Energy-saving device and method for preparing aminocapronitrile from cyclohexanone oxime liquid phase rearrangement product

Abstract

The present invention proposes an energy-saving device and method for preparing aminocapronitrile from a liquid-phase rearrangement product of cyclohexanone oxime, wherein the device and method rearrange the cyclohexanone oxime liquid phase and the caprolactam raw material liquid containing ammonium sulfate and water after neutralization in ammonia water is directly distilled, filtered, and concentrated after extraction to enter an aminating reactor for reaction to prepare aminocapronitrile. Compared with the prior art, the present invention integrates and optimizes the refining and aminating reaction of caprolactam, eliminates multiple unit steps such as water back extraction, ion exchange, multi-effect evaporation of water and distillation of caprolactam, greatly simplifies the process flow, greatly saves energy consumption and investment, reduces the production cost of 6-aminocapronitrile, and an appropriate amount of extractant enters the aminating reaction process to reduce the polymerization of raw material caprolactam and suppress the encapsulation pollution of the catalyst by the coke of the side reaction to a certain extent, thereby improving the product yield and extending the catalyst life.

Description

Technical Field

[0001] The invention belongs to the technical field of green chemical preparation, and specifically is an energy-saving device and method for preparing aminocapronitrile by using a liquid phase rearrangement product of cyclohexanone oxime. Background Art

[0002] Nylon 66 is a multi-purpose polymer material. With its excellent performance, the demand has been steadily increasing in recent years. Nylon 66 is made by polycondensation of hexamethylenediamine and adipic acid.

[0003] The existing production processes of hexamethylenediamine mainly include the butadiene method, the acrylonitrile method and the adipic acid method, but all of them have shortcomings (use of highly toxic chemicals, high energy consumption, low product selectivity, etc.). In comparison, the caprolactam method uses caprolactam as the raw material, generates 6-aminocapronitrile after ammonia dehydration, and then hydrogenates to generate hexamethylenediamine. The caprolactam method for producing hexamethylenediamine has the advantages of simple reaction steps, green process, sufficient raw material supply, and high product selectivity.

[0004] At present, the mainstream production process of caprolactam is to use benzene as raw material to make cyclohexanone, then use hydroxylamine to make cyclohexanone oxime, then use fuming sulfuric acid to perform Beckmann rearrangement to generate a caprolactam sulfuric acid mixture, and finally generate a crude caprolactam liquid containing ammonium sulfate through neutralization and crystallization. 60-70% of the crude caprolactam liquid containing ammonium sulfate is caprolactam, and the rest is impurities such as ammonium sulfate, water, cyclohexanone, benzene, toluene, and cyclohexanol; in order to improve the purity and quality of caprolactam, it needs to be purified through a caprolactam refining unit to obtain refined caprolactam.

[0005] At present, the process flow of caprolactam refining includes benzene extraction, water back extraction, ion exchange, caprolactam hydrogenation, multi-effect evaporation, caprolactam distillation and other steps. Extraction refining is an important part of caprolactam refining. First, the crude caprolactam liquid containing ammonium sulfate is extracted with an organic solvent (usually benzene) to remove most of the water-soluble impurities, and then the caprolactam benzene solution is back extracted with water to remove some residual organic impurities to obtain a caprolactam aqueous solution; ion exchange and hydrogenation are used to further remove organic impurities containing unsaturated bonds; multi-effect evaporation is then used to remove water from the caprolactam aqueous solution, and finally caprolactam is distilled to obtain high-quality caprolactam products. It is not difficult to see from the above steps that the refining of caprolactam requires the distillation of the extractant benzene and water, and caprolactam also needs to be gasified, which requires a lot of energy consumption. In addition, the introduction of a large amount of water in the water washing and back extraction steps also leads to an increase in wastewater discharge.

[0006] The existing technologies for caprolactam refining and caprolactam amination are mainly aimed at the process optimization of a single reaction or the development of new catalysts. For example, patent CN201620239506.2 reports a caprolactam refining device, which consists of an extraction tower, a refining tower, a hydrogenation reactor, a light removal tower, and a distillation device, and does not require water back extraction, ion exchange, evaporation and other steps; patent CN202220658386.5 reports a device for reducing steam consumption in the process of caprolactam refining, which reduces steam and circulating water consumption by making full use of the heat energy at the top of the tower; patent CN201711000196.4 reports a method for refining caprolactam, the process of which includes extraction with an extractant, washing with hydrogen peroxide, and washing with water. The extractant is washed with water, back-extracted with water, and ion exchange is performed to extend the life of the ion exchange resin; Patent CN201621187626.9 reports a low-energy caprolactam refining device, which adds an alkali washing tower, an acid washing tower, and a deweighting tower compared to the traditional caprolactam refining process, reduces water extraction, evaporation and other processes, and reduces wastewater generation; Patent CN113083270A reports the use of alkaline earth metal oxides, transition metal oxides, silicon oxide, and aluminum oxide as catalysts for the amination of caprolactam to produce 6-aminocapronitrile; Patent CN201910775834.2 reports the use of phosphate aluminum molecular sieve as a carrier, and the catalyst for the amination of caprolactam is prepared by impregnation of aluminum nitrate, magnesium nitrate, and nickel nitrate. CN16617690A reports a device and method for preparing 6-aminocapronitrile using crude caprolactam as raw material, using crude caprolactam containing water and impurities to replace the currently refined caprolactam as raw material, and preparing 6-aminocapronitrile through vacuum evaporation dehydration, vacuum evaporation of caprolactam and gas ammonia injection pressurization technology, thereby reducing the energy consumption of primary distillation and gasification refining of caprolactam.

[0007] Although the above technology has been optimized for the process flow and partially reduced energy consumption and raw material requirements, it still has the defects of complicated process steps, large amount of wastewater discharge and high production cost. Summary of the invention

[0008] In view of the problems of the prior art, the present invention proposes a novel, simplified, low-energy, low-pollution and highly feasible device and method for producing 6-aminocapronitrile, wherein a crude caprolactam liquid containing ammonium sulfate after liquid-phase rearrangement of cyclohexanone oxime is extracted by an extractant to obtain a crude caprolactam-extractant mixed liquid, which is then subjected to azeotropic dehydration and distillation recovery of the extractant before directly undergoing an amination reaction to obtain a 6-aminocapronitrile product liquid.

[0009] The present invention reduces the high energy consumption and high pollution caprolactam refining steps such as water back extraction, ion exchange, hydrogenation, and multi-effect evaporation, thereby greatly reducing energy consumption and production costs. In addition to the catalyst selectivity, the yield of aminocapronitrile in the caprolactam amination process is mainly affected by the liquid phase polymerization of caprolactam in the presence of water, especially because caprolactam has a high boiling point and needs to evaporate to above 260°C, while it starts to produce polymerization reaction at 130°C under water-containing conditions. Therefore, water control and gasification at low water content as much as possible are the most effective means to improve the yield of aminocapronitrile. The present invention uses a crude caprolactam-extractant mixed liquid, and the water content can be controlled below 100 ppm after azeotropic dehydration, which is much lower than the water content of 700 ppm in the high-grade caprolactam directly used as a raw material in the prior art, so the polymerization risk of caprolactam in the heating and gasification process can be greatly reduced; at the same time, it is verified by experiments that the organic impurities other than sulfide in the crude caprolactam-extractant mixed liquid have little effect on the conversion rate and selectivity of the amination reaction, and the presence of an appropriate amount of extractant in the amination process can also alleviate the polymerization of caprolactam in the evaporation process and inhibit the encapsulation and contamination of the catalyst by the coke products of the side reaction, which is beneficial to improving the selectivity of 6-aminocapronitrile; in addition, part of the extractant can be used as an azeotropic agent for entraining water, which is also very beneficial to reducing the water content of the system and reducing the generation of various polymers in the distillation process in the subsequent dehydration link of aminocapronitrile refining. The above advantages make the present invention have extremely high economic benefits in the field of nylon new material preparation.

[0010] To achieve the above object, the present invention adopts the following technical solution:

[0011] An energy-saving device for preparing aminocapronitrile from the liquid-phase rearrangement product of cyclohexanone oxime, comprising an extraction device, a first rectification device, a filter, a concentration system and a reaction system.

[0012] The inlet of the extraction device is connected to the extractant and the raw material liquid, and the raw material liquid is a caprolactam liquid containing water, ammonium sulfate and organic impurities.

[0013] The oil phase outlet of the extraction device is directly connected to the first distillation device, and the bottom outlet of the first distillation device is connected to the filter.

[0014] The liquid phase outlet of the filter is connected to the concentration system,

[0015] The tower bottom outlet of the concentration system is connected to the reaction system,

[0016] The reaction system comprises a reactor and a second distillation device which are arranged in sequence, wherein the reactor is a caprolactam ammoniation reactor, and the bottom outlet of the second distillation device is a crude aminocapronitrile mixed liquid outlet. A reaction mixed liquid containing NH3, water, 6-aminocapronitrile, caprolactam and light and heavy impurities is obtained at the reactor outlet, and after dehydration by the second distillation device, the obtained crude aminocapronitrile mixed liquid can be connected to an aminocapronitrile refining system. The aminocapronitrile refining system is prior art.

[0017] Preferably, the extraction device is a sieve plate extraction tower, a packed extraction tower, an improved pulsed sieve plate tower or a rotating disk extraction tower.

[0018] Preferably, the water phase outlet of the extraction device is connected to a wastewater treatment device.

[0019] Preferably, the top outlet of the first distillation device is connected to a stratifier, more preferably, the oil phase outlet of the stratifier is connected to the inlet of the extraction device, and the water phase outlet of the stratifier is connected to a wastewater treatment device. The extractant and water that form an azeotropic mixture are extracted from the top of the first distillation device. After stratification by the stratifier, the extractant of the oil phase can be recycled and reused, further saving costs.

[0020] More preferably, the wastewater treatment device is a distillation tower, and the top outlet of the tower is connected to the extraction device. The wastewater treatment device recovers a small amount of extractant in the wastewater through distillation separation for reuse, further saving costs and ensuring that the wastewater meets the discharge standards.

[0021] Preferably, the concentration system is a single-effect evaporation system, a multiple-effect evaporation system, a single-tower distillation system or a multi-tower distillation system. According to actual production conditions, a relatively lower-cost concentration system can be selected to further save costs.

[0022] Preferably, the top outlet of the concentration system is connected to the extraction device. The extraction agent obtained by separation at the top of the concentration system can be recycled and reused, further saving costs.

[0023] Preferably, the reactor is a fixed bed reactor or a fluidized bed reactor.

[0024] Preferably, the reaction system further comprises a mixing evaporator disposed before the reactor. The reaction raw materials are mixed in the mixing evaporator in the form of gas phase.

[0025] Preferably, the reaction system further comprises a cooling separator disposed between the reactor and the second distillation device, wherein the liquid phase outlet of the cooling separator is connected to the second distillation device. The cooling separator cools and separates the reactor discharge, and the separated liquid feed is sent to the second distillation device.

[0026] More preferably, the gas phase outlet of the cooling separator is connected to the mixing evaporator. The unreacted ammonia obtained by the cooling separator can be recycled as a reaction raw material, further saving costs.

[0027] Preferably, a distillation deamination tower is further provided between the second distillation device and the reactor, the bottom of the distillation deamination tower is connected to the second distillation device, and the top of the distillation deamination tower is connected to the mixing evaporator. The distillation deamination tower is used to remove the residual ammonia gas that has not been completely reacted, which can be recycled as a reaction raw material, further saving costs.

[0028] More preferably, the cooling separator is arranged before the distillation deamination tower.

[0029] Preferably, the top outlet of the second distillation device is connected to the second stratifier. More preferably, the oil phase outlet of the second stratifier is connected to the inlet of the extraction device, and the water phase outlet of the second stratifier is connected to the wastewater treatment device. Similar to the first distillation device, the top of the second distillation device is produced to form an azeotropic extractant and water produced in the reaction. After stratification by the second stratifier, the extractant of the oil phase can be recycled and reused, further saving costs.

[0030] The present invention further provides a method for preparing aminocapronitrile from a liquid phase rearrangement product of cyclohexanone oxime, comprising the following steps:

[0031] (1) adding an organic extractant to the raw material liquid for extraction, and obtaining an oil phase as a caprolactam extraction solution;

[0032] The raw material liquid is a liquid obtained by neutralizing cyclohexanone oxime rearrangement liquid with ammonia;

[0033] (2) directly distilling the caprolactam extraction solution to remove water and part of the organic extractant to obtain a caprolactam mixture containing impurities;

[0034] (3) filtering the caprolactam mixture containing impurities to remove impurities, and then concentrating to remove most or all of the extractant to obtain a caprolactam liquid;

[0035] (4) sending the caprolactam liquid into a reactor for an amination reaction to obtain a reaction mixture;

[0036] (5) The reaction mixture is distilled to remove water to obtain a crude aminocapronitrile mixture.

[0037] In the prior art, the feed liquid obtained by neutralizing the cyclohexanone oxime rearrangement liquid with ammonia is a caprolactam solution containing a large amount of ammonium sulfate, water and other small amounts of organic impurities obtained by the Beckmann rearrangement of cyclohexanone oxime under fuming sulfuric acid and then the ammonia neutralization step.

[0038] The present invention uses the solution as a raw material, and after extraction with an organic extractant, it is directly distilled and separated without conventional treatment steps such as back extraction, which can not only avoid the generation of a large amount of wastewater after the introduction of a large amount of water, but also can use the extractant and water to form an azeotropic system to reduce the distillation temperature, on the one hand, reduce the distillation energy consumption, and on the other hand, can effectively remove the water in the system. The obtained tower bottom discharge is almost free of water, and the ammonium sulfate dissolved in a small amount of water contained in the extract is very easy to precipitate and separate, and most or even all of the extractant can be removed by the concentration system after filtering. In the ammoniation reaction process, a small amount of residual extractant not only does not affect the reaction, but also can alleviate the polymerization of caprolactam in the vaporization process and inhibit the encapsulation and contamination of the catalyst by the coke of the side reaction, and can form an azeotropic system with the water generated in the reaction after the reaction, and effectively remove the water in the system with low energy consumption, so as to finally obtain the product with high efficiency, high selectivity and low cost.

[0039] Preferably, the concentration of caprolactam in the caprolactam extraction solution in step (1) is 5-40% by mass, preferably 15-30% by mass.

[0040] Preferably, the raw material liquid is derived from a hydroxylamine process of cyclohexanone or a hydroxylamine-free process of cyclohexanone.

[0041] Preferably, the hydroxylamine process of cyclohexanone is a Raschig process, a HSO process, a DSM / HPO process or a NO reduction process.

[0042] Preferably, the hydroxylamine-free process for preparing cyclohexanone is a methyl extractant process or a photonitrosation process.

[0043] Preferably, the organic extractant in step (1) is an organic substance that can form an azeotrope with water and is immiscible with water. More preferably, the organic extractant is one or a mixture of benzene, toluene, xylene, chloroform, carbon tetrachloride, cyclohexane, methylcyclohexane or methylcyclopentane.

[0044] Preferably, the top operating pressure of the distillation in step (2) is 30-120 KPa; the top operating temperature is 45-80°C, and the bottom operating temperature is 70-120°C. The first distillation tower uses low-pressure steam or steam condensate that is 10°C higher than the bottom temperature as a heat source; the second distillation tower uses saturated steam that is 5°C higher than the bottom temperature as a heat source.

[0045] Preferably, the content of caprolactam in the caprolactam solution in step (3) is 50-99.9% by mass, preferably in the range of 75-99.9%. The rest is organic extractant and organic impurities. The content of extractant in the caprolactam extraction solution is determined comprehensively based on the water content in the amination reaction product, the azeotropic composition of the extractant and water, and the steam energy consumption. For example, when benzene is used as the extractant, the benzene content is preferably 20-30%; when toluene is used, the toluene content is preferably 10-20%; when benzene and toluene are used as a composite extractant, the benzene content is preferably 10-20%, and the toluene content is preferably 5-10%.

[0046] The amination reaction of caprolactam can be carried out according to conventional techniques in the art, and the present invention has no particular limitation thereto. That is, caprolactam and ammonia are mixed in a certain proportion and introduced into a reactor to carry out the amination reaction under catalytic conditions.

[0047] The reaction pressure of caprolactam amination is between 90 and 1000 KPa.

[0048] The reaction temperature of caprolactam amination is between 250 and 400°C.

[0049] The reaction space velocity of caprolactam amination is 0.5~5h -1 .

[0050] The molar ratio of caprolactam to ammonia in the caprolactam amination reaction is 1:5~150.

[0051] In the distillation stage of the reaction mixture containing NH3, water, 6-aminocapronitrile, caprolactam and light and heavy impurities, the residual extractant from the previous step forms an azeotrope with water, which can reduce the water content after distillation to less than 200 ppm, thereby obtaining a dehydrated crude aminocapronitrile mixed solution.

[0052] The beneficial effects of the invention are:

[0053] The invention couples the caprolactam refining with the caprolactam amination reaction, and reduces the wastewater-generating stripping, ion exchange, hydrogenation steps, and high-energy-consuming multi-effect evaporation and distillation steps without affecting the production data (raw material conversion rate and product selectivity) of preparing 6-aminocapronitrile by caprolactam amination, thereby providing a new process flow for preparing 6-aminocapronitrile using crude caprolactam as a raw material.

[0054] (1) The present invention ingeniously utilizes the characteristics of azeotropic dehydration to remove water-soluble impurities such as ammonium sulfate that affect the amination reaction from the system, while the impurities contained in the remaining caprolactam extraction solution have basically no effect on the amination reaction. It directly skips high-energy consumption and high-pollution links such as water extraction, multi-effect evaporation, ion exchange, hydrogenation, and caprolactam refining, thereby simplifying the steps, reducing energy consumption, and reducing the generation of wastewater.

[0055] (2) The organic extractant used in the present invention is conducive to the dispersion of caprolactam, is not easy to polymerize and coke during the gasification process, inhibits side reactions and the encapsulation and contamination of the catalyst by viscous coke, is conducive to the continuity and stability of the amination reaction, can improve the product yield and extend the life of the catalyst.

[0056] (3) After azeotropic dehydration, the water content of the caprolactam extraction solution can be controlled below 100 ppm, which is much lower than the water content of 700 ppm in the superior grade caprolactam. Therefore, the polymerization risk of caprolactam during the heating and gasification process before the reaction can be greatly reduced.

[0057] (4) Before the amination reaction of the present invention, a small amount of organic extractant may be left in the raw material. After the small amount of residual organic extractant participates in the amination reaction, it can form an azeotrope with the water produced by the reaction in the subsequent separation process, thereby utilizing azeotropic dehydration to reduce the water content in the reaction product from 700-1000 ppm in ordinary distillation dehydration to less than 200 ppm, thereby greatly reducing the polymerization of unreacted caprolactam in the bottom of the tower in the subsequent refining unit, which is beneficial to improving the overall yield of 6-aminocapronitrile. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a schematic diagram of the device of Example 1.

[0059] Figure 2 This is a schematic diagram of the device of Example 2.

[0060] Figure 3 It is the chromatogram of the crude aminocapronitrile mixed solution obtained by the reaction in Example 1.

[0061] Among them, 1 is an extraction device, 2 is a wastewater treatment device, 3 is a first distillation device, 4 is a stratifier, 5 is a filter, 6 is a first distillation recovery tower, 7 is a second distillation recovery tower, 8 is a mixing evaporator, 9 is a reactor, 10 is a cooling separator, 11 is a distillation deamination tower, 12 is a second distillation device, and 13 is a second stratifier. DETAILED DESCRIPTION

[0062] The raw materials used in each embodiment of the present invention are specifically as follows:

[0063] The device used in each embodiment of the present invention includes an extraction device 1, a first distillation device 3, a filter 5, a concentration system and a reaction system, the inlet of the extraction device 1 is connected to the extractant and the raw liquid, the raw liquid is a caprolactam liquid containing water, ammonium sulfate and organic impurities, the oil phase outlet of the extraction device 1 is connected to the first distillation device 3, the bottom outlet of the first distillation device 3 is connected to the filter 5, the liquid phase outlet of the filter 5 is connected to the concentration system, the bottom outlet of the concentration system is connected to the reaction system, the reaction system includes a reactor 9 and a second distillation device 12 arranged in sequence, the reactor 9 is a caprolactam amination reactor, and the bottom outlet of the second distillation device 12 is a crude aminocapronitrile mixed liquid outlet.

[0064] The water phase outlet of the extraction device 1 is connected to the wastewater treatment device 2 .

[0065] The tower top outlet of the first distillation device 3 is connected to the separator 4 , the oil phase outlet of the separator 4 is connected to the inlet of the extraction device 1 , and the water phase outlet of the separator 4 is connected to the wastewater treatment device 2 .

[0066] The wastewater treatment device 2 is a distillation tower, and the top outlet of the tower is connected to the extraction device 1.

[0067] The tower top outlet of the concentration system is connected to the extraction device 1 .

[0068] The reaction system further includes a mixing evaporator 8 disposed before the reactor 9 .

[0069] The reaction system further includes a cooling separator 10 disposed between the reactor 9 and the second distillation device 12 , and a liquid phase outlet of the cooling separator 10 is connected to the second distillation device 12 .

[0070] The gas phase outlet of the cooling separator 10 is connected to the mixing evaporator 8 .

[0071] A distillation and deamination tower 11 is further provided between the second distillation device 12 and the reactor 9 . The bottom of the distillation and deamination tower 11 is connected to the second distillation device 12 , and the top of the distillation and deamination tower 11 is connected to the mixing evaporator 8 .

[0072] The cooling separator 10 is arranged before the distillation and deamination tower 11 .

[0073] The top outlet of the second distillation device 12 is connected to the second separator 13. The oil phase outlet of the second separator 13 is connected to the inlet of the extraction device 1, and the water phase outlet of the second separator 13 is connected to the wastewater treatment device 2.

[0074] Example 1

[0075] (1) The ammonium sulfate-containing caprolactam liquid obtained by the cyclohexanone oxime rearrangement process is used as the raw material liquid, benzene is used as the extractant, and a rotary disc extraction tower is used as the extraction device to perform countercurrent extraction. An aqueous solution containing ammonium sulfate is obtained at the bottom of the tower, and a crude caprolactam benzene solution with a caprolactam mass fraction of 25% is obtained at the top of the tower, wherein the water content is 3%, ammonium sulfate is dissolved in the water, and organic impurities include 180 ppm of cyclohexane, 68 ppm of cyclohexene, 41 ppm of cyclopentanone, 78 ppm of methylcyclopentane, etc.

[0076] (2) The crude caprolactam benzene solution enters the first distillation device 3, which is operated at normal pressure, with a tower top temperature of 68°C and a tower bottom temperature of 92°C. 2 kg of secondary low-pressure steam is used as a heat source. The azeotropic mixture of water and benzene produced from the tower top enters the separator 4, where water and oil are separated. The oil phase returns to the extraction device 1 for recycling, and the water phase enters the wastewater treatment device 2. The mixture at the bottom of the first distillation device 3 is filtered through a filter 5 to remove solid particles such as ammonium sulfate precipitated, and a benzene-hexyl mixed solution with a caprolactam concentration of 41.2% is obtained and enters the concentration system.

[0077] (3) The concentration system is a triple-effect evaporation system. After partially removing the benzene, a benzene-hexyl mixed solution with a caprolactam concentration of 80% is obtained. The evaporated benzene is cooled and then recycled in the rotary disc extraction tower.

[0078] (4) The benzene-hexyl mixed solution with a caprolactam concentration of 80% is vaporized and then enters the fixed-bed reactor for ammoniation. The catalyst is activated alumina, the reaction temperature is 330°C, the feed molar ratio of ammonia to caprolactam is 24:1, and the space velocity is 0.8h -1 The single-pass caprolactam conversion rate was 67.3%, the selectivity for 6-aminocapronitrile was 96.9%, the benzene content in the product was 18.8% by mass, and the water content was 7.8% by mass; in the liquid chromatography, there were still peaks at the positions of the original cyclohexane and methylcyclopentane, but cyclohexanone and cyclohexene were not seen, which should be converted into other by-products; in the 200-hour catalyst stability test, the average single-pass caprolactam conversion rate was 66.7%, and the average selectivity for 6-aminocapronitrile was 96.7%.

[0079] (5) A comparative experiment was conducted using a 80% benzene-hexyl mixture of commercial reagent-grade benzene and premium caprolactam: in the same fixed-bed ammonia reactor, the reaction temperature was 330 °C, the feed molar ratio of ammonia to caprolactam was 24:1, and the space velocity was 0.8 h -1 The single-pass caprolactam conversion rate was 67.8%, and the 6-aminocapronitrile selectivity was 96.3%.

[0080] (6) A comparative experiment was conducted using commercial premium caprolactam: in the same fixed-bed ammonia reactor, the reaction temperature was 330 °C, the feed molar ratio of ammonia to caprolactam was 24:1, and the space velocity was 0.8 h -1, the single-pass caprolactam conversion rate was 66.8%, and the 6-aminocapronitrile selectivity was 96.1%; in the 200-hour catalyst stability test, the single-pass caprolactam average conversion rate was 65.6%, and the average 6-aminocapronitrile selectivity was 96.0%.

[0081] (7) The reacted feed liquid is cooled by a cooling separator 10, deaminated by a distillation and deamination tower 11, and then enters a second distillation device 12, which is operated under a negative pressure of 2 KPa. A benzene-water azeotropic liquid and a mixed liquid of water, light components, etc. are obtained at the top of the tower. After separation by a second separator 13, part of the oil phase is returned to the second distillation device 12 as reflux with water, and part of it is returned to the rotary disc extraction tower. The water phase enters a wastewater treatment device 2. The water content at the bottom of the second distillation device 12 is 120 ppm (the water content of the feed liquid obtained by the reaction after distillation and dehydration in the prior art is about 500-600 ppm). After the dehydration, the material is sent to the aminocapronitrile refining system to obtain 6-aminocapronitrile with a purity of 99.5%. The unreacted caprolactam is recovered and returned to the evaporation system to continue to participate in the reaction.

[0082] Example 2

[0083] (1) The ammonium sulfate-containing caprolactam liquid obtained by the cyclohexanone oxime rearrangement process is used as the raw material liquid, and benzene is used as the extractant to perform countercurrent extraction in a 20-layer sieve plate tower. An aqueous solution containing ammonium sulfate is obtained at the bottom of the tower, and a crude caprolactam benzene solution with a caprolactam mass fraction of 30% is obtained at the top of the tower, wherein the water content is 3.5%, ammonium sulfate is dissolved in the water, and organic impurities include 120 ppm of cyclohexane, 40 ppm of cyclohexene, 52 ppm of methylcyclohexane, 35 ppm of 4,5,6,7-tetrahydro-1H-benzotriazole, etc.

[0084] (2) The crude caprolactam benzene solution enters the first distillation device 3, which is operated at a negative pressure of 70 KPa, with a tower top temperature of 68°C and a tower bottom temperature of 78°C. 5 kg of steam condensate is used as a heat source. The azeotropic mixture of water and benzene produced from the tower top enters the separator 4, where the water and oil are separated. The oil phase is returned to the extraction device 1 for recycling, and the water phase enters the wastewater treatment device 2. The mixture at the bottom of the first distillation device 3 is filtered through a filter 5 to remove solid particles such as ammonium sulfate precipitated, and the benzene-hexyl mixed solution with a caprolactam concentration of 35.7% is obtained and sent to the concentration system.

[0085] (3) The concentration system is a double-tower distillation system consisting of two vacuum distillation towers, wherein the first distillation recovery tower 6 is operated at 50 KPa, the tower top temperature is 58.7°C, the tower bottom temperature is 95°C, the caprolactam content in the tower bottom solution is 85.2%, and 90% of benzene is recovered by using 2 kg of waste heat steam as a heat source; the second distillation recovery tower 7 is operated at 50 KPa, the tower top temperature is 58.7°C, the tower bottom temperature is 204°C, and the tower bottom obtains caprolactam with a benzene content of about 0.5% and a purity of 99.5%. The evaporated benzene is cooled and returned to the extraction device 1 for recycling.

[0086] (4) Caprolactam with a purity of 99.5% is gasified and then enters the fixed bed reactor for ammoniation. The catalyst is activated alumina, the reaction temperature is 330°C, the feed molar ratio of ammonia to caprolactam is 18:1, and the space velocity is 0.8h -1 The single-pass caprolactam conversion rate was 61.7%, the selectivity of 6-aminocapronitrile was 95.7%, the benzene content in the product was 0.5% by mass, and the water content was 8.81% by mass; in the liquid chromatography, there were still tiny peaks at the positions of the original cyclohexane and methylcyclopentane, but cyclohexene was not seen, and the peak position of 4,5,6,7-tetrahydro-1H-benzotriazole overlapped with many miscellaneous peaks and was difficult to judge.

[0087] (5) The reacted feed liquid is cooled by a cooling separator 10, deaminated by a distillation and deamination tower 11, and then enters a second distillation device 12, which is operated under a negative pressure of 3 KPa. A benzene-water azeotropic liquid is obtained at the top of the tower. After separation by a second separator 13, part of the oil phase is returned to the second distillation device 12 as reflux with water, and part of it is returned to the extraction device 1. The water phase enters a wastewater treatment device 2. The water content at the bottom of the second distillation device 12 is 450 ppm, the caprolactam content is 38.3%, the aminocapronitrile content is 58.5%, and the rest are light and heavy impurities. This material is deaminocapronitrile and purified to obtain 6-aminocapronitrile with a purity of 99.5%. The unreacted caprolactam is recovered and returned to the evaporation system to continue to participate in the reaction.

[0088] Example 3

[0089] (1) The ammonium sulfate-containing caprolactam liquid obtained by the cyclohexanone oxime rearrangement process is used as the raw material liquid, and toluene is used as the extractant to perform countercurrent extraction in a packed extraction tower. An aqueous solution containing ammonium sulfate is obtained at the bottom of the tower, and a crude caprolactam toluene solution with a caprolactam mass fraction of 40% is obtained at the top of the tower. The water content is 4.1%, and ammonium sulfate is dissolved in the water. Organic impurities include 220 ppm of cyclohexane, 128 ppm of cyclohexene, 71 ppm of cyclopentanone, 12 ppm of cyclohexanol, 92 ppm of methylcyclohexane, etc.

[0090] (2) The crude caprolactam toluene solution enters the first distillation device 3 for azeotropic dehydration, operating at 60 KPa, with a tower top temperature of 69.5°C and a tower bottom temperature of 108°C. Secondary low-pressure steam at 124°C is used as a heat source. The azeotropic mixture of water and toluene produced from the tower top enters the separator 4, where water and oil are separated. The oil phase returns to the extraction device 1 for recycling, and the water phase enters the wastewater treatment device 2. The mixture at the bottom of the first distillation device 3 is filtered through a filter 5 to remove solid particles such as ammonium sulfate, and a toluene-hexane mixed solution with a caprolactam concentration of 50% is obtained and enters the concentration system.

[0091] (3) The concentration system is a triple-effect evaporation system. After partially removing toluene, a toluene-caprolactam mixed solution with a caprolactam concentration of 90% is obtained. The evaporated toluene is cooled and then returned to the extraction tower for recycling.

[0092] (4) The toluene-caprolactam mixed solution with a caprolactam concentration of 90% was gasified and then entered into an ammonia fixed bed reactor. The catalyst was activated alumina, the reaction temperature was 330°C, the feed molar ratio of ammonia to caprolactam was 18:1, and the space velocity was 0.8h -1 The single-pass caprolactam conversion rate was 62.3%, the 6-aminocapronitrile selectivity was 96.5%, the toluene content in the product was 9.4% by mass, and the water content was 8.1% by mass; there were no peaks at the positions of the original cyclohexane and methylcyclopentane in the liquid chromatography, and they should have been separated cleanly in the evaporation and concentration stage; cyclohexanone, cyclohexanol and cyclohexene were not found, and they should have been converted into other by-products.

[0093] (5) A comparative experiment was conducted using a 90% toluene-caprolactam mixture of commercial reagent-grade toluene and premium-grade caprolactam: in the same fixed-bed ammonia reactor, the reaction temperature was 330°C, the feed molar ratio of ammonia to caprolactam was 18:1, and the space velocity was 0.8 h -1 The single-pass caprolactam conversion rate was 62.7% and the 6-aminocapronitrile selectivity was 95.8%.

[0094] (6) The reacted feed liquid is cooled by the cooling separator 10, deaminated by the distillation and deamination tower 11, and then enters the second distillation device 12. The operation is carried out under a negative pressure of 2 KPa. A toluene-water azeotropic liquid and a mixed liquid of water, light components, etc. are obtained at the top of the tower. After separation by the second separator 13, part of the oil phase is returned to the second distillation device 12 with water as reflux, and part of it is returned to the extraction tower. The water phase enters the wastewater treatment device 2. The water content at the bottom of the second distillation device 12 is 150 ppm. The material after dehydration is sent to the aminocapronitrile refining system to obtain 6-aminocapronitrile with a purity of 99.5%. The unreacted caprolactam is recovered and returned to the evaporation system to continue to participate in the reaction.

[0095] Example 4

[0096] (1) The ammonium sulfate-containing caprolactam liquid obtained by the cyclohexanone oxime rearrangement process is used as the raw material liquid, and a mixed solvent of toluene and benzene is used as the extractant in a volume ratio of 1:1. The extraction is carried out in a bubbling tower containing an upper structured filler as a static mixer and a jet microbubble type bubbling tower in the middle section. The lower section is equipped with three layers of sieve plates. An aqueous solution containing ammonium sulfate is obtained at the bottom of the tower, and a crude caprolactam extractant solution with a caprolactam mass fraction of 40% is obtained at the top of the tower, wherein the water content is 4.3%, ammonium sulfate is dissolved in the water, and organic impurities include 90 ppm of cyclohexane, 56 ppm of cyclohexene, 32 ppm of cyclopentanone, 15 ppm of cyclohexanol, etc.

[0097] (2) The crude caprolactam extractant solution enters the first distillation device 3, which is operated at 80 kPa, with a tower top temperature of 59.6°C and a tower bottom temperature of 108.7°C. 5 kg of steam condensate is used as a heat source. The azeotropic mixture of water and the extractant produced from the tower top enters the separator 4, where the water and oil are separated. The oil phase returns to the extraction device 1 for recycling, and the water phase enters the wastewater treatment device 2. The mixture at the bottom of the first distillation device 3 is filtered through a filter 5 to remove solid particles such as ammonium sulfate precipitated, and a mixed solution with a caprolactam concentration of 42.8%, toluene 47.5%, and benzene 9.7% is obtained and enters the concentration system.

[0098] (3) The concentration system is a triple-effect evaporation system. After evaporating a portion of the extractant, a mixed solution with a caprolactam concentration of 90% is obtained. The evaporated extractant is cooled and then returned to the extraction tower for recycling.

[0099] (4) The caprolactam mixed solution with a caprolactam concentration of 90% was gasified and then entered into an ammoniation fixed bed reactor. The catalyst was activated alumina, the reaction temperature was 330°C, the feed molar ratio of ammonia to caprolactam was 18:1, and the space velocity was 0.8h -1 The single-pass caprolactam conversion rate was 62.7%, the 6-aminocapronitrile selectivity was 95.9%, the toluene content in the product was 9.5% by mass, and the water content was 8.1% by mass; there were no peaks at the positions of original cyclohexane and methylcyclopentane in the liquid chromatography, and they should have been separated cleanly in the evaporation and concentration stage; cyclohexanone, cyclohexanol and cyclohexene were not found.

[0100] (5) The reacted feed liquid is cooled by a cooling separator 10, deaminated by a distillation and deamination tower 11, and then enters a second distillation device 12. The feed liquid is operated under a negative pressure of 2 KPa. A benzene-toluene-water azeotropic liquid and a mixed liquid of water, light components, etc. are obtained at the top of the tower. After separation by a second separator 13, part of the oil phase is returned to the second distillation device 12 as reflux with water, and part of it is returned to the extraction device 1. The water phase enters the wastewater treatment device 2. The water content at the bottom of the second distillation device 12 is 170 ppm. The material after dehydration is sent to the aminocapronitrile refining system to obtain 6-aminocapronitrile with a purity of 99.5%. The unreacted caprolactam is recovered and returned to the evaporation system to continue to participate in the reaction.

[0101] Example 5

[0102] (1) The ammonium sulfate-containing caprolactam liquid obtained by the cyclohexanone oxime rearrangement process is used as the raw material liquid, and cyclohexane is used as the extractant to perform countercurrent extraction in a rotary disc extraction tower. An aqueous solution containing ammonium sulfate is obtained at the bottom of the tower, and a crude caprolactam cyclohexane solution with a caprolactam mass fraction of 30% is obtained at the top of the tower. The water content is 3.4%, ammonium sulfate is dissolved in the water, and organic impurities include 72 ppm of cyclohexene, 48 ppm of cyclopentanone, 34 ppm of cyclohexanol, 78 ppm of methylcyclohexane, etc.

[0103] (2) The crude caprolactam cyclohexane solution enters the first distillation device 3, which is operated at normal pressure, with a tower top temperature of 64.9°C and a tower bottom temperature of 90°C. 2 kg of secondary low-pressure steam is used as a heat source. The azeotropic mixture of water and cyclohexane produced from the tower top enters the separator 4, where the water and oil are separated. The oil phase returns to the extraction tower for recycling, and the water phase enters the wastewater treatment device 2. The mixture at the bottom of the first distillation device 3 is filtered through a filter 5 to remove solid particles such as ammonium sulfate precipitated, and a caprolactam cyclohexane solution with a caprolactam concentration of 34% is obtained and enters the concentration system.

[0104] (3) The concentration system is a triple-effect evaporation system. After partially removing the cyclohexane, a caprolactam cyclohexane solution with a caprolactam concentration of 75% is obtained. The evaporated cyclohexane is cooled and then recycled to the rotary disc extraction tower.

[0105] (4) The caprolactam cyclohexane solution with a caprolactam purity of 75% was vaporized and then entered into an ammonia fixed bed reactor. The catalyst was titanium silicon molecular sieve, the reaction temperature was 360°C, the feed molar ratio of ammonia to caprolactam was 24:1, and the space velocity was 2.4h -1 The single-pass caprolactam conversion rate was 68.4%, the 6-aminocapronitrile selectivity was 95.8%, the cyclohexane content in the product was 23.8% by mass, and the water content was 8.2% by mass; in the liquid chromatography, there was still a peak at the position of the original methylcyclopentane, but cyclohexanone, cyclohexanol and cyclohexene were not seen, which should be converted into other by-products.

[0106] (5) A comparative experiment was conducted using a 75% caprolactam cyclohexane solution prepared from commercial reagent-grade cyclohexane and premium-grade caprolactam: in the same fixed-bed reactor for ammoniation, the reaction temperature was 360°C, the feed molar ratio of ammonia to caprolactam was 24:1, and the space velocity was 2.4 h -1 , the single-pass caprolactam conversion rate was 67.7%, and the 6-aminocapronitrile selectivity was 95.7%; in the 200-hour catalyst stability test, the single-pass caprolactam average conversion rate was 67.1%, and the average 6-aminocapronitrile selectivity was 95.4%.

[0107] (6) A comparative experiment was conducted using commercial premium caprolactam: in the same fixed-bed reactor, the reaction temperature was 360°C, the feed molar ratio of ammonia to caprolactam was 24:1, and the space velocity was 2.4 h -1 The single-pass caprolactam conversion rate was 68.0%, and the 6-aminocapronitrile selectivity was 95.5%; in the 200-hour catalyst stability test, the single-pass caprolactam average conversion rate was 65.5%, and the average 6-aminocapronitrile selectivity was 95.4%.

[0108] (7) The reacted feed liquid is cooled by a cooling separator 10, deaminated by a distillation and deamination tower 11, and then enters a second distillation device 12, which is operated under a negative pressure of 2 KPa. A cyclohexane-water azeotropic liquid and a mixed liquid of water, light components, etc. are obtained at the top of the tower. After separation by a second separator 13, part of the oil phase is returned to the second distillation device 12 as reflux with water, and part of it is returned to the rotary disc extraction tower. The water phase enters the wastewater treatment device 2. The water content at the bottom of the second distillation device 12 is 80 ppm. The material after dehydration is sent to the aminocapronitrile refining system to obtain 6-aminocapronitrile with a purity of 99.5%. The unreacted caprolactam is recovered and returned to the evaporation system to continue to participate in the reaction.

[0109] Example 6

[0110] (1) The ammonium sulfate-containing caprolactam liquid obtained by the cyclohexanone oxime rearrangement process is used as the raw material liquid, and methylcyclohexane is used as the extractant. Countercurrent extraction is carried out in a packed extraction tower, and an aqueous solution containing ammonium sulfate is obtained in the bottom of the tower. A crude caprolactam methylcyclohexane solution with a caprolactam mass fraction of 5% is obtained at the top of the tower, wherein the water content is 0.7%, ammonium sulfate is dissolved in the water, and organic impurities include 210 ppm of cyclohexane, 135 ppm of cyclohexene, 28 ppm of cyclopentanone, 22 ppm of cyclohexanol, etc.

[0111] (2) The crude caprolactam methylcyclohexane solution enters the first distillation device 3, which is operated at normal pressure, with a tower top temperature of 69°C and a tower bottom temperature of 106°C. Secondary low-pressure steam at 126°C is used as a heat source. The azeotropic mixture of water and methylcyclohexane produced from the tower top enters the separator 4, where water and oil are separated. The oil phase returns to the extraction device 1 for recycling, and the water phase enters the wastewater treatment device 2. The mixture at the bottom of the first distillation device 3 is filtered through a filter 5 to remove solid particles such as ammonium sulfate precipitated, and a caprolactam methylcyclohexane solution with a caprolactam concentration of 8.5% is obtained and enters the concentration system.

[0112] (3) The concentration system is a triple-effect evaporation system. After partially removing the methylcyclohexane, a caprolactam methylcyclohexane solution with a caprolactam concentration of 85% is obtained. The evaporated methylcyclohexane is cooled and then returned to the extraction tower for recycling.

[0113] (4) A caprolactam methylcyclohexane solution with a caprolactam concentration of 85% was vaporized and then fed into an ammonia fixed bed reactor. The catalyst was titanium dioxide rich in oxygen vacancies. The reaction temperature was 400 °C. The feed molar ratio of ammonia to caprolactam was 20:1. The space velocity was 0.5 h -1 The single-pass caprolactam conversion rate was 84.8%, the selectivity for 6-aminocapronitrile was 94.6%, the methylcyclohexane content in the product was 14.1% by mass, and the water content was 10.2% by mass; no original cyclohexane, cyclohexene, cyclohexanone and cyclohexanol were found in the liquid chromatography, which should have been separated cleanly or converted into other by-products in the solvent distillation recovery link; after 200 hours of catalyst stability test, the average single-pass caprolactam conversion rate was 84.4%, and the average selectivity for 6-aminocapronitrile was 94.5%.

[0114] (5) A comparative experiment was conducted using 85% caprolactam methylcyclohexane solution prepared from commercial reagent-grade methylcyclohexane and premium-grade caprolactam: in the same fixed-bed ammonia reactor, the reaction temperature was 400 °C, the feed molar ratio of ammonia to caprolactam was 20:1, and the space velocity was 0.5 h -1 The single-pass caprolactam conversion rate was 85.1%, and the 6-aminocapronitrile selectivity was 94.3%.

[0115] (6) A comparative experiment was conducted using commercial premium caprolactam: in the same fixed-bed reactor, the reaction temperature was 400 °C, the feed molar ratio of ammonia to caprolactam was 20:1, and the space velocity was 0.5 h -1 , the single-pass caprolactam conversion rate was 84.9%, and the 6-aminocapronitrile selectivity was 94.6%; after 200 hours of catalyst stability test, the average single-pass caprolactam conversion rate was 84.1%, and the average 6-aminocapronitrile selectivity was 94.3%;

[0116] (7) The reacted feed liquid is cooled by a cooling separator 10, deaminated by a distillation and deamination tower 11, and then enters a second distillation device 12, which is operated under a negative pressure of 2 KPa. A water-methylcyclohexane azeotropic liquid and a mixed liquid of water, light components, etc. are obtained at the top of the tower. After separation by a second separator 13, part of the oil phase is returned to the second distillation device 12 as reflux with water, and part of it is returned to the extraction tower. The water phase enters the wastewater treatment device 2. The water content at the bottom of the second distillation device 12 is 130 ppm. The material after dehydration is sent to the aminocapronitrile refining system to obtain 6-aminocapronitrile with a purity of 99.5%. The unreacted caprolactam is recovered and returned to the evaporation system to continue to participate in the reaction.

[0117] Example 7

[0118] (1) The ammonium sulfate-containing caprolactam liquid obtained by the cyclohexanone oxime rearrangement process is used as the raw liquid, and carbon tetrachloride is used as the extractant to perform countercurrent extraction in a 20-layer sieve plate tower. Since the density of carbon tetrachloride is greater than that of water, the water phase is in the upper layer and the oil phase is in the lower layer. An aqueous solution containing ammonium sulfate is obtained at the top of the tower, and a crude caprolactam carbon tetrachloride solution with a caprolactam mass fraction of 25% is obtained at the bottom of the tower, wherein the water content is 1.6%, ammonium sulfate is dissolved in the water, and organic impurities include 90 ppm of cyclohexane, 36 ppm of cyclohexene, 38 ppm of methylcyclohexane, and 28 ppm of methylcyclopentane.

[0119] (2) The crude caprolactam carbon tetrachloride solution enters the first distillation device 3, which is operated at normal pressure, with a tower top temperature of 68.7°C and a tower bottom temperature of 90°C. 5 kg of steam condensate is used as a heat source. The azeotropic mixture of water and carbon tetrachloride produced from the tower top enters the separator 4, where water and oil are separated. The density of carbon tetrachloride is greater than that of water. At this time, the water phase is in the upper layer and the oil phase is in the lower layer. The oil phase is returned to the extraction tower for recycling, and the water phase enters the wastewater treatment device 2. After the solid particles such as ammonium sulfate precipitated are removed from the mixture at the bottom of the first distillation device 3 through the filter 5, the caprolactam carbon tetrachloride solution with a caprolactam concentration of 27.8% is obtained and enters the concentration system.

[0120] (3) The concentration system is a double-tower distillation system consisting of two vacuum distillation towers, wherein the first distillation recovery tower 6 is operated at 50 KPa, the tower top temperature is 56°C, the tower bottom temperature is 111°C, the caprolactam content in the tower bottom solution is 75.7%, and 2 kg of secondary steam is used as the heat source to recover 80% of the total solvent amount of carbon tetrachloride; the second distillation recovery tower is operated at 50 KPa, the tower top temperature is 56°C, the tower bottom temperature is 229°C, and the tower bottom obtains caprolactam with a carbon tetrachloride content of about 0.8% and a purity of 99.2%. The evaporated carbon tetrachloride is recycled in the extraction device 1 after cooling.

[0121] (4) Caprolactam with a purity of 99.2% is gasified and then fed into an ammoniation fixed bed reactor. The catalyst is a phosphorus aluminum molecular sieve supported palladium catalyst. The reaction temperature is 280°C, the feed molar ratio of ammonia to caprolactam is 36:1, and the space velocity is 1.0 h -1 The single-pass caprolactam conversion rate was 46.5%, the 6-aminocapronitrile selectivity was 99.6%, the carbon tetrachloride content in the product was 0.75% by mass, and the water content was 6.86% by mass; in the liquid chromatography, there were still peaks at the positions of the original cyclohexane, methylcyclohexane, and methylcyclopentane, but cyclohexene was not seen, which should have been converted into a by-product.

[0122] (5) The reacted liquid is cooled by a cooling separator 10, deaminated by a distillation and deamination tower 11, and then enters a second distillation device 12, which is operated at a negative pressure of 1.5 KPa. After the materials at the top of the tower are separated, part of the lower oil phase (the density of carbon tetrachloride is larger than that of water) is returned to the second distillation device 12 with water as reflux, and part of it is returned to the extraction device 1. The water phase enters the wastewater treatment device 2. The water content at the bottom of the second distillation device 12 is 390 ppm. The material after dehydration is sent to the aminocapronitrile refining system to obtain 6-aminocapronitrile with a purity of 99.5%. The unreacted caprolactam is recovered and returned to the evaporation system to continue to participate in the reaction.

[0123] Example 8

[0124] (1) The ammonium sulfate-containing caprolactam liquid obtained by the cyclohexanone oxime rearrangement process is used as the raw material liquid, and p-xylene is used as the extractant to perform countercurrent extraction in a rotary disc extraction tower. An aqueous solution containing ammonium sulfate is obtained at the bottom of the tower, and a crude caprolactam p-xylene solution with a caprolactam mass fraction of 20% is obtained at the top of the tower, wherein the water content is 1.5%, ammonium sulfate is dissolved in the water, and organic impurities include 80 ppm of cyclohexane, 34 ppm of cyclohexene, 25 ppm of cyclohexanone, 40 ppm of methylcyclopentane, etc.

[0125] (2) The crude caprolactam para-xylene solution enters the first distillation device 3, which is operated under a negative pressure of 50 KPa, with a tower top temperature of 87°C and a tower bottom temperature of 124°C. 5 kg of saturated steam is used as a heat source. The azeotropic mixture of water and para-xylene produced from the tower top enters the separator 4, where the water and oil are separated. The oil phase returns to the extraction tower for recycling, and the water phase enters the wastewater treatment device 2. After the solid particles such as ammonium sulfate precipitated are removed from the mixture at the bottom of the first distillation device 3 through the filter 5, the caprolactam para-xylene solution with a caprolactam concentration of 21% is obtained and enters the concentration system.

[0126] (3) The concentration system is a double-effect evaporation system. After evaporating a portion of the p-xylene, a caprolactam p-xylene solution with a caprolactam concentration of 92% is obtained. The evaporated p-xylene is cooled and then recycled in the extraction device 1.

[0127] (4) The caprolactam p-xylene solution with a caprolactam concentration of 92% was gasified and then entered into an ammonia fixed bed reactor. The catalyst was silicon-aluminum bimetallic oxide. The reaction temperature was 360°C. The feed molar ratio of ammonia to caprolactam was 42:1. The space velocity was 2.4 h -1The single-pass caprolactam conversion rate was 65.3%, the selectivity for 6-aminocapronitrile was 96.5%, the content of p-xylene in the product was 7.5% by mass, and the water content was 8.7% by mass; no original cyclohexane, methylcyclopentane, cyclohexene, and cyclohexanone were found in the liquid chromatography, which should have been separated cleanly or converted into other by-products in the solvent distillation recovery link; after 200 hours of catalyst stability test, the single-pass caprolactam conversion rate was 64.7%, and the selectivity for 6-aminocapronitrile was 96.3%.

[0128] (5) A comparative experiment was conducted using a 92% caprolactam p-xylene solution prepared from commercial reagent-grade p-xylene and premium-grade caprolactam: in the same ammonia fixed-bed reactor, the reaction temperature was 360°C, the feed molar ratio of ammonia to caprolactam was 42:1, and the space velocity was 2.4 h -1 The single-pass caprolactam conversion rate was 65.6%, and the 6-aminocapronitrile selectivity was 96.0%.

[0129] (6) A comparative experiment was conducted using commercial premium caprolactam: in the same fixed-bed ammonia reactor, the reaction temperature was 360°C, the feed molar ratio of ammonia to caprolactam was 42:1, and the space velocity was 2.4 h -1 , the single-pass caprolactam conversion rate was 65.3%, and the selectivity for 6-aminocapronitrile was 96.1%. After 200 hours of catalyst stability testing, the single-pass caprolactam conversion rate was 63.8%, and the selectivity for 6-aminocapronitrile was 96.2%;

[0130] (7) The reacted feed liquid is cooled by a cooling separator 10, deaminated by a distillation and deamination tower 11, and then enters a second distillation device 12, which is operated under a negative pressure of 2 KPa. A p-xylene-water azeotropic liquid and a mixed liquid of water, light components, etc. are obtained at the top of the tower. After separation by a second separator 13, part of the oil phase is returned to the second distillation device 12 as reflux with water, and part of it is returned to the rotary disc extraction tower. The water phase enters the wastewater treatment device 2. The water content at the bottom of the second distillation device 12 is 180 ppm, the caprolactam content is 34.7%, the aminocapronitrile content is 62.5%, and the rest are light and heavy component impurities. After the water is removed from this material, the material is sent to the aminocapronitrile refining system to obtain 6-aminocapronitrile with a purity of 99.5%. The unreacted caprolactam is recovered and returned to the evaporation system to continue to participate in the reaction.

[0131] Example 9

[0132] (1) The ammonium sulfate-containing caprolactam liquid obtained by the cyclohexanone oxime rearrangement process is used as the raw material liquid, and a mixed solvent of n-hexane and n-heptane is used as the extractant in a volume ratio of 1:2. The extraction is carried out in a bubbling tower having an upper section structured filler as a static mixer and a middle section as a jet microbubble type. The lower section is equipped with three layers of sieve plates. The bottom of the tower obtains an aqueous solution containing ammonium sulfate, and the top of the tower obtains a crude caprolactam extractant solution with a caprolactam mass fraction of 30%, wherein the water content is 3.2%, ammonium sulfate is dissolved in the water, and organic impurities include 63 ppm of cyclohexene, 40 ppm of cyclohexanone, 21 ppm of cyclohexanol, 18 ppm of methylcyclohexane, etc.;

[0133] (2) The crude caprolactam extractant solution enters the first distillation device 3, which is operated at normal pressure, with a tower top temperature of 64°C and a tower bottom temperature of 105°C. 5 kg of steam condensate is used as a heat source. The mixture of water and extractant produced from the tower top enters the separator 4, where water and oil are separated. The oil phase returns to the extraction tower for recycling, and the water phase enters the wastewater treatment device 2. The mixture at the bottom of the first distillation device 3 is filtered through a filter 5 to remove solid particles such as ammonium sulfate precipitated, and a mixed solution with a caprolactam concentration of 38.1%, n-hexane of 10.5%, and n-heptane of 51.4% is obtained and enters the concentration system.

[0134] (3) The concentration system adopts a triple-effect evaporation system. After evaporating part of the extractant, a mixed solution with a caprolactam concentration of 88% is obtained. The evaporated extractant is cooled and then returned to the extraction tower for recycling.

[0135] (4) The caprolactam mixed solution with a caprolactam concentration of 88% was gasified and then entered into an ammonia fluidized bed reactor. The catalyst was mesoporous alumina, the reaction temperature was 325°C, the feed molar ratio of ammonia to caprolactam was 24:1, and the space velocity was 0.8h -1 The single-pass caprolactam conversion rate was 59.7%, the selectivity of 6-aminocapronitrile was 97.5%, the content of n-hexane and n-heptane in the product was 11.3% by mass, and the water content was 7.7% by mass; there was still a peak at the position of methylcyclohexane in the liquid chromatography, but no other peaks were seen.

[0136] (5) The reacted feed liquid is cooled by a cooling separator 10, deaminated by a distillation and deamination tower 11, and then enters a second distillation device 12, which is operated under a negative pressure of 2 KPa. A mixture of n-hexane-n-heptane-water azeotropic liquid and water, light components, etc. are obtained at the top of the tower. After separation, part of the oil phase is returned to the second distillation device 12 as reflux with water, and part of it is returned to the extraction tower. The water phase enters the wastewater treatment device 2. The water content at the bottom of the second distillation device 12 is 160 ppm. The material after dehydration is sent to the aminocapronitrile refining system to obtain 6-aminocapronitrile with a purity of 99.5%. The unreacted caprolactam is recovered and returned to the evaporation system to continue to participate in the reaction.

[0137] Example 10

[0138] (1) The ammonium sulfate-containing caprolactam liquid obtained by the cyclohexanone oxime rearrangement process is used as the raw material liquid, and chloroform is used as the extractant to perform countercurrent extraction in a rotary disc extraction tower. An aqueous solution containing ammonium sulfate is obtained at the top of the tower, and a crude caprolactam chloroform solution with a caprolactam mass fraction of 15% is obtained at the bottom of the tower. The water content is 1.3%, and ammonium sulfate is dissolved in the water. Organic impurities include 190 ppm of cyclohexane, 63 ppm of cyclohexene, 38 ppm of cyclohexanone, 66 ppm of methylcyclohexane, 42 ppm of ethylcyclopentane, etc.

[0139] (2) The crude caprolactam chloroform solution enters the first distillation device 3, which is operated at normal pressure, with a tower top temperature of 57°C and a tower bottom temperature of 70.2°C. 2 kg of secondary low-pressure steam is used as a heat source. The azeotropic mixture of water and chloroform produced from the tower top enters the separator 4, where water and oil are separated, with the water phase on the top and the oil layer on the bottom. The oil phase returns to the extraction tower for recycling, and the water phase enters the wastewater treatment device 2. The mixture at the bottom of the first distillation device 3 is filtered through a filter 5 to remove solid particles such as ammonium sulfate, and a caprolactam chloroform mixed solution with a caprolactam concentration of 17.5% is obtained and enters the concentration system.

[0140] (3) The concentration system is a triple-effect evaporation system. After partially removing the chloroform, a chloroform mixed solution with a caprolactam concentration of 84% is obtained. The evaporated chloroform is cooled and then recycled in the rotary disc extraction tower.

[0141] (4) The mixed solution with a caprolactam concentration of 84% was vaporized and then entered into an ammoniation fixed bed reactor. The catalyst was a zinc-magnesium catalyst supported on a phosphorus-aluminum molecular sieve. The reaction temperature was 350°C. The feed molar ratio of ammonia to caprolactam was 26:1. The space velocity was 1.5 h -1 The single-pass caprolactam conversion rate was 66.8%, the 6-aminocapronitrile selectivity was 97.1%, the chloroform content in the product was 15.1% by mass, and the water content was 8.1% by mass; in the liquid chromatography, there were still peaks at the positions of the original cyclohexane, methylcyclopentane, and ethylcyclopentane, but cyclohexanone and cyclohexene were not seen, which should be converted into other by-products.

[0142] (5) A comparative experiment was conducted using a 84% mixture of commercial reagent-grade chloroform and premium caprolactam: in the same fixed-bed ammonia reactor, the reaction temperature was 350°C, the feed molar ratio of ammonia to caprolactam was 26:1, and the space velocity was 1.5 h -1 The single-pass caprolactam conversion rate was 66.5%, and the 6-aminocapronitrile selectivity was 96.8%.

[0143] (6) The reacted feed liquid is cooled by the cooling separator 10, deaminated by the distillation and deamination tower 11, and then enters the second distillation device 12. The operation is carried out under a negative pressure of 2 KPa. A chloroform-water azeotropic liquid and a mixed liquid of water, light components, etc. are obtained at the top of the tower. After separation by the second separator 13, part of the oil phase is returned to the second distillation device 12 with water as reflux, and part of it is returned to the rotary disc extraction tower. The water phase enters the wastewater treatment device 2. The water content at the bottom of the second distillation device 12 is 170 ppm. The material after dehydration is sent to the aminocapronitrile refining system to obtain 6-aminocapronitrile with a purity of 99.5%. The unreacted caprolactam is recovered and returned to the evaporation system to continue to participate in the reaction.

Claims

1. An energy-saving device for preparing aminocapronitrile from a liquid phase rearrangement product of cyclohexanone oxime, characterized in that: It comprises an extraction device (1), a first distillation device (3), a filter (5), a concentration system and a reaction system, The inlet of the extraction device (1) is connected to an extractant and a raw material liquid, wherein the raw material liquid is a caprolactam liquid containing water, ammonium sulfate and organic impurities. The oil phase outlet of the extraction device (1) is directly connected to the first distillation device (3), the bottom outlet of the first distillation device (3) is connected to the filter (5), and the top outlet of the first distillation device (3) is connected to the separator (4); The liquid phase outlet of the filter (5) is connected to the concentration system. The tower bottom outlet of the concentration system is connected to the reaction system, The reaction system comprises a reactor (9) and a second distillation device (12) which are arranged in sequence, the reactor (9) being a caprolactam amination reactor, and the bottom outlet of the second distillation device (12) being an outlet for a crude aminocapronitrile mixed liquid.

2. The energy-saving device according to claim 1, characterized in that: The extraction device (1) is a sieve plate extraction tower, a packed extraction tower, an improved pulse sieve plate tower or a rotary disc extraction tower.

3. The energy-saving device according to claim 1, characterized in that: The water phase outlet of the extraction device (1) is connected to the wastewater treatment device (2).

4. The energy-saving device according to claim 1, characterized in that: The oil phase outlet of the separator (4) is connected to the inlet of the extraction device (1), and the water phase outlet of the separator (4) is connected to the wastewater treatment device (2).

5. The energy-saving device according to claim 1, characterized in that: The concentration system is a single-effect evaporation system, a multi-effect evaporation system, a single-tower distillation system or a multi-tower distillation system.

6. The energy-saving device according to claim 1, characterized in that: The reactor (9) is a fixed bed reactor or a fluidized bed reactor.

7. The energy-saving device according to claim 1, characterized in that: The reaction system further comprises a mixing evaporator (8) arranged before the reactor (9).

8. The energy-saving device according to claim 1, characterized in that: The reaction system further comprises a cooling separator (10) arranged between the reactor (9) and the second distillation device (12), and a liquid phase outlet of the cooling separator (10) is connected to the second distillation device (12).

9. The energy-saving device according to claim 7, characterized in that: A distillation deamination tower (11) is further arranged between the second distillation device (12) and the reactor (9), the bottom of the distillation deamination tower (11) is connected to the second distillation device (12), and the top of the distillation deamination tower (11) is connected to the mixing evaporator (8).

10. The energy-saving device according to claim 1, characterized in that: The top outlet of the second rectification device (12) is connected to a second classifier (13).

11. A method for preparing aminocapronitrile from a liquid phase rearrangement product of cyclohexanone oxime, characterized in that: The steps include: (1) adding an organic extractant to the raw material liquid for extraction, and obtaining an oil phase as a caprolactam extraction solution; The raw material liquid is a liquid obtained by neutralizing cyclohexanone oxime rearrangement liquid with ammonia; (2) directly distilling the caprolactam extraction solution to remove water and part of the organic extractant to obtain a caprolactam mixture containing impurities; (3) filtering the caprolactam mixture containing impurities to remove impurities, and then concentrating to remove part or all of the extractant to obtain a caprolactam liquid; (4) sending the caprolactam liquid into a reactor for an amination reaction to obtain a reaction mixture; (5) distilling the reaction mixture to remove water to obtain a crude aminocapronitrile mixture.

12. The method according to claim 11, characterized in that The concentration of caprolactam in the caprolactam extraction solution described in step (1) is 5-40% by mass.

13. The method according to claim 12, characterized in that The concentration of caprolactam in the caprolactam extraction solution in step (1) is 15-30% by mass.

14. The method according to claim 11, characterized in that The organic extractant in step (1) is an organic substance that can form an azeotrope with water and is immiscible with water.

15. The method according to claim 14, characterized in that The organic extractant in step (1) is one or a mixture of benzene, toluene, xylene, chloroform, carbon tetrachloride, cyclohexane, methylcyclohexane or methylcyclopentane.

16. The method according to claim 11, characterized in that The top operating pressure of the distillation in step (2) is 30-120 KPa, the top operating temperature is 45-80°C, and the bottom operating temperature is 70-120°C.

17. The method according to claim 11, characterized in that The content of caprolactam in the caprolactam liquid in step (3) is 50-99.9% by mass.

18. The method according to claim 17, characterized in that The content of caprolactam in the caprolactam liquid in step (3) is 75-99.9% by mass.

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