Preparation device and method of catalyst for selectively synthesizing carbon nanotubes

Abstract

The invention relates to the technical field of preparation of catalysts for carbon nanotubes, and provides a preparation device and method for a catalyst for selective synthesis of carbon nanotubes, the device adopts a vertical layered design, and comprises a top feeding assembly, a middle multi-temperature-zone upper furnace body assembly and a bottom atomization lower furnace body assembly, the continuous operation of carrier feeding, active substance atomization loading, gradient calcination and particle size screening is realized through the synergistic effect of the annular feed opening, the inclined runner and the gravity grading discharge opening. According to the method, a dynamic correlation model of physical property parameters and process parameters is established, the feeding rate of the carrier is dynamically adjusted, the atomization pressure and the calcination time are regulated and controlled in real time, the limitation of traditional empirical value regulation and control is broken through, and the structural orderliness and the yield of the carbon nanotubes are remarkably improved. According to the invention, the problems of tedious flow, discrete particle size, complex tail gas and difficulty in continuous production in the traditional process are solved, and an efficient, environment-friendly and customizable solution is provided for industrial preparation of the carbon nanotubes.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation of carbon nanotubes, and in particular to a device and method for preparing a catalyst for selectively synthesizing carbon nanotubes. Background Art

[0002] Carbon is one of the most abundant elements in nature. Carbon atoms can form complex, cross-linked networks that are essential for organic chemistry and the existence of life. Carbon materials are unique, existing in nature in various forms from zero to three dimensions. Furthermore, carbon allotropes possess diverse physical and chemical properties. From the superhard material diamond to the soft material graphite, from the insulating material diamond to the semiconductor material graphite to the conductive material carbon nanotubes, carbon allotropes play a vital role. While carbon allotropes possess distinct structures and properties, one remarkable allotrope holds a unique and special place in the materials world: carbon nanotubes. Carbon nanotubes offer significant advantages in applications such as biosensors, lithium-ion batteries, drug delivery materials, and composite materials.

[0003] At present, the most critical part of preparing carbon nanotubes is still the structural control of the catalyst, and the key influencing point is the catalyst size. Therefore, various methods adopt the method of refining the catalyst. However, in the process of refining, complex steps and various equipment are required, and there are many instabilities. Only a single type of synthesis can be carried out, and it needs to be a separate process section, which greatly wastes the company's costs. The present invention is aimed at this problem and provides a reasonable and complete solution to help simplify, continuously and industrialize the preparation of carbon nanotubes.

[0004] Application publication number CN 116550323 A discloses a catalyst for preparing multi-walled carbon nanotubes. The carrier comprises polyvinyl pyrrolidone, indium nitrate, sodium hydroxide, and nitric acid, all of which are analytically pure reagents. The invention also relates to a method for preparing the catalyst. An FeO2N2 sample is prepared by calcining it in an NH3 atmosphere. The FeO2 is then prepared using a sol-gel method, ground, and calcined at 550°C in an NH3 atmosphere for 5 hours. The naturally cooled, pale yellow FeO2N2 powder is surface-treated with a mixed acid of hydrogen ions and nitrates. The active components are modified using aluminum oxide, magnesium oxide, ferric chloride, and magnesium aluminate to synthesize a highly active carbon nanotube catalyst. This method, a combination of sol-gel and structure control, can produce the desired carbon nanotube fractions, but the process is complex and requires a high level of preparation. Both the ammonia calcination and the acidification treatment pose significant safety and environmental risks, making it unsuitable for industrial production.

[0005] Application Publication No. CN 116135307 A discloses a method for preparing a carbon nanotube catalyst, comprising providing a catalyst support and an active metal salt solution; infiltrating and mixing the active metal salt solution with the catalyst support; passing an alkaline gas through the resulting mixture to deposit and age the active metal to prepare a catalyst precursor; and calcining, screening, and reducing the catalyst precursor to prepare a carbon nanotube catalyst. This method avoids solid-liquid separation and has the advantages of a short preparation cycle and high production efficiency. While this method enables the continuous preparation of the catalyst required for carbon nanotubes, it has numerous process limitations, making it difficult to scale up production, and has low production capacity, high impurities, and difficulty achieving uniformity between the various products. The method is more inclined towards a sealed co-precipitation method. The addition of alkaline gas complicates the exhaust gas composition and increases processing costs.

[0006] Existing methods usually use fixed empirical values ​​to control the feed rate, atomization pressure and calcination time, which leads to discrete particle size distribution, uneven active metal loading, damaged particle morphology and difficulty in continuous production of the device. Traditional devices need to complete carrier loading, calcination and screening in steps, and need to perform deposition, aging, calcination and other steps independently. The process is cumbersome and inefficient. Ammonia roasting and acid treatment produce complex tail gas, which increases the cost and safety risks of waste gas treatment. Alkaline gas deposition leads to complex components of the reaction system, which is difficult to scale up. Due to insufficient catalyst uniformity, the synthesized carbon nanotubes have structural disorder and low yield. The reason is that the parameter control is disconnected from the physical properties, and the atomization, calcination and screening links are separated, which cannot achieve continuous customized production. It is highly dependent on experience and lacks a quantitative model, resulting in poor process stability.

[0007] Therefore, it is of great significance to design a device and method for preparing a catalyst for selectively synthesizing carbon nanotubes to solve the above problems. Summary of the Invention

[0008] In order to solve the problems existing in the background technology, the present invention provides a device for preparing a catalyst for selectively synthesizing carbon nanotubes, which is provided with: The feeding assembly, located at the top of the device, includes: The feeding silo is used to store the carrier and is equipped with an agitator to prevent material accumulation; The motor has a power output connected to the screw feeder to control the carrier feeding rate; Screw feeder, the feed port is connected to the bottom of the feeding bin, and the discharge port is connected to the discharge port; There are 3-5 feeding ports, distributed in a circular pattern; The upper furnace assembly is arranged below the charging assembly and includes: The upper furnace body is connected to the discharge port at the top through an upper oblique opening, and is connected to the lower furnace body assembly at the bottom through a middle oblique opening; The heater wraps around the outer wall of the upper furnace body and provides zoned heating; Temperature sensors and temperature control sensors are installed on the furnace wall to monitor and control the temperature respectively; The upper discharge port, middle discharge port and lower discharge port are arranged at the bottom of the upper furnace body; Material level measurement points are distributed on the side wall of the upper furnace body to monitor the material height; The lower furnace body assembly is arranged below the upper furnace body and includes: The top of the lower furnace body is connected to the bottom of the upper furnace body through a middle bevel; Observation area, transparent window, set on the side wall of the lower furnace body; A lower bevel is provided at the bottom of the lower furnace body; Atomizing nozzle, installed at the lower bevel; The metering pump is connected to the atomizing nozzle through a delivery pipe.

[0009] In the preferred solution, the inclination angle of the middle oblique port is 45°–60°, guiding the mixed material to flow upward toward the furnace body; the inner diameters of the upper discharge port, the middle discharge port, and the lower discharge port decrease gradually, realizing gravity classification screening.

[0010] In the preferred solution, the heater is divided into zones with independent temperature control. The upper furnace body is divided into three temperature zones: 700°C in the upper section, 600°C in the middle section, and 500°C in the lower section. The atomization zone of the lower furnace body is 200°C. The distribution positions of the material level measurement points correspond to the three temperature zones of the upper furnace body.

[0011] In a preferred solution, the atomizing nozzle is equipped with a high-pressure gas-assisted structure, and the atomizing gas is air, nitrogen or argon; the observation area is made of high-temperature resistant quartz glass.

[0012] In a preferred solution, the upper discharge port is connected to a fine-particle catalyst delivery pipeline; the lower discharge port is connected to a coarse-particle catalyst delivery pipeline; the upper discharge port and the lower discharge port are sealed to the fluidized bed reactor through flanges.

[0013] The present invention provides a method for selectively synthesizing a catalyst for carbon nanotubes, comprising the following steps: S1, add the carrier to the feeding bin, inject the ferrocene ethanol solution into the liquid tank connected to the metering pump; set the catalyst particle size according to the target carbon nanotube type and carrier density ;based on and Calculating carrier feed rate ; S2: Purge the upper and lower furnace cavities with nitrogen at a pressure of 0.2–0.5 MPa for 5–10 minutes. After the leak test, set the heater zone temperatures as follows: 700°C for the upper section of the upper furnace; 600°C for the middle section; 500°C for the lower section; and 200°C for the atomization zone of the lower furnace. S3, start the motor to drive the screw feeder, The carrier is transported from the discharge port to the upper inclined port at a high speed; when the carrier reaches the lower furnace body after being detected by the material level measurement point, the metering pump and the atomizing nozzle are turned on; the atomization coverage status is monitored through the observation area; In step S4, the carrier loaded with active substances enters the upper furnace through the middle oblique port and is fluidized and calcined at the zone temperature for 1–4 minutes. After calcination, the particles follow the airflow into the upper, middle, and lower discharge ports, where they are screened by gravity classification. S5, transporting the catalyst from the upper discharge port or the lower discharge port to the fluidized bed to participate in the reaction of synthesizing carbon nanotubes.

[0014] In S1: add the carrier to the feeding bin, inject the ferrocene ethanol solution into the metering pump, start the motor to drive the screw feeder; control the carrier feeding rate according to the following formula: ; : carrier feed rate, unit: g / min; : adjustment coefficient, ranging from 0.05 to 0.12; : target catalyst particle size, unit: nm; : Carrier density, unit: g / cm³.

[0015] In S2: When the carrier enters the lower furnace through the discharge port, start the metering pump and the atomizing nozzle; monitor the coverage status through the observation area; and adjust the atomizing pressure according to the following formula: ; : Atomization pressure, unit: MPa; : natural logarithm operator; : carrier feed rate, unit: g / min; : Temperature of the upper section of the upper furnace, unit: °C; : Temperature of the lower section of the upper furnace body, unit: °C.

[0016] In S4, the formula for controlling the calcination time based on particle size and temperature difference is: ; : calcination time, unit min; : target catalyst particle size, unit: nm; : Upper furnace temperature difference, , unit: ℃.

[0017] The beneficial effects achieved by the present invention are: First, the present invention utilizes a vertically layered structure, integrating carrier loading, active material atomization loading, gradient calcination, and gravity screening within a single device. The coordinated design of an annular feed port and an inclined flow channel creates a continuous flow path for the material under the influence of gravity. Combined with the spatial arrangement of the atomizing nozzle and the multi-temperature zone furnace, this achieves a seamless transition from raw material to finished catalyst, transforming the traditional intermittent production model based on step-by-step operations. A single device can produce carbon nanotube catalysts of varying particle sizes and types, addressing the inefficiencies associated with switching between multiple devices.

[0018] Second, the present invention establishes a dynamic correlation model between physical and process parameters. This model mathematically correlates physical properties, such as target catalyst particle size and carrier density, with process parameters such as feed rate, atomization pressure, and calcination time, creating a closed-loop control mechanism. This model overcomes the limitations of traditional empirical control, ensuring that catalysts from different batches and specifications achieve a narrow particle size distribution, fundamentally addressing the structural disorder of carbon nanotubes caused by uneven active sites.

[0019] Third, this invention omits the ammonia roasting and acid treatment steps, instead employing an ethanol-based solution atomization loading process under an inert gas shield. This completely avoids the toxic gas emissions and use of highly corrosive reagents found in traditional methods. The device's fully sealed structure and simplified exhaust design eliminate the generation of complex waste gases at the source, significantly enhancing environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of a device for preparing a catalyst for selectively synthesizing carbon nanotubes according to the present invention; Figure 2 is a SEM image of multi-walled carbon nanotubes prepared in Example 1; Figure 3 This is the SEM image of the oligo-walled carbon nanotubes prepared in Example 2.

[0021] Numbers in the figure: 1. Feeding silo; 2. Agitator; 3. Motor; 4. Heater; 5. Temperature sensor; 6. Upper furnace body; 7. Lower furnace body; 8. Observation area; 9. Lower oblique port; 10. Metering pump; 11. Screw feeder; 12. Discharge port; 13. Upper discharge port; 14. Temperature control sensor; 15. Middle discharge port; 16. Lower discharge port; 17. Upper oblique port; 18. Middle oblique port; 19. Material level measurement point; 20. Atomizing nozzle. DETAILED DESCRIPTION

[0022] The technical solutions of the present invention will be described clearly and completely below in conjunction with the drawings in the present invention. In addition, the forms of the various structures described in the following embodiments are merely examples. The present invention is not limited to the various structures described in the following embodiments. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] Reference Figure 1-Figure 3 The present invention designs a preparation device for a catalyst for selectively synthesizing carbon nanotubes. The device adopts a vertical layered design and is provided with a top feeding assembly, including a feeding hopper 1 arranged at the top, in which an agitator 2 is installed to prevent the accumulation of carrier materials. The power output end of the motor 3 is connected to the screw feeder 11, and the carrier feed rate is precisely adjusted by controlling the screw speed. The feed port of the screw feeder 11 is connected to the bottom of the feeding hopper 1, and the discharge end extends to a ring-shaped discharge port 12, with a number of 3-5, to achieve uniform and dispersed material transportation. This design avoids blockage and improves feeding accuracy.

[0024] The middle upper furnace body assembly is located directly below the feeding assembly. The top of the upper furnace body 6 is connected to the discharge port 12 through an inclined upper bevel 17, and the bottom is connected to the lower furnace body 7 through a middle bevel 18 with an inclination of 45°-60°. This inclination design can guide the mixed material to flow upward. The outer wall of the upper furnace body is wrapped with a zoned heater 4 to provide independent temperature control capabilities; the furnace wall is embedded with a temperature sensor 5 and a temperature control sensor 14 to monitor and control the temperature in real time. The upper discharge port 13, the middle discharge port 15 and the lower discharge port 16 are set at the bottom of the furnace body, and their inner diameters decrease in a gradient, upper discharge port > middle discharge port > lower discharge port, and the catalyst particle size classification and screening is achieved by using gravity difference. The material level measurement points 19 distributed on the side wall correspond to the three temperature zone positions, and dynamically feedback the material height.

[0025] The lower furnace assembly is sealed to the upper furnace body 6 via a central bevel 18. An observation area 8 is provided on the sidewall of the lower furnace body 7, featuring a high-temperature resistant quartz glass window for monitoring the internal atomization state. An atomizing nozzle 20 is installed at the lower bevel 9 of the bottom. This nozzle features a high-pressure gas assist mechanism, with air, nitrogen, or argon as the gas of choice. This nozzle is connected to an external metering pump 10 via a delivery pipe, enabling precise atomization and spraying of the active solution. This design ensures uniform loading of the active material on the carrier surface.

[0026] The upper and lower discharge ports 13 and 16 are flange-connected to the fluidized bed reactor. The upper discharge port 13 delivers fine-particle catalyst to the array-type carbon nanotube synthesis system, while the lower discharge port 16 delivers coarse-particle catalyst to the multi-walled or oligo-walled carbon nanotube synthesis system. Heater 4 utilizes a zoned temperature control strategy, with three upper furnace temperature zones (700°C, 600°C, and 500°C) and a lower atomization zone at 200°C. This, combined with a gravity screening mechanism, allows for targeted regulation of catalyst particle size and activity.

[0027] The device forms a continuous and customizable catalyst production line through the material path of the feeding bin 1, screw feeder 11, discharge port 12, upper inclined port 17, atomization zone of the lower furnace body 7, middle inclined port 18, and calcination screening zone of the upper furnace body 6, in conjunction with the sensor network, including the temperature sensor 5, temperature control sensor 14, material level measurement point 19, and linkage control of the atomizing nozzle 20 of the metering pump 10.

[0028] The present invention designs a method for selectively synthesizing a carbon nanotube catalyst using the above-mentioned device, comprising the following steps:

[0029] S1, add the carrier to the feeding bin 1, and inject the ferrocene ethanol solution into the liquid tank connected to the metering pump 10; set the catalyst particle size according to the target carbon nanotube type. and carrier density ;based on and Calculating carrier feed rate In S1, the carrier is added to the feeding bin 1, the ferrocene ethanol solution is injected into the metering pump 10, and the motor 3 is started to drive the screw feeder 11; the carrier feed rate is controlled by the following formula: ; : carrier feed rate, unit: g / min; : adjustment coefficient, ranging from 0.05 to 0.12; : target catalyst particle size, unit: nm; : Carrier density, unit: g / cm³.

[0030] S2: Purge the upper furnace body 6 and the lower furnace body 7 with nitrogen at a pressure of 0.2–0.5 MPa for 5–10 minutes. After the sealing test, set the temperature of the four zones of the heater: 700°C for the upper section of the upper furnace body 6; 600°C for the middle section; 500°C for the lower section; and 200°C for the atomization zone of the lower furnace body 7. When the carrier enters the lower furnace body 7 through the discharge port 12, the metering pump 10 and the atomizing nozzle 20 are turned on; the coverage status is monitored through the observation area 8; and the atomizing pressure is adjusted according to the following formula: ; : Atomization pressure, unit: MPa; : natural logarithm operator; : carrier feed rate, unit: g / min; : Temperature of the upper section of the upper furnace body 6, unit: °C; : Temperature of the lower section of upper furnace body 6, unit: °C.

[0031] S3, start the motor 3 to drive the screw feeder 11, The carrier is transported to the upper inclined port 17 through the discharge port 12 at a certain speed; when the carrier reaches the lower furnace body 7 after being detected by the material level measurement point 19, the metering pump 10 and the atomizing nozzle 20 are turned on; the atomization coverage state is monitored through the observation area 8; In step S4, the carrier loaded with active substances enters the upper furnace body 6 through the middle oblique port 18 and is fluidized and calcined at the zoned temperature for 1–4 minutes. After calcination, the particles follow the airflow into the upper discharge port 13, the middle discharge port 15, and the lower discharge port 16, where they are screened by gravity classification. The formula for controlling the calcination time based on particle size and temperature difference is: ; : calcination time, unit min; : target catalyst particle size, unit: nm; : Upper furnace temperature difference, , unit: ℃.

[0032] S5, transporting the catalyst from the upper discharge port 13 or the lower discharge port 16 to the fluidized bed to participate in the reaction of synthesizing carbon nanotubes.

[0033] Example 1: This example uses a catalyst preparation device for selectively synthesizing carbon nanotubes to synthesize multi-walled carbon nanotube catalysts. The target product is multi-walled carbon nanotubes, corresponding to a coarse particle size catalyst. The device parameters are configured as follows: Carrier: Vermiculite density Active solution: nitrate mixture containing iron, nickel and molybdenum with a molar ratio of Fe:Ni:Mo = 5:3:2, target particle size Coarse particles, atomizing gas: nitrogen; The preparation process is as follows: Add the vermiculite carrier into the feeding bin 1 and start the agitator 2 to prevent accumulation.

[0034] According to the formula Pick , calculate the carrier feed rate: ; Motor 3 drives screw feeder 11, press The carrier is transported to the lower furnace body 7 through the annular discharge port 12 at a speed of 1.

[0035] When the material level measurement point 19 detects that the carrier has reached the lower furnace body 7 , the metering pump 10 and the atomizing nozzle 20 are turned on.

[0036] The nitrate solution was sprayed at a rate of 0.2 L / min, and the atomization pressure was dynamically adjusted according to the formula: ; The observation area 8 was used to confirm that the atomization evenly covered the support surface.

[0037] The carrier loaded with active substances enters the upper furnace body 6 through the middle oblique port 18 and is temperature-controlled in sections: 700°C for the upper section, 600°C for the middle section, and 500°C for the lower section.

[0038] The calcination time is calculated according to the formula: ; After calcination, the particles are classified by gravity, and the coarse particles >100 nm are discharged from the lower discharge port 16 and directly transported to the fluidized bed. The obtained multi-walled carbon nanotubes are as follows Figure 2 shown.

[0039] Example 2: This example is the preparation of oligo-walled carbon nanotube catalyst. The target product is oligo-walled carbon nanotube, corresponding to the fine particle size catalyst. The device parameter configuration is: Support: lamellar magnesium oxide density Active solution: ferrocene ethanol solution 3 g / L; Target particle size Fine particles; Atomizing gas: Argon; Preparation process: Add the lamellar magnesium oxide into the feeding bin 1 and calculate the feeding rate according to the formula: ; The carrier is transported at a low speed to ensure the integrity of the atomization coverage.

[0040] Dynamic control of atomization pressure: ; The ferrocene solution was atomized at 0.05 L / min to form a nanoscale active layer.

[0041] The upper furnace body maintains a high temperature gradient, calcination time: ; Fine particles are discharged from the upper discharge port 13 and transported to the CVD reactor. The obtained oligo-walled carbon nanotubes are as follows: Figure 3 shown.

[0042] Comparative Example 1: This comparative example is a control experiment of Example 2. The experimental conditions are: Support: lamellar magnesium oxide density , same as Example 2; active solution: ferrocene ethanol solution 3g / L, same as Example 2; target particle size: Same as Example 2; The difference from Example 2 is that the formula of Comparative Example 2 is not used to dynamically control the feed rate, atomization pressure and calcination time, but fixed empirical values ​​are used instead: Carrier feed rate: ; Atomization pressure: ; Calcination time: ; Other conditions are the same as those in Example 2, atomizing gas: argon; upper furnace temperature: upper , middle section , lower section ; Temperature of the atomization zone of the lower furnace: .

[0043] Table 1 Comparison of experimental results of Example 2 and Comparative Example 1

[0044]

[0045] Table 2 Experimental index description of Example 2 and Comparative Example 1

[0046]

[0047] As can be seen from Table 1, Comparative Example 1 did not follow the formula The feed rate is calculated, resulting in the accumulation of carriers in the lower furnace body and incomplete atomization coverage. The atomization pressure is fixed at , the droplet size is too large, and the active metal is locally agglomerated. Calcination time Excessive length leads to sintering of fine particles and insufficient decomposition of coarse particles, resulting in a reduced proportion of effective catalyst after screening. The number of carbon nanotube layers becomes discrete and defects increase, resulting in a 24% decrease in yield, demonstrating the necessity of the patented formula for precise control of active sites. This demonstrates that the present invention significantly improves catalyst uniformity and carbon nanotube selectivity by dynamically linking physical property parameters with process parameters.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A device for preparing a catalyst for selectively synthesizing carbon nanotubes, characterized in that: Its settings are: The feeding assembly, located at the top of the device, includes: The feeding silo is used to store the carrier and is equipped with an agitator to prevent material accumulation; The motor has a power output connected to the screw feeder to control the carrier feeding rate; Screw feeder, the feed port is connected to the bottom of the feeding bin, and the discharge port is connected to the discharge port; There are 3-5 feeding ports, distributed in a circular pattern; The upper furnace assembly is arranged below the charging assembly and includes: The upper furnace body is connected to the discharge port at the top through an upper oblique opening, and is connected to the lower furnace body assembly at the bottom through a middle oblique opening; The heater wraps around the outer wall of the upper furnace body and provides zoned heating; Temperature sensors and temperature control sensors are installed on the furnace wall to monitor and control the temperature respectively; The upper discharge port, middle discharge port and lower discharge port are arranged at the bottom of the upper furnace body; Material level measurement points are distributed on the side wall of the upper furnace body to monitor the material height; The lower furnace body assembly is arranged below the upper furnace body and includes: The top of the lower furnace body is connected to the bottom of the upper furnace body through a middle bevel; Observation area, transparent window, set on the side wall of the lower furnace body; A lower bevel is provided at the bottom of the lower furnace body; Atomizing nozzle, installed at the lower bevel; The metering pump is connected to the atomizing nozzle through a delivery pipe.

2. The device according to claim 1, wherein: The inclination angle of the middle oblique port is 45°–60°, guiding the mixed material to flow upwards into the furnace body; the inner diameters of the upper, middle and lower discharge ports decrease gradually, realizing gravity classification screening.

3. The device according to claim 1, wherein: The heater is divided into three temperature zones: the upper zone is 700°C, the middle zone is 600°C, and the lower zone is 500°C. The atomization zone of the lower furnace is 200°C. The material level measurement points are distributed in accordance with the three temperature zones of the upper furnace.

4. The device according to claim 1, wherein: The atomizing nozzle is equipped with a high-pressure gas-assisted structure, and the atomizing gas is air, nitrogen or argon; the observation area is made of high-temperature resistant quartz glass.

5. The device according to claim 1, wherein: The upper discharge port is connected to a fine-particle catalyst delivery pipeline; the lower discharge port is connected to a coarse-particle catalyst delivery pipeline; the upper discharge port and the lower discharge port are sealed and connected to the fluidized bed reactor through flanges.

6. A method for selectively synthesizing a catalyst for carbon nanotubes using the apparatus according to any one of claims 1 to 5, characterized in that: It includes the following steps: S1, add the carrier to the feeding bin, inject the ferrocene ethanol solution into the liquid tank connected to the metering pump; set the catalyst particle size according to the target carbon nanotube type and carrier density ;based on and Calculating carrier feed rate ; S2: Purge the upper and lower furnace cavities with nitrogen at a pressure of 0.2–0.5 MPa for 5–10 minutes. After the leak test, set the heater zone temperatures as follows: 700°C for the upper section of the upper furnace; 600°C for the middle section; 500°C for the lower section; and 200°C for the atomization zone of the lower furnace. S3, start the motor to drive the screw feeder, The carrier is transported from the discharge port to the upper inclined port at a high speed; when the carrier reaches the lower furnace body after being detected by the material level measurement point, the metering pump and the atomizing nozzle are turned on; the atomization coverage status is monitored through the observation area; In step S4, the carrier loaded with active substances enters the upper furnace through the middle oblique port and is fluidized and calcined at the zone temperature for 1–4 minutes. After calcination, the particles follow the airflow into the upper, middle, and lower discharge ports, where they are screened by gravity classification. S5, transporting the catalyst from the upper discharge port or the lower discharge port to the fluidized bed to participate in the reaction of synthesizing carbon nanotubes.

7. The method according to claim 6, wherein: In S1: Add the carrier to the feeding bin, inject the ferrocene ethanol solution into the metering pump, start the motor to drive the screw feeder; control the carrier feeding rate according to the following formula: ； : carrier feed rate, unit: g / min; : adjustment coefficient, ranging from 0.05 to 0.12; : target catalyst particle size, unit: nm; : Carrier density, unit: g / cm³.

8. The method according to claim 6, wherein: In S2: When the carrier enters the lower furnace through the discharge port, start the metering pump and atomizing nozzle; monitor the coverage status through the observation area; and adjust the atomizing pressure according to the following formula: ； : Atomization pressure, unit: MPa; : natural logarithm operator; : carrier feed rate, unit: g / min; : Temperature of the upper section of the upper furnace, unit: °C; : Temperature of the lower section of the upper furnace body, unit: °C.

9. The method according to claim 6, wherein: In S4, the formula for controlling the calcination time based on particle size and temperature difference is: ； : calcination time, unit min; : target catalyst particle size, unit: nm; : Upper furnace temperature difference, , unit: ℃.

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