A continuous nitration synthesis process of 1,3,5-trimethoxy-2,4,6-trinitrobenzene

Abstract

This invention addresses the shortcomings of existing 1,3,5-trimethoxy-2,4,6-trinitrobenzene synthesis processes by providing a continuous nitration synthesis process. Using 1,3,5-trimethoxybenzene as a raw material, dichloromethane as a solvent, 98% nitric acid as a nitrating agent, and 98% sulfuric acid as a catalyst, it employs an integrated process of "multi-unit continuous reaction - precise temperature control - efficient separation." Through a combination of microchannel reactors and dynamic tubular reactors, the continuous synthesis of 1,3,5-trimethoxy-2,4,6-trinitrobenzene is achieved, enabling precise temperature control and efficient mass transfer during the reaction process, reducing safety risks, improving product quality and production efficiency, and simultaneously reducing waste emissions.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical synthesis technology, specifically relating to a continuous nitration synthesis process and dedicated equipment for 1,3,5-trimethoxy-2,4,6-trinitrobenzene, which is particularly suitable for large-scale and safe industrial production of 1,3,5-trimethoxy-2,4,6-trinitrobenzene. Background Technology

[0002] 1,3,5-Trimethoxy-2,4,6-trinitrobenzene, as an important pharmaceutical intermediate and precursor for energetic materials, has irreplaceable application value in the fields of pharmaceutical chemistry and specialty materials. 1,3,5-Trimethoxy-2,4,6-trinitrobenzene is also an important intermediate in the synthesis of TATB (triaminotrinitrobenzene), a widely used safe explosive. Its traditional synthesis process uses 1,3,5-trimethoxybenzene as a raw material and prepares it through a nitration reaction. The mainstream process is the batch nitration method, which has the following significant drawbacks:

[0003] 1. High safety risks: Nitration is a strongly exothermic reaction. In batch reactions, materials are added in a concentrated manner, which can easily lead to a sudden increase in local temperature and enrichment of nitric acid concentration, causing side reactions or even explosions. The reaction system has a large liquid holdup, and the consequences of an accident are serious.

[0004] 2. Unstable product quality: Large differences in reaction temperature, stirring efficiency, and residence time between batches lead to fluctuations in product purity (usually between 95% and 97%), high content of by-products, and increased subsequent purification costs.

[0005] 3. Low production efficiency: A single batch of production includes feeding, reaction, discharge, cleaning and other steps, with a production cycle of 4-6 hours. The capacity per unit time is limited, making it difficult to meet the needs of large-scale production.

[0006] 4. Significant environmental impact: The solvent recovery rate in batch processes is low (usually below 85%), resulting in high waste acid emissions and significant difficulties in subsequent treatment, which does not meet the requirements for green chemical development.

[0007] While continuous nitration technologies have been attempted, they generally suffer from problems such as insufficient heat exchange efficiency, low precision in reaction parameter control, and poor equipment corrosion resistance. For example, when using ordinary tubular reactors for nitration, the limited heat exchange area makes it impossible to remove the heat of reaction in time, leading to uncontrolled reaction temperature. Some processes use a single reaction unit, making it difficult to achieve staged reaction control, and the incidence of side reactions remains high.

[0008] Therefore, developing an efficient, safe, and stable continuous nitration synthesis process for 1,3,5-trimethoxy-2,4,6-trinitrobenzene has become a pressing technical problem to be solved in this field. Summary of the Invention

[0009] In view of the shortcomings of the existing 1,3,5-trimethoxy-2,4,6-trinitrobenzene synthesis process, the purpose of this invention is to provide a continuous nitration synthesis process that achieves precise temperature control and efficient mass transfer in the reaction process, reduces safety risks, improves product quality and production efficiency, and reduces the emission of waste gas, wastewater, and solid waste.

[0010] To achieve the above objectives, the present invention provides the following technical solution: The continuous nitration synthesis process of 1,3,5-trimethoxy-2,4,6-trinitrobenzene of the present invention uses 1,3,5-trimethoxybenzene as raw material, dichloromethane as solvent, 98% nitric acid as nitrating agent, and 98% sulfuric acid as catalyst. It adopts an integrated process of "multi-unit continuous reaction - precise temperature control - high-efficiency separation" and realizes the continuous synthesis of 1,3,5-trimethoxy-2,4,6-trinitrobenzene through the combination of microchannel reactor and dynamic tubular reactor.

[0011] This invention achieves synthesis through a three-stage continuous reaction, comprising four units in sequence: raw material pretreatment, staged nitration, quenching and separation, and solvent recovery.

[0012] (1) 1,3,5-trimethoxybenzene and dichloromethane are added to the raw material mixing tank and stirred and dissolved at room temperature and pressure to form a homogeneous 1,3,5-trimethoxybenzene-dichloromethane solution;

[0013] (2) Prepare a mixed acid by mixing 98% nitric acid and 98% sulfuric acid, stir well and set aside;

[0014] (3) A three-stage continuous reaction system is adopted, with 1,3,5-trimethoxybenzene fed in batches. The feeding rate is controlled by interlocking the feed pump and the weighing module to achieve precise feeding.

[0015] (4) 50% of the 1,3,5-trimethoxybenzene / dichloromethane solution and the mixed acid are introduced into the microchannel reactor 1, and the heat exchange medium is circulated through the jacket to remove the heat released by the reaction.

[0016] (5) Pass the primary reaction solution and the remaining 50% of the 1,3,5-trimethoxybenzene-dichloromethane solution into the microchannel reactor 2 to maintain the circulation of the heat exchange medium and ensure temperature stability;

[0017] (6) The secondary reaction solution is introduced into a dynamic tubular reactor for maturation to complete the entire nitration reaction process;

[0018] (7) Pass the matured reaction solution into a dynamic quencher and contact it in the opposite direction with the quenching water at 5°C to control the quenching temperature, neutralize the excess acid and terminate the reaction.

[0019] (8) The quenched mixture is sent to a centrifugal extractor for liquid-liquid separation at room temperature and 0.25 MPa. The aqueous phase (containing waste acid) is sent to the recovery system, and the oil phase (containing 1,3,5-trimethoxybenzene TNB and dichloromethane) is sent to the intermediate storage tank.

[0020] (9) The oil phase is introduced into a scraped film evaporator to evaporate dichloromethane. The dichloromethane is condensed and recovered. The residue at the bottom of the tower is crude 1,3,5-trimethoxybenzene TNB, which has a purity of ≥98.5% after testing.

[0021] The raw material pretreatment unit includes steps (1) to (3);

[0022] The staged nitration unit includes steps (4) to (5);

[0023] The quenching separation unit includes steps (6) to (8);

[0024] The solvent recovery unit includes step (9).

[0025] Preferably, in the staged nitration unit, the primary nitration temperature is controlled at -10~10℃ and the residence time is 2~10min, the secondary nitration temperature is controlled at 10~40℃ and the residence time is 3~20min, and the reaction ripening temperature is maintained at 10~40℃ and the residence time is 10~60min.

[0026] Preferably, in the raw material pretreatment unit, the mass ratio of 1,3,5-trimethoxybenzene to dichloromethane is 1:5~10; the nitration system is a mixed acid, in which the mass ratio of 98% nitric acid to 98% sulfuric acid is 1:5~15, and the molar ratio of nitric acid to 1,3,5-trimethoxybenzene is 1.1~1.5:1.

[0027] Preferably, the staged nitration unit adopts a reaction system combining a microchannel reactor and a dynamic tubular reactor; primary nitration is carried out in microchannel reactor 1 at a reaction pressure of 0.1~0.5MPa, with heat exchange medium introduced through a jacket; secondary nitration is carried out in microchannel reactor 2 at a reaction pressure of 0.2~0.5MPa; and reaction maturation is carried out in the dynamic tubular reactor at a reaction pressure of 0.3~0.7MPa.

[0028] Preferably, in the quenching and separation unit, the matured reaction liquid is passed into a dynamic quencher and comes into countercurrent contact with quenching water at 0~10℃, and the quenching temperature is controlled to be ≤30℃; the liquid-liquid separation is completed by a centrifugal extractor at room temperature and 0.25MPa.

[0029] Preferably, the solvent recovery unit uses a scraped film evaporator to recover dichloromethane, with operating conditions of vacuum degree 0.05~0.2MPa, heating temperature 30~60℃, dichloromethane recovery rate ≥95%, and the purity of the crude 1,3,5-trimethoxybenzene TNB obtained after recovery ≥98.5%.

[0030] Beneficial effects of the invention

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. Significantly improved safety: The microchannel reactor has a small liquid holding capacity (≤10L), and the staged temperature control avoids local overheating. The explosion-proof rating reaches ExdⅡ BT4, which completely solves the safety hazards of traditional processes.

[0033] 2. High production efficiency: Enables continuous production with stable capacity, more than 3 times higher than intermittent processes, and batch-to-batch purity fluctuation ≤0.5%.

[0034] 3. Good environmental performance: Dichloromethane recovery rate ≥95%, waste acid emissions reduced by 30%, meeting the requirements of green chemical industry.

[0035] 4. Easy to operate: The skid-mounted design facilitates transportation and installation, the automated control system reduces manual intervention, and the fault response time is ≤8 hours. Attached Figure Description

[0036] Figure 1 This is a structural diagram of the reaction equipment required for this invention;

[0037] In the diagram: 1. Acid mixing tank 1; 2. Acid mixing tank 2; 3. Acid feed pump; 4. Raw material mixing tank 1; 5. Raw material mixing tank 2; 6. Raw material feed pump 1; 7. Raw material precooler 1; 8. Raw material feed pump 2; 9. Raw material precooler 2; 10. Dynamic tubular reactor; 11. Microchannel reactor 1; 12. Microchannel reactor 2; 13. Acid precooler; 14. Raw material mixing tank 3; 15. Raw material mixing tank 4; 16. Dynamic quencher; 17. Centrifugal extractor; 18. Scraped film evaporator; 19. Condenser; 20. Oil-water separator; 21. Dichloromethane recovery tank. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Please see the appendix Figure 1The continuous nitration synthesis process of 1,3,5-trimethoxy-2,4,6-trinitrobenzene of the present invention uses 1,3,5-trimethoxybenzene as raw material, dichloromethane as solvent, 98% nitric acid as nitrating agent, and 98% sulfuric acid as catalyst. It employs an integrated process of "multi-unit continuous reaction - precise temperature control - efficient separation," achieving continuous synthesis of 1,3,5-trimethoxy-2,4,6-trinitrobenzene through a combination of microchannel reactors and dynamic tubular reactors. Specifically, it includes the following steps:

[0040] (1) 1,3,5-trimethoxybenzene and dichloromethane are added to the raw material mixing tank and stirred and dissolved at room temperature and pressure to form a homogeneous 1,3,5-trimethoxybenzene-dichloromethane solution;

[0041] (2) Prepare a mixed acid by mixing 98% nitric acid and 98% sulfuric acid, stir well and set aside;

[0042] (3) A three-stage continuous reaction system is adopted, with 1,3,5-trimethoxybenzene fed in batches. The feeding rate is controlled by interlocking the feed pump and the weighing module to achieve precise feeding.

[0043] (4) 50% of the 1,3,5-trimethoxybenzene / dichloromethane solution and the mixed acid are introduced into the microchannel reactor 1, and the heat exchange medium is circulated through the jacket to remove the exothermic reaction.

[0044] (5) Pass the primary reaction solution and the remaining 50% of the 1,3,5-trimethoxybenzene-dichloromethane solution into the microchannel reactor 2 to maintain the circulation of the heat exchange medium and ensure temperature stability;

[0045] (6) The secondary reaction solution is introduced into a dynamic tubular reactor for maturation to complete the entire nitration reaction process.

[0046] (7) Pass the matured reaction solution into a dynamic quencher and contact it in the opposite direction with the quenching water at 5°C to control the quenching temperature, neutralize the excess acid and terminate the reaction.

[0047] (8) The quenched mixture is sent to a centrifugal extractor for liquid-liquid separation at room temperature and 0.25 MPa. The aqueous phase (containing waste acid) is sent to the recovery system, and the oil phase (containing 1,3,5-trimethoxybenzene TNB and dichloromethane) is sent to the intermediate storage tank.

[0048] (9) The oil phase is introduced into the scraped film evaporator to evaporate dichloromethane. The dichloromethane is recovered after condensation. The residue at the bottom of the tower is crude 1,3,5-trimethoxybenzene TNB, which has a purity of ≥98.5% after testing.

[0049] The raw material pretreatment unit includes steps (1) to (3);

[0050] The staged nitration unit includes steps (4) to (5);

[0051] The quenching separation unit includes steps (6) to (8);

[0052] The solvent recovery unit includes step (9).

[0053] Preferably, in the staged nitration unit, the primary nitration temperature is controlled at -10~10℃ and the residence time is 2~10min, the secondary nitration temperature is controlled at 10~40℃ and the residence time is 3~20min, and the reaction ripening temperature is maintained at 10~40℃ and the residence time is 10~60min.

[0054] Preferably, in the raw material pretreatment unit, the mass ratio of 1,3,5-trimethoxybenzene to dichloromethane is 1:5~10; the nitration system is a mixed acid, in which the mass ratio of 98% nitric acid to 98% sulfuric acid is 1:5~15, and the molar ratio of nitric acid to 1,3,5-trimethoxybenzene is 1.1~1.5:1.

[0055] Preferably, the staged nitration unit adopts a reaction system combining a microchannel reactor and a dynamic tubular reactor; primary nitration is carried out in microchannel reactor 1 at a reaction pressure of 0.1~0.5MPa, with heat exchange medium introduced through a jacket; secondary nitration is carried out in microchannel reactor 2 at a reaction pressure of 0.2~0.5MPa; and reaction maturation is carried out in the dynamic tubular reactor at a reaction pressure of 0.3~0.7MPa.

[0056] Preferably, in the quenching and separation unit, the matured reaction liquid is passed into a dynamic quencher and comes into countercurrent contact with quenching water at 0~10℃, and the quenching temperature is controlled to be ≤30℃; the liquid-liquid separation is completed by a centrifugal extractor at room temperature and 0.25MPa.

[0057] Preferably, the solvent recovery unit uses a scraped film evaporator to recover dichloromethane, with operating conditions of vacuum degree 0.05~0.2MPa, heating temperature 30~60℃, dichloromethane recovery rate ≥95%, and the purity of the crude 1,3,5-trimethoxybenzene TNB obtained after recovery ≥98.5%.

[0058] This invention is implemented according to the raw material specifications shown in Table 1:

[0059] Table 1 shows the raw material specifications:

[0060] Raw material name purity Manufacturer 1,3,5-Trimethoxybenzene ≥99% Shanghai Feili Chemical Reagent Co., Ltd. 98% nitric acid Industrial grade Ningbo Chemical New Materials Co., Ltd. 98% sulfuric acid Industrial grade Ningbo Chemical New Materials Co., Ltd. dichloromethane ≥99.5% Jiangsu Liwen Chemical Co., Ltd.

[0061] Example 1:

[0062] This embodiment uses the basic parameters in the above-mentioned operation step 3.2 to carry out the continuous nitration synthesis of 1,3,5-trimethoxy-2,4,6-trinitrobenzene, specifically as follows: the raw materials are 1,3,5-trimethoxybenzene with a purity of 99.2% and dichloromethane with a purity of 99.6%; the primary nitration temperature is 0℃, the secondary nitration temperature is 25℃, and the aging temperature is 20℃; the mass ratio of 1,3,5-trimethoxybenzene to dichloromethane is 1:7.5, and the molar ratio of nitric acid to 1,3,5-trimethoxybenzene is 1.2:1; the vacuum degree of the wiped-film evaporator is 0.08MPa, and the heating temperature is 40℃.

[0063] After 72 hours of continuous operation, samples were taken and tested every 8 hours, for a total of 9 sets of data. The results showed that the product purity was stable at 98.5%-99.0%, with an average purity of 98.7%; the yield was stable at 91.8%-92.5%, with an average yield of 92.1%; and the average recovery rate of dichloromethane was 95.3%. During the process, there were no abnormal fluctuations in the temperature and pressure of the reaction system, the equipment operated stably, and there were no blockages or corrosion phenomena.

[0064] Example 2:

[0065] In this embodiment, only the secondary nitration temperature was changed, while the other parameters were the same as in Example 1. The secondary nitration temperature was set to 20°C, and after running for 24 hours, the product purity was 98.3% and the yield was 91.5%.

[0066] Example 3:

[0067] In this embodiment, only the secondary nitration temperature was changed, while the other parameters were the same as in Example 1. The secondary nitration temperature was set to 30°C, and after running for 24 hours, the product purity was 98.2% and the yield was 90.8%.

[0068] Example 4:

[0069] In this example, the molar ratio of nitric acid to 1,3,5-trimethoxybenzene was 1.1:1, and all other parameters were the same as in Example 1. The process was run for 24 hours. The product purity was 97.8%, and the yield was 89.2%.

[0070] Example 5:

[0071] In this example, the molar ratio of nitric acid to 1,3,5-trimethoxybenzene was 1.3:1, and the remaining parameters were the same as in Example 1. After running for 24 hours, the product purity was 97.5% and the yield was 90.3%.

[0072] Example 6:

[0073] This process was scaled up to industrial-grade capacity (100 kg / h), with equipment specifications scaled up proportionally to the basic process: the heat exchange area of ​​the microchannel reactor was increased to 87.4 m², the liquid holding capacity of the dynamic tubular reactor was 700 L, and the processing capacity of the centrifugal extractor was 5800 L / h. Raw material consumption was increased tenfold compared to the basic process, and the process ran for 168 hours (7 days).

[0074] Experimental results: The average purity of the product was 98.6%, the average yield was 91.9%, and the dichloromethane recovery rate was 95.1%. All indicators were basically consistent with the small-scale test data. During equipment operation, the PLC control system precisely controlled all parameters, with temperature fluctuations ≤ ±1℃ and pressure fluctuations ≤ ±0.02MPa, demonstrating that this process has good scalability and is suitable for industrial mass production.

[0075] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A continuous nitration synthesis process for 1,3,5-trimethoxy-2,4,6-trinitrobenzene, characterized in that, Using 1,3,5-trimethoxybenzene as raw material, dichloromethane as solvent, and 98% nitric acid-98% sulfuric acid as nitration system, the synthesis was achieved through a three-stage continuous reaction, which included four units in sequence: raw material pretreatment, staged nitration, quenching and separation, and solvent recovery. Specifically, the following steps are included: (1) 1,3,5-trimethoxybenzene and dichloromethane are added to the raw material mixing tank and stirred and dissolved at room temperature and pressure to form a homogeneous 1,3,5-trimethoxybenzene-dichloromethane solution; (2) Prepare a mixed acid by mixing 98% nitric acid and 98% sulfuric acid, stir well and set aside; (3) A three-stage continuous reaction system is adopted, with 1,3,5-trimethoxybenzene fed in batches. The feeding rate is controlled by interlocking the feed pump and the weighing module to achieve precise feeding. (4) 50% of the 1,3,5-trimethoxybenzene / dichloromethane solution and the mixed acid are introduced into the microchannel reactor 1, and the heat exchange medium is circulated through the jacket to remove the heat released by the reaction. (5) Pass the primary reaction solution and the remaining 50% of the 1,3,5-trimethoxybenzene-dichloromethane solution into the microchannel reactor 2 to maintain the circulation of the heat exchange medium and ensure temperature stability; (6) The secondary reaction solution is introduced into a dynamic tubular reactor for maturation to complete the entire nitration reaction process; (7) Pass the matured reaction solution into a dynamic quencher and contact it in the opposite direction with the quenching water at 5°C to control the quenching temperature, neutralize the excess acid and terminate the reaction. (8) The quenched mixture is sent to a centrifugal extractor for liquid-liquid separation at room temperature and 0.25 MPa. The aqueous phase (containing waste acid) is sent to the recovery system, and the oil phase (containing 1,3,5-trimethoxybenzene TNB and dichloromethane) is sent to the intermediate storage tank. (9) The oil phase is introduced into a scraped film evaporator to evaporate dichloromethane. The dichloromethane is condensed and recovered. The residue at the bottom of the tower is crude 1,3,5-trimethoxybenzene TNB, which has a purity of ≥98.5% after testing. The raw material pretreatment unit includes steps (1) to (3); The staged nitration unit includes steps (4) to (5); The quenching separation unit includes steps (6) to (8); The solvent recovery unit includes step (9).

2. The process according to claim 1, characterized in that, In the staged nitration unit, the primary nitration temperature is controlled at -10~10℃ and the residence time is 2~10min, the secondary nitration temperature is controlled at 10~40℃ and the residence time is 3~20min, and the reaction ripening temperature is maintained at 10~40℃ and the residence time is 10~60min.

3. The process according to claim 1, characterized in that, In the raw material pretreatment unit, the mass ratio of 1,3,5-trimethoxybenzene to dichloromethane is 1:5~10; the nitration system is a mixed acid, in which the mass ratio of 98% nitric acid to 98% sulfuric acid is 1:5~15, and the molar ratio of nitric acid to 1,3,5-trimethoxybenzene is 1.1~1.5:

1.

4. The process according to claim 1, characterized in that, The staged nitration unit adopts a reaction system combining a microchannel reactor and a dynamic tubular reactor; primary nitration is carried out in microchannel reactor 1 at a reaction pressure of 0.1~0.5MPa, with heat exchange medium introduced through a jacket; secondary nitration is carried out in microchannel reactor 2 at a reaction pressure of 0.2~0.5MPa; and reaction maturation is carried out in the dynamic tubular reactor at a reaction pressure of 0.3~0.7MPa.

5. The process according to claim 1, characterized in that, In the quenching and separation unit, the matured reaction liquid is passed into a dynamic quencher and comes into countercurrent contact with quenching water at 0~10℃, with the quenching temperature controlled at ≤30℃; liquid-liquid separation is completed by a centrifugal extractor at room temperature and 0.25MPa.

6. The process according to claim 1, characterized in that, The solvent recovery unit uses a scraped film evaporator to recover dichloromethane. The operating conditions are a vacuum of 0.05~0.2MPa and a heating temperature of 30~60℃. The dichloromethane recovery rate is ≥95%, and the purity of the crude 1,3,5-trimethoxybenzene TNB obtained after recovery is ≥98.5%.

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