CN106748682A - A kind of method that 2,3 difluoro toluene continuous oxidation prepares 2,3 difluorobenzaldehydes - Google Patents

Abstract

The invention discloses a method for continuously oxidizing 2,3-difluorotoluene to prepare 2,3-difluorobenzaldehyde, belonging to the technical field of organic synthesis. The method uses 2,3-difluorotoluene compound as raw material, one or several metal ion complexes of cobalt, molybdenum, and bromine as catalyst, hydrogen peroxide as oxidant, and acetic acid as solvent, and the process is carried out continuously in a tubular reactor. Process technology for preparing 2,3-difluorobenzaldehyde by oxidation of 2,3-difluorotoluene. The method has mild conditions, short reaction time, high raw material utilization rate, effective control in the reaction process, safety and stability, continuous operation and high production efficiency.

Description

A kind of method for preparing 2,3-difluorobenzaldehyde by continuous oxidation of 2,3-difluorotoluene

technical field

The invention belongs to the technical field of organic synthesis technology, and relates to a method for continuously oxidizing 2,3-difluorotoluene to prepare 2,3-difluorobenzaldehyde under liquid-phase reaction conditions, more specifically, using 2,3-difluorotoluene Fluorotoluene is used as substrate, hydrogen peroxide is used as oxidant, one or several metal ion complexes of cobalt, molybdenum, and bromine are used as catalyst, and monocarboxylic acid is used as solvent. Continuously prepare 2 in tubular reactors with different microstructures, 3-Difluorobenzaldehyde product.

Background technique

2,3-Difluorobenzaldehyde, molecular formula: C ₇ H ₄ F ₂ O, molecular weight: 142.1, colorless to pale yellow liquid. The boiling point is 64-65°C, the density is 1.301g/ml, and the flash point is 58°C. It is an intermediate of medicine, pesticide, and liquid crystal material.

The current synthesis process method reported for 2,3-difluorobenzaldehyde is mainly prepared by the hydrolysis reaction of 2,3-difluorobenzyl chloride, and its specific synthetic route is as follows:

This method is to mix 2,3-difluorobenzyl chloride with urotropine, acetic acid and water for 4 hours, then add concentrated hydrochloric acid to reflux, extract with dichloromethane, wash with water and saturated sodium bicarbonate, collect the product, and the yield up to 68.8%. In the preparation process of the method, firstly, 2,3-difluorobenzyl chloride needs to be obtained by chlorination, and then hydrolyzed, and a large amount of catalyst is used to complete the reaction process. This method has the following defects: firstly, in chlorination, the control degree of chlorination is not easy to control; secondly, the consumption of catalyst is very large in this process; finally, this method will produce a large amount of waste acid waste water, causing three waste pollution , making the production cost increase. The continuous oxidation of 2,3-difluorotoluene to synthesize 2,3-difluorobenzaldehyde using a continuous flow tubular reactor with a specific structure can solve many shortcomings of the existing technology in many ways.

Tubular reactor is a general term for small reactors with microstructure. Compared with conventional reactors, tubular reactors have small volume, large specific surface area, easy enlargement, continuous process, good rapid mixing effect, and good heat transfer effect. With the characteristics of high temperature and high pressure resistance, the continuous flow tube reactor with a specific structure can effectively control the mixing of reaction materials, mass transfer and heat transfer process. By controlling the length of the tubular reactor and the reaction residence time, the distribution of raw materials and products can be further optimized and controllable; by adjusting the flow rate of the raw material pump, the substrate 2,3-difluorotoluene and the oxidant can enter in proportion The reaction in the tubular reactor greatly reduces the back mixing, further reduces the occurrence of side reactions, the stability of the oxidant and the selectivity of the target product are also greatly improved; by setting the pressure safety valve in the tubular reactor, it can be discharged in time The excess oxidant in the reactor ensures the safety of the reaction and minimizes the risk rate. The method for preparing 2,3-difluorobenzaldehyde by continuous oxidation of 2,3-difluorotoluene in a tubular reactor with a specific structure in the present invention has incomparable advantages over traditional batch production methods, and can be industrialized Improvement in continuous production provides an important avenue.

Contents of the invention

The present invention aims at the above shortcomings, and provides a method for continuously oxidizing 2,3-difluorotoluene in a tubular reactor to prepare 2,3-difluorobenzaldehyde. The method has short reaction time, high production efficiency, greatly optimized mass transfer and heat transfer, and a more stable and controllable reaction process. The further purpose of the present invention is to realize the stable and controllable continuous oxidation of 2,3-difluorotoluene and reduce the formation of by-products through the process method of the present invention. Through the intensification of mass transfer and heat transfer process and process optimization, the effective utilization rate of reaction materials can be improved, the usage of oxidants and catalysts can be further reduced, and the use of co-catalysts can be avoided in the reaction process, so as to effectively save production costs and improve the existing industrialization production method.

To achieve the above object, the technical solution adopted in the present invention is:

A method for preparing 2,3-difluorobenzaldehyde by continuous oxidation of 2,3-difluorotoluene by a tubular reactor with a special structure is carried out according to the following steps:

(1) First, at room temperature, stir and mix the substrate 2,3-difluorotoluene and the carboxylic acid solvent at a volume ratio of 1:1, mix the oxidizing agent and the carboxylic acid solvent at a volume ratio of 1:1, and then mix the metal The complex is mixed and poured into the 2,3-difluorotoluene-carboxylic acid solution, and the sodium salt is poured into the hydrogen peroxide-carboxylic acid solution; through the required reaction time, the different flow rates of the two materials are calculated and measured respectively The pump is pumped into the tubular reactor continuously, after preheating and mixing, it enters the reaction zone for reaction, and the reaction temperature is controlled by the external heat exchange system;

(2) Control the molar ratio of the reaction materials by adjusting the flow rate and weighing method, and control the residence time of the mixed reaction of the materials by 60-2000s by changing the inner diameter of the pipe of the tubular reactor from 0.5 to 15mm and the volume from 25 to 750ml; Finally, the product flows out from the end of the reactor into the collection tank, the product is rectified and separated, the unreacted 2,3-difluorotoluene is recycled, and the product 2,3-difluorobenzaldehyde is collected after rectification and purification, wherein the target product 2, The yield of 3-difluorobenzaldehyde can reach 5%-40%.

The catalyst described therein is one or more metal complex catalysts of cobalt, molybdenum and bromine, which mainly include: cobalt acetate, cobalt oxalate, cobalt carbonate, cobalt naphthenate, sodium molybdate, ammonium molybdate, bromide Sodium, ammonium bromide, etc., among which the oil-soluble catalyst is the main one, which can be fully dissolved in 2,3-difluorotoluene, and the molar ratio of its dosage to the substrate 2,3-difluorotoluene is (0.001～0.25): 1, wherein the preferred molar ratio is (0.01-0.15):1.

Wherein the oxidizing agent is hydrogen peroxide, and its solution concentration is 5%-50% in terms of mass concentration, preferably 10%-40%. The preferred molar ratio of hydrogen peroxide to the substrate 2,3-difluorotoluene is (1.0-7.0):1.

The hydrogen peroxide mentioned therein, in the tubular reactor, when the hydrogen peroxide passes through the reactor with a volume of 50ml, the hydrogen peroxide begins to decompose rapidly and release a large amount of molecular oxygen. When it passes through 100ml, it is almost in the form of molecular oxygen. Additional equal-concentration hydrogen peroxide is added to the reaction volume to participate in the reaction again.

Wherein the reaction temperature is 60-130°C, preferably the reaction temperature is 90-120°C, and the reaction residence time is 60s-2000s.

In a further technical solution, after the reaction is completed, sodium difluoromethane is used to quench the oxidizing agent not involved in the reaction, and then the target product is obtained by extraction with an organic solvent, separation and purification by distillation.

In the above technical solution, the reaction system includes different functional areas such as a raw material storage tank, a reaction area, and a product collection area. Reactor channel structures include: circular tube straight-through channel structure, round cake pulse variable diameter rectangular flat tube structure, oblique square cake pulse variable diameter rectangular flat tube structure, enhanced mixing circular cake type rectangular flat tube structure and Corning Heart Cell channel structure.

The present invention has the following advantages:

1. The present invention adopts a continuous production method with short reaction time, mild reaction conditions, safe and controllable process, and high production efficiency.

2. By adopting tubular reactors with different structures, the present invention can realize effective control of the reaction process, so that the reaction product stays in the aldol step.

3. Through the enhancement of mass transfer and heat transfer in the reaction process, the reaction rate and the utilization rate of raw materials are greatly improved, and the amount of oxidant and catalyst used is effectively reduced, and the use of co-catalyst is avoided, so that the production cost is effectively reduced saving.

4. The present invention has the advantages of simple operation, wide application range and flexible production, and the production scale can be enlarged through parallel connection of reaction devices.

Description of drawings

Fig. 1 is the process flow chart of the present invention for the continuous oxidation of 2,3-difluorotoluene to prepare 2,3-difluorobenzaldehyde.

Fig. 2 is the device figure of continuous flow tubular reactor used in the present invention: 1,2-raw material tank, 3,4-raw material metering pump, 5-preheating zone, 6,7-reaction zone, 8-product quenching collection area.

Fig. 3 is a schematic diagram of the channel structure of the tubular reactor used in the present invention, wherein a-straight-flow channel structure, b-round cake type pulse variable diameter rectangular flat pipe, c-orthorhombic cake type pulse variable diameter rectangular flat pipe , d-enhanced mixed round pie flat pipe, e-Corning's Heart Cell structure microchannel.

detailed description

Dissolve cobalt acetate and sodium molybdate in the 1# tank containing 2,3-difluorotoluene and acetic acid, and send it into the 5# preheating reactor through the 3# pump, and the preheating reactor is heated to 50 °C; Dissolve sodium bromide in the 2# tank with hydrogen peroxide and acetic acid, and send it into the 6# preheating reactor through the 4# pump. The preheating reactor is heated to 50 ° C, and then the two preheated materials are transported to 7 In # and 8# reactors, the temperature of the reactors was set at the required temperature for the reaction, and the product flowed out through the 8# reactor, cooled at 0°C, and the resulting product was collected.

The present invention will be described in detail below in conjunction with the examples, but the following examples are only preferred embodiments of the present invention, and the scope of protection of the present invention is not limited thereto, and any person familiar with the technical field of the present invention is within the technical scope disclosed in the present invention Within the technical scheme of the present invention and its inventive concept, any equivalent substitution or change shall be covered within the protection scope of the present invention.

Example 1

(1) Device: Refer to Figure 2 to determine the connection mode of the tubular reactor. The pipeline type is: (3a+3b) straight-line channel + round cake-type pulse variable-diameter rectangular flat pipeline. The inner diameter and volume of the pipeline are based on the flow rate and reaction residence time. The time is determined, and the heat exchange medium is heat transfer oil.

(2) Dissolve 2.02g cobalt acetate and 2.02g sodium molybdate in 200ml2,3-difluorotoluene and 200ml acetic acid respectively to form a mixed solution. At this time, n(cobalt acetate):n(2,3-difluorotoluene)= 0.005:1, 2.02g sodium bromide is dissolved in 15% H ₂ O ₂ to form H ₂ O ₂ -acetic acid solution, at this time n(sodium bromide):n(2,3-difluorotoluene)=0.005:1 , 2,3-difluorotoluene-acetic acid solution and H ₂ O ₂ -acetic acid solution were injected into the tubular reactor with continuous heat exchange through the constant flow pump at the flow rate of 5.33ml/min and 5.33ml/min respectively. n(H ₂ O ₂ ):n(2,3-difluorotoluene)=1:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 60°C, and the residence time was 60s. The outlet material was cooled at 0°C, and the reaction solution was quenched with difluoromethane. After GC analysis, the conversion rate of 2,3-difluorotoluene was 29.3%, and the yield of 2,3-difluorobenzaldehyde was 18.1%.

Example 2

(1) Device: Refer to Figure 2 to determine the connection mode of the tubular reactor. The pipeline type is: (3a+3c) straight-line channel + oblique square cake-type pulse variable-diameter rectangular flat pipeline. The inner diameter and volume of the pipeline are based on the flow rate and reaction. The residence time is determined, and the heat transfer medium is heat transfer oil.

(2) Dissolve 6.06g cobalt acetate and 6.06g sodium molybdate in 200ml2,3-difluorotoluene and 200ml acetic acid respectively to form a mixed solution. At this time, n(cobalt acetate):n(2,3-difluorotoluene)= 0.015:1, 6.06g sodium bromide is dissolved in 15% H ₂ O ₂ to form H ₂ O ₂ -acetic acid solution, at this time n(sodium bromide):n(2,3-difluorotoluene)=0.015:1 , 2,3-difluorotoluene-acetic acid solution and H ₂ O ₂ -acetic acid solution were injected into the tubular reactor with continuous heat exchange through the constant flow pump at the flow rate of 5.33ml/min and 37.31ml/min respectively. n(H ₂ O ₂ ):n(2,3-difluorotoluene)=7:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 70°C, and the residence time was 300s. The outlet material was cooled at 0°C, and the reaction solution was quenched with difluoromethane. After GC analysis, the conversion rate of 2,3-difluorotoluene was 55.07%, and the yield of 2,3-difluorobenzaldehyde was 42.07%.

Example 3

(1) Device: Refer to Figure 2 to determine the connection mode of the tubular reactor. The pipeline type is: (3a+3d) straight-through channel + enhanced mixing round cake type rectangular flat pipeline. The inner diameter and volume of the pipeline are based on the flow rate and reaction residence time. Make sure that the heat exchange medium is heat transfer oil.

(2) Dissolve 6.06g cobalt acetate and 6.06g sodium molybdate in 200ml2,3-difluorotoluene and 200ml acetic acid respectively to form a mixed solution. At this time, n(cobalt acetate):n(2,3-difluorotoluene)= 0.01:1, 6.06g sodium bromide is dissolved in 15% H ₂ O ₂ to form H ₂ O ₂ -acetic acid solution, at this time n(sodium bromide):n(2,3-difluorotoluene)=0.01:1 , 2,3-difluorotoluene-acetic acid solution and H ₂ O ₂ -acetic acid solution were injected into the tubular reactor with continuous heat exchange through the constant flow pump at the flow rate of 8.33ml/min and 16.67ml/min respectively. n(H ₂ O ₂ ):n(2,3-difluorotoluene)=2:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 90°C, and the residence time was 600s. The outlet material was cooled at 0°C, and the reaction solution was quenched with difluoromethane. After GC analysis, the conversion rate of 2,3-difluorotoluene was 41.8%, and the yield of 2,3-difluorobenzaldehyde was 24.2%.

Example 4

(1) Device: Refer to Figure 2 to determine the connection mode of the tubular reactor. The pipeline type is: (3a+3b) straight-line channel + round cake-type pulse variable-diameter rectangular flat pipeline. The inner diameter and volume of the pipeline are based on the flow rate and reaction residence time. The time is determined, and the heat exchange medium is heat transfer oil.

(2) 17.69g cobalt acetate and 17.69g sodium molybdate were dissolved in 200ml2,3-difluorotoluene and 200ml acetic acid respectively to form a mixed solution. At this time, n(cobalt acetate):n(2,3-difluorotoluene)= 0.15:1, 17.69g sodium bromide is dissolved in 25% H ₂ O ₂ to form H ₂ O ₂ -acetic acid solution, at this time n(sodium bromide):n(2,3-difluorotoluene)=0.15:1 , 2,3-difluorotoluene-acetic acid solution and H ₂ O ₂ -acetic acid solution were injected into the tubular reactor with continuous heat exchange through the constant flow pump at the flow rate of 5.33ml/min and 10.67ml/min respectively. n(H ₂ O ₂ ):n(2,3-difluorotoluene)=2:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 105°C, and the residence time was 900s. The outlet material was cooled at 0°C, and the reaction solution was quenched with difluoromethane. After GC analysis, the conversion rate of 2,3-difluorotoluene was 51.5%, and the yield of 2,3-difluorobenzaldehyde was 32.1%.

Example 5

(1) Device: Refer to Figure 2 to determine the connection mode of the tubular reactor. The pipeline type is: (3a+3c) straight-line channel + oblique square cake-type pulse variable-diameter rectangular flat pipeline. The inner diameter and volume of the pipeline are based on the flow rate and reaction. The residence time is determined, and the heat transfer medium is heat transfer oil.

(2) Dissolve 6.06g cobalt acetate and 6.06g sodium molybdate in 200ml2,3-difluorotoluene and 200ml acetic acid respectively to form a mixed solution. At this time, n(cobalt acetate):n(2,3-difluorotoluene)= 0.015:1, 6.06g sodium bromide is dissolved in 25% H ₂ O ₂ to form H ₂ O ₂ -acetic acid solution, at this time n(sodium bromide):n(2,3-difluorotoluene)=0.015:1 , 2,3-difluorotoluene-acetic acid solution and H ₂ O ₂ -acetic acid solution were injected into the tubular reactor with continuous heat exchange through the constant flow pump at the flow rate of 8.33ml/min and 16.67ml/min respectively. n(H ₂ O ₂ ):n(2,3-difluorotoluene)=2:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 90°C, and the residence time was 1000s. The outlet material was cooled at 0°C, and the reaction solution was quenched with difluoromethane. After GC analysis, the conversion rate of 2,3-difluorotoluene was 22.7%, and the yield of 2,3-difluorobenzaldehyde was 19.1%.

Example 6

(1) Device: Refer to Figure 2 to determine the connection mode of the tubular reactor. The pipeline type is: (3a+3d) straight-through channel + enhanced mixing round cake type rectangular flat pipeline. The inner diameter and volume of the pipeline are based on the flow rate and reaction residence time. Make sure that the heat exchange medium is heat transfer oil.

(2) Dissolve 6.06g cobalt acetate and 6.06g sodium molybdate in 200ml2,3-difluorotoluene and 200ml acetic acid respectively to form a mixed solution. At this time, n(cobalt acetate):n(2,3-difluorotoluene)= 0.015:1, 6.06g sodium bromide is dissolved in 25% H ₂ O ₂ to form H ₂ O ₂ -acetic acid solution, at this time n(sodium bromide):n(2,3-difluorotoluene)=0.015:1 , 2,3-difluorotoluene-acetic acid solution and H ₂ O ₂ -acetic acid solution were injected into the tubular reactor with continuous heat exchange through the constant flow pump at the flow rate of 5.56ml/min and 11.11ml/min respectively. n(H ₂ O ₂ ):n(2,3-difluorotoluene)=2:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 120°C, and the residence time was 1000s. The outlet material was cooled at 0°C, and the reaction solution was quenched with difluoromethane. After GC analysis, the conversion rate of 2,3-difluorotoluene was 51.7%, and the yield of 2,3-difluorobenzaldehyde was 43.0%.

Example 7

(1) Device: Refer to Figure 2 to determine the connection mode of the tubular reactor. The pipe type is: (3a+3e) straight-through channel + Corningde Heart Cell structure. The inner diameter and volume of the pipe are determined according to the flow rate and reaction residence time. The heat exchange medium For heat transfer oil.

(2) Dissolve 6.06g cobalt acetate and 6.06g sodium molybdate in 200ml2,3-difluorotoluene and 200ml acetic acid respectively to form a mixed solution. At this time, n(cobalt acetate):n(2,3-difluorotoluene)= 0.015:1, 6.06g sodium bromide is dissolved in 25% H ₂ O ₂ to form H ₂ O ₂ -acetic acid solution, at this time n(sodium bromide):n(2,3-difluorotoluene)=0.015:1 , 2,3-difluorotoluene-acetic acid solution and H ₂ O ₂ -acetic acid solution were injected into the tubular reactor with continuous heat exchange through the constant flow pump at the flow rate of 5.56ml/min and 11.11ml/min respectively. n(H ₂ O ₂ ):n(2,3-difluorotoluene)=2:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 120°C, and the residence time was 60s. The outlet material was cooled at 0°C, and the reaction solution was quenched with difluoromethane. After GC analysis, the conversion rate of 2,3-difluorotoluene was 8.5%, and the yield of 2,3-difluorobenzaldehyde was 3.5%.

Example 8

(1) Device: Refer to Figure 2 to determine the connection mode of the tubular reactor. The pipeline type is: (3a+3d) straight-through channel + enhanced mixing round cake type rectangular flat pipeline. The inner diameter and volume of the pipeline are based on the flow rate and reaction residence time. Make sure that the heat exchange medium is heat transfer oil.

(2) Dissolve 6.06g cobalt acetate and 6.06g sodium molybdate in 200ml2,3-difluorotoluene and 200ml acetic acid respectively to form a mixed solution. At this time, n(cobalt acetate):n(2,3-difluorotoluene)= 0.015:1, 6.06g sodium bromide is dissolved in 35% H ₂ O ₂ to form H ₂ O ₂ -acetic acid solution, at this time n(sodium bromide):n(2,3-difluorotoluene)=0.015:1 , 2,3-difluorotoluene-acetic acid solution and H ₂ O ₂ -acetic acid solution were injected into the tubular reactor with continuous heat exchange through the constant flow pump at the flow rate of 5.56ml/min and 11.11ml/min respectively. n(H ₂ O ₂ ):n(2,3-difluorotoluene)=2:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 120°C, and the residence time was 2000s. The outlet material was cooled at 0°C, and the reaction solution was quenched with difluoromethane. After GC analysis, the conversion rate of 2,3-difluorotoluene was 61.9%, and the yield of 2,3-difluorobenzaldehyde was 42.1%.

Example 9

(1) Device: Refer to Figure 2 to determine the connection mode of the tubular reactor. The pipeline type is: (3a+3c) straight-line channel + oblique square cake-type pulse variable-diameter rectangular flat pipeline. The inner diameter and volume of the pipeline are based on the flow rate and reaction. The residence time is determined, and the heat transfer medium is heat transfer oil.

(2) Dissolve 6.06g cobalt acetate and 6.06g sodium molybdate in 200ml2,3-difluorotoluene and 200ml acetic acid respectively to form a mixed solution. At this time, n(cobalt acetate):n(2,3-difluorotoluene)= 0.015:1, 6.06g sodium bromide is dissolved in 35% H ₂ O ₂ to form H ₂ O ₂ -acetic acid solution, at this time n(sodium bromide):n(2,3-difluorotoluene)=0.015:1 , 2,3-difluorotoluene-acetic acid solution and H ₂ O ₂ -acetic acid solution were injected into the tubular reactor with continuous heat exchange through the constant flow pump at the flow rate of 5.56ml/min and 11.11ml/min respectively. n(H ₂ O ₂ ):n(2,3-difluorotoluene)=2:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 120°C, and the residence time was 1500s. The outlet material was cooled at 0°C, and the reaction solution was quenched with difluoromethane. After GC analysis, the conversion rate of 2,3-difluorotoluene was 65.1%, and the yield of 2,3-difluorobenzaldehyde was 48.2%.

Claims (6)

1. a method for preparing 2,3-difluorobenzaldehyde by continuous oxidation of 2,3-difluorotoluene is characterized in that it is carried out according to the following steps: (1) First, at room temperature, stir and mix the substrate 2,3-difluorotoluene and the carboxylic acid solvent at a volume ratio of 1:1, mix the oxidizing agent and the carboxylic acid solvent at a volume ratio of 1:1, and then mix the metal The complex is mixed and poured into the 2,3-difluorotoluene-carboxylic acid solution, and the sodium salt is poured into the hydrogen peroxide-carboxylic acid solution; through the required reaction time, the different flow rates of the two materials are calculated and measured respectively The pump is pumped into the tubular reactor continuously, after preheating and mixing, it enters the reaction zone for reaction, and the reaction temperature is controlled by the external heat exchange system; (2) Control the molar ratio of the reaction materials by adjusting the flow rate and weighing method, and control the residence time of the mixed reaction of the materials by 60~2000s by changing the inner diameter of the pipe of the tubular reactor from 0.5 to 15mm and the volume from 25 to 750ml; after the reaction is completed Finally, the product flows out from the end of the reactor into the collection tank, the product is rectified and separated, the unreacted 2,3-difluorotoluene is recycled, and the product 2,3-difluorobenzaldehyde is collected after rectification and purification. 2. according to claims 1, a kind of 2,3-difluorotoluene continuous oxidation prepares the method for 2,3-difluorobenzaldehyde, it is characterized in that described catalyst is one or more of cobalt, molybdenum, sodium A metal complex catalyst, which mainly includes: cobalt acetate, cobalt oxalate, cobalt carbonate, cobalt naphthenate, sodium molybdate, ammonium molybdate, sodium bromide, ammonium bromide, etc., wherein the oil-soluble catalyst is the main one, It can be fully dissolved in 2,3-difluorotoluene, and the molar ratio of its dosage to the substrate 2,3-difluorotoluene is (0.001~0.25):1, and the preferred molar ratio is (0.01~0.15):1. 3. according to claims 1, a kind of 2,3-difluorotoluene continuous oxidation prepares the method for 2,3-difluorobenzaldehyde, it is characterized in that described oxygenant is hydrogen peroxide, and its solution concentration is in mass concentration 5%~50%, the preferred concentration is 10%~40%, and the preferred molar ratio of hydrogen peroxide to substrate 2,3-difluorotoluene is (1.0~7.0):1. 4. according to claim 1, a kind of 2,3-difluorotoluene continuous oxidation prepares the method for 2,3-difluorobenzaldehyde, it is characterized in that described carboxylic acid solvent comprises: formic acid, acetic acid, propionic acid , butyric acid, hexanoic acid, octanoic acid; the volume ratio of solvent to 2,3-difluorotoluene is (1~8):1. 5. A method for preparing 2,3-difluorobenzaldehyde by continuous oxidation of 2,3-difluorotoluene according to claim 1, characterized in that: the reaction temperature is 60~130°C, preferably the reaction temperature is 90 ~120℃, reaction residence time 60s~2000s. 6. according to the method for preparing 2,3-difluorobenzaldehyde by a kind of 2,3-difluorotoluene continuous oxidation described in claim 1, it is characterized in that whole reaction process is all continuous in the tubular reactor of specific structure The reaction system includes different functional areas such as raw material storage tanks, reaction areas, and product collection; the reactor channel structure includes: circular tube straight-through channel structure, circular cake-type pulse variable-diameter rectangular flat pipe structure, orthorhombic cake-type pulse Variable-diameter rectangular flat pipe structure, reinforced hybrid circular pie rectangular flat pipe structure, and heart-shaped channel structure.