A preparation method of No. Ⅱ medium fixative

Abstract

The present invention relates to a preparation method of a No. II neutralizing agent, comprising the following steps: step 1) adding N-methylaniline to an alkaline aqueous solution and mixing to obtain an N-methylaniline mixed solution; step 2) adding bis(trichloromethyl)carbonic acid to the N-methylaniline mixed solution and stirring the reaction; maintaining the reaction temperature less than 105°C by controlling the addition rate of bis(trichloromethyl)carbonic acid during the reaction to obtain a reaction product; step 3) performing solid-liquid separation on the reaction product to obtain No. I neutralizing agent. The present invention uses solid triphosgene as a raw material and adopts a one-pot method to prepare No. II neutralizing agent. The preparation process is stable. When solid phosgene is 105% to 110% of the theoretical feed, the reaction yield can reach more than 95%. At the same time, the entire preparation process is safe, stable, and less polluting during the entire reaction process.

Description

Technical Field

[0001] The present invention relates to the field of chemical industry, and in particular to a preparation method of a No. II neutralizing agent. Background Art

[0002] Neutralizers are widely used as stabilizers in explosives and propellants. Urea-based stabilizers are particularly popular both domestically and internationally due to their excellent compatibility. Nitrocellulose and nitroglycerin, the main components of explosives, decompose automatically at room temperature, but decomposition accelerates when heated. Under normal storage conditions, nitrocellulose undergoes slow thermal decomposition, breaking the nitrate ester bonds in its molecular chain, releasing large amounts of nitrogen oxide gas and heat, which further accelerates thermal decomposition and forms an autocatalytic process. Nitroglycerin, like nitrocellulose, also contains nitrate ester bonds in its molecular chain. At room temperature, high-purity nitroglycerin decomposes slowly, but nitroglycerin containing impurities will decompose spontaneously, releasing large amounts of nitrogen oxide gas and heat, which in turn catalyzes the thermal decomposition of nitroglycerin. Therefore, neutralizers are added during the production process to improve the stability of explosives and propellants.

[0003] Currently, the main application in China is the No. 2 neutralizer, but the existing preparation method of No. 2 neutralizer has the following shortcomings: first, phosgene must be used as a production raw material, which is highly dangerous and harmful to humans and the environment, posing a great pressure on safety and environmental protection; second, the product quality is unstable. The current production process purification technology of No. 2 neutralizer is vacuum distillation, and the resulting product quality is not stable enough; third, the traditional process is labor-intensive, and the production process is highly polluting and high-risk, posing a health hazard to employees. Therefore, we should increase efforts to promote the implementation of new technologies, complete technological upgrades, promote the upgrading of the neutralizer industry, enhance the supply chain risk response capabilities, build a safe and stable neutralizer supply system, and safeguard the security of my country's defense industry. Summary of the Invention

[0004] In order to solve the problems of complex process, high risk and unstable quality in the prior art, the present invention proposes a preparation method of No. II neutralizing agent.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A method for preparing a No. II medium-fixing agent comprises the following steps:

[0007] Step 1) adding N-methylaniline to an alkaline aqueous solution and mixing to obtain an N-methylaniline mixed solution;

[0008] Step 2) adding bis(trichloromethyl)carbonic acid to the N-methylaniline mixture and stirring to react; during the reaction, controlling the addition rate of bis(trichloromethyl)carbonic acid to maintain the reaction temperature below 105° C. to obtain a reaction product;

[0009] Step 3) The reaction product is subjected to solid-liquid separation to obtain a neutralizing agent No. 1.

[0010] Optionally, the pH of the alkaline aqueous solution in step 1) is 10-14.

[0011] Optionally, the mass fraction of N-methylaniline in the N-methylaniline mixed solution is 30-45%.

[0012] Optionally, in the step 2), the weight ratio of the added trichloromethylcarbonic acid to the N-methylaniline is controlled to be 0.48-0.52:1.

[0013] Optionally, in step 2), the stirring rate is controlled to be 200-400 r / min.

[0014] Optionally, in step 2), the relative pressure during the reaction is controlled to be lower than -0.03 MPa.

[0015] Preferably, the relative pressure during the vacuum distillation process is -0.01 to -0.03 MPa.

[0016] Optionally, in the step 2), during the reaction, an oily product in the upper layer of the N-methylaniline mixed solution is extracted, and the residual amine content in the oily product is detected. When the residual amine content is lower than 0.2%, the reaction is terminated.

[0017] Optionally, the solid-liquid separation in step 3) is followed by water washing to obtain a No. II neutralizing agent.

[0018] Optionally, the method further comprises:

[0019] Step 4) subjecting the No. II intermediate fixer prepared in step 3) to vacuum distillation to obtain refined No. II intermediate fixer.

[0020] Optionally, the relative pressure during the vacuum distillation process is lower than -0.1 MPa and the temperature is 205°C to 240°C.

[0021] Preferably, the relative pressure during the vacuum distillation process is -0.09 to -0.1 MPa.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] The present invention uses solid triphosgene as a raw material and adopts a one-pot process to prepare the No. II neutralizer. The preparation process is stable. When the solid phosgene is 105% to 110% of the theoretical feed, the reaction yield can reach over 95%. At the same time, the entire reaction process is safe, stable, and has low pollution. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions and advantages of the present invention more clear, the following will be further described in detail in conjunction with the embodiments of the present invention.

[0025] The present invention prepares neutralizer No. II by a one-pot method using N-methylaniline and bistrichloromethyl carbonate (solid triphosgene) under alkaline conditions. During the reaction, N-methylaniline chloride is first generated, which then undergoes a condensation reaction with N-methylaniline to form N,N-dimethyldiphenylurea (neutralizer No. II). The byproduct, hydrogen chloride, reacts with sodium hydroxide to form sodium chloride and water.

[0026] Reaction mechanism:

[0027]

[0028] Reaction equation:

[0029] No. Ⅱ intermediate fixative:

[0030]

[0031] Mother liquor:

[0032] HCl + NaOH → NaCl + H2O

[0033] Side effects:

[0034] Cl3CO-CO-OCCl3+12NaOH→3Na2CO3+6NaCl+6H2O

[0035] Test analysis methods

[0036] Residual amine detection method:

[0037] Take 1.0 g of crystals from the upper layer of the synthesis reactor, press dry with filter paper, and weigh on a balance (accurate to 0.01 g). Then place it in a mortar and add 30 ml of hydrochloric acid to grind. Pour the ground material into a beaker, rinse the mortar with distilled water, and add the solution to the beaker. The total volume of the solution should not exceed 300 ml. Add 10 ml of potassium bromide to the suspension in the beaker and titrate with 0.01 M sodium nitrite standard solution at 0°C-5°C until a blue spot appears on the starch potassium iodide test paper. The endpoint is that the spot does not disappear after 5 minutes. Record the number of milliliters titrated.

[0038] Calculate the residual amine content W1:

[0039]

[0040] Where:

[0041] w1——mass percentage of N-methylaniline

[0042] v1——mL of sodium nitrite solution consumed

[0043] c——molar concentration of sodium nitrite solution

[0044] 0.1212——milligram moles of N-methylaniline

[0045] G——sample weight (g)

[0046] Yield calculation

[0047]

[0048]

[0049] Where:

[0050] Yield (合成) ——Synthesis yield of crude methyl neutralizer

[0051] m1——mass of crude methyl neutralizer (g)

[0052] m2——Theoretical mass of methyl neutralizer product (g)

[0053] M——Molecular mass of methyl neutralizer (g / mol)

[0054]

[0055] Where:

[0056] Yield (精馏) ——Synthesis yield of crude methyl neutralizer

[0057] m3——Methyl neutralizer product mass (g)

[0058] m4——Mass of the front fraction (g)

[0059] m5——Mass of crude methyl neutralizer added (g)

[0060] Melting point test

[0061] Take a small amount of sample and grind it into the finest powder possible in a mortar. Put it into a clean, dry melting point tube. Take a dry glass tube (or plastic tube) with a length of at least about 800 mm, stand it upright on a glass plate, and drop the melting point tube containing the sample into it several times until the sample in the melting point tube is compressed to 2-3 mm high.

[0062] First, slowly raise the temperature of the heat transfer liquid to approximately 110°C, 10°C below the initial melting point range specified in the sample specifications. Attach the melting point tube containing the sample to the measuring thermometer, aligning the sample end of the melting point tube with the center of the mercury bulb. The mercury bulb should be located in the center of the heat transfer liquid. Maintain a steady heating rate of (1.0±0.1°C) / min. The temperature at which the sample shows obvious localized liquefaction is the initial melting temperature, and the temperature at which the sample is completely melted is the final melting temperature. Record the initial and final melting temperatures.

[0063] The melting point is the temperature from the initial melting point to the final melting point, and the final melting point minus the initial melting point is the melting range.

[0064] Example 1:

[0065] Sample synthesis:

[0066] (1) First, add 80.20g of water and 161.79g of 30% NaOH aqueous solution into the reactor, turn on the circulating water vacuum pump, start stirring, control the stirring speed at about 200 revolutions per minute, and then add 140.69g of N-methylaniline.

[0067] (2) Slowly add solid granular bis(trichloromethyl)carbonate to the reactor. When oil is generated in the reactor, maintain the reaction state. After a period of time, sample the upper layer of oil and analyze the residual aromatic amine. During the reaction, vacuum is applied to maintain the relative pressure at -0.02 MPa.

[0068] (3) Based on the results of the in-process control analysis, if the product meets the standards, stirring is stopped and the product is separated and washed. If the standards are not met, bis(trichloromethyl)carbonate is added to continue the synthesis reaction until the analytical results meet the standards. The highest temperature during the reaction is 102°C, and the amount of bis(trichloromethyl)carbonate used is 71.59g.

[0069] (4) Filter the obtained product, wash it with water, and then dry it until it is almost free of water.

[0070] (5) Record the product weight, crystal form, and appearance, and analyze the product amine residue, melting point, and melting range.

[0071] Examples 2 to 11

[0072] The amount of raw materials added and the maximum reaction temperature were adjusted as shown in Table 1. The other preparation processes were the same as in Example 1.

[0073] Comparative Examples 1 and 2

[0074] The amount of raw materials added and the maximum reaction temperature were adjusted as shown in Table 1. The other preparation processes were the same as in Example 1.

[0075] Table 1 Main data of synthesis process

[0076]

[0077] Table 2 Synthesis experiment results

[0078]

[0079]

[0080] As shown in Tables 1 and 2, when an excess of about 5% to 10% of bistrichloromethyl carbonate is added (i.e., the weight ratio of trichloromethyl carbonate to N-methylaniline is 0.48 to 0.52:1), the product yield tends to be stable and can reach about 96%. At this time, almost all of the N-methylaniline is converted into the neutralizing agent product, the residual aromatic amines in the product are less than 0.1%, the melting range of the product is between 115°C and 122°C, and the product purity is relatively high. Therefore, it is recommended to use an excess of 5% to 10% of bistrichloromethyl carbonate.

[0081] In addition to the feed ratio, the operational flow also plays a key role in the entire synthesis process. The synthesis reaction is exothermic, and solid phosgene must be slowly added to the system during the addition process. The maximum reaction temperature is generally controlled between 101°C and 105°C. This is to ensure that the solid phosgene fully reacts with the N-methylaniline, improving reaction efficiency and increasing yield. It also prevents excessive temperature increases, which can cause boiling and unnecessary losses.

[0082] Example 12

[0083] Vacuum distillation

[0084] (1) The crude neutralizer prepared in Example 1 was added to a distiller, and the vacuum pump was turned on to control the system pressure to -0.09 to -0.1 MPa, and the pipeline temperature was kept above 120 degrees Celsius.

[0085] (2) The crude product of the neutralizing agent is subjected to distillation treatment at 205°C-230°C. After the distilled sample becomes a colorless transparent liquid, it is collected into a finished product bottle to obtain a refined neutralizing agent finished product.

[0086] (3) Record the weight of the finished product and analyze the product, amine residue in the fore fraction, melting point, and melting range.

[0087] Examples 13 to 16

[0088] Adjust the reaction parameters as shown in Table 1.

[0089] Table 3 Distillation experimental results

[0090] Serial number temperature pressure Amine residual % Yield % Melting range (℃) Example 12 226 -0.093 0.01 93.6 121-122.5 Example 13 218 -0.095 0.01 96.4 120-122.5 Example 14 215 -0.095 0.01 97.8 120-122.5 Example 15 208 -0.097 0 96.0 120-122.5 Example 16 210 -0.096 0 98.6 120-122.5 Comparative Example 3 200 -0.095 0.01 89.1 121-122.5 Comparative Example 4 249 -0.087 0.02 90.8 119-121

[0091] As shown in Table 3, during distillation experiments, since the boiling point of the methyl neutralizer is 350°C at room temperature, it is difficult to remove by atmospheric distillation. Therefore, a certain degree of vacuum is required in the system. Generally speaking, the better the vacuum, the higher the yield of the finished product obtained by distillation. Therefore, during distillation experiments, the relative pressure must be maintained below -0.09 MPa, and the temperature must be controlled between 205°C and 240°C. Within this temperature range, the residual aromatic amines in the crude product are essentially removed, the product appearance is good, and the overall yield is relatively ideal. Furthermore, the distillation residue is a black solid without any odor. Composition analysis of the distillation residue revealed that it is primarily composed of inorganic salts, neutralizer residue, and organic high-boiling substances. Destructive testing of the residue, using a high-temperature spray gun, revealed that the residue poses no risk of explosion.

[0092] In summary, the present invention increases the amount of solid triphosgene used, based on a theoretical molar ratio of solid triphosgene to N-methylaniline of 1:6, to a 5%-10% excess of solid triphosgene and a maximum reaction temperature of 101-105°C. Using the improved process flow, the No. II intermediate stabilizer is prepared, resulting in a sample yield of 95%-96%, a stable process, and excellent performance of the product after distillation, all indicators exceeding national standards.

[0093] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a No. II intermediate fixative, characterized in that: The steps include: The method comprises the following steps: adding N-methylaniline to an alkaline aqueous solution and mixing the mixture to obtain an N-methylaniline mixed solution; the pH of the alkaline aqueous solution is 10 to 14; and the mass fraction of N-methylaniline in the N-methylaniline mixed solution is 30 to 45%. The method comprises the following steps: adding solid granular bistrichloromethyl carbonate to the N-methylaniline mixed solution and stirring the mixture to react; controlling the addition rate of the bistrichloromethyl carbonate to maintain the reaction temperature below 105° C. during the reaction to obtain a reaction product; and controlling the weight ratio of the bistrichloromethyl carbonate added to the N-methylaniline in the step 2) to be 0.48 to 0.52:

1. Step 3) The reaction product is subjected to solid-liquid separation to obtain a neutralizing agent No. II.

2. The method for preparing the No. II neutralizing agent according to claim 1, characterized in that: In the step 2), the stirring rate is controlled to be 200-400 r / min.

3. The preparation method of No. II neutralizing agent according to claim 1, characterized in that: In the step 2), the relative pressure during the reaction is controlled to be lower than -0.03 MPa.

4. The method for preparing the No. II neutralizing agent according to claim 1, characterized in that: In the step 2), during the reaction, the oily product on the upper layer of the N-methylaniline mixed solution is extracted, and the residual amine content in the oily product is detected. When the residual amine content is lower than 0.2%, the reaction is terminated.

5. The method for preparing the No. II neutralizing agent according to claim 1, characterized in that: After the solid-liquid separation in the step 3), the mixture is washed with water to obtain a No. II neutralizing agent.

6. The method for preparing the No. II neutralizing agent according to claim 1, characterized in that: The method further comprises: Step 4) subjecting the No. II intermediate fixer prepared in step 3) to vacuum distillation to obtain refined No. II intermediate fixer.

7. The method for preparing the No. II neutralizing agent according to claim 6, characterized in that: The relative pressure during the vacuum distillation process is lower than -0.1 MPa and the temperature is 205°C to 240°C.

Images