CN111039798A - Environment-friendly preparation method of 2-chloro-4-nitro-6-bromo-aniline - Google Patents
Environment-friendly preparation method of 2-chloro-4-nitro-6-bromo-aniline Download PDFInfo
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Abstract
A preparation method of 2-chloro-4-nitro-6-bromo-aniline comprises the following steps: (a) carrying out mixed acid nitration on o-dichlorobenzene, and continuously mechanically applying generated waste acid to the next batch of nitration reaction; (b) purifying the nitration product in an alcohol solvent to obtain 3, 4-dichloronitrobenzene, and continuously mechanically applying the recovered alcohol solvent to the next purification process; (c)3, 4-dichloronitrobenzene is subjected to ammonolysis in a water phase by adopting a specific catalyst to prepare o-chloro-p-nitroaniline, and the recovered liquid ammonia is continuously applied to the next batch of ammonolysis reaction; (d) the o-chloro-p-nitroaniline is brominated in a hydrogen bromide and oxidant system, and the bromination waste acid liquor and bromine are recovered and used in the next bromination reaction. The method has the advantages of high product yield, high purity and high quality, and simultaneously realizes the recycling of two waste acids and bromine and reduces the amount of waste water. Compared with the traditional process, the method has the advantages of obvious quality and environmental protection, and high production safety.
Description
Technical Field
The invention belongs to the technical field of dye intermediate preparation, and particularly relates to an environment-friendly preparation method of 2-chloro-4-nitro-6-bromo-aniline.
Background
2-chloro-4-nitro-6-bromo-aniline is an important dye intermediate, and the structural formula of the intermediate is shown as (I):
it is a raw material for synthesizing modified dispersed orange 61#, dispersed brown 19# and the like. The traditional synthesis process has serious pollution, low purity, poor quality and poor production safety, and products cannot reach the environmental protection and quality indexes required at present, so a green, safe and quality-meeting synthesis method needs to be found to replace the traditional process.
Disclosure of Invention
The invention aims to provide an environment-friendly preparation method of 2-chloro-4-nitro-6-bromo-aniline, which comprises the steps of recycling nitration waste acid liquor, recycling refined solvent, recycling surplus ammonia gas after ammonolysis reaction, selecting a specific catalyst for combined use in the ammonolysis reaction process, and recycling bromination waste acid liquor and bromine, so that the utilization rate of raw materials is improved, the amount of wastewater is reduced, the production safety is improved, qualified products are prepared, and the production process is more environment-friendly.
In view of the above, in order to achieve the above object, the present invention adopts the following technical solutions:
a method for preparing 2-chloro-4-nitro-6-bromo-aniline, comprising:
(a) nitration reaction: reacting o-dichlorobenzene with the mixed acid solution at a constant temperature to a terminal point to obtain a nitration crude product and a nitration waste acid solution, adding a dehydrating agent into the nitration waste acid solution, and then mechanically applying to the next nitration reaction for preparing the nitration mixed acid solution;
the mixed acid liquid is a mixed acid liquid containing nitric acid, sulfuric acid and water.
(b) And (3) purification: dissolving the nitration crude product obtained in the step (a) in an alcohol solvent, keeping the temperature, stirring, cooling, precipitating, filtering to obtain 3, 4-dichloronitrobenzene and filtrate, recovering an ethanol solvent from the filtrate, and applying the ethanol solvent to the next purification process as a solvent for purification;
(c) ammonolysis reaction: adding a catalyst into the 3, 4-dichloronitrobenzene prepared in the step (b) in a water phase, introducing liquid ammonia, heating, maintaining the pressure and the temperature until the reaction end point, filtering and washing to obtain o-chloro-p-nitroaniline, simultaneously recovering ammonia gas as liquid ammonia, and mechanically applying the recovered liquid ammonia to next batch of ammonolysis reaction for ammonolysis reaction;
the catalyst is a combination of a catalyst A and a catalyst B, wherein the catalyst A is selected from one or more of cuprous chloride, cuprous oxide, copper acetate and copper sulfate; the catalyst B is selected from one or more of benzyltriethylammonium chloride, tetrabutylammonium bromide and dodecyl trimethyl ammonium chloride for combined use;
(d) bromination reaction: adding the o-chloro-p-nitroaniline prepared in the step (c) into an acidic medium containing sulfuric acid, adding hydrobromic acid and an oxidant, reacting to the end point, evaporating bromine for recovery, performing suction filtration and washing to obtain 2-chloro-4-nitro-6-bromo-aniline and a bromination waste acid solution, and mechanically applying the bromination waste acid solution to the next bromination reaction to be used as the acidic medium.
Optionally, in the above method, in the step (a), the nitric acid and the sulfuric acid in the mixed acid solution have a molar ratio of nitric acid to sulfuric acid to water: 1: 1.95-2.05: 2.15-2.25;
optionally, the molar ratio of ortho-dichlorobenzene to nitric acid is: 1: 1.15-1.3;
optionally, the mixed acid solution is added into ortho-dichlorobenzene in a dropwise manner to react with the ortho-dichlorobenzene;
optionally, the temperature of the dropwise mixed acid is less than 35 ℃,
optionally, the temperature of the heat preservation reaction is 55-65 ℃.
Alternatively, in the above method, in the step (b), the dehydrating agent comprises one or more selected from sulfur trioxide, 105 acid, 65 acid,
optionally, when the dehydrating agent is sulfur trioxide, the weight ratio of the sulfur trioxide to the nitration waste acid liquid is 1: 0.125-0.135, and the utilization rate of the nitration waste acid liquid is 82-85%;
optionally, when the dehydrating agent is 105 acid, the weight ratio of the 105 acid to the waste nitration acid solution is 1: 0.23-0.24, and the utilization rate of the waste nitration acid solution is 73-76%;
optionally, when the dehydrating agent is 65 acids, the weight ratio of the 65 acids to the waste nitration acid solution is 1: 0.16-0.17, and the utilization rate of the waste nitration acid solution is 79-82%;
optionally, the molar ratio of the o-dichlorobenzene to the nitric acid in the mixed acid solution is 1: 1.03-1.06.
Optionally, in the above method, in the step (b), the alcohol solvent includes methanol or ethanol;
optionally, the concentration of the alcohol solvent is 78-88%;
optionally, the amount of the alcohol solvent is 2-3.5 times of the weight of the crude nitration product; the temperature of stirring is 35-40 ℃, and the time of stirring is 10-20 h;
optionally, the temperature for cooling and precipitating the 3, 4-dichloronitrobenzene is 0-2 ℃.
Optionally, in the method, the amount of the catalyst A is 1-1.5% of the weight of the o-chloro-p-nitrobenzene, and the amount of the catalyst B is 2-4% of the weight of the o-chloro-p-nitrobenzene; optionally, the molar ratio of the 3, 4-dichloronitrobenzene to the liquid ammonia is 1: 8-12; optionally, the concentration of the liquid ammonia is 35-40%; optionally, the reaction temperature is 135-150 ℃, and the reaction pressure is 3.0-3.5 MPa.
Optionally, in the above method, in step (d), the oxidizing agent is selected from hypochlorous acid, chloric acid, sodium hypochlorite, calcium hypochlorite, sodium chlorate, sulfur trioxide, chlorine gas, chlorine dioxide, or hydrogen peroxide;
optionally, the molar ratio of the o-chloro-p-nitroaniline to the hydrobromic acid to the oxidant is 1: 1.05-1.15: 0.35-0.38;
optionally, the amount of the sulfuric acid is 1.5-2.0 times of that of the o-chloro-p-nitroaniline;
optionally, the concentration of the sulfuric acid is 15-20%;
optionally, the oxidant is added into the reaction system in a dropwise manner;
optionally, the dropping temperature of the sodium chlorate is 15-35 ℃, and the heat preservation temperature is 65-70 ℃.
Optionally, in the method, the bromine recovery temperature is 80-90 ℃, and the recovered bromine is used for the next reaction;
optionally, the waste bromination acid solution is used in the next bromination reaction and used as an acidic medium, wherein the usage amount of the waste bromination acid is 4.7-5.2 times of that of the o-chloro-p-nitroaniline, the reusability of the waste bromination acid is 55-60%, the usage amount of sulfuric acid is reduced by 60-70%, and the usage amounts of hydrobromic acid and sodium chlorate are reduced by 3-4%.
The invention has the beneficial effects that:
the waste acid is greatly reduced, other waste water is obviously reduced, the material utilization rate is obviously improved, the ammonolysis pressure and the temperature are reduced, the production process is more environment-friendly, and the product purity is more than 98 percent.
Detailed Description
The present invention is further illustrated by the following examples, which should not be construed as limiting the scope of the invention.
Comparative example 1
(a) Nitration reaction: 290g of sulfuric acid, 93.7g of nitric acid and 57g of water, preparing a mixed acid solution, dropwise adding the mixed acid solution into 180g of o-dichlorobenzene, controlling the dropwise adding temperature to be 20-30 ℃, keeping the temperature at 60 ℃ for reaction to the end point, and layering to obtain 228.3g of a nitration crude product.
(b) And (3) purification: adding the crude product of the nitrated compound obtained in the step (a) into 585g of 80% ethanol, keeping the temperature at 35 ℃, stirring for 1h, cooling to 2 ℃, separating out and filtering to obtain 207.1g of high-purity 3, 4-dichloronitrobenzene with the purity of 99.1%, recovering 529g of ethanol from filtrate and the concentration of 78%.
(c) Ammonolysis reaction: adding 150g of the high-purity 3, 4-dichloronitrobenzene prepared in the step (b) into 200g of water, introducing 140g of liquid ammonia,
the reaction is heated to 170 ℃ and the pressure is 5.1MPa, the temperature is kept for 18h to the end point, and the reaction is cooled and washed to obtain 131.5g of o-chloro-p-nitroaniline with the purity of 97.3 percent.
(d) Bromination reaction: preparing base acid by 150g of sulfuric acid and 600g of water, adding 90g of o-chloro-p-nitroaniline prepared in the step (c) into the base acid, adding 46g of hydrobromic acid, preparing solution by 20g of sodium chlorate, slowly dripping at a temperature of less than 35 ℃, heating to 65 ℃ after dripping, keeping the temperature to a reaction end point, and performing suction filtration and washing to obtain 122.1g of 2-chloro-4-nitro-6-bromo-aniline with the purity of 98.9%.
Comparative example 2
(a) Nitration reaction: 290g of sulfuric acid, 93.7g of nitric acid and 57g of water, preparing mixed acid liquid, dropwise adding the mixed acid liquid into 180g of o-dichlorobenzene, controlling the dropwise adding temperature to be less than 30 ℃, preserving the temperature at 60 ℃ to the end point, and layering to obtain 228.1g of crude nitration product.
(b) And (3) purification: adding the crude product of the nitrated compound obtained in the step (a) into 585g of 80% ethanol, keeping the temperature at 35 ℃, stirring for 1h, cooling to 2 ℃, separating out, filtering to obtain 206.9g of high-purity 3, 4-dichloronitrobenzene with the purity of 99.2%, recovering ethanol from the filtrate, wherein the recovery amount is 535g, and the concentration of the ethanol is 78%.
(c) Ammonolysis reaction: adding 150g of the high-purity 3, 4-dichloronitrobenzene prepared in the step (b) into 200g of water, adding 1.5g of cuprous chloride, introducing 140g of liquid ammonia, reacting, heating to 155 ℃, keeping the pressure at 4.3MPa, keeping the temperature for 15h until the end point, cooling and washing to obtain 133.4g of o-chloro-p-nitroaniline with the purity of 98.7%.
(d) Bromination reaction: preparing base acid by 150g of sulfuric acid and 600g of water, adding 90g of o-chloro-p-nitroaniline prepared in the step (c) into the base acid, adding 46g of hydrobromic acid, preparing solution by 20g of sodium chlorate, slowly dripping at the temperature of less than 35 ℃, heating to 65 ℃ after dripping, keeping the temperature and reacting to the end point, and performing suction filtration and washing to obtain 122.2g of 2-chloro-4-nitro-6-bromo-aniline with the purity of 99.0%.
Comparative example 3
(a) Nitration reaction: 290g of sulfuric acid, 93.7g of nitric acid and 57g of water, preparing mixed acid liquid, dropwise adding the mixed acid liquid into 180g of o-dichlorobenzene, controlling the dropwise adding temperature to be less than 30 ℃, keeping the temperature at 60 ℃ for reaction to the end point, and layering to obtain 228.1g of crude nitration product.
(b) And (3) purification: adding the crude product of the nitrated compound obtained in the step (a) into 585g of 80% ethanol, keeping the temperature at 35 ℃, stirring for 1h, cooling to 2 ℃, separating out and filtering to obtain 207.0g of high-purity 3, 4-dichloronitrobenzene with the purity of 98.7%, and recovering ethanol from the filtrate with the recovery amount of 527g and the ethanol concentration of 79%.
(c) Ammonolysis reaction: adding 150g of the high-purity 3, 4-dichloronitrobenzene prepared in the step (b) into 200g of water, 3.5g of tetrabutylammonium bromide, introducing 140g of liquid ammonia, heating to 165 ℃, keeping the pressure at 4.7MPa for 15h to the end point, cooling and washing to obtain 133.5g of o-chloro-p-nitroaniline with the purity of 98.8%.
(d) Bromination: preparing a basic acid from 150g of sulfuric acid and 600g of water, adding 90g of o-chloro-p-nitroaniline prepared in the step (c) into the basic acid, adding 46g of hydrobromic acid, preparing a solution from 20g of sodium chlorate, slowly dripping at a temperature of less than 35 ℃, heating to 65 ℃ after dripping, keeping the temperature to the end point, and performing suction filtration and washing to obtain 122.4g of 2-chloro-4-nitro-6-bromo-aniline with the purity of 98.7%.
Example 1
(a) Reaction and nitration: taking 291g of nitrified waste acid recovered by the nitration reaction, and sequentially adding 69g of 105 acid and 81g of nitric acid to prepare nitric acid: sulfuric acid: water 1: 2: 2.2, dropwise adding the mixed acid liquid into 180g of o-dichlorobenzene at the molar ratio of o-dichlorobenzene to nitric acid of 1:1.21, controlling the dropwise adding temperature to be less than 30 ℃, keeping the temperature at 60 ℃ for reaction to the end point, and layering to obtain 233.1g of a crude nitration product.
(b) And (3) purification: adding the crude product of the nitrated compound obtained in the step (a) into 585g of purified and recycled 80% ethanol, keeping the temperature at 35 ℃, stirring for 1h, cooling to 2 ℃, separating out and filtering to obtain 212.3g of high-purity 3, 4-dichloronitrobenzene with the purity of 98.9%, recycling ethanol from filtrate with the recycling amount of 513g and the ethanol concentration of 81%.
(c) Ammonolysis reaction: adding 150g of the high-purity 3, 4-dichloronitrobenzene prepared in the step (b) into 200g of water, adding 1.5g of cuprous chloride and 3.5g of tetrabutylammonium bromide, introducing 65g of the recovered ammonia of the previous batch, supplementing 75g of liquid ammonia, heating to 145 ℃, keeping the temperature, reacting to the end point, cooling and washing to obtain 133.5g of o-chloro-p-nitroaniline with the purity of 98.5%.
(d) Bromination reaction: adding 60g of sulfuric acid and 240g of water into 450g of brominated waste acid to prepare a basic acid, adding 90g of o-chloro-p-nitroaniline prepared in the step (c) into the basic acid, adding 44g of hydrobromic acid, preparing 19.5g of sodium chlorate into a solution, slowly dripping at the temperature of less than 35 ℃, heating to 65 ℃ after dripping, carrying out heat preservation reaction to the end point, and carrying out suction filtration and washing to obtain 127.3g of 2-chloro-4-nitro-6-bromo-aniline with the purity of 98.5%.
Example 2
(a) Nitration reaction: 315g of nitrified waste acid recovered by nitration reaction is taken, 51g of 65 acid and 81g of nitric acid are sequentially added to prepare nitric acid: sulfuric acid: water 1: 2: 2.2, dropwise adding the mixed acid liquid into 180g of o-dichlorobenzene, controlling the dropwise adding temperature to be less than 30 ℃, keeping the temperature at 60 ℃ for reaction to the end point, and layering to obtain 232.9g of crude nitration product.
(b) And (3) purification: adding the crude product of the nitrated compound obtained in the step (a) into 585g of purified and recycled 80% ethanol, keeping the temperature at 35 ℃, stirring for 1h, cooling to 2 ℃, separating out and filtering to obtain 212.3g of high-purity 3, 4-dichloronitrobenzene with the purity of 99%, recycling ethanol from filtrate with the recycling amount of 523g and the ethanol concentration of 79%.
(c) Ammonolysis reaction: adding 150g of the high-purity 3, 4-dichloronitrobenzene prepared in the step (b) into 200g of water, adding 1.5g of cuprous chloride and 3.5g of tetrabutylammonium chloride, introducing 65g of the recovered ammonia of the previous batch, supplementing 75g of liquid ammonia, heating to 145 ℃, keeping the temperature, reacting to the end point, cooling and washing to obtain 133.8g of o-chloro-p-nitroaniline with the purity of 98.8%.
(d) Bromination reaction: adding 60g of sulfuric acid and 240g of water into 450g of brominated waste acid to prepare a basic acid, adding 90g of o-chloro-p-nitroaniline prepared in the step (c) into the basic acid, adding 44.2g of hydrobromic acid, preparing 19.5g of sodium chlorate into a solution, slowly dripping at the temperature of less than 35 ℃, heating to 65 ℃ after dripping, keeping the temperature, reacting to the end, carrying out suction filtration and washing to obtain 126.9g of 2-chloro-4-nitro-6-bromo-aniline with the purity of 99.1%.
Example 3
(a) Nitration reaction: taking 328g of nitrified waste acid recovered by nitration, and sequentially adding 42.7g of sulfur trioxide and 81g of nitric acid to prepare nitric acid: sulfuric acid: water 1: 2: 2.2, dropwise adding the mixed acid liquid into 180g of o-dichlorobenzene, controlling the dropwise adding temperature to be less than 30 ℃, keeping the temperature at 60 ℃ until the end point, and layering to obtain 233.1g of crude nitration product.
(b) And (3) purification: adding the crude product of the nitrated compound obtained in the step (a) into 535g of purified and recycled 82% ethanol, keeping the temperature at 35 ℃, stirring for 1h, cooling to 2 ℃, separating out and filtering to obtain 213.1g of high-purity 3, 4-dichloronitrobenzene with the purity of 98.5 percent, recycling 487g of ethanol from the filtrate, and ensuring the concentration of the ethanol to be 80 percent.
(c) Ammonolysis reaction: adding 150g of the high-purity 3, 4-dichloronitrobenzene prepared in the step (b) into 200g of water, adding 1.5g of copper acetate and 3.5g of benzyltriethylammonium chloride, introducing 65g of the recovered ammonia of the previous batch, supplementing 65g of liquid ammonia, heating to 145 ℃, keeping the temperature to the end point, cooling and washing to obtain 133.6g of o-chloro-p-nitroaniline with the purity of 98.4%.
(d) Bromination reaction: adding 60g of sulfuric acid and 240g of water into 450g of brominated waste acid to prepare a basic acid, adding 90g of o-chloro-p-nitroaniline prepared in the step (c) into the basic acid, adding 44.2g of hydrobromic acid, preparing 19.5g of sodium chlorate into a solution, slowly dripping at the temperature of less than 35 ℃, heating to 65 ℃ after dripping, keeping the temperature, reacting to the end, and performing suction filtration and washing to obtain 127.5g of 2-chloro-4-nitro-6-bromo-aniline with the purity of 98.7%.
Example 4
(a) Nitration reaction: 315g of nitrified waste acid recovered by nitration reaction is taken, 51g of 65 acid and 81g of nitric acid are sequentially added to prepare nitric acid: sulfuric acid: water 1: 2: 2.2, dropwise adding the mixed acid liquid into 180g of o-dichlorobenzene, controlling the dropwise adding temperature to be less than 30 ℃, keeping the temperature at 60 ℃ for reaction to the end point, and layering to obtain 232.7g of crude nitration product.
(b) And (3) purification: adding the crude product of the nitrated compound obtained in the step (a) into 650g of purified and recycled 85% methanol, keeping the temperature at 37 ℃, stirring for 1h, cooling to 2 ℃, separating out and filtering to obtain 209.3g of high-purity 3, 4-dichloronitrobenzene with the purity of 99.3%, recycling the methanol from the filtrate with the recycling amount of 587g and the methanol concentration of 80%.
(c) Ammonolysis reaction: adding 150g of the high-purity 3, 4-dichloronitrobenzene prepared in the step (b) into 200g of water, adding 1.5g of cuprous chloride and 3.5g of tetrabutylammonium bromide, introducing 65g of the recovered ammonia of the previous batch, supplementing 60g of liquid ammonia, heating to 140 ℃, keeping the temperature and reacting to the end point, cooling and washing to obtain 134g of o-chloro-p-nitroaniline with the purity of 99.2%.
(d) Bromination reaction: adding 60g of sulfuric acid and 240g of water into 450g of brominated waste acid to prepare a basic acid, adding 90g of o-chloro-p-nitroaniline prepared in the step (c) into the basic acid, adding 44.2g of hydrobromic acid, preparing 19.5g of sodium chlorate into a solution, slowly dripping at the temperature of less than 35 ℃, heating to 65 ℃ after dripping, keeping the temperature, reacting to the end, carrying out suction filtration and washing to obtain 127.7g of 2-chloro-4-nitro-6-bromo-aniline with the purity of 99.1%.
Examples 5 to 10
According to the process steps of the example 4, the nitration waste acid, the liquid ammonia and the bromination waste acid are continuously used in the previous example, the product quality and the yield are stable, and the product purity and the yield are shown in the table 1.
The purity and yield of the product of each example are shown in Table 1, the raw material consumption for producing 1000g of 2-chloro-4-nitro-6-bromo-aniline is shown in Table 2, and the amount of waste acid is shown in Table 3.
TABLE 1
TABLE 2
TABLE 3
TABLE 4
As can be seen from tables 1 to 4, according to the preparation method of 2-chloro-4-nitro-6-bromo-aniline of the present invention, on the premise of ensuring product quality and improving product overall yield, production environmental protection and safety of production process are significantly improved, specifically, consumption of sulfuric acid, nitric acid and liquid ammonia is greatly reduced, consumption of hydrobromic acid and sodium chlorate is also reduced to a certain extent, waste acid amount is greatly reduced, green recycling is achieved, and recycling of waste water does not reduce product purity and yield. The invention selects specific catalyst in the ammonolysis reaction process, not only accelerates the reaction speed and greatly shortens the reaction time, but also obviously reduces the ammonolysis reaction temperature and the reaction pressure and obviously improves the production safety.
The preferred embodiments of the present invention have been described in detail, but the present invention is not limited to the details of the above embodiments, and various simple modifications can be made to the technical solution within the technical idea scope, and such simple modifications are included in the protection scope of the present invention.
Claims (7)
1. A preparation method of 2-chloro-4-nitro-6-bromo-aniline is characterized by comprising the following steps:
(a) nitration reaction: reacting o-dichlorobenzene with the mixed acid liquor at a constant temperature until the end point to obtain a nitration crude product and a nitration waste acid liquor; adding a dehydrating agent into the waste nitration acid liquor, and then mechanically applying the waste nitration acid liquor to the next batch of nitration reaction for preparing a nitration mixed acid liquor;
the mixed acid liquid is a mixed acid liquid containing nitric acid, sulfuric acid and water;
(b) and (3) purification: dissolving the nitration crude product obtained in the step (a) in an alcohol solvent, keeping the temperature, stirring, cooling, precipitating, filtering to obtain 3, 4-dichloronitrobenzene and filtrate, recovering the alcohol solvent from the filtrate, and applying the alcohol solvent to the next purification process as a solvent for purification;
(c) ammonolysis reaction: adding a catalyst into the 3, 4-dichloronitrobenzene prepared in the step (b) in a water phase, introducing liquid ammonia, heating, maintaining the pressure and the temperature until the reaction end point, filtering and washing to obtain o-chloro-p-nitroaniline, simultaneously recovering ammonia gas as liquid ammonia, and mechanically applying the recovered liquid ammonia to next batch of ammonolysis reaction for ammonolysis reaction;
the catalyst is a combination of a catalyst A and a catalyst B, wherein the catalyst A is selected from one or more of cuprous chloride, cuprous oxide, copper acetate and copper sulfate; the catalyst B is selected from one or more of benzyltriethylammonium chloride, tetrabutylammonium bromide and dodecyl trimethyl ammonium chloride for combined use;
(d) bromination reaction: adding the o-chloro-p-nitroaniline prepared in the step (c) into an acidic medium containing sulfuric acid, adding hydrobromic acid and an oxidant, reacting to the end point, evaporating bromine for recovery, performing suction filtration and washing to obtain 2-chloro-4-nitro-6-bromo-aniline and a bromination waste acid solution, and mechanically applying the bromination waste acid solution to the next bromination reaction to be used as the acidic medium.
2. The method for preparing 2-chloro-4-nitro-6-bromo-aniline according to claim 1, wherein in the step (a), the molar ratio of nitric acid to sulfuric acid to water in the mixed acid solution is: 1: 1.95-2.05: 2.15-2.25;
alternatively, the molar ratio of ortho-dichlorobenzene to nitric acid is: 1: 1.15-1.3;
optionally, the mixed acid solution is added into o-dichlorobenzene in a dropwise manner to react with the o-dichlorobenzene;
optionally, the temperature of the dropwise adding mixed acid liquid is less than 35 ℃;
optionally, the temperature of the heat preservation reaction is 55-65 ℃.
3. The process for the preparation of 2-chloro-4-nitro-6-bromo-aniline according to claim 1 or 2, characterized in that in step (b) the dehydrating agent comprises one or more selected from sulfur trioxide, 105 acid, 65 acid;
optionally, when the dehydrating agent is sulfur trioxide, the weight ratio of the sulfur trioxide to the nitration waste acid liquid is 1: 0.125-0.135, and the utilization rate of the nitration waste acid liquid is 82-85%;
optionally, when the dehydrating agent is 105 acid, the weight ratio of the 105 acid to the waste nitration acid solution is 1: 0.23-0.24, and the utilization rate of the waste nitration acid solution is 73-76%;
optionally, when the dehydrating agent is 65 acids, the weight ratio of the 65 acids to the waste nitration acid solution is 1: 0.16-0.17, and the utilization rate of the waste nitration acid solution is 79-82%;
optionally, the molar ratio of the o-dichlorobenzene to the nitric acid in the mixed acid solution is 1: 1.03-1.06.
4. The process for the preparation of 2-chloro-4-nitro-6-bromo-aniline according to claim 1, wherein in step (b): the alcohol solvent comprises methanol or ethanol;
optionally, the concentration of the alcohol solvent is 78-88%;
optionally, the amount of the alcohol solvent is 2-3.5 times of the weight of the crude nitration product; the temperature of the heat preservation stirring is 35-40 ℃, and the time of the heat preservation stirring is 10-20 h;
optionally, the temperature for cooling and precipitating the 3, 4-dichloronitrobenzene is 0-2 ℃.
5. The method for preparing 2-chloro-4-nitro-6-bromo-aniline according to claim 1, wherein in step (c), the amount of catalyst A is 1-1.5% by weight of o-chloro-p-nitrobenzene, and the amount of catalyst B is 2-4% by weight of o-chloro-p-nitrobenzene;
optionally, the molar ratio of the 3, 4-dichloronitrobenzene to the liquid ammonia is 1: 8-12;
optionally, the concentration of the liquid ammonia is 35-40%;
optionally, the reaction temperature is 135-150 ℃, and the reaction pressure is 3.0-3.5 MPa.
6. The process for the preparation of 2-chloro-4-nitro-6-bromo-aniline according to claim 1,
in the step (d), the oxidant is selected from hypochlorous acid, chloric acid, sodium hypochlorite, calcium hypochlorite, sodium chlorate, sulfur trioxide, chlorine dioxide or hydrogen peroxide;
the mol ratio of the o-chloro-p-nitroaniline to the hydrobromic acid to the oxidant is 1: 1.05-1.10: 0.35-0.38;
optionally, the amount of the sulfuric acid is 1.5-2.0 times of that of the o-chloro-p-nitroaniline;
optionally, the concentration of the sulfuric acid is 15-20%;
optionally, the oxidant is added into the reaction system in a dropwise manner;
optionally, the dropping temperature of the oxidant is 15-35 ℃, and the heat preservation temperature is 65-70 ℃.
7. The method for preparing 2-chloro-4-nitro-6-bromo-aniline according to claim 1, wherein the bromine recovery temperature is 80-90 ℃;
optionally, the waste bromination acid solution is used in the next bromination reaction and used as an acidic medium, wherein the usage amount of the waste bromination acid is 4.7-5.2 times of that of the o-chloro-p-nitroaniline, the reusability of the waste bromination acid is 55-60%, the usage amount of sulfuric acid is reduced by 60-70%, and the usage amounts of hydrobromic acid and sodium chlorate are reduced by 3-4%.
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| CN111714921A (en) * | 2020-06-22 | 2020-09-29 | 浙江迪邦化工有限公司 | Solvent crystallization separation system for 3, 4-dichloronitrobenzene and 2, 3-dichloronitrobenzene |
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