CN116143632A - Preparation method of 2-chloro-4-nitroaniline and equipment for implementing preparation method - Google Patents
Preparation method of 2-chloro-4-nitroaniline and equipment for implementing preparation method Download PDFInfo
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Abstract
The invention provides a preparation method of 2-chloro-4-nitroaniline and equipment for implementing the preparation method. The preparation method of the 2-chloro-4 nitroaniline comprises the following steps: the pre-reaction step: placing ammonia water solution and 3, 4-dichloronitrobenzene in a microchannel reactor for pre-reaction to obtain a pre-reaction product; the reaction steps are as follows: continuously conveying the pre-reaction product to a circulating pipeline reactor for continuous reaction; obtaining a reaction product; post-treatment: and (3) carrying out post-treatment on the reaction product to obtain the 2-chloro-4 nitroaniline. The preparation method of the 2-chloro-4-nitroaniline combines rapid and severe heat release of the reaction at the early stage with the microchannel reactor, removes most of the reaction heat, and continuously completes the reaction by the subsequent coupling of the low-cost circulating pipeline reactor, thereby greatly reducing the safety risk and greatly improving the production efficiency, greatly reducing the equipment investment and the labor cost, and being more beneficial to improving the international competitiveness of the product.
Description
Technical Field
The invention relates to a preparation method of 2-chloro-4-nitroaniline and equipment for implementing the preparation method, in particular to a continuous preparation method of 2-chloro-4-nitroaniline and equipment for implementing the preparation method, belonging to the field of fine chemical engineering.
Background
The 2-chloro-4-nitroaniline is an important intermediate for disperse dyes such as red jade 2GFL, disperse dyes and pigment silver disk R, and can also be used for synthesizing the pyriproxyfen pesticide, and is also used as a medical intermediate in recent years.
At present, three main early methods for preparing o-chloro-p-nitroaniline are as follows: the first is that the p-nitrobenzene reacts with chlorine gas in dilute hydrochloric acid directly to prepare the catalyst; and the second is that the paranitroaniline reacts with sodium hypochlorite under the condition of dilute hydrochloric acid to indirectly obtain chlorine gas and the paranitroaniline. The third is a production method in which sodium hypochlorite is replaced with another oxidizing agent such as sodium chlorate. The essence of these three methods is the chlorination of chlorine-containing compounds with p-nitroaniline; however, the purity of the products obtained by the above processes is low (less than 95%), and the discharged industrial three wastes (waste gas, waste water and waste residue) are more.
In the prior art, 3, 4-dichloronitrobenzene and liquid ammonia are subjected to amination reaction at a certain temperature and pressure to obtain the catalyst; the finished product obtained by the method has high purity, does not contain forbidden dye components such as polychlorinated benzene or polychlorinated phenol, and is a new technology reformed in recent years. The process generally comprises the steps of carrying out batch reaction in an autoclave, wherein the single batch reaction time is generally about 1 day, and obtaining a finished product after separation, washing, filtering and drying after exiting the autoclave. However, international competitiveness is not strong due to relatively high production costs. In addition, the intermittent high-pressure ammonolysis reaction of 3, 4-dichloronitrobenzene needs to have the characteristics of large volume, high temperature and high pressure, toxic and harmful reaction, easy explosion and the like, the initial exothermic heat of the reaction is particularly severe, the temperature is rapidly increased, the control is difficult, the safety risk level of the reaction is high, the requirement on the equipment performance is high (the design pressure is often 1.5-2 times of the reaction pressure), the technical level of operators is also high, and the safety production cost is high.
Therefore, research on a safe, efficient and low-cost preparation method of 2-chloro-4-nitroaniline becomes a technical problem to be solved urgently.
Disclosure of Invention
Problems to be solved by the invention
In view of the technical problems existing in the prior art, for example: the invention firstly provides a preparation method of 2-chloro-4-nitroaniline, which has low purity, low safety, high cost, serious environmental pollution and the like. The preparation method combines rapid and violent heat release of the reaction at the early stage with the microchannel reactor, removes most of the reaction heat, and continuously completes the reaction in the subsequent coupling circulating pipeline reactor, so that the safety risk is greatly reduced by adopting intrinsically safe equipment and a continuous process, the production efficiency is greatly improved, the equipment investment and the labor cost are greatly reduced, and the international competitiveness of the product is better improved.
Solution for solving the problem
The invention provides a preparation method of 2-chloro-4 nitroaniline, which comprises the following steps:
the pre-reaction step: placing ammonia water solution and 3, 4-dichloronitrobenzene in a microchannel reactor for pre-reaction to obtain a pre-reaction product;
the reaction steps are as follows: continuously conveying the pre-reaction product to a circulating pipeline reactor for continuous reaction; obtaining a reaction product;
post-treatment: and (3) carrying out post-treatment on the reaction product to obtain the 2-chloro-4 nitroaniline.
The preparation method of the invention, wherein in the pre-reaction step, the mass concentration of the ammonia water solution is 20-55wt%, and the molar ratio of ammonia in the ammonia water solution to 3, 4-dichloronitrobenzene is 3-12:1.
The preparation method of the invention further comprises the step of heating the ammonia water solution and 3, 4-dichloronitrobenzene respectively before the pre-reaction step.
The preparation method of the invention, wherein the temperature of the ammonia water solution after heating is 80-140 ℃; the temperature of the 3, 4-dichloronitrobenzene after heating is 80-160 ℃.
The preparation method of the invention, wherein in the pre-reaction step, the temperature of the microchannel reactor is 170-200 ℃; the pressure of the micro-channel reactor is 3.5-8.5MPa; the residence time of the microchannel reactor is from 20 to 200 seconds.
The preparation method according to the present invention, wherein, in the reaction step, the residence time of the circulating pipeline reactor is 0.2 to 2 hours; the temperature of the circulating pipeline reactor is 170-200 ℃; the pressure of the circulating pipeline reactor is 3.5-8.5MPa.
The invention provides equipment for implementing the preparation method of 2-chloro-4 nitroaniline, which comprises a microchannel reactor and a circulating pipeline reactor which are connected.
The device according to the invention, wherein the microchannel reactor is further connected with an ammonia heat exchanger and a 3, 4-dichloronitrobenzene heat exchanger for heating an ammonia solution and 3, 4-dichloronitrobenzene, respectively.
The device according to the invention, wherein the circulating pipeline reactor is also connected with a transfer kettle for cooling and crystallizing the reaction product.
ADVANTAGEOUS EFFECTS OF INVENTION
The preparation method of the 2-chloro-4-nitroaniline combines rapid and severe heat release of the reaction at the early stage with the microchannel reactor, removes most of the reaction heat, and continuously completes the reaction by the subsequent coupling of the low-cost circulating pipeline reactor, thereby greatly reducing the safety risk and greatly improving the production efficiency, greatly reducing the equipment investment and the labor cost, and being more beneficial to improving the international competitiveness of the product.
Drawings
FIG. 1 shows a process flow diagram of one embodiment of the present invention;
wherein V1 is a melted 3, 4-dichloronitrobenzene storage tank, P1 is a 3, 4-dichloronitrobenzene delivery pump, and E1 is a 3, 4-dichloronitrobenzene heat exchanger; v2 is a prepared ammonia water solution storage tank, P2 is an ammonia water delivery pump, and E2 is an ammonia water heat exchanger; r1 is a micro-channel reactor, R2 is a circulating pipeline reactor, and R3 is a transfer kettle; m is a stirring motor.
Detailed Description
Various exemplary embodiments, features and aspects of the invention are described in detail below. The word "exemplary" is used herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a better illustration of the invention. It will be understood by those skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well known methods, procedures, means, equipment and steps have not been described in detail so as not to obscure the present invention.
Unless otherwise indicated, all units used in this specification are units of international standard, and numerical values, ranges of values, etc. appearing in the present invention are understood to include systematic errors unavoidable in industrial production.
In the present specification, the meaning of "can" includes both the meaning of performing a certain process and the meaning of not performing a certain process.
Reference throughout this specification to "some specific/preferred embodiments," "other specific/preferred embodiments," "an embodiment," and so forth, means that a particular element (e.g., feature, structure, property, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the elements may be combined in any suitable manner in the various embodiments.
In the present specification, the numerical range indicated by the term "numerical value a to numerical value B" means a range including the end point numerical value A, B.
In the present specification, when "normal temperature" or "room temperature" is used, the temperature may be 10 to 40 ℃.
<First aspect>
The first aspect of the present invention provides a method for preparing 2-chloro-4 nitroaniline, comprising the steps of:
the pre-reaction step: placing ammonia water solution and 3, 4-dichloronitrobenzene in a microchannel reactor for pre-reaction to obtain a pre-reaction product;
the reaction steps are as follows: continuously conveying the pre-reaction product to a circulating pipeline reactor for continuous reaction; obtaining a reaction product;
post-treatment: and (3) carrying out post-treatment on the reaction product to obtain the 2-chloro-4 nitroaniline.
The preparation method of the 2-chloro-4 nitroaniline does not use chlorine and does not introduce more chlorine atoms, so that the product obtained by the preparation method does not contain the by-products. The 2-chloro-4-nitroaniline obtained by the method is used for synthesizing disperse dyes, and cannot meet environmental protection indexes because the diazonium component contains forbidden compounds.
Pre-reaction step
The pre-reaction step is carried out in a micro-channel reactor, and specifically, an ammonia water solution and 3, 4-dichloronitrobenzene are placed in the micro-channel reactor for pre-reaction to obtain a pre-reaction product. The micro-channel reactor is advanced intrinsically safe equipment, the high temperature resistance of the general metal micro-reactor can reach more than 300 ℃, the pressure resistance is 10-20MPa, the micro-channel reactor has extremely large heat exchange area volume ratio, and the heat exchange efficiency can reach 10-30 times of that of the general reactor; the volume of the materials in the equipment is very small, the volume of the single industrial equipment is only 1-10L, and the equipment is full-automatic reaction equipment. The inventor of the present invention found that the reaction heat can be removed to the maximum extent after the microchannel reactor is used, and the safety risk caused by the burst of the chemical reaction heat of the present invention can be thoroughly restrained.
In some specific embodiments, in the pre-reaction step, the aqueous ammonia solution has a mass concentration of 20 to 55wt%, for example: 25%, 30%, 35%, 40%, 45%, 50%, etc. The inventor discovers that compared with the direct use of liquid ammonia, the pre-preparation of ammonia water with certain concentration firstly greatly reduces the fire hazard and explosion hazard in the reaction process; secondly, the ammonia concentration in the liquid ammonia is much higher than that of ammonia water, the pipeline pressure is also more than one time higher than that of the ammonia water, and safety accidents such as poisoning and the like are more easy to occur. Further, the molar ratio of ammonia to 3, 4-dichloronitrobenzene in the aqueous ammonia solution is 3-12:1, for example: 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, etc. When the molar ratio of ammonia in the ammonia water solution to 3, 4-dichloronitrobenzene is 3-12:1, 2-chloro-4 nitroaniline with high purity and high yield can be obtained.
In some embodiments, the method further comprises the step of separately heating the aqueous ammonia solution and 3, 4-dichloronitrobenzene prior to the pre-reaction step. The reaction can be orderly carried out by heating the ammonia water solution and 3, 4-dichloronitrobenzene respectively.
In general, the heating method is not particularly limited, and may be selected as needed. Specifically, in the present invention, in view of enabling the reaction to proceed continuously, it is preferable to heat the aqueous ammonia solution and 3, 4-dichloronitrobenzene using an aqueous ammonia heat exchanger and a 3, 4-dichloronitrobenzene heat exchanger, respectively.
In some embodiments, in view of the continuous progress of the reaction, in the present invention, it is generally continuous and continuously delivered to the microchannel reactor for the reaction. The flow rates of the aqueous ammonia solution and 3, 4-dichloronitrobenzene to be continuously fed are not particularly limited, and the flow rates can be set as required, so long as the molar ratio of ammonia in the aqueous ammonia solution to 3, 4-dichloronitrobenzene is 3-12:1.
Further, in some specific embodiments, the aqueous ammonia solution is heated to a temperature of 80 to 140 ℃, for example: 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃ and the like; the temperature of the 3, 4-dichloronitrobenzene after heating is 80-160 ℃, for example: 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, etc. When the temperature of 3, 4-dichloronitrobenzene is 80-160 ℃, the 3, 4-dichloronitrobenzene is basically in a molten state, so that the reaction can be more effectively carried out.
In some specific embodiments, in the pre-reaction step, the microchannel reactor has a temperature of from 170 ℃ to 200 ℃, for example: 175 ℃, 180 ℃, 185 ℃, 190 ℃, 195 ℃, etc.; the pressure of the microchannel reactor is 3.5-8.5MPa, for example: 4MPa, 4.5MPa, 5MPa, 5.5MPa, 6MPa, 6.5MPa, 7MPa, 7.5MPa, 8MPa and the like; the residence time of the microchannel reactor is from 20 to 200 seconds, for example: 40 seconds, 60 seconds, 80 seconds, 100 seconds, 120 seconds, 140 seconds, 160 seconds, 180 seconds, etc.
For residence time, it can be approximated as microreactor volume divided by feed rate (volume divided by volumetric flow rate equals time). For example, the total volume of the microchannel reactor was 860 ml/plate×5 plates=4.3L, and the total of the feed ammonia and 3, 4-dichloronitrobenzene volumetric flow rates was 516L/hr, then the residence time was 4.3/516×3600=30 seconds.
Reaction step
The reaction step is carried out in a circulating pipeline reactor, and specifically, the pre-reaction product is continuously conveyed to the circulating pipeline reactor for continuous reaction; the reaction product is obtained. The circulating pipeline reactor is a combined annular pipeline reactor with strong stirring and heat exchangers, and has higher safety and excellent mass and heat transfer functions. The inventors of the present invention found that the use of a circulating pipe reactor has the following functions: firstly, compared with a kettle-type reactor, the circulating pipeline reactor has smaller volume, is more resistant to high temperature and high pressure, and has higher safety; and secondly, the materials flow fully in the axial direction and the radial direction in the circulating pipeline reactor, and meanwhile, the heat exchange area and the volume ratio are large, so that the heat transfer performance is also good under the condition of ensuring good mass transfer.
According to the invention, the rapid and intense heat release of the early reaction and the micro-channel reactor are combined, most of the reaction heat is removed, and the subsequent coupling is carried out continuously by using the low-cost circulating pipeline reactor, so that the safety risk is greatly reduced, the production efficiency is greatly improved, and the equipment investment and the labor cost are greatly reduced.
In some specific embodiments, in the reacting step, the residence time of the recycle line reactor is from 0.2 to 2 hours, for example: 0.5 hours, 0.8 hours, 1 hour, 1.2 hours, 1.5 hours, 1.8 hours, etc.; in addition, the temperature and pressure of the recycle line reactor are generally the same as the microchannel reactor. Specifically, the temperature of the circulating pipeline reactor is 170-200 ℃, for example: 175 ℃, 180 ℃, 185 ℃, 190 ℃, 195 ℃, etc.; the pressure of the circulating pipeline reactor is 3.5-8.5MPa, for example: 4MPa, 4.5MPa, 5MPa, 5.5MPa, 6MPa, 6.5MPa, 7MPa, 7.5MPa, 8MPa, etc.
Post-treatment step
The post-treatment of the invention can be carried out in a transfer kettle, and the 2-chloro-4 nitroaniline is obtained by carrying out the post-treatment on the reaction product. Specifically, the reaction product can be subjected to solid-liquid separation after cooling crystallization in a transfer kettle, so as to obtain the 2-chloro-4 nitroaniline.
The 2-chloro-4 nitroaniline can be separated from the solid-liquid by cooling the reaction product to crystallize the 2-chloro-4 nitroaniline. The cooling temperature is not particularly limited in the present invention, and the cooling temperature may be reduced to normal temperature. Cooling, separating solid from liquid, washing and discharging. The mode of solid-liquid separation is not particularly limited, and may be a mode commonly used in the art, for example: filtration, centrifugation, and the like.
<Second aspect>
In a second aspect, the invention provides an apparatus for carrying out the process for the preparation of 2-chloro-4 nitroaniline according to the first aspect of the invention, comprising a microchannel reactor and a recycle line reactor connected. The circulating pipeline reactor is an annular reaction device with stirring and heat exchangers, and has strong stirring and mixing and higher area-volume heat exchange ratio.
According to the invention, the rapid and intense heat release of the early reaction and the micro-channel reactor are combined, most of the reaction heat is removed, and the subsequent coupling is carried out continuously by using the low-cost circulating pipeline reactor, so that the safety risk is greatly reduced, the production efficiency is greatly improved, and the equipment investment and the labor cost are greatly reduced. In the subsequent comparative case, it was found that a batch reactor with a daily throughput of 3.9 liter microreactors in combination with 270 liter tube reactors could reach and even exceed 10000 liter batch reactors.
In some specific embodiments, the microchannel reactor is further connected to an ammonia heat exchanger and a 3, 4-dichloronitrobenzene heat exchanger for heating the ammonia solution and 3, 4-dichloronitrobenzene, respectively.
In some specific embodiments, a transfer tank is also connected to the circulating pipeline reactor for cooling and crystallizing the reaction product.
Examples
Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
Example 1
Preparing molten 3, 4-dichloronitrobenzene solution and 20wt% ammonia solution in different containers respectively, and then conveying 3, 4-dichloronitrobenzene and ammonia by a constant flow pump A and a constant flow pump B respectively, wherein the flow rate of the pump A is set to be 3.84 g/min, and the flow rate of the ammonia by the pump B is set to be 20.4 g/min; so that the molar ratio of ammonia to 3, 4-dichloronitrobenzene is 12:1; the discharged material of the constant flow pump A is heated to 150 ℃ through a heat exchanger and then is input into the microchannel reactor through a check valve, the discharged material of the constant flow pump B is heated to 140 ℃ through the heat exchanger and then is subjected to the check valve, the discharged materials of the constant flow pump A and the constant flow pump B are kept to enter the microchannel reactor with the total volume of 40mL at the same time, the temperature in the microchannel reactor is controlled to be about 195 ℃, the pressure is controlled to be about 5MPa, and the residence time is 96 seconds; then the mixture enters a circulating pipeline reactor with the effective volume of 2500mL, the temperature and the pressure are the same as those in a microchannel reactor, the residence time is 1.67 hours, and finally the mixture enters two 5L transfer kettles. After the feeding is finished, the constant flow pump A is flushed with hot water and the materials in the microchannel reactor are replaced. And (3) decompressing the transfer kettle, cooling, decompressing all materials in the circulating pipeline reactor after the residence time of the materials reaches, discharging the materials to the transfer kettle, cooling, filtering and washing the materials to obtain the 2-chloro-4-nitroaniline product. The purity is 98.5% by HPLC detection; the calculated yield was 98%.
Example 2
Preparing molten 3, 4-dichloronitrobenzene solution and 47wt% ammonia solution in different containers respectively, and then conveying 3, 4-dichloronitrobenzene and ammonia by a constant flow pump A and a constant flow pump B respectively, wherein the flow rate of the pump A is set to be 42.24 g/min, and the flow rate of the ammonia is set to be 63.66 g/min; so that the molar ratio of ammonia to 3, 4-dichloronitrobenzene is 8:1; the discharged material of the constant flow pump A is heated to 140 ℃ through a heat exchanger and then is input into a microchannel reactor through a check valve, the discharged material of the constant flow pump B is heated to 100 ℃ through the heat exchanger and then enters the microchannel reactor through the check valve, the discharged material of the constant flow pump A and the discharged material of the constant flow pump B are kept to enter the microchannel reactor with the total volume of 50mL at the same time, the temperature in the microchannel reactor is controlled to be about 190 ℃, the pressure is about 7MPa, and the residence time is 29 seconds; then the mixture enters a circulating pipeline reactor with an overflow volume of 3000mL, the temperature and the pressure are the same as those in a microchannel reactor, the residence time is 0.5 hour, and finally the mixture enters two 10L transfer kettles. After the feeding is finished, the constant flow pump A is flushed with hot water and the materials in the microchannel reactor are replaced. The transfer kettle is decompressed firstly, cooled to below 60 ℃, then the pressure of the materials in the circulating pipeline reactor is decompressed completely after the residence time of the materials reaches, and the materials are discharged to the transfer kettle, cooled, filtered and washed to obtain the 2-chloro-4-nitroaniline product. The purity is 99.4% by HPLC detection; the calculated yield was 98.6%.
Example 3
Preparing molten 3, 4-dichloronitrobenzene solution and 38wt% ammonia solution in different containers respectively, and then conveying 3, 4-dichloronitrobenzene and ammonia by a constant flow pump A and a constant flow pump B respectively, wherein the pump A sets the flow rate to 69.12 g/min, and the pump B sets the flow rate of the ammonia to 96.62 g/min; so that the molar ratio of ammonia to 3, 4-dichloronitrobenzene is 6:1; the discharged material of the pump A is heated to 130 ℃ through a coil heat exchanger and then is input into a microchannel reactor through a check valve, the discharged material of the pump B is heated to 120 ℃ through the coil heat exchanger and then is subjected to the check valve, the discharged materials of the constant flow pump A and the constant flow pump B are kept to enter the microchannel reactor with the total volume of 160mL at the same time, the temperature in the reactor is controlled to be 185 ℃, the pressure is 5.8MPa, and the residence time is 59 seconds; then the mixture enters a circulating pipeline reactor with overflow volume of 5 liters, the temperature and the pressure are the same as those of a microchannel reactor, the residence time is 0.5 hour, and finally the mixture enters two 10L transfer kettles. After the feeding is finished, the constant flow pump A is flushed with hot water and the materials in the microchannel reactor are replaced. The transfer kettle is decompressed firstly, cooled to below 60 ℃, then the pressure of the materials in the circulating pipeline reactor is decompressed completely after the residence time of the materials reaches, and the materials are discharged to the transfer kettle, cooled, filtered and washed to obtain the 2-chloro-4-nitroaniline product. The purity is 99.3 percent through HPLC detection; the calculated yield was 98.7%.
Example 4
Preparing molten 3, 4-dichloronitrobenzene solution and 41wt% ammonia solution in different containers respectively, and then conveying 3, 4-dichloronitrobenzene and ammonia by a constant flow pump A and a constant flow pump B respectively, wherein the pump A sets the flow rate to 124.42 kg/h, and the pump B sets the flow rate of the ammonia to 214.94 kg/h; so that the molar ratio of ammonia to 3, 4-dichloronitrobenzene is 8:1; the discharged materials of the pump A are heated to 140 ℃ through a heat exchanger and then are input into a microchannel reactor through a check valve, the discharged materials of the pump B are heated to 110 ℃ through the heat exchanger and then are subjected to the check valve, the discharged materials of the constant flow pump A and the discharged materials of the constant flow pump B are kept to enter the microchannel reactor with the total volume of 3900mL at the same time, the temperature in the reactor is controlled to be 195 ℃, the pressure is 6.4MPa, and the residence time is 42 seconds; then the mixture enters a circulating pipeline reactor with overflow volume of 270 liters, the temperature and the pressure are the same as those of a microchannel reactor, the residence time is 0.8 hour, and finally the mixture enters two 3000L transfer kettles. After the feeding is finished, the constant flow pump A is flushed with hot water and the materials in the microchannel reactor are replaced. The transfer kettle is decompressed firstly, cooled to below 60 ℃, then the pressure of the materials in the circulating pipeline reactor is decompressed completely after the residence time of the materials reaches, and the materials are discharged to the transfer kettle, cooled, filtered and washed to obtain the 2-chloro-4-nitroaniline product. The purity is 99.5% by HPLC detection; the calculated yield was 99.0%. The daily output after stable production can reach 2655 Kg/day.
Comparative example 1
In a 2L stainless steel pressure reaction kettle, 1065 g of 28wt% ammonia water is added, and 240 g of 3, 4-dichloronitrobenzene is added with a molar ratio of 12:1; sealing the autoclave, stirring, heating by a jacket, maintaining the temperature at about 155 ℃, reacting for 12 hours, releasing pressure, cooling to below 60 ℃, pouring out materials, filtering, and washing with water to obtain the 2-chloro-4-nitroaniline product. The purity is 98.0% by HPLC detection; the calculated yield was 90%. The single batch of material stays in the reaction kettle for about 15 hours from feeding to discharging.
Comparative example 2
In a 10-cube high-pressure reaction kettle, 1700 kg of process water is firstly added, stirring is started, 1920 kg of melted 3, 4-dichloronitrobenzene is put in from a metering tank, then a liquid ammonia feeding valve and a jacket cooling water inlet and outlet valve of the reaction kettle are opened, 1700 kg of liquid ammonia is slowly added from a liquid ammonia metering tank with a weighing module, and ammonia is filled for about 2-3 hours; then opening the jacket steam of the reaction kettle to heat, reaching 160+/-3 ℃ after about 2.5 hours, keeping the temperature for 12 hours under the pressure of 4.8 MPa; then the exhaust valve is opened for decompression, the temperature is reduced to about 120 ℃, the jacket cooling water is slowly opened, the circulating water is used for cooling for crystallization, the temperature is reduced, after about 5 hours, the temperature is lower than 90 ℃, 2000 kg of process water with the temperature lower than 60 ℃ is added into the kettle, and then the process water is discharged to a transfer tank or filtering separation equipment, so that the 2-chloro-4-nitroaniline product is obtained. The purity is 99.0% by HPLC detection; the calculated yield was 97.1%. The whole process is to feed, raise the temperature, react with heat preservation, lower the temperature, crystallize and discharge, and the single batch of materials stays in the autoclave for about 22 hours.
Comparative example 3
Adding 3000 kg of process water, then adding 1475 kg of solid paranitroaniline, then adding 2100 kg of 30% hydrochloric acid, stirring and pulping for 3-4 hours, then cooling to 15-20 ℃, slowly dropwise adding 9000 kg of 8% sodium hypochlorite solution for 12 hours, controlling the dropwise adding temperature to 15-20 ℃, continuously preserving heat for 3-4 hours after the dropwise adding is finished, adding 75 kg of sodium metabisulfite or sodium thiosulfate after sampling and testing are qualified, stirring for half an hour to remove excessive chlorine, then transferring to a high-level tank, centrifuging, separating and washing to obtain a 2-chloro-4-nitroaniline product. The purity was 92.4% by HPLC and the calculated yield was 93.5%. The single batch remained in the kettle for about 21 hours.
It should be noted that, although the technical solution of the present invention is described in specific examples, those skilled in the art can understand that the present invention should not be limited thereto.
The foregoing description of embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described. The terminology used herein was chosen in order to best explain the principles of the embodiments, the practical application, or the technical improvements in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
Claims (9)
1. The preparation method of the 2-chloro-4 nitroaniline is characterized by comprising the following steps of:
the pre-reaction step: placing ammonia water solution and 3, 4-dichloronitrobenzene in a microchannel reactor for pre-reaction to obtain a pre-reaction product;
the reaction steps are as follows: continuously conveying the pre-reaction product to a circulating pipeline reactor for continuous reaction; obtaining a reaction product;
post-treatment: and (3) carrying out post-treatment on the reaction product to obtain the 2-chloro-4 nitroaniline.
2. The method according to claim 1, wherein in the pre-reaction step, the mass concentration of the aqueous ammonia solution is 20-55wt%, and the molar ratio of ammonia in the aqueous ammonia solution to 3, 4-dichloronitrobenzene is 3-12:1.
3. The method according to claim 1 or 2, further comprising the step of heating the aqueous ammonia solution and 3, 4-dichloronitrobenzene separately before the pre-reaction step.
4. The method according to claim 3, wherein the aqueous ammonia solution has a post-heating temperature of 80 to 140 ℃; the temperature of the 3, 4-dichloronitrobenzene after heating is 80-160 ℃.
5. The method according to any one of claims 1 to 4, wherein in the pre-reaction step, the temperature of the microchannel reactor is 170 to 200 ℃; the pressure of the micro-channel reactor is 3.5-8.5MPa; the residence time of the microchannel reactor is from 20 to 200 seconds.
6. The process according to any one of claims 1 to 5, wherein in the reaction step, the residence time of the circulating pipeline reactor is 0.2 to 2 hours; the temperature of the circulating pipeline reactor is 170-200 ℃; the pressure of the circulating pipeline reactor is 3.5-8.5MPa.
7. An apparatus for carrying out the process for preparing 2-chloro-4-nitroaniline according to any one of claims 1 to 6, comprising a microchannel reactor and a recycle line reactor connected.
8. The apparatus of claim 7, wherein the microchannel reactor is further connected to an ammonia heat exchanger and a 3, 4-dichloronitrobenzene heat exchanger for heating the ammonia solution and 3, 4-dichloronitrobenzene, respectively.
9. The apparatus according to claim 7 or 8, wherein the circulating pipeline reactor is further connected to a transfer reactor for cooling and crystallizing the reaction product.
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