Continuous preparation process of nitrobenzotrifluoride

Abstract

The invention relates to the technical field of fine chemical engineering, in particular to a continuous preparation process of nitrobenzotrifluoride, which at least comprises the following steps: S1, adding fuming nitric acid into sulfuric acid to obtain a mixed acid solution; s2, a metering pump is used for controlling the flow speed of the mixed acid solution and trifluorotoluene, the mixed acid solution and the trifluorotoluene sequentially pass through the two-stage dynamic tubular reactor, and the temperature of materials in the two-stage dynamic tubular reactor is controlled through external circulation; and S3, dropwise adding the mixture obtained after the reaction in the step S2 into water for quenching, then carrying out phase splitting, taking an upper-layer oil phase as a nitrobenzotrifluoride crude product, carrying out water washing and alkali washing to obtain nitrobenzotrifluoride, taking a lower-layer dilute sulphuric acid solution, further concentrating, and then applying in the next batch of nitration reaction, so that the online material quantity of the reaction is reduced, and the safety risk caused by thermal runaway of the reaction is avoided. Meanwhile, the concentration of sulfuric acid is reduced, so that the sulfuric acid is easier to recycle and reuse.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemicals, in particular to a continuous preparation process of nitrotrifluorotoluene. Background Art

[0002] Fluazifop is a substituted pyridinylanilide herbicide with both soil treatment activity and stem and leaf treatment activity. It is a broad-spectrum selective wheat field herbicide with a wide range of applications. As of November 30, 2022, there are 55 registration information of fluazifop on the China Pesticide Information Network. The production process of fluazifop is relatively simple. Usually, 2-chloronicotinic acid is first chlorinated to obtain 2-chloronicotinic acid chloride, and then condensed with 2,4-difluoroaniline and m-trifluoromethylphenol. Currently, m-trifluoromethylphenol is usually obtained by diazotization and hydrolysis reduction of m-trifluoromethylaniline. In order to improve the market competitiveness of fluazifop, it is necessary to produce m-trifluoromethylaniline independently, and accordingly, the demand for m-trifluoromethylaniline has also increased significantly.

[0003] A Chinese patent (publication number CN111499517A) discloses a method for preparing m-nitro trifluorotoluene, which uses trifluorotoluene with sulfuric acid and nitric acid in an organic solvent (chlorinated non-polar solvents such as dichloroethane or carbon tetrachloride) for nitration reaction, which takes 6-10 hours to complete, and does not meet the current safety supervision requirements for nitration reactions. And the use of 98% sulfuric acid is not convenient for recycling and reuse. The environmental impact report of Zhejiang Weihua New Materials Co., Ltd. "Zhejiang Weihua New Materials Annual Production of 5,000 Tons of Orthochlorobenzyl Chloride, 4,000 Tons of Trifluorotoluene Series, 13,500 Tons of Dichlorotoluene and 8,300 Tons of Dichlorotoluene Chlorination and Fluorination Series Products Project" (Project Code: 2012-330604-99-02-801387), in which nitro trifluorotoluene is prepared from trifluorotoluene, but still adopts a kettle reaction (the size of the nitration kettle is DN1400×2200), which does not meet the current safety supervision requirements for nitration reactions. Furthermore, the use of 98% sulfuric acid is not convenient for recycling and reuse. In the environmental impact assessment, sulfuric acid is sold as a by-product, but sulfuric acid still contains a small amount of organic matter, and the cost of using sulfuric acid is relatively high. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a continuous preparation process of nitrotrifluorotoluene, which reduces the amount of materials in the reaction line and avoids the safety risks caused by thermal runaway of the reaction. At the same time, it reduces the concentration of sulfuric acid, making it easier to recover and reuse sulfuric acid.

[0005] The present invention provides a continuous preparation process of nitrotrifluorotoluene, which comprises at least the following steps:

[0006] S1: adding fuming nitric acid into sulfuric acid to obtain a mixed acid solution;

[0007] S2: using a metering pump to control the flow rate of the mixed acid solution and trifluorotoluene to pass through the two-stage dynamic tubular reactor in sequence, and controlling the temperature of the materials in the two-stage dynamic tubular reactor through external circulation;

[0008] S3: The mixture after the reaction in step S2 is dropped into water for quenching, and then phase separation is performed. The upper oil phase is crude nitrotrifluorotoluene, which is washed with water and alkali to obtain nitrotrifluorotoluene. The lower layer is a dilute sulfuric acid solution, which is further concentrated and used in the next batch of nitration reaction.

[0009] As a preferred technical solution, the concentration of the sulfuric acid is 90-94wt%, preferably 91-93wt%, and most preferably 92wt%.

[0010] As a preferred technical solution, the molar ratio of the fuming nitric acid to the sulfuric acid is (1.0-1.2):(3-5); preferably (1.05-1.1):(3.5-4.5), and most preferably 1.05:4.

[0011] As a preferred technical solution, the specific gravity of the mixed acid at room temperature (20-30° C.) is 1.68-1.70 g / mL.

[0012] As a preferred technical solution, the molar ratio of trifluorotoluene to fuming nitric acid is 1:(1.0-1.2); preferably 1:(1.05-1.1).

[0013] As a preferred technical solution, the two-stage dynamic tubular reactor comprises a primary dynamic tubular reactor and a secondary dynamic tubular reactor in sequence.

[0014] As a preferred technical solution, the residence time of the material in the primary dynamic tubular reactor is 10-15 min, preferably 13-15 min, and most preferably 15 min.

[0015] As a preferred technical solution, the residence time of the material in the secondary dynamic tubular reactor is 10-15 min, preferably 13-15 min, and most preferably 15 min.

[0016] As a preferred technical solution, the material temperature in the primary dynamic tubular reactor is 10-30°C, preferably 10-20°C, and most preferably 10-15°C.

[0017] As a preferred technical solution, the material temperature in the secondary dynamic tubular reactor is 50-70°C, preferably 50-60°C, and most preferably 50-55°C.

[0018] As a preferred technical solution, the static liquid holding capacity of the vortex plate reactor and the dynamic tubular reactor is 1-5L.

[0019] As a preferred technical solution, the flow rate of the mixed acid and trifluorotoluene is 30-60 mL / min.

[0020] Preferably, the flow rate of the mixed acid is 40-60 mL / min, preferably 42-58 mL / min.

[0021] Preferably, the flow rate of trifluorotoluene is 30-50 mL / min, preferably 35-45 mL / min.

[0022] As a preferred technical solution, the alkali washing is performed using a 1-10wt% sodium carbonate aqueous solution.

[0023] The present invention realizes the continuous preparation of nitrobenzotrifluoride (the reaction is completed in 30 minutes) by comprehensively controlling the concentration of sulfuric acid in the preparation process of nitrobenzotrifluoride and coordinating various reaction conditions, while enabling the nitration reaction to be carried out gently, thereby avoiding thermal runaway when using concentrated sulfuric acid. The inventors found in the process of exploration that by using sulfuric acid with a concentration of 90-94wt% and optimizing the molar ratio of fuming nitric acid, sulfuric acid and benzotrifluoride, the risk of thermal runaway of the reaction is effectively reduced, and at the same time, the amount of isomer o-nitrobenzotrifluoride produced by the reaction is effectively reduced, thereby ensuring product quality.

[0024] Furthermore, the present invention designs the mixed acid and trifluorotoluene to pass through a two-stage dynamic tubular reactor in sequence, and comprehensively controls the temperature, flow rate and residence time of the materials in the two-stage dynamic tubular reactor, thereby greatly improving the yield of meta-nitrotrifluorotoluene and the content of meta-nitrotrifluorotoluene in the product.

[0025] In addition, the method provided by the present invention can effectively reduce the difficulty of sulfuric acid recovery and reuse. The sulfuric acid after the nitration reaction only needs to be concentrated to 90-92% before it can be recycled and reused, which reduces the equipment investment cost and is conducive to large-scale industrial production and promotion.

[0026] Beneficial Effects

[0027] 1. The present invention provides a continuous preparation process of nitrotrifluorotoluene, which reduces the amount of materials in the reaction line and avoids the safety risk caused by thermal runaway of the reaction. At the same time, it reduces the concentration of sulfuric acid, making it easier to recover and reuse sulfuric acid.

[0028] 2. The present invention realizes the continuous preparation of nitrobenzotrifluoride (reaction completed in 30 minutes) by comprehensively controlling the concentration of sulfuric acid in the preparation process of nitrobenzotrifluoride and coordinating the control of various reaction conditions. At the same time, the nitration reaction can be carried out gently, avoiding thermal runaway when using concentrated sulfuric acid.

[0029] 3. The present invention uses sulfuric acid with a concentration of 90-94wt% and optimizes the molar ratio of fuming nitric acid, sulfuric acid and trifluorotoluene, thereby effectively reducing the risk of thermal runaway of the reaction and effectively reducing the amount of isomer o-nitrotrifluorotoluene produced by the reaction, thereby ensuring product quality.

[0030] 4. The present invention designs the mixed acid and trifluorotoluene to pass through a two-stage dynamic tubular reactor in sequence, and comprehensively controls the temperature, flow rate and residence time of the materials in the two-stage dynamic tubular reactor, thereby greatly improving the yield of meta-nitrotrifluorotoluene and the content of intermediate nitrotrifluorotoluene in the product.

[0031] 5. The method provided by the present invention can effectively reduce the difficulty of sulfuric acid recovery and reuse. The sulfuric acid after nitration reaction only needs to be concentrated to 90-92% before it can be recycled and reused, which reduces the equipment investment cost and is conducive to large-scale industrial production and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a physical picture of the equipment used in the continuous preparation process of nitrotrifluorotoluene in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] Example 1

[0034] Embodiment 1 of the present invention provides a continuous preparation process of nitrobenzotrifluoride, comprising the following steps:

[0035] S1: adding fuming nitric acid into sulfuric acid to obtain a mixed acid solution;

[0036] S2: using a metering pump to control the flow rate of the mixed acid solution and trifluorotoluene to pass through the two-stage dynamic tubular reactor in sequence, and controlling the temperature of the materials in the two-stage dynamic tubular reactor through external circulation;

[0037] S3: The mixture after the reaction in step S2 is dropped into water for quenching, and then phase separation is performed. The upper oil phase is crude nitrotrifluorotoluene, which is washed with water and alkali to obtain nitrotrifluorotoluene. The lower layer is a dilute sulfuric acid solution, which is further concentrated and used in the next batch of nitration reaction.

[0038] The concentration of the sulfuric acid is 91 wt %.

[0039] The molar ratio of the fuming nitric acid to the sulfuric acid is 1.1:4.

[0040] The specific gravity of the mixed acid at room temperature (25° C.) is 1.68 g / mL.

[0041] The molar ratio of the trifluorotoluene to the fuming nitric acid (98 wt%) is 1:1.1.

[0042] The two-stage dynamic tubular reactor comprises a primary dynamic tubular reactor and a secondary dynamic tubular reactor in sequence.

[0043] The residence time of the material in the first-stage dynamic tubular reactor is 15 minutes.

[0044] The residence time of the material in the secondary dynamic tubular reactor is 15 minutes.

[0045] The material temperature in the first-stage dynamic tubular reactor is 11°C.

[0046] The material temperature in the secondary dynamic tubular reactor is 54°C.

[0047] The static liquid holding capacity of the vortex plate reactor and the dynamic tubular reactor is 1L.

[0048] The flow rate of the mixed acid was 56.32 mL / min.

[0049] The flow rate of the trifluorotoluene was 43.68 mL / min.

[0050] The alkali washing is performed using a 5 wt % sodium carbonate aqueous solution.

[0051] Example 2

[0052] Embodiment 2 of the present invention provides a continuous preparation process of nitrotrifluorotoluene, comprising the following steps:

[0053] S1: adding fuming nitric acid into sulfuric acid to obtain a mixed acid solution;

[0054] S2: using a metering pump to control the flow rate of the mixed acid solution and trifluorotoluene to pass through the two-stage dynamic tubular reactor in sequence, and controlling the temperature of the materials in the two-stage dynamic tubular reactor through external circulation;

[0055] S3: The mixture after the reaction in step S2 is dropped into water for quenching, and then phase separation is performed. The upper oil phase is crude nitrotrifluorotoluene, which is washed with water and alkali to obtain nitrotrifluorotoluene. The lower layer is a dilute sulfuric acid solution, which is further concentrated and used in the next batch of nitration reaction.

[0056] The concentration of the sulfuric acid is 92 wt %.

[0057] The molar ratio of the fuming nitric acid to the sulfuric acid is 1.05:4.

[0058] The specific gravity of the mixed acid at room temperature (25° C.) is 1.70 g / mL.

[0059] The molar ratio of the trifluorotoluene to the fuming nitric acid (98 wt%) is 1:1.05.

[0060] The two-stage dynamic tubular reactor comprises a primary dynamic tubular reactor and a secondary dynamic tubular reactor in sequence.

[0061] The residence time of the material in the first-stage dynamic tubular reactor is 15 minutes.

[0062] The residence time of the material in the secondary dynamic tubular reactor is 15 minutes.

[0063] The material temperature in the first-stage dynamic tubular reactor is 15°C.

[0064] The material temperature in the secondary dynamic tubular reactor is 50°C.

[0065] The static liquid holding capacity of the vortex plate reactor and the dynamic tubular reactor is 1L.

[0066] The flow rate of the mixed acid is 43.38 mL / min.

[0067] The flow rate of the trifluorotoluene was 39.95 mL / min.

[0068] The alkali washing is performed using a 5 wt % sodium carbonate aqueous solution.

[0069] Comparative Example 1

[0070] Comparative Example 1 of the present invention provides a conventional batch preparation process of nitrobenzotrifluoride, which specifically comprises the following steps:

[0071] S1: Prepare a mixed acid of 98.42% fuming nitric acid (7.86 g, 0.123 mol) and 97.9% sulfuric acid (40.07 g, 0.4 mol) and add it into a 50 mL constant pressure dropping funnel;

[0072] S2: Add trifluorotoluene (14.76 g, 0.1 mol) into a 100 mL four-necked reaction flask, control the material temperature at 10°C in a -15°C ethanol ice-water bath, and add the mixed acid dropwise for 15 minutes;

[0073] 3 minutes after the mixed acid was dripped, the material temperature suddenly rose sharply to 50°C. The -15°C ethanol ice water bath could not control the material temperature. Therefore, there is a risk of thermal runaway when using the traditional high-concentration sulfuric acid intermittent nitration process.

[0074] Performance Testing

[0075] The oil phases of the outlet materials of the primary dynamic tubular reactor and the secondary dynamic tubular reactor of Examples 1 and 2 were respectively taken for GC analysis to obtain the purity of m-nitrobenzotrifluoride; the yield of m-nitrobenzotrifluoride was calculated based on benzotrifluoride. The results are shown in Table 1.

[0076] Table 1

[0077]

Claims

1. A continuous preparation process of nitrotrifluorotoluene, characterized in that: At least the following steps are included: S1: adding fuming nitric acid into sulfuric acid to obtain a mixed acid solution; S2: using a metering pump to control the flow rate of the mixed acid solution and trifluorotoluene to pass through the two-stage dynamic tubular reactor in sequence, and controlling the temperature of the materials in the two-stage dynamic tubular reactor through external circulation; S3: The mixture after the reaction in step S2 is dropped into water for quenching, and then phase separation is performed. The upper oil phase is the crude nitrotrifluorotoluene, which is washed with water and alkali to obtain nitrotrifluorotoluene. The lower layer is a dilute sulfuric acid solution, which is further concentrated and used in the next batch of nitration reaction.

2. The continuous preparation process of nitrotrifluorotoluene according to claim 1, characterized in that: The concentration of the sulfuric acid is 90-94 wt %.

3. The continuous preparation process of nitrotrifluorotoluene according to claim 2, characterized in that: The molar ratio of the fuming nitric acid to the sulfuric acid is (1.0-1.2):(3-5).

4. The continuous preparation process of nitrotrifluorotoluene according to claim 3, characterized in that: The molar ratio of trifluorotoluene to fuming nitric acid is 1:(1.0-1.2).

5. The continuous preparation process of nitrotrifluorotoluene according to claim 1, characterized in that: The two-stage dynamic tubular reactor comprises a primary dynamic tubular reactor and a secondary dynamic tubular reactor in sequence.

6. The continuous preparation process of nitrotrifluorotoluene according to claim 5, characterized in that: The residence time of the material in the primary dynamic tubular reactor is 10-15 minutes; the residence time of the material in the secondary dynamic tubular reactor is 10-15 minutes.

7. The continuous preparation process of nitrotrifluorotoluene according to claim 5, characterized in that: The material temperature in the first-stage dynamic tubular reactor is 10-30°C.

8. The continuous preparation process of nitrotrifluorotoluene according to claim 5, characterized in that: The material temperature in the secondary dynamic tubular reactor is 50-70°C.

9. The continuous preparation process of nitrotrifluorotoluene according to claim 1, characterized in that: The flow rate of the mixed acid and trifluorotoluene is 30-60 mL / min.

10. The continuous preparation process of nitrobenzotrifluoride according to claim 9, characterized in that: The flow rate of the mixed acid is 40-60 mL / min, and the flow rate of the trifluorotoluene is 30-50 mL / min.

Images