CN108707077A - The method for preparing TNT as raw material one-step method using nitrotoleune - Google Patents

Abstract

The invention discloses a method for preparing TNT by using nitrotoluene as a raw material in one step, using p-nitrotoluene or o-nitrotoluene as a raw material, and a mixed system of fuming HNO ₃ /concentrated H ₂ SO ₄ as a nitrating agent. 2,4,6-trinitrotoluene TNT was prepared by nitration reaction, and its structure was characterized by melting point, thin-layer chromatography, mass spectrometry and liquid chromatography. The influence of the ratio of fuming HNO ₃ /concentrated H ₂ SO ₄ mixed system, feeding method and dosage on the product yield was discussed, and the reaction conditions were optimized. The present invention obtains TNT through one-step nitration synthesis using nitrotoluene as a raw material, avoids the pollution of the environment caused by a large amount of waste acid and red water, and reduces the energy and power consumption caused by reaction steps and nitration equipment.

Description

Taking nitrotoluene as the method for preparing TNT by one-step method of raw material

technical field

The invention relates to a method for preparing TNT by using nitrotoluene as a raw material in one-step method, belonging to the technical field of explosive preparation.

Background technique

2,4,6-Trinitrotoluene (TNT) is a high explosive first synthesized in 1863. It is produced in large quantities by nitration of toluene with nitric acid mixed acid. At present, most of the TNT produced at home and abroad use toluene as raw material, and carry out three-stage nitration process with nitric-sulfur mixed acid, using nine nitration machines, that is, toluene is nitrated into mononitrotoluene (MNT) in one-stage nitration, and one-stage nitration Nitrotoluene includes: o-nitrotoluene, p-nitrotoluene and m-nitrotoluene; MNT is nitrated into dinitrotoluene (DNT) in the second-stage nitration; DNT is nitrated into trinitrotoluene (TNT) in the third-stage nitration ). In a nutshell, it is to use toluene through a mixture of fuming nitric acid and concentrated sulfuric acid to obtain a mixture of dinitrotoluene isomers, and then convert the DNT mixture into TNT with a mixture of fuming nitric acid and SO3 _- containing fuming sulfuric acid, and finally It is then refined by sodium sulfite or refined by other methods. The synthetic route of the three-stage nitration is as follows:

During the preparation of TNT, when toluene is nitrated, the concentration of nitric acid is different for each nitro group on the benzene ring. This process will produce red water, which is a typical pollutant and waste in the TNT production process (Sun Rongkang, Ren Tesheng, Gao Huailin; Chemistry and Technology of Strong Explosives Beijing: National Defense Industry Press; 1981.07, 325-335 ; Nitro Compound Explosive Chemistry and Technology Sun Rongkang et al. Edited by Arms Industry Press 1992.11, 175-245). With the continuous progress of society, the shortcomings of production technology widely used in industry have become increasingly prominent, mainly as follows: produce asymmetric TNT (2,4,5-, 2,3,4-, 2,3,6-, 2,3,5- and 3,4,5-trinitrotoluene), while also producing large quantities of pollutants such as nitrogen oxides (NO _x ) and tetranitromethane (TNM), for example, using conventional manufacturing method, every 100 kilograms of TNT will produce 0.5% TNM, these pollutants need to be removed to prevent it from damaging the environment and causing harm to the environment; the large-scale use of strong acid has caused serious harm to the environment, and it has been unable to meet the economic needs of the environment. Sustained development; in industrial production, serious corrosion occurs to factory equipment; the sharp exotherm in the reaction process causes unstable operation, and safety accidents such as explosions are prone to occur in the production process; when nitric acid is excessive, oxidation is prone to occur Side reactions lead to the decomposition of explosives and a decrease in yield; there is no nitrification regioselectivity, a large amount of unnecessary organic isomers are produced, resulting in a large waste of resources; a large amount of waste acid is discharged, which increases the treatment cost.

Contents of the invention

The invention aims to provide a method for preparing TNT by using nitrotoluene as a raw material in one-step method, and its structure is characterized by mass spectrum, melting point, thin-layer chromatography and liquid chromatography, and the reaction conditions of synthesis are optimized.

The nitrotoluene used in the present invention includes p-nitrotoluene or o-nitrotoluene, and p-(o) nitrotoluene is derived from the first-stage nitration product of toluene and obtained through separation. It is mainly used as a reaction intermediate for the synthesis of organic matter, and p-nitrotoluene is used in two aspects: one is oxidation to prepare p-nitrobenzoic acid or p-nitrobenzaldehyde, and the other is catalytic hydrogenation to generate p-nitroaniline. O-nitrotoluene can be used to prepare organic intermediates such as m-cresol and m-toluidine. The invention uses nitrotoluene or o-nitrotoluene as a raw material, avoids environmental pollution caused by a large amount of waste acid and red water, and reduces energy and power consumption caused by reaction steps and nitration equipment.

The invention adopts concentrated sulfuric acid and fuming nitric acid as nitrating agents, p-(o) nitrotoluene as raw materials, and synthesizes TNT through one-step nitration.

The synthetic route of the present invention is:

.

The invention provides a method for preparing TNT with nitrotoluene as a raw material in one-step method, comprising the following steps:

(1) Prepare mixed acid:

Measure 25-30ml of H ₂ SO ₄ (98%) in a four-neck flask, then measure 5-10ml of HNO ₃ (98%) in a separatory funnel, the initial temperature is 20-40°C, turn on the automatic stirrer and Condensation reflux device, add HNO ₃ (98%) dropwise to H ₂ SO ₄ (98%), keep the temperature at 40~50°C;

The molar ratio of nitric acid and sulfuric acid is 1:2.5~4 respectively;

(2) Feeding:

After the mixed acid preparation is completed, when the temperature has a downward trend, slowly add 4-9g p-nitrotoluene or o-nitrotoluene, there is a tendency to increase the temperature, and keep the temperature at 80~90°C; after the addition, there is a downward trend;

(3) Reaction:

Begin to heat up the oil bath to 90-140°C, keep it warm for 3-8h (reaction time), keep stirring, and the rotation speed is 350-400r/min.

(4) Processing:

After the reaction is completed, start to cool down naturally, stir slowly, and cool down to 20-60°C, pour the solution into 50-100ml of cold water, stir while pouring, and smoke will come out, when the temperature drops to 30°C, start sand core suction filtration ; Then wash the product with hot water at 80-90°C until neutral, put the product in an evaporating dish, and place it in a drying oven at 40-60°C for 5-10 hours.

In the above method, the dropping rate of adding HNO ₃ (98%) into H ₂ SO ₄ (98%) is 0.5-2 mL/min.

In the above method, the yield of TNT is 89-95%.

In the above method, preferably, the reaction time is 4 hours, the reaction temperature is 110-115° C., and the molar ratio of 98% H ₂ SO ₄ to 98% HNO ₃ is 10:3.

As a kind of preferred technical scheme: the method for preparing TNT by one-step method, comprises the following steps:

(1) Measure 0.5 mol of 98% H ₂ SO ₄ in a four-necked flask, and then measure 0.15 mol of 98% HNO ₃ in a separatory funnel, at an initial temperature of 35°C, turn on the automatic stirrer and condensing reflux device, Add 98% HNO ₃ dropwise to 98% H ₂ SO ₄ and keep the temperature at 40~50°C;

(2) After the mixed acid is prepared, when the temperature has a downward trend, start to slowly add 0.05mol p-nitrotoluene or o-nitrotoluene, and keep the temperature at 80-90°C if there is a tendency to increase the temperature;

(3) Start the oil bath to heat up to 110-115°C, and react for 4 hours;

(4) After the reaction is completed, start to cool down naturally, stir slowly, and cool down to 40°C. Pour the solution into 100ml of cold water, stir while pouring, and smoke will come out. When the temperature drops to 30°C, start sand core suction filtration; Then wash the product with hot water at 100°C until neutral, put the product in an evaporating dish, place it in a drying oven at 60°C for 10 hours, measure the mass, and the yield of TNT can reach 92.2%.

Produce TNT by the method of the present invention, the amount of waste water that generates after reaction is few, and chemical oxygen demand is low, and methyl and nitro in (ortho) nitrotoluene have positioning effect, have avoided generating multiple other dinitrotoluenes (such as 2,3-Dinitrotoluene, 2,5-Dinitrotoluene, 3,4-Dinitrotoluene and 3,5-Dinitrotoluene, four types of dinitrotoluene), reducing tetranitromethane content.

Beneficial effects of the present invention:

The present invention obtains TNT through one-step nitration synthesis of nitrotoluene as raw material, avoids the disadvantage of polluting the environment caused by a large amount of waste acid and red water, and reduces energy and power consumption caused by reaction steps and nitration equipment.

Description of drawings

Fig. 1 is the impact diagram of the change of reaction temperature on TNT yield.

Fig. 2 is the impact diagram of the change of the molar ratio of nitric acid and concentrated sulfuric acid on the yield of TNT.

Detailed ways

The present invention is further illustrated by the following examples, but not limited to the following examples.

The invention provides a method for preparing TNT with nitrotoluene as a raw material in one-step method, comprising the following steps:

(1) Prepare mixed acid:

Measure 25-30ml of H ₂ SO ₄ (98%) in a four-neck flask, then measure 5-10ml of HNO ₃ (98%) in a separatory funnel, the initial temperature is 20-40°C, turn on the automatic stirrer and Condensation reflux device, add HNO ₃ (98%) dropwise to H ₂ SO ₄ (98%), keep the temperature at 40~50°C;

(2) Feeding:

After the mixed acid preparation is completed, when the temperature has a downward trend, slowly add 4-9g p-nitrotoluene or o-nitrotoluene, there is a tendency to increase the temperature, and keep the temperature at 80-90°C; after the addition, there is a downward trend;

(3) Reaction:

Begin to heat up the oil bath to 90-140°C, keep it warm for 3-8h (reaction time), keep stirring, and the rotation speed is 350-400r/min.

(4) Processing:

After the reaction is completed, start to cool down naturally, stir slowly, and cool down to 20-60°C, pour the solution into 50-100ml of cold water, stir while pouring, and smoke will come out, when the temperature drops to 30°C, start sand core suction filtration ; Then wash the product with hot water at 80-90°C until neutral, put the product in an evaporating dish, and place it in a drying oven at 40-60°C for 5-10 hours.

The method for synthesizing TNT by one-step method is illustrated below by specific examples.

Embodiment 1: the method for synthesizing TNT by one-step method

This embodiment has investigated the influence of reaction time on TNT yield:

Take 0.05 mol of p-nitrotoluene, 0.15 mol of nitric acid, and 0.5 mol of sulfuric acid, and the reaction temperature is 120°C. The reaction time is 3h, 4h, 5h, 6h, 7h, 8h respectively. The effect of reaction time on the product is shown in Table 1. As can be seen from Table 1, the yield of the product TNT increases first and then remains unchanged with the prolongation of time, and it is the best when the reaction is 4h.

The influence of table 1 reaction time on TNT yield

Optimization of reaction time: take 0.05 mol of p-nitrotoluene, HNO ₃ : H ₂ SO ₄ =3:10, 0.15 mol of nitric acid, 0.5 mol of sulfuric acid, and the reaction temperature is 120 degrees. The reaction time is 3h, 4h, 5h, 6h, 7h, 8h respectively. The product in 3h was a mixture (the reaction was not completed), and the other yields were 89%, indicating that the reaction was complete when the reaction was 4h.

Embodiment 2: the method for synthesizing TNT by one-step method

This embodiment has investigated the influence of temperature of reaction on TNT yield

Take 0.05 mol of p-nitrotoluene, HNO ₃ : H ₂ SO ₄ =1:3.5, 0.15 mol of nitric acid, 0.5 mol of sulfuric acid, and the reaction time is 4 hours. The reaction temperatures were 100°C, 110°C, 120°C, 130°C, and 140°C, respectively.

The effect of reaction temperature on the product TNT is shown in Figure 1. It can be seen from Figure 1 that the product yield increases first and then decreases, and the product yield is the highest at 110°C.

Optimization of the reaction temperature: take 0.05 mol of p-nitrotoluene, HNO ₃ : H ₂ SO ₄ =1:3.5, 0.15 mol of nitric acid, 0.5 mol of sulfuric acid, and the reaction time is 4 hours. The reaction temperatures were 100°C, 110°C, 120°C, 130°C, and 140°C, respectively. The yields were 90.8%, 92.2%, 89%, 89%, and 86%, respectively.

Embodiment 3: the method for one-step synthetic TNT

This embodiment has investigated the influence of nitric acid and the concentrated sulfuric acid mol ratio on TNT yield

Take 0.05mol of o-nitrotoluene, the reaction time is 4h, and the reaction temperature is 110°C. The ratio (molar ratio) of nitric acid to sulfuric acid is 1:2.5, 1:3, 1:3.5, 1:4 respectively. Product yield n(NA):n(SA) changes are shown in Figure 2. It can be seen from Figure 2 that the yield of the target product first increases and then decreases with the increase of concentrated sulfuric acid, and reaches the maximum when n(NA):n(SA)=1:3.5.

The optimization of the mixed acid ratio of nitric acid and sulfur in the reaction: take 0.05 mol of o-nitrotoluene, the reaction time is 4 hours, and the reaction temperature is 110 degrees. The ratio of nitric acid to sulfuric acid is 1:2.5, 1:3, 1:3.5, 1:4 respectively. The yields were 87%, 89%, 92.2%, and 89%, respectively.

Example 4:

The present invention has detected the process wastewater after the reaction, compared with the original TNT production process, the results are shown in table 2 below:

Table 2

Produce TNT by the method of the present invention, the amount of waste water generated after the reaction is small, the chemical oxygen demand is low, and the methyl and nitro groups in the nitrotoluene have a positioning effect, avoiding the generation of various dinitrotoluenes (which will not contain 2,3 - dinitrotoluene, 2,5-dinitrotoluene, 3,4-dinitrotoluene and 3,5-dinitrotoluene, four types of dinitrotoluene), reducing the content of tetranitromethane.

Claims (9)

1. take nitrotoluene as the method for raw material one-step preparation TNT, it is characterized in that: take nitrotoluene as raw material, fuming HNO ₃ /concentrated H ₂ SO ₄ mixed system is nitrating agent, one-step nitration reaction prepares 2, 4,6-trinitrotoluene TNT; The nitrotoluene includes p-nitrotoluene or o-nitrotoluene. 2. the method for preparing TNT by taking nitrotoluene as raw material one-step method according to claim 1, is characterized in that: comprise the following steps: (1) Prepare mixed acid: Measure 25-30ml of H ₂ SO ₄ into a four-neck flask, then measure 5-10ml of HNO ₃ into a separatory funnel, the initial temperature is 20-40°C, turn on the automatic stirrer and condensing reflux device, add HNO ₃ dropwise into H ₂ SO ₄ and keep the temperature at 40~50°C; H ₂ SO ₄ is concentrated sulfuric acid with 98% mass concentration, HNO ₃ is fuming nitric acid with 98% mass concentration; the molar ratio of nitric acid and sulfuric acid is 1:2.5~4 respectively; (2) Feeding: After the mixed acid preparation is completed, when the temperature has a downward trend, slowly add 4-9g p-nitrotoluene or o-nitrotoluene, there is a tendency to increase the temperature, and keep the temperature at 80~90°C; after the addition, there is a downward trend; (3) Reaction: Start the oil bath to heat up to 90-140°C, react for 3-8h, stir, and keep the stirring speed at 350-400r/min; (4) Processing: After the reaction is completed, start to cool down naturally, stir slowly, and cool down to 20-60°C, pour the solution into 50-100ml of cold water, stir while pouring, and smoke will come out, when the temperature drops to 30°C, start sand core suction filtration ; Then wash the product with hot water at 80-90°C until neutral, put the product in an evaporating dish, and place it in a drying oven at 40-60°C for 5-10 hours. 3. The method for preparing TNT by using nitrotoluene as a raw material in one-step method according to claim 2, characterized in that: the dropping rate of HNO ₃ into H ₂ SO ₄ is 0.5-2 mL/min. 4. the method for preparing TNT with nitrotoluene as a raw material one-step method according to claim 2, is characterized in that: the yield of TNT is 89-95%. 5. The one-step method for preparing TNT using nitrotoluene as a raw material according to claim 2, characterized in that: in step (3), the temperature of the oil bath is raised to 110-115° C., and the reaction time is 4 hours. 6. The method for preparing TNT by using nitrotoluene as a raw material according to claim 2, wherein the molar ratio of 98% H ₂ SO ₄ to 98% HNO ₃ is 10:3. 7. take nitrotoluene according to claim 2 as the method for raw material one-step method to prepare TNT, it is characterized in that: comprise the following steps: (1) Measure 0.5 mol of 98% H ₂ SO ₄ in a four-necked flask, and then measure 0.15 mol of 98% HNO ₃ in a separatory funnel, at an initial temperature of 35°C, turn on the automatic stirrer and condensing reflux device, Add 98% HNO ₃ dropwise to 98% H ₂ SO ₄ and keep the temperature at 40~50°C; (2) After the mixed acid is prepared, when the temperature has a downward trend, start to slowly add 0.05mol p-nitrotoluene or o-nitrotoluene, and keep the temperature at 80-90°C if there is a tendency to increase the temperature; (3) Start the oil bath to heat up to 110°C, and react for 4 hours; (4) After the reaction is completed, start to cool down naturally, stir slowly, and cool down to 40°C. Pour the solution into 100ml of cold water, stir while pouring, and smoke will come out. When the temperature drops to 30°C, start sand core suction filtration; Then wash the product with hot water at 100°C until neutral, put the product in an evaporating dish, and dry it in a drying oven at 60°C for 10 hours. 8. The method for preparing TNT with nitrotoluene as a raw material according to claim 7, characterized in that: after the product is dried, the quality is measured, and the yield of TNT reaches 92.2%. 9. according to any one of claim 1～8, take nitrotoluene as the method for raw material one-step method to prepare TNT, it is characterized in that: the waste water after reaction, waste water amount is few, chemical oxygen demand is low, in nitrotoluene The methyl group and the nitro group have a positioning effect, avoiding the formation of various dinitrotoluenes, and reducing the content of tetranitromethane.