CN112321439B - Method for high-pressure assisted synthesis of 6-chloro-2, 4-dinitroaniline - Google Patents
Method for high-pressure assisted synthesis of 6-chloro-2, 4-dinitroaniline Download PDFInfo
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- CN112321439B CN112321439B CN202011104721.9A CN202011104721A CN112321439B CN 112321439 B CN112321439 B CN 112321439B CN 202011104721 A CN202011104721 A CN 202011104721A CN 112321439 B CN112321439 B CN 112321439B
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Abstract
The invention discloses a method for high-pressure assisted synthesis of 6-chloro-2, 4-dinitroaniline, which comprises the following steps: (1) adding 2, 4-dinitroaniline and hydrochloric acid solution into a high-pressure reaction kettle, heating and pulping to obtain pulping liquid; (2) adding a sodium hypochlorite solution into the pulping liquid obtained in the step (1) to perform chlorination, performing heat preservation reaction for a period of time, and when the pressure in the high-pressure reaction kettle is stabilized between 0.11 and 0.15MPa and does not change any more within half an hour, indicating that the reaction is finished, performing pressure relief, and performing suction filtration on the obtained reaction liquid; (3) and (3) washing, filtering and drying the filter cake obtained by the filtering in the step (2) to obtain the 6-chloro-2, 4-dinitroaniline. The invention adopts a high-pressure auxiliary synthesis method to improve the traditional sodium hypochlorite chlorination method, greatly shortens the reaction period, ensures safer reaction process, greatly improves the product purity and yield, can recycle the mother liquor, reduces the post-treatment cost and improves the economic benefit.
Description
Technical Field
The invention relates to the technical field of dye intermediate synthesis, in particular to a method for high-pressure assisted synthesis of 6-chloro-2, 4-dinitroaniline.
Background
6-chloro-2, 4-dinitroaniline is an important intermediate of disperse dyes, has a large demand at home and abroad, is used as a diazo component in disperse dye synthesis, and is used for synthesizing disperse blue 270, 259, 264, 125, 130 and the like. The research and the production of the 6-chloro-2, 4-dinitroaniline have very important significance for promoting the upgrade of the dye varieties in China and improving the self-sufficiency of dye intermediates and dyes.
To date, there have been many methods for synthesizing 6-chloro-2, 4-dinitroaniline, which is generally obtained by chlorinating 2, 4-dinitroaniline, such as chlorine chlorination, sodium chlorate chlorination, hydrogen peroxide chlorination, and sodium hypochloriteMethods, and the like. Wherein, the chlorine chlorination method has two methods, one method adopts water-phase-through Cl 2 The cost is low, but the particle is large, the particle is easy to agglomerate and has no luster, and the product has more impurities; another is Cl introduction in organic medium (acetic acid, methanol) 2 The obtained product has good quality, but high cost and harsh reaction conditions; the sodium chlorate method has mature process, the product purity is up to 98 percent, but waste acid generated in the reaction process can not be recycled, and chlorine dioxide can be generated in the reaction process to influence the production environment of a workshop. The hydrogen peroxide chlorination method is a more environment-friendly chlorination method proposed in the last two years, the product purity is high, the mother liquor can be recycled, but the reaction process is complex, the reaction period is long, and the cost is high. In contrast, the conventional sodium hypochlorite method (e.g., patent documents EP0154239a2 and US 4613698A) has the disadvantages of complicated production process, long chlorination time, by-product generation during the reaction process, poor product quality and low equipment productivity.
In order to solve the problems, a production process which has high production efficiency, short reaction period, lower production cost and simple post-treatment is needed.
Disclosure of Invention
Aiming at the defects of the traditional sodium hypochlorite method production process, the invention provides a method for high-pressure auxiliary synthesis of 6-chloro-2, 4-dinitroaniline, which improves the production efficiency, shortens the reaction period, improves the product purity and yield, can recycle the mother liquor, reduces the post-treatment cost and improves the economic benefit.
A method for high-pressure assisted synthesis of 6-chloro-2, 4-dinitroaniline comprises the following steps:
(1) adding 2, 4-dinitroaniline and hydrochloric acid solution into a high-pressure reaction kettle, heating and pulping to obtain pulping liquid;
(2) adding a sodium hypochlorite solution into the pulping liquid obtained in the step (1) to perform chlorination, performing heat preservation reaction for a period of time, and when the pressure in the high-pressure reaction kettle is stabilized between 0.11 and 0.15MPa and does not change any more within half an hour, indicating that the reaction is finished, performing pressure relief, and performing suction filtration on the obtained reaction liquid;
(3) and (3) washing, filtering and drying the filter cake obtained by the filtering in the step (2) to obtain the 6-chloro-2, 4-dinitroaniline.
According to the invention, chlorination is carried out by means of a high-pressure reaction kettle, firstly, after hydrochloric acid and 2, 4-dinitroaniline are beaten, sodium hypochlorite is pumped into the high-pressure reaction kettle, the concentration of the hydrochloric acid is higher, the hydrochloric acid reacts with the sodium hypochlorite to generate chlorine, the chlorine quickly reacts with the 2, 4-dinitroaniline to generate electrophilic substitution to generate 6-chloro-2, 4-dinitroaniline, and HCl is generated at the same time. With the progress of the reaction, the concentration of hydrochloric acid is reduced due to the generation of water in the reaction process, while the sodium hypochlorite reacts with the low-concentration hydrochloric acid to generate hypochlorous acid which is unstable and is easy to decompose to generate HCl and oxygen; wherein, the hydrogen chloride can make up a part of HCl consumed by the chlorination reaction, but oxygen does not participate in the reaction, and the oxygen is gradually accumulated along with the reaction. The invention adopts the high-pressure reaction kettle, fully utilizes the generated oxygen, and the pressure in the reaction kettle gradually rises. Under the action of pressure, the mass transfer effect of chlorine and 2, 4-dinitroaniline is enhanced, so that the original slow chlorination reaction speed is accelerated. And finally, when the reaction reaches the final stage, the concentration of hydrochloric acid in the high-pressure reaction kettle is very low, the chlorination reaction in the system is difficult to carry out, and the high-pressure reaction kettle still maintains higher pressure, so that the collision probability of chlorine and 2, 4-dinitroaniline can be increased, the problem of slow reaction at the final stage of the chlorination reaction can be solved, the residual raw materials at the final stage of the chlorination reaction in the traditional sodium hypochlorite method production process are fully utilized, the utilization rate of the raw materials such as sodium hypochlorite and hydrochloric acid is remarkably improved, the use amount of the sodium hypochlorite and hydrochloric acid is reduced, and the obtained product after the reaction is finished has high purity and yield and good color. According to the characteristics of chlorination reaction, the reaction process pumps sodium hypochlorite into a high-pressure reaction kettle, and the chlorination reaction is promoted by means of high pressure generated by self reaction in the reaction process. The whole reaction process is short in time consumption and simple to operate, the using amount of sodium hypochlorite is small, the utilization rate of materials is improved, the whole reaction period is obviously shortened, the environmental pollution of reaction tail gas is small, and the mother liquor can be recycled.
Preferably, in the step (1), the total volume of the 2, 4-dinitroaniline and the hydrochloric acid solution accounts for 30-60% of the effective volume of the high-pressure reaction kettle, and a certain cavity rate is formed, so that on one hand, the pulping effect can be ensured, and on the other hand, the high-pressure reaction environment can be formed as soon as possible.
Preferably, the molar ratio of the sodium hypochlorite to the 2, 4-dinitroaniline in the sodium hypochlorite solution to the HCl in the hydrochloric acid solution is 0.9-1.6: 1: 2-6, so that the side reaction of amino groups can be effectively reduced, the side reaction of the sodium hypochlorite and the hydrochloric acid can be controlled, oxygen is generated, the pressure in the high-pressure reaction kettle is regulated, and the purity and the yield of the product are finally improved.
Preferably, in the step (1), the mass concentration of HCl in the hydrochloric acid solution is 20% to 32%. The hydrochloric acid solution with the concentration is beneficial to pulping 2, 4-dinitroaniline in the hydrochloric acid solution to form hydrochloride protective amino on one hand, and is beneficial to controlling the adding volume of the hydrochloric acid solution on the other hand, and the gas pressure generated in the chlorination reaction process is jointly regulated and controlled from the volume and the concentration.
Preferably, the purity of the 2, 4-dinitroaniline is 99.81% or more.
The high-pressure reaction kettle has the characteristics of high pressure resistance and strong acid corrosion resistance.
And (2) releasing heat in the pulping process, wherein the temperature is not too high in order to ensure that the subsequent chlorination reaction generates proper pressure, and the preferable temperature is 38-55 ℃ in the step (1) and the time is 0.5-1 h in order to ensure the uniformity of the pulped materials.
Preferably, in the step (1), the stirring speed in the high-pressure reaction kettle is 500-1000 rpm in the pulping process. As heterogeneous reaction, the stirring speed directly influences the mass transfer effect of the reaction, the stirring speed is too slow, the reaction speed is slow, and the reaction period is long.
In step (2), sodium hypochlorite is added (preferably pumped) into the autoclave in order to prevent side reactions from occurring when the addition is too fast. Preferably, in the step (2), the adding time of the sodium hypochlorite solution is 0.5-3 h.
Preferably, in the step (2), the mass content of sodium hypochlorite in the sodium hypochlorite solution is 7-10%.
Preferably, in the step (2), the temperature of the heat preservation reaction is 38-55 ℃.
In a preferable example, in the step (2), the time of the heat preservation reaction is 0.5 to 1 hour.
Preferably, in the step (2), the pressure-released tail gas is introduced into a tail gas absorption device, and the mother liquor obtained by suction filtration is returned to the step (1) to replace a hydrochloric acid solution for reuse, and is discharged into a sewage treatment system until the concentration of sodium chloride in the mother liquor is saturated.
Preferably, in the step (3), the filter cake is washed and filtered until the pH value is 6.0-7.0.
Compared with the prior art, the invention has the main advantages that:
the invention greatly shortens the reaction period by improving and optimizing the traditional sodium hypochlorite method production process, has less sodium hypochlorite and hydrochloric acid, reduces the raw material cost, improves the purity and yield of the product, can recycle the mother solution, has little pollution to the environment and improves the economic benefit.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The following examples are conducted under conditions not specified, usually according to conventional conditions, or according to conditions recommended by the manufacturer.
Example 1
The method for high-pressure assisted synthesis of 6-chloro-2, 4-dinitroaniline of the embodiment comprises the following steps:
130 g of 2, 4-dinitroaniline which is colloid-ground and has a water content of 9.1% and a solid purity of 99.81%, 381 g of hydrochloric acid having a mass concentration of 31.35% and 60 g of water are added to a high-pressure reaction vessel, the volume ratio of all the added substances in the high-pressure reaction vessel is about 47%, the mixture is stirred and pulped at a speed of 600rpm, the temperature is raised to 40 ℃, and the stirring is carried out for 0.5 hour.
Adding 640 g of 9.9 mass percent sodium hypochlorite into the beaten reaction liquid by a constant flow pump for about 1.5 hours, keeping the temperature at 40 ℃ for reaction for 30-40 minutes, reducing the pressure in the high-pressure reaction kettle to 0.12MPa, and stopping the reaction when the pressure is not reduced for half an hour.
After the reaction is finished, the product is obtained through suction filtration, washing and drying, the purity of the product is measured by liquid chromatography, the purity is 97.9 percent, the dried product has the mass of 142.4 grams, the solid content is 98.21 percent, the dried product has the mass of 136.9 grams, and the product yield is 97.68 percent. The filtrate is salt-containing separation liquid, and is sent back to the collection tank for recycling after being filtered. Wherein the HCl mass content in the filtrate is about 24 percent, and the HCl mass content can be adjusted to the content required by the reaction by using 32 percent concentrated hydrochloric acid, and the HCl mass content is used for producing 6-chloro-2, 4-dinitroaniline. 8 batches of mother liquor are continuously used, the average purity is 97.27 percent, and the yield is 97.21 percent.
Example 2
130 g of 2, 4-dinitroaniline which has a water content of 9.1% and a solid purity of 99.81% and has been colloid-ground, 381 g of hydrochloric acid having a mass concentration of 31.35% and 40g of water are added to a high-pressure reactor, the volume proportion of all the added substances in the high-pressure reactor is about 45%, the mixture is stirred and pulped at a speed of 800rpm, the temperature is raised to 43 ℃, and the stirring is carried out for 0.5 hour.
Adding 640 g of 9.9 mass percent sodium hypochlorite into the beaten reaction solution by an advection pump for about 2 hours, keeping the temperature at 43 ℃ for reaction for 30-40 minutes, reducing the pressure in the high-pressure reaction kettle to 0.11MPa, and stopping the reaction after half an hour.
After the reaction is finished, the product is obtained through suction filtration, washing and drying, the purity of the product is measured by liquid chromatography, the purity is 98.79%, the dried product is 142.81 g, the solid content is 98.64%, the dried product is 139.16 g, and the product yield is 99.29%. The filtrate is salt-containing separation liquid, and is sent back to the collection tank for recycling after being filtered. Wherein the HCl mass content in the filtrate is about 24 percent, and the HCl mass content can be adjusted to the content required by the reaction by using 32 percent concentrated hydrochloric acid, and the HCl mass content is used for producing 6-chloro-2, 4-dinitroaniline. 8 batches of mother liquor are continuously used, the average purity is 97.94 percent, and the yield is 98.81 percent.
Example 3
130 g of 2, 4-dinitroaniline which is colloid-ground and has a water content of 9.1% and a solid purity of 99.81%, 381 g of hydrochloric acid with a mass concentration of 31.35% and 40g of water are added into a high-pressure reaction kettle, the volume ratio of all the added substances in the high-pressure reaction kettle is about 45%, the materials are stirred and pulped at a rotating speed of 1000r/min, the temperature is raised to 50 ℃, and the stirring is carried out for 0.5 hour.
Adding 640 g of 9.9 mass percent sodium hypochlorite into the beaten reaction solution by a constant flow pump for about 1 hour, keeping the temperature at 50 ℃ for reaction for 1 hour, reducing the pressure in the high-pressure reaction kettle to 0.13MPa, and stopping the pressure reduction within half an hour, thus finishing the reaction.
After the reaction is finished, the product is subjected to suction filtration, washing and drying, and the purity of the product is measured by liquid chromatography, wherein the purity is 97.21%, the mass of the dried product is 143.1 g, the solid content is 98.66%, the mass of the dried product is 137.25 g, and the product yield is 97.93%. The filtrate is salt-containing separation liquid, and is sent back to the collection tank for recycling after being filtered. Wherein the HCl mass content in the filtrate is about 24 percent, and the HCl mass content can be adjusted to the content required by the reaction by using 32 percent concentrated hydrochloric acid, and the HCl mass content is used for producing 6-chloro-2, 4-dinitroaniline. 8 batches of mother liquor are continuously used, the average purity is 96.84 percent, and the yield is 96.31 percent.
Comparative example 1
The synthesis process for preparing 6-chloro-2, 4-dinitroaniline by the traditional sodium hypochlorite method comprises the following steps:
130 g of 2, 4-dinitroaniline which has a water content of 9.1% and a purity of 99.81% and has been colloid-milled, 381 g of hydrochloric acid having a concentration of 31.35% by mass and 40g of water are placed in a 1000mL flask and stirred at 600r/min for beating, the temperature being raised to 45 ℃ and stirring being carried out for 0.5 hour. The molar ratio of 2, 4-dinitroaniline to sodium hypochlorite is about 1: 1.3, slowly adding 640 g of sodium hypochlorite with the mass concentration of 9.95% into the pulping liquid at a constant speed by using a peristaltic pump, wherein the adding time is 7-8 hours, and after the adding of the sodium hypochlorite is finished, keeping the temperature at 45 ℃ for 2 hours under the normal pressure condition. After the reaction is finished, the product is obtained by suction filtration, washing and drying, the purity of the product is measured by liquid chromatography, the purity is 96.55%, the dried product has the mass of 141.52 g, the solid content of 98.06% and the dried product has 133.98 g, and the product yield is 95.60%.
Furthermore, it should be understood that various changes and modifications can be made by one skilled in the art after reading the above description of the present invention, and equivalents also fall within the scope of the invention as defined by the appended claims.
Claims (6)
1. A method for high-pressure assisted synthesis of 6-chloro-2, 4-dinitroaniline is characterized by comprising the following steps:
(1) adding 2, 4-dinitroaniline and hydrochloric acid solution into a high-pressure reaction kettle, heating and pulping to obtain pulping liquid; the total volume of the 2, 4-dinitroaniline and the hydrochloric acid solution accounts for 30-60% of the effective volume of the high-pressure reaction kettle; the mass concentration of HCl in the hydrochloric acid solution is 20-32%; the pulping temperature is 38-55 ℃, and the time is 0.5-1 h;
(2) adding a sodium hypochlorite solution into the pulping liquid obtained in the step (1) to perform chlorination reaction, performing heat preservation reaction at 38-55 ℃ for a period of time, and when the pressure in the high-pressure reaction kettle is stabilized between 0.11-0.15 MPa and does not change any more within half an hour, indicating that the reaction is finished, performing pressure relief, and performing suction filtration on the obtained reaction liquid;
the molar ratio of the sodium hypochlorite in the sodium hypochlorite solution to the 2, 4-dinitroaniline to the HCl in the hydrochloric acid solution is 0.9-1.6: 1: 2-6;
(3) and (3) washing, filtering and drying the filter cake obtained by the filtering in the step (2) to obtain the 6-chloro-2, 4-dinitroaniline.
2. The method according to claim 1, wherein in the step (1), the stirring speed in the high-pressure reaction kettle is 500-1000 rpm during the pulping process.
3. The method according to claim 1, wherein in the step (2), the sodium hypochlorite solution is added for 0.5-3 h.
4. The method according to claim 1, wherein in the step (2), the mass content of the sodium hypochlorite in the sodium hypochlorite solution is 7-10%.
5. The method as claimed in claim 1, wherein in the step (2), the pressure-released tail gas is introduced into a tail gas absorption device, and mother liquor obtained by suction filtration is returned to the step (1) to replace hydrochloric acid solution for reuse, and is discharged into a sewage treatment system until the concentration of sodium chloride in the mother liquor is saturated.
6. The method of claim 1, wherein in the step (3), the filter cake is washed and filtered to a pH of 6.0-7.0.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4613698A (en) * | 1984-03-01 | 1986-09-23 | Hoechst Aktiengesellschaft | Process for the preparation of 6-chloro-2,4-dinitroaniline |
| CN103539680A (en) * | 2013-10-23 | 2014-01-29 | 浙江闰土研究院有限公司 | Clean production process of 6-chloro-2,4-dinitroaniline |
| CN111170871A (en) * | 2019-12-30 | 2020-05-19 | 河南洛染股份有限公司 | Method for synthesizing 6-bromo-2, 4-dinitroaniline |
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- 2020-10-15 CN CN202011104721.9A patent/CN112321439B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4613698A (en) * | 1984-03-01 | 1986-09-23 | Hoechst Aktiengesellschaft | Process for the preparation of 6-chloro-2,4-dinitroaniline |
| CN103539680A (en) * | 2013-10-23 | 2014-01-29 | 浙江闰土研究院有限公司 | Clean production process of 6-chloro-2,4-dinitroaniline |
| CN111170871A (en) * | 2019-12-30 | 2020-05-19 | 河南洛染股份有限公司 | Method for synthesizing 6-bromo-2, 4-dinitroaniline |
Non-Patent Citations (1)
| Title |
|---|
| 6-氯-2,4-二硝基苯胺的研制;陈金业;《染料工业》;19901231;第27卷(第4期);第40页 * |
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