Production process of o-nitroaniline

Abstract

The invention discloses a production process of o-nitroaniline, and belongs to the technical field of chemical production. According to the production process, saturated sodium chloride brine is used as a reaction medium, o-nitrochlorobenzene and ammonia water are subjected to ammonolysis to prepare o-nitroaniline, and liquid ammonia is added in the reaction by adopting a staged ammonia adding method to supplement ammonia consumed in the early reaction. According to the method, while the high-concentration saline water is used for inhibiting side reaction, the density of a water phase is increased, the density difference between an oil phase and the water phase is enhanced, layering is accelerated, separation of the product o-nitroaniline and the water phase is achieved, generation and residues of impurities are reduced, the solubility of NH4Cl is remarkably reduced through the common ion effect, rapid precipitation of ammonium chloride in the cooling layering stage is achieved, and the quality of the product is improved. Residues of ammonium chloride in the product are reduced and the product purity is improved. Liquid ammonia is added in the reaction, ammonia consumption is supplemented, forward proceeding of the reaction is promoted, thorough reaction is ensured, raw material residues and side reaction risks are reduced, and the conversion rate of o-nitrochlorobenzene is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical production, and particularly relates to a production process of o-nitroaniline. Background Art

[0002] o-Nitroaniline is a major chemical raw material for the veterinary drug olaquindox and the pharmaceutical drug albendazole. It is also an intermediate in the orange-based GC chromogen for ice dyes and a rubber antioxidant, MB. o-Nitroaniline can be reduced to o-phenylenediamine, which is used in the synthesis of carbendazim and thiophanate-methyl. In recent years, my country's modern agricultural and animal husbandry industry has rapidly developed, leading to increased production of domestic veterinary drugs and new, highly effective, and low-toxic pesticides. o-Nitroaniline is a popular commodity in the market, and with growing demand in international markets, its export prospects are promising.

[0003] Currently, o-nitroaniline is produced through two methods: aniline acetylation-nitration and o-nitrochlorobenzene ammonolysis. The aniline acetylation-nitration method has a long process path, low product yield, and involves a hazardous nitration process. The ammonolysis method also has high reaction pressures and requires significant equipment investment. The byproduct, ammonium chloride, is highly corrosive to equipment, and titanium piping is required throughout the entire process.

[0004] However, due to its simple process and high product yield, the ammonolysis method is widely used by domestic manufacturers to produce o-nitroaniline. It uses o-nitrochlorobenzene and aqueous ammonia to react to produce o-nitroaniline, which is then deaminated, washed, and dried to obtain the final product. However, some ammonium chloride remains after washing, significantly affecting the purity of subsequent products. Therefore, reducing the ammonium chloride content in o-nitroaniline is crucial for improving the quality of o-nitroaniline products. Summary of the Invention

[0005] The invention provides a production process of o-nitroaniline, which can solve the problem of low o-nitroaniline product purity in the prior art.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A production process for o-nitroaniline comprises the following steps:

[0008] S1. Put saturated sodium chloride brine into a reactor, add o-nitrochlorobenzene and ammonia water, and stir to mix evenly;

[0009] S2. Raise the temperature to 170-180°C for aminolysis reaction, with the reactor pressure at 3-4 MPa, and continue the reaction for 2-3 hours;

[0010] S3, inject liquid ammonia through a high-pressure pump and continue the reaction for 4-10 hours;

[0011] S4. After the reaction is completed, the mixture is transferred to a flash tank to recover ammonia, cooled to 80-100°C, centrifuged and separated, the precipitate is filtered and removed, the aqueous phase is distilled to recover ammonia and the brine is recycled, the oil phase is washed with hot water and dried to obtain the final product.

[0012] Furthermore, the concentration of the ammonia water is 25-28%. The ammonia water concentration of 25-28% in the initial reaction is suitable for transportation and storage. The conventional ammonia water concentration of 28-30% is too high, and a large amount of ammonia gas will be rapidly released during the high-temperature reaction process, which will put pressure on the equipment.

[0013] Furthermore, the molar ratio of ammonia in the o-nitrochlorobenzene to the ammonia water is 1:8-10. When o-nitrochlorobenzene and ammonia water are used to prepare aniline, an excess of ammonia is required to promote the forward reaction and increase the conversion rate of o-nitrochlorobenzene.

[0014] Furthermore, the volume ratio of the saturated sodium chloride brine to ammonia water is 0.5-2:1. Saturated sodium chloride brine is used as the reaction medium. Since the reaction product o-nitroaniline is slightly soluble in water, the high concentration of brine will reduce the solubility of o-nitroaniline in water, promote the rapid separation of oil and water, reduce emulsification, avoid product loss due to emulsification and retention of the water phase, and thus improve the purity of the product. - Forming a buffer system with NH3 (NH3 / NH4 + ), preventing side reactions such as nitro group reduction that could occur due to localized high pH, ​​thereby improving product purity. Furthermore, the sodium chloride in the brine is stable at high temperatures and does not react with the reactants or products. The brine and ammonia can be recycled and reused at a low cost.

[0015] High-concentration brine significantly reduces the solubility of o-nitroaniline in the aqueous phase through the salting-out effect, pushing the reaction equilibrium toward the product.

[0016] Furthermore, the liquid ammonia is added so that the molar amount of ammonia in the liquid ammonia is 20-30% of the molar amount of ammonia in the aqueous ammonia. The aqueous ammonia initially provides the ammonia requirement for the initial reaction, while the mid-stage addition of liquid ammonia maintains a high ammonia concentration, resolving the kinetic bottleneck caused by ammonia volatilization, promoting the complete nucleophilic substitution reaction, and improving the conversion rate.

[0017] Adding ammonia in stages avoids the side reactions caused by excessive ammonia at one time, while high ammonia concentration inhibits the hydrolysis side reaction (generating o-nitrophenol).

[0018] Furthermore, during the injection of liquid ammonia, the system pressure is maintained at ±0.5 MPa, and the system temperature fluctuation is maintained at ±5°C. The high-pressure reaction conditions can increase ammonia solubility and promote contact between reactants. However, the addition of liquid ammonia can cause pressure and temperature fluctuations. Large fluctuations can affect the stability of the reaction system and hinder the reaction. It is necessary to control the system temperature and pressure by adjusting the liquid ammonia injection rate to maintain a relatively stable state.

[0019] Furthermore, the purity of o-nitroaniline in the final product is ≥99%.

[0020] Furthermore, the temperature of the hot water is 60-80° C. Hot water washing can dissolve residual inorganic salts (NaCl) and a small amount of water-soluble organic matter (such as trace aniline by-products), and further remove impurities.

[0021] Furthermore, the conversion rate of o-nitrochloramine is ≥95%.

[0022] Furthermore, the drying is performed by vacuum drying at a drying temperature of 50-60° C. Vacuum drying can avoid high-temperature oxidation. The melting point of o-nitroaniline is about 69-72° C. The drying temperature needs to be lower than the melting point to avoid melting and agglomeration of the material while ensuring sufficient evaporation of water.

[0023] Beneficial effects of the present invention:

[0024] (1) The present invention adds saturated brine as a reaction medium in the reaction system, utilizes high salt content to inhibit side reactions, and high-concentration brine increases the density of the water phase, enhances the density difference between the oil phase (o-nitroaniline) and the water phase (brine containing NH4Cl), accelerates stratification, strengthens the separation of the product and the water phase, and reduces the generation and residue of impurities. The solubility of NH4Cl is affected by the Cl in the solution. - Concentration influence: saturated brine significantly reduces the solubility of NH4Cl through the common ion effect, realizes the rapid precipitation of ammonium chloride in the cooling and stratification stage, reduces the residual ammonium chloride, and improves the purity of the product.

[0025] (2) The present invention adds ammonia in stages during the reaction. Ammonia water is added at the beginning of the reaction to ensure the progress of the reaction. Liquid ammonia is added in the middle of the reaction to supplement ammonia consumption, promote the forward progress of the reaction, ensure the complete reaction, reduce the risk of raw material residue and side reactions, and improve the conversion rate of o-nitrochlorobenzene.

[0026] (3) The present invention recovers the residual ammonia in the reaction product by flash evaporation, and combines centrifugal stratification with hot water washing to quickly remove inorganic and organic impurities and improve product purity. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0028] Example 1

[0029] This embodiment provides a production process of o-nitroaniline, which is carried out according to the following steps:

[0030] S1. Prepare o-nitrochlorobenzene with a purity of ≥99%, prepare saturated sodium chloride brine with a concentration of 340 g / L and ammonia water with an ammonia content of 28%, with the volume ratio of saturated sodium chloride brine to ammonia water being 1:1, put the saturated sodium chloride brine into the reactor, add o-nitrochlorobenzene and ammonia water, with the molar ratio of ammonia in o-nitrochlorobenzene to ammonia water being 1:8, and stir to mix evenly.

[0031] S2. The temperature of the reactor was raised to 175°C, and the ammonolysis reaction was carried out under constant temperature stirring. The pressure of the reactor was controlled at 3-4 MPa, and the reaction was continued for 2 h.

[0032] S3. Liquid ammonia is injected through a high-pressure pump. The molar amount of ammonia in the injected liquid ammonia is 20% of the molar amount of ammonia in ammonia water. During the injection of liquid ammonia, the injection rate is adjusted to ensure that the temperature fluctuation of the system is maintained at ±5°C and the pressure fluctuation is ±0.5 MPa. The reaction is continued for 6 hours.

[0033] S4. After the reaction is completed, the product is transferred to a flash tank to recover ammonia. The liquid after flashing is cooled to 80°C and separated by centrifugation. The precipitated precipitate is removed by filtration. The aqueous phase is distilled to recover residual ammonia to obtain brine, which is recycled. The oil phase is washed with hot water at 70°C and vacuum-dried at 60°C to obtain the final product. The purity of o-nitroaniline in the final product is determined to be 99.5%. The conversion rate of o-nitrochlorobenzene in this production process is 95.6%.

[0034] Example 2

[0035] The only difference from Example 1 is that the volume ratio of saturated sodium chloride brine to ammonia water is adjusted to 0.5:1.

[0036] This embodiment provides a production process of o-nitroaniline, which is carried out according to the following steps:

[0037] S1. Prepare o-nitrochlorobenzene with a purity of ≥99%, prepare saturated sodium chloride brine with a concentration of 340 g / L and ammonia water with an ammonia content of 28%, and the volume ratio of saturated sodium chloride brine to ammonia water is 0.5:1. Put the saturated sodium chloride brine into the reactor, add o-nitrochlorobenzene and ammonia water, and the molar ratio of ammonia in o-nitrochlorobenzene and ammonia water is 1:8, and stir to mix evenly.

[0038] S2. The temperature of the reactor was raised to 175°C, and the ammonolysis reaction was carried out under constant temperature stirring. The pressure of the reactor was controlled at 3-4 MPa, and the reaction was continued for 2 h.

[0039] S3. Liquid ammonia is injected through a high-pressure pump. The molar amount of ammonia in the injected liquid ammonia is 20% of the molar amount of ammonia in ammonia water. During the injection of liquid ammonia, the injection rate is adjusted to ensure that the temperature fluctuation of the system is maintained at ±5°C and the pressure fluctuation is ±0.5 MPa. The reaction is continued for 6 hours.

[0040] S4. After the reaction is completed, the product is transferred to a flash tank to recover ammonia. The liquid after flashing is cooled to 80°C and separated by centrifugation. The precipitated precipitate is removed by filtration. The aqueous phase is distilled to recover residual ammonia to obtain brine, which is recycled. The oil phase is washed with hot water at 70°C and vacuum-dried at 60°C to obtain the final product. The purity of o-nitroaniline in the final product is detected to be 99.2%. The conversion rate of o-nitrochlorobenzene in this production process is 95.3%.

[0041] Example 3

[0042] The only difference from Example 1 is that the volume ratio of saturated sodium chloride brine to ammonia water is adjusted to 2:1.

[0043] This embodiment provides a production process of o-nitroaniline, which is carried out according to the following steps:

[0044] S1. Prepare o-nitrochlorobenzene with a purity of ≥99%, prepare saturated sodium chloride brine with a concentration of 340g / L and ammonia water with an ammonia content of 28%, and the volume ratio of saturated sodium chloride brine to ammonia water is 2:1. Put the saturated sodium chloride brine into the reactor, add o-nitrochlorobenzene and ammonia water, and the molar ratio of ammonia in o-nitrochlorobenzene and ammonia water is 1:8, and stir to mix evenly.

[0045] S2. The temperature of the reactor was raised to 175°C, and the ammonolysis reaction was carried out under constant temperature stirring. The pressure of the reactor was controlled at 3-4 MPa, and the reaction was continued for 2 h.

[0046] S3. Liquid ammonia is injected through a high-pressure pump. The molar amount of ammonia in the injected liquid ammonia is 20% of the molar amount of ammonia in ammonia water. During the injection of liquid ammonia, the injection rate is adjusted to ensure that the temperature fluctuation of the system is maintained at ±5°C and the pressure fluctuation is ±0.5 MPa. The reaction is continued for 6 hours.

[0047] S4. After the reaction is completed, the product is transferred to a flash tank to recover ammonia. The liquid after flashing is cooled to 80°C and separated by centrifugation. The precipitated precipitate is removed by filtration. The aqueous phase is distilled to recover residual ammonia to obtain brine, which is recycled. The oil phase is washed with hot water at 70°C and vacuum-dried at 60°C to obtain the final product. The purity of o-nitroaniline in the final product is determined to be 99.7%. The conversion rate of o-nitrochlorobenzene in this production process is 95.1%.

[0048] Example 4

[0049] The only difference from Example 1 is that the liquid ammonia is added so that the molar amount of ammonia in the liquid ammonia is 25% of the molar amount of ammonia in the ammonia water.

[0050] This embodiment provides a production process of o-nitroaniline, which is carried out according to the following steps:

[0051] S1. Prepare o-nitrochlorobenzene with a purity of ≥99%, prepare saturated sodium chloride brine with a concentration of 340 g / L and ammonia water with an ammonia content of 28%, with the volume ratio of saturated sodium chloride brine to ammonia water being 1:1, put the saturated sodium chloride brine into the reactor, add o-nitrochlorobenzene and ammonia water, with the molar ratio of ammonia in o-nitrochlorobenzene to ammonia water being 1:8, and stir to mix evenly.

[0052] S2. The temperature of the reactor was raised to 175°C, and the ammonolysis reaction was carried out under constant temperature stirring. The pressure of the reactor was controlled at 3-4 MPa, and the reaction was continued for 2 h.

[0053] S3. Liquid ammonia is injected through a high-pressure pump. The molar amount of ammonia in the injected liquid ammonia is 25% of the molar amount of ammonia in ammonia water. During the injection of liquid ammonia, the injection rate is adjusted to ensure that the temperature fluctuation of the system is maintained at ±5°C and the pressure fluctuation is ±0.5 MPa. The reaction is continued for 6 hours.

[0054] S4. After the reaction is completed, the product is transferred to a flash tank to recover ammonia. The liquid after flashing is cooled to 80°C and separated by centrifugation. The precipitate is removed by filtration. The aqueous phase is distilled to recover residual ammonia to obtain brine, which is recycled. The oil phase is washed with hot water at 70°C and vacuum-dried at 60°C to obtain the final product. The purity of o-nitroaniline in the final product is determined to be 99.7%. The conversion rate of o-nitrochlorobenzene in this production process is 95.8%.

[0055] Example 5

[0056] The only difference from Example 1 is that the liquid ammonia is added so that the molar amount of ammonia in the liquid ammonia is 30% of the molar amount of ammonia in the ammonia water.

[0057] This embodiment provides a production process of o-nitroaniline, which is carried out according to the following steps:

[0058] S1. Prepare o-nitrochlorobenzene with a purity of ≥99%, prepare saturated sodium chloride brine with a concentration of 340 g / L and ammonia water with an ammonia content of 28%, with the volume ratio of saturated sodium chloride brine to ammonia water being 1:1, put the saturated sodium chloride brine into the reactor, add o-nitrochlorobenzene and ammonia water, with the molar ratio of ammonia in o-nitrochlorobenzene to ammonia water being 1:8, and stir to mix evenly.

[0059] S2. The temperature of the reactor was raised to 175°C, and the ammonolysis reaction was carried out under constant temperature stirring. The pressure of the reactor was controlled at 3-4 MPa, and the reaction was continued for 2 h.

[0060] S3. Liquid ammonia is injected through a high-pressure pump. The molar amount of ammonia in the injected liquid ammonia is 30% of the molar amount of ammonia in ammonia water. During the injection of liquid ammonia, the injection rate is adjusted to ensure that the temperature fluctuation of the system is maintained at ±5°C and the pressure fluctuation is ±0.5 MPa. The reaction is continued for 6 hours.

[0061] S4. After the reaction is completed, the product is transferred to a flash tank to recover ammonia. The liquid after flashing is cooled to 80°C and separated by centrifugation. The precipitated precipitate is removed by filtration. The aqueous phase is distilled to recover residual ammonia to obtain brine, which is recycled. The oil phase is washed with hot water at 70°C and vacuum-dried at 60°C to obtain the final product. The purity of o-nitroaniline in the final product is determined to be 99.4%. The conversion rate of o-nitrochlorobenzene in this production process is 95.8%.

[0062] Comparative Example 1

[0063] The only difference from Example 1 is that saturated sodium chloride brine is not added as a reaction medium in the production process.

[0064] This embodiment provides a production process of o-nitroaniline, which is carried out according to the following steps:

[0065] S1. Prepare o-nitrochlorobenzene with a purity of ≥99%, prepare ammonia water with an ammonia content of 28%, put o-nitrochlorobenzene and ammonia water into a reactor with a molar ratio of ammonia in o-nitrochlorobenzene to ammonia water of 1:8, and stir to mix evenly.

[0066] S2. The temperature of the reactor was raised to 175°C, and the ammonolysis reaction was carried out under constant temperature stirring. The pressure of the reactor was controlled at 3-4 MPa, and the reaction was continued for 2 h.

[0067] S3. Liquid ammonia is injected through a high-pressure pump. The molar amount of ammonia in the injected liquid ammonia is 20% of the molar amount of ammonia in ammonia water. During the injection of liquid ammonia, the injection rate is adjusted to ensure that the temperature fluctuation of the system is maintained at ±5°C and the pressure fluctuation is ±0.5 MPa. The reaction is continued for 6 hours.

[0068] S4. After the reaction is completed, the product is transferred to a flash tank to recover ammonia. The liquid after flashing is cooled to 80°C and separated by centrifugation. The aqueous phase is distilled to recover residual ammonia. The oil phase is washed with hot water at 70°C and vacuum dried at 60°C to obtain the final product. The purity of o-nitroaniline in the final product is detected to be 98.7%. The conversion rate of o-nitrochlorobenzene in this production process is 94.9%.

[0069] Comparative Example 2

[0070] The only difference from Example 1 is that ammonia is not added stage by stage in the production process, the concentration of the initial ammonia water is 35%, and no liquid ammonia is added during the reaction.

[0071] This embodiment provides a production process of o-nitroaniline, which is carried out according to the following steps:

[0072] S1. Prepare o-nitrochlorobenzene with a purity of ≥99%, prepare saturated sodium chloride brine with a concentration of 340 g / L and ammonia water with an ammonia content of 35%, with the volume ratio of saturated sodium chloride brine to ammonia water being 1:1. Pour the saturated sodium chloride brine into a reactor, add o-nitrochlorobenzene and ammonia water, with the molar ratio of ammonia in o-nitrochlorobenzene to ammonia water being 1:10, and stir to mix evenly.

[0073] S2. The temperature of the reactor was raised to 175°C, and the ammonolysis reaction was carried out under constant temperature stirring. The pressure of the reactor was controlled at 3-4 MPa, and the reaction was continued for 8 hours.

[0074] S3. After the reaction is completed, the product is transferred to a flash tank to recover ammonia. The liquid after flashing is cooled to 80° C. and separated by centrifugation. The precipitated precipitate is removed by filtration. The aqueous phase is distilled to recover residual ammonia to obtain brine, which is recycled. The oil phase is washed with hot water at 70° C. and vacuum-dried at 60° C. to obtain the final product. The purity of o-nitroaniline in the final product is determined to be 99.1%. The conversion rate of o-nitrochlorobenzene in this production process is 94.4%.

[0075] The production process for preparing o-nitroaniline in the above embodiment is simple, does not require the addition of additional catalysts or adsorbents, and has controllable costs. The o-nitroaniline product produced has high purity and a high conversion rate of o-nitrochlorobenzene, thereby improving product quality and reducing reactant loss.

[0076] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0077] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A production process for o-nitroaniline, characterized in that: The following steps are involved: S1. Put saturated sodium chloride brine into a reactor, add o-nitrochlorobenzene and ammonia water, and stir to mix evenly; S2. Raise the temperature to 170-180°C for aminolysis reaction, with the reactor pressure at 3-4 MPa, and continue the reaction for 2-3 hours; S3, inject liquid ammonia through a high-pressure pump and continue the reaction for 4-10 hours; S4. After the reaction is completed, the mixture is transferred to a flash tank to recover ammonia, cooled to 80-100°C, centrifuged and separated, the precipitate is filtered and removed, the aqueous phase is distilled to recover ammonia and the brine is recycled, the oil phase is washed with hot water and dried to obtain the final product.

2. A production process for o-nitroaniline according to claim 1, characterized in that, The concentration of the ammonia water is 25-28%.

3. A production process for o-nitroaniline according to claim 1, characterized in that, The molar ratio of the o-nitrochlorobenzene to the ammonia in the ammonia water is 1:8-10.

4. A production process for o-nitroaniline according to claim 1, characterized in that, The volume ratio of the saturated sodium chloride brine to the ammonia water is 0.5-2:

1.

5. A production process for o-nitroaniline according to claim 1, characterized in that: The liquid ammonia is added so that the molar amount of ammonia in the liquid ammonia is 20-30% of the molar amount of ammonia in the ammonia water.

6. A production process for o-nitroaniline according to claim 1, characterized in that, During the injection of liquid ammonia, the system pressure was maintained at ±0.5 MPa, and the system temperature fluctuation was maintained at ±5°C.

7. The production process of o-nitroaniline according to claim 1, characterized in that: The purity of o-nitroaniline in the final product is ≥99%.

8. The production process of o-nitroaniline according to claim 1, characterized in that: The temperature of the hot water is 60-80°C.

9. The production process of o-nitroaniline according to claim 1, characterized in that: The conversion rate of o-nitrochloramine is ≥95%.

10. The production process of o-nitroaniline according to claim 1, characterized in that: The drying is performed by vacuum drying at a drying temperature of 50-60°C.