A whole-process process for synthesizing nitrobenzene by using a micro-channel reactor

Abstract

This invention discloses a complete process for preparing nitrobenzene using a microchannel reactor, belonging to the field of nitrobenzene synthesis. The complete process includes mixed acid, microchannel nitration reaction, intermediate product cooling and stratification followed by water and alkali washing, crude product distillation, waste acid recovery, and wastewater treatment. Compared with existing nitrobenzene synthesis technologies, this invention has high mass transfer efficiency, significantly shortens the nitration reaction time, greatly improves production efficiency, enhances reaction safety, and simultaneously achieves waste acid recovery and wastewater treatment, ensuring safe, environmentally friendly, and stable production.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology, specifically relating to a complete process for synthesizing nitrobenzene using a microchannel reactor. Background Technology

[0002] Nitrobenzene is an important organic chemical raw material intermediate, widely used in pharmaceuticals, dyes, and other fields. The synthesis of nitrobenzene is typically carried out using a batch reactor method. This batch method poses significant safety risks because the synthesis of nitrobenzene involves a large amount of exothermic reaction. The long reaction time in batch processes makes it difficult to remove the heat in time, resulting in substantial safety hazards. Furthermore, batch reactions consume a high amount of acid, and the highly acidic wastewater generated during acid recovery is difficult to treat. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a complete process for synthesizing nitrobenzene using a microchannel reactor.

[0004] The technical solution adopted in this invention is:

[0005] A complete process for preparing nitrobenzene using a microchannel reactor includes the following steps:

[0006] (1) Mix concentrated sulfuric acid and nitric acid in a mixed acid preparation system to obtain a nitric acid-sulfur mixed acid solution;

[0007] (2) The nitrate-sulfur mixed acid solution and benzene are introduced into a microchannel reactor to react and obtain a mixture of nitrobenzene and acid;

[0008] (3) The mixture is sent to an intermediate tank for cooling and sedimentation stratification; the upper organic phase is sent to a water washing and alkali washing system for water washing and alkali washing; the lower waste acid is sent to a waste acid recovery system for distillation and concentration, and the concentrated sulfuric acid obtained from the concentration is returned to the mixed acid preparation system for reuse.

[0009] (4) The nitric acid-containing wastewater generated by the waste acid recovery system and the alkaline wastewater generated by the water washing and alkaline washing system are mixed and then enter the wastewater treatment system, and are discharged after treatment to meet the standards.

[0010] (5) The organic phase after water washing and alkali washing enters the crude product distillation system, and after distillation, nitrobenzene product is obtained.

[0011] Further, in step (1), the mass concentration of nitric acid is 60-68%, the mass concentration of concentrated sulfuric acid is 95-98%, and the molar ratio of nitric acid to concentrated sulfuric acid is 1:1.5-2.0.

[0012] Furthermore, in step (2), the molar ratio of benzene to nitric acid is 1:1.0-1.1.

[0013] Furthermore, in step (2), the microchannel reaction temperature is 45-75℃ and the reaction time is 0.5-6min.

[0014] Furthermore, in step (3), the settling temperature is 5-30℃ and the settling time is 0.5-3h.

[0015] Furthermore, in step (3), the water washing uses deionized water at a temperature of 10-30℃ and the water washing time is 0.5-1.5h.

[0016] Furthermore, in step (3), the alkaline washing uses a sodium hydroxide solution with a mass concentration of 30-32% and a temperature of 10-25℃, and the alkaline washing time is 0.3-0.5h.

[0017] Furthermore, the waste acid recovery system adopts a three-stage distillation and concentration process, with each stage having an evaporation temperature of 100-150℃ and an evaporation time of 30-50 minutes.

[0018] Furthermore, the wastewater treatment system includes a mesophilic catalytic wet oxidation module, a microbial anaerobic denitrification module, and an ozone oxidation deep treatment module connected in sequence. The mesophilic catalytic wet oxidation removes organic matter from the wastewater, the microbial anaerobic denitrification removes nitrate nitrogen from the wastewater, and finally, after ozone oxidation deep treatment, the wastewater COD ≤ 50 mg / L and total nitrogen ≤ 15 mg / L.

[0019] Furthermore, in step (5), the distillation temperature is 220-240℃ and the distillation time is 0.5-1.0h.

[0020] The beneficial effects of this invention are as follows: The use of a microchannel reactor for nitration to prepare nitrobenzene results in high mass transfer efficiency, significantly shortening the nitration reaction time, greatly improving production efficiency, and enhancing reaction safety. Multi-stage distillation is employed to recover waste acid, greatly reducing acid consumption. Furthermore, the strongly acidic wastewater generated during acid recovery is neutralized with the alkaline wastewater generated during alkali washing before entering the wastewater treatment system. Organic matter is removed from the wastewater through medium-temperature catalytic wet oxidation, nitrate nitrogen is removed through microbial anaerobic denitrification, and finally, the wastewater undergoes deep treatment via ozone oxidation to meet discharge standards. Attached Figure Description

[0021] Figure 1 This is a flowchart of the entire process for synthesizing nitrobenzene using a microchannel reactor according to the present invention. Detailed Implementation

[0022] See Figure 1 A complete process for preparing nitrobenzene using a microchannel reactor includes the following steps:

[0023] (1) Mix concentrated sulfuric acid and nitric acid in a mixed acid preparation system to obtain a nitric acid-sulfur mixed acid solution; the mass concentration of nitric acid is 60-68%, the mass concentration of concentrated sulfuric acid is 95-98%, and the molar ratio of nitric acid to concentrated sulfuric acid is 1:1.5-2.0.

[0024] (2) The nitrate-sulfur mixed acid solution and benzene are introduced into a microchannel reactor to react and obtain a mixture of nitrobenzene and acid; the molar ratio of benzene to nitric acid is 1:1.0-1.1; the microchannel reaction temperature is 45-75℃ and the reaction time is 30-360s.

[0025] (3) The mixture is fed into an intermediate tank for cooling and sedimentation stratification; the upper organic phase enters a water washing and alkali washing system for water washing and alkali washing; the lower waste acid enters a waste acid recovery system via a waste acid intermediate tank for atmospheric pressure distillation and concentration, and the concentrated sulfuric acid obtained is temporarily stored in a concentrated sulfuric acid receiving tank and pumped into a mixed acid preparation system for reuse; the sedimentation time is 0.5-3h, and the sedimentation temperature is 5-30℃; the water washing uses deionized water at a temperature of 10-30℃, and the water washing time is 0.5-1.5h. The alkali washing uses a sodium hydroxide solution with a mass concentration of 30-32% and a temperature of 10-25℃, and the alkali washing time is 0.3-0.5h.

[0026] (4) The nitric acid-containing wastewater generated by the waste acid recovery system and the alkaline wastewater generated by the water washing and alkaline washing system are mixed and then enter the wastewater treatment system, and are discharged after treatment to meet the standards.

[0027] (5) The organic phase after water washing and alkali washing enters the crude product distillation system and is distilled at atmospheric pressure to obtain nitrobenzene product.

[0028] The waste acid recovery system adopts a three-stage distillation concentration process, which is an existing technology. In this invention, the evaporation temperature of each stage is 100℃-150℃, and the evaporation time is 30min-50min.

[0029] The wastewater treatment system includes a mesophilic catalytic wet oxidation module, a microbial anaerobic denitrification module, and an ozone oxidation deep treatment module connected in sequence. The mesophilic catalytic wet oxidation module, the microbial anaerobic denitrification module, and the ozone oxidation deep treatment module are all existing technologies. In this invention, organic matter in the wastewater is removed by mesophilic catalytic wet oxidation, nitrate nitrogen in the wastewater is removed by the microbial anaerobic denitrification module, and finally, after oxidation treatment by the ozone oxidation deep treatment module, the wastewater COD ≤ 50 mg / L and total nitrogen ≤ 15 mg / L, meeting the discharge standards.

[0030] Example 1

[0031] (1) 98% sulfuric acid and 65% nitric acid are pumped to a mixed acid preparation system at a molar ratio of 1:1.5 to obtain a nitric acid-sulfuric acid solution.

[0032] (2) Benzene and nitric acid-sulfuric acid solution were fed into a microchannel reactor by a delivery pump for nitration reaction. The molar ratio of benzene to nitric acid was 1:1.0, the reaction temperature was 65℃, and the reaction time was 2min.

[0033] (3) The nitrated material flows out of the microchannel reactor and enters the intermediate tank. It is left to stand at 5°C for 2 hours. The organic phase and the acid phase are separated into layers. The upper organic phase enters the water washing and alkali washing system, and the lower waste acid enters the waste acid intermediate tank. The water washing temperature is 10°C and the water washing time is 0.5 hours. The alkali washing temperature is 10°C and the alkali washing time is 0.5 hours. The alkali solution used for alkali washing is 30% liquid alkali.

[0034] (4) The waste acid in the intermediate waste acid tank is pumped into the waste acid recovery system. The first stage evaporation temperature is 120℃ and the evaporation time is 30min; the second stage evaporation temperature is 100℃ and the evaporation time is 35min; the third stage evaporation temperature is 150℃ and the evaporation time is 35min. The waste acid obtained from evaporation is returned to the mixed acid preparation system for reuse.

[0035] (5) The nitric acid-containing wastewater generated by the waste acid recovery system and the alkaline wastewater generated by the water washing and alkaline washing system are mixed and then enter the wastewater treatment system. After treatment, the wastewater has a COD of 40 mg / L and a total nitrogen of 15 mg / L, and is discharged in compliance with the standards.

[0036] (6) The organic phase after water washing and alkali washing is fed into the crude product distillation system and distilled at 230°C and atmospheric pressure for 1.0 h to obtain nitrobenzene product.

[0037] Example 2

[0038] (1) 95% sulfuric acid and 60% nitric acid are pumped to a mixed acid preparation system at a molar ratio of 1:2.0 to obtain a nitric acid-sulfuric acid solution.

[0039] (2) Benzene and nitric acid-sulfuric acid solution were fed into a microchannel reactor by a delivery pump for nitration reaction. The molar ratio of benzene to nitric acid was 1:1.05, the reaction temperature was 65℃, and the reaction time was 30 seconds.

[0040] (3) The nitrated material flows out of the microchannel reactor and enters the intermediate tank. It is left to stand at 15°C for 2.5 hours. The organic phase and the acid phase are separated into layers. The upper organic phase enters the water washing and alkali washing system, and the lower waste acid enters the waste acid intermediate tank. The water washing temperature is 15°C and the water washing time is 1.0 hours. The alkali washing temperature is 15°C and the alkali washing time is 0.3 hours. The alkali solution used for alkali washing is 32% liquid alkali.

[0041] (4) The waste acid in the intermediate waste acid tank is pumped into the waste acid recovery system. The first stage evaporation temperature is 100℃ and the evaporation time is 30min; the second stage evaporation temperature is 120℃ and the evaporation time is 35min; the third stage evaporation temperature is 150℃ and the evaporation time is 35min. The waste acid obtained from evaporation is returned to the mixed acid preparation system for reuse.

[0042] (5) The nitric acid-containing wastewater generated by the waste acid recovery system and the alkaline wastewater generated by the water washing and alkaline washing system are mixed and then enter the wastewater treatment system. After treatment, the wastewater has a COD of 50 mg / L and a total nitrogen of 15 mg / L, and is discharged in compliance with the standards.

[0043] (6) The organic phase after water washing and alkali washing enters the crude product distillation system and is distilled at 225°C and atmospheric pressure for 1.0 h to obtain nitrobenzene product.

[0044] Example 3

[0045] (1) 98% sulfuric acid and 65% nitric acid are pumped to a mixed acid preparation system at a molar ratio of 1:1.6 to obtain a nitric acid-sulfuric acid solution.

[0046] (2) Benzene and nitric acid-sulfuric acid solution were fed into a microchannel reactor by a delivery pump for nitration reaction. The molar ratio of benzene to nitric acid was 1:1.1, the reaction temperature was 45℃, and the reaction time was 6min.

[0047] (3) The nitrated material flows out of the microchannel reactor and enters the intermediate tank. It is left to stand at 10°C for 1.5 hours. The organic phase and the acid phase are separated into layers. The upper organic phase enters the water washing and alkali washing system, and the lower waste acid enters the waste acid intermediate tank. The water washing temperature is 10°C and the water washing time is 1.0 hour. The alkali washing temperature is 10°C and the alkali washing time is 0.5 hours. The alkali solution used for alkali washing is 32% liquid alkali.

[0048] (4) The waste acid in the intermediate waste acid tank is pumped into the waste acid recovery system. The first stage evaporation temperature is 100℃ and the evaporation time is 50min; the second stage evaporation temperature is 120℃ and the evaporation time is 30min; the third stage evaporation temperature is 150℃ and the evaporation time is 30min. The waste acid obtained from evaporation is returned to the mixed acid preparation system for reuse.

[0049] (5) The nitric acid-containing wastewater generated by the waste acid recovery system and the alkaline wastewater generated by the water washing and alkaline washing system are mixed and then enter the wastewater treatment system. After treatment, the wastewater has a COD of 50 mg / L and a total nitrogen of 12 mg / L, and is discharged in compliance with the standards.

[0050] (6) The organic phase after water washing and alkali washing enters the crude product distillation system and is distilled at 240℃ and atmospheric pressure for 0.5h to obtain nitrobenzene product.

[0051] Example 4

[0052] (1) 98% sulfuric acid and 68% nitric acid are pumped to a mixed acid preparation system at a molar ratio of 1:1.8 to obtain a nitric acid-sulfuric acid solution.

[0053] (2) Benzene and nitric acid-sulfuric acid solution were fed into a microchannel reactor by a delivery pump for nitration reaction. The molar ratio of benzene to nitric acid was 1:1.1, the reaction temperature was 75℃, and the reaction time was 1 min.

[0054] (3) The nitrated material flows out of the microchannel reactor and enters the intermediate tank. It is left to stand at 20°C for 1.5 hours. The organic phase and the acid phase are separated into layers. The upper organic phase enters the water washing and alkali washing system, and the lower waste acid enters the waste acid intermediate tank. The water washing temperature is 20°C and the water washing time is 1.0 hour. The alkali washing temperature is 20°C and the alkali washing time is 0.5 hours. The alkali solution used for alkali washing is 32% liquid alkali.

[0055] (4) The waste acid in the intermediate waste acid tank is pumped into the waste acid recovery system. The first stage evaporation temperature is 100℃ and the evaporation time is 30min; the second stage evaporation temperature is 150℃ and the evaporation time is 30min; the third stage evaporation temperature is 120℃ and the evaporation time is 45min. The waste acid obtained from evaporation is returned to the mixed acid preparation system for reuse.

[0056] (5) The nitric acid-containing wastewater generated by the waste acid recovery system and the alkaline wastewater generated by the water washing and alkaline washing system are mixed and then enter the wastewater treatment system. After treatment, the wastewater has a COD of 45 mg / L and a total nitrogen of 12 mg / L, and is discharged in compliance with the standards.

[0057] (6) The organic phase after water washing and alkali washing is introduced into the crude product distillation system and distilled at 220°C and atmospheric pressure for 1.0 h to obtain nitrobenzene product.

[0058] Example 5

[0059] (1) 98% sulfuric acid and 60% nitric acid are pumped to a mixed acid preparation system at a molar ratio of 1:1.8 to obtain a nitric acid-sulfuric acid solution.

[0060] (2) Benzene and nitric acid-sulfuric acid solution were fed into a microchannel reactor by a delivery pump for nitration reaction. The molar ratio of benzene to nitric acid was 1:1.1, the reaction temperature was 60℃, and the reaction time was 4 min.

[0061] (3) The nitrated material flows out of the microchannel reactor and enters the intermediate tank. It is left to stand at 30°C for 3 hours. The organic phase and the acid phase are separated into layers. The upper organic phase enters the water washing and alkali washing system, and the lower waste acid enters the waste acid intermediate tank. The water washing temperature is 30°C and the water washing time is 0.5 hours. The alkali washing temperature is 25°C and the alkali washing time is 0.5 hours. The alkali solution used for alkali washing is 32% liquid alkali.

[0062] (4) The waste acid in the intermediate waste acid tank is pumped into the waste acid recovery system. The first stage evaporation temperature is 100℃ and the evaporation time is 30min; the second stage evaporation temperature is 120℃ and the evaporation time is 30min; the third stage evaporation temperature is 150℃ and the evaporation time is 50min. The waste acid obtained from evaporation is returned to the mixed acid preparation system for reuse.

[0063] (5) The nitric acid-containing wastewater generated by the waste acid recovery system and the alkaline wastewater generated by the water washing and alkaline washing system are mixed and then enter the wastewater treatment system. After treatment, the wastewater has a COD of 48 mg / L and a total nitrogen of 13 mg / L, which meets the discharge standards.

[0064] (6) The organic phase after water washing and alkali washing is fed into the crude product distillation system and distilled at 230°C and atmospheric pressure for 1.0 h to obtain nitrobenzene product.

[0065] Example 6

[0066] (1) 98% sulfuric acid and 66% nitric acid are pumped to a mixed acid preparation system at a molar ratio of 1:2.0 to obtain a nitric acid-sulfuric acid solution.

[0067] (2) Benzene and nitric acid-sulfuric acid solution were fed into a microchannel reactor by a delivery pump for nitration reaction. The molar ratio of benzene to nitric acid was 1:1.0, the reaction temperature was 75℃, and the reaction time was 30s.

[0068] (3) The nitrated material flows out of the microchannel reactor and enters the intermediate tank. It is left to stand at 25°C for 0.5h. The organic phase and acid phase are separated into layers. The upper organic phase enters the water washing and alkali washing system, and the lower waste acid enters the waste acid intermediate tank. The water washing temperature is 25°C and the water washing time is 0.5h. The alkali washing temperature is 25°C and the alkali washing time is 0.5h. The alkali solution used for alkali washing is 32% liquid alkali.

[0069] (4) The waste acid in the intermediate waste acid tank is pumped into the waste acid recovery system. The first stage evaporation temperature is 120℃ and the evaporation time is 30min; the second stage evaporation temperature is 120℃ and the evaporation time is 35min; the third stage evaporation temperature is 150℃ and the evaporation time is 50min. The waste acid obtained from evaporation is returned to the mixed acid preparation system for reuse.

[0070] (5) The nitric acid-containing wastewater generated by the waste acid recovery system and the alkaline wastewater generated by the water washing and alkaline washing system are mixed and then enter the wastewater treatment system. After treatment, the wastewater has a COD of 45 mg / L and a total nitrogen of 14 mg / L, and is discharged in compliance with the standards.

[0071] (6) The organic phase after water washing and alkali washing is fed into the crude product distillation system and distilled at 230°C and atmospheric pressure for 1.0 h to obtain nitrobenzene product.

[0072] Example 7

[0073] (1) 98% sulfuric acid and 68% nitric acid are pumped to a mixed acid preparation system at a molar ratio of 1:2.0 to obtain a nitric acid-sulfuric acid solution.

[0074] (2) Benzene and nitric acid-sulfuric acid solution were fed into a microchannel reactor by a delivery pump for nitration reaction. The molar ratio of benzene to nitric acid was 1:1.1, the reaction temperature was 70℃, and the reaction time was 3 min.

[0075] (3) The nitrated material flows out of the microchannel reactor and enters the intermediate tank. It is left to stand at 15°C for 3.0h. The organic phase and acid phase are separated into layers. The upper organic phase enters the water washing and alkali washing system, and the lower waste acid enters the waste acid intermediate tank. The water washing temperature is 15°C and the water washing time is 1.5h. The alkali washing temperature is 15°C and the alkali washing time is 0.5h. The alkali solution used for alkali washing is 32% liquid alkali.

[0076] (4) The waste acid in the intermediate waste acid tank is pumped into the waste acid recovery system. The first stage evaporation temperature is 120℃ and the evaporation time is 35min; the second stage evaporation temperature is 150℃ and the evaporation time is 40min; the third stage evaporation temperature is 150℃ and the evaporation time is 50min. The waste acid obtained from evaporation is returned to the mixed acid preparation system for reuse.

[0077] (5) The nitric acid-containing wastewater generated by the waste acid recovery system and the alkaline wastewater generated by the water washing and alkaline washing system are mixed and then enter the wastewater treatment system. After treatment, the wastewater has a COD of 44 mg / L and a total nitrogen of 15 mg / L, and is discharged in compliance with the standards.

[0078] (6) The organic phase after water washing and alkali washing enters the crude product distillation system and is distilled at 240℃ and atmospheric pressure for 1.0 h to obtain nitrobenzene product.

Claims

1. A complete process for preparing nitrobenzene using a microchannel reactor, characterized in that, Includes the following steps: (1) Mix concentrated sulfuric acid and nitric acid in a mixed acid preparation system to obtain a nitric acid-sulfur mixed acid solution; (2) The nitrate-sulfur mixed acid solution and benzene are introduced into a microchannel reactor to react and obtain a mixture of nitrobenzene and acid; (3) The mixture is sent to an intermediate tank for cooling and sedimentation stratification; The upper organic phase enters the water washing and alkaline washing system for water washing and alkaline washing; The lower layer of waste acid enters the waste acid recovery system for distillation and concentration. The concentrated sulfuric acid obtained from the concentration is returned to the mixed acid preparation system for reuse. (4) The nitric acid-containing wastewater generated by the waste acid recovery system and the alkaline wastewater generated by the water washing and alkaline washing system are mixed and then enter the wastewater treatment system, and are discharged after treatment to meet the standards. (5) The organic phase after water washing and alkali washing enters the crude product distillation system, and after distillation, nitrobenzene product is obtained.

2. The complete process for preparing nitrobenzene using a microchannel reactor according to claim 1, characterized in that, In step (1), the mass concentration of nitric acid is 60-68%, the mass concentration of concentrated sulfuric acid is 95-98%, and the molar ratio of nitric acid to concentrated sulfuric acid is 1:1.5-2.

0.

3. The complete process for preparing nitrobenzene using a microchannel reactor according to claim 1, characterized in that, In step (2), the molar ratio of benzene to nitric acid is 1:1.0-1.

1.

4. The complete process for preparing nitrobenzene using a microchannel reactor according to claim 1, characterized in that, In step (2), the microchannel reaction temperature is 45-75℃ and the reaction time is 0.5-6min.

5. The complete process for preparing nitrobenzene using a microchannel reactor according to claim 1, characterized in that, In step (3), the settling temperature is 5-30℃ and the settling time is 0.5-3h.

6. The complete process for preparing nitrobenzene using a microchannel reactor according to claim 1, characterized in that, In step (3), deionized water with a temperature of 10-30℃ is used for washing, and the washing time is 0.5-1.5h.

7. The complete process for preparing nitrobenzene using a microchannel reactor according to claim 1, characterized in that, In step (3), the alkaline washing uses a sodium hydroxide solution with a mass concentration of 30-32% and a temperature of 10-25℃, and the alkaline washing time is 0.3-0.5h.

8. The complete process for preparing nitrobenzene using a microchannel reactor according to claim 1, characterized in that, The waste acid recovery system adopts a three-stage distillation and concentration process, with each stage having an evaporation temperature of 100-150℃ and an evaporation time of 30-50 minutes.

9. The complete process for preparing nitrobenzene using a microchannel reactor according to claim 1, characterized in that, The wastewater treatment system includes a mesophilic catalytic wet oxidation module, a microbial anaerobic denitrification module, and an ozone oxidation deep treatment module connected in sequence. The mesophilic catalytic wet oxidation removes organic matter from the wastewater, the microbial anaerobic denitrification removes nitrate nitrogen from the wastewater, and finally, after ozone oxidation deep treatment, the wastewater COD ≤ 50 mg / L and total nitrogen ≤ 15 mg / L.

10. The complete process for preparing nitrobenzene using a microchannel reactor according to claim 1, characterized in that, In step (5), the distillation temperature is 220-240℃ and the distillation time is 0.5-1.0h.

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