CN113563201A - Method for continuously and efficiently synthesizing 3, 4-dichloroaniline based on fixed bed microreactor - Google Patents
Method for continuously and efficiently synthesizing 3, 4-dichloroaniline based on fixed bed microreactor Download PDFInfo
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Abstract
The invention discloses a method for continuously and efficiently synthesizing 3, 4-dichloroaniline based on a fixed bed microreactor, which comprises the following steps: (1) dissolving 3, 4-dichloronitrobenzene serving as a raw material in a solvent to serve as a substrate solution to be hydrogenated; (2) mixing a substrate solution to be hydrogenated and hydrogen in a micro mixer to form a gas-liquid mixture with a good gas-liquid micro dispersion state, and then reacting in a micro packed bed reactor filled with a solid particle catalyst; the reaction temperature is 30-150 ℃, and the pressure is 1-5 MPa; the residence time of the gas-liquid mixture in the micro packed bed reactor is 10-120 s; (3) and (3) carrying out gas-liquid separation on the gas-liquid mixture obtained after the reaction is finished, and enabling the liquid product to enter a subsequent separation and purification system. The method has the advantages of simple operation, controllable heat release, short reaction period, environmental protection, safety, manpower saving, high purity of the obtained product, little content of dechlorination byproducts and no need of additionally adding a dechlorination inhibitor.
Description
Technical Field
The invention relates to the technical field of 3, 4-dichloroaniline synthesis, and particularly relates to a method for continuously and efficiently synthesizing 3, 4-dichloroaniline based on a fixed bed microreactor.
Background
The 3, 4-dichloroaniline is a chemical intermediate commonly used in the fine chemical industry field, is mainly used for preparing pesticide, medicine and dye intermediates, and has the following structural formula:
3, 4-dichloroaniline is mainly used for synthesizing herbicides such as diuron, propanil, linuron and the like in the field of pesticide preparation; the method is mainly used for synthesizing the bactericide TCC in the field of medicine; the dye industry is mainly used for synthesizing azo dyes and disperse red; in addition, the 3, 4-dichloroaniline can be used for preparing 3, 4-dichlorophenol, wool fabrics and the like. In recent years, the market demand of the herbicide and the dye in China is increasing day by day, and the herbicide and the dye lay a good foundation for the wide application of the 3, 4-dichloroaniline, so that the development of a novel production process has a wide market prospect.
At present, the method for producing 3, 4-dichloroaniline at home and abroad mainly comprises an iron powder reduction method and a catalytic hydrogenation method. The iron powder reduction method uses 3, 4-dichloronitrobenzene as raw material, and the 3, 4-dichloroaniline can be obtained by neutralization, separation and refining after reduction by iron powder in dilute acid medium. The process route is simple, but the three wastes generated in the production process are more and serious in pollution, so that the process is an out-dated production process which is rejected by reintegration by the national development and improvement committee. The catalytic hydrogenation method is prepared by taking 3, 4-dichloronitrobenzene as a raw material, an alcohol solvent as a medium and adopting a proper catalyst to carry out hydrogenation reaction under the condition of heating and pressurizing, and has the advantages of lower raw material cost, high product yield and meeting the requirement of atom economy, thereby being more in line with the development requirement of a clean process. The process for producing 3, 4-dichloroaniline by catalytic hydrogenation in the current industrial production is mostly carried out in a traditional hydrogenation kettle, and has the following defects:
the catalytic hydrogenation reaction is a typical gas-liquid-solid three-phase reaction, and when the catalytic hydrogenation reaction is operated in an intermittent reaction kettle, high temperature and high pressure and long reaction time are usually required for ensuring the full contact of the three phases, so that the energy consumption is high; the batch reactor has large volume and poor safety; the back mixing in the batch kettle is serious, so that dechlorination impurities are easily generated in a reaction system, the purity of a final product is influenced, and the post-treatment is difficult; meanwhile, the reaction in the batch type reaction kettle has large consumption of the catalyst and is easy to lose. The micro-reactor has the advantages of high mixing efficiency, good mass transfer and heat transfer performance, intrinsic safety and the like, is applied to the field of organic synthesis, can realize the continuity of the reaction process, reduce the volume of the reactor, accurately control the reaction conditions and improve the yield and selectivity of the reaction. Therefore, the method for continuously synthesizing the 3, 4-dichloroaniline by catalytic hydrogenation is developed based on the microreactor technology, the volume of a reactor can be reduced, the process safety is improved, the production energy consumption is reduced, the product quality is improved, and the method has important economic, safe and environmental protection values.
Patent specification with publication number CN 107973720 a discloses a method for synthesizing 3, 4-dichloroaniline by a microchannel reactor, dissolving 3, 4-dichloronitrobenzene in a solvent, adding a Pd-loaded activated carbon catalyst, adding a dechlorination inhibitor, and preheating; after preheating, the reactant and hydrogen enter a reaction module group for reaction, and the 3, 4-dichloroaniline is obtained after post-treatment. It can be seen that the overall inventive concept and technical route of the patent technology are as follows: 1. firstly, forming a suspension of 3, 4-dichloronitrobenzene solution and catalyst, and adding a dechlorination inhibitor; 2. and preheating the suspension, and reacting the preheated suspension with hydrogen in a microchannel reactor to obtain the 3, 4-dichloroaniline. Specifically, the reaction pressure is only 0.5-1.5 MPa, which is limited by the maximum safe pressure 1.5-1.8 MPa that the reaction module can bear, and cannot be further improved, so the reaction efficiency is also limited. In addition, according to the method of adding the catalyst into the substrate solution to form the suspension for reaction in the patent technology, the problems of catalyst sedimentation, material back-mixing and the like inevitably exist in the reaction process can be reasonably presumed, and the subsequent step of separating and recovering the catalyst from the product 3, 4-dichloroaniline is inevitable, so that the operation is complicated.
Disclosure of Invention
Aiming at the technical problems and the defects in the field, the invention provides a method for continuously and efficiently synthesizing 3, 4-dichloroaniline based on a fixed bed microreactor, wherein a micro packed bed reactor filled with a solid particle catalyst is used as the fixed bed microreactor, and compared with the traditional reactor, the reactor has the advantages of high mass and heat transfer efficiency, continuous operation, capability of accurately controlling reaction time, small floor area, convenience in amplification, environmental friendliness, safety, environmental friendliness and the like; the method has the advantages of simple operation, controllable heat release, short reaction period, environmental protection, safety, manpower saving, high purity of the obtained product, little content of dechlorination byproducts and no need of additionally adding a dechlorination inhibitor.
A method for continuously and efficiently synthesizing 3, 4-dichloroaniline based on a fixed bed microreactor comprises the following steps:
(1) dissolving 3, 4-dichloronitrobenzene serving as a raw material in a solvent to serve as a substrate solution to be hydrogenated;
(2) the substrate solution to be hydrogenated and hydrogen enter a micro mixer to be mixed to form a gas-liquid mixture with a good gas-liquid micro dispersion state, and then the gas-liquid mixture enters a micro packed bed reactor filled with a solid particle catalyst to react;
the reaction temperature is 30-150 ℃, and the pressure is 1-5 MPa;
the residence time of the gas-liquid mixture in the micro packed bed reactor is 10-120 s;
(3) and (3) carrying out gas-liquid separation on the gas-liquid mixture obtained after the reaction is finished, and enabling the liquid product to enter a subsequent separation and purification system.
The conception and the technical route of the invention are as follows: 1. firstly, mixing a substrate solution to be hydrogenated containing 3, 4-dichloronitrobenzene with hydrogen in a micro mixer to form a gas-liquid mixture with good gas-liquid micro dispersion state; 2. the obtained gas-liquid mixture enters a micro packed bed reactor filled with solid particle catalyst for reaction, the catalyst is not carried out by reaction liquid, the product is still the gas-liquid mixture, and the solid particle catalyst does not need to be separated; 3. the fluid flow pattern in the micro packed bed reactor is ideal plug flow without obvious back mixing, thereby effectively inhibiting dechlorination reaction and prolonging the service life of the catalyst.
On the basis of the conception and the technical route, aiming at the gas-liquid mixture and the fixed bed microreactor, the invention further optimizes and controls the reaction temperature, the reaction pressure and the residence time of the gas-liquid mixture in the fixed bed microreactor filled with the catalyst, which are adaptive to the gas-liquid mixture and the fixed bed microreactor, and realizes the maximum reaction efficiency, the product yield and the purity. In the method, in the catalytic hydrogenation reaction process in the fixed bed microreactor, the reaction pressure can reach 5MPa, the reaction efficiency is obviously improved, and the reaction period is shortened.
The method utilizes the high-efficiency mass transfer and heat transfer performance of the micro packed bed reactor filled with the solid particle catalyst, strengthens gas-liquid-solid mass transfer in the hydrogenation reaction process, greatly reduces the retention time of the reaction, greatly inhibits the dechlorination side reaction by well controlling the reaction time distribution, the reaction temperature and the reaction pressure, improves the reaction conversion rate and the product purity, reduces the dechlorination content of the product to be not more than 0.3 percent under the condition of not using a dechlorination inhibitor, reduces the corrosion of the dechlorination product to the reaction equipment and the maintenance and nursing cost of the equipment, and avoids the problem that the dechlorination product is difficult to separate from the 3, 4-dichloroaniline.
In the step (1), the solvent is preferably at least one of methanol, ethanol, propanol, isopropanol and tetrahydrofuran.
The concentration of 3, 4-dichloronitrobenzene in the substrate solution to be hydrogenated influences the reaction conversion rate and the product purity. In the method system of the present invention, in the step (1), the mass concentration of the 3, 4-dichloronitrobenzene in the solvent is preferably 5 wt% to 40 wt%, and more preferably 5 wt% to 15 wt%.
In the step (2), the micro mixer preferably comprises one of a membrane dispersion reactor, a micro-sieve reactor and a T-shaped reactor, and can also be other micro reactors capable of realizing uniform mixing of a gas-liquid system.
Preferably, in the step (2), the reaction temperature is 50-70 ℃, and the pressure is 1.5-2.5 MPa;
the residence time of the gas-liquid mixture in the micro packed bed reactor is 30-100 s. The method has the advantages of lower reaction temperature, extremely high reaction efficiency, product yield and purity at low reaction temperature and in short reaction time.
In the step (2), the molar ratio of the 3, 4-dichloronitrobenzene to the hydrogen in the substrate solution to be hydrogenated is preferably 1: 3.5-10, and more preferably 1: 4-6.
In the technical scheme that the conventional catalyst and reaction liquid form suspension, the subsequent step of separating and recycling the catalyst is involved, and if the size of the catalyst is too small, the problems of incomplete separation of the catalyst and reaction products, high recycling difficulty and the like can be caused. The invention adopts a fixed bed micro-reactor, and does not relate to the subsequent separation process of the catalyst and the reaction product, so the size of the catalyst can be smaller, and the reaction efficiency, the product yield and the purity are higher. Preferably, in the step (2), the size of the solid particle catalyst is 50-1000 microns, and the solid particle catalyst can be matched with parameters such as reaction temperature, reaction pressure, residence time and the like in the catalytic hydrogenation process to perform synergistic action, so that the reaction efficiency, the product yield and the purity are further improved.
In the step (2), the solid particulate catalyst is preferably at least one of a platinum carbon catalyst, a platinum/alumina catalyst, a ruthenium carbon catalyst, a nickel/alumina catalyst, a nickel/silica catalyst, and a nickel/titania catalyst.
According to the method for continuously and efficiently synthesizing 3, 4-dichloroaniline based on the fixed bed microreactor, in the step (1), a dechlorination inhibitor is not required to be added into the substrate solution to be hydrogenated, the content of dechlorination byproducts in the obtained product is extremely low, and the material and process cost is saved.
In the step (3), the content of dechlorination byproducts in the gas-liquid mixture obtained after the reaction is finished is less than 0.3 wt%.
In the step (3), the gas obtained by gas-liquid separation contains hydrogen, can enter a tail gas treatment system, and can be recycled, for example, the hydrogen can be used for mixing with the substrate solution to be hydrogenated in the step (2).
Compared with the prior art, the invention has the main advantages that:
1) before and after the catalytic hydrogenation reaction, the conveyed materials are only gas-liquid mixtures all the time. In the process of continuously synthesizing 3, 4-dichloroaniline by catalytic hydrogenation, the gas-liquid-solid three-phase contact area in the micro packed bed reactor is large, the mass transfer efficiency is high, and the catalyst dosage and the equipment volume can be reduced.
2) The fluid flow pattern in the micro packed bed reactor is ideal plug flow without obvious back mixing, so that the dechlorination reaction is effectively inhibited and the service life of the catalyst is prolonged.
3) The reaction time is accurate and controllable, excessive dechlorination in the reactor is avoided, and the dechlorination by-product is less than 0.3 wt%.
4) The reactor has small volume and high safety.
Drawings
FIG. 1 is a schematic flow diagram of a method for continuously and efficiently synthesizing 3, 4-dichloroaniline based on a fixed-bed microreactor according to the invention;
in the figure: 1-micro mixer; 2-a micro packed bed reactor packed with solid particulate catalyst; and 3-a gas-liquid separation tank.
Detailed Description
The invention is further described with reference to the following drawings and specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The following examples are conducted under conditions not specified, usually according to conventional conditions, or according to conditions recommended by the manufacturer.
The invention discloses a method for continuously and efficiently synthesizing 3, 4-dichloroaniline based on a fixed bed microreactor, which comprises the following steps of:
(1) dissolving 3, 4-dichloronitrobenzene serving as a raw material in a solvent to serve as a substrate solution to be hydrogenated, namely a 3, 4-dichloronitrobenzene solution;
(2) the 3, 4-dichloronitrobenzene solution and hydrogen gas enter a micro mixer 1 to be mixed to form a gas-liquid mixture with good gas-liquid micro dispersion state, and then the gas-liquid mixture enters a micro packed bed reactor 2 filled with a solid particle catalyst to be reacted;
the reaction temperature is 30-150 ℃, and the pressure is 1-5 MPa;
the residence time of the gas-liquid mixture in the micro packed bed reactor is 10-120 s;
(3) and (3) carrying out gas-liquid separation on the gas-liquid mixture obtained after the reaction in a gas-liquid separation tank 3, wherein the gas containing hydrogen can enter a tail gas treatment system, and the liquid product containing 3, 4-dichloroaniline can enter a subsequent separation and purification system.
Example 1
According to the method, an experiment is carried out, an ethanol solution of 3, 4-dichloronitrobenzene is prepared, the concentration is 20 wt%, and the molar ratio of hydrogen to 3, 4-dichloronitrobenzene is controlled to be 8: 1; the solution and hydrogen were mixed in an inlet T-type micromixer, the resulting gas-liquid mixture was passed through a microfiltered bed packed with a platinum alumina catalyst (catalyst size 100 μm), the reaction temperature was set at 30 ℃, the reaction pressure was 5.0MPa, the residence time was 120s, the reaction product was collected at the outlet of the microfiltered bed reactor, and the obtained product was analyzed, whereby the conversion of 3, 4-dichloronitrobenzene was 100%, the yield of 3, 4-dichloroaniline was 99.8%, and the yield of dechlorinated aniline was 0.11%.
Example 2
According to the method, an experiment is carried out, a methanol solution of 3, 4-dichloronitrobenzene is prepared, the concentration is 5 wt%, and the molar ratio of hydrogen to 3, 4-dichloronitrobenzene is controlled to be 10: 1; the solution and hydrogen were mixed in an inlet membrane dispersion micromixer, the resulting gas-liquid mixture was passed through a microfilled bed packed with a ruthenium-carbon catalyst (catalyst size 600 μm), the reaction temperature was set at 50 ℃, the reaction pressure was 1.5MPa, the residence time was 70s, the reaction product was collected at the outlet of the microfilled bed reactor, and the obtained product was analyzed, whereby the conversion of 3, 4-dichloronitrobenzene was 100%, the yield of 3, 4-dichloroaniline was 99.5%, and the yield of dechlorinated aniline was 0.29%.
Example 3
According to the method, an experiment is carried out, a tetrahydrofuran solution of 3, 4-dichloronitrobenzene is prepared, the concentration is 15 wt%, and the molar ratio of hydrogen to 3, 4-dichloronitrobenzene is controlled to be 3.5: 1; the solution and hydrogen are mixed in an inlet micro-sieve pore micro-mixer, the formed gas-liquid mixture passes through a micro packed bed filled with a nickel silicon dioxide catalyst (the size of the catalyst is 50 microns), the reaction temperature is set to be 100 ℃, the reaction pressure is 2MPa, the residence time is 30s, reaction products are collected at the outlet of the micro packed bed reactor, and the obtained products are analyzed, so that the conversion rate of the obtained 3, 4-dichloronitrobenzene is 100%, the yield of the 3, 4-dichloroaniline is 99.5%, and the yield of the dechlorinated aniline is 0.21%.
Example 4
According to the method, an experiment is carried out, a methanol solution of 3, 4-dichloronitrobenzene is prepared, the concentration is 30 wt%, and the molar ratio of hydrogen to 3, 4-dichloronitrobenzene is controlled to be 4: 1; the solution and hydrogen are mixed in an inlet T-shaped micro mixer, the formed gas-liquid mixture passes through a micro packed bed filled with a platinum-carbon catalyst (the size of the catalyst is 1000 microns), the reaction temperature is set to be 60 ℃, the reaction pressure is 2MPa, the retention time is 50s, reaction products are collected at the outlet of the micro packed bed reactor, and the obtained products are analyzed, so that the conversion rate of the obtained 3, 4-dichloronitrobenzene is 100%, the yield of the 3, 4-dichloroaniline is 99.7%, and the yield of the dechlorinated aniline is 0.19%.
Example 5
According to the method, an experiment is carried out, a methanol solution of 3, 4-dichloronitrobenzene is prepared, the concentration is 15 wt%, and the molar ratio of hydrogen to 3, 4-dichloronitrobenzene is controlled to be 6: 1; the solution and hydrogen were mixed in an inlet T-type micromixer, the resulting gas-liquid mixture was passed through a microfiltered bed packed with a nickel-carbon catalyst (catalyst size 300 μm), the reaction temperature was set at 100 ℃, the reaction pressure was 2MPa, the residence time was 60s, the reaction product was collected at the outlet of the microfiltered bed reactor, and the obtained product was analyzed, with 100% conversion of 3, 4-dichloronitrobenzene, 98.9% yield of 3, 4-dichloroaniline, and 0.28% dechlorinated aniline.
Example 6
According to the method, an experiment is carried out, an isopropanol solution of 3, 4-dichloronitrobenzene is prepared, the concentration is 10 wt%, and the molar ratio of hydrogen to 3, 4-dichloronitrobenzene is controlled to be 8: 1; the solution and hydrogen are mixed in an inlet membrane dispersion micro mixer, the formed gas-liquid mixture passes through a micro packed bed filled with a nickel titanium dioxide catalyst (the size of the catalyst is 800 microns), the reaction temperature is set to be 90 ℃, the reaction pressure is set to be 2MPa, the residence time is 50s, reaction products are collected at the outlet of the micro packed bed reactor, and the obtained products are analyzed, so that the conversion rate of the obtained 3, 4-dichloronitrobenzene is 100%, the yield of the 3, 4-dichloroaniline is 98.77%, and the yield of the dechlorinated aniline is 0.27%.
Example 7
According to the method, an experiment is carried out, a methanol solution of 3, 4-dichloronitrobenzene is prepared, the concentration is 10 wt%, and the molar ratio of hydrogen to 3, 4-dichloronitrobenzene is controlled to be 4: 1; the solution and hydrogen were mixed in an inlet T-type micromixer, the resulting gas-liquid mixture was passed through a microfiltered bed packed with a nickel alumina catalyst (catalyst size 100 μm), the reaction temperature was set at 60 ℃, the reaction pressure was 2MPa, the residence time was 90s, the reaction product was collected at the outlet of the microfiltered bed reactor, and the obtained product was analyzed, with 100% conversion of 3, 4-dichloronitrobenzene, 99.34% yield of 3, 4-dichloroaniline, and 0.19% dechlorinated aniline.
Furthermore, it should be understood that various changes and modifications can be made by one skilled in the art after reading the above description of the present invention, and equivalents also fall within the scope of the invention as defined by the appended claims.
Claims (10)
1. A method for continuously and efficiently synthesizing 3, 4-dichloroaniline based on a fixed bed microreactor is characterized by comprising the following steps:
(1) dissolving 3, 4-dichloronitrobenzene serving as a raw material in a solvent to serve as a substrate solution to be hydrogenated;
(2) the substrate solution to be hydrogenated and hydrogen enter a micro mixer to be mixed to form a gas-liquid mixture with a good gas-liquid micro dispersion state, and then the gas-liquid mixture enters a micro packed bed reactor filled with a solid particle catalyst to react;
the reaction temperature is 30-150 ℃, and the pressure is 1-5 MPa;
the residence time of the gas-liquid mixture in the micro packed bed reactor is 10-120 s;
(3) and (3) carrying out gas-liquid separation on the gas-liquid mixture obtained after the reaction is finished, and enabling the liquid product to enter a subsequent separation and purification system.
2. The method according to claim 1, wherein in the step (1), the solvent is at least one of methanol, ethanol, propanol, isopropanol and tetrahydrofuran.
3. The method as claimed in claim 1 or 2, wherein the mass concentration of the 3, 4-dichloronitrobenzene in the solvent in the step (1) is 5-40 wt%.
4. The method of claim 1, wherein in step (2), the micromixer comprises one of a membrane dispersion reactor, a micromesh reactor, and a T-type reactor.
5. The method according to claim 1, wherein in the step (2), the reaction temperature is 50-70 ℃, and the pressure is 1.5-2.5 MPa;
the residence time of the gas-liquid mixture in the micro packed bed reactor is 30-100 s.
6. The method according to claim 1 or 5, wherein in the step (2), the molar ratio of the 3, 4-dichloronitrobenzene to the hydrogen in the substrate solution to be hydrogenated is 1: 3.5-10.
7. The method of claim 1, wherein in step (2), the size of the solid particulate catalyst is 50 to 1000 μm.
8. The method according to claim 1 or 7, wherein in the step (2), the solid particulate catalyst is at least one of a platinum carbon catalyst, a platinum/alumina catalyst, a ruthenium carbon catalyst, a nickel/alumina catalyst, a nickel/silica catalyst, and a nickel/titania catalyst.
9. The process according to claim 1, wherein in step (1), no dechlorination inhibitor is added to the solution of the substrate to be hydrogenated.
10. The method according to claim 1 or 9, wherein in the step (3), the content of dechlorinated by-products in the gas-liquid mixture obtained after the reaction is finished is less than 0.3 wt%.
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