CN106699526A - Method of preparing 2,4-dichlorobenzaldehyde through continuous oxidation of 2,4-dichlorotoluene - Google Patents

Abstract

The invention discloses a method for preparing 2,4-dichlorobenzaldehyde by continuous oxidation of 2,4-dichlorotoluene, which belongs to the technical field of organic synthesis technology. The method uses 2,4-dichlorotoluene 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. Process technology for preparing 2,4-dichlorobenzaldehyde by oxidation of 2,4-dichlorotoluene. 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 2,4-dichlorobenzaldehyde by continuous oxidation of 2,4-dichlorotoluene

technical field

The invention belongs to the technical field of organic synthesis technology, and relates to a method for preparing 2,4-dichlorobenzaldehyde by continuous oxidation of 2,4-dichlorotoluene under liquid-phase reaction conditions, more specifically, using 2,4-dichlorobenzaldehyde Chlorotoluene is used as a substrate, hydrogen peroxide is used as an oxidant, one or several metal ion complexes of cobalt, molybdenum, and bromine are used as catalysts, and monocarboxylic acids are used as solvents. Continuously prepare 2 in tubular reactors with different microstructures, 4-Dichlorobenzaldehyde product.

Background technique

2,4-Dichlorobenzaldehyde is a very important fine chemical, it is an intermediate in the synthesis of many important chemicals, 2,4-Dichlorobenzaldehyde is used to produce dye intermediates benzaldehyde-2,4-di Sulfonic acid, while benzaldehyde-2,4-disulfonic acid is used to synthesize active blue K-FGR, acid lake blue A, acid lake blue V, and 2,4-dichlorobenzaldehyde is also used to produce the pesticide diniconazole. It can be seen that 2,4-dichlorobenzaldehyde has shown a very broad application prospect. However, so far, the demand for 2,4-dichlorobenzaldehyde in my country is all imported, and the price is expensive, which greatly affects and limits the development of all aspects.

Present 2,4-dichlorobenzaldehyde reported synthetic technique method has following several kinds:

(1) Take 2,4-dichlorotoluene as the synthetic route of raw material

D.A. Xiao Lai of the United States once introduced that α, α-dibromo-2,4-dichlorotoluene can be prepared by bromination of 2,4-dichlorotoluene, and then 2,4-dichlorobenzaldehyde can be prepared by one-step reaction. Concrete reaction process is as follows:

Although the product yield and purity of the above-mentioned route are high, and the synthesis is simple, it is difficult to realize large-scale industrial application due to the need for a large amount of bromine with low cost.

(2) Chlorination reaction on the side chain

Hei Encheng and others also adopted the method of direct chlorination and hydrolysis in the synthesis research, considering the possibility of raw materials, catalysts and industrialization. The specific reaction method is as follows:

In the production process of the above method, it is necessary to strictly control the depth of chlorination to prevent side reactions; on, actually implement.

The method described above optimizes and improves the preparation of 2,4-dichlorobenzaldehyde by oxidation of 2,4-dichlorotoluene from different angles, but there are still some problems to be solved: firstly, batch stills are still mainly used in large-scale production. Batch production; Secondly, in the production process, the extensive use of catalysts, the control of the degree of chlorination and the monitoring of subsequent reactions all put forward strict requirements for industrial production. The continuous oxidation of 2,4-dichlorotoluene to synthesize 2,4-dichlorobenzaldehyde 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 2,4-dichlorotoluene 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 2,4-dichlorobenzaldehyde by continuous oxidation of 2,4-dichlorotoluene 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 2,4-dichlorotoluene in a tubular reactor to prepare 2,4-dichlorobenzaldehyde. 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 object of the present invention is to realize the stable and controllable continuous oxidation of 2,4-dichlorotoluene 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 2,4-dichlorobenzaldehyde by continuous oxidation of 2,4-dichlorotoluene by a tubular reactor of special structure, carried out according to the following steps:

(1) At first, at room temperature, the substrate 2,4-dichlorotoluene and part of the carboxylic acid solvent are stirred and mixed uniformly with a volume ratio of 1:1, and the oxidant and part of the carboxylic acid solvent are mixed uniformly with a volume ratio of 1:1, and then Mix the metal complex and pour it into the 2,4-dichlorotoluene-carboxylic acid solution, and pour the sodium salt into the hydrogen peroxide-carboxylic acid solution; through the required reaction time, calculate the different flow rates of the two materials, respectively It is continuously pumped into the tubular reactor by the metering pump, preheated and mixed, and then enters the reaction zone for reaction. 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 60-1800s 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 separated by rectification, the unreacted 2,4-dichlorotoluene is recycled, and the product 2,4-dichlorobenzaldehyde is collected after rectification and purification, wherein the target product 2, The yield of 4-dichlorobenzaldehyde can reach 20%-35%.

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 2,4-dichlorotoluene, and the molar ratio of its dosage to the substrate 2,4-dichlorotoluene is (0.001～0.15): 1, wherein the preferred molar ratio is (0.01-0.08):1.

Wherein the oxidizing agent is hydrogen peroxide, and its solution concentration is 5%-80% in terms of mass concentration, preferably 5%-60%. The preferred molar ratio of hydrogen peroxide to the substrate 2,4-dichlorotoluene is (1.0-8.0):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 said carboxylic acid solvent comprises: formic acid, acetic acid, propionic acid, butanoic acid, hexanoic acid, caprylic acid etc. Wherein the volume ratio of the solvent to 2,4-dichlorotoluene is (1-15):1.

Wherein the reaction temperature is 60-160°C, preferably the reaction temperature is 100-135°C, and the reaction residence time is 60s-1800s.

In a further technical solution, after the reaction is completed, sodium dichloromethane is used to quench the oxidant not involved in the reaction, and then extracted with an organic solvent, and the target product is obtained after 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 a process flow chart for preparing 2,4-dichlorobenzaldehyde by continuous oxidation of 2,4-dichlorotoluene in the present invention.

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 2,4-dichlorotoluene and acetic acid, and send them 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 1.01g of cobalt acetate and 1.01g of sodium molybdate in 200ml of 2,4-dichlorotoluene and 200ml of acetic acid respectively to form a mixed solution. At this time, n(cobalt acetate):n(2,4-dichlorotoluene)= 0.0025:1, 1.01g 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(2,4-dichlorotoluene)=0.0025:1 , 2,4-dichlorotoluene-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(2,4-dichlorotoluene)=2:1, 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 dichloromethane. After GC analysis, the conversion rate of 2,4-dichlorotoluene was 45.3%, and the yield of 2,4-dichlorobenzaldehyde was 23.1%.

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 of cobalt acetate and 6.06g of sodium molybdate in 200ml of 2,4-dichlorotoluene and 200ml of acetic acid respectively to form a mixed solution. At this time, n (cobalt acetate): n(2,4-dichlorotoluene)= 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(2,4-dichlorotoluene)=0.015:1 , 2,4-dichlorotoluene-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(2,4-dichlorotoluene)=3:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 75°C, and the residence time was 200s. The outlet material was cooled at 0°C, and the reaction solution was quenched with dichloromethane. After GC analysis, the conversion rate of 2,4-dichlorotoluene was 50.0%, and the yield of 2,4-dichlorobenzaldehyde was 28.7%.

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 of cobalt acetate and 6.06g of sodium molybdate in 200ml of 2,4-dichlorotoluene and 200ml of acetic acid respectively to form a mixed solution. At this time, n (cobalt acetate): n(2,4-dichlorotoluene)= 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(2,4-dichlorotoluene)=0.015:1 , 2,4-dichlorotoluene-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(2,4-dichlorotoluene)=3:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 95°C, and the residence time was 300s. The outlet material was cooled at 0°C, and the reaction solution was quenched with dichloromethane. After GC analysis, the conversion rate of 2,4-dichlorotoluene was 45.8%, and the yield of 2,4-dichlorobenzaldehyde was 28.2%.

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) Dissolve 6.06g of cobalt acetate and 6.06g of sodium molybdate in 200ml of 2,4-dichlorotoluene and 200ml of acetic acid respectively to form a mixed solution. At this time, n (cobalt acetate): n(2,4-dichlorotoluene)= 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(2,4-dichlorotoluene)=0.015:1 , 2,4-dichlorotoluene-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(2,4-dichlorotoluene)=2:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 100°C, and the residence time was 500s. The outlet material was cooled at 0°C, and the reaction solution was quenched with dichloromethane. After GC analysis, the conversion rate of 2,4-dichlorotoluene was 51.5%, and the yield of 2,4-dichlorobenzaldehyde was 28.1%.

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 of cobalt acetate and 6.06g of sodium molybdate in 200ml of 2,4-dichlorotoluene and 200ml of acetic acid respectively to form a mixed solution. At this time, n (cobalt acetate): n(2,4-dichlorotoluene)= 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(2,4-dichlorotoluene)=0.015:1 , 2,4-dichlorotoluene-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(2,4-dichlorotoluene)=3:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 105°C, and the residence time was 600s. The outlet material was cooled at 0°C, and the reaction solution was quenched with dichloromethane. After GC analysis, the conversion rate of 2,4-dichlorotoluene was 41.7%, and the yield of 2,4-dichlorobenzaldehyde was 30.1%.

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 of cobalt acetate and 6.06g of sodium molybdate in 200ml of 2,4-dichlorotoluene and 200ml of acetic acid respectively to form a mixed solution. At this time, n (cobalt acetate): n(2,4-dichlorotoluene)= 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(2,4-dichlorotoluene)=0.015:1 , 2,4-dichlorotoluene-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(2,4-dichlorotoluene)=2:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 135°C, and the residence time was 900s. The outlet material was cooled at 0°C, and the reaction solution was quenched with dichloromethane. After GC analysis, the conversion rate of 2,4-dichlorotoluene was 35.7%, and the yield of 2,4-dichlorobenzaldehyde was 20.5%.

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 of cobalt acetate and 6.06g of sodium molybdate in 200ml of 2,4-dichlorotoluene and 200ml of acetic acid respectively to form a mixed solution. At this time, n (cobalt acetate): n(2,4-dichlorotoluene)= 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(2,4-dichlorotoluene)=0.015:1 , 2,4-dichlorotoluene-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(2,4-dichlorotoluene)=2:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 90°C, and the residence time was 1200s. The outlet material was cooled at 0°C, and the reaction solution was quenched with dichloromethane. After GC analysis, the conversion rate of 2,4-dichlorotoluene was 35.8%, and the yield of 2,4-dichlorobenzaldehyde was 20.0%.

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 of cobalt acetate and 6.06g of sodium molybdate in 200ml of 2,4-dichlorotoluene and 200ml of acetic acid respectively to form a mixed solution. At this time, n (cobalt acetate): n(2,4-dichlorotoluene)= 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(2,4-dichlorotoluene)=0.015:1 , 2,4-dichlorotoluene-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(2,4-dichlorotoluene)=2:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 150°C, and the residence time was 1500s. The outlet material was cooled at 0°C, and the reaction solution was quenched with dichloromethane. After GC analysis, the conversion rate of 2,4-dichlorotoluene was 39.9%, and the yield of 2,4-dichlorobenzaldehyde was 24.1%.

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 of cobalt acetate and 6.06g of sodium molybdate in 200ml of 2,4-dichlorotoluene and 200ml of acetic acid respectively to form a mixed solution. At this time, n(cobalt acetate):n(2,4-dichlorotoluene)= 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(2,4-dichlorotoluene)=0.015:1 , 2,4-dichlorotoluene-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(2,4-dichlorotoluene)=2:1, the microchannel reactor shown in Figure 2 was used, the reaction temperature was controlled at 160°C, and the residence time was 1800s. The outlet material was cooled at 0°C, and the reaction solution was quenched with dichloromethane. After GC analysis, the conversion rate of 2,4-dichlorotoluene was 52.1%, and the yield of 2,4-dichlorobenzaldehyde was 29.2%.

Claims (6)

1. a kind of method that 2,4-dichlorotoluene continuous oxidation prepares 2,4-dichlorobenzaldehyde is characterized in that carrying out according to the following steps: (1) At room temperature, stir and mix the substrate 2,4-dichlorotoluene and part of the carboxylic acid solvent at a volume ratio of 1:1, mix the oxidant and part of the carboxylic acid solvent at a volume ratio of 1:1, and then mix the metal The complex is mixed and poured into the 2,4-dichlorotoluene-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 changing the pipe inner diameter of the tubular reactor from 0.5 to 15 mm and the volume from 25 to 750 ml; after the reaction is completed, the product The outflow from the end of the reactor enters the collection tank, the product is separated by rectification, the unreacted 2,4-dichlorotoluene is recycled, and the product 2,4-dichlorobenzaldehyde is collected after rectification and purification. 2. according to claims 1, a kind of 2,4-dichlorotoluene continuous oxidation prepares the method for 2,4-dichlorobenzaldehyde, 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 2,4-dichlorotoluene, and the molar ratio of its dosage to the substrate 2,4-dichlorotoluene is (0.001~0.15):1, and the preferred molar ratio is (0.01~0.08):1. 3. according to claims 1, a kind of 2,4-dichlorotoluene continuous oxidation prepares the method for 2,4-dichlorobenzaldehyde, it is characterized in that described oxygenant is hydrogen peroxide, and its solution concentration is in mass concentration The preferred concentration is 5%~80%, the preferred concentration is 5%~60%, and the preferred molar ratio of hydrogen peroxide to the substrate 2,4-dichlorotoluene is (1.0~8.0):1. 4. according to claim 1, a kind of 2,4-dichlorotoluene continuous oxidation prepares the method for 2,4-dichlorobenzaldehyde, 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 2,4-dichlorotoluene is (1~15):1. 5. A method for preparing 2,4-dichlorobenzaldehyde by continuous oxidation of 2,4-dichlorotoluene according to claim 1, characterized in that: the reaction temperature is 60~160°C, preferably the reaction temperature is 100°C ~135℃, reaction residence time 60s~1800s. 6. according to the method for preparing 2,4-dichlorobenzaldehyde by a kind of 2,4-dichlorotoluene continuous oxidation according to claims 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.