Process for directly preparing 6-aminocapronitrile from cyclohexanone oxime

Abstract

The present invention provides a process for directly preparing 6-aminocapronitrile from cyclohexanone oxime. Vaporized liquid ammonia and molten cyclohexanone oxime are mixed and then subjected to a one-stage amination reaction to obtain a 6-aminocapronitrile product material one; the 6-aminocapronitrile product material one is sequentially subjected to light component removal and distillation to obtain a product 6-aminocapronitrile and a by-product; the by-product obtained after distillation is mixed with vaporized liquid ammonia and then subjected to a two-stage amination reaction to obtain a 6-aminocapronitrile product material two, and the 6-aminocapronitrile product material two is merged into the above steps to obtain the product 6-aminocapronitrile. The technical solution of the present invention is used in the one-stage amination reaction. The cyclohexanone oxime conversion rate is 100%, the 6-aminocapronitrile selectivity is greater than 80%, and the caprolactam selectivity is 17%. The function of the two-stage amination reactor is to amination caprolactam to generate 6-aminocapronitrile. The caprolactam conversion rate of the two-stage amination reaction is 95%, and the 6-aminocapronitrile selectivity reaches 95%.

Description

Technical Field

[0001] The present application relates to the field of chemical technology, and in particular to a synthesis system and method for directly preparing 6-aminocapronitrile from cyclohexanone oxime. Background Art

[0002] Adiponitrile is the raw material for producing hexamethylenediamine, an important intermediate of nylon-66 and nylon-610. 6-Aminocapronitrile can replace adiponitrile to produce hexamethylenediamine.

[0003] In recent years, the domestic demand for nylon materials has grown rapidly, exacerbating the contradiction between raw material supply and product demand. Using 6-aminocapronitrile to replace adiponitrile to produce hexamethylenediamine can alleviate the domestic supply demand for hexamethylenediamine to a certain extent.

[0004] In addition to the aforementioned adiponitrile method, current industrial methods for producing hexamethylenediamine include the butadiene method, the caprolactam method, the hexamethylenediol method, and the adipic acid method. However, all of these methods have certain drawbacks. The butadiene method produces highly toxic hydrogen cyanide (HCN). The hexamethylenediol method has harsh reaction conditions, low conversion rates, and complex processes. The selectivity of the adipic acid liquid phase method is only 80%, while the selectivity of the adipic acid vapor phase method is only 90%, both of which are relatively low. The caprolactam method involves high-temperature ammoniation and dehydration of caprolactam to produce 6-aminocapronitrile, which is then hydrogenated to produce hexamethylenediamine. This method requires a large amount of solvent, has high equipment requirements, high energy consumption, and low conversion rates.

[0005] This process uses cyclohexanone oxime as a raw material to produce 6-aminocapronitrile. Cyclohexanone oxime is an isomer of caprolactam and can also replace caprolactam to prepare 6-aminocapronitrile. For example, patents CN213012649U and CN110835311A both use cyclohexanone oxime to prepare 6-aminocapronitrile. Both methods require large amounts of solvent, have high energy consumption, and have low conversion and selectivity.

[0006] The present invention discloses a method for preparing 6-aminocapronitrile by a combined reaction of cyclohexanone oxime and ammonia. This method does not require a solvent. In a first step, cyclohexanone oxime and ammonia are reacted in a fixed-bed reactor equipped with a molecular sieve to produce 6-aminocapronitrile, caprolactam, and a small amount of byproducts. After separation of the 6-aminocapronitrile, the product and ammonia are introduced into a second fixed-bed reactor equipped with another molecular sieve catalyst for ammonia dehydration, where the caprolactam is converted back into 6-aminocapronitrile. This two-step reaction achieves a cyclohexanone oxime conversion rate exceeding 100%, and a 6-aminocapronitrile yield exceeding 95%. Summary of the Invention

[0007] The main purpose of the present invention is to provide a process for directly preparing 6-aminocapronitrile from cyclohexanone oxime. The process can solve the problems of low conversion rate, poor selectivity, complex distillation and separation process, and high operating cost in the current preparation of 6-aminocapronitrile by high-temperature amination of cyclohexanone oxime.

[0008] The technical solution of the present invention:

[0009] The primary amination reactor is used to react cyclohexanone oxime with ammonia in the presence of a catalyst to undergo rearrangement and amination reactions. The amination reaction produces 6-aminocapronitrile, which in turn undergoes a rearrangement reaction to produce caprolactam. Using the technical solution of the present invention, the primary amination reaction achieves a cyclohexanone oxime conversion rate of 100%, a 6-aminocapronitrile selectivity of 80% or greater, and a caprolactam selectivity of 17% or greater.

[0010] The second-stage amination reactor is used to amination caprolactam to produce 6-aminocapronitrile. The caprolactam conversion rate of the second-stage amination reaction is 95% or higher, and the selectivity for 6-aminocapronitrile is 95% or higher.

[0011] The function of the circulating ammonia compressor is to compress the excess ammonia through the compressor and then recycle it.

[0012] The function of the light-removal tower is to extract components lighter than the product from the top of the tower, and the function of the product tower is to extract components heavier than the product from the bottom of the tower, and the product is extracted from the top of the product tower.

[0013] The function of the condenser in the present invention is to condense the vapor phase material at the top of the tower into a liquid phase. The function of the reboiler in the present invention is to heat the liquid phase at the bottom of the tower to generate a vapor phase, which is separated by mass transfer from the liquid phase cooled by the condenser.

[0014] The process for directly preparing 6-aminocapronitrile from cyclohexanone oxime mainly includes 2 reactors, 2 distillation towers, 11 heat exchangers, 1 gas-liquid separator, etc.

[0015] The process logistics connection is as follows:

[0016] (1) Vaporized liquid ammonia and molten cyclohexanone oxime are mixed and then subjected to a first stage of amination reaction to obtain 6-aminocapronitrile product material 1;

[0017] (2) removing light components and rectifying the 6-aminocapronitrile product material 1 to obtain the product 6-aminocapronitrile and by-products;

[0018] (3) The by-product obtained after distillation in step (2) is mixed with vaporized liquid ammonia and subjected to a two-stage amination reaction to obtain 6-aminocapronitrile product material 2, and the 6-aminocapronitrile product material 2 is combined with step (2) to obtain the product 6-aminocapronitrile.

[0019] The one-stage amination reaction in step (1) is carried out in a one-stage amination reactor, the one-stage amination reactor is an adiabatic fixed-bed reactor, and the catalyst in the one-stage amination reactor is a combination of one or more of a molecular sieve with an MFI topology structure, a molecular sieve with an Al-modified MFI topology structure, a molecular sieve with an Fe-modified MFI topology structure, a molecular sieve with a Ti-modified MFI topology structure, a molecular sieve with a Zn-modified MFI topology structure, a molecular sieve with a Co-modified MFI topology structure, and a molecular sieve with a Mn-modified MFI topology structure;

[0020] The combination methods include single layer, double layer, multi-layer or mixed filling, and the mixing methods include mechanical grinding or solvent co-impregnation.

[0021] The temperature of the first-stage amination reaction is 300-480°C, with the optimal range being 360-440°C. The reaction pressure is slightly positive. The molar ratio of ammonia to cyclohexanone oxime in the feed is 30-75, and the cyclohexanone oxime space velocity is 0.5-2 kg / (kgcat·h).

[0022] The 6-aminocapronitrile product obtained in step (1) and step (3) is cooled and separated, and the separated liquid phase enters a light component removal tower to remove the light components. The separated gas phase is deep-cooled and compressed to obtain ammonia, which is used as a raw material for a first-stage amination reaction.

[0023] The light component removal in step (2) is carried out in a light component removal tower, which is a plate tower or a packed tower with 15 to 40 theoretical plates, 8 to 20 feed positions, a reflux ratio of 2 to 6, a tower top temperature of 80 to 90°C, a tower bottom temperature of 150 to 170°C, and a tower top pressure of 5 to 20 kPaA.

[0024] A portion of the gas phase outlet at the top of the light-removing tower is circulated, and a portion is used to produce light components; the liquid phase material produced at the bottom of the light-removing tower enters the distillation tower.

[0025] The distillation in step (2) is carried out in a distillation tower, which is a plate tower or a packed tower with 15 to 35 theoretical plates, 8 to 17 feed positions, a reflux ratio of 3 to 8, a tower top temperature of 120 to 140°C, a tower bottom temperature of 160 to 180°C, and a tower top pressure of 5 to 15 kPaA.

[0026] The second-stage amination reaction in step (3) is carried out in a second-stage amination reactor, which is an adiabatic fixed-bed reactor. The catalyst in the reactor is a metal-supported molecular sieve catalyst, the active metal is selected from one or more combinations of titanium, zirconium, iron, vanadium, cobalt, molybdenum, manganese, nickel, copper, zinc, magnesium, and calcium, and the carrier is selected from one or more combinations of silicon molecular sieves, silicon-aluminum molecular sieves, titanium-silicon molecular sieves, and silicon-phosphorus-aluminum molecular sieves.

[0027] The mass fraction of the active metal relative to the carrier is 0.1-10wt%.

[0028] In some embodiments, the silicon-aluminum molecules are selected from ZSM-5, ZSM-23, ZSM-35, ZSM-48,

[0029] Any one.

[0030] In some embodiments, the titanium silicon molecular sieve is selected from TS-1.

[0031] In some embodiments, the silicon-phosphorus-aluminum molecules are selected from any of SAPO-11, SAPO-34, and SAPO-20.

[0032] One kind of meaning.

[0033] The two-stage amination reaction temperature is 300-500°C, with an optimal range of 350-450°C. The reaction pressure is slightly positive. The feed ammonia:caprolactam (molar ratio) is 20-40, and the caprolactam space velocity is 0.2-1.5 kg / (kgcat·h).

[0034] In the above process, the reaction system used is as follows:

[0035] The outlet of the liquid ammonia storage tank is connected to the inlet of the liquid ammonia feed pump, the outlet of the liquid ammonia feed pump is connected to the inlet of the liquid ammonia vaporizer, the outlet of the liquid ammonia vaporizer is connected to the inlet of the ammonia heat exchanger tube side, the outlet of the ammonia heat exchanger tube side is connected to the inlet of the ammonia heater, and the outlet of the ammonia heater is connected to the inlet of a counter-feed mixer.

[0036] In some specific embodiments, the liquid ammonia vaporizer is a kettle-type vaporizer, with the liquid ammonia flowing through the shell side. The heating medium is steam, which flows through the tube side. Temperature and pressure transmitters are installed in the vapor space of the liquid ammonia vaporizer to control the flow rate of the heating medium steam.

[0037] The outlet of the cyclohexanone oxime melting kettle is connected to the inlet of the cyclohexanone oxime feed pump, the outlet of the cyclohexanone oxime feed pump is connected to the shell side inlet of the cyclohexanone oxime heat exchanger, the shell side outlet of the cyclohexanone oxime heat exchanger is connected to the inlet of the cyclohexanone oxime heater, and the outlet of the cyclohexanone oxime heater is connected to the inlet of a reverse feed mixer.

[0038] The ammonia heater and the cyclohexanone oxime heater are explosion-proof electric heaters, and the temperature of the heated medium is controlled by changing the current of the heater.

[0039] The outlet of the first reaction feed mixer is connected to the inlet of the first stage ammoniation reactor, the outlet of the first stage ammoniation reactor is connected to the inlet of the reaction discharge mixer, the outlet of the discharge mixer is connected to the tube side inlet of the cyclohexanone oxime heat exchanger, the shell side outlet of the cyclohexanone oxime heat exchanger is connected to the shell side inlet of the ammonia heat exchanger, the shell side outlet of the ammonia heat exchanger is connected to the tube side inlet of the first stage cooler, the tube side outlet of the first stage cooler is connected to the tube side inlet of the second stage cooler, and the tube side outlet of the second stage cooler is connected to the inlet of the gas-liquid separation tank.

[0040] Preferably, the primary and secondary coolers are water-cooled coolers, and the cooling medium water flows through the shell.

[0041] Preferably, the gas phase discharge port of the gas-liquid separator is located at the top of the separator, serving as gas discharge, and the liquid phase discharge port is located at the bottom of the gas-liquid separator, serving as liquid discharge. The gas-liquid separator is provided with a liquid level indicator alarm for displaying the liquid level height, which can alarm when the liquid level is too high or too low. The gas-liquid separator is provided with a demisting net for capturing liquid droplets entrained in the gas phase.

[0042] The upper gas phase outlet of the gas-liquid separator is connected to the inlet of the ammonia cryocooler tube side, which is connected to the inlet of the circulating ammonia compressor, which is connected to the inlet of the ammonia heat exchanger tube side. The lower liquid phase outlet of the gas-liquid separator is connected to the inlet of the lightness removal tower feed pump, which is connected to the feed port of the middle part of the lightness removal tower.

[0043] Preferably, the ammonia cryogenic cooler is a chilled water cooler, and the cooling medium is ethylene glycol aqueous solution in the shell side.

[0044] Preferably, the circulating ammonia compressor can be a piston compressor or a screw compressor, preferably a screw compressor.

[0045] The outlet of the product tower bottom pump is connected to the inlet of the second-stage reaction electric heater, the outlet of the second-stage reaction electric heater is connected to the inlet of the second reactor feed mixer, the outlet of the second reactor feed mixer is connected to the inlet of the second-stage amination reactor, and the outlet of the second-stage amination reactor is connected to the inlet of the reaction discharge mixer.

[0046] Preferably, the heater is an explosion-proof electric heater, and the temperature of the heated medium is controlled by changing the current of the heater.

[0047] The gas phase outlet at the top of the lightness removal tower is connected to the shell-side inlet of the lightness removal tower condenser, which is connected to the inlet of the lightness removal tower reflux tank. The outlet of the lightness removal tower reflux tank is connected to the inlet of the lightness removal tower reflux pump. The outlet of the lightness removal tower reflux pump is connected to one channel and the reflux port on the top of the lightness removal tower. One channel is used for light component extraction. One outlet at the bottom of the lightness removal tower is connected to the inlet of the reboiler tube side of the lightness removal tower, and the outlet of the reboiler tube side of the lightness removal tower is connected to the lower inlet of the lightness removal tower. Another outlet at the bottom of the lightness removal tower is connected to the inlet of the lightness removal tower bottom pump, which is connected to the feed port in the middle of the product tower.

[0048] The gas phase outlet at the top of the product tower is connected to the shell-side inlet of the product tower condenser, the shell-side outlet of the product tower condenser is connected to the inlet of the product tower reflux tank, the outlet of the product tower reflux tank is connected to the inlet of the product tower reflux pump, one line of the product tower reflux pump outlet is connected to the reflux port at the top of the product tower, and the other line is connected to the inlet of the 6-aminocapronitrile product tank as the 6-aminocapronitrile product. The outlet at the bottom of the product tower is connected to the inlet of the product tower bottom pump, one line of the product tower bottom pump outlet is connected to the inlet of the waste liquid tank, and the other line is connected to the second-stage reaction electric heater.

[0049] Generally speaking, the production of 6-aminocapronitrile from cyclohexanone oxime theoretically involves a two-step reaction. First, cyclohexanone oxime undergoes rearrangement to form caprolactam (typically achieving 100% conversion of the raw material), followed by aminolysis of the caprolactam to produce 6-aminocapronitrile. These two reactions typically require different catalysts. This technology utilizes a two-catalyst combination to produce 6-aminocapronitrile from cyclohexanone oxime in a single reactor. However, a small amount of unreacted caprolactam may remain, requiring further conversion in a second amination reactor to improve overall yield. Existing patent CN113105363 A completes the reaction of cyclohexanone oxime to 6-aminocapronitrile in a single reactor, but the reaction occurs in a solvent system. Other patents, such as CN110835311 A and CN113087641 A, both involve the conversion of cyclohexanone oxime to caprolactam first, followed by conversion to 6-aminocapronitrile. This technology not only utilizes a combined catalyst to complete the conversion of most of the cyclohexanone oxime into 6-aminocapronitrile in the first step, but also does so without using a solvent. This can greatly reduce solvent loss and increased energy consumption caused by the need to distill the product from the solvent, thereby simplifying the product separation process.

[0050] Using the technical solution of the present application, the first-stage amination reaction achieves a cyclohexanone oxime conversion rate of 100%, a 6-aminocapronitrile selectivity of greater than 80%, and a caprolactam selectivity of 17% or greater. The second-stage amination reactor ammoniates caprolactam to produce 6-aminocapronitrile. The second-stage amination reaction achieves a caprolactam conversion rate of 95% or greater, and a 6-aminocapronitrile selectivity of 95% or greater. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0052] Figure 1 This is a process flow chart of a process (reaction system) for directly preparing 6-aminocapronitrile from cyclohexanone oxime;

[0053] Figure 2 This is a process flow chart of a process for directly preparing 6-aminocapronitrile from cyclohexanone oxime (distillation system);

[0054] In the figure: 1. Liquid ammonia storage tank; 2. Liquid ammonia feed pump; 3. Liquid ammonia vaporizer; 4. Ammonia heat exchanger; 5. Ammonia heater; 6. Cyclohexanone oxime melting kettle; 7. Cyclohexanone oxime feed pump; 8. Cyclohexanone oxime heat exchanger; 9. Cyclohexanone oxime heater; 10. First-stage feed mixer; 11. First-stage amination reactor. 12. Reaction discharge mixer; 13. Primary cooler; 14. Secondary cooler; 15. Gas-liquid separation tank; 16. Light-removal tower feed pump; 17. Ammonia cryogenic refrigerator; 18. Circulating ammonia compressor; 19. Light-removal tower; 20. Light-removal tower condenser; 21. Light-removal tower reflux tank; 22. Light-removal tower reflux pump; 23. Light-removal tower bottom pump; 24. Light-removal tower reboiler; 25. Product tower; 26. Product tower condenser; 27. Product tower reflux tank; 28. Product tower reflux pump; 29. Product tower bottom pump; 30. 6-aminocapronitrile product tank; 31. Waste liquid tank; 32. Second-stage reaction electric heater; 33. Second-stage reaction feed mixer; 34. Second-stage amination reactor. DETAILED DESCRIPTION

[0055] In order to make the purpose, features, and advantages of this application more obvious and easy to understand, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described below are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0056] The technical solution of the present application will be further explained below with reference to the accompanying drawings and through specific implementation methods.

[0057] In the description of this application, it should be understood that the terms "upper", "lower", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on this application.

[0058] Reference Figures 1 to 2 A process for directly preparing 6-aminocapronitrile from cyclohexanone oxime. The process of the invention comprises a reaction system and a distillation system.

[0059] The preparation method of the Al-modified MFI topology molecular sieve is as follows: using granular silica gel as the silicon source, sodium metaaluminate as the aluminum source, tetrapropylammonium hydroxide (TPAOH) as a structure-directing agent, and ammonium polyphosphate as a crystal face growth inhibitor. The specific synthesis formula is a molar ratio of SiO2 / Al2O3 = 120, Na2O / SiO2 = 0.20, TPAOH / SiO2 = 0.20, H2O / SiO2 = 15, and the amount of ammonium polyphosphate is such that the mass ratio of ammonium polyphosphate to silicon oxide is 15%. The specific implementation process is to dissolve sodium hydroxide, sodium metaaluminate, and tetrapropylammonium hydroxide in water, add granular silica gel and ammonium polyphosphate, continue stirring for two hours, then transfer to a crystallization kettle and crystallize at 180°C for 22 hours. After crystallization, cool to room temperature, filter, separate, dry, and calcine to obtain flaky ZSM-5 molecular sieve. The molecular sieve particle size is ~40nm×180nm×750nm.

[0060] The preparation method of Fe-modified MFI topology molecular sieve is the same as above, except that the iron source is ferric chloride.

[0061] The preparation method of the Ti-modified MFI topology molecular sieve is the same as above, except that the titanium source is tetrabutyl titanate.

[0062] The preparation method of the Zn-modified MFI topology molecular sieve is the same as above, except that the zinc source is zinc chloride.

[0063] The preparation method of the Co-modified MFI topology molecular sieve is the same as above, except that the cobalt source is cobalt chloride.

[0064] The preparation method of the Mn-modified MFI topology molecular sieve is the same as above, except that the manganese source is manganese chloride.

[0065] The present invention directly prepares 6-aminocapronitrile from cyclohexanone oxime process as follows:

[0066] Reaction system:

[0067] Liquid ammonia in liquid ammonia storage tank 1 is fed into liquid ammonia vaporizer 3 via liquid ammonia feed pump 2. The vaporizer vaporizes the liquid ammonia and mixes it with pressurized ammonia gas from circulating ammonia compressor 18. The mixed ammonia gas then passes through ammonia heater 4, exchanging heat with the reaction products and heating it to 420°C. A portion of the mixed ammonia gas is mixed with heated cyclohexanone oxime and enters the first-stage ammonia reactor 11, while the remaining portion enters the second-stage ammonia reactor 33.

[0068] 2. The solid cyclohexanone oxime raw material is added to the cyclohexanone oxime melting kettle 6. In the cyclohexanone oxime melting kettle 6, it is heated by the steam coil to melt into a liquid state and discharged through the cyclohexanone oxime feed pump 7. It exchanges heat with the reaction materials in the cyclohexanone oxime heat exchanger 8 to increase the temperature. After heating, it is heated by the cyclohexanone oxime heater 9 to 420°C. It is mixed with the heated ammonia gas through the first feed mixer 10 and enters the first amination reactor 11 together.

[0069] The first-stage amination reactor 11 is an adiabatic fixed-bed reactor filled with Fe-modified MFI molecular sieves. The materials from Steps 1 and 2 undergo amination and rearrangement reactions within the reactor. The initial reaction temperature is 420°C, the pressure is slightly positive, and the amination reaction is endothermic. The reactor outlet temperature is 390°C. The reaction products are 6-aminocapronitrile, caprolactam, and a small amount of by-products.

[0070] The feed ammonia:cyclohexanone oxime molar ratio was 65, and the cyclohexanone oxime space velocity was 1.2 kg / (kgcat·h). The first-stage amination reaction achieved 100% cyclohexanone oxime conversion, 80% selectivity for 6-aminocapronitrile, and 17% selectivity for caprolactam.

[0071] 4. The reaction product obtained in step 3 is mixed with the reaction product of the second-stage amination reactor 34 in the reaction discharge mixer 12, and then firstly heat-exchanged with cyclohexanone oxime in the cyclohexanone oxime heat exchanger 8 to reduce the temperature, and then heat-exchanged with ammonia in the ammonia heat exchanger 4 to reduce the temperature to 260°C, and then cooled to 40°C in the primary cooler 13 and the secondary cooler 14.

[0072] The cooled material from step 4 enters the gas-liquid separator 15, where ammonia and the reaction products undergo gas-liquid separation and are withdrawn from the top of the separator 15. The ammonia is cooled to 10°C in an ammonia cryocooler 17, pressurized by a circulating ammonia compressor 18, and then mixed with the vaporized ammonia for recycling. The liquid reaction products at the bottom of the gas-liquid separator 17 are pressurized by a light-removal tower feed pump 16 and then enter the light-removal tower 19.

[0073] 6. The rearrangement reaction product caprolactam and by-products separated in the product tower 25 of the subsequent separation system are sent to the second-stage reaction electric heater 32 via the product tower bottom pump 29. After being heated to 420°C, they are mixed with ammonia gas through the second-stage feed mixer 33 and enter the second-stage amination reactor 34. The two materials undergo an amination reaction in the presence of a vanadium-modified silica-alumina molecular sieve ZSM-48 catalyst (the amount of vanadium in the catalyst is 1.8 wt%) to obtain 6-aminocapronitrile and a small amount of by-products.

[0074] The second-stage amination reactor 33 is an adiabatic fixed-bed reactor.

[0075] After the two-step reaction, the conversion rate of cyclohexanone oxime can reach more than 100%, the yield of 6-aminocapronitrile is 95%, and the purity is 99.8%.

[0076] Distillation system:

[0077] 7 The liquid product of step 5 is pressurized by the de-lightness tower feed pump 16 and enters the de-lightness tower 19. The vapor phase in the de-lightness tower is extracted from the top of the tower, condensed into a liquid phase by the de-lightness tower condenser 20, and then enters the de-lightness tower reflux tank 21 for storage. The liquid in the reflux tank is pressurized by the de-lightness tower reflux pump 22, and part of the logistics is refluxed to the top of the de-lightness tower 19, and part is transported to the waste liquid tank 31 for storage as a light component.

[0078] A stream of material from the bottom of the light removal tower 19 is transported to the product tower 25 via the light removal tower bottom pump 23 .

[0079] After the material at the bottom of the light-removal tower 19 is heated by the light-removal tower reboiler 24, part of the gas phase is generated and enters the bottom of the light-removal tower 19. The gas phase at the bottom of the tower contacts the reflux liquid phase at the top of the tower on the tower plate, and vapor-liquid mass transfer exchange is carried out. The light components rise and the heavy components fall, thereby achieving the purpose of separation.

[0080] The light-removal tower 19 is a high-efficiency plate tower with 35 theoretical plates, 15 feed positions, a reflux ratio of 4.5, and a tower top pressure of 15 KPaA.

[0081] 8 The liquid phase of the light component removal tower bottom pump 23 described in step 7 is transported to the product tower 25 and enters the product tower 25. The vapor phase in the product tower is extracted from the top of the tower, condensed into a liquid phase by the product tower condenser 26, and then enters the product tower reflux tank 27 for storage. After the liquid in the reflux tank is pressurized by the product tower reflux pump 28, a part of the flow is pressurized by the product tower reflux pump 28 and refluxed to the top of the product tower 25, and a part is transported to the 6-aminocapronitrile product tank 30 for storage as a light component product.

[0082] The material at the bottom of the product tower 25 is heated by the coil reboiler built into the product tower, generating a partial gas phase which rises from the bottom of the product light removal tower 25 and contacts the reflux liquid phase at the top of the tower on the tower plates, undergoing vapor-liquid mass transfer exchange, causing the light components to rise and the heavy components to fall, thereby achieving the purpose of separation.

[0083] The product tower 25 is a high-efficiency plate tower with 30 theoretical plates, 12 feed positions, a reflux ratio of 4.6, and a tower top pressure of 8 KPaA.

[0084] Example 2

[0085] The same process as in Example 1 was used, except that the first-stage amination reactor 11 was an adiabatic fixed-bed reactor filled with Co-modified MFI topology molecular sieve.

[0086] The feed ammonia:cyclohexanone oxime molar ratio was 65, and the cyclohexanone oxime space velocity was 1.2 kg / (kgcat·h). The first-stage amination reaction achieved 100% cyclohexanone oxime conversion, 92% selectivity for 6-aminocapronitrile, and 6% selectivity for caprolactam.

[0087] In the second stage amination reactor 33, the two materials are reacted over a molybdenum-modified silicon-phosphorus-aluminum molecular sieve SAPO-34 catalyst (the amount of vanadium in the catalyst is 3.0 wt%).

[0088] After two steps of reaction, the conversion rate of cyclohexanone oxime can reach more than 100%, the yield of 6-aminocapronitrile is 97%, and the purity is 99.9%.

[0089] Example 3

[0090] The same process as in Example 1 was used, except that the first-stage amination reactor 11 was an adiabatic fixed-bed reactor filled with Mn-modified molecular sieves of MFI topology.

[0091] The feed ammonia:cyclohexanone oxime molar ratio was 65, and the cyclohexanone oxime space velocity was 1.2 kg / (kgcat·h). The first-stage amination reaction achieved 100% cyclohexanone oxime conversion, 94% selectivity for 6-aminocapronitrile, and 3% selectivity for caprolactam.

[0092] In the second stage amination reactor 33, the two materials are reacted over a nickel-modified titanium silicalite TS-1 catalyst (the amount of vanadium in the catalyst is 3.0 wt%).

[0093] After two steps of reaction, the conversion rate of cyclohexanone oxime can reach more than 100%, the yield of 6-aminocapronitrile is 98.8%, and the purity is 99.9%.

[0094] Example 4

[0095] The apparatus used in the above process has the following structure: an apparatus for directly preparing 6-aminocapronitrile from cyclohexanone oxime, wherein the outlet of a liquid ammonia vaporizer 3 is connected to an inlet of a counter-feed mixture 10;

[0096] The outlet of the cyclohexanone oxime melting kettle 6 is connected to the inlet of a counter-feed mixture 10;

[0097] An outlet of the first-stage feed mixture 10 is connected to an inlet of a first-stage amination reactor 11;

[0098] The outlet of the first stage amination reactor 11 is connected to the inlet of the gas-liquid separation tank 15;

[0099] The outlet of the gas-liquid separation tank 15 is connected to the inlet of the lightness removal tower 19;

[0100] The bottom outlet of the light removal tower 19 is connected to the upper inlet of the product tower 25;

[0101] The top outlet of the product tower 25 is connected to the inlet of the product tower condenser 26;

[0102] The outlet of the product tower condenser 26 is connected to the inlet of the product tower reflux tank 27;

[0103] The product tower reflux tank 27 is connected to the 6-aminocapronitrile product tank 30 via a product tower reflux pump 28 .

[0104] The bottom outlet of the product tower 25 is connected to the inlet of the second-stage reaction electric heater 32 through the product tower bottom pump 29;

[0105] The outlet of the second stage reaction electric heater 32 is connected to the inlet of the second reaction feed mixer 33;

[0106] The outlet of the liquid ammonia vaporizer 3 is connected to the inlet of the second reactor feed mixer 33;

[0107] The outlet of the second reactor feed mixer 33 is connected to the inlet of the second stage amination reactor 34;

[0108] The outlet of the second-stage amination reactor 34 is connected to the inlet of the gas-liquid separation tank 15 .

[0109] A liquid ammonia storage tank 1 is provided on the liquid ammonia vaporizer 3, and the two are connected by a liquid ammonia feed pump 2;

[0110] The outlet of the liquid ammonia vaporizer 3 is connected to the tube side inlet of the ammonia heat exchanger 4, the tube side outlet of the ammonia heat exchanger 4 is connected to the inlet of the ammonia heater 5, and the outlet of the ammonia heater 5 is connected to the inlet 10 of a reverse feed mixer.

[0111] The outlet of the cyclohexanone oxime melting kettle 6 is connected to the inlet of the cyclohexanone oxime feed pump 7, the outlet of the cyclohexanone oxime feed pump 7 is connected to the shell side inlet of the cyclohexanone oxime heat exchanger 8, the shell side outlet of the cyclohexanone oxime heat exchanger 8 is connected to the inlet of the cyclohexanone oxime heater 9, and the outlet of the cyclohexanone oxime heater 9 is connected to the inlet 10 of a counter-feed mixer.

[0112] The outlets of the first-stage amination reactor 11 and the second-stage amination reactor 34 are respectively connected to the inlet of the reaction discharge mixer 12, the outlet of the discharge mixer 12 is connected to the tube side inlet of the cyclohexanone oxime heat exchanger 8, the shell side outlet of the cyclohexanone oxime heat exchanger 8 is connected to the shell side inlet of the ammonia heat exchanger 4, the shell side outlet of the ammonia heat exchanger 4 is connected to the tube side inlet of the primary cooler 13, the tube side outlet of the primary cooler 13 is connected to the tube side inlet of the secondary cooler 14, and the tube side outlet of the secondary cooler 14 is connected to the inlet of the gas-liquid separation tank 15.

[0113] The upper gas phase outlet of the gas-liquid separation tank 15 is connected to the pipe side inlet of the ammonia cryogenic refrigerator 17, the pipe side outlet of the ammonia cryogenic refrigerator 17 is connected to the inlet of the circulating ammonia compressor 18, and the outlet of the circulating ammonia compressor 18 is connected to the pipe side inlet of the ammonia heat exchanger 4; the lower liquid phase outlet of the gas-liquid separation tank 15 is connected to the inlet of the de-light tower feed pump 16, and the outlet of the de-light tower feed pump 16 is connected to the middle feed port of the de-light tower 19.

[0114] The gas phase outlet at the top of the light-removal tower 19 is connected to the shell side inlet of the light-removal tower condenser 20, the shell side outlet of the light-removal tower condenser 20 is connected to the inlet of the light-removal tower reflux tank 21, the outlet of the light-removal tower reflux tank 21 is connected to the inlet of the light-removal tower reflux pump 22, the outlet of the light-removal tower reflux pump 22 is connected to the upper reflux port of the light-removal tower 19, and is connected to the light component partition.

[0115] One outlet at the bottom of the de-lightening tower 19 is connected to the pipe side inlet of the de-lightening tower reboiler 24, and the pipe side outlet of the de-lightening tower reboiler 24 is connected to the lower inlet of the de-lightening tower 19; another outlet at the bottom of the de-lightening tower 19 is connected to the inlet of the de-lightening tower bottom pump 23, and the outlet of the de-lightening tower bottom pump 23 is connected to the middle feed port of the product tower 25.

[0116] The gas phase outlet at the top of the product tower 25 is connected to the shell side inlet of the product tower condenser 26, the shell side outlet of the product tower condenser 26 is connected to the inlet of the product tower reflux tank 27, the outlet of the product tower reflux tank 27 is connected to the inlet of the product tower reflux pump 28, the outlet of the product tower reflux pump 28 is connected to the upper reflux port of the product tower 25 through one route, and the other route is connected to the inlet of the 6-aminocapronitrile product tank 30 as a 6-aminocapronitrile product.

[0117] The bottom outlet of the product tower 25 is connected to the inlet of the product tower bottom pump 29 . One outlet of the product tower bottom pump 29 is connected to the inlet of the waste liquid tank 31 , and the other outlet is connected to the second-stage reaction electric heater 32 .

Claims

1. A process for directly preparing 6-aminocapronitrile from cyclohexanone oxime, characterized in that: The steps include: (1) Vaporized liquid ammonia and molten cyclohexanone oxime are mixed and then subjected to a one-stage amination reaction to obtain a 6-aminocapronitrile product material 1; wherein the one-stage amination reaction is carried out in a one-stage amination reactor, the one-stage amination reactor is an adiabatic fixed-bed reactor, and the catalyst in the one-stage amination reactor is a Co-modified MFI topology molecular sieve or a Mn-modified MFI topology molecular sieve, or a combination of one or more of the above; the combination includes single-layer, double-layer, multi-layer or mixed loading, and the mixing includes mechanical grinding or solvent co-impregnation; (2) removing light components and rectifying the 6-aminocapronitrile product material 1 to obtain the product 6-aminocapronitrile and by-products; (3) The by-product obtained after the distillation in step (2) is mixed with vaporized liquid ammonia and then subjected to a two-stage amination reaction to obtain a second 6-aminocapronitrile product material, and the second 6-aminocapronitrile product material is combined with the product in step (2) to obtain a product 6-aminocapronitrile; the two-stage amination reaction is carried out in a two-stage amination reactor, which is an adiabatic fixed bed reactor, and the catalyst in the reactor is a metal-supported molecular sieve catalyst, the active metal is selected from one or more combinations of titanium, zirconium, iron, vanadium, cobalt, molybdenum, manganese, nickel, copper, zinc, magnesium, and calcium, and the carrier is selected from one or more combinations of silicon molecular sieve, silicon aluminum molecular sieve, titanium silicon molecular sieve, and silicon phosphorus aluminum molecular sieve.

2. The process for directly preparing 6-aminocapronitrile from cyclohexanone oxime according to claim 1, wherein The temperature of the first-stage amination reaction is 300-480°C, the reaction pressure is slightly positive, the feed ammonia:cyclohexanone oxime molar ratio is 30-75, and the cyclohexanone oxime space velocity is 0.5-2 kg / (kgcat·h).

3. The process for directly preparing 6-aminocapronitrile from cyclohexanone oxime according to claim 2, wherein: The temperature of the first stage amination reaction is 360~440℃.

4. The process for directly preparing 6-aminocapronitrile from cyclohexanone oxime according to claim 1, wherein The 6-aminocapronitrile product obtained in step (1) and step (3) is cooled and separated, and the separated liquid phase enters a light component removal tower to remove the light components. The separated gas phase is deep-cooled and compressed to obtain ammonia, which is used as a raw material for a first-stage amination reaction.

5. The process for directly preparing 6-aminocapronitrile from cyclohexanone oxime according to claim 4, wherein: The light component removal in step (2) is carried out in a light component removal tower, which is a plate tower or a packed tower with 15 to 40 theoretical plates, 8 to 20 feed positions, a reflux ratio of 2 to 6, a tower top temperature of 80 to 90°C, a tower bottom temperature of 150 to 170°C, and a tower top pressure of 5 to 20 kPaA.

6. The process for directly preparing 6-aminocapronitrile from cyclohexanone oxime according to claim 5, wherein: A portion of the gas phase outlet at the top of the light-removing tower is circulated, and a portion is used to produce light components; the liquid phase material produced at the bottom of the light-removing tower enters the distillation tower.

7. The process for directly preparing 6-aminocapronitrile from cyclohexanone oxime according to claim 1, wherein The distillation in step (2) is carried out in a distillation tower, which is a plate tower or a packed tower with 15 to 35 theoretical plates, 8 to 17 feed positions, a reflux ratio of 3 to 8, a tower top temperature of 120 to 140°C, a tower bottom temperature of 160 to 180°C, and a tower top pressure of 5 to 15 kPaA.

8. The process for directly preparing 6-aminocapronitrile from cyclohexanone oxime according to claim 1, wherein The mass fraction of the active metal in step (3) relative to the carrier is 0.1-10 wt %.

9. The process for directly preparing 6-aminocapronitrile from cyclohexanone oxime according to claim 7, wherein: The second-stage amination reaction temperature is 300 ~ 500 ° C, the reaction pressure is slightly positive, the feed ammonia:caprolactam (molar ratio) is 20 ~ 40, and the caprolactam space velocity is 0.2 ~ 1.5kg / (kgcat·h).

10. The process for directly preparing 6-aminocapronitrile from cyclohexanone oxime according to claim 9, wherein: The temperature of the second-stage amination reaction is 350-450°C.

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