Method for preparing aniline through nitrobenzene liquid phase hydrogenation

Abstract

The invention provides a method for preparing aniline through nitrobenzene liquid phase hydrogenation. The method comprises a main reactor, a protection reactor and a refining system, wherein the main reactor is provided with a reaction section and a refining section. Raw materials are subjected to hydrogenation reaction in the reaction section of the main reactor, gas-phase discharged materials of the reaction section are washed in the refining section to remove heavy components and then are subjected to condensation and liquid-liquid separation, the separated liquid phase enters the rectifying tower, and an aniline product is obtained through separation; the liquid phase discharged material of the reaction section is continuously subjected to hydrogenation reaction through the protection reactor, and part of liquid phase is extracted through solid-liquid separation and sent to the rectifying tower. According to the method, the generation amount of heavy component impurities can be reduced by 50%, and the steam energy consumption of a refining unit can be saved by 40%.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogenation refining, and particularly relates to a method for preparing aniline by liquid-phase hydrogenation of nitrobenzene. Background Art

[0002] Aniline is an important organic synthetic raw material, which is widely used in industries such as polyurethane, medicine, pesticide, rubber additive and resin synthesis. It is mainly used to prepare 4,4-diphenylmethane diisocyanate (MDI), a raw material for polyurethane. At present, the processes for preparing aniline mainly include nitrobenzene Fe powder reduction method, phenol ammonolysis method and nitrobenzene catalytic hydrogenation method. Among them, nitrobenzene catalytic hydrogenation method has the characteristics of easy raw material availability, fewer steps, large production capacity, good product yield and quality, etc. It is widely used in industrial production processes. At present, industrial production generally adopts nitrobenzene liquid phase hydrogenation process.

[0003] The current nitrobenzene liquid phase hydrogenation process, in order to achieve a high conversion rate of nitrobenzene, controls the lower nitrobenzene content in the crude product extracted from the reactor, which will cause obvious over-hydrogenation by-products in the hydrogenation reactor, and then needs to consume a large amount of steam in the distillation unit at the rear end to control the quality of the aniline product. The conventional distillation unit adopts a double distillation tower. The specific double distillation tower process is: the crude aniline obtained after the nitrobenzene hydrogenation reaction product extracted from the reactor is stratified and transported to the top of the light removal tower by a pump, and light components such as water, cyclohexanol and a small amount of aniline are extracted from the top of the tower. The bottom liquid phase is sent to the product tower, and the refined aniline product is obtained at the top of the tower. The bottom liquid is discharged into the residual liquid tank. The above-mentioned two-tower process needs to obtain the aniline product from the top of the second distillation tower, which consumes a lot of energy and has a large equipment investment. And aniline passes through two towers and a reboiler, and stays in the high temperature zone for a long time, which easily leads to problems such as thermal decomposition and oxidation of aniline.

[0004] Regarding the high energy consumption problem in the aniline production process, patent CN102381984A discloses a method for heat-integrated separation of hydrogen, water, aniline and tar by continuous side-line discharge tower and distillation and recovery tower, wherein a side-line discharge distillation tower is used to replace the primary distillation tower in the conventional double-tower distillation process, dehydration and detarring are achieved at one time, and more than 99% of crude aniline side line is obtained, and then refined in the distillation tower to obtain more than 99.9% of aniline products. However, this method still requires two towers, the side-line tower and the distillation tower. Patent CN102408341A discloses a heat-integrated process between the synthesis gas and the separation device in the aniline synthesis and separation process based on the nitrobenzene gas-phase hydrogenation aniline process. However, this method couples the hydrogenation reaction and the separation process intensity, the process operation is complicated and unreasonable, and there is still a lot of heat that needs to be cooled by circulating water, and energy saving is not maximized. Patent CN102701994A discloses a crude aniline separation and purification process, which uses a baffle tower to replace the dehydration tower and distillation tower in the traditional crude aniline distillation process. However, this method is limited by factors such as the large difference in boiling points of impurities that need to be removed in the nitrobenzene liquid phase hydrogenation process to produce aniline, and the energy-saving effect in the liquid phase hydrogenation process is not obvious. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a process for preparing aniline by liquid phase hydrogenation of nitrobenzene. By using this method, the amount of reaction by-products generated can be effectively reduced, the quality of the crude product extracted from the reactor can be controlled, and qualified aniline products can be extracted from the bottom of the light removal tower, solving the high energy consumption problem required for extracting aniline products from the top of the product tower in the conventional distillation process.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing aniline by liquid-phase hydrogenation of nitrobenzene, the method comprising the following process flow: reaction raw materials hydrogen, nitrobenzene and catalyst enter a main reactor from the bottom of the main reactor, and quenching water is introduced into the main reactor at the same time; in the reaction section of the main reactor, the nitrobenzene and hydrogen react under the action of the catalyst to generate aniline; liquid phase material I containing the catalyst is extracted from the liquid phase extraction port of the reaction section of the main reactor, continues hydrogenation reaction in a protection reactor, liquid phase material II extracted from the protection reactor is concentrated by a solid-liquid separation device, and the concentrated liquid phase material II is mixed with a fresh catalyst and then returned to the reactor, The separated liquid material III is sent to the de-heavy tower of the distillation system; the gaseous material I of the azeotrope of aniline and water overflows from the top of the reaction section and directly enters the refining section, where it is washed and de-heavy by the countercurrent liquid material IV, and the washed gaseous material II overflows from the top of the refining section of the main reactor; the gaseous material II passes through a condenser and a liquid-liquid separator in sequence to obtain an organic phase liquid material V, which is sent to the de-light tower for refining to obtain an aniline product; the liquid material IV enters the reactor at the feed inlet of the refining section of the main reactor, countercurrently washes the heavy components in the gaseous material I, and is extracted from the reactor together with the liquid material I.

[0008] In the present invention, the main reactor is a slurry bed reactor.

[0009] In the present invention, the mass ratio of the raw material nitrobenzene to hydrogen is 2:1-20:1.

[0010] In the present invention, the operating pressure of the reactor is 1.0-2.5MpaG and the temperature is 150-260°C.

[0011] In the present invention, the reactor uses one or more of noble metal, nickel, copper, zinc, and aluminum hydrogenation catalysts, preferably noble metal hydrogenation catalysts; preferably, the catalyst concentration of the reaction solution in the reactor is 0.2-3.0wt%.

[0012] In the present invention, the mass ratio of the liquid phase material I collected from the main reactor to the nitrobenzene fed into the reactor is 0.1-1.2; preferably, the content of nitrobenzene is controlled to be 0.1%-5%, preferably 0.3%-1.0%.

[0013] In the present invention, the liquid phase material I is passed through a protective reactor to further reduce the nitrobenzene content; preferably, the nitrobenzene content in the liquid phase material II extracted from the protective reactor is controlled to be 0-1000ppm, preferably 20-300ppm.

[0014] In the present invention, the operating pressure of the protective reactor is 0.7-2.3 MpaG, and the temperature is 80-230°C.

[0015] In the present invention, the mass ratio of nitrobenzene to feed hydrogen in the liquid phase material I is 2:1-20:1.

[0016] In the present invention, the main reactor is provided with a reaction section and a refining section, and the refining section is provided with a liner; preferably, the liner is one or more of a structured packing, a random packing, and a tray, preferably a random packing and / or a tray; preferably, the theoretical number of plates in the refining section is 3-40, preferably 6-15; preferably, the reaction section is provided with a liquid phase extraction port, and the ratio of the distance from the liquid phase extraction port to the refining section liner to the reactor diameter is 0.3-8.0. Controlling the distance between the two can ensure the residence time of the gas phase material I in this area, so as to reduce the liquid phase foam entrained in the gas phase material I, which is conducive to reducing the theoretical number of plates required for the refining section and the flow rate of the liquid phase stream IV.

[0017] In the present invention, the liquid material IV is one or more of the aniline product of the distillation unit, the liquid material V after liquid-liquid separation, and the liquid material VI at the top of the deweighting tower, preferably the aniline product of the distillation unit; preferably, the mass ratio of the liquid material IV to nitrobenzene is 0.1-1.2, preferably 0.2-0.6; preferably, the feed temperature of the liquid material IV is 40-250°C, preferably 120-200°C.

[0018] In the present invention, the liquid phase material II discharged from the protection reactor is separated into the liquid phase material III by a solid-liquid separator, wherein the mass ratio of the liquid phase material III to nitrobenzene is 0.05-0.8.

[0019] In the present invention, the liquid phase material V after liquid-liquid separation enters the light-removal tower from the middle of the light-removal tower, the light component is extracted from the tower top, and the aniline product is directly extracted from the tower bottom.

[0020] Another object of the present invention is to provide an aniline product.

[0021] An aniline product is prepared by the above-mentioned method for liquid phase hydrogenation of nitrobenzene.

[0022] Compared with the prior art, the positive effects of the present invention are:

[0023] The reactor and process for preparing aniline by hydrogenating nitrobenzene in liquid phase of the present invention make the process control of hydrogenation process more flexible by controlling the concentration of nitrobenzene in the reactor and protecting the reaction conditions of the reactor, and reduce the generation amount of over-hydrogenation byproducts by more than 50%. By adding a rectification section at the upper part of the reactor and using liquid phase material IV, the heavy components in the gas phase material I can be effectively removed, so that the heavy component content in the liquid phase material V is significantly lower than the heavy component content in the aniline product of the existing process, and the aniline product that meets the index requirements can be directly produced from the kettle of the light removal tower; the mass and heavy component content of the liquid phase material III entering the heavy removal tower in the new process are less than the feed mass and heavy component content entering the product tower in the conventional two-tower process, so its energy consumption will also be significantly lower than the product tower in the conventional two-tower process, and 40% of steam energy consumption can be saved compared with the traditional double-tower refining process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The process flow diagram of preparing aniline by liquid phase hydrogenation of nitrobenzene of the present invention is shown in the figure: 1 is a main reactor, 1-1 is a main reactor reaction section, 1-2 is a main reactor refining section, 2 is a protective reactor, 3 is a solid-liquid separator, 4 is a condenser, 5 is a liquid-liquid separator, 6 is a lightness removal tower, and 7 is a heavy removal tower protective reactor. Among them, 1-1 is a main reactor refining section, and 1-2 is a main reactor reaction section. The gas phase material II extracted from the main reactor passes through the condenser and the liquid-liquid separator in sequence and then enters the lightness removal tower; the liquid phase material I extracted from the main reactor passes through the protective reactor and the solid-liquid separator in sequence and then the liquid phase material III is collected and sent to the heavy removal tower.

[0025] Figure 2 It is a schematic diagram of the traditional double-tower refining process flow in the prior art. DETAILED DESCRIPTION

[0026] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0027] Gas chromatography analysis conditions: Agilent 7890B, chromatographic column: HP-5 (30m x 530μm x1.5μm), automatic sampler, injection port temperature: 280℃, septum purge flow: 3ml / min, split ratio: 10:1, injection volume: 0.8ul, programmed temperature: 50℃ for 1min, increase the temperature to 150℃ at 5℃ / min, maintain for 2min, increase the temperature to 160℃ at 10℃ / min, maintain for 1min, increase the temperature to 200℃ at 15℃ / min, maintain for 0min, increase the temperature to 280℃ at 20℃ / min, maintain for 5min, detector: 280℃, hydrogen flow: 40mL / min, air flow: 400mL / min, tail gas flow: 25mL / min.

[0028] Raw material: nitrobenzene, purity ≥99.8%, Wanhua Chemical Group.

[0029] Raw materials: hydrogen, purity ≥99.8%, Wanhua Chemical Group.

[0030] Raw material: aniline, purity ≥99.9%, Wanhua Chemical Group.

[0031] like Figure 1 The reaction system and process flow shown in the figure, in which the main reactor has a diameter of 30 mm, the reaction section height is 150 mm, and the refining section height is 60 mm. The position of the liquid phase outlet of the main reactor is fixed, and the distance from the liquid phase outlet to the distillation section packing is controlled by adjusting the installation position of the packing. The protection reactor is a stirred tank with a volume of 0.3m 2 , diameter 550mm.

[0032] Example 1

[0033] The refining section of the main reactor is filled with 3 random packings with a theoretical plate height, and the distance from the liquid phase extraction port to the refining section packing is 40mm. The main reactor uses a catalyst of platinum palladium noble metal supported by activated carbon, with a concentration of 0.8wt%, a nitrobenzene / hydrogen feed mass ratio of 13:1, and a water / nitrobenzene feed mass ratio of 0.9:1. Each stream of material is transported to the main reactor by a pump. The operating pressure of the reactor is 1.7MpaG and the temperature is 210°C. The aniline product is used as the liquid phase material IV to enter the main reactor from the feed port of the refining section of the main reactor, and the gas phase material I from the reactor reaction section is evenly distributed and countercurrently washed through a liquid distributor. The mass ratio of the flow rate of the liquid phase material IV to the nitrobenzene feed amount is 1.2:1, and the temperature is 180°C. The gas phase material II overflowing from the refining section of the reactor passes through a condenser and enters a chromatograph to obtain a crude aniline product (liquid phase material V). The crude aniline product enters the light-removing tower as a raw material, and the operating pressure of the light-removing tower is controlled to be 40kpaA, and the tower bottom temperature is 154°C to separate the light components, and the tower bottom obtains the aniline product. The mass ratio of the flow rate of the liquid material I taken from the reaction section of the main reactor to the nitrobenzene feed amount is 1.5:1, and the nitrobenzene content in the liquid material I is 0.1%. The hydrogenation reaction continues in the protection reactor. The temperature of the protection reactor is controlled to be 100°C, the pressure is 1.2MpaG, the mass ratio of nitrobenzene in the liquid material I to the hydrogen fed to the protection reactor is 13:1, and the nitrobenzene content in the produced liquid material II is controlled to be 100ppm. Liquid material II is produced from liquid material III after passing through a thickener, and the mass ratio of the flow rate to nitrobenzene is 0.35:1. Liquid material III is directly sent to the de-weighting tower, and the operating pressure of the de-weighting tower is controlled to be 13kpaA, and the tower bottom temperature is 182°C to separate the heavy components, and the aniline product is obtained at the top of the tower.

[0034] The device was operated stably for 2 months under the above conditions. The heavy component content in liquid material V was 36ppm, the heavy component content in liquid material III was 0.41%, and the heavy component content in the aniline product was 38ppm. The energy consumption of the light removal tower was calculated to be 128KW / ton of aniline product, and the energy consumption of the heavy removal tower was 120KW / ton of aniline product.

[0035] Example 2

[0036] The refining section of the main reactor is filled with 8 random packings with a theoretical plate height, and the distance from the liquid phase outlet to the refining section packing is 60mm. The main reactor uses a catalyst of platinum palladium noble metal supported by activated carbon, with a concentration of 0.8wt%, a nitrobenzene / hydrogen feed mass ratio of 13:1, and a water / nitrobenzene feed mass ratio of 0.9:1. Each stream of material is transported to the main reactor by a pump. The reactor operating pressure is 1.7MpaG and the temperature is 210°C. The aniline product is used as the liquid phase material IV to enter the main reactor from the feed port of the refining section of the main reactor, and the gas phase material I from the reactor reaction section is evenly distributed and countercurrently washed through a liquid distributor. The mass ratio of the flow rate of the liquid phase material IV to the nitrobenzene feed amount is 0.25:1, and the temperature is 140°C. The gas phase material II overflowing from the refining section of the reactor passes through a condenser and enters a chromatograph to obtain a crude aniline product (liquid phase material V). The crude aniline product enters the light-removing tower as a raw material, and the operating pressure of the light-removing tower is controlled to be 40kpaA, and the tower bottom temperature is 154°C to separate the light components, and the tower bottom obtains the aniline product. The mass ratio of the flow rate of the liquid material I taken from the reaction section of the main reactor to the nitrobenzene feed amount is 0.7:1, and the nitrobenzene content in the liquid material I is 0.4%. The hydrogenation reaction continues in the protection reactor. The temperature of the protection reactor is controlled to be 80°C, the pressure is 2MpaG, the mass ratio of nitrobenzene in the liquid material I to the hydrogen fed to the protection reactor is 13:1, and the nitrobenzene content in the produced liquid material II is controlled to be 40ppm. Liquid material II is produced after the thickener. Liquid material III is produced, and the mass ratio of flow rate to nitrobenzene is 0.28:1. Liquid material III is directly sent to the de-weighting tower, and the operating pressure of the de-weighting tower is controlled to be 13kpaA, and the tower bottom temperature is 182°C to separate the heavy components, and the aniline product is obtained at the top of the tower.

[0037] The device was operated stably for 2 months under the above conditions. The heavy component content in liquid material V was 16ppm, the heavy component content in liquid material III was 0.43%, and the heavy component content in the aniline product was 17ppm. The energy consumption of the light removal tower was calculated to be 120KW / ton of aniline product, and the energy consumption of the heavy removal tower was 104KW / ton of aniline product.

[0038] Example 3

[0039] The refining section of the main reactor is filled with 40 random packings with a theoretical plate height, and the distance from the liquid phase extraction port to the refining section packing is 60mm. The main reactor uses a catalyst of platinum palladium noble metal supported by activated carbon, with a concentration of 3wt%, a nitrobenzene / hydrogen feed mass ratio of 13:1, and a water / nitrobenzene feed mass ratio of 0.9:1. Each stream of materials is transported to the main reactor by a pump. The operating pressure of the reactor is 1.7MpaG and the temperature is 150°C. The aniline product is used as the liquid phase material IV to enter the main reactor from the feed port of the refining section of the main reactor, and the gas phase material I from the reactor reaction section is evenly distributed and countercurrently washed through a liquid distributor. The mass ratio of the flow rate of the liquid phase material IV to the nitrobenzene feed amount is 0.4:1, and the temperature is 250°C. The gas phase material II overflowing from the refining section of the reactor passes through a condenser and enters a chromatograph to obtain a crude aniline product (liquid phase material V). The crude aniline product enters the light-removing tower as a raw material. The operating pressure of the light-removing tower is controlled to be 40kpaA, and the tower bottom temperature is 154°C to separate the light components. The tower bottom obtains the aniline product. The mass ratio of the flow rate of the liquid material I taken from the reaction section of the main reactor to the nitrobenzene feed amount is 0.9:1, and the nitrobenzene content in the liquid material I is 0.9%. The hydrogenation reaction continues in the protection reactor. The temperature of the protection reactor is controlled to be 230°C, the pressure is 1.2MpaG, the mass ratio of nitrobenzene in the liquid material I to the hydrogen fed to the protection reactor is 7:1, and the nitrobenzene content in the produced liquid material II is controlled to be 2ppm. Liquid material II is produced after the thickener. Liquid material III is produced, and the mass ratio of flow rate to nitrobenzene is 0.23:1. Liquid material III is directly sent to the de-weighting tower, and the operating pressure of the de-weighting tower is controlled to be 13kpaA, and the tower bottom temperature is 182°C to separate the heavy components, and the aniline product is obtained at the top of the tower.

[0040] The device was operated stably for 2 months under the above conditions. The heavy component content in liquid material V was 22ppm, the heavy component content in liquid material III was 0.58%, and the heavy component content in aniline product was 22ppm. The energy consumption of the light removal tower was calculated to be 122KW / ton of aniline product, and the energy consumption of the heavy removal tower was 112KW / ton of aniline product.

[0041] Example 4

[0042] The refining section of the main reactor is filled with 20 random packings with a theoretical plate height, and the distance from the liquid phase extraction port to the refining section packing is 100mm. The main reactor uses a catalyst of platinum palladium noble metal supported by activated carbon, with a concentration of 0.2wt%, a nitrobenzene / hydrogen feed mass ratio of 6:1, and a water / nitrobenzene feed mass ratio of 1.1:1. Each stream of material is transported to the main reactor by a pump. The operating pressure of the reactor is 1.7MpaG and the temperature is 260°C. The aniline product is used as the liquid phase material IV to enter the main reactor from the feed port of the refining section of the main reactor, and the gas phase material I from the reactor reaction section is evenly distributed and countercurrently washed through a liquid distributor. The mass ratio of the flow rate of the liquid phase material IV to the nitrobenzene feed amount is 0.1:1, and the temperature is 40°C. The gas phase material II overflowing from the refining section of the reactor passes through a condenser and enters a chromatograph to obtain a crude aniline product (liquid phase material V). The crude aniline product enters the light-removing tower as a raw material. The operating pressure of the light-removing tower is controlled to be 40kpaA, and the tower bottom temperature is 154°C to separate the light components. The tower bottom obtains the aniline product. The mass ratio of the flow rate of the liquid material I taken from the reaction section of the main reactor to the nitrobenzene feed amount is 0.3:1. The nitrobenzene content in the liquid material I is 5%, and the hydrogenation reaction is continued in the protection reactor. The temperature of the protection reactor is controlled to be 100°C, the pressure is 1.6MpaG, the mass ratio of nitrobenzene in the liquid material I to the hydrogen fed to the protection reactor is 10:1, and the nitrobenzene content in the produced liquid material II is controlled to be 1000ppm. Liquid material II is produced from liquid material III after passing through a thickener, and the mass ratio of the flow rate to nitrobenzene is 0.13:1. Liquid material III is directly sent to the de-weighting tower, and the operating pressure of the de-weighting tower is controlled to be 13kpaA, and the tower bottom temperature is 182°C to separate the heavy components, and the aniline product is obtained at the top of the tower.

[0043] The device was operated stably for 2 months under the above conditions. The heavy component content in liquid material V was 33ppm, the heavy component content in liquid material III was 0.97%, and the heavy component content in aniline product was 33ppm. The energy consumption of the light removal tower was calculated to be 120KW / ton of aniline product, and the energy consumption of the heavy removal tower was 109KW / ton of aniline product.

[0044] Comparative Example 1

[0045] Compared with the embodiment, the main reactor in the comparative example only includes a reaction section and does not include a refining section. The main reactor uses a catalyst of activated carbon-supported platinum palladium noble metal, with a concentration of 0.8wt%, a nitrobenzene / hydrogen feed mass ratio of 13:1, and a water / nitrobenzene feed mass ratio of 0.9:1. Each strand of material is pumped to the main reactor. The reactor operating pressure is 1.7barG and the temperature is 210°C. The gas phase material I overflowing from the reactor enters the chromatograph after passing through the condenser to obtain a crude aniline product (liquid phase material V). The mass ratio of the flow rate of the liquid phase material I outside the reactor to the nitrobenzene feed amount is 0.45:1, and the nitrobenzene content in the liquid phase material I is 40ppm. The liquid phase material III is extracted after the thickener, and the mass ratio of the flow rate to nitrobenzene is 0.04:1. The liquid phase material V is mixed with the liquid phase material III and enters the light removal tower, and the light removal tower operating pressure is controlled to be 40kpaA, and the tower bottom temperature is 154°C to separate the light components. The bottom liquid of the light-removal tower is sent to the product tower, and the operating pressure of the product tower is controlled at 13kpaA and the bottom temperature is 182℃ to separate the heavy components, and the aniline product is obtained at the top of the tower.

[0046] The device was operated stably for 2 months under the above conditions. The heavy component content in liquid material V was 662ppm, the heavy component content in liquid material III was 2.2%, and the heavy component content in the aniline product was 56ppm. The energy consumption of the light-removal tower was calculated to be 120KW / ton of aniline product, and the energy consumption of the product tower was 260KW / ton of aniline product.

[0047] It can be seen from the above results that the use of the new process of the present invention can reduce the generation of heavy component impurities in the reactor by more than 50% and the steam energy consumption of the back-end refining unit by 40%.

[0048] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing aniline by liquid phase hydrogenation of nitrobenzene, characterized in that: The method comprises the following process flow: the reaction raw materials hydrogen, nitrobenzene and catalyst enter the main reactor from the bottom of the main reactor, and quenching water is introduced into the main reactor at the same time; in the reaction section of the main reactor, the nitrobenzene and hydrogen react under the action of the catalyst to generate aniline; The liquid material I containing the catalyst is extracted from the liquid phase extraction port of the reaction section of the main reactor, and continues the hydrogenation reaction in the protection reactor. The liquid material II extracted from the protection reactor is concentrated by the solid-liquid separation equipment, and the concentrated liquid material II is mixed with the fresh catalyst and returned to the reactor. The separated liquid material III is sent to the deweighting tower of the distillation system; The gaseous material I of the azeotrope of aniline and water overflows from the top of the reaction section and directly enters the refining section, where it is washed and de-heavy-componented by the countercurrent liquid material IV. The washed gaseous material II overflows from the top of the refining section of the main reactor; the gaseous material II passes through a condenser and a liquid-liquid separator in sequence to obtain an organic phase liquid material V, which is sent to a light-removing tower for refining to obtain an aniline product; the liquid material IV enters the reactor at the feed inlet of the refining section of the main reactor, countercurrently washes the heavy components in the gaseous material I, and is extracted from the reactor together with the liquid material I.

2. The method according to claim 1, characterized in that The main reactor is a slurry bed reactor; And / or, the mass ratio of raw material nitrobenzene to hydrogen is 2:1-20:1; and / or, the operating pressure of the reactor is 1.0-2.5MpaG and the temperature is 150-260°C; and / or, the reactor uses one or more of noble metal, nickel, copper, zinc, and aluminum hydrogenation catalysts, preferably noble metal hydrogenation catalysts; Preferably, the catalyst concentration of the reaction solution in the reactor is 0.2-3.0 wt%.

3. The method according to claim 1 or 2, characterized in that: The mass ratio of the liquid phase material I collected from the main reactor to the reactor feed nitrobenzene is 0.1-1.2; Preferably, the content of nitrobenzene is controlled to be 0.1%-5%, preferably 0.3%-1.0%.

4. The method according to any one of claims 1 to 3, characterized in that The liquid phase material I passes through the guard reactor to further reduce the nitrobenzene content; Preferably, the nitrobenzene content in the liquid phase material II extracted from the protection reactor is controlled to be 0-1000 ppm, preferably 20-300 ppm.

5. The method according to any one of claims 1 to 4, characterized in that The operating pressure of the protection reactor is 0.7-2.3MpaG, and the temperature is 80-230℃; And / or, the mass ratio of nitrobenzene to feed hydrogen in the liquid phase material I is 2:1-20:

1.

6. The method according to any one of claims 1 to 5, characterized in that The main reactor is provided with a reaction section and a refining section, and the refining section is equipped with a lining member; Preferably, the lining member is one or more of structured packing, random packing, and tower tray, preferably random packing and / or tower tray; Preferably, the number of theoretical plates in the refining section is 3-40, preferably 6-15; Preferably, the reaction section is provided with a liquid phase extraction port, and the ratio of the distance from the liquid phase extraction port to the lining of the refining section to the reactor diameter is 0.3-8.

0.

7. The method according to any one of claims 1 to 6, characterized in that The liquid material IV is one or more of the aniline product of the distillation unit, the liquid material V after liquid-liquid separation, and the liquid material VI at the top of the deweighting tower, preferably the aniline product of the distillation unit; Preferably, the mass ratio of liquid material IV to nitrobenzene is 0.1-1.2, preferably 0.2-0.6; Preferably, the feed temperature of the liquid phase material IV is 40-250°C, preferably 120-200°C.

8. The method according to any one of claims 1 to 7, characterized in that The liquid phase material II discharged from the protection reactor is separated into the liquid phase material III by a solid-liquid separator, wherein the mass ratio of the liquid phase material III to nitrobenzene is 0.05-0.

8.

9. The method according to any one of claims 1 to 8, characterized in that The liquid phase material V after liquid-liquid separation enters the light-removal tower from the middle part, the light components are taken out from the top of the tower, and the aniline product is directly taken out from the bottom of the tower.

10. An aniline product, which is prepared by the method for liquid phase hydrogenation of nitrobenzene according to any one of claims 1 to 9.

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