Method for continuously producing 2-chloro-4-fluoro-5-nitrobenzaldehyde

Abstract

The invention relates to the technical field of preparation of pesticide chemical intermediates, in particular to a method for continuously producing 2-chloro-4-fluoro-5-nitrobenzaldehyde. The invention discloses a method for continuously producing 2-chloro-4-fluoro-5-nitrobenzaldehyde. The method comprises the following steps: S1, mixing fuming nitric acid and concentrated sulfuric acid to prepare mixed acid A; s2, mixing the 2-chloro-4-fluorodichlorotoluene with an organic solvent to prepare a mixture B; s3, respectively pumping the mixed acid A and the mixture B into a temperature-controlled tubular continuous flow reactor, and carrying out a mixed reaction to obtain a reaction solution; and S4, collecting the reaction liquid, heating the reaction liquid, diluting, and crystallizing to obtain the 2-chloro-4-fluoro-5-nitrobenzaldehyde. According to the invention, the conversion rate of raw materials is improved, the use amount of nitric acid is small, the safety risk of nitration reaction can be reduced, the automation control degree and production efficiency of the device are improved, and a continuous nitration process is realized.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of pesticide chemical intermediates, and in particular to a method for continuously producing 2-chloro-4-fluoro-5-nitrobenzaldehyde. Background Art

[0002] 2-Chloro-4-fluoro-5-nitrobenzaldehyde is a pesticide chemical intermediate. The preparation methods of 2-chloro-4-fluoro-5-nitrobenzaldehyde can be divided into intermittent nitration and continuous nitration. At present, intermittent nitration is mostly used. Intermittent nitration mainly adopts kettle nitration, which has problems such as small production scale, low heat transfer efficiency, long production cycle, low production efficiency, and high safety risk. At present, the approval and production policies of nitration process are becoming more and more stringent, and the research on new continuous nitration process with high safety factor is gradually being paid attention to.

[0003] The Chinese patent with the patent publication number CN111848406A discloses a method for preparing 2-chloro-4-fluoro-5-nitrobenzaldehyde, which discloses that chlorine gas is introduced into 2-chloro-4-fluoro-toluene as a raw material under the irradiation of high-pressure ultraviolet light for chlorination reaction, the obtained product is hydrolyzed under the action of a catalyst, and a nitration reaction is carried out after the hydrolysis. After the nitration reaction, 2-chloro-4-fluoro-5-nitrobenzaldehyde is precipitated in ice water, and the yield is 98%; the Chinese patent with the patent publication number CN112225664A discloses a method for preparing nitrobenzaldehyde and 2-chloro-4-fluoro-5-nitrobenzaldehyde and its application, which adopts the method of adding substituted benzyl dichloride to a mixed solution of sulfuric acid and nitric acid, after the nitration reaction is completed, the reaction system is heated to 60-120°C, a hydrolysis reaction is carried out, and after the hydrolysis reaction stops, 2-chloro-4-fluoro-5-nitrobenzaldehyde is obtained by post-treatment, and the yield is 94.94%.

[0004] Therefore, providing a method for continuously producing 2-chloro-4-fluoro-5-nitrobenzaldehyde with reduced safety risks of nitration reaction, high production efficiency and high raw material conversion rate is the main technical problem that needs to be solved at present. Summary of the invention

[0005] In order to solve the above problem, the present invention provides a method for continuously producing 2-chloro-4-fluoro-5-nitrobenzaldehyde, comprising the following steps:

[0006] S1. The fuming nitric acid and concentrated sulfuric acid are mixed to prepare a mixed acid A;

[0007] S2. 2-chloro-4-fluorotoluene dichloride is mixed with an organic solvent to prepare a mixture B;

[0008] S3. The mixed acid A and the mixture B are pumped into a temperature-controlled tubular continuous flow reactor for mixed reaction to obtain a reaction solution;

[0009] S4. Collect the reaction solution, heat up, dilute and crystallize the reaction solution to obtain 2-chloro-4-fluoro-5-nitrobenzaldehyde.

[0010] In one embodiment, the mass concentration of the fuming nitric acid in S1 is ≥95%, and the mass concentration of the concentrated sulfuric acid is 90-98%.

[0011] In a preferred embodiment, the mass concentration of the fuming nitric acid in S1 is 95-98%.

[0012] In one embodiment, the mass concentration of the fuming nitric acid includes but is not limited to 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, and 98%.

[0013] In one embodiment, the mass concentration of the concentrated sulfuric acid includes but is not limited to 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, and 98%.

[0014] In one embodiment, the mass concentration of the fuming nitric acid is 95%.

[0015] In one embodiment, the mass concentration of the concentrated sulfuric acid is 93%.

[0016] In one embodiment, the mass concentration of the concentrated sulfuric acid is 95%.

[0017] In one embodiment, the molar ratio of fuming nitric acid to concentrated sulfuric acid in S1 is 1:(5-10).

[0018] In a preferred embodiment, the molar ratio of fuming nitric acid to concentrated sulfuric acid in S1 is 1:(8-10).

[0019] In a more preferred embodiment, the molar ratio of fuming nitric acid to concentrated sulfuric acid in S1 is 1:8.8.

[0020] In one embodiment, the organic solvent is selected from one or more combinations of 1,2-dichloroethane, dichloromethane, chloroform, n-pentane, n-hexane, and cyclohexane.

[0021] In one embodiment, the organic solvent is dichloromethane.

[0022] In one embodiment, the weight of the organic solvent in S2 is 20-120% of the weight of 2-chloro-4-fluorotoluene dichloride.

[0023] In one embodiment, the temperature-controlled tubular continuous flow reactor in S3 includes an external heat exchanger, and the temperature of the external heat exchanger is set to -6 to -2°C. By setting the temperature of the external heat exchanger to -6 to -2°C, the circulating temperature in the temperature-controlled tubular continuous flow reactor reaches equilibrium.

[0024] In one embodiment, in S3, the mixed acid A and the mixture B are respectively pumped into a temperature-controlled tubular continuous flow reactor through a horizontal flow pump for mixing reaction to obtain a reaction liquid.

[0025] In one embodiment, when performing the mixing reaction in S3, the molar ratio of 2-chloro-4-fluorodichlorotoluene in the mixture B to the fuming nitric acid in the mixed acid A is 1:(1-1.2).

[0026] In a preferred embodiment, when performing the mixing reaction in S3, the molar ratio of 2-chloro-4-fluorodichlorotoluene in the mixture B to the fuming nitric acid in the mixed acid A is 1:1.08.

[0027] The inventors found in the experimental process that the amount of nitric acid used can be reduced by pumping the mixed acid A and the mixture B into a temperature-controlled tubular continuous flow reactor for mixed reaction. When the molar ratio of 2-chloro-4-fluorodichlorotoluene and the fuming nitric acid in the mixed acid A used in the present application is 1:(1-1.2), the content of 2-chloro-4-fluoro-5-nitrobenzaldehyde can be increased to more than 95%, and the conversion rate of 2-chloro-4-fluorodichlorotoluene can be increased to more than 99%.

[0028] In one embodiment, when the mixing reaction is carried out in S3, the molar ratio of 2-chloro-4-fluorodichlorotoluene in the mixture B and the fuming nitric acid in the mixed acid A is controlled by adjusting the pumping flow rate of the mixed acid A in S3 pumped into the temperature-controlled tubular continuous flow reactor and the pumping flow rate of the mixture B pumped into the temperature-controlled tubular continuous flow reactor.

[0029] In one embodiment, the temperature of the material in the temperature-controlled tubular continuous flow reactor in S3 is controlled to be -10 to 5°C.

[0030] In a preferred embodiment, the reaction temperature of the mixed acid A and the mixture B in S3 is controlled to be -6 to -2°C.

[0031] In one embodiment, the temperature-controlled tubular continuous flow reactor in S3 realizes a cyclic reaction of the mixed acid A and the mixture B in the tubular continuous flow reactor.

[0032] In one embodiment, the outlet of the temperature-controlled tubular continuous flow reactor in S3 continuously discharges material, and the material circulates inside the tubular reactor through a pump, and the linear velocity of the material circulation is 0.2 to 2 m / s.

[0033] In one embodiment, the linear speed of the material circulation includes but is not limited to 0.2m / s, 0.3m / s, 0.4m / s, 0.5m / s, 0.6m / s, 0.7m / s, 0.8m / s, 0.9m / s, 1m / s, 1.1m / s, 1.2m / s, 1.3m / s, 1.4m / s, 1.5m / s, 1.6m / s, 1.7m / s, 1.8m / s, 1.9m / s, and 2m / s.

[0034] The inventors found in the experimental process that the mass concentration of concentrated sulfuric acid is 90-98%, the pumping flow rate of the mixed acid A in S3 pumped into the temperature-controlled tubular continuous flow reactor is 120-140 g / min; the pumping flow rate of the mixture B pumped into the temperature-controlled tubular continuous flow reactor is 35-42 g / min; the temperature-controlled tubular continuous flow reactor in S3 includes an external heat exchanger, and the temperature of the external heat exchanger is set to -6--2°C. By setting the temperature of the external heat exchanger to -6--2°C, the circulation temperature in the temperature-controlled tubular continuous flow reactor reaches equilibrium, and the outlet of the temperature-controlled tubular continuous flow reactor in S3 continuously discharges materials, and the materials circulate in the tubular reactor through a pump, and the linear speed of the material circulation is 0.2-2 m / s, which can increase the conversion rate of 2-chloro-4-fluorodichlorotoluene to more than 99%, and realize a continuous nitration process.

[0035] In one embodiment, the collected reaction solution is heated to 60-110° C. in S4.

[0036] In one embodiment, in S4, the collected reaction solution is heated to a temperature including but not limited to 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, and 110°C.

[0037] In one embodiment, in S4, the heated reaction solution is diluted and the temperature of the reaction solution is controlled to be no higher than 0° C., and solid-liquid separation is performed to obtain 2-chloro-4-fluoro-5-nitrobenzaldehyde.

[0038] In one embodiment, the reaction liquid is collected by a collecting tank in S4, and the reaction liquid in the collecting tank is transferred to a reaction kettle. The reaction liquid is heated to 100° C. and reacted until the residual amount of 2-chloro-4-fluoro-5-nitro-dichlorotoluene is less than 0.5%, and the reaction is stopped; the reaction system is cooled to below 0° C., and then slowly dripped into water, and the system temperature is controlled to be no higher than -2° C. by heat preservation. After the product crystallizes and precipitates, solid-liquid separation is performed to obtain 2-chloro-4-fluoro-5-nitrobenzaldehyde.

[0039] In order to solve the technical problem of continuous production of 2-chloro-4-fluoro-5-nitrobenzaldehyde, the inventors found during the experiment that a continuous nitration process can be carried out by adopting the above-mentioned preparation method, and the tubular reactor used in the present invention is simple and easy to operate. The use of a tubular reaction device can reduce the safety risk of the nitration reaction and improve the degree of automation control and production efficiency of the device.

[0040] Beneficial Effects

[0041] 1. In the present invention, by controlling the mass concentration of sulfuric acid and limiting the molar ratio of the mixed acid A and the mixture B, the conversion rate of the raw material 2-chloro-4-fluorodichlorotoluene can be increased, and the content of 2-chloro-4-fluoro-5-nitrobenzaldehyde can be increased.

[0042] 2. In the present invention, the mixed acid A and the mixture B are pumped into a temperature-controlled tubular continuous flow reactor for a mixed reaction, thereby reducing the amount of nitric acid used and the safety risk of the nitration reaction.

[0043] 3. The molar ratio of the mixed acid A to the mixture B in the present invention can increase the content of 2-chloro-4-fluoro-5-nitrobenzaldehyde to more than 95%, and can increase the conversion rate of 2-chloro-4-fluorodichlorotoluene to more than 99%.

[0044] 4. The present invention adopts a tubular continuous flow reactor with controllable temperature and cooling temperature control. The reactor is simple and easy to operate, and can reduce the safety risk of the nitration reaction and improve the degree of automation control and production efficiency of the device.

[0045] 5. The temperature-controllable tubular continuous flow reactor used in the present invention allows the circulating temperature in the temperature-controlled tubular continuous flow reactor to reach equilibrium, and the outlet of the temperature-controlled tubular continuous flow reactor in S3 continuously discharges materials, and the materials circulate inside the tubular reactor through a pump, thereby improving the conversion rate of the raw material 2-chloro-4-fluorodichlorotoluene and realizing a continuous nitration process. DETAILED DESCRIPTION

[0046] Example 1

[0047] This embodiment provides a method for continuously producing 2-chloro-4-fluoro-5-nitrobenzaldehyde, comprising the following steps:

[0048] S1. The fuming nitric acid and concentrated sulfuric acid are mixed to prepare a mixed acid A;

[0049] S2. 2-chloro-4-fluorotoluene dichloride and dichloromethane are mixed to prepare a mixture B;

[0050] S3. The mixed acid A and the mixture B are pumped into a temperature-controlled tubular continuous flow reactor for mixed reaction to obtain a reaction solution;

[0051] S4. Collect the reaction solution, heat up, dilute and crystallize the reaction solution to obtain 2-chloro-4-fluoro-5-nitrobenzaldehyde.

[0052] The mass concentration of the concentrated sulfuric acid is 93%.

[0053] The mass concentration of the fuming nitric acid is 95%.

[0054] The molar ratio of fuming nitric acid to concentrated sulfuric acid in S1 is 1:8.8.

[0055] The weight of dichloromethane in S2 is 80% of the weight of 2-chloro-4-fluorodichlorotoluene.

[0056] The temperature-controlled tubular continuous flow reactor in S3 includes an external heat exchanger, and the temperature of the external heat exchanger is set to -2°C. By setting the temperature of the external heat exchanger to -2°C, the circulating temperature in the temperature-controlled tubular continuous flow reactor reaches equilibrium.

[0057] In S3, the mixed acid A and the mixture B are respectively pumped into a temperature-controlled tubular continuous flow reactor through a horizontal flow pump for mixing reaction to obtain a reaction liquid.

[0058] The mixed acid A in S3 is pumped into the temperature-controlled tubular continuous flow reactor at a pumping rate of 129.73 g / min.

[0059] The mixture B was pumped into the temperature-controlled tubular continuous flow reactor at a pumping rate of 38.95 g / min.

[0060] When the mixing reaction is carried out in S3, the molar ratio of 2-chloro-4-fluorodichlorotoluene in the mixture B to the fuming nitric acid in the mixed acid A is 1:1.08.

[0061] The added mass of 2-chloro-4-fluorodichlorotoluene in S3 is 1000 g.

[0062] In S3, the reaction temperature of the mixed acid A and the mixture B for the mixed reaction is controlled to be -2°C.

[0063] The outlet of the temperature-controlled tubular continuous flow reactor in S3 continuously discharges materials, and the materials circulate inside the tubular reactor through a pump, and the linear speed of the material circulation is 1 m / s.

[0064] In the step S4, the reaction liquid is collected by a collecting tank, the reaction liquid in the collecting tank is transferred to a reaction kettle, the reaction liquid is heated to 100° C., and the reaction is performed until the residual amount of 2-chloro-4-fluoro-5-nitro-dichlorotoluene is less than 0.5% at the end, and the reaction is stopped; the reaction system is cooled to -2° C., and then 3.3 kg of water is slowly dripped into it, and the system temperature is controlled not to be higher than -2° C. by heat preservation. After the product is crystallized, solid-liquid separation is performed to obtain 2-chloro-4-fluoro-5-nitrobenzaldehyde.

[0065] Example 2

[0066] This embodiment provides a method for continuously producing 2-chloro-4-fluoro-5-nitrobenzaldehyde, comprising the following steps:

[0067] S1. The fuming nitric acid and concentrated sulfuric acid are mixed to prepare a mixed acid A;

[0068] S2. 2-chloro-4-fluorotoluene dichloride and dichloromethane are mixed to prepare a mixture B;

[0069] S3. The mixed acid A and the mixture B are pumped into a temperature-controlled tubular continuous flow reactor for mixed reaction to obtain a reaction solution;

[0070] S4. Collect the reaction solution, heat up, dilute and crystallize the reaction solution to obtain 2-chloro-4-fluoro-5-nitrobenzaldehyde.

[0071] The mass concentration of the concentrated sulfuric acid is 95%.

[0072] The mass concentration of the fuming nitric acid is 95%.

[0073] The molar ratio of fuming nitric acid to concentrated sulfuric acid in S1 is 1:8.8.

[0074] The weight of dichloromethane in S2 is 80% of the weight of 2-chloro-4-fluorodichlorotoluene.

[0075] The temperature-controlled tubular continuous flow reactor in S3 includes an external heat exchanger, and the temperature of the external heat exchanger is set to -2°C. By setting the temperature of the external heat exchanger to -2°C, the circulating temperature in the temperature-controlled tubular continuous flow reactor reaches equilibrium.

[0076] In S3, the mixed acid A and the mixture B are respectively pumped into a temperature-controlled tubular continuous flow reactor through a horizontal flow pump for mixing reaction to obtain a reaction liquid.

[0077] The mixed acid A in S3 is pumped into the temperature-controlled tubular continuous flow reactor at a pumping rate of 129.73 g / min.

[0078] The mixture B was pumped into the temperature-controlled tubular continuous flow reactor at a pumping rate of 38.95 g / min.

[0079] When the mixing reaction is carried out in S3, the molar ratio of 2-chloro-4-fluorodichlorotoluene in the mixture B to the fuming nitric acid in the mixed acid A is 1:1.08.

[0080] The added mass of 2-chloro-4-fluorodichlorotoluene in S3 is 1000 g.

[0081] In S3, the reaction temperature of the mixed acid A and the mixture B for the mixed reaction is controlled to be -2°C.

[0082] The outlet of the temperature-controlled tubular continuous flow reactor in S3 continuously discharges materials, and the materials circulate inside the tubular reactor through a pump, and the linear speed of the material circulation is 1 m / s.

[0083] In the step S4, the reaction liquid is collected by a collecting tank, the reaction liquid in the collecting tank is transferred to a reaction kettle, the reaction liquid is heated to 100° C., and the reaction is performed until the residual amount of 2-chloro-4-fluoro-5-nitro-dichlorotoluene is less than 0.5% at the end, and the reaction is stopped; the reaction system is cooled to -2° C., and then 3.3 kg of water is slowly dripped into it, and the system temperature is controlled not to be higher than -2° C. by heat preservation. After the product is crystallized, solid-liquid separation is performed to obtain 2-chloro-4-fluoro-5-nitrobenzaldehyde.

[0084] Example 3

[0085] This embodiment provides a method for continuously producing 2-chloro-4-fluoro-5-nitrobenzaldehyde, comprising the following steps:

[0086] S1. The fuming nitric acid and concentrated sulfuric acid are mixed to prepare a mixed acid A;

[0087] S2. 2-chloro-4-fluorotoluene dichloride and dichloromethane are mixed to prepare a mixture B;

[0088] S3. The mixed acid A and the mixture B are pumped into a temperature-controlled tubular continuous flow reactor for mixed reaction to obtain a reaction solution;

[0089] S4. Collect the reaction solution, heat up, dilute and crystallize the reaction solution to obtain 2-chloro-4-fluoro-5-nitrobenzaldehyde.

[0090] The mass concentration of the concentrated sulfuric acid is 93%.

[0091] The mass concentration of the fuming nitric acid is 95%.

[0092] The molar ratio of fuming nitric acid to concentrated sulfuric acid in S1 is 1:8.8.

[0093] The weight of dichloromethane in S2 is 80% of the weight of 2-chloro-4-fluorodichlorotoluene.

[0094] The temperature-controlled tubular continuous flow reactor in S3 includes an external heat exchanger, and the temperature of the external heat exchanger is set to -2°C. By setting the temperature of the external heat exchanger to -2°C, the circulating temperature in the temperature-controlled tubular continuous flow reactor reaches equilibrium.

[0095] In S3, the mixed acid A and the mixture B are respectively pumped into a temperature-controlled tubular continuous flow reactor through a horizontal flow pump for mixing reaction to obtain a reaction liquid.

[0096] The mixed acid A in S3 is pumped into the temperature-controlled tubular continuous flow reactor at a pumping rate of 152.62 g / min.

[0097] The mixture B was pumped into the temperature-controlled tubular continuous flow reactor at a pumping rate of 45.82 g / min.

[0098] When the mixing reaction is carried out in S3, the molar ratio of 2-chloro-4-fluorodichlorotoluene in the mixture B to the fuming nitric acid in the mixed acid A is 1:1.08.

[0099] The added mass of 2-chloro-4-fluorodichlorotoluene in S3 is 1000 g.

[0100] In S3, the reaction temperature of the mixed acid A and the mixture B for the mixed reaction is controlled to be -2°C.

[0101] The outlet of the temperature-controlled tubular continuous flow reactor in S3 continuously discharges materials, and the materials circulate inside the tubular reactor through a pump, and the linear speed of the material circulation is 1 m / s.

[0102] In the step S4, the reaction liquid is collected by a collecting tank, the reaction liquid in the collecting tank is transferred to a reaction kettle, the reaction liquid is heated to 100° C., and the reaction is performed until the residual amount of 2-chloro-4-fluoro-5-nitro-dichlorotoluene is less than 0.5% at the end, and the reaction is stopped; the reaction system is cooled to -2° C., and then 3.3 kg of water is slowly dripped into it, and the system temperature is controlled not to be higher than -2° C. by heat preservation. After the product is crystallized, solid-liquid separation is performed to obtain 2-chloro-4-fluoro-5-nitrobenzaldehyde.

[0103] Example 4

[0104] This embodiment provides a method for continuously producing 2-chloro-4-fluoro-5-nitrobenzaldehyde, comprising the following steps:

[0105] S1. The fuming nitric acid and concentrated sulfuric acid are mixed to prepare a mixed acid A;

[0106] S2. 2-chloro-4-fluorotoluene dichloride and dichloromethane are mixed to prepare a mixture B;

[0107] S3. The mixed acid A and the mixture B are pumped into a microchannel flow reactor for a mixed reaction to obtain a reaction solution;

[0108] S4. Collect the reaction solution, heat up, dilute and crystallize the reaction solution to obtain 2-chloro-4-fluoro-5-nitrobenzaldehyde.

[0109] The mass concentration of the concentrated sulfuric acid is 95%.

[0110] The mass concentration of the fuming nitric acid is 95%.

[0111] The molar ratio of fuming nitric acid to concentrated sulfuric acid in S1 is 1:8.8.

[0112] The weight of dichloromethane in S2 is 80% of the weight of 2-chloro-4-fluorodichlorotoluene.

[0113] The microchannel flow reactor in S3 includes an external heat exchanger, and the temperature of the external heat exchanger is set to -2°C

[0114] In S3, the mixed acid A and the mixture B are respectively pumped into a microchannel flow reactor by a horizontal flow pump to perform a mixing reaction to obtain a reaction solution.

[0115] The pumping flow rate of the mixed acid A in S3 pumped into the microchannel flow reactor is 129.73 g / min.

[0116] The pumping flow rate of the mixture B into the microchannel flow reactor was 38.95 g / min.

[0117] When the mixing reaction is carried out in S3, the molar ratio of 2-chloro-4-fluorodichlorotoluene in the mixture B to the fuming nitric acid in the mixed acid A is 1:1.08.

[0118] The added mass of 2-chloro-4-fluorodichlorotoluene in S3 is 1000 g.

[0119] In S3, the reaction temperature of the mixed acid A and the mixture B for the mixed reaction is controlled to be -2°C.

[0120] In the step S4, the reaction liquid is collected by a collecting tank, the reaction liquid in the collecting tank is transferred to a reaction kettle, the reaction liquid is heated to 100° C., and the reaction is performed until the residual amount of 2-chloro-4-fluoro-5-nitro-dichlorotoluene is less than 0.5% at the end, and the reaction is stopped; the reaction system is cooled to -2° C., and then 3.3 kg of water is slowly dripped into it, and the system temperature is controlled not to be higher than -2° C. by heat preservation. After the product is crystallized, solid-liquid separation is performed to obtain 2-chloro-4-fluoro-5-nitrobenzaldehyde.

[0121] Performance Testing

[0122] 1. Content test

[0123] The specific contents of the components of the 2-chloro-4-fluoro-5-nitrobenzaldehyde obtained in Example 1-4 were tested by gas chromatography. The test results are shown in Table 1. The conversion rate of 2-chloro-4-fluorodichlorotoluene was calculated. The test results are shown in Table 2.

[0124] Raw material conversion rate = reacted raw material mole amount / original raw material mole amount * 100%.

[0125] Table 1

[0126]

[0127] Table 2

[0128] Example Raw material conversion rate Example 1 99.77％ Example 2 100.00％ Example 3 99.81％ Example 4 97.69％

[0129] It can be seen from the test results in Table 1 that in Example 4, a microchannel reactor is used. Compared with Examples 1-3, the contents of impurities 2-chloro-4-fluoro-3-nitrobenzaldehyde and 2-chloro-4-fluoro-5-nitrobenzoic acid in Example 4 are increased, and the content of 2-chloro-4-fluoro-5-nitrobenzaldehyde in Example 4 is also reduced.

[0130] The description of the contents of the present invention is illustrative and is not intended to limit the scope of the present invention to the above-mentioned embodiments. Therefore, the present invention is not limited to the embodiments, and any technical solution obtained by equivalent replacement using the inventive concept of the present invention is within the scope of protection of the present invention.

Claims

1. A method for continuously producing 2-chloro-4-fluoro-5-nitrobenzaldehyde, characterized in that: The following steps are involved: S1. The fuming nitric acid and concentrated sulfuric acid are mixed to prepare a mixed acid A; S2. 2-chloro-4-fluorotoluene dichloride is mixed with an organic solvent to prepare a mixture B; S3. The mixed acid A and the mixture B are pumped into a temperature-controlled tubular continuous flow reactor for mixed reaction to obtain a reaction solution; S4. Collect the reaction solution, heat up, dilute and crystallize the reaction solution to obtain 2-chloro-4-fluoro-5-nitrobenzaldehyde.

2. The method for continuous production of 2-chloro-4-fluoro-5-nitrobenzaldehyde according to claim 1, characterized in that: The mass concentration of the fuming nitric acid in the S1 is ≥95%, and the mass concentration of the concentrated sulfuric acid is 90-98%.

3. The method for continuous production of 2-chloro-4-fluoro-5-nitrobenzaldehyde according to claim 1, characterized in that: The molar ratio of fuming nitric acid to concentrated sulfuric acid in S1 is 1:(5-10).

4. The method for continuous production of 2-chloro-4-fluoro-5-nitrobenzaldehyde according to claim 1, characterized in that: The organic solvent is selected from one or more combinations of 1,2-dichloroethane, dichloromethane, chloroform, n-pentane, n-hexane, and cyclohexane.

5. The method for continuous production of 2-chloro-4-fluoro-5-nitrobenzaldehyde according to claim 1, characterized in that: When the mixing reaction is carried out in S3, the molar ratio of 2-chloro-4-fluorodichlorotoluene in the mixture B to the fuming nitric acid in the mixed acid A is 1:(1-1.2).

6. The method for continuous production of 2-chloro-4-fluoro-5-nitrobenzaldehyde according to any one of claims 1 to 5, characterized in that: The temperature of the material in the temperature-controlled tubular continuous flow reactor in S3 is controlled to be -10 to 5°C.

7. The method for continuous production of 2-chloro-4-fluoro-5-nitrobenzaldehyde as claimed in claim 6, characterized in that: In the step S3, the reaction temperature of the mixed acid A and the mixture B for the mixed reaction is controlled to be -6 to -2°C.

8. The method for continuous production of 2-chloro-4-fluoro-5-nitrobenzaldehyde according to claim 1, characterized in that: The outlet of the temperature-controlled tubular continuous flow reactor in S3 continuously discharges materials, and the materials circulate inside the tubular reactor through a pump, and the linear speed of the material circulation is 0.2-2 m / s.

9. The method for continuous production of 2-chloro-4-fluoro-5-nitrobenzaldehyde according to claim 1, characterized in that: In the step S4, the collected reaction solution is heated to 60-110°C.

10. The method for continuous production of 2-chloro-4-fluoro-5-nitrobenzaldehyde according to claim 9, characterized in that: In the step S4, the heated reaction solution is diluted and then solid-liquid separation is performed to obtain 2-chloro-4-fluoro-5-nitrobenzaldehyde.

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