A method for synthesizing 2,4-dichloro-3,5-dinitrotrifluorotoluene

Abstract

The invention discloses a method for synthesizing 2,4-dichloro-3,5-dinitrobenzotrifluoride. 2,4-dichlorotoluene and nitric acid / sulfuric acid are used as raw materials, and a continuous flow reactor is used to synthesize 2,4-dichloro-3,5-dinitrotoluene under the action of a catalyst. The obtained 2,4-dichloro-3,5-dinitrotoluene has a content of ≥99%, a conversion rate of >99%, and a yield of >90%. Waste sulfuric acid can be recycled after being pretreated. Compared with the existing technology, the method has fewer steps, a simple process, low energy consumption, high product quality, and significantly improved process cleanliness and intrinsic safety.

Description

Technical Field

[0001] The invention relates to a method for synthesizing 2,4-dichloro-3,5-dinitrobenzotrifluoride, and in particular to a method for synthesizing 2,4-dichloro-3,5-dinitrobenzotrifluoride by using a continuous flow reactor. The method uses 2,4-dichlorobenzotrifluoride and nitric acid / sulfuric acid as raw materials, and uses a continuous flow reactor to synthesize 2,4-dichloro-3,5-dinitrobenzotrifluoride under the action of a catalyst. The method belongs to the technical field of compound synthesis. Background Art

[0002] 2,4-Dichloro-3,5-dinitrobenzotrifluoride is an important intermediate in fine organic synthesis, and is often used in the synthesis of pesticides, medicines and dyes. Hori Hitoshi et al. mentioned in the paper "Design and Synthesis of New Mitochondiral Cytotoxin N-Thiadiazolyanilines that Inhibit Tumor Cell Growth" that 50% concentration of fuming sulfuric acid and fuming nitric acid are first mixed into a mixed acid, and then added dropwise to 2,4-dichlorobenzotrifluoride, and stirred and kept warm at 80°C for 96 hours to synthesize the target compound 2,4-dichloro-3,5-dinitrobenzotrifluoride with a yield of about 60%.

[0003] Patent CN103304420A discloses a clean preparation method of 2,4-dichloro-3,5-dinitrobenzotrifluoride, and its process mainly includes washing, neutralizing, refining and vacuum drying the crude product of 2,4-dichloro-3,5-dinitrobenzotrifluoride to obtain a product, but the purity is low and does not meet the specified standards. Patent CN111533660 discloses a clean preparation method of 2,4-dichloro-3,5-dinitrobenzotrifluoride, which is synthesized using sulfuric acid, pyrosulfuric acid and nitric acid, with a reaction time of about 14.5 hours and a product yield of about 81%.

[0004] At present, emergency production requires that newly built, renovated and expanded nitration units should adopt continuous nitration production processes such as microchannels in principle to further improve the intrinsic safety of the process; however, the existing process for preparing 2,4-dichloro-3,5-dinitrotrifluorotoluene has the following disadvantages: (1) high side reactions, generally low conversion rates and yields; (2) low intrinsic safety of the reaction process, and the use of intermittent kettle heating is prone to local overheating, causing overheating or even explosion of materials; (3) complex process conditions, kettle nitration mostly uses step-by-step nitration, involving multiple sets of post-treatment, and the materials are all strong acids and highly corrosive, and the risk of secondary disasters caused by material leakage is also relatively high. Therefore, developing a green, environmentally friendly, simple to operate, and intrinsically safe continuous flow process from the perspective of the enterprise can not only ensure the long-term safe and stable operation of the enterprise, but also provide a protective barrier for the enterprise to operate in compliance with laws and regulations. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for synthesizing 2,4-dichloro-3,5-dinitrobenzotrifluoride in view of the deficiencies in the prior art. The method is a method for synthesizing 2,4-dichloro-3,5-dinitrobenzotrifluoride using a continuous flow reactor. The present invention uses 2,4-dichlorobenzotrifluoride, nitric acid and sulfuric acid as raw materials, uses a continuous flow reactor under the action of a catalyst, and synthesizes 2,4-dichloro-3,5-dinitrobenzotrifluoride by a continuous flow one-step method. The present invention uses a continuous flow process, the liquid holding capacity of the reaction process is low, sulfuric acid can be recycled after treatment, and the intrinsic safety of the process is significantly improved, which meets the current safety and environmental protection requirements; the whole process of the present invention produces less three wastes and has a high economic application value. Therefore, the preparation method of the present invention has a very good industrial prospect. Therefore, the present invention has the advantages of simple process, few operating steps, simple operation, high reaction conversion rate, safety and environmental protection.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for synthesizing 2,4-dichloro-3,5-dinitrobenzotrifluoride, using 2,4-dichlorobenzotrifluoride, nitric acid and sulfuric acid as raw materials, using a continuous flow reactor to synthesize 2,4-dichloro-3,5-dinitrobenzotrifluoride under the action of a catalyst, comprising the following steps:

[0008] 2,4-dichlorobenzotrifluoride is used as material A, and a mixture formed by dissolving nitric acid, sulfuric acid and a catalyst is used as material B. Material A and material B are simultaneously fed into a continuous flow reactor through a horizontal flow pump, and material A and material B react in the continuous flow reactor; the material obtained at the outlet of the continuous flow reactor is cooled, a solvent is added for extraction, and then allowed to stand for stratification, and the upper layer is sequentially alkali washed, water washed, recrystallized, filtered, dried, and granulated to obtain 2,4-dichloro-3,5-dinitrobenzotrifluoride. The reaction equation is as follows:

[0009]

[0010] In the above technical scheme, a lower acid layer is obtained during static stratification, and the acid layer is directly concentrated by sulfur trioxide and then used for nitration synthesis.

[0011] In the above technical solution, the molar ratio of 2,4-dichlorotrifluorotoluene to nitric acid is 1:2.05-3.5.

[0012] In the above technical solution, the molar ratio of 2,4-dichlorotrifluorotoluene to sulfuric acid is 1:5-12.

[0013] In the above technical solution, the weight ratio of the 2,4-dichlorotrifluorotoluene to the catalyst is 1:0.005-0.1.

[0014] In the above technical solution, the catalyst is any one of nano-iron, ferrocene, ferrous sulfate, and ferric chloride, or a mixture of any two or more of the nano-iron and ferrous sulfate in any proportion.

[0015] In the above technical solution, the solvent used in the extraction is a halogenated hydrocarbon solvent, preferably chloroform or dichloroethane.

[0016] In the above technical solution, the weight ratio of the solvent used in the extraction to 2,4-dichlorotrifluorotoluene is 2-8:1.

[0017] In the above technical solution, the solvent used in the recrystallization is a mixed solvent formed by an organic solvent and water, the organic solvent is any one of acetone, methanol, ethanol, and isopropanol, and the weight ratio of the organic solvent to water is 3-5:1.

[0018] In the above technical solution, the weight ratio of the solvent used in the recrystallization to 2,4-dichlorotrifluorotoluene is 1-5:1.

[0019] In the above technical solution, the feed flow rate of material A is 1-250g / min; the feed flow rate of material B is 1-200g / min.

[0020] In the above technical solution, after the material A and the material B enter the continuous flow reactor, their residence time in the continuous flow reactor is 0.5-60 min.

[0021] In the above technical solution, the temperature inside the continuous flow reactor is controlled to be 50-180°C.

[0022] In the above technical solution, the continuous flow reactor is a tubular reactor or a microchannel reactor.

[0023] In the above technical solution, the continuous flow reactor is made of silicon carbide, Hastelloy or glass.

[0024] In the above technical solution, the continuous flow reactor is fed with self-supplied pressure by a horizontal flow pump.

[0025] Beneficial effects of the present invention:

[0026] (1) The only by-product of the reaction of the present invention is water, and the reaction is green and environmentally friendly, with high atom economy and high degree of cleanliness.

[0027] (2) The post-processing of the present invention only requires layering, concentration, crystallization and drying to obtain the finished product. The process is simple to operate and easy to implement industrially.

[0028] (3) The present invention adopts a continuous flow reactor, the liquid holding capacity of the equipment is small, and the intrinsic safety of the process is significantly improved.

[0029] (4) The present invention uses a continuous flow reactor, which has high heat exchange efficiency and avoids the use of large-scale heating equipment. Compared with traditional intermittent reactors, it significantly reduces energy consumption.

[0030] (5) The present invention adopts a continuous flow reactor, and the reaction residence time is shortened from more than ten hours to a few minutes to tens of minutes, and the reaction efficiency is significantly improved.

[0031] (6) The present invention uses a continuous flow reactor to complete the reaction that originally required two steps of nitration in one step, avoiding the intermediate post-treatment process of the primary and secondary nitration processes, significantly simplifying the reaction process and facilitating the implementation of process production.

[0032] (7) The present invention adopts a continuous flow reactor, with a high reaction conversion rate of >98%, a yield of >94%, no side reactions other than water, and a product quality of >98%.

[0033] (8) The present invention uses a continuous flow reactor to achieve a high reaction conversion rate, that is, the reaction system is clean and the amount of impurities generated is small, thereby avoiding the enrichment of organic matter in sulfuric acid. After simple pretreatment and concentration, the process can be recycled and reused, thereby avoiding the generation of a large amount of waste acid. DETAILED DESCRIPTION

[0034] The specific implementation of the technical solution of the present invention is described in detail below, but the present invention is not limited to the following description:

[0035] The present invention will be described below in conjunction with specific embodiments:

[0036] Embodiment 1:

[0037] A method for synthesizing 2,4-dichloro-3,5-dinitrotrifluorotoluene using a continuous flow reactor, wherein the continuous flow reactor is a microchannel reactor made of silicon carbide, the microchannel single plate retention volume used is 10 mL, and a total of five plates are used, comprising the following steps: pre-controlling the temperature of the heat transfer oil in the continuous flow reactor to 80°C, mixing 200g of 2,4-dichlorotrifluorotoluene (material A), 500g of sulfuric acid, and 1g of ferrocene, and then mixing with 135g of nitric acid (material B) into the continuous flow reactor through a horizontal flow pump for mixing, heating and reaction, wherein the mixture A is controlled to be fed The flow rate is 22.1 g / min, the feed flow rate of material B is controlled to be 70.5 g / min, the residence time is controlled to be 1 min, the discharge from the reactor is collected in a 5L four-necked flask and then cooled to 30-40°C, 1000 g of chloroform is added and stirred for 0.5 h, and then transferred to a separatory funnel. The material in the separatory funnel is allowed to stand for 1 h and then separated into layers. The upper layer is sequentially washed with alkali, washed with water, the oil layer is crystallized by adding 80% acetone water, and filtered to obtain a wet basis of 2,4-dichloro-3,5-dinitrotrifluorotoluene. The dry basis after drying and granulation is 261.9 g, the content is 99.5%, and the yield is 92.3%.

[0038] Embodiment 2:

[0039] A method for synthesizing 2,4-dichloro-3,5-dinitrotrifluorotoluene using a continuous flow reactor, wherein the continuous flow reactor is a microchannel reactor, the material is Hastelloy, the retention volume of the microchannel single plate used is 10 mL, and a total of five plates are used, comprising the following steps: pre-controlling the temperature of the heat transfer oil in the continuous flow reactor to be 125°C, mixing 200g of 2,4-dichlorotrifluorotoluene (material A), 500g of sulfuric acid, and 1g of ferrocene, and then mixing with 135g of nitric acid (material B) into the continuous flow reactor through a horizontal flow pump for mixing and heating reaction, wherein the mixture A is controlled to enter The material flow rate is 29.5 g / min, the material B feed flow rate is controlled to be 94.0 g / min, the residence time is controlled to be 45 s, the reactor discharge is collected in a 5L four-necked flask and then cooled to 30-40°C, 1200 g of dichloroethane is added and stirred for 0.5 h, and then transferred to a separatory funnel. The material in the separatory funnel is allowed to stand for 1 h and then separated into layers. The upper layer is sequentially washed with alkali, washed with water, the oil layer is crystallized with 65% ethanol water, and filtered to obtain a wet basis of 2,4-dichloro-3,5-dinitrotrifluorotoluene. The dry basis after drying and granulation is 268.1 g, the content is 99.7%, and the yield is 94.5%.

[0040] Embodiment 3:

[0041] A method for synthesizing 2,4-dichloro-3,5-dinitrotrifluorotoluene using a continuous flow reactor, wherein the continuous flow reactor is a tubular reactor made of silicon carbide, and the effective residence volume of the reactor is 50 mL, comprising the following steps: pre-controlling the temperature of the heat transfer oil in the tubular reactor to 155° C., mixing 200 g of 2,4-dichlorotrifluorotoluene (material A), 500 g of sulfuric acid, and 2 g of ferrous sulfate, and then mixing with 135 g of nitric acid (material B) into the continuous flow reactor through a horizontal flow pump for mixing, heating and reaction, wherein the feed flow rate of the mixture A is controlled to be 1 8.9g / min, the feed flow rate of material B is controlled to 60.4g / min, the residence time is controlled to 70s, the discharge from the reactor is collected in a 5L four-necked flask and then cooled to 30-40°C, 1000g of chloroform is added and stirred for 0.5h, and then transferred to a separatory funnel. The material in the separatory funnel is allowed to stand for 1h and then separated. The upper layer is sequentially washed with alkali, washed with water, the oil layer is crystallized by adding 90% methanol water, and filtered to obtain a wet basis of 2,4-dichloro-3,5-dinitrotrifluorotoluene. The dry basis after drying and granulation is 259.9g, the content is 99.4%, and the yield is 91.6%.

[0042] Embodiment 4:

[0043] A method for synthesizing 2,4-dichloro-3,5-dinitrotrifluorotoluene using a continuous flow reactor, wherein the continuous flow reactor is a tubular reactor made of Hastelloy, and the effective residence volume of the reactor is 50 mL, comprising the following steps: pre-controlling the temperature of the heat transfer oil in the tubular reactor to 165° C., mixing 200 g of 2,4-dichlorotrifluorotoluene (material A), 500 g of sulfuric acid, and 2.2 g of ferrous chloride, and then mixing with 135 g of nitric acid (material B) into the continuous flow reactor through a horizontal flow pump for mixing, heating and reaction, wherein the feed flow rate of the mixture A is controlled to be 2 7.2g / min, the feed flow rate of material B was controlled at 65.1g / min, the residence time was controlled at 65s, the discharge from the reactor was collected in a 5L four-necked flask and then cooled to 30-40°C, 1200g of dichloroethane was added and stirred for 0.5h, and then transferred to a separatory funnel. The material in the separatory funnel was allowed to stand for 1h and then separated. The upper layer was washed with alkali, washed with water, the oil layer was crystallized with 85% methanol water, and filtered to obtain a wet basis of 2,4-dichloro-3,5-dinitrotrifluorotoluene. The dry basis after drying and granulation was 261.0g, the content was 99.2%, and the yield was 92.0%.

[0044] The above examples are only for illustrating the technical concept and technical features of the present invention, and cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for synthesizing 2,4-dichloro-3,5-dinitrobenzotrifluoride, using 2,4-dichlorobenzotrifluoride, nitric acid and sulfuric acid as raw materials, using a continuous flow reactor to synthesize 2,4-dichloro-3,5-dinitrobenzotrifluoride under the action of a catalyst, characterized in that: The following steps are involved: 2,4-dichlorobenzotrifluoride is used as material A, and a mixture formed by dissolving nitric acid, sulfuric acid and a catalyst is used as material B. Material A and material B are simultaneously fed into a continuous flow reactor through a horizontal flow pump, and material A and material B react in the continuous flow reactor; the material obtained at the outlet of the continuous flow reactor is cooled, a solvent is added for extraction, and then allowed to stand for stratification, and the upper layer is sequentially alkali washed, water washed, recrystallized, filtered, dried, and granulated to obtain 2,4-dichloro-3,5-dinitrobenzotrifluoride. The reaction equation is as follows: The molar ratio of 2,4-dichlorobenzotrifluoride to nitric acid is 1:2.05-3.5; the molar ratio of 2,4-dichlorobenzotrifluoride to sulfuric acid is 1:5-12; The catalyst is any one of nano-iron, ferrocene, ferrous sulfate, and ferric chloride, or a mixture of two or more of the nano-iron and ferrous chloride in any proportion; the weight ratio of 2,4-dichlorotrifluorotoluene to the catalyst is 1:0.005-0.1; The feed rate of material A is 1-250 g / min; the feed rate of material B is 1-200 g / min; After the materials A and B enter the continuous flow reactor, their residence time in the continuous flow reactor is 0.5-60 minutes; the temperature in the continuous flow reactor is controlled at 50-180°C.

2. The synthesis method according to claim 1, characterized in that When the stratification is allowed to stand, an acid layer is obtained at the bottom. The acid layer is directly concentrated by passing sulfur trioxide and then used for nitration synthesis.

3. The synthesis method according to claim 1, characterized in that The solvent used in the extraction is chloroform or dichloroethane, and the weight ratio of the solvent used in the extraction to 2,4-dichlorotrifluorotoluene is 2-8:

1.

4. The synthesis method according to claim 1, characterized in that The solvent used in the recrystallization is a mixed solvent formed by an organic solvent and water, and the weight ratio of the solvent used in the recrystallization to 2,4-dichlorotrifluorotoluene is 1-5:

1.

5. The synthesis method according to claim 4, characterized in that The organic solvent is any one of acetone, methanol, ethanol and isopropanol, and the weight ratio of the organic solvent to water is 3-5:

1.

6. The synthesis method according to claim 1, characterized in that The continuous flow reactor is a tubular reactor or a microchannel reactor; the continuous flow reactor is made of silicon carbide, Hastelloy or glass; the continuous flow reactor is fed with self-supplied pressure by a horizontal flow pump.

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