Method for continuously preparing chiral enriched single-walled carbon nanotubes by adopting fluidized bed
The fluidized bed method for preparing chiral enriched single-walled carbon nanotubes solves the problems of catalyst agglomeration and high cost in traditional methods, enabling continuous production and chiral enrichment of single-walled carbon nanotubes, thus improving production efficiency and product quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANXI NORTH UNIV CARBON-BASED THIN FILM ELECTRONICS RES INST
- Filing Date
- 2026-04-07
- Publication Date
- 2026-05-26
AI Technical Summary
Existing technologies make it difficult to achieve continuous preparation of single-walled carbon nanotubes, especially the mass production of chiral enriched single-walled carbon nanotubes. Traditional catalyst preparation methods suffer from high costs, easy agglomeration of metal particles, and poor performance stability.
Chiral enriched single-walled carbon nanotubes were prepared using a fluidized bed method. Microspherical catalyst precursors were prepared by adding metal catalyst salts, inorganic sol-carriers, pore-forming templates, and electrolyte gelling agents to water. After drying and annealing, fluidized bed catalysts with particle sizes of 50-200 micrometers were formed and used for the growth of single-walled carbon nanotubes in a fluidized bed. Continuous preparation was achieved through continuous catalyst delivery.
This method achieves concentrated diameter distribution and enriched semiconductor chirality in single-walled carbon nanotubes, enabling continuous production, improving the fluidization performance and reaction efficiency of the catalyst, and inhibiting the growth of multi-walled and large-diameter carbon nanotubes.
Smart Images
Figure CN122079141A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of carbon nanotube technology, and in particular to a method for the continuous preparation of chiral enriched single-walled carbon nanotubes using a fluidized bed. Background Technology
[0002] Carbon nanotubes (CNTs) are a novel type of nanomaterial discovered by Japanese scientist Sumio Iijima. Their characteristics include tiny size, cylindrical structure, and extremely high aspect ratio. Carbon nanotubes possess excellent tensile strength, high modulus, large aspect ratio, low density, good chemical and environmental stability, and excellent thermal and electrical conductivity, making them a high-performance carbon-based nanomaterial. These properties give them broad application potential in various fields.
[0003] Among them, single-walled carbon nanotubes (SWCNTs) are formed by rolling up a single layer of graphite sheets and have a cylindrical tubular structure. They are widely used in conductive materials, electromagnetic and microwave absorption, high-strength composite materials, fibers, sensors, field emission displays, inks, energy storage and conversion devices, radiation sources, and nanofabrication.
[0004] Currently, the main methods for preparing carbon nanotubes (SWCNTs) include arc discharge, laser ablation, and chemical vapor deposition (CVD). Among these, CVD is widely used for mass production of SWCNTs due to its advantages such as lower reaction temperature, lower cost, higher purity, and relatively higher product yield, showing promising industrialization prospects. Common CVD reactor types include horizontal and vertical. In horizontal fixed-bed reactors, the diffusion of carbon source gas into catalyst particles is the main factor limiting the reaction rate. As nanotubes grow, the catalyst surface is gradually covered, further reducing the contact between the carbon source and the catalyst. In contrast, fluidized-bed chemical vapor deposition (FB-CVD) suspends catalyst particles through upward-flowing gas, significantly improving heat and mass transfer performance and increasing the contact area between reactants and catalyst. This method effectively enhances chemical reaction and heat transfer efficiency, and is therefore considered the most promising technology for achieving mass production of SWCNTs.
[0005] However, current research on carbon nanotube preparation based on FB-CVD technology mainly focuses on few-walled or multi-walled carbon nanotubes, with relatively few reports on single-walled carbon nanotubes, especially the preparation of SWCNTs with single chirality, which is technically more challenging. Domestic and international scholars have conducted extensive research on the preparation of carbon nanotubes using FB-CVD technology and developed different catalyst preparation methods. For example, the SuguruNoda team in Japan used spray deposition to deposit metal nitrates onto the surface of fluidizable zirconium dioxide beads to form nanoscale catalyst films; Professor Wei Fei's team at Tsinghua University proposed the powder agglomeration fluidization theory and successfully achieved the industrial-scale preparation of few-walled or multi-walled carbon nanotubes.
[0006] In traditional CVD methods, the active centers of catalysts used for SWCNT growth are typically metal particles with a diameter of 1-10 nm. These particles are dispersed on inert supports with high specific surface area (such as alumina, magnesium oxide, or silica), thereby promoting SWCNT nucleation and growth. However, traditional catalyst preparation methods require the use of large amounts of solvent to dissolve the metal, followed by drying and annealing processes to produce catalyst powders with uniform metal distribution and small size. This method suffers from high costs, easy agglomeration of metal particles, and poor performance stability in mass production, and thus remains largely confined to laboratory research and development. Furthermore, traditional powder catalysts belong to Class C particles, whose strong cohesive forces make fluidization difficult, thus limiting their application in continuous FB-CVD processes.
[0007] Therefore, a production process capable of continuous preparation of SWCNTs is needed. Summary of the Invention
[0008] This invention aims to provide a method for the continuous preparation of chiral enriched single-walled carbon nanotubes using a fluidized bed, thereby overcoming the shortcomings of existing technologies. The technical problem to be solved by this invention is achieved through the following technical solution, including the following steps: S1. Preparation of fluidized catalyst: Metal catalyst salt, inorganic sol support, pore-forming template agent and electrolyte gelling agent are added sequentially to water and stirred evenly to prepare a gel; the gel is dried to form a microsphere catalyst precursor; the catalyst precursor is annealed in an oxygen-containing atmosphere to form a fluidized catalyst with a particle size of 50-200 micrometers and rich in mesoporous structure. S2. Catalyst reduction and activation: The fluidized catalyst is loaded into a catalyst pretreatment reactor and subjected to reduction treatment at 400℃-800℃ for 10-120 min under a reducing gas atmosphere to remove oxides on the catalyst surface and activate catalytic active centers. S3. Fluidized bed growth of carbon nanotubes: The reduced and activated fluidized catalyst is introduced into the main reactor. Carbon source gas and carrier gas are introduced from the air inlet of the main reactor at 600-1200℃. After being uniformly distributed by the gas distributor, the carbon source gas is decomposed and deposited at the active center of the fluidized catalyst, thereby growing single-walled carbon nanotubes. S4. Product transport and collection: After growth is completed, increase the carrier gas flow rate to blow the fluidized catalyst and the generated single-walled carbon nanotubes out of the main reactor and introduce them into the cooling separator through the gas delivery pipe. After cooling to room temperature under inert gas protection, the single-walled carbon nanotube product is exported. S5. Continuous preparation: After the main reactor is emptied, there is no need to cool it down. The next batch of fluidized catalyst that has been reduced and activated in the catalyst pretreatment reactor is introduced into the main reactor. Steps S3-S4 are repeated to achieve continuous preparation.
[0009] Furthermore, the drying process described in step S1 is one of spray drying, forced air drying, or freeze drying; When using spray drying, the inlet temperature is 200-350℃ and the outlet temperature is 80-150℃. When using forced-air drying, the drying temperature is 50-200℃ and the drying time is 10-100 hours; When freeze drying is used, the freeze drying time is 10-72 hours and the pre-freezing temperature is -40℃ to -10℃.
[0010] Further, the molar ratio of the inorganic sol-gel carrier dry base: metal catalyst: water: pore-forming template agent and electrolyte gel agent is 1:(0.02-0.3):(3.33-29.17):(0.08-0.36):(0.05-0.42).
[0011] Furthermore, the metal catalyst in the metal catalyst salt is selected from one or more of vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), tungsten (W), rhenium (Re), and platinum (Pt), preferably one or more of iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), and tungsten (W); The inorganic sol is one of silica sol, aluminum sol, silica-alumina sol or phospho-alumina sol, preferably silica sol or aluminum sol; The pore-forming template agent is one or more of organic quaternary ammonium salts, organic quaternary ammonium bases, organic acids, organic polymers, or organic surfactants, preferably urea, polyethylene glycol, and citric acid; The electrolyte gelling agent is one or more combinations of NH3·H2O, NH4Cl, (NH4)2SO4, NH4NO3, (NH4)2CO3, and NH4HCO3; Furthermore, the carbon source gas is one or more of CO, CH4, CH3CH2OH, CH3OH, C2H4, C2H2, and C2H6, the carrier gas is one of argon or nitrogen, and the reducing gas is hydrogen or carbon monoxide.
[0012] Furthermore, the reduction reaction uses hydrogen or carbon monoxide as the reducing gas, the reduction reaction temperature is 400℃-800℃, and the reduction reaction time is 10-120min.
[0013] Furthermore, the growth time and reaction temperature of single-walled carbon nanotubes are 600-1200℃, the reaction time is 20-300 minutes, and the gas space velocity is 600-60000 h⁻¹. -1 The gas velocity in the empty tower is 0.01-1 m / s.
[0014] Preferably, the growth time and reaction temperature of single-walled carbon nanotubes are 700-1000℃, and the reaction time is 30-120 minutes.
[0015] Furthermore, the electrolyte gelling agent is one or more combinations of NH3·H2O, NH4Cl, (NH4)2SO4, NH4NO3, (NH4)2CO3, and NH4HCO3.
[0016] Furthermore, in step S2, the catalyst pretreatment reactor is located above the main reactor and coupled to the main reactor. The reduced catalyst is transported to the main reactor through potential energy and the pressure difference between the main reactor and the catalyst pretreatment reactor.
[0017] Compared with related technologies, the technical solution of this application has at least the following advantages: The catalyst is prepared by using silica sol or alumina sol as a carrier and binder to disperse and fix the metal catalyst. After drying by spray drying, forced air drying or freeze drying, a catalyst with uniform metal dispersion, uniform particle size distribution and good fluidization performance is obtained. It can effectively disperse metal catalyst particles, block the bonding between metal catalysts, and inhibit the sintering and agglomeration of catalysts during calcination, reduction and growth processes, thereby inhibiting the growth of multi-walled carbon nanotubes and large-diameter carbon nanotubes during CVD. Therefore, it is possible to control the diameter and number of walls of carbon nanotubes, and thus obtain single-walled carbon nanotubes with concentrated diameter distribution and enriched semiconductor chirality. Attached Figure Description
[0018] Figure 1This is a schematic diagram of the fluidized bed reactor for the continuous preparation of single-walled carbon nanotubes according to the present invention; Figure 2 SEM images (a-b) of the catalyst microspheres prepared by spray drying in Example 1 and SEM images (c-d) of crude carbon nanotubes I grown in a fluidized bed. Figure 3 The UV-Vis-NIR absorption spectrum of the (9,8) enriched crude carbon nanotubes I prepared by the fluidized bed method in Example 1, after dispersion in a 2 wt% DOC aqueous solution.
[0019] Figure 4 The UV-Vis-NIR absorption spectrum of crude carbon nanotubes II grown by fluidized bed method in Example 2 was tested after dispersion in the organic phase of PCZ.
[0020] Figure 5 The fluorescence spectra of the crude carbon nanotubes II grown by fluidized bed method in Example 2, before and after removal of the support (left) and after removal of the support (right), were measured after dispersion in the organic phase of PCZ.
[0021] Figure 6 The UV-Vis-NIR absorption spectrum of crude carbon nanotubes III grown by fluidized bed method in Example 3 was tested after dispersion in a 2 wt% DOC aqueous solution.
[0022] Figure 7 The adsorption-desorption curves are for the catalysts prepared in Examples 1-3.
[0023] Figure 8 Raman spectra of crude carbon nanotubes I and III grown by fluidized bed method in Examples 1 and 3.
[0024] Figure 9 This is a TEM image of crude carbon nanotubes III grown by fluidized bed method in Example 3.
[0025] Figure 10 Thermogravimetric data for crude carbon nanotubes III grown by fluidized bed method in Example 3.
[0026] Figure 11 The UV-Vis-NIR absorption spectrum of crude carbon nanotubes IV grown by fluidized bed method in Example 4 was tested after dispersion in a 2 wt% DOC aqueous solution.
[0027] Figure 12 The image shows the Raman spectrum of crude carbon nanotubes V grown by FB-CVD using the catalyst prepared in Example 5. Detailed Implementation
[0028] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.
[0029] Figure 1 This is a schematic diagram of the fluidized bed reactor for the continuous preparation of single-walled carbon nanotubes according to the present invention, as shown below. Figure 1 As shown, the main reactor 1 is coupled to the catalyst pretreatment reactor 2, and both are equipped with external heating devices to heat the catalyst and reactant gases inside the reactors, maintaining a constant reaction temperature. The catalyst pretreatment reactor 2 is mainly used for calcination and reduction of the catalyst. It has an inlet and an outlet for introducing reducing gas or inert gas for treatment. The treated catalyst is introduced into the main reactor 1 through pipelines via potential and pressure differences. After the pretreatment reactor 2 is empty, it can continue to process the next batch of catalyst, ensuring the continuity of production.
[0030] The main reactor 1 is a tubular structure, with an inlet 8, a gas distribution plate 4, a catalyst loading zone 5, a settling section 6, a cyclone separator 7, and a gas delivery pipe 10 arranged sequentially from bottom to top. An outlet 9 is located at the top. The reaction gas enters through the inlet 8, is evenly distributed by the gas distribution plate 4, and comes into contact with the catalyst at the bottom, where the catalyst particles are fluidized by the gas flow. During the reaction, the carbon source gas undergoes high-temperature pyrolysis and deposition at the active center of the catalyst, growing to form single-walled carbon nanotubes. The settling section 6 is designed as an enlarged cavity structure, where the gas velocity is significantly reduced, achieving gas-solid separation. The catalyst solid is stably fluidized within the catalyst loading zone 5, and the reaction tail gas is purified by the cyclone separator 7 and discharged from the outlet 9.
[0031] After the carbon nanotubes have grown, the reaction products and catalyst are transported together to the cooling separator 3 by increasing the carrier gas velocity. The cooling separator 3 is equipped with a discharge port 11, an inlet 12, a filter 13, and an outlet 14 for cooling and separating the products. Under inert gas protection, the catalyst and carbon nanotube products are cooled to room temperature and then discharged through the discharge port 11; the products can be collected directly. This device is rationally designed, achieving continuous preparation of carbon nanotubes through the synergistic effect of the catalyst pretreatment reactor 2, the main reactor 1, and the cooling separator 3.
[0032] In another embodiment, a method for the continuous preparation of chiral enriched single-walled carbon nanotubes is provided. First, a fluidized bed catalyst is prepared by sequentially adding a metal catalyst salt, an inorganic sol-gel support, a pore-forming template agent, and an electrolyte gelling agent to water and stirring until homogeneous to form a gel. The molar ratio of the inorganic sol-gel support (dry basis): metal catalyst: water: pore-forming template agent and electrolyte gelling agent is 1:(0.02-0.3):(3.33-29.17):(0.08-0.36):(0.05-0.42). The metal catalyst in the metal catalyst salt is selected from one or more of vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), tungsten (W), rhenium (Re), and platinum (Pt), preferably one or more of iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), and tungsten (W); the inorganic sol is one of silica sol, aluminum sol, silica-alumina sol, or phospho-alumina sol, preferably silica sol or aluminum sol; the pore-forming template agent is one or more of organic quaternary ammonium salts, organic quaternary ammonium bases, organic acids, organic polymers, or organic surfactants, preferably urea, polyethylene glycol, and citric acid; the electrolyte gelling agent is one or more combinations of NH3·H2O, NH4Cl, (NH4)2SO4, NH4NO3, (NH4)2CO3, and NH4HCO3; The prepared gel is processed by forced-air drying, freeze-drying, or spray drying to form microsphere catalyst precursors. When using forced-air drying, the drying temperature is 50-200℃, and the drying time is 10-100 hours, resulting in a particle size of 50-200 μm. When using freeze-drying, the freeze-drying time is 10-72 hours, with a pre-freezing temperature of -40℃ to -10℃, resulting in a particle size of 50-200 μm. When using spray drying, the inlet temperature is 200-350℃, and the outlet temperature is 80-150℃, resulting in a particle size of 50-200 μm.
[0033] Subsequently, the catalyst precursor was annealed at high temperature to form a fluidized catalyst with a particle size distribution between 50 and 200 micrometers and rich in mesopores. The structural characteristics of this type of catalyst can provide good reactivity and efficient gas-solid contact conditions for the growth of carbon nanotubes.
[0034] The prepared catalyst is first subjected to reduction treatment in the catalyst pretreatment stage. The fluidized catalyst is placed in a reducing gas, and heating is used to remove oxides from its surface and activate the active sites of the catalyst. The reducing gas is selected from hydrogen or carbon monoxide, preferably hydrogen, the reduction temperature is 400-800 degrees Celsius, and the reduction time is 10-120 minutes. The reduced catalyst is then introduced into the reactor through a conduit for the growth of carbon nanotubes.
[0035] Carbon nanotube growth takes place in the main reactor. A fluidized bed catalyst is stably packed within the main reactor, and the temperature is controlled within the range of 600-1200℃. Carbon source gas and carrier gas are introduced through the reactor inlet. The carbon source gas is one or more of CO, CH4, CH3CH2OH, CH3OH, C2H4, C2H2, and C2H6. The carbon source gas undergoes cracking at the active sites of the catalyst, and carbon atoms are deposited on the catalyst surface, thus forming single-walled carbon nanotubes. After the carbon nanotubes have grown for a predetermined time, the reaction products (including carbon nanotubes and catalyst particles) are blown out of the main reactor by increasing the carrier gas flow rate and transported to a cooling separator via gas flow. In the cooling separator, the reaction products are cooled to room temperature, ultimately achieving the recovery of the chiral single-walled carbon nanotube product. During the cooling process, an inert gas is used to protect the structural stability of the carbon nanotubes.
[0036] Example 1
[0037] Cobalt sulfate (CoSO4·7H2O), silica sol (SiO2·10H2O), and citric acid were sequentially added to water and stirred until homogeneous. Ammonia was then added to adjust the solution to a viscous gel state. At this point, the molar ratio of the components in the solution was SiO2:CoSO4:H2O:C6H8O7:NH3·H2O = 4.8:0.28:50:0.45:0.25. The resulting gel was dried into microspheres as a catalyst precursor by spray drying. Subsequently, the catalyst precursor was calcined in air at 400°C for 30 minutes. After calcination, the catalyst precursor was sieved, and catalyst microspheres with a particle size between 50 and 200 micrometers were selected for later use.
[0038] Five grams of the annealed catalyst were loaded into a catalyst pretreatment reactor and reduced for 30 minutes at 500°C under a hydrogen atmosphere. The reduced catalyst was then introduced into a fluidized bed reactor with a diameter of 40 mm and a length of 2 m. The reactor temperature was maintained at 700°C and the pressure at atmospheric pressure. During the reaction, carbon monoxide gas was used as the carbon source for the growth of single-walled carbon nanotubes for 20 minutes at a space velocity of 24,000 h⁻¹. -1 The empty tower gas velocity was 0.073 m / s. After growth, the generated carbon nanotubes and catalyst were blown out of the reactor together by increasing the carrier gas flow rate and introduced into a cooling separator for cooling until room temperature. Finally, crude (9,8) single-chiral enriched semiconducting carbon nanotubes were obtained.
[0039] Figure 2SEM images (ab) of the catalyst microspheres prepared by spray drying in Example 1 and (cd) of the grown carbon nanotubes are shown. (ab) shows that the catalyst morphology is an irregular spherical or blocky shape of approximately 100 micrometers, exhibiting good fluidization properties. Its surface is composed of nano-SiO2 deposits, with metal catalyst particles dispersed within, demonstrating excellent resistance to sintering. (cd) shows that the catalyst surface after growth is covered with a large number of carbon nanotubes, which are small in diameter and of high quality.
[0040] Figure 3 The absorption spectrum of crude carbon nanotubes I prepared by fluidized bed method in Example 1 was measured after dispersion in a 2 wt% DOC aqueous solution. The results showed that it was a single-walled carbon nanotube enriched with a single chirality (9,8).
[0041] Example 2
[0042] Cobalt sulfate (CoSO4·7H2O), silica sol (SiO2·10H2O), and polyethylene glycol (PEG-6000) were sequentially added to deionized water and stirred until homogeneous. Ammonia was then added to adjust the solution to a viscous gel consistency. At this point, the molar ratio of the components in the solution was SiO2:CoSO4:H2O:PEG-6000:NH3·H2O = 4.8:0.15:18:1:0.85. The resulting gel was dried into a powder using a forced-air drying process. The dried powdered catalyst precursor was then calcined in air at 400°C for 60 minutes. The calcined catalyst precursor was sieved, and catalyst particles with a particle size of 50-200 micrometers were selected for later use.
[0043] 15 grams of annealed catalyst were loaded into a catalyst pretreatment reactor and reduced at 540°C under a hydrogen atmosphere for 60 minutes. The reduced catalyst was then introduced into a fluidized bed reactor with a diameter of 40 mm and a length of 2 m, where the reactor temperature was maintained at 780°C and the pressure at atmospheric pressure. During the reaction, single-walled carbon nanotubes were grown using carbon monoxide gas as the carbon source for 10 minutes at a space velocity of 6000 h⁻¹. -1 The empty tower gas velocity was 0.055 m / s. After growth, the catalyst and generated carbon nanotubes were blown out of the reactor by increasing the carrier gas flow rate and introduced into a cooling separator for cooling until room temperature. Finally, crude (9,8) single-chiral enriched semiconducting carbon nanotubes, product II, were obtained.
[0044] Figure 4 The absorption spectrum of crude carbon nanotubes II grown by FB-CVD using the catalyst prepared in Example 2, after dispersion in a PCZ organic phase, is shown. The results indicate that the carbon nanotubes are enriched with a single chirality (9, 8).
[0045] Figure 5The fluorescence spectrum of crude carbon nanotubes II grown by FB-CVD using the catalyst prepared in Example 2, after dispersion in a PCZ organic phase, is shown. The results also indicate that this sample exhibits high (9, 8) selectivity. The (9, 8) chiral purity is further improved compared to the sample without support (right panel) and the sample without support (left panel).
[0046] Example 3
[0047] Cobalt sulfate (CoSO4·7H2O), silica sol (SiO2·10H2O), and urea were sequentially added to deionized water and stirred until homogeneous. Ammonia was then added to adjust the solution to a viscous consistency, forming a gel. The molar ratio of the components in the solution was SiO2:CoSO4:H2O:CO(NH2)2:NH3·H2O = 4.8:0.50:50:1:0.30. The resulting gel was freeze-dried into a powder. The dried catalyst precursor was then calcined in air at 400°C for 60 minutes. The calcined catalyst precursor was sieved, and catalyst particles with a particle size of 50-200 mesh were selected for later use.
[0048] 50 grams of annealed catalyst were loaded into a catalyst pretreatment reactor and reduced at 540°C under a hydrogen atmosphere for 80 minutes. The reduced catalyst was then introduced into a fluidized bed reactor with a diameter of 40 mm and a length of 2 m. The reactor temperature was 850°C and the pressure was atmospheric pressure. During the reaction, carbon monoxide gas was used as the carbon source to grow single-walled carbon nanotubes for 240 minutes at a space velocity of 2400 h⁻¹. -1 The empty tower gas velocity was 0.073 m / s. After growth, the catalyst and generated carbon nanotubes were blown out of the reactor by increasing the carrier gas flow rate and introduced into a cooling separator for cooling until room temperature. Finally, crude (9,8) single-chiral enriched semiconducting carbon nanotubes, product III, were obtained.
[0049] Figure 6 The figures show the adsorption-desorption curves of the catalysts prepared in Examples 1-3. As can be seen from the figures, the catalysts prepared by this method contain abundant mesopores, providing ample space for the growth of carbon nanotubes.
[0050] Figure 7 The images show the Raman spectra of crude carbon nanotubes grown by FB-CVD using the catalysts prepared in Examples 1-3. The results show a high G / D ratio, and the breathing peaks indicate (9, 8) chiral enriched single-walled carbon nanotubes.
[0051] Figure 8The absorption spectrum of the crude carbon nanotubes III grown by FB-CVD using the catalyst prepared in Example 3 was measured after being dispersed in a 2 wt% DOC aqueous solution. The results show that it is a single-walled carbon nanotube enriched with a single chirality (9,8).
[0052] Figure 9 The image shows a TEM image of the crude carbon nanotubes III grown by FB-CVD using the catalyst prepared in Example 3. The carbon nanotubes are all single-walled tubes with a uniform diameter of about 1.17 nm.
[0053] Figure 10 The thermogravimetric data of crude carbon nanotubes III grown by FB-CVD using the catalyst prepared in Example 3 show that the carbon yield after carbon nanotube growth reaches 10.207%.
[0054] Example 4
[0055] Single-walled carbon nanotubes can also be obtained by preparing Fe-Co / SiO2 catalysts according to the method in Example 2. The specific steps are as follows: SiO2, Fe(NO3)3, Co(NO3)2, H2O, PEG-6000, and (NH4)2SO4 are prepared into a gel by a molar ratio of SiO2:Fe(NO3)3:Co(NO3)2:H2O:PEG-6000:(NH4)2SO4 = 4.8:0.2:0.2:20:1:0.85, and the gel is dried into a catalyst precursor by forced-air drying. The catalyst precursor is then calcined in a muffle furnace at 800°C for 60 minutes in air.
[0056] Five grams of the annealed catalyst were loaded into a catalyst pretreatment reactor, and the reactor temperature was set to 500°C. Reduction was then carried out for 20 minutes under a hydrogen atmosphere. The reduced catalyst was then introduced into a fluidized bed main reactor, where the temperature was set to 600°C and the pressure to atmospheric pressure. Under these conditions, carbon nanotubes were grown using ethanol vapor as the carbon source gas and argon as the carrier gas for 60 minutes at a space velocity of 2400 h⁻¹. -1 The empty tower gas velocity was 0.073 m / s. After the growth process, the catalyst and carbon nanotubes were blown out of the reactor together by increasing the carrier gas velocity and then introduced into a cooling separator to cool to room temperature. Finally, crude single-walled carbon nanotubes IV were obtained. Figure 11 The absorption spectrum of crude carbon nanotubes IV, grown by FB-CVD using the catalyst prepared in Example 4, was measured after dispersion in a 2 wt% DOC aqueous solution. Aqueous phase absorption analysis revealed that the product contained at least three types of single-walled carbon nanotubes with relatively rich semiconductor chiral distributions, and their diameters were small and similar.
[0057] Example 5
[0058] Single-walled carbon nanotubes can also be obtained by preparing Fe-Mo / Al2O3 catalyst according to the method in Example 2. The specific steps are as follows: aluminum sol, ferric nitrate, and ammonium heptamolybdate (NH4)6Mo7O 24 • 4H2O, polyethylene glycol and ammonia in a molar ratio of Al2O3:Fe(NO3)3:(NH4)6Mo7O 24 A mixture of 4H₂O, H₂O, PEG-6000, and NH₃·H₂O in a ratio of 4.8:0.14:0.02:50:1:1 was added sequentially to water and stirred until homogeneous. Ammonia was then added dropwise until a gel-like consistency was achieved. The resulting slurry was then dried using a forced-air drying method to obtain a microspherical catalyst precursor. The catalyst precursor was then calcined in a muffle furnace at 800°C for 300 minutes in air to form the catalyst.
[0059] Five grams of the annealed catalyst were loaded into a catalyst pretreatment reactor. The reactor temperature was set at 700°C, and reduction treatment was carried out under a hydrogen atmosphere for 15 minutes. The reduced catalyst was then introduced into a fluidized bed main reactor, where the reactor temperature was set at 900–1200°C and the pressure at atmospheric pressure. Under these conditions, carbon nanotubes were grown using methane as the carbon source for 30 minutes at a space velocity of 15,000 h⁻¹. -1 The air velocity in the empty tower is 0.018 m / s.
[0060] After the growth process is complete, the catalyst and carbon nanotubes are blown out of the reactor together by increasing the carrier gas velocity and then introduced into a cooling separator to cool to room temperature. Finally, crude single-walled carbon nanotubes V are obtained. Figure 12 The image shows the Raman spectrum of crude carbon nanotubes V grown by FB-CVD using the catalyst prepared in Example 5. Raman spectroscopy analysis confirms that the sample has the breathing peak of single-walled carbon nanotubes and has a high G / D ratio, indicating that the sample is a relatively high-quality single-walled carbon nanotube.
[0061] The catalyst in this invention is prepared by using silica sol or alumina sol as a carrier and binder to disperse and fix the metal catalyst, and then drying it by spray drying, forced air drying or freeze drying to obtain a catalyst with uniform metal dispersion, uniform particle size distribution and good fluidization performance. It can effectively disperse metal catalyst particles, block the bonding between metal catalysts, and inhibit the sintering and agglomeration of catalysts during calcination, reduction and growth processes, thereby inhibiting the growth of multi-walled carbon nanotubes and large-diameter carbon nanotubes during CVD. Therefore, it is possible to control the diameter and number of walls of carbon nanotubes, and thus obtain single-walled carbon nanotubes with concentrated diameter distribution and enriched semiconductor chirality.
[0062] The method for continuous preparation of chiral enriched single-walled carbon nanotubes of the present invention has continuous preparation capability. After the main reactor completes one round of carbon nanotube growth, a new batch of reduced catalyst is immediately introduced from the pretreatment reactor to achieve uninterrupted production. Through the coordinated work of the catalyst pretreatment unit, the main reactor, and the cooling separator, the preparation of single-walled carbon nanotubes can be completed efficiently, and the enrichment of specific chiral carbon nanotubes can be further achieved.
[0063] It should be noted that the above detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.
[0064] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0065] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.
[0066] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.
[0067] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways, such as rotated 90 degrees or in other orientations, and the spatial relative descriptions used herein will be interpreted accordingly.
[0068] In the detailed description above, reference has been made to the accompanying drawings, which form part of this document. In the drawings, similar symbols typically identify similar parts unless the context otherwise indicates otherwise. The illustrated embodiments described in the detailed specification, drawings, and claims are not intended to be limiting. Other embodiments may be used and other changes may be made without departing from the spirit or scope of the subject matter presented herein.
[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for continuous preparation of chiral enriched single-walled carbon nanotubes using a fluidized bed, characterized in that, Includes the following steps: S1. Preparation of fluidized catalyst: Metal catalyst salt, inorganic sol support, pore-forming template agent and electrolyte gelling agent are added sequentially to water and stirred evenly to prepare a gel; the gel is dried to form a microsphere catalyst precursor; the catalyst precursor is annealed in an oxygen-containing atmosphere to form a fluidized catalyst with a particle size of 50-200 micrometers and rich in mesoporous structure. S2. Catalyst reduction and activation: The fluidized catalyst is loaded into a catalyst pretreatment reactor and subjected to reduction treatment at 400℃-800℃ for 10-120 min under a reducing gas atmosphere to remove oxides on the catalyst surface and activate catalytic active centers. S3. Fluidized bed growth of carbon nanotubes: The reduced and activated fluidized catalyst is introduced into the main reactor. Carbon source gas and carrier gas are introduced from the air inlet of the main reactor at 600-1200℃. After being uniformly distributed by the gas distributor, the carbon source gas is decomposed and deposited at the active center of the fluidized catalyst, thereby growing single-walled carbon nanotubes. S4. Product transport and collection: After growth is completed, increase the carrier gas flow rate to blow the fluidized catalyst and the generated single-walled carbon nanotubes out of the main reactor and introduce them into the cooling separator through the gas delivery pipe. After cooling to room temperature under inert gas protection, the single-walled carbon nanotube product is exported. S5. Continuous preparation: After the main reactor is emptied, there is no need to cool it down. The next batch of fluidized catalyst that has been reduced and activated in the catalyst pretreatment reactor is introduced into the main reactor. Steps S3-S4 are repeated to achieve continuous preparation.
2. The method as described in claim 1, characterized in that, The drying process described in step S1 is one of spray drying, forced air drying, or freeze drying; When using spray drying, the inlet temperature is 200-350℃ and the outlet temperature is 80-150℃. When using forced-air drying, the drying temperature is 50-200℃ and the drying time is 10-100 hours; When freeze drying is used, the freeze drying time is 10-72 hours and the pre-freezing temperature is -40℃ to -10℃.
3. The method for continuous preparation of chiral enriched single-walled carbon nanotubes using a fluidized bed as described in claim 1, characterized in that, The molar ratio of the inorganic sol-gel carrier dry base: metal catalyst: water: pore-forming template agent and electrolyte gel agent is 1:(0.02-0.3):(3.33-29.17):(0.08-0.36):(0.05-0.42).
4. The method for continuous preparation of chiral enriched single-walled carbon nanotubes using a fluidized bed as described in claim 1, characterized in that, The metal catalyst in the metal catalyst salt is selected from one or more of vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), tungsten (W), rhenium (Re) and platinum (Pt), preferably one or more of iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo) and tungsten (W); The inorganic sol is one of silica sol, aluminum sol, silica-alumina sol or phospho-alumina sol, preferably silica sol or aluminum sol; The pore-forming template agent is one or more of organic quaternary ammonium salts, organic quaternary ammonium bases, organic acids, organic polymers, or organic surfactants, preferably urea, polyethylene glycol, and citric acid.
5. The method for continuous preparation of chiral enriched single-walled carbon nanotubes using a fluidized bed as described in claim 1, characterized in that, The carbon source gas is one or more of CO, CH4, CH3CH2OH, CH3OH, C2H4, C2H2, and C2H6, and the carrier gas is argon or nitrogen.
6. The method for continuous preparation of chiral enriched single-walled carbon nanotubes using a fluidized bed as described in claim 1, characterized in that, The reduction reaction uses hydrogen or carbon monoxide as the reducing gas, the reduction reaction temperature is 400℃-800℃, and the reduction reaction time is 10-120min.
7. The method for continuous preparation of chiral enriched single-walled carbon nanotubes using a fluidized bed as described in claim 1, characterized in that, The growth temperature of single-walled carbon nanotubes is 600-1200℃, the reaction time is 20-300 minutes, and the gas space velocity is 600-60000 h⁻¹. -1 The gas velocity in the empty tower is 0.01-1 m / s.
8. The method for continuous preparation of chiral enriched single-walled carbon nanotubes using a fluidized bed as described in claim 7, characterized in that, The growth temperature of single-walled carbon nanotubes is 700-1000℃, and the reaction time is 30-120 minutes.
9. The method for continuous preparation of chiral enriched single-walled carbon nanotubes using a fluidized bed as described in claim 1, characterized in that, The electrolyte gelling agent is one or more combinations of NH3·H2O, NH4Cl, (NH4)2SO4, NH4NO3, (NH4)2CO3, and NH4HCO3.
10. The method as described in claim 1, characterized in that, In step S2, the catalyst pretreatment reactor is located above the main reactor and coupled to the main reactor. The reduced catalyst is transported to the main reactor through potential energy and the pressure difference between the main reactor and the catalyst pretreatment reactor.