (net weight, pre-treated with DMF for anhydrous removal). After purging with nitrogen and hydrogen, pressurize the reactor with hydrogen to 0.5 MPa, turn on the chilled water to cool the reactor, and stir to cool to 15°C.

[0130] 1.3 Pressing: The white slurry material in the mixing vessel from step 2.1 is pumped into the hydrogenation pressure reactor using a diaphragm pump at a rate of 70–80 kg / hour. During pressing, the hydrogen pressure is controlled at 0.4–0.6 MPa and the temperature at 14–17°C. After 4–5 hours of feeding, the temperature is slowly raised to 17–21°C, and the reaction continues at 0.4–0.6 MPa for 6 hours. At this point, a sample of the reaction solution is taken for HPLC analysis. The remaining HBIW of the raw material is <1%, the intermediate is approximately 75%, and the TADBIW is >20%. The temperature is then slowly raised to 50–53°C. The reaction was continued at 0.4–0.6 MPa for 8 hours until the reaction consumed almost no hydrogen. HPLC analysis of the reaction solution at this point showed that the remaining HBIW from the starting material was almost undetectable, the remaining intermediate was <0.5%, and the TADBIW content was >95%. The temperature was lowered to 15–20°C, nitrogen was used for purging, and the mixture was centrifuged and filtered. The solid product was washed three times with DMF to remove impurities, and twice with deionized water to remove DMF. Centrifugation to dryness yielded 108.0 kg of a grayish-black tetraacetyldibenzylhexaazaisowrtzine product with 15% moisture content. No drying was required; it could be directly used for the next step of catalytic hydrogenation. HPLC analysis of the product showed a purity of 98.7%. After deducting the weight of water and the palladium-carbon catalyst, the separation yield of this hydrogenation step was 86.9%.

[0131] 2. Preparation of TAIW (tetraacetylhexaazaisowrutzane) by a second hydrogenation reaction.

[0132] A 1000L 316L hydrogenation reactor (self-priming four-layer propeller agitator, 300 rpm) was cleaned with deionized water. Then, 80.0 kg of deionized water, 450.0 kg of acetic acid, 1.30 kg of 7.0% (palladium in the catalyst, net weight) and 108.0 kg of the solution prepared in the previous steps were added sequentially. The TDABIW wet product was reacted in a reactor purged with nitrogen and hydrogen. The reactor was then pressurized with hydrogen to 0.5 MPa and slowly heated to 50–55°C with stirring. The reaction was continued at this temperature and 0.4–0.6 MPa for 16 hours until hydrogen consumption was minimal. The reaction solution was sampled and analyzed by HPLC. The total content of the raw materials and intermediates was 0.2%. Nitrogen purging was performed, and the catalyst was separated by hot filtration. The catalyst was then washed twice with deionized water. The filtrates were combined and transferred to a 1000L 316L stainless steel concentrator. The filtrate was concentrated to dryness under reduced pressure. 60.0 kg of acetic acid was added, and the mixture was stirred and heated to 100–105°C for 30 minutes. 240.0 kg of anhydrous ethanol was added, and the mixture was refluxed and stirred for another 2 hours. The mixture was then cooled to 25–30°C and filtered. The solid was washed twice with anhydrous ethanol and dried under vacuum to obtain 51.0 kg of a white powdery tetraacetylhexaazaisowulzane product with a purity of 99.7%. The hydrogenation separation yield for this step was 88.2%.

[0133] Figure 1 The image shown is a TAIW liquid chromatogram from this embodiment.

[0134] Figure 2 This is the TAIW 1H NMR spectrum in this embodiment.

[0135] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A process for the production of tetraacetylhexaazaisowurtzitane, characterized in that, It comprises the following steps: S1, the hexabenzyl hexaazaiswurtzitane is purified and refined with a mixed solvent; The method for purifying and refining the hexabenzyl hexaazaiswurtzitane of step S1 with a mixed solvent is as follows: hexabenzyl hexaazaiswurtzitane with a content of 95-98%, a mixed solvent and activated carbon are put into a reaction kettle, heated to 35-75℃ and kept for 15 min-2 h, the activated carbon and insoluble substances are removed by pressure filtration, the filtrate is stirred and cooled to-5℃-5℃ and kept for 30 min-2 h; the solid is precipitated, filtered, washed with a solvent and dried, and a powdery solid is obtained, which is the refined hexabenzyl hexaazaiswurtzitane; The mixed solvent is a combination of tetrahydrofuran and acetonitrile; The weight ratio of tetrahydrofuran: acetonitrile: activated carbon: hexabenzyl hexaazaiswurtzitane crude product is 0.5-2: 0.5-5: 0.01-0.05: 1.0; S2, first hydrogenation reaction: the hexabenzyl hexaazaiswurtzitane purified and refined in step S1, solvent A and catalytically activated agent A are uniformly mixed and stirred to prepare a slurry material; solvent B, catalytically activated agent B, acetic anhydride and catalyst A are uniformly mixed in a reaction kettle A, hydrogen is introduced, the reaction hydrogen pressure is controlled at 0.25-1.5 MPa, and the temperature is reduced to-10-30℃; then the slurry material is slowly pressed into the reaction kettle, the pressing time is controlled at 2-8 h, after the pressing is completed, the reaction is continued at-10-30℃ and 0.25-1.5 MPa for 2-8 h; then the temperature is increased to 30-60℃, the reaction is continued at 0.25-1.5 MPa for 2-8 h; the temperature is reduced to 15-30℃, and filtration and washing are performed to prepare tetraacetyldibenzylhexaazaiswurtzitane; The reaction kettle A is a high-pressure reaction kettle with a silicon carbide modified polytetrafluoroethylene material lining; The catalyst A is activated carbon supported palladium or palladium hydroxide catalyst; the loading weight ratio of palladium or palladium hydroxide in the catalyst is 3-5%; the amount of catalyst A is converted to 0.02%-0.15% according to the weight ratio of pure palladium in the catalyst to the refined hexabenzyl hexaazaiswurtzitane; The catalytically activated agent A and the catalytically activated agent B are benzyl bromide; S3, second hydrogenation reaction: solvent C, water, catalyst B and tetraacetyldibenzylhexaazaiswurtzitane are added to a reaction kettle B in a certain proportion, hydrogen is introduced, the reaction pressure is controlled at 0.25-1.5 MPa, and the temperature is 25-80℃ for 12-48 h; filtration, collection of the filtrate, reduced pressure concentration and drying are performed to prepare the tetraacetyldibenzylhexaazaiswurtzitane; The catalyst B is activated carbon supported palladium or palladium hydroxide catalyst; the loading weight ratio of palladium or palladium hydroxide in the catalyst is 5%-10%; the amount of catalyst B is converted to 0.02%-0.20% according to the weight ratio of pure palladium in the catalyst to the tetraacetyldibenzylhexaazaiswurtzitane.

2. The method for producing tetraacetyldibenzylhexaazaiswurtzitane according to claim 1, characterized in that, The weight ratio of the solvent A + solvent B, acetic anhydride, catalytically active agent A + catalytically active agent B, refined hexabenzylhexaazaisowurtzitane is 1-5: 0.6-2: 0.01-0.1: 1.0; Both the solvent A and the solvent B are DMF.

3. The method of producing tetraacetylhexaazaisowurtzitane according to claim 1, characterized by, In step S3, the weight ratio of the solvent C, water, tetraacetyl dibenzyl hexaazaisowurtzitane is 1-5: 0.6-2: 1.0; the solvent C is acetic acid.

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