Nitration mixture for nitrating 2,4- and 2,6-dinitrotoluene to 2,4,6-trinitrotoluene and process for obtaining 2,4,6-trinitrotoluene using the same
A nitration mixture of nitrogen oxide, nitric acid, and sulfuric acid addresses the challenges of waste sulfuric acid generation and safety in TNT production by reducing consumption and enabling recycling, enhancing process safety and efficiency.
Patent Information
- Application Number
- JP2024540574
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-07-13
- Filing Date
- 2023-07-13
- Publication Date
- 2025-07-25
AI Technical Summary
Existing nitration processes for producing 2,4,6-trinitrotoluene (TNT) generate large amounts of waste sulfuric acid, pose environmental threats, and involve hazardous secondary oxidation processes, leading to safety risks and high energy consumption.
A nitration mixture comprising 5-20% nitrogen oxide, 60-80% nitric acid, and 5-30% sulfuric acid is used, with a mass ratio of 10:1 or less, and a reaction temperature of 50-80°C for 4 hours, reducing sulfuric acid consumption and lowering secondary oxidation levels.
Significantly reduces sulfuric acid consumption by 38%, enhances process safety, and allows for nitric acid recycling, while maintaining high TNT yield and reducing hazardous by-products.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a nitration mixture for nitrating 2,4- and 2,6-dinitrotoluene to 2,4,6-trinitrotoluene and a process for obtaining 2,4,6-trinitrotoluene using the same.
[0002] 2,4,6-Trinitrotoluene (TNT) is one of the most frequently synthesized explosives in the world. It is obtained as a result of a three-step nitration of toluene. In the last step, dinitrotoluene is nitrated using a mixture consisting of fuming nitric acid (V), sulfuric acid (VI) and oleum, both on a laboratory scale and on an industrial scale (Patents US2475095, US3742072). The use of this method is accompanied by the production of large amounts of waste sulfuric acid (VI), the management of which is troublesome. Currently, after replenishing nitric acid (V), it is recycled to the previous stage of nitration. After recycling and reacting in the first stage, the acid is not suitable for use in the TNT production process and is subjected to a regeneration process, which essentially consists of: diluting to 70% with water, and precipitating nitro compounds, denitrifying (removing nitric acid (V) residues and nitrogen oxides), and concentrating (removing water). This process involves huge energy consumption and the production of toxic nitrogen oxides. In addition, sulfuric acid (VI) poses a threat to the environment.
[0003] The nitration of toluene in the third step is also carried out at a high temperature (around 100 °C), accompanied by a secondary oxidation process during which large amounts of gas and tetranitromethane are released. For this reason, the operation of this process is dangerous and has been the cause of accidents in TNT factories.
[0004] Other methods for the nitration of dinitrotoluene to trinitrotoluene are described in the literature. These are nitrations using the following nitration mixtures: nitrogen(V) oxide in sulfuric(VI) acid, nitric(V) acid in trifluoromethanesulfonic acid (US Patent 7767868), nitric(V) acid and sulfuric(VI) acid in polyfluorohydro-phenanthrene, nitric(V) acid and boron trifluoride (Patent US329310), tributylphosphine and nitric(V) acid in supercritical carbon(IV) oxide (Patent Application US20070232840). Mixtures containing trifluoromethanesulfonic acid and boron trifluoride do not contain sulfuric(VI) acid, but their components are harmful to the environment. The reaction of nitric(V) acid with tributylphosphine in supercritical carbon(IV) oxide requires high pressure and makes the production cost of trotyl higher. All the other mentioned systems contain sulfuric(VI) acid.
[0005] A promising nitration system seems to be nitro-oleum (a solution of nitrogen(V) oxide in nitric(V) acid), however, the nitration reaction of dinitrotoluene to trinitrotoluene using this system is extremely slow and requires the use of a large excess of nitrating agent.
Summary of the Invention
[0006] In the present invention, a nitration mixture consisting of nitro-oleum and sulfuric(VI) acid in a content less than that of the above-mentioned nitration mixtures was used.
[0007] The present invention relates to a nitration mixture for nitrating 2,4- and 2,6-dinitrotoluene to 2,4,6-trinitrotoluene, characterized in that it contains 5 to 20% by weight of nitrogen(V) oxide, 60 to 80% by weight of nitric(V) acid and 5 to 30% by weight of sulfuric(VI) acid. Preferably, the nitration mixture contains 10 to 20% by weight of nitrogen(V) oxide, 55 to 70% by weight of nitric(V) acid and 15 to 25% by weight of sulfuric(VI) acid.
[0008] The present invention further relates to a process for obtaining 2,4,6-trinitrotoluene, which comprises contacting 2,4- and 2,6-dinitrotoluene with the nitrating mixture according to the invention and heating the resulting reaction mixture, wherein the mass ratio of the nitrating mixture to 2,4- and 2,6-dinitrotoluene is 10:1 or less. Preferably, the process for obtaining 2,4,6-trinitrotoluene according to the invention is characterized in that the mass ratio of the nitrating mixture to 2,4- and 2,6-dinitrotoluene is in the range of 5:1 to 8:1.
[0009] Preferably, the process for obtaining 2,4,6-trinitrotoluene according to the invention is characterized in that the nitration reaction is carried out at a temperature of 50 to 80 °C. More preferably, the nitration reaction is carried out at a temperature of 60 to 70 °C.
[0010] Preferably, the process for obtaining 2,4,6-trinitrotoluene according to the invention is characterized in that the nitration reaction is carried out for 4 hours or more. Table 1 compares the amounts of waste sulfuric acid (VI) in different processes for obtaining TNT.
[0011]
Table 1
[0012] Based on Table 1, it can be seen that the present method significantly reduces the consumption of sulfuric acid (VI) in a trinitrotoluene production plant. It results in a 38% reduction compared to the conventional method. This can be particularly important when nitrating agents without sulfuric acid (VI) are used in the first and second stages of nitration, for example, fuming nitric acid (V) or nitrogen monoxide (V) in an organic solvent.
[0013] Furthermore, when nitration according to the present invention is carried out, the level of the secondary oxidation process is lower and the process temperature is lower than in the conventional method, which improves the safety of the process. In this method, it is possible to recycle nitric acid (V) and reuse it to prepare a solution of nitrogen monoxide (V) in nitric acid (V).
[0014] Examples Example 1 52 g of 2,4-dinitrotoluene, 200 g of 20% nitro-oleum and 60 g of 99% sulfuric acid (VI) were added in a water bath to a three-necked round-bottom flask equipped with a thermometer and a ball reflux condenser (Allihna) and placed on a magnetic stirrer. After adding the materials, stirring was started and the contents of the flask were heated to 70 °C. The reaction was carried out for 8 hours from the moment the set temperature was reached. After the set time had elapsed, the contents of the flask were cooled to room temperature and poured into a beaker containing water and ice. The precipitate was filtered through a Schott G2 funnel and washed with water until pH = 7. The precipitate was transferred to a crystallizer and dried at 60 °C to a constant weight in a dryer. The yield of the reaction was 85%, and the trinitrotoluene content in the sample measured by GC-MS was 99.85%.
[0015] Example 2 10 g of 2,4-dinitrotoluene and a nitration mixture containing 20% nitro-oleum and sulfuric acid (VI) with a purity of 99% or more as shown in Table 2 were added to a 100 mL three-necked round-bottom flask equipped with a magnetic stirrer, a thermometer, and a ball reflux condenser (Allihna) and placed in a water bath. The reaction was carried out for 8 hours. After the reaction was completed, the contents of the flask were poured into a beaker containing water and ice and extracted with dichloromethane (1 x 50 mL). The extract was washed twice with a 0.5% aqueous sodium hydrogen carbonate solution and adjusted to pH = 7 with distilled water. Then, a small amount of magnesium sulfate (VI) was poured into the extract, left overnight, and then filtered through a fluted filter, and the solvent was distilled off using a vacuum evaporator. The results of nitration and the sample composition of the nitration mixture are shown in Table 2.
[0016]
Table 2
[0017] Example 3 The reaction was carried out in the same manner as in Example 1, except that the amount of 99% sulfuric acid (VI) in the nitration mixture per 1 g of 2,4-DNT, the nitration reaction time, and the temperature were changed. The results are shown in Table 3.
Table 3
[0018] The composition of the nitration mixture according to the present invention and the disclosed process can be used in the manufacture of the explosive 2,4,6-trinitrotoluene (trotyl).
Claims
1. A nitration mixture for nitrating 2,4- and 2,6-dinitrotoluene to 2,4,6-trinitrotoluene, characterized in that it contains 5 to 20% by weight of nitrogen monoxide (V), 60 to 80% by weight of nitric acid (V) and 5 to 30% by weight of sulfuric acid (VI).
2. The nitration mixture according to claim 1, characterized in that it contains 10 to 20% by weight of nitrogen monoxide (V), 55 to 70% by weight of nitric acid (V) and 15 to 25% by weight of sulfuric acid (VI).
3. A process for obtaining 2,4,6-trinitrotoluene, comprising contacting 2,4- and 2,6-dinitrotoluene with the nitration mixture as defined in claim 1 or 2, and heating the reaction mixture thus formed, wherein the mass ratio of the nitration mixture to 2,4- and 2,6-dinitrotoluene is 10:1 or less.
4. The process for obtaining 2,4,6-trinitrotoluene according to claim 3, characterized in that the mass ratio of the nitration mixture to 2,4- and 2,6-dinitrotoluene is in the range of 5:1 to 8:
1.
5. The process for obtaining 2,4,6-trinitrotoluene according to claim 3 or 4, characterized in that the nitration reaction is carried out at a temperature of 50 to 80 °C.
6. The process for obtaining 2,4,6-trinitrotoluene according to claim 5, characterized in that the nitration reaction is carried out at a temperature of 60 to 70 °C.
7. The process for obtaining 2,4,6-trinitrotoluene according to any one of claims 3 to 6, characterized in that the nitration reaction is carried out for 4 hours or more.