Reaction device for preparing cyclohexanone through phenol hydrogenation based on fiber-based membrane reactor

Abstract

The invention belongs to the technical field of membrane catalysis, and relates to a continuous phenol hydrogenation cyclohexanone preparation reaction device based on a fiber-based membrane reactor. Comprising a lower assembly, a material storage tank and an upper assembly, and a plurality of fiber-based catalytic membranes are arranged between a small annular gasket and a large annular gasket. According to the invention, the flexible membrane material is adopted to buffer the impact force in the feeding process of liquid and gas, and the flexible membrane material is not easy to damage in the clamping and application process through the designed membrane assembly, so that the stability in the reaction process is ensured, and continuous, green and efficient preparation of cyclohexanone is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane catalysis, and relates to a reaction device for the hydrogenation of phenol to cyclohexanone based on a fiber-based membrane reactor. Background Art

[0002] As an important chemical raw material, cyclohexanone plays an important role in fields such as industrial production, fine chemical manufacturing, and daily life. In recent years, with the rapid development of the national industry, the usage of caprolactam has been increasing year by year, and the demand for cyclohexanone as a production raw material has also been increasing day by day.

[0003] Currently, in industrial production, the production processes of cyclohexanone mainly include: cyclohexane oxidation method, cyclohexene hydration method, and phenol hydrogenation method. The cyclohexane oxidation method has the characteristics of high energy consumption and low yield, and the cyclohexene hydration method faces problems such as a cumbersome process and complex operating procedures. The process of producing cyclohexanone by one-step hydrogenation of phenol has many advantages such as a simple process, low energy consumption, simple operation, few side reactions, and convenient separation and purification of products, and has obvious advantages under the background of carbon peaking and carbon neutrality. At present, researchers mainly focus on the development of high-performance phenol hydrogenation catalysts to promote the efficient and green synthesis of cyclohexanone. The basic sites in nitrogen-doped carbon (CN) can selectively adsorb phenol and cyclohexanone, realizing the selective hydrogenation of phenol to cyclohexanone, and it is one of the most widely studied supports for phenol hydrogenation catalysts in recent years. Patent (CN116440937A) reported the preparation of a Pd@CN catalyst by directly mixing 2-methylimidazole with a cobalt source and then calcining it, and its application in the liquid-phase reaction of phenol. When the reaction temperature is 100 o °C, the phenol conversion rate is 98.6%, and the cyclohexanone selectivity is 94.1%. (Phenol concentration 1 wt%). Patent (CN119524902A) reported a palladium-based catalyst supported on nitrogen-doped porous carbon spheres and its application in the one-step hydrogenation reaction of phenol. When the reaction temperature is 70 o °C, the phenol conversion rate is 33.7%, and the cyclohexanone selectivity is 90.6%. (25 mL of water and 0.5 mL of phenol). However, it is difficult to completely separate and recover the micro-nano particle catalyst from the reaction system by traditional separation methods during the recycling process. At the same time, the commonly used Pd-based noble metal catalysts in this process are costly, and the inevitable losses greatly increase the production cost, which limits the industrialization process of the one-step hydrogenation method of phenol.

[0004] Membrane catalytic technology can load active components onto membrane materials to construct catalytic membranes, effectively avoiding the separation problem between catalysts and products, realizing reaction-separation integration, improving reaction efficiency, saving energy and reducing consumption, and achieving continuous production processes. Flow-through reactors can enhance mass transfer, ensure sufficient contact between reactants and active components in the catalytic membrane, and improve catalytic efficiency. Currently, the mainstream supports for catalytic membranes are materials with underdeveloped pores, and the content of active components per unit volume of the catalytic membrane is lower than that of powder catalysts.

[0005] Therefore, there is an urgent need to develop catalytic membranes with well-developed pores and supporting continuous membrane reactor devices. Summary of the Invention

[0006] The present invention proposes a novel reaction device for continuous hydrogenation of phenol to cyclohexanone based on a fiber-based membrane reactor to address the problems existing in the industrial promotion of traditional continuous hydrogenation of phenol to cyclohexanone.

[0007] To achieve the above object, the present invention is implemented by the following technical solutions: A reaction device for hydrogenation of phenol to cyclohexanone based on a fiber-based membrane reactor, comprising a membrane reactor, a heating component for providing a constant temperature condition for the membrane reactor, and a power component for circulating the reaction materials. The membrane reactor includes a lower component, a storage tank, and an upper component. An inlet is provided on the side wall of the lower component, and the inlet communicates with the inner bottom surface of the lower component. Above the bottom surface of the lower component, a circular first step and a second step are sequentially provided. The outer diameter of the first step is equivalent to the inner diameter of the second step. A matching small circular gasket is provided on the first step, and a matching large circular gasket is provided on the second step. A plurality of fiber-based catalytic membranes are provided between the small circular gasket and the large circular gasket. The lower component is connected to the storage tank above. The storage tank is a hollow cylindrical structure. An upper component in the form of a thin sheet is provided on the upper part of the storage tank. A liquid outlet pipe is provided in the middle of the upper component. The top of the liquid outlet pipe is connected to a pressure gauge. The lower end of the liquid outlet pipe extends to the lower part of the storage tank. A liquid outlet pipe bypass for discharging materials is provided below the pressure gauge. A hydrogen exhaust pipe is provided on the side of the liquid outlet pipe, and the hydrogen exhaust pipe communicates with the top of the storage tank.

[0008] Preferably, the fiber-based catalytic membrane is prepared by the following steps: (1) Add zinc acetate and tetraethyl orthosilicate to N,N-dimethylformamide, mix evenly, and then add polyacrylonitrile and mix evenly to obtain a spinning solution.

[0009] (2) Electrospinning the spinning solution under the conditions of humidity of 36-42% and temperature of 20-28°C. The electrostatic voltage is set to 13.5-15.5 kV, the distance from the tip of the spinning needle to the collector is 140-210 mm, and the injection speed is set to 1.0-1.5 mL / h to obtain a precursor membrane.

[0010] (3) Calcinate the precursor film in an air atmosphere at a calcination temperature of 260 - 300 °C to obtain a pre-oxidized nanofiber film.

[0011] (4) Calcinate the pre-oxidized nanofiber film in an argon atmosphere at a calcination temperature of 700 - 800 °C to obtain a flexible carbon nanofiber film.

[0012] (5) Place the flexible carbon nanofiber film in a nitric acid solution with a concentration of 25 - 38 wt% and heat-etch it for 1 - 2 h for the first time. After the etching is completed, rinse it to neutral, and then add it to a sodium hydroxide solution with a concentration of 6 - 11 wt% and heat-etch it for 1 - 2 h for the second time. After the etching is completed, rinse the membrane material to neutral.

[0013] (6) Load the active component Pd by wet impregnation.

[0014] Preferably, a ring-shaped protrusion is provided at the center of the lower part of the storage tank. The outer diameter of the ring-shaped protrusion is the same as the outer diameter of the large ring gasket, and the sum of the height of the ring-shaped protrusion and the thickness of the large ring gasket is slightly greater than the height from the second step to the top of the lower component; a flange is provided at the outer edge of the lower part of the storage tank, and threaded holes are provided at corresponding positions of the flange and the lower component.

[0015] Preferably, a ring-shaped distributed connecting plate is provided at the outer edge of the upper part of the liquid storage tank. A ring-shaped groove is provided on the connecting plate, and a matching ring-shaped sealing ring is provided in the groove. The material of the sealing ring is perfluoroether; the upper component is sealed in cooperation with the connecting plate and the ring-shaped silica gel pad, and the liquid storage tank and the upper component are connected by a quick-release clamp.

[0016] Preferably, the thickness of the small ring gasket is equivalent to the height from the upper end of the first step to the lower end of the second step. The inner diameters of the large ring gasket and the small ring gasket are the same. The lower end of the liquid outlet pipe is 1 - 2 cm away from the fiber-based catalytic membrane. The materials of the small ring gasket and the large ring gasket are perfluoroether, and the hardness is 75 - 90.

[0017] Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1. The present invention proposes a continuous phenol hydrogenation to cyclohexanone reaction device based on a fiber-based membrane reactor, which solves the problem that it is difficult to completely recover micro-nano particle catalysts in the continuous phenol hydrogenation process.

[0018] 2. The carbon nanofiber-based catalytic membrane prepared by the present invention has a rich pore structure and a high specific surface area to volume ratio, which can significantly improve the membrane flux, the loading of active components and the catalytic performance, and solves the problems of less content of active components per unit volume and poor permeability of catalytic membranes with underdeveloped pores.

[0019] 3. The present invention uses a flexible membrane material to buffer the impact force during the feeding process of liquids and gases. And through the designed membrane module, it is ensured that the flexible membrane material is not easily damaged during the clamping and application processes, thus guaranteeing the stability during the reaction process.

[0020] 4. During the process of the reaction liquid circulating and flowing in the device in the present invention, it is beneficial to the disturbance of hydrogen, increasing the gas-liquid phase contact. And the position where the catalytic membrane is clamped is close to hydrogen, so the stirring step can be omitted during the heterogeneous phenol hydrogenation process, saving energy and reducing emissions, and achieving the continuous, green and efficient preparation of cyclohexanone. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of the membrane reactor.

[0022] Figure 2 It is a schematic structural diagram of the lower component.

[0023] Figure 3 It is the result of the cyclic reaction.

[0024] Each reference numeral is: 1 lower component, 2 storage tank, 3 upper component, 4 feed inlet, 5 liquid outlet pipe, 6 hydrogen exhaust pipe, 7 pressure gauge. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] In order to be able to more clearly understand the above-mentioned objects, features and advantages of the present invention, the following further describes the present invention in conjunction with specific embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0026] Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the present invention is not limited by the limitations of the specific embodiments disclosed in the following specification.

[0027] Example 1 This embodiment presents the specific structure of a continuous phenol hydrogenation to cyclohexanone reaction device based on a fiber-based membrane reactor. It mainly includes three parts: a membrane reactor, a heating component (a water bath is used in this embodiment) for providing a constant temperature condition for the membrane reactor, and a power component for circulating the reaction materials. A constant flow pump, along with corresponding pipelines and valves, is used as the power component in this embodiment. The membrane reactor includes a lower component 1, a storage tank 2, and an upper component 3. The bottom of the lower component 1 has a certain thickness, with a feed port 4 opened on the side wall and integrally connected to the through hole on the lower bottom surface of the lower component 1 for feeding. A section of feed pipe can be welded at the position of the feed port 4 on the side of the lower component 1. During use, the feed pipe is connected to the outlet end of the constant flow pump through a joint. Above the bottom surface of the lower component 1, a circular first step and a second step are sequentially arranged. The width of the upper surface of the first step is greater than that of the upper surface of the second step, and the outer diameter of the first step is approximately equal to the inner diameter of the second step. A matching small circular gasket is arranged on the first step, and a matching large circular gasket is arranged on the second step. A matching small circular gasket is arranged on the first step. The small circular gasket is stuck inside the first step, and the upper end of the small circular gasket is basically flush with the lower part of the second step. A fiber-based catalytic membrane is arranged between the small circular gasket and the large circular gasket. The diameter of the fiber-based catalytic membrane needs to be greater than the inner diameter of the small circular gasket and less than or equal to the outer diameter of the large circular gasket. Another purpose of setting the first step is to keep a certain distance, about 2 mm, from the reaction liquid feed hole at the bottom to maintain the smoothness of feeding. The purpose of setting the second step is to place a perfluoroether small gasket to enable the flexible catalytic membrane to bear pressure well at the bottom and ensure it is not damaged during the reaction process. The main body of the storage tank 2 is a hollow cylindrical structure with openings at both the top and the bottom. A circular protrusion is arranged at the center of the lower part of the storage tank 2. The outer diameter of the circular protrusion is the same as the outer diameter of the large circular gasket, and the inner diameter of the circular protrusion is the same as the inner diameter of the large circular gasket. The outer diameter of the storage tank 2 can be designed according to the requirement of the material volume. In order to store more materials, the outer diameter of the storage tank 2 can be larger than the circular protrusion, and the wall thickness of the storage tank 2 can be appropriately thinned to facilitate better heat transfer. The sum of the height of the circular protrusion and the thickness of the large circular gasket is slightly greater than the height from the second step to the top of the lower component 1; a flange is arranged at the outer edge of the lower part of the storage tank 2. Threaded holes are arranged at the corresponding positions of the flange and the lower component 1. The thickness of the small circular gasket is equivalent to the height from the upper end of the first step to the lower end of the second step. The large circular gasket has the same inner diameter as the small circular gasket. The lower end of the liquid outlet pipe 5 is 1 - 2 cm away from the fiber-based catalytic membrane. The circular protrusion at the center of the lower part of the storage pipe 2 can press the large circular gasket to play a fixing role. Since the large circular gasket and the small circular gasket have a certain elasticity, the sum of the thickness of the large circular gasket and the thickness of the circular protrusion at the center of the storage tank 2 is slightly higher than the distance from the second step to the top plane of the lower component 1, which can ensure the sealing performance. The storage tank 2 and the lower component 1 are connected by a flange. Flanges and threaded holes are respectively arranged in a circular corresponding manner at the upper part of the lower component 1 and the bottom of the storage tank 2.The upper component 3 is a thin sheet - type upper cover structure. The upper component 3 and the storage tank 2 are fixedly connected by a quick - installation clamp. Two pipelines are arranged to pass through the upper component 3. The middle one has a larger cross - sectional area and serves as the liquid outlet pipe 5. The liquid outlet pipe 5 extends deep below the storage tank 2. Next to the liquid outlet pipe 5 is the exhaust pipe, which is relatively thin. The exhaust pipe is equipped with an exhaust valve (closed during the reaction process), and the exhaust pipe only communicates with the inner side of the upper wall surface of the upper component 3, that is, the top of the storage tank 2, to prevent liquid from being discharged along the exhaust pipe. A pressure gauge 7 is connected to the upper end of the liquid outlet pipe 5. The side of the liquid outlet pipe 5 is connected to the inlet end of a constant - flow pump through a bypass pipeline. The outlet of the constant - flow pump is connected to the feed port 4 of the lower component 1 through a feed pipeline. In this embodiment, the hydrogen feed pipe and the reaction liquid feed pipeline are gathered near the feed port 4 through joints and pipelines, and after gathering, they enter the membrane reactor from the feed port 4 on the side of the lower component 1 uniformly. An annular - distributed connecting plate is arranged on the outer edge of the upper part of the storage tank 2. The connecting plate, flange, annular protrusion and the storage tank are all of an integral structure. An annular groove is arranged on the connecting plate, and a matching annular sealing ring is arranged in the groove. The sealing ring has a certain elasticity, and the upper end of the sealing ring is higher than the upper edge of the groove. The material of the sealing ring is perfluoroether, and the hardness is 80. The upper component 3 is a cover - shaped thin - sheet structure and serves as the upper cover. A linear protrusion part can be arranged on the lower bottom surface of the upper component 3 to clamp the annular silica gel pad for sealing. The lower end of the liquid outlet pipe 5 is 1 - 2 cm away from the fiber - based catalytic membrane. In this embodiment, the small annular gasket and the large annular gasket are made of perfluoroether, and the hardness is 80.

[0028] In this embodiment, the fiber membrane used is a carbon nanofiber membrane, with a sheet - type configuration. The mass of a single - piece carbon nanofiber membrane is 0.010 g, and the effective area is 4.9 cm 2 , and the thickness is 120 nm (the average value is taken by random inspection after batch preparation). The preparation process is as follows: 1.5 g of zinc acetate and 3.2 mL of tetraethyl orthosilicate are completely dissolved in 22 mL of N,N - dimethylformamide, and then 3.5 g of polyacrylonitrile is added and stirred at 60 o °C for 8 h to obtain a uniform orange spinning solution, and the stirring rate is 40 rpm / min. The electrostatic voltage is set to 13.5 kV, the distance from the tip of the spinning needle to the receiver is 180 mm, the injection speed is set to 1.5 mL / h, and during the electrospinning process, the humidity and temperature are maintained at 36 - 38% and 25 - 28 o °C respectively. After electrospinning for 2 h, a precursor membrane is obtained. The precursor membrane is placed in a muffle furnace and calcined in an air atmosphere. The temperature is raised to 280 o °C at a rate of 2 o °C / min, and after holding for 2 h at the target temperature, it is naturally cooled to obtain a pre - oxidized nanofiber membrane. The pre - oxidized nanofiber membrane is placed in a tubular furnace and calcined in an argon (70 mL / min) atmosphere. The temperature is raised at a rate of 2 oRaise the temperature to 700 at a rate of C / min o C, keep it at the target temperature for 2 h, and then let it cool naturally to obtain the flexible carbon nanofiber membrane. Pour 5 mL of nitric acid and 15 mL of deionized water into a 50 mL round-bottom flask, stir manually with a glass rod for 2 min, place the flexible carbon nanofiber membrane at the bottom of the round-bottom flask, and etch it at 60 o C in a constant temperature water bath for 1 h. Rinse the membrane material repeatedly with deionized water until it is neutral for standby; add 2 g of NaOH and 20 mL of deionized water to a 50 mL round-bottom flask respectively, stir at 50 rpm / min for 15 min until completely dissolved. Place the membrane material at the bottom of the round-bottom flask, and etch it at 60 o C in a constant temperature water bath for 2 h. Rinse the membrane material repeatedly with deionized water until it is neutral, and place it in an oven at 70 o C and dry it for 12 h. Add 6 mg of palladium acetate and 15 mL of acetone to the round-bottom flask, stir at 40 rpm / min for 15 min to completely dissolve the palladium acetate, put the dried fiber membrane from the previous step into the solution, immerse it in a constant temperature water bath at 30 °C for 12 h. After the loading is completed, wash the membrane with acetone repeatedly 5 times, and place it in an oven at 70 o C and dry it for 1 h.

[0029] The working process is as follows: Stack and clamp 3 carbon nanofiber catalytic membranes with large and small gaskets, place them above the first step of the lower component 1, and use hexagon head screws to connect and fix the upper storage tank 2. Pour 9.2 mL of 1 wt% phenol-cyclohexane solution into the storage tank 2, place a sealing gasket in the groove above the storage tank 2, and use a quick-release clamp to connect and fix the upper component 3 to complete the assembly of the fiber-based membrane reactor. Connect each pipeline of the reaction solution to both ends of the pump respectively. First, introduce hydrogen until the pressure reaches 0.2 MPa, close the cut-off valve of the liquid outlet pipeline, open the hydrogen cut-off valve to discharge hydrogen, and complete the hydrogen replacement after repeating it five times. Then introduce hydrogen again to 0.2 MPa. Place the fiber-based membrane reactor in a constant temperature water bath, and the liquid level of the constant temperature water bath is higher than half of the storage tank to ensure the temperature of the reaction system in the fiber-based membrane reactor. Wait until the constant temperature water bath is heated to 80 oAfter C, start the constant flow pump and set the flow rate of the constant flow pump to 0.55 mL / h. Under the action of the constant flow pump, the reaction liquid circulates and is forced to pass through the fiber-based catalytic membrane. At this time, hydrogen in the membrane reactor serves as the hydrogen source, and phenol is adsorbed on the fiber-based catalytic membrane, and the one-step liquid-phase hydrogenation reaction of phenol begins. During the reaction process, the reaction liquid is forced to flow through the fiber-based catalytic membrane, enhancing the mass transfer between the reactant phenol and the catalytic membrane. At the same time, the agitation is increased to make hydrogen more easily contact the fiber catalytic membrane. After the reaction is completed, turn off the constant flow pump, the stop valve of the pump inlet pipeline, the stop valve of the pump outlet pipeline, and the constant temperature water bath in sequence. After the temperature of the constant temperature water bath drops to room temperature, open the hydrogen stop valve to discharge the remaining hydrogen in the fiber-based membrane reactor. Open the connection clamp between the upper component 3 and the storage tank 2, pour out the liquid in the storage tank 2, and obtain the product located in the storage tank 2. After testing, the phenol conversion rate obtained by continuously reacting for 25 h using the fiber-based catalytic membrane reactor is 84.6%, and the cyclohexanone selectivity is 91.7%.

[0030] After the reaction is completed, add 50 mL of fresh cyclohexane to the storage tank 2. After assembling the pipeline and components, start the water bath. When heated to 60 o C, start the constant flow pump, set the flow rate of the constant flow pump to 50 mL / h, and the time to 2 h, and repeat 3 times. Use cyclohexane to repeatedly wash and remove the impurities adsorbed on the fiber-based catalytic membrane. After the washing is completed, open the upper component 3, pour out the cyclohexane, and place the storage tank 2, the lower component 1, and the fiber-based catalytic membrane in an oven at 70 o C for drying for 5 h, and then perform the next reaction under the same conditions and operations as in this example. The reaction results of continuous cycling 5 times are shown in Figure 3 . From Figure 3 it can be seen that after five cycles of utilization, the phenol conversion rate is 80.6%, and the cyclohexanone selectivity is 92.1%. Therefore, the fiber-based membrane reactor can efficiently prepare cyclohexanone and has good reusability.

[0031] Comparative Example 1 The difference between this comparative example and Example 1 is that 10 ml of nitric acid and 10 mL of deionized water are poured into a 50 mL round-bottom flask for pickling and etching, and the rest of the conditions and operation processes remain the same. After continuously reacting for 25 h, collect the product in the storage tank 2. Use gas chromatography to analyze the liquid-phase product, and calculate that the phenol conversion rate is 47.3%, and the cyclohexanone selectivity is 96.3%. The reason is that excessive pickling and etching will cause the mechanical properties of the catalytic membrane to decline, making it difficult to withstand the impact force during the liquid and gas feeding processes and resulting in breakage, causing unstable catalytic performance.

[0032] Comparative Example 2 The difference between this comparative example and Example 1 is that a constant flow pump is not used to force the reaction solution to flow through the catalytic membrane. Instead, the catalytic membrane is placed in the fiber-based membrane reactor for static reaction, and the remaining conditions and operation processes are kept the same. After continuous reaction for 25 h, the product located in the storage tank 2 is collected. The liquid-phase product is analyzed by gas chromatography, and the calculated phenol conversion rate is 52.7%, and the cyclohexanone selectivity is 94.8%. The reason is that the mass transfer effect between the catalytic membrane and the reactants is poor under the static state.

[0033] Comparative Example 3 The difference between this comparative example and Example 1 is that zinc acetate and tetraethyl orthosilicate are not added to the spinning solution to prepare the carbon nanofiber catalytic membrane, and the remaining conditions and operation processes are kept the same. After continuous reaction for 25 h, the product located in the storage tank 2 is collected. The liquid-phase product is analyzed by gas chromatography, and the calculated phenol conversion rate is 35.2%, and the cyclohexanone selectivity is 97.8%. The reason is that the catalytic membrane is brittle and difficult to withstand the impact force during the liquid and gas feeding processes, resulting in damage and unstable catalytic performance.

[0034] Comparative Example 4 The difference between this comparative example and Example 1 is that the gasket material is nitrile rubber for all. After continuous reaction for 25 h, the product located in the storage tank 2 is collected. The liquid-phase product is analyzed by gas chromatography, and the calculated phenol conversion rate is 0.3%, and the cyclohexanone selectivity is 100%. The reason is that the cyclohexane solution causes sulfur to precipitate from the nitrile rubber gasket, deactivating the catalytic membrane Pd in the fiber catalytic membrane.

[0035] Comparative Example 5 The difference between this comparative example and Example 1 is that a perfluoroether gasket with a hardness of 60 is used. After continuous reaction for 25 h, the gasket is damaged, resulting in air leakage in the fiber-based membrane reactor and volatilization of cyclohexane, and the product cannot be obtained in the storage tank 2.

[0036] Comparative Example 6 The difference between this comparative example and Example 1 is that a batch reactor is used for the phenol hydrogenation reaction. The same number of catalytic membranes are directly placed at the bottom of the reaction kettle. Since they cannot be fixed in the reaction kettle, the phenol-cyclohexane solution with the same concentration and dosage is then poured in. A small rotor is placed above the catalytic membrane, and hydrogen is introduced after displacing hydrogen five times. The hydrogen pressure is 0.2 MPa, and the stirring speed is 80 rpm / min. The reaction temperature is set at 80 o °C. The catalytic membrane is damaged after continuous reaction for 1 h. The reason is that mechanical stirring will damage the fiber-based catalytic membrane, making it difficult to recycle and use again.

[0037] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention to other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A phenol hydrogenation to cyclohexanone reaction device based on a fiber-based membrane reactor, characterized in that, It includes a membrane reactor, a heating component for providing constant temperature conditions for the membrane reactor, and a power component for circulating the reaction materials. The membrane reactor includes a lower component, a storage tank, and an upper component. An inlet is provided on the side wall of the lower component, and the inlet communicates with the inner bottom surface of the lower component. Above the bottom surface of the lower component, a circular first step and a second step are sequentially arranged. The outer diameter of the first step is equivalent to the inner diameter of the second step. A matching small circular gasket is arranged on the first step, and a matching large circular gasket is arranged on the second step. A number of fiber-based catalytic membranes are arranged between the small circular gasket and the large circular gasket. The lower component communicates with the storage tank above. The storage tank is a hollow cylindrical structure. An upper component in the form of a thin sheet is arranged at the upper part of the storage tank. A liquid outlet pipe is arranged in the middle of the upper component. The top of the liquid outlet pipe is connected with a pressure gauge. The lower end of the liquid outlet pipe extends to the lower part of the storage tank. A liquid outlet pipe bypass for discharging materials is arranged below the pressure gauge. A hydrogen exhaust pipe is arranged on the side of the liquid outlet pipe, and the hydrogen exhaust pipe communicates with the top of the storage tank.

2. The phenol hydrogenation to cyclohexanone reaction device based on the fiber-based membrane reactor according to claim 1, characterized in that, The fiber-based catalytic membrane is prepared by the following steps: (1) Zinc acetate and tetraethyl orthosilicate are added to N,N-dimethylformamide, mixed evenly, and then polyacrylonitrile is added and mixed evenly to obtain a spinning solution; (2)Electrospinning the spinning solution under the conditions of humidity of 36 - 42% and temperature of 20 - 28 o °C, setting the electrospinning voltage to 13.5 - 15.5 kV, the distance from the tip of the spinning needle to the collector to be 140 - 210 mm, and setting the injection rate to 1.0 - 1.5 mL / h to obtain a precursor film; (3)Calcine the precursor film in an air atmosphere at a calcination temperature of 260 - 300 o °C to obtain a pre-oxidized nanofiber film; (4) Calcinate the pre-oxidized nanofiber membrane in an argon atmosphere at a calcination temperature of 700 - 800 o °C to obtain a flexible carbon nanofiber membrane; (5) The flexible carbon nanofiber membrane is placed in a nitric acid solution with a concentration of 25-38wt% and etched by heating for 1-2h for the first time. After the etching is completed, it is rinsed to neutral, and then added to a sodium hydroxide solution with a concentration of 6-11wt% and etched by heating for 1-2h for the second time. After the etching is completed, the membrane material is rinsed to neutral; (6) The active component Pd is loaded by wet impregnation.

3. The phenol hydrogenation to cyclohexanone reaction device based on a fiber-based membrane reactor according to claim 1, wherein, A circular protrusion is arranged at the center of the lower part of the storage tank. The outer diameter of the circular protrusion is the same as the outer diameter of the large circular gasket. The sum of the height of the circular protrusion and the thickness of the large circular gasket is slightly larger than the height from the second step to the top of the lower component. A flange is arranged on the outer edge of the lower part of the storage tank, and threaded holes are arranged at the corresponding positions of the flange and the lower component.

4. The phenol hydrogenation to cyclohexanone reaction device based on the fiber-based membrane reactor according to claim 1, characterized in that, Circularly distributed connecting plates are arranged on the outer edge of the upper part of the storage tank. Annular grooves are arranged on the connecting plates, and matching annular sealing rings are arranged in the grooves. The material of the sealing ring is perfluoroether. The upper component is sealed in cooperation with the connecting plates and the annular silica gel pad. The storage tank and the upper component are connected by a quick-release clamp.

5. The phenol hydrogenation to cyclohexanone reaction device based on a fiber-based membrane reactor according to claim 1, characterized in that, The thickness of the small circular gasket is equivalent to the height from the upper end of the first step to the lower end of the second step. The inner diameter of the large circular gasket is the same as that of the small circular gasket. The lower end of the liquid outlet pipe is 1-2 cm away from the fiber-based catalytic membrane. The materials of the small circular gasket and the large circular gasket are perfluoroether, and the hardness is 75-90.

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