Method for preparing 2, 4-dichloro-3-fluoronitrobenzene

Abstract

The invention relates to a method for preparing 2, 4-dichloro-3-fluoronitrobenzene, which comprises the following steps: taking 2, 6-dichlorofluorobenzene as a raw material, and adopting a continuous tubular nitration reactor to react with a mixture of nitric acid and sulfuric acid to prepare the 2, 4-dichloro-3-fluoronitrobenzene, the sulfuric acid flowing out of the nitration reactor is concentrated and recycled; wherein the concentration of the nitric acid is 85%, and the volume ratio of the nitric acid to the sulfuric acid is (20-10): 1. The invention further provides a system for executing the method. According to the method, the production safety and the utilization efficiency of resources are remarkably improved.

Description

Technical Field

[0001] The invention relates to the field of chemical synthesis, in particular to a method for preparing 2,4-dichloro-3-fluoronitrobenzene. Background Art

[0002] As a key chemical intermediate, 2,4-dichloro-3-fluoronitrobenzene plays a vital role in the pharmaceutical and chemical fields. It is not only the core component of the synthesis of quinolone drugs, but also an indispensable raw material in the production of a variety of antibacterial agents, such as ofloxacin, lomefloxacin, tefloxacin, etc. These drugs have a significant share in the international market due to their wide application and significant therapeutic effects. As the main producer of these APIs, China's products and API exports account for more than 90% of the global market.

[0003] In the production process of APIs, such as 3,4-dichloroaniline, ofloxacin, levofloxacin and ciprofloxacin, a large number of by-products are produced. Traditionally, these by-products are often regarded as waste, which not only increases production costs but also causes potential pollution to the environment. However, through innovative process technologies, these by-products can be converted into valuable chemicals, which can not only reduce environmental pollution, but also create additional economic benefits for enterprises and achieve efficient use of resources.

[0004] In addition, 2,4-dichloro-3-fluoronitrobenzene also shows great potential in the production of liquid crystals and pesticide intermediates, especially for the synthesis of compounds such as 3,4,5-trifluorobromobenzene. The application of 2,4-dichloro-3-fluoronitrobenzene can significantly improve the quality and performance of the product, thereby enhancing its competitiveness in the international market.

[0005] Therefore, developing an efficient and environmentally friendly method for preparing 2,4-dichloro-3-fluoronitrobenzene can not only meet the demand for high-quality intermediates in the pharmaceutical and chemical industries, but also promote the effective utilization of related by-products, which is of great strategic significance for promoting the sustainable development of the entire industrial chain. Summary of the invention

[0006] In order to solve the problems in the prior art, the present application provides a method for preparing 2,4-dichloro-3-fluoronitrobenzene, which significantly improves production safety and resource utilization efficiency.

[0007] In order to solve the above technical problems, a technical solution provided by this application is:

[0008] A method for preparing 2,4-dichloro-3-fluoronitrobenzene comprises the following steps:

[0009] Using 2,6-dichlorofluorobenzene as a raw material, a continuous tubular nitration reactor is used to react with a mixture of nitric acid and sulfuric acid to prepare 2,4-dichloro-3-fluoronitrobenzene; and the sulfuric acid flowing out of the nitration reactor is concentrated and recovered;

[0010] The concentration of nitric acid is 85%, and the volume ratio of nitric acid to sulfuric acid is 20-10:1.

[0011] The method specifically comprises the following steps:

[0012] (1) controlling the temperature of the nitration reactor to 40-80° C. and the pressure to 0.5-1.0 MPa, and then delivering 2,6-dichlorofluorobenzene to the nitration reactor at a constant flow rate;

[0013] (2) introducing a mixture of nitric acid and sulfuric acid into the nitration reactor and mixing the mixture with 2,6-dichlorofluorobenzene to form a nitration reaction mixture;

[0014] (3) collecting and purifying the reaction product 2,4-dichloro-3-fluoronitrobenzene;

[0015] (4) Concentrating and recovering the sulfuric acid flowing out of the tubular nitration reactor.

[0016] The nitration reactor has a special structural design, wherein the special structural design includes: adding a stirring element in the pipeline, optimizing the flow channel design or filling inert materials.

[0017] The optimized flow channel design of the nitration reactor is that a multi-level spiral structure is arranged inside the flow channel.

[0018] Wherein, the flow rate of the 2,6-dichlorofluorobenzene into the nitration reactor is 1-3 L / h.

[0019] Wherein, the flow rate of the nitric acid into the nitration reactor is 2-6 L / h.

[0020] The method further comprises magnesium sulfate as a reaction catalyst, and magnesium sulfate is mixed with sulfuric acid and then introduced into the tubular reactor.

[0021] Wherein, the mass ratio of the magnesium sulfate to the sulfuric acid is 1:10-20.

[0022] Another technical solution provided by the present application is a system for preparing 2,4-dichloro-3-fluoronitrobenzene, which is used to perform any of the methods described above, and the system comprises:

[0023] (1) A feeding system for conveying 2,6-dichlorofluorobenzene, nitric acid and sulfuric acid;

[0024] (2) Temperature and pressure control systems for controlling reaction conditions;

[0025] (3) a product post-processing system for collecting and purifying 2,4-dichloro-3-fluoronitrobenzene;

[0026] (4) A sulfuric acid concentration recovery system for recovering sulfuric acid.

[0027] Wherein, the sulfuric acid concentration and recovery system comprises a vacuum distillation tower and a condensation recovery device.

[0028] The method for preparing 2,4-dichloro-3-fluoronitrobenzene provided in the present application, by adopting a pipelined nitration reactor, can achieve faster material mixing and more uniform reaction compared with the traditional kettle reactor, thereby improving production efficiency. The method of the present application does not require cooling after the reaction is completed, because the nitric acid is completely consumed, reducing the safety risks that may be caused by improper temperature control. In addition, the pressure of the reaction system is relatively low, further reducing the risks during operation. The method realizes the recovery and reuse of sulfuric acid, which not only reduces the consumption of sulfuric acid, but also reduces the discharge of waste, making the entire production process more green, environmentally friendly and sustainable. DETAILED DESCRIPTION

[0029] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the present invention.

[0030] In the traditional chemical industry, the preparation of 2,4-dichloro-3-fluoronitrobenzene usually adopts the kettle nitration method. However, this method has a series of problems and limitations, especially in terms of production efficiency and safety. Kettle nitration is a relatively primitive process. When preparing 2,4-dichloro-3-fluoronitrobenzene, the control of reaction conditions is not precise enough, resulting in low production efficiency and accompanied by high safety risks, which poses a serious challenge to the long-term development of enterprises.

[0031] In the traditional kettle nitration process, sulfuric acid as a reaction medium cannot be effectively recycled and reused, which not only increases production costs but also burdens the environment. In addition, the traditional process is difficult to promote when processing the production of liquid crystals and pesticide intermediates such as 3,4,5-trifluorobromobenzene, which limits the development and market competitiveness of related products.

[0032] In view of the above problems, the present invention provides a preparation method, which aims to improve the production efficiency of 2,4-dichloro-3-fluoronitrobenzene through technological innovation, while ensuring the safety of the production process to meet the needs of the long-term development of the enterprise. The new process significantly improves the utilization efficiency of resources by realizing the recovery and reuse of sulfuric acid, making the entire production process more environmentally friendly and sustainable. In addition, the improvement in safety of the new process also provides a strong guarantee for the stable operation and long-term development of the enterprise. Through these innovations, the present invention can not only improve product quality and production efficiency, but also bring greater market competitiveness and economic benefits to the enterprise.

[0033] The present application provides a method for preparing 2,4-dichloro-3-fluoronitrobenzene, comprising the following steps: using 2,6-dichlorofluorobenzene as a raw material, using a continuous tubular nitration reactor, and reacting with a mixture of nitric acid and sulfuric acid to prepare 2,4-dichloro-3-fluoronitrobenzene; concentrating and recovering the sulfuric acid flowing out of the nitration reactor; wherein the concentration of nitric acid is 85%, and the volume ratio of nitric acid to sulfuric acid is 20-10:1.

[0034] The present invention controls the ratio of nitric acid to sulfuric acid to promote the nitration reaction until the nitric acid is completely consumed and the heat is fully released, thereby reducing the pressure of the reaction system and improving the safety of the process. The sulfuric acid is recovered and reused after vacuum distillation to reduce the production cost of the entire process.

[0035] The method specifically comprises the following steps:

[0036] (1) controlling the temperature of the nitration reactor to 40-80° C. and the pressure to 0.5-1.0 MPa, and then delivering 2,6-dichlorofluorobenzene to the nitration reactor at a constant flow rate; (2) introducing a mixture of nitric acid and sulfuric acid into the nitration reactor and mixing it with 2,6-dichlorofluorobenzene to form a nitration reaction mixture; (3) collecting and purifying the reaction product 2,4-dichloro-3-fluoronitrobenzene; and (4) concentrating and recovering the sulfuric acid flowing out of the tubular nitration reactor.

[0037] The nitration reactor has a special structural design, wherein the special structural design includes: adding a stirring element in the pipeline, optimizing the flow channel design or filling inert materials.

[0038] The optimized flow channel design of the nitration reactor is that a multi-level spiral structure is arranged inside the flow channel.

[0039] Special structural designs also include but are not limited to: a multi-stage spiral structure is arranged inside the flow channel to increase the mixing and contact area of ​​the materials; the cross-section of the flow channel is designed to be non-circular to optimize the fluid dynamics characteristics and improve the mixing efficiency; the inner wall of the flow channel is made of corrosion-resistant materials to adapt to acidic and oxidizing environments; the flow channel design takes into account the heat exchange characteristics to control the reaction temperature and promote the effective transfer of heat; and inert materials are filled to increase the contact area of ​​the reactants and improve the reaction efficiency.

[0040] The flow rate of the 2,6-dichlorofluorobenzene into the nitration reactor is 1-3 L / h. The flow rate of the nitric acid into the nitration reactor is 2-6 L / h.

[0041] The method further comprises magnesium sulfate as a reaction catalyst, and magnesium sulfate is mixed with sulfuric acid and then introduced into the tubular reactor, wherein the mass ratio of magnesium sulfate to sulfuric acid is 1:10-20.

[0042] The method also includes precisely controlling the reaction conditions, including but not limited to temperature, pressure and reaction time, to optimize the reaction efficiency and product quality; and also includes treating the waste liquid and waste gas after the reaction to reduce environmental pollution and improve resource utilization.

[0043] Another technical solution provided by the present application is a system for preparing 2,4-dichloro-3-fluoronitrobenzene, which is used to perform any of the methods described above, and the system includes: (1) a feeding system for conveying 2,6-dichlorofluorobenzene, nitric acid, and sulfuric acid; (2) a temperature control and pressure control system for controlling reaction conditions; (3) a product post-processing system for collecting and purifying 2,4-dichloro-3-fluoronitrobenzene; (4) a sulfuric acid concentration and recovery system for recovering sulfuric acid. The sulfuric acid concentration and recovery system includes a vacuum distillation tower and a condensation recovery device, which can efficiently recover and purify sulfuric acid for reuse.

[0044] The method for preparing 2,4-dichloro-3-fluoronitrobenzene provided in the present application, by adopting a pipelined nitration reactor, can achieve faster material mixing and more uniform reaction compared with the traditional kettle reactor, thereby improving production efficiency. The method of the present application does not require cooling after the reaction is completed, because the nitric acid is completely consumed, reducing the safety risks that may be caused by improper temperature control. In addition, the pressure of the reaction system is relatively low, further reducing the risks during operation. The method realizes the recovery and reuse of sulfuric acid, which not only reduces the consumption of sulfuric acid, but also reduces the discharge of waste, making the entire production process more green, environmentally friendly and sustainable.

[0045] The preparation method of the present invention is specifically described below through multiple examples.

[0046] Examples 1-5

[0047] (1) controlling the temperature of the nitration reactor to 40-80° C. and the pressure to 0.5-1.0 MPa, and then delivering 2,6-dichlorofluorobenzene to the nitration reactor at a constant flow rate; (2) introducing a mixture of nitric acid and sulfuric acid into the nitration reactor and mixing it with 2,6-dichlorofluorobenzene to form a nitration reaction mixture; (3) collecting and purifying the reaction product 2,4-dichloro-3-fluoronitrobenzene; and (4) concentrating and recovering the sulfuric acid flowing out of the tubular nitration reactor.

[0048] The reaction conditions, utilization rates and product yields of Examples 1-5 are shown in Table 1.

[0049] Table 1

[0050]

[0051] According to the above principles, the present invention can also make appropriate changes and modifications to the above specific embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for preparing 2,4-dichloro-3-fluoronitrobenzene, characterized in that: The following steps are involved: Using 2,6-dichlorofluorobenzene as a raw material, a continuous tubular nitration reactor is used to react with a mixture of nitric acid and sulfuric acid to prepare 2,4-dichloro-3-fluoronitrobenzene; and the sulfuric acid flowing out of the nitration reactor is concentrated and recovered; The concentration of nitric acid is 85%, and the volume ratio of nitric acid to sulfuric acid is 20-10:

1.

2. The method according to claim 1, characterized in that The specific steps include: (1) controlling the temperature of the nitration reactor to 40-80° C. and the pressure to 0.5-1.0 MPa, and then delivering 2,6-dichlorofluorobenzene to the nitration reactor at a constant flow rate; (2) introducing a mixture of nitric acid and sulfuric acid into the nitration reactor and mixing the mixture with 2,6-dichlorofluorobenzene to form a nitration reaction mixture; (3) collecting and purifying the reaction product 2,4-dichloro-3-fluoronitrobenzene; (4) Concentrating and recovering the sulfuric acid flowing out of the tubular nitration reactor.

3. The method according to claim 1, characterized in that The nitration reactor has a special structural design, wherein the special structural design includes: adding a stirring element in the pipeline, optimizing the flow channel design or filling inert materials.

4. The method according to claim 3, characterized in that The optimized flow channel design of the nitration reactor is that a multi-level spiral structure is arranged inside the flow channel.

5. The method according to claim 1, characterized in that The flow rate of the 2,6-dichlorofluorobenzene into the nitration reactor is 1-3 L / h.

6. The method according to claim 1, characterized in that The flow rate of the nitric acid introduced into the nitration reactor is 2-6 L / h.

7. The method according to claim 1, characterized in that The method further comprises magnesium sulfate as a reaction catalyst, and magnesium sulfate is mixed with sulfuric acid and then introduced into the tubular reactor.

8. The method according to claim 7, characterized in that The mass ratio of the magnesium sulfate to the sulfuric acid is 1:10-20.

9. A system for preparing 2,4-dichloro-3-fluoronitrobenzene, for carrying out the method according to any one of claims 1 to 8, characterized in that: The system includes: (1) A feeding system for conveying 2,6-dichlorofluorobenzene, nitric acid and sulfuric acid; (2) Temperature and pressure control systems for controlling reaction conditions; (3) a product post-processing system for collecting and purifying 2,4-dichloro-3-fluoronitrobenzene; (4) A sulfuric acid concentration recovery system for recovering sulfuric acid.

10. The system according to claim 9, characterized in that The sulfuric acid concentration and recovery system comprises a vacuum distillation tower and a condensation recovery device.

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