Energy-saving refining process for aniline production

Abstract

The invention provides an energy-saving refining process for aniline production. The key impurity cyclohexanone with the boiling point similar to that of aniline in the aniline production process reacts with phenol to generate light components easier to separate, meanwhile, the byproduct Schiff base is decomposed into aniline, and the aniline yield is increased. According to the amination reduction process, the removal rate of cyclohexanone and phenol can reach 99% or above, and the problems that a traditional aniline refining process is long in process, high in energy consumption, high in product aniline consumption and the like are solved. The method has remarkable energy-saving and consumption-reducing effects and is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of aniline production, and more specifically to an energy-saving refining process for aniline production. Background Technology

[0002] Currently, the main production process of aniline is the hydrogenation reduction of nitrobenzene, using metals such as palladium, cobalt, and nickel as the active catalyst center. Under certain conditions, the nitro group is hydrogenated to an amino group. The reaction equation is shown in Formula I. This method is clean, has a high reduction yield, and produces high-quality products. Most of the impurities generated by the side reactions can be removed to a low level by distillation. However, the key impurities, cyclohexanone and phenol, have boiling points close to those of aniline and are difficult to remove from crude aniline by conventional physical methods such as distillation.

[0003] C6H5NO2 + 3H2 → C6H5NH2 + 2H2O (Formula I)

[0004] The current process is as follows: Figure 1 As shown, the material at the reactor outlet undergoes preliminary water separation in the intermediate tank area to obtain crude aniline with a water content of 4-10 wt%. Impurities in the crude aniline can be divided into light components (water, cyclohexylamine, etc.), heavy components (Schiff base, aminophenol, etc.), and key impurities cyclohexanone and phenol. The impurity removal steps of this process mainly include: 1) dehydrating and removing light components from the crude aniline; 2) the highly dehydrated crude aniline enters the Schiff reactor, where cyclohexanone reacts with aniline to convert it into the heavy component Schiff base; 3) removing heavy components and phenol from the crude aniline to finally obtain the refined aniline product.

[0005] The current process mainly has the following problems: 1. The Schiffki reactor has a large footprint, long residence time, and requires high temperature and negative pressure for the reaction. It also has strict requirements on the water content in crude aniline, which increases the energy consumption and residence time of the light component removal step; 2. Converting cyclohexanone into heavy components for removal requires aniline as a raw material, which will reduce the product yield; 3. Since the boiling points of phenol and cyclohexanone are closer, when removing phenol in the heavy component removal step, a near-vacuum negative pressure is required to increase the boiling point difference between phenol and aniline, and a high reflux ratio is required to reduce the phenol content to a qualified level, resulting in a large overall distillation energy consumption.

[0006] Patent CN110627651A provides a method for reducing the phenol content in aniline. It utilizes the waste heat from the vapor-phase hydrogenation of nitrobenzene and excess hydrogen to catalytically hydrogenate phenol in aniline to cyclohexanone, reducing phenol levels and saving steam consumption in distillation to remove phenol. However, the resulting cyclohexanone remains a difficult-to-remove impurity and consumes more aniline, lowering the aniline yield. Patent CN116496166A provides a method for reducing the cyclohexanone content in crude aniline. It reacts cyclohexanone with hydroxylamines to generate high-boiling-point impurities in an oxime reactor, avoiding distillation and dehydration steps, thus reducing energy consumption. The cyclohexanone is then separated by distillation in a wall column, achieving low-energy removal. However, this method is ineffective at removing phenol, and the overall refining system still has high energy consumption. Therefore, there is still room for further optimization in existing crude aniline refining processes. Summary of the Invention

[0007] To address the above issues, this patent proposes an energy-saving refining process for aniline production. By reacting cyclohexanone and phenol with an amine source and a hydrogen source to generate lighter components that are easier to remove, and by decomposing the already reacted Schiff base to generate cyclohexanone and aniline, the energy consumption of the light and heavy component removal towers can be significantly reduced, and the equipment floor space can be saved. Furthermore, this method does not require the consumption of aniline and can increase aniline yield, with a reaction yield of up to 99%.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] An energy-saving refining process for aniline production includes the following steps:

[0010] 1) Crude aniline raw material containing cyclohexanone, phenol, and Schiff base impurities, along with an amine source and a hydrogen source, are introduced into the amination reactor for reaction;

[0011] 2) The material emanating from the amination reactor is passed sequentially through a light residue removal tower and a heavy residue removal tower to obtain the product aniline.

[0012] The crude aniline raw material described in this invention is a crude product obtained by preliminarily separating water from the material exiting the nitrobenzene hydrogenation reactor in the aniline process in the intermediate tank area. The liquid-phase catalytic hydrogenation of nitrobenzene to produce aniline is a mature industrial process, which is described in detail in known technologies, such as the methods in patents CN114149330B and CN113600201B. The above is only a feasible example of the crude aniline and is not intended to limit the invention in any way.

[0013] As a preferred embodiment of the present invention, the crude aniline raw material comprises 84-95.5 wt% aniline, 4-10 wt% water, 0.05-3 wt% cyclohexanone, 0.003-1 wt% phenol, 0.03-2 wt% Schiff base, and optionally the balance impurities satisfying a total mass of 100 wt%.

[0014] As a preferred embodiment of the present invention, the amine source in step 1) includes one or more of ammonia, ammonia water, or hydrazine hydrate, preferably ammonia or ammonia water; the hydrogen source includes hydrogen and / or hydrazine hydrate.

[0015] Furthermore, the amount of amine source is 2-5 times, preferably 3-4 times, the total molar amount of cyclohexanone, phenol, and Schiff base in the crude aniline raw material; wherein, when ammonia water is selected as the amine source, the aforementioned amount of amine source refers to the amount of ammonia in the ammonia water. When ammonia water is used as the amine source, the ammonia concentration is preferably 15wt%-25wt%.

[0016] Furthermore, the amount of the hydrogen source substance is 3-10 times, preferably 5-8 times, the total molar amount of cyclohexanone, phenol and Schiff base in the crude aniline raw material.

[0017] The amine source has a low excess rate of cyclohexanone, phenol and Schiff base in crude aniline, which can save the cost of amine source while ensuring the complete reaction of the three impurities. In addition, the ammonia source and hydrogen source can be completely separated in the light removal tower without affecting the original process.

[0018] As a preferred embodiment of the present invention, step 1) the amination reactor further includes a catalyst, which includes a support, an active component and an auxiliary agent.

[0019] Specifically, the catalyst active component includes one or more of palladium (Pd), ruthenium (Ru), nickel (Ni), and cobalt (Co), preferably Pd and / or Ni; the support includes one or more of cerium dioxide (CeO2), aluminum oxide (Al2O3), silicon dioxide (SiO2), and carbon (C), preferably one or more of CeO2, Al2O3, and SiO2;

[0020] Specifically, the loading of the active component in the catalyst is 25wt%-70wt%, preferably 30wt%-60wt%, based on the total mass of the catalyst;

[0021] Specifically, one or more of the following additives, iron (Fe), vanadium (V), and magnesium (Mg), are added to the catalyst, preferably Fe and / or Mg, with an additive loading of 0.1 wt%-20 wt%, preferably 3 wt%-10 wt%, based on the total mass of the catalyst.

[0022] The catalyst described in this invention can be a commercially available product or can be prepared in-house. Specifically, it can be prepared by impregnation or hydrothermal synthesis, with impregnation being preferred. The impregnation method can include steps such as impregnation, drying, and reduction, and can be prepared with reference to existing technologies.

[0023] In step 1) of the present invention, cyclohexanone and phenol generate a lighter component that is easier to remove from the system through an amination reduction reaction, and decompose the Schiff base into cyclohexanone and aniline, and the decomposed cyclohexanone undergoes further reaction.

[0024] An example of the amination-reduction reaction principle of cyclohexanone is shown in Formula II:

[0025]

[0026] An example of the amination-reduction reaction principle of phenol is shown in Formula III:

[0027]

[0028] An example of the decomposition reaction principle of Schiff bases is shown in Equation IV:

[0029]

[0030] As a preferred embodiment of the present invention, in step 1), the reaction pressure in the amination reactor is 0.2-8 MPaA, preferably 0.5-5 MPaA, the temperature is 30-280℃, preferably 50-200℃, and the reaction residence time is 5-150 min, preferably 10-120 min.

[0031] In a preferred embodiment of the present invention, the amination reactor is a fixed-bed reactor;

[0032] Preferably, the amination reactor can be a single reactor, multiple reactors connected in series, or multiple reactors connected in parallel to better achieve the amination reaction;

[0033] Preferably, the gas in the amination reactor is fed through a gas feed distributor, which is either an annular gas distributor or a dendritic gas distributor, preferably an annular gas distributor.

[0034] Preferably, the liquid in the amination reactor is fed through a nozzle, the nozzle structure being either an annular venturi type or a straight pipe multi-nozzle type, preferably an annular venturi type, the number of nozzles being 1-8, preferably 3-6, and the angle of the nozzle relative to the reactor wall being preferably 30-150°.

[0035] In a preferred embodiment of the present invention, step 2) uses a packed tower for removing light-weight materials, with a packing height of 1-5m, preferably 1.5m-3m;

[0036] Preferably, the material effluent from the amination reactor is fed from the light-weight removal tower.

[0037] Preferably, the operating pressure of the light-light removal tower is 30-500 kPaA, more preferably 80-200 kPaA, and the tower bottom temperature is 120-230°C, more preferably 130-200°C.

[0038] Preferably, the deweight removal tower is a packed tower with a packing height of 2-7m, preferably 3m-6m;

[0039] Preferably, the material exiting the bottom of the light-weight removal tower is fed from the heavy-weight removal tower.

[0040] Preferably, the operating pressure of the deweight removal tower is 1-600 kPaA, more preferably 5-300 kPaA, and the tower bottom temperature is 120-250℃, more preferably 130-220℃. Preferably, the reflux ratio of the deweight removal tower is 0.8-8, more preferably 1-2.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] The method provided by this invention can reduce the content of cyclohexanone and phenol in crude aniline to extremely low levels through a single reactor, avoiding the low water content requirement for cyclohexanone removal in the original process, widening the pressure operating range of the heavy removal tower, reducing the reflux ratio of the heavy removal tower, significantly reducing the energy consumption of the light removal and heavy removal towers in the original process, optimizing the overall footprint and original process, saving aniline consumed in the reaction with cyclohexanone, improving product yield, and the reactor has a nitrobenzene hydrogenation function, which can handle incompletely reacted nitrobenzene under abnormal operating conditions of the upstream nitrobenzene hydrogenation reactor, improving the stability of the unit's operation and its ability to handle abnormalities. Attached Figure Description

[0043] Figure 1 Comparative Example 1: Aniline process flow diagram;

[0044] Figure 2 : Flowchart of the energy-saving refining process for aniline in this embodiment of the invention. Detailed Implementation

[0045] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0046] The main raw material information involved in the following examples is as follows:

[0047] Crude aniline raw material A: contains 3 wt% cyclohexanone, 1 wt% phenol, 2 wt% Schiff base, 4 wt% water, 87.82 wt% aniline, 1 wt% nitrobenzene, 0.04 wt% cyclohexylamine, 0.001 wt% cyclohexanol, and optionally the balance impurities satisfying a total mass of 100 wt%.

[0048] Crude aniline raw material B: contains 0.05 wt% cyclohexanone, 0.003 wt% phenol, 0.03 wt% Schiff base, 6.9 wt% water, 89.85 wt% aniline, 3 wt% nitrobenzene, 0.03 wt% cyclohexylamine, 0.006 wt% cyclohexanol, and optionally, the balance impurities satisfying a total mass of 100 wt%.

[0049] Crude aniline raw material C: contains 1 wt% cyclohexanone, 0.8 wt% phenol, 0.5 wt% Schiff base, 10 wt% water, 87.01 wt% aniline, 0.1 wt% cyclohexylamine, 0.016 wt% cyclohexanol, and optionally the balance impurities satisfying a total mass of 100 wt%.

[0050] Crude aniline raw material D: contains 0.35 wt% cyclohexanone, 0.04 wt% phenol, 0.15 wt% Schiff base, 7.5 wt% water, 91.31 wt% aniline, 0.3 wt% cyclohexylamine, 0.027 wt% cyclohexanol, and optionally the balance impurities satisfying a total mass of 100 wt%.

[0051] Unless otherwise specified, all other raw materials were obtained through commercial channels.

[0052] Analytical instrument: Agilent GC-8890, gas chromatography for material composition determination.

[0053] Preparation Example 1

[0054] Taking a 30wt% Ni / Al2O3 catalyst with 3wt% Mg as an example, 100g of commercially available γ-Al2O3 support was used. 138g of nickel nitrate and 22g of magnesium sulfate were dissolved in 500g of ultrapure water. The solution was added to a beaker containing the support while stirring. After complete addition, the mixture was dried in an oven at 100℃ for 18h. It was then removed and placed in a tube furnace, heated to 400℃, and reduced by 500ml / min of hydrogen gas for 3h. The mixture was then naturally cooled to room temperature to obtain the catalyst. All catalysts mentioned in this article can be prepared using this method, and will not be described in detail further.

[0055] Example 1

[0056] Hydrogen gas was introduced into the amination reactor along with a mixture of raw material A and 20 wt% ammonia water, wherein the molar amount of ammonia in the ammonia water was 5 times the total molar amount of cyclohexanone, phenol, and Schiff base, and the molar amount of hydrogen gas was 5 times the total molar amount of cyclohexanone, phenol, and Schiff base. The catalyst used was 30 wt% Ni-Al2O3 with 3 wt% Mg added. The reaction pressure was 5 MPaA, the reaction temperature was 50℃, and the residence time was 120 min.

[0057] The fixed-bed reactor is a single reactor; the reactor gas feed distributor is an annular gas distributor; the liquid is fed through annular Venturi nozzles, with 4 nozzles and the nozzles at an angle of 75° to the reactor wall.

[0058] Analysis of the reactor outlet material composition revealed 5.13 wt% cyclohexylamine, 0.0001 wt% cyclohexanone, 94.47 wt% aniline, with no detectable phenol, Schiff base, or nitrobenzene.

[0059] The reactor outlet material is passed through a light component removal tower. The tower is fed with a packing height of 1.5m, and the operating pressure is controlled at 200 kPaA. The bottom temperature of the tower is 180℃. Light components and water are collected from the top of the tower, and aniline after light component removal is collected from the bottom of the tower.

[0060] Analysis revealed that the material extracted from the bottom of the light-light removal tower contained 99.9523% aniline and 0.0001 wt% cyclohexylamine, while cyclohexanone, phenol, Schiff base, and nitrobenzene were not detected.

[0061] The material in the bottom of the light component removal tower is passed through the heavy component removal tower. The feed is fed into the tower, the packing height is 3m, the operating pressure is controlled at 300KPaA, the bottom temperature is 175℃, the reflux ratio is 1, the product aniline is collected from the top of the tower, and the heavy component is collected from the bottom of the tower.

[0062] Analysis revealed that the product extracted from the top of the tower contained 99.9741% aniline, 0.0001 wt% cyclohexylamine, and no cyclohexanone, phenol, Schiff base, or nitrobenzene were detected. The remainder was water.

[0063] Example 2

[0064] A mixture of hydrogen and ammonia is introduced into an amination reactor. The feedstock is A, wherein the molar amount of ammonia is 4 times the total molar amount of cyclohexanone, phenol, and Schiff base, and the molar amount of hydrogen is 7 times the total molar amount of cyclohexanone, phenol, and Schiff base. The catalyst is 50wt% Ni-Al2O3 / SiO2 with 10wt% Fe added. The reaction pressure is 0.5 MPaA, the reaction temperature is 200℃, and the residence time is 10 min.

[0065] The fixed-bed reactor is a single reactor; the reactor gas feed distributor is an annular gas distributor; the liquid is fed through annular Venturi nozzles, with 6 nozzles and the nozzles at an angle of 60° to the reactor wall.

[0066] Analysis of the reactor outlet material composition revealed 5.14 wt% cyclohexylamine, 0.0001 wt% cyclohexanone, 94.46 wt% aniline, with no detectable phenol, Schiff base, or nitrobenzene.

[0067] The reactor outlet material is passed through a light component removal tower. The tower is fed with a packing height of 3m, and the operating pressure is controlled at 80 kPaA. The tower bottom temperature is 200℃. Light components and water are collected from the top of the tower, and aniline after light component removal is collected from the bottom of the tower.

[0068] Analysis revealed that the material extracted from the bottom of the light-light removal tower contained 99.9499% aniline, while cyclohexylamine, cyclohexanone, phenol, Schiff base, and nitrobenzene were not detected.

[0069] The material from the bottom of the light component removal tower is passed through the heavy component removal tower. The feed is placed into the tower, the packing height is 6m, the operating pressure is controlled at 120 kPaA, the bottom temperature is 190℃, and the reflux ratio is 1.3. Aniline is collected from the top of the tower, and heavy components are collected from the bottom.

[0070] Analysis revealed that the product extracted from the top of the tower contained 99.9755% aniline, and no cyclohexylamine, cyclohexanone, phenol, Schiff base, or nitrobenzene were detected. The remainder was water.

[0071] Example 3

[0072] A mixture of hydrogen and ammonia was introduced into an amination reactor. The feedstock was B, in which the molar amount of ammonia was 3 times the total molar amount of cyclohexanone, phenol, and Schiff base, and the molar amount of hydrogen was 8 times the total molar amount of cyclohexanone, phenol, and Schiff base. The catalyst was 50wt% Ni-Al2O3 / SiO2 with 4wt% Mg added. The reaction pressure was 2 MPaA, the reaction temperature was 140℃, and the residence time was 15 min.

[0073] The fixed-bed reactor consists of two reactors connected in parallel; the reactor gas feed distributor is an annular gas distributor; the liquid is fed through annular Venturi nozzles, with five nozzles and the nozzles at an angle of 90° to the reactor wall.

[0074] Analysis of the reactor outlet material composition revealed that it contained 0.113 wt% cyclohexylamine, 92.865 wt% aniline, and no cyclohexanone, phenol, Schiff base, or nitrobenzene were detected.

[0075] The reactor outlet material is passed through a light component removal tower. The tower is fed with a packing height of 2m, and the operating pressure is controlled at 150 kPaA. The tower bottom temperature is 130℃. Light components and water are collected from the top of the tower, and aniline after light component removal is collected from the bottom of the tower.

[0076] Analysis revealed that the material extracted from the bottom of the light-light removal tower contained 99.9512% aniline, while cyclohexylamine, cyclohexanone, phenol, Schiff base, and nitrobenzene were not detected.

[0077] The material from the bottom of the light component removal tower is passed through the heavy component removal tower. The feed is fed into the tower, the packing height is 4m, the operating pressure is controlled at 5KPaA, the bottom temperature is 220℃, the reflux ratio is 1.7, the product aniline is collected from the top of the tower, and the heavy component is collected from the bottom of the tower.

[0078] Analysis revealed that the product extracted from the top of the tower contained 99.9769% aniline, and no cyclohexylamine, cyclohexanone, phenol, Schiff base, or nitrobenzene were detected. The remainder was water.

[0079] Example 4

[0080] A mixture of hydrogen and ammonia was introduced into an amination reactor. The feedstock was C, wherein the molar amount of ammonia was 4 times the total molar amount of cyclohexanone, phenol, and Schiff base, and the molar amount of hydrogen was 6 times the total molar amount of cyclohexanone, phenol, and Schiff base. The catalyst was 25 wt% Pd / CeO2 with 6 wt% Fe added. The reaction pressure was 1.0 MPa, the reaction temperature was 100 °C, and the residence time was 25 min.

[0081] The fixed-bed reactor consists of three reactors in series; the reactor gas feed distributor is an annular gas distributor; the liquid is fed through annular Venturi nozzles, with four nozzles and the nozzles at an angle of 120° relative to the reactor wall.

[0082] Analysis of the reactor outlet material composition revealed that it contained 2.1455 wt% cyclohexylamine, 0.0004 wt% cyclohexanone, 0.0001 wt% phenol, 0.0002 wt% Schiff base, and 87.386 wt% aniline.

[0083] The reactor outlet material is passed through a light component removal tower. The tower is fed with a packing height of 2.5m, and the operating pressure is controlled at 180 kPaA. The bottom temperature of the tower is 200℃. Light components and water are collected from the top of the tower, and aniline after light component removal is collected from the bottom of the tower.

[0084] Analysis revealed that the material extracted from the bottom of the light-light removal tower contained 99.9502% aniline, while cyclohexylamine, cyclohexanone, phenol, and Schiff base were not detected.

[0085] The material from the bottom of the light component removal tower is passed through the heavy component removal tower. The feed is fed into the tower, the packing height is 3.5m, the operating pressure is controlled at 70KPaA, the bottom temperature is 165℃, the reflux ratio is 1.5, the product aniline is collected from the top of the tower, and the heavy component is collected from the bottom of the tower.

[0086] Analysis revealed that the product extracted from the top of the tower contained 99.9788% aniline, and no cyclohexylamine, cyclohexanone, phenol, or Schiff base were detected. The remainder was water.

[0087] Example 5

[0088] Hydrogen gas was introduced into the amination reactor along with a mixture of raw material D and 25 wt% ammonia water, wherein the molar amount of ammonia in the ammonia water was 4 times the total molar amount of cyclohexanone, phenol, and Schiff base, and the molar amount of hydrogen gas was 8 times the total molar amount of cyclohexanone, phenol, and Schiff base. The catalyst used was 30 wt% Ni-Al2O3 with 5 wt% Mg added. The reaction pressure was 0.8 MPaA, the reaction temperature was 160℃, and the residence time was 30 min.

[0089] The fixed-bed reactor consists of two reactors in series; the gas feed distributor is an annular gas distributor; the liquid is fed through annular Venturi nozzles, with three nozzles and the nozzles being at an angle of 150° to the reactor wall.

[0090] Analysis of the reactor outlet material composition revealed 0.77 wt% cyclohexylamine, 0.0001 wt% cyclohexanone, 0.0001 wt% phenol, 91.39 wt% aniline, and no Schiff base was detected.

[0091] The reactor outlet material is passed through a light component removal tower. The tower is fed with a packing height of 2m, and the operating pressure is controlled at 190 kPaA. The tower bottom temperature is 160℃. Light components and water are collected from the top of the tower, and aniline after light component removal is collected from the bottom of the tower.

[0092] Analysis revealed that the material extracted from the bottom of the light-light removal tower contained 99.9476% aniline, while cyclohexylamine, cyclohexanone, phenol, and Schiff base were not detected.

[0093] The material from the bottom of the light component removal tower is fed into the heavy component removal tower. The packing height is 5.5m, the operating pressure is controlled at 270 kPaA, the bottom temperature is 210℃, and the reflux ratio is 2.0. Aniline is collected from the top of the tower, and heavy components are collected from the bottom.

[0094] Analysis revealed that the product extracted from the top of the tower contained 99.9767% aniline, and no cyclohexylamine, cyclohexanone, phenol, or Schiff base were detected. The remainder was water.

[0095] Comparative Example 1

[0096] Raw material A was fed into a light component removal tower with a packing height of 4m. The operating pressure was controlled at 130 kPaA, and the reboiler temperature was 155℃. Light components and water were collected from the top of the tower, while aniline after light component removal was collected from the reboiler. Analysis showed that the reboiler material contained 2.17 wt% cyclohexanone, 0.975 wt% phenol, 3.57 wt% Schiff base, 0.031 wt% water, 92.09 wt% aniline, and 0.9573% nitrobenzene. Cyclohexylamine was not detected.

[0097] The material from the bottom of the light-removal tower is fed into the Schiff reactor. The reactor pressure is controlled at 130 kPaA and the temperature at 155°C. The reactor outlet material contains 0.0015 wt% cyclohexanone, 0.965 wt% phenol, 6.21 wt% Schiff base, 0.028 wt% water, 91.62 wt% aniline, and 0.9356% nitrobenzene.

[0098] The effluent from the Schiff reactor was fed into a deweighting tower. The tower had a packing height of 5.5 m, an operating pressure of 25 kPa, a reboiler temperature of 170 °C, and a reflux ratio of 4.0. Aniline was collected from the top of the tower, and heavy components were collected from the bottom. Analysis revealed that the aniline collected from the top contained 0.0008 wt% cyclohexanone, 0.005 wt% phenol, 0.0004 wt% Schiff base, and 0.029 wt% heavy components.

[0099] Water, 99.41 wt% aniline, 0.5542 nitrobenzene.

[0100] Comparative Example 2

[0101] Hydrogen gas was introduced into the amination reactor. The feedstock was D, and the molar amount of hydrogen was 8 times the total molar amount of cyclohexanone, phenol, and Schiff base. The catalyst was 30 wt% Ni-Al2O3 with 5 wt% Mg added. The reaction pressure was 0.8 MPaA, the reaction temperature was 160℃, and the residence time was 30 min.

[0102] The fixed-bed reactor consists of two reactors in series; the gas feed distributor is an annular gas distributor; the liquid is fed through annular Venturi nozzles, with three nozzles and the nozzles being at an angle of 150° to the reactor wall.

[0103] The composition of the reactor outlet material was analyzed and found to contain 0.3 wt% cyclohexylamine, 0.35 wt% cyclohexanone, 0.04 wt% phenol, 0.15 wt% Schiff base, and 91.31 wt% aniline.

[0104] The reactor outlet material is passed through a light component removal tower. The tower is fed with a packing height of 2m, and the operating pressure is controlled at 190 kPaA. The tower bottom temperature is 160℃. Light components and water are collected from the top of the tower, and aniline after light component removal is collected from the bottom of the tower.

[0105] Analysis revealed that the material extracted from the bottom of the light-light removal tower contained 0.27 wt% cyclohexanone, 0.04 wt% phenol, 0.31 wt% Schiff base, and 91.23 wt% aniline.

[0106] The material from the bottom of the light component removal tower is fed into the heavy component removal tower. The packing height is 5.5m, the operating pressure is controlled at 270 kPaA, the bottom temperature is 210℃, and the reflux ratio is 2.0. Aniline is collected from the top of the tower, and heavy components are collected from the bottom.

[0107] Analysis revealed that the aniline product extracted from the top of the tower contained 0.13% cyclohexanone, 0.009% phenol, 0.06% Schiff base, 99.7967% aniline, and the remainder was water.

[0108] In addition, a comparative analysis was conducted on the product energy consumption of the processes in Example 1 and Comparative Example 1. The steam types used included 10S steam with a unit price of 226 yuan / ton and 40S steam with a unit price of 273 yuan / ton. The statistical results are shown in Table 1.

[0109] Table 1. Comparison of process energy consumption between Example 1 and Comparative Example 1

[0110]

[0111] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. An energy-saving refining process for aniline production, characterized in that, Includes the following steps: S1: In the amination reactor, crude aniline raw material, amine source, and hydrogen source are introduced to carry out the reaction; S2: The material emanating from the amination reactor passes sequentially through a light residue removal tower and a heavy residue removal tower to obtain the product aniline; The crude aniline raw material is produced by liquid-phase hydrogenation of nitrobenzene to aniline. The amine source includes at least one of ammonia, ammonia water, and hydrazine hydrate, and the hydrogen source includes hydrogen and / or hydrazine hydrate.

2. The process according to claim 1, characterized in that, In S1, the crude aniline raw material comprises 84-95.5 wt% aniline, 4-10 wt% water, 0.05-3 wt% cyclohexanone, 0.003-1 wt% phenol, 0.03-2 wt% Schiff base, and optionally the balance impurities satisfying a total mass of 100 wt%.

3. The process according to claim 1, characterized in that, In S1, the amination reactor is also filled with a catalyst, which includes a support, an active component, and an auxiliary agent. The active component includes one or more of Pd, Ru, Ni, and Co; the support includes one or more of CeO2, Al2O3, SiO2, and C; and the auxiliary agent includes one or more of Fe, V, and Mg.

4. The process according to claim 3, characterized in that, The loading of active components in the catalyst is 25wt%-70wt%, preferably 30wt%-60wt%, based on the total mass of the catalyst. And / or, the loading of promoters in the catalyst is 0.1wt%-20wt%, preferably 3wt%-10wt%.

5. The process according to claim 2, characterized in that, In S1, the amount of the amine source is 2-5 times the total molar amount of cyclohexanone, phenol and Schiff base in crude aniline, preferably 3-4 times; the amount of the hydrogen source is 3-10 times the total molar amount of cyclohexanone, phenol and Schiff base in crude aniline, preferably 5-8 times.

6. The process according to any one of claims 1-5, characterized in that, The amination reaction pressure described in S1 is 0.2-8 MPaA, preferably 0.5-5 MPaA, the temperature is 30-280℃, preferably 50-200℃, and the reaction residence time is 5-150 min, preferably 10-120 min.

7. The method according to claim 6, characterized in that, The amination reactor described in S1 is a batch reactor or a fixed-bed reactor; preferably, the amination reactor is a single reactor, multiple reactors connected in series, or multiple reactors connected in parallel. And / or, the gas feed of the amination reactor is a gas feed distributor, which is one of annular gas distributor or dendritic gas distributor; And / or, the liquid is fed through a nozzle, which is either an annular venturi type or a straight multi-nozzle type; preferably, the number of nozzles is 1-8, more preferably 3-6, and the angle of the nozzle relative to the reactor wall is 30-150°.

8. The process according to claim 1, characterized in that, In S2, the light-weight product removal tower is a packed tower with a packing height of 1-5m, preferably 1.5m-3m; And / or, the effluent from the amination reactor is fed from the light-weight removal tower; And / or, the operating pressure of the light-removal tower is 30-500 kPaA, preferably 80-200 kPaA, and the tower bottom temperature is 120-230°C, preferably 130-200°C.

9. The process according to claim 1 or 8, characterized in that, In S2, the deweight removal tower is a packed tower with a packing height of 2-7m, preferably 3m-6m; And / or, the material exiting the reboiler of the light-weight removal tower is fed from the heavy-weight removal tower; And / or, the operating pressure of the deweighting tower is 1-600 kPaA, preferably 5-300 kPaA, the tower bottom temperature is 120-250°C, preferably 130-220°C, and the reflux ratio is 0.8-8, preferably 1-2.

Images