CN115057781B - Production method of nitrobenzene - Google Patents
Production method of nitrobenzene Download PDFInfo
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- CN115057781B CN115057781B CN202210741547.1A CN202210741547A CN115057781B CN 115057781 B CN115057781 B CN 115057781B CN 202210741547 A CN202210741547 A CN 202210741547A CN 115057781 B CN115057781 B CN 115057781B
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- C07C201/06—Preparation of nitro compounds
- C07C201/08—Preparation of nitro compounds by substitution of hydrogen atoms by nitro groups
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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: benzene and acid are mixed and then sent into a micro-reactor for nitration reaction; and then delivering the mixture into a centrifugal machine for centrifugation, sequentially carrying out pre-washing, alkaline washing and final washing on the obtained organic phase by a second centrifugal machine, a third centrifugal machine and a fourth centrifugal machine, and finally discharging nitrobenzene obtained by centrifugal washing from an organic phase discharge port of the fourth centrifugal machine. The application provides a new process for continuously producing nitrobenzene by adopting a micro-reactor for nitrification and dilution and adopting a centrifugal machine 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 application belongs to the field of nitrobenzene production, and particularly relates to a nitrobenzene production method.
Background
Nitrobenzene is an important chemical intermediate, which is used as raw material for producing aniline, and also used in organic synthesis industry for producing dye, perfume, explosive, etc.
At present, most domestic enterprises adopt a kettle type reactor to produce nitrobenzene, but because the kettle type reactor has larger volume (the volume of a single kettle is generally more than or equal to 10 m) 3 ) The materials are stored in a large quantity, and the danger is high once accidents occur. Meanwhile, in the subsequent separation, as the separation is carried out by adopting the tower, the volume of the tower is large, the storage quantity of the tower is large, and the 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 higher efficiency.
The micro-reaction technology originates from Europe in the beginning of the 90 th century, 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, super large specific surface area per unit volume, fast heat transfer speed, strong heat exchange capability and easy temperature control. Microreactors include microchannel reactors, tubular reactors, and other similar reactors.
The micro-reactor is particularly suitable for dangerous reactions such as nitration and the like because the micro-reactor is small in volume, and even if dangerous reactions occur, the smaller liquid can not cause larger 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 reaction part of the micro-channel is small, the liquid storage amount is increased by the existence of a subsequent stirring kettle, which is not beneficial to the nitrification safety. In addition, the nitrobenzene produced is crude nitrobenzene containing acid, without purification.
In addition, after the reaction of traditional nitrobenzene, tower separation or other large-liquid-storage-amount type containers are generally adopted to separate acid and organic matters, which also causes the increase of the retention amount of liquid in a tower and has great potential safety hazard.
Disclosure of Invention
In view of the above, the present application aims to provide a method for producing nitrobenzene. The method adopted by the scheme of the application has the advantages of high nitrobenzene yield, intrinsically safe process, high treatment efficiency and the like.
The application provides a production method of nitrobenzene, which comprises the following steps:
benzene and acid liquor are mixed and then sent into a main feed inlet of a micro-reactor for partial nitration reaction; then mixing the mixture with acid liquid which is added into the micro-reactor through a first feed inlet to carry out complete nitration reaction; then mixing the water with water added into the micro-reactor through a second feed inlet for dilution; then discharging the micro-reactor from the discharge port;
products discharged from the discharge port of the microreactor enter a first centrifugal machine for centrifugal separation, and the obtained organic phase sequentially passes through a second centrifugal machine, a third centrifugal machine and a fourth centrifugal machine for centrifugal washing to obtain nitrobenzene;
the centrifugal washing step specifically comprises the following steps: sending the organic phase obtained by centrifugation in the first centrifugal machine into a first feeding port of a second centrifugal machine, mixing the organic phase with water added through the second feeding port of the second centrifugal machine, and performing centrifugal pre-washing; feeding the organic phase obtained by centrifugal pre-washing into a first feed inlet of a third centrifugal machine, mixing with alkali liquor added through a second feed inlet of the third centrifugal machine, and performing centrifugal alkali washing; feeding the organic phase obtained by centrifugal alkaline washing into a first feed inlet of a fourth centrifugal machine, mixing with water added through a second feed inlet of the fourth centrifugal machine, and performing centrifugal final washing, wherein the obtained organic phase is discharged out of the centrifugal machine from an organic phase discharge outlet of the fourth centrifugal machine; in the centrifugal washing process, the water phase is discharged out of the centrifugal machine from a water phase discharge port of the centrifugal machine.
Preferably, the microreactor is a microchannel reactor or a tubular reactor.
Preferably, 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 the nitric acid is 25-38%, and the mass content of the sulfuric acid is 52-66%.
Preferably, the mass ratio of benzene to nitric acid in the acid solution for the reaction (partial nitration reaction and complete nitration reaction) is 1: (1.05-1.1).
Preferably, the acid solution used for carrying out the partial nitration reaction and the complete nitration reaction is added into the microreactor for 2 to 3 times.
Preferably, when the acid liquor is added for 2 times according to the total addition amount of the acid liquor, the addition ratio is (55-68) weight percent: (45-32 wt.%) and the total addition amount is 100 wt.%; when the mixture is added for 3 times, the adding proportion is (45-52) weight percent: (33-40 wt%): (8-22 wt%) and its total addition quantity is 100wt%.
Preferably, 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 1.4MPa.
Preferably, after the dilution, the mass percentage concentration of sulfuric acid in the system is 60-75%.
Preferably, the alkali liquor is a soda solution with the weight percent of 5-15%.
Preferably, in the centrifugal pre-washing process, the mass ratio of the organic phase to the water is 1: (0.11-0.28); in the centrifugal alkaline washing process, the mass ratio of the organic phase to the alkaline liquid is 1: (0.12 to 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 application provides a production method of nitrobenzene, which comprises the following steps: benzene and acid are mixed and then sent into a micro-reactor for nitration reaction; and then delivering the mixture into a centrifugal machine for centrifugation, sequentially carrying out pre-washing, alkaline washing and final washing on the obtained organic phase by a second centrifugal machine, a third centrifugal machine and a fourth centrifugal machine, and finally discharging nitrobenzene obtained by centrifugal washing from an organic phase discharge port of the fourth centrifugal machine. The application provides a process method for continuously producing nitrobenzene by adopting a micro-reactor for nitrification and dilution and adopting a centrifugal machine 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 being intrinsically safe, high in product selectivity, high in production efficiency and the like, and has a wide market prospect.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present application, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a nitrobenzene production process provided by an embodiment of the application.
The figures are marked as follows: t1 is benzene buffer device, T2 is acidizing fluid buffer device, T3 is acid diluent buffer device, T4 is pre-wash buffer device, T5 is alkali lye buffer device, T6 is final wash buffer device, C1 is first centrifuge, C2 is second centrifuge, C3 is third centrifuge, C4 is fourth centrifuge, 1 is the heat medium feed inlet of micro-reactor heating section jacket layer, 2 is benzene buffer device feed inlet, 3 is acidizing fluid buffer device first feed inlet, 4 is acidizing fluid buffer device second feed inlet, 5 is acid diluent buffer device feed inlet, 6 is micro-reactor's main feed inlet, 7 is micro-reactor's first branch feed inlet, 8 is micro-reactor's second branch feed inlet, 9 is first centrifuge feed inlet, 10 second centrifuge's first feed inlet, 11 is first centrifuge's aqueous phase discharge outlet, 12 is second centrifuge's second feed inlet, 13 is third centrifuge's aqueous phase discharge outlet, 14 is second centrifuge's aqueous phase discharge outlet, 15 is first centrifuge's first feed inlet, 16 is second centrifuge's second feed inlet, 16 is fourth centrifuge's aqueous phase buffer device feed inlet, 16 is fourth centrifuge's second feed inlet, 17 is fourth centrifuge's aqueous phase buffer device's second feed inlet, 7 is 16 is the third centrifuge's aqueous phase buffer device's second feed inlet, 7 is the second centrifuge's fourth feed inlet, and the fourth centrifuge's fourth feed inlet is the second centrifuge's 16 feed inlet is the second centrifuge's fourth feed inlet is the feed inlet.
Detailed Description
The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The application provides a production method of nitrobenzene, which comprises the steps of performing nitration reaction in a microreactor, diluting a mixture obtained by the nitration reaction with water, and centrifugally separating to obtain crude nitrobenzene, and centrifugally washing the crude nitrobenzene, so that the conversion rate, the reaction efficiency and the product purity are effectively improved, and the specific process is as follows:
1) Acid and alkali regulation:
under stirring, adding sulfuric acid and nitric acid into an acid liquor buffer device (T2) from a first feed port (3) of the acid liquor buffer device and a second feed port (4) of the acid liquor buffer device according to a certain proportion; benzene is added into the benzene buffer device (T1) from the feed port (2) of the benzene buffer device under 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 benzene to nitric acid is preferably 1 (1.05-1.1). The acid liquor buffer device (T2) is provided with a jacket, and condensed water is led into the jacket so as to dissipate heat generated during mixing.
Under stirring, adding sodium carbonate and water into the alkali liquor buffer device (T5) from a first feed inlet (15) of the alkali liquor buffer device and a second feed inlet (16) of the alkali liquor buffer device according to a certain proportion. Wherein, the alkali liquor is preferably 5-15% sodium carbonate solution. The alkali buffer device (T5) is provided with a jacket, and condensed water is led into the jacket so as to dissipate heat generated during mixing.
2) Nitration reaction:
the mixed acid in the benzene buffer device (T1) and the acid liquid buffer device (T2) is conveyed to a main feed inlet (6) of the micro-reactor through a pump to enter the micro-reactor for nitration reaction, and at the moment, part of benzene and part of nitric acid are nitrated; and then, the mixed solution after the nitrification reaction is continuously subjected to complete nitrification with mixed acid entering the micro-reactor through the first feed inlet (7) to obtain the mixed solution after the complete nitrification reaction. The main components of the mixed solution are nitrobenzene, a small amount of unreacted nitric acid and sulfuric acid with catalytic action.
In the application, in order to ensure the relative stability of the reaction temperature, the jacket layer of the heating section of the micro-reactor is preferably maintained at the temperature by using hot water with a certain temperature entering from the heating medium feed port (1), and the hot water flows out from the heating medium discharge port (23).
In the application, mixed acid added into a main feed inlet (6) and a first branch feed inlet (7) of the micro-reactor can be added into the micro-reactor for 2-3 times; when the mixture is added for 2 times according to the total addition amount, the preferable addition ratio is (55-68) weight percent (45-32) weight percent, and the total addition amount is 100 weight percent; when the mixture is added for 3 times, the preferable proportion of the mixture is 45-52 wt% (33-40 wt% (8-22 wt%) and the total addition amount is 100wt%.
In the present application, the temperature at the time of the nitration reaction is preferably controlled to 40 to 48℃and the pressure at the time of the nitration reaction is preferably controlled to 0.9 to 1.4MPa.
3) Dilution:
in order to reduce the dissolution of nitrobenzene in sulfuric acid, water is continuously added into the microreactor after the nitration reaction, and the sulfuric acid in the mixed solution is diluted. The water in the acid diluent buffer device (T3) is conveyed to a second feed inlet (8) of the microreactor by a pump to enter the microreactor, and is mixed with the mixed solution after complete nitration reaction in the microreactor to dilute sulfuric acid.
In the application, in order to ensure the relative stability of the separation temperature, the jacket layer of the heating section of the micro-reactor is preferably maintained at the temperature by using the hot water with a certain temperature entering from the heating medium feed port (1) and the hot water flows out from the heating medium discharge port (23).
In the present application, the number of dilution is preferably 1 to 3. The concentration of the diluted sulfuric acid is preferably 60% -75%.
4) Separating:
the diluted mixed solution enters a centrifugal machine (C1) through a first centrifugal machine feed inlet (9) for centrifugal separation, and sulfuric acid of heavy components obtained by separation is output through a first centrifugal machine water phase discharge outlet (11); the obtained organic phase (crude nitrobenzene) is output through a first centrifuge outlet and then enters a second centrifuge (C2) through a second centrifuge first inlet (10).
In the application, the output liquid from the water phase discharge port (11) of the first centrifugal machine is preferably 60-75% sulfuric acid. After being concentrated by an acid concentration device, the sulfuric acid can be used as concentrated acid to be continuously recycled.
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 a certain temperature so as to prevent the solidification of nitrobenzene.
5) Washing:
and (3) continuously inputting the crude nitrobenzene obtained by separation into a centrifugal machine, and performing centrifugal washing. The centrifugal washing sequence is pre-washing, alkaline washing and final washing, and specifically comprises the following steps:
pre-washing: the crude nitrobenzene which is conveyed to the first feed inlet (10) of the second centrifuge and the water which is conveyed to the second feed inlet (12) of the second centrifuge by a pump are fully mixed at the lower end of the centrifuge (C2), and then centrifugal separation is carried out. Outputting the separated water phase from a water phase discharge port (14) of the second centrifugal machine; the obtained organic phase (pre-washed nitrobenzene) is output and then enters a third centrifugal machine (C3) through a first feed inlet (13) of the third centrifugal machine. Through the continuous pre-washing, most of the dissolved acid in the crude nitrobenzene can be washed.
Alkali washing: and fully mixing the pre-washed nitrobenzene conveyed to the first feed inlet (13) of the third centrifugal machine with excessive sodium carbonate solution conveyed to the second feed inlet (17) of the third centrifugal machine through a pump at the lower end of the centrifugal machine (C3), and then carrying out centrifugal separation. Outputting the separated water phase from a water phase discharge port (19) of the third centrifugal machine; the obtained organic phase (nitrobenzene after alkaline washing) is output and then enters a fourth centrifugal machine (C4) through a first feed inlet (18) of the fourth centrifugal machine. Through this continuous alkali washing, all acid in nitrobenzene can be washed away.
And (3) final washing: and (3) fully mixing the alkaline-washed nitrobenzene conveyed to the first feed inlet (18) of the fourth centrifugal machine with water conveyed to the second feed inlet (20) of the fourth centrifugal machine through a pump at the lower end of the centrifugal machine (C4), and then carrying out centrifugal separation. The separated water phase is output from a fourth centrifuge organic phase discharge port (22); the obtained organic phase is output from a water phase discharge port (21) of the fourth centrifugal machine, and nitrobenzene with higher purity is obtained. By the continuous final washing, a small amount of alkali in nitrobenzene can be washed.
In the present application, in order to ensure the relative stability of the pre-washing, alkaline washing and final washing temperatures, the outer jacket layer of the centrifuge is maintained at a temperature by using hot water of a certain temperature to prevent the nitrobenzene from solidifying.
In the application, in the pre-washing process, the mass ratio of the organic matters to the washing reagent water is preferably 1 (0.11-0.28); in the alkaline washing process, the detergent is preferably 5-15% of sodium carbonate solution, and the mass ratio of the organic matters to the detergent sodium carbonate 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 application has the following advantages:
1) The benzene conversion rate is high: the micro-reactor is adopted for nitration reaction, and when mixed acid is fed for a plurality of times, the benzene conversion rate is high;
2) The reaction and separation process is safe, fast and efficient: the micro-reactor is adopted in the reactor and diluter types, so that the problem of high safety caused by large liquid storage amount in the traditional kettle type reaction is solved, and the method has the advantage of intrinsic safety. In addition, the residence time of the materials in the micro-reactor is about 5-15 seconds, the defect that the residence time in the traditional kettle-type reactor is more than 30 minutes is overcome, and the method has the characteristics of obvious and rapid reaction speed and high reaction efficiency;
3) The washing purification efficiency is high: when the centrifugal machine is used for pre-washing, alkaline washing and final washing, the defect of high risk of large liquid storage amount in the traditional tower washing is overcome due to small liquid storage amount in the centrifugal machine, and the retention time of materials in the centrifugal machine is about 2-7 seconds, so that the centrifugal machine has the advantages of high washing and purifying speed and high efficiency.
For the sake of clarity, the following examples and comparative examples are described in detail.
Example 1
The nitration reaction is carried out in a microchannel reactor, the process flow is shown in figure 1, and the specific process is as follows:
benzene and mixed acid are conveyed to a main feed inlet (6) of the microchannel reactor through a pump and enter the microchannel reactor to carry out nitration reaction, and at the moment, part of benzene and part of nitric acid complete nitration; then, the mixed solution after the nitration reaction is continuously completely nitrated with mixed acid entering the microchannel reactor through a first feed inlet (7) to obtain the mixed solution after the complete nitration reaction; the mixed solution is mixed with water conveyed in an acid diluent buffer device (T3) at a second feed inlet (8) and enters a microchannel reactor to dilute sulfuric acid; the diluted mixed liquid enters a centrifugal machine (C1) through a first centrifugal machine feed inlet (9) for centrifugal separation; the sulfuric acid of the heavy components 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 centrifugal machine (C2) through a first feeding port (10) of the second centrifugal machine, and is fully mixed with a measured amount of water which is conveyed to a second feeding port (12) of the second centrifugal machine through a pump, and is centrifugally separated at the lower end of the centrifugal machine (C2); the separated water phase is output from a water phase discharge port (14) of the second centrifugal machine, the obtained organic phase enters a third centrifugal machine (C3) through a first feed port (13) of the third centrifugal machine, and is fully mixed with sodium carbonate solution conveyed to a second feed port (17) of the third centrifugal machine through a pump at the lower end of the centrifugal machine (C3) for centrifugal separation; the separated water phase is output from a water phase discharge port (19) of the third centrifugal machine, the obtained organic phase enters a fourth centrifugal machine (C4) through a first feed port (18) of the fourth centrifugal machine, and is fully mixed with water conveyed to a second feed port (20) of the fourth centrifugal machine through a pump, and centrifugal separation is carried out at the lower end of the centrifugal machine (C4); separating the obtained water phase and outputting the water phase from a fourth centrifugal machine organic phase discharge port (22), and obtaining an organic phase from a fourth centrifugal machine water phase discharge port (21);
in the embodiment, the mass content of nitric acid in the mixed acid is 25 percent, the mass content of sulfuric acid is 66 percent, and the mass ratio of benzene to nitric acid in the mixed acid is 1:1.05; the mixed acid is added into the micro-channel reactor for 2 times, and the proportion of the mixed acid added for 2 times is 55wt% to 45wt% according to the total amount; the water at the second feed inlet (8) enters the microchannel reactor for 3 times, and the water consumption ratio of the 3 times is 2:3:5; the mass percentage concentration of the diluted sulfuric acid is 60%; the temperature of the nitration reaction is controlled at 40 ℃ and the pressure is controlled at 0.9MPa;
in this embodiment, in order to ensure the relatively stable reaction temperature, the jacket layer of the heating section of the microreactor preferably maintains the temperature by using hot water with a certain temperature entering through the heating medium feed port (1), and the hot water flows out from the heating medium discharge port (23);
in the embodiment, the concentration of sulfuric acid output by the water phase discharge port (11) of the first centrifugal machine is 60%, and the sulfuric acid is concentrated by an acid concentration device and then is used as concentrated acid to be continuously recycled;
in the embodiment, in the second centrifugal machine (C2), the mass ratio of organic matters to water at a second feed inlet (12) of the second centrifugal machine is 1:0.11; in the third centrifuge (C3), the concentration of the soda solution at the second feed inlet (17) is 5wt%; the mass ratio of the organic matters to the sodium carbonate solution is 1:0.12; in the fourth centrifugal machine (C4), the mass ratio of organic matters to water at a second feed inlet (20) of the fourth centrifugal machine is 1:0.11;
in this example, to ensure a relatively stable temperature during centrifugation, the centrifuge outer jacket was maintained at a temperature by using hot water at a temperature to prevent 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 is as follows:
benzene and mixed acid are conveyed to a main feed inlet (6) of the microchannel reactor through a pump and enter the microchannel reactor to carry out nitration reaction, and at the moment, part of benzene and part of nitric acid complete nitration; then, the mixed solution after the nitration reaction is continuously completely nitrated with mixed acid entering the microchannel reactor through a first feed inlet (7) to obtain the mixed solution after the complete nitration reaction; the mixed solution is mixed with water conveyed in an acid diluent buffer device (T3) at a second feed inlet (8) and enters a microchannel reactor to dilute sulfuric acid; the diluted mixed liquid enters a centrifugal machine (C1) through a first centrifugal machine feed inlet (9) for centrifugal separation; the sulfuric acid of the heavy components 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 centrifugal machine (C2) through a first feeding port (10) of the second centrifugal machine, and is fully mixed with a measured amount of water which is conveyed to a second feeding port (12) of the second centrifugal machine through a pump, and is centrifugally separated at the lower end of the centrifugal machine (C2); outputting the water phase obtained by pre-washing separation from a water phase discharge port (14) of the second centrifugal machine; the obtained organic phase (pre-washed nitrobenzene) enters a third centrifugal machine (C3) through a first feeding port (13) of the third centrifugal machine, and is fully mixed with sodium carbonate solution which is conveyed to a second feeding port (17) of the third centrifugal machine through a pump, and is centrifugally separated at the lower end of the centrifugal machine (C3); outputting the separated water phase from a water phase discharge port (19) of the third centrifugal machine; the obtained organic phase (nitrobenzene after alkaline washing) enters a fourth centrifugal machine (C4) through a first feeding port (18) of the fourth centrifugal machine, and is fully mixed with water conveyed to a second feeding port (20) of the fourth centrifugal machine through a pump, and is centrifugally separated at the lower end of the centrifugal machine (C4); the separated water phase is output from a fourth centrifuge organic phase discharge port (22); the obtained organic phase is discharged from a water phase discharge port (21) of a fourth centrifugal machine;
in the embodiment, the mass content of nitric acid in the mixed acid is 38 percent, the mass content of sulfuric acid is 52 percent, and the mass ratio of benzene to nitric acid in the mixed acid is 1:1.1; the mixed acid is added into the micro-channel reactor for 2 times, and the proportion of the mixed acid added for 2 times is 68wt percent to 32wt percent according to the total amount; 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%; the temperature of the nitration reaction is controlled at 48 ℃, and the pressure is controlled at 1.4MPa;
in this embodiment, in order to ensure the relatively stable reaction temperature, the jacket layer of the heating section of the microreactor preferably maintains the temperature by using hot water with a certain temperature entering through the heating medium feed port (1), and the hot water flows out from the heating medium discharge port (23);
in the embodiment, the concentration of sulfuric acid output by the water phase discharge port (11) of the first centrifugal machine is 75%, and the sulfuric acid is concentrated by an acid concentration device and then is used as concentrated acid to be continuously recycled;
in the embodiment, in the second centrifugal machine (C2), the mass ratio of organic matters to water at a second feed inlet (12) of the second centrifugal machine is 1:0.28; in the third centrifuge (C3), the concentration of the soda solution at the second feed inlet (17) is 15wt%; the mass ratio of the organic matters to the sodium carbonate solution is 1:0.24; in the fourth centrifugal machine (C4), the mass ratio of organic matters to water at a second feed inlet (20) of the fourth centrifugal machine is 1:0.26;
in this example, to ensure a relatively stable temperature during centrifugation, the centrifuge outer jacket was maintained at a temperature by using hot water at a temperature to prevent 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 is as follows:
benzene and mixed acid are conveyed to a main feed inlet (6) of the microchannel reactor through a pump and enter the microchannel reactor to carry out nitration reaction, and at the moment, part of benzene and part of nitric acid complete nitration; then, the mixed solution after the nitration reaction is continuously completely nitrated with mixed acid entering the microchannel reactor through a first feed inlet (7) to obtain the mixed solution after the complete nitration reaction; the mixed solution is mixed with water conveyed in an acid diluent buffer device (T3) at a second feed inlet (8) and enters a microchannel reactor to dilute sulfuric acid; the diluted mixed liquid enters a centrifugal machine (C1) through a first centrifugal machine feed inlet (9) for centrifugal separation; the sulfuric acid of the heavy components 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 centrifugal machine (C2) through a first feeding port (10) of the second centrifugal machine, and is fully mixed with a measured amount of water which is conveyed to a second feeding port (12) of the second centrifugal machine through a pump, and is centrifugally separated at the lower end of the centrifugal machine (C2); outputting the water phase obtained by pre-washing separation from a water phase discharge port (14) of the second centrifugal machine; the obtained organic phase (pre-washed nitrobenzene) enters a third centrifugal machine (C3) through a first feeding port (13) of the third centrifugal machine, and is fully mixed with sodium carbonate solution which is conveyed to a second feeding port (17) of the third centrifugal machine through a pump, and is centrifugally separated at the lower end of the centrifugal machine (C3); outputting the separated water phase from a water phase discharge port (19) of the third centrifugal machine; the obtained organic phase (nitrobenzene after alkaline washing) enters a fourth centrifugal machine (C4) through a first feeding port (18) of the fourth centrifugal machine, and is fully mixed with water conveyed to a second feeding port (20) of the fourth centrifugal machine through a pump, and is centrifugally separated at the lower end of the centrifugal machine (C4); the separated water phase is output from a fourth centrifuge organic phase discharge port (22); the obtained organic phase is discharged from a water phase discharge port (21) of a fourth centrifugal machine;
in the embodiment, the mass content of nitric acid in the mixed acid is 30% and 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; the mixed acid is added into the micro-channel reactor for 2 times, and the proportion of the mixed acid added for 2 times is 70wt percent to 30wt percent according to the total amount; 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%; the temperature of the nitration reaction is controlled at 45 ℃ and the pressure is controlled at 1.0MPa;
in this embodiment, in order to ensure the relatively stable reaction temperature, the jacket layer of the heating section of the microreactor preferably maintains the temperature by using hot water with a certain temperature entering through the heating medium feed port (1), and the hot water flows out from the heating medium discharge port (23);
in the embodiment, the concentration of sulfuric acid output by the water phase discharge port (11) of the first centrifugal machine is 70%, and the sulfuric acid is concentrated by an acid concentration device and then is used as concentrated acid to be continuously recycled;
in the embodiment, in the second centrifugal machine (C2), the mass ratio of organic matters to water at a second feed inlet (12) of the second centrifugal machine is 1:0.20; in the third centrifuge (C3), the concentration of the soda solution at the second feed inlet (17) is 10wt%; the mass ratio of the organic matters to the sodium carbonate solution is 1:0.18; in the fourth centrifugal machine (C4), the mass ratio of organic matters to water at a second feed inlet (20) of the fourth centrifugal machine is 1:0.19;
in this example, to ensure a relatively stable temperature during centrifugation, the centrifuge outer jacket was maintained at a temperature by using hot water at a temperature to prevent nitrobenzene from solidifying.
Example 4
The nitration reaction is carried out in a microchannel reactor, the process flow is shown in figure 1, and the specific process is as follows:
benzene and mixed acid are conveyed to a main feed inlet (6) of the microchannel reactor through a pump and enter the microchannel reactor to carry out nitration reaction, and at the moment, part of benzene and part of nitric acid complete nitration; then, the mixed solution after the nitration reaction is continuously completely nitrated with mixed acid entering the microchannel reactor through a first feed inlet (7) to obtain the mixed solution after the complete nitration reaction; the mixed solution is mixed with water conveyed in an acid diluent buffer device (T3) at a second feed inlet (8) and enters a microchannel reactor to dilute sulfuric acid; the diluted mixed liquid enters a centrifugal machine (C1) through a first centrifugal machine feed inlet (9) for centrifugal separation; the sulfuric acid of the heavy components 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 centrifugal machine (C2) through a first feeding port (10) of the second centrifugal machine, and is fully mixed with a measured amount of water which is conveyed to a second feeding port (12) of the second centrifugal machine through a pump, and is centrifugally separated at the lower end of the centrifugal machine (C2); outputting the water phase obtained by pre-washing separation from a water phase discharge port (14) of the second centrifugal machine; the obtained organic phase (pre-washed nitrobenzene) enters a third centrifugal machine (C3) through a first feeding port (13) of the third centrifugal machine, and is fully mixed with sodium carbonate solution which is conveyed to a second feeding port (17) of the third centrifugal machine through a pump, and is centrifugally separated at the lower end of the centrifugal machine (C3); outputting the separated water phase from a water phase discharge port (19) of the third centrifugal machine; the obtained organic phase (nitrobenzene after alkaline washing) enters a fourth centrifugal machine (C4) through a first feeding port (18) of the fourth centrifugal machine, and is fully mixed with water conveyed to a second feeding port (20) of the fourth centrifugal machine through a pump, and is centrifugally separated at the lower end of the centrifugal machine (C4); the separated water phase is output from a fourth centrifuge organic phase discharge port (22); the obtained organic phase is discharged from a water phase discharge port (21) of a fourth centrifugal machine;
in the embodiment, the mass content of nitric acid in the mixed acid is 31 percent, the mass content of sulfuric acid is 59 percent, and the mass ratio of benzene to nitric acid in the mixed acid is 1:1.08; the mixed acid is added into the microchannel reactor for 3 times, and the proportion of the mixed acid added for 2 times is 45 weight percent to 42 weight percent to 13 weight percent according to the total amount; the water of the second feed inlet (8) enters the micro-channel reactor for 2 times, and the water consumption ratio of 2 times is 2:3; the mass percentage concentration of the diluted sulfuric acid is 70%; the temperature of the nitration reaction is controlled at 41 ℃ and the pressure is controlled at 1.1MPa;
in this embodiment, in order to ensure the relatively stable reaction temperature, the jacket layer of the heating section of the microreactor preferably maintains the temperature by using hot water with a certain temperature entering through the heating medium feed port (1), and the hot water flows out from the heating medium discharge port (23);
in the embodiment, the concentration of sulfuric acid output by the water phase discharge port (11) of the first centrifugal machine is 70%, and the sulfuric acid is concentrated by an acid concentration device and then is used as concentrated acid to be continuously recycled;
in the embodiment, in the second centrifugal machine (C2), the mass ratio of organic matters to water at a second feed inlet (12) of the second centrifugal machine is 1:0.19; in the third centrifuge (C3), the concentration of the soda solution at the second feed inlet (17) is 10wt%; the mass ratio of the organic matters to the sodium carbonate solution is 1:0.17; in the fourth centrifugal machine (C4), the mass ratio of organic matters to water at a second feed inlet (20) of the fourth centrifugal machine is 1:0.18;
in this example, to ensure a relatively stable temperature during centrifugation, the centrifuge outer jacket was maintained at a temperature by using hot water at a temperature to prevent nitrobenzene from solidifying.
Example 5
The difference was that the reactor was a tubular reactor as in example 1.
Example 6
The difference was that the reactor was a tubular reactor as in example 2.
Example 7
The difference was that the reactor was a tubular reactor as in example 3.
Example 8
The difference was that the reactor was a tubular reactor as in example 4.
Comparative example 1
And adding nitrobenzene into a first-stage kettle of a 3-stage reaction kettle which is continuously connected in series by adopting a metering pump, and adding mixed acid of nitro and sulfur into a third-stage kettle, wherein the nitrobenzene and the mixed acid adopt countercurrent flow in order to maintain the reaction stability and prevent the reaction from being too severe. After the reaction is completed, the separated lower acid is put into a dilution tower for 1 time of dilution and liquid separation, and the concentration of the lower sulfuric acid is kept at 60 percent. The 3 towers are connected in series, the separated upper organic matters are sequentially pre-washed, alkali washed and final washed by water, sodium carbonate solution and water, the organic matters and the flow direction of the detergent are countercurrent during washing, namely, the water phase detergent enters from the lower part of the tower, the water phase detergent is reserved from the upper part, and the 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 sulfuric acid is 66%, the reaction temperature is 40 ℃, and the pressure is normal pressure.
The washing solutions of the pre-washing, the alkaline washing and the final washing are water, 5% sodium carbonate solution and water respectively, and the mass ratio of organic matters to the washing reagent in the pre-washing, the alkaline washing and the final washing is 1:0.11, 1:0.12 and 1:0.11 respectively.
Comparative example 2
And adding nitrobenzene into a first-stage kettle of a 3-stage reaction kettle which is continuously connected in series by adopting a metering pump, and adding mixed acid of nitro and sulfur into a third-stage kettle, wherein the nitrobenzene and the mixed acid keep countercurrent in order to prevent the reaction from being too severe. After the reaction is completed, the separated lower acid is put into a dilution tower for 1 time of dilution and liquid separation, and the concentration of the lower sulfuric acid is kept at 75 percent. The 3 towers are connected in series, the separated upper organic matters are sequentially pre-washed, alkali washed and final washed by water, sodium carbonate solution and water, the organic matters and the flow direction of the detergent are countercurrent during washing, namely, the water phase detergent enters from the lower part of the tower, the water phase detergent is reserved from the upper part, and the 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 solutions of the pre-washing, the alkaline washing and the final washing are respectively water, 10% sodium carbonate solution and water, and the mass ratio of organic matters to washing reagents in the pre-washing, the alkaline washing and the final washing is respectively 1:0.28, 1:0.24 and 1:0.26.
Comparative example 3
And adding nitrobenzene into a first-stage kettle of a 3-stage reaction kettle which is continuously connected in series by adopting a metering pump, and adding mixed acid of nitro and sulfur into a third-stage kettle, wherein the nitrobenzene and the mixed acid keep countercurrent flow for preventing the reaction from being too severe, and the reaction temperature is 45 ℃ and the pressure is normal pressure. After the reaction is completed, the separated lower acid is put into a dilution tower for 1 time of dilution and liquid separation, and the concentration of the lower sulfuric acid is kept at 70 percent. The 3 towers are connected in series, the separated upper organic matters are sequentially pre-washed, alkali washed and final washed by water, sodium carbonate solution and water, the organic matters and the flow direction of the detergent are countercurrent during washing, namely, the water phase detergent enters from the lower part of the tower, the water phase detergent is reserved from the upper part, and the 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 mass content of the nitric acid in the prepared mixed acid is 24% and the mass content of the sulfuric acid is 69%.
The washing solutions of the pre-washing, the alkaline washing and the final washing are water, 15% sodium carbonate solution and water respectively, and the mass ratio of organic matters to the washing reagent in the pre-washing, the alkaline washing and the final washing is 1:0.20, 1:0.18 and 1:0.21 respectively.
Experimental results
The experimental results of examples 1 to 8 and comparative examples 1 to 3 are summarized in Table 1:
TABLE 1 Experimental results for nitrobenzene production
The foregoing is merely a preferred embodiment of the present application and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present application, which are intended to be comprehended within the scope of the present application.
Claims (8)
1. A method for producing nitrobenzene, comprising the steps of:
benzene and acid liquor are mixed and then sent into a main feed inlet of a micro-reactor for partial nitration reaction; then mixing the mixture with acid liquid which is added into the micro-reactor through a first feed inlet to carry out complete nitration reaction; then mixing the water with water added into the micro-reactor through a second feed inlet for dilution; then discharging the micro-reactor from the discharge port;
adding acid liquor used for carrying out the partial nitration reaction and the complete nitration reaction into a microreactor for 2-3 times; when the acid liquor is added for 2 times according to the total addition amount of the acid liquor, the adding proportion is (55-68) weight percent: (45-32 wt.%) and the total addition amount is 100 wt.%; when the mixture is added for 3 times, the adding proportion is (45-52) weight percent: (33-40 wt%): (8-22 wt.%) and the total addition is 100 wt.%;
products discharged from the discharge port of the microreactor enter a first centrifugal machine for centrifugal separation, and the obtained organic phase sequentially passes through a second centrifugal machine, a third centrifugal machine and a fourth centrifugal machine for centrifugal washing to obtain nitrobenzene;
the centrifugal washing step specifically comprises the following steps: sending the organic phase obtained by centrifugation in the first centrifugal machine into a first feeding port of a second centrifugal machine, mixing the organic phase with water added through the second feeding port of the second centrifugal machine, and performing centrifugal pre-washing; feeding the organic phase obtained by centrifugal pre-washing into a first feed inlet of a third centrifugal machine, mixing with alkali liquor added through a second feed inlet of the third centrifugal machine, and performing centrifugal alkali washing; feeding the organic phase obtained by centrifugal alkaline washing into a first feed inlet of a fourth centrifugal machine, mixing with water added through a second feed inlet of the fourth centrifugal machine, and performing centrifugal final washing, wherein the obtained organic phase is discharged out of the centrifugal machine from an organic phase discharge outlet of the fourth centrifugal machine; in the centrifugal washing process, the water phase is discharged out of the centrifugal machine from a water phase discharge port of the centrifugal machine.
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 performing 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 to 38%, and the mass content of sulfuric acid is 52 to 66%.
4. The method according to claim 1, wherein the mass ratio of benzene to nitric acid in the acid liquid for reaction is 1: (1.05-1.1).
5. The production method 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 1.4MPa.
6. The method according to claim 3, wherein the concentration of sulfuric acid in the system after the dilution is 60 to 75% by mass.
7. The process according to claim 1, wherein the lye is a soda solution of 5 to 15 wt%.
8. The method according to claim 1, wherein the mass ratio of organic phase to water during the centrifugal pre-washing is 1: (0.11-0.28); in the centrifugal alkaline washing process, the mass ratio of the organic phase to the alkaline liquid is 1: (0.12 to 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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| 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 |
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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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