CN115057781A - Production method of nitrobenzene - Google Patents
Production method of nitrobenzene Download PDFInfo
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- CN115057781A CN115057781A CN202210741547.1A CN202210741547A CN115057781A CN 115057781 A CN115057781 A CN 115057781A CN 202210741547 A CN202210741547 A CN 202210741547A CN 115057781 A CN115057781 A CN 115057781A
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- C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
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Abstract
The application belongs to the field of nitrobenzene production, and particularly relates to a nitrobenzene production method. The method comprises the following steps: mixing benzene and acid, and feeding the mixture into a micro-reactor for nitration reaction; and then, the organic phase is sent to a centrifugal machine for centrifugation, the obtained organic phase is sequentially subjected to prewashing, alkaline washing and final washing through a second centrifugal machine, a third centrifugal machine and a fourth centrifugal machine, and finally nitrobenzene obtained by centrifugal washing is discharged out of the centrifugal machine from a discharge port of the organic phase of the fourth centrifugal machine. The invention provides a new technology for continuously producing nitrobenzene, which carries out nitration and dilution through a microreactor and adopts a centrifuge for washing and separation. When the microreactor is used for nitration, the mass transfer and heat transfer effects in the reaction process are good, and the separation efficiency of centrifugal equipment is high. The method has the advantages of intrinsic safety, high product selectivity, high production efficiency and the like.
Description
Technical Field
The invention belongs to the field of nitrobenzene production, and particularly relates to a nitrobenzene production method.
Background
Nitrobenzene is an important chemical intermediate, is used as a raw material for producing aniline, and is also used for producing organic synthesis industries such as dye, spice, explosive and the like.
At present, most domestic enterprises adopt a kettle type reactor to produce nitrobenzene, but the volume of the kettle type reaction kettle is large (generally, the volume of a single kettle is more than or equal to 10 m) 3 ) The material stock is more, and once an accident occurs, the danger is very high. Meanwhile, in the subsequent separation, because the tower is adopted for separation, the tower has large volume and large storage amount, and great potential safety hazard exists. Therefore, it is very important to find an industrial production method of nitrobenzene with wide raw material source, intrinsic safety, good selectivity and high efficiency.
The micro-reaction technology originates from Europe in the early 90 s of the 20 th century, the size of a reactor channel is micron-sized, and compared with the traditional reactor, the micro-reactor has the advantages of short molecular diffusion distance, fast mass transfer, laminar flow in the channel, narrow residence time distribution, no back mixing, overlarge specific surface area of unit volume, fast heat transfer speed, strong heat exchange capacity and easy temperature control. Microreactors include microchannel reactors, tubular reactors, and other similar reactors.
Because the micro-reactor has small volume, the liquid storage capacity is small, the micro-reactor is particularly suitable for dangerous reactions such as nitration and the like, and even if danger occurs, the held small liquid can not cause more serious consequences.
Patent CN101613285 discloses a method for preparing nitrobenzene by using a tubular reactor, but a kettle type stirring device is adopted after the reaction, and although the liquid storage amount of the microchannel reaction part is less, the liquid storage amount is increased by the existence of the subsequent stirring kettle, which is not beneficial to the nitration safety. In addition, the nitrobenzene produced was crude nitrobenzene containing acid and was not purified.
In addition, after the reaction of the traditional nitrobenzene, tower separation or other containers with large liquid storage amount are generally adopted to separate acid and organic matters, which can also cause the retention amount of liquid in a tower to be increased and has larger potential safety hazard.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for producing nitrobenzene. The method adopted by the scheme of the invention has the advantages of high nitrobenzene yield, intrinsically safe process, high treatment efficiency and the like.
The invention provides a production method of nitrobenzene, which comprises the following steps:
mixing benzene and acid liquor, and feeding the mixture into a main feed inlet of a micro-reactor to perform partial nitration reaction; then mixing the mixture with acid liquor added into the microreactor through the first feed inlet to perform complete nitration reaction; then mixing with water added into the microreactor through a second feed inlet for dilution; then discharging the microreactor from a discharge hole;
the product of the microreactor is discharged from the discharge hole and enters a first centrifuge for centrifugal separation, and the obtained organic phase is sequentially subjected to centrifugal washing by a second centrifuge, a third centrifuge and a fourth centrifuge to obtain nitrobenzene;
the centrifugal washing step specifically comprises the following steps: sending the organic phase obtained by centrifugation in the first centrifuge into a first feed port of a second centrifuge, mixing the organic phase with water added through a second feed port of the second centrifuge, and then carrying out centrifugal prewashing; feeding the organic phase obtained by centrifugal prewashing into a first feed inlet of a third centrifuge, mixing the organic phase with alkali liquor added through a second feed inlet of the third centrifuge, and then carrying out centrifugal alkali washing; sending the organic phase obtained by the centrifugal alkali washing into a first feed port of a fourth centrifuge, mixing the organic phase with water added through a second feed port of the fourth centrifuge, and then carrying out centrifugal final washing, wherein the obtained organic phase is discharged out of the centrifuge from an organic phase discharge port of the fourth centrifuge; and in the centrifugal washing process, the water phase is discharged out of the centrifuge from a water phase discharge port of the centrifuge.
Preferably, the microreactor is a microchannel reactor or a tubular reactor.
Preferably, the acid solution used for the partial nitration and the complete nitration is a mixed acid solution containing nitric acid and sulfuric acid, wherein the mass content of the nitric acid is 25-38%, and the mass content of the sulfuric acid is 52-66%.
Preferably, the amount ratio of the benzene to the nitric acid in the acid solution for reaction (partial nitration reaction and complete nitration reaction) is 1: (1.05-1.1).
Preferably, the acid solution used for the partial nitration and the complete nitration is added into the microreactor for 2-3 times.
Preferably, when the acid solution is added for 2 times, the adding proportion is (55-68) wt% in sequence according to the total adding amount of the used acid solution: (45-32) wt%, the total addition amount being 100 wt%; when the materials are added for 3 times, the adding proportion is (45-52) wt%: (33-40) wt%: (8-22) wt%, and the total amount added is 100 wt%.
Preferably, the temperature of the partial nitrification reaction and the temperature of the complete nitrification reaction are independently selected to be 40-48 ℃, and the pressure of the partial nitrification reaction and the pressure of the complete nitrification reaction are independently selected to be 0.9-1.4 MPa.
Preferably, after the dilution, the mass percentage concentration of the sulfuric acid in the system is 60-75%.
Preferably, the alkali liquor is 5-15 wt% of soda ash solution.
Preferably, in the centrifugal prewashing process, the mass ratio of the organic phase to the water is 1: (0.11-0.28); in the centrifugal alkali washing process, the mass ratio of the organic phase to the alkali liquor is 1: (0.12-0.24); in the centrifugal final washing process, the mass ratio of the organic phase to the water is 1: (0.11-0.26).
Compared with the prior art, the invention provides a production method of nitrobenzene, which comprises the following steps: benzene and acid are mixed and then are sent into a micro reactor for nitration reaction; and then, the organic phase is sent to a centrifugal machine for centrifugation, the obtained organic phase is sequentially subjected to prewashing, alkaline washing and final washing through a second centrifugal machine, a third centrifugal machine and a fourth centrifugal machine, and finally nitrobenzene obtained by centrifugal washing is discharged out of the centrifugal machine from a discharge port of the organic phase of the fourth centrifugal machine. The invention provides a process method for continuously producing nitrobenzene, which carries out nitration and dilution through a microreactor and adopts a centrifuge for washing and separation. When the microreactor is used for nitration, the mass transfer and heat transfer effects in the reaction process are good, and the separation efficiency of centrifugal equipment is high. The method has the advantages of intrinsic safety, high product selectivity, high production efficiency and the like, and has wide market prospect.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a flow chart of a nitrobenzene production process provided by the embodiment of the invention.
The drawings are numbered as follows: t1 is a benzene cache device, T2 is an acid liquor cache device, T3 is an acid diluent cache device, T4 is a prewash liquor cache device, T5 is an alkali liquor cache device, T6 is a final wash liquor cache device, C1 is a first centrifuge, C2 is a second centrifuge, C3 is a third centrifuge, C4 is a fourth centrifuge, 1 is a heating medium feed inlet of a microreactor heating section jacket layer, 2 is a benzene cache device feed inlet, 3 is an acid liquor cache device first feed inlet, 4 is an acid liquor cache device second feed inlet, 5 is an acid diluent cache device feed inlet, 6 is a main feed inlet of the microreactor, 7 is a first branch feed inlet of the microreactor, 8 is a second branch feed inlet of the microreactor, 9 is a first centrifuge feed inlet, 10 is a first feed inlet of the second centrifuge, 11 is a water phase discharge outlet of the first centrifuge, 12 is a second feed inlet of the second centrifuge, 13 is a first feed inlet of the third centrifuge, 14 is a water phase discharge hole of the second centrifuge, 15 is a first feed hole of the alkali liquor caching device, 16 is a second feed hole of the alkali liquor caching device, 17 is a second feed hole of the third centrifuge, 18 is a first feed hole of the fourth centrifuge, 19 is a water phase discharge hole of the third centrifuge, 20 is a second feed hole of the fourth centrifuge, 21 is an organic phase discharge hole of the fourth centrifuge, 22 is a water phase discharge hole of the fourth centrifuge, and 23 is a heat medium discharge hole of a micro-reactor heating section jacket layer.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a production method of nitrobenzene, which comprises the following steps of carrying out nitration reaction in a micro-reactor, diluting a mixture obtained by the nitration reaction with water, carrying out centrifugal separation to obtain crude nitrobenzene, and carrying out centrifugal washing on the crude nitrobenzene, thereby effectively improving the conversion rate, the reaction efficiency and the product purity, and comprising the following specific processes:
1) acid and alkali regulation:
adding sulfuric acid and nitric acid into an acid liquor caching device (T2) from a first feeding hole (3) of the acid liquor caching device and a second feeding hole (4) of the acid liquor caching device according to a certain proportion under stirring; benzene was added to the benzene buffer (T1) from benzene buffer feed inlet (2) with stirring. Wherein the mass content of the nitric acid is preferably 25-38%; the mass content of the sulfuric acid is preferably 52-68%; the mass ratio of the benzene to the nitric acid is preferably 1 (1.05-1.1). The acid buffer device (T2) is provided with a jacket, and condensed water is introduced into the jacket to dissipate heat generated during mixing.
Under stirring, adding soda ash and water into the alkali liquor buffer device (T5) from the first feed inlet (15) and the second feed inlet (16) of the alkali liquor buffer device according to a certain proportion. Wherein, the alkali liquor is preferably a 5-15% sodium carbonate solution. The alkali buffer device (T5) is provided with a jacket, and condensed water is introduced into the jacket to dissipate heat generated during mixing.
2) Nitration reaction:
conveying benzene in the benzene buffer device (T1) and mixed acid in the acid liquor buffer device (T2) to a main feed inlet (6) of the microreactor through a pump to enter the microreactor for nitration reaction, wherein part of the benzene and part of the nitric acid are nitrified; and then, the mixed solution after the nitration reaction is continuously subjected to complete nitration with the mixed acid entering the micro-reactor through the first feed inlet (7) to obtain the mixed solution after the complete nitration reaction. The main components of the mixed solution are nitrobenzene, a small amount of unreacted nitric acid and sulfuric acid with a catalytic effect.
In the invention, in order to ensure the relative stability of the reaction temperature, the heating section jacket layer of the micro-reactor is preferably maintained at a certain temperature by hot water at a certain temperature entering from a heating medium inlet (1) of the micro-reactor, and the hot water flows out from a heating medium outlet (23).
In the invention, the mixed acid added into the main feed inlet (6) and the first branch feed inlet (7) of the microreactor can be added into the microreactor for 2-3 times; when the materials are added for 2 times, the preferable adding proportion is (55-68) wt% to (45-32) wt% in sequence according to the total adding amount, and the total adding amount is 100 wt%; when the materials are added for 3 times, the preferable adding proportion is (45-52) wt%, (33-40) wt%, (8-22) wt%, and the total adding amount is 100 wt%.
In the present invention, the temperature during the nitration reaction is preferably controlled to 40 to 48 ℃ and the pressure during the nitration reaction is preferably controlled to 0.9 to 1.4 MPa.
3) Diluting:
in order to reduce the dissolution of nitrobenzene in sulfuric acid, water is continuously added into the microreactor after nitration reaction, and the sulfuric acid in the mixed solution is diluted. And conveying water in the acid diluent buffer device (T3) to a second feed inlet (8) of the microreactor through a pump, entering the microreactor, and mixing the water with the mixed solution after complete nitration in the microreactor to dilute the sulfuric acid.
In the invention, in order to ensure the relative stability of the separation temperature, the heating section jacket layer of the micro-reactor is preferably maintained at a certain temperature by hot water at a certain temperature entering from a heating medium inlet (1) of the micro-reactor, and the hot water flows out from a heating medium outlet (23).
In the present invention, the number of dilution is preferably 1 to 3. The concentration of the diluted sulfuric acid is preferably 60 to 75 percent.
4) Separation:
the diluted mixed solution enters a centrifuge (C1) through a first centrifuge feed inlet (9) for centrifugal separation, and the sulfuric acid of the separated heavy component is output through a first centrifuge aqueous phase discharge outlet (11); the resulting organic phase (crude nitrobenzene) is discharged through the discharge of the first centrifuge and then through the first feed inlet (10) of the second centrifuge into the second centrifuge (C2).
In the invention, the output liquid of the water phase discharge port (11) of the first centrifuge is preferably 60-75% sulfuric acid. After being concentrated by the acid concentration device, the sulfuric acid can be continuously recycled as concentrated acid.
In order to ensure the relative stability of the separation temperature, the outer jacket layer of the centrifugal machine maintains the temperature by using hot water with certain temperature so as to prevent the nitrobenzene from being solidified.
5) Washing:
and (4) continuously inputting the crude nitrobenzene obtained by the separation into a centrifuge for centrifugal washing. The centrifugal washing sequence comprises pre-washing, alkali washing and final washing, and specifically comprises the following steps:
pre-washing: the crude nitrobenzene fed to the first inlet (10) of the second centrifuge is thoroughly mixed at the lower end of the centrifuge (C2) with a metered amount of water pumped to the second inlet (12) of the second centrifuge and then centrifuged. The water phase obtained by separation is output from a water phase discharge port (14) of a second centrifuge; the obtained organic phase (the pre-washed nitrobenzene) is output and then enters a third centrifuge (C3) through a first feed inlet (13) of the third centrifuge. Through this continuous prewashing, can wash away the majority of acid that dissolves in crude nitrobenzene.
Alkali washing: and fully mixing the pre-washed nitrobenzene conveyed to the first feed port (13) of the third centrifuge and the excess soda solution conveyed to the second feed port (17) of the third centrifuge through a pump at the lower end of the centrifuge (C3), and then carrying out centrifugal separation. The water phase obtained by separation is output from a water phase discharge port (19) of a third centrifuge; the resulting organic phase (nitrobenzene after alkaline washing) is discharged and then enters a fourth centrifuge (C4) through a fourth centrifuge first feed inlet (18). By this continuous alkaline washing, all the acid in the nitrobenzene can be washed away.
Final washing: and fully mixing the nitrobenzene subjected to the alkaline washing and conveyed to the first feed inlet (18) of the fourth centrifuge and the water conveyed to the second feed inlet (20) of the fourth centrifuge by a pump at the lower end of the centrifuge (C4), and then performing centrifugal separation. The water phase obtained by separation is output from a discharge port (22) of the organic phase of the fourth centrifuge; and the obtained organic phase is output from a water phase discharge port (21) of a fourth centrifugal machine to obtain nitrobenzene with higher purity. Through this continuous final washing, a small amount of alkali in nitrobenzene can be washed away.
In the invention, in order to ensure the relative stability of the temperature of the pre-washing, the alkali washing and the final washing, the outer jacket layer of the centrifuge maintains the temperature by using hot water with certain temperature so as to prevent the nitrobenzene from being solidified.
In the invention, in the pre-washing process, the mass ratio of the organic matter to the washing reagent water is preferably 1 (0.11-0.28); in the alkali washing process, a 5-15% soda solution is preferably selected as a washing agent, and the mass ratio of an organic matter to the washing agent soda solution is preferably 1 (0.12-0.24); in the final washing process, the mass ratio of the organic matters to the washing reagent water is preferably 1 (0.11-0.26).
The production method of nitrobenzene provided by the invention has the following advantages:
1) the conversion rate of benzene is high: a micro reactor is adopted for nitration reaction, and when mixed acid is fed for multiple times, the conversion rate of benzene is high;
2) the reaction and separation process is safe, fast and efficient: in the reactor and diluter type, a micro-reactor is adopted, so that the problem of great safety caused by large liquid storage amount in the traditional kettle type reaction is solved, and the method has the advantage of intrinsic safety. Moreover, the material stays in the microreactor for about 5-15 seconds, the defect that the stay time in the traditional kettle-type reactor is over 30 minutes is overcome, and the method has the characteristics of obvious high reaction speed and high reaction efficiency;
3) the washing and purifying efficiency is high: when this adopts centrifuge to carry out prewashing, alkali wash and end and wash, because the liquid volume of depositing in the centrifuge is few, the big dangerous not enough of liquid volume of depositing when having overcome traditional tower washing, and the material dwell time is about 2 ~ 7 seconds in centrifuge, has the advantage that washing purification is fast, efficient.
For the sake of clarity, the following examples and comparative examples are described in detail below.
Example 1
The nitration reaction is carried out in a microchannel reactor, the process flow is shown in figure 1, and the specific process comprises the following steps:
conveying benzene and mixed acid to a main feed inlet (6) of the microchannel reactor through a pump to enter the microchannel reactor for nitration reaction, wherein part of the benzene and part of the nitric acid are nitrated; then, the mixed solution after the nitration reaction is continuously subjected to complete nitration with the mixed acid entering the micro-channel reactor through the first feed inlet (7) to obtain the mixed solution after the complete nitration reaction; the mixed liquid is mixed with water conveyed by an acid diluent buffer device (T3) at a second feed inlet (8) and enters a microchannel reactor to dilute sulfuric acid; the diluted mixed solution enters a centrifuge (C1) through a first centrifuge feed inlet (9) for centrifugal separation; the sulfuric acid of the heavy component obtained by separation is output through a water phase discharge port (11) of a first centrifugal machine; the obtained organic phase (crude nitrobenzene) enters a second centrifuge (C2) through a first feeding hole (10) of the second centrifuge, and is fully mixed with water with a metered amount which is conveyed to a second feeding hole (12) of the second centrifuge through a pump at the lower end of the centrifuge (C2) for centrifugal separation; the separated water phase is output from a water phase discharge port (14) of the second centrifuge, the obtained organic phase enters a third centrifuge (C3) through a first feed port (13) of the third centrifuge, and is fully mixed with the soda solution conveyed to a second feed port (17) of the third centrifuge through a pump at the lower end of the centrifuge (C3) for centrifugal separation; the separated water phase is output from a water phase discharge port (19) of the third centrifuge, the obtained organic phase enters a fourth centrifuge (C4) through a first feed port (18) of the fourth centrifuge, and is fully mixed with water conveyed to a second feed port (20) of the fourth centrifuge through a pump at the lower end of the centrifuge (C4) for centrifugal separation; the separated water phase is output from a fourth centrifuge organic phase discharge port (22), and the obtained organic phase is output from a fourth centrifuge water phase discharge port (21);
in the embodiment, the mass content of nitric acid in the mixed acid is 25%, the mass content of sulfuric acid is 66%, and the mass ratio of the benzene to the nitric acid in the mixed acid is 1: 1.05; adding the used mixed acid into a microchannel reactor for 2 times, wherein the ratio of adding the mixed acid for 2 times is 55 wt% to 45 wt% according to the total amount of the added mixed acid; water at a second feed inlet (8) enters the microchannel reactor for 3 times, and the water consumption ratio of 3 times is 2:3: 5; the mass percentage concentration of the diluted sulfuric acid is 60 percent; the temperature of the nitration reaction is controlled at 40 ℃, and the pressure is controlled at 0.9 MPa;
in the embodiment, in order to keep the reaction temperature relatively stable, the heating section jacket layer of the microreactor is preferably maintained at a certain temperature by hot water at a certain temperature entering from a heating medium inlet (1) of the microreactor, and the hot water flows out from a heating medium outlet (23);
in the embodiment, the concentration of sulfuric acid output from a water phase discharge port (11) of the first centrifuge is 60%, and the sulfuric acid is concentrated by an acid concentration device and then continuously recycled as concentrated acid;
in the present example, in the second centrifuge (C2), the mass ratio of organic matter to water at the second feed inlet (12) of the second centrifuge is 1: 0.11; in the third centrifuge (C3), the concentration of the soda solution at the second feeding port (17) is 5 wt%; the mass ratio of the organic matter to the soda solution is 1: 0.12; in the fourth centrifuge (C4), the mass ratio of the organic matters to the water at the second feed inlet (20) of the fourth centrifuge is 1: 0.11;
in this embodiment, in order to ensure the relative stability of the temperature during centrifugation, the outer jacket layer of the centrifuge maintains the temperature by using hot water at a certain temperature, so as to prevent the nitrobenzene from solidifying.
Example 2
The nitration reaction is carried out in a microchannel reactor, the process flow is shown in figure 1, and the specific process comprises the following steps:
conveying benzene and mixed acid to a main feed inlet (6) of the microchannel reactor through a pump to enter the microchannel reactor for nitration reaction, wherein part of the benzene and part of the nitric acid are nitrated; then, the mixed solution after the nitration reaction is continuously subjected to complete nitration with the mixed acid entering the micro-channel reactor through the first feed inlet (7) to obtain the mixed solution after the complete nitration reaction; the mixed liquid is mixed with water conveyed by an acid diluent buffer device (T3) at a second feed inlet (8) and enters a microchannel reactor to dilute sulfuric acid; the diluted mixed solution enters a centrifuge (C1) through a first centrifuge feed inlet (9) for centrifugal separation; the sulfuric acid of the heavy component obtained by separation is output through a water phase discharge port (11) of a first centrifugal machine; the obtained organic phase (crude nitrobenzene) enters a second centrifuge (C2) through a first feeding hole (10) of the second centrifuge, and is fully mixed with water with a metered amount which is conveyed to a second feeding hole (12) of the second centrifuge through a pump at the lower end of the centrifuge (C2) for centrifugal separation; the water phase obtained by pre-washing and separating is output from a water phase discharge port (14) of a second centrifuge; the obtained organic phase (the pre-washed nitrobenzene) enters a third centrifuge (C3) through a first feeding hole (13) of the third centrifuge, and is fully mixed with the soda solution conveyed to a second feeding hole (17) of the third centrifuge through a pump at the lower end of the centrifuge (C3) for centrifugal separation; the water phase obtained by separation is output from a water phase discharge port (19) of a third centrifuge; the obtained organic phase (nitrobenzene after alkali washing) enters a fourth centrifuge (C4) through a first feeding hole (18) of the fourth centrifuge, and is fully mixed with water conveyed to a second feeding hole (20) of the fourth centrifuge through a pump at the lower end of the centrifuge (C4) for centrifugal separation; the water phase obtained by separation is output from a discharge port (22) of the organic phase of the fourth centrifuge; the obtained organic phase is discharged from a water phase discharge port (21) of a fourth centrifuge;
in the embodiment, the mass content of nitric acid in the mixed acid is 38%, the mass content of sulfuric acid is 52%, and the mass ratio of benzene to nitric acid in the mixed acid is 1: 1.1; adding the used mixed acid into a microchannel reactor for 2 times, wherein the ratio of adding the mixed acid for 2 times is 68 wt% to 32 wt% according to the total amount of the added mixed acid; the water of the second feed inlet (8) enters the microchannel reactor for 2 times, and the water consumption ratio of 2 times is 3: 2; the mass percentage concentration of the diluted sulfuric acid is 75 percent; the temperature of the nitration reaction is controlled at 48 ℃, and the pressure is controlled at 1.4 MPa;
in the embodiment, in order to keep the reaction temperature relatively stable, the heating section jacket layer of the microreactor is preferably maintained at a certain temperature by hot water at a certain temperature entering from a heating medium inlet (1) of the microreactor, and the hot water flows out from a heating medium outlet (23);
in the embodiment, the concentration of sulfuric acid output by a water phase discharge port (11) of the first centrifuge is 75%, and the sulfuric acid is concentrated by an acid concentration device and then is continuously recycled as concentrated acid;
in this example, in the second centrifuge (C2), the mass ratio of organic matter to water at the second feed inlet (12) of the second centrifuge is 1: 0.28; in the third centrifuge (C3), the concentration of the soda solution at the second feeding hole (17) is 15 wt%; the mass ratio of the organic matter to the soda solution is 1: 0.24; in the fourth centrifuge (C4), the mass ratio of the organic matters to the water at the second feed inlet (20) of the fourth centrifuge is 1: 0.26;
in this embodiment, in order to ensure the relative stability of the temperature during centrifugation, the outer jacket layer of the centrifuge maintains the temperature by using hot water at a certain temperature, so as to prevent the nitrobenzene from solidifying.
Example 3
The nitration reaction is carried out in a microchannel reactor, the process flow is shown in figure 1, and the specific process comprises the following steps:
conveying benzene and mixed acid to a main feed inlet (6) of the microchannel reactor through a pump to enter the microchannel reactor for nitration reaction, wherein part of the benzene and part of the nitric acid are nitrated; then, the mixed solution after the nitration reaction is continuously subjected to complete nitration with the mixed acid entering the micro-channel reactor through the first feed inlet (7) to obtain the mixed solution after the complete nitration reaction; the mixed liquid is mixed with water conveyed by an acid diluent buffer device (T3) at a second feed inlet (8) and enters a microchannel reactor to dilute sulfuric acid; the diluted mixed solution enters a centrifuge (C1) through a first centrifuge feed inlet (9) for centrifugal separation; the sulfuric acid of the heavy component obtained by separation is output through a water phase discharge port (11) of a first centrifugal machine; the obtained organic phase (crude nitrobenzene) enters a second centrifuge (C2) through a first feeding hole (10) of the second centrifuge, and is fully mixed with water with a metered amount which is conveyed to a second feeding hole (12) of the second centrifuge through a pump at the lower end of the centrifuge (C2) for centrifugal separation; the water phase obtained by pre-washing and separating is output from a water phase discharge port (14) of a second centrifuge; the obtained organic phase (the pre-washed nitrobenzene) enters a third centrifuge (C3) through a first feeding hole (13) of the third centrifuge, and is fully mixed with the soda solution conveyed to a second feeding hole (17) of the third centrifuge through a pump at the lower end of the centrifuge (C3) for centrifugal separation; the water phase obtained by separation is output from a water phase discharge port (19) of a third centrifuge; the obtained organic phase (nitrobenzene after alkali washing) enters a fourth centrifuge (C4) through a first feeding hole (18) of the fourth centrifuge, and is fully mixed with water conveyed to a second feeding hole (20) of the fourth centrifuge through a pump at the lower end of the centrifuge (C4) for centrifugal separation; the water phase obtained by separation is output from a discharge port (22) of the organic phase of the fourth centrifuge; the obtained organic phase is discharged from a water phase discharge port (21) of a fourth centrifuge;
in this example, the mass content of nitric acid in the mixed acid was 30%, the mass content of sulfuric acid was 59%, and the mass ratio of benzene to nitric acid in the mixed acid was 1: 1.08; adding the used mixed acid into a microchannel reactor for 2 times, wherein the ratio of adding the mixed acid for 2 times is 70 wt% to 30 wt% according to the total amount of the added mixed acid; the water at the second feed inlet (8) enters the microchannel reactor for 1 time, and the mass percentage concentration of the diluted sulfuric acid is 70 percent; the temperature of the nitration reaction is controlled at 45 ℃ and the pressure is controlled at 1.0 MPa;
in the embodiment, in order to keep the reaction temperature relatively stable, the heating section jacket layer of the microreactor is preferably maintained at a certain temperature by hot water at a certain temperature entering from a heating medium inlet (1) of the microreactor, and the hot water flows out from a heating medium outlet (23);
in the embodiment, the concentration of sulfuric acid output from a water phase discharge port (11) of the first centrifuge is 70%, and the sulfuric acid is concentrated by an acid concentration device and then continuously recycled as concentrated acid;
in the present example, in the second centrifuge (C2), the mass ratio of organic matter to water at the second feed inlet (12) of the second centrifuge is 1: 0.20; in the third centrifuge (C3), the concentration of the soda solution at the second feeding port (17) is 10 wt%; the mass ratio of the organic matter to the soda solution is 1: 0.18; in the fourth centrifuge (C4), the mass ratio of the organic matters to the water at the second feed inlet (20) of the fourth centrifuge is 1: 0.19;
in this embodiment, in order to ensure the relative stability of the temperature during centrifugation, the outer jacket layer of the centrifuge maintains the temperature by using hot water at a certain temperature, so as to prevent the nitrobenzene from solidifying.
Example 4
The nitration reaction is carried out in the microchannel reactor, the process flow is shown in figure 1, and the specific process comprises the following steps:
conveying benzene and mixed acid to a main feed inlet (6) of the microchannel reactor through a pump to enter the microchannel reactor for nitration reaction, wherein part of the benzene and part of the nitric acid are nitrated; then, the mixed solution after the nitration reaction is continuously subjected to complete nitration with the mixed acid entering the micro-channel reactor through the first feed inlet (7) to obtain the mixed solution after the complete nitration reaction; the mixed liquid is mixed with water conveyed by an acid diluent buffer device (T3) at a second feed inlet (8) and enters a microchannel reactor to dilute sulfuric acid; the diluted mixed solution enters a centrifuge (C1) through a first centrifuge feed inlet (9) for centrifugal separation; the sulfuric acid of the heavy component obtained by separation is output through a water phase discharge port (11) of a first centrifugal machine; the obtained organic phase (crude nitrobenzene) enters a second centrifuge (C2) through a first feeding hole (10) of the second centrifuge, and is fully mixed with water with a metered amount which is conveyed to a second feeding hole (12) of the second centrifuge through a pump at the lower end of the centrifuge (C2) for centrifugal separation; the water phase obtained by pre-washing and separating is output from a water phase discharge port (14) of a second centrifuge; the obtained organic phase (the pre-washed nitrobenzene) enters a third centrifuge (C3) through a first feeding hole (13) of the third centrifuge, and is fully mixed with the soda solution conveyed to a second feeding hole (17) of the third centrifuge through a pump at the lower end of the centrifuge (C3) for centrifugal separation; the water phase obtained by separation is output from a water phase discharge port (19) of a third centrifuge; the obtained organic phase (nitrobenzene after alkali washing) enters a fourth centrifuge (C4) through a first feeding hole (18) of the fourth centrifuge, and is fully mixed with water conveyed to a second feeding hole (20) of the fourth centrifuge through a pump at the lower end of the centrifuge (C4) for centrifugal separation; the water phase obtained by separation is output from a discharge port (22) of the organic phase of the fourth centrifuge; the obtained organic phase is discharged from a water phase discharge port (21) of a fourth centrifuge;
in this example, the mass content of nitric acid in the mixed acid is 31%, the mass content of sulfuric acid is 59%, and the mass ratio of benzene to nitric acid in the mixed acid is 1: 1.08; adding the used mixed acid into a microchannel reactor for 3 times, wherein the ratio of adding the mixed acid for 2 times is 45 wt% to 42 wt% to 13 wt% according to the total adding amount; the water of the second feed inlet (8) enters the microchannel reactor for 2 times, and the water consumption ratio of 2:3 is obtained after 2 times; the mass percentage concentration of the diluted sulfuric acid is 70 percent; the temperature of the nitration reaction is controlled at 41 ℃, and the pressure is controlled at 1.1 MPa;
in the embodiment, in order to keep the reaction temperature relatively stable, the heating section jacket layer of the microreactor is preferably maintained at a certain temperature by hot water at a certain temperature entering from a heating medium inlet (1) of the microreactor, and the hot water flows out from a heating medium outlet (23);
in the embodiment, the concentration of sulfuric acid output from a water phase discharge port (11) of the first centrifuge is 70%, and the sulfuric acid is concentrated by an acid concentration device and then continuously recycled as concentrated acid;
in this example, in the second centrifuge (C2), the mass ratio of organic matter to water at the second feed inlet (12) of the second centrifuge is 1: 0.19; in the third centrifuge (C3), the concentration of the soda solution at the second feeding port (17) is 10 wt%; the mass ratio of the organic matter to the soda solution is 1: 0.17; in the fourth centrifuge (C4), the mass ratio of the organic matters to the water at the second feed inlet (20) of the fourth centrifuge is 1: 0.18;
in this embodiment, in order to ensure the relative stability of the temperature during centrifugation, the outer jacket layer of the centrifuge maintains the temperature by using hot water at a certain temperature, so as to prevent the nitrobenzene from solidifying.
Example 5
The same as example 1 except that the reactor was a tubular reactor.
Example 6
The same as example 2, except that the reactor was a tubular reactor.
Example 7
The same as example 3, except that the reactor was a tubular reactor.
Example 8
The same as example 4, except that the reactor was a tubular reactor.
Comparative example 1
A metering pump is adopted to add nitrobenzene into a first-stage kettle and add mixed acid of nitric acid and sulfur into a third-stage kettle of 3-stage reaction kettles which are continuously connected in series, and in order to maintain stable reaction and prevent over violent reaction, the nitrobenzene and the mixed acid adopt reverse flow. After the completion of the reaction, the separated lower acid was diluted 1 time in a dilution tower and separated, and the lower sulfuric acid concentration was maintained at 60%. And 3 towers are connected in series, the separated upper-layer organic matter is sequentially subjected to pre-washing, alkali washing and final washing by using water, soda ash solution and water, the flow direction of the organic matter and a detergent is countercurrent during washing, namely, a water-phase detergent enters from the lower part of the tower and is retained from the upper part, and an organic phase flows out from the lower layer.
The mass ratio of the benzene to the nitric acid in the mixed acid is 1:1.05, the mass content of the nitric acid in the mixed acid is 25%, the mass content of the sulfuric acid in the mixed acid is 66%, the reaction temperature is 40 ℃, and the pressure is normal pressure.
The washing liquid of the pre-washing, the alkali washing and the final washing are respectively water, 5% of soda solution and water, and the mass ratio of the organic matter to the washing reagent in the pre-washing, the alkali washing and the final washing is respectively 1:0.11, 1:0.12 and 1: 0.11.
Comparative example 2
A metering pump is adopted to add nitrobenzene into a first-stage kettle and add mixed acid of nitric acid and sulfur into a third-stage kettle of 3-stage reaction kettles which are continuously connected in series, and in order to prevent the reaction from being too violent, the nitrobenzene and the mixed acid keep reverse flow. After the completion of the above reaction, the separated lower acid was diluted 1 time in a dilution tower and separated, and the lower sulfuric acid concentration was maintained at 75%. And 3 towers are connected in series, the separated upper-layer organic matter is sequentially subjected to pre-washing, alkali washing and final washing by using water, soda ash solution and water, the flow direction of the organic matter and a detergent is countercurrent during washing, namely, a water-phase detergent enters from the lower part of the tower and is retained from the upper part, and an organic phase flows out from the lower layer.
The mass ratio of the benzene to the nitric acid in the mixed acid is 1:1.08, the mass content of the nitric acid in the prepared mixed acid is 38%, the mass content of the sulfuric acid is 52%, the reaction temperature is 48 ℃, and the pressure is normal pressure.
The washing liquid of the pre-washing, the alkali washing and the final washing are respectively water, 10% of soda solution and water, and the mass ratio of the organic matter to the washing reagent in the pre-washing, the alkali washing and the final washing is respectively 1:0.28, 1:0.24 and 1: 0.26.
Comparative example 3
Nitrobenzene is added into a first-stage kettle and mixed acid of nitric acid and sulfur is added into a third-stage kettle of 3-stage reaction kettles which are continuously connected in series by adopting a metering pump, in order to prevent the reaction from being too violent, the nitrobenzene and the mixed acid keep reverse flow, the reaction temperature is 45 ℃, and the pressure is normal pressure. After the completion of the reaction, the separated lower acid was diluted 1 time in a dilution tower and separated, and the lower sulfuric acid concentration was maintained at 70%. And 3 towers are connected in series, the separated upper-layer organic matter is sequentially subjected to pre-washing, alkali washing and final washing by using water, soda ash solution and water, the flow direction of the organic matter and a detergent is countercurrent during washing, namely, a water-phase detergent enters from the lower part of the tower and is retained from the upper part, and an organic phase flows out from the lower layer.
The mass ratio of the benzene to the nitric acid in the mixed acid is 1:1.1, and the prepared mixed acid contains 24% by mass of nitric acid and 69% by mass of sulfuric acid.
The washing liquid of the pre-washing, the alkali washing and the final washing are respectively water, 15% of soda solution and water, and the mass ratio of the organic matter to the washing reagent in the pre-washing, the alkali washing and the final washing is respectively 1:0.20, 1:0.18 and 1: 0.21.
Results of the experiment
The experimental results of examples 1-8 and comparative examples 1-3 are summarized in Table 1:
TABLE 1 Experimental results of Nitrobenzene production
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A production method of nitrobenzene is characterized by comprising the following steps:
mixing benzene and acid liquor, and feeding the mixture into a main feed inlet of a micro-reactor to perform partial nitration reaction; then mixing the mixture with acid liquor added into the microreactor through the first feed inlet to perform complete nitration reaction; then mixing with water added into the microreactor through a second feed inlet for dilution; then discharging the microreactor from a discharge hole;
the product of the microreactor is discharged from the discharge hole and enters a first centrifuge for centrifugal separation, and the obtained organic phase is sequentially subjected to centrifugal washing by a second centrifuge, a third centrifuge and a fourth centrifuge to obtain nitrobenzene;
the centrifugal washing step specifically comprises the following steps: sending the organic phase obtained by centrifugation in the first centrifuge into a first feed port of a second centrifuge, mixing the organic phase with water added through a second feed port of the second centrifuge, and then carrying out centrifugal prewashing; feeding the organic phase obtained by centrifugal prewashing into a first feed inlet of a third centrifuge, mixing the organic phase with alkali liquor added through a second feed inlet of the third centrifuge, and then carrying out centrifugal alkali washing; sending the organic phase obtained by the centrifugal alkali washing into a first feed port of a fourth centrifuge, mixing the organic phase with water added through a second feed port of the fourth centrifuge, and then carrying out centrifugal final washing, wherein the obtained organic phase is discharged out of the centrifuge from an organic phase discharge port of the fourth centrifuge; and in the centrifugal washing process, the water phase is discharged out of the centrifuge from a water phase discharge port of the centrifuge.
2. The production method according to claim 1, wherein the microreactor is a microchannel reactor or a tubular reactor.
3. The production method according to claim 1, wherein the acid solution used for the partial nitrification reaction and the complete nitrification reaction is a mixed acid solution containing nitric acid and sulfuric acid, wherein the mass content of nitric acid is 25-38%, and the mass content of sulfuric acid is 52-66%.
4. The production method according to claim 1, wherein the mass ratio of benzene to nitric acid in the acid solution for reaction is 1: (1.05-1.1).
5. The production method according to claim 1, wherein the acid solution used for the partial nitrification and the complete nitrification is added to the microreactor in 2 to 3 times.
6. The production method according to claim 5, wherein the adding proportion is (55-68) wt% after 2 times according to the total adding amount of the acid liquor: (45-32) wt%, the total addition amount being 100 wt%; when the materials are added for 3 times, the adding proportion is (45-52) wt%: (33-40) wt%: (8-22) wt%, and the total amount added is 100 wt%.
7. The production process according to claim 1, wherein the temperature of the partial nitrification reaction and the complete nitrification reaction is independently selected from 40 to 48 ℃, and the pressure of the partial nitrification reaction and the complete nitrification reaction is independently selected from 0.9 to 1.4 MPa.
8. The production method according to claim 3, wherein the mass percentage concentration of sulfuric acid in the system after the dilution is 60-75%.
9. The production method according to claim 1, wherein the alkali liquor is a 5-15 wt% soda ash solution.
10. The production method according to claim 1, wherein in the centrifugal prewashing process, the mass ratio of the organic phase to the water is 1: (0.11-0.28); in the centrifugal alkali washing process, the mass ratio of the organic phase to the alkali liquor is 1: (0.12-0.24); in the centrifugal final washing process, the mass ratio of the organic phase to the water is 1: (0.11-0.26).
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| CN1406151A (en) * | 2000-03-02 | 2003-03-26 | 陶氏环球技术公司 | Tubular reactor, process for conducting liquid/liquid multiphase reactions in a tubular reactor, and a process for ring-nitrating aromatic compounds |
| CN101759568A (en) * | 2008-12-25 | 2010-06-30 | 南化集团研究院 | Thermal insulation production method of nitrobenzene |
| CN102516082A (en) * | 2011-11-28 | 2012-06-27 | 烟台万华聚氨酯股份有限公司 | Method for preparing nitrobenzene through reacting benzene with mixed acid and washing crude nitrobenzene product |
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| CN103044261B (en) * | 2013-01-18 | 2014-09-17 | 徐德良 | Safe production method of nitro-compound |
| CN113248385B (en) * | 2021-05-31 | 2024-01-16 | 中石化南京化工研究院有限公司 | Method for reducing alkali consumption of acidic nitrobenzene |
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| CN101759568A (en) * | 2008-12-25 | 2010-06-30 | 南化集团研究院 | Thermal insulation production method of nitrobenzene |
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