CN108794311B - Method for preparing o-chlorobenzaldehyde by continuously oxidizing o-chlorotoluene - Google Patents

Method for preparing o-chlorobenzaldehyde by continuously oxidizing o-chlorotoluene Download PDF

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CN108794311B
CN108794311B CN201810780724.0A CN201810780724A CN108794311B CN 108794311 B CN108794311 B CN 108794311B CN 201810780724 A CN201810780724 A CN 201810780724A CN 108794311 B CN108794311 B CN 108794311B
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chlorotoluene
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chlorobenzaldehyde
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hydrogen peroxide
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CN108794311A (en
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刘建武
蒋晗
张跃
严生虎
沈介发
马晓明
陈代祥
辜顺林
张勇超
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Changzhou University
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    • C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
    • C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
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    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/0006—Controlling or regulating processes
    • B01J19/0013—Controlling the temperature of the process
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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Abstract

The invention discloses a method for preparing o-chlorobenzaldehyde by continuously oxidizing o-chlorotoluene, belonging to the technical field of organic synthesis processes. The method is a process technology for preparing o-chlorobenzaldehyde by continuously oxidizing o-chlorotoluene in a tubular reactor by taking an o-chlorotoluene compound as a raw material, one or more metal ion complexes of cobalt, molybdenum and bromine as a catalyst, hydrogen peroxide as an oxidant and acetic acid as a solvent. The method has the advantages of mild conditions, short reaction time, high utilization rate of raw materials, capability of realizing effective control in the reaction process, safety, stability, continuous operation and high production efficiency.

Description

Method for preparing o-chlorobenzaldehyde by continuously oxidizing o-chlorotoluene
Technical Field
The invention belongs to the technical field of organic synthesis processes, and relates to a method for preparing o-chlorobenzaldehyde by continuously oxidizing o-chlorotoluene under the condition of liquid phase reaction, in particular to a method for continuously preparing o-chlorobenzaldehyde products in a tubular reactor with different microstructures by taking o-chlorotoluene as a substrate, hydrogen peroxide as an oxidant, one or more metal ion complexes of cobalt, molybdenum and bromine as a catalyst and monocarboxylic acid as a solvent.
Background
O-chlorobenzaldehyde, also known as 2-chlorobenzaldehyde, is an important raw material in fine chemical engineering and an important intermediate in organic synthesis. The method is widely applied to the industries of pesticide, medicine, dye and the like. The product is used for producing a high-efficiency low-toxicity mite killer with large domestic demand in the pesticide industry; the method is used for producing o-chlorobenzaldehyde oxime, o-chlorobenzaldehyde oxime chloride and cloxacillin sodium in the pharmaceutical industry; sodium o-benzaldehyde sulfonate can be produced in the dye industry, is a raw material of food pigment acid blue No. 1, and is also used as an additive of a plating bath to improve the brightness. Currently, swiss CIBA company uses it to produce a high-grade optical brightener zelaibao for laundry cleaning. In addition, it is also useful as an intermediate in lachrymatory products, etc. The market capacity of the o-chlorobenzaldehyde is more than 2000t/a, the application field of the o-chlorobenzaldehyde is continuously extended along with the continuous development of downstream products of the o-chlorobenzaldehyde, and the demand for the o-chlorobenzaldehyde is more and more increased at home and abroad. According to the current domestic and foreign markets, the supply of o-chlorobenzaldehyde products is not in demand, domestic production enterprises are required to combine various advanced production processes, a new o-chlorobenzaldehyde production process is researched and developed, economic benefits are created, pollution is reduced, waste is changed into valuable, and the two purposes are achieved.
The existing synthesis production method of o-chlorobenzaldehyde mainly comprises the following steps: the o-chlorotoluene chlorination hydrolysis method, the o-chlorotoluene direct oxidation acyl chloride reduction method, the carboxylic acid reduction method and the like have the advantages that the selected reduction method has higher technical difficulty and high production cost, and the application in industrial production is rarely reported, but the chlorination hydrolysis method is most widely applied.
The current industrial synthesis methods of o-chlorobenzaldehyde comprise the following steps:
(1) chlorination hydrolysis method
Among chemical methods, the most traditional process for synthesizing o-chlorobenzaldehyde is the o-chlorotoluene chlorination hydrolysis method, which comprises the steps of chlorinating the side chain of o-chlorotoluene under the action of a catalyst to prepare o-chlorotrifluorobenzyl, and hydrolyzing under the action of a hydrolysis catalyst to generate o-chlorobenzaldehyde. The catalysts used in the catalytic hydrolysis are generally transition metal salts M Xn such as: SnCl4，ZnCl2. The process flow for synthesizing the o-chlorobenzaldehyde by taking the o-chlorotoluene as the raw material is as follows:
Figure BDA0001732490900000011
in the production of the method, chlorination results are different due to different chlorination depths, and byproducts such as o-chlorobenzyl chloride, o-chlorotrifluorobenzyl chloride and the like with different degrees are generated in chlorination. In addition, the hydrolysis reaction is mostly catalyzed by concentrated sulfuric acid, the yield is only about 80%, a large amount of waste acid is generated, and the environment is seriously polluted.
(2) Chlorination oxidation process
The chlorination-oxidation method is to perform side chain chlorination on o-chlorotoluene to generate an o-chlorobenzyl chloride compound, and then oxidize the o-chlorobenzyl chloride compound by an oxidant to generate corresponding benzaldehyde. The reaction formula is as follows:
Figure BDA0001732490900000021
the selected oxidants are different, and the oxidation conditions required by the oxidation reaction are also different. Urotropine is usually used as an oxidant, and aldehyde is obtained by heating and refluxing in an ethanol and hydrochloric acid system. And HNO3As an oxidant, o-chlorobenzyl chloride is firstly oxidized into o-dichlorobenzyl chloride, and then the o-dichlorobenzyl chloride is hydrolyzed to obtain aldehyde. However, this method requires a large amount of catalyst consumption in production and causes a large amount of wastewater pollution, which increases production costs and also pollutes the environment.
(3) Direct oxidation process
The direct oxidation method is to directly oxidize methyl in o-chlorotoluene into aldehyde group. Generally, the oxidation method is classified into manganese dioxide/sulfuric acid oxidation method, catalytic air or oxygen oxidation method, etc. according to the selected oxidant. The reaction formula is as follows:
Figure BDA0001732490900000022
the catalytic oxidation method is to take o-chlorotoluene as a raw material and carry out direct oxidation reaction by air in the presence of catalysts such as bismuth oxide, molybdenum oxide, cobalt acetate, manganese acetate, cobalt acetate, sodium bromide, cobalt acetate, lithium bromide and the like to generate aldehyde. The reaction conversion rate is 20-50%, the selectivity is 70%, the actual yield is 20%, and the product purity is 99%. The method has simple process, low cost and high product purity. However, the requirements for the apparatus are high due to the gas phase reaction, and the process is still under further investigation.
(4) Indirect electrooxidation process
The Ten claw is closed etc. and adopts Mn (III) as oxidation medium, uses o-chlorotoluene as raw materials, and benzene is the solvent, and under concentrated sulfuric acid exists, uses methylbutylammonium bromide as phase transfer catalyst, has synthesized o-chlorobenzaldehyde with indirect electrooxidation, optimum reaction condition: the concentration of sulfuric acid is 8.0mol/L, the reaction temperature is 63 ℃, and o-chlorotoluene and [ Mn ] are reacted3+]The raw material ratio is 5:4, the reaction time is 4h, and the highest yield reaches 55%. Electrolyzing MnSO with sulfuric acid as medium3To produce Mn3+Oxidizing o-chlorotoluene into o-chlorobenzaldehyde, and obtaining the optimal electrolysis condition through an electrolytic oxidation orthogonal experiment and a MnSO3 single-factor experiment: concentrated H2SO46.8mol/L, the temperature is 80 ℃, the ratio of the raw materials to the sulfuric acid is 1:3, and the stirring speed is 500 r/min. Under the optimized condition, the current efficiency reaches 84.30 percent, the yield of the o-chlorobenzaldehyde reaches 90.63 percent, and the reaction rate is 6.183 multiplied by 10-3mol/(L.min). The process route is simple, but the production cost is high, and the process is not suitable for large-scale popularization at present.
The method optimizes and improves the preparation of o-chlorobenzaldehyde by oxidizing o-chlorotoluene from different angles, but still has some problems to be solved: firstly, batch production of batch kettles is mainly adopted in large-scale production; secondly, the method still has the main reasons of excessive catalyst consumption, excessive wastewater generated by hydrolysis, excessive chlorination depth, increased side reactions and low selectivity and yield of target products, and the continuous oxidation of the o-chlorotoluene by using the continuous flow tubular reactor with a specific structure is used for synthesizing the o-chlorobenzaldehyde, so that the defects of the prior art can be overcome in many aspects.
The tubular reactor is a general name of a small reactor with a microstructure, compared with a conventional reactor, the tubular reactor has the characteristics of small volume, large specific surface area, easiness in amplification, continuous process, good quick mixing effect, good heat transfer effect, high temperature and high pressure resistance and the like, and the continuous flow tubular reactor with a specific structure can effectively control the mixing and mass and heat transfer processes of reaction materials. The design of the structure and the size of the pipeline can effectively increase the contact area between reactants, enhance the mass and heat transfer effect, improve the utilization rate of the oxidant, reduce the use amount of the oxidant, avoid the use of a cocatalyst and solve the temperature runaway phenomenon caused by local overheating in the reaction process. The distribution of the raw materials and the products can be further optimized and controlled by controlling the length of the tubular reactor and the reaction residence time; the substrate o-chloro-o-chlorotoluene and the oxidant can enter the tubular reactor in proportion to react by adjusting the flow rate of the raw material pump, so that the back mixing is greatly reduced, the side reaction is further reduced, and the stability of the oxidant and the selectivity of a target product are greatly improved; through set up the pressure relief valve in tubular reactor, can in time discharge the excessive oxidant in the reactor, guarantee the safe of reaction and go on, reduce the danger to minimum. Compared with the traditional batch production method, the method for preparing the o-chlorobenzaldehyde by continuously oxidizing the o-chlorotoluene by adopting the tubular reactor with the specific structure has incomparable advantages, and can provide an important way for improving the industrial continuous production of the o-chlorobenzaldehyde.
Disclosure of Invention
Aiming at the defects, the invention provides a method for preparing o-chlorobenzaldehyde by continuously oxidizing o-chlorotoluene in a tubular reactor. The method has the advantages of short reaction time, high production efficiency, greatly optimized mass transfer and heat transfer, and more stable and controllable reaction process. The invention further aims to realize the stability and controllability of the continuous oxidation of the o-chlorotoluene and reduce the generation of byproducts by the process method. The effective utilization rate of reaction materials is improved through the strengthening of the mass transfer and heat transfer process and the process optimization, the use amount of an oxidant and a catalyst is further reduced, and a cocatalyst is avoided in the reaction process, so that the production cost is effectively saved, and the existing industrial production method is improved.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for preparing o-chlorobenzaldehyde by continuously oxidizing o-chlorotoluene by adopting a tubular reactor with a special structure comprises the following steps:
(1) firstly, at room temperature, uniformly stirring and mixing a substrate o-chlorotoluene and a carboxylic acid solvent in a volume ratio of 1:1, uniformly mixing an oxidant and a part of the carboxylic acid solvent in a volume ratio of 1:1, then mixing and pouring a metal complex catalyst into an o-chlorotoluene-carboxylic acid solution, and pouring a sodium salt into an oxidant-carboxylic acid solution; calculating different flow rates of two materials according to the required reaction time, continuously pumping the two materials into a tubular reactor through metering pumps respectively, preheating and mixing the two materials, and then feeding the two materials into a reaction zone for reaction, wherein the reaction temperature is controlled by an external circulation heat exchange system;
(2) controlling the molar ratio of the reaction materials by adjusting the flow rate and weighing, and controlling the retention time of the material mixing reaction for 60-1800 s by changing the inner diameter of a pipeline of the tubular reactor to be 0.5-15 mm and the volume to be 25-750 ml; after the reaction is finished, the product flows out of the tail end of the reactor and enters a collecting tank, the product is rectified and separated, unreacted o-chlorotoluene is circularly reacted, the product o-chlorobenzaldehyde is rectified and purified and then is collected, and the yield of the target product o-chlorobenzaldehyde can reach 35-45%.
Wherein the metal complex catalyst is one or more of cobalt, molybdenum and bromine, and mainly comprises: the catalyst is characterized by comprising cobalt acetate, cobalt oxalate, cobalt carbonate, cobalt naphthenate, sodium molybdate, ammonium molybdate, sodium bromide, ammonium bromide and the like, wherein an oil-soluble catalyst is taken as a main component, the catalyst can be fully dissolved in o-chlorotoluene, the molar ratio of the usage amount of the catalyst to a substrate o-chlorotoluene is (0.005-0.15) to 1, and the preferred molar ratio is (0.01-0.12) to 1.
Wherein the oxidant is hydrogen peroxide, and the concentration of the solution is 5-50% by mass concentration, preferably 10-35% by mass concentration. The optimal molar ratio of the hydrogen peroxide to the substrate o-chlorotoluene is (1.0-8.0) to 1.
In the tubular reactor, when the hydrogen peroxide passes through the reactor by 50ml, the hydrogen peroxide is quickly decomposed to release a large amount of molecular oxygen, and when the hydrogen peroxide passes through 100ml, the molecular oxygen is almost in a molecular oxygen form, and at the moment, hydrogen peroxide with equal concentration is additionally supplemented at the reaction volume of 100ml to enter and participate in the reaction again.
Wherein said carboxylic acid solvent comprises: formic acid, acetic acid, propionic acid, butyric acid, caproic acid, caprylic acid, and the like. Wherein the volume ratio of the solvent to the o-chlorotoluene is (1-5) to 1.
Wherein the reaction temperature is 60-130 ℃, the preferable reaction temperature is 90-125 ℃, and the reaction residence time is 60-1800 s.
In a further technical scheme, after the reaction is finished, dichloromethane sodium is used for quenching the oxidant which does not participate in the reaction, and then the target product is obtained after organic solvent extraction, distillation, separation and purification.
In the technical scheme, the reaction system comprises a raw material storage tank, a reaction area, a product collecting area and other different functional areas. The tubular reactor channel structure comprises: the device comprises a round pipe straight-flow type channel structure, a round cake type pulse reducing type rectangular flat pipeline structure, an oblique square cake type pulse reducing type rectangular flat pipeline structure, a reinforced mixed type round cake type rectangular flat pipeline structure and a Heart Cell channel structure of Corning.
The invention has the following advantages:
1. the invention adopts a continuous production mode, has short reaction time, mild reaction condition, safe and controllable process and high production efficiency.
2. The invention can realize effective control of the reaction process by adopting tubular reactors with different knot structures, so that the reaction product stays in one step of the aldol reaction.
3. The reaction rate and the utilization rate of raw materials are greatly improved by strengthening mass transfer and heat transfer in the reaction process, the use amount of an oxidant and a catalyst is effectively reduced, the use of a cocatalyst is avoided, and the production cost is effectively saved.
4. The invention has simple operation, wide application range and flexible production, and can enlarge the production scale by connecting the reaction devices in parallel.
Drawings
FIG. 1 is a process flow diagram for preparing o-chlorobenzaldehyde by continuous oxidation of o-chlorotoluene.
FIG. 2 is a diagram of a continuous flow tubular reactor apparatus used in the present invention: 1. 2-raw material tank, 3, 4-raw material metering pump, 5-preheating zone, 6, 7-reaction zone and 8-product quenching collecting zone.
FIG. 3 is a schematic diagram of the channel structure of the tubular reactor used in the present invention, wherein a is a straight-flow channel structure, b is a flat rectangular pipe with a cone-shaped pulse diameter-variable structure, c is a flat rectangular pipe with a square cone-shaped pulse diameter-variable structure, d is a flat pipe with a reinforced mixed cone-shaped pulse diameter-variable structure, and the micro-channel with an e-Corning Heart Cell structure.
Detailed Description
As shown in FIG. 2, cobalt acetate and sodium molybdate were dissolved in a 1# tank containing o-chlorotoluene and acetic acid and pumped by a 3# pump into a 5# pre-heating reactor, which was heated to 50 ℃; dissolving sodium bromide in a No. 2 tank filled with hydrogen peroxide and acetic acid, pumping the solution into a No. 6 preheating reactor through a No. 4 pump, heating the preheating reactor to 50 ℃, conveying two preheating materials into a No. 7 reactor and a No. 8 reactor, setting the temperature of the reactors at the temperature required by the reaction, flowing out a product through the No. 8 reactor, cooling the product at 0 ℃, and collecting the obtained product.
The present invention is described in detail with reference to the following examples, which are only preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution of the present invention and the inventive concept within the technical scope of the present invention.
Example 1
(1) The device comprises the following steps: the connection of the tubular reactor is determined with reference to fig. 2, the pipe types being: (3a +3b) a straight-flow channel and a round-cake type pulse variable-diameter rectangular flat pipeline, wherein the inner diameter and the volume of the pipeline are determined according to the flow velocity and the reaction residence time, and the heat exchange medium is heat conduction oil.
(2) 3.03g of cobalt acetate and 3.03g of sodium molybdate were dissolved in 200ml of o-chlorotoluene and 200ml of acetic acid, respectively, to prepare a mixed solution, in which case n (cobalt acetate): n (o-chlorotoluene) ═ 0.0075:1, 3.03g of sodium bromide was dissolved in 5% H2O2Form H2O2-acetic acid solution, when n (sodium bromide): n (o-chlorotoluene) ═ 0.0075:1, o-chlorotoluene-acetic acid solution and H2O2The acetic acid solution was injected into the tubular reactor with continuous heat exchange by a constant flow pump at flow rates of 8.33ml/min and 16.67ml/min, respectivelyAt this time n (H)2O2): n (o-chlorotoluene) ═ 2:1, a microchannel reactor shown in FIG. 2 is adopted, the reaction temperature is controlled at 60 ℃, and the retention time is controlled at 60 s. The outlet material was cooled at 0 ℃ and the reaction was quenched with dichloromethane. By GC analysis, the conversion rate of o-chlorotoluene is 65.3 percent, and the yield of o-chlorobenzaldehyde is 37.1 percent.
Example 2
(1) The device comprises the following steps: the connection of the tubular reactor is determined with reference to fig. 2, the pipe types being: (3a +3c) a straight-flow channel and an oblique square-cake type pulse variable-diameter rectangular flat pipeline, wherein the inner diameter and the volume of the pipeline are determined according to the flow velocity and the reaction residence time, and the heat exchange medium is heat conduction oil.
(2) 6.06g of cobalt acetate and 6.06g of sodium molybdate were dissolved in 200ml of o-chlorotoluene and 200ml of acetic acid, respectively, to prepare a mixed solution, in which case n (cobalt acetate): n (o-chlorotoluene) ═ 0.015:1, 6.06g of sodium bromide was dissolved in 15% H2O2Form H2O2-acetic acid solution, when n (sodium bromide): n (o-chlorotoluene) ═ 0.015:1, o-chlorotoluene-acetic acid solution and H2O2The acetic acid solution was injected into the tubular reactor with continuous heat exchange by a constant flow pump at flow rates of 8.33ml/min and 16.67ml/min, respectively, when n (H)2O2): n (o-chlorotoluene) ═ 2:1, the microchannel reactor in FIG. 2 was used, the reaction temperature was controlled at 90 ℃ and the residence time was controlled at 200 s. The outlet material was cooled at 0 ℃ and the reaction was quenched with dichloromethane. By GC analysis, the conversion rate of o-chlorotoluene is 63.0 percent, and the yield of o-chlorobenzaldehyde is 41.7 percent.
Example 3
(1) The device comprises the following steps: the connection of the tubular reactor is determined with reference to fig. 2, the pipe types being: (3a +3d) a direct-flow channel and an enhanced mixed round-cake rectangular flat pipeline, wherein the inner diameter and the volume of the pipeline are determined according to the flow rate and the reaction residence time, and the heat exchange medium is heat conduction oil.
(2) 6.06g of cobalt acetate and 6.06g of sodium molybdate were dissolved in 200ml of o-chlorotoluene and 200ml of acetic acid, respectively, to prepare a mixed solution, in which case n (cobalt acetate): n (o-chlorotoluene) ═ 0.015:1, 6.06g of sodium bromide was dissolved in 15% H2O2Form H2O2-acetic acid solution, when n (sodium bromide): n (o-chlorotoluene) ═ 0.015:1, o-chlorotoluene-acetic acid solution and H2O2The acetic acid solution was injected into the tubular reactor with continuous heat exchange by a constant flow pump at flow rates of 8.33ml/min and 16.67ml/min, respectively, when n (H)2O2): n (o-chlorotoluene) ═ 2:1, the microchannel reactor in FIG. 2 was used, the reaction temperature was controlled at 105 ℃ and the residence time was controlled at 600 s. The outlet material was cooled at 0 ℃ and the reaction was quenched with dichloromethane. Through GC analysis, the conversion rate of o-chlorotoluene is 60.8 percent, and the yield of o-chlorobenzaldehyde is 35.2 percent.
Example 4
(1) The device comprises the following steps: the connection of the tubular reactor is determined with reference to fig. 2, the pipe types being: (3a +3b) a straight-flow channel and a round-cake type pulse variable-diameter rectangular flat pipeline, wherein the inner diameter and the volume of the pipeline are determined according to the flow velocity and the reaction residence time, and the heat exchange medium is heat conduction oil.
(2) 6.06g of cobalt acetate and 6.06g of sodium molybdate were dissolved in 200ml of o-chlorotoluene and 200ml of acetic acid, respectively, to prepare a mixed solution, in which case n (cobalt acetate): n (o-chlorotoluene) ═ 0.015:1, 6.06g of sodium bromide was dissolved in 25% H2O2Form H2O2-acetic acid solution, when n (sodium bromide): n (o-chlorotoluene) ═ 0.015:1, o-chlorotoluene-acetic acid solution and H2O2The acetic acid solution was injected into the tubular reactor with continuous heat exchange by a constant flow pump at flow rates of 8.33ml/min and 16.67ml/min, respectively, when n (H)2O2): n (o-chlorotoluene) ═ 2:1, the microchannel reactor in FIG. 2 was used, the reaction temperature was controlled at 115 ℃ and the residence time was controlled at 600 s. The outlet material was cooled at 0 ℃ and the reaction was quenched with dichloromethane. By GC analysis, the conversion rate of o-chlorotoluene is 71.5 percent, and the yield of o-chlorobenzaldehyde is 42.1 percent.
Example 5
(1) The device comprises the following steps: the connection of the tubular reactor is determined with reference to fig. 2, the pipe types being: (3a +3c) a straight-flow channel and an oblique square-cake type pulse variable-diameter rectangular flat pipeline, wherein the inner diameter and the volume of the pipeline are determined according to the flow velocity and the reaction residence time, and the heat exchange medium is heat conduction oil.
(2) 6.06g of cobalt acetate and 6.06g of sodium molybdate were dissolved in 200ml of o-chlorotoluene and 200ml of acetic acid, respectively, to prepare a mixed solution, in which case n (cobalt acetate): n is(o-chlorotoluene) ═ 0.015:1, 6.06g of sodium bromide was dissolved in 25% H2O2Form H2O2-acetic acid solution, when n (sodium bromide): n (o-chlorotoluene) ═ 0.015:1, o-chlorotoluene-acetic acid solution and H2O2The acetic acid solution was injected into the tubular reactor with continuous heat exchange by a constant flow pump at flow rates of 8.33ml/min and 16.67ml/min, respectively, when n (H)2O2): n (o-chlorotoluene) ═ 2:1, the microchannel reactor in FIG. 2 was used, the reaction temperature was controlled at 115 ℃ and the residence time was controlled at 600 s. The outlet material was cooled at 0 ℃ and the reaction was quenched with dichloromethane. By GC analysis, the conversion of o-chlorotoluene was 53.7% and the yield of o-chlorobenzaldehyde was 35.1%.
Example 6
(1) The device comprises the following steps: the connection of the tubular reactor is determined with reference to fig. 2, the pipe types being: (3a +3d) a direct-flow channel and an enhanced mixed round-cake rectangular flat pipeline, wherein the inner diameter and the volume of the pipeline are determined according to the flow rate and the reaction residence time, and the heat exchange medium is heat conduction oil.
(2) 6.06g of cobalt acetate and 6.06g of sodium molybdate were dissolved in 200ml of o-chlorotoluene and 200ml of acetic acid, respectively, to prepare a mixed solution, in which case n (cobalt acetate): n (o-chlorotoluene) ═ 0.015:1, 6.06g of sodium bromide was dissolved in 25% H2O2Form H2O2-acetic acid solution, when n (sodium bromide): n (o-chlorotoluene) ═ 0.015:1, o-chlorotoluene-acetic acid solution and H2O2The acetic acid solution was injected into the tubular reactor with continuous heat exchange by a constant flow pump at flow rates of 5.56ml/min and 11.11ml/min, respectively, when n (H)2O2): n (o-chlorotoluene) ═ 2:1, the microchannel reactor in FIG. 2 was used, the reaction temperature was controlled at 115 ℃ and the residence time was controlled at 900 s. The outlet material was cooled at 0 ℃ and the reaction was quenched with dichloromethane. By GC analysis, the conversion rate of o-chlorotoluene is 54.7 percent, and the yield of o-chlorobenzaldehyde is 35.0 percent.
Example 7
(1) The device comprises the following steps: the connection of the tubular reactor is determined with reference to fig. 2, the pipe types being: (3a +3e) a direct-flow channel + Corning Heart Cell structure, wherein the inner diameter and the volume of the pipeline are determined according to the flow rate and the reaction retention time, and the heat exchange medium is heat conduction oil.
(2) 6.06g of cobalt acetate and 6.06g of sodium molybdate were dissolved in 200ml of o-chlorotoluene and 200ml of acetic acid, respectively, to prepare a mixed solution, in which case n (cobalt acetate): n (o-chlorotoluene) ═ 0.015:1, 6.06g of sodium bromide was dissolved in 25% H2O2Form H2O2-acetic acid solution, when n (sodium bromide): n (o-chlorotoluene) ═ 0.015:1, o-chlorotoluene-acetic acid solution and H2O2The acetic acid solution was injected into the tubular reactor with continuous heat exchange by a constant flow pump at flow rates of 5.56ml/min and 11.11ml/min, respectively, when n (H)2O2): n (o-chlorotoluene) ═ 2:1, the microchannel reactor in FIG. 2 was used, the reaction temperature was controlled at 90 ℃ and the residence time was controlled at 900 s. The outlet material was cooled at 0 ℃ and the reaction was quenched with dichloromethane. By GC analysis, the conversion rate of o-chlorotoluene is 52.8 percent, and the yield of o-chlorobenzaldehyde is 39.0 percent.
Example 8
(1) The device comprises the following steps: the connection of the tubular reactor is determined with reference to fig. 2, the pipe types being: (3a +3d) a direct-flow channel and an enhanced mixed round-cake rectangular flat pipeline, wherein the inner diameter and the volume of the pipeline are determined according to the flow rate and the reaction residence time, and the heat exchange medium is heat conduction oil.
(2) 6.06g of cobalt acetate and 6.06g of sodium molybdate were dissolved in 200ml of o-chlorotoluene and 200ml of acetic acid, respectively, to prepare a mixed solution, in which case n (cobalt acetate): n (o-chlorotoluene) ═ 0.015:1, 6.06g of sodium bromide was dissolved in 25% H2O2Form H2O2-acetic acid solution, when n (sodium bromide): n (o-chlorotoluene) ═ 0.015:1, o-chlorotoluene-acetic acid solution and H2O2The acetic acid solution was injected into the tubular reactor with continuous heat exchange by a constant flow pump at flow rates of 5.56ml/min and 11.11ml/min, respectively, when n (H)2O2): n (o-chlorotoluene) ═ 2:1, the microchannel reactor in FIG. 2 was used, the reaction temperature was controlled at 100 ℃ and the residence time was controlled at 900 s. The outlet material was cooled at 0 ℃ and the reaction was quenched with dichloromethane. By GC analysis, the conversion rate of o-chlorotoluene is 47.9 percent, and the yield of o-chlorobenzaldehyde is 36.1 percent.
Example 9
(1) The device comprises the following steps: the connection of the tubular reactor is determined with reference to fig. 2, the pipe types being: (3a +3c) a straight-flow channel and an oblique square-cake type pulse variable-diameter rectangular flat pipeline, wherein the inner diameter and the volume of the pipeline are determined according to the flow velocity and the reaction residence time, and the heat exchange medium is heat conduction oil.
(2) 6.06g of cobalt acetate and 6.06g of sodium molybdate were dissolved in 200ml of o-chlorotoluene and 200ml of acetic acid, respectively, to prepare a mixed solution, in which case n (cobalt acetate): n (o-chlorotoluene) ═ 0.015:1, 6.06g of sodium bromide was dissolved in 50% H2O2Form H2O2-acetic acid solution, when n (sodium bromide): n (o-chlorotoluene) ═ 0.015:1, o-chlorotoluene-acetic acid solution and H2O2The acetic acid solution was injected into the tubular reactor with continuous heat exchange by a constant flow pump at flow rates of 5.56ml/min and 11.11ml/min, respectively, when n (H)2O2): n (o-chlorotoluene) ═ 2:1, the microchannel reactor in FIG. 2 was used, the reaction temperature was controlled at 130 ℃ and the residence time was 1800 s. The outlet material was cooled at 0 ℃ and the reaction was quenched with dichloromethane. By GC analysis, the conversion rate of o-chlorotoluene is 75.1 percent, and the yield of o-chlorobenzaldehyde is 44.2 percent.

Claims (1)

1. A method for preparing o-chlorobenzaldehyde by continuously oxidizing o-chlorotoluene by adopting a tubular reactor with a special structure is characterized by comprising the following steps:
(1) firstly, at room temperature, uniformly stirring and mixing a substrate o-chlorotoluene and a carboxylic acid solvent in a volume ratio of 1:1, uniformly mixing an oxidant and a part of the carboxylic acid solvent in a volume ratio of 1:1, then mixing and pouring a metal complex catalyst into an o-chlorotoluene-carboxylic acid solution, and pouring a sodium salt into an oxidant-carboxylic acid solution; calculating different flow rates of two materials according to the required reaction time, continuously pumping the two materials into a tubular reactor through metering pumps respectively, preheating and mixing the two materials, and then feeding the two materials into a reaction zone for reaction, wherein the reaction temperature is controlled by an external circulation heat exchange system;
(2) controlling the molar ratio of the reaction materials by adjusting the flow rate and weighing, and controlling the retention time of the material mixing reaction for 60-1800 s by changing the inner diameter of a pipeline of the tubular reactor to be 0.5-15 mm and the volume to be 25-750 ml; after the reaction is finished, the product flows out of the tail end of the reactor and enters a collecting tank, the product is rectified and separated, unreacted o-chlorotoluene is circularly reacted, and the product o-chlorobenzaldehyde is rectified and purified and then is collected;
wherein the metal complex catalyst is: cobalt acetate, sodium molybdate and sodium bromide;
wherein the molar ratio of the consumption of the metal complex catalyst to the substrate o-chlorotoluene is (0.005-0.15) to 1;
wherein the oxidant is hydrogen peroxide, the concentration of the solution is 10-35% by mass concentration, and the optimal molar ratio of the hydrogen peroxide to the substrate o-chlorotoluene is (1.0-8.0) to 1;
wherein, in the tubular reactor, when the hydrogen peroxide passes through 50ml of the reactor volume, the hydrogen peroxide is quickly decomposed to release a large amount of molecular oxygen, when the hydrogen peroxide passes through 100ml, the molecular oxygen is almost in a molecular oxygen form, and at the moment, hydrogen peroxide with equal concentration is additionally supplemented at the 100ml reaction volume to enter and participate in the reaction again;
wherein the carboxylic acid solvent is: formic acid, acetic acid, propionic acid, butyric acid, caproic acid, caprylic acid; wherein the volume ratio of the solvent to the o-chlorotoluene is (1-5) to 1;
wherein the reaction temperature is 90-125 ℃.
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