CN115057781B - Production method of nitrobenzene - Google Patents

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

A kind of production method of nitrobenzene

technical field

The invention belongs to the production field of nitrobenzene, in particular to a production method of nitrobenzene.

Background technique

Nitrobenzene is an important chemical intermediate, used as a raw material for the production of aniline, and also used in the production of dyes, spices, explosives and other organic synthesis industries.

At present, most domestic enterprises use tank reactors to produce nitrobenzene. However, due to the large volume of tank reactors (generally, the volume of a single tank is ≥ 10m ³ ) and the large stock of materials, once an accident occurs, the risk is very high. big. At the same time, in the follow-up separation, since the tower is used for separation, and the tower has a large volume and a large storage, there is a great potential safety hazard. Therefore, it is very important to find a kind of industrial production method of nitrobenzene with wide sources of raw materials, intrinsic safety, good selectivity and high efficiency.

Micro-reaction technology originated in Europe in the early 1990s. The size of the reactor channel is on the micron scale. Compared with traditional reactors, the micro-reactor has short molecular diffusion distance, fast mass transfer, laminar flow in the channel, and narrow residence time distribution. , No back mixing, super large specific surface area per unit volume, fast heat transfer speed, strong heat transfer capacity, and easy temperature control. Microreactors include microchannel reactors, tubular reactors, and other similar reactors.

Due to the small size of the microreactor itself, the liquid storage capacity is not large, and it is especially suitable for dangerous reactions such as nitrification. Even if danger occurs, the smaller liquid it holds will not cause greater serious consequences.

Patent CN101613285 discloses a method for preparing nitrobenzene using a tubular reactor, but after the reaction, a tank-type stirring device is used. Although the amount of liquid in the microchannel reaction part is small, the existence of the subsequent stirring tank increases The amount of liquid stored is not conducive to the safety of nitrification. In addition, the nitrobenzene produced is crude nitrobenzene containing acid without purification.

In addition, after the traditional nitrobenzene reaction, tower separation or other containers with large storage capacity are generally used to separate acid and organic matter, which will also lead to an increase in the amount of liquid staying in the tower, posing a major safety hazard.

Contents of the invention

In view of this, the object of the present invention is to provide a kind of production method of nitrobenzene. The method adopted in the scheme of the present invention has the advantages of high nitrobenzene yield, intrinsically safe process, and high processing efficiency.

The invention provides a kind of production method of nitrobenzene, comprises the following steps:

Mix benzene with acid solution and send it to the main feed port of the microreactor for partial nitration reaction; then mix it with the acid solution fed into the microreactor through the first feed port for complete nitration reaction; The second feed port is added to the water in the microreactor to mix and dilute; then the microreactor is discharged from the feed port;

The product discharged from the microreactor from the discharge port enters the first centrifuge for centrifugation, and the organic phase of the gained is successively centrifuged and washed by the second, third and fourth centrifuges to obtain nitrobenzene;

The step of centrifugal washing is specifically: sending the organic phase centrifuged in the first centrifuge into the first feed port of the second centrifuge, and mixing with the water added through the second feed port of the second centrifuge Afterwards, carry out centrifugal pre-washing; the organic phase obtained by centrifugal pre-washing is sent to the first feed port of the third centrifuge, and is mixed with the lye added through the second feed port of the third centrifuge to carry out centrifugal alkaline washing; The washed organic phase is sent to the first feed port of the fourth centrifuge, mixed with the water added by the second feed port of the fourth centrifuge, and then centrifuged for final washing. The discharge port is discharged from the centrifuge; during the centrifugal washing process, the water phase is discharged from the centrifuge from the 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 reaction and complete nitration 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%.

Preferably, the mass ratio of the benzene to the 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 the partial nitration reaction and complete nitration reaction is added to the microreactor in 2 to 3 times.

Preferably, calculated according to the total amount of the acid solution used, when adding in 2 times, the ratio of adding successively is (55-68)wt%: (45-32)wt%, the total adding amount is 100wt%; adding in 3 times , the successive addition ratio is (45-52)wt%: (33-40)wt%: (8-22)wt%, and the total addition is 100wt%.

Preferably, the temperature of the partial nitration reaction and the complete nitration reaction are independently selected to be 40-48° C., and the pressures of the partial nitration reaction and the complete nitration reaction are independently selected to be 0.9-1.4 MPa.

Preferably, after the dilution, the mass percent concentration of sulfuric acid in the system is 60-75%.

Preferably, the lye is 5-15wt% soda ash solution.

Preferably, in the centrifugal pre-washing process, the mass ratio of the organic phase to water is 1:(0.11-0.28); in the centrifugal alkaline washing process, the mass ratio of the organic phase to the lye is 1:(0.12-0.24 ); in the centrifuge final washing process, the mass ratio of the organic phase to water is 1: (0.11-0.26).

Compared with the prior art, the present invention provides a production method of nitrobenzene, comprising the following steps: mixing benzene with acid and sending it into a micro-reactor for nitration reaction; sending it into a centrifuge for centrifugation, and the obtained organic phase is successively The second, third, and fourth centrifuges are used for prewashing, alkali washing, and final washing, and finally the nitrobenzene obtained by centrifugal washing is discharged from the centrifuge from the organic phase outlet of the fourth centrifuge. The invention provides a process method for continuously producing nitrobenzene through micro-reactor for nitration and dilution, and adopting centrifuge for washing and separation. When the microreactor is used for nitration, the mass transfer and heat transfer effect of the reaction process are good, and the separation efficiency of the centrifugal equipment is high. The method has the advantages of intrinsic safety, high product selectivity, high production efficiency, etc., and has broad market prospects.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

Fig. 1 is the flow chart of the production process of nitrobenzene provided by the embodiment of the present invention.

The marks in the drawings are as follows: T1 is a benzene buffer device, T2 is an acid buffer device, T3 is an acid diluent buffer device, T4 is a pre-wash buffer device, T5 is an alkali buffer device, T6 is a final wash buffer device, C1 is the first centrifuge, C2 is the second centrifuge, C3 is the third centrifuge, C4 is the fourth centrifuge, 1 is the heat medium feed inlet of the jacket layer of the heating section of the microreactor, and 2 is the benzene buffer device Feed port, 3 is the first feed port of the acid buffer device, 4 is the second feed port of the acid buffer device, 5 is the feed port of the acid dilution buffer device, 6 is the main feed port of the microreactor, 7 is the first feed inlet of microreactor, 8 is the second feed inlet of microreactor, 9 is the first centrifuge feed inlet, 10 the first feed inlet of the second centrifuge, 11 is The water phase discharge port of the first centrifuge, 12 is the second feed port of the second centrifuge, 13 is the first feed port of the third centrifuge, and 14 is the water phase discharge port of the second centrifuge, 15 is the first feed port of the lye buffer device, 16 is the second feed port of the lye buffer device, 17 is the second feed port of the third centrifuge, and 18 is the first feed of the fourth centrifuge Port, 19 is the water phase discharge port of the third centrifuge, 20 is the second feed port of the fourth centrifuge, 21 is the organic phase discharge port of the fourth centrifuge, and 22 is the water phase of the fourth centrifuge The discharge port, 23, is the heat medium discharge port of the jacket layer in the heating section of the microreactor.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The invention provides a production method of nitrobenzene, which comprises performing nitration reaction in a microreactor, diluting the mixture obtained from the nitration reaction with water and centrifuging to obtain crude nitrobenzene, and centrifugally washing the crude nitrobenzene, which effectively improves the Conversion rate, reaction efficiency and product purity, the specific process is as follows:

1) Adjust acid and base:

Under stirring, add sulfuric acid and nitric acid into the acid buffer device (T2) from the first feed port (3) of the acid buffer device and the second feed port (4) of the acid buffer device according to a certain ratio; under stirring, Benzene is fed into the benzene buffer device (T1) from the feed port (2) of the benzene buffer device. 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 liquid buffer device (T2) has a jacket, and condensed water is passed through the jacket to dissipate the heat generated during mixing.

Under stirring, soda ash and water are added into the lye buffer device (T5) from the first feed port (15) of the lye buffer device and the second feed port (16) of the lye buffer device according to a certain ratio. Wherein, the lye is preferably 5-15% soda ash solution. The alkali buffer device (T5) has a jacket, and the condensed water is passed through the jacket to dissipate the heat generated during mixing.

2) Nitrification reaction:

The benzene in the benzene buffer device (T1) and the mixed acid in the acid buffer device (T2) are delivered to the main feed port (6) of the microreactor by a pump and enter the microreactor for nitration reaction. At this time, part of the benzene and Part of the nitric acid completes nitration; subsequently, the mixed solution after the nitration reaction continues to be completely nitrated with the mixed acid that enters the microreactor through the first feed port (7), to obtain a mixed solution after the complete nitration reaction. The main components of the mixed solution are nitrobenzene, a small amount of unreacted nitric acid and catalytic sulfuric acid.

In the present invention, in order to ensure the relative stability of the above-mentioned reaction temperature, the jacket layer of the heating section of the microreactor preferably utilizes the hot water of a certain temperature entered by its heat medium feed port (1) to maintain the temperature, and the hot water is discharged from the heat medium. Material opening (23) flows out.

In the present invention, the mixed acid added to the main feed port (6) and the first branch feed port (7) of the microreactor can be added to the microreactor in 2 to 3 times; calculated according to the total amount, add in 2 times When adding the ratio successively, preferably (55～68) wt%: (45～32) wt%, the total addition is 100wt%; when adding in 3 times, the ratio of adding successively is preferably (45～52) wt%: (33 ～40) wt%: (8～22) wt%, the total addition is 100wt%.

In the present invention, the temperature during the nitration reaction is preferably controlled at 40-48° C., and the pressure during the nitration reaction is preferably controlled at 0.9-1.4 MPa.

3) Dilution:

In order to reduce the dissolution of nitrobenzene in sulfuric acid, after the nitration reaction, continue to add water in the microreactor to dilute the sulfuric acid in the mixed solution. The water in the acid dilution buffer device (T3) is pumped to the second feed port (8) of the microreactor to enter the microreactor, and mixed with the mixed solution after the complete nitration reaction in the microreactor , to dilute sulfuric acid.

In the present invention, in order to ensure the relative stability of the above-mentioned separation temperature, the jacket layer of the heating section of the microreactor preferably utilizes the hot water of a certain temperature entered by its heat medium feed port (1) to maintain the temperature, and the hot water is discharged from the heat medium. Material opening (23) flows out.

In the present invention, the number of dilutions is preferably 1 to 3 times. The concentration of sulfuric acid after dilution is preferably 60% to 75%.

4) Separation:

The diluted mixed solution enters the centrifuge (C1) through the first centrifuge inlet (9) for centrifugation, and the sulfuric acid of the heavy component of the separation gained is output through the first centrifuge water phase outlet (11); the obtained organic The phase (crude nitrobenzene) is output through the outlet of the first centrifuge, and then enters the second centrifuge (C2) through the first inlet (10) of the second centrifuge.

In the present invention, preferably 60%-75% sulfuric acid is output from the water phase outlet (11) of the first centrifuge. After being concentrated by an acid concentration device, the sulfuric acid can be continuously recycled as a concentrated acid.

In order to ensure the relative stability of the above-mentioned separation temperature, the outer jacket layer of the centrifuge uses hot water of a certain temperature to maintain the temperature to prevent the solidification of nitrobenzene.

5) Washing:

The crude nitrobenzene obtained by the above separation is continuously input into the centrifuge for centrifugal washing. The centrifugal washing sequence is pre-washing, alkaline washing, and final washing, specifically:

Pre-washing: the above-mentioned crude product nitrobenzene delivered to the first feed port (10) of the second centrifuge and the water of the metered amount delivered to the second feed port (12) of the second centrifuge by the pump, in the centrifuge (C2) The lower end is thoroughly mixed, and then centrifuged. The separated aqueous phase is output from the second centrifuge water phase discharge port (14); the gained organic phase (nitrobenzene after pre-washing) is output and then enters the third centrifuge through the first feed port (13) of the third centrifuge. Centrifuge (C3). This continuous prewash washes away most of the acid dissolved in the crude nitrobenzene.

Alkali washing: the above-mentioned nitrobenzene after the pre-washing that is delivered to the first feeding port (13) of the third centrifuge and the excess soda ash solution that is delivered to the second feeding port (17) of the third centrifuge by a pump, in The lower end of the centrifuge (C3) is fully mixed, and then centrifuged. The separated aqueous phase is output from the third centrifuge water outlet (19); the gained organic phase (nitrobenzene after alkali washing) is output and then enters the fourth centrifuge through the first feed port (18) of the fourth centrifuge. Centrifuge (C4). Through this continuous alkali washing, all the acids in the nitrobenzene can be washed away.

Final washing: the above-mentioned nitrobenzene after the alkaline cleaning delivered to the first feed port (18) of the fourth centrifuge and the water delivered to the second feed port (20) of the fourth centrifuge by a pump are washed in the centrifuge (C4) The lower end is fully mixed, and then centrifuged. The separated aqueous phase is output from the organic phase outlet (22) of the fourth centrifuge; the organic phase is output from the aqueous phase outlet (21) of the fourth centrifuge to obtain nitrobenzene with higher purity. Through this continuous final washing, a small amount of alkali in the nitrobenzene can be washed away.

In the present invention, in order to ensure the relative stability of the above-mentioned prewashing, alkali washing and final washing temperatures, the outer jacket layer of the centrifuge utilizes hot water at a certain temperature to maintain the temperature to prevent the nitrobenzene from solidifying.

In the present invention, in the above-mentioned prewashing process, the mass ratio of organic matter and cleaning reagent water is preferably 1: (0.11～0.28); The mass ratio of organic matter to washing reagent water is preferably 1:(0.12-0.24); in the final washing process, the mass ratio of organic matter to washing reagent water is preferably 1:(0.11-0.26).

The production method of nitrobenzene provided by the invention has the following advantages:

1) High conversion rate of benzene: the nitration reaction is carried out in a microreactor, and the conversion rate of benzene is high when the mixed acid is fed multiple times;

2) The reaction and separation process is safe, fast, and efficient: in the type of reactor and diluter, micro-reactors are used, which overcome the large safety problems caused by the large amount of liquid in the traditional tank reaction, and have the advantages of The advantage of intrinsic safety. Moreover, the residence time of the material in the microreactor is about 5 to 15 seconds, which overcomes the defect of more than 30 minutes in the traditional tank reactor, and has the characteristics of obviously fast reaction speed and high reaction efficiency;

3) High washing and purification efficiency: When using a centrifuge for pre-washing, alkali washing and final washing, due to the small amount of liquid in the centrifuge, it overcomes the shortcomings of the large amount of liquid in the traditional tower washing, and the high risk of the material The residence time in the centrifuge is about 2-7 seconds, which has the advantages of fast washing and purification speed and high efficiency.

For the sake of clarity, detailed description will be given below through the following examples and comparative examples.

Example 1

Carry out nitration reaction in microchannel reactor, its technological process is as shown in Figure 1, and concrete process is:

Benzene and mixed acid are transported to the main feed port (6) of the microchannel reactor through the pump and enter the microchannel reactor for nitration reaction. At this time, part of the benzene and part of nitric acid have completed nitration; subsequently, the mixed solution after the nitration reaction continues to Carry out complete nitration with the mixed acid that enters the microchannel reactor through the first feed inlet (7) to obtain the mixed solution after the complete nitration reaction; The water transported in (T3) is mixed and enters the microchannel reactor to dilute the sulfuric acid; the diluted mixed solution enters the centrifuge (C1) through the first centrifuge feed port (9) for centrifugation; The sulfuric acid that divides is exported by the first whizzer water outlet (11); The water of the metered amount that is transported to the second centrifuge second feed port (12) by pump is fully mixed and centrifuged at the centrifuge (C2) lower end; the separated aqueous phase is from the second centrifuge water phase discharge port ( 14) output, gained organic phase enters the 3rd centrifuge (C3) by the 3rd centrifuge first feed port (13), with the soda ash solution that is transported to the 3rd centrifuge second feed port (17) by pump, Fully mix at the lower end of the centrifuge (C3) and carry out centrifugation; the separated aqueous phase is output from the third centrifuge water phase outlet (19), and the resulting organic phase enters the first centrifuge through the fourth centrifuge first feed port (18). Four centrifuges (C4), with the water that is delivered to the second feed port (20) of the fourth centrifuge by the pump, fully mix and carry out centrifugation at the lower end of the centrifuge (C4); Phase discharge port (22) output, gained organic phase is from the 4th centrifuge water phase discharge port (21);

In the present 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 benzene and nitric acid in the mixed acid is 1:1.05; Quantitative calculation, the ratio of adding mixed acid for 2 times successively is 55wt%: 45wt%; The water of the second feed inlet (8) enters the microchannel reactor in 3 times, and the water consumption ratio successively 3 times is 2:3:5 The mass percent concentration of sulfuric acid after dilution is 60%; the nitrification reaction temperature is controlled at 40°C, and the pressure is controlled at 0.9MPa;

In this embodiment, in order to keep the relative stability of the above-mentioned reaction temperature, the jacket layer of the heating section of the microreactor preferably utilizes the hot water of a certain temperature entering from the heat medium feed port (1) to maintain the temperature, and the hot water flows from the heat medium The discharge port (23) flows out;

In this embodiment, the concentration of sulfuric acid output from the water phase outlet (11) of the first centrifuge is 60%, and after being concentrated by an acid concentration device, it is continuously recycled as concentrated acid;

In the present embodiment, in the second centrifuge (C2), the mass ratio of organic matter to the second feed port (12) water of the second centrifuge is 1:0.11; in the third centrifuge (C3), the first The concentration of two feed inlets (17) soda ash solution is 5wt%; The mass ratio of organic matter and aforementioned soda ash solution is 1:0.12; In the 4th centrifuge (C4), organic matter and the 4th centrifuge second feed inlet ( 20) The mass ratio of water is 1:0.11;

In this embodiment, in order to ensure a relatively stable temperature during centrifugation, the outer jacket layer of the centrifuge uses hot water at a certain temperature to maintain the temperature to prevent the nitrobenzene from solidifying.

Example 2

Carry out nitration reaction in microchannel reactor, its technological process is as shown in Figure 1, and concrete process is:

Benzene and mixed acid are transported to the main feed port (6) of the microchannel reactor through the pump and enter the microchannel reactor for nitration reaction. At this time, part of the benzene and part of nitric acid have completed nitration; subsequently, the mixed solution after the nitration reaction continues to Carry out complete nitration with the mixed acid that enters the microchannel reactor through the first feed inlet (7) to obtain the mixed solution after the complete nitration reaction; The water transported in (T3) is mixed and enters the microchannel reactor to dilute the sulfuric acid; the diluted mixed solution enters the centrifuge (C1) through the first centrifuge feed port (9) for centrifugation; The sulfuric acid that divides is exported by the first whizzer water outlet (11); The metered amount of water delivered to the second feed port (12) of the second centrifuge by the pump is fully mixed at the lower end of the centrifuge (C2) for centrifugation; the water phase obtained by pre-washing and separation is discharged from the water phase of the second centrifuge Port (14) output; Gained organic phase (nitrobenzene after pre-washing) enters the third centrifuge (C3) through the first feeding port (13) of the third centrifuge, and is transported to the third centrifuge by the pump. The soda ash solution of two feed inlets (17) fully mixes at the centrifuge (C3) lower end, centrifugation; The aqueous phase of separation gained is exported from the third centrifuge water phase discharge outlet (19); Gained organic phase (after alkali washing Nitrobenzene) enters the fourth centrifuge (C4) by the first feed port (18) of the fourth centrifuge, and the water delivered to the second feed port (20) of the fourth centrifuge by the pump, in the centrifuge (C4) The lower end is fully mixed and centrifuged; the separated aqueous phase is output from the organic phase outlet (22) of the fourth centrifuge; the organic phase is output from the fourth centrifuge aqueous phase outlet (21);

In the present 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 and nitric acid in the mixed acid is 1:1.1; Quantitative calculation, the ratio of adding mixed acid for 2 times successively is 68wt%: 32wt%; The water of the second feed inlet (8) enters the microchannel reactor in 2 times, and the ratio of water consumption for 2 times successively is 3:2; The mass percent concentration of the final sulfuric acid is 75%; the nitrification reaction temperature is controlled at 48°C, and the pressure is controlled at 1.4MPa;

In this embodiment, in order to keep the relative stability of the above-mentioned reaction temperature, the jacket layer of the heating section of the microreactor preferably utilizes the hot water of a certain temperature entering from the heat medium feed port (1) to maintain the temperature, and the hot water flows from the heat medium The discharge port (23) flows out;

In this embodiment, the concentration of sulfuric acid output from the water phase outlet (11) of the first centrifuge is 75%, and after being concentrated by the acid concentration device, it is continuously recycled as concentrated acid;

In the present embodiment, in the second centrifuge (C2), the mass ratio of organic matter to the second feed port (12) water of the second centrifuge is 1:0.28; in the third centrifuge (C3), the first The concentration of two feed inlets (17) soda ash solution is 15wt%; The mass ratio of organic matter and aforementioned soda ash solution is 1:0.24; In the 4th centrifuge (C4), organic matter and the 4th centrifuge second feed inlet ( 20) The mass ratio of water is 1:0.26;

In this embodiment, in order to ensure a relatively stable temperature during centrifugation, the outer jacket layer of the centrifuge uses hot water at a certain temperature to maintain the temperature to prevent the nitrobenzene from solidifying.

Example 3

Carry out nitration reaction in microchannel reactor, its technological process is as shown in Figure 1, and concrete process is:

Benzene and mixed acid are transported to the main feed port (6) of the microchannel reactor through the pump and enter the microchannel reactor for nitration reaction. At this time, part of the benzene and part of nitric acid have completed nitration; subsequently, the mixed solution after the nitration reaction continues to Carry out complete nitration with the mixed acid that enters the microchannel reactor through the first feed inlet (7) to obtain the mixed solution after the complete nitration reaction; The water transported in (T3) is mixed and enters the microchannel reactor to dilute the sulfuric acid; the diluted mixed solution enters the centrifuge (C1) through the first centrifuge feed port (9) for centrifugation; The sulfuric acid that divides is exported by the first whizzer water outlet (11); The metered amount of water delivered to the second feed port (12) of the second centrifuge by the pump is fully mixed at the lower end of the centrifuge (C2) for centrifugation; the water phase obtained by pre-washing and separation is discharged from the water phase of the second centrifuge Port (14) output; Gained organic phase (nitrobenzene after pre-washing) enters the third centrifuge (C3) through the first feeding port (13) of the third centrifuge, and is transported to the third centrifuge by the pump. The soda ash solution of two feed inlets (17) fully mixes at the centrifuge (C3) lower end, centrifugation; The aqueous phase of separation gained is exported from the third centrifuge water phase discharge outlet (19); Gained organic phase (after alkali washing Nitrobenzene) enters the fourth centrifuge (C4) by the first feed port (18) of the fourth centrifuge, and the water delivered to the second feed port (20) of the fourth centrifuge by the pump, in the centrifuge (C4) The lower end is fully mixed and centrifuged; the separated aqueous phase is output from the organic phase outlet (22) of the fourth centrifuge; the organic phase is output from the fourth centrifuge aqueous phase outlet (21);

In the present embodiment, the mass content of nitric acid in the mixed acid is 30%, the mass content of sulfuric acid is 59%, and the mass ratio of benzene and nitric acid in the mixed acid is 1:1.08; Quantitative calculation, the ratio of adding mixed acid for 2 times successively is 70wt%: 30wt%; The water of the second feed inlet (8) enters the microchannel reactor once, and the mass percent concentration of sulfuric acid after dilution is 70%; The nitrification reaction temperature is controlled at 45°C, and the pressure is controlled at 1.0MPa;

In this embodiment, in order to keep the relative stability of the above-mentioned reaction temperature, the jacket layer of the heating section of the microreactor preferably utilizes the hot water of a certain temperature entering from the heat medium feed port (1) to maintain the temperature, and the hot water flows from the heat medium The discharge port (23) flows out;

In this embodiment, the concentration of sulfuric acid output from the water phase outlet (11) of the first centrifuge is 70%, and after being concentrated by an acid concentration device, it is continuously recycled as concentrated acid;

In the present embodiment, in the second centrifuge (C2), the mass ratio of organic matter to the second feed port (12) water of the second centrifuge is 1:0.20; in the third centrifuge (C3), the first The concentration of two feed inlets (17) soda ash solution is 10wt%; The mass ratio of organic matter and aforementioned soda ash solution is 1:0.18; In the 4th centrifuge (C4), organic matter and the 4th centrifuge second feed inlet ( 20) The mass ratio of water is 1:0.19;

In this embodiment, in order to ensure a relatively stable temperature during centrifugation, the outer jacket layer of the centrifuge uses hot water at a certain temperature to maintain the temperature to prevent the nitrobenzene from solidifying.

Example 4

Carry out nitration reaction in microchannel reactor, its technological process is as shown in Figure 1, and concrete process is:

Benzene and mixed acid are transported to the main feed port (6) of the microchannel reactor through the pump and enter the microchannel reactor for nitration reaction. At this time, part of the benzene and part of nitric acid have completed nitration; subsequently, the mixed solution after the nitration reaction continues to Carry out complete nitration with the mixed acid that enters the microchannel reactor through the first feed inlet (7) to obtain the mixed solution after the complete nitration reaction; The water transported in (T3) is mixed and enters the microchannel reactor to dilute the sulfuric acid; the diluted mixed solution enters the centrifuge (C1) through the first centrifuge feed port (9) for centrifugation; The sulfuric acid that divides is exported by the first whizzer water outlet (11); The metered amount of water delivered to the second feed port (12) of the second centrifuge by the pump is fully mixed at the lower end of the centrifuge (C2) for centrifugation; the water phase obtained by pre-washing and separation is discharged from the water phase of the second centrifuge Port (14) output; Gained organic phase (nitrobenzene after pre-washing) enters the third centrifuge (C3) through the first feeding port (13) of the third centrifuge, and is transported to the third centrifuge by the pump. The soda ash solution of two feed inlets (17) fully mixes at the centrifuge (C3) lower end, centrifugation; The aqueous phase of separation gained is exported from the third centrifuge water phase discharge outlet (19); Gained organic phase (after alkali washing Nitrobenzene) enters the fourth centrifuge (C4) by the first feed port (18) of the fourth centrifuge, and the water delivered to the second feed port (20) of the fourth centrifuge by the pump, in the centrifuge (C4) The lower end is fully mixed and centrifuged; the separated aqueous phase is output from the organic phase outlet (22) of the fourth centrifuge; the organic phase is output from the fourth centrifuge aqueous phase outlet (21);

In the present embodiment, 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 and nitric acid in the mixed acid is 1:1.08; Quantitative calculation, the ratio of adding mixed acid for 2 times successively is 45wt%: 42wt%: 13wt%; The water of the second feed inlet (8) enters the microchannel reactor in 2 times, and the water consumption ratio successively 2 times is 2: 3. The mass percent concentration of sulfuric acid after dilution is 70%; the nitrification reaction temperature is controlled at 41°C, and the pressure is controlled at 1.1MPa;

In this embodiment, in order to keep the relative stability of the above-mentioned reaction temperature, the jacket layer of the heating section of the microreactor preferably utilizes the hot water of a certain temperature entering from the heat medium feed port (1) to maintain the temperature, and the hot water flows from the heat medium The discharge port (23) flows out;

In this embodiment, the concentration of sulfuric acid output from the water phase outlet (11) of the first centrifuge is 70%, and after being concentrated by an acid concentration device, it is continuously recycled as concentrated acid;

In the present embodiment, in the second centrifuge (C2), the mass ratio of organic matter to the second feed inlet (12) water of the second centrifuge is 1:0.19; in the third centrifuge (C3), the first The concentration of two feeding inlets (17) soda ash solution is 10wt%; The mass ratio of organic matter and aforementioned soda ash solution is 1:0.17; In the 4th whizzer (C4), organic matter and the 4th whizzer second feeding inlet ( 20) The mass ratio of water is 1:0.18;

In this embodiment, in order to ensure a relatively stable temperature during centrifugation, the outer jacket layer of the centrifuge uses hot water at a certain temperature to maintain the temperature to prevent the nitrobenzene from solidifying.

Example 5

Same as Example 1, the difference is that the reactor is a tubular reactor.

Example 6

Same as Example 2, the difference is that the reactor is a tubular reactor.

Example 7

Same as Example 3, the difference is that the reactor is a tubular reactor.

Example 8

Same as Example 4, the difference is that the reactor is a tubular reactor.

Comparative example 1

Using a metering pump, add nitrobenzene to the first stage of the continuous series of 3-stage reactors, and add nitric acid mixed acid to the third stage. In order to maintain the stability of the reaction and prevent the reaction from being too violent, nitrobenzene and mixed acid are reverse flow. After the foregoing reaction is completed, the separated lower layer acid enters the dilution tower for 1 dilution and liquid separation, and the concentration of sulfuric acid in the lower layer remains at 60%. Three towers are used in series, and the above-mentioned separated upper layer organic matter is pre-washed, alkali washed and finally washed with water, soda solution and water in sequence. The upper part is set aside, and the organic phase flows out from the lower layer.

The molar ratio of the above-mentioned benzene to nitric acid in the mixed acid is 1:1.05, the mass content of nitric acid in the mixed acid is 25%, the mass content of sulfuric acid is 66%, the reaction temperature is 40°C, and the pressure is normal pressure.

The washing liquids of the above-mentioned prewash, alkali wash and final wash are water, 5% soda ash solution and water respectively, and in the prewash, alkali wash and final wash, the mass ratios of organic matters and washing reagents are 1:0.11, 1:0.12 respectively , 1:0.11.

Comparative example 2

Using a metering pump, add nitrobenzene to the first stage of the continuous series of three-stage reactors, and add nitric acid mixed acid to the third stage. In order to prevent the reaction from being too violent, the nitrobenzene and the mixed acid keep flowing in reverse. After the aforementioned reaction was completed, the separated lower layer acid was entered into the dilution tower for 1 dilution and liquid separation, and the concentration of the lower layer of sulfuric acid remained at 75%. Three towers are used in series, and the above-mentioned separated upper layer organic matter is pre-washed, alkali washed and finally washed with water, soda solution and water in sequence. The upper part is set aside, and the organic phase flows out from the lower layer.

The molar ratio of the above-mentioned benzene to nitric acid in the mixed acid is 1:1.08, the mass content of nitric acid in the prepared mixed acid is 38%, the mass content of sulfuric acid is 52%, the reaction temperature is 48°C, and the pressure is normal pressure.

The washing liquids of the above-mentioned prewash, alkali wash and final wash are water, 10% soda ash solution and water respectively. In the prewash, alkali wash and final wash, the mass ratios of organic matters to washing reagents are 1:0.28, 1:0.24 respectively , 1:0.26.

Comparative example 3

Using a metering pump, add nitrobenzene to the first-stage kettle of the 3-stage reactor in series, and add nitric-sulfur mixed acid to the third-stage kettle. is 45°C, and the pressure is normal pressure. After the foregoing reaction is completed, the separated lower layer acid is entered into the dilution tower for 1 dilution and liquid separation, and the concentration of the lower layer of sulfuric acid is maintained at 70%. Three towers are used in series, and the above-mentioned separated upper layer organic matter is pre-washed, alkali washed and finally washed with water, soda solution and water in sequence. The upper part is set aside, and the organic phase flows out from the lower layer.

The mass ratio of benzene to nitric acid in the mixed acid is 1:1.1, and the mass content of nitric acid in the prepared mixed acid is 24%, and the mass content of sulfuric acid is 69%.

The washing liquids of the above-mentioned prewash, alkali wash and final wash are water, 15% soda ash solution and water respectively, and in the prewash, alkali wash and final wash, the mass ratios of organic matters and washing reagents are respectively 1:0.20, 1:0.18 , 1:0.21.

Experimental results

The experimental results of Examples 1-8 and the experimental results of Comparative Examples 1-3 are summarized, see Table 1 for details:

Table 1 nitrobenzene production experimental results

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

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).