Method and reaction system for liquid-phase Beckmann rearrangement reaction of cyclohexanone oxime catalyzed by solid acid

Abstract

The invention discloses a method and a reaction system for liquid-phase Beckmann rearrangement reaction of cyclohexanone oxime catalyzed by solid acid, and belongs to the technical field of caprolactam preparation. The method comprises the following steps: mixing a specific solvent and cyclohexanone-oxime according to a ratio, dewatering, feeding into kettle type reaction equipment, carrying out liquid-solid two-phase rearrangement reaction (the reaction temperature is 80-130 DEG C, the pressure is 50-100Pa, and the retention time is 1-5 hours) under the catalysis of solid acid, directly collecting the product, and generating no ammonium sulfate byproduct. The reaction system comprises a solvent storage tank, a raw material tank, a water removal device, kettle type reaction equipment, a catalyst tank, a condenser, a backwashing tank and a finished product tank, and continuous production can be realized. The method eliminates ammonium sulfate by-products, solves the problem that concentrated sulfuric acid corrodes equipment, and is short in process, low in energy consumption, capable of being transformed based on existing equipment, short in investment payback period and suitable for industrial application, and the caprolactam selectivity is larger than or equal to 99%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of caprolactam preparation, in particular to a method and a reaction system for solid acid catalyzed Beckmann rearrangement reaction of cyclohexanone oxime in liquid phase. BACKGROUND

[0002] Caprolactam is a key raw material for producing polycaprolactam (nylon 6) and has important application value in the chemical industry. At present, the ammonia oximation method, which has a short process and good environmental performance, has become the mainstream process in caprolactam production. After technical improvement, the product quality of the ammonia oximation method is close to or even better than that of the traditional DSM-HPO method. However, there is a core bottleneck in the rearrangement stage of the ammonia oximation method, which is the by-product ammonium sulfate. This problem seriously restricts the cost optimization of caprolactam.

[0003] Specifically, in the production of caprolactam by the existing ammonia oximation method, the intermediate cyclohexanone oxime needs to undergo Beckmann rearrangement reaction under the catalysis of concentrated sulfuric acid. After the reaction, the excess concentrated sulfuric acid needs to be neutralized with ammonia, thereby producing ammonium sulfate as a by-product. The production of 1 ton of caprolactam requires the production of 1.5-1.6 tons of low-value-added ammonium sulfate, and a complete set of ammonium sulfate production devices, packaging lines and large warehouses need to be built, which significantly increases the investment and operating costs.

[0004] At the same time, the use of concentrated sulfuric acid also has multiple disadvantages: first, the strong corrosive nature of concentrated sulfuric acid requires high-quality equipment materials (acid-resistant alloys), which significantly increases the cost of equipment purchase and maintenance; second, the leakage or wastewater discharge of concentrated sulfuric acid can cause serious environmental pollution, which is contrary to the concept of green production; third, the entire process needs to go through multiple steps such as "cyclohexanone oxime preparation - concentrated sulfuric acid catalytic rearrangement - ammonia neutralization and acid removal", which is long and energy-intensive.

[0005] The closest prior art to the present application is "Preparation of caprolactam by gas phase Beckmann rearrangement of cyclohexanone oxime without ammonium sulfate", which realizes the production of caprolactam without ammonium sulfate byproduct by vaporizing cyclohexanone oxime and then performing gas phase rearrangement reaction under the action of a solid acid catalyst. However, this technology has problems such as high energy consumption for vaporizing cyclohexanone oxime, strict requirements for temperature control precision in gas phase reaction (which can easily lead to decomposition of raw materials), and high requirements for equipment sealing, making it difficult to apply in industrialization. SUMMARY

[0006] The present application provides a method and a reaction system for solid acid catalyzed Beckmann rearrangement reaction of cyclohexanone oxime in liquid phase, to solve the problems of "by-product ammonium sulfate, severe equipment corrosion, long process, poor environmental performance" in the existing caprolactam production process. This method not only avoids the disadvantages of concentrated sulfuric acid, but also overcomes the energy consumption and control difficulties of gas phase rearrangement, achieving green and low-cost production of caprolactam.

[0007] To solve the above technical problems, the technical scheme adopted by the present application is: a method for solid acid catalytic liquid phase Beckmann rearrangement reaction of cyclohexanone oxime, comprising the following steps: Step S1, preparing solvent and raw material: the solvent is selected from one or more of isopropyl alcohol, n-butanol, acetonitrile, formamide, acetone, dioxane, dimethyl sulfoxide, tetrahydrofuran, ethyl acetate, N,N-dimethylformamide, and is stored in a solvent storage tank at 40-100°C; the cyclohexanone oxime is stored in a raw material tank at 40-100°C; the molar ratio of the solvent to the cyclohexanone oxime is 2-10:1; Step S2, water removal pretreatment: after the solvent and the cyclohexanone oxime in step S1 are mixed, they are sent to a water removal device to remove water at 50-250°C; Step S3, solid-liquid phase rearrangement reaction: after water removal, the material is sent to a kettle type reaction equipment, and 0.1-0.5% of solid acid catalyst based on the total mass of the material is added, and a solid-liquid two-phase reaction is carried out under mechanical stirring; the reaction conditions are: temperature 80-130°C, pressure 50-100Pa, and material residence time 1-5h; Step S4, product collection: after reaction, the product is sent to a finished product tank at 40-100°C, and the gas phase at the top of the reaction equipment is condensed and recovered by a condenser; if the membrane tube in the reaction equipment is blocked, backwashing is carried out by a backwashing tank.

[0008] In the step S1, the molar ratio of the solvent to the cyclohexanone oxime is 5-8:1.

[0009] In the step S2, the temperature of the water removal device is 150-200°C, and the water content of the removed material is ≤0.1%.

[0010] In the step S3, the reaction temperature is 100-120°C, the reaction pressure is 80-90Pa, and the material residence time is 3-4h.

[0011] In the step S3, the solid acid catalyst accounts for 0.3-0.4% of the total mass of the material.

[0012] The present application also provides a reaction system for solid acid catalytic liquid phase Beckmann rearrangement reaction of cyclohexanone oxime, comprising: A solvent storage tank is provided with a 40-100°C temperature control module for storing the solvent; A raw material tank is provided with a 40-100°C temperature control module for storing the cyclohexanone oxime; A water removal device is connected to the mixed discharge pipe of the solvent storage tank and the raw material tank at the inlet and connected to the reaction equipment at the outlet, and is provided with a 50-250°C temperature control module; The kettle type reaction equipment is provided with a built-in mechanical stirring device and a membrane tube assembly, an inlet connected with a water removal device, a catalyst inlet arranged on the side, a gas phase outlet arranged on the top, and a product outlet arranged on the bottom; and is provided with a temperature control module of 80-130 DEG C and a pressure control module of 50-100 Pa; The catalyst tank is connected with the catalyst inlet of the reaction equipment through a metering pump, and is used for storing the solid acid catalyst; The condenser is connected with the gas phase outlet of the reaction equipment, and is used for condensing and recovering the solvent; The backwashing tank is communicated with the membrane tube assembly of the reaction equipment through a pipeline, and is used for backwashing; The finished product tank is connected with the product outlet of the reaction equipment, and is provided with a temperature control module of 40-100 DEG C.

[0013] The temperature control module of the water removal device is 150-200 DEG C.

[0014] The temperature control module of the kettle type reaction equipment is 100-120 DEG C, and the pressure control module is 80-90 Pa.

[0015] The method and the reaction system for the Beckmann rearrangement reaction of cyclohexanone oxime liquid phase by using the solid acid catalyst have the following beneficial effects: 1. No by-product of ammonium sulfate is produced, and the cost bottleneck is broken. The solid acid catalyst is used to replace concentrated sulfuric acid, and no ammonia neutralization step is needed after the reaction, so that the by-product of ammonium sulfate is completely eliminated, the matching investment (including packaging and warehouse) of the ammonium sulfate device is avoided, the treatment cost of the low-value-added by-product is reduced, and the production cost of caprolactam is significantly optimized.

[0016] 2. The equipment corrosion is small, and the maintenance cost is low. The solid acid catalyst has no strong corrosion, and the equipment can be made of conventional carbon steel (without acid-resistant alloy), so that the equipment purchase cost is reduced; meanwhile, the maintenance frequency caused by corrosion is reduced, and the service life of the equipment is prolonged.

[0017] 3. The process is short, the energy consumption is low, and the continuous production can be realized. The process is shortened compared with the concentrated sulfuric acid method by omitting the steps of 'concentrated sulfuric acid neutralization-ammonium sulfate separation'; and the high-energy-consumption vaporization step in the gas phase rearrangement is avoided through the liquid phase reaction, and the continuous operation is realized (the conversion rate of cyclohexanone oxime is greater than 50%, and the selectivity of caprolactam is greater than or equal to 99%).

[0018] 4. The environmental protection performance is good, and the compatibility is strong. No acid-containing wastewater is discharged, and the amount of three wastes is only less than 10% of that of the concentrated sulfuric acid method; and the reaction system can be upgraded and modified based on the existing caprolactam device, the additional investment is small, and the investment recovery period is shortened. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The figure shows the flow diagram of the solid acid rearrangement reaction system without ammonium sulfate.

[0020] Figure: 101 - solvent storage tank; 102 - raw material tank; 2 - water removal device; 301 - kettle type reaction equipment; 302 - catalyst tank; 303 - condenser; 304 - backwash tank; 4 - finished product tank. DETAILED DESCRIPTION

[0021] The method and reaction system of the present application for Beckmann rearrangement reaction of cyclohexanone oxime catalyzed by solid acid will be described in detail below with reference to the accompanying drawings.

[0022] The method and reaction system of the present application for Beckmann rearrangement reaction of cyclohexanone oxime catalyzed by solid acid will be described in detail below with reference to the accompanying drawings. Figure 1 , comprising the following steps: Step S1, preparing solvent and raw material: the solvent is selected from one or more of isopropyl alcohol, n-butanol, acetonitrile, formamide, acetone, dioxane, dimethyl sulfoxide, tetrahydrofuran, ethyl acetate, N,N - dimethylformamide, and stored in a solvent storage tank 101 at 40-100℃; cyclohexanone oxime is stored in a raw material tank 102 at 40-100℃; the molar ratio of the solvent to cyclohexanone oxime is 2-10:1; Step S2, water removal pretreatment: after mixing the solvent and cyclohexanone oxime in step S1, they are sent into a water removal device 2 to remove water at 50-250℃; Step S3, solid-liquid phase rearrangement reaction: after water removal, the material is sent into a kettle type reaction equipment 301, and 0.1-0.5% of solid acid catalyst based on the total mass of the material is added, and a solid-liquid two-phase reaction is carried out under mechanical stirring; the reaction conditions are: temperature 80-130℃, pressure 50-100Pa, and material residence time 1-5h; Step S4, product collection: after reaction, the product is sent into a finished product tank 4 at 40-100℃, and the solvent is recovered by condensation of the gas phase at the top of the reaction equipment 301 through a condenser 303; if the membrane tube in the reaction equipment 301 is blocked, backwashing is carried out through a backwash tank 304.

[0023] The reaction system for the Beckmann rearrangement reaction of cyclohexanone oxime liquid phase catalyzed by solid acid, comprising: a solvent storage tank 101, which is provided with a 40-100 DEG C temperature control module and is used for storing solvent; a raw material tank 102, which is provided with a 40-100 DEG C temperature control module and is used for storing cyclohexanone oxime; a water removal device 2, which is connected with the mixed discharge pipe of the solvent storage tank 101 and the raw material tank 102 at the inlet and is connected with a reaction equipment 301 at the outlet and is provided with a 50-250 DEG C temperature control module; the kettle type reaction equipment 301, which is internally provided with a mechanical stirring device and a membrane tube assembly, is connected with the water removal device 2 at the inlet, is provided with a catalyst inlet at the side, is provided with a gas phase outlet at the top and is provided with a product outlet at the bottom; and is provided with an 80-130 DEG C temperature control module and a 50-100 Pa pressure control module; a catalyst tank 302, which is connected with the catalyst inlet of the reaction equipment 301 through a metering pump at the outlet and is used for storing solid acid catalyst; a condenser 303, which is connected with the gas phase outlet of the reaction equipment 301 at the inlet and is used for condensing and recovering solvent; a backwashing tank 304, which is communicated with the membrane tube assembly of the reaction equipment 301 through a pipeline and is used for backwashing; and a finished product tank 4, which is connected with the product outlet of the reaction equipment 301 at the inlet and is provided with a 40-100 DEG C temperature control module.

[0024] Example 1 The method for the Beckmann rearrangement reaction of cyclohexanone oxime liquid phase catalyzed by solid acid, comprising the following steps: Raw material and solvent: the solvent is selected from isopropyl alcohol, is stored in the solvent storage tank 101, and the temperature control is 60 DEG C; the cyclohexanone oxime is stored in the raw material tank 102, and the temperature control is 60 DEG C; the molar ratio of the solvent and the cyclohexanone oxime is 5:1; Water removal treatment: the mixture is sent into the water removal device 2, the temperature control is 150 DEG C, and the water content is less than or equal to 0.1% after water removal; Rearrangement reaction: after water removal, the material is sent into the kettle type reaction equipment 301, 0.3% of the total mass of the material is added to the solid acid catalyst; the reaction temperature is controlled to be 100 DEG C, the pressure is controlled to be 80 Pa, the mechanical stirring speed is controlled to be 300 rpm, and the material residence time is controlled to be 3 h; The conversion rate of the cyclohexanone oxime is 55%, the selectivity of the caprolactam is 99.2%, and no by-product of ammonium sulfate is generated; after the reaction, the isopropyl alcohol in the gas phase is recovered through the condenser 303, and the recovery rate is more than 95%.

[0025] Example 2 The method for the Beckmann rearrangement reaction of cyclohexanone oxime liquid phase catalyzed by solid acid, comprising the following steps: Raw material and solvent: the solvent is selected from isopropyl alcohol, is stored in the solvent storage tank 101, and the temperature control is 60 DEG C; the cyclohexanone oxime is stored in the raw material tank 102, and the temperature control is 60 DEG C; the molar ratio of the solvent and the cyclohexanone oxime is 5:1; Dehydration treatment: the mixture is sent to the dehydration device 2, the control temperature is 200℃, and the water content is less than or equal to 0.1% after dehydration; Rearrangement reaction: after dehydration, the material is sent to the kettle type reaction equipment 301, and 0.4% of the total mass of the material is added as a solid acid catalyst; the reaction temperature is controlled at 120℃, the pressure is 90Pa, the mechanical stirring speed is 350rpm, and the material residence time is 4h; The results show that the conversion rate of cyclohexanone oxime is 58%, the selectivity of caprolactam is 99.5%, and there is no by-product of ammonium sulfate; the solvent recovery rate is more than 96%.

Claims

1. A method for the liquid-phase Beckmann rearrangement of cyclohexanone oxime catalyzed by a solid acid, characterized in that: Includes the following steps: Step S1, prepare solvent and raw materials: The solvent is selected from one or more of isopropanol, n-butanol, acetonitrile, formamide, acetone, dioxane, dimethyl sulfoxide, tetrahydrofuran, ethyl acetate, and N,N-dimethylformamide, and is stored in a solvent storage tank (101) at 40-100℃; the cyclohexanone oxime is stored in a raw material tank (102) at 40-100℃; the molar ratio of solvent to cyclohexanone oxime is 2-10:1; Step S2, water removal pretreatment: The solvent in step S1 is mixed with cyclohexanone oxime and then sent to the water removal device (2) to remove water at 50-250℃; Step S3, solid-liquid phase rearrangement reaction: The dehydrated material is fed into a batch reactor (301), and a solid acid catalyst accounting for 0.1-0.5% of the total mass of the material is added. The solid-liquid two-phase reaction is carried out under mechanical stirring. The reaction conditions are: temperature 80-130℃, pressure 50-100Pa, and material residence time 1-5h. Step S4, Product collection: After the reaction, the product is sent to the finished product tank (4) at 40-100℃. The gas phase at the top of the reaction equipment (301) is condensed and the solvent is recovered by the condenser (303). If the inner membrane tube of the reaction equipment (301) is blocked, it is backwashed through the backwash tank (304).

2. The method for the solid acid-catalyzed liquid-phase Beckmann rearrangement of cyclohexanone oxime according to claim 1, characterized in that: In step S1, the molar ratio of solvent to cyclohexanone oxime is 5-8:

1.

3. The method for the liquid-phase Beckmann rearrangement of cyclohexanone oxime catalyzed by solid acid according to claim 1, characterized in that... In step S2, the temperature of the dehydration device (2) is 150-200℃, and the moisture content of the material after dehydration is ≤0.1%.

4. The method for the liquid-phase Beckmann rearrangement of cyclohexanone oxime catalyzed by solid acid according to claim 1, characterized in that... In step S3, the reaction temperature is 100-120℃, the reaction pressure is 80-90Pa, and the material residence time is 3-4h.

5. The method for the solid acid-catalyzed liquid-phase Beckmann rearrangement of cyclohexanone oxime according to claim 1, characterized in that... In step S3, the solid acid catalyst accounts for 0.3-0.4% of the total mass of the material.

6. A reaction system for the liquid-phase Beckmann rearrangement of cyclohexanone oxime catalyzed by a solid acid, characterized in that... include: Solvent storage tank (101): Equipped with a 40-100℃ temperature control module for storing solvents; Raw material tank (102): Equipped with a 40-100℃ temperature control module for storing cyclohexanone oxime; Dehydration device (2): The inlet is connected to the mixing outlet pipe of the solvent storage tank (101) and the raw material tank (102), and the outlet is connected to the reaction equipment (301). It is equipped with a temperature control module of 50-250℃. The reactor (301) has a built-in mechanical stirring device and membrane assembly, an inlet connected to a dehydration device (2), a catalyst inlet on the side, a gas outlet at the top, and a product outlet at the bottom; it is equipped with a temperature control module of 80-130℃ and a pressure control module of 50-100Pa. Catalyst tank (302): The outlet is connected to the catalyst inlet of the reaction equipment (301) via a metering pump and is used to store solid acid catalyst; Condenser (303): The inlet is connected to the gas phase outlet of the reaction equipment (301) and is used for condensing and recovering the solvent; Backwash tank (304): Connected to the membrane assembly of the reaction equipment (301) via a pipeline, used for backwashing; Finished product tank (4): The inlet is connected to the product outlet of the reaction equipment (301), and is equipped with a temperature control module of 40-100℃.

7. The reaction system for the solid acid-catalyzed liquid-phase Beckmann rearrangement of cyclohexanone oxime according to claim 6, characterized in that... The temperature control module of the water removal device (2) is 150-200℃.

8. The reaction system for the solid acid-catalyzed liquid-phase Beckmann rearrangement of cyclohexanone oxime according to claim 6, characterized in that... The temperature control module of the batch reactor (301) is 100-120℃, and the pressure control module is 80-90Pa.

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