CN113214087B - Preparation method and application of 4-chloro-3, 5-dinitro-benzotrifluoride - Google Patents
Preparation method and application of 4-chloro-3, 5-dinitro-benzotrifluoride Download PDFInfo
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- C07—ORGANIC CHEMISTRY
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- C07C205/00—Compounds containing nitro groups bound to a carbon skeleton
- C07C205/07—Compounds containing nitro groups bound to a carbon skeleton the carbon skeleton being further substituted by halogen atoms
- C07C205/11—Compounds containing nitro groups bound to a carbon skeleton the carbon skeleton being further substituted by halogen atoms having nitro groups bound to carbon atoms of six-membered aromatic rings
- C07C205/12—Compounds containing nitro groups bound to a carbon skeleton the carbon skeleton being further substituted by halogen atoms having nitro groups bound to carbon atoms of six-membered aromatic rings the six-membered aromatic ring or a condensed ring system containing that ring being substituted by halogen atoms
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- C07C201/06—Preparation of nitro compounds
- C07C201/08—Preparation of nitro compounds by substitution of hydrogen atoms by nitro groups
Abstract
The invention relates to the field of organic fine synthesis, in particular to a preparation method and application of 4-chloro-3, 5-dinitro-benzotrifluoride. Taking p-chlorotrifluoromethane as a raw material, carrying out mononitration substitution in a microchannel reactor, leading out a mononitration product, and then entering the microchannel reactor and an external reactor for carrying out dinitration substitution. The process for preparing the 4-chloro-3, 5-dinitro-benzotrifluoride through the matching of the microchannel reactor and an external reactor and the substitution reaction of mononitration, derivation and dinitration is safer, the product yield is high, five groups of special impurity removal steps are adopted, and the method is suitable for industrial application.
Description
Technical Field
The invention relates to the field of organic fine synthesis, in particular to a preparation method and application of 4-chloro-3, 5-dinitro-benzotrifluoride.
Background
The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.
4-chloro-3, 5-dinitro-benzotrifluoride is an intermediate of a plant growth regulator, flumetralin and a herbicide, trifluralin, and is commonly used as an organic synthesis intermediate and an intermediate of a medicinal dye. The chlorine-3, 5-dinitro-benzotrifluoride is mainly used in the industrial fields of pesticide production, medicine production and the like, is an intermediate of a dry-land herbicide trifluralin, and the herbicide such as trifluralin produced by the intermediate has the characteristics of safety, high efficiency, low toxicity, low residue and the like.
In the prior art, benzotrifluoride is usually used as a raw material, and p-chlorotrifluoromethane and half waste acid (dinitration waste acid) are reacted to prepare mononitrate 4-chloro-3-nitro-benzotrifluoride. And then carrying out nitration reaction on the primary nitration product by using a mixed acid nitration method to obtain a dinitration product 4-chloro-3, 5-dinitro-benzotrifluoride, wherein the dinitration method adopts a freshly prepared mixed acid, and because the sulfuric acid-nitric acid mixture used for primary nitration contains water and generates a large amount of water after the nitration reaction, the water and the mixed acid are mutually soluble, the concentration of the acid is diluted, the nitration reaction cannot be continuously carried out, and meanwhile, the mixed acid cannot be concentrated, and only can be neutralized by alkali and then discharged. The method has the advantages of serious emission pollution, strong corrosivity, more byproducts and serious tail gas pollution.
At present, the 4-chloro-3, 5-dinitro-benzotrifluoride is prepared by a two-step nitration method by using benzotrifluoride and mixed acid as raw materials in the domestic preparation process of the 4-chloro-3, 5-dinitro-benzotrifluoride. The two-step nitration method usually adopts batch production in an intermittent mode and a kettle mode, has small production scale, low speed, long reaction period, difficult control of the process, low yield, poor quality, difficult treatment and recycling of waste acid, serious resource waste and serious environmental pollution, needs to be carried out at lower temperature, needs a large amount of cold sources to remove reaction heat, has high water consumption and energy consumption, and is easy to explode and other accidents if not operated properly.
Kwiatkowski, pikarski proposed a scheme for the preparation of 4-chloro-3, 5-dinitrobenzotrifluoride from 4-chlorotrifluoroethylene. The first step is to convert 4-chlorotrifluoromethylene to 4-chloro-3-nitrotrifluorotoluene (mononitro) as completely as possible with a mixed acid (mixture of nitric acid and oleum). The second step helps to achieve as much separation of mononitrated compounds from spent acid as possible by adding dichloroethane. Thirdly, dinitration is carried out on the mononitro by using fresh mixed acid, and then the 4-chloro-3, 5-dinitrobenzotrifluoride is separated from the waste acid. The method also needs to recover dichloro, which increases the equipment investment.
The laboratory method of Schneider consists in carrying out a mononitration reaction with 4-chlorotrifluoromethane and mixed acid and then in adding the mononitrated product obtained to the mixed acid. The method has high conversion rate and yield, but the reaction temperature is low, and a large amount of energy is needed for cooling, thereby causing energy waste. The reaction period is very long, and the nitric acid is volatilized, so that waste is caused.
The inventor researches and finds that the existing method for preparing the 4-chloro-3, 5-dinitro-benzotrifluoride has the problems of low yield of mononitration and dinitration products, more impurities and difficult separation, and also comprises a step of removing dichloroethane, so that the nitration reaction speed has poor control precision and is very easy to cause explosion accidents.
Disclosure of Invention
In order to solve the problems of low yield, more impurities and difficult separation of mononitration and dinitration products in the prior art and the problems of complicated steps for removing dichloroethane, poor control precision of nitration reaction speed and high possibility of explosion accidents, the invention provides a preparation method of 4-chloro-3, 5-dinitro-benzotrifluoride, which comprises the steps of adding raw materials and mixed acid into a microchannel reactor according to a certain proportion and flow rate, leading out a mononitration substitution product, and then feeding the product into the microchannel reactor and an external reactor for reaction. The preparation method can improve the yield of the 4-chloro-3, 5-dinitro-benzotrifluoride, greatly reduce the explosion risk, avoid using dichloroethane by leading out the mononitration product and then carrying out the reaction, improve the product purity, and reduce byproducts and operation difficulty.
Specifically, the invention is realized by the following technical scheme:
the first aspect of the invention provides a preparation method of 4-chloro-3, 5-dinitro-trifluorotoluene, which is characterized in that para-chlorotrifluoromethane is taken as a raw material, mononitrate substitution is carried out in a microchannel reactor, a mononitrate product is led out, and then dinitro substitution is carried out in the microchannel reactor and an external reactor.
In a second aspect, the invention provides the application of a preparation method of 4-chloro-3, 5-dinitro-benzotrifluoride in a process for preparing the 4-chloro-3, 5-dinitro-benzotrifluoride.
One or more embodiments of the present invention have the following advantageous effects:
1) By the method of firstly leading out the mononitrated product and then carrying out the reaction, dichloroethane can be avoided, the product purity is improved, and byproducts and operation difficulty are reduced.
2) The micro-channel reactor is only used for conducting heat in time, but the yield of dinitro product is low and is only 30-40%, and the micro-channel reactor and the external reactor are used for carrying out the second-step nitration reaction of the chlorotrifluoromethane, so that the reaction time of dinitro substitution in the micro-channel reactor and the external reactor is regulated, and the yield of dinitro substitution is 90.35-96.55%.
3) The process for preparing the 4-chloro-3, 5-dinitro-benzotrifluoride through the matching of the microchannel reactor and an external reactor and the substitution reaction of mononitration, derivation and dinitration is safer, the product yield is high, five groups of special impurity removal steps are adopted, and the method is suitable for industrial application.
Detailed Description
The invention will be further illustrated with reference to the following 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 experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
Nitration, the nitration of an organic compound molecule by the introduction of a nitro group (-NO)2) The nitro group is a monovalent radical formed by nitric acid losing one hydroxyl group. The mechanism of the nitration of aromatic compounds is that the-OH group of the nitric acid is protonated, followed by the dehydration agent which removes a molecule of water to form the nitroxyl cation (NO)2) And finally, carrying out electrophilic aromatic substitution reaction with a benzene ring, and removing one molecule of hydrogen ions.
In such nitration reaction, the electron density of the aromatic ring determines the reaction rate of the nitration, and the higher the electron density of the aromatic ring, the faster the reaction rate. Since nitrate is basically an electrophile, the electron density of the aromatic ring is decreased after the first nitration, which may inhibit the second and subsequent nitration reactions. It is necessary to operate under more severe reaction conditions (e.g.elevated temperatures) or with stronger nitrating agents.
The commonly used nitrating agent mainly comprises concentrated nitric acid, fuming nitric acid, mixed acid of the concentrated nitric acid and concentrated sulfuric acid or a dehydrating agent matched with the nitrating agent.
Therefore, when the monochlorotrifluorotoluene is substituted by mononitro or dinitro, the following problems occur:
(1) The reaction heat in the nitration production is large, and the temperature is not easy to control. The nitration reaction generally occurs at a relatively low temperature, is prone to heat release, and is not easy to control, so the nitration needs to be carried out at a low temperature. In the nitration reaction, if operation negligence exists, such as: the reaction temperature may be suddenly increased, the oxidation capability of the mixed acid is enhanced, and polynitro compounds are generated to easily cause ignition and explosion due to the reasons of midway stirring stop, dropping of the stirring paddle, poor cooling effect, too high feeding speed, improper feeding ratio, out-of-control reaction temperature and the like.
(2) The reaction components are not uniformly distributed or contacted, and local overheating may occur. The nitration reaction is carried out in a heterogeneous phase, i.e. the organic phase is dispersed in the acid phase solution under vigorous stirring, the distribution and contact of the reaction components is not easy to be uniform, and the danger is caused by local overheating. In addition, if stirring is stopped, the two phases are easily layered, and a large amount of active nitrating agent is accumulated in the acid phase to cause local overheating of the contact surfaces of the two phases; when the stirring is restarted, a violent reaction is easily caused, and excessive heat is instantaneously released to cause explosion.
(3) The nitration reaction is easy to generate side reaction and over reaction, and the dinitrate and polynitro compounds have explosive characteristics.
(4) The organic matter is oxidized accidentally and is easy to explode. Because a large amount of strong oxidizing reagents exist in the reaction system, acid is frequently added in the experimental process or impurities enter the reaction system in the reagent adding process, so that the oxidation reaction is easily caused, the temperature is sharply increased, and the explosion is caused.
In order to solve the problems, the invention provides a method for preparing 4-chloro-3, 5-dinitro-benzotrifluoride, which is characterized in that the benzotrifluoride is used as a raw material, mononitro substitution is carried out in a microchannel reactor, a mononitro product is led out, and dinitrate substitution is carried out in the microchannel reactor and an external reactor.
In order to avoid the explosion risk caused by uneven stirring or untimely heat transfer, the invention adopts the microchannel reactor to carry out the synthesis reaction of the 4-chloro-3, 5-dinitro-benzotrifluoride, the microchannel reactor is not only easy to react, but also can be used as a mixing device and a reaction device to complete the mixing and reaction processes in the microchannel reactor. In addition, the microchannel reactor has small channel size, and cooling water and circulating water are arranged outside the microchannel reactor, so that heat can be conducted in time, and implosion and explosion are avoided.
Different from the conventional continuous nitration reaction or two-step nitration reaction, in the invention, dichloroethane can be avoided by the method of firstly leading out the mononitration product and then carrying out the reaction, the product purity is improved, and the byproducts and the operation difficulty are reduced.
In some embodiments of the invention, the process of standing, layering and separating the product after the export is also included, and because the mononitration reaction is carried out in the microchannel reactor, the reaction is sufficient, dichloroethane is not required to be used as a layering agent, and the purification difficulty is reduced.
After the reaction solution was separated, it was washed with an aqueous sodium bicarbonate solution and separated again to obtain 4-chloro-3-nitrobenzotrifluoride.
Although the heat can be conducted in time only by using the microchannel reactor, the number of sheets required by the microchannel reactor is large, the size is large, the yield of dinitro products is difficult to be obviously improved, and the yield is only 30-40%.
The process for preparing the 4-chloro-3, 5-dinitro-benzotrifluoride through the matching of the microchannel reactor and an external reactor and the substitution reaction of mononitrate, lead-out and dinitrate is safer, the product yield is high, five groups of special impurity removal steps are adopted, and the method is suitable for industrial application.
In one or more embodiments of the invention, the mononitration and dinitration substitution process is further carried out by introducing mixed acid. The mixed acid is a mixture of fuming nitric acid and fuming sulfuric acid.
The mixed acid is added to provide sufficient oxidation environment for the nitration reaction and to facilitate the nitration reaction.
Preferably, the molar ratio of fuming nitric acid to fuming sulfuric acid is 1;
the molar ratio of fuming nitric acid to fuming sulfuric acid affects the rate of substitution of the nitrating reactive groups, and when the molar ratio of fuming nitric acid to fuming sulfuric acid is 1.
Preferably, the mass fraction of the fuming nitric acid is 95-98%, and the mass fraction of the fuming nitric acid is 95-105%.
The concentration of nitric acid and sulfuric acid is high, on one hand, the existence of moisture is reduced, the influence on the substitution reaction is avoided, on the other hand, the oxidation degree is improved, the substitution effect is improved, and meanwhile, explosion caused by over substitution can be avoided.
In the invention, reactants and mixed acid flow and reaction sites in the mononitration and dinitration substitution reactions are not completely the same:
in the mononitration, the density of the mixed acid is 1.8-1.95mL/min, preferably 1.828 or 1.86mL/min. Too high or too low a density of the mixed acid is not favorable for uniform mixing of the two phases.
Preferably, the molar ratio of fuming nitric acid to p-chlorotrifluoromethane is 1-1.
The feeding amount of the p-chlorotrifluoromethane is 8-15mL/min, the feeding amount of the mixed acid is 18-30mL/min, preferably, the feeding amount of the p-chlorotrifluoromethane is 10mL/min, and the feeding amount of the mixed acid is 25.81mL/min.
The feeding amount of the raw materials and the mixed acid affects the mixing effect and the mono-nitro substitution effect, if the raw materials are added too fast, the yield of the mono-nitro product is low, and if the raw materials are added slowly, di-nitro substitution and even multi-nitro substitution can occur, so that the explosion risk is increased.
The mononitration reaction is carried out at 90-120 deg.C for 120-300 deg.C, preferably 110-110 deg.C for 150-260s, more preferably 110 deg.C for 155.48s.
In the mononitration, the reaction temperature and time are important factors influencing the reaction, and if and only if the mononitration temperature is the parameters, the mononitration can be realized, and at the moment, the yield and the purity of the mononitration product are high,
in the dinitration substitution, the mixed acid density is 1.8-1.95mL/min, preferably 1.904mL/min. The mixed acid density in the dinitrate reaction is higher than that in the mononitration substitution reaction because the dinitrate substitution is more difficult, and if the mixed acid density is too low, the acid content is low, which is not beneficial to the dinitrate reaction, and directly leads to the reduction of the yield and purity of the dinitrate product.
Preferably, the molar ratio of mononitrated product (i.e., dinitro reaction starting material) to fuming nitric acid is 1:1.3.
the feeding amount of the dinitrate product in the microchannel reactor is 3-10mL/min, the feeding amount of the mixed acid is 8-12mL/min, preferably, the feeding amount of the mononitrate product is 5mL/min, and the feeding amount of the mixed acid is 9.6mL/min.
The reaction temperature in the dinitro-substitution middle micro-channel reactor is 120-140 ℃, the reaction time is 300-400s, preferably 130-135 ℃,350-380s, and further preferably 130 or 135 ℃,361.64s;
compared with the mononitration reaction, the feeding amount of a reaction substrate (mononitration product) and mixed acid is reduced in the dinitration reaction, so that the difficulty of the dinitration reaction is high, the feeding amount is reduced, the reaction substrate and the mixed acid can be ensured to stay in a microchannel reactor for a longer time, and the success rate of the dinitration reaction is improved.
Preferably, the external reactor for dinitro substitution is selected from a reaction kettle, a flask or a reaction tower, as long as dinitro substitution reaction can be carried out in the outside.
In the invention, the mononitration reaction is carried out in the microchannel reactor, the dinitration reaction is carried out in the microchannel reactor and the external reactor, and the external reactor is added relative to the mononitration device due to higher difficulty in dinitration substitution. In addition, the inventor researches and discovers that the effect of promoting the dinitrate reaction by using the microchannel reactor is limited, and if the dinitrate substitution reaction is completely carried out in the microchannel reactor, although the mixing and heat conduction can be facilitated, the yield of the dinitrate product is only 30-40%, so that the dinitrate substitution is completed by introducing an external reactor into the dinitrate reaction and matching with the microchannel reactor.
It should be noted that, in the dinitrate substitution reaction, the timing of transferring from the microchannel reactor to the external reactor is very important, if the transfer is too early, the mononitrate product and the new mixed acid are not mixed uniformly, or the reaction system is not completely oxidized, and if the transfer is too late, the improvement of the yield of the dinitrate product is not significant, and the number of sheets or pipes of the microchannel reactor is increased, which increases the production cost.
It was found that the dinitrate product is of high purity, high yield and low impurities when the temperature in the external reactor is between 100 and 140 c, preferably between 110 and 135 c.
More preferably, the temperature is maintained at 110 ℃ for 0.5 to 1.5 hours, further preferably at 130 ℃ for 0.5 to 2.5 hours, still further preferably at 110 ℃ for 1 hour, and further preferably at 130 ℃ for 1 hour or 2 hours.
Different temperatures are used for heat preservation in the external container, and the purpose is that the temperature is increased from low temperature heat preservation to high temperature heat preservation, so that safety accidents caused by the fact that the proportion of nitric acid which just enters the external container for reaction is too high and the material is flushed and exploded can be effectively avoided.
In a second aspect, the invention provides the application of a preparation method of 4-chloro-3, 5-dinitro-benzotrifluoride in a process for preparing the 4-chloro-3, 5-dinitro-benzotrifluoride.
The present invention is described in further detail below with reference to specific examples, which are intended to be illustrative of the invention and not limiting.
Example 1
Preparing a nitric acid and sulfuric acid molar ratio of 1:4, mixed acid: taking a three-mouth bottle, putting the three-mouth bottle into an ice water tank, slowly adding 2895.69g of 97.3 percent sulfuric acid when the temperature is reduced to about 10 ℃, beginning to dropwise add 97.8 percent fuming nitric acid (463 g), and controlling the temperature in the bottle to be not more than 20 ℃ in the dropwise adding process. After the mixed acid is prepared, the density of the mixed acid is measured as follows: 1.86 g/mL. Respectively feeding mixed acid and p-chlorotrifluoromethane into a microchannel reactor (10 plates) by using a continuous feeding pump, wherein the feeding amount of the p-chlorotrifluoromethane is 10mL/min, the feeding amount of the mixed acid is 23.96mL/min, the temperature of an integrated machine is controlled at 110 ℃, the retention time is 155.48s, a jet-shaped gas is generated in a tube during discharging, and a gas phase detection result after sampling comprises that 0.74 percent of raw material remains, and mononitrate: 98.83%, impurities: 0.12 percent.
Example 2
Preparing a nitric acid and sulfuric acid molar ratio of 1:4, mixed acid: putting a three-mouth bottle into an ice water tank, slowly adding 1500.8g of 97.3% sulfuric acid when the temperature is reduced to about 10 ℃, starting to dropwise add 97.8% fuming nitric acid (239.96 g), and controlling the temperature in the bottle to be not more than 20 ℃ in the dropwise adding process. After the mixed acid is prepared, the density of the mixed acid is measured as follows: 1.86 g/mL. Respectively feeding mixed acid and p-chlorotrifluoromethane into a microchannel reactor (10 plates) by using a continuous feeding pump, wherein the feeding amount of the p-chlorotrifluoromethane is 10mL/min, the feeding amount of the mixed acid is 25.81mL/min, the temperature of an integrated machine is controlled at 110 ℃, the retention time is 155.48s, a jet-shaped gas is generated in a tube during discharging, and a gas phase detection result after sampling comprises that 0.66 percent of raw material remains, and mononitrate: 98.93%, impurities: 0.27 percent.
Example 3
Preparing a nitric acid and sulfuric acid molar ratio of 1:2, mixed acid: putting a three-mouth bottle into an ice water tank, slowly adding 694g of 105% sulfuric acid when the temperature is reduced to about 10 ℃, starting to dropwise add 97.8% fuming nitric acid (246.66 g), and controlling the temperature in the bottle to be not more than 20 ℃ in the dropwise adding process. After the mixed acid is prepared, the density of the mixed acid is measured as follows: 1.828g/mL mixed acid and p-chlorotrifluoromethane respectively enter a microchannel reactor (10 sheets) by using a continuous feed pump, the feeding amount of the p-chlorotrifluoromethane is 10mL/min, the feeding amount of the mixed acid is 10.91mL/min, the temperature of an integrated machine is controlled at 110 ℃, the retention time is 252.52s, a jet-shaped gas is generated in a tube during discharging, and a gas phase detection result after sampling comprises that 5.64 percent of raw material remains, and mononitro: 94.02%, impurities: 0.08 percent.
Example 4
Preparing a nitric acid and sulfuric acid molar ratio of 1:2, mixed acid: putting a three-mouth bottle into an ice water tank, slowly adding 694g of 105% sulfuric acid when the temperature is reduced to about 10 ℃, starting to dropwise add 97.8% fuming nitric acid (246.66 g), and controlling the temperature in the bottle to be not more than 20 ℃ in the dropwise adding process. After the mixed acid is prepared, the density of the mixed acid is measured as follows: 1.828 g/mL. Respectively feeding mixed acid and p-chlorotrifluoromethane into a microchannel reactor (10 plates) by using a continuous feeding pump, wherein the feeding amount of the p-chlorotrifluoromethane is 10mL/min, the feeding amount of the mixed acid is 10.91mL/min, the temperature of an integrated machine is controlled at 100 ℃, the retention time is 252.52s, a jet-shaped gas is generated in a tube during discharging, and a gas phase detection result after sampling comprises that 19.17 percent of raw materials remain, and mononitrate: 80.39%, impurities: 0.1 percent.
Example 5
Configuration 1:4, mixed acid: putting a three-mouth bottle into an ice water tank, slowly adding 105% sulfuric acid 1863.2g when the temperature is reduced to about 10 ℃, starting to dropwise add 97.8% fuming nitric acid (308.9 g), and controlling the temperature in the bottle to be not more than 20 ℃ in the dropwise adding process. After the mixed acid is prepared, the density of the mixed acid is measured as follows: 1.904g/mL of mixed acid and 4-chloro-3-nitrobenzotrifluoride (mononitration product) are respectively fed into a microchannel reactor (10 pieces) by a continuous feed pump, the feeding amount of the 4-chloro-3-nitrobenzotrifluoride is 5mL/min, the feeding amount of the mixed acid is 9.6mL/min, the temperature of an integrated machine is controlled at 140 ℃, the retention time is 361.64s, a material receiving port is connected with an 8m coil pipe and placed into an oil bath pot for heating (140 ℃) and sampling (gas phase detection result: 70.55% of the residual raw material, 28.41% of product and 1.04% of by-product), and the mixed acid and the mononitration product are connected into a three-mouth flask for heating from 110 ℃ to 130 ℃ (after being kept for 1h, the temperature is raised to 130 ℃ and kept for 1 h), and stirring, sampling and detection is carried out. (2 h, detection of 1.47% of raw material, 95.51% of product and 2.86% of byproduct)
The samples were taken from the coil in order to preliminarily test the yield of the product, etc.
Example 6
Preparing nitric acid and sulfuric acid 1:4, mixed acid: putting a three-necked bottle into an ice water tank, slowly adding 105% sulfuric acid 1863.2g when the temperature is reduced to about 10 ℃, starting to dropwise add 97.8% fuming nitric acid (308.9 g), and controlling the temperature in the bottle to be not more than 20 ℃ in the dropwise adding process. After the mixed acid is prepared, the density of the mixed acid is measured as follows: 1.904g/mL of mixed acid and 4-chloro-3-nitrobenzotrifluoride (mononitration product) are respectively fed into a microchannel reactor (10 pieces) by a continuous feeding pump, the feeding amount of the 4-chloro-3-nitrobenzotrifluoride is 5mL/min, the feeding amount of the mixed acid is 9.6mL/min, the temperature of an integrated machine is controlled at 140 ℃, the retention time is 361.64s, a material receiving port is connected with an 8m coil pipe and placed into an oil bath pot for heating (140 ℃) and sampling (gas phase detection result: 71.73 percent of the residual raw material, 27.48 percent of the product and 0.79 percent of by-product), the mixed acid and the 4-chloro-3-nitrobenzotrifluoride are connected into a three-neck flask for heating from 110 ℃ to 130 ℃ (after being kept for 1h, the temperature is raised to 130 ℃ and kept for 1 h), and stirring, sampling and detection are carried out. (2 h for detecting 6.21 percent of raw material, 90.35 percent of product and 3.51 percent of byproduct)
Example 7
Preparing nitric acid and sulfuric acid 1:4, mixed acid: putting a three-mouth bottle into an ice water tank, slowly adding 105% sulfuric acid 1863.2g when the temperature is reduced to about 10 ℃, starting to dropwise add 97.8% fuming nitric acid (308.9 g), and controlling the temperature in the bottle to be not more than 20 ℃ in the dropwise adding process. After the mixed acid is prepared, the density of the mixed acid is measured as follows: 1.904g/mL of mixed acid and 4-chloro-3-nitrobenzotrifluoride (mononitration product) respectively enter a microchannel reactor (10 sheets) by using a continuous feeding pump, the feeding amount of the 4-chloro-3-nitrobenzotrifluoride is 5mL/min, the feeding amount of the mixed acid is 9.6mL/min, the temperature of an integrated machine is controlled at 130 ℃, the retention time is 361.64s, a material receiving port is connected with an 8m coil pipe and placed into an oil bath pot to be heated to (130 ℃) for sampling (gas phase detection result: 76.02 percent of the rest of raw materials, 23.29 percent of products and 0.51 percent of byproducts), and the mixed acid and the mononitration product are connected into a three-neck flask to be heated to 135 ℃ from 110 ℃ and stirred (heated to 135 ℃ after being kept for 1h and kept for 2 h) for sampling detection. (3 h for detecting 0.91 percent of raw material, 96.55 percent of product and 2.54 percent of byproduct)
Example 8
Preparing nitric acid and sulfuric acid 1:4, mixed acid: putting a three-necked bottle into an ice water tank, slowly adding 105% sulfuric acid 1863.2g when the temperature is reduced to about 10 ℃, starting to dropwise add 97.8% fuming nitric acid (308.9 g), and controlling the temperature in the bottle to be not more than 20 ℃ in the dropwise adding process. After the mixed acid is prepared, the density of the mixed acid is measured as follows: 1.904g/mL of mixed acid and 4-chloro-3-nitrobenzotrifluoride (mononitration product) are respectively fed into a microchannel reactor (10 pieces) by a continuous feeding pump, the feeding amount of the 4-chloro-3-nitrobenzotrifluoride is 5mL/min, the feeding amount of the mixed acid is 9.6mL/min, the temperature of an integrated machine is controlled at 130 ℃, the retention time is 361.64s, a material receiving port is connected with an 8m coil and placed into an oil bath pot to be heated (130 ℃) for sampling (gas phase detection result: 83.10 percent of the rest of raw materials, 16.35 percent of products and 0.55 percent of byproducts), and the mixed acid and the mononitration product are connected into a three-neck flask to be heated from 110 ℃ to 135 ℃ and stirred (heated to 135 ℃ after being kept for 1 h) for sampling detection. (2 h detection of 6.36% of raw material, 91.27% of product and 2.37% of by-product)
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A preparation method of 4-chloro-3, 5-dinitro-trifluorotoluene is characterized in that the chlorotrifluoromethane is taken as a raw material, mononitrate substitution is carried out in a microchannel reactor, a mononitrate product is led out, and then dinitrate substitution is carried out in the microchannel reactor and an external reactor;
mixed acid is also introduced in the mono-nitro substitution and the di-nitro substitution;
the mixed acid is a mixture of fuming nitric acid and fuming sulfuric acid;
the molar ratio of fuming nitric acid to fuming sulfuric acid is 1;
the mass fraction of the fuming nitric acid is 95-98%, and the mass fraction of the fuming sulfuric acid is 95-105%;
the molar ratio of the fuming nitric acid to the p-chlorotrifluoromethylene is 1-1;
the feeding amount of the p-chlorotrifluoromethane is 8-15mL/min, and the feeding amount of the mixed acid is 18-30mL/min;
the temperature of the mononitration reaction is 90-120 ℃ and the time is 120-300s;
the molar ratio of the mononitrated product to fuming nitric acid is 1:1.25;
the feeding amount of the mononitrate product in the microchannel reactor is 3-10mL/min, and the feeding amount of the mixed acid is 8-12mL/min;
the reaction temperature in the dinitrate substituted middle micro-channel reactor is 120-140 ℃ and the reaction time is 300-400s;
the external reactor in the dinitrate substitution is selected from a reaction kettle, a flask or a reaction tower;
the temperature in the external reactor is kept at 110 ℃ for 0.5-1.5h, and then kept at 130 ℃ for 0.5-2.5h;
wherein the density of the mixed acid in the dinitration reaction is higher than that in the mononitration substitution reaction.
2. The process according to claim 1 for the preparation of 4-chloro-3, 5-dinitro-trifluorotoluene, wherein the molar ratio of fuming nitric acid to fuming sulfuric acid is 1.
3. The process according to claim 1, wherein the amount of p-chlorotrifluoromethane fed in the mononitration is 10mL/min and the amount of mixed acid fed in the mononitration is 25.81mL/min.
4. The process for the preparation of 4-chloro-3, 5-dinitro-trifluorotoluene according to claim 1, wherein the mononitration is carried out at a temperature of 110 ℃ for a period of 155.48 seconds.
5. The method of claim 1, wherein the mononitrate substitution is carried out at a rate of 5mL/min and the mixed acid is carried out at a rate of 9.6mL/min.
6. The method for preparing 4-chloro-3, 5-dinitro-trifluorotoluene according to claim 1, wherein the reaction temperature in the dinitro substitution microchannel reactor is 130-135 ℃ and the reaction time is 350-380s.
7. The process of claim 6, wherein the reaction temperature in the dinitro-substituted microchannel reactor is 130 or 135 ℃ and the reaction time is 361.64s.
8. The process for the preparation of 4-chloro-3, 5-dinitro-trifluorotoluene according to claim 1, wherein the temperature in the external reactor is maintained at 110 ℃ for 1 hour and then at 130 ℃ for 1 or 2 hours.
9. Use of a process for the preparation of 4-chloro-3, 5-dinitro-trifluorotoluene according to any one of claims 1 to 8 in a process for the preparation of 4-chloro-3, 5-dinitro-trifluorotoluene.
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