Continuous industrial preparation method of fiber-loaded carbon nanotube

Abstract

The invention relates to the technical field of preparation of fiber-loaded carbon nanotubes, and provides a continuous industrial preparation method of fiber-loaded carbon nanotubes, which comprises the following steps: fiber purification treatment, fiber pulping and modification, catalyst loading in a processor, airflow crushing, gas replacement, fluidized bed reduction, carbon nanotube growth and product collection. By regulating and controlling the flow and the temperature field of the catalyst precursor in stages, the gradient uniform dispersion of the catalyst on the fiber surface layer is realized, and the fiber-CNT interface shear strength is improved; annular dispersion feeding, aerosol countercurrent mixing, partitioned temperature control calcination and gravity grading screening are integrated, gas phase atomization is used for replacing an impregnation method, metal-containing waste liquid is eliminated, and the catalyst utilization rate is increased; the method is compatible with substrates such as carbon fibers and glass fibers, is suitable for small-diameter high-conductivity or large-diameter high-strength customized products, and has the advantages of high efficiency, environmental protection and low energy consumption.

Description

Technical Field

[0001] The invention relates to the technical field of fiber-loaded carbon nanotube preparation, and in particular to a method for continuous industrialized preparation of fiber-loaded carbon nanotubes. Background Art

[0002] Carbon nanotubes, also known as buckytubes (CNTs), are one-dimensional quantum materials composed of single or multiple layers of graphene coiled around a central axis at a specific helical angle. The aspect ratio and carbon purity of carbon nanotubes, two key indicators of conductivity, directly determine their product performance. The thinner the diameter and the longer the length of the carbon nanotube, the better the conductivity.

[0003] The vapor deposition (CVD) method involves introducing hydrocarbons or carbon-containing oxides into a high-temperature device containing a catalyst, where they undergo catalytic decomposition to form carbon nanotubes. This production method is suitable for large-scale industrial production and primarily involves equipment such as horizontal reactors, fluidized bed reactors, and vertical reactors. With recent technological advances, more suitable equipment for CVD has been developed, and production equipment costs have decreased year by year. CVD has become the preferred process for industrial production of carbon nanotubes. However, it still suffers from the following key drawbacks: Existing impregnation methods often result in random catalyst distribution on the fiber surface and lack gradient control. Catalyst particles adhere only to the fiber surface and are unable to penetrate the micropores, resulting in low fiber-CNT interface shear strength. Furthermore, conventional processes cannot achieve uniform catalyst dispersion on the fiber surface, leading to uneven CNT growth and large fluctuations in aspect ratio. Existing equipment relies on tube furnaces for carrier fixation or plasma activation, making continuous feeding difficult. Existing technologies require carrier fixation at specific angles, resulting in poor equipment compatibility and limited production capacity. Batch production is subject to frequent interruptions during material transfer, and catalyst impregnation generates large amounts of heavy metal-containing wastewater, increasing environmental pressure. In conventional processes, purification, loading, and reaction stages in each unit operate independently, lacking system integration. Poor oxygen content control during the gas exchange stage leads to catalyst deactivation during the reduction phase. Low cooling efficiency during the reaction termination phase allows residual carbon source to easily form amorphous carbon. Furthermore, the inert gas is not recycled, resulting in high unit costs. Existing methods cannot grade catalyst-loaded fibers of varying particle sizes. Although existing technologies can grow CNTs on the surface of carbon fibers, they lack grading mechanisms such as gravity screening, making it difficult to customize production for either fine-diameter high-conductivity or large-diameter high-strength requirements.

[0004] Therefore, it is of great significance to design a method for continuous industrial preparation of fiber-loaded carbon nanotubes that solves the above problems. Summary of the Invention

[0005] To solve the problems existing in the background technology, the present invention provides a method for continuous industrial preparation of fiber-loaded carbon nanotubes, comprising the following steps: S1, fiber purification treatment: the fiber is treated in a high temperature, low pressure environment to remove the surface epoxy coating and pollutants; S2, fiber pulping and modification: the purified fiber is mixed with ethanol solvent and modifier by ball milling and then pulped; S3, loading the material into the processor; the slurry is transported to the storage tank at the upper end of the processor, and the catalyst precursor solution is added to the storage tank at the lower end of the processor; S4, loading catalyst: the fiber and catalyst precursor are mixed, adsorbed, dried, and calcined in the processor to load the catalyst active components on the fiber surface; S5, crushing: transporting the catalyst-loaded fiber material to a jet mill for simple crushing to avoid fiber agglomeration or entanglement; S6, gas replacement: replace the crushed material with an inert gas environment; S7, catalyst reduction: reducing the catalyst precursor metal into active metal nanoparticles by introducing a reducing gas into the fluidized bed reducer; S8, carbon nanotube growth; introducing a carbon source gas and a carrier gas into the fluidized bed reactor to complete the growth of fiber-supported carbon nanotubes; S9, terminate the reaction and cool; after stopping the carbon source gas, continue the carrier gas purge; S10, product collection and circulation; the material is transported to the storage tank and circulated for the next batch of production.

[0006] Furthermore, in S1, the fiber is carbon fiber or glass fiber; in S2, the modifier is PVP, i.e., polyvinyl pyrrolidone. After thorough mixing for 30 minutes, the modifier introduces functional groups to enhance the binding ability between the fiber surface and the catalyst.

[0007] Furthermore, the processor is provided with: The feeding assembly, located at the top of the device, includes: a feeding silo for storing carriers, which is equipped with an agitator to prevent material accumulation; a motor with a power output connected to a screw feeder to control the carrier feeding rate; a screw feeder with a feed port connected to the bottom of the feeding silo and a discharge port connected to a discharge port; the discharge ports are 3-5 in number and distributed in a ring. The upper furnace body assembly is located below the charging assembly and includes: an upper furnace body, the top of which is connected to the discharge port via an upper oblique opening, and the bottom is connected to the lower furnace body assembly via a middle oblique opening; a heater wrapping around the outer wall of the upper furnace body to provide zoned heating; a temperature sensor and a temperature control sensor installed on the furnace wall to monitor and control the temperature respectively; an upper discharge port, a middle discharge port, and a lower discharge port installed at the bottom of the upper furnace body; and material level measurement points distributed on the side walls 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 lower furnace body, the top of which is connected to the bottom of the upper furnace body through a middle oblique opening; an observation area with a transparent window arranged on the side wall of the lower furnace body; a lower oblique opening arranged at the bottom of the lower furnace body; an atomizing nozzle installed at the lower oblique opening; and a metering pump connected to the atomizing nozzle through a delivery pipe. The inclination angle of the middle bevel is 45°–60°, guiding the mixed material to flow upward into the furnace body; the inner diameters of the upper, middle, and lower discharge ports decrease gradually to achieve gravity-based grading and screening; 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.

[0008] Furthermore, the specific process of S4 includes: S41, fiber slurry feeding: The fiber slurry is evenly introduced into the upper furnace body of the processor through 3-5 feeding ports distributed in an annular manner on the processor; the slurry enters the lower furnace body through the upper inclined port with an angle of 45°-60°; S42, catalyst precursor atomization: The atomizing nozzle sprays the catalyst precursor solution and uses nitrogen gas high-pressure atomization to form micron-sized droplets; the atomization state is monitored in real time through a high-temperature resistant quartz observation area; S43, gas-solid mixing and graded reaction: Atomized droplets collide with fibers in a countercurrent flow in the lower furnace at 200°C, modifying the functional groups on the fiber surface to adsorb metal ions. The mixed material enters the upper furnace through a 45°-60° inclination. The temperature is raised and calcined in stages: the bottom stage is 200°C to completely evaporate the solvent and enhance physical adsorption; the middle stage is 300°C for pyrolysis to remove modifiers and ethanol residues; the upper stage is 400°C to decompose metal oxides into nano-active particles. S44, gravity classification output: the material is graded and output through the upper discharge port, the middle discharge port and the lower discharge port with decreasing inner diameter gradient: the upper discharge port with the largest inner diameter outputs fine-particle catalyst-loaded fibers, and the lower discharge port with the smallest inner diameter outputs coarse-particle catalyst-loaded fibers.

[0009] Furthermore, in S42 and S43, dynamic gradient load control is performed, and the specific process is as follows: H1: This is the initial infiltration stage. During this stage, the metering pump is adjusted so that the flow rate of the precursor solution is: ; : Real-time precursor flow; : Target basal concentration 5 g / L; : incremental concentration 0.5–1 g / L; : Fiber feed rate 200 g / min; ;The concentration of the storage liquid in the catalyst precursor storage tank; The furnace temperature is kept constant under control , promoting the catalyst to penetrate into the fiber micropores; H2: This is the gradient uniform dispersion stage, in which the precursor flow rate is reduced according to the exponential decay function: ; : attenuation amplitude coefficient; : Dynamic attenuation coefficient 0.05–0.1 s⁻¹; : exponential decay function starting from 30 s; Synchronously control the temperature of the upper furnace partition: ; :high Real-time temperature at : Maximum temperature difference 150℃; : Total height of upper furnace body; : time attenuation coefficient; The catalyst precursor is evenly dispersed on the fiber surface in a gradient manner.

[0010] H3: s is the stable calcination stage, during which the catalyst precursor flow rate is maintained at a fixed value; the temperature of the bottom section of the upper furnace is controlled at 200°C to completely evaporate the solvent and enhance physical adsorption; the temperature of the middle section is 300°C, and thermal decomposition is performed to remove the modifier and ethanol residues; the temperature of the upper section is 400°C, and the metal oxides are decomposed into nano-active particles.

[0011] Furthermore, the specific process of S5 includes: The catalyst-loaded fiber material is introduced into the air flow crushing equipment through a pneumatic conveying system and crushed for 3-5 minutes under the conditions of a pressure of 0.5-0.8 MPa and an air flow velocity of 80-120 m / s; the particle size of the material after crushing is controlled at 100-500 μm to prevent the fibers from entanglement and agglomeration.

[0012] Furthermore, the specific process of S6 includes: S61, after crushing, the material is transported to the displacement tank and first evacuated to an absolute pressure of <10 kPa; S62, nitrogen is introduced to normal pressure, and the vacuum-filling-nitrogen operation is repeated three times; S63, maintain the oxygen content in the tank <50 ppm and the temperature at 40-60℃.

[0013] Furthermore, the specific process of S7 includes: S71, the replaced material is quantitatively transported to the fluidized bed reducer at a rate of 1000 g / batch; S72, introduce a mixture of hydrogen and nitrogen with a total flow rate of 60 L / min; S73, reducing the metal oxides to nano-metal particles at 450±50°C for 10 minutes.

[0014] Furthermore, the specific process of S9 includes: after cutting off the propylene supply, maintaining the nitrogen purge flow rate at 100 L / min for 5 minutes to reduce the material temperature from 750°C to below 300°C.

[0015] Furthermore, the specific process of S10 includes: conveying the cooled material to an intermediate tank under a positive pressure of 0.1-0.3 MPa; spraying an inert cooling medium into the intermediate tank and cooling it to room temperature within 10 minutes.

[0016] The beneficial effects achieved by the present invention are: First, the present invention designs a scheme for regulating catalyst loading in stages. In the initial penetration stage, high-pressure atomization combined with a low-temperature environment is used to promote the deep penetration of the catalyst precursor into the fiber micropores; in the gradient uniform dispersion stage, the precursor flow is dynamically reduced through an exponential decay function, and a sinusoidal temperature field is superimposed to control the catalyst so that the catalyst is evenly dispersed on the fiber surface; finally, in the stable calcination stage, the zoned temperature control is used to achieve a step-by-step transformation of solvent evaporation, organic matter pyrolysis and metal oxide decomposition, which significantly enhances the bonding force between the fiber and the carbon nanotubes and improves the interface bonding strength.

[0017] Second, the present invention has designed a vertical continuous processor that integrates four functional modules: annular dispersed feeding, aerosol countercurrent mixing, zoned temperature-controlled calcination, and gravity grading screening. The annular discharge port and the atomizing nozzle form a countercurrent contact zone to enhance the gas-solid mass transfer efficiency; the upper furnace body has a three-section independent temperature control system, including an evaporation zone, a pyrolysis zone, and a calcination zone, to achieve precise control of the phase change and chemical reaction of the material; the gradient inner diameter discharge port separates loaded fibers of different particle sizes based on the principle of gravity screening, replacing the impregnation method with gas phase atomization loading to completely eliminate pollution from metal-containing waste liquid; the gravity grading output provides a physical carrier for customized catalyst loading, meeting the needs of differentiated products such as fine diameter high conductivity or coarse diameter high strength.

[0018] Third, the present invention designs a closed production line with a processor as the core, integrating airflow milling, gas displacement, and a fluidized bed reactor in series. Pneumatic conveying enables seamless material transfer; the fluidized bed reactor utilizes segmented gas programming and temperature ramp control; inert gas is recycled in a closed loop during the displacement, reduction, and purge stages, eliminating interruptions and losses in batch production and enabling industrial continuous operation. The equipment is also collaboratively designed to be compatible with multiple substrates, including carbon fiber and glass fiber, breaking through the limitations of traditional processes on carrier types.

[0019] Fourth, the present invention adopts a gas-phase atomization process to eradicate heavy metal wastewater produced by the impregnation method, performs three vacuum-evacuation and nitrogen-filling operations on the displacement tank to reduce the oxygen content, and recycles the nitrogen in the reduction and growth stages; a large-flow nitrogen purge in the reaction termination stage simultaneously achieves cooling and removal of residual carbon sources, thereby eliminating catalyst metal pollution and organic waste gas emissions from the source, and meeting green manufacturing standards; the gas circulation and efficient mass transfer design reduce the unit consumption of raw materials and energy, and improve economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a flow chart of a method for continuous industrial preparation of fiber-supported carbon nanotubes; Figure 2 is an SEM image of carbon fiber loaded with carbon nanotubes prepared in Example 1; Figure 3 is an SEM image of carbon fiber loaded with carbon nanotubes prepared in Example 2; Figure 4 is an SEM image of glass fiber-loaded carbon nanotubes prepared in Example 3; Figure 5 It is a structural schematic diagram of the reactor designed by the present invention.

[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 5 This embodiment provides a method for the continuous industrial preparation of fiber-loaded carbon nanotubes, comprising the following steps: S1, fiber purification treatment; the fiber is treated in a high temperature, low pressure environment to remove the surface epoxy coating and pollutants; in S1, the fiber is carbon fiber or glass fiber.

[0024] S2, fiber pulping and modification; the purified fiber is mixed with ethanol solvent and modifier by ball milling and then pulped; the modifier in S2 is PVP, i.e. polyvinyl pyrrolidone, which is fully mixed for 30 minutes to introduce functional groups into the modifier to enhance the binding ability between the fiber surface and the catalyst.

[0025] S3, loading the material into the processor; the slurry is transported to the storage tank at the upper end of the processor, and the catalyst precursor solution is added to the storage tank at the lower end of the processor; S4, loading catalyst: The fiber and catalyst precursor are mixed, adsorbed, dried, and calcined in the processor to load the catalyst active components on the fiber surface. The specific process of S4 includes: S41, fiber slurry feeding: The fiber slurry is uniformly introduced into the upper furnace body 6 of the processor through 3-5 feeding ports 12 distributed in an annular manner on the processor; the slurry enters the lower furnace body 7 through the upper inclined port 17 with an inclination angle of 45°-60°; S42, catalyst precursor atomization: the atomizing nozzle 20 sprays the catalyst precursor solution and uses nitrogen gas high-pressure atomization to form micron-sized droplets; the atomization state is monitored in real time through the high-temperature resistant quartz observation area 8; S43, gas-solid mixing and graded reaction: Atomized droplets collide with fibers in a countercurrent flow in the lower furnace body 7 at 200°C, causing functional groups on the modified fiber surface to adsorb metal ions. The mixed material enters the upper furnace body 6 through the middle oblique port 18 at a 45°-60° angle, where it is heated and calcined in stages: the bottom section is at 200°C to completely evaporate the solvent and enhance physical adsorption; the middle section is at 300°C for pyrolysis to remove the modifier and ethanol residue; and the upper section is at 400°C to decompose the metal oxide into nano-active particles. S44, gravity classification output: the material is graded and output through the upper discharge port 13, the middle discharge port 15 and the lower discharge port 16 with decreasing inner diameter gradient: the upper discharge port with the largest inner diameter outputs fine-particle catalyst-loaded fibers, and the lower discharge port with the smallest inner diameter outputs coarse-particle catalyst-loaded fibers.

[0026] In S42 and S43, dynamic gradient load control is performed, and the specific process is as follows: H1: This is the initial infiltration stage. In this stage, the metering pump 10 is adjusted so that the flow rate of the precursor solution is: ; : Real-time precursor flow rate L / min; : Target basal concentration 5 g / L; : incremental concentration 0.5–1 g / L; : Fiber feed rate 200 g / min; ;The concentration of the storage liquid in the catalyst precursor storage tank; The temperature of the furnace body 7 is kept constant under control. , promoting the catalyst to penetrate into the fiber micropores; H2: This is the gradient uniform dispersion stage, in which the precursor flow rate is reduced according to the exponential decay function: ; : Attenuation amplitude coefficient 0.4–0.6; : Dynamic attenuation coefficient 0.05–0.1 s⁻¹; : exponential decay function starting from 30 s; Synchronously control the temperature of the 6 zones of the upper furnace: ; :high Real-time temperature at ℃; : Maximum temperature difference 150℃; : Total height of upper furnace body m; : time decay coefficient 0.02–0.05 s⁻¹; The catalyst precursor is evenly dispersed on the fiber surface in a gradient manner.

[0027] H3: s is the stable calcination stage, during which the catalyst precursor flow rate is maintained at a fixed value; the temperature of the bottom section of the upper furnace body 6 is controlled at 200°C to completely evaporate the solvent and enhance physical adsorption; the temperature of the middle section is 300°C, and thermal decomposition is performed to remove the modifier and ethanol residues; the temperature of the upper section is 400°C, and the metal oxide is decomposed into nano-active particles.

[0028] exist In the initial penetration stage, high flow Spraying, combined with low temperature, allows the catalyst to penetrate into the fiber micropores.

[0029] exist In the gradient uniform dispersion stage, the flow rate is reduced according to the exponential decay function, and the Increase the temperature to make the surface catalyst gradient evenly dispersed.

[0030] exist s is the stable calcination stage, which maintains a fixed flow rate and high temperature to complete external calcination.

[0031] S5, crushing; the catalyst-loaded fiber material is transported to the air flow milling equipment for simple crushing to prevent the fibers from clumping or entanglement; the specific process of S5 includes: introducing the catalyst-loaded fiber material into the air flow milling equipment through a pneumatic conveying system, and crushing it for 3-5 minutes under the conditions of a pressure of 0.5-0.8 MPa and an air flow velocity of 80-120 m / s; after crushing, the particle size of the material is controlled at 100-500 μm to prevent the fibers from entanglement and agglomeration.

[0032] S6, gas replacement: replace the crushed material with an inert gas environment; the specific process of S6 includes: S61, after crushing, the material is transported to the displacement tank and first evacuated to an absolute pressure of <10 kPa; S62, nitrogen is introduced to normal pressure, and the vacuum-filling-nitrogen operation is repeated three times; S63, maintain the oxygen content in the tank <50 ppm and the temperature at 40-60℃.

[0033] S7, catalyst reduction: reducing gas is introduced into the fluidized bed reducer to reduce the catalyst precursor metal into active metal nanoparticles. The specific process of S7 includes: S71, the replaced material is quantitatively transported to the fluidized bed reducer at a rate of 1000 g / batch; S72, introduce a mixture of hydrogen and nitrogen with a total flow rate of 60 L / min; S73, reducing the metal oxides to nano-metal particles at 450±50°C for 10 minutes.

[0034] S8, carbon nanotube growth; introducing carbon source gas and carrier gas into the fluidized bed reactor; the specific process of S8 includes: S81, material transfer and preheating: The reduced active metal nanoparticle-loaded fiber material is transported to the fluidized bed reactor at a constant rate; nitrogen is introduced as a carrier gas, and the reactor temperature is uniformly increased from 450°C to 650°C within 5 minutes to complete the material preheating.

[0035] S82, segmented gas programmed growth, specific indicators are shown in Table 1.

[0036] Table 1 Growth indexes of fiber-supported carbon nanotubes in a fluidized bed reactor

[0037] Time (min) Nitrogen flow rate (L / min) Propylene flow rate (L / min) Temperature (℃) effect 0–5 100 0 650 Preheating stability 5–15 70 30 750 Main growth period 15–20 80 20 700 Morphology control

[0038] The carbon source was disabled during the initial growth phase to avoid localized overheating. During the main growth phase, the propylene content was maintained at 30 vol% to promote rapid carbon nanotube growth. The propylene content was reduced to 20 vol% during the final phase to minimize amorphous carbon formation. The temperature during the main growth phase was maintained at 750°C to optimize carbon deposition rate, and the temperature was lowered to 700°C during the final phase to stabilize the nanotube diameter. The gas velocity was maintained at 0.3–0.5 m / s to ensure adequate fluidization and dispersion of the fibers.

[0039] S9, terminate the reaction and cool; after stopping the carbon source gas, continue the carrier gas purge; the specific process of S9 includes: after cutting off the propylene supply, maintain the nitrogen purge flow rate of 100 L / min for 5 minutes to reduce the material temperature from 750°C to below 300°C.

[0040] S10, product collection and recycling: the material is transported to a storage tank and recycled for the next batch of production. The specific process of S10 includes: after cooling, the material is transported to an intermediate tank under a positive pressure of 0.1-0.3 MPa; an inert cooling medium is sprayed into the intermediate tank, cooling it to room temperature within 10 minutes.

[0041] The processor designed by the present invention includes: The feeding assembly, located at the top of the device, includes: a feeding silo 1 for storing carriers, which is equipped with an agitator 2 to prevent material accumulation; a motor 3, whose power output end is connected to a screw feeder 11 to control the carrier feeding rate; a screw feeder 11, whose feed port is connected to the bottom of the feeding silo 1 and whose discharge port is connected to a discharge port 12; the discharge ports 12 are 3-5 in number and distributed in a ring shape; The upper furnace body 6 assembly is arranged below the charging assembly and includes: the upper furnace body 6, the top of which is connected to the discharge port 12 through the upper oblique port 17, and the bottom is connected to the lower furnace body 7 assembly through the middle oblique port 18; the heater 4, which wraps the outer wall of the upper furnace body 6 to provide zoned heating; the temperature sensor 5 and the temperature control sensor 14, which are arranged on the furnace wall to monitor and control the temperature respectively; the upper discharge port 13, the middle discharge port 15, and the lower discharge port 16, which are arranged at the bottom of the upper furnace body 6; and the material level measurement points 19, which are distributed on the side walls of the upper furnace body 6 to monitor the material height. The lower furnace body 7 assembly is arranged below the upper furnace body 6 and includes: the lower furnace body 7, the top of which is connected to the bottom of the upper furnace body 6 through the middle bevel 18; the observation area 8, which is a transparent window, is arranged on the side wall of the lower furnace body 7; the lower bevel 9 is arranged at the bottom of the lower furnace body 7; the atomizing nozzle 20 is installed at the lower bevel 9; and the metering pump 10 is connected to the atomizing nozzle 20 through a delivery pipe. The inclination angle of the middle bevel 18 is 45°-60°, guiding the mixed material to flow toward the upper furnace body 6; the inner diameters of the upper discharge port 13, the middle discharge port 15, and the lower discharge port 16 decrease gradually to achieve gravity classification screening; the atomizing nozzle 20 is equipped with a high-pressure gas auxiliary structure, and the atomizing gas is air, nitrogen or argon; the observation area 8 is made of high-temperature resistant quartz glass.

[0042] The feeding components of the annular discharge port 12 and the screw feeder 11 ensure uniform dispersion of the fiber slurry to avoid clogging; the metering pump 10, the high-pressure atomizing nozzle 20, and the atomizing component of the quartz observation area 8 realize the injection of micron-level droplets of the catalyst precursor, thereby improving the gas-solid contact efficiency; the temperature zoning system realizes three-section independent temperature control of the upper furnace body 6, and cooperates with the gravity classification outlet to make the material undergo evaporation at 200°C, pyrolysis at 300°C, and calcination at 400°C in sequence, and simultaneously screen fine and coarse particle size catalyst-loaded fibers; the inclination design of the middle oblique port at 1845°-60° guides countercurrent mixing and enhances catalyst adsorption; the processor designed in the present invention completely eliminates the pollution of the waste liquid of the impregnation method, forms a vertical continuous production line, significantly improves the catalyst loading efficiency, and the graded output provides a basis for the regulation of carbon nanotube morphology.

[0043] Example 1: In this example, the fiber is carbon fiber, and the catalyst precursor is ferrocene ethanol solution; the specific implementation process is as follows: The carbon fibers were placed in a high-temperature crucible and purified for 300 minutes at 1800°C and <100Pa to remove the epoxy coating and contaminants on the surface. 1500g of the purified carbon fibers were mixed with 1500g of ethanol, and 20g of polyvinylpyrrolidone (PVP) was added. The mixture was ball-milled for 30 minutes to form a slurry. The slurry was transferred to the upper storage tank of the processor, while 2L of a 5g / L ferrocene ethanol solution was added to the lower storage tank. The processor was heated in stages: 400°C in the upper section, 300°C in the middle section, and 200°C in the bottom section. The fiber slurry was fed at 200g / min, and the catalyst precursor was atomized and sprayed in at 0.1L / min, supplemented by a 10L / min nitrogen flow. Using a dynamic gradient model, an effective concentration of 6g / L was achieved at an initial flow rate of 0.15L / min for 30s, followed by an exponential decay to 0.05L / min over the next 60s, achieving a gradient loading of the catalyst. The loaded material was pulverized by airflow at a pressure of 0.7 MPa and a flow rate of 100 m / s for 4 minutes, reducing it to a particle size of 300 μm. The material was then vacuumed and replaced with nitrogen three times. After replacement, 1000 g of the material was reduced in a fluidized bed reducer at 450°C and 60 L / min of hydrogen for 10 minutes. The fluidized bed reactor was then preheated to 650°C with 100 L / min of nitrogen for 0-5 minutes. Carbon nanotubes were grown at 750°C with 70 L / min of nitrogen and 30 L / min of propylene for 5-15 minutes. Morphology was then controlled at 700°C with 80 L / min of nitrogen and 20 L / min of propylene for 15-20 minutes. After the reaction is completed, propylene is cut off and nitrogen is purged at 100 L / min for 5 minutes to reduce the temperature to 250°C. Finally, the mixture is transported to an intermediate tank under a positive pressure of 0.2 MPa and sprayed with nitrogen to cool to room temperature. The aspect ratio of carbon fiber-supported carbon nanotubes is measured to be about 1000, and the fiber-CNT interface shear strength is 51.2 MPa. Figure 2 , Figure 2(a) and (b) are images obtained at different point locations, and (c) and (b) are images obtained at different magnifications at the same point location. Figure 2 It can be seen that the carbon fibers loaded with carbon nanotubes prepared in this embodiment have good uniformity.

[0044] Example 2. In this example, the fiber is a carbon fiber, and the catalyst precursor is a nickelocene ethanol solution; the specific implementation process is as follows: the carbon fiber purification parameters are the same as in Example 1. 1.3wt% PVP modifier is added during pulping. The catalyst is changed to 5g / L nickelocene ethanol solution, and the flow program of the processor load stage remains unchanged. The reduction and growth process are the same as in Example 1, but the temperature during the main growth period is adjusted to 730°C to adapt to the characteristics of the nickel catalyst. The final product, carbon fiber-loaded carbon nanotubes, presents a multi-walled structure with a thicker tube diameter, an aspect ratio reduced to 600-800, and an interfacial shear strength of 49.8MPa. Figure 3 . Figure 3 (a) and (b) are images obtained at different point locations, and (c) and (b) are images obtained at different magnifications at the same point location. Figure 3 It can be seen that the carbon fibers loaded with carbon nanotubes prepared in this embodiment have good uniformity.

[0045] Example 3. In this example, the fiber is glass fiber, and the catalyst precursor is ferrocene ethanol solution; the specific implementation process is as follows: the glass fiber is chemically cleaned and soaked in 10% hydrochloric acid for 30 minutes instead of high-temperature purification. The mass ratio of ethanol to fiber during pulping is 1:1, and the amount of PVP added is increased to 25g to enhance surface modification. The processor loading stage uses the same ferrocene solution and gradient model as in Example 1. Due to the low heat resistance of glass fiber, the reduction temperature is reduced to 400°C, and the maximum temperature in the growth stage is limited to 700°C, 0-5min 650°C; 5-15min 700°C; 15-20min 680°C. The obtained glass fiber-loaded carbon nanotubes have an aspect ratio of about 800 and an interfacial shear strength of 43.7MPa, indicating that the method of the present invention is also applicable to the preparation of non-carbon-based fiber-loaded carbon nanotubes, such as Figure 4 . Figure 4 (a) and (b) are images obtained at different point locations, and (c) and (b) are images obtained at different magnifications at the same point location. Figure 4 It can be seen that the glass fiber loaded carbon nanotubes prepared in this embodiment has good uniformity.

[0046] Comparative Example 1: In this comparative example, the fiber type was carbon fiber (same as in Example 1), and the catalyst precursor was ferrocene ethanol solution (same as in Example 1). All other conditions were the same as in Example 1, except that in S4, gradient control was not used, and constant parameters were used instead. The precursor flow rate was constant at 0.1 L / min. The processor temperature was kept constant at 400°C, and the staged temperature increase and gradient loading model were omitted. All other steps were identical to those in Example 1.

[0047] Table 2 Comparison of experimental indicators between the comparative example and examples 1, 2 and 3

[0048] index Comparative Example 1 Example 1 Example 2 Example 3 Fiber-CNT interface shear strength 32.5 MPa 51.2 MPa 49.8 MPa 43.7 MPa Catalyst utilization 82% 95% 93% 90% Aspect ratio of carbon nanotubes 650 1000 800 800 Pipe diameter uniformity ±25% ±8% ±12% ±10%

[0049] In Table 2, fiber-CNT interface shear strength refers to the bond strength between carbon nanotubes and the fiber matrix, expressed in MPa, reflecting the strength of the interfacial bonding force; catalyst utilization indicates the percentage of catalyst actually participating in CNT growth out of the total added amount, expressed as a percentage, characterizing the catalyst loading efficiency; carbon nanotube aspect ratio is the ratio of CNT length to diameter, used to measure the morphological quality of the CNT; the higher the ratio, the better the conductivity; tube diameter uniformity refers to the consistency of CNT diameter, expressed as the percentage of standard deviation to the mean; the smaller the value, the higher the uniformity. The experimental process of Table 2 is as follows: 1. Experimental method for fiber-CNT interface shear strength test: Fiber-CNT composite strips were prepared and short beam shear tests were performed in a universal material testing machine. Loading rate: 1 mm / min; calculation formula: ;in is the maximum load, is the specimen width, For thickness.

[0050] 2. Catalyst Utilization Test Method: Collect the residual catalyst wastewater and loaded fibers after the reaction. Digest the fiber sample with concentrated nitric acid to extract the metal catalyst that did not participate in the reaction. Measure the metal ion concentration using inductively coupled plasma optical emission spectrometry (ICP-OES). .

[0051] 3. Experimental method for carbon nanotube aspect ratio: Disperse CNT-loaded fibers in ethanol and ultrasonicate for 10 minutes. Observe the macroscopic morphology of CNTs using a scanning electron microscope. Measure the diameter of a single CNT using a transmission electron microscope. Randomly select 50 CNTs and measure their length ( ) and diameter ( ). Aspect ratio = .

[0052] 4. Experimental method for tube diameter uniformity: SEM captures high-resolution images with multiple fields of view. Measure the diameters of 100 CNTs using software. .

[0053] As shown in Table 2, the use of dynamic gradient loading control increased the fiber-CNT interface shear strength from 32.5 MPa to 51.2 MPa and 43.7 MPa, an increase of over 57%. Catalyst utilization increased from 82% to 95%, reducing wastewater pollution and raw material costs. The aspect ratio of carbon nanotubes increased from 650 to 1000, and the diameter uniformity was optimized from ±25% to ±8%, indicating significant improvements in CNT conductivity and structural consistency.

[0054] The key indicator analysis of Example 2 and Example 3 shows that the present invention achieves a gradient uniform dispersion of the catalyst on the fiber surface through a three-step gradient loading combined with zoned temperature control, solves the problem of uneven loading in the traditional impregnation method, greatly improves the interface shear strength, and simultaneously optimizes the CNT aspect ratio and uniformity. The gas phase atomization loading completely eliminates the impregnation waste liquid, and the catalyst utilization rate is improved. The seamless series connection of the processor, fluidized bed and pneumatic conveying system of the present invention realizes feed-output closed-loop production with high batch processing capacity. The graded screening outlet can separate catalyst-loaded fibers of different particle sizes, providing a technical basis for customized CNT morphology and meeting diversified application needs. The present invention solves the key bottlenecks of environmental protection and industrial efficiency while improving product performance through the collaborative innovation of gradient load control and continuous equipment, and provides a technical paradigm for the large-scale application of fiber-loaded CNTs.

[0055] 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 method for the continuous industrial preparation of fiber-loaded carbon nanotubes, characterized in that: The steps include: S1, fiber purification treatment: the fiber is treated in a high temperature, low pressure environment to remove the surface epoxy coating and pollutants; S2, fiber pulping and modification: the purified fiber is mixed with ethanol solvent and modifier by ball milling and then pulped; S3, loading the material into the processor; the slurry is transported to the storage tank at the upper end of the processor, and the catalyst precursor solution is added to the storage tank at the lower end of the processor; S4, loading catalyst: the fiber and catalyst precursor are mixed, adsorbed, dried, and calcined in the processor to load the catalyst active components on the fiber surface; S5, crushing: transporting the catalyst-loaded fiber material to a jet mill for simple crushing to avoid fiber agglomeration or entanglement; S6, gas replacement: replace the crushed material with an inert gas environment; S7, catalyst reduction: reducing the catalyst precursor metal into active metal nanoparticles by introducing a reducing gas into the fluidized bed reducer; S8, carbon nanotube growth; introducing a carbon source gas and a carrier gas into the fluidized bed reactor to complete the growth of fiber-supported carbon nanotubes; S9, terminate the reaction and cool; after stopping the carbon source gas, continue the carrier gas purge; S10, product collection and circulation; the material is transported to the storage tank and circulated for the next batch of production.

2. The method according to claim 1, characterized in that In S1, the fiber is carbon fiber or glass fiber; in S2, the modifier is PVP, i.e., polyvinyl pyrrolidone. After thorough mixing for 30 minutes, the modifier introduces functional groups to enhance the binding ability between the fiber surface and the catalyst.

3. The method according to claim 1, characterized in that The processor is provided with: The feeding assembly, located at the top of the device, includes: a feeding silo for storing carriers, which is equipped with an agitator to prevent material accumulation; a motor with a power output connected to a screw feeder to control the carrier feeding rate; a screw feeder with a feed port connected to the bottom of the feeding silo and a discharge port connected to a discharge port; the discharge ports are 3-5 in number and distributed in a ring. The upper furnace body assembly is located below the charging assembly and includes: an upper furnace body, the top of which is connected to the discharge port via an upper oblique opening, and the bottom is connected to the lower furnace body assembly via a middle oblique opening; a heater wrapping around the outer wall of the upper furnace body to provide zoned heating; a temperature sensor and a temperature control sensor installed on the furnace wall to monitor and control the temperature respectively; an upper discharge port, a middle discharge port, and a lower discharge port installed at the bottom of the upper furnace body; and material level measurement points distributed on the side walls 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 lower furnace body, the top of which is connected to the bottom of the upper furnace body through a middle oblique opening; an observation area with a transparent window arranged on the side wall of the lower furnace body; a lower oblique opening arranged at the bottom of the lower furnace body; an atomizing nozzle installed at the lower oblique opening; and a metering pump connected to the atomizing nozzle through a delivery pipe. The inclination angle of the middle bevel is 45°–60°, guiding the mixed material to flow upward into the furnace body; the inner diameters of the upper, middle, and lower discharge ports decrease gradually to achieve gravity-based grading and screening; 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.

4. The method according to claim 3, characterized in that The specific process of S4 includes: S41, fiber slurry feeding: The fiber slurry is evenly introduced into the upper furnace body of the processor through 3-5 feeding ports distributed in an annular manner on the processor; the slurry enters the lower furnace body through the upper inclined port with an angle of 45°-60°; S42, catalyst precursor atomization: The atomizing nozzle sprays the catalyst precursor solution and uses nitrogen gas high-pressure atomization to form micron-sized droplets; the atomization state is monitored in real time through a high-temperature resistant quartz observation area; S43, gas-solid mixing and graded reaction: Atomized droplets collide with fibers in a countercurrent flow in the lower furnace at 200°C, modifying the functional groups on the fiber surface to adsorb metal ions. The mixed material enters the upper furnace through a 45°-60° inclination. The temperature is raised and calcined in stages: the bottom stage is 200°C to completely evaporate the solvent and enhance physical adsorption; the middle stage is 300°C for pyrolysis to remove modifiers and ethanol residues; the upper stage is 400°C to decompose metal oxides into nano-active particles. S44, gravity classification output: the material is graded and output through the upper discharge port, the middle discharge port and the lower discharge port with decreasing inner diameter gradient: the upper discharge port with the largest inner diameter outputs fine-particle catalyst-loaded fibers, and the lower discharge port with the smallest inner diameter outputs coarse-particle catalyst-loaded fibers.

5. The method according to claim 4, characterized in that In S42 and S43, dynamic gradient load control is performed, and the specific process is as follows: H1: This is the initial infiltration stage. During this stage, the metering pump is adjusted so that the flow rate of the precursor solution is: ； : Real-time precursor flow; : Target basal concentration 5 g / L; : incremental concentration 0.5–1 g / L; : Fiber feed rate 200 g / min; ;The concentration of the storage liquid in the catalyst precursor storage tank; The furnace temperature is kept constant under control , promoting the catalyst to penetrate into the fiber micropores; H2: This is the gradient uniform dispersion stage, in which the precursor flow rate is reduced according to the exponential decay function: ； : attenuation amplitude coefficient; : Dynamic attenuation coefficient 0.05–0.1 s⁻¹; : exponential decay function starting from 30 s; Synchronously control the temperature of the upper furnace partition: ； :high Real-time temperature at : Maximum temperature difference 150℃; : Total height of upper furnace body; : time attenuation coefficient; Make the catalyst precursor dispersed evenly and gradiently on the fiber surface; H3: s is the stable calcination stage, during which the catalyst precursor flow rate is maintained at a fixed value; the temperature of the bottom section of the upper furnace is controlled at 200°C to completely evaporate the solvent and enhance physical adsorption; the temperature of the middle section is 300°C, and thermal decomposition is performed to remove the modifier and ethanol residues; the temperature of the upper section is 400°C, and the metal oxides are decomposed into nano-active particles.

6. The method according to claim 1, characterized in that The specific process of S5 includes: The catalyst-loaded fiber material is introduced into the air flow crushing equipment through a pneumatic conveying system and crushed for 3-5 minutes under the conditions of a pressure of 0.5-0.8 MPa and an air flow velocity of 80-120 m / s; the particle size of the material after crushing is controlled at 100-500 μm to prevent the fibers from entanglement and agglomeration.

7. The method according to claim 1, characterized in that The specific process of S6 includes: S61, after crushing, the material is transported to the displacement tank and first evacuated to an absolute pressure of <10 kPa; S62, nitrogen is introduced to normal pressure, and the vacuum-filling-nitrogen operation is repeated three times; S63, maintain the oxygen content in the tank <50 ppm and the temperature at 40-60℃.

8. The method according to claim 1, characterized in that The specific process of S7 includes: S71, the replaced material is quantitatively transported to the fluidized bed reducer at a rate of 1000 g / batch; S72, introduce a mixture of hydrogen and nitrogen with a total flow rate of 60 L / min; S73, reducing the metal oxides to nano-metal particles at 450±50°C for 10 minutes.

9. The method according to claim 1, characterized in that The specific process of S9 includes: after cutting off the propylene supply, maintaining the nitrogen purge flow rate at 100 L / min for 5 minutes to reduce the material temperature from 750°C to below 300°C.

10. The method according to claim 1, characterized in that The specific process of S10 includes: the cooled material is transported to an intermediate tank under a positive pressure of 0.1-0.3 MPa; an inert cooling medium is sprayed into the intermediate tank and the temperature is cooled to room temperature within 10 minutes.

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